Abstract:
A clutch comprising a pump is disclosed. The pump is operatively connected to the clutch such that a clutch slip event will cause the pump to delivery fluid from a fluid source to a region surrounding the friction plates of the clutch. The operation of the pump manages heat that is generated by the dynamic friction of the slipping clutch plates. The pump and associated fluid delivery methods are removably securable to an upstream end of an input shaft of the clutch. This allows the pump and associated fluid delivery methods to be used as modular components, that are easy to remove and replace for maintenance purposes, it also allows easier access to the internals of the clutch for maintenance.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to a clutch including a pump, and particularly to a clutch for a winch including a pump, and methods for removing heat from a clutch and assembling a clutch. 
       BACKGROUND 
       [0002]    When using a winch to raise a payload, a winch cable is attached to a motor-driven drum at one end and the payload at the other. The motor is driven to rotate the drum in order to gather up the winch cable on the outer circumference of the drum. In a modern hoist or winch system, a clutch is provided to limit the torque applied to the drum. The clutch comprises input and output friction plates that are biased together into frictional engagement with each other, to allow the transfer of drive from the motor to the drum through the clutch. The biasing of the plates is set to allow the plates to slip relative to each other at a particular maximum torque value suitable for the clutch. The slipping of the plates will disconnect the motor from driving the drum. The clutch therefore prevents an overload from damaging the winch, motor or the structure it is attached to. 
         [0003]    When the plates slip relative to each other the dynamic friction between them will generate significant heat. If unchecked, this heat may cause damage to the plates or other internal components of the clutch. This may compromise the lifetime or effectiveness of the clutch/winch system. 
       SUMMARY 
       [0004]    It is the aim of the present disclosure to manage the heat generated when the clutch slips to improve the overall lifetime and effectiveness of the clutch. 
         [0005]    It will be appreciated by one skilled in the art that “winch” or “hoist” refer to the same apparatus, and for the purposes of this disclosure, the terms may be used interchangeably. Only a winch shall be referred to in the description, however, in accordance with the above, any reference to a winch could equally refer to a hoist. 
         [0006]    From a first aspect, the present disclosure provides a clutch for driving a winch. The clutch comprises an input shaft, an output shaft and a pump. The input shaft is configured for connection to a motor and is operatively connected to at least one input friction plate for rotation therewith. The output shaft is configured for driving a winch, is coaxial with and has at least a portion radially within the input shaft, and is operatively connected to at least one output friction plate for rotation therewith. The at least one input friction plate and the at least one output friction plate are in contact with each other so that torque can be transferred from the input shaft to the output shaft via the input and output friction plates. The pump comprises an inlet, an outlet, an outer rotor, and an inner rotor. The inlet is configured for connection to a fluid source. The outlet is in fluid communication with the input and output friction plates. The outer rotor is operatively connected to the input shaft for rotation therewith. The inner rotor has at least a portion radially within the outer rotor and is operatively connected to the output shaft for rotation therewith. Differential rotation of the input shaft and the output shaft causes the pump to pump fluid to the friction plates. 
         [0007]    It is to be understood that, for the purposes of this disclosure, a first rotating member (e.g. a shaft or rotor) having “at least a portion radially within” a second rotating member means at least an axial portion of the first rotating member is located inside the second rotating member relative to the axis of rotation of the rotating members. 
         [0008]    In accordance with an embodiment of the first aspect, the outer rotor is arranged to rotate about a first axis and the inner rotor is arranged to rotate about a second axis that is not aligned with the first axis (i.e. the first and second axis are not coaxial). 
         [0009]    In accordance with an embodiment of the first aspect, the pump is a positive displacement pump. For instance, in one particular embodiment, the pump is a gerotor pump. 
         [0010]    In accordance with an embodiment of the first aspect, the output shaft comprises an outer shaft and an inner shaft. The inner shaft is disposed coaxially with and has at least a portion radially within the outer shaft and is operatively connected to the outer shaft for rotation therewith. The inner rotor may be in operative connection with the output shaft via the inner shaft. 
         [0011]    In accordance with an embodiment of the first aspect, the inner shaft further comprises a central bore in fluid communication with the outlet of the pump and first fluid delivery channels in fluid communication with the input and output friction plates. 
         [0012]    In accordance with an embodiment of the first aspect, the outer shaft includes second fluid delivery channels therethrough which are in fluid communication with the first fluid delivery channels of the inner shaft and the input and output friction plates. 
         [0013]    In accordance with an embodiment of the first aspect, the pump further comprises an outlet plate operatively connected to the inner rotor such that the inner rotor rotates therewith. The outlet plate further comprises one or more first protrusions extending therefrom. The inner shaft includes one or more first recesses at a connection end thereof and the one or more first protrusions engage with the one or more first recesses to operatively connect the inner rotor to the inner shaft. 
         [0014]    In accordance with an embodiment of the first aspect, the outer rotor comprises one or more second recesses on an outer surface thereof. An inner surface of the input shaft includes one or more second protrusions extending therefrom, and the one or more second protrusions engage the one or more second recesses to operatively connect the outer rotor to the input shaft. 
         [0015]    In accordance with an embodiment of the first aspect, the input shaft includes a first end located adjacent the at least one input friction plate (e.g. radially aligned with the input friction plate) and an opposed, open second end. The pump has at least a portion radially within the input shaft and is accessible or removable via the second end. 
         [0016]    The pump may be located completely within the input shaft, for example, at or near the second end of the input shaft. The pump may be removably attached to the input and output shafts such that it can be removed therefrom via the second end of the input shaft. 
         [0017]    In accordance with an embodiment of the first aspect, the pump further comprises an inlet seal. The inlet seal seals the pump radially within the input shaft. 
         [0018]    In accordance with an embodiment of the first aspect, the inner shaft is removably secured to the outer shaft. 
         [0019]    From a second aspect, the present disclosure provides a clutch for driving a winch. The clutch comprises an input shaft, an output shaft and a pump. The input shaft is configured for connection to a motor and is operatively connected to at least one input friction plate for rotation therewith. The output shaft is configured for driving a winch, is coaxial with and has at least a portion that is radially within the input shaft, and is operatively connected to at least one output friction plate for rotation therewith. The at least one input friction plate and the at least one output friction plate are in contact with each other so that torque can be transferred from the input shaft to the output shaft via the input and output friction plates. The pump has an inlet for connection to a fluid source and an outlet in fluid communication with the input and output friction plates. Differential rotation of the input shaft and the output shaft causes the pump to pump fluid to the input and output friction plates. 
         [0020]    It is to be understood that any of the embodiments described in relation to the first aspect above apply equally to the second aspect. 
         [0021]    From a third aspect, the present disclosure provides a method for removing heat from a clutch in accordance with any of the above embodiments or aspects. The method comprises the step of delivering fluid from a fluid source to the input and output friction plates during a clutch slip event. 
         [0022]    In accordance with an embodiment of the third aspect, the clutch slip event provides differential rotation of the inner rotor and the outer rotor of the pump to deliver fluid from the fluid source to the friction plates. 
         [0023]    From a fourth aspect, the present disclosure provides a method of assembling a clutch. The clutch comprises an input shaft and an output shaft. The input is configured for connection to a motor and has a first end located adjacent at least one input friction plate for rotation therewith and an opposed second end. The output shaft is configured for driving a winch, is coaxial with and has at least a portion radially within the input shaft, and is operatively connected to at least one output friction plate for rotation therewith. The at least one input friction plate and the at least one output friction plate are in contact with each other so that torque can be transferred from the input shaft to the output shaft via the input and output friction plates. The method comprises the step of removably securing a pump to the second end of the input shaft. The pump comprises an inlet, an outlet, an inner rotor and an outer rotor. The inlet is configured for connection to a fluid source. The outlet is in fluid communication with the friction plates. The outer rotor is operatively connected to the input shaft for rotation therewith. The inner rotor has at least a portion radially within the outer rotor and is operatively connected to the output shaft for rotation therewith. 
         [0024]    In accordance with an embodiment of the fourth aspect, the step of removably securing the pump includes using an inlet seal to seal the pump radially within the input shaft. 
         [0025]    In accordance with an embodiment of the fourth aspect, the output shaft comprises an outer shaft and an inner shaft and the method further comprises the step of removably securing the inner shaft coaxially with and at least partially within the outer shaft for rotation therewith, prior to the step of removably securing the pump. 
         [0026]    In accordance with an embodiment of the fourth aspect, the inner shaft and pump are removably engaged with each other. 
         [0027]    Although the clutch of the above aspects is primarily directed towards a clutch for a winch, it should be understood that the clutch may also be suitable for any other clutch application where dynamic friction between slipping clutch plates generates unwanted heat. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    Exemplary embodiments and features of the present disclosure will now be described by way of example only, and with reference to  FIGS. 1 to 3   c , of which: 
           [0029]      FIG. 1  is an overview of a winch system, in accordance with the present disclosure; 
           [0030]      FIG. 2  is a cross-section of a clutch, in accordance with one embodiment of the present disclosure; 
           [0031]      FIG. 3 a    is a view of a pump of the clutch of  FIG. 2  in accordance with an embodiment of the present disclosure; 
           [0032]      FIG. 3 b    is a view of a pump and an inner shaft of the clutch of  FIG. 2  in accordance with an embodiment of the present disclosure; 
           [0033]      FIG. 3 c    is an exploded view of  FIG. 3   b.    
       
    
    
     DETAILED DESCRIPTION 
       [0034]      FIG. 1  shows an overview of a typical winch system  1 , as is known in the art. A driving means, such as a motor  2 , is operatively connected to a brake  4  through gearing  3 , which is operatively connected to a clutch  5 , which is operatively connected to a drum  7  through gearing  6 . The motor  2  is activated to provide drive to the drum  7  through the gearing  3 , brake  4 , clutch  5  and gearing  6 , in order to reel in (or out) a winch cable  7   a  to lift (or drop) a payload  8 . The drum  7  and cable  7   a  together form a winch  9 . The brake  4  is provided as a means to stop cable winding without disengaging motor  1 , whereas clutch  5  acts as a moderating means for the drive, allowing the drum  7  to be disconnected from the motor  2  should the drum  7  become overloaded (as described above). 
         [0035]      FIG. 2  shows a cross-section of an exemplary embodiment of a clutch  105  in accordance with this disclosure. 
         [0036]    The component parts that make up clutch  105 , and an explanation of the basic operation of clutch  105  in order to transfer and moderate drive from motor  2  to drum  7 , will now be described. 
         [0037]    Clutch  105  comprises an input shaft  110  connected to motor  2  (not shown) and rotatable about axis X. Clutch  105  also comprises an output shaft  112  arranged co-axially with the input shaft  110  and rotatable about axis X. Output shaft  112  is supported in place by a roller bearing  111   a  disposed between its outer surface and an inner surface of input shaft  110 . The roller bearing allows input shaft  110  and output shaft  112  to rotate relative to each other. Output shaft  112  further comprises an output gear  113  at an output end thereof, in order to facilitate transfer of drive to the winch drum  7  (not shown). 
         [0038]    The clutch  105  may be attached to a support structure (not shown). The support structure may be part of the apparatus the winch is installed on. The winch may be installed on a vehicle, for example an aircraft, such as a helicopter, or may be installed on a something other than a vehicle, for example a crane (whether stationary or mobile) or on a building. 
         [0039]    The clutch  105  is used to selectively transfer the rotation (drive) of the input shaft  110  to the output shaft  112 . 
         [0040]    Input friction plates  144  are operatively connected to the input shaft  110  via a ball-ramp assembly  141 , and intervening output friction plates  132  attached to an output flange  134 , which is fixedly attached to output shaft  112  for rotating therewith. 
         [0041]    Input friction plates  144  are attached to ball-ramp flange  142  of ball-ramp assembly  141 . Ball-ramp assembly  141  is operatively connected to input shaft  110  via balls  141   a,  which are held in a recess  141   c  at one end of flange  142  and a recess  141   b  in input shaft  110 . 
         [0042]    Clutch  105  further comprises a spring pack  148  comprising disc springs (i.e. Belleville springs or washers). In this particular embodiment, the disc springs are co-axial with the output shaft  112  and centred around the output shaft  112 . The spring pack  148  is held in place via a spring pack retaining flange  150 . In this particular embodiment, retaining flange  150  includes a thread  150   a  on an inner surface thereof, which is configured to co-operatively engage with a thread  112   a  on the outer surface of output shaft  112 . The threads maybe acme threads or any other suitable thread type. The spring pack  148  and the spring pack retaining flange  150  rotate with the output shaft  112  (about axis X). 
         [0043]    It is to be understood that this retaining flange  150  is only exemplary for illustration purposes and any other suitable method of retaining spring pack  148  may be used within the scope of this disclosure. For instance, in one alternative embodiment, retaining flange may be fixed to output shaft and rotatable therewith. In another alternative embodiment, spring pack  148  may be retained by the output shaft directly rather than by a retaining flange. For instance spring pack  148  may be retained in a notch in the output shaft. 
         [0044]    The spring pack  148  is in mechanical communication with a connecting arm  146  and a plurality of ball bearings  142   a,  so that it can rotate relative to the ball ramp flange  142 . The connecting arm  146  is supported around output shaft  112  by a roller bearing  111   b.  Bearing  142   a  is located in recesses in the flange  142  and the connecting arm  146 . Spring pack  148  is fixed to retaining flange  150 , such that it exerts a spring bias on connecting arm  146 . 
         [0045]    Clutch  105  allows rotation of the input shaft  110  to be transferred to the output shaft  112  via spring loaded engagement of the input friction plates  144  with the output friction plates  132 , and the maximum permitted amount of torque transferred from the input shaft  110  to the output shaft  112 , and vice versa, can be controlled by adjusting the degree of spring loading. 
         [0046]    Ball-ramp assembly  141  is used to moderate and minimise the torque setting variation encountered when operating the clutch  105 , by adjusting the force with which the input plates  144  are pressed upon output plates  132 . As described above, ball  141   a  engages the input shaft  110  and the ball-ramp flange  142  in opposing recesses  141   b,    141   c  therein. As is known in the art, such as disclosed in U.S. Pat. No. 3,511,349, the recesses are shaped to act as cam members that cams the ball  141   a  to increase or decrease the separation between the pairs of recesses  141   b,    141   c  that hold each ball  141   a  in place. 
         [0047]    As the friction characteristics of the friction plates  132 ,  144  vary, the force exerted by the input friction plates  144  on the output friction plates  132  varies. If the coefficient of friction between the input and output friction plates  132 ,  144  increases, the maximum torque able to be transmitted through the clutch  105  before slipping will also increase. However, as the torque transmitted through the clutch  105  increases, the separating force between the recesses  141   a,    141   b  will increase and thus, the friction between friction plates  132 ,  144  will decrease. As such, the maximum transmitted torque before slipping will subsequently decrease. As will be understood by one skilled in the art, the ball-ramp assembly  141  therefore counteracts the effects of friction variations at the friction plates  132 ,  144 , and thus minimises them to retain the torque slipping thresholds of the clutch  105 . This provides an advantage over clutches not having a ball-ramp assembly. 
         [0048]    It is to be understood, however, that clutch  105  need not include a ball-ramp assembly. For instance, the input shaft may further comprise an input plate flange that is operatively connected to the input friction plates and is biased directly by the spring pack, rather than through a ball-ramp assembly, as illustrated. 
         [0049]    Additional components of the clutch  105  and methods of operation used to achieve the aims of the present disclosure will now be described. 
         [0050]    Clutch  105  further comprises an inner shaft  170  fitted co-axially inside output shaft  112 . Inner shaft  170  is secured to the output shaft  112  via a snap ring  170   b  and locking nut  170   c.  Inner shaft  170  is further supported by roller bearing  170   a  disposed between the input shaft  110  and the outer surface of the chamber  170 . Inner shaft  170  further comprises a central bore  171   a  along a portion of the axial extent thereof and first delivery channels  172   a  through a radial width thereof First delivery channels  172   a  are in fluid communication with second delivery channels  172   b  in the output shaft  112 . The first and second delivery channels  172   a,    172   b  allow delivery of hydraulic fluid (e.g. oil) to the friction plate region of the clutch for heat management and/or lubrication, as will be described further below. 
         [0051]    Clutch  105  further comprises a pump  200 , located radially within the input shaft  110 . 
         [0052]    Pump  200  is in fluid communication with a hydraulic fluid supply (e.g. a hydraulic fluid reservoir)(not shown), and is operable during a clutch slip event to pump hydraulic fluid through inner shaft  170  and to the friction plates  132 ,  144  (via first and second delivery channels  172   a,    172   b ). This operation of pump  200  is used to cool the friction plates  132 ,  144 , by removing heat generated by the dynamic friction between friction plates  132 ,  144  during a clutch slip event (e.g. by dissipating heat to other areas of the clutch  105  or to the surroundings). 
         [0053]    As can be seen in  FIGS. 2 and 3   a - 3   c,  pump  200  comprises an outer rotor  208  and an inner rotor  206  disposed radially within the outer rotor  208 . Inner rotor  206  is mounted off-centre relative to a central axis of outer rotor  208  (e.g. off-centre of axis X). Outer rotor  208  comprises grooves therein and inner rotor  206  comprises teeth that fit within the grooves. The rotors  206 ,  208  are secured between inlet plate  205  and outlet plate  209  by fastener  204 . Inlet plate  205  and outlet plate  209  feature inlet and outlet apertures  205   a,    209   c  therein, that allow communication of fluid in to and out of the pump, respectively. The inlet plate  205  and outlet plate  209  each include projections  209   b  that protrude through the inner rotor  205  and support it for rotation inside the outer rotor  208 . Fastener  204  secures the plates  205 ,  209  together by passing through a threaded section in the protrusions  206   b.  Pump  200  further comprises an inlet seal  202 , comprised of two sealing support rings  202   a,    202   b  and a washer  202   c.  As shown in  FIGS. 3 b  and 3 a   , washer  202   c  is disposed in inlet plate  205  to help secure fastener  204  therein. 
         [0054]    It will be apparent to one skilled in the art that pump  200  acts as a positive displacement pump, and specifically is a gerotor pump. It should be understood, however, than any suitable positive displacement pump mechanism, as would be apparent to one skilled in the art, may be used within the scope of this disclosure. 
         [0055]    As shown in  FIG. 2 , support rings  202   a,    202   b  secure and seal the pump  200  concentrically within extending portions of the input shaft  110 . Removal of support rings  202   a,    202   b  allow removal of the pump  200  from the clutch  150 , for instance, for repair/replacement purposes. Outer rotor  208  features recesses  208   a  that are secured by retaining pins  208   b  which are fixedly secured to the extending portions of the input shaft  110 . The engagement of recesses  208   a  via retaining pins  208   b  fixedly secures the outer rotor  208  to the output shaft  110 , such that it rotates therewith. Outlet plate  209  features one or more dogs  209   a  that secure into recesses  171   b  in inner shaft  170 . This allows fluid communication from the output aperture  209   c  of the pump  200  to central bore  171   a  in inner shaft  170 . As will now be appreciated, this allows communication of fluid from pump  200  to the friction plate region of clutch  105 . In addition, the securing of outlet plate  209  to inner shaft  170  allows rotation of the output shaft  112  to drive rotation of the inner rotor  206 . Therefore, rotation of the inner rotor  206  is driven by rotation of the output shaft  112  and the rotation of the outer rotor  208  is driven by rotation of the input shaft  110 . 
         [0056]    The operation of pump  200  will now be described with reference to  FIGS. 2 and 3   a - 3   c.    
         [0057]    As inner rotor  206  is off-centre relative to the outer rotor  208 , small gaps will be left between some of the teeth of the inner rotor  206  and some of the grooves of the outer rotor  208 . These gaps allow the communication of fluid into and through the pump  200 . Rotation of the inner rotor  206  relative to the outer rotor  208  will draw fluid into the gaps through inlet aperture  205   a  and drive the fluid around the pump  200  and out through outlet apertures  209   c.  In embodiments of the present disclosure, this will deliver hydraulic fluid to the friction plate region (as discussed above). 
         [0058]    As will be understood by one skilled in the art, when clutch  105  is transferring drive from the motor  2  to the drum  7  under normal operating conditions the input shaft  110  and the output shaft  112  rotate at the same speed. This will mean that inner rotor  206  and outer rotor  208  rotate at the same speed, and so do not exhibit relative rotation to each other. Therefore under normal operating conditions of clutch  105  pump  200  will not operate. However, when a slip event occurs, either of the input shaft  110  or the output shaft  112  will be rotating at a faster or slower rate relative to each other. This will provide a relative rotation between inner rotor  206  and outer rotor  208 , which will operate pump  200 . As will now be apparent, the operation of pump  200  in clutch  105  will only be activated during a clutch slip event. Therefore, pump  200  will only deliver hydraulic fluid to the friction plate region of clutch  105  when either of the input or output friction plates  144 ,  132  are slipping. This will supply hydraulic fluid to the friction plate region of the clutch  105  to manage heat generated by the dynamic friction between slipping friction plates  144 ,  132 . As will be appreciated by one skilled in the art, a slip event is when such heat management is needed most. 
         [0059]    In the illustrated embodiment, clutch  105  is a dry-type clutch and hydraulic fluid is only present at the friction plates  132 ,  144  when pumped there by pump  200  during a clutch slip event. It should be understood, however, that within the scope of this disclosure, clutch  105  may also be a wet-type clutch. In such a wet-type clutch, the friction plate region and/or other clutch regions are already immersed in hydraulic fluid (e.g. oil), as in known in the art. In such a system, operation of pump  200  will encourage re-circulation of the hydraulic fluid to aid heat management during a clutch slip event, as opposed to introducing fluid to initially cool the region. 
         [0060]    A wet-type clutch may provide advantages over a dry-type clutch during normal clutch operation, such as better lubrication and/or heat management, as would be apparent to one skilled in the art. A dry-type clutch, however, may provide other advantages such as simplicity, cost and maintenance. 
         [0061]    It is to be understood that the construction and operating characteristics of pump  200  and/or inner shaft  170  allow them to act advantageously as a modular or stand-alone component or components. In previous pumps for clutches, the pump has been known to be integral to the clutch itself, for instance, pump rotors may be integrated with the input and output shafts directly, or the pump disposed at an internal connection therebetween. Such a construction may provide added complexity and costs compared to that of the present disclosure. The design of the pump  200  and/or inner shaft  170  and the attachment features therebetween or relative to the input shaft  110  and output shaft  112 , make them easy to remove and/or replace. This provides advantages over the aforementioned previous clutches. 
         [0062]    Although the figures and the accompanying description describe particular embodiments, it is to be understood that the scope of this disclosure is not to be limited to such specific embodiments, and is, instead, to be determined by the scope of the following claims.