Abstract:
A rigging, operable to raise and lower the platform, passes through a restraint device comprising a tension holder. The tension holder comprises a first body having a substantially planar face surface and a rear portion having a divot disposed therein. A second body, substantially similar to the first body; and having a substantially planar face surface; is disposed in a substantially facing arrangement with the first body to permit a line to pass between the substantially planar face surfaces. A lever is disposed in the divot of the first body and is operable to draw together the substantially planar face of the first body and the substantially planar face of the second body whereby friction can be selectively applied to the line when the line is disposed between the substantially planar first surface and said substantially planar second surface.

Description:
BACKGROUND 
       [0001]    Tension holders are used in a variety of load-lifting applications such as elevated platforms for building maintenance. Such platforms can be used in conjunction with a motorized hoisting device, whereby the hoisting device is attached to the platform of an elevated platform or basket that may then be raised or lowered using the hoisting device. The hoisting device and associated rigging typically comprises a tension holder, whereby a continuous lines such as a cable or rope passes through the tension holder. The tension holder is used to keep tension on the line when it would otherwise be slack. 
         [0002]    A tension holder may also be associated with a fairlead, which is a device such as a ring or a block that has a guide opening, typically used to guide a rigging such as a line, such as wire or nylon rope or other cable, around an object, or to stop the rigging from moving laterally. 
         [0003]    A tension holder is used in a variety of applications in which riggings are used, including marine vehicles, loading devices, and various hoisting applications such as elevated platforms for building maintenance. A tension holder is typically used on a suspended scaffold work basket or platform to keep tension on the line whenever the unit is not suspend in the air and line has the capability to go slack. In a hoisting application, an elevated platform or basket is typically raised or lowered using a powered hoisting device attached to the platform. The hoisting device utilizes a cable that is guided through a fairlead and then through a tension holder. A tension holder has a wear surface that conforms to the diameter of a line to keep tension on the line. It is used to keep the line taught and in place and also to prevent the lines from entangling with other items or themselves. 
         [0004]    Prior art tension holders are made up of a number of parts including rollers with bearings which increase assembly and service time. 
       SUMMARY OF THE INVENTION 
       [0005]    In one embodiment, a platform has a hoisting machine mounted thereon. A rigging, operable to raise and lower the platform, passes through a restraint device comprising a tension holder. The tension holder comprising a first body having a substantially planar face surface and a rear portion having a divot disposed therein. A second body, substantially similar to the first body; and having a substantially planar face surface; is disposed in a substantially facing arrangement with the first to permit a line to pass between the substantially planar face surfaces. A lever is disposed in the divot of the first body and is operable to draw together the substantially planar face of the first body and the substantially planar face of the second body whereby friction can be selectively applied to the line when the line is disposed between the substantially planar first surface and said substantially planar second surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The foregoing summary, as well as the following detailed description of preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purposes of illustration, there is shown in the drawings exemplary embodiments; however, the present disclosure is not limited to the specific methods and instrumentalities disclosed. In the drawings: 
           [0007]      FIG. 1  is a diagram illustrating an example apparatus in which aspects of the described embodiments may be incorporated. 
           [0008]      FIG. 2  is a diagram illustrating an embodiment of a hoisting device. 
           [0009]      FIG. 3  is an isometric diagram illustrating a restraint assembly for use in a hoisting device and incorporating aspects of the present invention. 
           [0010]      FIG. 4  is an isometric diagram of a tension holder that may be incorporated into a restraint assembly and incorporating aspects of the present invention. 
           [0011]      FIG. 5  is a side view diagram of the tension holder of  FIG. 5  that may be incorporated into a restraint assembly and incorporating aspects of the present invention. 
           [0012]      FIG. 6A  is an isometric diagram illustrating a body subassembly that may incorporated into the tension holder of  FIGS. 4 and 5 . 
           [0013]      FIG. 6B  is a cut-away side view diagram illustrating the body subassembly of  FIG. 6A  that may incorporated into the tension holder of  FIGS. 4 and 5 . 
           [0014]      FIG. 6C  is a face view diagram illustrating the body subassembly of  FIG. 6A  that may incorporated into the tension holder of  FIGS. 4 and 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    It is to be understood that the embodiments disclosed herein are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
         [0016]    The tension holder described herein reduces parts, reduces service and improves production performance. The tension holder incorporates a wear resistant material which is made as two identical halves reducing parts on hand. There are no rollers with bearings to reduce wear, which increase assembly and service time. 
         [0017]    The tension holder assembly may be used in conjunction with hoisting devices that are used to elevate platforms or baskets typically associated with large structure service and maintenance, such at buildings, bridges, towers, and the like.  FIG. 1  depicts an example platform apparatus  10  for supporting at least one person and associated work equipment. As shown in the figure, a platform  20  can be a flat surface, scaffolding, basket or cabin. The platform is of sufficient size to carry at least one worker and work equipment. In some embodiments, the platform  20  can support a plurality of workers. The platform is typically coupled to at least one powered hoisting device  30  such that the platform can be elevated or lowered in the vertical dimension. A hoist is a device used for lifting or lowering a load by means of a drum or lift-wheel around which a line wraps. The platform may be further secured with safety lines and guidelines. When maintaining or constructing structures of various kinds, a platform apparatus of this kind provides transport of personnel and materials to and from the various landings of the structure. For example, the platform may be able to move vertically along stacked mast tower sections. The platform apparatus may also be used for work on various elevated areas of the structure. Such a platform is commonly used on large scale construction projects, such as high-rise buildings and other large structures. A platform such as that described may carry personnel and materials quickly between the ground and higher floors, or between upper floors or act as a platform for working on the curtain wall or other structures of the building. 
         [0018]      FIG. 2  depicts another example of a hoisting device  200  that may be used to elevate a platform or basket. The hoist may be manually operated, electrically or pneumatically driven and may use chain, fiber or other types of line as its lifting medium. The powered type hoist can be either electric motor or air motor. A hoist can be built as one integrated package unit or it can be built as a built-up custom unit. In this example, a drum hoist  240  is used that is located under the platform. 
         [0019]    Line  230  may be securely attached to the top of the structure to be traversed. Line  230  is further guided at the top of the hoisting device  200  by a restraint assembly  210 . Such a restraint assembly guides the line  230  from the drum  240  to the top of the platform by preventing the line or cable from moving laterally and otherwise prevent the line or cable from snagging. The restraint assembly  230  also prevents the line  230  from vibrating or rubbing on other surfaces. 
         [0020]    The restraint device  210  typically comprises a fairlead, which is a member such as a ring or a block that has a guide opening, and a tension holder. The tension holder, as described more fully herein is a device that keeps tension in the line  230  when the hoisting device  200  is in a position that would cause the line  230  to go slack. The restraint assembly  210  operates to restrain movement of a line  230  passing through an opening  306  of the restraint assembly. The line  230  may be any type of rigging operable to elevate or lower a platform to be controlled by the hoisting device, and is typically a wire, rope or cable. 
         [0021]    An embodiment of tension holder  303  is further illustrated in  FIG. 4 . The tension holder comprises substantially identical bodies  401   a  and  401   b . When the tension holder  303  is closed, as shown, a line (e.g.,  230  not shown) is clamped when passing between bodies  401   a  and  401   b  via the opening  407  formed by opposing grooves in the bodies  401   a  and  401   b . The clamping of the line between the two bodies  401   a  and  401   b , prevents the line from moving and acts to keep a certain amount of tension in the line, preventing it from going slack. A slack line could bunch up on the platform and become entangled on itself or other objects. 
         [0022]    The clamping occurs when the bodies  401   a  and  401   b  are drawn together by a combination of hardware. In particular, a cylinder  405  is placed proximate a divot  409  that transverses body  401 ( a ). Strap  409  is secured at one end to body  401   b  and at another end to cylinder  405 . Strap  409  thereby secures the cylinder  405  to the tension holder assembly. A lever  403  is attached to cylinder  405  to provide a rotational moment about an axis  406  when the lever is manually rotated. Rotating the lever  403  upwardly causes the cylinder  405  to rotate in a clockwise direction. Rotating the lever  403  downwardly causes the cylinder to rotate in a counter clockwise direction. The counter-clockwise rotation causes the tension assembly to clamp shut on the line (e.g.,  230 ). 
         [0023]    Spring loaded pins  404   a  and  404   b  are disposed between the cylinder and the body  401   a . The spring loaded pins transfer the rotational force of the cylinder into a pressing force against body  401   a . In particular, the rotation of the cylinder  405  forces the spring loaded pins  404   a ,  404   b  against body  401   a  thereby clamping the bodies  401   a ,  401   b  together about a line (e.g.,  230 ). 
         [0024]      FIG. 5  further illustrates aspects of tension holder  303 . Here, tension holder  303  is illustrated from a side view in the open position. Lever  405  is rotated upwardly, releasing spring loaded pins (not shown) and allowing bodies  401   a  and  401   b  to separate. This view also illustrates that cylinder  403  rotates about an eccentric axis  406 . When the bodies  401   a  and  401   b  are separated, the clamping force is removed from the line (e.g.,  230 ) allowing the line freedom of travel through the restraint assembly  210 .  FIG. 5  further illustrates the use of guide pins  503   a  and  503   b . The guide pins are attached to one body, e.g.  401   a  and travel through bore holes (not shown) in the opposing body, e.g.,  401   b . Preferably there are two guide pins e.g.,  503   a  and  503   b  per each body  401   a  and  401   b  for a total of four guide pins. 
         [0025]      FIGS. 6A through 6C , further illustrate the subassembly comprising the body  401   a  and spring loaded pin(s)  404   a . As shown in the figures, body  401   a  has substantially hollow openings  601  and has ears  604  on either side of the body. Body  401   a  is preferably made of nylon and more preferably made of Nylatron GSM®. Nylatron GSM® is a cast, partially cross-linked, Nylon 6 material modified by a molybdenum disulphide additive. Nylatron GSM® has suitable wear resistance, self-lubrication and low friction characteristics. 
         [0026]      FIG. 6B  illustrates a cutaway view of body subassembly along the line B-B of  FIG. 6A . The cutaway portion illustrates spring loaded pin assembly  404   a  protruding into a bore in the body  401   a . The spring loaded pin assembly comprises a spring  607  and a screw  609  where the shaft of the screw protrudes into the coil of the spring  607 . As such, when the cylinder  405  ( FIG. 4 ) rotates about its eccentric axis, it force the screw  609  to compress spring  607  to thereby clamp the two bodies  401   a  and  401   b  together. 
         [0027]      FIG. 6C  further illustrates aspects of the body  401   a . Body  401   a  has a substantially planar face  602  such that the two bodies  401   a  and  401   b  can clamp together in facing relation. A groove  603  runs lengthwise along proximately the center of the substantially planar face  602 . The groove  603  provides a channel through which a line is guided or allows the tension holder to stayed substantially aligned with the line (e.g.,  230 ). Ears  604  extend from either side of body  401   a . The ears make assembly easier and provide a guide for straps  409 . Bore holes  605  provide a alignment of the bodies  401   a  and  401   b  during opening and closing. Bore holes  605  accept guide pins e.g.,  503   a ,  503   b  ( FIG. 5 ). 
         [0028]    A further feature of the embodiment described above is that tension holder assembly comprised of two bodies  401   a  and  401   b  and is designed such that the bodies are substantially similar. As such it provides for ease of manufacturability and a reduction of parts required. The same part may be used for both bodies  401   a  and  401   b.    
         [0029]    The various embodiments of the fairlead may be composed of appropriate materials that provide durability, resilience, abrasion resistance and strength. For example, thermoplastic polymers such as nylon and its various embodiments such as Nylatron may be used and can be fabricated using a single injection mold. In other embodiments other types of polymers can be used. However, the materials that may be used to fabricate the disclosure described herein are not limited to polymers. The present disclosure contemplates the use of various materials such as metal, plastic, or wood as may be useful for various applications and embodiments. 
         [0030]    It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. Although the more detailed examples provided above relate to traction sheaves in hoisting devices associated with elevated platforms for building maintenance, it should be apparent to one of ordinary skill in the art that the apparatus and methods described herein will find application to other systems that utilize traction sheaves. Additionally, the foregoing description has set forth various embodiments of the apparatus and methods via the use of diagrams and examples. While the present disclosure has been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present disclosure without deviating there from. Furthermore, it should be emphasized that a variety of applications, including marine and transportation systems, are herein contemplated. Therefore, the present disclosure should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the appended claims. Additional features of this disclosure are set forth in the following claims.