US2999526A - Machine for stretch bending metal moulding - Google Patents

Description

Sept. 12, 1961 w. WILLIAMSON 2,999,526

MACHINE FOR STRETCH BENDING METAL MOULDING Filed March 17, 1958 8 Sheets-Sheet 1 "v w Q a je x X IN VEN TOR.

P 1961 R. w. WILLIAMSON 2,999,526

MACHINE FOR STRETCH BENDING METAL MOULDING Filed March 17, 1958 8 Sheets-Sheet 2 IN VEN TOR.

FaZerZ 77742773072 7 BY I Sept. 12, 1961 R. w. WILLIAMSON MACHINE FOR STRETCH BENDING METAL MOULDING Filed March 17, 1958 8 Sheets-Sheet 5 INVENTOR. 70.2677 14 14 z/Z d77/s07z rvvi/vE/sr p 1961 R. w. WILLIAMSON 2,999,526

MACHINE FOR STRETCH BENDING METAL MOULDING Filed March 17, 1958 8 Sheets-Sheet 4 ok/VI/S Sept. 12, 1961 R. w. WILLIAMSON MACHINE FOR STRETCH BENDING METAL MOULDING 8 Sheets-Sheet 5 Filed March 1'7,

INVENTOR. FaZeri hizuzzs'wz Sept. 12, 1961 R. w. WILLIAMSON MACHINE} FOR STRETCH BENDING METAL MOULDING Filed March 17, 1958 8 Sheets-Sheet 6 BY W, i

Sept. 12, 1961 R. w. WILLIAMSON 2,999,526

MACHINE FOR STRETCH BENDING METAL MOULDING Filed March 17, 1958 8 Sheets-Sheet 7 IN V EN TOR. 70287; zz dwsoz Sept- 1961 R. w. WILLIAMSON 2,999,526

MACHINE FOR STRETCH BENDING METAL MOULDING Filed March 17, 1958 8 Sheets-Sheet 8 INVENTOR. X4287; n4 Mlzz km oz 19 ax/vzv a United States Patent G!" 2,999,526 MACHINE FOR STRETCH BENDING METAL MOULDING Robert W. Williamson, New Baltimore, Mich, assignor, by direct and mesne assignments, of one-fourth to 0. D. Herron, Grosse Pointe, one-fourth to Dudley A. Hunter, Utica, and one-fourth to Haven Manufacturiung Corporation, New Haven, Mich, a corporation of Michigan Filed Mar. 17, 1958, Ser. 'No. 721,748 17 Claims. (Cl. 153-32) he present invention relates to a machine for forming metal strips and more particularly, to an improved machine for stretch bending strips of metal moulding.

It is an object of the present invention to provide an improved machine of the above mentioned type which is simple in design, rugged in construction, economical and efficient in operation, and durable and reliable in use.

It is also an object of the present invention to provide an improved machine for strip bending strips of metal moulding in which primary and auxiliary power means are combined to provide an extremely eflicient use of the power supplied'to the machine.

Another object of the present invention is to provide an improved machine for stretch bending strips of metal moulding in which the tension produced in the strip during the stretching thereof is employed to provide a moment urging the operative parts of the machine from the start position toward the finish position, and more specifically, to provide such a machine in which this moment varies between the start and finish of the bending operation and attains a maximum at an intermediate point in the bending operation.

A further object of the present invention is to provide such an improved machine in which the clamping means is automatically positioned so that the jaws are at all times parallel to the adjacent portion of the strip so that the clamp exerts a straight pull on the strip.

It is also an object of the present invention to provide an improved machine of the above mentioned type includ ing means for releasing the tension in the strip prior to opening of the clamp means holding the strip.

Another object of the present invention is to provide an improved machine of the above mentioned type capable of stretch bending strips of metal moulding and performing secondary operations on the strip, such as cutting the strip, and which includes means automatically releasing the tension on the strip prior to the performance of the secondary operation.

Other and more detailed objects of the present invention will be apparent to those skilled in the art from a consideration of the following specification, the appended claims and the accompanying drawings wherein:

FIGURE 1 is a perspective view looking from front to rear of a machine embodying the present invention;

FIGURE 2 is a broken enlarged perspective view sho\ving the front of the right-hand end portion of the machine illustrated in FIGURE 1, and showing the parts in the start position and prior to the placing of a strip of metal moulding in the machine.

FIGURE 3 is a broken enlarged perspective view of the right-hand end portion of the machine as viewed in the direction of the arrow 3 in FIGURE 1, and prior to the placing of a strip of metal moulding in the machine;

FIGURE 4 is a broken enlarged perspective view of the right-hand end portion of the machine illustrated in FIG- URE 1 showing a strip of metal moulding in place in the machine and the parts in the finish position after the completion of stretch bending of the strip, parts being broken away to show a portion of the drive mechanism below the table top, the drive mechanism parts being shown below their normal position to facilitate the showing thereof;

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FIGURE 5 is a diagrammatic view of the structure illustrated in FIGURE 1, taken generally along the line 5-5 thereof;

FIGURE 6 is a diagrammatic plan view of the righthand end portion of the machine illustrated in FIGURE 1, showing the start position in full lines and showing an intermediate and the finish positions in broken lines;

FIGURE 7 is a fragmentary perspective view looking from the rear of the machine at a modification of the rear end portion of the right-hand cam member shown in FIG- URE 1;

FIGURE 8 is a fragmentary perspective view of a cutting device located between the ends and supported on top of the form shown in FIGURE 1;

FIGURE 9 is a transverse sectional view of the metal moulding strip showing diagrammatically in broken lines the jaws of the clamp;

FIGURE 10 is a sectional View of the structure illustrated in FIGURE 7, taken substantially along line 10-- 19 thereof;

FIGURE 11 is a broken enlarged plan type perspective view showing the right-hand end portion of the machine illustrated in FIGURE 1 and showing the parts in the start position prior to the placing of a strip of metal moulding in the machine; and

FIGURE 12 is a broken enlarged plan type perspective view of the right-hand end portion of the machine illustrated in FIGURE 1 and showing the parts in the finish position after the removal of a strip of metal moulding from the machine.

Referring to the drawings, and particularly to FIG- URES l to 4, inclusive, thereof, the machine there illustrated comprises a support generally indicated at 16 and including legs 12 upon which are mounted, by suitable framework 14, a pair of spaced horizontally disposed plates 16. Centrally of the support It is a form generally indicated at 18 which is supported above and extends outwardly partially over the spaced plates 16.

The improvements of the present invention may be embodied in machines for forming moulding strips of a wide variety of shapes which may, or may not, include substantially straight portions and may, or may not, be symmetrical. As best illustrated in the diagrammatic view FIGURE 6, the form 18, in the preferred embodiment illustrated, is symmetrically shaped and includes a central portion 20 which is substantially straight. and similar end portions 22 of increased curvature. The machine illus trated in FIGURE 1 is symmetrical and each of the plates 16 supports apparatus for gripping an end portion of a strip of moulding generally indicated at 23, and bending the strip about the form 18.

Referring to the right-hand end portion of the machine illustrated in FIGURE 1, which end portion is illustrated in FIGURES 2, 3 and 4, the plate 16 supports a carriage arm 24 which is pivotally supported in a bearing 26 mounted on plate 16 for rotation about an axis 28 illustrated in FIGURE 6, the axis 28 being at right angles to the plane of FIGURE 6 at the point indicated by the reference character 28. The outer end of the carriage arm 24 is supported on a guide bar 30 which is best illustrated in FIG- URE 3. The guide bar 3% is concentric with the axis 28 and the carriage arm 24 carries rollers 32 and 34 which engage, respectively, the upper and lower surfaces of the guide bar 30. The arm 24 carries a slide 36 which is provided with channel-shaped edge portions 38 which fit over and slide along the outer edge portions of slide bars 40 carried by the arm 24.

The slide 36 carries a cam follower arm 44 upon which are carried cam follower rollers 46 and 48; These rollers cooperate with an arcuately shaped cam generally designated 50 which is formed in two parts. The adjacent ends of the forward part 50 and the rear part 50 are pivotable about a pivot pin 52 mounted in a fixed support 54 secured to the plate 16. A plate 56 is mounted on the support 54 above the cam 50 and is engaged by the upper portions of the rollers 46 and 48. to effect a smooth transfer of these rollers between the cam portion 50 and 50". The cam '50 is disposed, as best illustrated in FIGRUE 6, so that its forward end is at a minimum distance from the axis 28 and is so shaped that the distance or" the cam from the axis 28 increases toward the rear end of the cam, as there illustrated. The cam member 58 co-operates with the rollers 46 and 48 to control the position of the slide 36 during a stretch binding operation of the machine. This cam 50 includes a forward portion 58 (see FIGURES 4 and 6) engaged by the roller 46 when the carriage arm 24 is in the start postion and during its initial movement from the start position. It will be noted that the slope of the cam portion 58 is substantially greater than that of the remainder of the cam 50 so that as the roller 46 moves along the portion 58*from the start position, its distance from the axi 28 increases at a more rapid rate than during movement of the roller 46 along the balance of the cam 50.

During a stretch bending operation of the machine, the slide 36 is urged outwardly along the carriage arm 24 in a direction away from the axis 28 by a power means, which in the preferred embodiment illustrated, consists of a pair of air cylinders 64, best illustrated in FIGURE 4, which extend along opposite sides of the carriage arm 24 and have one end thereof secured by pivot pins 66 to laterally extending supports 68 mounted on the carriage arm 24. The piston rods 70 extend outwardly of the other ends of the cylinders 64 and are pivotally connected as indicated a 72 to the channel-shaped portions 38 on the opposite edges of the slide 36.

The forward cam part 50' has a forward extension '74 extending forwardly beyond the portion 58, as best illustrated in FIGURE 4. At its forward end this extension 74 is supported on a block 76 mounted on the plate 16 which is provided with a pair of screws 78 engaging opposite edges of the cam part 50 for pivotally adjusting the bar about the pivot pin 52. The rear end of the cam part 50" is supported on a similar block 80 and also provided with screws 82 for holding it in adjusted position.

The slide 36 carries a head 84 which, in the preferred embodiment illustrated, is journalled for rotation about a generally vertically disposed axis in a bearing 86 mounted on the slide 36. The head 84 carries a clamp generally indicated at 88 which is mounted on a plate 99 forming a part of the head 84. The clamp 88 which is illustrated and described in greater detail in my copending application Serial No. 733,751; filed May 7, 1958, now Patent No. 2,941,432, is adapted to be operated from its open position illustrated in FIGURES 1, 2 and 3 to the closed position illustrated in FIGURE 4 to grip the end portion of the strip of metal moulding 23.

In the preferred embodiment illustrated, the strip of moulding 23, as illustrated in FIGURE 9, is of T-shape cross section and the clamp 88 has a stationary jaw 92, a lower movable jaw 94, and a front movable jaw 96, all of which are diagrammatically illustrated in FIGURE 9, which co-operate to grip the strip 23. The clamp 88 includes a body 98, the lower edge of which is welded or otherwise suitably secured to the plate 99. The stationary jaw 92 is fixed to one side of the body 98, the lower movable jaw 94 is disposed below the stationary jaw 92 at the same side of the body 98 and carried by an arm 99 which is pivotally connected to the body for rotation about the pivot pin 100. The flange 102 of the moulding 23 is received in the slot 104 (see FIGURE 3) be tween the stationary jaw 92 and the movable jaw 94. This slot 104, when the clamp 88 is in its open position, need only be of a width sufficiently great to permit easy movement of the flange 102 into and out of place in the slot 104. Accordingly, it will be appreciated that only a relatively limited movement of the arm 99 and the jaw 94 is required. The front movable jaw 96 is carried on tion of the body 98 for pivotal movement about the pivot pin 108 (see FIGURE 4). The clamp 88 is operated between the open position illustraed in FIGURES 1, 2 and 3 and the closed position illustrated in FIGURE 4 by power means which, in the preferred embodiment illustrated, is a pneumatic cylinder 110 which is pivotally mounted on a bracket 112 having an arm 114 by which it is pivotally mounted on thelower jaw arm 99.

The piston rod 116 of the cylinder 110 has its outer end pivotally connected to the pivot pin 108. The arm 114 of the bracket 112 also carries a pair of cam followers 118 and 120. The rear end portion 121 of the arm 106 is downwardly turned to provide an inner cam surface 122 and an outer cam. surface 124. Also, the downwardly turned end portion 121 of the arm 106 has a cam surface 126 on the end thereof which is engaged by the cam follower 118 when the clamp 88 is in the closed position, as shown in FIGURE 4. When the clamp is in the open position illustrated in FIGURES l, 2 and 3, the downwardly turned end portion 121 extends between the cam followers 118 and 120. When air is supplied to the cylinder 110 through the line 128, forcing the piston rod 116 outwardly of the cylinder 110, the cylinder supporting bracket 112 and the arm 114 thereof pivot in a clockwise direction as viewed in FIGURE 3, about the pin 130 which pivotally connects the arm 114 to the lower movable jaw arm 99. During this. movement the cam follower 118 moves along the cam surface 122 co-operating therewith to pivot the arm 106 about the pivot pin 108 in a clockwise direction, as viewed in FIGURE 4.

It will be seen that the shape of the cam surface 122 is i such that during this portion of the movement ofthe piston rod 116 a rapid pivotal movement of the outer movable jaw arm 106 is effected. Just before the arm 106 and the arm 99 reach their full closed positions the cam follower 118 reaches the lower edge of the cam surface 122 and moves onto the intersecting cam surface 126 on the end of the arm portion 121. This cam surface 126 is sloped to provide a relatively small movement of the arms 106 and 99 and a large mechanical advantage by which the jaws 92, 94 and 96 may be caused to grip the end portion of the strip 23 with a desired high clamping force.

When it is desired to open the clamp 88, air is supplied to the cylinder 110 through the line 132 and the other end of the cylinder is vented through the line 128. This produces rotation of the cylinder bracket 112 and its arm 114 in a counterclockwise direction as viewed in FIGURE 3, during which movement the cam follower 118 moves to the right as viewed in FIGURE 4 and out of engagement with the cam surface 126 and the cam follower moves into engagement with the outer cam surface 124 and cooperates therewith to produce rapid pivotal movement of the arm 106 in a counterclockwise direction as viewed in FIGURE 4, about the pin 108, to return the arm 106 to the open position illustrated in FIGURES 1, 2 and 3. At the same time, the lower movable jaw arm 99 is moved through a small arc in a counterclockwise direction as viewed in FIGURE 3, to the open position there illustrated.

The head 84 also carries a cam follower bar 134 which is also mounted on the plate 90 and which extends parallel to the end portion of the strip 23 gripped by the clamp 88. This cam follower bar 134 engages a earn 136 which is mounted below and similar in shape to the curved end portion 22 of the form 18. The cam follower bar 134 is held against the cam 136 by an air cylinder 138, the rear end of which is connected to the slide 36 by a bracket 140. The outer end of the cylinder piston rod 142 is pivotally connected to a bar 144 mounted on the head 84. It will now be appreciated that during the operation of the machine for bending a metal moulding strip 23, there is a progressively shortening portion of the strip 23 between the clamp 88 and the point at which the strip 23 converges with the form 18. The cam follower bar 134 and the cam 136 cooperate to position the head 84 so that at the start of and throughout the bending operation, the clamp 88 exerts a straight pull on strip 23 and the end portion of the strip 23 held in the clamp 88 is not cocked relative to this free portion of the metal strip 23.

During the actual stretch bending operation the tension in the strip 23 serves to hold the cam follower bar 134 against the cam 136 because of the fact that the line of action 1460f the force exerted on the clamp by the strip 23 passes outside of the axis 148 of the bearing 86, thus exerting a moment on the head 84 urging the cam follower bar 134 against the cam 136. It will thus be seen that the air cylinder 138 functions primarily to position the cam follower bar 134 against the cam 136 in the start position of the machine and to hold the cam follower bar 134 against the cam 136 during return movement of the carriage arm 24 from the finish position to the start position.

Referring to FIGURES 4 and 5, the carriage arm 24 has a shaft 152 which extends downwardly through the bearing 26 and plate 16 and carries a gear 154 which engages with a rack 156 which is operatively connected to and reciprocable by the piston rod 157 of a pneumatic cylinder 160. As pointed out previously, there is at the left-hand end of the machine illustrated in FIGURE 1, apparatus similar to that illustrated in FIGURE 4, which also'includes a shaft 152 depending from the carriage arm and which similarly carries a gear 154 engaged by a rack 156 which is operated by the piston rod 158 of an air cylinder 160.

As diagrammatically shown in FIGURE 5, the cylinders 161) are located adjacent the opposite ends of the machine and the racks 156 extend toward the center of the machine on opposite sides of the gears 154. The adjacent ends of the racks 156 are interconnected by a turnbuckle 162 to insure simultaneous rotation of the shafts 152 and therefore, simultaneous operation of the mechanisms at the two ends of the machine. FIGURE 5 shows the parts in the start position and it will be seen that as air is supplied under pressure to the upper ends of the two cylinders 160, the shaft 152 in the upper portion of FIGURE 5 is turned in a counterclockwise direction and the shaft 152 in the lower portion of FIGURE 5 will be turned in a clockwise direction.

The operation of the machine above described is as follows. Starting with the parts of the machine in the start position, illustrated in FIGURES 1, 2, 3, 5 and 6, a strip 23 is placed in the machine by placing the center of the strip against the center of the form 18 and inserting the end portions of the strip into clamps 88. Air is then supplied under pressure to the air cylinders 110 through the lines 128 which operates to close the clamps 88 to grip the strip 23 as above described. At this time the head 84 is being held in its start position by air pressure supplied to the cylinder 138 through a line 164 which acts as above described to hold the cam follower arm 134 against the cam 136. Once the strip 23 is thus properly in place, with the clamps 88 closed, air under pressure is then supplied to the cylinders 64 through lines 166 and to the upper ends of the cylinders 160 as viewed in FIGURE 5. I

Application of the air pressure to the cylinders 64, as above described, acts to urge the slides 36 outwardly and force the cam followers 46 against the portion 58 of the cam 50. This pressure exerted by the cam follower 46 on the cam 50 has a component urging the carriage arms 24 to pivot about the axis 28 from the start position toward the finish position. At the same time, the force exerted in the cylinders 166 acts to turn the shafts 152 depending from the carriage arms 24 so as to cause the arms 24 to pivot from the start position toward the finish position. During the ensuing movement of the carriage arms 24 from the start position illustrated in 8 FIGURES 1, 2, 3, 5 and 6 (full lines) to the finish position illustrated in FIGURE 4 and illustrated in the lefthand one of the two dotted line positions illustrated in FIGURE 6, the slide 36 is moved outwardly along the carriage arm 24 as best illustrated in FIGURE 6 and the head 84 is oscillated relative to the slide 36 about the axis 148 from the full line position illustrated in FIG- URE 6 through intermediate positions, one of which is illustrated in the right-hand dotted line position illustrated in FIGURE 6, to the finish position illustrated in the lefthand dotted line position of FIGURE 6 in which it has returned to substantially the same position relative to the slide 36 as it occupied in the start position of the arm 24.

Attention is directed to the fact that throughout the movement of the carriage arm 24 from the start position to the finish position, the line of action 146 of the force exerted on the clamp 88 by the strip 23 passes between the axis 28 and the form 18 and produces a moment about the axis 28 urging the carriage arm 24 toward the finish position. This results from the fact that the axis 28 is disposed outwardly of a tangent to the inner end of the curved portion 22 of the form 18. This tangent is represented in FIGURE 6 by the start position of the strip 23.

The axis 28 is also disposed outwardly of a line 168 tangent to the curved form portion 22 at its outer end. During the bending operation the moment about the axis 28, which is always in a direction urging the carriage arm toward the finish position, has a moment arm which varies from a starting length represented by the bracket 170, and increases to a maximum represented by the bracket 172 and subsequently decreases to a length at the finish position represented by the bracket 174. During this stretch bending operation the roller 48 follows the outer edge of the cam 50. Except for this, the moments exerted on the arm 24 would cause it to immediately swing to its finish position without the inner roller 46 following the inner edge of the cam 50. By using the outer roller 48 in engagement with the outer edge of the cam 51) to insure that the slide 36 will have the desired movement, the speed of movement of the arm 24 may be controlled as desired by controlling the supply of air to the cylinders 64 through the lines 166 and the venting of the opposite ends through the lines 176.

Also, it will be appreciated from a consideration of FIGURE 6 that throughout the bending operation the moment exerted on the head 84 by the tension in the strip 23, is always in a direction to hold the cam follower bar 134 against the cam 136. This is because in all positions of the machine, the line of action 146 of the force exerted on the clamp 88 by the strip 23 always passes outside of the axis 148 about. which the head 84 pivots with respect to the slide 36. When the carriage arms 24 reach the finish positions, the clamps 88 may be opened by supplying air to the cylinders 118 through the lines 132 and the bent strip may then be removed from the machine. The machine is then re turned to the start position by supplying air to the lower ends of the cylinders as viewed in FIGURE 5. During this return movement of the carriage arm 24, air is also supplied to the cylinder 138 through the line 164 so as to hold the cam follower bar 134 in engagement with the cam 136 and return the head to its start position. The carriage arm 24 is stopped when it reaches the start position by a stop 178 mounted on the plate 16 and best illustrated in FIGURE 4. A similar positive stop, not shown, is mounted on the plate 16 to engage the arm 24 when it reaches the finish position.

The machine may also include means for releasing the tension on the strip 23 when the carriage arm 24 has reached the finish position. A preferred form of tension releasing means is shown in FIGURES 7 and 10, in which it will be seen that the rear end portion of the cam member 50 includes a cam segment 60 which is mounted on the cam 50 for pivotal movement with respect thereto about a pivot pin 180. The cam segment 60 has a depending portion 61 which is movable in a recess 62 in the cam 50 and which is engaged by the roller 48 when the arm 24 is in the finish position. A valve 182 is mounted on the plate 16 and is engaged by the slide 36 when the carriage arm 24 reaches the finish position. The valve 182 supplies air to an air cylinder 184, one end of which is connected to a block 186 mounted on the plate 16 and the piston shaft 188 of which is pivotally connected to an arm 189 carried by the cam segment 6%. When the valve 182 is actuated by the slide 36, air is supplied to the cylinder 184 through a line 190. This causes the cam segment 60 to pivot forwardly about the pivot pin 180 toward the axis 28 moving the depending portion 61 inwardly of the recess 62. This causes the slide 36 to move forwardly on the carriage arm 24 and release the tension in the strip 23.

A mechanism for performing a cutting operation is illustrated in FIGURE 8. In the construction there illustrated the cutting is performed at the midpoint of the form 18 and is effected by means of a generally L-shaped cutter generally indicated at 192, which is pivotally mounted above the form 18 on a supporting bracket 194 by a pivot pin 195 and includes a short knife arm 196 adapted to cut through the strip 23 and move into a notch 198 in the form 18. The cutter 192 also includes a long arm 2% extending upwardly and rearwardly from its pivotal connection to the supporting bracket 194. Movement of the cutter 192 is effected by a cylinder 202', the lower end of which is pivotally connected to a supporting block 204 fixed on the plate 16 and the piston rod 206 of which extends upwardly therefrom and is pivotally connected as indicated at 298 to the upper end of the arm 200. When the machine is equipped as illustrated in FIGURE 8 to perform the secondary operation of cutting the strip 23, the machine also preferably includes a stretch release mechanism such, for example, as that illustrated in FIGURE 7. Prior to the actuation of the strip cutting mechanism illustrated in FIGURE 8, the tension release mechanism is actuated to avoid tearing of the strip during the cutting operation.

It will be appreciated by those skilled in the art that numerous modifications and changes may be made without departing from the spirit of the present lnvention.

What is claimed is:

1. A machine for stretch bending strips of metal moulding comprising a support, a form mounted on said support adapted to engage said moulding during the bend ng thereof, means for holding one portion of a moulding strip in engagement with one portion of said form, a carriage anm mounted on said support in spaced relation to said form for rotation about a first axis, a slide mounted on said carriage arm for reciprocation therealong, a head mounted on said slide for rotation relative thereto about a second axis, clamp means mounted on said head and adapted to grip an end portion of said moulding, a cam follower mounted on said slide, a cam mounted on said support for engagement by said cam follower, power means acting between said carriage arm and said slide for urging said slide in one direction relative to said arm and forcing said follower against said cam, said cam being so shaped and disposed that said power means in forcing said follower against said cam produces a moment urging said carriage arm to rotate about said first named axis in the direction of rotation thereof during operation of said machine forbending a strip of metal moulding, a second cam mounted on said support and a second follower on said head cooperating to control the rotation of said head about said second axis during said operation of said machine.

2. A machine for stretch bending strips of metal moulding as defined in claim 1, wherein said first named cam has a portion engaged by said first named cam follower during the initial portion of said operation of said machine which is of increased slope relative to the adjacent portion of said first named cam.

3. A machine for stretch bending strips of metal moulding as defined in claim 1, including auxiliary power means for rotating said carriage arm.

4. A machine for stretch bending strips of metal moulding as defined in claim 1, including means independent of said strip of moulding urging said second follower against said second cam during the return movement of said machine after a stretch bending operation so that said head is returned to its starting position.

5. A machine for stretch bending strips of metal moulding as defined in claim 1, wherein said first named axis is so disposed that during operation of said machine to bend a strip of moulding the tension in said strip acting on said clamp produces a moment urging said carriage arm to rotate in said direction.

' 6. A machine for stretch bending strips of metal moulding as defined in claim 5, wherein said carriage arm, said slide, said head and said clamp are so constructed and so arranged relative to each other and relative to said form that the force exerted by a said strip of metal moulding on said clamp during operation of said machine to stretch bend said strip has a moment arm with respect to said first named axis which varies during said operation of said machine and is a maximum intermediate the beginning and end of said operation.

7. A machine for stretch bend-ing strips of metal moulding as defined in claim 1, wherein said first named axis is disposed externally of said form and said clamp is so disposed on said head that throughout a major portion of said operation of said machine the strip of moulding extends between said form and said first named axis.

8. Amachine for stretch bending strips of metal moulding as defined in claim 7, wherein said clamp is so disposed on said head that throughout a major portion of said operation of said machine said strip of moulding intersects a line between said axes.

9. A machine for stretch bending strips of metal moulding comprising a support, a form mounted on said support adapted to engage said moulding during the bending thereof and including a curved portion, means for holding one portion of a moulding strip in engagement with said form, a carriage arm mounted on said support in spaced relation to said form for rotation about a first axis, said axis being disposed with respect to said form on the opposite side of a first line tangent to said curved portion of said form adjacent one end thereof and on the opposite side of a second line tangent to said curved portion adjacent the other end thereof, said carriage arm being movable between a start position in which it extends away from said form and converges with said first line and a finish position in which it extends generally along said second line in a direction toward said form, a slide mounted on said arm for reciprocation therealong, a head mounted on said slide for rotation about a second axis, a clamp mounted on said head adapted to grip an end portion of said strip, a cam follower carried by said slide, a cam mounted on said support, power means acting between said carriage arm and said slide for moving said slide away from said first axis and forcing said follower against said cam, said cam having a first portion disposed to be engaged by said follower when said arm is in said start position and during initial movement of said arm toward said finish position, an end portion disposed to be engaged by said follower when said follower is in said finish position and an intermediate portion, the distance of said intermediate portion from first axis increasing from said first portion of said cam to said end portion of said cam, a second cam mounted on said support, a second cam follower mounted on said head and co-operating with said second cam to limit rotation of said head in one direction relative to said form during movement of said carriage arm from said start position to said finish position to an angle substantially equal to the angle between said first line and said second line, said clamp being disposed, when said second follower is engaging said second cam, on the opposite side, with relation to said form, of a line intersecting said second axis and through the closest point of engagement of said form with said strip.

10. A machine for stretch bending strips of metal moulding as defined in claim 9, including an arcuately shaped guide concentric with said first axis, and co-operating means on said carriage arm engaging said guide to support said carriage arm against movement at right angles to the plane of said guide.

11. A machine for stretch bending strips of metal moulding as defined in claim 9, including auxiliary power means for rotating said carriage arm.

12. A machine for stretch bending strips of metal moulding as defined in claim 1, including means actuated in response to movement of said first named cam follower to one end of said first named cam at the completion of a said operation of said machine for stretch bending a strip of moulding to move said slide relative to said arm in a direction opposite to that in which said slide is urged by said power means.

13. A machine for stretch bending strips of metal moulding as defined in claim 9, wherein said end portion of said first named cam is mounted for pivotal movement relative to said intermediate portion, and means responsive to movement of said first named cam follower along said end portion of said cam for pivoting said end portion to move said slide in a direction toward said first axis.

14. A machine for stretch bending strips of metal moulding as defined in claim 9, wherein the distance of said first portion of said cam from said first axis increases toward said intermediate portion at a faster rate than said increase in distance of said intermediate portion from said first axis.

15. A machine for stretch bending strips of metal moulding comprising a support, a form mounted on said support generally centrally thereof and having a central portion and curved end portions, said central portion of said form being adapted to engage and support the central portion of a said strip received in said machine for bending thereby, means mounted on said support at each end of said form for engaging said strip and stretch bending it about said form, said means comprising a carriage arm mounted on said support for rotation about a first axis, a slide mounted on said arm for reciprocation therealong, a head mounted on said slide for rotation relative thereto about a second axis, a clamp mounted on said head and adapted to grip an end portion of said strip, a cam follower mounted on said slide, a cam mounted on said support, power means acting between said carriage arm and said slide for moving said slide in one direction relative to said arm to force said follower against said cam, said carriage arm rotating in one direction during operation of said machine for bending a said strip and said cam being disposed and shaped to co-operate with said follower to provide a moment about said first axis urging said arm in said one direction, a second cam mounted on said support, a second cam follower on said head co-operating with said cam during operation of said machine to bend a said strip to control the rotation of said head about said second axis, power means individual to said carriage arms mounted on said support and engaging said carriage arms for elfecting rotation thereof, and means interconnecting said carriage arms for simultaneous rotation.

16. A machine for stretch bending strips of metal moulding comprising a support, a form mounted on said support generally centrally thereof and having a central portion and curved end portions, said central portion of said form being adapted to engage and support the central portion of a said strip received in said machine for bending thereby, means mounted on said support at each end of said form for engaging said strip and stretch bending it about said form, said means comprising a carriage arm mounted on said support for rotation about a first axis, a slide mounted on said arm for reciprocation therealong, a head mounted on said slide for rotation relative thereto about a second axis, a clamp mounted on said head and adapted to grip an end portion of said strip, a cam follower mounted on said slide, a cam mounted on said support, power means acting between said carriage arm and said slide for moving said slide in one direction relative to said arm to force said follower against said cam, said carriage arm rotating in one direction during operation of said machine for bending a said strip and said cam being disposed and shaped to co-operate with said follower to provide a moment about said first axis urging said arm in said one direction, a second cam mounted on said support, a second cam follower on said head co-operating with said cam during operation of said machine to bend a said strip to control the rotation of said head about said second axis, and means eifective upon the completion of the stretch bending of a said strip and before the opening of said clamps for moving at least one of said slides relative to the arm upon which it is mounted and in a direction opposite to said one direction.

17. A machine for stretch bending strips of metal moulding comprising a support, a form mounted on said support generally centrally thereof and having a central portion and curved end portions, said central portion of said form being adapted to engage and support the central portion of a said strip received in said machine for bending thereby, means mounted on said support at each end of said form for engaging said strip and stretch bending it about said form, said means comprising a carriage arm mounted on said support for rotation about a first axis, a slide mounted on said arm for reciprocation therealong, a head mounted on said slide for rotation relative thereto about a second axis, a clamp mounted on said head and adapted to grip an end portion of said strip, a cam follower mounted on said slide, a cam mounted on said support, power means acting between said carriage arm and said slide for moving said slide in one direction relative to said arm to force said follower against said cam, said carriage arm rotating in one direction during operation of said machine for bending a said strip and said cam being disposed and shaped to co-operate with said follower to provide a moment about said first axis urging said arm in said one direction, a second cam mounted on said support, a second cam follower on said head co-operating with said cam during operation of said machine to bend a said strip to control the rotation of said head about said second axis, means for performing a secondary operation on a said strip after the stretch bending thereof is completed and while said clamps continue to grip the end portions thereof, and means for simultaneously moving said slides relative to said arms upon which they are mounted and in a direction opposite to said one direction to release the tension in said strip prior to operation of said means for performing a secondary operation.

References Cited in the file of this patent UNITED STATES PATENTS 1,968,010 Bailey July 31, 1934 2,292,731 Amiot Aug. 11, 1942 2,442,268 Fields May 25, 1948 2,619,149 Self Nov. 25, 1952 2,830,644 Walker Apr. 15, 1958 FOREIGN PATENTS 482,769 Great Britain Apr, 5, 1938

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