Abstract:
A high speed safety block assembly includes a first and second cheek plates with a sheave and axle installed between the cheek plates. The cheek plates each have a recessed area on their inner surfaces and have interlocking ears which increase the safety of the block assembly by preventing the block assembly from coming apart in the event of a screw failure. The sheave of the high speed safety block assembly includes a needle bearing which rolls on the bearing surface of the axle, permitting much higher loads and speeds when the high speed safety block assembly is used.

Description:
RELATED APPLICATIONS 
   This application is a continuation of Ser. No. 10/351,624, filed Jan. 23, 2003 and now issued as U.S. Pat. No. 6,651,962, which was in turn a continuation of Ser. No. 09/879,860, filed Jun. 11, 2001 and now abandoned, which was in turn a continuation of Ser. No. 09/166,835, filed Oct. 5, 1998 and now issued as U.S. Pat. No. 6,244,570. 

   BACKGROUND OF THE INVENTION 
   The field of the invention is block assemblies for suspending equipment and things with cables and the like. 
   Block assemblies have long been used to provide a mechanical advantage to reduce the pulling force required to support the load being suspended. For example, when a pair of block assemblies are used together, a 2:1 mechanical advantage is gained. When two pairs of block assemblies are used together, a 4:1 mechanical advantage is provided. Additional mechanical advantage is achieved by increasing the number of block assemblies used. Alternatively, a single block assembly can be used as a pulley to support a load without any mechanical advantage. 
   In the motion picture industry, especially in the stunt business, equipment and other items are frequently suspended from above with cables or ropes over block assemblies. Typically, the block assembly is high overhead and is not easily seen or inspected. Stunt persons and other actors are also frequently supported by cables using block assemblies. Thus, safety is a great concern, particularly with the reliability of the block assemblies. 
   When block assemblies are used in the stunt business, there are frequently high performance, reliability and safety demands placed on the equipment used. Thus, there is a need for a block assembly that is capable of supporting very high loads at high rates of speed, while maximizing the safety and reliability of the device. 
   SUMMARY OF THE INVENTION 
   To these ends, there is provided a high speed safety block assembly having first and second cheek plates with a sheave and axle located therebetween. The cheek plates each have a recessed area on their inner surfaces and have interlocking ears that increase the safety of the block assembly. The sheave of the high speed safety block assembly includes a needle bearing that rolls on the bearing surface of the axle. Other and further objects and advantages will appear hereinafter. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, wherein similar reference characters denote similar elements throughout the several views: 
       FIG. 1  is an exploded perspective view of a high speed safety block assembly. 
       FIG. 2  is a perspective view of a high speed safety block assembly in a closed position. 
       FIG. 3  is a perspective view of a high speed safety block assembly in an open position. 
       FIG. 4  depicts the combination of block assemblies to gain a mechanical advantage. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Turning in detail to the drawings,  FIG. 1  depicts a preferred embodiment of high speed safety block assembly  10 . Block assembly  10  is comprised of a first cheek plate  12  and a second cheek plate  14 . Held between cheek plates  12  and  14  is sheave  16  which is supported between cheek plates  12  and  14  by an axle  18 . Block assembly  10  is held together with screw  20  and nylon washer  24  and steel washer  22 . 
   In a preferred embodiment, first cheek plate  12  and second cheek plate  14  are machined from aluminum and each have a top end  58  and a bottom end  60  and an inner surface  56  and an outer surface  57 . Machined into inner surface  56  of cheek plates  12  and  14  is a recessed area  28 . Recessed area  28  is slightly larger in diameter than sheave  16  and also has a through hole  36  centrally located. Recessed area  28  preferably also includes a raised shoulder  30  surrounding hole  36 . Recessed area  28 , into which sheave  16  fits, provides an additional measure of safety when block assembly  10  is in use as shown in  FIG. 4 . Recessed area  28  prevents cable  62  from slipping down onto axle  18  in the event cable  62  comes off of sheave  16 . 
   Also machined into first cheek plate  12  and second cheek plate  14  are raised ear sections  46 . Ear sections  46  are located at top end  58  and bottom end  60  of cheek plates  12  and  14 . Ear sections  46  extend from inner surface  56  and define slots  44  between inner surface  56  and ear sections  46 . Slot  44  is open at end  45  of each ear section  46 . As shown in  FIG. 1 , ear sections  46  are arranged in opposite directions such that slot  44  and end  45  of ear section  46  at top end  58  of cheek plates  12  and  14  face the opposite direction of slot  44  and end  45  of ear section  46  at bottom end  60  of cheek plates  12  and  14 . When block assembly  10  is assembled, as shown in  FIG. 2 , ear sections  46  on first cheek plate  12  fit into slots  44  on second cheek plate  14 , and vice versa. The interlocking of ear sections  46  on cheek plates  12  and  14  provides and extra measure of safety by holding block assembly  10  together should screw  20  fail. 
   Cheek plates  12  and  14  also include a through hole  32  at top end  58  at ear section  46 . Hole  32  serves as a point of attachment for block assembly  10 , as shown in  FIG. 4 . 
   In a preferred embodiment of block assembly  10 , cheek plates  12  and  14  are also provided with a slotted hole  34  through the plates at bottom end  60 . Slotted hole  34  serves as a point of attachment when block assemblies  10  are combined to provide a mechanical advantage, as shown in  FIG. 4 . Slotted hole  34  advantageously allows for some tolerance when block assembly  10  is being rigged for use. Typically, a caribeener or shackle  64  is placed through slotted hole  34  which also provides an extra measure of safety in keeping block assembly  10  closed. 
   In a preferred embodiment of block assembly  10 , sheave  16  is a single circular piece of machined aluminum. Sheave  16  includes a groove  42  around the periphery of its rim  43 . Groove  42  supports cable  62  when block assembly  10  is in use, as shown in  FIG. 4 . Sheave  16  has a through hole  38  located through the center of sheave  16 . 
   Sheave  16  also includes a needle bearing  26  installed into hole  38 . In a preferred embodiment, needle bearing  26  is press fit into hole  38 . 
   Axle  18  is preferably machined from hardened steel and includes a bearing surface  51 , a first end  50 , and a second end  52 . Axle  18  preferably has a threaded hole  54  through the longitudinal axis of axle  18 . The outside diameter of bearing surface  51  of axle  18  is matched to the inside diameter of needle bearing  26  such that when block assembly  10  is in use, needle bearing  26  of sheave  16  rolls on bearing surface  51  of axle  18 . Axle  18  also advantageously includes a small transverse lubrication hole  48  through one side of bearing surface  51  to the center space defined by threaded hole  54 . When block assembly  10  is in use, a lubricant is preferably put into threaded hole  54  whereby the lubricant will self lubricate roller bearing  26  through lubrication hole  48 . 
   In a preferred embodiment, first end  50  of axle  18  has a larger outside diameter than second end  52 . In this configuration, first end  50  of axle  18  is press fit into hole  36  on first cheek plate  12 . With axle  18  press fit into hole  36  on first cheek plate  12 , sheave  16 , with needle bearing  26  already installed, can then be fitted onto axle  18  such that needle bearing  26  rolls on bearing surface  51  of axle  18 . Second cheek plate  14  is then placed onto axle  18  with second end  52  of axle  18  fitting within hole  36  on second cheek plate  14 . When block assembly  10  is in a closed position, such as shown in  FIG. 2 , block assembly  10  will hold together despite the absence of screw  20 . To securely hold together block assembly  10 , screw  20  is installed through hole  36  on second cheek plate  14  and into threaded hole  54  on second end  52  of axle  18 . Preferably, nylon washer  24  and steel washer  22  are also used. Additionally, a second screw  20  (not shown) can be installed into threaded hole  54  at first end  50  of axle  18 . This screw is not essential to hold block assembly  10  together, however, because first end  50  of axle  18  is press fit into hole  36  on first cheek plate  12 . 
     FIG. 4  depicts the use of a combination of two pairs of block assemblies  10  to gain a 4:1 mechanical advantage. When block assemblies  10  are used side by side, as shown in  FIG. 4 , it is advantageous to arrange the block assemblies  10  such that first plate  12  of one block assembly  10  is set face to face with first cheek plate  12  of another block assembly  10 . In this configuration, screw  20  is not installed into threaded hole  54  at first end  50  of axle  18  of either block assembly  10  so that the two block assemblies  10  may flush against each other, as shown in  FIG. 4 . Thus, when block assemblies  10  are combined or “ganged” together, no separate spacer (not shown) is required between the block assemblies  10 . 
   Once assembled, block assembly  10  can be opened as shown in  FIG. 3 . When cheek plates  12  and  14  are counter rotated, as shown in  FIG. 3 , access to sheave  16  is gained. In this fashion, a cable  62  or rope can be placed onto groove  42  of sheave  16  without having to disassemble block assembly  10 . When rotated back to the closed position shown in  FIGS. 2 and 4 , block assembly  10  is ready for use. 
   When in use, block assembly  10  is capable of supporting greater loads and much higher rates of speed than prior devices. Prototypes of block assembly  10  have safely supported 5000 pound loads up to 2000 RPM (revolutions per minute) as well as 3000 pound loads up to 5000 RPM. 
   Lastly, while the features shown and described above exemplify the present invention, various modifications may be made without departing from the spirit and scope of the invention.