US2078408A - Polishing machine - Google Patents

Description

April 27, 1937. T, F PH P, 2,078,408

POLISHING MACHINE Original Filed July 26, 1933 4 Sheets-Sheet l April 27, 1937. T. F. PHILIPPI POLISHING MACHINE Original Filed July 26, 1933 4 Sheets-Sheet 2 April 27, 1937. PH|-| |PP| 2,078,408

' POLISHING MACHINE Original Filed July 26, 1933 4 SheetsSheet 3 3nventor 7 Gttorneg S.

April 27, 1937. T. F. PHILIPPI POLISHING MACHINE Original Filed July 26, 1933 4 Sheets-Sheet 4 lnventor Q2 (Ittorneg5 Patented Apr. 27, 1937 UNITED STATES PATENT OFFICE 682,192. Patent 2,015

,495, dated September 24,

1935. Divided and this application August 19,

1935, Serial No. 36,787

Claims.

My invention relates to polishing machines, and is a division of my copending application Serial No. 682,192, filed July 26, 1933', now Patent No. 2,015,495, issued September 24, 1935 for patent for a Polishing machine of the type wherein the article that is to be polished is moved back and forth under a polishing device by a. reciprocating table. The principal object of this invention is to devise a simple, eflicient and easily operable manually controlled mechanism for reciprocating the work table. The invention consists in the polishing machine and in the parts and combinations and arrangements of parts hereinafter described and claimed.

In the accompanying drawings,which form part of this specification and wherein like reference symbols refer to like parts wherever they occur,

Fig. 1' is a plan view of a polishing machine embodying my invention,

Fig. 2 is a side elevation of'the polishing machine,

Fig. 3' is an end view of the parts located atthe rear end of the machine,

Fig. 4' is a side view of the machine with a number of parts broken away to show the mechanism for driving and reciprocating the work supporting table,

Fig. 5 is a fragmentary plan view of the parts of the machine that support the work supporting 30 table.

Fig; 6 i'sa sectional view along'the line S -Ii' in Fig. 5,

Fig. 7 is an enlarged sectional view along the line 1-! in Fig. 5,

Fig; 8 isa rear view of a resilient link connection between the rear end of a balancing bar and the frame,

Fig. 9 is an enlarged sectional view along the line 99' of Fig. 2',

Fig. 10' is a fragmentary plan View of a mechanism located at the front end of the machine for liftingthe polishing" unit off the work,

Fig. 11 is a sectional view along the line I I-I I in Fig. 10,

Fig. 12 is an enlarged fragmentary side view of the mechanism located at the front end of the machine for stopping the operation of the work supporting carriage,

Fig. 13 is an end view of the parts shown in Fig. 12",

Fig. 14 is a' sectional view along" the line I-4--I-4 in Fig. 13,

Fig. 15 is: a fragmentary plan view of the swivel connection between the control rod and the reversing" mechanism; and" Fig. 16 is a diagrammatic view showing two types of bumpers'that may be polished by the machine together with the corresponding cam plates used to control the movement of the work supporting table in polishing the particular bumpers. 5

The polishing machine shown in the accompanying drawings is especially adapted for simultaneously polishing a plurality of automobile bumpers A having curved ends. In general, said machine comprises a framework having awork 10 table B mounted thereon for supporting: the bumpers A and having two frame arms C'pivotally mounted on the frame work and carrying polishing wheels D adapted to engage and polish the bumpers. top of. a carriage E that is arranged to travel back and forth on the framework to move the bumpers. endwise under the polishing wheels D so that they are polished throughout their" entire length. 20

The framework comprises longitudinal side members or rails I that are fixed near their rear ends to upright side frame members of standards 2 whose bottoms'are shapedv to form short leg members 3. The longitudinal side members I are supported at their front ends by short uprig t members or legs 4 fixed thereto and provided with foot flanges. The longitudinal side members I at their extreme rear ends are rigidly connected by a suitable cross-member 5 fixed to their bottoms; and a plate or shelf 6 extends from standard 2 to standard 2 with. its ends resting on and rigidly secured to the tops thereof. I

The portions of the longitudinal members; I that are located forward of the shelf '6" constitute a track for the carriage E that carries the work table B. The carriage comprises longitudinal side members I that are connected. by two spaced parallel cross-members 8 secured to 40 the tops of said side members I; and flanged wheels 9 run on the side frame members I and are supported in brackets I t! that are fixed to the bottoms of the carriage side members. I near their ends. The work table B is mounted upon the cross angle-irons 8 of the carriage for movement transversely of the direction in which the carriage moves. The work table B comprises a flat top I I having suitable fixtures I2 on its top for removably securing the ends of the bumpers thereto, said fixtures being arranged so that the bumpers will extend parallel to the line of travel of the carriage. Depending from the bottom of the work table top II near each side thereof are a pair of spaced brackets. I 3. 5

The work table B is mounted on 15 Each pair of these brackets has a longitudinal shaft l4 extending through them with wheels I5 fixed on the shaft for running on the cross angle-irons 8 of the carriage frame. One of the shafts l4 extends beyond the front end of the work table B and is provided with a hand wheel Ma for moving the work table transversely. By means hereinafter described, the work table B may be held in fixed position on the carriage E when polishing bumpers of certain types.

The parts that support the polishing wheel supporting arms C, together with the mechanism for driving the polishing wheels D, are supported on top of the shelf 5 at the rear end of the machine. Secured to the top of the shelf 8 near the front edge thereof are suitable bearing brackets I6 that support a cross-shaft ll. Each frame arm C is provided at its rear end with collars l8 that are rotatably mounted on the cross-shaft I! so as to permit free vertical swinging movement of said arm on said shaft. The front or free end of each frame arm C has a shaft is journaled therein on which is mounted the polishing wheel D carried by said arm. Said shaft 59 has a pulley 20 fixed thereon that is driven by a belt El which passes around a pulley 22 fixed on the arm sup porting shaft H. The shaft ll is preferably driven by an electric motor 23 seated on the shelf 6, one end of said shaft having a pulley 2 t fixed thereon that is driven by a belt 25 mounted around a pulley 25 fixed to the armature shaft of the motor 23.

Each frame arm C is supported near its free end by a balancing lever 21 fulcrumed near its center on a bracket 28 that is mounted on an angle iron 29 that extends along the front edge of the shelf 6 with its end secured to the bearings 16 for the-cross-shaft IT. The counterbalancing lever 2'! is connected near its front end to the frame arm C by an adjustable connecting device and is provided near its rear end with a weight 33 that partially counterbalances the frame arm and its polishing wheel D. As shown in Fig. 9, the adjustable connecting device comprises a stirrup 3i pivotally suspended from the front arm of the counterbalancing lever 2'7 and an inverted stirrup 32 pivotally secured to a bracket 33 fixed on the frame arm with an adjusting screw member 34 extending through the bottom portions of the two stirrup members and having a hand wheel 35 fixed thereon between said stirrups. Pivotally secured to the rear arm of each counterbalancing lever 21 rearwardly of the weight 39 thereon is an elongated stirrup 36 (see Fig. 8) that contains a long coil spring 31. Disposed within the coil spring 31 is a pipe 38 whose bottom rests on the closed lower end of the stirrup 36; and slidably mounted within said pipe is a rod 39 whose upper end extends beyond the top of the pipe and has an adjusting nut 40 threaded thereon for engaging the top of said coil spring. By means of this nut, the force exerted by the coil spring 3? is readily varied. The bottom portion of said rod 59 extends through the bottom of the stirrup and is fixed to the upper end of a chain GI whose low er end is attached to the rear cross-member 5 of the framework. By this arrangement, the compression of the coil spring 3? tends to relieve the pressure of the polishing wheel D on the bumper A as it travels up and down the downwardly curved end portions thereof. Accordingly, the effective weight of the polishing wheel on the bumper is substantially equalized throughout the entire length of the bumper in consequence of which an even polishing action is assured over its entire surface. Preferably, removable weights 42 are provided on the front end of the counter balancing lever 21, which weights, together with the adjustable connection between said lever and. the arm frame C, provide a. delicate adjustment for obtaining proper working pressure of the polishing wheel on the bumper.

Connected to the rear end of each counterbalancing lever 2! is a chain 43 that is attached to one arm of a bent lever iethat is pivoted in a bearing 45 fixed to the rear cross-member 5. The other arm of the lever 44 is pivotally connected to the rear end of an actuating rod 46 that extends alongside the longitudinal side member I of the framework and is operatively connected at its front end to a foot treadle lever ll fulcrumed on a pin 43 projecting laterally from a post on a supporting bracket 49 that is fixed to said longitudinal side frame member. By this arrangement, the foot treadle lever 11 may be operated to swing the front end of the polishing wheel frame arm C upwardly and thus lift the polishing wheel D off the bumper; and the foot treadle lever is provided with a suitable latching device 67a for holding the polishing wheel and its supporting structure in such position.

The motor 23 that drives the polishing wheels D is operatively connected to the carriage E for moving it back and forth on its tracks. Mounted in bearings 58 secured to the standards 2 slightly above the longitudinal side frame members i is a cross shaft 5! having a sprocket wheel 52 fixed thereon. A pair of spaced cross-members 53 is secured to the bottoms of the longitudinal side frame members i below the polishing wheels, and fixed on these cross-members 53 are bearings 54 in which is jcurnaled a shaft 55 having a sprocket wheel 56 fixed thereon. Mounted around the sprocket wheel 56 and the sprocket wheel 52 is an endless sprocket chain 51. Secured to the bottoms of the cross angle-irons 3 of the carriage E intermediate its longitudinal side members is a tongue arm 58 that extends beyond the rear end of said carriage and is attached to the upper stretch of the sprocket chain 51. Fixed to the cross'shaft 5i carrying the rear sprocket wheel 52 are two pulleys 59. J ournaled in bearings til provided therefor at the rear of the shelf t are two spaced parallel cross-shafts 5! provided with gears 2 that intermesh with each other. Cine of these gear shafts 6! has fixed on its end a pulley 63 that is driven by a belt B l that is mounted around a pulley 65 fixed on the end of the cross shaft ll. By this arrangement, one of the two gear shafts BI is driven in one direction by the belt 64 while the other of said gear shafts is driven in the opposite direction by the intermeshing gears 62 on the corresponding ends of said shafts. Each gear shaft St has a pulley 66 fixed thereto that has a belt ii! loosely mounted around it and around one of the pulleys fixed on the sprocket wheel cross-shaft 5i. Accordingly, if these belts are alternately tightened, the sprocket wheel cross-shaft 5! will rotate in one direction and then in the opposite direction to cause the riage to travel back and forth. The belts are tightened by means of a V-shaped rocker arm iii fixed at its apex on a rocker shaft 69 that is located directly below the sprocket wheel shaft El and journaled in suitable bearings it fixed to the standards 2 near their bottoms. The V- shaped rocker arm 68 has stub shafts ll that project laterally in opposite directions from the ends of the two fingers l2 of said rocker arm, and mounted on these shafts are idler pulleys l3 jour- 12,078,408 vnaled therein 7 adapted .to engage the loosely mounted :belts 1 :for tightening them. By this arrangement, when the rocker arm 68 is tilted forwardly one of the idler pulleys 13 will engage and tighten one of the loosely mounted belts :6 to cause the sprocket wheel shaft :5I to rotate in one direction, and when the rocker arm 'is tilted rearwardly the other idler :pulley 13 will engage and tighten the other loosely mounted belt 51 to cause said sprocket wheel shaft to rotate in the opposite direction.

The rocker or carriage reversing shaft 69 Ls operated by'a control rod that extends alongside the path of travel of the carriage E and is slidably-supported near its front-end'ina bracket 15 secured to one of the longitudinal side members I of the frame work. The rear end of the carriage reversing or control rod 14 has .-a swivel pin connection 16 with the free end of an upstanding rooker arm 11.fixed to the rocker shaft 69. The .control rod 14 .is slid back and forth to actuate the rocker arm 68 and thus reverses the travel of the carriage .E by a pin 18 depending from the carriage E in position to abut against the opposing ends of two sleeves 19 slidably mounted on said rod in longitudinallyspaced relation. Each of the sleeves 19 is movable along the rod I I between twostops located at opposite ends'of a stop bracket 81, the larger stop being sleeved on said rod to permit adjustment of the stop bracket longitudinally thereof and being fixed to said rod by set screws 82. A coil spring 83 is sleeved on the rod 14 between each sleeve 19 and the large stop at one end of the stop bracket 8I for saidsleeve. By this arrangement, the pin 18 presses against one of the axially yieldable sleeves 19 as the carriage nears the end of its travel,.thereby shifting the rod 1-0 in adirection that will reverse the travel of saidcarriage.

Fixed on the end of the rocker shaft 69 is a rocker arm 84 that extends upwardly along the outside of one of the standards 2. Mounted on a bracket 85 that projects rearwardly from the shelf 6 are two abutment memberstt that are arranged one on each side of the free upper end of the rocker arm 84 and serve to limit its rock ing movement. Mounted on a horizontal pivot fixed to the standard 2 located adjacent to the arm '84 is a lever 81 having a weight -88 fixed on its front arm and having its rear arm pivotally connected to the lower end of a link 89 whose upper end is pivotally connected by means of a pin 90 to the upper end of the rockerarm '85. When the rocker arm 84 is in neutral position, it extends vertically, and the connecting link "89 also extends vertically so that the weight 88 is in dead center position and will not affect the movement of said rocker arm. However, when the control rod 14 is shifted by the carriage E in 'eitherdirection to cause the rocker arm 84 to move out of dead center position, the weight on the lever 81 will assist in moving said rocker arm and also hold it in position against one of the abutment members 86 and prevent the idler pulley 13 on the V-shaped rocker arm 08 from backing away from the belt 51 engaged by said pulley. Sleeved on the pivot pin '90 between the arm .84 and the link 89 is a friction disk 9I that is clamped between said arm and said link by means of a coil spring 92 sleeved on said pin between the outer face of said arm and the hub of a wheel 93 that is threaded on the outer end of said pin. By this arrangement, the friction disk 9| operates to prevent the arm 84 from rebounding after striking the :abutments '86, the friction being regulated bymeans-of the wheel 9.3.

vIn order to stop the movement of the carriage, the rocker arm '68 must beheld in neutral vertical position. This is accomplished by a collar 94., which is :iixed to the control rod 14 near its front end and is provided with a depending lug 95 that loosely engages a recess '96 provided therefor in the .upper end of an arm 91 pivoted on a bracket 98 fixed to the outer side of the adjacent longitudinal side member I. Fixed to the arm 91 is a handle 99 that extends slightly beyond the front end of the :machine, and by manipulating this handle, the control rod 14 can be :held in neutral position. A latching mechanism is provided on the bracket for latching thehandle with the control rod in neutral position. Said mechanism :preferably comprises an arm I00 pivoted at its lower end on the bracket 98 for vertical swinging movement towards and away from the inner face of the arm 91. The upper end of the lock arm I00 is provided with a notch IOI adapted to cooperate with a pin I02 on the rod operating arm 91 and thus .lock the same against movement. The lockarm I00 is actuated by means of a handle I0Ia located just below the handle 99 of the rod operating arm '91.

In the drawings, the work table B is provided with a sufiicient number of fixtures I2 for accommodating eight bumpers; said fixtures being arranged so that said bumpers will be spaced equal distances apart on said table. The work table is moved transversely of the carriage by means of the hand wheel I 4a to bring a bumper directly beneath a polishing wheel .D; and means are 'provided for locking said work table to the carriage so as to hold said bumpers in line with said polishing wheels. Said table locking means preferably comprises a horizontal cross-bar I03 slidable endwise in brackets I04 fixed to the tops of the longitudinal side members 1 of the carriage and provided with four vertical holes I05 for receiving the lower end of a pin I06 slidably mounted in a bracket I01 fixed to the underside of the work table. A compression spring I08 is interposed between the top of the pin I06 and the bottom of the work table for keeping the lower end of said pin in the holes I05 in the cross-bar I03. The pin I06 is disengaged from the holes I05 in the-cross-bar I03 by means of a hand lever I09 pivoted to swing vertically in a bracket IIO fixed to the underside of the work table. The outer arm of the lever I09 extends outwardly beyond the front end of thetable; and the rear arm of said'lever is provided with an'opening for receiving a pin III that projects horizontally from the stop pin I06 through a vertical slot H2 provided therefor in the pin supporting bracket I01. By this arrangement, when the outer arm of the band lever IDS is moved downwardly the inner arm thereof will swing upward and disengage the stop pin I06 from'the holes I05 in the cross bar I03 and thus, release the carriage and allow it to be moved over to its next position. In this connection, it is important to note that the four holes I05 in the cross-bar I03 are located in such position and'spaced at such distances apart that each hole determines one of the four polishing positions of'the work table. One end of the crossbar I03 is provided With a vertical pin II3 on which is journaled a roller H4, the purpose of which will hereinafter appear. The other end of the cross-bar I03 is provided with a depending flange II-5 that overhangs the adjacent longitudinal side member 1 of the carriage and is provided with an adjustable stop screw I I which is yieldably held in abutting relation to said longitudinal side member by means of coil springs II? fastened at one end to the opposite longitudinal side member I of the carriage and at the other end to a bracket I I8 fixed to said cross-bar intermediate the ends thereof.

In order to polish bumpers of the type that are bent edgewise, after the manner of the bumpers A and A illustrated in Fig. 16, master forms I I9 and I29, respectively, are bolted to a longitudinal supporting bar IZI which is fixed to brackets I22 secured to the longitudinal side member I located adjacent to the roller end of the cross-bar I03. The longitudinal bar is provided with a series of vertical holes 23 for bolting thereon a master form for the particular shape of edge bent bumper that is to be polished. Each master form I I9, I20 comprises a plate member or the like having a cam surface, which is shaped to correspond to that of a bumper and is adapted to be engaged by the roller I M on the end of the cross-bar I03 when the carriage is moved back and forth. By this arrangement, the Work table in moving back and forth will also move laterally against the tension of the coil springs ii! and thus keep the surface of the particular bumpers being polished in contact with the polishing wheels.

The hereinabove described polishing machine is operated as follows: The group of bumpers A to be polished is fixed on the work table B. The hand lever IE9 extending from the front of the Work table is actuated to disengage the locking pin Iilfi from the cross-bar I93. The table is then moved crosswise of the carriage E by means of the hand wheel Mo to bring the first bumper directly below the one polishing wheel and the fifth bumpor directly below the other polishing whel. The table is then looked in such position by releasing the handle lever me and allowing the locking pin I06 to seat itself in the registering hole ms in the cross-bar Hit. The work table is then set in motion by releasing the control rod latch handle l'fiIa and by operating the control rod hand lever 99 to shift the control rod 74 out of neutral position and thus cause the rocker shaft 69 and the V-shaped rocker arm 68 to move into such position that one of its idler pulleys I3 will engage one of the loosely mounted belts 6? to tighten the same and thus cause the sprocket wheel shaft 5i to rotate and move the carriage in one direction. At the end of the travel of the carriage in this particular direction, the pin member '58 which depends from said carriage will engage one of the sleeves to on the control rod and shift it far enough in the direction of travel of the carriage to rotate the rock arm 68 and bring the other idler pulley 13 into engagement with the other loosely mounted belt to tighten the same and thus cause the carriage to reverse its direction of travel. Thus, the two belts 61 are loosened and tightened alternately, thereby imparting a continuous back and forth or reciprocating movement to the carriage.

The polishing wheels D are engaged with the bumpers by releasing the foot treadle if at the front end of the machine. Assuming that the tensioning mechanism has been properly adjusted by means of the adjusting nuts MI, and the proper weights 42 for the particular weight of polishing wheels have been placed on the front end of the counterbalancing levers 27, the polish ing wheels will bear against the central portion of the bumpers with substantially the same pressure as it will bear against the curved ends thereof.

Accordingly, an even polishing action takes place throughout the entire length of the bumpers.

After the first and fifth bumpers have been thoroughly polished, the foot treadle 41 is again actuated to raise the polishing wheels and the control rod hand lever 99 is operated to stop the movement of the carriage. It is to be noted that these operations do not require stopping the motor 23 driving the polishing wheels. After the carriage is stopped, the hand lever I99 extending in front of the work table is actuated to release the work table from the carriage and the hand wheel Ma is then operated to move said work table transversely of said carriage to bring the second and sixth bumpers beneath the grinding wheels. In this connection, it is to be noted that the hand lever I59 of the work table is depressed for a fraction of a second and then released so that, as soon as the table has moved over far enough, the coil spring 498 will automatically force the locking pin EBB into the second hole in the cross-bar I03 so that the Work table will stop in its second polishing position. In the third polishing position of the table, the third and seventh bumpers are polished, while in the fourth position of said table the fourth and eighth. bumpers are brought into position beneath the polishing wheels.

When it is desired to polish bumper bars that are curved edgewise after the manner of the bumper bars shown in Fig. 16, it is necessary to shift the reciprocating bars laterally so as to bring the curved portions thereof beneath the polishing wheels. This lateral movement of the bumper bars during the endwise reciprocating movement thereof is brought about by the use of a cam plate or master form of the kind shown in Fig. 16, having a curved cam edge corresponding to the curvature of the edge bent bumper bars that are to be polished. As stated above, such cam plate is rigidly secured to the frame of the machine with its cam edge in position to be engaged by the roller H4 at the end of the cross-bar I93. With this arrangement, the roller II-i at the end of the cross-bar 5G3 follows the cam edge of the plate during the reciprocating movement of the table and thus imparts to the table the lateral movement necessary to keep the bumpers in line with the polishing wheels.

Obviously, the hereinbefore described polishing machine admits of considerable modification without departing from the invention. Therefore, I do not wish to be limited to the precise construction and arrangements of parts shown and described.

What I claim is:

l. A reversing mechanism for a polishing machine or the like including a reciprocating work table, said mechanism comprising two oppositely rotating drive shafts, pulleys fixed to the respective drive shafts, a driven shaft adapted to be -12.

operatively connected to said table to actuate the same, two pulleys fixed to said driven shaft, loose belts connecting the drive shaft pulleys and the driven shaft pulleys, respectively, an upright rocker arm mounted to swing crosswise of said belts, pulleys journaled on the upper end of said rocker arm and adapted to bear against the respective belts, means adapted to be operatively connected to said table for actuating said rocker arm to cause the pulleys thereon to bear alternately against said belts, said means including a manually operable lever for moving said rocker arm to inoperative position, and separate manually operable means associated with said manual arm holding lever for locking the same in such position.

2. A reversing mechanism for a polishing machine or the like including a reciprocating work table, said mechanism comprising two spaced par allel drive shafts, gearing connecting said shafts whereby one shaft drives the other in a reverse direction, pulleys fixed to the respective drive shafts, a driven shaft adapted to be operatively connected to said table to actuate the same, two pulleys fixed to said driven shaft, loose belts connecting the drive shaft pulleys and the driven shaft pulleys, respectively, an upright rocker arm pivotally mounted at its lower end to swing crosswise of said belts, pulleys journaled on the upper end of said rocker arm and adapted to bear against the respective belts, a slide rod adapted to be operatively connected to said table for actuating said rocker arm to cause the pulleys thereon to bear alternately against said belts, and means operable in the operative positions of said arm for increasing the pressure of the pulleys thereon against the respective belts.

3. A reversing mechanism for a polishing machine or the like including a reciprocating work table, said mechanism including two oppositely operating loose belts adapted to effect the reciprocating movement of said table, means adapted to be operated by the reciprocating movement of said table for alternately tightening said belts, said means comprising a rocker arm mounted to swing crosswise of said belts, friction pulleys journaled on said rocker arm and adapted to bear against the respective belts, a slide rod adapted to be operatively connected to said table for actuating said rocker arm to cause the pulleys thereon to bear alternately against said belts, an arm mounted to swing with said rocker arm, stops on said machine for limiting the swinging movement of said arm, a lever pivoted on said machine adjacent to said arm, a weight fixed to one arm of said lever, and a link pivoted at one end to said machine and at the other end to said the other arm of said lever.

4. A reversing mechanism for a polishing machine or the like including a reciprocating Work table, said mechanism including two oppositely operating loose belts adapted to effect the reciprocating movement of said table, means adapted to be operated by the reciprocating movement of said table for alternately tightening said belts, said means comprising a rocker arm mounted to swing crosswise of said belts, friction pulleys journaled on said rocker arm and adapted to bear against the respective belts, a slide rod adapted to be operatively connected to said table for actuating said rocker arm to cause the pulleys thereon to bear alternately against said belts, an arm mounted to swing with said rocker arm, stops on said machine for limiting the swinging movement of said arm, a lever pivoted on said machine adjacent to said arm, a weight fixed to one arm of said lever, a link pivoted at one end to the other arm of said lever, a pin pivotally connecting the other end of said link to said arm, a friction disk sleeved on said pin between said arm and said link, a wheel threaded on said pin, and a coil spring sleeved on said pin between said arm and said wheel.

5. A reversing mechanism for a polishing machine or the like including a reciprocating work table, said mechanism including two oppositely operating loose belts adapted to effect the reciprocating movement of said table, means adapted to be operated by the reciprocating movement of said table for alternately tightening said belts, said means comprising a rocker arm mounted to swing crosswise of said belts, friction pulleys journaled on said rocker arm and adapted to bear against the respective belts, a slide rod adapted to be operatively connected to said table for actuating said rocker arm to cause the pulleys thereon to bear alternately against said belts, a manually operable lever pivotally supported on said machine and operatively connected to said slide rod for holding the rocker arm actuated thereby in inoperative position, a second manually operable lever pivotally mounted on said machine and cooperating with said first mentioned lever for locking the same in such position and means operable in the operative position of said rocker arm for increasing the pressure of the pulleys thereon against the respective belts.

THEODORE F. PHILIPPI.

Images