GB2543366A

GB2543366A - Self-Braking Pulley

Info

Publication number: GB2543366A
Application number: GB1519354.3A
Authority: GB
Inventors: griffiths Stephen
Original assignee: Swisslogo AG
Current assignee: Swisslogo AG
Priority date: 2015-10-12
Filing date: 2015-11-02
Publication date: 2017-04-19
Also published as: GB2585595A; GB201518027D0; GB201519354D0; GB202014339D0; GB2585595B

Abstract

A self-braking pulley (100, Fig 1), for controlling a rate of extraction of a tether 300 coupled with it, comprises a housing 110a, 110b and a spool 127, the spool being rotatably coupled with the housing and arranged to receive the tether. The pulley further comprises a braking assembly for applying a braking force to the spool, comprising of a braking member 132 rotatably coupled to the spool and arranged to engage with the housing in dependence of a rotational speed of the spool. The braking member may comprise a spring-biased rotatable pawl and the housing may include a plurality of notches or serrations (137, Fig 3) with which the pawl can engage. A shock absorbing leash (200, Fig 6) is also presented; comprising an elongate body which is folded upon itself about a fold line (202, Fig 6) to form a first (203, Fig 6) and second (204, Fig 6) body portion. The two body portions are stitched together at a plurality of regions (205, Fig 6) disposed along the body portions such that a force required to separate the two body portions must break the stitches in a direction along the body portions and toward the fold line.

Description

SELF-BRAKING PULLEY

The present invention relates to a self-braking pulley.

It is well known for individuals working or operating at height to use a tether to secure themselves to a suitable support to arrest their fall should they unexpectedly fall or otherwise need to escape from their position. The tether is typically secured at one end to the support and at the other end to the individuals harness and as such, while the tether may arrest their fall, there can be a significant jolt upon the individual as the tether becomes taught. Moreover, the tether can present a tripping hazard to the users and neighbouring persons and can become tangled as the user moves around.

We have now devised a self-braking pulley.

According to a first aspect of the invention, there is provided a self-braking pulley for controlling a rate of extraction of a tether coupled with the pulley, the pulley comprising a housing and a spool rotatably coupled with the housing, the spool being arranged to receive the tether, the pulley further comprises a braking assembly for applying a braking force to the spool, the braking assembly comprising a braking member rotatably coupled to the spool, the braking member being arranged to engage with the housing in dependence of a rotational speed of the spool.

In an embodiment, the spool is rotatably coupled with the housing via an axle. The axle comprises longitudinal end portions which are preferably supported within the housing by a respective bearing arrangement.

In an embodiment, the braking member is arranged to engage with a braking portion of the housing. The braking portion may be formed integrally with the housing and comprises a substantially cylindrical housing portion centred upon a rotational axis of the spool. The housing portion preferably comprises a plurality of notches or serrations formed around an inner side thereof, which are angularly separated around the inner side of the housing portion. The notches or serrations preferably extend longitudinally of the housing portion.

The braking member comprises a pawl which is rotatably coupled at a proximal end thereof to the spool. A distal end of the pawl is free to move radially of the spool in dependence of a rotational speed of the spool, to engage with the braking portion. In an embodiment, the pawl is biased radially inwardly of the spool, away from the braking portion, by a biasing member, such as a spring and comprises a locating member disposed at the distal end thereof for locating within a notch or serration formed within the housing portion.

The pulley further comprises a swivel secured to the housing for coupling the pulley to an anchor point, such as a ceiling joist. The swivel comprises a base which is rigidly secured to the housing and a head which is rotatably coupled to the base, such that the pulley can rotate relative to the anchor point. The pulley preferably further comprises a leash for coupling the pulley to the anchor point. The head preferably comprises coupling means, such as an eyelet or hook or other coupling device to facilitate the coupling of the leash thereto.

The leash preferably comprises a shock absorbing section disposed intermediate opposite ends thereof, to reduce the shock transmitted to a user when the tether becomes suddenly taught.

In an embodiment, the tether is wound upon the spool and is coupled at a proximal end thereof to the spool. A distal end of the tether is arranged to extend out from the pulley via a tether guide.

In an embodiment, the pulley further comprises means for enabling the tether to retractably extend from the pulley housing. The pulley preferably further comprises means for biasing the spool to rotate in a direction which causes the tether to retract upon the spool. Preferably, the means for biasing the spool comprises a coil spring which is coupled at one end to the housing and at the other end to the spool.

According to a second aspect of the invention, there is provided a shock absorbing leash for reducing a jolt experienced by a user coupled to the leash when the leash becomes suddenly taught, the leash comprising an elongate body which is folded upon itself about a fold line disposed intermediate opposite longitudinal ends of the body to form a first and second body portion which extend from the fold line, the first and second body portions being stitched together using a thread at a plurality of stitching regions disposed along the body portions, wherein a force required to separate the first and second body portions at the stitching regions by breaking the stitches increases in a direction which is along the body portions, toward the fold line.

In an embodiment, the stitches associated with each stitching region conform to a stitching pattern, which may comprise a plurality of rows of stitches which extend across the first and second body portions and which may be joined to form a continuous stitch pattern.

In an embodiment, a thickness of the thread associated with each stitching region varies between the stitching regions, and preferably increases between the stitching regions, along the body portions, in a direction toward the fold line.

In a further embodiment, the stitching regions are separated by unstitched regions and the body portions are foldable upon each other about fold lines disposed within the unstitched regions, to form a folded arrangement of body portions.

In a further embodiment, the leash further comprises a wrapper securable around the body portions, to hold the body portions in the folded arrangement, and coupling means, such as an eyelet, looped region hook or similar, disposed at the longitudinal ends of the body for coupling the body and thus the leash to a user and anchor point, for example.

Whilst the invention has been described above, it extends to any inventive combination of features set out above or in the following description. Although illustrative embodiments of the invention are described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to these precise embodiments.

Furthermore, it is contemplated that a particular feature described either individually or as part of an embodiment can be combined with other individually described features, or parts of other embodiments, even if the other features and embodiments make no mention of the particular feature. Thus, the invention extends to such specific combinations not already described.

The invention may be performed in various ways, and, by way of example only, embodiments thereof will now be described, reference being made to the accompanying drawings in which:

Figure 1 is a perspective view of a self-braking pulley according to an embodiment of the present invention;

Figure 2 is an exploded view of a self-braking pulley illustrated in figure 1;

Figure 3a is a side view of the spool of the pulley, illustrating the location of the braking member disposed thereon;

Figure 3b is a perspective view of a housing section illustrating the location of the braking member relative to the housing, with the spool and wall removed for clarity;

Figure 4 is a magnified view of the swivel;

Figure 5 is a magnified exploded view of a housing section, illustrating the axle and spool, with the tether removed for clarity; and,

Figure 6a is a perspective view of a shock absorbing leash according to an embodiment of the present invention in an unfolded configuration;

Figure 6b is a side view of the shock absorbing leash illustrated in figure 6a, in a folded configuration and positioned within a wrapper (shown in sectional view); and,

Figure 7 is a perspective view of a self-braking pulley according to a further embodiment of the present invention.

Referring to figure 1 of the drawings, there is illustrated a self-braking pulley 100 according to an embodiment of the present invention, which is arranged to arrest a fall or descent of a user (not shown) from a height. The pulley 100 comprises a pulley housing 110 which is secured to an anchor point, such as a ceiling joist (not shown) or other support using a leash 200, and a tether 300 which is arranged to retractably extend from the housing 110. The tether 300 comprises a hook, karabiner or similar coupling device 301 disposed at a free end thereof, for securing the tether 300 to a harness (not shown) worn by a user.

Referring to figure 2 of the drawings, the housing 110 comprises a first and second housing section 110a, 110b which may be formed of a rigid plastics material or a composite plastics material, such as glass reinforced plastic. In an embodiment, it is envisaged that the composite material comprises at least a 50% w/w glass component and preferably at least a 60% glass component. Each housing section 110a, 110b comprises an end panel 111a, 111b having a substantially circular shape and a wall 112a, 112b which extends around a periphery of the respective panel 111a, 111b to define a respective first and second drum 113a, 113b. The first and second housing sections 110a, 110b further comprise a section 114a, 114b of an anchor housing 114 and tether guide sections 115a, 115b of a tether guide housing 115, formed at diametrically opposite positions on the first and second drum 113a, 113b.

Referring to figure 5 of the drawings, each anchor section 114a, 114b comprises a collar portion 116a (only one of which is illustrated) which extends radially of the respective drum 113a, 113b from a semi-circular slot 117a (only one of which is illustrated) formed within the wall of the housing section 110a, 110b. The slots 117a comprise a radius which is greater than a radius of the collar portion 116a, such that the slots 117a form a shoulder at the side of the collar portion 116a which is radially inwardly of the respective drum 113a, 113b. Each tether guide section 115a, 115b comprises substantially planar portion 118a, 118b of the wall 112a, 112b of the respective drum 113a, 113b and a rectangular shaped notch 119a, 119b formed within the planar wall portion 118a, 118b.

Referring again to figure 2 of the drawings, the first and second housing sections 110a, 110b are detachably coupled together by passing fasteners 120 through apertures 121 through flanged portions 122a, 122b on the wall 112a, 112b of each drum 113a, 113b, to form a substantially cylindrical housing 110. Once coupled, the anchor sections 114a, 114b formed on each housing section 110a, 110b cooperate to form a substantially cylindrical collar 116 which extends from a disc shaped cavity (not shown) formed between cooperating semi-circular slots 117a. Similarly, the planar wall portions 118a, 118b and notches 119a, 119b formed therein cooperate to form tether guide housing 115 having an aperture (not shown) having a substantially square shape.

The first and second housing sections 110a, 110b further comprise a recess 123a, 123b formed in the end panels 111a, 111b thereof, having a substantially circular cross-sectional shape which is centred on a central portion of the respective panel 111a, 111b. Each recess 123a, 123b is arranged to receive a bearing arrangement 124 for supporting an axle 125 across the housing sections 110a, 110b. The bearing arrangements 124 comprise a shape which is sized to provide a friction fit within the respective recess 123a, 123b and comprise an aperture 126 formed at a central region thereof for receiving a longitudinal end of the axle 125, such that the axle 125 can freely rotate within the bearing arrangements 124.

The pulley 100 further comprises a spool 127 which is arranged to rotate within the first and second drum 113a, 113b of the first and second housing sections 110a, 110b. The spool 127 is coupled to the axle 125 and comprises a cylindrical body (not shown) through which the axle 125 extends and a first and second annular flange 128, 129 formed at each end of the body (not shown), which act to form an annular channel 130 therebetween. The spool 127 is arranged to receive the tether 300 which is wound upon the cylindrical body (not shown) between the annular flanges 128, 129.

Referring to figures 3a and 3b of the drawings, the pulley 100 further comprise a braking assembly 131 for braking the rotation of the spool 127 and comprises a braking member such as a pawl 132, which is rotatably coupled at a proximal end thereof to an outer side of the first annular flange 128, via a pivot 133. The pawl comprises an arcuate shape and extends along an arc from the pivot 133 around the axle 125 and is arranged to rotate about the pivot in a plane which extends substantially parallel to a plane comprising the first annular flange 128. A distal end of the pawl 132 comprises a locating member, namely a protuberance 134, which extends from the pawl 132, radially outwardly of the annular flange 128. The braking assembly 131 further comprises a biasing member, such as an extension spring 135, which is coupled at one end to the outer side of the first annular flange 128 and at the other end to the distal end of the pawl 132 and is arranged to bias the pawl 132 and thus the protuberance 134 radially inwardly of the first annular flange 128.

Referring to figures 3 and 5 of the drawings, the first annular flange 128 of the spool 127 is arranged to extend adjacent the first housing section 110a and an inner side of the first housing section 110a comprises a housing portion 136 having a substantially cylindrical shape. The housing portion 136 is formed integrally with the housing section 110a and forms part of the braking assembly 131 of the spool 127. The housing portion 136 is centred upon the axle 125 and is arranged to extend from the end panel 111a of the first housing section 110a, toward the first annular flange 128, to surround the pawl 132. The housing portion 136 comprises an internal surface having a plurality of notches 137 or serrations formed therein, which are angularly separated around the inner periphery of the housing portion 136. The notches 137 or serrations extend longitudinally of the housing portion 136 and are shaped to receive the protuberance 134 formed at the distal end of the pawl 132.

The second annular flange 129 of the spool 127 is arranged to extend adjacent the second housing section 110b, but is spaced therefrom to form a cavity (not shown) for receiving a coil spring 138. The coil spring 138 extends around the axle 125 and is rigidly coupled at one end to an outer side of the second annular flange 129 and at the other end to a coupling point (not shown) formed within the cavity on the end panel 111 b of the second housing section 110b.

Referring to figure 4 of the drawings, the pulley 100 further comprises a swivel 139 located within the anchor housing 114, and comprises a base 139a which is arranged to locate within the collar 116 and a head 139b which is rotatably coupled to the base 139a via a spindle 140. The base 139a comprises a cylindrical body 141 which is shaped to extend through the collar 116 and a flanged portion 142 which locates within the disc shaped cavity formed between cooperating slots 117a in the anchor sections 114a, 114b to prevent the base 139a and thus the swivel 139 from being pulled out from the anchor housing 114. The head 139b of the swivel comprises a yolk 143 and a fastener 144 which extends between the ends of the arms 145a, 145b of the yolk 143 to secure the leash 200 thereto for coupling the pulley 100 to an anchor point (not shown).

The tether 300 is wound upon the spool 127 and is rigidly coupled at one end to the spool body (not shown). The other end of the tether 300 is arranged to pass out from the housing 110 via the aperture (not shown) located within the tether guide housing 115, which is located diametrically opposite the housing 110 from the anchor housing 114. In order to minimise any fraying of the tether 300 as it passes through the aperture (not shown), the aperture (not shown) may comprise a plug 146 positioned therein, which extends around an inner periphery of the aperture, through which the tether 300 can pass. In addition, the pulley 100 may further comprise a compressible member 147, which may be formed of a rubber, for example, which is arranged to extend around the tether 300, adjacent the coupling with the karabiner 301 for example, or located adjacent the plug 146, to prevent the karabiner 301 from striking the housing 110 as the tether 300 retracts into the housing 110.

In an embodiment, the leash 200 comprises a shock absorbing section 201 disposed intermediate opposite ends thereof. The shock absorbing section 201 may comprise a folded portion of the leash 200 which is sewn together and/or a tearable webbing portion, of which the stitching is designed to break when the tether 300 becomes suddenly taught to reduce the shock transmitted to a user (not shown). Referring to figure 6a of the drawings there is illustrated a shock absorbing leash 200 according to an embodiment of the present invention. The leash 200 comprises an elongate body, such as a length of webbing, and the shock absorbing section 201 is formed by folding the webbing upon itself, to create a fold line 202 across the webbing, intermediate opposite longitudinal ends thereof. The folded webbing thus forms a first and second webbing portion 203, 204, which extend from the fold line 202.

The first and second webbing portions 203, 204 are stitched together at a plurality of stitching regions 205, which are separated along the length of the first and second webbing portions. Each region 205 comprises a continuous stitch pattern having a plurality of rows of stitches 206 which extend back and forth across a width of the folded webbing portions 203, 204. In an embodiment which includes a webbing having a width of substantially 45mm, it is envisaged that opposite ends of the rows 206 will be spaced from the edge of the webbing by approximately 5mm, such that the rows of stitches 206 extend through approximately 35mm across the width of the webbing. The region 205 preferably extend along the folded webbing portions 203, 204 through a distance of approximately 128mm and are separated along the length of the folded webbing portions 203, 204 to leave regions 207 of the first and second webbing portions unstitched. In an embodiment, the region 205 are configured such that the gauge of the thread, namely the thread thickness, associated with each region 205 increases along the length of the folded webbing portions 203, 204 toward the fold 202, such that each region 205 comprises a progressively thicker thread forming the stitch.

Referring to figure 6b of the drawings, in use, the leash 200 is further folded upon itself at fold lines disposed within the unstitched regions 207 to create a compacted folded arrangement, and the leash 200 is held in this further folded arrangement by a wrapper 208 which may comprise a heat shrinkable cover, or a fabric sack for example, which is placed over the series of folds in the webbing portions 203, 204.

In use, the pulley 100 is secured to an anchor point (not shown) which may comprise a support platform or a ceiling joist or similar, using the coupling means, such as an aperture 209 for example, disposed at one one end of the leash 200. The other end of the leash 200 is secured to the head 139b of the swivel 139 by positioning a looped end or aperture 209 formed in the the leash 200 between the arms 145a, 145b of the yolk 143 and securing the fastener 144 between the arms 145a, 145b, through the looped end. The free end of the tether 300 is then coupled to the harness (not shown) worn by the user using at hook, karabiner or similar coupling device 301 disposed at the free end of the tether 300. When the user wishes to escape quickly from their raised position, or when a user unexpectedly falls from the raised position, the tether 300 will become extracted from the housing 110 as it unwinds from around the spool 127. As the user continues to fall, the coil spring 138 will begin to further coil around the axle 125 and the resilient bias associated with the spring 138 will result in the coil spring 138 acquiring potential energy. At the same time, as the rotational speed of the spool 127 increases, the distal end of the pawl 132 will begin to move radially outwardly of the spool 127 against the bias of the extension spring 135, due to the centrifugal force. When a threshold rotational speed has been reached, the pawl 132 will rotate about the pivot 133 so that the protuberance 134 formed at the distal end thereof will engage with an inner side of the housing portion 136 and locate within one of the notches 137 or serrations.

When the protuberance 134 locates within a particular notch 137, the pawl 132 and thus the spool 127 will become locked to the housing 110, which will prevent the spool 127 from further rotating. This will prevent any further extraction of the tether 300 from the spool 127 and thus result in the tether 300 becoming suddenly taught. However, to reduce the sudden force upon the user, the shock absorber 201 associated with the leash 200 is arrange to absorb at least some of the force by allowing the stitching associated with the folded webbing portion 203, 204.

In particular, the wrapper 208 will first break away from the folded arrangement of the webbing portions 203, 204 and the stitching region 205 located proximate the free ends 200a, 200b of the leash 200 will tear to absorb the energy associated with the fall. Depending on the rate of descent and the weight of the user, subsequent regions 205 of stitches may also tear to further absorb the impact, but owing to the progressive increase in the thickness of the threads associated with each subsequent region 205, further regions 205 of stitches will present more resistance to tearing and thus progressively decelerate the user, rather than simply allowing the leash 200 to become suddenly taught.

It is found that the pawl 134 will locate with the housing portion 136 quickly after a user begins to fall. The rotational speed of the spool 127 is found to reach the threshold rotational speed after the user has only fallen or descended 1-2m. Accordingly, it is anticipated that the impact upon the user caused by the tether 300 becoming taught will be relatively small, since the user will not be travelling at a significant speed. Once the fall of the user has been arrested, the user can then climb back onto the platform or further descend using a ladder (not shown) or similar, in which case, the tension in the tether 300 will be relieved and the pawl 134 will move radially inwardly of the spool 127 under the bias of the extension spring 135 to rotationally unlock the spool 127 from the housing 110. If the user subsequently ascends to the original position or otherwise uncouples the tether 300 from their harness (not shown), then the energy stored within the coil spring 138 will cause the spool 127 to rotate so that the tether 300 becomes wound upon the spool 127 and thus retracted into the housing 110.

In a further embodiment of the invention as illustrated in figure 7 of the drawings, it is envisaged that two or more pulleys 100 may be secured to a leash 200 via an intermediate strap 400 or similar. In this case, while several users may be separately coupled to a pulley 100, each pulley 100 may be coupled to a common anchor point (not shown) by a common leash 200.

Claims

1. A self-braking pulley for controlling a rate of extraction of a tether coupled with the pulley, the pulley comprising a housing and a spool rotatably coupled with the housing, the spool being arranged to receive a tether, the pulley further comprises a braking assembly for applying a braking force to the spool, the braking assembly comprising a braking member rotatably coupled to the spool, the braking member being arranged to engage with the housing in dependence of a rotational speed of the spool.

2. A self-braking pulley according to claim 1, wherein the spool is rotatably coupled with the housing via an axle.

3. A self-braking pulley according to claim 2, wherein the axle comprises longitudinal end portions which are supported within the housing by a respective bearing arrangement.

4. A self-braking pulley according to any preceding claim, wherein the braking member is arranged to engage with a braking portion of the housing.

5. A self-braking pulley according to claim 4, wherein the braking portion is formed integrally with the housing.

6. A self-braking pulley according to claim 5, wherein the braking portion comprises a substantially cylindrical housing portion centred upon a rotational axis of the spool.

7. A self-braking pulley according to claim 6, wherein the housing portion comprises a plurality of notches or serrations formed around an inner side thereof, which are angularly separated around the inner side of the housing portion.

8. A self-braking pulley according to claim 7, wherein the notches or serrations extend longitudinally of the housing portion.

9. A self-braking pulley according to any preceding claim, wherein the braking member comprises a pawl which is rotatably coupled at a proximal end thereof to the spool.

10. A self-braking pulley according to claim 9 as appended to claim 4, wherein a distal end of the pawl is free to move radially of the spool in dependence of a rotational speed of the spool, to engage with the braking portion.

11. A self-braking pulley according to claim 9 as appended claim 4, wherein the pawl is biased away from the braking portion, by a biasing member.

12. A self-braking pulley according to claim 9 as appended to claim 7, wherein the pawl comprises a locating member disposed at the distal end thereof for locating within a notch or serration formed within the housing portion.

13. A self-braking pulley according to any preceding claim, further comprising a swivel secured to the housing for coupling the pulley to an anchor point.

14. A self-braking pulley according to claim 13, wherein the swivel comprises a base which is rigidly secured to the housing and a head which is rotatably coupled to the base.

15. A self-braking pulley according to any preceding claim, further comprising a leash for coupling the pulley to an anchor point.

16. A self-braking pulley according to claim 14 and 15, wherein the head comprises coupling means to facilitate the coupling of the leash thereto.

17. A self-braking pulley according to claim 15, wherein the leash comprises a shock absorbing section disposed intermediate opposite ends thereof, to reduce the shock transmitted to a user when the tether becomes suddenly taught.

18. A self-braking pulley according to any preceding claim wherein the tether is wound upon the spool and is coupled at a proximal end thereof to the spool and a distal end of the tether is arranged to extend out from the pulley via a tether guide.

19. A self-braking pulley according to any preceding claim, further comprising means for enabling the tether to retractably extend from the pulley housing.

20. A self-braking pulley according to claim 19, wherein the means for enabling the tether to retractably extend comprises a coil spring which is coupled at one end to the housing and at the other end to the spool.

21 .A shock absorbing leash for reducing a jolt experienced by a user coupled to the leash when the leash becomes suddenly taught, the leash comprising an elongate body which is folded upon itself about a fold line disposed intermediate opposite longitudinal ends of the body to form a first and second body portion which extend from the fold line, the first and second body portions being stitched together using a thread at a plurality of stitching regions disposed along the body portions, wherein a force required to separate the first and second body portions at the stitching regions by breaking the stitches increases in a direction which is along the body portions, toward the fold line.

22. A shock absorbing leash according to claim 21, wherein the stitches associated with each stitching region conform to a stitching pattern.

23. A shock absorbing leash according to claim 22, wherein the stitching pattern comprises a plurality of rows of stitches which extend across the first and second body portions.

24. A shock absorbing leash according to claim 23, wherein the rows of stitches are joined to form a continuous stitch pattern.

25. A shock absorbing leash according to claim 22, wherein each stitching region comprises the same stitching pattern.

26. A shock absorbing leash according to claim 21, wherein a thickness of the thread associated with each stitching region varies between the stitching regions.

27. A shock absorbing leash according to claim 21, wherein a thickness of the thread associated with the stitching regions increases between the stitching regions, along the body portions, in a direction toward the fold line.

28. A shock absorbing leash according to claim 21, wherein the stitching regions are separated by unstitched regions.

29. A shock absorbing leash according to claim 28, wherein the body portions are foldable upon each other about fold lines disposed within the unstitched regions, to form a folded arrangement of body portions.

30. A shock absorbing leash according to any of claims 29, further comprising a wrapper securable around the body portions, to hold the body portions in the folded arrangement.

31. A shock absorbing leash according to any of claims 21 to 31, further comprising coupling means disposed at the longitudinal ends of the body.