Abstract:
The present invention is a shrinker stretcher machine that uses four distinct and separate tool cartridges to perform both shrinking and stretching operations by simply removing, rotating each tool cartridge 180 degrees, and reattaching it in its designated position. Each tool cartridge removably carries a jaw that can be removed and securely replaced with either a shrinker or stretcher jaw to accommodate the operation being performed. Each tool cartridges and jaw is firmly held in place by magnets and interlocking keyed surfaces to properly align and hold the tool cartridges and jaws.

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention relates to a power shrinker stretcher machine for shaping sheet metal that includes tool cartridges that allow easy conversion from shrinking to stretching. 
     BACKGROUND OF THE INVENTION 
     Sheet metal shrinking and stretching machines are well known. These machines include a first set of four tool cartridges that are specifically for shrinking sheet metal, and a second set of four tool cartridges that are specifically for stretching sheet metal. Each cartridge has a jaw for compressible engaging and gripping a sheet metal workpiece. When the upper and lower jaws are separated, the sheet metal is placed between the gap between them. The operation of the machine brings the jaws into compressed engagement with the sheet metal, which is located between the upper and lower jaws. The jaws firmly hold the sheet metal in place between the upper and lower jaws. During shrinking mode, further compression of the jaws causes the right and left jaw sets to move toward each other so that a thin strip of the sheet metal between the right and left jaw sets is compressed or shrunk. During the stretching mode, further compression of the jaws causes the right and left jaw sets to move apart so that a thin strip of the sheet metal between the right and left jaw sets is stretched. 
     A problem with conventional shrinker stretcher machines is that switching from the shrinking mode to the stretching mode requires two tool units, each containing four tools, for a total of eight tools. One shrinker unit must be removed and replaced with a stretcher unit. The operator must have both tool units on hand in order to make the switch. 
     Another problem with conventional shrinker stretcher machines is that a shrinker unit includes four integral tools. If one tool in the shrinker unit breaks or becomes jammed, then the entire unit (all four tools) are rendered unusable. Similarly, if one tool in the stretcher unit breaks or becomes jammed, then the entire unit (all four tools) are rendered unusable. As a result, the efficient operation of a conventional shrinker stretcher machine typically requires one extra shrinker unit and one extra stretcher unit to be on hand to prevent costly machine down time. Yet, each shrinker unit and each stretcher unit is relatively expensive. 
     A still further problem with conventional shrinker stretcher machines is that each shrinker unit includes four integral jaws. Yet, different sheet metal thicknesses or materials such as aluminum, copper, copper-nickel, mild steel, steel, stainless steel work best with different types of jaw surfaces textures to grip the sheet metal during operation. Different jaw surface textures produce the different gripping power needed to shrink or stretch different materials or material thicknesses. In addition, some job specifications require minimal surface distortion to achieve a necessary level of smoothness in the finished workpiece. While a knurled or low grit jaw surface may work best for a particular material, material thickness or project specification, a serrated jaw surface may work best for another, and a large grit or hard grit or even diamond grit surface may work best for yet another. Yet, because the jaws are integral components of the shrinker or stretcher tool units for conventional shrinker stretcher machines, multiple shrinker tool units or stretcher tool units are required to effectively handle a wide variety of sheet metals materials, sheet metal thicknesses or project specifications. 
     A still further problem with conventional shrinker stretcher machines is their limited range of use. While the machines produce enough gripping power to adequate handle softer sheet metal materials, such as aluminum, copper, copper-nickel or mild steel, they do not produce enough gripping power to adequately handle harder materials, such as steel or stainless steel. The gripping power of many conventional machines also limits the thickness of the sheet metal workpieces they can handle, as thicker sheets require more gripping power to shrink or stretch the metal. 
     The present invention is intended to solve these and other problems. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention pertains to a shrinker stretcher machine that uses four distinct and separate tool cartridges to perform both shrinking and stretching operations by simply removing, rotating each tool cartridge 180 degrees, and reattaching it in its designated position. Each tool cartridge removably carries a jaw that can be removed and securely replaced with either a shrinker or stretcher jaw to accommodate the operation being performed. Each tool cartridges and jaw is firmly held in place by magnets and interlocking keyed surfaces to properly align and hold the tool cartridges and jaws. 
     One advantage of the present shrinker stretcher machine is that switching from shrinking mode to stretching mode only requires one set of four tool cartridges. The tool cartridges are removed, rotated 180 degrees, and resecured to the machine to convert from shrinking mode to stretching mode. Accordingly, the operation of the machine does not require a first set of four tool cartridges that are specifically for shrinking sheet metal, and a second set of four tool cartridges that are specifically for stretching sheet metal. 
     Another advantage of the present shrinker stretcher machine is that it uses four separate tool cartridges. If one tool cartridge breaks or becomes jammed, only that cartridge need be replaced. The machine can continue using the other three tool cartridges. The efficient operation of the present shrinker stretcher machine requires only one or two extra cartridges to avoid costly machine down time. 
     A still further advantage of the present shrinker stretcher machine is that each tool cartridge can accommodate multiple jaws with multiple surface textures. For the low cost of obtaining multiple jaws and surface textures, the machine can properly handle different sheet metal thicknesses or different materials such as aluminum, copper, copper-nickel, mild steel, steel and stainless steel. The jaw surface texture that produces the proper gripping power can be cost effectively selected to shrink or stretch different materials or material thicknesses. In addition, the appropriate jaw surface texture can be cost effectively chosen for job specifications that require minimal surface distortion to achieve a necessary level of smoothness in the finished workpiece. While a knurled or low grit jaw surface can be used for a particular material, material thickness or project specification, a serrated jaw surface can be swapped for another type of job, and a large grit or hard grit or even diamond grit surface can be used for yet another job. Costs are kept to a minimum because only different jaws need be obtained, not entire conventional shrinker tool units or entire conventional stretcher tool units. 
     A still further advantage of the present shrinker stretcher machines is its power and durable design. The hydraulic power unit is capable of producing 2,000 psi of hydraulic pressure, which produces about 10,000 lbf at the piston rod of the hydraulic cylinder and about 40,000 lbf at the drive rod or the driven ram. Accordingly, the machine is capable of handling a wide variety of sheet metal materials and material thicknesses. The machine can handle softer materials, such as aluminum, copper, copper-nickel and mild steel, and harder materials, such as steel and stainless steel. The machine also produces sufficient gripping power to handle thicker sheet metals workpieces of up to about ⅛ inch thick aluminum or 14 gauge steel, but can be scaled up to handle ¼ thick steel. 
     A still further advantage of the present shrinker stretcher machine is its adjustability during operation to control the incremental amount of shrinking or stretching during each compression stroke and sheet metal movement cycle of the machine. A stroke length adjustment mechanism is provided to allow some adjustment in the tool stroke length of the machine. A gap adjusting wheel also allows the operator to control the gap between the jaws and the tool during operation. These adjusting mechanisms allow the operator to control the incremental amount of shrinking or stretching during each compression stroke of the machine. 
     A still further advantage of the present shrinker stretcher machine is its adjustability to accommodate different sheet metal materials and thicknesses. The jaws can slip when handling harder materials or thicker sheet metal workpieces because more gripping force between the jaws is needed to firmly grip the workpiece before shrinking or stretching occurs. The tools of the present shrinker stretcher machine are adjustable to achieve higher or lower gripping force between the jaws and the sheet metal before the shrinking or stretching occurs. 
     Other aspects and advantages of the invention will become apparent upon making reference to the specification, claims and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the inventive shrinker stretcher machine  10  showing its support frame  11 , upper support structure  20 , fixed anvil  30 , moving ram  40 , tools  60 , power supply and control system  110  and tool drive assembly  130 . 
         FIG. 2  is an enlarged view of the shrinker stretcher machine  10  showing its support structure  20 , fixed anvil  30  and ram  40 , tools  60  and tool drive assembly  130 . 
         FIG. 3  is an exploded view of the shrinker stretcher machine  10  showing its fixed anvil  30 , ram  40 , tools  60  and tool drive assembly  130 . 
         FIG. 4A  is an exploded view of four tools  61 - 64  arranged in shrinking alignment. 
         FIG. 4B  is an exploded view of four tools  61 - 64  arranged in stretching alignment. 
         FIG. 5A  is an enlarged view the four tools  61 - 64  with shrinker jaws  101  and arranged in shrinking alignment. 
         FIG. 5B  is an enlarged view the four tools  61 - 64  with stretcher jaws  102  and arranged in stretching alignment. 
         FIG. 6A  is a side plan view showing a sheet metal workpiece  5  located in the Gap between tools  60  when ram  40  and piston rod  120  are in release positions  57  and  127 . 
         FIG. 6B  is a side plan view showing a sheet metal workpiece  5  being initially gripped by the tools  60  when ram  40  and piston rod  120  are in gripping positions  58  and  128 . 
         FIG. 6C  is a side plan view showing a sheet metal workpiece  5  between tools  60  when ram  40  and piston rod  120  are in their fully extended positions  59  and  129 . 
         FIG. 7A  is an enlarged front view showing a sheet metal workpiece  5  located in the Gap between tools  60  equipped with shrinker jaws  101  when ram  40  and piston rod  120  are in release positions  57  and  127 . 
         FIG. 7B  is an enlarged front view showing a sheet metal workpiece  5  being initially gripped by tools  60  with shrinker jaws  101  when ram  40  and piston rod  120  are in gripping positions  58  and  128 . 
         FIG. 7C  is an enlarged front view showing a sheet metal workpiece  5  when ram  40  and piston rod  120  are in their fully extended positions  59  and  129 , and when the cams  80  and moving blocks  75  of each cartridges  70  have moved toward the machine centerline  55  to shrink the area of the workpiece  5  between tools  60 . 
         FIG. 8A  is an enlarged front view showing a sheet metal workpiece  5  located in the Gap between tools  60  equipped with stretcher jaws  102  when ram  40  and piston rod  120  are in release positions  57  and  127 . 
         FIG. 8B  is an enlarged front view showing a sheet metal workpiece  5  being initially gripped by tools  60  with stretcher jaws  102  when ram  40  and piston rod  120  are in gripping positions  58  and  128 . 
         FIG. 8C  is an enlarged front view showing a sheet metal workpiece  5  when ram  40  and piston rod  120  are in their fully extended positions  59  and  129 , and when the cams  80  and moving blocks  75  of each cartridges  70  have moved away from the machine centerline  55  to stretch the area of the workpiece  5  between tools  60 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While this invention is susceptible of embodiment in many different forms, the drawings show and the specification describes in detail a preferred embodiment of the invention. It should be understood that the drawings and specification are to be considered an exemplification of the principles of the invention. They are not intended to limit the broad aspects of the invention to the embodiment illustrated. 
     The present invention relates to a power shrinker stretcher machine for shaping a workpiece  5  such as a sheet of metal. The shrinker stretcher machine is generally depicted as reference number  10  in  FIG. 1 . The shrinker stretcher machine  10  is mounted on a support frame  11  that includes a base  12  that rests on the floor of a building. The base  12  has a wide footprint to stabilize during operation. The frame  11  has a central post  13  extending upwardly from the base  12  to elevate a workpiece receiving area  15  of the machine  10  about three feet above the floor to facilitate ease of use and material handling during operation. The machine  10  is secured to the top of the post  13  via brackets  14 , and is about four and a half feet tall and has a front  16  to back  17  depth of about one and a half feet. While the machine  10  is particularly suited for shaping sheet metal  5 , it should be understood that the broad aspects of the invention are not limited to sheet metal. 
     The shrinker stretcher machine  10  includes a support structure or plate  20  for attaching many of the various other components forming the machine. The plate  20  is robustly designed and about two inches thick to withstand the significant cyclical loads produced by the machine  10 . The support plate  20  has parallel and planar side surfaces, and is oriented perpendicular to the ground. The support plate  20  has a generally round C-shaped configuration and perimeter. The C-plate  20  forms a rear hinge  21  with a hinge hole, an upper pivot hole  22 , forward anvil guide slots  23  and a large central opening  24  extending inwardly from a front mouth  25  of the machine. The C-shaped plate  20  defines the upper and lower jaws  26  and  27  located above and below its mouth  26  for receiving the workpiece  5 . The mouth  26  generally forms the working area  15  of the machine  10 . The upper jaw  26  has a flat vertical front surface  28  proximal the guide slots  23  and is slightly recessed from the lower jaw  27 . The lower jaw  27  has a flat horizontal upper surface  29 . 
     A fixed anvil or plate  30  is secured to the lower jaw  27  of the C-plate  20 . The fixed anvil  30  has a U-shaped configuration with a lower flat bottom slot surface  32  that flushly engages the flat upper surface  29  of the plate  20 . The fixed anvil  30  is slightly wider than the C-plate  20  so that its sides snuggly overlap the plate  20  to prevent side-to-side movement. The sides of the anvil  30  are also rigidly secured to the C-plate  20  via bolts or the like. The upper surface  35  of the anvil  30  is generally horizontal and flat, except for right  36  and left  37  tool slots. The tool slots  36  and  37  are parallel to each other, and in generally linear alignment with C-plate  20 . The slots  36  and  37  are spaced apart a predetermined distance of about 1.82 inches, each being spaced equidistantly from the center of the plate  20 , anvil  30  and machine centerline  55  as discussed below. 
     A driven anvil  40  is positioned directly above and in registry with the fixed anvil  30 . The driven anvil  40  has an 1-beam shape configuration with an upper flange  41 , a central web  42  and a lower flange  43 . The lower flange  43  has a lower surface  45  that is about the same size as the upper surface  35  of the fixed anvil  30 . The lower surface  45  of the lower flange  43  is generally horizontal and flat, except for right  46  and left  47  tool slots. The tool slots  46  and  47  are parallel to each other, and in generally linear alignment with C-plate  20 . The slots  46  and  47  are spaced apart a predetermined distance of about 1.82 inches, each being spaced equidistantly from the center of the plate  20 , lower flange  43  and machine centerline  55 . As a result, the slots  46  and  47  of the driven anvil  40  are directly above and in parallel registry with the slots  36  and  37  of the fixed anvil  30 . 
     A guide  50  movingly holds the driven anvil  40  to the upper jaw of the C-plate  20 . The guide includes two spaced side brackets  51  joined by a front bracket  52 . The side brackets  51  are flushly and snuggly received by the slots  23  of the C-plate  20  so that they extend horizontal at a predetermined location relative to the mouth  25  and upper and lower jaws  26  and  27  of the C-plate  20 . The front bracket  52  forms a flat vertical inwardly facing slot  53 . The drive anvil  40  is received between the guide  50  and upper jaw  26  of C-plate  20 . The anvil web  42  has flat front and rear surfaces that flushly and slidably engage the flat front surface  28  of the upper jaw  26  and front slot  53  of the guide  50 . The sides of the anvil web  42  flushly and slidably engage the side brackets  51  of the guide  50 . The length of the web  42  is longer than the side brackets  51  so that the outer ends of the flanges  41  and  43  extend over and outwardly from the side brackets  51  to form limit stops for the driven anvil  40 . The upper flange  41  forms the lower limit stop of movement for the drive anvil  40  to prevent inadvertent damage to the tools during the operation of the machine  10  as described below. 
     The parallel side surfaces of the support plate  20  and guide  50  define a centerline  55  of ram  40  movement for the machine  10 . The anvil  30  and ram  40  are symmetrical about centerline  55 . The driven anvil  40  is free to slide up and down in the guide  50  along a vertical path of travel  56  in linear alignment with the machine centerline  55  as shown in  FIGS. 5A and 5B . As discussed below, during each cycle of operation, the ram or driven anvil  40  travels between a raised or retracted position  57  shown in  FIGS. 6A ,  7 A and  8 A, a partially extended workpiece gripping position  58  shown in  FIGS. 6B ,  7 B and  8 B, and a fully extended workpiece formed position  59  shown in  FIGS. 6C ,  7 C and  8 C. 
     The machine  10  is fitted with four tools  60 . Two tools  62  and  64  are secured to the fixed anvil  30 . Two tools  61  and  63  are secured to the moving anvil or ram  40 . The first and second tools  61  and  62  on the right side of the machine centerline  55  form a first workpiece gripping set  65 , and the third and fourth tools  63  and  64  on the left side form a second workpiece gripping set  66 . Each cartridge  70  has a width of about 1-⅝ inches, depth of about 1-⅜ inches and height of about 1-⅞ inches including jaws  100 . The cartridge  70  has substantially flat, opposed outer end surfaces  67  and  68  with substantially the same footprint. Both surfaces  67  and  68  are in spaced substantially horizontal alignment. The spacing between the surfaces  67  and  68  changes when outer rotating surface  68  moves sideways in a rotational manner relative to fixed surface  67  during the operation of the machine  10  as discussed below. Still, these surfaces  67  and  68  remain in substantially parallel alignment throughout the operation of the machine  10 . 
     Each tool  60  includes a cartridge  70  having a matched set of fixed  71  and moving  75  block halves. Each set of block halves  71  and  75  is aligned in mating registry. Each block half  71  and  75  has about the same width, depth and height. Each fixed block half  71  has a predominantly flat outer surface  72  (cartridge surface  67 ) with a linear outwardly extending rib  73  extending from the front to the rear of the block. The ribs  73  and  77  are located at the center of their respective block half  71  and  75 . Each moving block half  75  has an opposed predominantly flat outer surface  76  (cartridge surface  68 ) with a linear outwardly extending rib  77  extending from the front to the rear of the block. The linear rib  77  is parallel to rib  73  but offset from the centerline of the moving block half  75  about 0.050 inch (when in home position  87 ). The inner surface of each block  71  and  75  forms a pocket  74  or  78  with a constant radius groove and an adjacent slot. One pocket  74  and  78  is located on each side of the ribs  73  and  77 . Each block  71  and  75  also holds two disc shaped magnets  79  in holes  79   a  formed in its outer surface  72  and  76 . The outer surface of each magnet  79  is flush with the outer surface  72  or  76  of its block  71  or  76 . Each magnet  79  is rigidly held in its respective block  71  or  75  by a set screw. One magnet  79  is located on each side of the ribs  72  and  77 . While magnets  79  are shown holding the tool cartridges  70  to the fixed anvil  30  and ram  40  for ease of securement and removal, it should be understood that the tools could be secured with screws or other forms of securement without departing from the broad aspects of the invention. 
     Each cartridge  70  holds two rigid metal cams  80  aligned in parallel relation. The cams are like-shaped and spaced apart to form a parallelogram. One cam  80  is located on each side of the ribs  73  and  77  of its cartridge  70 . Each cam  80  has opposed stationary  81  and rotating  82  ends. The stationary end  81  of each cam  80  has a constant radius that flushly and pivotally engages the constant radius groove of the interior pocket  74  of its fixed block half  71 . Likewise, the rotating end  82  of each cam  80  has a constant radius that flushly and pivotally engages the constant radius groove of the interior pocket  74  of its moving block half  75 . Each cam  80  has a length of about 1⅜ inches, a height of about ⅞ inch, a width of about ¼ inch, and maintains its shaped during the operation of machine  10 . Each elongated cam  80  extends from the front to the rear of the cartridge  70 . 
     Each cam  80  has an adjacent resilient spring sleeve  85  aligned parallel to and engaging the cam through its full length. The resilient sleeve springs  85  are relatively hard to compress, and are preferably made of polyurethane with a hardness of about a 90 durometers. Each sleeve spring  85  has a uniform cylindrical shape with a diameter of about ⅜ inch, and a length that extends about the width of the cartridge  70 . One spring sleeve  85  is held in the pocket  74  of the fixed block  71 , and one spring sleeve is held in the pocket  78  of the moving block  75 . One cam  80  and spring sleeve  85  set is located on each side of the central ribs  73  and  77  of the cartridge  70 . 
     When each cartridge  70  is assembled, the shape and orientation of the pockets  74  and  78 , cams  80  and sleeve springs  85  bias the cartridge  70  and its block halves  71  and  75  into a home position  87  as in  FIGS. 6A ,  7 A and  8 A. In the home position  87 , the cams  80  lean at about a 15° angle from normal to the surfaces  67  and  68  of the cartridge and the machine centerline  55 . The sleeve springs  85  snuggly engage the cams  80 . Although the cam  80  is shown as a cylinder, it should be understood that the cams could take a variety of shapes without departing from the broad aspects of the invention. 
     The cartridges  70  of the tools  60  can compress from home position  87  ( FIGS. 6A-B ,  7 A-B and  8 A- 6 B) to compressed position  89 . ( FIGS. 6C ,  7 C and  8 C). This compression causes the cams  80  to rotate and moving block half  75  to shift laterally relative to its fixed block  71 . The cams  80  rotate when they press into their adjacent polyurethane sleeves  85  with sufficient force to compress the sleeve. The hardness or resistance to compression of the sleeve  85  can be increased to achieve a higher gripping force between the tools  60  and the sheet metal  5  when in home position  87  ( FIGS. 6B ,  7 B and  8 B) before shrinking or stretching of the sheet metal  5  occurs as the tools compress to compressed position  89  as in  FIGS. 6C ,  7 C and  8 C. The shape of the pockets  74  and  78  and angle of the cams  80  when in the home position  87  can also be changed to adjust the amount of gripping force between the tools  60  and the sheet metal  5  before shrinking or stretching occurs. 
     Cover plates  90  are placed over and secured to the front and rear ends of each cartridge  70 . The cover plates  90  are firmly secured to the fixed block halves  71 , and movingly held by the moving block halves  75  via slots in the cover plate and a split pin inserted into holes in the block halves  75 . The cover plates  90  help keep the cams  80  and sleeves  85  in place, help keep debris out of the interior of the cartridge  70 , and help protect the operator during operation. 
     Each cover plate  90  is marked with the letters “M,” “X” and “U” to designate in which of the four tool positions the tools  61 - 64  are to be placed on the machine  10 . The “M” designates the side of the cartridge where the moving block half  75  is located. Each cartridge  70  is positioned with the “M” positioned toward the working area of the machine  10  where the sheet metal  5  is located between the tools  60  as shown in  FIGS. 2 ,  7 A-C and  8 A-C. The “X” and “U” designates the direction in which the moving block half  75  will move during operation. The lateral movement of the moving block  75  occurs in the direction of the “X” and away from the “U.” For shrinking, the tools  60  and cartridges  70  are inwardly oriented  96  with the “X” located toward the centerline  55  of machine  10  as in  FIGS. 7A-C . When the tools  61 - 64  are in this shrinking orientation  96 , each moving block  75  moves along a lateral path of travel  97  toward the machine centerline  55 . For stretching, the tools  60  and cartridges  70  are outwardly oriented  98  with the “U” located toward the centerline  55  of machine  10  as in  FIGS. 8A-C . When the tools  61 - 64  are in this stretching orientation  98 , each moving block  75  moves along a lateral path of travel  99  away from the machine centerline  55 . 
     Each tool  60  has a gripping jaw  100  secured to its moving block  75 . There are generally two types of gripping jaws  100 . Shrinking jaws  101  are best shown in  FIG. 4A . Stretching jaws  102  are best shown in  FIG. 4B . Shrinking jaws  101  have opposed mating teeth  103  to prevent the sheet metal  5  from buckling when the sheet segment between the opposed jaws is compressed. Stretching jaws  102  do not have teeth as the sheet segment between the opposed jaws is being stretched. For a shrinking operation, each of the four tool cartridges  70  holds one shrinking jaw  101  as in  FIGS. 7A-C . For a stretching operation, each of the four tool cartridges  70  holds one stretching jaw  102  as in  FIGS. 8A-C . 
     Each cartridge  70  is structures to align and releasably secure or hold any one shrinking jaw  101  or any one stretching jaw  102  during the operation of the machine  10 . Each jaw  101  and  102  has a flat lower surface  104  with a central slot  105  extending from the front to the back of the tool  60 . The central slot  105  is keyed to the rib  77  of the moving block  75  of its cartridge  70 , the components of which form a jaw alignment mechanism  108  to align the jaws of the matched sets of tool cartridges with each other and a predetermined distance from the machine centerline  55 . While the magnets  79  in the moving blocks  75  hold their respective jaw  100  to the cartridge  70 , the keyed engagement prevents side-to side movement of the jaw relative to the fixed block. While the holding power of the magnets  79  is sufficient to hold the jaws  100  to their respective cartridge  70  during operation, this holding power is readily overcome by the operator to remove the jaws when desired. While magnets  79  are shown holding the jaws  100  to the tool cartridges  70  for ease of securement and removal, it should be understood that the jaws could be secured with screws or other forms of securement without departing from the broad aspects of the invention. 
     Each shrinking  101  or stretching  102  jaw has a roughened outer surface  106  to bit into and grip the sheet metal  5 . Different types of jaws  101  and  102  can be secured to the tools  60  to accommodate different types of sheet metal materials and thicknesses, or to obtain a desired sheet metal finish depending on whether the finished surface is to be extra smooth or extra rough. 
     Each anvil  30  and  40  is structured to align and releasably secure or hold two tool cartridges  70  during the operation of the machine  10 . The fixed block  71  of each cartridge  70  is releasably secured to one of the anvils  30  and  40 . The central rib  73  is keyed to one of the slots  36 ,  37 ,  46  or  47  to prevent side-to side movement of the fixed block  71 , the components of which form first and second cartridge alignment mechanisms  109  to align the cartridges  70  to the fixed anvil  30  or drive ram  40 , and to align the matched sets of cartridges  70  in registry with each other and a predetermined distance from the machine centerline  55 . While the magnets  79  in the fixed blocks  71  hold the cartridge  70  to its respective anvil  30  or  40 , the keyed engagement prevents side-to side movement of the fixed block  71  relative to the anvil. While the holding power of the magnets  79  is sufficient to hold the cartridge  70  to their respective anvil  30  or  40  during operation, this holding power is readily overcome by the operator to remove the cartridges when desired. 
     The ram or driven anvil  40  moves cyclically between a fully retracted position  57  and a fully extended position  59  as shown in  FIGS. 6C ,  7 C and  8 C. The distance between the upper surface  35  of the fixed anvil  30  and the lower surface  45  of the driven anvil  40  when the driven anvil is at its bottom-most or bottom dead center position  56  constitutes the “gap” between the workpiece forming tools  30  and  40 . The linear movement  56  of the anvil  40  between its bottom dead center  59  and upper position  57  constitutes the stroke length SL of the anvil  41 . As discussed more fully below, the size or height of the gap can be adjusted during the operation of the machine  10 . While anvil  30  remains fixed during operation, the bottom dead center position  59  of anvil  40  can be adjusted up or down to increase or decrease the size of the gap. Adjusting the size or height of the gap does not impact the stroke length SL of the anvil  40 . Adjusting the gap moves the entire stroke of the anvil  40 . Both the top  57  and bottom  59  positions of the stroke move an equal amount when setting the gap. 
     The shrinker stretcher machine  10  includes a power supply and control system  110  for cyclically driving anvil  40  as shown in  FIG. 1 . The power supply and control system  110  includes a conventional hydraulic power unit  111 , a conventional air compressor  115 , a foot pedal  114  and a hydraulic cylinder  120 . The hydraulic power unit  110  is secured to the base  12  of the frame  11 . The hydraulic power unit  111  draws power via an electric cord plugged into a standard electric outlet. When activated by its on/off switch, the power unit  111  pressurizes the hydraulic fluid in its reservoir to up to 5,000 psi. An internal valve allows the pressurized fluid in the reservoir to selectively pressurize hydraulic fluid in a high pressure line  112 . A foot pedal  114  is used to selectively open and close this internal valve, and thereby selectively pressurize fluid in line  112 . The air compressor  115  drives the return stroke of the piston rod  125 . The air compressor  115  pressurizes air in pneumatic line  117  in pneumatic communication with the air inlet port  124  of hydraulic cylinder  120 . The air compressor  115  draws power via an electric cord plugged into a standard electric outlet. 
     The hydraulic cylinder  120  is secured to the rear of the upper support structure  20  of the machine  10 . The lower portion or high pressure side of the cylinder housing  121  is pin  122  to the hinge  21  of the C-plate  20 . The cylinder housing  121  has a hydraulic fluid port  123  and an air port  124 . The hydraulic fluid port  123  is in fluid communication with high pressure hydraulic fluid line  112  and an interior fluid manifold inside its housing  121 . An internal solenoid operating via the pressurized fluid in the manifold cyclically opens and closes an activation valve about once every two seconds to allow the hydraulic fluid in the manifold to pressurize a drive piston and piston rod  125 . When the valve is open, the pressurized hydraulic fluid pushes and extends the piston and drive rod  125  from a retracted or home position  127  to an extended position  129 . The piston has a bore diameter of about 2-12 inches, so the output or driving force of the piston rod  125  during its power stroke is about 10,000 pounds-force. 
     When activated by its on/off switch, the compressor  115  sends pressurizes air through air line  117  to the air inlet port  124  of the hydraulic cylinder  120 , which is in pneumatic communication with the opposite side of the piston. When the activation valve of the hydraulic cylinder  120  is closed, the pressurized air pushes the piston and retracts its drive rod  125 . As long as the hydraulic power unit  111  and air compressor  115  are turned on and the operator is depressing the foot pedal  114 , the piston rod  125  will be cyclically extended and retracted about once every two seconds. Although the power supply system  110  is shown and described as a power system with a power unit  111  and hydraulic cylinder  120 , it should be understood that other types of power supply systems could be used without departing from the broad aspects of the present shrinker stretcher machine invention. 
     The hydraulic power unit  111  and cylinder  120  power a ram drive assembly  130  best shown in  FIGS. 1-3  and  6 A. The ram drive assembly  130  is secured to the upper support structure  20  of the machine  10 . The assembly  130  includes a piston rod coupling  141 , reciprocating lever  150 , drive coupling  160  and drive shaft  170 . The couplings, pins, rods, lever and shaft components forming the drive assembly  130  are robustly designed to withstand the sufficient loads generated by the shrinker stretcher machine  10 . The hydraulic cylinder  120 , lever  150  and drive coupling are pivotally secured to the support plate  20 . The piston rod  125 , piston rod coupling  141  and drive coupling  141  are not directly secured to support plate  20 . The ram or moving anvil  40  is movingly held between its guide  50  and the upper jaw  26  of the support plate  20 . 
     The piston rod  125  extends upwardly from the hydraulic cylinder  120 . The piston rod  125  has an adjustable stroke length of about ½ to 1 inch as best shown in  FIGS. 6A-C . The stroke length of the piston rod  125  can be selectively varied (i.e., increased or decreased) via a stroke adjustment mechanism  126  located at the upper end of the cylinder  120 . This is done by rotating threaded cap  126   a  as discussed below. As noted above, the lower end of the hydraulic cylinder is pinned  122  to the hinge  21  at the rear of the support plate  20 . The upper end of the piston  125  is threadably secured to the lower end  142  of the piston coupling  141 . The upper end  143  of the coupling  141  is pinned  144  to the reciprocating lever  150 . The rod  125  remains substantially vertically oriented during the operation of the machine  10 . The piston rod  125  extends or elevates the ram drive assembly  130  above machine opening  24  so that the ram  40  can move up and down relative to the working area  15  of the machine  10 . This stroke of the piston rod  125  is sufficient to permit the ram  40  to be raised to its elevated or retracted position  57 , and stroked linearly downward toward the fixed anvil  30  to its lower or bottom dead center position  59 . 
     The piston rod  125  returns its upper end and coupling  141  to the same upper most extended position  129  during each cycle of the hydraulic cylinder  120 . The lever drive assembly  130  is made of rigid metal components that extend and retract the piston rod  125  and one end of the lever  150  in a rigid movement. 
     The reciprocating lever  150  is about 17 inches long and is located at the top of the machine  10  to accommodate and span the central opening  24 . The lever  150  has opposed ends  151  and  152  and is formed by two uniformly spaced plates  153  that straddle C-plate  20 . The rear end  151  is pivotally joined to the piston coupling  141  by pin  144 . The front end  152  is pivotally joined to the drive coupling  161  by its pin shaped ends  162 . The lever  150  reciprocally pivots about a pivot pin  155  that serves as a fulcrum for the lever. This fulcrum pin  155  is preferably located about 3.5 inches from the center of the front pivot point  164  and 14 inches from the center of the rear pivot point  144 . The uniform spacing of the plates  153  is maintained by the piston coupling  141 , a spacing collar  156  on the fulcrum pin  155  and a spacer  158  towards the rear of the lever  150 . 
     The drive coupling  161  transitions the pivoting motion of reciprocating lever  150  into the linear motion of ram  40 . During operation, the lever  150  remains substantially horizontal, but pivots about ½° to 2° in either direction. The drive coupling  161  is pivotally joined to the front ends of the lever plates  153  via its pin shaped ends  164 . A central threaded hole  165  is provided for rigidly and adjustably joining the drive shaft  170  of the ram  40 . The drive rod  170  is joined to the ram  40  via a greesed radiused pocket. 
     A gap adjustment assembly  180  is provided to set the “Gap” between the surface  35  and  45  of the anvil  30  and ram  40  when the ram is at its lower most position  59 . The gap adjustment assembly  180  includes the threaded hole  165  of the drive coupling  161 , the threadably joined drive rod  170 , the ram  40  and a turn wheel  185 . The wheel  185  is rotated to move the drive rod  170  and ram or moving anvil  40  between a maximum and minimum gap positions set by the upper and lower limit stops or flanges  41  and  43  of the ram  40 . The gap adjustment assembly  180  allows for continuous adjustment of the Gap, so the Gap can be set to any of an infinite number of positions between lower  41  and upper  43  limit stops. 
     The stroke adjustment mechanism  126  is operated by turning threaded cap  126   a  to set the stroke of the stroke lengths “SL” of piston rod  125  and ram  40 . Turning the cap  126   a  one way elongates cylinder  120  and increases the stroke length “SL” of the piston rod  125 , which in turn sets the stroke length “SL” of ram  40 . Turning the cap  126   a  the other way shortens the length of the cylinder  120  and decreases the stroke length “SL” of piston rod  125  and ram  40 . As fulcrum  155  of lever  150  is four times closer to the front of the lever than the rear of the lever, an adjustment in the stroke length of piston rod  125  produces a one quarter adjustment in the stroke length of ram  40 . The stroke length adjustment mechanism  126  allows for continuous adjustment of the stroke length SL of the ram  40  so the stroke length can be set to any of an infinite number of lengths between its maximum and minimum settings. The adjustment mechanism  126  selectively sets the full ram extension position  59 , but has little or no effect on its retraction position  57 . 
     Although the operation of the machine  10  should be readily understood based on the above description, the following is provided to assist the reader. The operator turns on the machine  10  by activating its power supply and control system  110 . This is done by turning on the hydraulic power unit  111  and air compressor  115  shown in  FIG. 1 . Turning on the machine  10  does not automatically activate or pressurize the hydraulic cylinder  120 , which requires the operator to depress the foot pedal  114 , so the ram  40  and piston  125  remain in their retracted positions  57  and  127 , respectively. To perform a shrinking operation, each tool  61 - 64  has its cartridge  70  positioned so that its cams  80  lean toward the centerline  55  of the machine  10  and is fitted with a shrinker jaw  101 . (FIGS.  5 A and  7 A-C). The “X” marks on the cover plates  90  of the cartridges  70  are near the machine centerline  55 . To perform a stretching operation, each tool  61 - 64  has its cartridge positioned (e.g., rotated 180°) so that its cams  80  lean away from the centerline  55  of the machine  10  and is fitted with a stretcher jaw  102 . (FIGS.  5 B and  8 A-C). The “U” marks on the cover plates  90  of the cartridges  70  are near the machine centerline  55 . 
     The sheet metal workpiece  5  is then placed in the Gap between the jaws  100  of the tools  60 . The workpiece does not fill the entire Gap. The operator sets the desired Gap by turning the wheel  185  of the Gap adjustment assembly  180  to position the ram  40  and jaws  100  of the upper tools  61  and  63  at the desired retracted position  57  and  127  for the specific workpiece  5 . Setting the Gap can be done before or after activating the machine  10 , or even on the fly during the operation of the machine. Similarly, the operator can adjust the stroke length SL of the ram  40  and upper jaws  100  by turning the cap  126   a  of the cylinder  120  to set the fully extended positions  59  and  129  of the ram  40  and upper jaws  61  and  63 , respectively. Setting the stroke length SL can be done before or after activating the machine  10 . The area of the workpiece to be worked is positioned along the centerline  55  of the machine between the right set of tools  61  and  62  and the left set of tools  63  and  64 . 
     The operator depresses foot pedal  114  to activate or pressurize hydraulic cylinder  120 , and initiate the cycling of the piston rod  125  about once every two second. The cyclical movements of the ram  40 , piston rod  125  and ram drive assembly  130  are the same each cycle for both shrinking and stretching operations. Each cycle of the machine  10  has a pressure stroke and a return stroke. The pressure stroke includes a first or gripping phase and a second or working phase. During the gripping portion or phase, the cylinder  120  and piston rod  125  longitudinally extend the ram  40  from retracted position  57  ( FIGS. 6A ,  7 A and  8 A) to position  58  where the jaws  100  engage and grip two portions  7  of the workpiece  5 . ( FIGS. 6B ,  7 B and  8 B). During the working phase, the cylinder  120  and piston rod  125  further longitudinally extend the ram  40  from gripping position  58  ( FIG. 7B  or  8 B) to position  59  where the jaws  100  have moved laterally  97  or  99  to shrink or stretch the ungripped portion  8  of the workpiece  5 . ( FIG. 7C  or  8 C). 
     Toward the end of the first or workpiece  5  gripping portion or phase of the pressure stroke, the tools  60  compress two gripped portions  7  of the workpiece  5  located on opposed sides of the machine centerline  55 . The jaw  100  of each upper tool  61  or  63  compresses one of these gripped portions  7  against its respective jaw  100  of its lower tool  62  or  64 . The jaw pressure produced by the cylinder  125 , lever  150 , angle of cams  80 , and jaw surface areas  106 , enables the jaws  100  to frictionally grip the surfaces  6  of the workpiece  5 . Jaws  100  with roughened surfaces  106  can bite into the opposed surfaces  6  of the workpiece  5  to enhance this gripping action. The tools  60 , jaws  100 , cylinder  120  and lever  150  work in unison to generate a gripping force sufficiently strong to prevent the jaws from slipping on the workpiece  5  when the machine  10  begins to shrink or stretch the ungripped portion  8  of the sheet metal  5  between the jaws  100  of the right and left sets of tools  65  and  66  during the working portion of the pressure stroke. 
     During the workpiece  5  working portion of the pressure stroke, the tools  60  move the jaws  100  laterally to shrink or stretch the ungripped portion  8  of the workpiece  5  between the tools. During this portion of the pressure stroke, the force exerted by the cams  80  on the adjacent resilient compressible sleeves  85  reaches and exceeds a threshold level sufficient to actively compress the sleeves  85 . The sleeves  85  uniformly compress due to the symmetry of the anvil  30 , ram  40  and tools  60  about the machine centerline  55 , as well as the geometry (e.g., flat and/or parallel surfaces) of these components and the sheet metal workpiece  5 . The uniform compression of sleeves  85  causes the cams  80  to uniformly rotate in their tools  60 . For a shrinking operation ( FIGS. 7A-C ), the cams  80  rotate toward the machine centerline  55 . The cams  80  in tools  61  and  64  rotate clockwise, and the cams in the tools  62  and  63  rotate counterclockwise. This rotational movement of the cams  80  cause their moving blocks  75  and jaws  100  to move laterally while the fixed blocks  71  of the upper tools  61  and  63  continue move longitudinally with the ram  40  toward the fixed blocks  71  of the lower tools  62  and  63 . 
     While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the broader aspects of the invention.