Patent Publication Number: US-7900752-B2

Title: Dual actuator friction brake assembly

Description:
This application claims priority to and is a continuation of U.S. patent application Ser. No. 11/263,395 filed Oct. 31, 2005 now U.S. Pat. No. 7,556,128, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to brakes and, more particularly, to a brake in which tension and emergency braking are initiated at opposite axial ends of the brake. 
     2. Disclosure of Related Art 
     A conventional water cooled disc brake includes a stationary housing disposed about a rotating shaft. A plurality of friction plates are coupled to the housing and fixed against rotation relative to the housing, but axially moveable relative to the housing. These friction plates define fluid jackets through which cooling liquids are circulated. Another plurality of friction plates are coupled to the shaft for rotation therewith and are axially movable relative to the shaft. The plates coupled to the shaft are interleaved with the plates coupled to the housing. An emergency or safety brake actuator is disposed at one axial end of the brake and applies a constant force in an axial direction to bring the plates into contact with one another. A tension brake actuator is disposed at the same axial end of the brake and applies a variable force for controlled braking torque. 
     In some conventional brakes, the tension brake actuator applies a force in the opposite axial direction relative to the emergency brake actuator and controlled braking is accomplished by the combination of forces from the two actuators. In these brakes, however, the amount of tension braking force that can be applied and the ability to control the tension braking force are limited because of the need to offset the force of the emergency brake actuator. Commonly assigned U.S. Pat. No. 6,029,782 discloses an improved brake in which an additional actuator is employed to counter the force applied by the emergency brake actuator. In this manner, tension braking is made responsive solely to the tension brake actuator. Although the brake in U.S. Pat. No. 6,029,782 represents an improvement relative to previous brake designs, the improved brake suffers from packaging limitations and renders maintenance of the brake actuators and other brake components relatively difficult. Further, the brake design cannot be readily applied to modify existing brakes having only a tension brake actuator. Rather, substantial modifications to the brake are required. 
     The inventors herein have recognized a need for a brake that will minimize and/or eliminate one or more of the above-identified deficiencies. 
     SUMMARY OF THE INVENTION 
     The present invention provides a brake having emergency and tension brake actuators disposed at opposite axial ends of the brake. 
     A brake in accordance with the present invention includes a housing disposed about a driven shaft. The driven shaft rotates about a rotational axis. The brake further includes a first friction plate coupled to the driven shaft for rotation therewith and axially movable relative to the shaft. The brake also includes a second friction plate coupled to the housing and fixed against rotation relative to the housing, but axially movable relative to the housing. The second friction plate defines a fluid jacket configured for passage of a fluid. The brake further includes a first end cap assembly disposed at a first axial end of the housing and coupled to the housing. The first end cap assembly includes a first pressure plate and means for applying a variable control force to the first pressure plate to urge the first pressure plate in a first axial direction towards the first and second friction plate. The brake further includes a second end cap assembly disposed at a second axial end of the housing. The second end cap assembly is coupled to the housing and includes a second pressure plate. The second cap assembly also includes means for applying a setting force to the second pressure plate in a second axial direction to urge the second pressure plate towards the first and second friction plates and means for selectively applying a release force in the first axial direction against the setting force. 
     A brake in accordance with the present invention has significant advantages relative to conventional brakes. First, packaging of the brake is improved by locating the tension and emergency brake actuators at opposite axial ends of the brake. Second, accessibility for maintenance is improved. Finally, existing brakes employing only tension brakes can be easily modified to incorporate emergency brake functions. 
     These and other advantages of this invention will become apparent to one skilled in the art from the following detailed description and the accompanying drawings illustrating features of this invention by way of example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a split cross-sectional view of a brake in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     Referring now to the drawings wherein like reference numerals are used to identify identical components in the various views,  FIG. 1  illustrates a brake  10  in accordance with the present invention. Brake  10  may be provided for heavy duty industrial use (e.g., on oil drilling equipment). Brake  10  includes a housing  12 , two sets of friction plates  14 A-E,  16 A-D, and end cap assemblies  18 ,  20 . Brake  10  may also include a spacer  22 . 
     Housing  12  provides structural support to the other components of brake  10 . Housing  12  may be made from conventional metals, metal alloys and/or plastics. Housing  12  is disposed about a driven shaft  24  and may be centered about the rotational axis  26  of the shaft  24 . Housing  12  may be substantially circular in shape and unitary in construction or composed of multiple pieces joined together. Housing  12  defines axially extending bores  28 ,  30  at either end configured to receive fasteners  32 ,  34  used to connect end cap assemblies  18 ,  20 , respectively, to housing  12 . Housing  12  also defines a plurality of radial openings  36  sized for receipt of hoses and connectors (not shown). Housing  12  includes a plurality of spline teeth  38  on a radially inner surface for a purpose described hereinbelow. One or more mounting brackets  40 ,  42  or feet, may extend from housing  12  to allow brake  10  to be mounted to a surface extending substantially parallel to axis  26 . 
     Friction plates  14 A-E are provided to transmit a braking torque to friction plates  16 A-D and to shaft  24  upon engagement of plates  14 A-E,  16 A-D. Friction plates  14 A-E may include a plurality of spline teeth  44  disposed on radially outer surfaces of plates  14 A-E that are configured to mate with teeth  38  of housing  12  thereby preventing relative rotation of plates  14 A-E relative to housing  12 , but allowing axial movement of plates  14 A-E relative to housing  12 . Friction plates  14 A-E may be biased apart by springs  46  that are disposed between each pair of plates  14 A-E and are disposed about pins  48  extending through plates  14 A-E. Although five friction plates  14 A-E are shown in the illustrated embodiment, it should be understood that the number of friction plates can be varied to vary braking torque. Each of friction plates  14 A-E includes one or more plates  50  and a fluid jacket  52 . 
     Plates  50  are conventional in the art and may be made from a variety of conventional metals and metal alloys including iron or copper. Plates  50  may be connected to one or both sides of each fluid jacket  52  using fasteners  54  such as bolts or screws or pins. 
     Fluid jackets  52  are provided to allow for circulation of a cooling liquid such as water or another conventional liquid within brake  10  to allow for transfer of frictional heat generated within brake  10 . Jackets  52  are conventional in the art and include an annular body that defines a fluid manifold through which liquid circulates and which provides a surface on which plates  50  are mounted. Jackets  52  may define a plurality of concentric flow passages  56  and radial flow passages  58  that place concentric passages  56  in fluid communication with fluid inlets  60  and outlets (not shown). 
     Friction plates  16 A-D are provided to transfer braking torque from friction plates  14 A-E to shaft  24 . Friction plates  16 A-D may be made from conventional metals and metal alloys such as iron and copper. Plates  16 A-D include a plurality of spline teeth  64  at a radially inner surface that are configured to engage with teeth  66  of shaft  24  (or a hub mounted to shaft  24 ) to couple friction plates  16 A-D to shaft  24 . Plates  16 A-D may include a conventional friction material  68  connected to each side of plate  16 A-D by fasteners  70  such as bolts or screws. Again, although four plates  16 A-D are shown in the illustrated embodiment, it should be understood that the number of plates  16  can be varied to vary braking torque. 
     End cap assembly  18  closes one axial end of housing  12  and provides support for a tension brake actuator. End cap assembly  18  includes an end plate  72 , a pressure plate  74 , and means, such as bladder  76 , for applying a variable control force to pressure plate  74  to urge pressure plate  74  in an axial direction (to the left in  FIG. 1 ) towards friction plates  14 A-E,  16 A-D. 
     End plate  72  is annular in construction and is fastened to housing  12  using one or more fasteners  32 . Plate  72  defines an annular recess  78  configured to receive bladder  76 . Plate  72  also defines an axial bore  80  through which pneumatic or hydraulic fluid is provided to bladder  76  via a hose (not shown). 
     Plate  74  is provided to compress plates  14 A-E,  16 A-D to create a braking torque on shaft  24 . Plate  74  is conventional in the art and may be made from conventional metals and metal alloys. Plate  74  is annular in construction. 
     Bladder  76  provides a means for applying a variable control force to plate  74  and serves as a tension brake actuator. Bladder  76  is conventional in the art. When fluid is supplied to bladder  76 , bladder  76  expands and urges pressure plate  74  in an axial direction (to the left in  FIG. 1 ) against the force of springs  46  to compress, and cause engagement of, friction plates  14 A-E,  16 A-D. When fluid pressure is removed from bladder  76 , springs  46  bias friction plates  14 A-E,  16 A-D apart. 
     End cap assembly  20  closes an opposite axial end of housing  12  and provides support for a safety or emergency brake actuator. End cap assembly  20  includes an end plate  82 , a pressure plate  84 , means, such as springs  86 , for applying a setting force to pressure plate  84  in an axial direction (to the right in  FIG. 1 ) to urge pressure plate  84  towards friction plates  14 A-E,  16 A-D, and means, such as piston  88  and one or more fasteners  90 , for selectively applying a release force in an opposite axial direction (to the left in  FIG. 1 ) against the setting force. 
     End plate  82  is annular in construction and is fastened to housing  12  using one or more fasteners  34 . Plate  82  defines an annular recess  92  configured to receive plate  84 . Plate  82  further defines a plurality of recesses  94  opening into recess  92 . Each recess  94  is configured to receive one end of a spring  86 . 
     Pressure plate  84  is provided to compress plates  14 A-E,  16 A-D to create a braking torque on shaft  12 . Plate  84  is conventional in the art and may be made from conventional metals and metal alloys. Plate  84  is annular in construction and defines one or more stepped diameter bores  96  configured to receive corresponding fasteners  90 . Plate  84  may also define one or more recesses  98  on a side of plate  84  opposite friction plates  14 A-E,  16 A-D. Each recess  98  is configured to receive one end of a corresponding spring  86 . 
     Springs  86  provide a means for applying a setting force against pressure plate  84  to urge plate  84  in an axial direction (to the right in  FIG. 1 ) to compress plates  14 A-E,  16 A-D. Springs  86  are disposed within recesses  94 ,  98  in end plate  82  and pressure plate  84 , respectively. Springs  86  are conventional in the art any may comprise coil springs or other conventional springs. Springs  86  may be circumferentially spaced about axis  26  and may be disposed at varying radial distances from axis  26 . 
     Piston  88  selectively urges fasteners  90  and plate  84  in an axial direction (to the left in  FIG. 1 ) against the setting force of springs  86 . Although a single, annular piston  88  is shown in the illustrated embodiment, multiple pistons  88  could be employed. Piston  88  is disposed on one side of end plate  82  opposite pressure plate  84 . Piston  88  defines one more through bores  100  through which fasteners  90  extend. Piston  88  also defines one or more fluid chambers  102  opening in the direction of end plate  82 . A body  104  (or bodies) may be disposed in the fluid chamber  102  (or chambers  102 ), bearing against end plate  82 . A seal (not shown) disposed between body  104  and the walls of chamber  102  prevents fluid leakage. 
     Fasteners  90  couple pressure plate  84  and piston  88  for movement together. Fasteners  90  may extend through pressure plate  84 , end plate  82  and piston  88  and may include a female part  105  and a male part  106 . In the illustrated embodiment, each female part  105  has a stepped diameter at one end configured to be received within bores  96  in pressure plate  84 . Male part  106  extends into female part  105  and is secured for movement with female part  105 . Male part  106  includes a head that bears against the outer surface of piston  88 . 
     Brake  10  is released by providing fluid to chambers  102 . The expanding fluid volume within chambers  192  causes piston  88  to move away from end plate  82  in an axial direction (to the left in  FIG. 1 ) against the force of springs  86 . Piston  88  pulls fasteners  90  and pressure plate  84  in the same direction. When fluid pressure is removed from chambers  102 , springs  86  force pressure plate  84  in the opposite axial direction (to the right in  FIG. 1 ) to reset the brake  10 , returning piston  88  to its original position. 
     Spacer  22  provides means for adjusting an axial position of end cap assembly  20  relative to housing  12 . Although spacer  22  is illustrated in  FIG. 1  for use in adjusting the axial position of end cap assembly  20  relative to housing  12 , it should be understood that spacer  22  could be employed on the opposite side of brake  10  to allow adjustment of the axial position of end cap assembly  18  relative to housing  12 . Spacer  22  may comprise one or more shims disposed between end cap assembly  20  and housing  12 . The shims may be disposed about the circumference, or a portion of the circumference, of fasteners  34 . As the brake wears, fasteners  34  may be loosened to allow removal of one or more shims thereby enabling end cap assembly  20  to be drawn closer to housing  12  and to compensate for wear. 
     A brake in accordance with the present invention has significant advantages relative to conventional brakes. First, packaging of the brake is improved by locating the tension and emergency brake actuators at opposite axial ends of the brake. Second, accessibility for maintenance is improved. Finally, existing brakes employing only tension brakes can be easily modified to incorporate emergency brake functions. 
     While the invention has been shown and described with reference to one or more particular embodiments thereof, it will be understood by those of skill in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.