US2904110A - Timing device - Google Patents

Description

.Sept. 15, 1959 EN 2,904,110

TIMING DEVICE Filed July 14, 1954 v 3 Sheets-Sheet 1 Sept. 15,1959

Filed July 14, 1954 R. 'B. EGGEN TIMING DEVICE 3 Sheets-Sheet 2 IN VEN TOR.

' Fdykah JZ Zygerz Sept. 15, 1959 v R. B. EGGEN TIMING DEVICE Filed July 14, 1954 s Sheets-Sheet s Z/z E v United States Patent C 2,904,111) TIMING DEvicE Raymond B. Eggen, Detroit, Mich. Application July 14, 1954, Serial No. 443,315 16 Claims. 01. 1611) The present invention relates generally to timing devices and, more particularly, to timing devices capable of performing a series of control operations at definitely timed intervals.

Heretofore, various types of timing devices have been suggested and used. While some of these have been satisfactory in their use, they were complicated and expensive in their construction and maintenance. Accordingly, it is the primary object of this invention to provide an improved timing device which is simple and inexpensive in its construction and maintenance, and at the same time, one which is accurate and easy to operate.

It is another object of the invention to providean improved timing device which consists of a minimum number of parts, and one which can be conveniently used.

It is a further object of this invention to provide an improved timing device which can be easily and quickly reset after one desired time cycle of operation has elapsed for the next time cycle, and at .the same time, a timing device in which the setting is more accurate and positive than any other timer heretofore proposed. i

It is a still further object of this invention to provide a timing device especially adapted for on and off .operations, as for example, starting a movie camera after a first desired time interval and stopping it after a second desired time interval.

It is another object of this invention to provide a timing device capable of being used in numerous associations, as for example, with cameras, radios, .gas

stoves, and the like.

Other objects and advantages of the invention will become apparent from the following detailed description of the embodiments illustrated in the accompanyingdrawings, in which:

Figure 1 is a perspective view of a timing-device embodying the features of the invention and being mounted on a movie camera for use therewith;

Figure 2 is a rear elevational view of the timing device illustrated in Figure 1;

Figure 3 is a'horizontal view, partly in section, of the structure illustrated in Figure 2, taken along the line 3--3 thereof;

Figure 4 is an elevational view, partly in section, of the structure illustrated in Figure 2, taken alonglthe line 4-4 thereof;

Figure 5 is a rear elevational view, similar to theFigure 2, of the timing .device illustrated in Figure 1, but showing the control member in a position for the start of a timing cycle; 7

Figure 6 is a rear elevational view of asecond timing device embodying the features of the invention;

Figure 7 is a horizontal view, partly in-section, of the structure illustrated in Figure 6, taken along the'line 7-7 thereof;

Figure 8 is an elevational view, partlyjin section, of

the structure illustrated in Figure 6, taken. alongjthecline .8-8 thereof;

2,904,110 Patented Sept. 15, 1959 2 Figure 9 is a front elevational view of a third timing device embodying the features of the invention;

; Figure 10 is an elevational view, partly in section, of the structure illustrated in Figure 9, taken along the line ice : Ill-10 thereof;

cam means employed in the timing device illustrated in Figs. 9-11.

Referring more particularly to the drawings, in Figure 1 there is illustrated a first embodiment of the improved timing device, indicated by the numeral 10, which is shown mounted for operation on a conventional movie camera 12. The timing device 10 comprises a housing or body member having top and bottom Walls 14 and 16 respectively, side walls 18 and 20, and a front wall 22. There is no back wall shown but one may be provided if desired.

As is best seen in Figure 3, a conventional clock-work 7 mechanism 24 is provided between the front wall 22 and T an intermediate wall 25 and may be held therebetween by any suitable means. The clock-work mechanism 24 is adapted to drive the shaft 26 which fixedly carries on the front end thereof a control element or indicator 28 I and on the rear end thereof a drive gear 30. The drive gear 30 meshably engages a similar driven gear 32 which is fixed on the rear end of a rotatable shaft 34 which is journaled in the intermediate wall 25 and the front wall 22. The shaft 34 is adjustable axially and carries on the I front end thereof a second control element or indicator 36. Intermediate the indicator 36 and the front wall 2 2 is a spring biasing means 38 adapted to bias the shaft 34 forwardly into its normal position but which permits the shaft 34 to be adjusted axially to permit adjustment of driven gear 32 relative to drive gear 30. A spacer washer 41 is provided between the intermediate wall 25 and driven gear 32. A support member 40 is provided between the intermediate wall 25 and front wall 22 and surrounding shaft 34. The numeral 42 indicates the position of indicator 36 when the shaft 34 is axially adjusted to disengage driven gear 32 from drive gear 30,

"and the position of driven gear 32 in such case is indicated by the numeral 44. The indicators 28 and 36 may be suitably fixed on their respective shafts as by the set screw 37.

As is best seen in Figure 1, the front wall 22 is provided .onthe outer side thereof with indicia which could indicate seconds, minutes or hours, dependingon the type clock work mechanism used and the purpose for which the timing device is to be used. The indicia is used for setting theindicators 28 and 36.

Theupper portion of the side -wall 20 is provided with ,an aperture 46 therethrough in which is slidably mounted aca'rrier member 48 having an enlarged head portion 50.

, Thejcarrier member 48 is provided with an axial aperture 52 which is adapted to slidably carry the rear end of a control member 54. The upper portion of the side wall 18 is provided with an aperture 56 therethrough in which 5431s by the set screw 60. A biasing means 62 is carried 'by the control member 54 between the side wall 18 and the collar 58.

Another biasing means 64 is carried by j the control member 54 between the collar 58 and the carrier head portion 50.

As is best seen in Figures 2 and 3, a pin 66 having a head portion 68 is centrally located in the intermediate wall 25 and pivotally carries thereon a pair of releasable holding means 70 and 72 adapted to engage the collar 58 and head portion 50 respectively. The holding means 70 comprises a substantially horizontal portion 74 integral with a substantially vertical cam follower portion 76. The horizontal portion 74 is provided with a pin 78 against which is acting a leaf spring 80 having an anchor means 81. The leaf spring 80 acts to bias holding means 70 upwardly so that a catch 82 on means 70 will engage the collar 58 and hold it until the cam follower 76 is actuated to release collar 58 in a manner as explained more fully later on herein. A pin 84 is provided on the driven gear 32 and is adapted to engage a portion 86 on the cam follower portion 76 to pivot the holding means 70 about pin 66 and disengage catch 82 from collar 58.

The holding means 72 is similar in construction and operationto holding means 70- and comprises a substantially horizontal portion 88 integral with a substantially vertical cam follo we-r portion 90. The horizontal por tion 88 is provided with :a pin 92 against which is acting one end of a leaf spring 94 having the other end thereof anchored by means 81. The leaf spring 94 acts to bias the holding means 72 upwardly so that a catch 100 on means 72 will engage the carrier head portion 50 and hold it until the cam follower 90 actuated to release head portion 50 by means of pin 96 on gear 30 contacting portion 98 of follower 90. Suitable means may be provided to retain the holding means 70 and 72 on the pin 66, as for example, cotter pin 102.

At this point, the indicator 28 is released and the timing device starts to operate. The clock-work mechanism will drive the indicator 28 back to its starting position at zero and during the time interval it takes to do that, the camera 12 will be automatically started and stopped as follows. The pins 84 and 96 are positioned on the gears 30 and 32 so that 'when the gears are adjusted relative to each other the pin 84 will be advanced relative to the pin 96. Therefore, when the clock-work mechanism 24 is released for action, the gears 30 and 32 will rotate as shown by the arrows in Figure 5. The pin 84 on gear 32 will thus be brought against portion 86 on cam follower 76, whereby holding means 70 will be pivoted so as to release catch 82 from collar 58, thereby permitting spring 64 to push collar 58 and its associated control member 54 forwardly against the less powerful spring 62.

The control member front end 57 will pivot lever 114,

7 which will in turn depress camera actuating switch 116.

I lease catch 100 from the carrier head portion 50, thereby permitting spring 62 to push collar 58 and its asso- For purposes of illustration, the improved timing detrols of camera 12, an adapter means including plate;

110 may be suitably attached to the front end of the timing device, as by means of screws 112. The plate 110 carries means 113 on which is pivotally supported a lever 114 adapted to have one end thereof abut the forward end 57 of control member 54 and to have the other end thereof abut the actuating switch 116 of camera 12.

It will be understood, that when the timing device is applied to a camera, a clock-work mechanism 24 will be used which will be calibrated to operate in seconds or minutes, as desired.

If the operator of the camera desires to include himself in the picture to be taken by the camera, he first decides how much time he wants to have to get in front of the camera and get positioned, before the timing device starts the camera. Accordingly, in order to set the timing device for this pre-picture interval, the timing device indicator 36 is pushed inwardly to the position 42 to disengage driven gear 32 from drive gear 30. The indicator 36 is then turned counter-clockwise, as viewed in Figure 1, to the correct indicia marking, as for ex-' ample if the clock-work mechanism is operating in seconds. Then the indicator 36 is released to permit spring 38 to move the shaft 34 axially forward and reengage driven gear 32 with drive gear 30.

The next step is to set the camera running time by means of indicator 28. This is accomplished by turning indicator 28 clockwise, as viewed in Figure 1, to an indicia reading equal to the 15 seconds pro-picture time plus the desired running time. If a second running time is desired then indicator 28 is set at seconds.

Before the indicator 28 is released, the control member 54 is pushed inwardly until the front end 104 of collar 58 is caught and held by catch 82 on holding means '70. The carrier member 48 is also pushed inciated control member 54 backwardly and thus release the camera actuating switch 116 to complete the cycle. The indicator 28 will have been returned to its initial starting position and the timing device is ready for another cycle setting.

Figures 6, 7 and 8 show a second timing device embodying the principles of the invention. This second timing device comprises a housing or body member having side walls 120 and 122, front and back walls 124 and 126 respectively, and a top wall 127. A bottom wall may be provided if desired. The back wall may be suitably fastenedto the side walls as by screws 128.

As, is best seen in Figure 7, a conventional clock-work mechanism 130, similar to mechanism 24, is provided between the front wall 124 and the back wall 126 and may be held therebetween by any suitable means. The clock-work mechanism 130 is adapted to drive the shaft 132 which fixedly carries on the front end thereof a control element or indicator 134. On the rear end of shaft of the pin 149. This structure permits the driven gear wardly until the rear edge 106 of carrier 50 is caught j i 142 to be adjusted relative to the drive gear 136. As is best seen in Figure 6, the shaft 144 is permitted to move in a slot as 151 in the front and rear walls. The carrier 148 has a lower projection 150 engaged by a spring means 152 which is anchored to the side wall 120 as by means of screw 154. The spring 152 acts to bias the gear 142 into a meshable engagement with gear 136. A stop member 156 is provided to control the action of spring 152. i

A carrier member 160 is slidably mounted in an aperture 162 in side wall 122, and is provided with a head portion 164 "and an aperture 166 in which is slidably carried the rear end of a control member 167. The front end of control member 167 projects through the aperture 168 in the front Wall '120 as is shown at 170. A collar 172 is fixed on the control member 167 at an intermediate position and a spring biasing means 174 is carried on the control member 167 between the collar 172 and the front wall 120. A spring biasing means 176 is carried by the control means or member 167 between the collar 172 and the head portion 164.

A journal member 178 is mounted in the rear wall 126 bver the driven gear 142 and carries a rotatable pin 180. Fixedly mounted on the outer end of the pin 180 is a lever 182. The pin is held in the journal member 178 by the screw 184. The lever 182 is adapted to engage a pin 186 mounted on the driven gear 142. Operatively mounted on the inner end of the pin 180 is a cam 188 which is biased upwardly by a spring 190 and which has a catch thereon 192 adapted to engage and hold the collar 172. A second journal member 194 is provided above the drive gear 136 and carries a pin 196 which has a lever 198 suitably fixed on the outer end thereof. The pin 196 is held in the journal by a screw 200. The lever 198 is adapted to engage a pin 202 on the drive gear 136. Operatively mounted on the inner end of the pin 196 is a cam 204 which is biased upwardly by a spring 206 and which has a catch thereon 208 adapted to engage and hold the carrier head portion 164.

The operation of the second embodiment shown in Figures 6, 7 and 8 is similar to the first embodiment. The only difference being that the actuating pins 186 and 202 are located on the outer sides of the gears 142 and 136 respectively, rather than on the inside as shown by the first embodiment. This difference calls for different- 1y formed releasable holding means 188 and 204 but they operate the same as the holding means 70 and 72 in the first embodiment. A second difference comes in the way that the driven gear 142 is disengaged from the drive gear 136. In the second embodiment the driven gear 142 is pivoted around pin 149 to a position as shown by numeral 210 to permit adjustment of the gears. Other than the enumerated differences the first and second embodiments function similarly.

A third embodiment embodying the principles of the invention is shown in Figures 9 through 12. The main difference between this third embodiment and the first and second embodiments lies in the means for operating the releasable holding means.

The numeral 250 represents the front wall of the timing device housing, which is also provided with a top wall 252, bottom wall 254 and rear wall 256. The side walls are numbered 257. The timing device is provided with a carrier member 258, similar to that in the other embodiments, and having a head portion 260 and an axial aperture 262 in which is slidably carried the rear end of a control member 264. A collar 266 is fixedly carried on the control member 264 and secured thereto as by a set screw 268. A biasing means 270 is carried by the control member between the collar 266 and the front side wall 257. A biasing means 272 is carried by the control member 264 between the collar 266 and the head portion 260.

A pair of releasable holding means 274 and 276 are pivotably mounted on a pin 277 which is suitably carried by the front wall 250. The holding means 274 and 276 have attached thereto downwardly extending cam follower arms 278 and 280 respectively, and said means are biased upwardly by spring means 282 and 284 which are anchored by pin 277. The releasable means 274 is released by means of the cam 286 on cam disk 288 engaging the cam follower 280. The releasable means 276 is released by means of the cam 290 on cam disk 292 en gaging the cam follower 278.

The cam disk 292 is fixed on the shaft 294 of the clockwork mechanism 296 which is suitably fixed to the rear Wall 256. The cam disk 292 carries a stop member 298 adapted to abut a similar stop member 300 on the stationary clock-work mechanism 296. A ratchet wheel 302 having ratchet teeth 304 is fixedly carried on shaft 294. A spring washer 306 is disposed between ratchet wheel 302 and cam disk 288. Cam disk 288 carries a pawl 308 adapted to engage the teeth 304 on ratchet wheel 302.

The front wall 250 is provided with an aperture 310 in which is slidably mounted a shaft 312 to which the cam disk 288 is fixed and in which the shaft 294 is slid- 6 ably mounted. A spring means 314 is provided inter mediate cam disk 288 and the front wall 250 and is adapted to bias the cam disk 288 rearwardly. -An indicator 316 is fixed on the outer end of shaft 312 and cooperates with an indicia ring 318 on the outer face of the front wall. 250 to facilitate setting the timing device.

In operation, the embodiment of Figures 9 through 12 would be set for a pre-picture time by pulling out on in dicator 316 so as to disengage the pawl 308 from ratchet teeth 304. The indicator is then turned counter-clock wise and set according to the inner ring of indicia. When the desired time mark is reached the pawl 308 is again allowed to engage the ratchet teeth 304. The in dicator is then turned clockwise to the desired running time according to the marking on the outer ring of indicia. The indicator is then released and the control means will be operated in a manner similar to the first two embodiments. The big advantage olfered by the third embodiment over the other two timing devices is that the third type is more compact and can be made cheaply and easily.

Although only one control member has been shown in all the three embodiments, it will be obvious that more than one control member could be used, but of course additional pairs of gears and release means would also have to be employed. Such a plural arrangement may be useful if more than two operations are desired.

It will also be understood, that the present timing device is not limited to use on a camera, but that it may be used generally on many other timing operations.

While it will be apparent that the preferred embodiments of the invention herein disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. A timing device comprising, a timing mechanism, a first rotatable means operatively connected to said timing mechanism, a second rotatable means operatively connected to said first rotatable means, -a movably mounted carrier, a control means movably mounted on said carrier, 2. first releasable holding means engageable with said carrier, a second releasable holding means engageable with said control means, said holding means being operative to hold said control means and carrier in an operative position, whereby when said timing mechanism is actuated for a first predetermined interval, said second rotatable means will release said second releasable holding means to permit the control means to initiate a cycle of operation, said timing mechanism then continuing for a second predetermined interval after which said first rotatable means will release said first releasable holding means to permit the carrier to move the control means to terminate the cycle of operation.

2. The invention as set forth in claim 1 wherein, said first rotatable means is mounted co-axially with said sec- 0nd rotatable means.

3. The invention as set forth in claim 1 wherein, said first and second rotatable means are mounted on parallel disposed shafts.

4. The invention as set forth in claim 3 wherein, the shaft carrying the second rotatable means is axially movable to permit the rotatable means to be disengaged from each other and adjusted relative to each other to determine said predetermined intervals.

5. The invention as set forth in claim 3 wherein, the shaft carrying the second rotatable means is laterally movable relative to the shaft carrying the first rotatable means to permit the rotatable means to be disengaged from each other and adjusted relative to each other to determine said predetermined intervals.

6. A timing device comprising, a timing mechanism, a first rotatable means operatively connected to said timing mechanism, a second rotatable means operatively connected to said first rotatable means, a movably mounted carrier a control means movably mounted on said carrier, a biasing means operatively engaging said control means, a first releasable holding means engageable with said carrier, a second releasable holding means engageable with said control means, said holding means being operative to hold said control means and carrier in a cooked position against the action of said biasing means, whereby when said timing mechanism is actuated for a first predetermined interval said second rotatable means will release said second releasable holding means to permit said biasing means to move the control means to a position to initiate a cycle of operation, said timing mechanism then continuing for a second predetermined interval after which said first rotatable means will release said first releasable holding means to permit said biasing means to move the control means to a position to terminate the cycle of operation.

7. In a timing device, a control member, a carrier member, said control member being movably mounted on said carrier member, a first biasing means disposed intermediate said members, a second biasing means carried on said control member, a timing mechanism, a first means releasably engageable with said control member and being operable by said timing mechanism at a first predetermined interval to permit said first biasing means to bias said control member into an operative position to initate a cycle of operation, and a second means releasably engageable with said carrier member and being operable by said timing mechanism at a second predetermined interval to permit said second biasing means to move said carrier member and control member into an inoperative position to terminate the cycle of operation.

8. The invention as set forth in claim 7 wherein, said first and second means include a plurality of releasable holding means and cam means for operating said releasable holding means.

9. The invention as set forth in claim 7 wherein, said first and second means include a plurality of releasable holding means and gear means for operating said releasable holding means.

10. In a timing device, a control member, a carrier member, said control member being movably mounted on said carrier member, biasing means carried on said control member and operatively engaging said carrier member, a timing mechanism, a first means releasably engageable with said control member and being operable by said timing mechanism at a first predetermined interval to permit said biasing means to move said control member into an operative position to initiate a cycle of operation, and a second means releasably engageable with said carrier member and being operable by said timing mechanism at a second predetermined interval to permit said biasing means to move said carrier member and control member into an inoperative position to terminate the cycle of operation.

11. In a timing device, a control member, a carrier member, said control member being movably mounted on said carrier member, a first biasing means disposed intermediate said members, a second biasing means carried on said control member, a timing mechanism, a first rotatable means operatively connected to said timing mechanism, a second rotatable means operatively connected to said first rotatable means, a first releasable holding means engageable with and operable by said first rotatable means, a second releasable holding means engageable with and operable by said second rotatable means, said holding means being operative to hold said control member in a cocked position against the action of said biasing means, whereby when said timing mechanism is actuated for a first predetermined interval said second rotatable means will release said second releasable holding means to permit said first biasing means to move the control member to a position to initiate a cycle of operation, said timing mechanism then continuing for a second predetermined interval after which said first rotatable means will release said first releasable holding means to permit said second biasing means to move the control member to a position to terminate the cycle of operation.

12. In a timing device, a timing element adapted to be rotated manually in one direction from a starting position to determine a time interval for an operation, clockwork means connected to said timing element for rotating said element in the opposite direction to return it to the starting position, drive means connected to said clockwork means, a driven means operatively connected to said drive means and being adjustable relative to the drive means, an actuator movably mounted on the device for starting a cycle of operation, a first releasable holding means engageable with said actuator, a second releasable holding means engageable with said actuator, said holding means being operative to hold said actuator in an operative position, said driven means being engageable with and adapted to operate said second releasable holding means, said drive means being engageable with and adapted to operate said first releasable holding means, whereby when said clock-work means drives said timing element towards the starting position, at a predetermined portion of the time interval set by the timing element, said driven means will operate said second releasable holding means to permit the actuator to initiate a cycle of operation, and when the timing element reaches the starting position said drive means will operate said first releasable holding means to permit the actuator to terminate the cycle of operation.

13. The invention as set forth in claims 12, wherein, said drive means includes a cam means and a ratchetwheel, and said driven means includes a cam means and a dog adapted to operatively engage said ratchet-wheel.

14. The invention as set forth in claim 12, wherein, said drive means includes gear means, and said driven means includes gear means meshable with the gear means of the drive means.

15. In a timing device, a timing element adapted to be rotated manually in one direction from a starting position to determine a time interval for an operation, clockwork means connected to said timing element for rotating said element in the opposite direction to return it to the starting position, drive means operatively connected to said clock-work means, a driven means operatively connected to said drive means and being adjustable relative to the drive means, a control member, a carrier member, said control member being movably mounted on said carrier member, a first biasing means disposed intermediate said members, a second biasing means carried on said control member and being of a strength less than said first biasing means, a first releasable holding means engageable with said carrier member, a second releasable holding means engageable with said control member, said holding means being operative to hold said control member in a cocked position against the action of said biasing means, said driven means being engageable with and adapted to operate said second releasable holding means, said drive means being engageable with and adapted to operate said first releasable holding means, whereby when said clock-work means drives said timing element towards the starting position, at a predetermined portion of the time interval set by the timing element, said driven means will operate said second releasable holding means to permit said first biasing means to move the control member against the biasing action of said second biasing means to a position to initiate a cycle of operation, and when the timing element reaches the starting position said drive means will operate said first releasable holding means to permit said second biasing means to move the control member and carrier to a position to terminate the cycle of operation.

16. A timing device, comprising: a housing having a front wall and a pair of side walls; a control member disposed in said housing and having the outer end thereof slidably mounted through a first one of said pair of side walls and having said outer end extended outwardly of said housing; a carrier member having an axial bore and being slidably mounted through the second side wall and having an inner end provided with an enlarged head disposed inside of the housing; the inner end of said control member being slidably mounted in the bore of said carrier member, from the inner end of the carrier member; a collar fixedly mounted on said control member between the first side wall and the head on the carrier member; a first coil spring mounted on said control member and having one end abutting said first side wall and the other end abutting one side of said collar on the control member; a second coil spring of a greater strength than said first coil spring mounted on said control member and having one end abutting the other side of said collar and the other end abutting the head on said carrier member; said springs normally tending to bias the control and carrier members to an inoperative position with the head on the control member against the second side wall; a first releasable holding means adapted to engage said head on the carrier member and hold it in an operative cocked position in said housing when the carrier member is manually moved inwardly of said housing against the biasing pressure of said springs; a second releasable holding means adapted to engage said collar on said control member and to hold it and the control member from being moved toward said first wall by said second spring when said carrier member is manually moved inwardly to the operative cocked position; a first rotatable means mounted in said housing; a first release means carried on said first rotatable means for engaging said first releasable holding means when said first rotatable means is rotated for releasing said collar, whereby, said second spring will bias the collar and the control member outwardly of said first wall to an operative position; a second rotatable means mounted in said housing; a second release means carried on said second rotatable means for engaging said second releasable holding means when said second rotatable means is rotated for releasing said head, whereby, said second spring will bias the carrier member toward the second side wall to the inoperative position and said first spring will bias said control member inwardly of said first side wall to an inoperative position; a clock-Work means mounted in said housing and being drivably connected to said second rotatable means; means for drivably and selectively connecting said second rotatable means to said first rotatable means, whereby, the first release means on said first rotatable means will release said first releasable holding means a predetermined time interval before the second release means on said second rotatable means releases the second releasable holding means; and, means for setting said clock-work means for a predetermined time interval.

References Cited in the file of this patent UNITED STATES PATENTS 478,180 Waters July 5, 1892 628,042 Schulze July 4, 1899 753,330 Thielenhaus et al Mar. 1, 1904 761,699 Ney et al June 7, 1904 1,026,586 Howlin May 14, 1912 2,056,400 Holtz Oct. 6, 1936 2,152,947 Blomerius Apr. 4, 1939 2,182,894 Hammell Dec. 12, 1939 2,396,809 Addison Mar. 19, 1946 2,551,445 Lindsay et al May 1, 1951 2,688,366 Morrison Sept. 7, 1954

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