Abstract:
A winch is provided wherein braking is achieved by a pair of torque coils frictionally interlocking the brake shaft to the cable drum. A planetary gear reduction mechanism is provided between the shaft and drum and is prevented by such interlocking from producing differential rotation of the drum and thus it effects lockup or braking of the drum.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to winches and more particularly to a braking mechanism for a winch.  
       BACKGROUND OF THE INVENTION  
       [0002]     Winches are commonly used in off road vehicles and industrial applications. In vehicular applications, winches are commonly mounted to the front bumper of a vehicle. The winch includes a cable drum, and cable wound onto and off of the drum, and a motor and brake mechanism that controls the drum rotation. Vehicular winches can be used to pull the vehicle up steep hills, through mud, and for lowering small vehicles down steep slopes. Lowering a vehicle down a steep slope, in particular, creates a braking problem for the winch. The heavy weight or force pulls against the cable and urges unwinding of the cable from the drum. The drum can be locked against rotations from unwinding quite satisfactorily with a number of brake designs. When the cable is to be controllably played off the winch, such as when lowering the vehicle down a slope, the braking action needs to controllably resist or slow the drum rotation and thereby maintain control over the play out.  
         [0003]     Commonly assigned U.S. Pat. Nos. 5,261,646 and 5,482,255 each disclose satisfactory designs while achieving this purpose. However, it is still desirable to provide a simpler brake design that is easier to assemble and has fewer components.  
       SUMMARY OF THE INVENTION  
       [0004]     Accordingly, the present invention provides a braking mechanism for a winch, wherein the braking mechanism is contained within the winch drum and consists of an input coupler connected to a drive shaft and an output coupler connected to a braking shaft. The output coupler is connected through a gear train to the winch drum. The brake mechanism includes two torque coils that are intertwined in an inverse wrapped spiral configuration to transmit braking torque between an inside surface of the winch drum and the output coupler.  
         [0005]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0007]      FIG. 1  is a schematic view of a winch incorporating the brake mechanism according to the principles of the present invention;  
         [0008]      FIG. 2  is a partial cross-sectional view of the winch mechanism incorporating the braking mechanism according to the principles of the present invention;  
         [0009]      FIG. 3  is an exploded perspective view of the brake mechanism according to the principles of the present invention; and  
         [0010]      FIG. 4  is an assembled perspective view of the brake mechanism according to the principles of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0011]     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0012]     With reference to  FIGS. 1 and 2 , the illustrated winch  10  includes a cable drum  12  that is supported in a winch housing  14  by bushings  16 ,  18  as best illustrated in  FIG. 2 , for axial rotation relative to the stationary housing  14 A,  14 B. Cable  20  is wound on the drum  12  and is confined by drum flanges  22 ,  24  which abut against bushings  18 ,  16 , respectively. Cable  20  is either wound onto or off of the drum  12  with rotation of the drum  12 . A motor  26  is mounted to the housing end  14 A and turns a drive shaft  28 . The drive shaft  28  is coupled to a braking mechanism  30  which is coupled to a brake shaft  32 . The brake shaft  32  is coupled to a planetary gear assembly  34  contained in the housing end  14 B. The planetary gear assembly  34  is engaged with a cable drum  12 , as is known in the art. Thus, the motor  26  rotatively drives the drive shaft  28  which transmits torque to the brake shaft  32  via the braking mechanism  30  which rotatively drives the planetary gear assembly  34 . The function of the planetary gear assembly  34  is to reduce the rate of rotation so that the drum  12  is rotated by the planetary gear assembly  34  at a rate that is a fraction of the rotation of the drive shaft  28 . Such gear reduction multiplies the torque produced by the motor  26  as transmitted to the drum  12 . The brake mechanism  30  is mounted to the drive shaft  28  and brake shaft  32 . The brake mechanism  30  functions to lock the brake shaft  32  to the drum  12 . The planetary gear assembly  34  is thus unable to generate the rotational difference between the brake shaft  32  and the drum  12 . The drum  12 , the brake shaft  32  and the winch housing  14 A,  14 B are thus interlocked and rotation of the brake shaft  32  and the drum  12  are thereby stopped or braked.  
         [0013]     In reference to  FIGS. 3 and 4 , the brake mechanism  30  will now be described in greater detail. The brake mechanism  30  includes an input coupler  40 , an output coupler  42  and a pair of torque coils  44 ,  46 . The input coupler  40  is adapted to couple to the drive shaft  28  of the motor  26 . In particular, the input coupler  40  includes an internally hexed or otherwise splined opening  48  provided in an end flange  50  which extends radially outward from a body portion  52 . The body portion  52  is generally cylindrical in shape and includes a pair of axially extending arms  54 A,  54 B extending on opposite sides thereof and spaced approximately 180° from one another.  
         [0014]     The output coupler  42  also includes a body portion  60  with a radially extending flange portion  62  extending therefrom. The end of the output coupler  42  is provided with a similar bore having an internally hexed or otherwise splined surface (not shown) that is similar to the bore  48  provided in the input coupler  40 . A pair of axially extending arms  62 A,  64 B are provided on opposite sides of the cylinder body  60  and are spaced 180° from one another. Each of the axially extending arm portions  64 A,  64 B includes an axially extending slot or spring perch  66  provided in the outer surface thereof. The axially extending arm portions  64   a,    64   b  also include a recess  68  provided at an end thereof.  
         [0015]     The pair of torque coils  44 ,  46  are each inversely wound and intertwined with the end of each torque coil  44 ,  46  being bent inwardly to define a tang  70 ,  72  at each end thereof. The tangs  70 , provided at a first end of the torque coil, are received in the spring perch  66  of the output coupler  42 . The tangs  70  of the intertwined torque coils  44 ,  46  are opposed by  1800  from one another to provide symmetrical distribution of the braking torque against the inside surface of the winch drum  12 . The second ends of the torque coils  44 ,  46  define free floating spring tangs  72  which are bent inward and which are free floating relative to the input and output couplers  40 ,  42 . The torque coils  44 ,  46  surround the axially extending legs  54 A,  54 B and  64 A,  64 B of the input and output couplers  40 ,  42  which straddle one another such that the body portions  52 ,  60  of the input coupler  40  and output coupler  42  oppose one another.  
         [0016]     When the motor  26  is at rest and a torque is applied to the winch drum  12  in the direction that would unwind the cable  20 , the brake mechanism  30  is automatically actuated. The spring perches  66  of the output coupler  42  engage the spring tangs  70  from the output end of the intertwined torque coils  44 ,  46  and apply a moment on the torque coils  44 , 46  causing them to pivot about the spring perches  66  in a direction that causes the torque coils  44 ,  46  to be displaced outward radially, thereby transmitting braking torque between the output coupler  42  and the inside surface of the winch drum  12 . Additionally, the brake mechanism  30  is self-energizing due to friction between the outside diameter of the torque coils  44 ,  46  and the inside surface of the winch drum  12 , encouraging the torque coils  44 ,  46  to expand against the winch drum  12  further increasing the braking force. The input end of the intertwined torque coils  44 ,  46  are unrestrained and allow compliance with the braking demands of the system. The free floating ends  72  of the torque coils  44 ,  46  help dampen the rotational speed difference between the output coupler  42  and the winch drum  12 . Brake mechanism  30  is released when the motor  26  is powered in either direction. When the motor  26  is powered in a direction that would wind the cable  20  out, the input coupler  40  engages the free-floating end  72  of the intertwined torque coil  44 ,  46  in a manner that relaxes the braking force being exerted on the inside surface of the drum  12  by the torque coils  44 ,  46 .  
         [0017]     If the motor  26  is powered in a direction that would wind the cable inward, the input coupler  40  directly engages the output coupler  42  which drives the intertwined torque coils in a direction that relaxes the braking force against the inside surface of the drum  12  by causing the torque coils  44 ,  46  to be displaced radially inward. The direct engagement of the input coupler  40  to the output coupler  42  provides a solid coupling between the motor  26  and winch gear train  34 , eliminating the transmission of winch driving torque to the intertwined torque coils  44 ,  46 . If the rotational speed of the output coupler  42  exceeds the rotational speed of the input coupler  40 , the solid coupling between these components ceases to exist and the brake will automatically actuate since the torque coils  44 ,  46  would be caused to expand radially outward such as when the motor is at rest. With the brake mechanism  30  of the present invention, the number of components is significantly reduced and the assembly of the brake mechanism is simplified.  
         [0018]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.