Abstract:
A block has a sheave ( 4 ) mounted for rotation about an axis with first bearing elements ( 6   a,    6   b ) that transfer both axial and radial loads and second bearing elements ( 12 ) that transfer both radial loads, so increasing load capacity.

Description:
TECHNICAL FIELD 
       [0001]    Blocks with sheaves mounted for rotation about an axis are used on yachts and other sea going vessels. The blocks are typically exposed to sea water, sand and other contaminants. 
         [0002]    The invention relates to a rolling element block with improved load bearing and efficiency with minimal increase in overall weight and an improved connection, leading to lower cost and weight compared to existing blocks with similar load bearing capacity. 
       BACKGROUND ART 
       [0003]    Rolling element blocks have used sheaves having parallel sides, the width of these sheaves having the minimum width possible for a given single rope groove size, increased loads being obtained by increasing the diameters. 
         [0004]    These blocks fall into two categories: 
         [0005]    The first category is a ball bearing block having two rows of ball bearings set on either side of the block centerline. These blocks rely on the balls to take both the radial and axial loads applied to the block 
         [0006]    The second category is a roller bearing block with a central row of rollers and two side rows of balls. Both rollers and balls fall almost entirely possible width commensurate with the size of the rope groove. 
         [0007]    These blocks also utilize various methods of connection to a load point. 
         [0008]    Tapered roller bearings are not a practicable option for taking of both axial and radial loads in blocks used on sea going vessels due to their cost, precision required and contamination by sand, salt and other contaminants. Accordingly, the aim of embodiments of the invention is to provide an improved block that does not utilize tapered roller bearings. 
         [0009]    One aim of embodiments of the invention is to significantly increase the load bearing capacity of rolling element blocks while allowing higher efficiency, by increasing bearing area and at the same time providing a simpler connection without significantly increasing size, cost, or weight of the block. 
       SUMMARY OF THE INVENTION 
       [0010]    In one broad form the invention provides a block having a sheave mounted for rotation about an axis on a first race, the sheave having a sheave race and a peripheral circumferentially extending groove for receiving a flexible tension member, the sheave having a sheave width and the groove having a groove width, the sheave race including 
         [0011]    two spaced apart first surfaces that engage first rolling elements located between the sheave race and corresponding second surfaces on the first race 
         [0012]    and at least one third surface that engages second rolling elements located between the sheave race and corresponding fourth surfaces the first race, wherein
   A) the first and second surfaces are shaped so the first rolling elements transfer both axial and radial loads between the sheave race and the first race, and the third and fourth surfaces are shaped so the second rolling elements transfer radial loads between the sheave race and the first race, or   B) the ratio of:   
 
         [0015]    B1)sheave width to groove depth is equal to or more than about 2.5:1, or 
         [0016]    B2)sheave diameter to sheave width is less than about or equal to 3.2:1, or 
         [0017]    B3)the ratio of sheave width to groove depth is equal to or more than about 2.5:1 and the ratio of sheave diameter to sheave width is less than about or equal to 3.2:1, 
         [0018]    or
   C) the first and second surfaces are shaped so the first rolling elements transfer at least axial loads between the sheave race and the first race, and the third and fourth surfaces are shaped so the second rolling elements transfer radial loads between the sheave race and the first race, and   
 
         [0020]    the ratio of: 
         [0021]    C1) sheave width to groove depth is equal to or more than about 2.5:1, or 
         [0022]    C2) sheave diameter to sheave width is less than about or equal to 3.2:1, or 
         [0023]    C3) the ratio of sheave width to groove depth is equal to or more than about 2.5:1 and the ratio of sheave diameter to sheave width is less than about or equal to 3.2:1. 
         [0024]    The at least one first surface may include a first portion extending generally parallel to the axis and a second portion extending generally perpendicular to the axis. 
         [0025]    The second portion may extend radially inwards from the first portion. 
         [0026]    The second portion may extend radially outwards from the first portion. 
         [0027]    The third surface may include a third portion extending generally parallel to the axis. 
         [0028]    The at least one first surface and corresponding second surface may comprise parallel surfaces extending at an angle to the axis. Non tapered roller bearings may be used as the first rolling elements. The angle of the at least one first surface to the axis may be up to about 30 degrees. 
         [0029]    The third surface may be located between the two first surfaces. 
         [0030]    At least one line extending perpendicular to the axis may pass through the third surface and a first surface, i.e. the third surface and a first surface may overlap. 
         [0031]    The third portion may have a width substantially equal to the sheave width. 
         [0032]    The first and second surfaces may be contiguous. 
         [0033]    The third portion may be located radially inwards compared to a first portion. 
         [0034]    The second rolling elements may be located radially inwards compared to the first rolling elements. 
         [0035]    The second rolling elements may include at least two parallel sets of rolling elements. 
         [0036]    The first rolling elements may be located substantially within the groove width. 
         [0037]    The first rolling elements may extend significantly beyond the groove width, i.e. more than just the clearance width. 
         [0038]    The center of each first rolling element may be located substantially outside the groove width. 
         [0039]    The first rolling elements may be located substantially outside the groove width. 
         [0040]    The first rolling elements may comprise ball bearings or non tapered roller bearings. 
         [0041]    The second rolling elements may comprise ball bearings, roller bearings or both ball bearings and roller bearings. In preferred implementations the roller bearings are non tapered. 
         [0042]    The ratio of sheave width to groove depth may be greater or equal to about 4:1. 
         [0043]    The second rolling elements may comprise a single line of non tapered roller bearings. These may have a length substantially the same as the sheave width. 
         [0044]    The first and second surfaces may be shaped so the first rolling elements only transfer radial loads between the sheave race and the first race. 
         [0045]    The first and second surfaces may be shaped so the first rolling elements transfer both axial and radial loads between the sheave race and the first race. 
         [0046]    The third and fourth surfaces may be shaped so the second rolling elements only transfer radial loads between the sheave race and the first race. 
         [0047]    An advantage of at least one implementation of the present invention is to provide a ball bearing block for a single line, having an additional row or rows of central balls in addition to the traditional outer balls, which carry both radial and side loads. Said central balls carrying radial loads, provide a block similar in size cost and weight to a traditional block but have significant extra radial load capacity and efficiency. 
         [0048]    Another advantage of at least one implementation of the present invention is to provide a ball bearing block for a single line, having an additional row or rows of central rollers in addition to the traditional outer balls. With said central rollers carrying radial loads, it provides a block similar in size cost and weight to a traditional block but having significant extra radial load capacity and efficiency. 
         [0049]    Another advantage of at least one implementation of the present invention is to provide a roller bearing block for a single line, with the sheave of said block having a slight increase in width compared to the groove width. This allows rollers to be wider, enabling said rollers to carry additional radial loads, providing a slightly wider block than a traditional block but having significant extra radial load capacity and efficiency for a slight increase in cost and weight. 
         [0050]    An additional advantage of at least one implementation of the present invention is to provide a roller bearing block with the sheave of said block having an increase in width compared to the groove width having the two outer rows of ball bearings carrying side loads as well as carrying additional radial loads. This provides a block with a slight increase in width cost and weight to a traditional block to have significant extra radial load capacity and efficiency. 
         [0051]    A further advantage of at least one implementation of the present invention is to provide an improved roller bearing block with a simpler, light weight rope connection. 
         [0052]    Another advantage of at least one implementation of the invention is to provide lubricating plastic dividers between some of the rolling element balls and or rollers to reduce the friction and enhance the efficiency of the block. 
         [0053]    The foregoing features of the invention may be combined in any combination of features where features are not mutually exclusive. 
         [0054]    Unless the context clearly requires otherwise, throughout the description and the claims the words ‘comprise’, ‘comprising’, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0055]    FIG. shows an existing prior art ball bearing block section; 
           [0056]      FIG. 2  shows an existing prior art roller bearing block section; 
           [0057]      FIG. 3  shows a ball bearing block section with extra load capacity; 
           [0058]      FIG. 3   a  shows a ball bearing block section with extra load capacity compared to block of  FIG. 3 ; 
           [0059]      FIG. 4  shows a ball roller bearing block section with extra load capacity, as well as an improved rope connection; 
           [0060]      FIG. 4   a  shows a ball roller bearing block of  FIG. 4  with an alternate rope loop; 
           [0061]      FIG. 5  shows a rolling element bearing block section with extra width and extra load capacity rollers; 
           [0062]      FIG. 6  shows a rolling element bearing block section with extra width and extra load capacity rollers and balls, as well as an improved rope connection; 
           [0063]      FIG. 6   a  shows a further arrangement rolling element bearing block section with extra width and extra load capacity rollers and balls; 
           [0064]      FIG. 6   b  shows a cross section of an alternative roller bearing block according to the present invention; 
           [0065]      FIG. 7  shows a sectioned ball bearing row with ball lubricating element; and 
           [0066]      FIG. 7   a  shows a sectioned roller bearing row with roller lubricating element. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0067]      FIGS. 1 &amp; 2  show sections of single line prior art blocks.  FIG. 1  has sides  5   a  and  5   b,  sheave  3  has two rows of balls  1   a  and  1   b  carrying both radial and side loads. Typically sheave width  9  to groove depth  7  is approximately 1.3:1. 
         [0068]    Prior art block of  FIG. 2  has sides  15   a  and  15   b  and sheave  11  with rollers  21  which take radial loads. Side balls  13   a  and  13   b  lie almost entirely within width  19  and said side balls take only side loads. Typically also this block has a width  19  to groove depth  17  approximately 1.3:1. 
         [0069]      FIG. 3  shows a cross section of a single line ball bearing block according to the present invention with traditional body  2 , sheave  4  with side balls  6   a  and  6   b  where said side balls carry radial loads shown by arrows  8   a  and  8   b  as well as side loads  10   a  and  10   b.  Also shown is an additional row of balls  12 , which allow the block to take additional radial loads  14 , within a similar sized block, compared to existing ball bearing block of  FIG. 1 . 
         [0070]      FIG. 3   a  shows a cross section of a single line ball bearing block according to the present invention similar to that of  FIG. 3  with traditional body having sides  23   a  and  23   b,  sheave  21  with side balls  33   a  and  33   b  where said side balls carry radial loads shown by arrows  41   a  and  41   b  as well as side loads  43   a  and  43   b.  This block has an additional two rows of balls  25   a  and  25   b , which allow the block to take additional radial loads  45   a  and  45   b,  within a slightly wider block, compared to existing ball bearing block of  FIG. 1 . Central balls are separated by divider  27 , which may be integral with sheave  21  or a separate washer. 
         [0071]      FIG. 4  shows a cross section of a single line ball bearing block according to the present invention with body  16 , side balls  20   a  and  20   b  carrying both radial loads  24   a  and  24   b  as well as side loads  26   a  and  26   b,  as well as additional central row of rollers  22  carrying additional significant radial loads  30  within a similar sized block, compared to that of the ball bearing block of  FIG. 1 . The ratio of widths  29  and  29   a  to depth of groove  31  is significantly greater than the corresponding ratio of the block of of  FIG. 1 , with ratio of width  9  to groove depth  7 , which has a ratio of approximately 1.3:1. 
         [0072]      FIG. 4  also shows body  16  having sides  28   a  and  28   b  with connection points  32   a    32   b  and screw connection  32   c.  Sides  28   a  and  28   b  have posts  34   a  and  34   b,  forming shoulders  36   a  and  36   b.  Cross section of a loop  38  is shown with one end of loop  38  hooked over shoulder  34   b  at  40 . Loop  38  passes through center of body  28  through load point  41  back through center of body  28  and across over opposite post  34   a  engaging opposing shoulder  34   a  at point  36   a  so as to provide a simple lightweight tensile connection between block and load point  41 . 
         [0073]      FIG. 4   a  shows an alternative loop with spliced ends  61   a  and  61   b.    
         [0074]      FIG. 5  shows a cross section of a single line roller bearing block according to the present invention having a traditional body formed by sides  43   a  and  43   b,  sheave  42  with roller  44  carry radial loads  54 . Block has side balls  46   a  and  46   b  where said side balls carry side loads shown by arrows  52   a  and  52   b.  By way of comparison dotted lines  48   a  and  48   b  show the corresponding position of the parallel sides of the prior art block of  FIG. 2 and 50   a  and  50   b  show the corresponding position of the side balls  13   a  and  13   b  of the prior art block of  FIG. 2 . The width of dotted lines to groove depth is usually about 2.1:1 whereas the width  51  of sheave  42  compared to groove depth  53  is approximately 4:1. 
         [0075]    Block of  FIG. 5  has an additional width of sheave shown at  54   a  and  54   b  and corresponding extra width of roller  44 , shown at  56   a  and  56   b.  Extra width rollers at  56   a  and  56   b  allow the block of  FIG. 5  to carry significantly more load compared to block with dotted lines  48  because of the extra width compared to existing blocks with similar groove sections and diameters. 
         [0076]    The extra width can also be expressed with reference to sheave diameter. In one implementation the sheave has an outside diameter of about 80 mm, the groove depth is about 8 mm to 10 mm and the sheave has a width of about 25 mm, giving a ratio of sheave diameter to sheave width of about 3.2. This compares with prior art bocks in which the ratio of sheave diameter to sheave width is greater than about 3.75. 
         [0077]      FIG. 6  shows a cross section of a roller bearing single line block according to the present invention which is similar to block of  FIG. 5  having extra width  72   a  and  72   b  compared to existing block sheaves with width shown by the dotted lines  70   a  and  70   b.    
         [0078]    Sides  64   a  and  64   b  are arranged to have shoulders  66   a  and  66   b  engaging bottom of side balls  68   a  and  68   b.  Chamfered sheave has sides  78   a  and  78   b,  so that side balls  68   a  and  68   b  carry both side loads  74   a  and  74   b  as well as extra radial loads  76   a  and  76   b  without any extra width compared to block of  FIG. 5 . This provides a block with significant extra load carrying capacity and efficiency compared to the existing block of  FIG. 2 , with only slightly extra weight, cost and size. 
         [0079]      FIG. 6  also shows connection screws  80   a  and  80   b  having shoulders  82   a  and  82   b  in sides  64   a  and  64   b.  Rope or flexible loop  8  has two ends. One end of the loop section  88  engages the underside of shoulder  82   b  at  86   b  then passes through the center of body  64  down the side of the block, at least once around the load bearing point  90 , back though the center of the block, crossing over loop end  80   b  to engage shoulder  82   a  at  86   a  to form an easily connected and disconnected lightweight tensile connection which provides a distributed load to block center adding to screw connection  80 . The overlapping connection loop  88  can take any form and is not limited to one pass through the block center. 
         [0080]    Also shown in  FIG. 6  is additional loop which in addition to passing at least once through the center of block at  79 , also passes through the bottom opening at  81  to give additional distribution of loop load. 
         [0081]      FIG. 6   a  shows a cross section of an alternative roller bearing block  FIG. 6  with sheave section  116  and sides  114   a  and  114   b  with roller  106  and side balls  102   a  and  102   b.  Side balls  102   a  and  102   b  take side loads  110   a  and  110   b,  and extend past existing block sides shown by dotted lines  108   a  and  108   b.  Sides  114   a  and  114   b  extend past the balls and wrap back over balls  102   a  and  102   b  at  103   a  and  103   b,  bearing extra radial loads at  112   a  and  112   b  such that both balls  108   a  and  108   b  and extended rollers  106  and extended sheave  104   a  and  104   b  all simultaneously carry radial loads giving substantial increased load compared to just the load bearing between dotted lines  108   a  and  108   b  of an existing block. 
         [0082]      FIG. 6   b  shows a cross section of two alternative roller bearing block according to the present invention with features similar to that of block of  FIG. 6  with sheave section  116  and sides  114   a  and  114   b,  but with added becket loop  154 . The figure is split along vertical centerline to show tow variations. On the right hand side of  FIG. 6   b  a current becket block  140  is shown. In order for substantial becket load  150  not to compress sides and balls  68   a  and  68   b , side must be extended upwards and a compression piece  142  employed in order for block to operate efficiently. 
         [0083]    If the block is constructed as in left hand side of  FIG. 6   b , with becket loop  154  attaching to bobbin  152  which bobbin has sufficient width so that compression loads from becket  154  do not pinch sides but are absorbed by central portion of block at  156   a  and  156   b  then a lighter more advanced becket block is provided. It should be noted that becket loop  154  may pass through center of block or bypass block at  154 . 
         [0084]      FIG. 7  shows a section of a ball bearing row  120  with balls  122  and non bearing element lubricating spacer  124  between selected balls. The lubricating element shown at  126  is made of a plastic such as Teflon which rubs against balls  122  during use, leaving a coating of lubricating plastic on balls  122  and race  120 . Element  126  is shaped to fit in race  120  and has opposing concavities  128   a  and  128   b  to provide the maximum of contact area and the minimum of space between balls  122 , such that bearing loads are not significantly increased. 
         [0085]      FIG. 7   a  shows a cross section of a roller bearing row  130  with balls  132  and cross section of lubricating element  134  between selected rollers. The element shown at  136  is made of a plastic such as Teflon which rubs against rollers  132  during use, leaving a coating of lubricating plastic on rollers  132  and race  130 . Element  136  is shaped to fit in race  130  and has opposing concavities  138   a  and  138   b  to provide the maximum of contact area and the minimum of space between rollers  132 , such that bearing loads are not significantly increased. 
         [0086]    This lubrication of balls and rollers reduces both wear as well as friction and hence increases the efficiency of the bearing. 
         [0087]    It should be understood that the concepts disclosed are not meant to be complete or define a particular model or limit the concept or application in any way. 
         [0088]    Whilst it is preferred to utilize ball bearings for the taking of axial and radial loads it is within the scope of the invention to utilize relatively short plain, non tapered, roller bearings between substantially parallel bearing faces. Whilst this results in some scrubbing, if the angle to the rotational axis is no more than about 30 degrees and the rollers are not too long, the amount of scrubbing is acceptable. 
         [0089]    From the foregoing it should be readily evident that there has been provided a significantly improved, simple, lightweight, high load block assembly which is more efficient. 
         [0090]    The features of the invention described or otherwise disclosed in the text and drawings may be combined in any combination of features where such features are not mutually exclusive. 
       INDUSTRIAL APPLICABILITY 
       [0091]    The invention has industrial applicability to blocks.