US2722184A - Power control units for sewing machines - Google Patents

Description

Nov. 1, 1955 R. D. SWEET 2,722,184

POWER CONTROL UNITS FOR SEWING MACHINES Filed May 5, 1954 I 5 Sheets-Sheet l INVENTOR. Ray 0. Sweet WITNESS BY ATTORNEY Nov. 1, 1955 R. D. SWEET POWER CONTROL UNITS FOR SEWING MACHINES- 5 Sheets-Sheet 2 Filed May 5, 1954 INVENTOR. Ray D. Sweet BY 4 4% C21.

ATTORNEY WITNESS Nov. 1, 1955 R.. D. SWEET 2,722,184

POWER CONTROL UNITS FOR SEWING MACHINES Filed May 5, 1954 5 Sheets-Sheet 3 Fig. 5.

Air Supply INVENTOR. F lg. 4. Ray 0. Sweet WITNESS BY AITORNE'Y United States Patent ()1 POWER CONTROL UNITS FOR SEWING MACHINES Ray D. Sweet, Bridgeport, Conn., assignor to The Singer Manufacturing Company, Elizabeth, N. J., a corporation of New Jersey Application May 5, 1954, Serial No. 427,796

7 Claims. (Cl. 11267) This invention relates to sewing machines and, more particularly, to power operated means for controlling the actuation of a sewing machine as well as for controlling the operation of mechanism which is associated with a sewing machine and which is incident to the operation thereof.

It is an object of this invention to provide means under control of the sewing machine operator for utilizing a source of power to control the operation of the sewing machine and to control the operation of mechanism appurtenant to the sewing machine.

It is also an object to provide a power operated control means whereby manipulation of a single control member by the machine operator will serve to control both the sewing machine actuation and the operation of mechanism ancillary to the sewing machine.

It is an object to provide power control means of the above character in which a proper sequence of operation of a group stitch sewing machine and of the ancillary mechanism is predetermined.

A further object of this invention is to provide a fluid pressure operated power control unit in the nature of an attachment to the sewing machine.

It is also an object of this invention to provide electrically operated controls for a sewing machine power control unit of the above character.

With the above and other objects and advantages in view as will hereinafter appear, this invention comprises the devices, combinations and arrangements of parts hereinafter described and illustrated in the accompanying drawings of a preferred embodiment in which:

Fig. 1 is a right side elevational view, partly in section, of a group-stitch sewing machine which is adapted to have the power control unit of my invention applied thereto. The side cover plate has been removed and a portion of the base has been broken away better to expose the mechanism of the sewing machine.

Fig. 2 is a front elevational view of the power control unit of my invention shown as applied to the sewing machine of Fig. 1, of which a portion is shown in vertical cross section taken substantially along line 22 of Fig. 1.

Fig. 3 represents an enlarged bottom plan view of the power control unit.

Fig. 4 represents a diagrammatic view of the fluid pressure circuit of the power control unit of my invention.

Fig. 5 represents a diagrammatic view of the electrical circuit for the power control unit of Figs. 1, 2 and 3.

Fig. 6 represents a diagrammatic view of a modified form of an electrical circuit for my power control unit.

My power control unit is preferably adapted for use with a group-stitch sewing machine such as is illustrated in Figs. 1 and 2. Being designed to stitch buttons or the like to garments, the machine is equipped with a clamp designed to support the button or the like and to grip the work fabric during stitching, and with a stop-motion mechanism which is effective to terminate the operation of the stitch forming instrumentalities after a predeter mined number of stitches have been formed. The details of construction of the sewing machine, which do not per se form a part of this invention, are illustrated and described in greater detail in my copending patent application Serial No. 413,228, filed March 1, 1954, to which reference maybe had for a more complete description thereof.

The sewing machine is supported on a sub-base 11 which is spaced by resilient pads 12 from the top of a supporting platform 13. Journaled in a bed 14, which is mounted upon the sub-base, is a main shaft 15. The bed 14 is also formed with a forwardly projecting work supporting arm 16 within which is journaled a rotary chain-stitch looper 17 which is driven from the main shaft. Rising from the bed is a standard 18 from which extends a bracket arm 19 which overhangs the worksupporting arm 16. A needle bar 20 which carries a needle 21 for cooperation with the looper 17 in the formation of stitches, is journaled for endwise reciprocation in a gate (not shown) which is pivoted within the bracket arm. The needle bar is reciprocated endwise by suitable connections with an oscillatory shaft 22 which is journaled in the bracket arm and is actuated from the main shaft 15 by means of a pitman 23. The needle is jogged laterally of the work-supporting arm 16 so that it may penetrate alternately one pair of holes of a button. This lateral jogging of the needle results from oscillation of the pivoted gate in which the needle bar is journaled, which oscillation is effected by means of a follower lever 24 which tracks a groove in the upper surface of a pattern cam 25 which is fast on a cam-shaft 26. The camshaft 26 is driven by a worm 27 and a worm wheel 28 from the main shaft 15. The cam shaft 26 also carries at its lower extremity a pattern cam 29 which is grooved in its top surface to accommodate a follower lever 30 which serves to shift a work clamp 31 lengthwise of the work-supporting arm 16 so as to shift a second pair of holes of a button to a position beneath the jogging needle.

The work clamp 31 is of the conventional type and includes a lower jaw 32 which is slidably supported against the work-supporting arm 16 and an upper jaw 33 which is pivoted, as at 34, to the lower jaw and which is formed with button-gripping fingers 35. The upper jaw 33 of the work clamp is biased downwardly against the lower jaw 32 by means of a plunger 36 which is journaled in the bracket arm and biased downwardly by a coil spring 37. The upper jaw may be raised, however, to open a space between the jaws for admission or withdrawal of a ply of garment fabric by means of a pivoted link 38 which connects the clamp with a rock arm 39 fast on a rock shaft 40 which is journaled in the bracket arm 19. A second rock arm 4'1 on the rock shaft 40 is connected by means of a link 42 to a push rod 43 which is journaled for vertical reciprocation in the standard 18. The push rod is fitted at its lower end with a collar 44 which serves to confine a coil spring 45 by which the clamp-lifting linkage is biased into inoperative position corresponding to the lowered position of the upper jaw 33. The collar 44 also serves to provide an enlarged abutment on the push rod 43 against which a clamp-lifting bell crank 46 is adapted to bear. The bell crank 46 is pivoted, as at 47, to the sub-base 11 and is provided with an operating chain 48, which, in the usual prior construction, was connected to a treadle or knee press for manual operation of the clamp-lifting linkage. In the machine embodying my invention the operating chain 48 is instead connected to the power control unit as will be described hereinafter.

The stop-motion mechanism, as best illustrated in Fig. 1, serves to control transmission of power to the main shaft 15 of the sewing machine from a continuously operated belt 50, and to stop the main shaft in a definite angular position when the belt 50 has been operatively disconnected therefrom.

The transmission of power from the belt 50 to the main shaft is regulated by means of a two-part pulley on the main shaft of which a first part 51 is fixed for rotation with the main. shaft while a second part 52 is journaled freely thereon and is shiftable axially on the main shaft so that it may be shifted to wedge the belt operatively against the fast pulley part 51. The axial position of the loose pulley part 52 is determined by a leaf spring 53 which is fixed on a bracket 54 secured to the machine bed 14. The spring 53 is embraced by a slotted tang 55 which extends from a stop-motion control lever 56 which is pivoted at 57 to a bracket 58 secured to the machine standard.

Also carried by the control lever 56 is a plunger 59 which is resiliently centered by coil springs 60 and 61 and which carries at its lower extremity a stop block 62 which is disposed for engagement with a stop cam 63 formed as an integral part of the fast pulley part 51.

Secured to the stop-motion control lever 56 is an operating arm 64 which is connected by means of a pivoted link 65 with a push rod 66 which is journaled for vertical sliding motion in the machine frame. A coil spring 67 on the rod 66 is confined between the frame and a collar 68 and serves to bias the control lever 56 into an extreme counterclockwise direction which corresponds to the stopped position of the machine. In this position, as shown in Fig. 1, the stop block 62 is shifted into engagement with the stop cam 63 and the leaf spring 53 is relaxed so that the belt 50 is free of the fast pulley part 51.

A bell crank lever 69 which is pivoted as at 70 to the sub-base 11 may be turned by depression of a pull chain 71 to engage beneath and raise the push rod 66 in opposition to the coil spring 67. Such raising of the push rod 66 will turn the stop-motion control lever 56 in a clockwise direction to effect initiation of a cycle of operation of the sewing machine. Such movement will first shift the stop block 62 out of engagement with the stop cam 63 and, second, will act through the leaf spring 53 to reestablish driving connection between the belt 50 and the main shaft 15.

The collar 68 is shouldered to provide abutment surfaces 72 and 73 which are spaced axially of the push rod 66 and which cooperate with a latch lever 74 pivoted, as at 75, to the machine bed to hold the push rod 66 in raised position until the end of the cycle. Accordingly, a coil spring 76 urges the latch lever 74 to underride the lowermost abutment 73 of the collar 68 when the push rod is raised. The latch lever 74, however, is controlled by a cam plate 77 which is secured to the lower pattern v cam 29 of the sewing machine. The cam plate 77 is formed with two difierent cam surfaces 78 and 79 which act in seriatim upon the latch lever 74. The cam surface 78 is effective several stitches prior to the end of a stitching cycle to shift the latch lever 74 from abutment 73 to abutment 72 on the collar 68 thus permitting the stop-motion control lever 56 to turn sufficiently to release the driving belt 50 from the fast pulley part 51. As the machine then coasts to a stop, the second cam surface 79 of cam plate 77, trips the latch lever from the abutment 72 of the collar 68 which completely releases the stop-motion control lever 56 so that the stop block 62 is shifted into engagement with the stop cam 63 to bring the machine to a halt in a definite and predetermined position of parts.

The operating chain 71 for the stop-motion mechanism and the chain 48 by which the work clamp may be opened were attached in prior arrangements to separate manually operable treadles. With this arrangement, the sewing machine operator had not only to operate two separate treadles, but each time a sewing cycle was to be initiated, she was called upon to exert suffieient effort to overcome the springs 67 and 53, in the stop-motion mechanism which together average approximately 1015 lbs. Moreover, whenever the work clamp was to be opened, the

4 operator had to oppose springs 45 and 37 which together average approximately l520 lbs. The present invention provides a power control unit whereby the operation of this machine may be effected by a single manual control member which may be operated with but an ounce or two of force.

The power control unit of my invention, as illustrated in Fig. 2 of the drawings, comprises an assembly of devices carried on a plate 80 which is secured beneath the sewing machine supporting platform by fastening bolts 81, and an assembly of devices mounted on a bracket 82 which is secured to the sewing machine standard by fastening screws 83. My control unit, therefore, may be in the nature of an attachment to the sewing machine.

The devices which are secured to the plate 80 include a pair of fluid pressure operated cylinders 84 and 85. Depending from the plate 80 is a fulcrum bracket 86 which pivotally supports a clamp-opening lever 87 and a stopmotion control lever 88. The clamp-opening lever 87 is pivoted in a knuckle 89 which is secured to the free end of a piston rod 90 which depends from the fluid cylinder 84. The chain 48, which depends from the clamp-opening bell crank 46, is operatively connected to the lever 87 and provided with a turnbuckle 91 by which the parts may be adjusted for proper operation. In a like manner the stopmotion control lever 88 is pivoted in a knuckle 92 which is secured to a piston rod 93 which depends from the fluid cylinder 85. The stop-motion controlling chain 71 is similarly connected through a turnbuckle 94 to the lever 88.

Associated with the cylinders 84 and 85 are electrically operated valves 95 and 96. These valves are similar and are of the type in which the valve is normally closed and may be opened by impressing a voltage across the electrical leads thereof. As shown in Figs. 2 and 3, fluid under pressure is directed to both of the valves 95 and 96 from a single flexible tube 97 which extends from a suitable source of supply. The tube 97 terminates in a Y connection 98 of which one end leads directly to the valve 96 while the opposite end is connected by means of a flexible tube 99 to the valve 95. In Fig. 2 parts of the tube 99 are broken away to expose the structure therebehind. It will be appreciated that any suitable fluid may be utilized, and in fact, air pressure is completely satisfactory for the successful operation of my power control unit. The air pressure may be obtained from any suitable supply, and it may be derived directly from an air pump mounted upon the sewing machine driving motor. The patent application of Reynold Happe, Serial No. 134,958, filed December 24, 1949, illustrates such an air pump. Fig. 4 shows diagrammatically the above described fluid circuits of the present invention.

The preferred form of the electrical circuit of my control unit, as illustrated in Figs. 2 and 3, is represented diagrammatically in Fig. 5. This circuit comprises an arrangement of switches including one foot or treadle operated switch 101 whereby the electrically operated valves 95 and 96 may be actuated in proper sequence to start the sewing machine at the will of the operator and to open the work clamp only after the machine is stopped. The basic components of this circuit include a line switch 100 and the single-pole double-throw switch 101 by which either one of two branches of the circuit may be energized, each branch having one of the electrically operated valves 95 and 96 and one of the mechanically operated singlepole single- throw switches 102 and 103.

The switch 101 is preferably of the dead center position type so that the work clamp may be reopened before the machine is started. A snap-action switch may be used in which case closing of the clamp will start the machine.

The support plate 80 of the control unit, as shown in Fig. 3, has fixed thereto an angle bracket 104 to which is secured the line switch 100 and three electrical connectors, including a terminal 105 having two pins 106 and 107 which is adapted to receive a connector for a two wire conductor 108 a terminal 109 having three pins 110, 111 and 112 which is adapted to receive a connector for a three wire conductor 113, and a terminal 114 having four pins 115, 116, 117 and 118 which is adapted to receive a connector for a four wire conductor 119. Also carried on the supporting plate 80 is an insulated junction block 120 provided with a plurality of sections 121, 122 and 123 each comprising a length of metal conductor such as that shown at 124 with a fastening screw 125 provided at each end to accommodate wire leads. The electrically operated valve 95 is provided with two wire leads 126 and 127 which are connected to sections 121 and 122 respectively of the junction block 120. Similarly, the electrically operated valve 96 is provided with two wire leads 128 and 129 which are connected to sections 122 and 123, respectively, of the junction block.

The section 122 of the junction block, to which Wires 127 and 128 are connected one from each of the valves 95 and 96, is connected by means of a wire 130 to the line switch 100 which in turn is connected by a wire 131 to the pin 106 of the two pin terminal 105. The conductor 108 leading from the terminal 105 terminates in a connector plug 132 of the usual type which is adapted to be connected to any conventional 115 volt electrical outlet.

The other pin 107 of the terminal 105 is connected by a Wire 133 to pin 110 of the three pin terminal 109. The three wire conductor 113 is directed to the single-pole double-throw switch 101 which in the preferred embodiment, as illustrated in Fig. 2, may be in the form of a foot switch. The foot switch is biased in one direction so that when not depressed by the operator, the terminal pin 110 is connected electrically with the pin 112 and when the foot switch is depressed the pin 110 is electrically connected with the pin 111.

The pin 112 of the three pin terminal 109 is connected by a wire 134 to the pin 115 of the four pin terminal 114, and pin 111 of terminal 109 is connected by a wire 135 to the pin 116 of the terminal 114. The four wire conductor 119, as best shown in Fig. 2, leads to a four pin terminal 136 which is secured to the machine standard 18. From the terminal 136 two wire leads 137 and 138 are directed to the single-pole single-throw switch 102 which is secured to the bracket 82 on the machine standard. A second pair of wire leads 141 and 142 are directed from the four pin terminal 136 to the switch 103 which is also fastened upon the bracket 82. The terminals 136 and 114 are so arranged that the switch 102 controls the electrical connection between pins 115 and 117 of the terminal 114 and that the switch 103 similarly controls the electrical con nection between the pins 116 and 118 of the terminal 114. The pin 117 of the terminal 114 is connected by a wire 143 to the section 121 of the junction block 120 while the pin 118 of the terminal 114 is connected by a wire 144 to the section 123 of the junction block.

As shown in Figs. 1 and 2, the switches 102 and 103 are of the type each having an operating plunger 145, 146, respectively, and as shown in Fig. 1, the switches are staggered so as to position the plungers along the path of motion of a pin 147 which projects from the operating arm 64 of the stop-motion control lever 56. The switches 102 and 103 are disposed such that when the machine is stopped and, consequently, when the lever 56 is turned into its extreme counterclockwise position, as illustrated in Figs. 1 and 2, the pin 147 engages and depresses the plunger 145 of the switch 102. When the stop-motion mechanism is in running position as it is during the course of each stitching cycle, the pin 147 engages and depresses the plunger 146 of the switch 103. The switch 102, as indicated on the diagram of Fig. 5, is of the type which is normally open while the switch 103 is of the type which is normally closed. It will be apparent, therefore, that with this arrangement the switches 102 and 103 are either both open or both closed, i. e., when the sewing machine is stopped both are closed, and during operation of the machine both are open.

When the line switch is closed, therefore, the power control unit of the present invention becomes operative. Assuming the machine to be in stopped position and consequently for the switches 102 and 103 both to be closed, the foot switch 101 determines which of the electric valves 95 and 96 is to be actuated. In the normal position of the foot switch, as when the operators foot is removed therefrom, the foot switch 101 is biased so as to impress a voltage across the valve 95 which acts to admit pressure to operate the clamp-lifting cylinder 84. Initial depression of the foot switch opens the circuit to the clamp-lifting electric valve 95 so that the clamp will be closed. When the preferred form of foot switch 101 is used having a dead center position, the work clamp may be reopened as long as the foot switch is only partially depressed, i. e., depressed into but not beyond the dead center position. From this dead center position, the clamp may be reopened simply by the release of the foot switch 101 to reenergize the electrically operated valve 95.

When the preferred form of foot switch 101 is depressed fully and contact is made with the opposite pole of the switch, or when a snap action switch is shifted from one pole to the other, the normally closed switch 103 will provide a closed circuit for the electrically operated stopmotion control valve 96 which will admit pressure to operate the cylinder 85. As the stop-motion control lever 56 is swung in a clockwise direction by the admission of pressure to the cylinder 85', the pin 147 on the operating arm 64 of the lever 56 will release the plunger of the switch 102 and will depress the plunger 147 of the switch 103 thus opening both of the switches 102 and 103. The opening of both of the switches 102 and 103 has two effects, first insofar as the switch 102 is concerned it insures positively that the work clamp cannot be opened during the operation of the machine and, second, opening of the switch 103 insures that only one cycle of machine operation will occur since this provides a trip-free operation of the stop-motion control. In other words, the stop-motion control valve 96 is deenergized the moment that the machine starts by the opening of the switch 103 which gives the machine operator an added increment of time to release the foot switch 101. When the machine stops at the end of a cycle of operation, the movement of the pin 147 away from the plunger 146 of the switch 103 allows this switch to move into its normally closed position which readies the stop-motion control circuit for the succeeding cycle of operation. Movement of the pin 147 then depresses the plunger 145 which closes the switch 102. The foot switch being completely released, the clamp-lifting circuit is automatically made continuous and the valve 95 is actuated to raise the clamp for removal and reinsertion of the work.

On the part of the machine operator, therefore, the power control unit of this invention requires only the manipulation of a foot switch or the like which may be accomplished with a force of but a few ounces. The power control unit provides its own safety interlocks which prevent lifting of the clamp until the machine has completed its cycle of operation and which provides trip free operation of the stop-motion device.

Many cogent reasons exist which make it desirable in certain instances to provide two separate manually operable controls for a cyclically operated sewing machine. Not the least important of these reasons is that of the work habits of certain machine operators who prefer to have two foot treadles, one for operation of the stop-motion mechanism and the other for opening the work clamp, or a foot treadle and a knee shifter device for this purpose simply because most prior art arrangements used two separate controls and these operators are reluctant to change their work habits. Because of this, I have illustrated diagrammatically in Fig. 6 a modified form of electrical circuit for my power control unit in which two separate manually controllable double-pole double- throw switches 150 and 151 are utilized. As depicted in Fig. 6, each of the switches 150 and 151 may be -arranged in separate foot actuated containers 152 and 153, respectively, or they may be arranged for operation by separate foot treadles or knee shifters if sodesired. Each of the switches 150 and 151 is formed in a well known manner with two poles which are mechanically linked for actuation together, one pole being normally open and the other being normally closed and these switches are connected in the circuit so that one set of poles of each switch is arranged in series with a respective one of the valve controlling solenoid coils 95 and 96. The stop-motion controlled switches 102 and 103 are similarly utilized as described above to provide trip free operation of the power control unit.

In the diagram of Fig. 6, the switches 150 and 151 are shown in at rest or inoperative positions. Switch 150 controls the clamp-lifting control valve 95' in that when the switch 150 is closed, a circuit is established through the valve 95 and the clamp-opening motor is actuated. By the same token, whenever the clamp is opened the switch 150 also opens that branch of the circuit in which the stopmotion control valve 96 is located so that the machine cannot be started with the work clamp in raised position.

The switch 151 controls the stop-motion mechanism since when the switch 151 is closed and switch 150 is in its normal position the circuit containing the stop-motion valve 96 will be completed and the machine will be started. The switches 102 and 103 both act as always to open as soon as the machine actuation has begun to provide a trip-free operation as explained above.

Having thus described the nature of my invention, what I claim herein is:

1. in a cyclically operated sewing machine having a work clamp and a stop-motion mechanism, power operated means for opening said clamp, power operated stopmotion controlling means for shifting said stopmotion mechanism into running position, electrically operated control means for said power operated means, comprising a circuit including electrically actuated means arranged to render said power operated clamp opening means effective, a circuit including electrically actuated means arranged to render said power operated stop-motion controlling means effective, a double throw switch operatively connected to impress an actuating voltage across a respective one of said circuits in each position of said switch, means biasing said double throw switch into a position closing the circuit which includes the means arranged to render said power operated clamp opening means effective, and means under control of the sewing machine operator for actuating said double throw switch in opposition to said biasing means.

2. A device as set forth in claim 1, an on-off switch arranged in each of said circuits, means carried by said stop-motion mechanism effective to shift each of said on-ofi switches to the off position when the stop-motion mechanism occupies a running position.

3. In a cyclically operated sewing machine having a work clamp and a stop-motion mechanism, fluid pressure operated means for opening said clamp, a valve arranged to control the flow of fiuid under pressure to said means, fluid pressure operated stop-motion controlling means adapted to shift said stop-motion mechanism into running position, a valve arranged to control the flow of fluid under pressure to said stop-motion controlling means, electrically operated control means for each of said valves and a double throw switch under control of the sewing machine operator, said switch being operatively connected to impress an actuating voltage across a respective one of said electrically operated valve control means in each position of said switch.

4. A device as set forth in claim 3, an on-oif switch arranged in each of said solenoid circuits, means carried by said stop-motion mechanism efifective to shift each of said on-oif switches to the off position when the stop'motion mechanism occupies a running position.

5. A power control unit for a sewing machine having stitch-forming instrumentalities, a stop-motion mechanism for'said stitch-forming instrumentalities, and a workholding clamp, comprising, a pair of motors, a first of said motors being operatively connected to open said work-holding clamp, the other of said motors being operatively connected to shift said stop-motion mechanism into running position, electrically operated control mechanism associated with each of said motors, an electrical circuit for energizing said electrically operated motor control mechanism, means in said electrical circuit under control of the sewing machine operator for selectively impressing a voltage upon the control mechanism for one or the other of said motors, and means in said electrical circuit under control of said sewing machine for opening said electrical circuit during operation of said stitchforming instrumentalities.

6. A power control unit for a sewing machine having stitch-forming instrumentalities, a stop-motion mechanism for said stitch-forming instrumentalities, and a workholding clamp, comprising, power operated work clamp opening means, electrically operated mechanism for controlling the transmission of power to said work clamp opening means, power operated means for shifting said stop-motion mechanism intorunning position, electrically operated mechanism for controlling the transmission of power to said stop-motion shifting means, a pair of electrical switches carried by said sewing machine and arranged each to control one of said electrically operated mechanisms, means associated with said stop-motion mechanism for opening said switches while said stopmotion mechanism occupies a running position, and means under control of the sewing machine operator for impressing an operating voltage across a selected one of said electrically operated mechanisms.

7. A power control attachment for cyclically operated' sewing machines having stitch-forming instrumentalities and a work manipulating device, comprising, an attachment frame, a pair of operating levers pivoted to said frame, means adapting a first of said levers to con- .trol the operation of said stitch-forming instrumentalities, and means adapting a second of said levers to control said work manipulating devices, a first and a second fluid pressure operated motor each carried by said frame and operatively associated with a respective one of said levers, a pair of electrically operated valve means disposed in communication each with one of said fluid pressure operating motors, an operator controlled double throw switch arranged so as to impress an actuating voltage across a selected one of said electrically operated valves, and means rendered effective by the operation of 'said first fluid pressure operated motor for preventing operation-of said second motor during operation of said stitch-forming instrumentalities.

References Cited in the file of this patent UNITED STATES PATENTS 2,604,062 Rich July 22, 1952 FOREIGN PATENTS 509,072 Belgium Feb. 29, 1952

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