GB2392947A

GB2392947A - A safety clamp for use within a fall arrest system

Info

Publication number: GB2392947A
Application number: GB0220925A
Authority: GB
Inventors: Stephen Murten
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-09-10
Filing date: 2002-09-10
Publication date: 2004-03-17
Anticipated expiration: 2022-09-10
Also published as: GB2392947B; GB0220925D0

Abstract

A safety clamp 11, which in use is clamped around a vertical scaffolding pole 102, comprise a collar section 201 which surrounds the pole and a levered braking means 211. The levered braking means comprises first and second brake arms (302, 303, Fig 3) having first and second brake pads (307, Fig 3), 310 and a central brake arm (306, Fig 3) which is pivoted to the collar section. The first brake pad is pivoted on the first brake arm and located in a brake arm housing 210 of the collar. The levered braking means acts to stop the motion of the safety clamp along the pole in either direction. This is useful in the situation where the pole has buckled and bent over as it stops the safety clamp travelling back up the pole, in direction 602 . An operative (106, Fig 1) is attached to the safety clamp via lanyard (109, Fig 1) and karabiner 110.

Description

Safety Clamp Background of the Invention

1. Field of the Invention

5 The present invention relates to a safety clamp, in particular to a safety clamp for use within a fall arrest system.

2. Description of the Related Art

Safety equipment for use within a variety of fall arrest systems are 10 known. Known personal safety equipment for operatives erecting structures, such as scaffold structures, consists of a safety harness worn by the operative, and a lanyard tethering the safety harness to an anchoring point upon any of the scaffold poles that constitute the scaffold structure. A problem with this system is that to move between anchoring points at 15 different heights, the lanyard must be released from the previous anchoring point, at which point the operative is not provided with any fall protection.

Safety apparatus for the erection of structures is disclosed in international patent publication no. WO 01/27411 in the name of the present applicant. The safety apparatus comprises a safety cable extending between 20 two substantially vertical supports. The supports are configured to be adjustable in length and include releasable fixing means, to enable the height of the safety cable to be adjusted as the structure is being erected.

The safety apparatus is adjustable whilst an operative is connected to the safety cable, thus, an operative can carry out work in safety at substantially 25 all times.

Brief Summary of the Invention

According to a first aspect of the present invention there is provided a safety clamp for use within a fall arrest system in which said clamp in 5 operation is clamped around an elongate support member, wherein said clamp comprises levered braking configured to activate under a force applied to the lever in either direction along the longitudinal axis of the support member.

According to a second aspect of the present invention, there is to provided a safety clamp comprising levered braking means, wherein the levered braking means is a double brake.

Brief Description of the Several Views of the Drawings

The invention will now be described by way of example, with reference to the accompanying drawings of which: Figure 1 shows operatives each connected by a safety clamp embodying the present invention to a scaffold pole constituting part of a scaffold structure; Figure 2 shows an enlarged view of a safety clamp shown in Figure 1, 20 clamped around a scaffold pole; Figure 3 shows an enlarged view of the levered braking means of the safety clamp shown in Figure 2; Figure 4 shows the safety clamp shown in Figure 2 responding to the fall of the connected operative, at a first stage of buckling of the scaffold pole 25 around which the safety clamp is clamped;

Figure 5 shows the safety clamp shown in Figure 2 responding to the fall of the connected operative, at a second subsequent stage of buckling of the scaffold pole around which the safety clamp is clamped; and Figure 6 shows the safety clamp shown in Figure 2 responding to the 5 fall of the connected operative, at a third subsequent stage of buckling of the scaffold pole around which the safety clamp is clamped.

Written Description of the Best Mode for Carrying Out the Invention

Figure 1 to A scaffold structure 101 is shown in Figure 1, having vertical scaffold poles 102, horizontal scaffold poles 103, transversal scaffold poles 104 and flat sections 105. In addition, the scaffold structure 101 may also include diagonal strengthening poles.

In Figure 1, an operative 106 is shown traversing around open trap door 107 in flat section 105. Operative 106 is wearing a safety harness 108, to which a first end of a lanyard 109 is connected. The other end of lanyard 109 is connected to a karabiner 110, which is connected to a safety clamp 111 according to a preferred embodiment of the present invention. Safety clamp 111 is clamped around a vertical scaffold pole 102, thus lanyard 109 no extends between operative 106 and scaffold structure 101. Safety clamp 111 is personal safety equipment, configured to be carried by operative 106, and in operation, configured to be used exclusively by operative 106.

Safety clamp 111 provides a first safety connection for operative 107, and is configured to arrest a fall of operative 106. Karabiner 110 provides a as convenient releasable connection between lanyard 109 and safety clamp 111, thus enabling operative 106 to connect to safety clamp 111 quickly

and easily.

Figure 2 Figure 2 shows an enlarged view of safety clamp 111 in operation, in 5 the closed configuration, clamped around vertical scaffold pole 102. Safety clamp 111 includes a collar 201, comprising a first collar section 202 and a second collar section 203, which can swing relative to each other about a spring loaded hinge 204. Safety clamp 111 also comprises an automatic locking mechanism 205, configured to lock first collar section 202 and to second collar section 203 together, in the closed configuration. Automatic locking system 205 is configured to simplify the installation of safety clamp 111 around a scaffold pole 102, by enabling operative 106 to clamp safety clamp 111 around scaffold pole 102 with a single operation. Automatic locking system 205 is a releasable locking mechanism, to enable safety 15 clamp 111 to be conveniently relocated.

A feature of safety clamp 111 is a handgrip 206, located on second collar section 202, which functions to assist operative 106 in opening first collar section 202 and second collar section 203 apart from each other, for example, when operative 106 is unclamping safety clamp 111 from around 20 scaffold pole 102.

Safety clamp further comprises two adjacent spaced apart positioning plates 207, located on and projecting from the outer surface of first collar section 201. Positioning plates 207 are arranged longitudinally upon first collar section 201, at a first edge of collar 201, and each 25 positioning plate 207 defines an aperture (not shown) configured to receive a pivot bolt 208 therethrough.

Safety clamp 111 also comprises brake arm housing 209 which comprises side walls, a bottom wall and front walling within which a brake arm slot 210 is defined. Brake arm housing 209 is located on, and projects from, first collar section 201, at the other edge of collar 201. Brake arm housing 209 also defines the perimeter of an aperture (not shown) in first collar section 202.

Safety clamp 111 includes levered braking means 211. Preferably, as shown in Figure 2, levered braking means 211 and automatic locking mechanism 205 are located upon collar 201 opposite each other, such that 10 force acting upon lever handle 301, transferred through safety clamp 111, will act through the automatic locking mechanism 205.

Figure 3 Levered braking means 211 is shown in further detail in Figure 3.

1 According to the preferred embodiment of the present invention, levered braking means 211 is substantially shaped as a three pronged fork, having a lever handle 301, a first brake arm 302, a second brake arm 303 and a central brake arm 304. Lever handle 301 defines a connection aperture 305, which provides a means for attaching lanyard 209 to safety clamp 111.

To Preferably, as shown in Figure 2, lanyard 109 is connected to levered braking means 211 by means of karabiner 110, which is configured to be loaded along the spine thereof. In addition, central brake arm 304 defines a central pivot aperture 306 which is also configured to receive a pivot bolt 208 therethrough.

: As shown in Figure 3, first brake arm 302 comprises a first brake pad 307. First brake pad 307 is pivotally attached to the free end of first brake

arm 302, which defines an aperture (not shown). Extending substantially perpendicularly from first brake pad 307 is a connection portion 308, which also defines an aperture (not shown). To assemble first brake pad 307 onto first brake arm 302, a bolt 309 is inserted through the aperture defined by first brake arm 302 and the aperture defined by connection portion 308, and is then secured in position, by for example a nut (not shown). Thus, bolt 309 acts as a pivot for first brake pad 307.

Second brake arm 303 comprises a second brake pad 310. Second brake pad 310 is attached directly to the free end of second brake arm 303.

10 According to an alternative embodiment, second brake pad 310 is pivotally connected to second brake arm 303, as described above with reference to first brake arm 302 and first brake pad 307. Preferably, both first brake pad 307 and second brake pad 310 have a corrugated surface contour 311.

Figure 3 also shows a spring 312, positioned around first brake arm 302.

1 Referring to Figure 2, positioning plates 207 are spaced apart sufficiently to allow the insertion of central brake arm 304 between them.

During assembly of safety clamp 111, a pivot bolt 208 is inserted sequentially through the aperture (not shown) defined in a first positioning plate 207, through central aperture 306 defined in levered braking means go 206 and through the aperture (not shown) defined in the second positioning plate 207. Pivot bolt 208 is then secured in position, by for example a nut (not shown). Thus, pivot bolt 208 functions to connect levered braking means 211 to first collar section 201. In addition, pivot bolt 208 acts as a pivot for levered braking means 206.

:s As shown in Figure 2, levered braking means 206 is connected to and aligned with collar 201 such that first brake arm 302 extends to one

side of central brake arm 304, and slots into brake arm slot 210 of brake arm housing 209 such that first brake pad 307 is located facing the aperture (not shown) defined in first collar section 201, and second brake arm 303 extends to the other side of central brake arm 304, such that second brake 5 pad 310 is located outside the nearest perimeter of collar 201.

Thus, with levered braking means 206 assembled to collar 201 as described above, spring 312, positioned around first brake arm 302, is located within brake arm housing 209. Spring 312 is placed in compression when placed inside brake arm housing 209. Thus, one end of spring 312 10 applies a force against the front walling of brake arm housing 209 and the other end applies a force against first brake pad 307. With the levered arrangement of braking means 211, which is pivoted about pivot bolt 208, first brake pad 307 is pushed into contact with scaffold pole 102 under the action of spring 312. As previously described, preferably both first brake 15 pad 307 and second brake pad 310 have a corrugated surface contour 311.

This feature functions to allow water upon scaffold pole 102, to drain through the brake pad, thus preventing contact between the brake pad and the scaffold pole 102 from being broken by the presence of water between them. 20 The vertical position of safety clamp 111 upon scaffold pole 102 is maintained by the action of spring 312. The degree of contact between first brake pad 307 and scaffold pole 102 under the force of the spring 312, however, allows safety clamp 111 to rotate around scaffold pole 102. Thus, if a force applied to lanyard 109 causes lanyard 109 to change direction, for 25 example when operative 106 moves from a first previous position to a second new position, safety clamp 111 can correspondingly rotate to align

with the new direction of lanyard 109. This is advantageous in reducing cross-loading of lever handle 301 of levered braking means 211, in the event of a fall of operative 106.

Safety clamp 111 is configured such that safety clamp 111 will move 5 up scaffold pole 102, in the direction of arrow 212, under a component of force applied to collar 201, in the direction of arrow 212. Similarly, safety clamp 111 is configured such that safety clamp 111 will move down scaffold pole 102, in the direction of arrow 213, under a component of force applied to collar 201, in the direction of arrow 213. Thus, operative 106 can o conveniently adjust the vertical positioning of safety clamp 111 upon scaffold pole 102 using a single hand.

Levered braking means 211 is configured such that when safety clamp 111 is in operation clamped around scaffold pole 102, levered braking means 211 is configured to activate under a force applied to lever 5 handle 301 in either direction along the longitudinal axis of scaffold pole 102. Referring to Figure 3, with levered braking means 211 pivoted about central pivot aperture 306, a component of force applied to lever arm 301 in the direction of arrow 313 (anti-clockwise) will cause first brake arm 302, and thus first brake pad 307, to advance in the direction of arrow 314 (anti 20 clockwise). Similarly, a component of force applied to lever arm 301 in the direction of arrow 315 (clockwise) will cause second brake arm 303, and thus second brake pad 310, to advance in the direction of arrow 316 (clockwise). First brake pad 307 and second brake pad 310 each provide a braking contact region. A braking contact region is a region which, when in 25 contact with the support member upon which the safety clamp 111 is mounted, will provide a means of braking the safety clamp 111. Preferably,

l l Ale as shown in Figure 3, levered braking means 211 is a double brake, configured to provide more than one braking contact region.

Levered braking means 211 is configured to prevent the safety clamp 111 from travelling in either direction along the longitudinal axis of 5 the scaffold pole 102, under a component of force applied to the lever handle 301.

Figure 4 As shown in Figure 4, operative 106 has fallen from flat section 105 of to scaffold structure 101, under the action of gravity, in the direction of arrow 401. The fall of operative 106 is arrested by safety clamp 111, which is clamped around vertical scaffold pole 102.

As previously described, a first end of lanyard 109 is connected to the safety harness 108 worn by operative 106, and the other end of lanyard 109 15 iS connected to karabiner 110, which in turn is connected to levered braking means 211 of safety clamp 111. Thus, at the end of the fall, operative 106 is suspended from scaffold pole 102, by means of safety clamp 111, karabiner 110, lanyard 109 and safety harness 108. In this way, operative 106 is supported by scaffold pole 102.

20 At the end of the fall, the force applied to lanyard 109 by the weight of operative 106 causes lanyard 109 to become taut, resulting in the transfer of the force through karabiner 110 to lever handle 301 of levered braking means 211. The component of force applied in the direction of arrow 401 (anti 25 clockwise) upon lever handle 301, activates levered braking means 211 such that first brake arm 302 is advanced in the direction of arrow 402 (anti

clockwise). Thus, a component of force applied to lever handle 301, in the direction of arrow 401 or arrow 402 (anti-clockwise) causes levered braking means 211 to respond by forcing first brake pad 307 further into contact with scaffold pole 102. With this arrangement, an increase in the component of 5 force applied to lever handle 301, in the direction of arrow 401 or arrow 402 (anti-clockwise), will increase the force with which first brake pad 307 is pushed, in the direction of arrow 402, against scaffold pole 102. The contact between first brake pad 307 and scaffold pole 102 inhibits safety clamp 111 from travelling along scaffold pole 102, in the direction of arrow 403, under a 10 component of force applied, in the direction of arrow 401 or arrow 402 (anti clockwise) , to lever handle 301.

As previously described, following a fall, operative 106 is supported by scaffold pole 102, which is a tubular, elongate member. Figure 4 shows that vertical scaffold pole 102 is braced at the level of flat section 105, by 15 means of brace 404, with the free end of vertical scaffold pole 102 located above the level of flat section 105. As shown in Figures 1 and 4, safety clamp 111 is located on the section 405 of scaffold pole 102 between the free end of scaffold pole 102 and brace 404.

As can be seen from Figure 4, scaffold pole 102 has buckled at 20 buckle point 406, above brace 404, such the free end of scaffold pole 102 has moved in the direction of arrow 401. This first stage of buckling is a result of the force acting on scaffold pole 102, in the direction of arrow 401, due to the weight of fallen operative 106. In the first stage of buckling, the free end of scaffold pole 102 has moved in the direction of arrow 401, such 25 that the section of scaffold pole 102 extending between the free end of scaffold pole 102 and buckle point 406 becomes orientated along a

negative gradient, above horizontal scaffold pole 103. Correspondingly, collar 201 of safety clamp 111 is orientated along a negative gradient.

According to this orientation, and as described above, first brake pad 307 functions to arrest the fail of operative 106. As previously described, first brake pad 307 is pivoted with respect to first brake arm 302, to increase the contact area between the outer surface of first brake pad 307 and the scaffold pole 102.

It can be seen from Figure 4 that, according to the present described embodiment of the present invention, when first brake pad 307 is in contact to with scaffold pole 102, there is no contact between second brake pad 310 and scaffold pole 102.

Figure 5 Figure 5 shows scaffold pole 102 at a second subsequent stage of s buckling about buckle point 406. The buckling of scaffold pole 102 is a result of the force acting on scaffold pole 102 in the direction of arrow 401, due to the weight of fallen operative 106.

It can be seen from Figure 5, that in the second stage of buckling, the free end of scaffold pole 102 has moved further in the direction of arrow JO 401, such that the section of scaffold pole 102 extending between the free end of scaffold pole 102 and buckle point 406 is orientated substantially horizontal. With this orientation, collar 201 of safety clamp 111 is correspondingly substantially horizontal, and lever handle 301 of levered braking means 211 is orientated substantially vertically. Thus, the 25 component of force acting on lever handle 301 of levered braking means 211, in the direction of arrow 401, due to the weight of fallen operative 106,

causes first brake arm 302 and second brake arm 303 to balance about pivot bolt 208. As a result, contact between first brake pad 307 and scaffold pole 102 can be lost. Consequently, operative 106 is supported by means of the safety clamp 111 resting upon scaffold pole 102. However, a 5 component of force acting in the direction of arrow 501 (anti- clockwise) upon lever handle 301, will cause first brake pad 307 to be applied to scaffold pole 102. Similarly, a component of force acting in the direction of arrow 502 (clockwise) upon lever handle 301, will cause second brake pad 310 to be applied to scaffold pole 102.

Figure 6 This operation of safety clamp 111 is illustrated further in Figure 6, which shows scaffold pole 102 at a third subsequent stage of buckling about buckle point 406. The buckling of scaffold pole 102 is a result of the 15 force acting on scaffold pole 102 in the direction of arrow 401, due to the weight of fallen operative 106. In the third stage of buckling, the free end of scaffold pole 102 has moved further in the direction of arrow 401, such that the section of scaffold pole 102 extending between the free end of scaffold pole 102 and buckle point 406 becomes orientated along a positive 20 gradient. Correspondingly, collar 201 of safety clamp 111 is orientated along a positive gradient.

The component of force applied in the direction of arrow 401 (clockwise) upon lever handle 301, activates levered braking means 211 such that second brake arm 303 is advanced in the direction of arrow 601 25 (clockwise). Thus, a component of force applied to lever handle 301, in the direction of arrow 401 or arrow 601 (clockwise) causes levered braking

means 211 to respond by forcing second brake pad 310 into contact with scaffold pole 102. It can be seen from Figure 6 that, according to the described embodiment of the present invention, when first brake pad 307 is in contact with scaffold pole 102, there is no contact between second brake pad 310 and scaffold pole 102.

The contact between second brake pad 310 and scaffold pole 102 prevents safety clamp 111 from travailing along scaffold pole 102, in the direction of arrow 602, under a component of force applied, in the direction of arrow 401 or arrow 601 (clockwise), to lever handle 301. This feature to functions to prevent the safety clamp 111 from travailing in the direction of arrow 602, towards the free end of scaffold pole 102, preventing safety clamp 111 from falling off free end of scaffold pole 102, thus preventing operative 106 from falling from scaffold pole 102, and therefore from scaffold structure 101. 5 Levered braking means 211 is configured to activate to prevent the safety clamp 111 from travailing in either direction along the longitudinal axis of the scaffold pole 102, under a component of force applied to the lever handle 301 in either direction along the longitudinal axis of the scaffold pole 102. According to the present described embodiment of the no present invention, if operative 106 is swinging in mid air, for example as a result of movement of the scaffold pole 102 under the weight of fallen operative 106, the application of the first brake pad 307 and the second brake pad 310 to scaffold pole 102 would alternate, according to the oscillation of the swing.

According to an alternative embodiment of the present invention, safety clamp 111 comprises a fall arrest webbing (not shown) connected to

lever handle 301. To assemble the webbing to safety clamp 111, a first end of the webbing is passed through connection aperture 305, doubled back upon itself and stitched together. The other end of the webbing can be connected to safety harness 108 worn by operative 106, by means of a 5 karabiner, such as karabiner 110. The webbing comprises a rip stitch energy absorbing length, which is preferably concertinaed and stitched into a protective cover. The stitching is configured to break in the event of a fall of operative 106, to release the energy absorbing length. This action functions to reduce the fall arrest forces, and to control the deceleration o distance. Safety clamp 111 is suitable for use in a fall restraint system. Fall restraint systems are configured to prevent operatives from falling.

Referring to Figure 1, which illustrates a fall arrest system, operative 106 is able to reach at least one edge of flat section 105 of scaffold structure 101.

5 According to a fall restraint system, operative 106 would not be able to reach an edge of flat section 105. Thus, the risk of operative 106 falling from flat section 105 is reduced. A way of achieving such a system is to reduce the length of lanyard 109, which extends between safety clamp 111 and operative 106. Alternatively, if a fall restraint lanyard is used, which has 20 a plurality of connection points along the length thereof, operative 106 could connect to a connection point closer to the safety clamp 111, thus reducing the effective length of the fall restraint lanyard. In addition, there is an inverse relationship between the height at which safety clamp 111 is located upon a scaffold pole 102, relative to the level of flat section 105 25 upon which operative 106 is standing, and the distance operative 106 can walk upon flat section 105 from the scaffold pole 102. Furthermore, with a

fixed length lanyard 109, the distance that operative 106 could fall from flat section 105 is reduced as the height of safety clamp 111 upon scaffold pole 102 is increased. Thus, increasing the height of safety clamp 111 relative to operative 106 can increase the level of safety provided by using safety 5 clamp 111 within a fall arrest or a fall restraint system.

Claims

Omr - Claims

1. A safety clamp for use within a fall arrest system in which said clamp in operation is clamped around an elongate support member, 5 wherein said clamp comprises levered braking means configured to activate under a force applied to the lever in either direction along the longitudinal axis of the support member.

2. A safety clamp according to claim 1, wherein said levered 0 braking means is a double brake.

3. A safety clamp according to claim 2, wherein said safety clamp comprises a collar, said double brake comprises a central brake arm disposed between a first brake arm and a second brake arm, and said central brake arm is pivotally connected to said collar.

4. A safety clamp according to claim 3, wherein said first brake arm comprises a first brake contact region at the free end thereof, and said second brake arm comprises a second brake pad at the free end thereof.

5. A safety clamp according to claim 4, wherein at least one of said first and second brake pads is pivotally connected to a brake arm.

6. A safety clamp according to claim 4 or claim 5, comprising as resilient means configured to provide, in operation, a degree of contact between one of said first and second brake pads and said elongate support

member.

7. A safety clamp according to any of claims 4 to 6, wherein at least one of said first and second brake pads has a corrugated contour.

8. A safety clamp according to any preceding claim, wherein said levered braking means defines a connection aperture.

9. A safety clamp comprising levered braking means 10 substantially as herein described with reference to and as shown in Figures 1-6.