Patent Publication Number: US-2020289898-A1

Title: Spring Force Bolt Hanger

Description:
TECHNICAL FIELD 
     The present invention relates to protective and safety anchoring systems used in the field of climbing, and more particularly to a type of fixed protection known as a bolt hanger. 
     BACKGROUND 
     A bolt hanger, also sometimes known as a fixed hanger, is a very common type of rock climbing protection that comprises a combination of a bolt and a hanger. Described very generally, bolt hangers are placed along climbing routes to provide fixed protection points. First, a bore is drilled into the rock. A bolt is extended through a hole in the hanger and the bolt is threaded into the bore in the rock and secured to thereby secure the hanger in place on the rock. The hanger has a second opening, a carabiner loop. A climber may clip a carabiner into the loop in the hanger and a climbing rope, or other type of protection such as a quickdraw or a sling, may be clipped into the carabiner. 
     As would be expected, there are many different types of bolt hangers, including a variety of bolts and hangers that are used with them. As for the bolts, the most common bolts that are used are either self-anchoring expansion bolts such as those commonly referred to as Rawl bolts. The Rawl bolts known as “five piece” bolts are known to be quite effective. Other types of bolts are secured to the rock with adhesive. The type of metal used in any particular bolt effects performance and different metals are appropriate for different locations. For example, a stainless steel bolt would be appropriate in a setting where corrosion is a concern, such as a rock wall near a body of salt water. 
     There are also many different types of hangers, including many different shapes and hangers of a variety of different types of metal. The preferred alloys are 304 stainless steel and 316 stainless steel. 
     When placing a bolt and hanger on a rock wall, the orientation of the carabiner loop on the hanger must be taken into consideration in relation to the forces that are applied to the hanger under load—such as when a climber falls and the hanger arrests the fall. It will be appreciated that significant force can be applied to the hanger, and bolt, when a climber falls. Depending upon the orientation of the hanger, the force applied to the hanger can cause downward pressure, and a rotational moment of the hanger around the bolt. The rotational force can cause the hanger to rotate relative to the bolt. This is undesirable because it can weaken the connection to the rock and the bolt hanger. If the rotational moment is such that the force is in the direction that would cause the hanger to rotate in a clockwise direction, then any force applied to the bolt by the hanger would be in the direction of tightening the bolt. On the other hand, if the rotational moment is such that the force is in the direction that would cause the hanger to rotate in a counterclockwise direction, then any force applied to the bolt by the hanger would be in the direction of loosening the bolt. Because this later situation is undesirable it is preferred, if possible, to orient the hanger so that the forces applied under load with an expected fall direction would tend to cause a clockwise rotational moment. Of course, to minimize the amount of the rotational force it is desirable to position the carabiner loop on the hanger as close as possible to the axis of the bolt—i.e., to reduce the length of the lever arm. Thus, stopping the rotation of the bolt hanger will reduce the chance that the bolt will become unthreaded from the expansion mechanism that is part of the bolt. 
     Moreover, when the hanger is secured to the rock wall the device may be “nested” in the wall when the bolt is tightened. This is especially true with relatively softer rock, and the nesting may help to overcome rotational forces when under load. The climber may use a hammer to break out some of the rock to increase the depth at which the peripheral edge of the hanger “nests” into the wall. Since bolts can be torqued up to 25 ft. lbs., the perimeter of the hanger may be indented, or “nested,” into the rock by the act of tightening the bolt. 
     Most commercially available hangers have a rock-facing surface that is essentially planar. Some manufacturers adopt anti-rotation features such as nubs that protrude from the rock-facing surface, and which are designed to press into the rock to prevent or minimize rotation. But even when a hanger is nested in a rock wall, rotation can occur when the hanger is under load, especially when the bolt is loose, so bolt loosening is an ever-present problem. 
     Because bolt hangers are fixed protection, they can stay in place in the rock for many years. Regardless of the type of bolt that is used to anchor a hanger to the rock, the bolts can loosen over time due to repeated loading or twisting, and also due to the innate environmental conditions such as freeze/thaw cycles, heat, etc. Bolts can also corrode and bend. A loose, corroded, or otherwise compromised bolt presents a serious safety concern since the bolt could break or be pulled out of the bore in the rock when under a heavy shock or load, such as when a climber falls. The same concerns apply to the hangers. Corrosion and wear over time may weaken the hanger and present safety problems. 
     As a result of the concerns detailed above about the risks associated with aging bolt hangers, several climbing organizations have programs in place to encourage the replacement of old, deteriorating bolts and hangers. For example, the American Safe Climbing Association (ASCA) encourages replacement of deteriorating bolts with stainless steel bolts. The ASCA&#39;s website at www.safeclimbing.org provides much information about the program. 
     In view of the known problems with bolt hangers, there is a need for a bolt hanger system that provides longer life and safety for a longer period of time in order to overcome the problems cause by, for instance, loosening bolts. The present invention is a hanger that is designed to overcome the problems associated with present hangers. More specifically, the improved bolt hanger described herein defines a hanger that exerts an outward force on the bolt, urging the bolt under tension outwardly, away from the rock, and thereby helps to prevent the bolt from coming loose over time. The improved bolt hanger has a concave shape formed into it centered around the bolt hole. As the bolt is tightened into the bore in the rock, the head of the bolt (and/or an underlying washer) causes the concave portion to compress. This compression causes the concave portion of the hanger to exert an outward force on the bolt, which makes loosening of the bolt more difficult. Furthermore, in an embodiment of the hanger according to the present invention the rock-facing surface of the hanger has a geometric configuration that aids in the prevention of rotation of the hanger when under load. The invention further comprises an improved expansion bolt adapted for use with the hanger according to the present invention also improves securement of the hanger to a rock wall. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood and its numerous objects and advantages will be apparent by reference to the following detailed description of the invention when taken in conjunction with the following drawings. 
         FIG. 1A  is an elevation view of the combination of a bolt and hanger in an assembly according to the present invention. 
         FIG. 1B  is a perspective view of the bolt and hanger shown in  FIG. 1 , wherein the combination is rotated to a different angle. 
         FIG. 2  is a sectional elevation view of the bolt and hanger shown in  FIG. 1A , taken along the line  2 - 2  of  FIG. 1A , and illustrating the bolt and hanger secured to a rock. 
         FIG. 3  is a perspective view of a first embodiment of a hanger according to the present invention, shown in isolation. 
         FIG. 4  is top plan view of the hanger shown in  FIG. 3 . 
         FIG. 5  is a perspective and partially sectioned view of a hanger of the type shown in  FIG. 3 . 
         FIG. 6A  is an elevation and partially sectioned view of a bolt and hanger according to the present invention in which the hanger is in an uncompressed condition. 
         FIG. 6B  is a view similar to  FIG. 6A  except showing compression of the hanger as the bolt is tightened in the rock; in  FIG. 6B  the compression is shown somewhat exaggerated to illustrate the structure and function of aspects of the invention. 
         FIG. 7  is a bottom plan view of the rock-contacting surface of a hanger according to the present invention. 
         FIG. 8  is an elevation view of the bolt and hanger assembly according to the present invention. 
         FIG. 9A  is a plan view of a first embodiment of a bolt sleeve according to the invention. 
         FIG. 9B  is a plan view of a second embodiment of a bolt sleeve according to the invention. 
         FIG. 10A  is a top plan view of a cupped washer for use with the present invention. 
         FIG. 10B  is a perspective view of the cupped washer shown in  FIG. 10A . 
         FIG. 11  is a top plan view of a hanger according to the invention and a cupped washer for use therewith shown next to the hanger, wherein the cupped washer is shown in an inverted position to illustrate the side of the cupped washer that faces the hanger in the assembly. 
         FIG. 12  is an elevation view of the hanger shown in  FIG. 7 , wherein the hanger is positioned with the base of the hanger on a flat rock surface. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS 
     With reference now to the drawings, a bolt hanger  10  according to the invention is shown in various views. The bolt hanger  10  is an assembly comprising the combination of a bolt  12  and the hanger  14  and in some embodiments, a specially adapted washer  18 . The hanger  14  according to the invention may advantageously be used with any number of bolts  12  that are on the market. The bolt  12  illustrated in  FIG. 1  is a prior art stainless steel expansion bolt. It is similar to a well-known “Rawl 5 piece” bolt. The choice of what type bolt to use, what material, what length and what width, depends on considerations such as the environment where the bolt will be used, the type and hardness of the rock, etc. As noted, the hanger  14  of the invention may be used with many different types of bolts. The bolt  12  includes a head  16 , and a washer  18  may be utilized. In some embodiments, detailed below, a modified cupped washer has been adapted for use with the hanger  14  according to the invention. And in some embodiments the present invention further comprises certain modifications to the bolt that improve functionality, longevity and safety of the bolt/hanger combination. 
     The hanger  14  is a monolithic, unitary metallic member that defines two segments that are oriented at an angle to one another. As used herein, the first portion is referred to base  20 . Base  20  has two sides, an “upper” surface  21  and a “lower” surface  23 . As detailed below, the lower surface  23  of hanger  14  defines the surface of the hanger that faces and makes contact with the rock when the bolt hanger  10  is bolted in place; the upper surface faces away from the rock. In the embodiment of  FIG. 1  the lower surface  23  is essentially planar. In other embodiments described below, the lower surface defines a sloping geometry. A bore  24  is formed through base  20  and the bolt  12  extends through the bore  24  in the assembly. The second segment of hanger  14  is referred to herein as the carabiner loop portion  22 . It is angularly disposed relative to base  20 ; and in the embodiments illustrated herein the angle between the base  20  and the carabiner loop portion  22  is around 90 degrees. It will be appreciated that the angle between these two segments may be varied according to need, and that the overall geometric shape of the hanger can vary widely from the embodiments illustrated. 
     Turning to  FIG. 2 , hanger  14  is shown bolted to a bore  25  in a rock  26 . It may be seen that lower surface  23  of base  20  faces and makes contact with the rock, and that the carabiner loop portion  22  is not in contact with the rock and extends away from it. The lower surface  23  is sometimes identified as the rock-facing surface  32 , and the opposite surface of base  20 , that is, upper surface  21 , is at times identified as the outward-facing surface  34 . The carabiner loop portion  22  has an opening that defines a carabiner loop  28 . In use, a carabiner is attached to hanger  14  at carabiner loop  28 . The preferred alloy for fabricating hanger  14  is  316  stainless steel but other alloys of stainless steel may also be used, such as  304  stainless steel. The bolt  12  shown in  FIG. 2  is an expansion bolt and it is shown being used with a conventional washer  18 . 
     The area of base  20  that surrounds bore  24  defines a concave area that is identified with reference number  30 . The concavity of concave area  30  extends in the direction from the lower surface  23  of hanger  14  toward the upper surface  21 , as illustrated with arrow A in  FIG. 2 . The concave area  30  surrounds and is concentric with the axis through bore  24  and as may be seen in the cross-sectional view of  FIG. 2 , defines a frustoconical sidewall surface  36 . With brief reference to  FIGS. 4 and 5 , it may be seen that the peripheral edge  38  of bore  24  is chamfered to define a beveled or chamfered edge  40  around the interior of the bore. As detailed below, he concave area  30  defines a spring that forces the bolt away from the rock. The concave area is typically formed with and appropriately formed punch and die, and using a hydraulic press. 
     In one preferred embodiment of hanger  14  according to the present invention, the hanger includes a geometric configuration applied to the base  20  that is designed to improve the anti-rotation properties of the hanger, and which helps reduce the tendency of the bolt hanger to rotate or spin around the bolt, as described above, thereby contributing to preventing the bolt from loosening. The geometric configuration is best illustrated in  FIG. 7 , which shows the lower surface  23  of base  20 . In the embodiment of  FIG. 7 , the lower surface  23  is not planar. Instead, the surface that surrounds the concave portion  30 , and which extends to the perimeter  50  of base  20  is formed into an irregularly shaped funnel with gently sloping walls that run into the concave portion  30 . The irregular funnel shape is identified generally with reference number  42 . The lower surface  23  has three primary rock-contacting areas, essentially feet, shown generally in  FIG. 7  with circles  44 ,  46  and  48  that come into contact first, before other parts of the hanger make contact with the rock. When the hanger is positioned against a rock, which for purposes of this description may be assumed to be planar, the hanger and the rock make contact at the rock-contacting areas  44 ,  46  and  48 , generally positioned around the perimeter  50  in a triangular arrangement. Thus, if a line is drawn from rock-contacting area  44  to area  46  (dashed line  52 ), from area  46  to area  48  (dashed line  54 ), and from area  48  to area  44  (dashed line  56 ), as shown schematically in  FIG. 7 , the three lines  52 - 54 - 56  trace a triangle, in this instance a scalene triangle. Along each of those lines, the perimeter of the hanger is formed into an arc that curves away from the rock, that is, away from the lower surface  23 . This may be seen in  FIG. 12  where the hanger  14  is illustrated resting on a flat surface  58  (which represents a rock  26  having a planar upper surface), there is a gap  60  defined between the hanger and the surface  58  between contact areas  44  and  46 . Similarly, a gap  62  is between the hanger and the surface  58  between contact areas  46  and  48 , and a gap  64  between the hanger and the surface  58  between contact areas  48  and  44 . The purpose of this geometry is detailed below. Thus, when the hanger  14  is lying on a planar surface such as in  FIG. 12 , it may be seen that the three rock-contacting areas are located below the remaining surface area of the lower surface  23  and lie in a common plane when all three are against a planar surface. In the non-compressed state (as in  FIG. 12 ), the perimeter of the hanger between the rock-contacting areas curves away from the rock surface and do not make contact with it. 
     With reference now to  FIGS. 1A and 1B, 8, 9A and 9B, and 10A and 10B , embodiments of a bolt  12  that has been modified for use with the hanger  14  according to the invention is shown. The bolt  65  that is shown in the drawings is a standard bolt that has a threaded shaft  66  and a head  68  at the proximate end. A sleeve  70  that has at least one, and typically two or more (see  FIG. 1B ), longitudinally extending slits  72  that extend from the distal end of the sleeve  70  to a point midway along the sleeve. The proximate end of sleeve  70  has been modified so that it flares outwardly at a flared rim  76 . The diameter of the sleeve  70  is preferably very slightly less than the diameter of bore  24  through base  20  of hanger  14 , but the diameter of the sleeve at flared rim  76  matches the diameter of the chamfered edge  40  of bore  24  in base  20 . A threaded, tapered plug  78  is threaded onto the bolt  65  at the distal end  79  of the bolt. A cupped washer  80  is used with the bolt  65  of this embodiment and the washer has a diameter (line D in  FIG. 11 ) that is equal to the diameter of the concave portion  30  of hanger  14  (line E in  FIG. 11 ). The cupped washer  80  has a central bore  82  that is slightly greater in diameter than the diameter of the bolt  65  and a chamfered peripheral edge  84 . As with the concave area  30 , the cupped washer may be formed with an appropriate punch and die with a hydraulic press. 
     The assembled bolt hanger  10  is shown in a modified exploded view in  FIG. 8 . The cupped washer  80  is slid onto bolt  65  with the bolt extending through the central bore  82  of the washer, and such that the curvature of the cupped washer is oriented downwardly, toward the distal end  79  of the bolt. Optionally, as shown in  FIGS. 1 and 2 , a secondary washer  81  may be added to the bolt between the bolt head  68  and the cupped washer  80 . The sleeve  70  is then slid onto the bolt such that the flared rim  76  is oriented toward the cupped washer  80 . Hanger  14  is then assembled with the bolt by inserting the distal end of the bolt through bore  24  of base  20  of the hanger and such that the sleeve  70  slips into the bore. The tapered plug is then threaded onto the distal end  79  of bolt  65  such that the smaller diameter of the tapered plug is oriented toward the sleeve. 
     When the bolt hanger  10  is assembled as just described, it is ready to be installed into a bore in a rock. The hanger  14  is slid along the sleeve  70  until the chamfered edge  40  of bore  24  mates with flared rim  76  of sleeve  70 . The hanger  14  and the sleeve  70  may then be slid along the bolt until the cupped washer  80  comes into contact with the upper margin of flared rim  76  and the base  20  around the concave area  30 . At this point the threads on the distal end  79  of bolt  65  are exposed and the tapered plug is threaded onto the bolt. 
     The distal end of the assembled bolt hanger  10  is then inserted into a bore  25  in a rock  26 . The bore  25  is sized so that the diameter of the threaded plug is slightly greater than the bore in the rock (see, e.g.,  FIG. 2 )—it is typical that the bolt must be hammered into the bore. With the bolt fully inserted such that the lower side  23  of base  20  of the hanger abuts the rock surface, the bolt may be tightened. As the bolt rotates, the oversized tapered plug is bound to the rock and is drawn along the rotating bolt in the direction from the distal to the proximate end. As this happens the tapered plug slides beneath the distal end of the sleeve  70 , with the plug between the bolt and the sleeve. As the plug translates along the bolt as the bolt is rotated, the plug causes the sleeve to expand along slits  72  and the sleeve is thus pressed tightly against the interior wall of the bore in the rock. The bolt is thus secured to the rock with as much as 25 ft. lbs. of torque. 
     Importantly, the bolt hanger  10  according to the invention provides an additional safety feature that helps to maintain the bolt tightly in the bore in the rock. Specifically, as the bolt is tightened as described in the previous paragraph, the head  68  is forced against cupped washer  80 . With the hanger  14  fixed in position against the face of the rock wall, the lower, interior surface of the cupped washer exerts significant pressure against the flared rim  76  of sleeve  70 . This drives the flared rim  76  into a tight, seating position in the chamfered edge  40  of bore  24 . As the bolt head, cupped washer and flared rim are compressed together, the cupped washer comes into contact with the concave portion  30  around bore  24 . Continuing tightening of the bolt causes deformation and compression of the base  20  at the concave portion  30 , around bore  24 . Because the steel that is used to fabricate hanger  14  is inherently somewhat springy and resilient, the compression causes the compressed concave portion to exert an outward pressure against the bolt head. That is, the bolt is placed under tension. This pressure/tension is maintained once the bolt is fully tightened and helps to prevent loosening of the bolt. 
     Reference is now made to  FIGS. 6A and 6B . In these figures the sleeve  70  and cupped washer  80  are not shown in order to better view the compression of concave area  30  more clearly; a standard washer  18  is shown. In  FIG. 6A  the bolt  65  is not tightened. Head  68  is shown resting on a washer  18  that spans bore  24  at concave area  30 . In  FIG. 6A  the bolt has been fully tightened into the rock, as described above. It may be seen that the concave area  30  has been compressed relative to the state of the concave area shown in  FIG. 6A  by pressure applied to the concave portion in the direction illustrated by arrow B in  FIG. 6B . This compression results in significant force applied against the bolt head  68  in the opposite direction, shown with arrow C in  FIG. 6B . 
     The geometric configuration of base  20  is yet another feature of a preferred embodiment of the invention that aids in preventing rotation of the hanger relative to the rock. Specifically, when a hanger  14  of the design shown in  FIG. 12  is used with the bolt and washer described above, the three rock contacting areas  44 ,  46  and  48  are driven with significant force against the face  58  of the rock as the bolt is tightened in place. Many types of rock are relatively soft compared to the steel that is used to fabricate hanger  14 . As such, as the bolt is tightened the three rock contacting areas dig into the underlying rock, thereby nesting the hanger in the rock and inhibiting rotation of the hanger relative to the rock. Even in very hard types of rock, the three rock contacting areas provide substantially greater anti-rotation friction than a planar hanger or a hanger that has, for instance, bosses that protrude from the lower side of the hanger base. As the bolt is torqued to tighten the hanger in place the concave area  30  compresses into a spring-like mechanism. Moreover, the remainder of the base  20  may also be deformed, causing the funnel-shaped lower surface to compress toward the rock face. As this happens, the perimeter edges of the base  20  between the rock-contacting areas may be pressed into contact with the rock as well. 
     It will be appreciated by those of skill in the art that certain modification may be made to the various embodiments described above and shown in the drawings without departing from the scope of the claimed inventions. For example, in the embodiment of  FIG. 7  the lower surface  23  of the base  20  of hanger  14  has three rock-contacting surfaces. With this embodiment, the number of such surfaces may be as few as one or greater than three. Moreover, the arrangement of the rock-contacting surfaces need not trace any geometry in particular, and the irregular funnel shape of the lower surface of the hanger may be arranged with different sloping surfaces from that shown. Also, the gaps between the rock-contacting surfaces  44 ,  46  and  48  may be accomplished with a hanger that has a planer perimeter  51  but in which the rock-contacting surfaces are defined by protrusions or bosses that extend from the lower surface of the hanger base. 
     While the present invention has been described in terms of preferred and illustrated embodiments, it will be appreciated by those of ordinary skill that the spirit and scope of the invention is not limited to those embodiments, but extend to the various modifications and equivalents as defined in the appended claims.