High load descender with adaptive release linkage

A high load descender for rope access and rescue has a ratcheting sheave mounted to a pivoting arm, which translate with rope tension against a fixed shoe. The ratcheting sheave has a groove that grips rope during descent while allowing free rotation for ascent and progress capture. An adaptive release linkage enhances ease of operation and control while maintaining convenient handle position in a variety of conditions.

FIELD OF THE INVENTION

The present invention relates generally to the field of rope access and rescue. More particularly, the present invention relates to a descender that is typically attached to an operator's harness to allow controlled descent down a fixed rope. Descenders may be used in other applications that require holding and controlled release of a rope under load.

BACKGROUND

Descenders are widely used in the field of rope access and rescue for controlling the descent of people or equipment suspended by rope. Descenders are commonly used by operators to descend down a rope that is affixed overhead. Descenders may also be attached to an anchor position to allow an operator to control the descent of one or more people or gear from a remote location. Typically, descenders are comprised of elements that clamp or pinch the rope and are self-energized by load applied to the rope in one direction through the device. Controlled release is typically achieved by actuation of a lever which alleviates the clamping force holding the rope, allowing controlled release of rope through the device. Under certain circumstances it is necessary to pull rope through the descender, thereby reversing the direction of travel. In these cases the descender serves as a turning point for the rope and a means of progress capture.

Descenders commonly incorporate a “panic” safety feature such that if the means of release is inadvertently actuated too far, the descender will cease the release of rope, preventing an uncontrolled freefall of the suspended persons or equipment.

Descenders that are currently available have some recognized limitations. Compact descenders of the type that would be worn on a harness do not excel at handling the greater loads involved with a two person descent, as is common in a rescue situation. The maximum working load specification of commonly available descenders does not accommodate requirements of two person rescue, or requires additional hardware to configure the device for high loads. The effort required to initiate release at higher loads is difficult, and controllability is diminished. At these higher loads, descenders commonly have the undesirable effect of flattening the rope or milking the rope sheath due to the aggressive localized pinching employed to grip the rope. Additionally, compromises made to make the device perform well over a wide range of loads contribute to poor performance at low loads. For example, a user may find difficulty initiating descent of a light weight load due to high friction in the device, or may find that the release is initiated at a handle position very near the point of panic relock, making operation frustrating.

As such, there is a need for a compact descender capable of managing a large range of loads while maintaining easy and controlled release.

SUMMARY

A descender for controlling descent of a load along a rope includes a chassis and an opening plate pivotably attached to the chassis. A generally circular sheave having a groove around its circumference is attached to one end of a pivot arm. The other end of the pivot arm is pivotably attached to the chassis. Each of a guide and a shoe are attached to the chassis and are positioned on substantially opposite sides of the sheave.

When the opening plate is in an open position, the rope may be installed by inserting the rope past the guide, around a significant portion of the circumference of the sheave, and past the shoe. When the opening plate is in a closed position, a path for a rope is formed through the descender such that the rope slides against the guide and shoe, and is selectively forced into the groove on the sheave. The second end of the pivot arm is biased toward the shoe so that when the rope is in tension, the sheave is rotated toward the shoe, trapping the rope there between.

A handle is attached to the chassis and engaged with the pivot arm such that movement of the handle controls the amount of force biasing the pivot arm against the shoe, which allows a user to selectively reduce the force between them. By reducing the force between the sheave and the shoe, the tension of the rope is able to overcome frictional force holding the descender in place, thus allowing the descender to move along the rope.

An attachment hole is provided that passes through the chassis and the opening plate such that when the opening plate is in the closed position, an operator can lock the descender in the closed position by inserting any suitable attachment means through the attachment hole, including but not limited to a carabiner.

It will be understood by those skilled in the art that one or more aspects of this invention can meet certain objectives, while one or more other aspects can lead to certain other objectives. Other objects, features, benefits and advantages of the present invention will be apparent in this summary and descriptions of the disclosed embodiment, and will be readily apparent to those skilled in the art. Such objects, features, benefits and advantages will be apparent from the above as taken in conjunction with the accompanying figures and all reasonable inferences to be drawn therefrom.

DETAILED DESCRIPTION

As shown inFIG. 1, the present invention is a descender1having a chassis10, which together with swing plate12contain rope28. Rope28is reeved such that a load to be managed pulls in direction A. Swing plate12is pivotably attached to chassis10, which allows a user to rig the descender1. Hole10aprovides a means of attachment, typically accomplished with a carabiner, but any other suitable attachment may alternatively be used. Hole10apasses through the swing plate12and the chassis10so that when descender1is in use and a carabiner or other attachment means is in use, the swing plate12cannot open. Handle subassembly31is pivotally mounted to chassis10and comprises at least one handle member30. In the embodiment shown, handle subassembly31includes two handle members30that are attached to each other to enclose components described in detail below. An operator can control the release of rope28by rotating handle subassembly31in direction D.

FIG. 2shows descender1with swing plate12pivoted to an open position, which is only made possible if there is no attachment means passing through hole10a. Sheave22has an acutely V-shaped groove22aabout its circumference that enhances the frictional interface between rope28and sheave22as tension is applied to rope28. Sheave22is rotatably mounted to pivot arm20and has a one-way ratchet which only allows rotation in one direction. In the embodiment shown inFIG. 2, the ratchet allows rotation in direction B. In this embodiment, one-way rotation of sheave22is achieved by a pawl that engages teeth integrally formed in sheave22. Of course, any suitable ratchet or backstopping clutch that only allows rotation of sheave22in direction B relative to pivot arm20may be used without departing from the invention. The one-way rotation of sheave22enables the descender1to act as an efficient pulley if ascent is required because free movement of sheave22in direction B means that the frictional forces between sheave22and rope28need not be overcome.

As shown inFIG. 2a user may install rope28by inserting the rope into the chassis10at guide16and wrapping the rope around sheave22, and exiting the chassis at shoe18. Pivot arm20constrains motion of the sheave22such that the resultant force of the rope on the sheave clamps the rope between the sheave and shoe18. Alternative mechanical means of constraining motion of sheave may be also employed without departing from the invention. Guide16and shoe18may alternatively be rotating rollers, but shown here are fixed deflection locations having low friction surfaces to keep the descender compact and to minimize cost.

As shown inFIG. 3, release mechanism cover14is attached to chassis10on the opposite side of swing plate12and provides pivot locations for components within the descender1.FIG. 4shows descender1with release mechanism cover14removed. Bellcrank40, is attached to chassis10and pivots about axis E. Bellcrank opening40aengages pivot arm boss20b. Bellcrank40is rotatably attached to chassis10. As shown inFIG. 4, bellcrank spring42biases bellcrank40in direction F, maintaining contact between bellcrank opening40aand pivot arm boss20b. Maintaining contact between bellcrank opening40aand pivot arm boss20bis critical because it ensures that the actuation of handle member30is reliably transferred to bellcrank40. Handle member30pivots about axis G and may be actuated in direction D. Such actuation causes motion to be transmitted from selector link32to bellcrank40, which transfers motion to pivot arm20and, ultimately, to sheave22. As such, the actuation of handle member30causes the pivot arm20to pivot about axis J, thereby allowing a user to regulate clamping force between rope28and shoe18. Regulating the clamping force between rope28and shoe18allows rope28to travel through the descender at varying load. Handle subassembly31pivots about axis G and, as shown inFIG. 6, is rotatably attached to selector link32.

As can be seen inFIG. 4, selector link32engages handle subassembly31via selector link pin32b, which may move from a notch30ato slot30b. As shown inFIG. 5, handle spring44is positioned between handle subassembly31and chassis10. Handle spring44engages handle spring pocket43, which is formed in chassis10and handle subassembly31. Handle spring44biases handle subassembly31and selector link32in rotational direction H about axis G. As can be seen inFIG. 6, selector link spring38engages selector link lobe32c, and serves to both bias selector link pin32binto the notch30aand bias selector link32to rotate in direction I and against stop pin34.

Referring back toFIGS. 1 and 2, when descender1is in use, a carabiner links through hole10ato attach the descender to an operator's harness or any other suitable anchor point. As tension is applied to rope28in direction A, the aforementioned ratchet mechanism causes sheave22to resist rotation in the direction opposite of direction B. The resulting moment causes sheave22and pivot arm20to rotate in direction C about axis J, thereby clamping rope28between shoe18and sheave22. As such, rope28is forced into groove22aof sheave22by shoe18, initiating holding forces and further driving rope28into the groove. Frictional forces between rope28and sheave22are great enough to resist motion of the rope in direction A. These relationships describe the self-energizing braking action that occurs as tension exists in rope28in direction A.

Controlled release of rope28is initiated by the operator pulling handle subassembly31, pivoting said handle subassembly in direction D as shown inFIG. 4. As handle subassembly31rotates in direction D, so too does selector link32until one of notches32aengages boss40bof bellcrank40, thereby rotating pivot arm20and sheave22in rotational direction opposite of direction C, thereby reducing the force on rope28between sheave22and shoe18. Reduced force on rope28between sheave22and shoe18reduces the total frictional force applied to rope28by the descender, thereby allowing rope28to slip past the sheave. Regulation of the rate of slipping of rope28is achieved by the operator input to the handle, thereby regulating the clamping force on rope28between sheave22and shoe18. A large mechanical advantage is achieved via the leverage of handle subassembly31to selector link32, and from bellcrank40to pivot arm20, which yields a high degree of control of descent with minimal operator effort applied to handle subassembly31.

When holding rope28under load, certain conditions will affect the resting angular position of pivot arm20about axis J. Variations in rope diameter will affect the distance between sheave22and shoe18. Likewise, different rope constructions may have different rates of compressibility, which will affect the distance between sheave22and shoe18. Additionally, different magnitudes of load applied to the descender via the rope will result in different amounts of compression of the rope, which will affect the distance between sheave22and shoe18. These variables introduce the reality of different angular positions of pivot arm20and sheave22about axis J for the same holding (no motion) condition. It follows that bellcrank40will also reside in different angular positions about axis E when holding the rope based on the same variables of rope diameter, construction, and tension. It also follows that, when in the state of holding the rope, boss40bof bellcrank40may reside in different positions based on the variables of rope diameter, construction, and tension. As such, when the operator initiates release by rotating handle subassembly31with selector link32in direction D, selector link32will engage the most appropriate of notches32awith boss40baccording to the position of bellcrank40. The interaction between notches32aand boss40bprovides the benefit of automatically adjusting the effective length of selector link32to the variables of rope diameter, construction, and tension. This feature ensures that the operator will experience similar handle subassembly31positions during the act of releasing the rope28, regardless of rope diameter, construction, and tension.

If an operator inadvertently actuates handle subassembly31too far in direction D, travel of selector link32between the circular paths of selector link pin32band boss40bwill reach a position where selector link32will contact panic trigger pin36. Continuation of handle motion in direction D past this position will cause selector link pin32bto become dislodged from a notch30ain handle subassembly31, and selector link pin will overcome selector link spring38, traveling into slot30bin handle subassembly31. The result is that handle subassembly31is unable to drive selector link32, so bellcrank40counter rotates on axis F resuming the clamping force on rope28between sheave22and shoe18, allowing sheave22to resume holding of rope28. Release of handle subassembly31by the operator will enable handle spring44to rotate handle subassembly31in direction H to the starting position of the handle, and allows selector link spring38to return selector link pin32bto a notch30a, thereby resetting the handle mechanism and making it again ready to initiate release.

In an alternative embodiment of a descender2in accordance with the invention shown inFIG. 7, a sheave52is rotatably mounted to a chassis50, with guide54and shoe roller56mounted on a first link58which constrains motion but allows the guide and the shoe roller to translate relative to the chassis and sheave. In the embodiment shown, sheave52may only rotate in direction R. Guide54is mounted to first link58, which pivots about axis N. Guide54is linked to shoe roller56via second link60. Shoe roller56is mounted to third link62and pivots about axis O. As tension is applied to rope28in direction Q, guide54is forced in direction R about axis N, forcing shoe roller56against rope28, which forces the rope into a groove in sheave52, initiating holding forces and further driving rope28into groove of sheave52. Frictional forces between rope28and sheave52are great enough to resist motion of rope28in direction Q. These relationships describe the self-energizing braking action that occurs as tension exists in rope28in direction Q. Handle64rotates about axis P and operates in conjunction with selector link66in a manner comparable to handle subassembly31and selector link32in the preferred embodiment.

An alternative embodiment of a descender3in accordance with the invention is shown inFIG. 8and includes a chassis410, which together with opening plate412, contains rope28. Rope28is reeved such that the load to be managed pulls in direction S. Hole410aprovides a means of attachment, typically accomplished with a carabiner although any suitable means of attachment may also be used. Handle430is pivotally mounted to chassis410, and control of the rope through the descender is achieved by an operator rotating the handle in direction T.

The means of gripping the rope in this embodiment is substantially similar to the device shown inFIG. 1and described above. The rope28is captured between sheave422and rollers454and456. Although rollers454and456are shown, any suitable bearing surface may be used without departing from the invention. As shown inFIG. 14, pivot arm420supports sheave422and is rotatably attached to chassis410such that the pivot arm can move about axis U. Applying tension to rope28in direction S results in translation of sheave422toward roller456, which forces rope28into a groove422aof sheave422. As the tension on rope28increases, so does the force moving sheave422toward roller456. As with the device shown inFIG. 1, frictional forces between rope28and sheave422are great enough to resist motion of rope28in direction S.

As shown inFIGS. 10-13, a pivot arm roller424is attached to pivot arm420and extends into opening428. A cam90is rotatably attached to the chassis410and can rotate about boss426. Cam spring91forces cam90in direction T relative to chassis410, initiating and maintaining contact between cam surface90aand pivot arm roller424. Handle430contains handle pawl80which is rotatably mounted to the handle about axis W. Handle pawl spring81engages with handle pawl80and biases it in direction X about axis W. Handle pawl80includes handle pawl teeth80aand handle pawl tail80b. Boss432protrudes from handle430and serves to limit angular rotation of handle430when assembled.

FIG. 13shows a control ring434and control ring aperture436of chassis410. As seen inFIG. 10, handle430pivots about boss426of chassis410. Handle pawl80engages control ring434to control which positions of handle430will allow handle pawl teeth80ato mesh with cam teeth90b.FIG. 11shows handle430in a stowed position, i.e. positioning handle430such that handle pawl tail80bcontacts control ring434, which causes handle pawl80to rotate, thereby providing clearance between handle pawl teeth80aand cam90.FIG. 10shows handle430in an operable position, i.e. positioning handle430in an angular position such that handle pawl tail80bis positioned in aperture436, handle pawl spring81causes handle pawl80to rotate in direction X about axis W, thereby making handle pawl teeth80aavailable to engage cam90.

Handle430may be rotated in direction T from the stowed position shown inFIG. 11to the operable position shown inFIG. 10. As previously explained, aperture436of chassis410enables handle pawl teeth80ato engage with cam teeth90a. Meshing handle pawl teeth80awith cam teeth90blinks the motion of handle430and cam90while handle pawl tail80bof handle pawl80is positioned in control ring aperture436. From the handle operable position, controlled release of rope28is achieved by the operator pulling handle430in direction T, which rotates cam90in the same direction. Contact between cam90and pivot arm420via cam surface90aand pivot arm roller424causes pivot arm420and sheave422to rotate about axis U, thereby reducing the force on rope28between sheave422and roller456. Reducing the force applied to rope28between sheave422and roller456reduces the total frictional force between the rope and the descender3, allowing rope28to slip past the sheave422.

Cam90will also reside in different angular positions depending on the angle of pivot arm roller424in relation to cam surface90a. The plurality of cam teeth90ballows the descender3to adapt to variations in rope diameter, construction, and tension in the same way that the multiple notches of the selector link does in the first embodiment described above. This release mechanism allows the handle430to rotate much further than previous descenders, making it possible to create a “stowed” position where the handle is out of the way when not needed for release.

Using cam90to achieve the mechanical advantage required for controlled release of rope28allows the mechanical advantage to be easily tuned and optimized for the magnitude of force applied to the rope—the highest loads typically equate to the furthest rotation of the cam, and the corresponding area of the cam surface can be made more gradual to provide greater mechanical advantage. The teeth of the handle pawl and cam allow for much finer resolution of the adaptive release, which maximizes the release travel better than what was possible with the selector link of the first embodiment. Another advantage of this design is that it is very easy to incorporate the panic locking function. By controlling the size and location of the aperture436, the handle can be disconnected from the cam if the handle is swung too far because handle pawl tail80bwill come in contact with control ring434, rotating handle pawl80and disengaging handle pawl teeth80afrom cam teeth90b.

As shown inFIGS. 15-20, opening plate412is hinged about the ends of roller pins70such that opening plate412opens relative to chassis410. In the embodiment shown, rollers454and456are attached to opening plate412. Roller pins70include spherical heads72(seeFIG. 18) that engage sockets440shown inFIG. 13. Other means of articulation including but not limited to pinned joints may alternatively be used without departing from the invention. With opening plate412fully opened, the space between chassis410, opening plate412, and rollers454and456is large enough to enable a bight of rope to be inserted and guided about sheave422as shown inFIG. 16. This simplified approach to rigging greatly reduces the likelihood of an operator incorrectly rigging the descender3and causing an unsafe condition. The carabiner used to attach the descender through hole410amaintains closure of the plates when the unit is under load. Additional latches and/or magnets may be also be used to enhance the security of closure.

Although the invention has been herein described in what is perceived to be the most practical and preferred embodiments, it is to be understood that the invention is not intended to be limited to the specific embodiments set forth above. Rather, it is recognized that modifications may be made by one of skill in the art of the invention without departing from the spirit or intent of the invention and, therefore, the invention is to be taken as including all reasonable equivalents to the subject matter of the appended claims and the description of the invention herein.