US2994263A

US2994263A - Apparatus for marking articles

Info

Publication number: US2994263A
Application number: US624865A
Authority: US
Inventors: Albert F Rus
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1956-11-28
Filing date: 1956-11-28
Publication date: 1961-08-01
Anticipated expiration: 1978-08-01

Description

Aug. 1, 1961 A. F. RUS 2,994,263

APPAR TUS FOR MARKING ARTICLES Filed Nov. 28, 1956 4 Sheets-Sheet l ATTORNEY Aug. 1, 1961 A. F. RUS

APPARATUS FOR MARKING ARTICLES 4 Sheets-Sheet 2 Filed Nov. 28, 1956 Aug. 1, 1961 A. F. RUS

APPARATUS FOR MARKING ARTICLES Filed NOV. 28, 1956 4 Sheets-Sheet 3 INVENTOR A. E Hus ATTORNEY Aug. 1, 1961 RUS 2,994,263

APPARATUS FOR MARKING ARTICLES Filed Nov. 28, 1956 '4 Sheets-Sheet 4 ,2 FIG. /2

89 START I26- f q Z4 48 nvvnvrofi A. E Hus -82 X av 2,994,263 APPARATUS FUR MARKING ARTICLES Albert F. Rus, Riverside, Ill., assignor to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Filed Nov. 28, 1956, Ser. No. 624,865 11 Claims. (Cl. 101-11) This invention relates to apparatus for marking articles and more particularly to an apparatus for branding pigmented indicia onto thermoplastic protector sleeves on electrical resistors to indicate the resistance values thereof.

An object of the present invention is to provide a new and improved machine for marking articles.

Another object of the invention is to provide a machine for automatically feeding articles having thermoplastic protective sleeves thereon and for branding pigmented indicia onto the sleeves.

An apparatus illustrating certain features of the invention may include a hopper for feeding individual resistors into the trailing open ends of successive pairs of arcuate slots in a pair of flanges on a feed wheel which carries the resistors into engagement with a pigment coated tape on a heated branding die and which rolls the resistors over and presses them against the tape and the heated die to effect the branding of pigmented code marks into the thermoplastic protective sleeves on the resistors which then roll out of the slots and drop from the feed wheel as the slots travel upwardly. Driven feed rolls pull the tape at a uniform velocity and a yieldably mounted roller deflects the tape to form a taut loop therein between the feed rolls and the branding element whereby when the tape is temporarily gripped between the branding die and a resistor being branded and the loop is shortened thereby, the yieldable roller is moved by the loop as the loop is being shortened and then reforms the loop after the branded resistor releases the tape.

Other objects and advantages of the invention will become apparent by reference to the following detailed description and the accompanying drawings illustrating a preferred embodiment thereof, in which:

FIG. 1 is an enlarged perspective view of a resistor branded by the apparatus embodying the present invention;

FIG. 2 is an enlarged perspective view of a portion of a pigment coated tape used in the branding apparatus;

FIG. 3 is a side elevational view of the branding apparatus embodying the present invention;

FIG. 3 is an enlarged detailed vertical sectional view through a portion of the apparatus showing the resistors being fed from a supply hopper onto a feed wheel;

FIG. 4 is a front view of the branding apparatus;

FIG. 5 is an enlarged fragmentary vertical cross sectional view taken along line 5-5 of FIG. 3 and showing the tape feeding rolls of the apparatus;

FIG. 6 is an enlarged fragmentary plan sectional view of the apparatus with parts omitted taken along line 6-6 of FIG. 3;

FIG. 7 is a fragmentary vertical sectional view of the apparatus taken along line 7-7 of FIG. 6;

FIG. 8 is a perspective view of a supporting block component of the apparatus;

FIG. 9 is a perspective view of the branding die of the apparatus;

FIG. 10 is a fragmentary vertical sectional view of the apparatus taken along line 10-10 of FIG. 7;

FIG. 11 is an enlarged fragmentary vertical sectional view through a portion of the machine similar to FIG. 10 showing a resistor in branding position; and

FIG. 12 is an electrical diagram of the motor control for the apparatus.

The present branding apparatus 18 is designed to im- Patented Aug. 1, 1961 ice press code marks or numbers 20 (FIG. 1) on thermoplastic protective sleeves 22 of resistors 24 to indicate the resistance values thereof. The resistors 24 are of the type having a ceramic rod with a spiral stripe of carbon thereon to which terminal caps are connected with leads 29 extending axially therefrom on opposite ends of the resistor. The code mark 20 is formed by branding a pigment into the thermoplastic sleeve 22.

The apparatus 18 generally comprises a hopper 30 (FIGS. 3 and 4) for receiving and holding a supply of the resistors 24 and guiding them through a predetermined path into engagement with a pair of flanges 32 of a rotary feed wheel 34 and for feeding individual resistors 24 into the trailing open ends 35 of successive pairs of aligned arcuate slots 36 in the flanges for movement with the wheel 34 into engagement with a heated branding element or die 38 (FIGS. 3 and 7) positioned below the feed wheel 34. A tape 40 (FIG. 2) comprising a web of plastic material 41 having a coating 42 of dry pigment thereon is positioned over the branding die with the pigment coating uppermost and as the resistor 24 is carried into engagement with the tape on the branding die it is rolled over the tape and the die by the feed wheel 34 and pressed tightly thereagainst by a layer of resilient material 44 on the rim 45 of the feed wheel during which rolling movement of the resistor 24 on the die 38, the code mark 20 is branded onto the sleeve 22. As the feed Wheel 34 continues rotating the resistor 24 rolls out of the slots 36 and drops from the feed wheel.

The hopper 30 is supported on the upper end of a pair of brackets 47 fixed to and extending upwardly from a base plate 48 of the apparatus. The resistors 24 in the hopper 30 are formed into a row as they pass downwardly through a narrow passageway 50 in the hopper and engage a bottom 'wall 51 which extends inwardly between the flanges 32 of the feed wheel and directs the resistors inwardly toward the wheel, whereby as the resistors pass through a discharge opening 52 in the hopper the lead wires 29 thereof engage the periphery of the flanges 32 of the feed wheel and drop into the open ends 35 of a pair of slots 36 of the feed wheel. A lip 53 on the hopper limits the movement of the row of resistors 24 to permit the positioning of only one of the resistors 24 in the open ends: 35 of each pair of the slots 36) so that as the feed wheel continues its rotation shoulders 55 on the flanges 32 of the wheel at the trailing open end of the pair of slots 36 serve to remove a single resistor from the hopper with the sleeve 22 disposed between the flanges and supported on the resilient peripheral layer 44 of the feed wheel and with the leads 29 of the resistor extending laterally from the slots 36 of the flanges of the wheel. As the slots 36 and the resistors 24 therein pass over the center of the wheel and move downwardly, the resistors roll to the leading closed ends of the slots 36. To insure that this occurs a jet of air is directed through an air pipe 57 (FIG. 1) against the resistors.

The feed wheel '34 is secured to a horizontally disposed shaft 60 which is journaled in bearing brackets 61 mounted on the base plate 48 and the base plate 48 may be supported on a suitable work bench or frame. A motor 62 and gear reducer drive unit 63 are pivotally mounted at 64 on the base plate 48 and are connected through a pulley and belt drive connection 65 to the shaft 60 for driving the feed wheel 34 in a clockwise direction as viewed in FIG. 1.

The branding die 38 (FIG. 9) is in the form of a rectangular slug having the predetermined indicia impressing embossments on the upper end thereof and may be made from individual printer types bonded together. A chase 69 has a recess for receiving the branding element 38 which is locked therein by means of an eccentric 70 and the chase has an annular shoulder or flange 71 and a threaded lower end 72 which is screwed into an electrical heating rod or element 73 (FIG. 10) for heating the branding die. The heating rod 73 as shown herein is shown in the form of a commercial soldering iron unit with the tip removed therefrom. The branding die 38 and the chase 69 fit into

apertures

76 and 77 in a supporting block '78 (FIGS. 7, 8, and 10) on the base plate 48 and is clamped with the flange 71 in engagement with the lower surface thereof by an annular member 79 which is screwed into a threaded opening 80 in the base plate. The annular member 79 has a flange 81 formed thereon to which is secured a guard 82 for the heating element 73.

The supporting block 78 is removably secured to the base plate 48 and comprises a flat horizontally disposed plate 85 and a member 86 extending upwardly therefrom along the centerline thereof. Plates 88 and shims 89 secured by screws 90 to the upper and lower sides of the plate 85 along opposite edges thereof are adapted to slidably engage in a slideway formed by the base plate 48 and of a pair of guide members 91 secured thereto by screws 92 (FIG. 6). A pin 93 on the base plate 48 engages the end of the supporting block 7 8 to stop it in a predetermined position to support it and the branding die 38 beneath and in vertical alignment with the center of the feed wheel 34. A pair of horizontally disposed tracks 96 is formed on the upper portion of the member 86 with the upper surface of the tracks disposed slightly below the upper embossed surface of the branding die 38 for supporting the cylindrical resistors 24 for horizontal rolling movement along a portion thereof as the resistors are rolled into engagement with the branding die by the feed wheel 34 during the branding operation. A handle 98 is formed on the block 86 by means of which the supporting block 78 may be removed from the apparatus after the branding die 38 has been removed therefrom, and the block 86 has guide slots 99 formed therein for guiding the tape 40. The position of the upper face of the branding die 38 may be adjusted relative to the feed Wheel 34 by removing the supporting block 78 and changing the shims 89 from one side of the plate 85 to the other.

A supply roll of the tape 40 is suitably supported on or near the apparatus and the tape therefrom passes around a guide rod 103 (FIG. 3) against which it is pressed by a tension device 104. The tape 40 is directed under a pin 105 (FIG. 7) in the supporting block 78, over the branding die '38, under a movable roller 106, onto a guide plate 107 and between a pair of

feed rolls

108, 109. The

feed rolls

108, 109 which have meshing teeth or positively gripping and feeding the tape are rotatably supported in bearing brackets 110 mounted on the base plate 48, and the upper feed roll 108 has a shaft 111 extending from opposite ends thereof on which is rotatably mounted a pulley 112. This pulley is connected by a belt 113 (FIG. 4) to a pulley 114 on the drive shaft 60 and for driving it, and the pulley 112 (FIG. is connected to the shaft 111 through a one-way clutch 116 to drive the

rolls

108 and 109 in one direction to feed the tape 40 and to permit manual rotation of the feed rolls when the drive shaft 60 is not rotating. A hand wheel 118 is fixed to the other end of the shaft 111 and may be manually turned to rotate the

feed rolls

108 and 109 for threading the tape 40 between the feed rolls.

The roller 106 (FIG. 7) under which the tape 40 passes is rotatably mounted in one end of a pair of arms 119 which are pivoted at their other ends of a pin 120 mounted in the brackets 110. A coil spring 121 stresses the arms 119 in a clockwise direction as viewed in FIG. 7 to a normal position in engagement with the base plate 48 to cause roller 106 to form a taut loop 122 in the tape 40 between the branding die 38 and the

feed rolls

108, 109. Thus, while a resistor 24 is being rolled over the branding die 38 by the feed wheel 34 and the tape 40 is being pulled at a uniform velocity by the

feed rolls

108, 109, the loop 122 formed by the roller 106 is progressively shortened and held under tension by the roller 106 until the resistor 24 is rolled off of the branding die and releases the tape at which time the roller 106 moves to its normal position, thereby increasing the length of the loop and quickly advancing the tape over the branding die 38 to present an unused portion of the tape on the die for the next branding operation.

The motor 62 is connected across a power line 123 (FIG. 12) in series with relay contacts 1241 of a relay 124 which is connected in series with a normally open start switch 125 across the power lines. The relay 124 is energized by closing the start switch 125 which closes the contact 1241 to start the motor 62, and the relay locks itself in by its contacts 124-2 which are connected in series with a microswitch 126 and a stop switch 127 which are connected across the start switch 125. The switch 126 (FIG. 3) is provided for stopping the motor 62 in the event that the supply of resistors in the hopper is depleted and it is supported on one of the brackets 47 and has an elongated curved arm 127 positioned above the feed wheel 34 between the flanges 32 thereof for engaging the resistor 24 on the feed wheel and being actuated thereby to close the switch. The arm 127, being long enough to engage a pair of resistors 24 disposed in consecutive slots 36, is held in its closed position by engagement with the resistors 24 on the feed wheel 34, and the arm 127 drops to open the switch 126 and stop the motor 63 when resistors 24 are absent from two successive slots 36 in the feed wheel 34.

Means are also provided to insure that the machine cannot be stopped while a resistor is in contact with the heated branding die 38. A normally open microswitch 131 is connected in parallel with the starting switch 125 and is suitably supported on one of the brackets 47 in a position to be actuated to closed position by cams 132 mounted on one side of the feed wheel 34 (FIG. 3). The cams 132 are arranged to actuate a switch arm 133 (FIG. 4) to close the switch 131 during the intervals that the resistors are normally being branded and in engagement with the heated branding die 38.

In the operation of the device after the apparatus has been started the resistors 24 in the hopper 30 are guided thereby individually into the open ends 35 of successive pairs of slots 36 in the feed wheel 34 and are carried thereby in a downward direction, causing the articles to move into engagement with the leading closed ends of the slots. Each of the resistors 24, in the leading ends of a pair of slots 36, is carried into engagement with the tracks 96 adjacent the branding die 38 and into engagement with the tape 40 on the branding die, and the cylindrical resistor 24 is then rolled along a portion of the track 96 and rolled over the slightly raised embossed end of the branding die 38 and the tape 40 thereon and pressed tightly thereagainst by the resilient layer 44 on the feed wheel 34 during which rolling movement of the resistor across the face of the branding die, the pigmented layer 42 of the tape 40 is heated and a pigmented code mark 20 is branded into the plastic sleeve 22 of the resistor. The resistor is then carried upwardly by the wheel and rolls down the slots 36 and drops therefrom through the open ends 35 of the slots onto an inclined plate 135 (FIG. 7) which is suitably supported on the apparatus. The resistors 24 may roll down the plate into a receptacle (not shown) or be removed by the operator.

In the event a resistor 24 does not roll out of the slots 36 and drop from the feed wheel 34 as it should, a stripper plate 136 is provided to engage such resistors and positively remove them from the feed wheel.

It is to be understood that the above-described arrangements are simply illustrative of the application of the principles of this invention. Numerous other arrangements may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

1. In a machine for marking cylindrical articles, a base, a track for supporting a cylindrical article for rolling movement along a predetermined path, a marker mounted on said base and in slightly raised relation to said track for marking the articles, a feed wheel mounted on said base for rotation above said marker and having a resilient periphery for rolling said articles along the track and over the marker and pressing them thereagainst, a pair of spaced flanges on said wheel having arcuate slots concentric with the resilient periphery for receiving and supporting the articles for revolving movement therewith into engagement with the marker and permitting rolling movement of the article along said track between the resilient periphery of the Wheel and the marker, said slots having radially extending open trailing ends for ingress and egress of the articles, a hopper for holding a supply of said articles and guiding them in a row into engagement with the flanges of the wheel and for movement of articles individually into the open ends of successive pairs of the slots, and means for rotating said feed wheel.

2. In a machine for marking cylindrical resistors having coaxial leads on the ends thereof, a base, a marker on the base, a rotatable wheel mounted on the base above the marker and having a cylindrical resilient periphery engageable with the periphery of the resistors, a pair of parallel flanges on said feed wheel spaced apart for receiving the resistors therebetween and provided with a plurality of pairs of aligned arcuate slots concentric with the axis of the Wheel for receiving the leads of the resistors and supporting the resistors for revolving movement with the wheel and for rolling movement on the periphery thereof, each of said slots having a closed leading end portion and a transversely directed open trailing end portion providing ingress and egress for said leads, means for rotating said wheel, a hopper mounted on said base for holding a supply of the resistors and guiding them in a row toward the feed wheel to cause the leads of the first resistor in said row to engage the flanges of the wheel at a point thereon above the center of the wheel and move into the open end portion of the slots, and means on said hopper extending between said flanges for limiting the movement of the row of resistors to permit the successive movement of only the first resistor of said row into successive slots of the feed wheel.

3. In a machine for marking cylindrical articles, a rotatable wheel having a pair of parallel circular members provided with a plurality of opposed slots for receiving and holding the articles for revolving movement therewith, each of said slots having an outwardly directed open trailing end portion providing ingress and egress for the article and an arcuate portion concentric with the axis of rotation of the wheel permitting rolling movement of the articles relative to the wheel, means for rotating said wheel about a substantially horizontal axis, a hopper for guiding articles through a predetermined path into engagement with the periphery of the circular members and for movement of one of the articles into the open trailing end portion of the slots therein whereby successive articles are automatically fed into successive slots in the wheel, a marking element stationarily mounted in a predetermined position below the wheel for rolling engagement of the articles thereover, tape guide means for guiding a tape along a predetermined path and over the marking element, means for pulling the tape over the marking element at a predetermined velocity, said guide means for guiding the tape over said marking element including a member yieldably mounted for movement to a predetermined position for deflecting the tape and forming a taut loop therein between the marker and the feed means to permit the length of the loop to be temporarily reduced when the tape is gripped between the marker and the article as it is rolled between the tape and the marker by the wheel.

4. In a machine for branding cylindrical articles, a rotary feed wheel, a circular flange mounted on each side of the feed Wheel having a periphery extending beyond the periphery of the feed wheel and having a plurality of slots, each slot having a radial section extending to the periphery of the flanges for ingress and egress of an article and a section concentric with the periphery of the wheel and in communication with the radial section permitting movement of the article along a predetermined path, a branding element positioned to engage each article advanced by the wheel, a track positioned to engage and support the articles in the slots for rolling movement to and from the branding element, a resilient rim on the periphery of the feed wheel for rolling the articles along the track and over the branding element, a tape feeding mechanism for continuously feeding a marking tape at a uniform velocity between the articles and the branding element, and a loop forming member for yieldably holding the tape to permit a continuous feed thereof while the tape is held between an article and branding element.

5. In a machine for marking articles, a horizontal shaft, a feed wheel mounted on the shaft, means for rotating the wheel in a predetermined direction, said feed wheel having a plurality of circumferentially spaced slots each having one open end, each of the slots having a section radially extending to the periphery of the wheel adjacent the open end of the slot and having an arcuate section extending concentric to the axis of the shaft and in the direction of rotation of the wheel, means for dropping articles into the open ends of the slots as the wheel moves the slots to the top of the arc of rotation of the wheel, whereafter the articles move along the arcuate slots as the wheel moves the slots toward the bottom of the arc of rotation, and marking means positioned at the bottom of the arc of rotation of the wheel for engaging and moving articles in the slots along the arcuate sections of the slots into the radial sections of the slots Whereafter the articles fall from the radial sections open ends of the slots as the wheel advances the slots toward the top of the arc of rotation.

6. A machine for branding cylindrical articles which comprises, a block having a groove therein and an aperture extending through the block intersecting the groove, a track formed on either side of the groove for supporting the cylindrical articles thereon, a branding element mounted in the aperture and extending a short distance above said tracks, means for heating said branding element, a continuous feed means for pulling a pigmented tape along the groove and over said branding element, a hopper for retaining articles, a feed wheel rotatably mounted in spaced relation to said branding element, resilient means secured to said feed wheel substantially concentric to the axis thereof, said feed wheel having a plurality of circumferentially spaced open-ended slots adjacent said resilient means, means to rotate said feed wheel, means for feeding articles into the open ends of the slots in one position thereof for free traveling rotation therein as said feed wheel rotates, said branding element being poistioned with respect to said feed wheel so as to press the articles firmly into engagement with said resilient means to grip said tape between said branding element and the articles and to roll the articles in the slots along said resilient means during the marking process, said tracks engaging the articles prior to the marking process to also press the same into firm engagement with said resilient means to roll the articles in the slots along said resilient means, whereby the articles have rolling movement prior to their engagement with said branding element, each article ultimately falling from its respective slot through the open end thereof after the marking process is completed, and a spring biased means for forming a loop in said tape between said branding element and said feed means to permit the length of the loop to shorten upon said tape being gripped between the articles and said branding element.

7. In a machine for marking articles, a marker, a feed wheel rotatably mounted in spaced relation to said marker, resilient means secured to said feed wheel substantially concentric to the axis thereof, said feed wheel having a plurality of circumferentially spaced open-ended slots adjacent said resilient means, means to rotate said feed wheel, and means for feeding the articles into the open ends of the slots in one position thereof for free traveling rotation therein as said feed wheel rotates, the articles being carried in the slots from the position in which they are fed into the slots to a marking position by the rotation of said feed wheel, said marker being positioned with respect to said feed wheel so as to engage the articles and press the same into firm engagement with said resilient means during the marking process, whereby as each article is marked it is rolled in its respective slot along said resilient means, the article ultimately falling from the slot through the open end thereof after the marking process is completed.

8. In a machine for marking articles, a marker, a feed wheel rotatably mounted in spaced relation to said marker, resilient means secured to said feed wheel substantially concentric to the axis thereof, said feed wheel having a plurality of circumferentially spaced open-ended slots adjacent said resilient means, means to rotate said feed wheel, means for feeding the articles into the open ends of the slots in one position thereof for free travel ing rotation therein as said feed wheel rotates, the articles being carried in the slots from the position in which they are fed into the slots to a marking position by the rotation of said feed wheel, and a track positioned forward of said marker, said marker and said track being positioned with respect to said feed wheel so as to engage the articles and press the same into firm engagement with said resilient means, whereby prior to and during the marking of each article it is rolled in its respective slot along said resilient means, each article ultimately falling from its respective slot through the open end thereof after the marking process is completed.

9. In a machine for marking articles, a marker, a feed wheel rotatably mounted in spaced relation to said marker, resilient means secured to said feed wheel substantially concentric to the axis thereof, said feed wheel having a plurality of circumferentially spaced open-ended slots adjacent said resilient means, means to rotate said feed wheel, means for feeding the articles into the open ends of the slots in one position thereof for free traveling rotation therein as said feed wheel rotates, the articles being carried in the slots from the position in which they are fed into the slots to a marking position by the rotation of said feed wheel, continuous feed means for pulling a pigmented tape over said marker, said marker being positioned with respect to said feed wheel so as to press the articles firmly into engagement with said resilient means to grip the tape between said marker and the articles and to roll the articles in the slots along said resilient means during the marking process, each article ultimately falling from its respective slot through the open end thereof, and a spring biased means for forming a loop in said tape between said marker and said feed means to permit the length of the loop to shorten when the tape is being gripped between the articles and said marker.

10. In a machine for marking articles, a marker, a feed wheel rotatably mounted in spaced relation to said marker, resilient means secured to said feed wheel substanti-ally concentric to the axis thereof, said feed wheel having a plurality of circumferentially spaced open-ended slots adjacent said resilient means, means to rotate said feed wheel, means for feeding the articles into the open ends of the slots in one position thereof for free traveling rotation therein as said feed wheel rotates, the articles being carried in the slots from the position in which they are fed into the slots to a marking position by the rotation of said feed wheel, said marker being positioned with respect to said feed wheelso as to engage the articles and press the same into firm engagement with said resilient, means during the marking process, whereby as each article is marked it is rolled in its respective slot along said resilient means, the article ultimately falling from the slot through the open end thereof after the marking process is completed, means movably mounted adjacent the-periphery of said feed wheel and in a position to engage a pair of articles in their respective slots simultaneously, and switch means operated by said lastrneutionedmeans and operatively connected to said feed wheel rotating means, said movably mounted means being moved inwardly towards said feed wheel when a pair of empty slots pass thereby, to de-actuate said switch means and stop the rotation of said feed wheel.

- 11. Ina machine for marking articles, a marker, a feed wheel rotatably mounted in spaced relation to said marker, resilient means secured to said feed wheel substantially concentric to the-axis thereof, said feed wheel having a plurality of circum'ferentially spaced open-ended slots adjacent said resilient means, means to rotate said feed wheel, means for feeding the articles into the open ends of the slots in one position thereof for free traveling rotation therein as said feed wheel rotates,'the articles being carried in the slots from they position in which they are fed into the slots to a marking position by the rotation of said feed wheel, said marker being positioned with respect to'said feed wheel so as to engage the articles and press the same into firm engagement with said resilient means during the marking process, whereby as each article is marked it is rolled in its respective slot along said resilient means, the article ultimately falling from the slot through the open end thereof after the marking process is completed, a series of circumferentially spaced projecting members mounted on said feed Wheel, and switch means mounted adjacent said feed wheel in a position to engage said projecting members and be held in a closed position thereby whenever an article is in engagement with said marker, whereby the rotation of said feed wheel will not be interrupted during a marking operation.

References Cited in the file of this patent UNITED STATES PATENTS 553,480 Wood Jan. 21, 1896 1,341,449 Wilkinson May 25, 1920 1,569,224 Hale Jan. 12, 1926 1,981,892 Zimber et al Nov. 27, 1934 2,288,298 Norman et al. June 30, 1942 2,362,663 Redin et al. Nov. 14, 1944 2,562,168 Blanchette July 31, 1951