US2934864A

US2934864A - Belt-grinding machine

Info

Publication number: US2934864A
Application number: US782501A
Authority: US
Inventors: Karbowski Sylvester
Original assignee: PROGRESSIVE TOOL AND Manufacturing CO
Current assignee: PROGRESSIVE TOOL AND Manufacturing CO
Priority date: 1958-12-23
Filing date: 1958-12-23
Publication date: 1960-05-03
Anticipated expiration: 1977-05-03

Description

May 3, 1960 s. KARBOWSKI BELT-GRINDING MACHINE 4 Sheets-Sheet 1 Filed Dec. 23, 1958 INVENTOR Ha rbowsfi i Sylvester May 3, 1960 s. KARBOWSKI BELT-GRINDING MACHINE Filed Dec. 25, 1958 4 Sheets-Sheet 2 INVENTOR Sq/vester Karbows/{i 480M r @cvrfiomw ATTORNEYS May 3, .1960 s. KARBOWSKI 2,934,864

BELT-GRINDING museum 4 Sheets-Sheet 3 Filed Dec. 23, 1958 INVENTOR Sylvester Harbocus/ii ATTORNEYS S. KARBOWSKI BELT-GRINDING MACHINE May 3, 1960 Filed Dec. 23, 1958 4 Sheets-Shag: 4

1 N VENTOR Ha rbowshi ATTORNEYS BELT-GRINDING MACHINE Sylvester Karbowski, New Haven, Conn., assignor to Progressive Tool & Manufacturing Company, East Haven, Conn., a partnership Application December 23, 1958, Serial No. 782,501

9 Claims. (Cl. 51-141) One object of the invention is to provide an improved grinding machine of this type.

Another object is to provide a beltgrinding machine having great flexibility of operation.

Another object is to provide, in such a machine, an angularly adjustable grinding head and improved means for gauging the degree of adjustment of the head.

Still another object is to provide an angularly adjustable grinding head having, in projecting relation therefrom, interchangeable belt-backing members.

In the drawings:

Fig. l is a side elevational view of a belt-grinding machine embodying the invention;

Fig. 2 is a top plan view of the machine;

Fig. 3 is a vertical sectional view taken on line 3-3 of Fig. 1;

Fig. 4 is an enlarged sectional view taken on line 4-4 of Fig. 3; i

Fig. 5 is a sectional view taken on line55 of Fig. 3;

Fig. 6 is a sectional view taken on line 6-6 of Fig. 1;

Fig. 7 is an elevational rear view of one of the projecting belt-backing members;

Fig. 8 is a side elevational view; partially in section, illustrating the belt-backing member of Fig. 7;

Fig. 9 is a view similar to Fig. 8, but illustrating a beltbacking member of somewhat different form and dimensions than that shown in Fig. 8, and interchangeable with the latter; v

Fig. 10 is a fragmentary view similar to. Fig. 7, but illustrating the backing member of Fig. 9;

Fig. 11 is a diagrammatic view on a smaller scale illustrating the belt-grinding machine grinding an external surface of an article; and

Fig. 12 is a diagrammatic view on a still smaller scale illustrating the belt-grinding machine grinding the internal surface of an article. a

In the drawings, the reference numeral 10 indicates the support or table of the machine. In the illustrated form this table is of oblong form and is provided at one end portion with an upright standard 11 fixed thereto. At the otherend portion thereof the table 10 is provided with a fixed upstanding block 12. A removable worksupporting member 13 has a depending block 14 fixed thereto and slidable on the block 12 lengthwise of the table. The block 14 may have a rearwardly projecting part 15 provided at its rear extremity with a pointer 16 and having at the rear portion thereof a dependingele ment in fixed relation thereto and supporting a screw 17 in axially fixed relation thereto. The screw 17 is arranged lengthwiseof the table and has at the rear of the depending element 20 a hand wheel 21 fixed thereto. The forward end portion of the screw 17 is threaded in a bore 22 provided in the block 12. It will be manifest from the foregoing that the operation of the hand wheel 21 effects nited States Patent 0 adjustment of the work-supporting member 13 lengthwise of the table. The hand wheel 21 may be provided with circumferential calibrations 21 (see Fig. 2) cooperating with the pointer 16 to indicate the degree of movement of the work-supporting member as it is shifted longitudinally of the table by operation of the hand wheel. A conventional manually operated clamping member, indicated generally at 23, is arranged transversely of the table 10 and extends through the blocks 12 and 14 to clamp the blocks to one another so that the work-supporting member 13 may be held in adjusted position during a grinding operation.

The upright standard 11 fixed to the table 10 extends into a vertically arranged tubular part 24 which is movable up and down on the standard 11. The tubular part 24 has a fixed closure element 25 at its upper end and a hand wheel 26 is journaled in the element 25 in axially fixed relation thereto. The hand wheel 26 is fixed to one end of a screw 27 which extends downwardly in a bore 28 in the standard 11 and having a threaded portion 28 The arrangement is such that operation of the hand wheel 26 effects vertical adjustment of the tubular part 24. At the upper end portion thereof the tubular part 24 carties in fixed relation a horizontal projecting arm 29 which, at its distal end, has an offset portion 30 which is thickened and which may have the form best shown in Figs. 2 and 3. The thickened portion 30 of the arm may be recessed, as at 30*, to reduce the weight of the arm. The arm 29 extends rearwardly from the tubular part 24 and lengthwise of the table 10. Adjacent one side thereof the thickened and offset portion 30 of the arm is provided with a longitudinal bore extending therethrough to receive, in slidable but non-rotatable relation, a motor support 31 of elongate form. A screw 32 is threaded in the threaded portion 33 of a bore 33 in the support 31 to effect adjustment of the motor support 31 lengthwise of the arm 29 and the table 10, the screw being supported in axially fixed relation by a part of the arm portion 30 and being provided with a hand wheel 34 to effect rotary movement of the screw. An electric motor 35 is supported by the support 31 in a manner whichwill appear hereinafter. The motor 35 has an output shaft 36 which extends through a horizontally elongated slot 37 in the arm 29, the output shaft 36 having a pulley 38 thereon to drive and endless grinding belt 39. It will be understood from the foregoing that the slot 37 in the arm provides clearance for the output shaft 36 of the motor when the motor is adjusted lengthwise of the arm.

The motor 35 has a fixed attaching plate 40 clamped to a plate 41 by screws 42 which extend through corner flanges 43 overlying portions of the plate 40 and fixed to the plate 41, as shown in Figs. 1 and 2. As shown in Fig. l, the plates 40 and 41 are arranged vertically. A horizontally disposed plate 44 extends between the upper pair of corner flanges 43 and receives trunnion members 45 (see Fig. 2) pivoting the plate 41 for vertical swinging movement on the plate 44. The plate 44 is supported on the upper edge of a plate 46 arranged vertically in spaced relation to the plate 41. The plate 44 is pivoted to the upper edge of the plate 46, as at 47, the pivot (see Fig.2) being disposed adjacent one side edge of the plate 46- and the arrangement being such that the plate 44 may swing horizontally on the plate 46. The central portion of the plate 46 is fixed by any suitable means to the forward end of the motor support 31. To adjust the plate 44 angularly with respect to the plate 46, the plate 44 is provided with a flange 48 carrying, in axially fixed relation thereof, an adjusting screw 49 threaded into the plate 46 adjacent the side thereof remote from the pivot 47.

To control the swinging movement of the plate 41 on the plate 44 the arm 29 carries a conventional pressure device, indicated generally at 50, and of the adjustable type, having a plunger 51 bearing against a lower portion of the plate 41 to urge the latter in a generally forward direction. It will be apparent from the foregoing that the pivotally mounted plate 41, swingable on the trunnion members 45 and under the control of the pressure device 50, mounts the motor 35 in the manner tending to lessen or absorb shock or strain imposed on the belt 39. The pivotal plate 44, mounted on the plate 46 and controlled by the adjusting screw 49, permits movement of the motor to adjust the angular position of its driving pulley 38 in accordance with the run of the belt 39.

The grindingbelt 39 is directed over an idler pulley 52 provided on an angularly adjustable grinding head, indicated generally at 53, mounted on the portion 30 of the arm 29. An idler pulley 54 is provided on the head 53. While, in the operation of the machine, the belt always passes over the pulley 52, the belt may or may not be trained over the pulley 54, depending upon the nature of the grinding operation, as will appear hereinafter. The head 53 is provided with an elongated, projecting beltbacking member, indicated generally at 55, having one end removably secured to the head and having a roller 55* at the other end thereof. The grinding belt 39 rides over the length of the backing member 55 and is trained over the roller 55*. The

pulleys

38, 52 and 54, as well as the roller 55*, may be crowned to facilitate the centering of the belt on the pulleys and the roller. As shown in Fig. 1, the belt passes from the driving pulley 38 to the idler pulley 52 and then over the roller 55 The belt may return directly to the driving pulley from the roller 55 or, if the grinding operation requires it, the belt may pass over the idler pulley 54 (as shown in broken lines in Fig. 1) before returning to the driving pulley. To slacken the belt 39 sufficiently to train it over the pulley 54 the motor carrying the driving pulley must be shifted rearwardly or outwardly on the arm 29 by operation of the hand wheel 34.

Turning to the details of the grinding head 53 and the parts associated therewith, it will be seen that, as shown in Fig. 5, the grinding head may be of rectangular outline. The head may take the form of a rather thin block and may be mounted on the thickened portion 30 of the arm by a shaft 56 extending transversely through the last-mentioned portion of the arm and revoluble therein. The shaft 56 is inserted in the arm 29 from the right side of the latter, as viewed in Fig. 3, and has a fixed collar 57 which may abut the last-mentioned side of the arm when the head 53 is clamped to the arm. The left end of the shaft as viewed in Figs. 3 and 6 may be threaded, as at 58, and received in a correspondingly threaded bushing 59 fixed in the grinding head. The shaft 56 at the side of the arm at which the collar 57 is disposed, has fixed thereto a crank arm 60 for manipulation by the operator of the machine. The arrangement of the shaft 56 is such that it normally servesto clamp the angularly adjustable head 53 against the corresponding side of the arm 29. However, when the crank arm 60 is rotated by the operator in a direction to tend to unt'hread the shaft 56 from the head-53, the clamping pressure of the shaft 56 is removed and the head 53 may be angularly adjusted with respect to the arm 29 and the shaft 56 on which the head is pivoted. The manner of effecting angular adjustment of the head 53 will appear hereinafter.

The inner face of the block forming the head 53 may be recessed, as at 61 and 62, to reduce the weight of the head. The inner face of the head is also provided with upwardly spaced

grooves

63 and 64 arranged in parallel relation to one another and extending generally lengthwise of the arm 29. The rear end of the groove 64 terminates in a recess 64* in the rear edge of the head 53, while the rear end of the groove 63 terminates in a recess 63 formed in the rear edge of the head. The

recess 64- provides a rearwardly facing shoulder 64 on the head and the recess 63 provides a rearwardly facing shoulder 63 on the head. The groove 64 in the head receives a correspondingly shaped slide 65 flush with the inner face of the head while the groove 63 receives a similar slide 66, the slides being arranged for lengthwise movement in their respective grooves. The rear end of the slide 66 carries, at right angles and in fixed relation thereto, an arbor 66 for the idler pulley 54. The slide 65 carries, in like manner, an arbor 65 for the idler pulley 52. The

arbors

65 and 66 extend through the recesses 64* and 63 respectively. The shoulder 69 provides an abutment for the arbor 65 to limit forward adjustment of the idler 52 carried by the slide 65. The shoulder 63 serves as an abutment for the arbor 66 to limit forward adjustment of the idler pulley 54- carried by the slide 66. As shown in Fig. 5, a clamping screw 68 extends downwardly in the head 53 from the top thereof to clamp the slide 65 in adjusted position. As shown in the last-mentioned view, a longer clamping screw 69 is similarly arranged in the head 53 to clamp the slide 66 in adjusted position.

To adjust the head 53 angularly with respect to the arm 29 and the work-supporting member 13 once the head has been unclamped from the arm 29 by operation of the crank arm 60, the head is provided with a stub shaft 79 fixed thereto and extending into a' recess 71 in the thickened portion 3-6 of the arm. As best shown in Fig. 4, the recess 71 is elongated lengthwise of the arm 29 and provides vertical clearance for the shaft 70 so that the head 53 may be .angularly adjusted within limits. A compression spring 72 carrying a follower '73 is interposed between the. forward endof the elongated recess 71 and the stub shaft 76 to urge the shaft generally rearwardly so that the head 53 is angularly biased. The follower 73 of the spring may bear against a flat 76* pro- 4 vided on the shaft 70 best shown in Fig. 5. An adjus-tin screw '75 ('see Fig. 4) is threaded forwardly through the rear or distal end of the aim 29 to bear against the stub shaft 76. By turning the adjusting'screw '75 in a direction to feed 'it forwardly, the stub shaft '70, against the pres sure of the spring 72, may be moved generaliy forwardly to effect movement of the head 53 in a counterclockwise direction as viewed in Fig. 1. When the adjusting screw 75 is turned in the other direction, that is, in a direction to retract it, the stub shaft 71 under the influence of the spring 72, follows the screw 75 and clockwise movement of the head 53 is effected. Thus it will be understood that the spring 72 and the follower 73, together with the adjusting screw 75, jointly control the angular adjustment of the head 53 through the stub shaft 7 it.

To facilitate the adjustment of the grinding head to the proper angular position before the commencement of a grinding operation, a gauge, indicated generally at 7 is provided to give the machine operator a visual indication of the extent, as in degrees, to which the grinding head is tipped. The gauge 76, which may be of conventional construction, has a dial 78 provided with suitable indicia circumferentially thereof, and the gauge has a pointer 79 for cooperation with the dial and actuated by the usual plunger or feeler 80. As best shown in Fig. 4, the gauge 76 is mounted on the upper surface of the arm 29 and the feeler 80 of the gauge extends downwardly into the arm and into therecess 71 provided in the arm, the lower end of the feeler being engageable with the stub shaft 70. The feeler 80 of the gauge rides on the curved surface of the stub shaft 70 and the arrangement is such that when the shaft 70 is rotated on the axis of the shaft 56, the shaft 70 effects vertical movement of the feeler 80. The vertical position of feeler 80 is indicated by the position of the pointer 79 on the dial 78. After the grinding head 53 is adjusted to the desired position by operation of the adjusting screw 75, the head may be clamped in adjusted position by operation of the crank arm 60.

aasasea The belt-backing member 55 which, when assembled with the grindingrhead- 53 projects downwardly from the latter, is best shown in Figs. 7 and 8. The member 55 includes a bar 82 of rectangular cross section having one end thereof removably secured to an attaching plate 83 by a manually operable screw 84. The attaching plate 83 has a flange 85 to abut an edge portion of the bar 82 and prevent angular movement of the bar 82 relatively to the plate 83. As shown in Fig. 7, the attaching plate 83 is notched, as at 86. A manually operable screw extends into the notch 86 and is threaded into the rear edge portion of the head 53 to removably clamp, the attaching plate 83 to the rear edge of the head 53, as shown in Fig. 5. On the forward face and adjacent the lower extremity thereof, the bar 82 is provided with a forwardly projecting block 87 and is recessed, as at 88. A bifurcated holder 89 is provided to hold the roller 55 on the bar 82, the arms of the holder 89 being disposed at opposite sides of the block 87, as shown in Fig. 7. The holder 89 extends into the recess 88 in the bar 82. The holder 89 is supported on the bar 82 by a bolt 91 having a threaded portion received in a correspondingly threaded bushing 92 fixed in the bar 82. The bolt 91 has a shank .portion extending through a bore 93 provided in the holder 89, the last-mentioned shank portion having clearance with the bore 93. The bolt 91 has a tapered head portion 94 received in a correspondingly formed seat provided in the holder 89. The arrangement of the bolt 91. in the holder 89 permits the holder 89 to be tipped slightly forwardly at its lower end when the bolt 91 is not threaded into the bushing 92 as far as it will go, to hold the holder in flatwise engagement with the bar 82, as shown in Fig. 8, but is loosened suificiently to permit this forward tipping movement, which may be deemed necessary to adjust the roller 55 generally forwardly or rearwardly. To maintain the holder 89 in a tipped position, a screw 95 is provided to .extend through. the holder 89 in threaded relation thereto .so as to bear against the forward face of the bar 82.

The holder 89 is provided with depending ears or lugs 96 which support the roller 55* from its respective ends, adjacent but slightly spaced from the lower extremity of the bar 82. To mount the roller 55 on the lugs 96, the lugs are provided with trunnion members 97, and the trunnion members, in turn, support suitable antifriction members 98 extending into the respective ends of the roller 55 in supporting relation to the latter. To provide as much support as possible for the belt throughout the length of the belt-backing member 55, the rear face of the bar 82 approaches the periphery of the roller 55 This is achieved by curving the lower extremity of the bar 82, as at 100. A portion of the holder 89 is provided with a corresponding curvature, as at 101. To enable the roller holder 89 to be angularly'adjusted on the axis of the bolt 91, after the bolt 91 has first been loosened, the arms of the holder 89 are provided with two adjusting screws 182 which bear against opposite sides of the block 87 on the bar 82.

The belt-backing member 103, shown in Figs. 9 and 10, and which is similar to the belt-backing member 55 and interchangeable with the latter, is of somewhat different form and of smaller dimensions. A narrower grinding belt may be used on the machine when the beltbacking member 103 is employed, and it will be understood that the member 103 is employed on the grinding machine when it is desired to grind or polish smaller surfaces than the surfaces ground by the machine when the backing member 55 is employed thereon. In the form of the backing member shown in Figs. 9 and 10, the roller 104, similar to the roller 55, may be of truly cylindrical form, if desired.

The operation of the belt-grinding machine will be manifest in view of the foregoing description of its construction, To set up the machine for a particular grind- 6. ing operation, it is first-necessary to choose or decide upon a belt of the proper abrasive quality and of the proper width. A belt-backing member must be chosen in accordance with the requirements of the particular job and the width of the belt. The belt-backing member is then attached to the head 53. If an internal surface is to be ground, the idler or guide

pulleys

52 and 54 must be adjusted generally lengthwise of the arm 29 so .that the belt may run smoothly and closely over the rear face of the belt-backing member and rather closely over the roller holder 89 on the forward face of the beltbacking member. The motor-driven pulley 38 may be adjusted lengthwise of the arm 29 by operation of the hand, wheel 34 so that the belt may be slipped over the last-mentioned pulley and then given the proper tension. The grinding head 53, with the belt-backing member attached to it, may then be angularly adjusted to meet the requirements of the particular grinding operation. The driving pulley 38 may also be angularly adjusted in accordance with the run of the belt. The arm 29 carrying the grinding head 53 may be raised or lowered by operation of the hand wheel 26 and the work previously clamped (not shown) to the work-supporting member 13 may be advanced toward or retracted from the beltbacking member by operation of the hand' wheel 21. The motor 35 may then be started to commence the grinding of an internal surface, such an operation being shown diagrammatcally in Fig. 12.

When an external surface of an article is to be ground, the belt is removed from the idler or guide pulley 54 to reduce flexing of the belt. The belt passes directly from the belt-backing member to the driving pulley 38. To remove the belt from the pulley 54, the belt may first be slackened by operation of the hand wheel 34. After the belt has been removed from the pulley 54, it may be tensioned by again working the hand wheel 34. To grind an external surface of an article the arm 29 may be low- .ered to an extent that the belt-backing member extends through .the work-supporting member 13. To provide clearance for the belt-backing member and the belt, the work-supporting member 13 is slotted, as at 13. Such a grinding operation is shown diagrammatically in Fig. 11.

In view of the foregoing disclosure, it will be evident that there is provided an improved belt-grinding machine which may be employed for grinding both external and internal surfaces of articles. One advantage of the beltgrinding machine is its great fiexibilty of operation. A further advantage of the machine is that it includes an angularly adjustable grinding head and improved means for gauging the degree of adjustment of the head. Still another feature of the machine resides in the provision of an angularly adjustable grinding head having, in projecting relation therefrom, improved and interchangeable belt-hacking members.

It will be apparent to those versed in the art that the grinding machine illustrated in the drawings and described above is susceptible of various modifications and changes in details without departing from the principles of the invention and the scope of the appended claims.

What I claim is:

1. A belt-grinding machine comprising a support having front and rear ends, a standard rising from the support at the front end, a horizontally and rearwardly extending arm adjustable up and down on the standard, a grinding head pivotally mounted on one side of the rear portion of the arm for angular adjustment in a vertical plane, means carried by the arm and cooperating with the head for effecting angular adjustment of the latter, a motor-driven pulley, means mounting the motordriven pulley on the arm forwardly of the head, said means mounting the pulley tor rectilinear adjustment along a portion of the arm and also mounting the pulley for angular movement in two planes at right angles to each other, an endless abrasive belt trained over the pulley to be driven by the latter, a belt-backing member on the grinding head, and a pair of guiding rollers mounted on the head to guide the belt relatively to the belt-backing member, the driving pulley being shit-table rectilinearly so that the belt may be disengaged from one of said guide pulleys and run free from the latter.

2. A belt-grinding machine as defined in claim 1, wherein the belt-backing member is of elongate form and projects generally downwardly from the grinding head.

3. A belt-grinding machine as defined in claim 1, wherein a Work-supporting member is mounted on said support below the grindingv head, the work-supporting member being mounted on said said support for adjustment toward and away from the front end of the latter, and the work-supporting member having an opening therein providing clearance for the belt-backing member and the belt. I

4. In .a bah-grinding machine, a driving pulley, an endless abrasive belt trained over the pulley to be driven by the latter, a support, a cantilever member mounted on the support, a grinding head pivotally mounted on the distal end portion of the member for vertical swinging movement, the grinding head having a pulley carried thereby and over which the belt is trained, means carried by said portion of the member and cooperating with the head to effect angular adjustment of the latter on its pivotal axis, and gauge means mounted on said portion of the member and cooperating with the first-named means to provide a visual indication of the degree of angular adjustment of the head.

5. In a belt-grinding machine, :a support, a driving pulley, an endless abrasive belt trained over the pulley to be driven by the latter, a grinding head mounted on the support for angular adjustment with respect to the latter,

a belt-backing member of elongate form having one end thereof removably mounted on the grinding head and having the other end projecting outwardly from the head and having at the last-mentioned end a holder for a roller over which the belt may be trained, the holder being mounted on the member for angular adjustment in two planes which are at right angles to each other, a guide pulley :adjustably mounted on the head for guiding the belt relatively to one side of the belt-backing member, a second guide pulley adjustably mounted on the head for guiding the belt-relatively to the remote side of the belt-backing member, and the driving pulley being adjustably mounted on the support so that the belt may be slackened and tensioned to enable the belt to be disengaged trom one of the guide pulleys and run free from the latter.

6. In a belt-grinding machine, a drive pulley, an endless abrasive belt trained over the pulley to be driven by the latter, a support, a cantilever member mounted on the support, a grinding head pivotally mounted on the distal end portion of the member for vertical swinging movement, a belt-backing member of elongate form projecting from the head in fixed relation thereto and over which the belt is trained, guide means on the head for guiding the belt relatively to the belt-backing member, means carried by said portion of the cantilever member and cooperating with the head to effect angular adjustment of the latter on its pivotal axis, and gauge means mounted on said portion of the cantilever member and cooperating with the first-named means to provide a visual indication of the degree of angular adjustment of the head.

7. In a belt-grinding machine, a drive pulley, an endless abrasive belt trained over the pulley to be driven by the latter, a support, a cantilever member mounted on the support, a grinding head pivotally mounted on the distal end portion of the member, the grinding head having a pulley carried thereby and over which the belt is trained, the head also having a fixed stub shaft in eccentric and parallel relation to the pivotal axis of the head, the stub shaft extending with clearance into a recess formed in said portion of the member, a spring disposed in said recess and urging the head in one rotary direction through pressure on the stub shaft, a screw carried by said portion of the member and bearing against the stub shaft to move the head in the other rotary direction, and means mounted on said portion of the member and cooperating with the head to provide a visual indication of the degree of angular adjustment of the latter.

8. A belt-grinding machine as defined in claim 7', wherein the means for indicating the angular adjustment of the head comprises a gauge carried by said portion of the member and having a movable part riding on the stub shaft.

9. A belt-grinding machine as defined in claim 8, wherein the grinding head is pivoted to the cantilever member by an axially adjustable shaft extending into the member and the head, the shaft being rotatable relatively to the member and to the head and having means thereon to clamp the head to the member when the head is in angular adjusted position.

References Cited in the file of this patent UNITED STATES PATENTS 1,019,066 Mary et al. Mar. 5, 1912 1,257,691 Fraser 'Feb. 26, 1918 1,820,377 Curtis Aug. 25, 1931 1,974,806 Curtis et al Sept. 25, 1934 2,061,607 Andrie Nov. 24, 1936 2,463,287 Krueger Mar. 1, 1949 2,470,615 Grover May 17, 1949 2,573,220 Riedesel et a1 Oct. 30, 1951 FOREIGN PATENTS 85,425 Czechoslovakia Dec. 1, 1955