Abstract:
A braking system for a drive mechanism for a hoist and similar operating motors used on heavy equipment. A rotor is fixedly mounted to a shaft of the drive mechanism. Actuators having brake shoes are mounted strategic to the rotor. The brake shoes are forced against the rotor by springs of the actuators to produce a braking action. The shoes are released from the rotor by hydraulic pressure compressing the springs of the actuators. Controls are provided to coordinate the action of the actuators with the function of the drive mechanism.

Description:
FIELD OF THE INVENTION 
     This invention relates to a brake mechanism for releasable braking, e.g., of a cable drum used in heavy equipment. 
     BACKGROUND OF THE INVENTION 
     Heavy equipment used for lifting, hoisting, scraping, etc. has moving components such as scoops and blades. These components may be raised or lowered by winding in or playing out cables from a winch, turning gears and the like. Such movements are ongoing continuously in the use of the heavy equipment and will involve something like raising a scoop with product, stopping the scoop at a desired travel level, moving the scoop to a deposit site, lowering the scoop and dumping the product. The cable is repetitively wound onto and off of the winch&#39;s drum and/or gears are repeatedly engaged and turned, and at the end of each movement, a brake is applied to stop and then hold the position. 
     Brakes that are used on such winches or other apparatus are typically complex and expensive, they rapidly wear and are difficult and expensive to repair or replace, and they are noisy. 
     It is an objective of the present invention to provide an improved braking system for such winches or similar apparatus. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In a preferred embodiment of the present invention, a rotor is mounted to the drive shaft of a hoist drum. A pair of brake shoes are movably mounted to each side of the rotor and are slidable into and out of engagement with the rotor. A plunger mechanism or actuator is independently mounted behind each brake shoe. A piston within the mechanism is spring biased to urge the brake shoe into engagement with the rotor and hydraulic pressure urges the piston away from the brake shoe allowing the brake shoe to disengage from the rotor. 
     A single hydraulic fluid source can service a plurality of the plunger mechanisms each having a remote controlled pump. In its simplest form, the brake is released by operation of the hydraulic fluid pump and sequencing the brake release and engagement of the electric winch motor produces acceptably smooth transition between them. However, a switching system may be used to enhance the cooperative action between brake release/engagement and the power applied to the hoist drum. 
     Whereas the brake shoes are independently mounted, they can be serviced with little problem or down time. The brake mechanism of the invention outlasts known braking mechanism and is far simpler in its operation and less noisy. The benefits will be more fully understood by reference to the following detailed description and the drawings referred to therein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view of an example of an article of heavy equipment incorporating the brake system of the present invention; 
     FIG. 2 is a view of the brake system of the present invention applied to a drive system of a cable drum of the article of FIG. 1; 
     FIG. 3 is an exploded view of the brake system of the present invention including brake shoe actuators as one of the components; 
     FIG. 4 is an exploded view of the actuators of the brake system of FIG. 3; 
     FIG. 5 is a cross section of the brake system for illustrating its operation; and 
     FIGS. 6 a  and  6   b  are electrical schematics illustrating a suggested type of control over the braking operation. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Refer now to FIG. 1 of the drawings which illustrates by example a portion of an article of heavy equipment  10  that incorporates the brake system of the present invention. The equipment contemplated herein is of the type that has functional components that are moved by drive systems. In the example of FIG. 1, the equipment  10  has grappling forks  11  that are elevated and lowered by the operation of a cable drum assembly  12 . When the cable  14  is deployed off the drum assembly  12 , the forks  11  of equipment  10  are lowered. When the cable  14  is wound onto the drum assembly  12 , the forks  11  of the equipment  10  are elevated. The proper operation of the drum assembly  12  requires that the drive system  16  of the drum assembly  12  is lockable into a desired position. The drive system  16 , for example, is energized to rotate in one direction to wrap cable  14  onto the drum assembly  12  to elevate the forks  11  of the equipment  10 . When the forks  11  have been elevated to the desired elevation, the drive system  16  is de-energized and a braking system is required to maintain the drive system in a set position and, therefore, maintain the forks  11  of the equipment  10  at the desired elevation. In this embodiment the brake system of the present invention is applied to the drive system  16  of the cable drum assembly  12 . 
     The drive system  16  for the cable drum assembly  12  includes an electric motor  20  as illustrated in more detail in FIG.  2 . The motor  20  is rotatably driven in one direction to deploy cable  14  off the drum  12  and is rotated in the opposite direction to reel cable  14  onto the drum assembly  12 . Basically, the brake system of the present invention has a rotor  22  fixedly mounted to the end of a splined drive shaft (hidden from view but note center line  23  representing the axis of the drive shaft) of the motor  20 . Brake shoes  24  positioned at opposite sides of the rotor are urged into frictional contact with the rotor  22  by spring biased pistons contained within actuators  32 . The brake shoes  24  have pads  25  (FIG. 3) that engage the rotor  22 . The braking pressure of the actuators  32  is released by hydraulic action acting on the pistons of the actuators  32 . The brake system of the present invention thus has the braking force applied by the spring biased pistons of the actuators  32 , and the braking force is released by the hydraulic pressure acting in opposition to the spring pressure applied to the pistons which is discussed in detail with reference to FIGS. 3 and 4. 
     Refer now to FIG. 3 of the drawings which illustrates an exploded view of the braking system of the present invention. An end bracket  40  is mountable to the housing of the motor  20  by conventional fasteners. The bracket  40  has spacer blocks  42  mounted on two of its peripheral edges. The bracket  40  has a center bore  44  which receives a bearing  46  that supports the end of the motor shaft. The bearing is retained in the bore  44  by a bearing keeper  48 . The bracket  40  thus rotatably supports the end of the shaft of the motor  20 . A support bracket  52  is fixedly attached to the blocks  42  of the bracket  40 . The bracket  52  is a shaped member that is arranged to support a spacer block  54  and actuators  32 . The spacer block  54  and actuators  32  are fixedly mounted to the bracket  52  by conventional fasteners  53 . An actuator  32  is mounted on each side of the spacer block  54 . 
     The actuators  32  have extending ears  36  that have bores  37  that mate with bores  57  of the spacer block  54  to facilitate mounting the actuators  32  to the spacer block  54  and to the bracket  52 . The mating bores of the bracket  52  are out of view in FIG.  3 . Conventional fasteners fasten the actuators  32  to the spacer block  54  and bracket  52 . As shown in FIG. 4, one of the actuators has an extending ear  36  with only one bore  37 . Additional fasteners, such as pins  38  that fit into bores  39  are provided to further secure the actuator  32  against movement relative to the spacer block  54 . 
     An adapter  60  which has internal splines  62  is mounted on the end of the splined motor shaft and retained by fastener  63 . A rotor  22  is fixedly mounted to the adapter  60  by fasteners  23  and thus the rotor will rotate with the shaft of the motor  20 . Brake pads  24 , one on each side of the rotor  22 , are slidably mounted on pins  64  that are insertable into the spacer block  54 . The pins  64  are secured by a clip  65 . 
     The actuators  32  are further illustrated in FIG.  4  and as previously mentioned, one actuator is mounted on one side of the spacer block  54  and the other actuator is mounted on the other side of the spacer block  54 . Each actuator  32  has a piston  66  (plunger) that is received in a bore  68  of the actuator  32  and end  70  of the piston  66  is slidably movable in a bore  74  of the actuators  32 . The bore  68  and the piston  66  define an expandable chamber within the actuator  32 . A spring  30  is in abutment with the piston  66  and is retained in the bore  68  by an end cap  78 . In this embodiment the spring  30  is a plurality of bevel washers. However it will be appreciated that other types of springs may be employed such as a coil spring. The end cap  78  is threadably installed in the bore  68  and is also utilized to adjust the compression of the spring  30 . Bolt or screw  69  screwed into the cap  78  serves as a piston stop. Each bore  68  has a port  67  for connecting a hydraulic line  81  (FIG.  1 ). 
     The brake assembly of the present invention is mounted on the drive motor as illustrated in FIG. 2. A hydraulic pump and reservoir  80  (FIG. 1) provides the flow of hydraulic fluid under pressure via hydraulic line  81  to each actuator  32  to move the pistons  66  against the springs  30 . The braking action is caused by the springs  30  of each actuator  32  moving the ends  70  of the pistons  66  against the brake shoes  24  which forces the brake shoes  24  into frictional contact with the rotor  22 . Release of the brake is accomplished by applying hydraulic pressure against the piston  66  of each actuator  32  to compress the springs  30  and thus to relieve the force urging shoes  24  against the rotor  22 . (See FIG. 5) 
     In operation (FIGS.  1  and  5 ), when the drive system  16  is idle, (no hydraulic pressure applied), the brake shoes  24  are forced against the rotor  22  by action of the springs  30  acting against plungers  66  (indicated by double arrows  71 ) to thus lock the motor  20  in a fixed position. Controls  84  are provided to coordinate the release of the brake when the drive motor  20  is energized and to apply the brake when the drive motor  20  is de-energized. When energy is applied to the drive motor  20  to rotate the drum assembly  12  in either direction, the controls  84  will control a hydraulic valve  82  to supply hydraulic pressure through lines  81  to the pistons  66  of the actuators  32 . The hydraulic pressure applied to the pistons  66  will force the pistons  66  against the springs  30  to L compress the springs  30 , thus releasing the pressure applied by piston  66  against the brake shoes  24  and thus release of the brake shoes applied against the rotor  22 . This permits free rotation of the rotor and the drum assembly  12 . When the drive motor  20  is de-energized, the control  84  will control the valve  82  to release the hydraulic pressure against the piston  66  and the springs  30  will force the pistons  66  and thus the brake shoes  24  against the rotor  22  to again create a braking action to maintain the drive in a set position. 
     One of the features of the present invention is the ready replacement of the brake shoes  24  when it is required to replace them due to wear or other causes. When it is necessary to replace the brake shoes  24 , the drum assembly  12  is rotated by operation of the motor  20  to a static state. That is, where a braking force is not required. Hydraulic pressure is applied to the pistons  66  of the actuators  32  to release the brake shoes from the rotor  22 . The brake shoe retaining pins  64  are simply removed to disassemble the brake shoes from the spacer block and the old brake shoes are simply removed from between the rotor and the actuator  32 . Replacement shoes  24  are simply inserted in position to receive the pins  64  slidably connecting the shoes to the spacer block  54  and the brake assembly is ready for operation. 
     Whereas separate switches may be manually engaged/disengaged to initiate motor and brake actuation, a single switch may be employed to initiate a desired sequence of these actions. FIGS. 6 a  and  6   b  illustrate circuitry that may be employed to this end. Those skilled in the art will, without further disclosure or discussion, understand the application of such circuitry and/or related circuitry to satisfy this objective. 
     Those skilled in the art will recognize that modifications and variations may be made without departing from the true spirit and scope of the invention. For example, whereas the disclosure uses as an example the raising and lowering of grappling forks by a winch, even in the machine that is illustrated, the invention can be applied to the opening and closing action of the tusks (overlying the forks), it can be applied to tilting of the forks and even to the steering of the machine. The latter applications likely are operated by intermeshing gears rather than winches. The invention is therefore not to be limited to the embodiments described and illustrated but is to be determined from the appended claims.