US2788620A - Grinding apparatus - Google Patents

Description

April 16, 1957 J. R. MARCUS ET AL GRINDINGQPPARATUS 3 Sheets-Sheet 1 Filed Dec. 50, 1954 JR. MRRCUG 3 W 3 9 ll 2 o 1 2 z 6 F RHDHKOV/CH HTTORNE April 16, 1957 J. R. MARCUS ET AL 2,788,620

GRINDING APPARATUS Filed Dec 30, 1954 5 Sheets-Sheet 2 I r I //l 13/ 32 129 A38 F76 5 3 I30 HTTORNEY April 16, 1957 J. R. MARCUS ET 2,788,620

GRINDING APPARATUS Filed Dec. 30, 1954. 3 Shets-Sheet 3 IN V5 N T OR 3 JR. nRcua F RHDHKO V/CH QTTd/e/JEY United States Patent 9 2,7ss,s20

GRINDING APEARATUS Jerome R. Marcus and Fred Radakovich, Chicago, Ill., assignors'to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application December 30, 1954, Serial No. 47 8,638

13 Claims. ((11. 51-131) This invention relates to grinding apparatus particularly adapted for grinding surfaces of articles.

Various articles which are to become parts of units or equipment for the communication arts must be formed Willi consideration given to the requirements necessary for their efficient use. In the present embodiment of the invention a ferrite shell which is cupshaped in general contour has an outer edge at the lip of the cup-shaped formation which must lie in a plane parallel with and at a predetermined distance from the inner bottom. surface of the cup-shaped article.

The object of the invention is an apparatus wherein articles of this type may be accurately and efficiently ground to the contours and measurements desired.

With this and other objects in View, the invention comprises a mandrel adapted to receive articles singly and hold them accurately relative to a rotatable grinding wheel movable to grind one surface with relation to another, the position of the grinding wheel being controlled by the mandrel.

In the present embodiment of the invention, the mandrel is rotated at a fixed position while an arm is actuated in timed relation to a holding unit to eject a finished articlefrom the mandrel and feed a new article thereto, after which the new article is held so that the inner surface thereof rests firmly against a reference'surface of the mandrel, after which the grinding wheel is moved rapidly toward the article, to initially position it to start the grinding, after which a slower feeding movement is given to the grinding Wheel to bring about grinding of the adjacent surface to given dimensions and in a plane parallel with the inner surface of the article.

Other objects and advantages will be apparent from the-following detailed description when considered in conjunction with the accompanying drawings, wherein:

Fig. 1 is a top plan view of the apparatus showing the various units thereof in their respective positions during grinding of an article;

Fig. 2 is "a vertical sectional VlEZW takensubstantially along the line 2-2 of Fig; 1;

Fig. 3 is "an enlarged sectional view takensubstantially alongthe line 33 of Fig; 1;

Fig. 4 is an enlarged isometric View of one of the articles to be ground;

Fig. 5 is a top plan view of the driving mechanism disposed under the table supporting the structure shown in Figs. 1 and 2;

Fig. 6 is a fragmentary sectional viewtaken substantially along the line 6-6 of Fig. 5;

Fig. 7 is a fragmentary sectional view taken along the line 77 of Fig. 5, and

Fig: 8 is a fragmentary sectional view'taken along theline 8-'8-of Fig. 5.

Referringnow to thedrawings, attention is directed first to Fig. 4 which shows the circular article '10 as being cup-shapedand having'an inner surface bottomll which may-be termeda reference surface'andan outer surface or lip 12 which must be ground to within a given distance of and parallel with the surface 11. The article has a central aperture 14 therein which is utilized in locating the article on a mandrel 15 of vthe apparatus.

The mandrel15 is journalled for rotation in suitable bearings disposed in a housing 16 and supports a pulley 17 freely rotatable adjacent one end thereof. A conventional clutch 18'includes a drive member fixed to the pulley 17 and a driven. member keyed to the mandrel and normally urged to engagement with the drive member by a spring 2%. A yoke 21 straddling the driven member is carried by rod 35 slidable in bracket 22.:

Adjustable nuts 24 and the bracket 22 control the yoke and its driven clutch member to permit spring 20 to actuate clutch 18 to rotatemandrel 15.from. a drive including a pulley 25 prior to engagement of a cup-shaped grinding wheel '26 with an article it) abuttingrefer ence surface 28 of the mandrel where a pin.29 enters aperture 14.

The Wheel 26 has a radial face 27 adapted to engage lip 12 of the article, and ismounted on shaft 31 of motor 32 fixed to carriage 30 mounted slidably on. guides 33 of .a table 34. Bracket 22 is mounted on andmovable with-carriage 30. A valve 36 forsupplying coolant to wheel 26 through hose 37 and nozzle 38 mounted on table 34 opens supply line 39 when control member 40 on carriage-30 is moved to right.

Articles 10 are fed seriatim to the bottom of chute 42 where a permanent magnet 33 is adapted to lift each leading article from the chute and transfer it to arbor 15.

The magnet 43 has a U-shaped body 41 with oneleg thereof fixed to a rocker arm 44 which is fixedly mounted on a rocking shaft 45. There are. companion arcuate members 46 (Fig. 2), with cam-like surfaces 47 (Fig. 1),

centered on the shaft 45 and movable therewith to straddle the mandrel 15 to eject each ground article 10- from-the mandrel and cause it to drop down a chute 48- while the next article to be ground is moved toward.

the mandrel by the magnet 43. The smaller or inner member 46 is fixed to the arm 44 while the larger or outer memberdfi is fixed to the adjcent outer leg of the body 41. Arcuate offset pole pieces 49 (Figs. 1 and 2) of the legs of the magnet &3 are disposed in their receiving positions to enter an open side portion of the chute 42 (Figs. 1 and 2) to engage and remove the leading article from the chute. The pole pieces 4?, following the arcuate members 46 in the feeding, rocking motion of the arm 44 and the shaft 45 are caused to straddle or move on each side of the mandrel to position each article between.-

and in alignment with the mandrel and the holding unit 59. Arm 44 is linked with unit 50 so that, after the magnet straddles the end of mandrel 15to position the'article between the mandrel and unit 5% shaft 45 is moved axially to cause the magnet 43 to'move the article r on the "mandrel. This isefifected by a yoke 51 connected to a collar 52 on shaft 45 and a collar 53 on a shaft 54- rotatably supporting the. unit 5%; The unit Stihas an outer shell 55 apertured at 56 for an abutting element 57' having an outer surface 58 positioned to engage the adjacent outer surface of article "19, a convexed surface 59 and 'a flange 60 to normally engage the outer shell. The surface 59 of elementSl is nested in'a concave depression 61 of a member 62 normally urged outwardly by a spring 63. This structure permits surface 58 to engage and lie flushwith theouter surface of the article although it may benecessary for the elem'ent 57 to rock or move inthe depression 61.

Astheyoke 51 is movedxto the left, as viewed in Fig. 1, to place the article-moving with the-magnet 43- and the arm 44, on the mandrel, anarm7 fixed to the yoke moves a -rod '6 to the letttomove-arelieved non blocking por-' tion 1 out of chute 42 and a blocking portion 2 of rod 6 into the chute to block articles above the portion 2. Simultaneously, arm 7 moves a blocking portion of a rod 4 out of the chute and a relieved non-blocking portion 3 into the chute to permit the lowest article to move to the bottom of the chute. By viewing Fig. 2 it will be noted that the rods 4 and 6 are circular in cross-section and that they are movable longitudinally in like apertures in the chute, the ends of the apertures, in the sides of the chute, being circular in cross-section while the intermediate portions of the apertures are semi-circular in cross-section. The term block portion 25 defines a full non-reduced portions of the rods which, when in the path of the articles in the chute will stop advancement of the article or articles in the chute as shown at 5 in Fig. 2. The relieved non-blocking portions 1-3 defines portions of the rods 4 and 6, as shown at 1 in Figure 2, with their upper halves removed to leave flat surfaces lying in the plane of the surface of the chute on which the articles roll so that the leading article may move over the relieved non-blocking portion 3 when this portion is in the chute and the next leading article may move over the relieved non-blocking portion 1 when this portion is in the chute. Arm 44 then is returned to its lowest position, and then yoke 51 pulls rods 4 and 6 and arm 44 back to the right. On the start of the feed stroke of arm 44, the legs of the body 41 moving therewith lifts a side portion 8 of chute 42 pivoted on a pin 9, and then portion 8 falls back to retain the next article in the chute prior to the arrival of that article. Arm 44 with the body 41 and the projections 49 clear the portion 8 completely on their return stroke due to axial movement of the shaft (hereinafter described) to move them laterally away from the portion 8.

The driving mechanism for the apparatus (Figs. 5, 6, 7 and 8) includes a motor having pulleys 66 and 67 mounted on the ends of its shaft. The pulley 66 drives the endless belt 25 for driving the mandrel 15 while pulley 67 is connected through a belt 68 and pulley 69 to an input shaft 78 of a speed reducing unit 71. The output shaft '72 of the unit 71 is connected through a flexible coupling 73 to a shaft 74. A Geneva drive member 76 mounted on the shaft 74 is adapted to intermittently move a Geneva driven member 77, which is mounted upon a shaft 78. A gear 79, mounted on the shaft '78 and interengaging a pinion 88 mounted on a cam shaft 81, causes one complete revolution of the shaft 81 for each quarter revolution of the shaft 78. This is due to the ratio between the gear 79 and the pinion 80.

A cam 84 of substantially the contour shown in Figs. 5 and 8 is mounted on the shaft 81. The annular controlling surface 85 of the cam 84 has a roller 86 riding thereon, the roller being supported for rotation at the lower end of a cam lever 87 which is pivotally supported at 38 and connected at 89 to a rod 90 which is slidably mounted in a housing 91. The lever 87 extends through an aperture 92 in the table 34 so that the rod 90, while connected at 93 to the yoke 51, may impart like simultaneous axial movements to the shafts 45 and 54. The collar 53 on the shaft 54 engaged by the yoke 51 is backed up by a spring 95. Other spring means if needed may be provided to hold the cam roller 86 in engagement with the controlling surface 85 of the cam 84.

The shaft 45, which supports the arm 44 including the ejector 46 and the permanent transfer magnet 43, has a pinion 97 mounted thereon adjacent the collar 52 for engagement with a gear segment 98. The gear segment 98 (Fig. 7) is connected through a link 99 to a cam lever 100 pivotally supported at 101 and carrying the cam roller or pin 102 at its lower end for interengagement with a groove 103 of a cam 104.

The segment 98 is pivotally supported at 105 and is rocked between given limits during each cycle of rotation of the cam 104 which is mounted on the shaft 81. The

rocking action of the segment .98 is sufficient to controlthe action of the feeding arm 46 holding it in the position shown in Fig. 1 during the grinding operation and bringing about the other actions to eject the finished or ground article in advance of feeding another article to be ground to the mandrel.

The control means for the grinding wheel 26 is included in the upper portion of Fig. 5 and Fig. 6. The shaft 74 has cams and 111 mounted thereon. The cam 110 is adapted to be driven one complete revolution for each grinding operation and includes a cam groove 11?; to receive the conventional cam roller (not shown) supported at 114 on a cam lever 115. The cam lever 115 is pivotally supported at 116 by any suitable means (not shown) and has its outer end pivotally connected at 117 to an element 118. The element 118 is apertured to receive parallel rods 119, the ends of which are firmly secured at a head 120 and a foot 121. The foot 121 is secured in any suitable manner to a bracket 122 Figs. 1

' and 5. The bracket 122 may be of any desired structure to provide a positive connection between the foot 21 and the carriage 3t). Springs 123 disposed concentric with the rods 119 and interposed between the element 118 and the foot 121 normally urge the element 118 against the I head 128 but permit movement of the element on the I threaded bracket 138 fixed to the table of the machine.

The spindle 128 has a pinion 131 fixed thereto for interengagement with a gear or gear segment 132. The gear 132 is rotatably mounted on a spindle 133 and connected through a link 134 to a cam lever 135 pivotally supported at 136 and under the control of a cam groove 137 in the earn 111.

Considering now the operation of the apparatus, let it be assumed that the apparatus is in operation grinding the article shown in Fig. 1 with the feeding or transfer arm 46 in the position shown in Figs. 1 and 2. At the completion of the grinding operation, the synchronized driving mechanism will cause movement of the grinding wheel 26 and its driving motor 32 to the left (Fig. 1) and movement of the rod 98 through action of the cam 84 to the right moving the holding unit 50 free of the finished article and moving the permanent magnet 43 toward and into engagement with the leading article 10 in the chute 42. This may be defined as the starting of a new cycle of operation of the apparatus. When the magnet 43 of the transfer arm 46 has been moved into engagement with the leading article of the chute the cam 104 will cause actuation of the segment 98 to rotate the pinion 97 first in one direction to rock the shaft 45 to move the article 18 from the chute and position it adjacent and in front of the mandrel 15. During this action of the transfer armthe finished article which has been released by the holding unit 58 if tending to remain on the mandrel will be forced therefrom through the action of the cam-like surfaces 47 of the transferarm. The pole pieces 49 of the magnet 43 straddle the mandrel 15 to initially position the cupshaped article 10 in front of the mandrel and as the holding unit 50 is again moved toward the mandrel, the transfer arm with the magnet 43 will move the article longitudinally of the mandrel, maintining the accurate position of the article with the aperture 14 in alignment with the pin 29 untilthe article is positioned with its inner surface 11 engaging the reference surface 28 of the mandrel. At this time, the holding unit 50 is positioned to engage the outer surface of the article while the transfer arm is moved free essence movement of the shaft 45 withoutdisengagingthepinion 97 therefrom.

The construction of the holding unit 50is such that the outer surface as of the abuttinggelemen't 57 may lie flush With the outer bottom surface of the article 10 and apply uniform pressure thereto originating in the spring 95 although the inner and outer surfaces of the article may not be parallel. The timed relations of these various movements in ejecting a finished article and positioning another article for grinding occur While the grinding Wheel is aWay from the grinding position. However, When the new article is in position for grinding a fast motion is imparted to the carriage 3% of the grinding Wheel and its driving motor to bring the grinding Wheel rapidly toward the article and'then a slow feeding motion is imparted .to the grinding Wheel carriage 3t) during'the actual grinding operation. These combined actions are brought about through the camslltlandlll. The cam llflwill actuate its lever li5to move the-element 118 rapidly in a direction to move the thrust bearing. 127 intoengage ment with the pinion 131. During this portion of the operation the element 113 is forced against the springs 119 moving the bracket 122 and the motor carriage 30 with its grinding wheel 22 apredetermined distance to close the gap between the grinding 'surface'of the Wheel 26 and the surface 12 of the article to be ground. This action is sufficient to locate theelement 118*away from the head 12th so that whenthe cam 111 is actuated so as to rock the gear 332. in one direction to rotate the pinion 13?, in a direction to drive the threaded hollow shaft 128, the result will produce a slow feeding motion of the grind ing wheel and its motor. This motion is the result of a force stored in the springs 123 but is regulated solely by the driving motion applied to the threaded shaft 128 originating in the earn 111. This action is such that the feeding motion may continue a predetermined distance to grinding the surface 12 to Within a predetermined distance of the inner surface 11 assuring a result wherein these surfaces will be parallel. When this controlling motion of the slow grinding feed has been completed, the cam 111 will return the threaded shaft to'its starting position so that during the next rapid feed of the grinding Wheel, the Wheel will be stopped in its rapid feed closely adjacent the next article to be ground. The extreme for Ward or feeding movement of the carriage 39 may be varied by adjustment of the bushing 129 in the bracket 130.

It is to be understood that the above described arrangements are simply illustrative of the application of the principles of the 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. An apparatus for grinding articles comprising a rotatable mandrel having a flat reference surface at one end thereof lying in a plane perpendicular to the mandrels axis, means actuable to move cup-shaped articles singly into alignment with the mandrel and to move the articles axially of the mandrel to position a flat inner bottom surface of each article in engagement with the flat reference surface of the mandrel, a rotatable grinding Wheel having a flat article engaging surface parallel With the flat reference surface of the mandrel, and means to cause relative axial movement of the grin-dingwheel and the mandrel to cause the flat surface of the wheel to grind the lip of each cup-shaped article until its ground surface is fiat and parallel with the-flat inner bottom surface thereof.

2. An apparatus for grinding. articles comprising a rotatable mandrel having a flat reference surface at one end thereof lying in a"planeperpendicular to the mandrels axis, means actuable to move cup-shaped articles singly into alignment with the mandrel and to move the articles axially of the mandrel to position a flat inner bottom surface "of each' article -'in engagement witli fitlie flat reference surface of the-mandrel, means-actuabletd hold the articles singly in close engagement with the reference surface, a rotatablegrindingwheel having a flat article engaging 'surface parallel with the flat' reference surface of the mandrel, and means to cause relative axial movement of the grinding wheel and 'the mandrelto cause the fiat surface of the -'wheel to grind the 'lip'of each cup-shaped article until its ground surface is flat and parallel With the flat inner bottom surface thereofi 3. An apparatus for grinding articles comprising a-rotatahle mandrel having a reference surface at one-end thereof, means actuable to move cup-shaped articles singly into alignment with'the'mandrel and to move the articles axially of the mandrel to position an inner bottom" surface of each article in engagement with the reference surface of tl e mandrel, an element adapted to engage the outer bottom surface of each cup-shaped article-under pressure and be caused to shift its position until its engag ing surface is parallel Withthe outer bottom surface and to apply a given force'thereto to hold the inner bottom surface in close engagement With the reference'surface; a rotatable grinding-Wheel having an article engaging surface parallel with the reference surface of the'mandr'el,

arm parallel with the mandrel to causethe locati'ng pin' to enter the apertures of the articles singly and the innerbottom surfaces to engage and lie parallel with the refer-' ence surface singly, means actuable to holdthe articles singly against the reference surface of the mandrel, a r0-" tatable grinding Wheel having an article engaging surface parallel with the reference'surface of the mandrel, and means to cause relative axial. movement of the grinding wheel and the mandrel to cause saidsurface of the Wheel to grind the outer surface of the lip of each cup-shaped article until the ground surface is parallel With the inner bottom surface thereof.

5. An apparatus for grinding articles-comprising a rotatable mandrel having a reference surface and a locating pin disposed at one end thereof, an arm actuable to movecup-shaped articles having apertures in the bottoms there'- of singly into alignment with the mandrel with the aperture in alignment With the locating pin, means to movethe arrn parallel with the mandrel to cause the locating pin to enter the apertures of the articles singly and-the'innerbottom surfaces to engage and lie parallel Withthe reference surface-singly, means actuable-tohold-the"articles singly against'the reference surface of the 'mandrel,*a'-rotatable grinding Wheel mounted for axial movementrel'a tive to an article on the mandrel, driving means for the mandrel, a clutch adapted when engaged 'tooperatively connect the mandrel and the driving means, means-to move the grinding Wheel into engagement with the lip of the article on the mandrel, and means-responsive tothe movement of the grinding Wheel to actuate the clutch into and out of engagement.

6. An apparatus for'grincling articles 'comprisinga rotatable mandrel havinga reference surface and a locating pin disposed at one end thereof, an arm actuable to move cup-shaped articles having apertures in the bottoms there of singly into alignment with the mandrel with the aperture in alignment with the locating pin, means to'movethe arm parallel with the mandrel tocause the locatingpin'to enter the apertures of the articles singly and the inner bottom surfaces to engage and lie parallel with the reference surface singly, means actuable to hold the articles singly against the reference surface of the mandrel, a rotatable grinding wheel mounted for axial movement relative to an article on the mandrel, driving means for the mandrel, a clutch adapted when engaged to operatively connect the mandrel and the driving means, means to move the grinding wheel into engagement with the lip of the article on the mandrel, and means responsive to the movement of the grinding wheel to cause engagement of the clutch prior to the grinding wheel reaching the article on the mandrel.

7. An apparatus for grinding articles comprising a rotatable mandrel having a free end, means to feed circular articles successively to a receiving position, a magnet having a body portion and laterally offset pole pieces, an arm to support the magnet mounted for rocking movement about an axis parallel with the mandrel, for movement, and means to rock the arm and move it axially to move the magnet relative to the receiving position to cause it to pick up an article therefrom, move it into alignment with the mandrel and while the magnet straddles the mandrel move the article axially of the mandrel onto the free end thereof,

8. In an apparatus for grinding articles comprising a rotatable mandrel having a free end to receive successive circular articles to be ground, means to feed the articles successively to a receiving position spaced from the mandrel, a spindle disposed parallel with the mandrel and supported for rocking and axial movement, an arm mounted on the spindle, a magnet having a body mounted on the arm and offset pole pieces positioned to pick up an article at the receiving position and straddle the mandrel tolocate the article in alignment with the free end thereof, and means to impart alternate axial and rocking movements to the spindle and arm to cause the magnet to attract an article at the receiving position, move it into alignment with the mandrel, move it onto the end of the mandrel and move free of the article.

9. In an apparatus for grinding articles comprising a rotatable mandrel having a free end to receive successive circular articles to be ground, means to feed the articles successively to a receiving position spaced from the mandral, a spindle disposed parallel with the mandrel and supported for rocking and axial movement, an arm mounted on the spindle, a magent having a body mounted on the arm and oifset pole pieces positioned to pick up an article at the receiving position and straddle the mandrel to locate the article in alignment with the free end thereof, means to impart alternate axial and rocking movements to the spindle and arm to cause the magnet to attract an article at the receiving position, move it into alignment with the mandrel, move it onto the end of the mandrel and move free of the article, and a reciprocable element movable to engage and hold the article on the end of the mandrel.

10. In an apparatus for grinding articles comprising a rotatable mandrel having a free end to receive successive circular articles to be ground, means to feed the articles successively to a receiving posit-ion spaced from the mandrel, a spindle disposed parallel with the mandrel and supported for rocking and axial movement, an arm mounted on the spindle, a magnet having a body mounted on the arm and oifset pole pieces positioned to pick up an. article at the receiving position and straddle the mandrel to locate the article in alignment with the free end thereof, mean-s to impart alternate axial and rocking movements to the spindle and arm to cause the magnet to attract an article at the receiving position, move it into alignment with the mandrel, move it onto the end of the mandrel and move free of the article, and an arcuate member mounted on the arm to move a ground article free ,of the mandrel in advance of the magnetpositioning the article carried thereby in alignment with the mandrel.

11. *In an apparatus for grinding articles comprising a rotatable mandrel having a free end to receive successive circular articles to be ground, means to feed the articles successively to a receiving position spaced from the mandrel, a spindle disposed parallel with the mandrel and supported for rocking and axial movement, an arm mounted on the spindle, a magnet having a body mounted on the arm and offset pole pieces positioned to pick up an article at the receiving position and straddle the mandrel to locate the article in alignment with the free end thereof, means to impart alternate axial and rocking movements to the spindle and arm to cause the magnet to attract an article at the receiving position, move it into alignment with the mandrel, move it onto the end of the mandrel and move free of the article, and means movable by the spindle, moving means to cause articles to advance to the receiving position successively.

12. In an apparatus for grinding articles comprising a rotatable mandrel having a free end to receive successive circular articles to be ground, means to feed the articles successively to a receiving position spaced from the man drel, a spindle disposed parallel with the mandrel and supported for rocking and axial movement, an arm mounted on the spindle, a magnet having a body mounted on the arm and offset pole pieces positioned to pick up an article at the receiving position and straddle the mandrel to locate the article in alignment with the free end thereof, means to impart alternate axial and rocking movements to the spindle and arm to cause the magnet to attract an article at the receiving position, move it into alignment with the mandrel, move it onto the end of the mandrel and move free of the article, a rotatable grinding Wheel supported for axial movement, and means to move the grinding wheel relative to the mandrel to grind a face of the article.

13. In an apparatus for grinding articles comprising a rotatable mandrel having a free end to receive successive circular articles to be ground, means to feed the articles successively to a receiving position spaced from the mandrel, a spindle disposed parallel with the mandrel and supported for rocking and axial movement, an arm mounted on the spindle, a magnet having a body mounted on the arm and offset pole pieces positioned to pick up an article at the receiving position and straddle the mandrel to locate the article in alignment with the free end thereof, means to impart alternate axial and rocking movements to the spindle and arm to cause the magnet to attract an article at the receiving position, move it into alignment with the mandrel, move it onto the end of the mandrel and move free of the article, a rotatable grinding wheel supported for axial movement, means to move the grinding Wheel relative to the mandrel to grind a face of the article, driving means for the mandrel including a normally engaged clutch, and means under the control of the support for the grinding Wheel to disengage the clutch. when the grinding wheel is moved away from the article.

References Cited in the file of this patent UNITED STATES PATENTS 1,008,784 Cahill Nov. 14, 1911 1,736,159 Johnson Nov. 19, 1929 1,926,959 Quimby Sept. 12, 1933 1,945,662 Smith Feb. 6, 1934 2,092,895 Stevens Sept. 14, 1937 2,117,917 Silven May 17, 1938 2,229,312 Silven Jan. 21, 1941 2,406,526 Reynolds Aug. 27, 1946 2,671,293! Grobey Mar. 9, 1954 FOREIGN PATENTS 273,013 Germany Apr. 16, 1914

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