Abstract:
A drive unit for a press uses an oil shear brake and an oil shear clutch which are located axially along the output member of the drive unit. A multiple piece piston moves between a brake applied/clutch disengaged position to a brake released/clutch engaged position under the influence of a hydraulic pressure. Cooling and lubrication oil is provided to the drive unit through the output member and lubricating oil is received from the drive member through a stationary support member. An adjustment member is capable of adjusting the gap between the piston and the clutch and brake units in order to eliminate any overlap between these two units.

Description:
FIELD OF THE INVENTION 
     The present invention relates to press drives. More particularly, the present invention relates to a single speed, hydraulic actuated press drive which utilizes an oil shear clutch unit, an oil shear brake unit and a hydraulically actuated actuator having a replaceable cylinder sleeve which simultaneously operates both the clutch unit and the brake unit. 
     BACKGROUND OF THE INVENTION 
     Press drives having dry friction clutch/brake units depend on the rubbing of a dry friction material against dry reaction members to start and stop the press. This dry friction rubbing causes wear of both the friction material and the reaction members as well as the generation of heat due to this rubbing. The faster the press operates and/or the faster the flywheel rotates, the greater the wear and heat generated. This generation of wear and heat requires periodic gap adjustments between the dry friction material and the dry reaction members to keep the press operating correctly. 
     Some dry friction clutch units and brake units in press drives are mechanically interlocked. Mechanical interlocking of the dry friction clutch and the brake units means that a single piston releases the brake and then engages the clutch when the press is started. For stopping the press, the clutch is first released and then the brake is applied by the piston. These mechanically interlocked units have a significant portion of the mass of the clutch and brake units mounted on the drive shaft and this can represent as much as 80% of the total inertia of the press that the press drive must start and stop. Mechanical interlocking of the dry friction clutch and brake units reduces the frequency required for gap adjustments because the two units are never simultaneously engaged, but mechanical interlocking does not eliminate the adjustment procedure. Adjustment for these dry friction units is still necessary when the gap has increased to the point that the response of the press is adversely affected. 
     Press drive builders have introduced lower inertia clutch and brake designs in an effort to reduce the start/stop inertia and thus increase the useful life of these drives. These low inertia drives typically require separate pistons to release the brake and to engage the clutch. The start-stop inertia with these drives has been reduced to approximately 60% of the total inertia. In order for the press drive to function correctly, the separate pistons must be properly synchronized to prevent overlap of the clutch and brake units. When the clutch starts to engage before the brake is fully released, or, when the brake starts engaging before the clutch is fully disengaged, excessive heat is generated and wear of the friction material and the reaction member is greatly increased. Conversely, if there is too much time between the engage/release of the clutch/brake, drifting occurs resulting in sluggish operation and if the drift is high enough, it can result in unsafe operation of the press. 
     In addition to the issues discussed above, the trip rate for a press equipped with a dry friction clutch/brake unit in the press drive is limited because the mass of the unit determines its heat capacity. If the mass is increased to increase its heat capacity, the inertia that must be stopped and started is also increased. The two factors define a closed loop from which it is impossible to escape when trying to increase the performance of the system. 
     The continued development of press drives includes the development of clutch and brake units which address the problems associated with dry friction clutch and brake units, the high inertia associated with the clutch and brake units and the synchronization for the operation of the clutch and brake units. 
     SUMMARY OF THE INVENTION 
     The present invention provides the art with a press drive system which utilizes oil shear brake and clutch units. The entire system uses hydraulic actuation instead of air actuation. The clutch and brake units are arranged axially along the output shaft to minimize the outer size of the unit and thus reduce the inertia of the system. The clutch and brake units are mechanically interlocked using a multiple piece piston that moves in response to the pressurized hydraulic fluid. The system includes a replaceable cylinder sleeve for the piston and an adjustment system for setting the gap and thus the time between release of the brake and engagement of the clutch. 
     The oil shear design for the clutch and brake units offer the advantages of little or no wear for the friction material and the reaction members. In addition, the oil shear design does not have the problem of brake fade. This provides a more precise operation of the press and dramatically increases press up-time. The oil from within these oil shear units carries the heat generated by start-stops away from the friction material and the reaction members. This removal of heat offers the advantages that there is now no practical limit for the press trip rate and flywheel speed plus it provides unlimited inching capabilities. 
     The clutch and brake units of the present invention utilize a disc stack of multiple discs. These multiple disc surfaces can be used to greatly reduce the clutch/brake inertia thereby allowing the mechanical interlocking of the clutch and brake units without inertia penalty. In addition, the axial positioning of these two units also helps in the reduction of the clutch/brake inertia. 
     Finally, the mechanical interlocking of the clutch and brake units eliminates the need for any gap adjustment since the friction material and the reaction members experience little or no wear. The present invention provides for a unique system for setting the initial gap and could be used during the extended life of the press drive to reset the gap if desired. 
     Other advantages and objects of the present invention will become apparent to hose skilled in the art from the subsequent detailed description, appended claims and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings which illustrates the best mode presently contemplated for carrying out the present invention: 
     FIG. 1 is a side view, partially in cross-section, of a press drive unit in accordance with the present invention; and 
     FIG. 2 is an enlarged cross-section of the brake and clutch units illustrated in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings in which like reference numerals designate like or corresponding parts throughout the several views, there is shown in FIGS. 1 and 2 a press drive which includes a clutch and a brake unit in accordance with the present invention and which is designated generally by the reference numeral  10 . Press drive  10  comprises a rotatable housing assembly  12  having a pair of end wall members  14  and  16  which are spaced axially or longitudinally along a rotational drive shaft  18 . Housing assembly  12  forms an outer hub assembly  20  for operatively connecting a rotatable flywheel  22  to shaft  18 . Flywheel  22  defines a central axial extending bore  24  spaced radially outwardly from drive shaft  18  to define one wall portion of an internal cavity  26  within which are located a clutch unit  28  and a brake unit  30 . One axial end of cavity  26  is closed by end wall member  16  which is fixedly secured to flywheel  22  by a plurality of bolts  32  with a seal  34  being provided between a shoulder  36  formed on end wall member  16  and a mating shoulder  38  formed on flywheel  22 . The end of cavity  26  opposite to end wall member  16  is adapted to be closed by end wall member  14 . End wall member  14  is fixedly secured to flywheel  22  by a plurality of bolts  40  with a seal  42  being provided between a shoulder  44  formed on end wall member  14  and a mating shoulder  46  formed on flywheel  22 . End wall member  16  is preferably provided with a plurality of circumferentially spaced ribs or fins  48  for purposes of heat dissipation. 
     End wall member  14  defines a central bore  50  within which is disposed an axially extending support member  52 . A bearing  54  is disposed between end wall member  14  and support member  52 . A first bearing retainer  56  is secured to end wall member  14  by a plurality of bolts  58  for retaining bearing  54 . A second bearing retainer  60  is secured to support member  52 . A seal  62  is disposed between first bearing retainer  56  and second bearing retainer  60 . A seal  64  seals the interface between bearing retainer  56  and end wall member  14 . Thus, flywheel  22  is rotatably supported with respect to support member  56  by bearing  54  and cavity  26  is sealed by seal  62 . Support member  52  defines a plurality of bores  66  to suitably secure support member  52  to a non-rotatable structure  68  using a plurality of bolts  70 . A second bearing  72  is disposed between support member  52  and drive shaft  18  to rotatably support drive shaft  18 . Bearing  72  is retained on drive shaft  18  by a retainer  74  which is threadingly received on drive shaft  18 . An oil supply housing  76  is secured to support member  52  by a plurality of bolts  78 . A rotary union  80  is threadingly received within a bore  82  extending into drive shaft  18  for providing pressurized hydraulic fluid to clutch unit  28  and brake unit  30  as is detailed below. 
     End wall member  16  defines a central opening  90  through which drive shaft  18  extends. A bearing  92  is disposed between end wall member  16  and drive shaft  18 . A first bearing retainer  94  is secured to end wall member  16  using a plurality of bolts  96  and a second bearing retainer  98  is secured to drive shaft  18  for retaining bearing  92 . A seal  100  is disposed between end wall member  16  and retainer  94  and a seal  102  is disposed between retainers  94  and  98  to seal cavity  26 . 
     Briefly, in operation, flywheel  22  rotates by receiving power from a plurality of V-belts or by other means known in the art. Rotation of flywheel  22  is selectively transmitted to drive shaft  18  through clutch unit  28 . Normally, brake unit  30  prohibits rotation of drive shaft  18 . When it is desired to power drive shaft  18  by flywheel  22 , brake unit  30  is released and then clutch unit  28  is engaged. Subsequently, when it is desired to stop drive shaft  18 , clutch unit  28  is disengaged and then brake unit  30  is applied. 
     Mounted on drive shaft  18  for rotation with drive shaft  18  within cavity  26  is an annular brake hub  110 . A retaining ring  112  located within a groove in drive shaft  18  retains brake hub  110  in its axial position. The outer periphery of brake hub  110  is formed with a plurality of axially extending splines  114  which receive a plurality of brake friction discs  116 . Discs  116  are allowed to move axially along splines  114  but they are prohibited from rotating with respect to splines  114  and thus discs  116  rotate with brake hub  110  and drive shaft  18 . 
     A series of friction brake plate members  118  are interleaved with brake friction discs  116  and are provided with a plurality of circumferentially spaced slots for keyed engagement with a plurality of circumferentially spaced drive lugs  120  that are mounted on a support member  122  disposed within cavity  26  coaxially with respect to drive shaft  18 . Friction plate members  118  are allowed to move axially with respect to lugs  120  but they are prohibited from rotating with respect to lugs  120 . Support member  122  is splined or keyed to support member  52  and retained in position by a retainer  124 . Thus, drive lugs  120  and support member  122  provide a stationary reaction member for brake unit  30 . Mounted on the end of hub  110  adjacent support member  122  is an annular radially extending adjustable abutment ring assembly  128  that confronts friction discs  116 . Ring assembly  128  provides a unique system for the adjustment of clutch unit  28  and brake unit  30  as is detailed below. 
     Disposed axially from brake hub  110  is a clutch hub  130  which is also mounted on drive shaft  18  for rotation therewith. The outer periphery of clutch hub  130  is formed with a plurality of axially extending splines  132  which receive a plurality of clutch friction discs  134 . Preferably, friction discs  134  are identical to friction discs  116 . Discs  134  are allowed to move axially along splines  132  but they are prohibited from rotating with respect to splines  132  and thus discs  134  rotate with clutch hub  130  and drive shaft  18 . 
     A series of friction clutch plate members  136  are interleaved with clutch friction discs  134  and are provided with a plurality of circumferentially spaced slots for keyed engagement with a plurality of circumferentially spaced drive lugs  138  that are formed on an axial extension of end wall member  16 . Preferably, friction clutch plate members  136  are identical to friction brake plate members  118 . Friction clutch plate members  136  are allowed to move axially with respect to lugs  138  but they are prohibited from rotating with respect to lugs  138 . Thus, friction clutch plate members  136  rotate with end wall member  136  and flywheel  22 . Mounted on the axially outer end of clutch hub  130  is an annular, radially extending abutment ring  140  which is welded or otherwise secured to clutch hub  130 . Abutment ring  140  confronts clutch friction discs  134 . 
     Clutch hub  130  is formed with a plurality of axially extending circumferentially spaced bores  142  which each receive and support a helical coil spring  144 . Coil springs  144  operate to place press drive  10  in its normal configuration with brake unit  30  applied and clutch unit  28  disengaged as described below. Clutch hub  130  is also formed with a plurality of axially extending spaced fluid passages  146  which open into a specified number of bores  142 . Fluid passages  146  provide for the distribution of cooling and lubricating oil as described below. 
     Disposed axially between clutch plate member  136  and brake plate members  118  is an annular piston assembly  150 . Piston assembly  150  includes a first abutment face  152  engage able with brake friction discs  116  and a second abutment surface  154  engageable with clutch friction discs  134 . Piston assembly  150  moves axially along a sleeve  156  which is secured to drive shaft  18 . A seal  158  seals the interface between piston assembly  150  and sleeve  156  and a seal  160  seals the interface between drive shaft  18  and sleeve  156 . Piston assembly  150  also moves axially with respect to an annular ring  162  which is also secured to drive shaft  18 . A seal  164  seals the interface between annular ring  162  and piston assembly  150  and a seal  166  seals the interface between annular ring  162  and drive shaft  18 . Annular ring  162  and piston assembly  150  define a sealed fluid chamber  168  which is utilized for operating press drive  10  as described below. Coil springs  144  react against piston assembly  150  to urge piston assembly  150  away from clutch friction discs  134  and toward brake friction discs  116 . Thus, coil springs  144  place press drive  10  in its normal position with brake unit  30  applied and clutch unit  28  disengaged. 
     Piston assembly  150  comprises a brake reaction member  170 , a clutch reaction member  172  and a replaceable cylinder sleeve  174 . Cylinder sleeve  174  slidably engages both sleeve  156  and annular ring  162 . Brake reaction member  170  and clutch reaction member  172  are both mounted on cylinder sleeve  174  using a plurality of bolts  176 . Cylinder sleeve  174  is the only member of piston assembly  150  which exhibits sliding motion with respect to sleeve  156  and annular ring  162 . Thus, any wear caused by this sliding movement will occur in cylinder sleeve  174 . Wear of cylinder sleeve  174  can occur due to contaminants in the pressurized hydraulic fluid which is introduced into chamber  168  and/or contaminants which are present within the cooling and lubricating oil which is supplied to cavity  26  and which therefor bathes piston assembly  150 . These contaminants can come from wear of the components of press drive  10  including any wear of discs  116  and  134  and any wear from plate members  118  and  136 . By having multiple piece piston assembly  150 , only the component experiencing the wear need be replaced thus reducing the costs associated with an overhaul or reconditioning of press drive  10 . 
     Piston assembly  150  moves between clutch unit  28  and brake unit  30  from a normal position where brake unit  30  is applied and clutch unit  28  is disengaged to an actuated position where brake unit  30  is released and clutch unit  28  is engaged. During the movement between these two positions, it is imperative that any overlap between the application of brake unit  30  and the engagement of clutch unit  28  is avoided. If brake unit  30  is partially applied and clutch unit  28  is simultaneously partially engaged, excessive heat and wear of discs  116  and  134  and plate members  118  and  136  will occur. The control of this zone where brake unit  30  is released and clutch unit  28  is disengaged is accomplished by controlling the gap between piston assembly  150 , brake unit  30  and clutch unit  28 . The present invention utilizes unique adjustable abutment ring assembly  128  to control this gap. 
     Adjustable abutment ring assembly  128  comprises a stationary ring  180 , a movable ring  182  and a plurality of bolts  184 . Stationary ring  180  is secured to brake hub  110  by being positioned in a groove  186 . Stationary ring  180  includes a plurality of through bores  188  alternated with a plurality of threaded bores  190  circumferentially spaced around ring  180 . Movable ring  182  includes a plurality of threaded bores  192  circumferentially spaced around ring  182  in registry with the plurality of through bores  188  in ring  180 . Bolts  184  are disposed through bores  188  and threadingly received within bores  192  to produce a pulling bolt system and bolts  184  are threadingly received within bores  190  to produce a pushing bolt system. Thus, in order to control the gap between piston assembly  150 , brake unit  30  and clutch unit  28 , movable ring  182  is positioned with respect to stationary ring  180  by adjusting the push and pull bolts  184 . Due to the minimal wear of brake unit  30  and clutch unit  28 , this initial adjustment should keep the gap within acceptable limits for the life of press drive  10 . When press drive  10  is torn down for rework and/or refurbishing, the gap can again be set using push-pull bolts  184 . 
     Drive shaft  18  is provided with a plurality of axially and radially extending bores, all of which serve a specific purpose. Bore  82  extends axially down the centerline of drive shaft  18  where it mates with one or more radially extending bores  200 . Bores  200  are open to chamber  168 . As stated previously, rotary union  80  is threadingly received within bore  82 . Pressurized fluid is supplied to chamber  168  through rotary union  80 , bore  82  and bores  200  to operate press drive  10  as detailed below. A second axial bore  202  extends through drive shaft  18  to mate with one or more radial bores  204 . Bores  204  open at a position radially inward from brake friction discs  116  and brake plate members  118  to provide cooling and lubricating oil for brake unit  30 . The oil supplied through bores  204  passes between discs  116  and plate members  118  and into cavity  26 . Oil is supplied to bore  202  through an oil inlet  206  extending through oil supply housing  76  and a radial bore  208 . The end of axial bore  202  is sealed with a plug  210 . A third axial bore  212  extends through drive shaft  18  to mate with one or more radial bores  214 . Bores  214  open at a position radially inward from clutch friction disc  134  and clutch plate member  136  to provide cooling and lubricating oil for clutch unit  28 . An oil guide ring  216  is positioned between clutch hub  130  to direct oil into fluid passages  146 . Ring  216  also includes at least one bore  218  which directs lubricating oil towards bearing  92 . The oil supplied through bores  214  flows into passages  146 , through a plurality of oil ports  220  extending through clutch hub  130 , past clutch friction discs  134  and clutch plate members  136  into cavity  26 . The axial end of bore  212  is sealed by a plug  222 . Oil is supplied to bore  212  through oil inlet  206  and a radial bore  224 . The lubricating oil supplied to cavity  26  from bores  202  and  212  fills cavity  26  and it eventually leaves cavity  26  through a fluid outlet  226  extending through support member  52 . The lubricating oil from outlet  226  is cleaned and cooled before being returned to cavity  26  through inlet  206 . 
     The operation of press drive  10  begins with flywheel  22  rotating on bearings  54  and  92  with drive shaft  18  being held stationary by brake unit  30  due to the compression of the pack of brake friction discs  116  and brake plate members  118 . This compression locks drive shaft  18  to stationary member  52 . When it is desired to power drive shaft  18  by flywheel  22 , pressurized hydraulic fluid is provided to sealed chamber  168  through rotary union  80 , bore  82  and bores  200 . The pressurized hydraulic fluid reacts against piston assembly  150  to overcome the biasing of coil springs  144  and move piston assembly  150  towards clutch unit  28 . The movement of piston assembly  150  towards clutch unit  28  first removes the compression between brake friction discs  116  and brake plate members  118  to release brake unit  30  and then it applies compressive loads to clutch friction discs  134  and clutch plate members  136  to engage clutch unit  28 . The timing between the release of brake unit  30  and the engagement of clutch unit  28  is controlled by the gap for piston assembly  150  which is built into press drive  10  using adjustable abutment ring assembly  128  as described above. The engagement of clutch unit  28  powers drive shaft  18  by flywheel  22  through discs  134  and plate members  136 . Flywheel  22  will power drive shaft  18  as long as pressurized hydraulic fluid is supplied to chamber  168 . When pressurized fluid is released from chamber  168 , coil springs  144  move piston assembly  150  towards brake unit  30  to disengage clutch unit  28  and apply brake unit  30  as described above. The use of hydraulic fluid or oil for press drive  10  provide the advantage of minimizing the size of chamber  168  when compared with air actuated press drives. The minimizing of the size of chamber  168  also aids in lowering the inertia for press drive  10  as described above. 
     While the above detailed description describes the preferred embodiment of the present invention, it should be understood that the present invention is susceptible to modification, variation and alteration without deviating from the scope and fair meaning of the subjoined claims.