US1838197A - Machine for expanding slitted metal sheets - Google Patents

Description

Dec. 29, 1931. T. A. SINDELAR MACHINE FOR EXPANDING SLITTED METAL SHEETS Filed Jan. 18, 1930 10 Sheets-Sheet 1 gwm'ntoz HammAJu'mhr dbtozmq Dec. 29, 1931. T A. SINDELAR MACHINE FOR EXPANDING SLITTED METAL SHEETS Fil ed Jan. 18, 1930 10 Sheets-Sheet 2 Nmq Dec. 2 9, 1931. $|NDELAR 1,838,197

MACHINE FOR EXPANDING SLITTED METAL SHEETS Filed Jan. 18, 1930 10 Sheets-Sheet 3 '3 w IIIIIK. a

CD4 I '5 E I ;III' i 8 w grmmflfoz Thomas A. Szhdelar Dec. 29, 1931. T. A. SINDELAR MACHINE FOR EXPANDING SLITTED METAL SHEETS 10 Sheets-Sheet 4 Filed Jan. 18, 1930 gnmifloz Thomas A @fizdelczr Dec. 29, 1931. slNDELAR 1,838,197

MACHINE FOR EXPANDING SLITTED METAL SHEETS Filed Jan. 18, 1930 10 Sheets-Sheet 5 Dec. 29, 1931. T. A. SINDELAR 1,838,197

MACHINE FOR EXPANDING SLITTED METAL SHEETS Filed Jan. 18, 1950 10 Sheets-Sheet 6 Dec. 29, 1931. T. A. SINDELAR MACHINE FOR EXPANDING SLITTED METAL SHEETS 1o Sheets-Sheet '7 Filed Jan. 18, 1930 Dec 29, 1931. T. A. SINDELAR MACHINE FOR EXPANDING SLITTED METAL. SHEETS 10 Sheets-Sheet 8 Filed Jan. 18, 1930 gnwnfoq,

dthouuzq & TjzomasA W101 Dec. 29, 1931. T. A. SINDELAR 1,838,197

MACHINE FOR EXPANDING SLITTED METAL SHEETS Filed Jan. 18, 1950 10 Sheets-Sheet 9 Dec. 29, 1931. T. A. SINDELAR MACHINE FOR EXPANDING SLITTED METAL SHEETS Filed Jan, 15, 1930 10 Sheets-Sheet l0 T120120 (w A Ginrielar Clflouwq Patented Dec. 29, 1931 UNITED [STATES PATENT OFFICE THOMAS -A SIN DELAR, OF CANTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO REPUBLIC STEEL CORPORATION, OF YOUNGSTOWN, OHIO, CORPORATION OF NEW JERSEY MACHINE EXPANDING SLITTED METAL SHEETS Application filed January 18, 1930. Serial No. 421,742.

This 'i'n'v ention relates to machines for spreading or expandingslitted metal sheets for the purpose of forming expanded metal iath and th'elike.

The primary object of the invention is to provide a machine which wil'l'automatically and successively feed a slitted sheet into a predetermined position, accurately and simu ltane'ously gauge the front and rear edges "of the sheet, iirmly clamp the gauged edges,

' move the clamped edges away from each other to thereby spread or expand the sheet, shear the ends of the expanded sheet and at thesame time feed the finished she'etout of the machine, and repeat this cycle of opera- -of;the invention is better understood, the

same consists in the novel construction, com bination and arrangement of parts hereinafter more fully described, illustrated and claimed.

A preferred and practical embodiment of the invention is shown, in the accompanying drawings, wherein:

Fig. a plan view of the machine;

F 2 and 3, taken together, comprise a 3 front elevation of the machine;

i Fig. 6 is an enlarged View of a portion. of

Fig. 5

Fig. 7 is a. view similar to Fig. 5 but showing the feeding mechanism'and relative positions of the clamping bars at the termination of the expanding operation;

Fig. 8 is a cross-section taken on the line I Fig. 12 is a side elevation of the synehro- 'nizing mechanism;

Fig. 13 is a cross-section taken through the-shearing mechanism on the line 1313 of Fig. 1;

Fig. 1 1 is a fragmentary cross-section, taken on the line 1414 of Fig. 8 and showing the manner in which the movable clamping mechanism is mounted;

Fig. 15 is a perspective view of oneof the clamping members; and

Fig. 16 is an enlarged cross-section taken on the line 16-16 of Fig. 7.

Referring more particularly to the drawings wherein like reference characters designate corresponding parts throughout the several figures, the machine consists essentially of the following major units, i. e. base, stationary clamping mechanism, sheet feeding mechanism, movable clamping mechanism, rear gauging mechanism, shearing mechanism, and driving mechanism. Each of these major units will now be described in detail, and the method of operation of the'machine as av whole will then be described.

Base

The base of the machine is preferably made of a single casting 1, having secured at spaced apart points on the upper surface thereof steel bearing plates 2, constituting tracks for the movable clamping and shearing mechanisms to be presently described.

Stationary clamping mechanism The stationary clamping mechanism includes a left hand housing 3 and a right hand housing 4, having therein guides 3a and 4a respectfully, and provided with bearing portions 3?) and 46 respectively which support a shaft 5. The housings are secured to each other and to the base 1 by means of a bed plate 6, thus forming a rigid, stationary structure.

Secured to the upper face of the bed plate 6 is a bar holder 7 in which a lower clamping bar 8 is secured. This bar may be a single piece of steel of the desired cross-sectional contour, but owing to the diificulty of accurately machining a long, thin bar, as well as to the tendency of such a bar to warp upon being heat treated, the bar preferably consists of a plurality of separate members 8a. The relatively short length of these members, as shown in Fig. 15, permits them to be easily machined, readily assembled in the bar holder 7, and longitudinally aligned thereby. The members So have a slight pivotal movement, and in order to maintain them in alignment a plurality of flat springs 9 are provided, the lower ends of which are secured to the bar holder 7 and the free ends of which abut the members Set, as clearly shown in Fig. 6. Altho the springs 9 maintain the members 8a in alignment, they permit individual members to pivot and thereby adjust their positions to compensate for variations in the thickness of the sheet at the edges thereof. As a result, the clamping action is sufiiciently positive throughout the length of the sheet to permit expansion of two or more sheets simultaneously.

For the purpose of facilitating insertion of the sheet to be expanded into the machine a bar 10 is provided, this bar being yieldably supported on a plurality of coil springs 10b, for reciprocal movement in a recess 7a of bar holder 7. As shown in Fig. 6, the top of the bar 10 is beveled as at 10a so that a sheet entering the machine will strike the beveled surface and ride up over the lower clamping bar 8.

A ram 11 of truss-like construction is mounted for vertical reciprocal movement above the bar plate 6, the ends 11a of the ram, constituting bearing blocks, lying within the guides 3a and 4a of housings 3 and 4 an upper clamping bar 14. The bar14 is beveled as at 14a and this beveled surface lies directly above the upper edge of the lower clamping bar 8.

An angle 15 supports guide members 16 and an angle 17 secured in spaced relation to the angle 15 supports guide members 18. The angle 15 is secured to the bed plate 6 in such position that the openings between guide members 16 and 18 are substantially in the same horizontal plane as the upper edge of the lower clamping bar 8.

Double faced cams 19 of the groove and roller type are mounted adjacent the ends of shaft 5 outside the housings 3 and 4. Each of these cams has a groove 19a in the face nearest the housings and a groove 1% in its opposite face, as shown in Fig. 8. Bell-crank levers 20 are pivotally mounted on the housings 3 and 4. One end of each of these bellcrank levers is provided with a. roller 21 which lies within the grooves 19a of the cams 19, and the other end of each of these levers is pivotally secured to one end of a push rod 22. The opposite ends of the push rods 22 are pivotally secured to the studs 12 on the ends of the ram 11.-

Sheet feeding mechanism Secured to the front of the bed plate 6 is a table 23, having in its ends grooves 236; which serve as guides for a cross-head 24 mounted for reciprocal movement therein. The table 23 has in its top a plurality of spaced slots 236, through which front gauges 25, secured to the cross-head 24, project.

Pivotally secured to opposite ends of the cross-head 24 are adjustable links 26, the other ends of which are pivotally secured to levers 27, providedintermediate their ends with rollers 28. The levers 27 are rigidly secured at their lower ends to a shaft 29, supported by bracket bearings 30. The bracket bearings 30 are mounted on the front of the bed plate 6.

Arms 31 are rigidly secured to the shaft 29 adjacent the levers 27. Cams 32 are rigidly secured to the shaft 5 and coil springs 33, secured at one end to bed plate 6 and at the other end to the arms 31, serve to maintain the rollers 28 in contact with the peripheral surfaces of these cams.

. 11 ovable clamping mechanism The movable clamping mechanism includes a left hand housing 34 and a right hand housin 35. having therein guides 34a and 35a respectively, and provided with hearing portions 34?) and 35?) respectively, which support a shaft 36. The housings are secured to each other by means of a bed plate 37, and a brace 38, thus forming a rigid, movable structure. Wheels 39 are secured to the housings 34 and 35 and are guided for movement on the rails 2 of the base 1.

at its ends with studs 46. 1

Secured to the upper face ofithe bed plate 37 is a bar holder 40to which initurn'is secured a lower' 'clampingbar 41. The bar 41 isbeveled as at 41a. 1

In order to facilitate insertion 'of-asheet to be expanded into the machine, as well as its removal from the machine after expansion, a guide bar 42 is provided, having a sloping upper portion 1 42a. This bar is mounted for vertical sliding movement upon bar holder 40, and is 1 yiel'dablysupported upon coil springs 43 enclosed in boxes 44 secured to the bed plate 37. When in its uppermost position, as shown in Fig. 6, the sloping portion 42a of the guide bar is above the beveled surface 41a of the lower clamping barand therefore. prevents abutment of a moving sheet against the lower. clamping bar.

A ram 45, of truss-like construction, is mounted for vertical. reciprocating movement above the bed plate 37, the ends 45a of the ram, constituting bearing blocks, lying within the guides 34a and 35a of housings 34 and 35 respectively. The ram 45 is provided Secured to the lower face of the ram 45 is a bar holder 47 in'which an upper clamping bar 8, consisting of a 1 plurality of longitudinally aligned'me'mbers 8a, is secured and so positionedthat the edges of these members are directly above the beveled surface 41a of lowerclamping bar- 41. The members 8a h-avea -slight pivotal movement and in order to retain them in alignment a' plur'alitv of flat'sprin'gs 9 are provided, the upper-ends of which are secured to the bar holder 47 and the free ends of which abut the members 8a, as clearly shown in Fig. 6. Adjustably secured to the ram 45 are push rods 48, which are adapted to depress the guidebar 42 when the ram 45 is lowered to thepositi'on shown in Fig. 7. a V

Single-faced cams 49 of the groove and roller type -are mountedadj'acent the ends of shaft 36, outside the housings 34 and 35. As

shown in Fig. 8, each of these cams has a groove 49a in the faceinearest the housings. Bell-crank levers 50 are pivotally mounted on the housings 34 and35'. One endof each of these bell-crank levers is provided with a roller 51, which lies within the groove 49a of the cam 49, and the other end ofie'ach of these levers is pivotally secured to one end of a push rod 52. The opposite ends of the push rods '52 are pivotally secured to the 'studs 46 on the ends of the ram 45.

Levels 53., having cross-head guides 53a at their upper ends,=are pivotally secured to bearings 54 mounted on the base 1. These levers are provided intermediate their-ends withrollers 55, which lie within the grooves 196 of cams 19. Adjustably secured within thegui-des 53a arecross-h-eads' 56, to which are pivotally secured adjustable connecting rods 57. The-opposite end'of one 'of-theconnecti'ng rods 57 is pivotally secured to the housing 34, and the opposite end of the other connecting rod is pivotally secured to the housing 35. The degree of expansion of the slitted sheet may bevaried by. adjusting the cross heads 56 towards or away from the bearings 54. This serves to decrease or increase the extent of movement of the housings 34 and 35.

Rear gauging mechanism For the purpose of positioning the rear edge of the sheet, a plurality of gauge pins 58 are provided, these pins extending through aligned openings in the bed plate 37, bar holder4'0 and lower clamping bar 41. The gauge pins are adapted to be moved vertically by means of levels 59, rigidly secured intermediate their ends upon ashaft 60, which is pivotally mounted in bearings 61, secured to the bed plate 37. Each of the levers 59 is provided at one end with a counterweight 62, having a beveled surface 62a, and one of the levers is provided at its opposite end with a in 63.

-' ounted on the base 1, in the rear'of bed plate 37 is a pedestal 64, having at its upper end aplate portion 64a, which is partly cut away to provide a sloping surface 645. One end of a swinging guide 65 is journaled in the plate portion 64a the free end thereof resting on the sloping surface 646, as shown in solid lines in Fig. 5.

Secured to the lower rear side of the'bed plate 37 is a bracket bearing 66, upon which a lever 67 is pivotally mounted. The lever 67 has an open slot 67 a in one end thereof and is provided at its opposite end with a roller 68. 'The pin 63 of the lever 59 lies within the slot 67a and during the operation of the machine the roller 68 is adapted to ride on the sloping surface 645 of the pedestal.

Ashaft 69, pivotally mounted in bearings 70, has rigidly secured thereto a'pedal 71, a 'cam 72 and an arm 73 and is normally maintained in the position shown in Fig. 7 by means of a coil spring 74 secured to the arm 73 and the bed plate 6. Positioned above and at right angles to the shaft 69 is a stub shaft 75 provided at one end with a support 76 and at its opposite end with a spring arm 77 and a ball arm 78. The support 76 is provided with a flat portion 76a. As shown in Fig.2, acoil spring 7 9, acting upon the arm 77-maintains the ball arm 78 in contact with the face of the cam 72, and the support 76 in position to support one of the counterweights 62, asshown in Fig. 5.

Shearing mechanism mounted in bearing boxes 84, which are secured in guidesin the housings 34 and 35. The arbor 82 is adapted to be driven by means of a pinion 85 secured thereto, and transmits motion to the arbor 83 through the inter: mediary of ears 86. For the purposeeof positively moving the expanded sheet through the shearing mechanism coacting rollers 87 of rubber or the like, are secured to the arbors 82 and 83.

As shown in Figs. 1 and 5, brackets 88 are secured at their lower ends to the base 1 and are previded with horizontally extending portions 88a to which are secured angle guides 89. Spaced guides 90, secured to the clutch 93 having a trip 94 secured to the pe riphery thereof. Springs 95 abutting a collar 96 rigidly secured to the shaft urge the clutch 93 into rotating engagement with the clutch plate 92. A solenoid 97 mounted on Y thehousing 4 is provided with a retractable pin 97 a, which at intervals between the operation cycles cooperates with the trip 94 to hold the clutch 93 out, of engagement With the clutch plate 92. v

A jack shaft 98 mountedin suitable bearings has keyed thereto. near one end, a pinion 99in mesh with gear 91 and is connected at its other end to the low speed shaft of a gear reduction unit 100 by means of a flexible coupling 101. The high speed shaft of this reduction unit is connected to the main drive shaft 102- by means of a flexible coupling 103. The main drive shaft is ournaled in bearings 104 mounted on the base 1 and has an opening 102d of square outline extending longitudinally therethrough. A gear 105 is keyed to the main drive shaft 102 and is adapted to be rotated by means of a motor 106 through the intermediary of a chain belt 107.

The clutch fordriving the movable clamping and shearing mechanism is similar to the clutch for the stationary. clamping mechanism and includes a solenoid 108 mounted on housing and a gear 109 rotatably mounted shaft of a gear reductionunit'112'bv means of a flexible coupling 113. The gear reduction unit 112is mounted on a support 114 secured to and movable with the housing 35 and the high speed shaft thereofis connected to. one

Q end of a shaft 115by means of a universal 'joint 116. One end of the shaft 115 is of substantiallyisqua're cross-section, as shown in Fig. 10, and has a sliding fit within the opening 102a in the main drive shaft 102. This spline-like connection permits the shaft115 to move axially with respect to the main drive shaft without interruption of its rotation. 7

As shown in Figs. 11 and 12 means for energizing the solenoids 97 and 108 is provided and includes a switch 117 mounted on the base 1. This switch is adapted to, be closed by means of a link 118 pivotallyconnected at its ends to a switch arm'117a and to a lever 119 secured to a shaft 120. This shaft is mounted for pivotal movement 'ina bracket 121 mounted on thebasel, and has rigidly secured thereto a lever 122 provided at its end with a roller 123. A coil spring 124 connected at one end to the bracket 121 normally holds, the levers 119 and 122 inthe position shown in solid lines in Fig. 12. A lever 125 rigidly secured to one end of the shaft 69 is resiliently connected to the lever 119 by means of a coil spring 126. r

For the purpose of synchronizing the operation of the solenoids with the other parts of the machine a cam 127 is rigidly secured to the gear 91 and rotatestherewith. This cam has in opposite sides of one face thereof grooves 127 a, the ends of which .lie in the pe riphery of the cam. Corresponding ends of the grooves 127a are closed by means of guards 128 hinged to the cam and'normally maintained in the position shown in solid lines on Fig. 12 by means of coil springs 129.

Operation .The present machine is of the continuous power, intermittent operation type, that is, the motor and driving mechanism are in constant operation while the machine proper is caused to operate at the will of an operator by means of clutches of the single revolution type. In; this conn'eotiomit should be noted that the gear 91, clutch plate 92 and cam 127 rotatecontinuously onshaft 5, and that gear 109 and its clutch platerotate continuously on shaft 36, the shearing mechanism being continuously driven by the gear 109. The direction of rotation of these elements is indicated byarrowsin the drawings;

With the clamping mechanisms in the position shown in Fig. 5, and the front gauges occupying the position shown in broken lines in Fig. 7, the operator places a slitted sheet on'the't'able 23 with its front edge abutting the gauges 25 and its rear edge lying above the bar 10. He then depresses the pedal 71, therebycausing the's'haft 69 and cam 72 to rotate through a small arc. Rotation of this camforces the ball arm 78 on the stub shaft 75 to the position shown in dotted lines in Fig. 16, thereby causing a slight counter clockwise rotation of this shaft. This rotation is sufficient to swing the fiat portion 7 6a of the support 76 from'its position under one of the counterweights 62, thereby permitting the counterweight to drop, causing the shaft to turn and move the levers 59 to the position shown in broken lines in Fig. 5. The levers thereupon lift the gauge pins 58 and the lever 67 is simultaneously swung to the position shown in broken lines-in this er enters the groove, and through the intermediary'of the levers 119 and 122 and link 118, closes the switch 117.

The pedal? 1 is then released and the roller 123 follows the groove to the guard 128, swings this guard outwardly, as shown in broken lines in Fig. 12, and resumes its initial position, thereby openingthe switch 117.

The closing-of the switch 117 completes an electric circuit passing through the solenoid 97,:causing the bar 97a thereof to be retract-.

ed. This retraction releases the trip 94.on

the clutch 93 and permits the clutch 93 to, be forced by the springs 95 into engagement means of the solenoid 108 (see Fig. 1, which.

releases theclutch associated with gear 109.

The rotation of cams 32, mounted on the shaft'5, moves the levers 27, cross-head 24 and front gauges 25 from the position shown in broken lines to the position shown in solid lines in 7,.the front gauges 25 moving the sheet into the machine; Duringthis movement, the sheet is supported .on the guides 16, andthe rear edge of the sheet is held above the lower clamping bar 41 by the sloping portion 42a. of the guide bar 42 and comes into abutment with the gauge pins 58. The front gauges 25 position the front edge of the sheet and prevent. the sheet from rebounding from the gaugepins 58-.

Occasionally, owing to variations in the hardness of the metal, the slitted sheets vary in width, i. e., some sheetsare of greater width than normal. By gauging both edges of the sheets simultaneously, the abnormally wide sheets are flexed to the degree necessary to insure that the clamping bars will always grip the'unslitted' edge portions of the sheet and permit the entire slitted'portion to be freely expanded.

The rotationof cams 19, mounted on the shaft 5, causes the bell crank levers 20 to pivot, thereby moving the ram 11 downwardly to the position shown in Fig. 7 to clamp the front edge of the sheet between the beveled surface 14a of the upper clamping bar and the upper edgesof the lower clamping barmembers 8a. The lower portion of. the upper clamping bar 14 depresses the resiliently mounted bar 10 and bends the edge of the sheet substantially parallel with the beveled surface 1 4a.

' The rotation of the cams 49, mounted on shaft 36, causes the bell crank levers 50 to pivot, thereby moving the ram 15 downwardly to the position shown in Fig. 7, to clamp the rear edge of the sheet between the edges of the upper clamping bar members 8a and the beveled surface 41a of the lower clamping bar 41, bending the edge of the sheet sub stantiallyparallelwith this beveled surface. In the descent of the ram 45, the push rods 48 depress the resiliently mounted guide bar 42 away from the sheet and the bar holder 47 partially depresses the g'auge'pins 58'.

After the edges of the sheet'have been firmly clamped, the entire movable clamping mechanism is moved rearwardly away from the stationary clamping mechanism to expand the slitted portion'of the'sheet intome'shwork;

This is accomplished by the rotation of earns 19 acting upon levers 53 and connecting rods 57. The rearward movement of the movable clamping mechanism first brings the,

roller 68 into Contact with the sloping surface 646 of the pedestal 64 andthen causes the roller to ride up 011 this surface, lifting'the thereby permitting the gauge pins58 to move downwardly out of the path of the sheet.'

When the roller reachesits extreme rear position, as shown in Fig. 7, the swinging guide 65 returns to its initial horizontal'position, providing a trackway for the forward movement of the roller.

After the sheet has been expanded, con-- tinued rotation of the shafts 5 and 36 reverses the clamping operation, releasing bothedges of the sheet, and returns the movable clamping mechanism'to its initial position, while maintaining the front gauges 25 in theposition shownin solidlines in Fig. 7. The return movement of the movable clamping mechanism brings the rotating coacting rollers' 87 into contact with the rear edge of the mechanism is being returned to its initial position, theroller 68'rides on the upper sur- The finished sheet is then deposited 41 by the upward movement of the released guide bar42. W'hen the'movable clamping mechanism has been returned to the position shown in Fig. 5, one of the counterweights 62 will rest upon the fiat portion 76a of the support 76 and the roller 68 will be out of,

contact with the swinging guide 65. The sheet feeding mechanism then returns to the position shown in broken lines in Fig. 7

When the movable .clamping mechanism and sheet feeding mechanism have been returned to their respective initial positions the rotation of shaft 5 is stopped by the trip 94 coming intocontact with the bar 970 of the solenoid 97 thereby moving the clutch 93 out of engagement with the clutch plate 92. In similar manner, solenoid 108 stops the rotation of shaft 36. The stopping of the rotation of these shafts occurs with all of the elements of the machine in position to receive another sheet, and to repeat the cycle of operations.

From the foregoing it will be apparent that the present machine will fulfill the objects herein set forth, and without further description, it is thought that the features and ad vantages thereof will be readily apparent to those skilled in the art, it being of'course understood that changes in the form, proportion and minor details of construction may be resorted to without departing from the scope of the appended claims.

Claims:

1. In a machine for expandingslitted metal sheets, means'for clamping the opposite edges of a sheet, means for positively feeding the sheet to a position in which its edges may be clamped by said clamping means and means formoving said clamping means relatively apart to expand the sheet.

2. A structure as defined in claim 1, a table on which sheets to be expanded are adapted to be laid, said sheet feeding means comprising gauges projecting through said table and adapted to move the sheets to a position in which their edges may be clamped by said clamping means.

3. In a machine for expanded slitted metal 5. In a. machine forexpanding slitted metal sheets, stationary clamping means for clamping one edge of a sheet to be expanded, movable clamping means for clamping the opposite edge of such a sheet, means for moving said movable clamping means away from said stationary clamping means toexpand the sheet, means for releasing the clamped edges ofthe sheet after expansion, means for returning the movable clamping means to its initial position, and means for preventing movement of the expanded sheet during the return movement of said movable. clamping means to its initial position.

6. A structure as defined in claim 5, in which shearing means are provided and are brought into engagement with theeexpanded sheet upon the'return of said movable clamping means to its initial position.

7. A structure as defined in claim 5, in which shearing means are provided which are brought into engagement with the expanded sheet upon the return of said movable clamping means to its initial position, and means for feeding the sheet between said shearing means to'thereby trimthe ends of the expanded sheet.

8. In a machine for expanding slitted metal sheets, stationary clamping means for clamping one edge of a sheet to be expanded, movable clamping means for clamping the opposite edge of such a sheet, and means for moving said movable clamping means away from said stationary clamping means to expand the sheet, each-of said clamping means including a bar comprising a plurality of relatively short pivoted dog members.

'9. A structure as defined in claim 8, and means for maintaining said relatively short members in alignment with each other.

10. In a machine for expanding slitted meta-l sheets, stationary clamping means for clamping one edge of a sheet to be expanded, movable clamping means for clamping the opposite edges of such a sheet, and means for moving said movable clamping means away from said stationary clamping means to expand the sheet, each of said clamping means including a clamping bar having a beveled face and a clamping bar opposed to said first-named bar and comprising a plurality of longitudinally aligned relatively short pivoted dog members cooperating with said beveled face for gripping an edge of the sheet therebetween on separation of said clamping means.

11. In a machine for expanding slitted metal sheets, stationary clamping means for clamping one edge of a sheet to be expanded, movable clamping means for clamping the opposite edges ofsuch a sheet, and means for moving said movable clamping means away from said stationary clamping means to expand the sheet, each of said clamping means including a bar holder, a clamping bar having a beveled face secured thereto, a second bar holder, and a plurality of longitudinally aligned pivoted dog members mounted on said second bar holder and cooperating with said beveled face for gripping an edge of the sheet therebetween on separation of said clamping means.

In testimony whereof I affix my signature.

THOMAS A. SINDELAR;

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