GB2044414A

GB2044414A - Self-locking descender

Info

Publication number: GB2044414A
Application number: GB8005866A
Authority: GB
Original assignee: PETZL P
Current assignee: PETZL P
Priority date: 1979-03-23
Filing date: 1980-02-21
Publication date: 1980-10-15
Also published as: FR2451752A1; ES489557A1; GB2044414B; IT1128043B; FR2451752B1; IT8067402A0

Abstract

A self-locking descender enabling its user to make a controlled descent down an anchored rope has the rope 12 wound in an S-shape around a movable pulley 16 and a fixed pulley 14, the movable pulley 16 comprising protuberances 50, 52, one of which co-operates with a locking element 54 to form a rope brake operative when a control lever 42 rigidly secured to the pulley 16 is in a top or bottom end position. The user's weight, acting via the snap hook 36 of his harness, effects clockwise rotation of the control lever 42 and urges it into its top end position as shown. When the control lever 42 is moved into an intermediate position (Figure 4, not shown), the rope 12 runs freely over the pulleys 14, 16 allowing descent of the user. The descender is of use in connection with potholing, mountain climbing, and construction sites. <IMAGE>

Description

SPECIFICATION Self-locking descender This invention relates to a descender enabling its user to make a controlled descent down a vertical rope secured at an anchorage point above him.

A known descender comprises: first and second parallel cheeks, the second cheek being pivotable relative to the first cheek to enable the rope to be wound in an S-shape around a movable pulley and a stationary pulley both disposed in a transverse gap between the cheeks; a rope brake comprising the movable pulley co-operating with a locking element to vary the size of the rope gap between a minimum rope-locking value and a maximum rope released value; and a control lever rigidly secured to the movable pulley and adapted to pivot between a top rope-locking position and a bottom rope-releasing position.

In the known descender, the locking element comprises a shoe mechanically connected to the movable pulley by a linkage having a number of pivot spindles. In pothoiing the aggressive environment in underground caves may cause the linkage to seize up so that it becomes impossible to use the rope brake.

It is an object of this invention to provide a reliable self-locking descender which is of simplified construction and reduced size and which is of use for potholing, mountaineering and construction sites.

Accordingly, the invention provides a descender enabling its user to make a controlled descent down a vertical rope secured at an anchorage point above him, which descender comprises a movable pulley and a stationary member supported between first and second parallel cheeks so that the rope may be wound in an Sshape around the movable pulley and stationary member, a rope brake formed by the movable pulley co-operating with a locking element to vary the size of a rope gap therebetween, and a control lever rigidly secured to the movable pulley, in which descender the movable pulley is rotatable through a predetermined angle corresponding to movement of the control lever between first and second end positions, and the movable pulley is cam-shaped for clamping the rope against the locking element in a rope-locking condition of the rope brake with the control lever in its first end position.

Desirably, the second cheek is pivotable relative to the first cheek to enable the rope to be wound in an S-shape around the movable pulley and the stationary member, and the movable pulley is rotatable about the pivot axis of the second-cheek.

The movable pulley may have a first radial protuberance serving to clamp the rope against the locking element with the control lever in its first end position, rope release occurring upon movement of the control lever away from its first towards its second end position.

The stationary member may be a fixed pulley and, in one form of the invention, the fixed pulley is the locking element of the rope brake.

The descender may include locking-inhibiting means associated with the movable pulley and having a first operative position neutralizing the rope brake by preventing the control lever from moving to its first end position in response to a pull on the rope and a second inoperative position in which the control lever is free to move into its first end position.

When the descender is inoperative, the movable pulley may be biased by a return spring towards the second end position of the control lever.

In order that the invention may be readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which: FIGURE 1 is an elevation of a self-locking descender according to a first embodiment of the invention, the descender being shown in a position in which the cheeks are pivoted apart from one another so that the rope can be wound around the pulleys; FIGURES 2 and 3 are views similar to Figure 1 but with the cheeks in the closed position, the rope brake being in two different locking positions associated with the lowering (Figure 2) and the raising (Figure 3) of the control lever; FIGURE 4 is a view similar to Figure 2 and 3 and shows the descender in the rope-releasing position; FIGURE 5 is a side view corresponding to Figure 2; FIGURE 6 shows a second embodiment of a descender according to the invention;; FIGURE 7 shows a third embodiment of a descender according to the invention; FIGURE 8 shows part of Figure 7, namely the fixed pulley and movable pulley of the descender, after removal of the pivotal cheek; FIGURE 9 is a partial inverted plan view corresponding to Figure 7 after removal of the stationary cheek and shows the control plate and the release handle return spring; FIGURE 10 is a partial exploded view corresponding to Figure 7 and shows how the movable pulley and control plate are disposed between the two cheeks; FIGURE 11 is a partial view of Figure 7 with the cheeks in the closed position and the rope brake released; and FIGURE 12 is a side view corresponding to Figure 7 but with the cheeks in the closed position.

Referring to Figures 1 to 5, a self-locking descender 10 enables a mountain climber or potholer to make a controlled descent down a smooth vertical rope 1 2 secured to an anchor plate (not shown) higher up. The rope 12 cooperates frictionally with a pair of pulleys 14, 16 received in a transverse gap 1 8 (Figure 5) between two parallel elongate cheeks 20, 22. The top or fixed pulley 1 4 is a stationary member secured to the first cheek 20 by a screw 24 and secured in rotation to the inside surface of cheek 20 placed in a yroove 26 in pulley 14.The bottom or movable pulley 1 6 is rigidly secured to a control plate 28 which is separated from the first cheek 20 by a predetermined clearance and pivotally mounted on a stationary spindle 30 perpendicuiar to the cheeks 20, 22. The second cheek 22 is mounted with clearance on the pulley 16 and can pivot on the spindle 30 for a scissors operation between an open position (Figure 1) in which the cheeks 20 and 22 are perpendicular to one another and a closed position (Figure 2) in which the cheeks 20, 22 are aligned to trap the rope in the gap 1 8. The first cheek 20 is formed at its bottom end below the pulley 1 6 with an oblong slot 32 which, when the cheeks 20, 22 are in the closed position, is opposite a half-open aperture 34 in the second cheek 22 for the passage of a snap-hook 36 connected to the user's rope harness (not shown). A pawl 38 pivoted to the cheek 22 is associated with a return spring biasing the pawl into a position closing the aperture 34 to lock the snap-hook 36 in the aligned apertures 32, 34 thus preventing any accidental separation of the cheeks 20, 22. The screw 24 of the top pulley 14 engages in a locating slot 40 in the cheek 22 when actuated towards the closed position.

The pivotable control plate 28 carrying the pulley 1 6 has a manual release control lever 42 and a lug 44 which, with the lever 42 in a bottom end position (Figure 2), projects from the gap 18.

Lug 44 is provided with a hole 46 adapted to receive a securing member in the form of an auxiliary snap-hook 48 for neutralizing the rope brake. The brake comprises the bottom pulley 1 6 which is shaped as a double cam with two radial protuberances 50, 52 at an angular offset from one another and adapted to co-operate alternately with a locking pin or peg or the like 54 disposed on the first cheek 20 between the top pulley 14 and the control plate 28. A gap 56 for the rope 12 is defined between the pin 54 and the pulley 1 6 and has a thickness which varies in accordance with the angular position of the lever 42.The thickness of the gap 56 is a minimum to lock the rope 12 in both a first or top end position (Figure 3) and a second or bottom end position (Figure 2) of the lever 42, and a maximum (Figure 4) when the lever 42 is in an intermediate position, the rope 12 then sliding freely over the pulleys 1 6, 14.

The system embodied by the lever 42, plate 28 and bottom pulley 1 6 thus forms the movable jaw of a locking mechanism having two locking positions.

The descender shown in Figures 1 to 5 operates as follows: After moving the cheeks 20, 22 apart from one another to the open position (Figure 1), the user winds the rope 12 around the bottom pulley 1 6 and top pulley 14 to form an S-shaped loop whose intermediate run or section is disposed in the gap 56 between pin 54 and pulley 1 6. The cheeks 20, 22 are then closed, whereafter the snap-hook 36 of the user's rope harness is connected. The pawl 38 is in the position locking the aperture 34 and prevents any accidental opening of the cheek 22.

The friction of the rope 12 on the bottom pulley 1 6 urges the lever 42 into its top position (Figure 3) by clockwise rotation of the plate 28. The gap 56 is at its minimum size and the protuberance 50 of pulley 1 6 clamps the intermediate run of the Sshaped section of the rope 12 against the pin or peg 54 and locks the rope 12.

The user's descent is initiated by lowering the lever 42 to an intermediate position (Figure 4), causing the plate 28 and associated pulley 16 to pivot in the anticlockwise direction into the ropereleasing position. The gap 56 is at its maximum size for the user to descend by the rope 12 running freely over the pulleys 1 6, 14. Should the user be injured or sick, the lever 42 automatically returns to its top position when released (Figure 3) and descent is stopped by the rope 12 locking on the pin 54 because of the clamping of the pulley protuberance 50. The lever 42 has an abutment to engage with the first cheek 20 to prevent the lever 42 from pivoting beyond its top position.

The rope 12 also locks automatically, being clamped by the pulley protuberance 52 against the pin 54 (Figure 2), when the lever 42 is held in its bottom position. The descender 10 therefore has a locking mechanism with two locking positions corresponding to the end positions of the control lever 42, and the user can choose either the top position or bottom position to check his descent.

Self-locking of the rope 12 may be undesirable in special cases, inter alia when the descender 10 is used by potholers who have to descend narrow diaclases. To neutralize self-locking in one of the end positions of the control lever the auxiliary snap-hook 48 is engaged in the orifice 56 of the lug 44 (Figure 4). The reaction of the rope 12 on the pulley 1 6 urges lever 42 into its intermediate position, preventing further pivoting into the top position, and the locking of the rope by the protuberance 50. In the absence of manual actuation of the lever 42, the same is retained in the stable intermediate position and the gap 56 is at its maximum for movement of the rope 12.

However, the rope can be locked at any time by the lever 42 being moved manually into its other end position to engage with the cheek 20 so that the rope 12 is locked or jammed by the protuberance 52 (Figure 2).

In the embodiment shown in Figure 6 like references denote like elements in Figures 1 to 5.

The pin 54 is omitted and the protuberances 50, 52 of the bottom pulley 16 co-operate directly with the top pulley 14 to bound the variable rope gap 56. Operaticn is exactly as previously described.

In a possible variant (not shown) the stationary top pulley 14 may be omitted and the rope 12 wound in an S around the single pulley 16 (which is a double cam device) and around the peg 54 (which constitutes a stationary member) to form a locking mechanism having two locking positions like that of the other two embodiments shown in Figures 1 to 6.

The descender 10 is made mainly of toughened duralumin and the protuberances 50, 52 are produced either by a ribbed stainless steel member fitted directly to the pulley 16 or by projections or flaps force-fitted in apertures in the vee of the pulley 16.

Figures 7 to 12 show a third embodiment in which like references denote elements which correspond to elements in Figures 1 to 6. In this embodiment the descender 10 has a single radial protuberance 50 which is disposed on the movable pulley and which co-operates with the fixed pulley 14 to form a locking mechanism having one rope-locking position corresponding to the top end position of the lever 42. The fixed pulley 14 comprises a plane locking surface 60 extending obliquely of the longitudinal centre plane X--X' of the stationary cheek 20. The protuberance 50 is connected to the movable pulley 1 6 by a plane surface 62 which, with the lever 42 in its bottom position, is substantially parallel to the surface 60.The hole 46 in the plate 28 for receiving the snap-hook securing member (not shown) is disposed opposite to the protuberance 50 as referred to the axis X-X1. The lever 42 is returned to its bottom position when the pull of the rope is not applied to the locking mechanism, inter alia when the descender is inactive. The lever 42 is returned automatically to its bottom position by means of a spiral spring 64 (Figure 9) received in a circular recess 66 in the plate 28. A stationary terminal part of the spring 164 extends into an aperture (not shown) in the cheek 20 and the recess 66 is coaxial with central ibore 68 of the movable pulley 16. The plate 28 has an abutment 70 adapted to engage with the cheek 20 to prevent the lever 42 from moving beyond its top position, something which in the absence of rope 12 might damage the surface 60.

The top edges 72, 74 of the cheeks 20, 22 are bent to engage around the rope 12 and are 'bevelled to facilitate the positioning of the rope 1 2 in the descender 1 0. The edge 72 extends obliquely relatively to the axis X--X' and forms an acute angle dwith the surface 60 of the pulley 14.

Referring to Figure 10, the stationary pivot 30 for pivoting of the movable cheek 22 and movable pulley 1 6 takes the form of a screw 76 extending through two apertures 78, 80 in the cheek 20, 22 and an intermediate tubular thimble 82 received in the bore 68 of pulley 1 6. The two cheeks 20, 22 are assembled by a clamping nut 84 which is screwed to the end of screw 76 and which comprises a collar 86 for centring the movable cheek 22. Collar 86 engages in aperture 80 to enable the moving cheek 22 to pivot freely towards the position in which the two cheeks 20, 22 are separate from one another, the movable pulley remaining stationary when the lever 42 is in its bottom position.

The operation of the descender shown in Figure 7 to 12 is similar to that of the embodiments previously described. With the lever 42 in its bottom position the running of the rope over the pulleys 14, 1 6 is improved by the oblique rope gap 90 between the fixed pulley 14 and the cheek edges 72, 74 and by the plane surfaces 60, 62 bounding the intermediate gap 56. The plane locking surface 60 of the pulley 14 increases the locking action on the intermediate run or section of the rope 12 when the lever 42 is urged upwards by the pull of the rope.

Claims

1. A descender enabling its user to make a controlled descent down a vertical rope secured at an anchorage point above him, which descender comprises a movable pulley and a stationary member supported between first and second barallel cheeks so that the rope may be wound in an S-shape around the movable pulley and stationary member, a rope brake formed by the movable pulley co-operating with a locking element to vary the size of a rope gap therebetween, and a control lever rigidly secured to the movable pulley, in which descender the movable pulley is rotatable through a predetermined angle corresponding to movement 'of the control lever between first and second end positions, and the movable pulley is cam-shaped .for clamping the rope against the locking element in a rope-locking condition of the rope brake with the control lever in its first end position.

2. A descender according to claim 1, wherein the second cheek is pivotable relative to the first cheek to enable the rope to be wound in an Sshape around the movable pulley and the stationary member, and the movable pulley is rotatable about the pivot axis of the second cheek.

3. A descender according to claim 1 or 2, wherein the movable pulley has a first radial protruberance serving to clamp the rope against the locking element with the control lever in its first end position, rope release occurring upon movement of the control lever away from its first towards its second end position.

4. A descender according to claim 3, wherein the movable pulley has a second radial protruberance circumferentially offset from the first radial protruberance by a predetermined angular distance and serving to clamp the rope against the locking element with the control lever in its second end position, rope release occurring with the control lever in a position intermediate its first and second positions.

5. A descender according to any preceding claim, wherein the said stationary member constitutes the locking element of the rope brake.

6. A descender according to any one of claims 1 to 4, wherein the stationary member is a fixed pulley.

7. A descender according to claim 6 wherein the fixed pulley constitutes the locking element of the rope brake.

8. A descender according to claim 6, wherein the locking element of the rope brake comprises a pin or peg or the like disposed in the rope gap between the movable and fixed pulleys.

9. A descender according to claim 7, when appendant to claim 3 or 4, wherein the fixed pulley has a plane locking surface and the first radial protruberance is connected to the movable pulley by a plane connecting surface which is substantially parallel to the locking surface when the control lever is in its second end position.

10. A descender according to any preceding claim, including locking-inhibiting means associated with the movable pulley and having a first operative position neutralizing the rope brake by preventing the control lever from moving to its first end position in response to a pull on the rope and a second inoperative position in which the control lever is free to move into its first end position.

11. A descender according to claim 10, wherein the locking-inhibiting means comprise a control plate carrying the movable pulley and having a leg for attachment of a securing member which engages in the said first operative position of the control plate with at least one of the cheeks to keep the rope gap at a maximal rope-releasing value.

12. A descender according to claim 11, wherein the control lever is rigidly secured to the control plate.

13. A descender according to claim 12, wherein the control lever or the control plate comprises an abutment adapted to bear on one of the cheeks to prevent the lever from pivoting beyond its first end position.

14. A descender according to any preceding claim wherein the movable pulley is biased by a return spring towards the second end position of the control lever when the descender is inoperative.

1 5. A descender according to any preceding claim wherein edges of the cheeks which are above the stationary member are bent towards one another to engage around the rope, the said edges of the cheeks, extending obliquely of a central longitudinal axis of the descender.

1 6. A descender substantially as hereinbefore described with reference to Figures 1 to 5 of the accompanying drawings.

1 7. A descender substantially as hereinbefore described with reference to Figure 6 of the accompanying drawings.

1 8. A descender substantially as hereinbefore described with reference to Figures 7 to 12 of the accompanying drawings.

1 9. Any novel feature or combination of features herein disclosed.