The invention relates to a self-arresting rope belay device comprising a cam arranged to clamp the rope when the rope is under tension, and a lever arranged to act on the cam to progressively release the rope by manual action on the lever. The lever acts on the cam respectively with a geared-down effect in an initial part of its release travel, and with a direct effect in a final part of its travel. This results in the relative movement of the cam with respect to the lever being smaller in the initial part of the travel than in the final part, which enables accurate adjustment of the braking effort and of the running speed of the rope in the initial part of travel of the lever.

BACKGROUND OF THE INVENTION

The invention relates to a self-arresting belay device for a rope, able to act as descender or to belay a climber. Such a device is designed to clamp the rope automatically as soon as the rope is under tension. If the user wants to let the rope run free, he has to perform manual operation on a lever.

STATE OF THE ART

FIG. 1partially represents a conventional self-arresting device in situation, as described in European Patent EP0398819. The device comprises a pair of pulleys12,14housed between two parallel flange-plates, one18of which, hereafter called base flange-plate, is represented. The first pulley12is fixedly mounted on base flange-plate18by means of a securing element22. Pulley12is equipped with a circular top sector having a guide groove for guiding rope26, and with a braking surface28situated facing the second pulley14. Braking surface28is substantially flat.

Second pulley14is secured to a support plate30mounted pivotally around a pivot pin32of flange-plate18.

Pulley14is shaped as a cam that is eccentric with respect to pivot pin32. This cam14comprises a circular bottom sector having a groove34for receiving rope26, this groove34being centred on an imaginary axis slightly offset with respect to pin32. Opposite groove34, there is located a wedge36designed to jam rope26against braking surface28when support plate30rotates clockwise due to the effect of the tension of the rope and of the friction force of the rope on cam14.

A second braking surface38and a guiding surface40of rope26extend between wedge36and circular groove34of cam14. Surface38is substantially flat and is located farther away from pin32than surface40.

The position of pin32of cam14is such that wedge36never comes into engagement against braking surface28of pulley12.

In an extreme, arresting position, when the tension of rope26exceeds a set threshold of the apparatus, plate30pivots until first and second surfaces28,38are facing one another, parallel to one another, and clamp rope26. This position occurs when the user falls.

A whole range of braking positions exists between this arresting position and the free position represented inFIG. 1, the braking effect being all the greater as plate30pivots in the clockwise direction and wedge36clamps the rope.

The bottom part of base flange-plate18is provided with an opening48in which an attachment carabiner (not represented) can be inserted.

An operating lever58is associated with support plate30to make cam14pivot, by manual action, around pin32from an arresting position to a releasing position. Operating lever58is articulated on plate30by a pivot pin60situated opposite pivot pin32with respect to groove34, and operates in conjunction with a return spring62which biases lever58to a rest position in alignment with pivot pins32and60. The working position of lever58is illustrated by a mixed line inFIG. 1and is obtained by lowering lever58counterclockwise, against the return force of spring62.

In operation, the device is attached to a user by a carabiner passing through opening48, and the rope exiting the device via cam14is under tension, for example under the weight of the user when the device is used as a descender. This tension makes plate30and cam14pivot clockwise and causes progressive jamming of the rope between wedge36and surface28without any other action from the user. If the user wants to continue his progression, he has to release the rope manually by pulling on operating lever58counterclockwise.

With this type of device, the useful range of braking positions is located within a small travel of lever58, whereby the user has difficulties in finding a suitable braking position enabling him to progress continuously at the desired speed. Furthermore, the effort required to make cam14move from the arresting position to a position where the rope can start to run is considerably greater than the effort required to modulate the braking effect on a free running rope. This results in the user progressing by jerks, always seeking the right position between the arresting position and the released position.

SUMMARY OF THE INVENTION

There is therefore a need for a rope belay device allowing the user to easily find a braking position enabling progression at a continuous desired speed.

To satisfy this need, a self-arresting rope belay device is provided comprising a cam arranged to clamp the rope when the rope is under tension, and a lever arranged to act on the cam to progressively release the rope by manual action on the lever. The lever acts on the cam respectively with a geared-down effect in an initial part of its releasing travel and with a direct effect in a final part of its travel.

This results in the relative movement of the cam with respect to the lever being smaller in the initial part of the travel than in the final part of the travel, enabling accurate adjustment of the braking effort and of the rope running speed in the initial part of travel of the lever.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

FIG. 2represents an exploded perspective view of an embodiment of a belay device offering an accurate control of the running speed of the rope. Elements having similar functions as those of the conventional device ofFIG. 1are shown, and they are designated by the same reference numbers, even if they sometimes have different shapes.

Flange-plate18acting as a reference part for assembling the other component parts is shown. Cam14and plate30form a single part articulated around pivot pin32. This single part will hereafter be designated by ‘cam14’.

Lever58, articulated on cam14by means of pivot pin60, is represented in the rest position, folded back to follow the overall profile of the device.

To enable accurate control of the running speed of the rope, the base of lever58, on the side opposite a part forming a handle, is provided with a stud100parallel to pivot pin60. In the represented rest position of the lever, stud100is situated on the opposite side from pivot pin32with respect to pivot pin60. This stud100extends downwards and beyond the top plane of flange-plate18. Flange-plate18is carved out at102to enable stud100to move freely over the majority of the travel of lever58between its rest position and its folded-out active position.

Flange-plate18presents a stop104terminating recess102against which stud100presses when lever58is folded-out towards its active position, as will be described in greater detail with the help ofFIG. 4a.

In order to limit caulking of flange-plate18by stud100at the level of recess102, this stud is surrounded by a ring106of larger internal diameter than the diameter of the stud. This ring is floating and, to keep it in place, it is guided in a groove formed by the wall of recess102and the upwardly-extending walls of cam14.

Operation of the device will be better understood with the help ofFIG. 3and the following.

To complete the description ofFIG. 2, fixed pulley12ofFIG. 1is replaced by a part12held by pivot pin22and presenting a braking surface28. Part12is rotationally stopped by a tab12-1engaged in a notch18-1of flange-plate18.

Pivot pins22and32are represented separated from flange-plate18for reasons of visibility. In a normal configuration, these pivot pins22and32are secured to flange-plate18.

A second flange-plate20serves the purpose of closing the device and keeping the rope in place. It is articulated on flange-plate18by pivot pin22to allow the rope to be inserted and removed. It is held in the closed position by a carabiner (not shown) inserted through opening48of flange-plate18and a conjugate hole50of flange-plate20.

A molded resin form108fills the unused empty space between flange-plates18and20and ensures protection of the mechanism.

FIG. 3represents a front view of the device ofFIG. 2with a rope26installed, in its arrested position. A portion of lever58and of flange-plate18is not represented in order to show how cam14acts on rope26.

Cam14has substantially the shape of the cam ofFIG. 1. It comprises in particular a wedge shaped portion36for jamming the rope against braking surface28.

Rope26enters the device from the right, passes underneath cam14, and exits at the left between wedge36and braking surface28. The device is hooked onto a user by means of a carabiner (not shown) passing through opening48. The right-hand part of the rope is under tension either due to the weight of the user when the device is used as a descender or by the traction exerted by a person to be belayed when climbing. This tension biases cam14in counterclockwise rotation around pivot pin32resulting in wedge36clamping the rope against braking surface28all the more firmly as the tension increases.

To leave this arresting position, the user needs to rotate cam14clockwise around pivot pin32to move wedge36away from braking surface28. To do so, the user pulls on lever58after unfolding it clockwise around pivot pin60.

FIG. 4arepresents the device ofFIG. 3with lever58unfolded in a position where biasing of cam14can begin in order to perform releasing. A part of lever58is not represented so as to show the position of stud100. Ring106surrounding the stud can also be seen.

As shown, stud100presses on stop104of flange-plate18between pivot pins32and60of the cam and lever. From this position, if the user pulls on the lever clockwise, cam14is biased clockwise with a geared-down effort compared with a conventional arrangement of the lever. The gear-down factor is equal to the ratio of the distance between stud100and the center of the part forming the handle of the lever over the distance between stud100and pivot pin60.

Furthermore, the rotational movement of cam14with respect to the rotational movement of lever58is inversely proportional to this factor.

These effects result in the user having to use very little energy to exert a large force on the cam to overcome the force required to release the rope, and to then adjust the position of cam14accurately to modulate the clamping of the rope and thereby to accurately adjust the running speed of the rope.

By suitably choosing the distance between stud100and pivot pin60and the position of stop104, it can be ensured that a gearing-down effect is obtained over the whole useful adjustment range, i.e. so long as stud100remains in contact with stop104.

When the user has finished using the device, on a slack rope, he wants to be able to remove the rope quickly, i.e. move cam14up against a stop opposite braking surface28.

FIG. 4brepresents the device ofFIG. 3in a released position obtained when the user continues pulling on the lever clockwise from the position ofFIG. 4a. At a given moment, between the positions ofFIGS. 4aand4b, stud100disengages from stop104and presses against a wall of cam14, as shown inFIG. 4b. Lever58is then fully unfolded with respect to cam14, in an arrangement corresponding to a conventional lever configuration without gearing-down. Cam14then moves fast.

FIG. 5represents another embodiment of the belay device, in particular of the elements cooperating between lever58and flange-plate18to achieve gearing-down at the beginning of the release travel of cam14.

In comparison withFIGS. 2 to 4b, flange-plate18no longer comprises a groove102terminated by a stop surface104. Instead of this, flange-plate comprises a pin104′ perpendicular to the plane of the flange-plate, located at substantially the same location as stop wall104of the previous figures. Lever58no longer comprises stud100. Instead of this, it comprises a nose100′ at substantially the same location as stud100of the previous figures.

Nose100′ is arranged so as to come into contact with pin104′ between pivot pins32and60when lever58is unfolded to its active position represented inFIG. 5, where movement of cam14with gearing-down can begin.

After lever58has been turned clockwise over an initial travel, nose100′ disengages from pin104′. At this moment, it is desirable for cam14to be driven directly by lever58over the remainder of its travel. This is performed by a key60-1of pivot pin60movable in an enlarged groove58-1of the lever. Key60-1and groove58-1are configured in such a way that the key is driven by a wall of the groove when nose100′ disengages from pin104′.