Abstract:
A thermoforming trim press has one or more connecting arms for a movable platen which each have a pivotal connection between the adjacent ends of two adjacent sections into which each connecting arm is divided. The pivotal connection is normally locked to keep the sections in end to end alignment during normal press operation, but can be released to allow pivoting between the sections to be able to draw the movable platen further back from the normal retracted position to increase the available clearance when changing or maintaining tools mounted on the movable platen. The pivoting ability of the connecting arm sections also simplifies adjusting the stroke of the press while this is normally done by relocating a crank pin on flywheels driving the connecting arms. The change of position does not affect the movable platen when the arm sections may pivot with respect to each other allowing relocating the crank pins to adjust the stroke without requiring disassembling of the crank pins. A counterweight may be driven by the crank pins to match the press stroke adjustments and to thereby correspond the movement of the counterweight to the movement of the movable platen.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional patent application Ser. No. 62/103,112 filed on Jan. 14, 2015; and U.S. provisional patent application Ser. No. 62/257,338 filed on Nov. 19, 2015. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This application concerns presses such as trim presses used in thermoforming products to cut the individual molded parts free from the plastic sheeting in which the parts have been thermoformed. 
         [0003]    Such presses are designed to be used to trim different parts by changing tools mounted in the press. 
         [0004]    A movable platen has a tool mounted thereto, and is typically reciprocated by a rotating pair of flywheels, the flywheels driven by a motor with interposed gearing or belt drives. The flywheels drive the movable platen by means of a pair of connecting arms, each driven by a respective flywheel. Each connecting arm has a crank pin housing at one end having a bore receiving a crank pin secured to the flywheel at an off center location. An opposite end of each connecting arm is pivotally connected to one side of the movable platen. Rotation of the flywheels causes stroking of the movable platen by the connecting arms, which causes the tool on the platen and a mating stationary tool to cut thermoformed parts free from the sheet. 
         [0005]    The sheet with the parts formed thereon is fed into the press step by step, advanced after each cycle of the press to bring the next set of parts to be trimmed from the sheet into alignment with the tool. 
         [0006]    In order to trim a different part the tool for a given part must be removed from the press and a different tool to be used with each different part installed in its place. 
         [0007]    The tools are typically complex and bulky, having ejectors, take off tubes, etc., installed thereon which make it difficult to change tools. 
         [0008]    The tool often must be partially disassembled while still in the press in order to be removed, since the movable platen cannot be retracted sufficiently to create a enough clearance to remove the tool with the attachments on the tool still installed. 
         [0009]    This process is very time consuming and results in an extended shutdown of the trim press, as much labor is required to accomplish a tool changeover if the tool must be at partially disassembled. 
         [0010]    As noted above, it is also sometimes necessary to perform maintenance on the tool such as sharpening the cutting edges, and the small clearances available when the platen is fully retracted often makes maintenance on the tool while in the press difficult or impracticable. 
         [0011]    Another difficulty is encountered in the changing of the stroke of the press, which often must be done when a different part is to be trimmed. This requires a radial relocation of the connection of each crank pin assembly on an associated flywheel either closer to its center or further away. Since two crank pins are present, each on a respective flywheel, the crank pins must be completely removed from the associated connecting arm. This is because the movable platen is mounted on linear bearings and shifting a crank pin to adjust the stroke would tend to cause movement of the movable platen by the connecting arm since it is connected to the crank pin. If only one crank pin is adjusted at a time, binding of the platen on the linear bearings would result. Thus, the crank pins must usually be completely detached and then installed at the new location so as to avoid binding of the platen. 
         [0012]    A time consuming complete detachment of each of the crank pins from the associated connecting arm is required to change the press stroke by the conventional practice. 
         [0013]    Such presses also often have counterweights which are driven by the press in the opposite direction from the movable platen to balance out the momentum of the platen and thereby allow higher speeds of operation by minimizing movement of the press caused by reaction forces generated by reversing movement of the movable platen and tool. 
         [0014]    However, changing the stroke of the movable platen can result in causing the platen momentum to be unbalanced by the counterweight motion, limiting operational speeds and causing rapid wear of some of the mechanical components. 
         [0015]    Accordingly, it is an object of the present invention to provide a press which quickly and easily allows a temporary greater extent of retraction movement of the movable platen so as to be sufficient to create a clearance adequate to accommodate the removal of a complete tool with accessories attached; and, to also allow maintenance to be carried out on the tool while it is still in place in the press. 
         [0016]    It is a further object of the present invention to provide an arrangement for adjusting the stroke of a press in which the crank pins do not have to be detached from the connecting arms in order to shift the location of their attachment to the flywheel to change the press stroke. 
         [0017]    It is another object of the invention is to provide a counterweight system which has a counter movement which is changed correspondingly when a change in the stroke of the press is carried out. 
       SUMMARY OF THE INVENTION 
       [0018]    The above recited objects and other objects of the present invention which will be understood by those skilled in the art are achieved by incorporating connecting arms which are each made in two sections with adjacent ends which are pivotally connected to each other. However, the connecting arms are normally fixedly held in end to end alignment with a locking arrangement so as to be able to function normally when in use. If a tool is to be removed or maintained, the pivotal connection is activated by release of the locking arrangement which only requires removing or loosening a few fasteners to allow the connecting arm sections to pivot with respect to each other. The connecting arm sections of each connecting arm which are nearest the flywheels are first locked to an associated flywheel by installation of temporary pins. The flywheels are then manually rotated with a handwheel which swings both of the connecting arm sections down. 
         [0019]    This mutual pivoting motion of the connecting arm sections draws the movable platen substantially further back from its normal fully open position to create a much greater available clearance around the tool than exists after stroking the press to the fully retracted platen position. 
         [0020]    This allows much greater clearance for removing and replacing the tools in a completely assembled state; or, to carry out maintenance on the tool while still in place installed in the press. 
         [0021]    Adjustment of the press stroke can also be much more quickly and easily carried out after the connecting arm sections are released to be able to be pivoted. 
         [0022]    The attachment of the bolts connecting the crank pins to respective flywheels are removed (along with a locating dowel) to allow shifting of each of the crank pins to a radially shifted position corresponding to the desired new press stroke and the bolts (and the dowel pin) reinstalled. 
         [0023]    This shifting adjusting of the position of the crank pins only results in relative pivoting of the connecting arm sections and is not transmitted to the movable platen, so that each crank pin can be adjusted separately to different positions on the flywheel corresponding to the desired press stroke while still being connected to the connecting arms. 
         [0024]    The connecting arm sections are then restored to their aligned run condition, and the locking arrangement restored to be made ready for normal press operations. 
         [0025]    A counterweight connecting arm is pinned to a counterweight drive link which is positively engaged to an end of each crank pin so as to be driven thereby by the associated flywheel which also drives the associated connecting arm and movable platen. The drive link has a series of holes along its length, each corresponding to one of the adjusted positions of the crank pin end on the flywheel so the counterweight stroking movement is changed in correspondence with the stroke change of the press platen itself. The weight of the counterweight is set approximately to that of the movable platen plus the average tool weight so as to maintain a substantial momentum balance between the platen and counterweight in each adjusted press stroke setting. 
     
    
     
       DESCRIPTION OF THE DRAWING FIGURES 
         [0026]      FIG. 1  is a pictorial view of a trim press according to the features of the present invention. 
           [0027]      FIG. 2  is a side elevational view of the trim press shown in  FIG. 1  with certain components removed for the sake of clarity. 
           [0028]      FIG. 3  is an exploded pictorial view of the components of a connecting arm according to the present invention with a fragmentary portion of a connected movable platen. 
           [0029]      FIG. 3A  is an enlarged partially sectional view of parts of the trim press shown in  FIG. 3 . 
           [0030]      FIG. 4  is an exploded pictorial view of the components driving the connecting arm by an associated flywheel. 
           [0031]      FIG. 4A  is an enlarged end view of a crank pin assembly shown in  FIG. 4 . 
           [0032]      FIGS. 5A and 5B  are simplified end views of a crank pin assembly and a connecting arm sections depicting manual rotation of an associated flywheel to position the connecting arm sections. 
           [0033]      FIG. 6  is a pictorial view of a counterweight mechanism associated with a crank pin assembly and flywheel. 
           [0034]      FIG. 6A  is a side view of the counterweight mechanism. 
           [0035]      FIG. 6B  is an enlarged side view of a drive link and a portion of a counterweight connecting arm included in the counterweight mechanism shown  FIG. 6 . 
           [0036]      FIG. 7  is an exploded pictorial view of a fine shut height adjust arrangement incorporated in a connecting arm according to the invention. 
           [0037]      FIG. 7A  is an enlarged side view of the fine shut height adjust arrangement shown  FIG. 7 , in partial section. 
       
    
    
     DETAILED DESCRIPTION 
       [0038]    In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims. 
         [0039]    Referring to the drawings and particularly  FIGS. 1 and 2 , a trim press  10  is shown, with various conventional components omitted for the sake of clarity. The invention is applicable to other presses as well. A press frame  12  supports a pair of conventional rotary flywheels  14 , each driven by drive belts  16  (only one shown) driven by a conventional drive  18  which may be comprised of an electric motor, belt sheaves, etc. (partially shown in  FIG. 6 ). 
         [0040]    The flywheels  14  are connected to each other with a shaft  20  to insure synchronous rotation of the two flywheels  14 . 
         [0041]    A movable platen  22  is supported by the frame  12  on linear ways so as to be able to be reciprocated by a pair of connecting arms  24  according to the invention pivotally connected at one end by end fitting  25  driving the platen  22  on by a connection including pins  26  extending through bushings and received bores in clevises  28  in the conventional manner. 
         [0042]    The other end of each of the connecting arms  24  is connected to a respective crank pin assembly  30  which includes a crank pin  32  fixed to an associated flywheel  14  (see  FIG. 4 ) at a selective one of a series of locations each radially offset from the centerline of the flywheel  14  as described hereinafter. 
         [0043]    Rotation of the flywheels  14  rotates the respective crank pins  32  in a bore housing block  34 , and thereby reciprocates the associated connecting arms  24  fixed at the other end to the housing block  34  with an interposed fine adjustment connection  36 . 
         [0044]    The fine adjustment connection  36  has been previously in commercial use, but will be described in detail hereinafter in the interests of completeness. 
         [0045]    Suffice it to say, the overall lengths of the two connecting arms  24  must be precisely set to insure that the platen  12  is properly driven, and located in its advanced position to achieve proper trimming, and this may be accomplished by a shut height adjustment assembly  38  located next to each connecting arm end fitting  40  engaged with the platen  22 . The shut height adjustment assemblies  28  allow adjustment to an approximate the position of the movable platen  22  when fully advanced. 
         [0046]    The shut height adjustment assemblies  38  shown have been in commercial use previously and include a threaded shaft portion  42  of end fittings  40 . A pair of semicircular pieces  44  are assembled together to form a sleeve enclosing at one end the threaded end of the fittings  40  and  42 , an end of a shaft  46  connected to the connecting arm drop connections  48  according to the invention. The semicircular pieces  44  are tightened together thereon by machine screws  50  so as to tightly clamp the sleeve  50  formed onto the threaded end fitting  42  and shaft  46 . 
         [0047]    By loosening the screws  50 , the sleeves formed can be rotated to advance or retract the end fittings  40  and thus change the position assumed by the movable platen  22  at the end of the stroke of the press  10  and thus vary the shut height in a manner well known in the art. 
         [0048]    The connecting arm drop pivot connection  48  generally allows either of the two sections  24 A,  24 B of each of the connecting arms  24  on either side of the drop pivot connection  48  to either be held straight in alignment, so as to function in the normal fashion, or to be able to be pivoted with respect to each other allowing the connecting arm sections  24 A,  24 B to drop down and form a sharp angle with respect to each other (see  FIGS. 5 and 5A ). 
         [0049]    A generally U-shaped piece  52  is attached to the shaft segment  46  projecting from the shut height adjustment assembly  38 , threaded into a shallow hole  53  in the end wall  54  and secured therein with a bolt  56  threaded in a threaded hole  58  in the shaft  46  ( FIG. 3A ). 
         [0050]    A plate  60  is attached to the upper threaded side of the U-shaped piece with screws  62 . 
         [0051]    A bolt  64  is inserted through a central hole  66  in the plate and threaded into a threaded hole  68  in the top of an end fitting  70  on the other arm section. 
         [0052]    A pair of aligned larger diameter bores  72  in the sidewalls  74  of the piece  52  are aligned with a bore  76  in end fitting  70  when the end fitting  70  is inserted between the sidewalls  74 . 
         [0053]    A pair of through slots  78  extend into the end faces of sidewalls  74  and notches  80  are machined into the opposite side of the bores  72  create sufficient compliance to releasably grip a pivot pin  82  when a pair of screws  84  are advanced and into threaded holes  87  extending across slots  78  and tightened. 
         [0054]    Thus, when bolt  64  is installed, pivoting between the two connecting arm sections  24 A,  24 B is prevented. 
         [0055]    The pivot pin  82  also has a flat formed thereon which when the pivot pin  82  is installed is aligned with a small hole  84  which receives a tapered pin  86  which creates a wedged locking of the pin  82  when threaded set screws  88  are installed. Thus, pivot pin  82  is locked in the bore  76  of end fitting  70 . This insures that when the pivot pin  82  is gripped, relative rotation between the two connecting arm sections  24 A,  24 B is prevented. 
         [0056]    It will be appreciated by those skilled in the art that the connection must be very precise and secure to be able to withstand trimming operations conducted at high speed for extended periods. The fixing measures including the pivot pin  70  are necessary to avoid problems when the trimming operations are underway. 
         [0057]    The bolt  64  is removed and the screws  84  are loosened to create a drop condition of the connecting arm sections  24 A,  24 B. Preparatory to setting up the connecting arm drop condition, temporary locking pins  90  are installed to lock each block  34  to a respective flywheel  14 . 
         [0058]    This prevents the adjacent ends of the two connecting arm sections  24 A,  24 B from dropping down when allowed to pivot with respect to each other, and this also enables manual lowering movement of the arm sections  24 A,  24 B to a sharply angled, relative position and rotation back up into alignment after the tool replacement or maintenance task has been completed. 
         [0059]    A manual actuation wheel  92  ( FIGS. 5, 5A ) usually provided for such press mates with a power take off (not shown) from the flywheel drive  18  and is used to manually rotate the flywheels  14  and lower the connecting arm sections  24 A,  24 B to the sharply angled condition of  FIG. 5A . 
         [0060]    This further retracts the movable platen  22  a substantial distance from its normal fully retracted position to allow ample clearance for removal of the assembled tool or to do maintenance on the tool when remaining in the press. 
         [0061]    It will be understood by those skilled in the art that an overhead canopy is provided by conventional practice is not shown in the drawings which supports the sheet with parts formed therein, and a guide assembly for the sheet guiding (also not shown) are both moved out of the way when this operation is conducted which is also done when changing tools in the conventional manner according to the prior practices. 
         [0062]    Referring to  FIG. 4 , details are shown of the adjustable connection between each crank pin  32  and an associated flywheel  14  and its relationship with the block crank pin housing  36 . 
         [0063]    A flanged portion  100  of the crank pin  32  is provided, formed with a pairs of bolt holes  102  located on each side for receiving bolts  104  (only two shown) which are used to attach the crank pin  32  to the face of a flywheel  14  at four different radially offset locations, each corresponding to a one of the four stroke lengths available in the press shown. 
         [0064]    The holes  102  in the housing block  36  are large enough to allow a socket wrench to pass through to tighten the bolts  104  and secure the crank pin  32  to the radial face of the flywheel  14  at any adjusted position. 
         [0065]    A series of locator holes  108  are also provided for receiving a threaded locator dowel pin  108  for precision location of the crank pin  32  with respect to the flywheel  14 . 
         [0066]    The end face of the flange  100  of the crank pin  32  slides across the face  112  of the flywheel  14  when making a stroke adjustment, hence a recess  110  is machined into the flywheel radial face  112  to provide a smooth surface, and also to precisely locate the position of the crank pin  32  in the proper location with respect to the platen  22  and the mounting surface of the other end of the connecting arm  24  as will be understood by those skilled in the art. 
         [0067]    A pair of guides  114  are secured to the flywheel face with screws  115  at respective locations above and below the crank pin  32  so as to hold the crank pin  32  in position after the bolts  104  are removed while allowing sliding stroke adjustment movement. Cutouts  116  provide clearance for the heads of bolts  104  when installed. 
         [0068]    A mechanical adjustment operator bolt  20  for moving the crank pins  32  is created by a U-shaped piece  118  attached to one side of the crank pin  32 , capturing the head of the operator bolt  120  which is threaded along its entire length to be able to be threaded into an anchor element  122  fixed to the flywheel face  110 . A small hex end  124  allows a ratchet wrench to be used for carrying out the stroke change adjustments by shifting the crank pin  32  radially across the flywheel recess  110 . 
         [0069]    The steps involved in creating a drop away action of the connecting arms  24  comprise: 
         [0070]    1. First, the moving platen  22  is manually retracted to its full open position by use of the manual actuator wheel  92  described above. 
         [0071]    2. The locking pins  90  are installed to connect each of the housing blocks  34  to a respective flywheel  14 . This locks sections  24 A,  24 B of each connecting arm  24  to a respective one of the flywheels  14  to cause them to rotate together and also prevents the connecting arm sections  24 A,  24 B from free falling when releasing the locking arrangement allowing a pivotal connection between the sections  24 A,  24 B. For safety, the pins  90  are tied to an e-stop circuit and must be removed before the master control (not shown) is enabled in the well known manner. 
         [0072]    3. The main press drive safety pin (not shown) is installed to insure that no powered platen or flywheel movement occurs during maintenance. 
         [0073]    4. The main connection bolt  64  is removed and two clamping screws  84  are loosened on each connecting arm  24  (for each flywheel) to release the pivot connection. 
         [0074]    5. The flywheel hand wheel  92  is engaged with a power take off of the press drive and rotated so as to move the two sections  24 A,  24 B of each of the connecting arms  24  to an angled position relative each other ( FIG. 5A ), further retracting the moving platen  22  a substantial distance from the normal retracted position, allowing better access to the trim tooling installed on the moving platen. 
         [0075]    6. To reconnect, the steps are reversed with the connecting arm sections  24 A,  24 B manually positioned to again be aligned by rotation of the handwheel  92  ( FIG. 5 ). 
         [0076]    7. The two clamping screws  84  are retightened and the main connection bolt  64  reinstalled. 
         [0077]    Replacing a tool involves conventional steps including moving the trim tool elevator (now shown) forward and then lowering the same to be level with a pair of roller supports (not shown) on either side of the press. The existing tool after having been detached from the platen  22  and the lube lines thereto (not shown) disconnected, is then rolled out of the press and onto one of the roller supports on the other side of the press. The new tool is then rolled in from the other roller support. The trim tool elevator is then raised to align the new tool with the platen  22  and reattached. 
         [0078]    The drop away arm sections  24 A,  24 B are pivoted to be aligned by normal operation of the press drive as described above, and the locking arrangement  48  reinstalled. 
         [0079]    The locking pins  90  are removed and stored in a fixture and associated safety keys (not shown) inserted. 
         [0080]    The flywheels  14  are manually moved to the advanced position. 
         [0081]    The treadle and guides are lowered and canopy moved forward (neither shown). 
         [0082]    The shoe bolts (not shown) replaced. 
         [0083]    These carrying out of these steps can be viewed on a video at https://www.youtube.com/watch?v=9rjvpbr-ido, which is hereby incorporated by reference. 
         [0084]    The steps for a simpler, faster stroke adjustment comprise: 
         [0085]    1. The moving platen  22  is retracted to its full open position by use of the manual actuation wheel  92 . 
         [0086]    2. The pins  90  are installed into the body of each of the connecting arm sections  24 B. These pins  90  lock the body of each of the sections  24 B connecting arms  24  to a respective flywheel  14  and also prevent both of the connecting arms sections  24 A,  24 B from free falling when releasing the pivot connection. For safety, the pins  90  are tied to the e-stop circuit (not shown), and must be removed before the master control (not shown) is enabled. 
         [0087]    3. The main drive safety pin (not shown) is installed to insure no powered platen or flywheel movement occurs during maintenance. 
         [0088]    4. The bolt  64  is removed and two clamping screws  84  are loosened on each connecting arm  24 . 
         [0089]    5. The flywheel hand wheel  92  is installed and rotated to locate the crank pin  32  in the stroke change position shown in  FIG. 4 . 
         [0090]    6. The counterbalance drive arms are disconnected (if the counter balance arrangement described below is included). 
         [0091]    7. The bolts  104  retaining the crank pins  32  to the respective flywheels  14  are removed. 
         [0092]    8. The dowel pins  108  that locate the crank pins  32  to the flywheels  14  are removed. 
         [0093]    9. The desired stroke adjustment is carried out by a ratchet wrench rotating stroke setting bolt  120 . 
         [0094]    10. The crank dowel pins  108  are reinstalled. 
         [0095]    11. The crank pin to flywheel retaining bolts  104  are reinstalled and tightened. 
         [0096]    12. The flywheel hand wheel  92  is rotated until the sections  24 A,  24 B of the connecting arms  24  are in their straight aligned position. 
         [0097]    13. The bolts  64  are installed and screws  84  tightened. 
         [0098]    14. The counter balance drive arms are connected to the end of the respective crank pins  32  (described below) if the counterbalance is included. 
         [0099]    15. The locking pins  90  are removed and reinstalled into an e-box. 
         [0100]    16. The platen shut height is adjusted if needed. 
         [0101]    The system may optionally incorporate an arrangement for driving a counterbalance weight which is improved over the prior practice. 
         [0102]    The arrangement achieves improved balancing between the trim tooling and platen momentum and the counterbalance weight momentum. This is accomplished by making the stroke of the counterbalance weight motion adjustable to always be equal to the stroke of the moving platen, establishing approximately equal inertia between the platen and tool weight and the counter balance weight. The counterbalance weight is selected to be equal to the combined weight of the moving platen and average moving tool weight. This will improve the performance of the trim press by allowing the press to run at increased speeds with considerably less trim press movement. It will also reduce the wear on some of the mechanical components due to the improved stability of the press. 
         [0103]    Referring to  FIGS. 6A and 6B , the counterbalance weight  26  is slidably mounted on the press frame  12  on horizontally extending rails  128 . 
         [0104]    A counterbalance connecting arm  130  is provided for each flywheel  14  pivotally connected at one end to the counterweight  126  by a bracket  132 . 
         [0105]    The other end of the counterweight connecting arm  130  is connected to a counterweight drive link  134  which has a linear series of holes  136  formed therein along its length, the other end of the connecting arm  130  attachable to one of those holes  136  matched to the stroke adjustment set so that both the movable platen  22  and counterweight  26  have identical but opposite synchronized strokes. The drive link  134  is non-rotatably attached at one end to the non-round end  138  of the crank pin  32  projecting out of the housing block  34  by being clamped thereto. 
         [0106]    That is, an end piece  140  has a cut out  144  matching the circular half portion of the non-round end  138 , with the link body  142  having an aligned angled cut outs  146  having sides engaging the flat portions of the crank pin end  138 , and screws  148  secure the end piece  140  against the end of the link  134  to create a positive drive connection between the crank pin  32  and the link. 
         [0107]    If the counterbalance weight is not included a clamping cap is installed to retain the crank pin  32  in the housing block  34 . 
         [0108]    The fine adjust mechanism  36  heretofore has been previously in use and does not itself comprise the present invention. 
         [0109]    The final advanced position of the movable platen  22  (the shut height) must be set in order to properly carry out the trim operation by movement of the tool mounted to the movable platen  26 . The shut height mechanism  36  which has heretofore been known may be used to do this. 
         [0110]    The accuracy of that shut height adjustment may not be sufficient, and the fine adjustment mechanism  36  may enable a final setting of the shut height. 
         [0111]    Referring to  FIGS. 7 and 7A  the fine adjust shut height mechanism  36  includes an end block  150  connected to the connecting arm section  24 B by a bolt  152  inserted into a counter bore  153  therein and threaded into a threaded hole  154 . The round end  71  of the fitting is itself received in a bore  73  and engaged by a key  75  to prevent rotation therein. 
         [0112]    A wedge plate  156  is interposed between end block  150  and the right side of connector block  35  described above as viewed in  FIG. 7A . Four screws  158  pass through holes  159  in the end block  150  and elongated slots  160  in the wedge plate  156  and threaded into aligned threaded holes  162  in the abutting side of the connector block  35  ( FIG. 7 ) to secure these components stacked together when the screws  158  are tightened down. 
         [0113]    Two spring loaded screws  164  are also installed in offset respective holes  151  and slots  161  but are only loosened into not removed when making adjustments, which are provided to hold the stacked components in contact together when making these adjustments. 
         [0114]    A top plate  166  is attached to block  35  with four screws  168 , with a stepped end  170  projecting over the top of the wedge plate  156  with a clearance therebetween. 
         [0115]    A threaded sleeve  172  is threaded into a threaded bore  174  in the stepped end  170  and projects onto the top of the wedge plate  156 . An inner screw  176  extends within the sleeve  172  and is received in a threaded hole  178  in the top  179  of the wedge plate  156 . 
         [0116]    The vertical movement up or down of the wedge plate  156  causes a slight lengthening or shortening of the overall length of the connecting arm  24 . Tightening of the screws  158 ,  164 , and a lock nut  180  secures the length adjustment set.