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 single 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.

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 single piece hydraulically actuated actuator 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. 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 first releases the brake and then engages the clutch for starting of the press. 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 inertial of the press that the press drive must stop and start. 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 this 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 designs typically require separate pistons to release the brake and engage the clutch. The start-stop inertia with these designs 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 increased. These 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 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 uses oil shear brake and clutch drives. 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 single piece piston that moves in response to the presence of pressurized hydraulic fluid. 
     The oil shear design for the clutch and brake units offers the advantage 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 film 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 advantage 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 completely eliminates the need for any gap adjustment since the friction material and the reaction members experience little or no wear. 
     Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings which illustrate 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 clutch and brake units illustrated in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawing, there is shown in FIG. 1 a press drive which includes the clutch and brake units 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 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 fixably secured to flywheel  22  by a plurality of bolts  32  with a seal  34  being provided between a shoulder formed on end wall member  16  and a mating shoulder formed by flywheel  22 . The end of cavity  26  opposite to end wall member  16  is adapted to be closed by end wall member  14  and a generally axially and radially outwardly extending enclosure member  40 . Member  40  is formed with a radially inwardly extending flange section  42  which is fixedly secured to end wall member  14  by a plurality of bolts  44 . A seal  46  seals the interface between members  14  and  40 . The opposite end of member  40  is formed with an axial extending section  48  which is adapted to engage a recess formed in flywheel  22 . A seal  52  seals the interface between member  40  and flywheel  22 . Member  40  is secured to flywheel  22  using a plurality of bolts  54 . Members  16  and  40  are preferably provided with a plurality of circumferentially spaced ribs or fins  56  for purposes of heat dissipation. 
     End wall member  14  defines a central bore within which is disposed an axially extending support member  60 . A bearing  62  is disposed between end wall member  14  and support member  60 . A bearing retainer  64  is secured to end wall member  14  by a plurality of bolts  66  for retaining bearing  62 . A seal  68  is disposed between bearing retainer  64  and support member  60 . A seal  70  seals the interface between bearing retainer  64  and end wall member  14 . Thus, flywheel  22  is rotatably supported with respect to support member  60  by bearing  62  and cavity  26  is sealed by seal  68 . Support member  60  defines a plurality of bores to suitably secure support member  60  to a non-rotatable structure  74  using a plurality of bolts  76 . A second bearing  78  is disposed between support member  60  and drive shaft  18  to rotatably support drive shaft  18 . Bearing  78  is retained on drive shaft  18  by a retainer  80  which is threadingly received on drive shaft  18 . An oil supply housing  82  is secured to support member  60  by a plurality of bolts  84  and it acts as a bearing retainer for bearing  78  with respect to support housing  60 . A rotary union  86  is threadingly received within a bore  88  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 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 . A seal  100  is disposed between end wall member  16  and retainer  94  and a seal  102  is disposed between retainer  94  and drive shaft  18  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 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 coaxially with respect to drive shaft  18 . Friction brake 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  60  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  by a plurality of bolts  126  is an annular radially extending abutment ring  128  that confronts friction discs  116 . 
     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 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  16  and flywheel  22 . Mounted at 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 stepped 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. 
     Disposed axially between clutch plate members  136  and brake plate members  118  is an annular piston  150 . Piston  150  includes a first abutment surface  152  engageable with brake friction discs  116  and a second abutment surface  154  engageable with clutch friction discs  134 . Piston  150  moves axially along a sleeve  156  which is secured to drive shaft  18 . A seal  158  seals the interface between piston  150  and sleeve  156  and a seal  160  seals the interface between sleeve  156  and drive shaft  18 . Piston  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  150  and a pair of seals  166  seal the interface between annular ring  162  and drive shaft  18 . Annular ring  162  and piston  150  define a scaled fluid chamber  168  which is utilized for operating press drive  10  as described below. Coil springs  144  react against piston  150  to urge piston  150  away from clutch friction discs  134  and towards 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  is disengaged. 
     Drive shaft  18  is provided with a plurality of axially and radially extending bores, all of which serve a specific purpose. Bore  88  extends axially down the center line of drive shaft  18  where it mates with a radially extending bore  170 . Bore  170  is open to chamber  168 . As stated previously, rotary union  86  is threadingly received within bore  88 . Pressurized fluid is supplied to chamber  168  through rotary union  86 , bore  88  and bore  170  to operate press drive  10  as detailed below. A second axially extending bore  172  extends through drive shaft  18  to mate with a plurality of second radial bores  174 . Axial bore  172  also mates with a third radial bore  176  which opens to an oil supply port  178  extending through oil supply housing  82 . A plug  180  seals the axial end of bore  172 . Lubricating oil is provided to cavity  26  through oil supply port  178  and bores  176 ,  172  and  174 . Bores  174  are in communication with the plurality of stepped bores  142  within clutch hub  130 . An oil guide ring  186  is positioned between clutch hub  130  and bearing  92  to direct oil into bores  142 . Ring  186  also includes at least one bore  188  which directs lubricating oil towards bearing  92 . The flow of lubricating oil for press drive  10  begins in oil supply port  178  and bore  176  to bore  172 , to bores  174 , to bores  142  through a plurality of oil ports  190  extending radially through clutch hub  130 , past clutch friction discs  134  and clutch plate members  136  into cavity  26 . Oil also flows from bores  174  through bore  188  and into cavity  26 . The lubricating oil fills cavity  26  and it is directed through brake friction discs  116  and brake plate members  118  through an internal bore  192  defined by oil supply housing  82  and finally out a fluid passage or port  194  extending through support member  60 . The lubricating oil from port  194  is cleaned and cooled before being returned to cavity  26  through oil supply port  178 . 
     The operation of press drive  10  begins with flywheel  22  rotating on bearings  62  and  92  with drive shaft  18  being held stationary by brake unit  30 . Coil springs  144  bias piston  150  towards brake unit  30  to compress the pack of brake friction discs  116  and brake plate members  118  to apply brake unit  30  and lock drive shaft  18  to stationary member  60 . When it is desired to power drive shaft  18  by flywheel  22 , pressurized hydraulic fluid is provided to sealed chamber  168  through rotary union  86 , bore  88  and bore  170 . The pressurized hydraulic fluid reacts against piston  150  to overcome the biasing of coil springs  144  and move piston  150  towards clutch unit  28 . The movement of piston  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 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  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 from press drive  10  provides the advantage of minimizing the size of chamber  168  when compared with air activated 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.