GB2229630A - Rope braking device - Google Patents

Abstract

A rope braking device for braking descent, for example, of a human being, down a rope (11) has a rotatably mounted shaft (12), spaced apart guides (18) and means (19) in said guides (18) to engage a rope wrapped helically about said shaft (12) to have its turns (21) separated by said guides (18), and brake means (16) for limiting the rotational speed of the shaft (12). <IMAGE>

Description

ROPE BRAKING DEVICE The invention concerns a rope-braking device, and has more particular reference to a device for use in, for example, the contained movement of a load up or down a rope.

Circumstances may arise in which a person is trapped, say by fire, in an upstairs room, access being denied that person to a staircase or other route to a safe location. Whilst local fire services do provide a means of rescue, time is usually very much of the essence and any delay in the arrival of suitable equipment will prejudice the chances of survival.

It is an object of the present invention to provide a personal escape means which is of such construction as can be used without training or supervision and on the basis simply of minimal written instruction.

It is a further object of the invention to provide a simple braking device for application to a rope which will enable loads to be moved up or down said rope in a controlled manner, whether continuously or in stepwise fashion.

According to the invention there is proposed a device for the controlled movement of a body along a rope comprising a shaft rotatably mounted in bearings fixedly secured to the body, a plurality of spaced apart guides adjacent said shaft and disposed at respective axial locations relative thereto, a rope wrapped in multiple turns about the shaft and engaging said guides, the guides being adapted to separate and to locate successives ones of the said multiple turns existing about the shaft, and braking means operable on the shaft to limit the rotational speed thereof.

According to a preferred feature, the guides comprise fixed annular discs arranged coaxially with the shaft and having respective apertures therein, the apertures of successive discs being displaced at 1800 centres about the axis of the shaft.

According to a further preferred feature, a sleeve of high friction material is provided about the shaft to minimise sliding movement of the rope relative thereto.

The invention will now be described further, by way of example only, with reference to the accompanying diagrammatic drawings illustrating two embodiments thereof, and in which : Fig. 1 is a front elevation, partly in section, of a first form of invention; Fig. 2 is a section on line Il-Il of the arrangement shown in Fig. 1; Fig. 3 is a front elevation, similar to Fig. 1, and shows a second embodiment of the invention; Fig. M is a diagrammatic front elevation of a third embodiment of the invention; Fig. 5 is a view on line 5-5 of Fig. 4; Fig. 6 is a view on line 6-6 of Fig. 4; and Fig. 7 is a diagrammatic illustration of the locking means embodied in the arrangement shown in Fig. 4.

Referring now to the drawings and particularly to Figs.

1 and 2 thereof, a device for controlling the rate of descent of a body, typically a human being, down a rope 11 the upper end of which is secured to an elevated fixed point (not shown) comprises a shaft 12 freely rotatable in bearings 13 provided on a plate 14 to be secured to a harness, not shown, for wear by the intended user and braking means 16 at the respective ends of the said shaft 12, the braking means including a control lever 17 for applying the brake to said shaft 12 as required.

A rope 11 is arranged in plural turns about the said shaft 12, there typically being two turns, and successive ones of the said turns are controlled axially of the shaft by annular spacers 1 8 arranged coaxially with the shaft at respective positions longitudinally thereof, the said spacers 18 being fixedly mounted relative to the said plate 14 and there being apertures 19 therein to receive the rope 11 therethrough, the apertures 19 in the successive spacers 18 being arranged at 1800 centres about the axis of the shaft.

By virtue of the capstan effect of the plural rope turns about the shaft, the rope being under tension at least at that part thereof lying above the shaft, the rope will be advanced relative to the device in contact with the shaft and at the surface speed thereof the individual part turns 21 of the rope 11 being kept separate by the spacers 18. Indeed, as illustrated, successive 1800 wraps of the rope about the shaft 12 are separated one from another. In moving through the device in contact with the shaft 12, the rope 11 passes progressively through the apertures 19 in the successive spacers 18 and interference between successive part turns of the rope such as might otherwise be likely to give rise to a malfunction of the device will be avoided.

The braking means 16 are each of the conventional expanding shoe kind, and comprise a drum 22 secured to the shaft 12 for rotation therewith and the control lever 17 aforesaid, lever 17 being of arcuate form pivotally mounted on the cover 23 of the brake means 16 so as partially to embrace the shaft 12, the control levers 17 of the respective brake means being connected by a yoke 24 extending longitudinally of the device positioned adjacent the periphery of the spacers 18 and being operable in a manner hereafter to be made apparent.

The device is completed by an operating means engageable with the yoke 24 in such manner as to pivot the control levers 17 in a sense appropriate to operate the brake, the said operating means 26 comprising a rectangular frame 27 mounted for pivotal motion about the axis of shaft 12, yoke 24 lying in the path of movement of said frame 27, a knob 28 secured to one end of the frame 27 in alignment with the pivot axis thereof and a calibration means 30 at the opposite end of the frame, the calibration means 30 providing a means whereby the brake might be preloaded according to the weight of the user.

Pivotal motion of the operating means 26 via the knob 28, to bring the rectangular frame 27 into pressure contact with the yoke 24, provides for brake actuation, the degree of braking being determined, inter alia, by the magnitude of the pressure applied.

In use, in say abseiling down a cliff face or descending from an upstairs window, a device as hereinproposed is strapped about the waist of the intended user by means of a suitable harness, not shown, and the calibration means 28 is set according to the weight of such user. The device is now ready for use. In its simplest method of use, the user relies merely on the pre-loading of the brake to provide a predetermined and constant rate of descent, the rate of rotation of the shaft, and hence the rate of linear advance of the rope relative to the device, being governed by the extent of preloading applied by the calibration means.

If it is desired to arrest the descent, or to reduce the rate of descent, the operating means is pivoted about the axis of the shaft to increase the pressure brought to bear on the yoke by the rectangular frame of the said means and hence increase the braking effect.

As will be appreciated, the rate of descent for a particular person can be varied at will, and whilst for the layman a relatively slow rate of descent is desirable, circumstances do exist where a rapid rate of descent is envisaged.

In such circumstances the pre-loading is minimal and reliance is placed by the user on that users own ability to operate the braking means via the operating lever to effect braking as necessary.

A modified form of the device shown in Figs. 1 and 2 may be used as an aid in climbing up a rope, an appropriate arrangement being shown in Fig. 3.

Thus, referring now to Fig. 3, in which like reference numerals to those of Figs. 1 and 2 are used for the same or similar parts, various elements such as the brake lever and operating means being omitted in the interests of clarity, the device further includes a ratchet and pawl mechanism 29 provided in the hub of each brake drum and the shaft 12, to give a free wheeling capability such as will permit rotation of the shaft 12 in a direction consistent with movement up the rope but preclude rotation in the opposite direction.

A releasable clamp 31 is provided at the underside of the plate and is fixed in position at the lower end of a rope guide 32 via a tension spring 33. The clamp 31 comprises oppositely directed L-shaped levers pivotal on a bracket 34 secured to the spring, corresponding first limbs 36 of the levers extending downwardly and being disposed one at either side of the rope 11 and the second limbs 37 thereof extending radially outwardly of the rope and defining respective foot-rests one on either side of the rope. The levers are lightly biassed in such manner as to load limbs 36 away from the rope. As is apparent from the drawing, the inwardly facing surfaces 38 of the said first limbs 36 are of corrugated profile for better rope engagement.

In use, assuming a starting position wherein the user has the device strapped to his waist by suitable harness means and his feet on respective ones of the second limbs 37 of the pivoted levers with the spring 33 extended, the user applies the manual brake via knob 28 sufficiently fully to lock the brake drum. On removal of the loading applied to the levers by the user the clamping effect of the levers on the rope is released and the spring 33 contracts to move the clamp up the rope 11, the position of the user relative to the rope being maintained by the uni-directional clutch precluding rotation of the shaft.The user then applies pressure to the footrests defined by the first lever limbs 37, the application of a load thereto clamping the levers to the rope at their elevated position thereon, and on straightening his legs causes the shaft to move up the rope by rotation in contact therewith. The procedure is repeated and the user thus moves up the rope in stepwise manner.

The capstan principle as embodied in the arrangements hereinbefore disclosed is of application to safety equipment for use in escaping from, say, a burning building, one form of such equipment being shown diagrammatically in Figs. 4 to 6.

Referring now to Figs. 4 to 6, a device of the general character of that shown in Figs. 1 and 2 is provided in a casing 41 to be strapped to the user as a back pack by a harness, not shown, the upper end of the rope 11 carrying a hook 42 for secure attachment to a fixed point adjacent an exit window and a requisite length of rope being stored within the casing and being automatically releasable therefrom on use of the equipment.

As with the Fig. 1 embodiment, controlled movement down the rope 11 is achieved by means of a braked shaft 12 about which the rope 11 is lapped in multiple turns, successive turns or part turns being separated by apertured spacers 18 arranged coaxially with the shaft, the spacers 18 being fixed against rotation and the braking means 16 being pre-loaded, according to the weight of the user, to give an acceptable rate of descent.

The arrangement shown in Figs. 4 to 6, is ordinarily locked against operation, but the lock is released automatically in two stages on donning the equipment and on using the same, there being a pivotally mounted contact pad 43 between the user and the casing 41 displacement of which readies the braking means 1 6 for use and a release catch means 44 sensitive to shaft rotation to permit application of the brake at the pre-loaded level. In addition to effecting brake application, actuation of the release catch means 44 serves also to open a spring-loaded panel 46 at the underside of the casing 41, thus to release the rope stored in a lower compartment 47 therein.

Thus, referring now to Figs. 4 to 6, the capstan device is provided in an upper compartment 48 of the casing, the rope 11 passing to the said device from the lower compartment via lower guide 49 and from the said device through an upper guide 51.

As the construction and operation of the capstan device is substantially as described in relation to the embodiment of Figs.

1 and 2, further detailed description thereof is thought unnecessary save only as regards any specific differences which exist.

In this latter regard means whereby pre-loading of the brake is effected comprises an arcuate lever 52 pivotally mounted at its lower end for motion in a diametral plane of the shaft, the upper end 53 of the arcuate lever being connected with the yoke through a coil spring 54. A lever arm 56 is formed integrally with the arcuate lever 52 and extends radially outwardly from the lower end thereof, the lever arm 56 being secured to a screw adjustment means 57 carried in a fixed bracket 58 whereby the angular position of the arcuate lever 52, and thus the loading applied to the yoke, may be varied.

It is to be observed that the capstan device of Fig.

4 does not include the rectangular frame of the Fig. 1 embodiment, since no manual control of braking is provided in the present instance.

The angular position of the arcuate lever 52 is shown on an indicator means 59 operatively connected with the lever arm 56 by a Bowden cable arrangement 61, longitudinal motion of the cable being converted nto rotary motion by conventional means to move a pointer 62 relative to a circular scale 63, the scale being calibrated to show weight and the appropriate adjustment in any given circumstances being by reference to the weight of the intended user.

In the arrangement illustrated in Fig. 4, a sleeve 64 of high friction material is provided about the shaft 12 to minimise or to avoid slippage of the rope relative to the shaft.

The locking means is shown diagrammatically in Fig.6 and comprises a disc 66 arranged in a common plane with the arcuate lever 52 and rotatably supported by and between two fixed discs 67 of like dimensions, there being correspondingly positioned detents 68 in the respective peripheries of the discs to receive the depending lip 69 of a pivoted catch operable by the contact pad 43, the lip 69 being disengaged from the detents 68, thus to allow rotational movement of the intermediate disc, on application of pressure to the contact pad.

The intermediate disc 66 carries a radially outwardly extending pin 71 at a position on the periphery thereof angular spaced from the detent 68, the pin 71 being engageable with a slot 72 provided in an extension 73 to the yoke 24 and serving to hold the yoke 24 in a position consistent with a "released" condition of the brake.

Rotation of the intermediate disc 66 is further controlled by the release catch means 44 , sensitive to shaft rotation, application of pressure to the contact pad and the attainment of a minimum rate of shaft rotation being required for full release of the locking means.

The release catch means 44 comprises a rod 74 extending normal to the surface of the discs 66, 67 and of which the free end is engaged with a through hole in an outer disc 67 and engageable with a through hole adjacent the periphery of the intermediate disc 66 the through hole in the intermediate disc being so positioned angularly thereof as to be in alignment with the rod 74 when the detents in the three discs are in alignment to receive the lip. The rod 74 is connected with a further rod 76 arranged coaxially with the shaft 11 by a linkage 77 such that axial movement of the further rod 76 in a given sense effects a corresponding movement of rod 74 in the opposite sense.The remote end of the further rod carries a flanged boss 78 freely rotatable thereon, whilst the end of the shaft supports a collar 79 carrying weights 81 thereon in pivotal manner, the weights 81 being adapted to effect axial displacement of the flanged boss 78, and thus of the further rod 76, on radially outward movement of the weights under centrifugal forces. Thus, on attainment of a predetermined shaft speed, the weights 81 operate to disengage the rod 74 from the intermediate disc 66, thus to allow rotation thereof,subject to disengagement of the lip 69 of pivotted catch from the peripheral detent in such disc, and release of the pin 71 from the slot 72 in the extension 73 to the yoke 24.On release of the locking means the coil spring 54 draws the yoke in a direction to apply the brake means at the predetermined braking load Release of the rod 74 from its enagement with the intermediate disc 66 is effected as a direct consequence of shaft rotation, movement of the capstan device down the rope, as by the gravitational movement of a wearer of the equipment relative to the rope, serving to effect such rotation.

The invention is not restricted to the detail of the embodiments hereinbefore described since alternatives will readily present themselves to one skilled in the art.

The inventive concept disclosed is of application in a range of contexts in which movement up or down a rope is required, the use of the capstan principle and of the controlled braking of a shaft in combination being thought to be of widespread use.

Indeed, it may be found practical to utilise a non-rotatable shaft about which a rope is lapped in multiple turns in accordance with the invention and to rely upon the application of tension to that part of the rope existing below the shaft in order to effect braking.

In view of the heat generated by braking, and particularly during the course of a long descent, a heat shield may be provided about the brake drums, thus to protect the user.

Claims (14)

1. A device for the controlled movement of a body along a rope comprising a shaft rotatably mounted in bearings fixedly secured to the body, a plurality of spaced apart guides adjacent said shaft and disposed at respective axial locations relative thereto, a rope wrapped in multiple turns about the shaft and engaging said guides, the guides being adapted to separate and to locate successive ones of the said multiple turns existing about the shaft, and braking means operable on the shaft to limit the rotational speed thereof.

2. Apparatus as claimed in claim 1, wherein the guides comprise fixed annular discs arranged coaxially with the shaft and having respective apertures therein, the apertures of successive discs being displaced at 1800 centres about the axis of the shaft.

3. Apparatus as claimed in claim 1 or 2, wherein a sleeve of high friction material is provided about the shaft to minimise sliding movement of the rope relative thereto.

4. Apparatus as claimed in claim 1, 2 or 3 and including a harness for a human being.

5. Apparatus as claimed in claims 1 to 4, wherein the braking means includes manually-actuable control means.

6. Apparatus as claimed in claims 1 to 4, wherein automatic speed-regulating means is provided.

7. Apparatus as claimed in any preceding claim, wherein means are provided to calibrate the brake in accordance with a user's weight.

8. Apparatus as claimed in any preceding claim, wherein the brake is a drum brake.

9. Apparatus as claimed in any preceding claim and including means whereby a user can ascend a rope.

10. Apparatus as claimed in any preceding claim and including additional foot-operable brake means.

11. Apparatus as claimed in any preceding claim, a housing being provided to contain a rope.

12. Apparatus as claimed in claim 11 and forming part of an emergency escape system.

13. Apparatus as claimed in any preceding claim, wherein the shaft is of or incorporates a layer of high friction material.

14. A rope braking device substantially as described with reference to the accompanying drawings.