US3490863A - Sterilizing system and method - Google Patents

Description

Jan. 20, 1970 R. 1.. SCHUMANN E AL 3,490,863

STERILIZING SYSTEM AND METHOD Filed Sept. 18, 1967 2 Sheets-Sheet 1 1 I I I I I I I I I 25 l I I I I I I I l I I INVENTOES M LZJ, Ifii ATTORNEYQ Jan,2 O, .l9 70 H ETAL STERILIZING SYSTEM AND METHOD Filed Sept. 18. 1967 2 Sheets-Sheet 2 WW I United States Patent Cffiee 3,490,863 Patented Jan. 20, 1970 3,490,863 STERILIZIN G SYSTEM AND METHOD Russell L. Schumann, Murray Hill, N.J., and Hugo Sonnenschein, 809 Lincoln, Winnetka, Ill. 60093; said Schumann assignor to said Sonnenschein Filed Sept. 18, 1967, Ser. No. 668,402 Int. Cl. A611 13/00, 3/00 US. CI. 2158 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a gas sterilizing system in which a predetermined quantity of liquid such as, for example, ethylene oxide is dispensed from a container and then flash evaporated into a gas for introduction into a sterilizing chamber containing articles to be sterilized.

Prior to sterilization, the articles are usually sealed in plastic bags which are permeable to the sterilizing gas but substantially impermeable to air-borne bacteria. A number of such bagged articles are loaded in the sterilizing chamber and the volume'they occupy may vary radically from one load to the next load. For instance, there may be times when only a very small article is placed in the sterilizing chamber, and, at other times, several bulky items may be placed in the chamber to occupy most of its volume.

Such a sterilizing system is disclosed in copending application S.N. 592,127 filed Nov. 4, 1966, entitled, Sterilizing Method and Apparatus. In the system disclosed in that application, the sterilizing gas is generated from a liquid dispensed from an aerosol supply cartridge. The cartridge has sufiicient liquid to generate a quantity of gas to fill a substantially empty chamber with a predetermined concentration of sterilizing gas. When the chamber is filled to any appreciable extent with articles, there is an excess of liquid and gas available. To obtain the best results, however, the concentration of gas in the chamber should be controlled to a predetermined value irrespective of the chamber volume then being occupied.

It has been found that if the chamber is relatively full, then an excess of gas may be admitted and result in pressures in the chamber sufliciently large to break the hermetically sealed chamber, for example, by opening the access door to the chamber. In the above identified aplication, an operator manually controls the dispensing of liquid ethylene oxide, and, when the proper gas concentration is reached, the operator stops further dispensing of liquid. When the operator stops the dispensing, there is a residue in the aerosol canister of liquid which is potentially dangerous if the canister is incinerated.

Accordingly, a general object of the invention is to provide an improved and automatic gas sterilizing system to limit gas concentration in the chamber to a predetermined concentration.

A further object of the invention is to provide a predetermined concentration of gas in a sterilizing system irrespective of the amount of volume occupied by articles therein and to dissipate any residue of dispensing liquid or resulting gas.

Other objects and advantages of the invention will be apparent from the foregoing detailed description of the invention taken in connection with the accompanying drawings in which:

FIGURE 1 is a perspective view of a gas sterilization apparatus embodying the novel features of the present invention;

FIGURE 2 is a diagrammatic illustration of the operative connections between the operating elements with the sterilizing apparatus of FIGURE 1; and

FIGURE 3 is an exploded perspective view of the operating elements in a control unit .of the sterilizing apparatus of FIGURE 1.

As shown in the drawings for purposes of illustration,- the invention is embodied in a sterilizing apparatus 11 which includes a housing 13 with a top cover 15 which opens to expose an interior chamber 17 (FIGURE 2) into which are placed the articles to be sterilized. Adjacent the chamber housing 13 is a control unit 19 for evacuating the chamber 17 and generating a sterilizing gas, such as ethylene oxide. The control unit is connected by a conduit line 23 to the interior chamber 17 in the housing.

Typically, the articles to be sterilized are packaged in bags usually of polyethylene or other plastic material which can be penetrated by the ethylene oxide gas but which is impermeable to air-borne bacteria. To assist in the penetration of the bags by the gas and to assure a better microbicidal action, the chamber is subjected to partial vacuum prior to the introduction of the sterilizing gas into the chamber.

The system will be first described, very generally, as it relates to the system disclosed in copending application S.N. 592,127 filed Nov. 4, 1966 and entitled Sterilizing Method and Apparatus, which is hereby incorporated by reference as if fully reproduced herein. Referring now to FIGURE 1 of the present disclosures, the operator places the articles in the enclosed chamber 13, closes the cover 15 for the chamber and fastens a latch 27 to hermetcally seal the chamber. An aerosol cartridge 25 is disposed within a cylindrical housing 29 which is fastened on the control unit 19 and a switch is operated to begin an operating cycle. During the first portion of the cycle, an exhaust means 31 in the form of a vacuum pump (FIGURE 2) is operated to exhaust the interior of the enclosed chamber. After a predetermined period .of time, usually four minutes, the vacuum pump automatically shuts off and an electrically controlled dispensing valve 33 opens and permits the liquid ethylene oxide to flow past it and through a passageway into a heater 35. The liquid ethylene oxide then evaporates into a gaseous state. Because the liquid ethylene oxide is heated and subjected to the reduced pressure of the enclosed chamber 17 through the conduit 23 and the dispensing valve 33, it flash evaporates and quickly moves into the chamber 17. To offset cooling during the evaporation process, the electrical resistance heater 35 is provided with a tortuous passage to assist in a heat exchange from the heater to the evaporating liquid and gas. If the cooling is not offset, the rate of evaporation is reduced considerably. It is most desirable that the liquid ethylene oxide evaporates as it may polymerize and clog the conduit 23 and the dispensing valve 33.

In the system described in the copending application, the operator watched a pressure gauge 37 (FIGURE 1) on the cover 15 which indicated the build up of gas pressure within the housing chamber 17. When the pressure reached ambient pressure, the operator then unscrewed the aerosol container housing 29 which automatically operated the electrical switch resulting in closure of the dispensing valve 33. The spring loaded valve in the dispensing cartridge 25 also automatically closed and stopped he dispensing of liquid ethylene oxide from the cartridge.

While the foregoing system operated satisfactorily and Was much faster in operation than systems of the prior 1ft, it sometimes occurred that the operator did not watch he pressure gauge 37 or would be slow in turning the car- Lridge housing 29 to cut off the dispensing of liquid. In he meantime, the ethylene oxide gas would continue to Je generated and the concentration of gas within the housng would increase beyond that desired for best microaicidal action. Also the build up of excessive gas pres- ;ure in the housing exerted tremedous forces on the latch 27 and, in some cases, the housing lid could not be reained in the sealed position.

It will be appreciated that the housing chamber 13 has 1 fixed, volumetric capacity and the portion thereof oc- :upied by the articles being sterilized often varies sub- ;tantially from load to load. By necessity, the aerosol conainer 25 is sized to dispense sufiicient liquid ethylene )xide to provide the proper gas concentration for a virually empty chamber. When the chamber was loaded vith an appreciable volume of articles, the operator had diligently watch the pressure gauge 37 and shut off he system beforfe excessive concentration and pressures vere achieved in the chamber 17.

In accordance with the present invention, the proper :oncentration of gas is achieved within the chamber 17 rrespective of the volume occupied by articles being steriized. Also, as a safety precaution the aerosol containers 15 are fully exhausted of liquid ethylene oxide automatcally during each gas generation cycle. This is most deirable, as otherwise, operators may try to use a partially ull cartridge for a subsequent sterilizing operation and lnbeknown to them there will be insuflicient liquid for terilizing. In such a case, the articles would not, in fact, )e sterilized although the operator may mistakenly think hat they are sterilized because of having gone through t cycle with the apparatus. Also, incineration of cartridges laving liquid ethylene oxide therein could result in an exalosion.

To achieve the foregoing, the preferred embodiment of he invention contemplates monitoring the concentration f gas within the chamber and, when the concentration eaches a predetermined desired value, terminating the ntroduction of gas into the chamber followed by exlausting the remaining gas in the cartridge before terninating the cycle and removing the cartrige. As a result, he concentration of gas in controlled accurately and the langers of undissipated liquid in the cartridge are avoided.

Referring now in detail to the apparatus similar to that .isclosed in the above identified copending application .nd illustrated in FIGURE 3, the ethylene oxide cartridge 25 has a self-sealing valve and stem 43 (FIGURE 3) rom which it will dispense a predetermined quantity of lquid which, in this instance, for a chamber having a apacity of three cubic feet of gas at ambient room temerature and pressure is approximately 90 grams of liquid thylene oxide at a pressure of approximately 7 to 8 ounds per square inch at room temperature. The presure is furnished by vapor pressure within the cartridge lhiCh is readily available as a standard item.

After loading the chamber 17 with the bagged articles nd fastening the latch 27 to seal the cover 15, the oprator places the cartridge 25 within the hollow cylindrial housing 29 with the stem 43 pointed downwardly.

Prior to beginning a sterilization cycle, the removable ousing 29 is unthreaded from an upstanding sleeve on a ase 45 secured on the outside of a top plate of the ontrol unit 19. Then, the end of the cartridge opposite 1e stem 43 of the valve is inserted endwise into the bore f the bore of the receiver housing toward its upper adial end wall 47 and the housing is again threaded on 1e base. The valve stem 43 projects downwardly and its rifice is aligned with a bore or opening 49 extending xially through the receiver base 45. The lower end of 1e valve stem is positioned on the upper end wall of the base and over the bore 49 in the latter. With the receiver housing 29 telescoped over the cartridge with its top wallv 47 hearing against the now upstanding bottom end of the cartridge, an aperture 51 in the top wall of the housing is blocked by the adjacent cartridge end. The aperture 51 serves as an air inlet when not blocked by this end of the cartridge.

As the housing 29 is turned and threaded onto the receiver base 45, the lower end (FIGURE 3) of the housing moves into sealingly engagement with an annular outwardly projecting collar 54 (FIGURE 3) formed on the sleeve at the bottom of the external thread, and simultaneously the self-sealing stem of the valve of the aerosol cartridge is forced upwardly in the cartridge and opens to allow the liquid ethylene oxide to flow downwardly from the cartridge into the vertical, internal bore 49 in the receiver base and then to flow down through a depending threaded cylindrical sleeve 55 (FIGURE 3) screwed into a bore 57 in a top wall of the dispensing valve 36. Thus, it will be seen that the valve stem is spring biased to a closed position and the housing top wall 47 forces the cartridge to move down relative to the stem on the base and thereby the stern valve is opened.

Simultaneously with the screwing down of the housing 29 and the release of the liquid ethylene oxide, a microswitch 59 is operated to begin operation of a control circuit including a timer mechanism '61 (FIGURE 3). The timer mechanism is a commercially available timer having a motor (not shown) which is energized over leads 63. An upstanding pin 65 on the microswitch 59 extends through an opening in an outwardly extending radial flange on the receiver base 45 to be depressed by the rim of the outer housing 29. The pin opens and closes contacts (not shown) which are connected to the timer mechanism 61 by leads 67 (FIGURE 3).

The timing motor begins a five-minute operation, after which, the timing motor automatically shuts off. During the first four minutes of timing motor operation, a vacuum pump motor 69 is operated to evacuate the chamber 17. The pump motor 69 is fastened within the control unit and has its driving shaft connected to an impeller of a vacuum pump 71 which is fastened at one end of the motor. As the vacuum pumps turns, it creates a suction in a conduit 73 extending from an inlet port 75 for the pump to a port 77 of an electrically operated, check valve 79. This check valve is normally closed and is operated to its open position only when the pump motor 69 is energized by the timing mechanism. The check valve 79 in its closed position prevents ambient air from leaking through the pump 71 and conduit 73 to the chamber 17 during the gas generation and sterilizing operations as will be explained.

The exhaust pump 71 exhausts through the check valve 79, which is now in an open position, and in fluid communication with a port of a multiported connector 81 which has a second port 83 in fluid communication with the conduit line 23 extending to the interior of the enclosed chamber 17. According to the preferred manner of operation, the vacuum pump 71 operates for approximately four minutes and reduces the pressure in the chamber to a predetermined vacuum, which is in the preferred embodiment of the invention, a vacuum of about 26 inches of mercury. The degree of evacuation of the enclosed chamber 17 may be varied, for instance, in the 'copending application the vacuum used was about 20 inches of mercury.

After the pump 71 has evacuated the chamber 17 for a predetermined period of time, the timing mechanism 61 de-energizes the pump motor 69 and closes the check valve 79; and simultaneously, the timing mechanism 61 energizes the solenoid operated dispensing valve 33 to release the sterilizing liquid for flash evaporation. The dispensing valve 33 is fixed to the bottom of the base 45 holding the cartridge 25 with its inlet opening 57 aligned and in fluid communication with the open stem valve of the cartridge 25. The dispensing valve 33 is normally in its closed position so that the liquid ethylene oxide is being blocked from moving toward the enclosed chamber 17. As the dispensing valve is operated to its open position, the liquid ethylene oxide is free to flow past its valve member (not shown) into a conduit pipe 85 leading to a tortuous passageway through the electrical heater 35 which is being operated by electrical resistance heaters under the control of the timing mechanism. The outlet of the heater passageway is connected by pipe 87 and pipe 89 to the multiported conhector81 leading to the line 23 extending to the evacuated chamber 17. The liquid ethylene oxide flowing from the dispensing cartridge 25 is subjected to the pressure difierentiallemanating from the evacuated chamber 17 and this'causes a flash evaporation of the liquid into a gas. The gas rapidly moves through the heater 35 into the enclosed" chamber causing the pressure within the chamber to rise.

It will be appreciated that the liquid within the aerosol container 25 is being rapidly discharged and that the flash evaporation quickly generates the ethylene oxide gas so that the pressure within the chamber 17 rises quite rapidly. In the preferred cycle, the contents of the aerosol cartridge 25will be dispensed through the valve 33 within one minute.

Referring now in detail to the preferred apparatus for practicing the improved method, the apparatus disclosed in the above identified copending application is modified by the addition of a vent control valve 39 which controls the flow of gas from the h'eater35 and a monitoring unit 41 which monitors the concentration of gas within the chamber and controls the vent control valve in accordance with changes in the concentration. Conveniently, the monitoring unit determines the gas concentration by sensing its pressure within the chamber. To. fill the chamber to the desired concentration, the movable element of the vent control valve is in a first position connecting the passages 87' and 89 between the heater "and the chamber until the'desired concentration is sensed by the monitoring unit. Then, the valve is actuated and its movable element is shifted to a second position to'connect the heater line to an exhaust or'bypass line 99 which is connected continuously to a common exhaust line 101 on the outlet side of the vacuum pump 31.

The monitoring device 41 herein is in the form of a pressure differential device with a pneumatically operated diaphragm 91 which has one side exposed to the ambient pressure and its other side exposed to the chamber pressure through a conduit pipe 93 connected to a port 94 for the multiported connector 81. Thus, the monitoring device 41 continually monitors the pressure of the gas within the chamber 17. In the present system, the proper gas concentration in the chamber 17 is obtained when the pressure in the chamber reaches ambient air pressure. It is within the purview of the invention that the pressure differential device be capable of adjustment to operate at pressures other than ambient. As the pressure in the chamber approaches ambient pressure, the diaphragm in the pressure sensing devise moves to a, position to operate an electrical switching device 97 which is open until the pressure differential is reduced to thev point where the diaphragm which, in this instance, are electrical contacts, cause the contacts to close. These contacts control the electrical energizing circuit for a solenoid operating the vent control valve 39, which solenoid then becomes energized and causes a valve element to move to a position in which the valve connects the pipe 87 from the heater to a venting or bypass line 99. The bypassing line 99 is in turn connected to a common exhaust line 101 extending from the vacuum pump 71. The gas, it any, being generated from the surplus or residue liquid in the cartridge 25 or other connected apparatus is then diverted and exhausted from the system. The vent valve 39 remains in this position for the remainder of the five minute timer control cycle, which allows sufficient time to assure that all of the ethylene oxide gas is evaporated from the aerosol cartridge 25, valve 33 and heater 35. At the end of the timing cycle, the timing mechanism 61 de-energizes the solenoid for the dispensing valve 33 which then moves to its closed position. The solenoid for the vent valve 39 is also de-energized at this time by the timing mechanism and returns to its normally open first position. Since both the dispensing valve 33 and the check valve 79. are closed, there will be no leakage from theenclosedchamber 17 through the control unit 19 during the sterilizing portion of the cycle.

.For items which are extremely heat sensitive, it has been found that a three hour sterilizing cycle at room temperature is usually sufficient. Provision is made, however, to heat the chamber 17 and it has been found that the time required for sterilizing articles can be reduced considerably when heat and some moisture are employed with the gas. For example, when the chamber is maintained at approximately F., a typical sterilization cycle can be reduced from a cycle of about three hours at room temperature to a cycle of about 48 minutes.

After the articles have been subjected to a gas for a suflicient time, the operator detaches the cartridge housing 29 and removes the cartridge 25. The operator then resecures the housing 29 on the base 45 and thereby operates the switch 65. With operation of this switch 65, the timer mechanism 61 begins a new cycle and causes the motor 69 to turn the vacuum pump 71 to evacuate the ethylene oxide gas from the chamber 17 and exhaust the same from the exhaust pipe 101 connected to the outlet side of the vacuum pump 71. After about four minutes, the pump motor 69 shuts down and the timing mechanism operates the valve 33 to its open position so that air may rush through the air inlet opening 51 of the now empty cartridge housing 29 and through the valve 33 and the heater 35 and, now open, vent valve 39 into the exhaust chamber. At this time, the first wash cycle is completed. It is usually desirable to employ several washing cycle. Therefore, the operator will again unscrew the receiver housing 29 and then screw the same now to reactivate the microswitch 65.

As an aid to understanding the invention, the operation of the improved apparatus will be reviewed.

Assuming the articles occupy approximately 1 cubic feet of the three-foot chamber and that the cover 15 has been locked in place with the latch 27, an operator telescopes the housing 29 over an aerosol cartridge 25 and fastens the housing to the base 45 whereby the microswitch 65 is operated to begin the gas generating cycle. As the housing was fixed to the base, the spring bias valve from "the aerosol cartridge was opened and liquid ethylene oxide was admitted to the inlet opening 57 of the dispensing control valve 33. However, no gas is generated so long as the valve 33 is closed.

The microswitch causes energization of the timing motor for the timing mechanism 61 which causes the operation of the vacuum pump motor 69 and the energization of the normally closed check valve 79 to its open position. The vacuum pump 71 operates for approximately four minutes at which time the evacuated chamber 17 has reached a vacuum corresponding to about 26 inches of mercury. At this time, the timing mechanism 61 deenergizes the motor 69 and the check valve solenoid, and

the check valve then closes the line 73 from the vacuum pump 71 to the chamber 17 to prevent any leakage of air through the pump to the chamber.

During the opeartion of the vacuum pump 71, electrical heater elements in the heater 35 were operating to bring the heater up to temperature. When the vacuum pump 71 has shut down, the dispensing valve solenoid is energized to open the valve 33 and the ethylene oxide flows into the heater and flash evaporates in the presence of the subatmospheric pressure from the chamber 17. As the ethylene oxide evaporates, it flows into the chamber 17 and the pressure within the chamber rises as indicated y the pressure gauge 37. The rise in pressure in the hamber is sensed by the monitoring unit 41, the inreasing pressure indicating an increase in gas concentraion in the chamber. When approximately half of the iquid from the dispensing cartridge has vaporized and .as moved into the chamber 17, the pressure therein will e approximately ambient pressure at which time the monitoring unit 41 will close an electrical switching deice 97 which operates the vent valve 39 to its second osition in which the ethylene oxide gas is diverted hrough it to a conduit 99 leading to the exhaust line 01. The vent valve 39 in this position closes the port :ading from the line 89 and chamber 17. The timing iechanism 61 continues until the end of its cycle and hen automatically shuts olf, at which time the dispensing 'alve 33 returns to its closed position and the solenoid for enting valve 39 is de-energized to return its valve to s first or straight through position in which the chamber 7 is connected to the heater and to the now closed ispensing valve 33.

By this time, the cartridge 25 has been emptied of its ntire liquid contents and the gas concentration within 1e chamber 17 is being maintained at that concentration est suited for microbicidal action. The articles are alwed to remain in the enclosed chamber 17 for a period sually ranging from about minutes to about three ours, depending on the type of sterilizing desired.

When the operator has decided that the articles have een exposed for a sufficient time to the ethylene oxide as, the operator will unscrew the cartridge housing 29 nd remove the cartridge 25 to expose the air inlet openlg 51 at the top of the housing. Then, by screwing the artridge housing 29 back on the base 45, the microswitch 5 is again operated to start a new cycle of the timing iechanism 63. The timing mechanism operates the motor 3 to evacuate the ethylene oxide gas from the chamber lrough the now open check valve 79. The pump 71 'ill now operate again for approximately four minutes remove the ethylene oxide gas from the bags and the rticles. The timing mechanism will then cause the disensing valve 33 to open so that ambient air may flow lrough the air inlet opening 51 and through the valve 3 to wash the same and into the chamber 17. When the ronitoring device 41 detects ambient pressure within the iamber 17, it will operate the vent valve 39 to a posion to let air flow from it for any remaining portion of re timing cycle. Usually, the operation will perform two 1ch washing cycles to assure removal of the ethylene xide from the various passageways and valves in the /stem. If the ethylene oxide is allowed to remain in the Istem, it will polymerize and eventually block passageays and cause the valves to stick in a given position. ince the pressure within the chamber 17 is at ambient ressure at the end of a wash cycle, the cover 15 may be pened and the articles removed.

From the foregoing it will be seen that the present in- :ntion provides an effective method and apparatus for ltomatically controlling the gas concentration within the erilizing chamber, limiting the pressure of the gas on re chamber cover and emptying the dispensing cartridge E liquid ethylene oxide.

While a preferred embodiment has been shown and :scribed, it will be understood that there is no intent I limit the invention by such disclosure but, rather it intended to cover all modifications and alternate conructions falling Within the spirit and scope of the invenon as defined in the appended claims.

What is claimed is:

1. In a gas sterilizing apparatus, a chamber having a redetermined capacity for receiving various volumes of tides to be sterilized, a cover for closing an article ac- :ss opening in said chamber, an aerosol cartridge having valve and having a sterilizing liquid and a propellant gas therein for dispensingsaid sterilizing liquid, means for holding said valvedaerosol cartridge in position to open said valve to dispense said liquid, said aerosol cartridge having a predetermined quantity of said liquid, means including a pump for evacuating said chamber to a reduced pressure below ambient pressure, means including a passageway from said aerosol cartridge to saidchamber in which said liquid will flash evaporate as it is exposed to said reduced pressure,'means to sense the pressure of said gas Within said chamber and to cause termination of flow of sterilizing gas into said chamber, control means operable by said sensing means sensing a predetermined gas pressure, and means operable by said control means for stopping the flow of gas to said chamber and for sweeping the remaining excess sterilizing gas to exhaust, the sweeping being done by the propellant gas, so that said chamber has a predetermined concentration of sterilizing gas therein irrespective of the volume of the chamber that is occupied by goods to be sterilized and so that said aerosol cartridge is exhausted during the sterilizing period.

2. The apparatus of claim 1 including a timer mechanism operable for a predetermined cycle, said timer mechanism operating said pump to cause operation of said pump for a predetermined portion of said cycle, a dispensing valve, said timer mechanism subsequently operating said dispensing valve for controlling a dispensing of said sterilizing liquid for a time sufficient to discharge all of said liquid sterilizing medium from said supply cartridge to said passageway and, said timer mechanism operating said dispensing valve to return it to its closed position after said surplus gas has had sufiicient time to exhaust through said valve.

3. The method of sterilizing articles with a gas such as ethylene oxide comprising the steps of: placing the articles into a sealed chamber having a predetermined volume, evacuating air from the chamber to create a partial vacuum within the chamber, connecting a supply cartridge having a valve and containing ethylene oxide with a propellant gas therein for vaporization and passage as a gas into the'chamber to provide a predetermined gas concentration for a substantiallly empty chamber, opening said valve to dispense said gas, introducing said gas through conduits into this sealed chamber, monitoring the concentration of gas within said chamber to achieve a predetermined concentration of sterilizing gas in said chamber irrespective of the volume of the chamber that is occupied by -goods to be sterilized, terminating the introduction of gas into said chamber when the concentration of gas in the chamber reaches said predetermined value, forcing said surplus gas being generated from said cartridge to exhaust by said propellant gas so that said supply cartridge is empty and may be immediately removed prior to sterilization of said articles, sterilizing said articles for a given period of time, and conveying air through said conduits and chamber to wash the residue of ethylene oxide therefrom.

References Cited UNITED STATES PATENTS 2,899,266 8/1959 Gewalt et al. 219l XR 3,054,270 9/1962 Huston 2158 XR 3,068,064 12/1962 McDonald 2157 XR 3,088,179 5/1963 Leuthner 21-9l 3,163,494 12/1964 Kaye 2158 MORRIS O. WOLK, Primary Examiner D. G. MILLMAN, Assistant Examiner US. Cl. X.R. 2 l-91

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