Abstract:
A hydraulic fluid pressure operated torque transmitting assembly for use as a brake or clutch which utilizes hydraulic pressure operated cylinders in a housing moveable with respect to an axially stationary spring housing to move a pressure plate against rotating discs and reaction plates. Hydraulic fluid pressure disengages the torque transmission and loss of hydraulic pressure enables springs in the spring housing to move the pressure plate to engage the friction discs for torque transmission. Radially removable spacers permit the spring housing position on mounting studs to be adjusted for compensating for friction disc wear. The hydraulic cylinders each have a drain port communicating with an annular collector groove in the cylinder bore. The drain ports are interconnected through flexible conduits connected to a master drain port in the cylinder housing.

Description:
BACKGROUND 
       [0001]    The present disclosure relates to fluid pressure operated rotary torque transmitting devices for use in brakes and clutches. Heretofore, fluid pressure operated clutches and brakes have typically employed a pneumatically pressurized bladder for actuating brake shoes or have employed pistons for providing pressure against friction discs; and, have typically used pneumatic pressure from available air compressors. These types of pneumatically operated brakes and clutches are limited in their power transmitting density by virtue of the limits of available air compressors which generally do not provide air pressure higher than 150 psi (1.034 MPa). Thus, for relatively high power or torque transmission, the volume or size of the brake or clutch required to provide the desired torque transmission has resulted in prohibitively large power transmission assemblies for the desired application. This has particularly been a problem for relatively large clutches/brakes capable of transmitting torque of at least one hundred eighty thousand (180,000) pound-feet (2.43×10 5  Newton-meters). Thus, it has been found desirable to provide fluid pressure operated brakes and clutches which may be operated with commercially available higher pressure hydraulic fluid pressure sources, thereby eliminating the cost of specialized high pressure pneumatic compressor equipment. An example of such a hydraulically operating brake or clutch which disengages upon release of the hydraulic pressure is that described in U.S. Pat. No. 4,615,418 and U.S. Pat. No. 5,383,544. Such devices thus provide for engagement in the event of loss of hydraulic fluid pressure. 
         [0002]    However, as the annular friction discs wear in service, in the aforesaid type hydraulically operated brakes and clutches, the engagement position of the discs and reaction members or plates is shifted to a position more distant from the actuating springs. Wear thus moves the springs closer to their free length position and therefore reduces the spring force available for engagement. Heretofore, in order to maintain a desired engagement force of the springs, after significant wear of the friction discs, it has been necessary to remove the brake or clutch from service, disassemble the unit and either reposition the mounting of the springs to accommodate the wear on the friction discs or to replace the friction discs. 
         [0003]    It has therefore been desired to provide a convenient way or means of adjusting the engagement position of the friction discs in a hydraulically operated brake or clutch assembly of the type which is disengaged by release of the hydraulic pressure without disassembly of the unit. 
       SUMMARY 
       [0004]    The present disclosure provides a torque transmitting assembly which is operated by hydraulic fluid pressure; and, utilizes hydraulic fluid pressure to disengage the frictional force of friction discs against reaction plates when fluid pressure is applied. The assembly has a plurality of fluid pressure cylinders disposed about a unitary cylinder housing; and, upon release of the hydraulic fluid pressure from the cylinders, a plurality of circumferentially spaced spring sets provide the desired axial force to cause the reaction members to contact the friction discs and produce the desired torque against a retaining member. The retaining member may either be stationary for use as a brake or mounted on a rotating output shaft for use as a clutch. 
         [0005]    The assembly of the present disclosure addresses the above-described problem of accommodating wear of the friction discs in a hydraulically operated brake or clutch, where engagement is accomplished by spring force, by providing removable spacers for locating the spring housing on the base or mounting member. In the disclosed version of the present hydraulically operated clutch/brake assembly, the spring housing is secured against a plurality of spacers on studs extending from the mounting member and retained thereon by threaded fasteners. One of the spacers on each stud is configured to be radially removed without requiring disassembly of the entire brake/clutch. The radially removable spacer of the assembly of the present disclosure is slit radially and has a portion of the wall thereof opposite the slit weakened to permit opening of the spacer by insertion of a tool in the slit for opening and radial removal of the spacer from the mounting stud. Upon removal of the radially slit spacer, the threaded fasteners on the studs may then be tightened to reposition the spring housing against the remaining spacers and thus accommodate for wear in the friction discs, thereby retaining the compression of the springs and maintaining the engagement force of the brake/clutch assembly without the need for removal of the assembly from service and disassembly for repositioning the spring housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is an axonometric view of the brake/clutch assembly of the present disclosure; 
           [0007]      FIG. 2  is a left-hand end view of the assembly of  FIG. 1 ; 
           [0008]      FIG. 3  is a view of  FIG. 1  quarter sectioned along section indicating lines  3 - 3  to illustrate the interior components; 
           [0009]      FIG. 4A  and  FIG. 4B  together along parting line A-A are an exploded view of the assembly of  FIG. 1 ; 
           [0010]      FIG. 5  is an enlarged view of the section of  FIG. 3 ; 
           [0011]      FIG. 6  is an enlarged view of another portion of the section of  FIG. 3 ; 
           [0012]      FIG. 7  is an enlarged view of a portion of  FIG. 6 ; 
           [0013]      FIG. 8  is an axonometric view of the removable spacer of the assembly of  FIG. 1 ; 
           [0014]      FIG. 9  is a top view of the spacer of  FIG. 8 ; 
           [0015]      FIG. 10  is an enlarged portion of the section view of  FIG. 3  showing one of the cylinder drain ports; 
           [0016]      FIG. 11  is a portion of a section view of one of the piston cylinders with the piston removed; 
           [0017]      FIG. 12  is an enlarged view of portion of  FIG. 1 ; AND 
           [0018]      FIG. 13  is a section view taken along section indicating lines  13 - 13  of  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Referring to  FIGS. 1 through 7 , the hydraulically operated brake/clutch assembly of the present disclosure is indicated generally at  10  and includes an annular base or mounting member  12  which has a plurality of axially extending mounting studs  14  attached thereto in circumferentially spaced arrangement. It will be understood that for brake applications of the assembly  10 , the base or mounting member  12  is attached to a stationary structure (not shown); whereas, for a clutch application, the mounting member  12  would be attached to a rotating output shaft (not shown). 
         [0020]    Each of the studs  14  has received thereover an elongated tubular spacer  16  and a radially removable annular spacer  18 . Each of the spacers  18  is radially removable without disassembly of the brake/clutch  10  as will hereinafter be described; and each spacer  18  has an axial length pre-determined to permit adjustment for wear in service after their removal. 
         [0021]    A plurality of annular reaction plates  20  each have apertures  22  formed about the periphery thereof which are received over the spacers  16  in an axially spaced arrangement and sized so as to be in sliding engagement on the spacers  16 . Disposed between each of the reaction plates  20  and the mounting member  12  is an annular friction disk  24  having friction material  26  provided on opposite axial faces thereof as denoted in  FIG. 5 . Each of the annular discs  24  has grooves or spline surfaces  28  formed about the inner periphery thereof. The spline surfaces are configured for engagement with corresponding surfaces  30  provided on an input shaft or driving gear  32 , as illustrated in  FIG. 4 . 
         [0022]    A return spring  34  is disposed over each of the spacers  16  between the reaction plates and the mounting plate  12  and an annular pressure plate  36  which is also provided with apertures  38  for being slidably received over the spacers  16  on mounting studs  14 . The springs  34  thus urge the reaction plates apart in the disengaged state to release friction between the discs  26  and the reaction plates  20 . 
         [0023]    An annular spring housing  40  has a plurality of circumferentially spaced apertures  42  which are located such that each is received over one of the studs  14 ; and, the spring housing is secured against spacers  16  by threaded fasteners such as lock nuts  44 . The spring housing  40  has a plurality of circumferentially spaced pockets  46  formed therein into each of which is received one reaction end of a spring set indicated generally at  48 . The reaction end opposite the one reaction end of each spring set  48 , is received in one of a plurality of circumferentially spaced recesses  50  formed about the axial face of the pressure plate  36  which faces opposite the friction discs. 
         [0024]    The axial face of the spring housing  40  opposite the face with recesses  50 , has provided thereon a plurality of circumferentially spaced pistons  52  extending axially therefrom and which may be integrally formed with the spring housing  40 , as for example, by casting. 
         [0025]    A cylinder housing  56  has a plurality of circumferentially spaced apertures  58  which are located so as to be secured by bolts  60  and spacers  62  with the bolts  60  engaging threaded apertures  64  provided in pressure plate  36 . The pressure plate  36  thus moves axially with the cylinder housing  56 . The cylinder housing  56  has a plurality of bores  66  located so as to have received in each thereof one of the pistons  52  provided on the spring housing  40 . The cylinder housing has a plurality of fluid pressure ports  68 , each of which communicates with one of the cylinder bores  66  for enabling introduction of hydraulic fluid pressure into the cylinder bores. 
         [0026]    Each of the spring sets  48  includes a plurality of coil springs  70  which are sized and configured to provide the desired axial force. Spring set  48  may include an end plate  72 , to which the springs  70  may be attached at one reaction end, for facilitating assembly. 
         [0027]    In operation, as hydraulic fluid is introduced through port  68  into the cylinder bores  66 , the hydraulic fluid pressure acting on the ends of the pistons  52  causes the cylinder housing  56  to move leftward or in a direction to effect pulling of the pressure plate  36  away from the friction discs  24  and reaction plates  20  to disengage the frictional contact between the reaction plates and the friction discs thus preventing transmission of torque between the input or drive shaft  32  and retaining member  12 . Upon release of the hydraulic fluid pressure in the cylinders  66 , the spring sets  48  exert sufficient axial force upon the pressure plate  36  to move the pressure plate  36  and reaction plate  20  into frictional driving contact with their adjacent friction discs  24  and effect torque transmission between the input shaft  32  and the retaining member  12 . 
         [0028]    As the friction discs  24  wear in service, the position of the pressure plate  36  at the point of engagement is moved axially rightward or in a direction toward the mounting plate  12 , such that the springs  70  in the spring set  48  are extended incrementally toward their free length. This extension of the spring set  48  decreases the axial force at the point of engagement of the pressure plate  36  with the friction discs  24 . This results in decreased friction force available for torque transmission at engagement. In the event that the wear has decreased the frictional force available for torque transmission to an unacceptable level, the spacers  18  may be removed, without disassembly of the unit  10 , to enable tightening of the lock nuts  44  to reposition the spring housing to compress spring sets  48  to retain the desired axial force on the pressure plate  36 . 
         [0029]    Referring to  FIGS. 8 and 9 , one of the removable spacers  18  is shown in greater detail, wherein the spacer has a radial slit  74  formed through the wall to enable insertion of a tool to pry the spacer  18  to an open condition sufficient to enable removing the spacer radially from the studs  14 . In the version shown in  FIGS. 8 and 9 , the spacer  18  includes a pre-weakened area formed in the wall thereof diametrically opposite the slit  74  as denoted by reference number  76 . The notch  76  thus reduces the thickness of the spacer wall to facilitate opening of the spacer for removal from stud  14 . Alternately, the pre-weakened region may be provided by forming the spacer with a radially thinner wall section in the region diametrically opposite the slit  74 . 
         [0030]    Referring to  FIG. 10 through 13 , each of the piston cylinder bores  66  has a radially extending drain port  78  which extends through the wall of the cylinder bore; and, each port  78  which has at its radially outer end thereof provided with a counter bore  80 , which may be threaded for insertion of a fitting as will hereafter be described. Each of the radial drain ports  78  communicates at its radially inner end with an annular collector groove  82  formed in the wall of the bore  66 . With reference to  FIG. 13 , a three-way or “T” fitting  84  is provided and has its common end received in threaded engagement with the counter bore  80 . The opposite ends of the three-way fitting are connected to flexible hoses  86 , each of which communicates with the interior passage in the three-way fitting and thus with the piston bore  66 . The hoses  86  have their opposite ends connected to an adjacent three-way fitting provided for each of the adjacent piston cylinders  56  such that the hoses are disposed in circumferential arrangement in the annular space radially outwardly of each of the cylinder bores  66 . The hoses are connected by a separate (unshown) three-way fitting to a master drain port  88  provided in the end face of the cylinder housing  56  as denoted by reference numeral  90  in  FIG. 12 . This arrangement permits draining of all the hydraulic cylinder bores  66  into a common return line to the hydraulic fluid source. 
         [0031]    A hydraulically operated torque transmitting assembly of the present disclosure thus provides a clutch or brake disengaged by introduction of hydraulic fluid pressure and upon loss of hydraulic fluid pressure, engaged by springs. The assembly has radially removable spacers provided on the mounting studs which, upon axial wear of the friction discs, may be radially removed to permit tightening of the threaded fasteners or lock nuts thereby moving the spring housing axially against the remaining spacers on the mounting studs to move the engagement springs to accommodate the pressure plate engagement point to thus accommodate the wear of the friction discs without requiring disassembly of the unit. The hydraulic piston cylinder bores each have a drain port. The drain port communicates with the annular collector groove formed in the inner periphery of the cylinder. The cylinder bore drain ports are interconnected by hoses which are connected to a master drain port in the cylinder housing. 
         [0032]    The exemplary versions have been described with reference to the drawings. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary versions be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.