Abstract:
Hoists for hoisting loads by means of a cable are in existence for a long period. There are various types of hoists, which include winches and capstans. Generally, the principle of operation of a hoist is based on the cable being driven by adherence of the cable to the drum of the hoist. A hoist is described according to an embodiment of the present invention. The hoist comprises a drum, a plurality of guides, a guide support and a biasing device for displacing a portion of a cable away from the guide when the drum is rotationally displaced to thereby hoist a load.

Description:
FIELD OF INVENTION 
       [0001]    The invention relates generally to load hoisting, and more particularly to a hoist for hoisting a load by means of a cable. 
       BACKGROUND 
       [0002]    Hoists for hoisting loads by means of a cable have long existed. Generally, the principle of operation of a hoist is based on the cable being driven by adherence of the cable to the drum of the hoist. The drum holds the cable by friction, which operates as the principal power means for drawing in the cable for winding around the drum. As tension that is applied to the cable increases, the cable stretches and its linear speed decreases accordingly. 
         [0003]    There are various types of hoists, which include winches and capstans. A winch is used to wind up a cable in which one end of the cable is fixed and the cable is generally stored on the drum of the winch. Besides industrial applications, for example on lifting cranes, winches are also used on vehicles for towing cars and boats. Winches are widely used for hoisting loads as they provide mechanical advantage to users. However, a drawback of using a winch to hoist a load is that sufficient tension must be constantly maintained on the turns for the cable to be suitably wound and stored on the drum. Typically, a guide mechanism is used for progressively guiding the cable across the length of the drum as the cable is being wound onto the drum. 
         [0004]    Capstans are similar to winches with the exception that the cable is not stored on the drums. Hence, capstans do not have the problem of constantly maintaining sufficient tension on the turns for the cable to be suitably wound and stored on the drums. Capstans are rotating machines used to apply force to another element and are typically used on board ships and on dock walls for heaving or veering ropes, cables and hawsers. When a capstan is in operation, only a portion of the cable is wound around the drum of the capstan. A load can be attached to one of the free ends for the capstan to hoist the load. However, as the cable is driven by adherence of the cable to the drum of the capstan, sufficient frictional force is needed between the cable and the drum for operation of the capstan. 
         [0005]    Japanese Patent Application Number 20040163404 to Fumiaki discloses an endless type winch having a configuration capable of towing and driving a winch without winding a rope by utilising a part around a driving mechanism of an existing winch as it is. The endless type winch comprises a winding drum having a rope channel at the outer periphery, a pair of rope gripping guide sheaves and a supporting frame. The pair of rope gripping guide sheaves is arranged in positions where the rope winds around the rope channel of the winding drum so as to increase contact frictional force of the rope for the rope channel. However, as the rope elastically contracts due to its tension diminishing in passing through the endless type winch, the length of the rope changes continuously. The rope slides against the rope channel of the winding drum for accommodating the changing rope length, which results in wear and tear of the rope. Further, the sliding of the rope against the rope channel increases slippage of the rope between the drum and the rope gripping guide sheave. 
         [0006]    Therefore, there is a need for a hoist, which addresses at least one of the aforementioned problems. 
       SUMMARY 
       [0007]    The present embodiment of the invention disclosed herein provides a hoist for hoisting a load by means of a cable. 
         [0008]    In accordance with a first aspect of the invention, a hoist comprising a drum, a biasing mechanism and at least one guide is disclosed. The drum comprises a drum surface for supporting a cable thereon and the cable has an anchored end. The at least one guide is coupled to the biasing mechanism and the biasing mechanism is for biasing the at least one guide towards the drum for clasping at least one portion of the cable between the at least one guide and the drum. This is to substantially adhere the clasped at least one portion of the cable to the drum surface. When a portion of the cable extending between the anchored end and the drum is in tension, slippage between the drum surface and the clasped at least one portion of the cable is substantially impeded and the drum is rotationally displaceable for displacing the clasped at least one portion of the cable away from the at least one guide. 
         [0009]    In accordance with a second aspect of the invention, a hoist comprising a drum, a plurality of guides, a guide support and a biasing device is disclosed. The drum comprises a drum surface for supporting a cable thereon and the cable has an anchored end. The guide support is for inter-coupling the plurality of guides. The biasing device cooperates with the guide support for biasing the plurality of guides towards the drum for clasping at least one portion of the cable between the plurality of guides and the drum. This is to substantially adhere the clasped at least one portion of the cable to the drum surface. When a portion of the cable extending between the anchored end and the drum is in tension, slippage between the drum surface and the clasped at least one portion of the cable is substantially impeded and the drum is rotationally displaceable for displacing the clasped at least one portion of the cable away from the plurality of guides. 
         [0010]    In accordance with a third aspect of the invention, a cable adherence apparatus comprising a plurality of guides, a guide support and a biasing device is disclosed. The guide support is for inter-coupling the plurality of guides and is coupled to the biasing device. The biasing device is couplable to a drum assembly that comprises a drum. The drum has a drum surface for supporting a cable thereon and the cable has an anchored end. The biasing device is for cooperating with the guide support for biasing the plurality of guides towards the drum for clasping at least one portion of the cable between the plurality of guides and the drum. This is to substantially adhere the clasped at least one portion of the cable to the drum surface. When a portion of the cable extending between the anchored end and the drum is in tension, slippage between the drum surface and the clasped at least one portion of the cable is substantially impeded and the drum is rotationally displaceable for displacing the clasped at least one portion of the cable away from the plurality of guides. 
         [0011]    In accordance with a fourth aspect of the invention, a hoist comprising a drum and a plurality of guide members is disclosed. The drum has a drum surface for supporting a cable thereon and the cable has an anchored end. The plurality of guide members are one of biasable toward and displaceable away from the drum surface. The plurality of guide members comprise a first guide member and second guide members. The first guide member guides the cable to the drum and the second guide members clasp at least one portion of the cable between the second guide members and the drum. Guidance of the cable via the first guide member biases the second guide members toward the drum surface to substantially adhere the clasped at least one portion of the cable to the drum surface. When a portion of the cable extending between the anchored end and the drum is in tension, slippage between the drum surface and the clasped at least one portion of the cable is substantially impeded and the drum is rotationally displaceable for displacing the clasped at least one portion of the cable away from the plurality of guide members. 
         [0012]    In accordance with a fifth aspect of the invention, a hoist comprising a drum, a plurality of guide members and a biasing device is disclosed. The drum has a drum surface for supporting a cable thereon and the cable has an anchored end. The plurality of guide members are one of biasable toward and displaceable away from the drum surface. The plurality of guide members comprise a first guide member and second guide members. The first guide member guides the cable to the drum and the second guide members clasp at least one portion of the cable between the second guide members and the drum. The biasing device cooperates with the plurality of guide members whereby biasing of the second guide members toward the drum surface releases tension in the biasing device and the displacement of the second guide members away from the drum surface producing tension in the biasing device. When a portion of the cable extending between the anchored end and the drum is in tension, slippage between the drum surface and the clasped at least one portion of the cable is substantially impeded and the drum is rotationally displaceable for displacing the clasped at least one portion of the cable away from the second guide members. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    An embodiment of the invention is described hereinafter with reference to the following drawings, in which: 
           [0014]      FIG. 1  shows a front elevation of a hoist according to an embodiment of the invention; 
           [0015]      FIG. 2  shows a cross sectional view of the hoist of  FIG. 1  along line A-A; 
           [0016]      FIG. 3   a  shows a side view of a first configuration of a hoist in accordance with another embodiment of the invention, the first configuration comprises a drum, a biasing device, a plurality of guides, a plurality of the guide support and a lever member; 
           [0017]      FIG. 3   b  shows a cross sectional view of the hoist of  FIG. 3   a  along line B-B′; and 
           [0018]      FIG. 3   c  shows a side view of a second configuration of the hoist of  FIG. 3   a , wherein a plurality of cables are wound round the drum. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    A hoist for hoisting a load by means of a cable is described hereinafter for addressing at least one of the aforementioned problems. 
         [0020]    For purposes of brevity and clarity, the description of the invention is limited hereinafter to applications relating to hoists. This however does not preclude various embodiments of the invention from other applications. The fundamental concepts of the embodiments of the invention shall remain common throughout the various embodiments. 
         [0021]    A first embodiment of the invention described in the detailed description provided hereinafter is in accordance with  FIG. 1  to  FIG. 2  of the drawings, in which like elements are numbered with like reference numerals. 
         [0022]    With reference to  FIG. 1  and  FIG. 2 , a hoist  10  is described according to the first embodiment of the invention. The hoist  10  generally comprises a drum  12 , a biasing device  14 , a plurality of guides  16 , a guide support  18  and a housing  19 . The biasing device  14  and the guide support  18  form a biasing mechanism. The hoist  10  further comprises an actuator (not shown) operable for controlling rotational displacement of the drum  12 . The actuator is preferably an electric motor. Alternatively, the actuator comprises a crank assembly operable for rotationally displacing the drum  12 . The drum  12  comprises a drum surface  20  for supporting a cable  22 , such as a rope, with the cable  22  having an anchored end  24  and a free end  26 . Preferably, the cable  22  is wound around the drum  12  three times, as shown in  FIG. 2 . However, the cable  22  can be wound around the drum  12  more than three times. Alternatively, the cable  22  is wound around the drum  12  only once. Preferably, the drum surface  20  is substantially cylindrical. Alternatively, the drum surface  20  is substantially hyperbolical. 
         [0023]    Furthermore, the drum  12  preferably comprises a groove (not shown) formed on the drum surface  20  that spirals a number of times around the drum  12 . The groove is for locating the cable  22  within the groove when the cable  22  is being wound around the drum  12 . This is for impeding lateral slippage or travel of the cable  22  off the drum surface  20  when the drum  12  is rotationally displaced. Additionally, the groove is preferably coated with a layer of material for hardening the surface of the groove. The surface of the groove after coating is preferably smooth for reducing friction between the cable  22  and the groove, thus reducing wear and tear of the cable  22 , when the drum  12  is rotationally displaced. 
         [0024]    Alternatively, the groove formed on the drum surface  20  spirals only once around the drum  12  for locating the cable  22  within the groove. The cable  22  is thus wound around the drum  12  only once. 
         [0025]    The guide support  18 , such as a chain or roller chain, comprises a first end  28  and a second end  30 , and is preferably elongated. The guide support  18  is for inter-coupling the guides  16 . Preferably, each of the guides  16  is a roller being rotatably coupled to the guide support  18 . 
         [0026]    The guide support  18  is further coupled to the biasing device  14 . The biasing device  14  is preferably an assembly of one or more springs made from a coil of wire or elastic materials such as polyurethane. The biasing device  14  is coupled to the guide support  18  at the first end  28  and the second end  30  for biasing the first end  28  away from the second end  30 . The biasing mechanism is coupled to and supported by the housing  19 , which is coupled to the drum  12 . Alternatively, the housing  19  is coupled to a frame (not shown) instead of the drum  12 . Operatively, the biasing device  14  is for cooperating with the guide support  18  for biasing the guides  16  towards the drum  12  for clasping a portion of the cable  22  between the guides  16  and the drum  12 . This is to substantially adhere the clasped portion of the cable  22  to the drum surface  20 . 
         [0027]    Additionally, more than one portion of the cable  22  is claspable between the guides  16  and the drum  12 . To clasp more than one portion of the cable  22 , more than one biasing device  14  and one guide support  18  are needed. As illustrated in  FIG. 2  where the cable  22  is wound around the drum  12  three times, preferably two portions of the cable  22  are being substantially adhered to the drum surface  20  in which each of the two portions of the cable  22  is being clasped by one biasing device  14  together with one guide support  18 . In particular, one of the two clasped portions is a part of the first wind of the cable  22  around the drum  12  and the other of the two clasped portions is a part of the last wind of the cable  22  around the drum  12 . This is to ensure that the free end  26  of the cable  22  continues to wind around a portion of the drum  12  after the free end  26  travels across the guides  16  during rotational displacement of the drum  12 . 
         [0028]    Preferably, the biasing mechanism comprises the biasing device  14  and the guide support  18  for biasing the guides  16  towards the drum  12 . Alternatively, another type of biasing mechanism comprising a plurality of biasing arms such as lever arms (not shown) can be provided for biasing the guides  16  towards the drum  12 . Each of the guides  16  is coupled to each of the biasing arms and each of the biasing arms is for biasing each of the guides towards the drum  12 . 
         [0029]    A hoist (not shown) according to a second embodiment of the invention comprises the drum  12 , the biasing device  14 , the guide support  18  and the housing  19 , in which the biasing device  14  and the guide support  18  form a biasing mechanism, as in the hoist  10  of  FIG. 1  and  FIG. 2  with the exception that this hoist comprises a single guide  16  instead of the plurality of guides  16 . Furthermore, as there is only one guide  16  being coupled to the guide support  18 , the guide support  18  is only for cooperating with the biasing device  14  for biasing the guide  16  towards the drum  12 . 
         [0030]    Alternatively, instead of providing the biasing mechanism comprising the biasing device  14  and guide support  18  for biasing the guide  16  towards the drum  12 , another type of biasing mechanism comprising a biasing arm (not shown) for coupling the guide  16  thereto, is provided for biasing the guide  16  towards the drum  12 . 
         [0031]    Additionally, it is known in the art that besides the biasing mechanism described in each of the first and second embodiments of the invention, other types of biasing mechanism for biasing the guides  16  towards the drum  12  are implementable. Further, the preferred embodiment of the invention is the hoist  10  as described according to the first embodiment of the invention, which comprises the guides  16  and the type of biasing mechanism that comprises the biasing device  14  and the guide support  18 . 
         [0032]    Referring back to  FIG. 1  and  FIG. 2 , when the hoist  10  is in use for hoisting a load (not shown), the portion of the cable  22  extending between the anchored end  24  and the drum  12 , as well as the portion of the cable  22  wound into the groove are in tension. Consequently, slippage between the drum surface  20  and the two clasped portions of the cable  22  is substantially impeded. Further, the drum  12  is rotationally displaceable for displacing the two clasped portions of the cable  22  away from the guides  16 . The guides  16  which are biased onto the cable  22  apply sufficient force thereto for adhering the cable  22  to the drum surface  20  without impeding travel of the cable  22  across the guides  16  when the drum  12  is rotationally displaced to thereby hoist the load. Further, the free end  26  of the cable  22  can be collected using a wheeler (not shown) as the drum  12  is being rotationally displaced. 
         [0033]    A hoist  40  according to a third embodiment of the invention is shown in  FIG. 3   a ,  FIG. 3   b  and  FIG. 3   c . The hoist  40  is preferably implemented in a first configuration  40   a  as shown in  FIG. 3   a  and a second configuration  40   b  as shown in  FIG. 3   c.    
         [0034]      FIG. 3   a  provides a side view of the first configuration  40   a  of the hoist  40  and  FIG. 3   b  provides a cross sectional view of the first configuration  40   a  of the hoist  40  along line B-B′.  FIG. 3   c  provides a side view of the second configuration  40   b  of the hoist  40 . 
         [0035]    Referring to  FIG. 3   a , the first configuration  40   a  comprises the drum  12 , the plurality of guides  16 , a plurality of the guide support  18  and a lever member  42 . The plurality of guides  16  preferably comprise a first guide member  16   a  and second guide members  16   b . The plurality of the guide support  18  preferably comprise at least a first guide support member  18   a  and a second guide support member  18   b . The first configuration  40   a  further comprises the biasing device  14 , one or more pressure rollers  44 , a first stopper member  46   a  and a second stopper member  46   b . Each of the first and second guide support members  18   a / 18   b  inter-couples the second guide members  16   b.    
         [0036]    The first and second guide support members  18   a / 18   b  and the lever member  42  are preferably inter-coupled by a first coupling member  48   a . The lever member  42  is preferably further coupled, by a second coupling member  48   b , to a common structure  50 . The second coupling member  48   b  is preferably a pivot point about which the lever member  42  pivots. Preferably, the first stopper member  46   a  is also coupled to the common structure  50 . 
         [0037]    The pressure rollers  44  are coupled to the drum  12 , along its periphery. Each of the pressure rollers  44  is preferably individually coupled to the periphery of the drum  12 . Alternatively, each of the pressure rollers  44  is inter-coupled to another to form a pressure roller unit (not shown) prior to being coupled along the periphery of the drum  12 . Each of the pressure rollers  42  are inter-coupled to each other by, for example, a chain or roller chain. In one variation, each of the pressure rollers  44  has a substantially smooth surface. In another variation, each of the pressure rollers  44  comprises a plurality of grooves (not shown) such that each of the pressure rollers  44  has a grooved surface. 
         [0038]    The second guide members  16   b  are rotatable and a portion of the cable  22  is clasped between the second guide members  16   b  and the drum  12 . The clasped portion of the cable  22  is substantially adhered to the drum surface  20 . In an event where the clasped portion of the cable  22  is not fully adhered to the drum surface  20 , the pressure rollers  44  serve to further adhere the clasped portion of the cable  22  to the drum surface  20 . 
         [0039]    In one example, the first and second guide support members  18   a / 18   b  and the lever member  42  form a biasing mechanism. In another example, the biasing device  14 , the first and second guide support members  18   a / 18   b , the lever member  42  and the first and second stopper members  46   a / 46   b  form a biasing mechanism. The biasing device  14  is, for example, a spring member and tension is provided by the biasing mechanism upon the biasing device  14  being compressed. 
         [0040]    In a first exemplary operation where the biasing mechanism comprises the first and second guide support members  18   a / 18   b  and the lever member  42 , the second guide members  16   b  are biased toward the drum surface  20  of the drum  12 , prior to introduction of the cable  22  to the drum  12  by, for example, gravity. In this instance the biasing mechanism is substantially tensionless. 
         [0041]    Upon introduction of the cable  22  to the drum  12  via the first guide member  16   a , the lever member  42  pivots about the second coupling member  48   b . The cable  22  is preferably introduced via the first guide member  16   a  such that the cable  22  presses against the first guide member  16   a . As the cable  22  presses against the first guide member  16   a , the second guide members  16   b  are further biased toward the drum surface  20  of the drum  12 . 
         [0042]    The cable  22  can be pressed against the first guide member  16   a  by, for example, loading and biasing the cable  22  towards the first guide member  16   a  via a pulley (not shown). 
         [0043]    The cable  22  contacts the second guide members  16   b  so that the second guide members  16   b  are displaced away from the drum surface  20  of the drum  12 . Therefore tension is provided by the biasing mechanism, further adhering the clasped portion of the cable  22  to the drum surface  20 . 
         [0044]    In a second exemplary operation where the biasing mechanism of the first exemplary operation further comprises the biasing device  14  and the first and second stopper members  46   a / 46   b , the second stopper member  46   b  is moved towards the first stopper member  46   a  as the lever member  42  is pivoted such that the second guide members  16   b  are displaced away from the drum surface  20  of the drum  12 . The biasing device  14  is consequently compressed between the first and second stopper members  46   a / 46   b . As the basing device  14  is compressed, tension is provided by the biasing mechanism. 
         [0045]    As mentioned earlier, the tension provided serves to further adhere the clasped portion of the cable  22  to the drum surface  20 . Apparent from the above, the second guide members  16   b  can function as a fulcrum for the lever member  42 . The amount of tension provided is controllable by adjusting displacement of the fulcrum and the second coupling member  48   b.    
         [0046]      FIG. 3   c  provides a side view of the second configuration  40   b . As shown, a plurality of cables  22  are wound round the drum surface  20 . Tension is applied to each of the plurality of cables  22  as described in the exemplary operations of the first configuration  40   a.    
         [0047]    Each of the hoist  10  and the hoist  40  is implementable in several ways with three exemplary configurations described hereinafter for hoisting the load (all not shown). In each of the exemplary configurations, the load is a gondola suspendable and positionable along a face of a fixed structure such as a building. The exemplary configurations are described hereinafter with respect to the hoist  10 . It can be appreciated that the hoist  40  can also be implemented similarly to the hoist  10 . 
         [0048]    In a first exemplary configuration for implementing the hoist  10 , the anchored end  24  is anchored to the top of a structure, for example a building, with the hoist  10  being mounted to the gondola. 
         [0049]    In a second exemplary configuration for implementing the hoist  10 , the anchored end  24  is anchored to the gondola with the hoist  10  being mounted to the top of the building. 
         [0050]    In a third exemplary configuration for implementing the hoist  10 , both the anchored end  24  and the hoist  10  are respectively anchored and mounted to the top of the building. The portion of the cable  22  extending between the anchored end  24  and the drum  12  forms a loop with a pulley being mounted to a portion thereof. The pulley is mounted to the gondola for connecting the gondola with the hoist  10  by means of the cable  22 . 
         [0051]    In each of the three exemplary configurations, when the hoist  10  is in operation, the gondola is positionable along the face of the building for lifting or lowering objects or individuals contained in the gondola. 
         [0052]    In the foregoing manner, a hoist for hoisting a load is described according to embodiments of the invention for addressing at least one of the foregoing problems. Although only a few embodiments of the invention are disclosed, the invention is not to be limited to specific forms or arrangements of parts so described and it will be apparent to one skilled in the art in view of this disclosure that numerous changes and/or modification can be made without departing from the scope and spirit of the invention.