GB2347360A

GB2347360A - Expandable anchor point

Info

Publication number: GB2347360A
Application number: GB9904700A
Authority: GB
Inventors: John Michael Peter Arran
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-03-02
Filing date: 1999-03-02
Publication date: 2000-09-06
Anticipated expiration: 2019-03-02
Also published as: GB2347360B; GB9904700D0

Abstract

A camming device for removably inserting into openings when climbing comprises: a support means; and a plurality of cam means A and B mounted on said support means, at least two of the cam means being rotatable about a pivot means C between extended (Fig 2.1) and contracted (Fig 2.3) positions, and at least one of the cam means being able to rotate through a greater angle than at least one other cam. The device preferably includes first L and second E/K actuator means for moving the cam means towards the extended and contracted positions, respectively. The pivot means may comprise a single axle which may be straight (Fig 3.1), stepped (Figure 3.2) or curved so that the cams are offset. The pivot means may also comprise more than one axle. On pulling handle H the cams A rotate, when ball F meets loop G cams B rotate. Thus cams A may rotate further than cams B. The cams may be different sizes and have an arcuate cam surface. The support means may have a receiving means N for receiving a rope used in climbing.

Description

EXPANDABLE ANCHOR POINT Field of the Invention This invention relates to a camming device and, more particularly, relates to an expandable camming device that is particularly useful for climbing.

Background of the Invention In many circumstances there arises a need to obtain a secure but readily removable fixing in parallel sided or similar fissures in rocks or other similar materials.

A common example is that of rock climbers who require to affect anchor points known as'belays'or'running belays'in order to protect themselves as they ascend their chosen route up a cliff.

Several devices have been devised to achieve this end. In one particular type of device one or more pairs of cams are mounted on an axle and urged apart by springs so that the cam surfaces contact the walls of the fissure.

In the'Friend'device invented by Jardine the axle is mounted on a support bar on which slides an operating bar. The operating bar is connecte to the cams in such a way that it may be employed to disengage the cams from the walls of the fissure. At the end of the support bar remote from the axle there is an attachment point which may be used to connect the Friend with the climbing rope or other desired equipment.

The cam angle may be defined as the difference in angle between the wall of the fissure at its contact point with the cam surface and a line joining this contact point to the axle on which the cam pivots (see angle 8 in Figure 1). It has been found that in order for the Friend or other devices of this type to grip the walls of a fissure reliably at varying degrees of expansion it is desirable that the cam angle should remain constant.

It is clearly desirable that a device of this type should function correctly in a wide range of sizes of fissure. However there are limitations. If the cam angle 0 is reduced by modifying the arcuate surface of the cams, the expansion range is increased but the security is diminished. Although the optimum cam angle varies with rock type it has been found by practical experiment with fissures in various types of rock that a cam angle 0 of approximately 76 degrees provides security in most types of rock which dimbers encounter.

The maximum size of the device when fully expanded is limited by the size of the cams. The minimum size of the device when fully contracted is reached when the tips of the cams (the part of each cam furthest from the axle) abut on the opposite walls of the fissure (see Figure 1.) In this position the cams do not present their minimum dimension to the fissure.

Various means have been developed to reduce this limitation.

The'Camalot'device employs two axles separated in a direction perpendicular to the support piece. This separation is claimed to increase the expansion ratio, albeit with a substantial weight penalty.

Another invention, the'Fancam', incorporates a plurality of cams which are engaged sequentially to allow a greater total expansion ratio. Such devices are necessarily very wide and heavy due to the large number of cams involved, and they have not achieved commercial exploitation.

Summary of the Invention In the present invention one or more pairs of opposing cams are mounted on one or more axles which are in tum mounted on a support means to which a load may be applied. For the purposes of clarity the invention will be described in the context of a particular embodiment wherein all pairs of cams are mounted on a single axle.

A means is provided by which the cams are hinged into an extended position where they present a maximum dimension in a direction perpendicular to the axle.

A means is also provided whereby the cams may be contracted against the action of the extending means.

The object of the invention is to provide that the minimum dimension of the device in a direction perpendicular to the axle closely approaches the dimension of the largest of its cams when said cam is rotated in such a way as to present a minimum dimension in that direction.

Opposing members of a pair of cams are differentially rotated such that in the fully contracted position the tips of both cams lie substantially at opposite ends of a line section drawn through the axle.

In Figure 2 the cams A and B rotate about an a) de C.

A means is provided to hinge the cams into an extended position as in Figure 2.1. An example of such a means would be one or more springs.

A further means is provided to hinge the cams into a contracted position (as in Figure 2.3) against the extending means. This means is so arrange that while cam B rotates through approximately 90 degrees to present its minimum dimension to a fissure, cam A rotates through approximately 270 degrees in the opposite direction, allowing cam A also to present its minimum dimension to the fissure whilst maintaining its cam surface in contact with the wall of the fissure.

One or more of a number of options may be used to prevent Cam A from coming into contact with the opposing wall of the fissure. Such methods include, but may not be limited to, the following: -Cam A is smallerthan cam B (see Figure 3.1).

-The axle about which cam A and cam B both rotate is stepped or otherwise curved (see Figure 3.2).

-Cam A and cam B rotate about different axles.

The mechanism by which cam A and cam B are rotated through different angles may be effected either by cam B remaining stationary for some or all of the period in which cam A rotates, or by both cams rotating at different angular velocities.

Embodiment of the Invention One possible embodiment of the invention is shown in Figure 4.

Two pairs of cams A and B rotate about axle C. Axle C is attached to a support piece to which a load may be applied at point N. Each pair of cams is urged into an extended position by a spring L. A user of the device may then oppose the action of springs L by pulling on handle mechanism H which will differentially rotate the cams into their contracted position for insertion into a fissure. For stability and ease of use the two wires E to which the handle H is attached pass through small holes in part of the support piece M.

Wire E is attached to cam A at a fixing point J. Wire E is then wound around axle C and held in place by pulley D. A second wire K is attached to cam B at fixing point 1.

The other end of wire K terminates in a closed loop G around wire E. Handle H is pulled by the user of the device and initially causes cam A to rotate. Fixed to a point of wire E is a ball F of sufficient size so as not to be able to pass through loop G. After cam A has rotated through approximately 180 degrees ball F comes into contact with loop G. Further pull on handle H then causes both wire E to further rotate cam A and wire K to rotate cam B.

Claims

Claims 1. A device for providing an anchor at various sizes of openings in a surface, said device comprising : support means having a body portion insertable into an opening in a surface ; and a plurality of cam means mounted on said body portion of said support means with at least two of said cam means being movable by rotation between an extended position and a contracted position relative to said body portion, and with at least one of said cam means moving a distance greater in angle than at least one other of said cam means when said cam means are moved from said extended position to said contracted position, whereby said device can be utilised over an extended size range of openings in said surface.
2. The device of claim 1 wherein said support means is an elongated arm having said plurality of cams mounted at one end thereof.
3. The device of claim 1 wherein said support means is a closed loop having said plurality of cams mounted at one end thereof.
4. The device of claim 1 wherein said body portion includes pivot means, and wherein said plurality of cam means are mounted for pivotal movement on said pivot means to effect movement of said cam means between said extended and said contracted positions.
5. The device of claim 4 wherein said device includes actuator means with said actuator means including first means for moving said cam means toward said extended position, and second means for urging said cam means toward said contracted position.
6. The device of claim 5 wherein said first means includes spring means, and wherein said second means includes cable means.
7. The device of claim 1 wherein said plurality of cam means includes at least two cams which are offset from one another when in said contracted position to present a minimum dimension of the device in a direction across the cam means which is not substantially greater than the largest such minimum dimension of any of said cam means, to thus enable said device to be utilised over said extended size range of openings.
8. The device of claim 1 wherein said cam means includes at least one pair of opposing cams which are asymmetrically or differentially pivoted.
9. A device for providing an anchor in different sized openings in a surface to be climbed, said device comprising; an elongated support means having a first end insertable into said opening in said surface; a plurality of cam means having a pivot portion mounted for pivotal movement at and with respect to said first end of said support means, with each of said cam means including an arcuate cam surface spaced from said first end of said support means so that said cam surface is moved between a first position spaced outwardly from the first end of said support means and to a second position closer to said first end of said support means, and with at least one of said cam means pivoting through a substantially greater angle than that of at least one other of said cam means such that when at said second position the said cam surface of at least one of said cam means is closer to said first end of said support means than the said cam surface of at least one other of said cam means, whereby the alignment of said cam means permits anchoring of said device over an extended size range of said openings in said surface ; an actuator means to effect movement of said cam means to at least said extended position; and an actuator means to effect movement of said cam means to at least said contracted position.
10. The device of claim 9 wherein said support means indudes a pair of spaced members having a pivot pin extending therebetween to receive said pivot portion of said cam means thereon to establish a common pivot line for said cam means.
11. The device of daim 9 wherein said support means indudes a pair of spaced members having a stepped or otherwise curved pivot pin extending therebetween to receive said pivot portion of said cam means thereon.
12. The device of claim 9 wherein said support means indudes a pair of spaced members having more than one pivot pin extending therebetween to receive said pivot portion of said cam means.
13. The device of daim 9 wherein said plurality of cam means includes at least two cams mounted on said pivot portion.
14. The device of daim 9 wherein said plurality of cam means indudes at least two pairs of cam means mounted on said pivot bar.
15. The device of claim 9 wherein said support means indudes a receiving means for receiving a rope used in climbing.
16. The device of daim 9 wherein said support means includes a receiving means for enabling use of said device when in place with and without said rope.
17. The device of claim 9 wherein said cam surfaces have different angles of curvature to facilitate anchoring of said device.