US2880284A - Switch assembly - Google Patents

Description

March 31, 1959 E. J. LAETE SWITCH ASSEMBLY Filed Nov. 5, 1956 2 Sheets-Sheet l INVENTO J 44 m ,9 9, Z J y .1.JMW. WW I March 1959 E. J. LAETE 2,880,284

SWITCH ASSEMBLY Filed NOV. 5, 1956 R \E- im A 3 2 Sheets-Sheet 2 ig i 6 1 Fra s.

INVENTOR.

United States Patent SWITCH ASSEMBLY Edward J. Laete, Sturgis, Mich., assignor to Wade Electric Products Co., Sturgis, Mich., a corporation of Michigan I 7 Application November 5, 1956, Serial No. 620,300

13 Claims. (Cl. 200-16) This invention relates to electrical switches and more particularly to electrical switches of the reciprocating type capable of controlling a plurality of electrical circuits.

It is an important object of the present invention to provide an electrical switch embodying improved means for effecting a quick opening and closing action for controlling electrical circuits.

It is another object of the present invention to provide an electrical switch including contact means and movable bridging means having improved means for operatively urging the bridging means to slide and tilt in its movement with respect to the contact means to quickly open and close electrical circuits.

It is another object of the present invention to provide an electrical switch embodying improved means for retaining the actuated means in its several selectively settable positions.

It is another object of the present invention to provide improved means for resiliently associating the bridging means to the actuated means.

It is still another object of the present invention to provide an improved electrical switch having relatively few parts which may be economically manufactured and assembled on a mass production basis.

The above and other objects of the present invention will be apparent during the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Figure 1 is a side elevation, partly in section, of the switch embodying the present invention;

Fig. 2 is an elevational view from the left of the structure shown in Fig. 1;

Fig. 3 is a sectional view along the line 3-3 of Fig. I viewed in the direction indicated;

Fig. 4 is a sectional view along the line 44 of Fig. I viewed in the direction indicated;

Fig. 5 is an exploded view of the several parts of the switch embodying the present invention; and

Figs. 6, 7, 8 and 9 are diagrammatic views in plan and elevation showing the operation of the switch embodying the present invention.

The switch includes generally a housing 11, an insulated mounting 13 carrying contact means, actuated means generally designated 15 carrying bridging means for cooperation with the contact means, and operating means in the form of a lever 17 for moving the actuated means.

Referring to the figures in more detail, the housing 11 has a bottom wall section 19 and side wall sections 21, 23. The bottom wall section 19 has a central depression 18 forming ledges 20, 22. The actuated means supported away from the bottom wall 19 slides on the ledges 20, 22 in its travel in the housing 11. The bottom wall section 19 has a pair of mounting holes 25, 27. Likewise, the side wall section 21 has a pair of mounting holes 29, 31 which may be used for mounting the switch in a numice her of different positions. The switch is suited for mounting on the dashboard or other supporting structure of an automotive vehicle and is particularly adapted for controlling the front and rear speakers of a dual speaker audio system incorporated in the radio of such vehicle. The housing has four tangs 33, 35, 37, 39 which cooperate with notches 41, 43, 45, 47 formed in the in-' sulator mounting 13. The tangs are bent over the back of the insulator mounting as shown in Fig. 2 for rigidly securing the insulator mounting 13 to the housing 11. The side wall 21 of the housing has a centrally located slot 49 through which the lever 17 protrudes, the slot defining the length of travel of the lever within the housing. The insulator mounting 13 carries stationary contact means in the form of three terminal contacts 51, 53, 55 extending through the insulator mounting. One extremity of each of the terminal contacts is staked over, as at 57, for cooperating with the enlarged flange portions, as at 52, for anchoring the terminal contacts to the insulator mounting. Contact bosses 54, 56, 58 protrude from the surface of the insulator mounting. Near the other extremity of the terminal contacts are annular grooves, as at 59, for cooperating with a conductor receptacle to bring current into and away from the terminals.

The actuated means 15 includes a slide block 61 preferably formed of molded insulating material for carrying bridging means 63 in the form of an I-shaped plate, and resilient means 65 in the form of a compression spring.

The base of the slide block includes extended feet, as at 62, for stability which feet are arcuately shaped so that they will be spaced from the mounting holes 25, 27 in the extreme positions of the slide block in the switch housing. The slide block 61 has a pair of open-ended rectangular shaped apertures 67, 69 (permitting molding by a simple mold having axially extending core pins) formed with shoulder portions 71, 73 which cooperate with depending legs 75, 77 on the bridging means 63 in a manner to be hereinafter described. The slide block 61 also has a well 79 for receiving the resilient means 65. The bridging means 63 is stamped from sheet metal and has a flat surface portion 80 and legs 75, 77, outwardly bent from the fiat surface portion 80 to form the fiat surface portion into an I shape. The fiat surface portion 80 serves to bridge two or more of the contact bosses to conduct current between those making contact with the same. The legs 75, 77 have inwardly turned books 74, 76 formed at the extremities. The flat surface portion 80 has depressions 81, 83, 85 formed therein and disposed at the apices of a triangle. The depressions 81, 83, 85 cooperate with the contact bosses 54, 56, 58, which are likewise triangularly disposed in the insulator mounting 13. In assembling the actuating means 15, the resilient means 65 is placed in the well 79 of the slide block 61 and the legs 77, of the bridging means 63 are inserted into the apertures 67, 69 of the slide block at an angle to place the inwardly turned hooks 74, 76 on the legs of the bridging means beyond the shoulder portions 71, 73 on the apertures 67, 69 so thatthey cooperate to retain the bridging means on the slide block 61, this feature forming a part of the invention described and claimed in a copending application Serial No. 610,582, filed September 18, 1956, of Jasper Long assigned to the assignee hereof. The remainder of the assembly is completed by placing the insulator mounting 13 over the actuated means with the contact bosses 54, 56, 58 engaging the surface portion of the bridging means so as to align with the depressions 81, 83 and 85. The

tangs 33, 35, 37, 39 on the housing are then bent over to secure the insulator mounting to the housing. The slide block 61, the resilient means 65, and the bridging means 63 are retained as a unit and slide within the agssonss housing 11 as such. The resilient means 65 urges the bridging means 63 against the contact bosses 54, 56, 58 mounted on the insulator housing and urges the slide block 61 against the bottom wall section 19 of the housing 11. The resilient means 65 is freely guided in the well 7-9 and produces a yieldable'force-at nearly point contact on the hat surface portion 80 of the bridging means and is not afiixed either to the slide block 61* or to the bridging means 63. It is retained between the bridging means and the slide block in the free position by theicoaction of the hooks 74, 76 against the shoulders 71,73 of the apertures in the slide block 61 to facilitate assembly. In its operative position within the switch housing, it'is-retained under compressionwithin the well 79 of the slide block through the coaction of the latter against the switch housing and the-bridging means against the contact bosses on theinsulator housing. The bridgi'ng means 63 is floatably carried by themanner of its retention within the slide block 61 and is free to tilt about substantially any line lying in the plane of its surface portion 80. Fig. 2,. in dotted lines, shows an intermediate position as at 63 and one extreme position asat 63 of the bridging means within the switch housing The slide block 61 is manually actuated by the lever 17 which is molded integral with the slide block 61. It will be apparent that other operating means may be employed for moving the actuated means other than a lever integral with the slide block. The operating means shown is the preferred one, but, for example, a toggle type'lever could be used to move the actuated means.

Figs. 6, 7, 8 and 9 diagrammatically show the operation of the switch and in each of the figures there is shown a plan and elevational view of the bridging means 63 the contact bosses 54, 56, 58, and the resilient means 65. Fig-6 shows the intermediate position of the bridging. means wherein the depressions S1, S3, 85" mate with the contact bosses 54, 56, 58. The resilient means 65 is disposed substantially centrally of the triangle 87 defined by the location of the contact bosses 54, 56, 58. The imaginary triangle 87 has one leg 89 joining the contact bosses 56, 58 and another leg 91 joining the contact bosses 54, 56. Each of the legs 89, 91 is disposed at an angle to the direction of movement of the bridging means. In the operation of the switch, the-contact bosses remain stationary and the actuated means, including the resilient means 65 and the bridging means 63,-move relative to the contact bosses. In the position shown in Fig. 6 the coaction of the contact bosses and the depressions in the bridging means serves to yieldably retainthe bridging means in the intermediate position When the bridging means is moved to either extreme position with respect to the'contact bosses, the bridging means is'immediately depressed as the contact bosses ride upv the sides of the depressions and immediately the bridging. means snaps ba'ck into a raised position, such as shown in'Fig. 7, all the time'maintainingcontact with the three contact bosses. Fig. 7 shows the relation of the bridgingmeans to the contact bosses whenthe bridging means has been moved slightly to the right toward one of its extreme positions just after the bridging means has been depressed by the action of the contact bosses moving. out-of-the depressions on the bridgingmeans; The center'ofthe resilient means 65 is still within the triangle 87 and the contact bosses have been continually engaging thebridging means so that no tilting action occurs. Fig.- 8 shows the relative positions of the contact bosses and the bridging means when the bridging means have been nieved to a position still' further to the right. The: resilient means 65 has now passed beyond the leg. 89 of the triangle 87 joining contact bosses 56,. 58. Substantially'immediately as'the' resilient meanspas'ses} beyondthe leg 89 of the triangle 87 there iscreatedunbalanced tor'ces'a'nd the bridging means is tilted about an axis de= firi'e'd by the leg 89' of the'ti'iangle. The bridging means qtiickly disengages from contact boss 54. The contact bosses 56, 58 have never lost contact with the bridging means during this tilting action. The elevational view in Fig. 8 showing the bridging means in the tilted position is exaggerated to show that the front surfaces of the bridging means, as at 97, are lower than the back surfaces, as at 95. Contact boss 56 of course, contacts the rear surface of the bridging means, while contact boss 58 contacts the front surface ofthe bridging means, as clearly shown in Fig. 8. Fig. 9 shows the bridging means after having been moved to one of theextreme positions.- The bridging means is further tilted from the position shown in Fig. 8 due to the greater leverage action of theyieldable force of the resilient-means tilting the bridging means about an axis joining the contact bosses. This tilting of the bridging" means as it moves to its extreme positions serves the additional useful function of aiding in yieldably retaining the actuated means in its extreme positions; Only slight force is required to move the actuated; means back to the intermediate position and in so doing the reverse action takes place; that is, theresilient means moves toward the leg 89 of the triangle 87 as the actuated-'means' is moved to theleft. The tilt of the bridging means is gradually decreased as it passes through the position shown in Fig. 8 until the point is reached where the center of the resilient means passes under the leg 89 of the triangle 87. At this point, the bridging means quickly assumes the position shown in Fig. 7 due to the unbalanced force exerted on the bridging means by the resilient means to engage the contact boss 54. Further movement of the actuated means to the left causes the bridging. means to snap into the intermediate position shown in Fig. 6. The cooperation of the contact bosses with thedepressions in the bridging means yieldably retains the bridging means in the intermediate position and further movement of the actuated means to the left causes a similar action to that shown in Figs. 69, except that the tiltingof thebridging means occurs in a clockwise direction. That is, the bridging means 63 would be tilted about an axis defined by the leg 91 of the triangle 87 substan tially immediately as the resilient means passes beyondthe leg 91 to effect a quick break of the bridging means-63 from the contact boss 58 in this instance and contactbosses 54 and 56 would continue in their engagement with the bridging means.

It will be evident that the switch can control a plurality of circuits, an example being dual speakers inthe audio circuit of an automobile radio. In operating! the front and rear speakers on an automotive vehicle, theswitch would be mounted on the dashboard, for example, and the central terminal 53 would be connected by a conductor to one sideof the battery. The other two terminals 51, 55 would be connected by suitable conductors to one side of the front and rear speakers. The other sides of the front and rearspeakerswould both be electrically connected to the other side of the battery,.i.e., the side which is not connected to the central terminal 53.- The switch of course would be employed in conjunction with the on-otf switch of the radio and with the latter switch on and with the actuated means 15 of the switchof the present invention in the intermediate position both speakers would be operating simultaneously. Manual actuation of the lever 17 to one extreme position of the switch would quickly disengage the rear speaker, for example, while the front speaker continued to operate. Actuation of the lever 17 to the other extreme position would first quickly engage the rear speaker at the intermediate position of the switch before disengaging the front speaker. Continued actuation of the lever 17 to the otherextreme position would-quickly disengage the front speaker while the rear speaker continued to operate. Inadditionto controlling dual speakers in the audio sec'tio'nofa radio, the switch may be employed to control a variety" of'difierent electrical circuits, as it will be observed that the eentact boss 54 on the central orinter;

mediate terminal 53 is electrically bridged with the bosses 54, 58 on the end terminals 51, 55 in the intermediate position of the actuated means and is electrically disconnected with one and then the other in the extreme positions. Likewise, the contact bosses 54, 58 on end terminals 51, 55 are electrically bridged in the intermediate position and are electrically disconnected from each other in the extreme positions of the actuated means. It will be apparent that one of the terminals need not be connected to a conductor at all but may be a dummy terminal, in which case it would be used purely for its mechanical function of cooperating with the other contact means to act in concert with the bridging means to elfect an efficient tilting action to quickly open and close the circuits and to aid in retaining the actuated means in its extreme positions.

The particular manner in which the slide block 61 carries the bridging means 63 is such that the bridging means is free to tilt about substantially any line in the contacting surface of the bridging means. This is accomplished by providing a nearly point contact resilient support for the bridging means and by forming the rectangular apertures 67, 69 in the slide block so that they are oversize with respect to the size of the leg portions 75, 77 on the bridging means. The walls of the apertures 67, 69 loosely guide the legs 75, 77 in their movement within these apertures. This is the preferred construction of the actuated means. The hooks 74, 76 formed on the ends of the leg portions 75, 77 aid in the assembly of the switch by cooperating with the shoulder portions 71, 73 on the aper: tures 67, 69 to retain the bridging means 63 on the slide block 61 as a unitary subassembly. It will be apparent that the rectangular apertures 67, 69 could be formed so that the length of the rectangular cross section of the apertures would closely approach the width of the leg portions of the bridging means. Two of the walls of each of the apertures 67, 69 would then act as restraining guides on the leg portions 75, 77 of the bridging means and prevent the bridging means from tilting about a longitudinal axis and allow it to tilt only about a transverse axis. The preferred construction above described wherein the bridging means is free to tilt about substantially any axis lying in the plane of its operating surface contributes to the exceptionally quick make and break action of the bridging means with respect to one and the other of the end contact bosses. The manner of thus mounting the bridging means on the slide block so that it is able to freely tilt about the resilient means increases the speed of the make and break action between the bridging means and the contact means by reason of the shorter distance that the resilient means has to pass beyond the legs of the imaginary triangle above referred to before the unbalanced force created by the resilient means causes the bridging means to tilt about two of the contact means. The end portion of the bridging means then dips away from the end contact means disposed at the apex of the triangle with respect to the axis of tilting, and the speed of the make and break action is enhanced by virtue of the increased distance of the end portion of the bridging means from the axis of tilting, the linear velocity of the end portion being proportional to this distance and the angular velocity of the bridging means about the axis of tilting. While it has been shown that the preferred disposition of the contact bosses are at the apices of a triangle, it will be apparent that the contact bosses could be arranged in other ways and likewise more than three contact bosses could be employed. It will be equally apparent that While the bridging means prefer- 'ably is formed with depressions to create a snap action between the contact means and the bridging means during the movement of the actuated means through the intermediate position and for aiding in retaining the actuated means in the intermediate position, the bridging means may be formed with a smooth surface. However, an especially quick and efiicient snap action is effected if the diameter of the depressions on the bridging means is appreciably less than the radius of curvature of the contact bosses so that substantially line contact only is provided between the contact bosses and the bridging means in the intermediate position of the actuated means whereby the snap action is emphasized.

While the preferred embodiment of the invention has been shown and described, it is to be understood that various modifications, changes in size, shape and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is:

1. In an electric switch, spaced apart contact means including an intermediate contact means, and end contact means, yieldably mounted bridging means having an intermediate position engaging said intermediate contact means and each of said end contact means, operating means including resilient means cooperative with said contact means to slide said bridging means in one direction from said intermediate position to tilt said bridging means about said intermediate contact means and one of said end contact means to quickly disengage said bridging means from the other of said end contact means and to slide said bridging means in the opposite direction from said intermediate position to tilt said bridging means about said intermediate contact means and said other contact means to quickly disengage from said one contact means.

2. In an electric switch, a mounting member and spaced apart contact means affixed to said mounting member and projecting above the surface thereof, bridging means with depressions to receive and engage the contract means, reciprocating means for moving said bridging means with respect to the contact means, and resilient means yieldably pressing the bridging means against the contract means and cooperating with the contact means to tilt said bridging means about an axis joining two of the sadi contact means as the said bridging means is reciprocated.

3. In an electric switch, actuated means including resilient means and bridging means yieldably mounted on said resilient means with respect to said actuated means, said bridging means slidably engaging said contact means upon movement of said actuated means, and operating means for moving said actuated means to an extreme position, said resilient means and said contact means functioning to tilt said bridging means about an axis joining two of said contact means to yieldably retain said actuated means in said extreme position.

4. In an electric switch, a housing, actuated means slidably carried by said housing, bridging means carried by said actuated means, resilient means for yieldably mounting said bridging means on said actuated means, spaced apart stationary contact means, said bridging means having an intermediate position and an extreme position, and operating means to move said bridging means from said intermediate position to said extreme position to cause said bridging means to slidably engage said contact means, said resilient means cooperating with said contact means to tilt said bridging means at a predetermined distance in the movement of said bridging means toward said extreme position, the arrangement of said contact means and said resilient means being such that the tilting of said bridging means occurs about two of the contact means disposed so as to define an axis of tilting which makes an angle with the direction of movement of said bridging means.

5. In an electric switch, a housing, actuated means slidably carried by said housing, bridging means carried by said actuated means, resilient means making nearly point contact with said bridging means for yieldably mounting the same on said actuated means, a mounting member secured to said housing, spaced apart contact means extending through said mounting, said bridging meanscontinually engaging one of i said contact means, and" meansfor' moving said brid ging' means to an ex treme'position,.saidresilient nie'a'ns cooperating with" said contactm'eans to tilt"saidbridgingmeans about said one contact means a'nd'anothero'f said contact means after a predetermined distance i'ri'tlie movement of said bridgingimea'ns' toward said ex'tr'em'e" position, said one contact" rne'aris'and said other contact means being disposed to de'fine an" axis of"tilti'ngwhichis at an angle to the direction ofmovementofsaid'bridging means.

6". Iii an electric" switch, a housing, actuated means slidably carried by said housing, bridging means yieldably mounted on said actuated means, operating means for moving said actuated means to cause said bridging means to move in one direction and in the opposite direction, and spaced apart contact means for slidably engaging said bridging means including two contact means disposed along a line at an angle with respect to said one direction of movement of said bridging means and two contact means disposed along a line at an angle with respect to said opposite direction of movement of said bridging means, the yieldable action of said bridging means functioning to tilt the same about said first mentioned two contact means when said actuated means is moved in said one direction and to tilt said bridging means about said second mentioned contact means when said actuated means is moved in said opposite direction.

7. In an electric switch, spaced apart contact means, bridging means for slidably engaging said contact means, resilient means for yieldably mounting said bridging means, and means for moving said bridging means in one direction to an extreme position, said Contact means including two contact means disposed along a line at' an angle to the direction of movement of said bridging means, said resilient means cooperating with said contact means to cause said bridging means to tilt about said two contact means at a predetermined distance in the movement of said bridging means toward said ex treme position.

8. In an electric switch, spaced apart contact means, bridging means for slidably engaging said contact means, resilient means for yieldably mounting said bridging means at nearly point Contact, and means for moving said resilie'ntm'eans and said bridgingimeans in one direction to an extreme position, said contact means including two contacts disposed along a line at an angle to the direction of movement of said bridging means, said resilient means functioning to tilt said bridging means about said two contact means substantially immediately as said point contact passes by a straight line joining said two contact means in the movement of said bridging means toward said extreme position.

9. In an electric switch, a housing having a back' wall and spaced side walls integral with said back wall, an insulator mounting secured to said side wall so as to be disposed in faced opposed relation to said back wall having contact bosses protruding from the surface of one face thereof, said contact bosses being arranged at the apices of a triangle, a slide block slidably carriedby said housing having a lever adapted to be actuated for moving said slide block from an intermediate position to extreme positions in opposite directions, mounting apertures in said back wall adjacent the ends of said housing, said slide block having a base slidably supported by said back wall including a raised central body portion with a top surface raised from said base and a foot member integral with and extending from each end of said base, a well centrally formed in said body portion and a pair of openendecl rectangular apertures each of which is spaced from i and disposed on one side of saidwell, each of said apertures being formed by coaxial rectangular openings of different sizes, the largest of said openings extending inwardly into said body portion from said base, the smaller of saidopenings extending inwardly into said body portion fromthe' top surface thereof, whereby'shonlder portions' are formed ineach of said apertures at'the junction ofeacli ofsaidop'enings, bridging means including a' fiat surface'I plate anda pair'of inturned legs each of which is integral" with one side of the web of s'aid'l pla'te, said pair of legs terminating in hooks'to cooperate with'the shoulderportions in said'pair of apertures so'as'to retain said bridging'means affixed to said slide blo'ck, the width of each of said legs being lessthan'the width of each of said apertures, a compression spring disposed in said well so as to yieldably urge said l-plate' against said contact bosses and to yieldably urge the'base'ofsaid slide block against said back wall, the yieldable action of 'said' compression spring against said I-plate functioning upon actuation of said lever to tilt said I-plate' at a predetermined distance in the movement of said slide block in one'of'saidopposite directions about a first and second of said contact bosses to quickly disengage said I-plate from a' third of said contact bosses andto tilt said l-plate at a; predetermined distance in the movement of said slide block in the other of said opposite directions'about said first and third contact bosses to quickly disengage said l-plate from said second contact boss.

10. In an electric switch, a housing having aback wall and spaced side walls integral with said back wall, a centrally located slot in said side wall, said back wall having a longitudinally extending central depression formed therein and a pair of parallel ledges on' one face thereof spaced from said central depression, an insulator mounting secured to said side walls so as to be disposed parallel to said back wall and having one face in face opposedrelati'on with said one face of said back wall,,three terminal contacts secured to and extending through said I mounting and disposed at the apices of a triangle, each of said terminal contacts having a contact boss protrudingfrom the surface of said one face of said insulator mounting, a slide block slidably carried by said housing having a base including extended feet slidably supportedby said pair of parallel ledges so as to be spaced from said central depression, said slide block having a weil centrally formedtherein and a pair of open-ended rectangular apertures spaced from said Welland formed with shoulder portions, bridging means having a flat surface portion and a pair of legs outwardly'bent from said fiat surface portion each of which is loosely disposed in one of said rectangular apertures and terminates in a hook to cooperate with the shoulder portion in said one aperture to retain said bridging means on said. slide block, three depressions formed in one face of said flat surface portion and disposed at the apices of a triangle so as to mate with said contact bosses, a compression spring disposed in said well so as to yieldably urge said one face of said fiat surface portion against said contact bosses and to yieldably urge the base of said slide block against said one face of said back wall, a lever integral with said slide block adapted to protrude through said slot in said one side wall for moving said slide block from an inter mediate position in opposite directions, the yieldable action of said compression spring against saidflat surface portion functioning upon actuation of said lever at a predetermined distance in the movement of said slide block in each of said opposite directions to snap said fiat surface portion out of said intermediate position to a raised level position While maintaining said fiat surface portion in mechanical and electrical contact with each of said contact means, and thereafter to tilt said flat surface portion at a further predetermined distance in the movement of said slide block in one of said opposite directions about a first and second of said contact bosses to quickly dis engage said flat surface portion from a third of said contact bosses and to tilt said flat surface portion at a further predetermined distancein the movement of said slide block in the other of said opposite directions about said first and third contact bosses to quickly disengage said flat surface portion from said second contact boss.

11. In an electric switch, a housing having a floor with a pair of contacts therein, a conductive bridge having a portion parallel to said floor and slidable thereon, said bridge being rockable about an axis substantially parallel to the floor, a spring pressing said bridge portion against said floor, said spring being located so that the force applied by it to said bridge goes across the line of centers between said contacts when said bridge is moved between positions in which it interconnects and does not interconnect said contacts, and means rockably supporting said bridge so that it tilts about said axis when said spring force crosses said line of centers.

12. The invention set forth in claim 11 wherein said contacts project above said floor and said bridge portion 10 has depressions therein facing said floor and spaced to receive and engage said contacts.

13. The invention set forth in claim 12 wherein said depressions are smaller than said contacts.

References Cited in the file of this patent UNITED STATES PATENTS 2,132,218 Oflicer et a1. Oct. 4, 1938 2,203,309 Schmid June 4, 1940 2,226,850 Foster Dec. 31, 1940 2,267,427 Schmid Dec. 23, 1941 2,666,101 Ellithorpe Ian. 12, 1954 2,683,193 Barcus July 6, 1954

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