DEPARTMENT OF COMMERCE UNITED STATES PATENT OFFICE

EXAMINATION FOR REGISTRATION TO PRACTICE

NOVEMBER 19, 1968

Paper No. 1 Time: 3 hours

Paper No. 1 consists of 20 questions. Make your answers brief and to the point. Number each answer and leave at least two lines between answers. Write on only one side of the paper.

1. On July 5~ 1966, a patent containing one claim was issued to patentee George, the claim reading as follows:

In an internal combination engine, the combination comprising a housing, a shaft in the housing, a first series of compression cylinders at one end of the housing, a second series of compression cylinders at the other end of the housing in alignment with said first series of compression cylinders and the shaft, double headed pistons in the aligned cylinders or the two series~ and a cam motlnted on the shaft for rotation by the pistons.

On September 12, 1968, George applies f'or a reissue patent with an aeded claim reading as follows:

In an internal combination engine~ the combination comprising a housing, a shaft rotatable in the housing, a first series of compression cylinaers at one end of the housing, a second series of compression cylinders at the other end of the housing in axial alignment with said first series of compression cylinders and the shaft, double headed pistons in the axially aligned cylinders of the two seriesj and a circular cam mounted within said housing for rotation by the pistons.

Paper No. l -Page One ·

- - -------

Is the filing of the application timely under the statute? Please explain.

2. Applicant Norman Bryant retained registered patent agent Burton Brooks to prepare and file a patent application on a camping tent. Bryant paid Brooks $400. for the preliminary search and preparation of the application together with the filing fee, and the application was filed without any definite arrangement as to payment of fees for prosecution. All claims in the application were rej e·cted in an Office action dated March 7, 1968, and a 3 month period was set for response. Upon attempting to ootify Bryant of the action on March 12, 1968, Brooks ·· was informed DY Bryant's office personnel that he was on a sailing trip in the South Seas and could not be reached. On May 27, 1968, Brooks made a further effort to reach Bryant but is told that he still could not be reached.

(a) Under the circumstances, was it proper for Brooks to assume that he was under no obligation to Bryant to prepare and file a response?

(b) Would your answer be different if Brooks had been a registered attorney instead of an agent?

3. Attorney Davis, after receiving an Ex parte Quayle action requiring certain drawing corrections, filed an amendment complying with the Examimer•s requirement, but in addition added one claim broader than any allowed claim, stating that it was necessary to complete the scope of protection that his client is entitled to under the statutes. What sort of response might Davis expect from the Patent Office?

4. Attorney Jones received an action from the Office having a three month shortened statutory period. One month before the time period is up and just when Jones is about to draft his response, he receives an Office action by the Primary Examiner suggesting a claim to be copied for interference purposes. He is given 30 days in which to respond. · .

(a) What should Jones do about the pending Office action?

(b) What is your answer to (a) above if instead of a suggested claim actionJ Jones received from the Board of Patent Interferences a declaration of interference notice?

Paper No. 1 - Pag~ Two

5. Attorney Nelson received an Office action in which a restriction requirement was made. In order to protect his right to petition under Rule 144, Nelson complied with the requirement but traversed by asserting, "Although applicant provisionally elects Group I, it is respectfully but strenuously pointed out that the Examiner has erred, ia mistaken, and is otherwise wrong in his requirement". Nelson was incensed upon receiving the next correspondence from the Office which gave notice of an Examiner's Amendment cancelling the claims in the non-elected groups and included a statement that prosecution was closed and a notice of allowance would be mailed in due course.

Is there any action Nelson may take to overcome the requirement? If so, what? If not, why not?

6. Allen M. Jones, president of a small corporation seeks your advice about an invention developed by one of the corporation emplqyees which has only limited commercial possibilities. He thus wants to avoid an expensive patent prosecution, but at the same time does not want someone else to patent something similar.

vfuat action, if any, can be taken in the Patent Office to accomplish Mr. Jones' purpose?

7. As attorney for Albert Roberts, who is the junior party in an interference, you have received an adverse decision by the Primary Examiner on a motion by the senior party to dissolve the interference as to two of the four counts involved. Roberts finds what he feels is faulty reasoning in the examiner's decision and wants reconsideration.

(a) May a petition for reconsideration properly be filed, and, if so, within what time period?

(b) Under the facts above, what is your answer to question (a) if the Primary Examiner dissolved the interference as to a third count on his own motion for the first time unmer Rule 237?

8. Attorney Barrett, r~nning short of time in the period set for response to a final rejection, prepared an amendment under Rule 116. Since he felt the Examiner would not be inclined to allow the case based on this amendment and because he wanted to protect himself against the case becoming abandoned, he filed his appeal notice and fee concurrently with his amendment.

How should the Examiner treat the amendment assuming that the amendment fails to place the case in condition for allowance?

Paper No. 1 - Page Three

9. {a) What are three courses of action open to an applicant who is dissatisfied with a decision of the Board of Appeals?

(b) What are the time periods within which each must be taken?

10. {a) Attorney Taylor filed an application containing claims to (1) a crane structure and (2) an internal combustion engine for use in the crane. What sort of action might Taylor expect?

(b) How must Taylor respond and what must he do if he disagrees with this action?

11. Attorney Adams amended the specification of his case by inserting additional subject matter. The Patent Office Examiner on the next Office action objected to the specification amendment as new matter and required its cancellation. Attorney Adams disagrees and thinks the amendment is pro~erly supported.

are

(a)

(b) involved

What is Attorney Adams' course of action?

Is there a different course of action if the claims too? Explain.

12. Attorney Bryant arrived at his office one morning and discovered three cases requiring immediate attention.

(a) Case A in which a 3-month shortened statutory . period of response was to end that day but a long amendment is required which could never be finished in one day.

(b) Case B in which a 3-month shortened statutory period of response ended yeaterday 1 and it is a very important case, the loss of which might cost Attorney BpYant the account.

(c) Case C in which the time limit for response for copying suggested claims expired yesterday .

. What is the proper course of action for Attorney Bryant

to take to save each case?

13. Fritz filed his Gebraucnmuster (utility model) patent application in Germany on June 22, 1966, on a device he designated as Universal Maehine 100, and his Auslegeschrift (Printed Patent Applicati~n} on that device was published on January 5, 1967. He

P'-per No. 1 --Page Four

thought so much of his invention that he filed in Belgium and Great Britain on June 20, 1967, asking for and receiving foreign priority rights. The first half of 1968 showed a continued rise in sales so that expansion into the Western markets would be advisable. On August 1, 1968, with still no patent issued to him, Fritz, on a visit to the U.S., arrives in your office to discuss preparation of a U.S. patent application for his invention. He knows that there is a great deal of activity in this country on his invention, so he is hoping to gain foreign priority rights.

What is your advice to Fritz and why?

14. Under the facts in the preceding question, assume that although sales on Universal Machine 100 were doing fine, there was a flaw in the design which Fritz corrected with two improved models called Universal Machine 200 and Universal Machine 300. On July 3, 1967, Fritz filed in Holland on Model 200 and on September 8, 1967, Fritz filed in Denmark on Model 300.

Assuming each of the improved models will support a separate patent application, what do you advise Fritz as to his foreign priority rights on these last two models?

15. Attorney Lawson received an Office action rejecting his 83 claims as being unduly multiplied and stating that the Examiner was of the opinion that ten claims would be adequate to cover the invention. Lawson files a timely response pointing out how the claims differ from each other and requesting reconsideration of the rejection.

Is the response complete? If so, why? If not, why not?

16. Attorney Adams had been prosecuting Inventor's Ingrarn 1 s application even after Ingram had assigned his rights to M Corporation. Ingram died suddenly one day, and his legal representatives ca.IIE to Adams and stated that they would appreciate it if Adams would continue prosecuting his case. The day came for Adams to file a respense in Ingram 1 S case, but,upon attempting to do so, his• amendment was returned along with a letter from the Patent Office stating that M Corporation had just appointed another attorney and that Adams' power had been revoked. Does Adams have any standing to question the propriety of this action? If so why? If not, why not?

Paper No. 1 - Page Five

17. As attorney for applicant John Newton you have filed an amendment cancelling all of the reJected claims in NewtonYs case. Upon inquiry te the Patent Office you have been informed that the case has been forwarded to Issue and Gazette Branch for typing and mailing of the Notice of Allewanee. Before the notice is mailed you are asked by Newton to add a claim broad enough tG cover a device similar to his which has just appeared on the market.

(a) May Newton have his new claim considered aa a matter of right or merely as a matter of grace? Explain.

(b) Would your answer be different if the Notice of Allowance had been received by you before the amendment is submitted? If so, why? If not, why not?

18. Attorney Miller, having received an Office action dated April 9, 1968, setting a 3 month period for response, found that he needed an adGitional two weeks. On July 8, 1968, he called the Patent Office Examiner and was told that · a written request for extension of the period for one month would be ap~roved. On July 11, 1968, Miller filed a properly supported written request for extension. What action by Miller is necessary if the prosecution is to be carried forward? Explain,

19. Your client Young is upset because yQu have just received a final action on a case in which the Examiner rejected newly added claims on newly cited references. He asks about petitioning the Commissioner in order to urge that making the aetion final is premature because you were never able to respond to the new references and to develop any issues regarding them should the case go to appeal. What do you advise Young as to a petition and why?

20. Attorney Brown in his brief,on appeal to the Board of Appeals responded to each of the Examiner's rejections except for one group of claims. Brown didn't feel the need to respond as to this particular group of claims because he had, he felt, done such a thorough job of meeting the Examiner's holdings as to those claims in his fir&t amendment. Brown decided he would let the Bmrd handle the Examiner and in his brief referred generally to the application record a$ supporting his conviction that the rejection was in error.

Is this course of action acceptable? If so, why? If not, why not?

Paper No. · 1 - Page Six

Paper No. 2

DEPARTMENT OF COMMERCE UNITED STATES PATENT OFFICE

EXAMINATION FOR REGISTRATION TO PRACTICE

NOVEMBER 19, 1968

Time: 3 hours

This paper ls in two parts. The first part requires the analysis and critlcism of claims drawn to an apparatus. The second part requires the drafting of three claims relating to either one of two disclosures.

PART NO. 1

READ INSTRUCTIONS CAREFULLY

This part of the examination requires analysis of the four following claims proposed to be added to an application . having the accompanying specification and drawings. The claims all would be subject to rejection.

Identify the portions or attributes of each claim that afford gro~nds for rejection and make a short statement for each as to why rejection is in order.

5. A self-priming pump system comp!'ising a pump, an inlet for said pump, an outlet therefor, and means automatically supplying liquid to prime said pump when insufficient liquid is present at the pump inlet, said means including a suction well and an automatic valve regulatlng the f1ow of reprlming liquid to said well.

' 6. A self-priming pump system comprisin~ a pumpa~e supply (2L a suctlon casing (4), a pump l20), a drive motor (26), an automatic valve (30), and a drain pipe (9) communicating w1th .the said valve.

Paper No. 2 - Part No. 1 - Page One

7. A self-priming pump system comprising a pump having a horizontal inlet and an outlet3 a suction well having a cavity which is partially below said inlet~ the suction line opening into the suction well at a level above said inlet to supply liquid to the cavity, a suction skirt having a lower end positioned in said cavity below said inlet and having an upper end connected to ' said inlet. A portion of said upper end is elevated above said inlet, reservoir means for repriming liquid having a~ upstream end connected to said outlet of said pump, a reprlmlng valve connected to said pump outlet, a drain conduit connecting sald valve to said suction well, means in the inlet of said valve for detecting a drop in liquid velocity, a valve device within the repriming valve biast~d to closed posi :ion1 a discharge column leading from said valve, and an air relief conduit extending from ·said discharge column to a point upstream of said inlet.

8. A self-priming pump system as described in claim 7 in which said upper end of said suction skirt extends up to but not above tne pump inlet and in which the said fluid responsive detecting means includes ~ Venturi passage.

Paper No. 2 - Part No. 1 - Page Two

------- ---- - ·---- ·

SELF-PRIMING SYSTEM FOR IIORIZONTAL PUMPS

FIG. I

1.0

4

Paper No. 2 - Part No. 1 - Page Three

FIG.2

Paper No. 2 - Part No. 1 - Page Four

36

37

SELF-PRIMING SYSTEM FOR HORIZONTAL PUl\1PS

ABSTRACT OF THE DISCLOS.URE During repriming of a horizontal pump by recycling

liquid from the discharge conduit of the pump to the suction well for the pump, air is displaced from the suction well through an air vent, Air may also be bled from the impeller casing of the pump, preferably by a conduit leading to the upper portion of the suction well ..

Background of the invention

The present invention relates to a self-priming pump­ing system. In the past, there have been many different devices developed to a)l'!omatically prime a liquid pump when tbe pump runs dry due to an insufficient amount of liquid being present at the pump inlet and to prevent air from being introduced to the suction side of the pump. These devices are essential to the efficient operation of a pumping system, since, as is well known, once air is admiHed to the suction passage in sufficient quantities to allow the pump to exhaust the supply of liquid in the suclion well, the pump no longer is able to maintain suction to pump the liquid. Consequently, the pumping operation would be stopped and the at.tention of an operator would be required if no automatic means for repriming the system is provided.

Summary of tlze iflvention

In accordance with the present invention, a horizontal pump is primed by liquid from a suction well or reser­voir located at the pump inlet. The suction well is nor­mally supplied with liquid to be pumped by a suction line communicating with the liquid source of pumpage. A repriming valve is located in the pump discharge column to allow automatic recycling of liquid from the discharge line to ihe suction well when the pump has lost suction. A one-way check valve is positioned downstream from the repriming valve and allows fluid movement only in the downstream direction, and thus limits the quantity of liquid which may be recycled to tha·t in the system be· tween the· repriming valve and the check valve. An air relief line with a one-way check valve connects the top of the suction well to the discharge column intermediate the first mentioned check valve and the reprimlng valve. Air Is displaced from .the suction well through the air relief line by the liquid which is recycled from the dis­charge column through the repriming valve to the suction well . When a portion of the recycled liquid flows from the suction well into the pump inlet, the liquid will be pumped into the discharge column causing the repriming valve to close. If the pump is not fully reprimed, the re­priming valve will thereafter again allow the same liquid to be recycled to the suction well. This recycling will continue in this fashion until the normal pumping cycle is restored.

The present invention is designed for autmoatically re-

priming single or multi-stage pumps employing any rea­sonable length suction line. In the event of loss of suction head due to the pump running dry, there is no danger of pump damage since the system will continue to reprime itself.

According to a further feature of the invention, an air relief llne may vent air from the impeller inlet casing . It bas been found that when liquid in ·the suction well is exhausted and air is sucked into the pump, an air Jock may be formed between· the inlet of the pump intake line and the impeller. This entrapped air may keep liquid from reaching that point in the impeller section of the pump where sufficient velocity can be imparted to it to force the liquid and the entrapped air into the discharge column. ·By the use of an air relief line extending through the casing· of the pump impeller chamber, a path is pro­vided for venting· such entrapped air when the repriming fluid flows into the pump inlet.

It is a principal object of the present invention to pro­vide novel apparatus for automatically repriming a pwnp­ing system which is fed by a suction intake line.

Another object of the present invention is to provide a self-priming pumping system for a horizontal p~p ca­pable of developing a suction head by recycling its prim­ing fluid.

Another object is to provide a self-priming pumping system capable of repeatedly developing a suction head to draw liquid up through a relatively long suction line.

A further object of the invention is to provide a self­priming pumping system wherein the component parts, in­cluding the pump, can be conveniently located to facilitate replacement or ~ervicing, if necessary.

A still further object of the invention is to provide a self-priming pumping system that is rugged, positive in operation, and capable of pumping any sort of pumpage without becoming clogged or jammed.

An even further object of the present invention is to provide a self-priming pumping system for a horizOntal pump that is compact, contains a minimum of moving parts, and is economical to manufacture.

The above and still further objects, features, and ad· vantages of {he present invention will become ·more ap­parenf as this description proceeds.

Brief description of the drawing

FIGURE 1 is a side elevational view, partially in sec­tion, illustrating one embodiment of the present invention.

·FIGURE 2 is a vertical sectional view of (he reprimlng valve employed as part of ·the present invention.

Description of the preferred embodiments

Referring to FIGURE 1. reference numeral 4 desig­nates a suction well or casing which ach as a reservoir for priming liquid 3. In normal operation, liquid 3 is sup­plied to the suction well through a suction line 40 which has its other end immersed in pumpage 2. A suction skirt 5 is positioned ~ith its lower end adjacent the bottom of suction well 4, and is connected at its other end to an in- .

Paper No. 2 - Part Mo. 1 - Page Five

let 6 of a horizontal pump 20 which is driven by a motor 26. In the illustra•ed embodiment, suction skirt 5 has a curved upper ponic>n, the lower inner surface of which is approximately level with the upper inner surface of the eye of the impeller, i.e., the horizontal inlet 6. A small aperture may be provided in the curved upper portion of the skirt S ·to function as an air bleed between this portion of the skirt and the top of the suction well 4. It is also possible to connect the vertically extending portion of skirt S to the pump inlet without elevating the upper por-

tion of the skirt above the pump inlet 6, for example, by means of a 90• pipe elbow.

Pump 20 pumps fluid through an outlet 7, and a re­priming valve assembly 30 to be described hereinafter in­to a discharge column 8. A one-way check valve 12 is positioned at the upper end of the discharge column 8 and connects the discharge column to a discharge line 42. A drain pipe 9 leads from valve 30 to the top of the suc· tion well 4 so that liquid may be recycled in a manner to be described hereinafter to reprime the pump 20. The liquid in discharge ·column 8 and the quantity of liquid in repriming valve 30 above the level of drain pipe 9 are available to reprime the pump. Therefore, the dis· charge column 8 and the above mentioned portion of re· priming valve 30 effectively function as a reservoir for repriming liquid. The volumetric capacity of this reser· voir is at least sufficient to ensure that the quantity of liquid available to reprime the pump is sufficient to fill the pump inlet, inlet 6, skirt 5 and suction well 4 to a level corresponding to the level o( the eye of the pump impeller.

An air relief conduit 10 leads from the top of the en· closed suction well 4 to the upper end of the discharge column 8 upstream from the check valve 11. A one-way check valve 11 in conduit 10 allows fluid movement only in a direction towards discharge column 8 to prevent liq· uid in column 8 from returning to the su<:tion well via conduit 10.

FIGURE 2 illustrates a presently preferred repriming valve assembly 30. Valve assembly 30 basically com· prises an inner casing 34 which has a lower portion in the shape of a venturi. The upper portion of the casing part of the reservoir section for the repriming liquid forms a cage structure for a plurality of peripherally spaced pop­pet valves 31 and the associated valve seats. A tube 35 is connected from each of four openings 32 in the throat of the venturi to a chamber formed by a cylinder 36 and a cooperating piston 38 which is connected to a valve 31 by a valve stem SO. A spring 37 botween ·lhe head of each cylinder 36 and the associated piston 38 functions to normally bias each poppet valve .31 towards its open posi· lion which is shown by dashed lines in FIGURE 2. A jacket 39 surrounds the valve assembly and together with casing 34 forms an enclosed space 33 wbkh is in com­nmnication with the drain pipe 9.

When liquid is being pumped during normal opera· lion, the poppet valves 3~ are maintained in their closed position by a pressure differential between the liquid in the upper portion of casing 34 and the liquid in cylinders 36, which pressure differential is of sufficient magnitude to overcome the bias of the springs 37. This pressure dif· ferential is established by the venturi in the lower section of casing 34 and control tubes 35 leading from openings 32 in the venturi to the cylinders J6. Since the tubes 35 communicate with the venturi, the stalic pressure· In the

venturi is present in the tubeS, and in the cylinders 36. Due to the magnitu!k of the dynamic pressure factor fiowing through the venturi which is proportional to the square of the velocity of the liquid, the static pressure in the venturi and hence in cylinders 36 is less than the static pressure acting upon the poppet valves 31 in the enlarged upper portion of C3sing 34. It is evident that the velocity ot the liquid in the venturi is greater than the ambient .velocity in the upper portion of casing 34 and therefore the pressure in conduits 35 is lower than the ambient pressure in the upper portion of the casin& 34. Thus, a drop fu pressure is created in cylinders 36 which permits pressure against valves 31 to force the valves 31 against their valve seat3 in opposition to the bias of springs 37. When the velocity of liquid flowing through the re· priming valve reaches a predetermined low value, for ex­ample, when air is introduced into the system, and the pressure differential is sufficiently reduced in magnitude, the bias of springs 37 is effective to open the poppet valves Jl. When the poppet valves open, liquid may flow throu~h the valve ports into the space 33 and then into drain pipe 9. . .

The operation of {be FIGURE 1 embodiment Will now be described. With the suction wet! 4 filled with liquid to a level above the pump inlet 6, liquid pumped into dis­charge column 8 by pump 20 creates a suction_ which draws more liquid into the suction well from suction !me 40. As long as liquid flow continues, repriming valve 30 and check valve 11 remain closed.

However if air or other gas enters the suction well and suction is l~t the pumping action slops when the liquid in the suction 'well is depleted. When the liquid flow from the outlet 7 of the pump stops, the pressure dfferenti~l holding the poppet valves 31 in their closed positions ts reduced and the valves are opened by springs 37. Liquid now flo..;,.s out of valve assembly 30 and discharge column 8 1hrougb the ports associated with poppet valves 31, i~to space 33, and through drain pipe 9 back to th'? suchon well 4. As the repriming liquid enters the suchon weJ.I, air is displaced through air relief conduit 1 ~ and check valve 11 into the now empty upper end of dtscbarge col­umn 8. When the repriming ~uid from the suction well passes through the suction skirt 5 into the pump inlet 6, the pump 20 then draws the repriming liquid out of the suction well and pumps It into the discharge column 8. The fiow of the repriming liquid from the pump outlet reestablishes the pressure differential which causes the poppet valves 31 to move to the closed _position. Check valve 11 closes as the liquid enters the dlllcharge column 8 and the air which has entered the discharge column i; now forced through check valve 12 into discharge line 42. The removal of liquid from the suction well 4 re­duces the pressure at the opening of suction line 40 s<? t~al liquid is drawn upward therein. When .the r~Pri!fllOC liquid is depleted, the cycle is repeated unbl suction IS re· established for the pump 20. Factors such as th~ length in diameter of the suction line 40 will determine bow many times the pump will be reprimed before full pump-age flow is reestablished. . .

In one of the embodiments tested, a suctiOn !me 22 feet long and 14 inches in diameter achieved fu.n discharge after three repriming cycle$ wbicb toolcplace m less than a minute.

Paper No. 2 - Part No. l - Page Six

PAR'!' NO. 2

CLAIM DRAli''l'IlfCI

Draft three claims of subltantially varying scope covering either (A) the method or photo­conductor preparation or (B) the method ot making elastic filaments described in the following drawings· and specifications. Write all claims 1n independent form, The claims ahould not distinguish from eaoh other by merely immaterial limitations and should distinguish over any prior art described in the specifications.

A.

PHOTOCO\"(DUCTOR PREPARATION

This invention relates to sintered photoconductors which are particularly useful as elements in bigh speed photologie devices. The invention Is more particularly directed to a method for preparing stable sintcrcd pboto­conducton which are capable of swltchina over large impedance changes at millisecond intervals.

A photoconduclor element or cell is one wbicb has the property of conducting an electric current when light ia applied to the element. In an absence of lisht it Is de• ~ired that the conductivity of the element be very low. The dark current resistivity of the photoconductor ele­ment must therefore be very high. When light is applied to the element a hish uniform current ftow should begin to llow within milliseconds a-fter application. In turn, when the light is removed, current should atop fiowini within milliseconds.

A photologic devi~e may be defined as a device having the property of producing an electrical change of condi• tian upon stimulation of a change in light or other radiant energy condition or vice versa. A photoconductor eli· ment may be used in conjunction with, for example, a . neon light source, an electroluminescent 90urce or their. equivalent to form a photologic device. Photologic de· vices must be able to change their electrical condition• in milliseconds, therefore, its elements must likewise have this property.

Cadmium sulfide and' cadmium selenide are well known photoconductive material•. They have been used in pre­paring polycrystalline layer pbotoconductora by addition of suitable flux and doping agents, and sintering the mix-

ture at an elevated temperature .· Thci phoioc.onductor product of this prior art procedure makes accepta'ble pho­toconductor elements for general usc. However, the prior art pbotoconductor element is wholly inadequate for use . as an element of a photologic device because of its rela­tively 11low response characteristics. . The high response a·nd. senaitivi.tyPf"O"Penies of "Cadmi­um sulfide and cadmium selenide photooonductor elements may be sreatly improved by use of blah levels of electron acceptora, such as copper and silver • . However, tbe proa­ence of these elements in the sintered product cau:~e1 the pbotoconductor element to be unstable to light and tcm• perature over given periods of time. ~n ~bject of this invention i~ to provide a hiah speed

swatclung photoconductor havmg improved light aod temperature stability.

Another object of this invention is to provide a higb speed switching pbotoconductor that may be utiliz.ed as nn element of a photQlogic device.

A further object of this inven<ion is to prowde a meth­o<J for producios polycrystalline laycn of photoconductors capable of swltchios over large impedance cba.naes at millisecond intervals and which have improved light and temperature stability.

Theie and other objects are accomplished io accord­ance with the broad aspects of the present it1ventioa by preparing the pbotoconductor material in tbe form of a paste, to which Is added certain cuefully controlled elec- . trically active impurities and a chemical fiux. Tbe elec­trical impurities fall inro two aroups according to the nature of the. Impurity level they introduce in encrl}' band gap. Those producing levels lying close to tbe con­duction band 11re coasidered to be electron donors and

Paper No. 2 - Part Ho. 2 - Page One

those creating levels close to the valance band are con· sidered to ·he electron acceptors. Donor elements are selected from the third and seventh columns of the peri· odic table. Useful acceptor elements are copper and sil· ver. By adding a 6light excess of acceptors over donors, the photoconductor will act as ·an insulator in the dark and a conduotor when illuminated with visible light.

The thin Jnyer of paste is applied to an inert 4Ubstrate in a uniform layer or !aye~. The coated substrate is then placed in a furnace which ha~ an inert atmosphere an<! sintered at a high temperature. During this sinter· ing process the large crystals of the photoconductive rna· terial grow at the expense of the smaller ones. The crys· tals grow together and adhere to each other to produce a continuous layer. The sintcred photoconductor mate· rial is then allowed to cool to room temperature. The photoconductor is post-treated ·in an inert Jlu.id containini either sulfur or selenium at a temperature of approximate· ly 180-220• C. for a predetermined time.

The foregoing and other objects, features and advan· tages of the invention will ·be apparent from the 'following more particullJ.I description of the preferred embodiments of the invention,· as illustrated in the accompanying draw. ings.

In the drawings: FIGURE 1 is a flow chart illustrating the steps of the

novel process; FlGURE 2 is a plane view of the completed pbotocon·

ductor device; FIGURE 3 is a graphical presentation of room tempera.

ture aging of sulfur vapor post-treated photocooducton with variation in copper concentration; and

·FIGURES 4 and .S are graphical representations com· paring the aging of sulfur vapor phase post-treated, selcni· urn liquid phase post-treated and unposHreated photo. conductors.

Referring now, more particularly to FIGURE 1, a suitable substrate for the application of a polycrystalline photoconductor is thoroughly cleaned. A suitable sub­strate must have the properties of mechanical strength, high electrical ·insulation, high thermo-conductivity and good mechanical bonding to the pbotoconductor material. Sub~trates which have these properties include aluminum, -a high percentage aluminum oxide ceramic, anodized alu· minum and high purity chemical and thermally resist• .ance glasses. Washing of the substrate may be aocom· plished by heating the substrate in hot distilled water con· taining a detergent and agitating the liquid ultrasonically. The substrate is then (horoughly rinsed in hot distilled water and dried .

The electrode connections to the sintered pbotocon­ductor layers may be applied either over the sintered photocell by, for example, a painting procedure or by ap· plying the electrodes to the substrate, then covering the electrodes with the pbotoconductor material and sioterini the photoconductor materi;ll. lt is preferred that the electrodes be applied prior to application of the photo­conductor paste to the substrate. Using this alternative, an ~ppropriatc electrode paste, for example, a 35% plati· num paste, may be applied by silk-screening onto the subslr11te in the desired geometry. The paste is then fired at a high temperature in a furnace, cooled, rinsed in hot water and dried,

An example o( the photoconductor paste formulation follows:

Cadmium sulfide or cadmium selenidc ___ grams •• 60.00 Cadmium chloride --------------------do.___ 6.40 Glycerine ------------------- - - - ------do ____ 211.80 Copper chloride in aqueous solution-Copper concentra-

tion 2570 atom p .p.m. of cuumium sulfiuc or cadmium seleniue.

The ingredi~nt.~ are intimately mixed and applied to the substrate in the desired geometry by any conventional application procedure such as spraying, brushing or silk· screening.

The proportions of the additives cadmium chloride and copper chloride may be varied . The percenta(!e of cad· mium chloride in the paste may be varied from 7% to up­wards of 20% by weight. Below the 7% level the sintered paste has poor mechanical properties and above the 20% level, sl:\nsitivity of the photoconductor is decreased due to what is believed to be the formation of pin holes in the photoconductor layer as the cadmium chloride evap· orates. High acceptor concentration in the form of cop­per or silver ion in the photoconductor paste produces a polycrystalline photoconductor after sintering having a very high dark resistance. lt has been found that tho higher the acceptor concentration, the higher is the sen· sitivity and switching speed of the polycrystalline photo· conductor layer.

The photoconuuctor paste coated substrnte is then placed in a furnace having a temperature of upwards of soo• C. The atmosphere in the furnace must be inert and is preferably a wet nitrogen atmosphere. The photo­conductor p~~te is sintered in the imnace and the re· sultant photoconductor layer is continuous and polycrys­talline. After cooling, the photoconductor is soaked in warm distilled water for a period of time to removl:\ any remaining cadmium chloride Hux .

The post-treatment of the photoconductor layer may take one of two forms, treatment in a vapor phase or in a liquid phase. The active treating material is either sul­fur or selenium . In each form there is required an inert media in which the active treating material is present and that the temperature during the time of treatment be maintained between approximately 180 and 220• C .

The photoconductor in the vapor phase form of post­treatment is dipped in a saturated solution of sulfur in carbon bisulfide and then dried. It is then placed in a vacuum oven and brought to a temperature of 180-220• C. while maintaining the pressure at approllimatcly 100 microns. The photocontluctor is maintained at this tem­perature for approximately 2~ minutes and then the power is cut off to the oven. The vacuum pump is turned off and the photoconductor removed from the oven when the temperature reaches too• C . or lower .

The liquid pha~e pest-treatment system has the active treating agent, sulfur or selenium, ,u, pended or dissolved in a high boiling inert liquid such as ethylene glycol or glycerine. Approximately 0,5% by weight of sulfur or selenium is dissolved or maintnined in fine suspension in the inert liquid . Solubility of the selenium is in­creased by the addition of a base such as sodium carbon· ate or sodium hydroxide to the system . The photocon­tluctor to be post· treated is placed in the prepared liquid nnd the liquid is heated to approximately 180-220' C. )nd maintained at this tempernlllrc for approximately 30

Paper No. 2 - Part No. 2 - Page Two

minutes. Where: ethylene glycol is used as the inert liquid media, it is brought to its boiling point of 197• C. and simply boiled at that temperature for the required post-treating time. The photoconductor is removed from the liquid when the system has cooled to 60• C. or lower and washed thoroughly in distilled water and dried.

FIGURE 2 illustrates one form which the photocon· ductor device might take. Three photoconductor ele­ments or cells in the form of layers 1 are located over conducting Jines 2. The conducting Jines are deposited in an appropriate geometry over a nonconducting sub­strate 3. Over the surfaces of the photoconductor layers 1 is a protective coating (not shown).

FIGURES 3, 4, and S show typical results obtained from the aging of a cadmium selenide photoconductor that has been post-treated in comparison to an untreated cadmium selenide photoconductor. The curve 11 of FIG­URE 3 shows that the ratio of the pre<;ent photocurrent to the initial photocurrc[l~ rem~ins at approximatelv 1 • regardless of copper concentration where the pholocon­ductor bas been post-treated. This particular sarr.ple was post-treated in sulfur. vapor media and the a{l'ing was done at room temperature for a period of 1 SO day.s. CUrve U illustrates the rapid deterioration of the ratio of present current to initial photocurrent on the unpost· treated photoconduclor sample.

FIGURE 4 compares the .effectiveness of the 5elenium liquid phase posHreated, the sulfur vapor phase post· treated and unpost-treated photoconductors under the severe aging conditions. The photoconductor samples were subjected to a flashing neon light with an 83 percent duty cycle (the light is oo 83 percent and off 17 percent

of the time) while maintained at ss· c. The selenium liquid phase post-treatment, curve 13, responded very well and the photocurrent was reduced only slightly. Tho sulfur vapor phase post-treatment, curve 14, responded almost as well as the selenium liquid phase treatment. The rapid deterioration of the uopost-treated photocon­ductor is shown in cun.:e 15 wherein the photocurrent Ia reduced to a low value quite rapidly as compared to tho post-treated photoconductors.

FIGURE $ illustrates longer aging of selenium liquid phase post-treated and sulfur vapor phase post-treated photoconductors. These photoconductors were aged at a temperature 105' C. in the dark. The selenium liquid phase, curves 16, and the sulfur vapor phase, curves 17, post-treated photoconductors performed well under the aging test. The unpost-treated photoconductors deterior­ated BO rapidly under this test that they cannot be shown on the figure separate from the vertical graph line.

The pbotocooductors are then preferably encapsulated in a resin or glass protective layer. The application of the protective coating material may be by any conven­tional technique such as silk-screening, brushing or spray. in g.

The invention thus provides a method for producina photoconductors capable of high speed switching. The procedure produces a product which is light and tempera­ture stable even under somewhat severe conditions. The pbotoconductor element of the invention may be used in conjunction with, for example, a neon light source, an electroluminescent source or their equivalent to form a photo!ogic device. Furthermore, the method is suitable for automatic production aod will permit fabrication of large numbers of these devices at a low cost.

Paper No. 2 - Part No. 2 - Page Three

FIG. t

NIX PHOTOCONOUCTOR PASTE

FIG. 2

FIG. 5

20 40 60 TI NE IN DAYS

PHOTOCONDUCTOB PREPARATION

3

I

10.0 FIG.3

II 'ro to

0.1 ~----+:--:-~~-3 6 9 I Z 15 18 21 -- Calpp"'X10 ·l-

FIG.4

s 12 18 24 30 TINE IN MINUTES

Paper No. 2 - Part No. 2 - Page Four

B.

METHOD OF MAKING ELASTIC FILAMENTS

This invention relates to the process of producing elas· tic filam~nts qerived from segmented polyurethane poly­men and more panicularly to a .process wh~reby the modulus and elongation properties of these elastiC fila· ments can be conveniently regulated by controlling the degree of covalent cross linking.

The solution method for the production of shaped articles based on the class of segmented polymers com­monly referred to as polyurethanes can, in general con· veniently be divided into three phases. The first phase involves the production of a so-called prepolymer which can be prepared by heating a difunctional hydroxyl termi­nated polymer with a molar excess of an organic diiso­cyanate to produc:e a low molecular weight isocyanate­terminated prepolymer. The second phase involves the reaction of the prepolymer with a compound containing, in geneml, at !east two active hydrogens in the presence of a solvent to form a solution containing the resultllnt polymer or elastomer. The third phase involv~s the for­mation of t~e polym~r in a suitable or d~sired ahape such as by cxtrudins the polymer soluliou through a srinnerette to form filaments or by ca~ting or dip-coating the solution to form &elf supporting films.

According to this invention, which is particularly con· cc rned with the latter two phases, n relatively low mo­lecular weight difunctional hydroxy terminated polymer such as a polyester glycol or a polyether glycol Is reacted with a molar excess of an organic diisocyante to form a pre polymer. The prcpolymer, having terminal isocyanate groups. is then reacted is solution with less than the stoi· chiometric amount of a diamioe to form what will here­ina rtrr be referred to for convenience as a &emi-polymer solution. An additional amount of an organic diisocya. nate is then mi:~ed in with the semi·polymer solution and the mixture is formed into tbc desired shape and cured. Advantageously the mixtwc can be extruded or spun throush a spinnereue into a bath containing water, or into a healed inert atmosphere contnlning for example nitrogen ilnd vapors of the solvent used in solution forma· tion, removed, and then cured. By regulating the amount or addition~) diisocynnnte whicb is auded to the semi· polymer solution, the elongation and mollulus properties of the da.~tic filaments are accordingly regulated. With the use of greater amounts of the diisocysnnle, the elon· galion of the clastic lil:~ments is decreased while the mod1rlus is correspondingly increased.

Various difunctional hydroxyl terminated -polymers includins polyether glycols and polyester glycols can be med to form the prepolymers according to this inven· tion. The ~nolcculnr weight of the difunctionnl hydroJtyl term inn ted polymers can advantageously be maintained above about 700 nnd preferably between about 1,000 nnd 4,000. D ifunctionnl hydroxy terminated polymers having a molecular weight below about 700 can also be used. but they generally do not result in end products having ela.~tic i ty ns advantageous as from those hydroxy polymers of higher molecular weight. TI1e value of such .

products produced with hydroxy polyme.rs having lower molecular weight will depend upon the end use of the prod­uct and the elasticity desired for that particular use. Gene.rally as the molecular weight of the bydroxy poly­mer. 1s decrcnscd. the elongation decreases and the modu­lus mcreascs. The use of a polymer having a molecular

w_elaht ia an excess of about 4,000 present• conalderable dll1icultle• In tbc aub!ICqucnt formation of the polymer solution and the tranaformatlon of auch aolutlooa into suitable and useful products due to diflkultiu In main· tainin11 acc:eptablc .rheological propertiea iu the result!n11 polymer 110lutions.

The hiab molecular weight polyester glycob which can be used according to this invention are those wbich contain terminal hydroxyl aroups. The eaten can be -prepared by various known methods by re~tin11 diacid.s diesters, or di~id halides with alycols. Suitable glycol~ which can be used to pr~pare the polyester &fyools In· elude polyalkyleoe glycols 111ch as methylene, ethyleoe, propylene and butylene K)ycols. Substituted polya!kyl. ene glycols such as 2,2-dimethyl-1,3-propene diolu well u heterocyclic glycols SIICh as cyclohexanonc can also be used. Eumples of acids which can be uaed to pre­pare ~he polyester gl)'cols include succinic, adipic, suberic, scbac1c, terephthalic, as well aa various alkyl and balo­gen substituted derivatives of the acids. Tbe polyester glycol may for example be prepared by rea.cting the proper molar ratio of the acids or cster-Cormin1 deriva­tives of the acids with the alycola to produce the high molecular weight polymers. The polymer aJycob pre. pared by ieacting 2 mols of polyethyleoe glycol or poly­propylc~ al~l with I mol of .adipic ll.Cid and tmn re­moving the alycol with heat and vacuum until a molec­Ulat" weiaht of about 2,000 is reac~ can advantageously be used to form ·prepolym~n accordilll to thil invcn· tion.

The polyether l!lycols which can be uxd to form the prepolymera according to this invention are polyal..kylcnc ether glycols having terminal hydroxy voups. The poly. alkylcne ether glycols can be prepared In known manners and are scnerally prepared by the polymerization of cyclic ethen auch as alkylene oxides or from coodcnsa- · tion of gl)'l:Ois. The polyalkylene ether glycols aR repre· sented by the formula HO(RO)DH in which R b an alkyletu: radical and n Ia an illteger sufficiently large ao that the polyalkylene glycol has a molecular weight in excess of about 700 and preferably in exc:ess of ·about 1,000. The polyallcylene glycols can be prepared by co­polymerizing mi:JUures of different alkylenc: oxides or gly· cols. Examples of polyallcylene ether alyc:ols which can be used In thia Invention include polyprOpylene ether glycol, 'polytetnunetb.ylene ether glycol, polyethyleoe ether alycol, 1,2-polydimethylethylenc ether glycol, poly­decamethylcne ether glyc:ol, and so forth. Further u· amples of polyalkylene ether glycol$ which c:a.n be u5ed according to this Invention are described In Patent No. 2,492,959.

Paper No. 2 - Part No. 2 - Page Ftve

Various organic diisocyanates can be used to react with the difuoctional hydroxy polymers to fonn the pre. polymer. Aromatic, aliphatic, as well as cydoaliphatic di­isocyanates or combinations thereof, can be used. Repre­sentative diisocyanates includes 4-methyl-m-pbenylene di­isocyanate, m-phenylene diisocyanale, 4,4'-biphenylene di­isocyanate, methylene bis( 4-phenylisocyanate), 4-cbloro-1,3-pheoylene diisocyanatc, l,S-naphthylene diisocyanate 1,4--tetramethylcne diisocyanate, 1,6-hexamethylene dii~ cyanate, l,Hklecamethylene diisocyanate, 1,4-cyclohexyl­ene diisocyanale, 4,4' -methylene-bis( cyclohexylisocyan­atc), and l,S-tetrahydronaphthalene diisocyanate. Aryt. ene diisocyanates, i.e ., those in which each of the isocya­nate groups is attach£d directly to an aromatic ring are prefcred. In general, they react more rapidly than do the alkylene diisocyanates. The diisocyanates may conta-in other substituents, although tbose which are frte from reactive groups other than the .two isocyanate groups are ordinarily pn:ferred. In the case of the aromatic com­pounds the isocyanate groups may be attached either to the same or to different rings. Dime~ of the monomeric di­isocyanates and diisocyanatoaryl)-ureas, such as di(3· isocyanate-4-mctbylpheilyl) urea may also be used.

The patents to Fran~enbnrg No. 2,957 ,852, Winde­mulh No. 2,948,691 and Hill No. 2,929,800 further show how the prepolymers can be prcpnred, as well as the reactants used in their preparation acconling to this invention.

It bas heretofore been customary to prepare a so-called polymer solution by reacting a prepolymer with a diamine in essentially stokhiometric proportions in ndmixture with a solvent to produce a high molecular weight polymer solution suitable for formation into films, extrusion into a water bath to form filaments and so forth. These solu­tions generally contain about 15 to 25% by weigbt polymer.

The method of this invention involves an improvement in the preparation of n polymer solution and the trans­formation of the polymer solution into clastic products.

According to this invention the prcpolymer is reacted with a diamine in less than stoichiometric proportions to form a semi-polymer solution. The prepolrmcr is in­completely reacted and still contains unrenctcu terminal isocyanate 11roups. Additionnllliisocyan;ltc is then mixed in with tbc semi-polymer 30!Ution, the mixture is either dry spun or wet spun, i.e., either extruded into a heated inert atmosphere containing solvent vn[lors or extruded into a liquid bath, and heat cured. In the curing step the free isocyanate groups are caused to react wilh urethane hydrogens along the semipolymer chain Lhus resulting in covalent trosslinks.

The amount of diamioe that can be used to Corm the semi-polymer solution can be varic<J cousi<Jcrably depend· ing on a number of factors such as the particular diamioe used to react with the prepolymcr, tlte reactants used to form the pre polymer, the propeftics d~sired to be possessed by the end products and so forth . These noll other fac­tors will be apparent lo those skilled in tbe art and the exact amount of diamine that cnn most advantar;cously be used to prepare the semi-polymer can be re~dlly deter­mined by those skilled in the art by routine cxperimenta· tion. Generally, the reaction of the prepolym~r with the diamine in a molar r~tio of about 5:4 is Ddvnnt.agcous.

As a I: 1 ratio is approached, the viscosity of t!Je solu­tion increases and requires the usc of. a<.Jvitional solvent whi~h results in a decrease of the polymer solids coutent of the solution. With many intermediate~ it is not pos­sible, as a practical matter, to extrude, or otberwise form, a prepolymer into a final product baving desirable and useable elastic products and it is therefore necessary to use a sufficient amount of a diaminc to form a semi­polymer solution having suitable characteristics (or for­mation into useful elastic products. As rhc molar ratio of prepolymer to diamine is incrcasc<J, polrmcr solutions tend to lose their advantageous extrusion characteristics and the formation of products thcrc(rom become more difficult. The amount of diaminc reacted with the pre­polymer should generally be selected on the basis of the exlrudability of the semi-polymer solution ~nd the amount of solvent required to produce an extrudable semi-polymer solution.

The gradual addition of the diamine to the prepolymer solution results in the gradual increase in the viscosity of the solution. The extent and rate of the viscosity increase will depend to a great degree oo the particular diamine being used to form the semi-polymer. It is advisable to add sufficient diamine to increase the viscosity of the solution to at least ahout 50 poises to obtain a solution which, when mixed in with addilional diisocyannte, can be easily extruded. Generillly, it is more advantageous to extrude solutions having viscosities between about 100 to 500 poises.

The amount of additional diisocyanatc w!Jich can be added to the semi-polymer solution can IJc readily varie(.! in order to regulate the elongation and modulus chnrac­tcristtcs of tbe resulting elastic !ilamcnls. As shown in the following examples, when the higber amounts of the addi­tional diisocyanate are used, the elongation of the result· in-g elastic filament& are decreased while the modulus ii correspondingly increased. The actual amount of addi­tional diisocyanate can vary considerably depending upon the properties desired in the final product and can be readily detennined by routine experimentation. Addi· tiona] diiroeyanate has bet:n advantageously employed in amounts equivalent to from about 0.2 to 1 mol of diiso­cyanate to 1 mol of prepolymcr used. Of cou~. con­siderably higher or lower proportions can also be used.

The diisocyanate which Is used can be any of those dC!iCribed above which are used in the formation of the prcpolymer. The diisocyanate which is employed in the preparation of the prepolymer can be the same or diiTercnt fxom the diisocyanatc which Is added to the semi-polymer.

Variollll primary and secondary diamines can be used to form the semi-polymers according to this invention in· eluding aliphatic, allocyclic and inorganic diamlnes. Generally, the same diamines can be used as have previ­ously been known to be useful in the prior process in which 5UbStantially a stoichiometric amount of diamine is react· ed with the prepolymer. The particular diamines which can be used according to this invention will thus be ap­parent to those sk.illed in the art. Specific eumples of a number of diamines which can be used are hydrazine, ethylene diamine, piperazine, 1,4--diamine-2-metbyl piper· azine, 1,4-d.ia.mine-l,S-dimethyl piperazine, methylimino bis propylamine, etc. Jt should also be apparent to those skilled in the an that combinations of two or more di­amines may be used in the semi-polymer formation step.

Paper No. 2 - Part No. 2 - Page Six