US2795968A

US2795968A - Eccentric drives, particularly for sewing machines

Info

Publication number: US2795968A
Application number: US286772A
Authority: US
Inventors: Eriksson Allan Herman
Original assignee: Husqvarna Vapenfabriks AB
Current assignee: Husqvarna Vapenfabriks AB
Priority date: 1951-09-13
Filing date: 1952-05-08
Publication date: 1957-06-18
Anticipated expiration: 1974-06-18

Description

June 18, 1957 sso I 2,795,968

ECCENTRIC DRIVES, PARTICULARLY FOR SEWING MACHINES Filed May 8, 1952 I 5 Sheets-Sheet 1 FIGS In vnfo/ AZZan H. Efilksqorz y I W A Hw- June 18, 1957 A. H. ERIKSSON 2,795,958

ECCENTRIC DRIVES, PARTICULARLY FOR SEWING MACHINES S Sheets-Sheet 2 Filed May 8, 1952 Jun 1957 A. H. ERIKSSON ECCENTRIC DRIVES, PARTICULARLY FOR SEWING MACHINES Filed May 8, 1952 3 sh ets-sheei a MVE/VTOI? All/M H. ER/KSSON United States FatentQ ECCENTRIC DRIVES, PARTICULARLY'FOR SEWING MACHINES Allan Herman Eriksson, Huskvarna, Sweden, assignorto Husqvarna V'apenfabriks Aktiebolag, Huskvarna, Sweden, *a'c'orporation 'of Sweden Application May 8, 1952, Serial No. 286,772

Claims priority, application Sweden September 13, 1951 11 Claims. (Cl. 74-571) The present invention refers to'eccentric drives adapted to facilitate an accurate adjustment in the transmission of motion from a rotating shaft by means of an eccentric to a reciprocating member. The driving means in consideration is particularly intended for sewing machines but can be generally used in such cases where a rotary motion is to be transformed into a reciprocating motionv through the intermediary of an eccentric.

For the purpose of changing the eccentricity of an eccentric driving device it is known to arrange an eccentric to be radially displaceable on the shaft, rigidly interconnected wedge members or the like being used for this purpose, which are adapted to be adjusted axially so as to cause said radial displacement of the eccentric. An accurate adjustment of the eccentricity supposes in such case that the wedges fit exactly in the corresponding wedge seats of the eccentric. As a result, the adjustment of the wedges hasrequired a considerable force and also a fine and expensive accuracy in manufacture.

One object of the invention is to obviate said drawback. A further object is to provide an eccentric drive of the type in consideration, wherein an accurateadjustment of the eccentricity is made possible.

The substantial distinguishing feature of the invention resides, aboveall, in that the wedge members or the like have individually a limited mutual mobility in the axial direction while being resiliently actuated in the wedging directions. he mutual mobility of the wedge members provides for facilities in varying the distance between the wedge surfaces of the wedge members and the corresponding wedge seats of the eccentric at the displacement of the latter to alter the eccentricity. In shifting, an incidental reduction of this distance may thus be obtained initially, so that the wedge members can readily slide on the corresponding surfaces of the eccentric. Spring actuation of the wedge members involves that the incidental play is nullified anew, so that the eccentric will be safely retained in its position after an adjustment.

Further features characteristic of the invention will apppear from the following description of a form of embodirnent illustrated in the accompanying drawings.

Fig. 1 shows the eccentric drive in axial section.

Fig. 2 shows a corresponding radial section on line II II in Fig. 1.

Fig. 3 shows a corresponding horizontal projection.

Fig. 4 shows an endwise view of an eccentric slide.

Figs. 5 and 6 show two projections of a spring for the actuation. of the wedge members, said projections being taken at right anglesto each other.

Fig. 7' illustrates the application of the invention to :a sewing machine and shows a vertical section through the machine.

Fig. Sshows a hor'montal projection'of a detail of'the machine: according to Fig. 7.

Fig. 9 shows a transverse section on'the broken line IX-IX in Fig. 7 and Fig. 9a an axial section of apart'of Fig. 9 on an en larged scale.

2,795,968 Patented June 18, 1957 Fig. 10 shows a transverse section on line X-X in Fig. 7.

In Figs. 1-3 of the drawings, 10 designates a rotary shaft, which carries an eccentric disk 14 adapted to be peripherally adjusted and to be secured to said shaft by meansof a screw 12, said eccentric disk permitting of being locked by means of said screw in any suitable angular position on the shaft. The eccentric disk 14 is pro vided with a radial groove 16 in the one lateral surface thereof, said groove receiving an eccentric slide 18 to bedisplaceably guided therein. The eccentric .slide is formed with an eccentric 20 surrounded by an eccentric strap 22 on an eccentric rod 24. Theeccentric 20 has bearing surfaces for slidable engagement with the disk 14. preferably at one side only. A plate 26 secured to the free end surface. of the eccentric 20 keeps the eccentric strap in position on the eccentric against an abutment 28, on theeccentric slide 18, which in turn is retained in the guiding groove of the eccentric disk by means of arcuateiguide bars 30 secured .to the eccentric disk by means of screws 32.

The eccentric slide 18 is provided with mutually

parallel guide surfaces

34, 36 extending obliquely to the shaft 10, said guide surfaces being adapted to guide wedge members 38, 40 displaceable on the shaft and fitting 'displ'aceably into grooves 42, 44, said grooves forming recesses in the slide 18 at the passage opening of the latter'for the shaft 19 '(Fig. 3). The wedge members 38, 40 are actuated by springs 46 which preferably take the form of leaf springs of the configuration shown in Figs. 5 and 6. These -springs are secured to the left end surface of the wedge member 40 in Fig. l and press with their-free end, which is bent outwardly in an unloaded condition, against the corresponding end surface of the wedge member 38. The wedge angle of the wedge members may preferably be selected so as to make the wedge members self-locking in combination with the springs 46, so that the wedge members will not be unintentionally displaced under the influence of the forces in the eccentric rod 24.

The wedge members 38, 40 may be displaced along the shaft by means of an operating member in the form of a sleeve 48 having a pair of radial flanges 50 limiting a circumferentially extending groove and an attachment 52 for acarrier 54, said attachment being formed on the one-end surface of said sleeve and projecting laterally of the shaft (behind the same). The carrier 54 may be adjustably arranged on the attachment 52, for instance by means of screws 51 threaded into the carrier 54 and extendingthrough apertures 53 provided in the attachment, said apertures having a diameter larger than that of the stems of thescrews. The carrier is provided with

pins

56, 58 extending in the transverse direction of the shaft and engaging

recesses

60, 62 in the wedge members 38 and 40 respectively. The diameter of the pins is 'smaller'than the distance between the lateral surfaces of the

recesses

60, 62 intended for cooperation with the pins, so that a slight play is provided between the pins and said surfaces. If the shaft 10 rotates, the whole drive including the operating sleeve 48 will be carried along in the movement, the wedge member 40 being preferably provided with a pin 64 for a rotary movement of said sleeve, said pin-64 bearing against the pin 58 on the carrier 54 duringthe rotary movement. The mode of operation of theeccentric drive as described is broadly as follows:

Fig. 1 shows the device with the eccentric slide in a middle position. corresponding to the eccentricity naught. If'the operatin-g sleeve 48 is displaced to the right in Fig. 1 (the direction of the arrow 66), the wedgememb'ers 38, 40.will:be carried-along in-the movement by means ofithe carrier 54'sozaszto be displaced through 3 the cooperation between the wedge surfaces thereof and the

oblique surfaces

34, 36, the displacement taking place axially into the grooves 42, 44, so that the eccentric shde .18 will be displaced radially in the groove 16 from the zero position to a position corresponding to a certain eccentricity. Displacement of the operating sleeve 48 and the wedge members in the other direction from the middle position by the same distance as before brings about the same eccentricity of the motion, but the radius of the eccentric will now be reversed by 180 in comparison with the former case.

The displacement of the wedge members 38-40 takes place with the aid of the springs 46. At the displacement to the right (the arrow 66) the pin 58 bears on the right hand side of the recess 62 in the wedge member 40, there being a certain play S between said pin 58 and the other side of the recess 62. When the wedge member 40 is displaced under the action of the pin 58, it carries the wedge member 38 along with it by means of the springs 46 hearing on the left end surface of the wedge member 38. The springs 46 tend to keep the wedge member pressed toward the right so far that the left lateral surface of the recess 60 bears on the pin 56 while a play S is provided between the pin 56 and the opposite, that is to say the right-hand lateral surface of the same recess. Should the Wedge member 38 meet with so great a resistance that the springs 46 are unable to displace the wedge member 38, the pin 56 strikes against the right hand lateral surface of the wedge recess so as to positively carry the wedge member 38 along with it.

The cycle of operations will be analogous to the cycle described above when the operating sleeve is displaced to the left.

The mobility of the wedge members relatively to the carrier under the spring action as described involves that a play between the wedge members and the

wedge surfaces

34, 36 in the eccentric slide 18 is entirely eliminated and that the displacement of the wedge members is facilitated, inasmuch as jamming of the wedge members in the wedge grooves is avoided. It is to be noted that the wedge members upon a displacement for the purpose of altering the eccentricity generally adjust them selves so that there will be a play between each pin and the corresponding lateral surfaces in the two wedge members. Only hereby will every play be eliminated between the wedge members and the eccentric slide.

in applying the invention to zigzag sewing machines, the means described may be used for the longitudinal movement of the feed dog and/or the lateral oscillatory movement of the needle bar, particularly if it be supple mented in the manner to be described hereinafter:

In the longitudinal vertical section through the sewing machine provided with two eccentric drives according to the invention as illustrated in Fig. 7, the same reference numerals have been used as in Figs. 1 and 2 for corresponding parts. Here, the shaft constitutes the arm shaft of the sewing machine and thus drives the needle rod 68 of the sewing machine. The eccentric and the eccentric rod 24 are adapted to drive the feeding mechanism of the sewing machine to bring about the longitudinal movement thereof. For the vertical movement of the feeder an eccentric 72 is formed on a hub portion 70 of the eccentric disk 14, said eccentric 72 being surrounded by an eccentric strap 74 on an eccentric rod 76. The longitudinal movement of the feeder must permit of being easily varied to provide for different lengths of the stitches and for difierent feeding directions, and this is facilitated by one of the eccentric drives.

An operating device is provided for the adjustment of the operating sleeve 48 displaceable on the arm shaft 10 and thus of the wedge members for the purpose of varying the eccentricity of the eccentric drive, said operating device consisting of an arm 78, which is swingably mounted on a pin'80 (Fig. 8) on the inside of the .machine housing 82 while being provided with a pin 84 which carries a ball bearing 86 engaging between the flanges 50 of the operating sleeve as shown in Fig. 7. The arm 78 is connected by a link 88 to a crank arm 90, which is splined onto a shaft 92 in a bearing 94 formed on the wall of the machine housing, and is provided with an operating lever 96 on the outside of said wall. The arm 78 is formed with two

curved surfaces

98, 100, the arcuate contours of which converge at a point 102, the radial distance of which from the center of rotation (the pin is smaller than that of any other points of the curved surfaces. A manually adjustable abutment, preferably in the form of a regulating screw 104 fitted into a nut sleeve 106 secured in the wall 82 of the machine housing, is adapted to cooperate with the curved surfaces, so that the arm 78 is permitted at operation forwards and backwards to take angular positions corresponding to the desired length of the stitches, in accordance with the distance to which the screw 104 is screwed into the nut sleeve 106. The screw carries a manipulating knob 108 secured thereto for the operation thereof. The position shown with the screw at the point 102 corresponds to the zero position of the eccentric, that is to say to the stitch length naught. If the screw 104 is screwed out, the arm 78 may be swung in the one or the other direction through an angle, the magnitude of which is dependent on the position of the screw. A stop pin 110 secured in the nut sleeve 106 and extending inwardly toward the screw between two shoulders 112 thereon serves to limit the movement of the screw, so that the curves cannot be swung entirely past the inner end of the screw.

To facilitate operation, a spring 114 may be stretched between a lug 116 on the wall of the machine housing and a pin 118, for example, on the crank arm 90, in a manner such that it will move the link 88 to the right in Fig. 8 in order thus to set the curved surface 98 against the inner end of the screw when the latter is screwed out.

.To adjust the mechanism so that the curved surface 100 will instead be set against the screw, it will be necessary ,to swing the crank arm in a clockwise direction by the eccentric and the zero position of the control curve (98,

) determined by the set screw 104, it might become necessary in mounting to work the curved surfaces. This fitting work, which is frequently troublesome, may be avoided by forming the curved surfaces on a special member 105, which is preferably pivoted about the hearing pin 80, said member being locked to the arm 78, for instance by means of a screw 107 threaded into the arm 78 and extending through a slit 109 in the curved member 105. The member 105 may then be adjusted into its proper position by a small turning adjustment relatively to the arm 78, whereupon locking may be effected by means of the screw 107.

The movements of the

eccentric rods

24 and 76 can be transferred to the feed mechanism of the sewing machine in any suitable manner. In Figs. 9 and 10 the lower end of the eccentric rod 24 is journalled in a crank lever 120 on a longitudinal axis 122 which adjacent to the feed lever 124 is provided with a second crank lever 126 adjustably attached to the shaft and having the feed lever 124 pivotally connected therewith. Reciprocat-ion of the crank lever 120 by the eccentric rod 24 causes reciprocating turning movements of the shaft 122 so that the crank lever 126 obtains a corresponding oscillatory movement and the feed lever 124 a corresponding reciprocating movement horizontally. The lower end of the eccentric rod 76 is journalled on a crank lever 128 keyed to a longitudinal shaft 130 which carries a crank lever 132 adjustably clamped thereto. Said crank lever has a pin 134, which engages a guide 136 formed in the feed lever 124. The eccentric rod 76 imparts an oscillatory movement to the crank lever 128 and thus to the crank lever 132, whereby the pin 134 will reciprocate vertically and thereby impart the vertical movement to the feed dog.

The manual measures for the control of the feeding and thus of the length of the stitches will be very simple with the arrangement described, inasmuch as substantially only the regulating screw 104 requires to be screwed in or out into a position corresponding to the desired stitch length. The spring 114- then keeps the curved surface 98 set against the end of the screw, and in accordance with the movement of the screw the curved arm is then swung in a manner such that the curved surface '93 slides on the end of the screw. At the same time the operating sleeve 48 is moved to the right in Fig. 7 with the aid of the arm 78 and the ball bearing 86 under the influence of the spring power, the wedge members 38, 40 being thus displaced in the same direction in the manner hereinbefore described, so that the eccentric 20 is caused to move radially upwards in Fig. 7 to increase the eccentricity. The crank movement of the eccentric rod 24 is then actuated so that the feeding mechanism provides for an increased stitch length. If it is desired instead to operate backwards and to maintain the adjusted stitch length, it is only necessary to press the operating lever 96 against the action of the spring 114 so that the arm 78 is swung in a clockwise direction in Fig. 7, until the corresponding point on the curved surface 100 strikes against the regulating screw 104 (the

curved surfaces

98, 100 are taken to be symmetrical with respect to the point 102). The operating sleeve 48 and the wedge members 38, 40 are then moved to the left in Fig. 7, while the eccentric 20 is moved downwardly so as to pass the zero position. In other words, the position of the eccentric radius will be reversed by 180 while being of the same magnitude as before.

The eccentric drive adapted to the zigzag motion is analogous with that previously described but differs structurally in several respects therefrom, among other things depending upon the fact that in this case no reverse of the feed direction of the driven element is required.

The eccentric drive obtains its movement by a gear wheel 201 on the arm shaft 10 said gear meshing with a gear wheel 214 of a double size which in turn is peripherally adjustably keyed by a screw 212 to a transverse hollow shaft 210. This shaft has its'one end journalled in a cover 217 in one wall of the machine housing 82 and its other end in a bushing 202 which is keyed in a projecting portion of the opposite wall of the machine housing. An adjustable ring 203 locked to the latter shaft end retains the shaft 210 in an axially fixed position. The shaft 210 presents two longitudinal diametrically opposite slots 204 for a transverse pin 254 in an operating rod 252 displaceable in the shaft 210. The pin 254 can be adjusted about its shaft and be fixed in the adjusted position by a screw 251. One end 256 of the pin is eccentric and engages a transverse recess 260 in the bottom of the wedge 238, a play (for example 0.2-0.35 mm.) being present between the sides of the recess and the pin. The other end 258 of the pin 254 which is concentric with the main portion of the pin engages a circular bore in the wedge 240 the same play being present at this end. Leaf springs 246 of the same construction as those illustrated in Figs. 5-6 are secured to the wedge 240 by a screw 205. The pin 254 entrains the rod 252 as the shaft 210 rotates.

Mounted on the gear wheel 214 analogously with the eccentric slide 18 in Figs. 1-7 is an eccentric slide 218, which carries an eccentric 220 surrounded by an eccentric strap 222 having an eccentric rod 224. The eccentric slide 218 cooperates With the

wedges

238, 240 similarly to the cooperation of the slide 18 with the wedges 38, 40 illustrated in Fig. 1.

For the adjustment of the wedges there is an operating mechanism which, in addition .to the above mentioned pi'n 254 and the operating rod'252, comprises a pressure spring 206 inserted in the bore of the shaft 210, a ball 286 and a shaft 292 having a hand wheel 296. The operating rod 252 is pressed against the ball 286 by the pressure spring 206, the ball in turn engaging an enlarged end portion 207 of the shaft 292. The shaft 292 has exterior screw threads and is fitted into a screw threaded sleeve 208 which is screwed into a cover 209 attached in an aperture in the wall of the machine housing. The cover 209 has a collar 213 surrounding a flange 208a on the screw-threaded sleeve 208*andhaving a stop screw 211. The screw-threaded sleeve may be keyed in an adjusted position by tightening the stop screw 211 at the flange 208a. The collar 213 has graduations, for example in the form'of a number of circumferential grooves 215-located along the collar and corresponding to various breadth of the zigzag seam.

The eccentric rod 224 is articulated toa known oscillatory needle bar frame (Fig. 7) in which the needle bar 68 is displace'ably journalled in a known manner. The oscillatory needle bar frame 150 is journalled in the machine head on a'horiz'ontal shaft 152 and is adapted to be oscillated on said shaft by the eccentric rod 224. Simultaneously the needle bar 68 is reciprocated vertically by a crank mechanism known per se and substantially comprising a crank lever 154 attached to the fore end of the arm shaft 10 and a crank rod 158 journalled on a crank pin 156 of said lever 154, the crank rod 158 carrying a slide block 160 displaceable in a guide 162 which is engaged displaceably byacross pin 164 attached to the needle bar '68-.

The eccentric drive'last described is operated for obtaining different breadths of the zigzag scam in the following manner:

The operating mechanism is suitably set in a zero positioncorresponding'to straight seam, when the hand wheel 296 is entirely "extracted as in the position illustrated in Fig. 9. The enlarged-end portion 207 of the hand wheel shaft 292 now engages the inner end of the screw-threaded sleeve 208. By rotation said sleeve 208 may be adjusted so as to take a position corresponding to the zero position, in which itcan be locked by the set screw 211. By screwing thewheel shaft 292 inward by'rneans of the hand wheel'296, the operating rod 252 may be displaced to the left in Fig. 9, and as a result the pin 254 carries one of the

wedges

238, 240 and, by wayof the springs 246, also-the other of these wedges. Simultaneously the eccentric slide 218 is displaced and the eccentricity changed in the manner previously describedin connection with Figs. 12 so that the eccentric rod 224- obtains a reciprocating motion, the magnitude of which is dependent upon the adjusting position of the operating wheel. The movement is transmitted .to the oscillatory needle bar frame, which imparts a corresponding oscillation to the needle bar'68, and at the same time the needle bar 68 obtains a vertical reciprocation by the arm shaft 10 and the crank mechanism 154-164.

In this eccentric drive there is no need for a reverse of the direction of the eccentric radius. In sewing zigzag seam the needle bar oscillates about a central position corresponding to straight seam. The plays at the

end portions

256, 258 of the pin 254 in the

Wedges

238, 240 can be adjusted to a suitable magnitude by rotation of the pin 254. Such an adjustment corresponds to an adjustment of the position of a carrier 54 in the eccentric drive illustrated in Fig. 2.

Though the eccentric drive first described is mentioned to cooperate with the feed mechanism it may be used also for the zigzag motion. Likewise the eccentric drive last described can be modified to be employed for the operation of feed mechanism in sewing machines and also for other purposes and in other combinations than in sewing machines.

What I claim is:

1. An eccentric driving mechanism for transmitting motion of a rotary shaft, comprising an eccentric, having wedge seats slanting to the shaft, means on the shaft for guiding said eccentric radially relatively to the shaft, wedge members mounted axially displaceably at opposite sides of the shaft and engaging said wedge seats, the wedging direction of one of said wedge members being axially reverse to the wedging direction of the other wedge member, means for resilient actuation of the wedge members in the wedging directions, and operating means for axial displacement of the wedge members permitting limited mutual mobility of the wedge members.

2. An eccentric driving mechanism for transmitting motion of a rotary shaft, comprising an eccentric formed with wedge seats located obliquely to the shaft, means on the shaft for guiding said eccentric radially to the shaft, axially displaceable Wedge members mounted at opposite sides of the shaft for engagement with said seats, the wedge members having reverse wedging directions, an operating member common to the Wedge members for positive actuation of one of the wedge members reversely to the wedge direction, and resilient means for transmitting the actuation of the operating member to the other of the wedge members.

3. An eccentric driving mechanism as claimed in claim 2, in which the resilient means comprises a spring attached to one of the wedge members and engaging the other.

4. An eccentric driving mechanism as claimed in claim 2, in which the resilient means comprises a leaf spring secured to an end surface of one of the wedge members and acting upon an end surface of the other wedge member in its wedging direction.

5. An eccentric driving mechanism for transmitting motion of a rotary shaft, comprising an eccentric formed with parallel wedge seats extending obliquely to the shaft, means on the shaft to guide said eccentric radially to the shaft, axially displaceable wedge members mounted at opposite sides of the shaft for engagement with said seats, an operating member common to both wedge members, entraining means connected with the operating member and engaging both wedges, an axial play being present between engaging surfaces of the operating member and corresponding engaging surfaces of the wedges, and means for resilient actuation of the wedge members in the Wedging directions.

6. An eccentric driving mechanism as claimed in claim 5 in which the entraining means comprise pins projecting in the transverse direction of the shaft, the wedges being formed with recesses for receiving said pins.

7. An eccentric driving mechanism for transmitting motion from a rotary shaft, comprising an eccentric formed with wedge seats one slanting to and the other slanting from the shaft, means for guiding said eccentric radially to the shaft, means to key said guiding means to the shaft to cause the eccentric to rotate with the shaft, wedge members mounted axially displaceably at opposite sides of the shaft and engaging said wedge seats, said wedge members having reverse wedging directions, means for resilient actuation of the wedge members in the wedging directions, an operating sleeve for the axial displacement of the wedge members, the wedge members being movable to a limited extent relatively to said sleeve and to one another, and means for carrying along the sleeve in the rotary movement of the wedge and the shaft.

8. An eccentric driving mechanism for transmitting motion from a rotary shaft, comprising an eccentric formed with wedge seats disposed obliquely to the shaft, said eccentric having radial guide surfaces at its one side, axiallydisplaceable wedge members mounted on a cylindrical portion of the shaft for cooperation with said wedge seats, a carrying member formed with radial guides for engagement with the radial guide surfaces of the eccentric, said carrying member being peripherally adjustably keyed to the shaft, operating means for axially displacing the wedge members relatively to the eccentric to cause radial adjustment thereof for changing the eccentricity of the drive, said operating means comprising resilient means for transmitting its axial operating movement from one wedge member to the other.

9. An eccentric driving mechanism comprising a shaft with an axial bore and slots extending from the exterior surface of the shaft to said bore, guide means attached to the shaft for rotation therewith, an eccentric carried by said guide means and guided for radial adjustment thereon, said eccentric being formed with wedge seats disposed obliquely to the shaft, axially displaceable wedge members mounted at opposite sides of the shaft for engagement with said seats, said Wedge members having radial recesses, and operating means for the axial displacement of the wedge members on the shaft to cause radial displacement of the eccentric for changing the eccentricity of the drive, said operating means comprising an operating rod mounted for axial displacement in the bore of the shaft, a pin attached transversely to said rod and extending with its end portions through said slots into the recesses of the wedge members, play being present laterally between said recesses and said pin end portions.

10. An eccentric driving mechanism as claimed in claim 9 in which one end portion of the transverse pin is eccentric on the pin, the pin being mounted for rotary adjustment in said operating rod, and means being pro- 'vided to lock the pin in its adjusted positions.

11. An eccentric driving mechanism as claimed in claim ,9 and further comprising a screw-threaded operating shaft, a hand wheel keyed to said shaft for rotary adjustment thereof, a sleeve having a screw thread engaged by said shaft, said sleeve being adjustable and adapted to be locked to the machine housing for adjustment of the zero position of the operating means.

References Cited in the file of this patent UNITED STATES PATENTS