Abstract:
Climbing or rigging block having two portions held together by magnetic attraction. The climbing or rigging blocks may be installed or retrieved from the ground using only a throw line, a throw bag, and a retrieval ball. When in position, magnetic attraction between the two component blocks forms a single unit. The block sets may be provided in several sizes having different supporting capacities.

Description:
RELATED APPLICATIONS 
     This application is a Continuation-in-Part of U.S. Provisional Patent Application Ser. No. 61/113,758 filed Nov. 12, 2008 and claims priority thereto in accordance with 35 U.S.C. §1.78. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to rigging and climbing blocks and, more particularly, to two-part, magnetically-secured climbing and rigging blocks installable and removable from the ground. 
     2. Discussion of the Related Art 
     Numerous climbing devices, systems, and methods of support are presently available to the arborist engaged in the care and maintenance of trees. As used hereinafter, the term “arborist” is intended to include any workman working in an elevated position wherein a climbing or rigging block is useful in pursuit of their work. An arborist will employ an aerial lift device or use climbing techniques when working in an elevated position. Climbing techniques involve using one or more climbing ropes in combination with a climbing harness. Aerial lift devices range from large, truck-mounted, systems employing buckets disposed at the end of hydraulic-powered, multi-axis articulating boom to smaller units capable of being towed by small vehicles, a.k.a. “pull behind” models. 
     Selection of the method and apparatus to be used in a particular application depends on a number of factors including height, location and accessibility of the job site (i.e., tree, foliage and branch density proximate the regions of interest), as well as the nature and amount of work to be performed. For example, an aerial lift may be desirable for use in the removal of a large number of branches from curbside trees which threaten electrical power lines or the like passing nearby; whereas, climbing techniques may be advantageously employed to trim deadwood from an exotic tree species located in a private garden which is otherwise inaccessible by an aerial lift. 
     Tree crotches, the V-shaped junctions between two limbs or between a limb and the main stem or trunk of a tree, are routinely used to support a climbing or rigging line rope. In one technique, a length of rope is disposed in the crotch and fixedly attached to a climbing harness at one end thereof. The free portion of the rope is attached to the harness with a friction knot, after being passed around the limb or stem. Such a scheme is advantageous in that the arborist may work efficiently in several areas by moving relatively freely about a limited region of the tree through adjustment of the rope loop length supported in the crotch. But such movement routinely results in significant abrasion damage to the bark and often damages the underlying cambium layer of the tree necessary for secondary growth. Such techniques also accelerate climbing rope abrasion and wear, necessitating replacement of the costly rope. 
     Additional pads of leather or other sacrificial material may be attached to the tree in an attempt to protect both the tree and rope; however, such devices are difficult to employ effectively, due to the tendency of the climbing rope to slip off the pad during use due to changes in orientation and attitude of the arborist relative to the support location. Such devices are also typically unwieldy and bulky, requiring proximate positioning of the arborist for proper manual installation and retrieval. 
     Protection of the tree from direct abrasion due to movement of the climbing rope may also be effected by the use of lifting slings, similar in configuration to those typically employed in the movement of cargo by cranes or other lifting devices. For example, a continuous loop of rope or webbing may be employed in a conventional choker hitch configuration in a tree crotch or around a tree limb. A climbing rope may pass through the free end loop formed therein to support the arborist as discussed hereinabove. While generally reducing bark abrasion, such a configuration can damage the tree if the load being supported exceeds the capability of the limb, if the constriction of the limb becomes too great, or if the sling slips and moves while under load. 
     An additional problem with the use of a conventional loop sling in combination with a climbing rope is the problem of installation and removal of the sling in the tree. Conventional methods of ascending the tree, including the use of ladders, climbing spikes or solely ropes which abrade the bark, must often be employed to permit the arborist to reach a suitable location for installation of the sling. Generally, a relatively high altitude location is chosen to afford advantageous support for one or more targeted work regions. Once there, the arborist installs the sling on the limb and couples the climbing rope thereto, at which point the arborist may safely descend and begin work. Since the arborist may be some distance from the original support location after completing work in one region of the tree, a second sling may have to be employed to establish a second suitable support location for completing additional work in another region of the tree. In this manner, numerous slings may be required to adequately perform the desired maintenance on the tree. 
     In addition to the weight and bulk of the slings which must be carried by the arborist, retrieval thereof is problematic, requiring either individually revisiting the support locations to manually remove the slings or attempting to remove them remotely, for example by pulling on separate ropes attached to the slings themselves. Remote retrieval may be frustrated by catching, snagging or wedging of the loop sling in a tree crotch or on a branch, ultimately necessitating manual removal of the sling. The additional retrieval ropes may also become entangled with the climbing rope, arboreal equipment or other portions of the tree. Further, uncontrolled remote retrieval poses a potential safety hazard both to the arborist and to others working in the vicinity due to the free-falling sling, as well as to the tree which may be damaged if the sling becomes caught on inaccessible limbs, branches or foliage and must be forcibly removed. 
     One solution to the problems discussed hereinabove is provided in U.S. Pat. No. 5,785,146 for ARBOREAL CLIMBING AND SUPPORT METHOD AND APPARATUS, issued Jul. 28, 1998 to Kenneth Michael Palmer. PALMER provides a variant on a traditional sling wherein rings attached to two ends of a web have two different inside diameters. When used in cooperation with a shot or throwbag and a throw line, the PALMER device may be installed in a tree from the ground. Likewise, when no longer needed, the PALMER device may be extracted from a tree by a person on the ground. 
     Neither this patent nor any other known prior art, taken singly or in any combination, are seen to teach or suggest the novel climbing or rigging blocks of the present invention. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention there is provided climbing or rigging blocks having two portions held together by magnetic attraction. The climbing or rigging blocks may be installed or retrieved from the ground using only a throw line, a throw bag, and a retrieval ball. 
     It is, therefore, an object of the invention to provide a two-part climbing or rigging block readily installable and retrievable from the ground. 
     It is another object of the invention to provide a two-part climbing or rigging block installable using only a throw line, throw bag and retrieval ball. 
     It is an additional object of the invention to provide a two-part climbing or rigging block wherein two individual blocks are joined together into one complete working unit. 
     It is a further object of the invention to provide a two-part climbing or rigging block that creates a basket hitch and allows for the working load to be applied to one side while the retaining load is applied to the opposite side, thereby splitting the load between the individual blocks. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various objects, features, and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein: 
         FIGS. 1   a  and  1   b  are pictorial perspective views of rigging blocks of the prior art; 
         FIGS. 2   a  and  2   b  are rear elevational views of the two portions of the climbing or rigging blocks of the invention; 
         FIGS. 3   a  and  3   b  are front elevational views of the climbing or rigging blocks of  FIGS. 2   a  and  2   b , respectively; 
         FIG. 4   a  is a left side elevational view of the climbing or rigging block of  FIGS. 2   a  and  3   a;    
         FIG. 4   b  is a right side elevational view of the climbing or rigging block of  FIGS. 2   b  and  3   b;    
         FIG. 5  is a side elevational view of the climbing or rigging blocks of  FIGS. 2   a  and  2   b  in a joined, operational configuration; and 
         FIGS. 6   a  and  6   b  are schematic, perspective views of two embodiments of an installation and/or retrieval tool. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Arborists and other persons working in trees or other elevated environments must often ascend from the ground to a work site by climbing a rope. In addition, elevated workmen often rely on one or more pulleys and ropes to raise and lower materials. In the case of an arborist topping a tree, the object to be lowered to the ground may be a heavy limb severed from the tree. Other workmen may need to raise an object from the ground to an elevated position. Solutions to such problems generally include securing a pulley at a height above the desired elevated work site. 
     One technique for securing an elevated pulley is to use a so-called throw bag (e.g., “shot” bag) to place a throw line over an elevated tree limb or other structure. The throw line may then be used to pull a climbing line or other rope over the limb. 
     Several problems are associated with this simple technique, the worst being friction. When an arborist uses the climbing line to ascend, the line abrades the bark on the limb and may potentially cause serious damage thereto. Simple pads, often referred to as cambium savers, placed over the limb have been used both to lower friction and to protect the cambium layer (bark) of the limb. Such pads are generally difficult to use and the climbing line or other ropes has a tendency to wander off the protective pad as an arborist moves in the tree. 
     Friction may be further reduced by installing a pulley through which the climbing line passes. By securing the puller to a tree limb, no abrasion of the tree limb occurs due to the rubbing of the climbing line. However, depending on the load on the pulley, a supporting rope may cut into the cambium. 
     Specialty pulleys, typically called climbing or rigging blocks, have been devised and are well known in the prior art for such climbing and rigging applications. While the terms “pulley” and “block” or “rigging block” are sometimes used interchangeably, there are technical differences. For example, pulleys are typically rated for a static load. However, as an arborist cuts a limb, it may fall a short distance before being caught by a suspending rope, thereby imposing an impact load on the pulley. Rigging blocks are typically constructed and rated to absorb such impact loads. 
     A typical rigging block has a pulley, pin, or other attachment mechanism used for suspending the rigging block, and a lower pulley to support a working rope or line. Often, one side of the rigging block may be opened to allow placement of the rope, cable, or line over the working pulley. For purposes of this disclosure, a block is defined as a solid member, preferably rectangular in shape, as depicted in the preferred embodiment described herein, but other shapes of blocks can be used without departing from the scope of the invention.  FIGS. 1   a  and  1   b  show two different typical rigging blocks of the prior art. In  FIG. 1   a , a working pulley  100  has a spring-loaded pin for an axle  102 . An end of spring-loaded axle is received in an opening  104  in cheek plate  106  during normal operation. Cheek plate  106  is free to rotate around an upper pin  108  such that a rope or line, not shown, may be placed around the working pulley  100  and/or support pin  108 . 
     In  FIG. 1   b  a working pulley  120  is supported by an axle bolt  122  having a threaded end  132 . Axle bolt  122  is first passed through cheek plate  128  and then through working pulley  120 . Then threads  132  are retained in matching threads  126  in cheek plate  130 . Thus, the disassembly of the rigging block allows placing a rope or line over working pulley  120  and/or sheave  134 . 
     By properly designing a climbing or rigging block, installation of the block from the ground may be accomplished. 
     Referring now to  FIGS. 2   a  and  2   b , there are shown rear elevational views of a large opening  212  in block  200  and a small opening  212 ′ of block  200 ′, respectively, in accordance with the present invention. Blocks  200 ,  200 ′ are substantially identical with the exception of a pin  202  disposed in small opening block  200 ′ and discussed in detail hereinbelow. 
     Blocks  200 ,  200 ′ each have a body  204  having a rear surface  206 . Body  204  is formed from rectangular tubing, typically anodized aluminum. It will be recognized by those of skill in the art that bodies  204  may be fabricated from other suitable materials including but not limited to steel, titanium, plastic, polymers, carbon fiber composites, and in other shapes. Consequently, the invention is not considered limited to a particular material or to fabrication from a particular shape. 
     Extruded aluminum tubing is chosen in this embodiment because of its mechanical properties, particularly grain structure running parallel to a major axis of the body  204 . The grain structure imparts material strength to blocks  200 ,  200 ′ useful in handling the working load applied to blocks  200 ,  200 ′ during normal operation thereof. The solid, one-piece construction of body  204  distributes a working load evenly throughout. Unlike rigging blocks of the prior art having individual cheek plates that swing open, the solid, one piece construction of body  204  and two pairs of magnets, discussed below, also prevent twisting, contorting, or free play of blocks  200 ,  200 ′ even under heavy loads. 
     Magnets  208   a ,  208   b  are embedded in rear surface  206  of body  204 . Magnets  208   a ,  208   b  are typically rare earth (i.e., Neodymium) permanent magnets chosen for their magnetic strength. It will be recognized that other magnets may be substituted therefor. Typically, magnets  208   a  have a north pole exposed while magnets  208   b  have a south pole exposed. It will further be recognized that the poles could be reversed (i.e., magnets  208   a  could expose a south pole and magnets  208   b  could expose a north pole). The reason underlying the arrangement of magnets  208   a ,  208   b  is discussed in detail hereinbelow. 
     A polymer nose cone  210  is disposed in an upper portion of body  204 . Nose cone  210  is typically formed from 6/6/Nylon having a tensile strength of approximately 10,000 psi. It will be recognized that other suitable materials may exist for forming nose cone  210 . Consequently, the invention is not limited to the material chosen for purposes of disclosure. Rather, the invention includes any suitable material. 
     Nose cone  210  is tapered on all sides resulting in an inverted, truncated pyramid or pyramidal frustum having several functions. First the lower, truncated pyramid section allows blending into the bracket body for smooth passage over surfaces for “kick out” and “kick up.” Further, nose cone  210  serves to protect the sling eye, not shown, in sling rope  222  that is attached to mandrel  220  as discussed in detail hereinbelow. 
     An opening  212 ,  212 ′ in rear surface  206  reveals a lower portion of a pulley or sheave  214 . Sheave  214  is supported on axle  216 . Sheave  214  is relatively wide, filling substantially the entire width of body  204 , leaving only a minimal gap  218  between the vertical surface of the sheave  214  and the vertical side surface of body  204 . The width of sheave  214  allows for better weight distribution of the load over sheave  214  and in transference of the load to axle  216 . The sheave width allows minimal traveling or wandering of sheave  214  back and forth over axle  216 , thereby reducing free play. 
     Sheave  214  has several important design features. Sheave  214  has a “rope track” (i.e., rope-receiving contour)  232  that closely matches the size and thickness of the rope or line, not shown. This allows sheave  214  to cradle the rope during use, keeping the rope centered on the sheave  214 , not allowing it to wander over the surface or roll out of the sheave  214 . For proper operation of the novel climbing or rigging blocks  200 ,  200 ′, it is important that the rope travel in the true center of the sheave  214 . This center traveling facilitates even distribution of the load through the sheave  214 , then transferring the load evenly across the axle  216 . 
     Sheave  214  may have a high tensile bushing, not shown. The bushing is typically oil impregnated to provide constant lubrication during the rolling of the bushing over axle  216 . In climbing block versions of the novel climbing or rigging blocks  200 ,  200 ′, a set of high tensile thrust bearings, not shown, may also be installed. These thrust bearings are installed to relieve side load pressure that may be generated under heavy loading. 
     A mandrel  220  supports a sling rope  222 . Sling rope  222  is looped either directly over mandrel  220  or, for large blocks  200 ,  200 ′, over a sheave  236 , shown in  FIG. 5 , supported by mandrel  220 . The preferred slinging material is typically a high tensile strength rope. A rope construction consisting of a solid braid over an inner core has been found satisfactory for making sling rope  222  for use with climbing blocks. For rigging block use, hollow braid material has been found satisfactory. It will be recognized, however, that other suitable materials can be substituted therefor. 
     An eye  223  is formed in both ends of sling rope  222  by spliced or stitched eye to form a strong, yet low profile hitching point for connecting the sling rope  222  to mandrel  220 . Mandrel  220  allows proper fit of the eye  223  while spreading the load over the surface of mandrel  220 . Mandrel  220  is machined to proper industry standard bend radii dimensions corresponding to the specific dimensions of sling rope  222 . Bend radii dimensions are believed known to those of skill in the art and are not further discussed herein. The mandrel allows proper fit of the eye while spreading the load over the surface of mandrel  220 . 
     Sling rope  222  exits rigging and climbing blocks  200 ,  200 ′ via an entry point  224  in nose cone  210 . 
     Sling rope  222  is typically surrounded by an anti-abrasion sleeve  234  ( FIG. 5 ) made from Cordura® or a similar material. Abrasion sleeve  234  acts as both a protective cover and a housing for sling rope  222  when engaging the bark or another contact surface, not shown. Friction against the working surface tends to hold sleeve  234  stationary while the sling rope  222  may slide within sleeve  234 . This ability of sling rope  222  to slide within sleeve  234  allows the blocks  200 ,  200 ′ to rotate and move freely under a load while the blocks remain joined. Sleeve  234  is necessary to keep blocks  200 ,  200 ′ joined, thereby maintaining alignment and not allowing separation of blocks  200 ,  200 ′ from one another during working loading. 
     Referring now also to  FIGS. 3   a  and  3   b , there are shown front elevational views of climbing or rigging blocks  200 ,  200 ′, respectively. Sheaves  214  are more clearly visible in  FIGS. 3   a  and  3   b.    
     Referring now to  FIGS. 4   a  and  4   b , there are shown a left side elevational view of block  200  and a right side elevational view of block  200 ′, respectively. An optional heat shrinkable material  228  may cover bottom region  226  of the eye splice and extends slightly beyond the lower end of bottom region  226  of the eye splice. 
     Referring now also to  FIG. 5 , there is shown a side elevational view of blocks  200 ,  200 ′ mated face-to-face in an operational configuration. Sling rope  222  joins block  200  to block  200 ′. 
     Optional heat shrinkable material  228  (best seen in  FIGS. 4   a  and  4   b ) for use with either spliced or stitched eye, protects the eye region of sling rope  222  from unnecessary wear and damage that could induce failure of the sling. Further, heat shrinkable material  228  provides a predetermined stiffness in the bottom region  226  at the entry point  224  into the nose cone  210 , thus creating a lead in taper  230 . Lead in taper  230  works in conjunction with the nose cone  210  for retrieving climbing or rigging blocks  200 ,  200 ′ as described in detail hereinbelow. Further, lead in taper creates a rise in the sling upon entry in the tree crotch, not shown, or while being pulled over a branch, not shown. This rise allows the nose cone  210  to engage the wood or surface of the branch and, consequently to kick upwards and pass over the branch or enter a tree crotch and subsequently kick out for easy retrieval. 
     Referring now to  FIGS. 6   a  and  6   b , there are shown top plan views of an installation/retrieval tool, also known as throw bag, and a retrieval ball. 
     As seen in  FIG. 6   a , installation tool  230  is typically a throwbag having a tapered nose region  238  at a distal end and a body  242  having a diameter  244  selected to readily pass through front opening  212  of large opening block  200 ; body  242  is too large to pass through front opening  212 ′ of small opening block  200 ′ because pin  202  blocks its passage. 
     Installation/retrieval tool  230  (e.g., a throw bag) at a proximal end of body  242  has an aperture  240  adapted to receive a throw line or the like. 
     As shown in  FIG. 6   b , retrieval ball  250  has a body  252  having a diameter  254  selected to allow easy passage of retrieval ball  250  through opening  212  of block  200  but too large to pass through opening  212 ′ of block  200 ′ because pin  202  blocks its passage. 
     Retrieval ball  250  has a stepped hole  256  through center of body  252 . The use of installation/retrieval tool  230  and retrieval ball  250  is discussed in detail hereinbelow. 
     In operation, the novel climbing or rigging blocks  200 ,  200 ′ adhere to one another as shown in  FIG. 5 . The dual sheave design (i.e., the combination of sheaves  214  in each of blocks  200 ,  200 ′) causes a load on a rope passing thereover to be transferred to the sheaves  214 , creating a horizontal side load that forces the two blocks  200 ,  200 ′ together. This side load magnifies the holding power of the magnets  208 . 
     After installation, the blocks  200 ,  200 ′ align the sheaves  214  at a calculated spacing from one another. This spacing creates a bend radius significantly larger than the bend radius of industry standard three ton rigging blocks known to those of skill in the art. This oversize bend radius meets or exceeds industry standards set for proper rope bend and wear. This bend radius is important for ease of use of the blocks  200 ,  200 ′ and for rope life and wear. 
     The novel construction of climbing or rigging blocks  200 ,  200 ′ allows the installation and subsequent removal of the blocks from the ground, a great convenience to an arborist or other such workman. 
     To install climbing or rigging blocks  200 ,  200 ′, the following procedure has been found useful. First, a throw line, not shown, is lobbed over a desired tree limb or other structure, not shown, from which the climbing or rigging blocks  200 ,  200 ′ are to be suspended. This is typically accomplished using a throw or shot bag  230  ( FIG. 6   a ). Throw lines, throw bags, and retrieval ball form no part of the invention. They are considered to be well known by those of skill in the art. This technique is believed to be well known to arborists and the like. 
     The throw bag  230  is then lowered and untied from the end of the throw line. This end of the throw line is hereinafter referred to as the “bag end.” The opposite end of the throw line is hereinafter referred to as the “feed end.” The bag end of the throw line is inserted through opening  212 ′ from the rear surface  206  of block  200 ′ (i.e., the block having the smaller opening created by pin  202 ) and passed out through rear surface of block  200 ′. 
     An installation tool  230  as shown in  FIG. 6   a  is then attached to the bag end of the throw line using an appropriate knot or hitch. Suitable knots and/or hitches are known to those of skill in the art and are not further described herein. 
     The supply end of the throw line is then passed through block  200  (i.e., the block without pin  202 ) also from front face  206 . Once the blocks  200 ,  200 ′ are so configured with respect to the throw line, the supply end of the throw line is pulled to raise blocks  200 ,  200 ′ connected by sling rope  222  into the air towards the limb or other support structure over which the supply line has previously been lobbed. 
     Continued tension on the feed end of the throw line pulls block  200 ′ over the limb or support. Once block  200 ′ has been pulled over the top of the limb or support, both blocks  200  and  200 ′ are supported by sling rope  222 . As they approach one another, blocks  200 ,  200 ′ are oriented such that magnets  208  attract the two blocks  200 ,  200 ′ which magnetically aligns and locks to one another into a single unit, as seen in  FIG. 5 . 
     The installation tool is then lowered to the ground and disconnected. The eye of a climbing or rigging line, not shown, may then be connected to the throw line and pulled upwards through both blocks  200 ,  200 ′ over respective sheaves  214  ( FIGS. 2   a ,  2   b ). As the climbing or rigging line is pulled through first small opening block  200 ′ and then large opening block  200 , the blocks  200 ′,  200 , if not already aligned and locked to one another, are drawn together, thereby ensuring alignment. 
     When work utilizing the novel climbing or rigging blocks  200 ,  200 ′ is complete, the blocks may be retrieved from the ground. This is accomplished by attaching retrieval ball  250  and the end of a throw line to the end of the climbing or rigging line closest to block  200  (i.e., the block with the larger opening). 
     The opposite end of the climbing or rigging line is pulled, thereby drawing the retrieval ball  250  and throw line over sheave  214  of block  200 ′. However, when retrieval ball  250  encounters pin  202  of block  200 ′, further progress of retrieval ball  250  is prevented. It should be noted that the throw line continues to pass through block  200 . 
     Additional pulling on the climbing or rigging line pulls block  200 ′ away from block  200  by overcoming the magnetic attraction of magnets  208 . Once separated, block  200 ′begins descending as the climbing or rigging line is pulled. As block  200 ′ descends, block  200  ascends, pulled by sling rope  222 . 
     Eventually, block  200  and the throw line are pulled up and over the limb or other support. Once block  200  clears the limb or support, the throw line is still in place over the limb or support. 
     Tension on the throw line keeps blocks  200 ,  200 ′ and sling rope  222  from falling. As throw line is let out, the descent is controlled until blocks  200 ,  200 ′ and sling rope  222  are safely on the ground. 
     The install tool  230  is again attached (if it has been unattached since the installation process). The opposite end of the throw line is pulled, thereby raising the installation tool  230 . Eventually the installation tool  230  passes through the large opening in block  200 . As installation tool  230  cannot freely pass through the opening in block  200 ′, the pressure of installation tool  230  against block  200 ′ results in separating blocks  200  and  200 ′ from one another. 
     Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the example chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention. 
     Having thus described the invention, what is desired to be protected by Letters Patent is presented in the subsequently appended claims.