The present application claims priority from Australian Provisional patent application No 2009902729 filed 12 Jun. 2009 and entitled “Improved Descender” the entire content of which is incorporated herein by reference.
The present application relates to a descender for use in abseiling and belaying and in particular to an improved descender of the type which incorporates a self-acting brake.
Abseiling is a technique used to descend steep surfaces such as cliff faces and is often used by persons involved in activities such as mountain climbing, canyoning and caving. In order to abseil down a cliff face, one end of a rope is made fast at the top of the cliff and the person making descent then slides down the rope. The rope is passed either around the body of the person or, more usually, through a descender attached to a harness worn by the person such that the passage of the rope around the body or through the descender provides sufficient friction to slow the rate of descent to a safe speed.
A descender comprises rope engaging services around and between which the rope travels along a tortuous path, to provide frictional engagement between the rope and the descender. The rate of descent is normally controlled by holding the free or tail end of the rope to control the tension on the rope where it emerges from the descender and thereby to control the degree of friction engagement between the rope and descender which in turn controls the rate of descent.
Descenders used in abseiling vary greatly in performance and complexity, there being a variety of relatively simple devices which rely on frictional engagement between the rope and metal rings or racks about which the rope is wrapped, and a number of more complex descenders which incorporate a braking mechanism which allows friction between the rope and descender to be varied other than by simply controlling the free or tail end of the rope. The earliest of these more complex devices have a handle or lever which when operated tended to increase the friction between the descender and the rope. This type of descender was not a great improvement over the more simple devices as the brake was not self engaging and therefore, if the user was knocked unconscious, he or she would fall in the same way as a user of the earlier devices.
A number of devices now include automatic braking mechanisms in which a handle is operated by a person using descender to control their speed of descent and if the handle is released a brake actuates and prevents a user falling uncontrollably. Australian Patent Application No 16132/95 discloses such a descender which provides an automatic locking system for the descender operated by a lever, in which operation of the lever by a person using the descender releases a braking means and allows the person to descend, and in which should the person using descender release the lever, the braking system will automatically apply and prevent the person falling uncontrollably.
A similar type of descender is disclosed in U.S. Pat. No. 4,596,314.
There are two problems associated with the descenders of the type shown in AU 16132/95. The first problem is that the descender cannot be used for belaying. Belaying is a well known technique, used in climbing. A climber (the belayee) will descend or climb a cliff face, or the like, while roped to the cliff face via pitons. A belayer will hold the rope and allow the belayee only as much rope as he or she requires in order to move a short distance up or down the cliff face. Thus, if the belayee falls their fall will be arrested by the rope and the belayer. However, descenders such as that shown in AU 16132/95 cannot be used for belaying.
A second disadvantage of the descender described in AU 16132/95 is that the rate of descent cannot be preselected by a person using the device as a descender.
International Patent Application No PCT/AU97/00147 discloses an improved descender with an automatic braking means that allows it to be used as a descender for use in abseiling, or belaying. However, a problem with the descender is that it does not function effectively, when used as an ascender to raise an object, body or the like, and has a tendency to jam.
The present invention aims to alleviate the above mentioned problems of PCT/AU97/00147.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.
Thus, according to the present invention there is provided a descender for use in abseiling, or belaying, comprising:
a base having a connection means for connecting the descender to a harness or the like;
an arm pivotally mounted on the base at a pivot axis extending generally normal to the base;
the base having first and second spaced projections for engaging a rope, the projections both extending generally parallel to the pivot axis;
the arm having a third projection for engaging a rope, the projection extending generally parallel to the pivot axis, the projection being located so that when the arm is pivoted towards the base the projection is located to one side of a longitudinal axis passing through the first and second spaced projections on the base and is spaced further from the pivot axis than the second projection, but closer to the pivot axis than the first projection, and
a retention plate; characterised by:
a fourth projection disposed generally between the first and second spaced projections and adjacent an edge of the base located so as to separate a portion of rope passing into the descender around the first projection and around the third projection from the portion of the same rope passing out of the descender between the third and second projections.
Typically, the fourth projection is mounted on the end of an arm pivoted to the base for movement between a first operative position adjacent the first projection and a second non-operative position.
The projections will typically be sheaves. Typically the first second and third projections will be of generally similar size of the order of 3 cm in diameter while the fourth projection will be relatively smaller and about 1 cm in diameter
Advantageously, as well as being capable of operating as a normal descender and as a belay, the descender of the present invention may also be used to pull a person or object upwards for example out of a shaft up a face of a cliff, building or the like. In this case one end of a rope threaded through the descender is securely attached to the top of the shaft, cliff face etc. and the descender is fixed to a harness worn by the person being raised. The free end of the rope is held by a person at the top of the shaft, cliff or the like pulling the person/object upwards. The person at the top of the cliff can pull the rope upwards in the direction B (shown in
In a preferred embodiment, the descender may also include means for biasing the arm to rotate about the pivot away from the base, and stop means for preventing the arm from pivoting further than a predetermined angle away from the base; and
second stop means for restricting the distance the arm can travel towards the base when the biasing means is overcome and the arm pivoted towards the base, said second stop means being adjustable;
the arrangement being such that, in use, with a rope passing below the first projection, above and around the third projection and above the second projection, the resistance force applied to the rope is a maximum when the arm is pivoted so that the third projection is closest to the longitudinal axis, the descender being operable in two modes:—
a first mode in which the descender operates as a descender for controlling the rate of descent of a person sliding down the rope, in which mode the adjustable second stop means can be used to control the rate of descent; and
a second mode wherein the descender is used as a belay with substantially no tension on the rope passing through the descender, such that rope can be fed through the descender, in which mode the biasing means keep the arm and base apart to allow rope to be fed through the descender relatively freely, but in which mode sudden increases in tension in the rope, cause the biasing means to be overcome and the pivot arm to be pulled towards the base thus locking the rope between the first and second projections and preventing uncontrolled descent.
In this embodiment the descender may be used either as a belay or as a descender.
When used as a belay the device allows a rope to run freely through it provided that movements are slow. If the rope starts to move quickly through the descender which would happen if the belayee fell, the arm is pulled towards the base and the device automatically locks. When used as a descender, the adjustable second stop means can be used to control rate of descent.
The automatic braking occurs when pressure is placed on the rope between fixed end sheaves (defined by the first and second projections) and the pivotable centre sheave, defined by the third projection.
In a preferred embodiment, the biasing means comprise a spring acting on a protrusion defined on the arm and the stop means is a catch defined on the base, the catch being movable to allow the descender to be opened.
In one embodiment, the adjustable stop means comprises:
a lever pivoted on the base, said lever being associated with a cam and defining a cam surface;
a cam follower being located on the arm; said cam and cam surface being configured such that when the cam is positioned at either end of the cam surface, the arm can pivot closer to the base than when the cam is in a more central location on the cam surface than when the cam is located at either end of the cam follower, so that in use the resistance force applied to the rope is a maximum when the cam is disposed at or close to either end of the cam surface and a minimum when the cam is disposed between the ends of the cam surface, such that by manipulating the lever the resistance to movement may be set by locating the cam on a particular area on the cam follower and wherein if the handle is not locked in position, sudden movements of the rope through the descender cause the pivot arm to be pulled towards the base thus locking the rope between the first and second projections the lever is lockable in position.
This allows the rate of descent to be preset.
In a preferred embodiment, the lever includes an extension arm which is hinged to the lever which can be folded to the lever for storage and extended for use to increase the effective length of the lever.
Where the descender includes automatic stop means of one type or another, and is fixed to a harness worn by a person, it is also possible for that person to pull themselves up a face of a cliff, building or the like, by pulling on the rope and pulling themselves upwards. The descender moves upwards on the rope and when the person lets go of the rope, the automatic stop means lock and prevent the descender moving downwards on the rope. When the fourth sheave is in an operative position it prevents jamming, as the fourth projection keeps the parts of the rope entering and leaving the descender apart and prevents them from rubbing against each other when the person hauls themselves up the rope.
The invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:—
Referring to the drawings,
The arm 12 is mounted above the base plate 10 by means of a pivot 14, so that the arm is free to rotate relative to the base plate about that pivot. First and second spaced sheaves, 16 and 18, respectively, are mounted on the base plate. The sheaves are non-rotatable. The sheaves are configured so that parts of the arm 12 can be interposed below the sheaves, between the sheaves and the base 10, as will be explained later with particular reference to
A lever 20 is also mounted to the base plate by means of a pivot 22. In FIGS. 1,1A and 1B, the lever is represented by line 20, to avoid obscuring other components of the descender. A cylindrical bearing 24 which defines a cam, is attached to the lever 20, adjacent the pivot. A cam surface/cam follower 26 is riveted to the arm. When the cam 24 is in contact with the cam surface 26, pivoting the lever 20 about the pivot 22 moves the bearing surface 24 relative to the cam surface 26 and the arm is, in consequence, moved about the pivot 14, to move the arm towards, or away from, the base 10. Consequently sheave 28, which is mounted on the arm 12, moves towards, or away from, sheave 18. As can be seen in
A spring and stop arrangement, not illustrated in
The arm 12 can be locked to the base plate 10 by passing a bolt, or similar device, through small, aligned, holes 30 and 32 in the base plate and retention plate respectively and larger hole 34 in the arm which allows limited movement of the arm about the pivot. This feature is particularly useful if children are using the descenders to prevent them being opened in use, which would be dangerous.
Also shown in
With reference to
When descending/abseiling, as shown in
The device can also be used as a belay for use in descending or ascending a mountain, cliff face or the like in which case part of the rope will be securely attached to a mountain or cliff face and a person also attached to the rope, the belayer, will feed a limited amount of rope to the belayee as the belayee climbs up or down. The belayer, who may be on the cliff face above or below the belayee or standing at the top or bottom of the cliff face, wears the descender attached to a harness. The spring and stop mechanism keeps the arm 12 apart from the base 10, thus keeping sheaves 28 and 16 apart and allowing the rope to run relatively freely through the descender so that rope is supplied as the belayee/climber requires it hence the belayee can climb freely. If the belayer is also on the cliff face the belayer does not need to use their hands to feed rope to the belayee and can use both hands to grip the cliff face. If the belayer falls the increased tension in the rope will easily overcome the biasing spring and the arm will move towards the base to slow, and regulate, the rate of descent.
To lower the belayee, the belayer can simply operate the lever 20 to control the descent of the belayee.
In a similar arrangement shown in
It is also possible for a person wearing the harness to which the descender is attached, to pull themselves up a face of a cliff, building or the like, by pulling on the rope and pulling themselves upwards. The descender moves upwards on the rope and when the person lets go of the rope, the stop means lock and prevent the descender moving downwards on the rope. When the fourth sheave is in an operative position it prevents jamming as the fourth projection keeps the parts of the rope entering and leaving the descender apart and prevents them from rubbing against each other when the person hauls themselves up the rope.
It is to be noted that if the sheave 156 is not in position, and the rope is pulled upwards in the direction B, the part of the rope which travels downwards into the descender will contact and rub against the rope as it passes put of the descender adjacent the sheave 16 as the sheave 156 is not present to keep them separate. Pulling on the rope in the direction B in that case tends to pull the arm 12 clockwise and jams the rope in the descender preventing the rope form being pulled through.
The sheave 156 obviates this problem by keeping the two sections of the rope apart and generally parallel but separate, as shown in
Having described the general features and principal of operation of the descender, some specific features of the descender particularly relating to the construction of the descender will now be described in more detail with reference to
Also shown in
The configuration of the surface 100 and location of pivot 96 are such that as the arm is closed, rod 94 pushes the catch clockwise about pivot 96 to open the catch automatically.
Referring now to
Because the lever can be locked in position the rate of descent can be preset by an operator. The preset rate of descent can be overridden by operation of the lever.
The spring and stop arrangement allow the descender to be used for belaying by keeping the arm and base apart and preventing locking of the rope when movement of the rope through the descender is slow.
As discussed above the sheave 156 allows the descender to be used to raise a person or object by keeping the two sections of the rope apart and generally parallel but separate, as shown in
It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.
Number | Date | Country | Kind |
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2009902729 | Jun 2009 | AU | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/AU2010/000714 | 6/9/2010 | WO | 00 | 1/30/2012 |