GB2191710A

GB2191710A - Climbing aid

Info

Publication number: GB2191710A
Application number: GB08714436A
Authority: GB
Inventors: Derek John Ryden
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-06-20
Filing date: 1987-06-19
Publication date: 1987-12-23
Also published as: GB8714436D0; GB2191710B; GB8615164D0

Abstract

A climbing aid (100) comprises a body (102) and at least one cam member (104). The or each cam member (104) has a profile (134) adapted to engage the walls (152 and 154) of a crack (150). The or each cam member (104) is slidable on the body about an axis C to a position in which it can engage the walls (152 and 154) of the crack (150). The profile (134) is adapted to present a contact angle ( alpha ) to the walls of the crack which is substantially constant when said walls of the crack are parallel. This arrangement enables the climbing aid to be at least partially retained in cracks having inwardly flaring walls, parallel walls, and outwardly flaring walls. <IMAGE>

Description

SPECIFICATION Climbing aid This invention relates to a climbing aid.

More particularly the invention relates to a climbing aid ofthe type which can be inserted into a crack or hole in a rock, sothata climbing rope can be secured to the rock.

Climbing aids ofthis general type have been known for many years and are described, for example, in GB-A-1588317, GB-A-2175219, US-A-3877679, and EP-A-214603.

All of the climbing aids described in these specifications use cam members, pivotable on a spindle, which engagethewalls of a crackor hole bytheircam profiles.

These climbing aids are often of complex construction and can be difficult to use in certain circumstances.

Cracks can be generally divided into three types: those with parallel walls; those with inwardlyflared walls; and those with externally flared walls. Cracks with inwardly flared walls are such that the thickness of the crack increases with increased distance into the crack. Cracks with outwardlyflared walls are such that the thickness of the crack decreases with increasing distance into the crack.

In EP-A-0047232 there is described a climbing aid having two movable cam members which are slidably mounted to one another. One problem with the climbing aid described in this specification is that it will only work with cracks having parallel walls and with cracks having inwardly flaring walls. It will not work with cracks having outwardly flaring walls.

A more recent development in this type of climbing aid is described in US-A-4572464. Again, the climbing aid described in this specification is not suitable for use with outwardly flaring cracks.

It is an object of the present invention to provide an improved climbing aid.

According to the present invention there is provided a climbing aid comprising a body and at least one cam member, the or each cam member having a profile adapted to engage the walls of a crack or hole, wherein the or each cam member is slidable on the body about an axis to a position in which it can engagethewallsof the crack or hole, and wherein, when the walls of the crack are parallel, said profile is adapted to presenta contact angleto thewalls of the crackwhich is substantially constant. This enables the climbing aid to beat least partially retained in said crack or hole.

Advantageously the body is provided with a convex external surface on which the cam member can slide.

The cam member may be provided with a concave inner surface, preferably of the same profile as said outer surface of the body, so that the inner surface of the cam member can slide over said outersurface.

Preferably the inner and outersurfaces are of circular configuration so thatthe axis lies atthe centre of the circle.

Desirably guide means is provided for guiding sliding movement ofthe cam member on the body.

The contactangle can be defined for any point Pon the cam profile as the angle between a linetransverse to the tangentto the profile at P and a line passing through the axis and through P.

It should be noted that the contact angle is only constant for cracks having the same degree offlaring. Thus the contact angle is constant for all cracks having parallel walls. Also the contact angle would be constantfor all cracks having a specific degree offlaring.

In the preferred embodimentthecam member is slidablealong an arcofa circle in which casetheaxis lies at the centre ofthe circle.

In this embodiment it is preferred thatthe cam profile is configured as a curve generated by a logarithmic function.

In one construction the cam profile can be generated by thefunction r = a e OtOflo where: a is the contact angle a is the minimum thickness ofthe cam rand 6 are polar coordinates representing the position of the cam profile relative to the centre ofthe profile.

The climbing aid according to the invention can be used with outwardly flared cracks having walls flared at an angle to one another almost up to the value of the contact angle. When the angle of outward flaring is greaterthanthecontactangle,the climbing aid can no longer grip the walls ofthe crack effectively. Thus, in orderto handle a large variety of cracks the contact angle should be as large as possible. However, it has been found that if the contact angle is too large, the friction between the cam member and the body becomes too great and prevents the climbing aid from gripping the walls of the crack effectively.

It is preferred that the cam profile is such that when it is used with cracks having parallel walls the contact angle is in the range 100 to 20 , more preferably 1 20to 170, most preferably substantially 140.

An attachment point for a climbing rope may be provided on one end of the body.

Desirably operating means is provided to permit a climber two slide the cam member on the body. This enables the cam member to be easilydisengagedfromthewalls of the crack or hole by the climber.

Securing means may be provided to secure the cam member to the main body, but permit sliding movement ofthe cam member on the main body.

Biasing means, which may be in the form of a spring, can be provided to bias the cam membertowards a particular position relative to the body.

When more than one cam member is provided it is possibleforthe cam members to be movable on the same side ofthe body or on opposite sides of the body. When cam members are provided on opposite sides of the body then the walls ofthe crack or hole can be engaged by the cam members alone. However, when the cam members are provided on the same side of thebody, or when oniy one cam member is provided, then one wall ofthe crack or hole is engaged by the body.

When the body engages the wall ofthe crack or hole, then it can be provided with either a flat or a curved configuration.

The climbing aid according to the invention can be disposed in a crack with the cam membertouching one wall of the crack and the body, or another cam member, touching the other wall of the crack. In this position the climbing aid will remain in place due to the frictional forces acting between the walls and the climbing aid surfaces in contactwiththewalls.

If a downward loading is applied to the device any slippage occurring between the body and the wall ofthe crack will result in the or each cam member sliding overthe body; this increases the effective thickness ofthe climbing aid in the crack until slippage stops.

Reference is now made to the accompanying drawings,in which Figure lisa schematic view of a climbing aid according to the invention disposed in a crack; Figure2 is a perspective view of part of a climbing aid according to the invention; Figure 3 is a side view of part of a climbing aid according to the invention; Figure 4 is a view on lines 4-4 of Figure 3; Figure5is aviewon iines 5-5 of Figure4; Figure 6is a frontview of a further embodiment of climbing aid according to the invention; Figures 7and 8are sideviews ofthe climbing aid shown in Figure 6 in first and second positions respectively; Figures9to 11 are side views ofpartofthe climbing aid of Figures 6 to 8 in cracks having parallel walls of different spacings; and Figures l2to 14 are side views of part of the climbing aid of Figures 6 to 8 in cracks having outwardlyflared walls of different angles.

In Figures 1 to 5 an embodiment of a climbing aid is generally designated 10.

The climbing aid 10 comprises a body 12, a cam member 14 and attachment means 16forattaching a climbing rope (not shown).

The attachment means 16 comprises a loop offlexible steel cable which is threaded through two apertures 18 provided in the body 12.

Securing means in the form oftwo elongate elements 20 is provided to secure the cam member 14 loosely to the body 12. Each element 20 extends between an aperture 22 in the body 12 and one of two apertures 24 in the cam member 14.

The body 12 is provided with a convex, circular, external surface 26 which is in engagement with a curved, circular, inner surface 28 of the cam member 14.

The cam member 14can slide overthe surface 26; the circular nature ofthe surface 26 causes the cam member 14to slide in a rotational fashion about centre 30 of the circle corresponding to the surface 26.

The surfaces 26 and 28 are provided with respective cooperating formations 32 and 34. The cooperating formations 32 and 34 serve as guide means to guide the sliding movement of the cam member 14 on the body 12, and helpto retain the cam member on the body 12.

The formations 32 comprise recesses in the surface 26, whilst formations 34 comprise projections on the surface 28.

The body 12 has upper and lower ends 38 and 40 respectively; the attachment means 16 is looped around the upper end 38.

The thickness of the cam member 14 increases from the upper end 38to the lower end 40 of the body 12.

Figure 1 shows the climbing aid 10 partially inserted in a crack 42 of a rock 44. An external surface 46 ofthe body 12, opposite the surface 26, engages a wall 48 ofthe crack 42. An external surface 36 of the cam member 14 engages an opposite wall 50 of the crack 42. In use, the climbing aid 10 is inserted into the crack 42 in such a mannerthatthe upper end 38 is inserted first.

As can be seen from Figure 1, the climbing aid 10 is retained in the crack 42 by the frictional forces, between the surface 36 and the wall 50, between the surface 46 and the wall 48, and between the surfaces 26 and 28.

If a downward force is applied to the attachment means 1 6the body 12 will tend to move downwardly relative to the cam member 14, causing the cam member 1 4to slide on the body 12. This increases the thickness ofthe cam member 14 and the body 12 which increases the frictional forces and prevents further downward movement.

The profile 36 is configured to present a constant angle to the wall 50 during rotation about the centre 30.

This is described in greater detail with reference to Figures 9 to 14.

Figures 6to 8 showa furtherembodiment of climbing aid generally designated 100.

The climbing aid 100 comprises a body 102, a cam member 104 and attachment means 106forattaching a climbing rope (notshown).

The attachment means 106 comprises a length of flexible steel cable the ends of which are crimped together to form a continuous loop. This is threaded through two apertures 108 provided in the body 12(only one aperture 108 is shown). The attachment means 106 defines an eye 110which the climbing rope can be attached.

Operating means generally designated 112 is provided for sliding the cam member 104 on the body 102.

The operating means 112 comprises an operating member 114, biasing means in the form of a spring 116, two elongatetubular members 118 and two elongate elements 120. The operating member 114 is disposed at one end of the spring 116, and a retaining member (notshown) can be provided at the other end of the spring 116.

The cableofthe attachment means 116 extendsthroughthetubular members 1 18sothatthetubular members 118 are slidable along the cable. The operating member 1 14is secured to one end ofthetubular members 118, and the elongate elements 120 are secured to the other end of the tubular members 118. Each elongate element 120 is secured to a respective side of the cam member 104. The tubular members 118 may be rigidly secured together.

The body 102 is provided with a convex, circular, external surface 122 which is in engagement with a curved, circular, inner surface 124 of the cam member 104.

The cam member 104 can slide overthesurface 122; the circular nature of the surface 122 causesthecam member to rotate about an axis (not shown in Figures 6 to 8) which lies outsidethe body 102.

The surface 122 is provided with a formation 125 which receives cam member 104; the formation 126 is in the form of a recess, and the surface 122 is provided in the recess. The formation 126 acts as guide meansto guide the sliding movement of the cam member 104.

The body 102 is provided with an upper end 128 and a lower end 130. The thickness of the cam member 104 increases in the direction from the upper end 128 of the body to the lower end 130.

Figures7 and 8showthe climbing aid 100 partially inserted in the crack 42 ofthe rock44. An external surface 132 of the body 102, opposite the surface 122, engages the wail 50 ofthe crack 42. An external surface 134 ofthe cam member 104 engages the opposite wall 48 of the crack 42. In use, the climbing aid 100 is inserted into the crack 42 in such a mannerthatthe upper end 128 is inserted first.

As can be seen in Figure 7, the climbing aid 100 is retained in the crack 42 bythefrictional forces between the surface 134and the wall 48, between the surface 132 and thewall 50, and between the surfaces 122 and 124.

If a downward force is applied to the attachment means 106 the body 102 will tend to move downwardly relative to the cam member 104, causing the cam member 104to slide on the body 102. This increases the combined thickness of the cam member 104 and body 102, which increases the frictional forces and prevents further downward rd movement.

The operating means 112 enablestheclimbing aid 100 to be easily inserted into and removed from the crack42. As shown in Figure 8, the operating member 1 14 can be pulled downwardly causing the elongate elements 120 to slide the cam member 104 relative to the body 102. As the sliding movement continuesthe thickness of the cam member 104 and body 102 decreases which releases the surfaces 132 and 1 34from engagement with the walls 50 and 48 of the crack 42, so that the climbing aid 100 can be removed from or inserted into the crack 42.

In Figures 9to 11 the body 102 and cam member 104 are shown in three cracks 150. The cracks 150 have parallel walls 152 and 154. The spacing between the walls 152 and 154 is least in Figure 9 and is greatest in Figure 11.

Figures 9to 11 illustrate the contact angle which is constant for all three positions ofthe cam member 104, and is constantforany position ofthe cam member 104 when used with cracks having parallel walls. The angle a in Figures 9 to 11 is about 14".

The surface 122 ofthe body is circular and has a centre C. The internal surface 124 ofthe cam member 104 is also circularand has the same curvature as the surface 122. Thus, the cam member 104 slides with circular movement about an axis coincident with the centre C.

The contact angle is defined for any point P', P" or P"' on the external cam surface 134, as the angle between a lineT1 transverse to a tangentTthrough P', P", or P"', and a line L passing through C and through P', P" or P'".

It will be observed that the tangent T corresponds to the wall 154.

The clim bing aid 102 can also be used in outwardly flaring cracks, as illustrated in Figures 1 2 to 14: in Figure 2 the walls 152 and 154 ofthe crack 150 are flared at and angle of 6" to one another; in Figure 13the walls 152 and 154 of the crack 150 are flared at an angle of 8 to one another; and in Figure 14thewalls 152 and 164 ofthe c;ack acle 150 are flared at an angle of 10 to one another.

It will be seen thatthe contact angle ' is less than 140 in Figures 12to 14. In fact, ' can be determined by the following equation a =a-F where a is the contactangleforcracks having parallel walls and Fisthe angle offlaring. For any given angle offlaring, a' will be constant. Thus, in Figure 12 α'is 8 , in Figure 13 α' is 6 , and in Figure 14α'is 4 .

The climbing aid 100 will continue to grip onto the walls 152 and 154ofthe crack l50forangles offlaring up to values closeto 14".

Means to reduce the friction between the cam member surface 124 and the body surface 122 may be provided. This may comprise, for example, a PTFE pad (not shown) adhered to the surface 122.

Claims

1. A climbing aid comprising a body and at least one cam member, the or each cam member having a profile adapted to engage the walls of a crack or hole, wherein the or each cam member is slidable on the body about an axis to a position in which it can engage the walls of the crack or hole, and wherein, when the walls ofthe crack are parallel, said profile is adapted to present a contact angle (as defined hereinbefore)to the walls ofthe crack which is substantially constant.

2. A climbing aid according to Claim 1 in which the body is provided with a convex external surfaceon which the cam member can slide.

3. A climbing aid according to Claim 2 in which the cam member is provided with a concave innersurface having the same profile as said external surface of the body.

4. A climbing aid according to Claim 3 in which the inner surface and the external surfaceareofsubstanti- ally circular configuration so that the axis lies at the centre of the circle.

5. A climbing aid according to any preceding claim in which guide means is provided for guiding the sliding movement ofthe cam member on the body.

6. Aclimbing aid according to any preceding claim in which the contact angle is in the range 10"to20".

7. A climbing aid according to any of Claims 1 to 5 in which the contact angle is in the range 1 2"to 170.

8. A climbing aid according to any of Claims 1 to 5 in which the contact angle is substantially 14 .

9. A climbing aid according to any preceding claim in which said cam profile is configured as a curve generated buy a lothrigmicfunction.

10. A climbing aid according to any preceding claim in which operating means is provided to enable a climber to slide the cam member on the body.

11. A climbing aid according to any preceding claim, further comprising friction reducing means disposed between the body and the cam member.

12. A climbing aid substantially as herein described with reference to and as shown in the accompanying drawings.