GB2428731A

GB2428731A - Safety anchor

Info

Publication number: GB2428731A
Application number: GB0516056A
Authority: GB
Inventors: Ian Perry; John Rollason; Graham Martin; Owen Morris
Original assignee: PRO NET UK Ltd
Current assignee: PRO NET UK Ltd
Priority date: 2005-08-04
Filing date: 2005-08-04
Publication date: 2007-02-07
Also published as: GB0516056D0

Abstract

A safety anchor (10) comprises a C-shaped bracket (12), a cam (14), pivoted at the end of a bottom leg of the bracket about a clamp axis (16). The cam has a clamp-part (54) and a hook-part (58). The cam is spring biased about the clamp axis to close the mouth (100) of the anchor. A hook (18) is pivoted about a hook axis (20) on said hook part of the cam. A rope (106) hooked in the hook (18) is prevented from escaping by first flange (56), although its release can be achieved by pivoting the hook over lug flange (58) to open the hook's mouth (68).

Description

I

Safety Anchor This invention relates to anchors for use on building constructions for the attachment of safety nets and ropes.

BACKGROUND

EP-A-1124027 discloses an adjustable anchor for attachment to the underside of an I-shaped girder. It comprises two hook-clamps latching onto each bottom edge of the girder with a strap adjusting the distance between them for the purpose of initial attachment and clamping of the clamps to the girder, as well as to accommodate girders of different size. The hook-clamps have depending hooks on which ropes of a safety net may be hitched. A problem with the arrangement is that the hooks face each other and make attachment of ropes to both hooks simultaneously almost impossible. This is especially the case on the, increasingly common, narrow girder type, where the two facing hooks physically interfere with one another. Moreover, there is nothing to prevent ropes from becoming detached on a windy day when nets tend to behave like billowing sails and when conditions on a building construction site are most likely to lead to an unintended fall. Indeed, once the "pull" of the net is removed from the smaller hooks their larger attached semi circular plate hooks easily slip backwards and fall off the girders all together. Moreover, the attachment depends on the strap and how tight it is connected. Over time, it is feasible for the strap to loosen and the anchorage to lose.

It is an object of the present invention to provide an anchor which does not suffer from, or at least mitigates the effects of, the aforementioned disadvantages.

BRIEF SUMMARY OF THE DISCLOSURE

In accordance with the present invention, there is provided an anchor comprising: a C- shaped bracket having a top leg, a bottom leg and a back leg defining a swing plane, which swing plane is, in normal use of the anchor, arranged vertically; a cam pivoted at the end of the bottom leg about a clamp axis perpendicular the swing plane, which cam has a clamp-part and a hook-part, the clamp pivot being between said parts, the cam being spring biased about said clamp pivot to close a gap between the clamp-part and said top leg; and a hook pivoted about a hook axis on said hook part of the cam.

In use, the top leg of the C-shaped bracket engages a top surface of the bottom flange of an I-shaped beam or girder. The back leg abuts the edge of the flange, and the bottom leg is separated by a variable distance from a bottom surface of the flange, the distance depending on the thickness of the flange. It goes without saying that the anchor is designed to fit a number of typical girder sizes and it may be that the back leg does not abut the flange edge before the top leg engages the web of the girder. This is not preferred and if the flange is too short, the anchor cannot be used with reliability.

Likewise, the anchor cannot be used on girders having flanges which are too thick to fit between the top and bottom legs. However, the anchor can be designed to fit most girders used in typical building constructions, and can be provided in different sizes to fit other less typical sizes of girders, for example, even circular scaffolding tube.

The spring of the anchor cam biases the clamp-part towards the bottom surface of the flange. Preferably, the clamp-part is provided with a serrated surface. This grips the bottom surface of the flange and holds the anchor on the girder. However, it is only when force is applied to the cam by weight being hung on the hook that the clamping force on the girder becomes strong. This is by virtue of the leverage applied by the weight, the clamp axis forming a fulcrum. Indeed, it is intended that a safety net be hung on the hook and so the strength of connection of the anchor to the girder maximises as the load hung from the hook also maximises.

Preferably, the cam is a plastics moulding over a sheet metal skeleton. The skeleton preferably includes an eye around said clamp axis. The skeleton preferably includes notch in its edge around said clamp axis, a corresponding notch also being formed in said moulding. Preferably, slots are formed in said moulding on either side of an open mouth of said notches, whereby tabs may be inserted in said slots to close said notches, thereby trapping and holding the formed hook into the cam. Alternatively, the cam could comprise a casting or forging.

Preferably, said hook comprises a closed ring rod-steel bent and folded into a hook shape. The ring is preferably folded a first time about a first-fold axis comprising a diameter of said ring until two sides on either side of the fold are parallel, and a second fold intermediate the first fold about a second-fold axis orthogonal said first-fold axis.

Preferably, said first fold forms a hinge and a lip of the hook, and said second fold forms a pair of hinge-legs and a pair of lip-legs of the hook, the radius of curvature of said first fold being more than half the thickness of said moulding so that, when said hinge is received in said notches, the hinge-legs depend on either side of said moulding, said hinge- and lip-legs being arranged parallel said swing axis. Preferably, the radius of curvature of the second fold is substantially the same as that of the first fold, said legs being inclined towards one another. Preferably, said lip-legs are kinked in said swing plane near the lip to open a mouth of the hook between said hinge and lip.

Although reference is made to "folding", this is not to be understood as limited to a product, for example, a bar, being worked by bending and folding into the shape described. Rather it is to be understood as descriptive of the final result, regardless of how the shape is actually achieved.

Nevertheless, said hook preferably comprises a bar that has been bent into the shape defined above and the ends welded to form a continuous ring.

Preferably, said cam includes a tail extending beyond said hook axis, said lip defining an arc of rotation about said hook axis when the hook is pivoted about said axis, said tail closing said mouth in most rotational positions of the hook with respect to the cam except in at least one open position. Preferably, said open position is where tension on the hook in a direction away from said hook axis applies a torque greater than zero on said cam about said clamp axis opposite to said spring bias.

Preferably, a lug is provided on the tail to engage said lip and resist rotation of the hook to said open position.

Furthermore, preferably, the hook is prevented from opening so far that it is opened (whereby net or like ropes retained by the hook might and accidentally release or drop off) by two protruding stop-lugs positioned on ether side of the cam that limit the pivot of the hook. Preferably, said limit corresponds with the lip of the hook just reaching the end of said tail.

Preferably, said cam and bottom leg define a notch between them to receive temporarily ropes of a safety net to be engaged with the anchor, said cam having a protrusion over which said ropes pass to enter said mouth of the hook.

Preferably, said bracket comprises at least first second and third elements punched from sheet metal, said first and second elements forming side elements and said third element being between said side elements and connecting them together. Preferably, said first and second elements are parallel and said third element is orthogonal to said side elements.

Alternatively, said bracket may comprise a casting, for example of aluminium. In this event, the casting is preferably two separate castings connected together side by side.

They may be arranged to interlock through a series of corresponding lugs and notches, and the two parts bolted together. This split arrangement not only facilitates assembly but also allows the carriage to have two perfectly parallel draft free sides between which the cam is positioned.

Preferably, a spring lever is mounted in said bracket to lock the cam in a rotational position, ratchet latches being formed on the cam and engaged by the lever permitting rotation of the cam to close said gap between the clamp-part and said top leg. The anchor has front and rear sides, the front side being defined by said gap. Preferably, said lever is arranged to be accessible by a human thumb whose hand is grasping the anchor with fingers around the front side of said cam and thumb behind said bracket, whereby said gap may be opened by the thumb actuating said lever and the user squeezing said cam and bracket together to pivot them with respect to one another about said clamp axis.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are further described hereinafter, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a front perspective view of a safety anchor in accordance with the present invention; Figure 2 is a rear perspective view of the safety anchor of Figure 1; Figures 3a, b and c are, respectively, a side view of a skeleton of a cam of the safety anchor of Figures 1 and 2, a side view of the cam, and a section on the line C-C in Figure 3b; Figures 4a and b are, respectively, a side view of the safety anchor of Figure 1 being connected to a girder, and a detail of element B in Figure 4a; Figures 5a, b and c are side views of the anchor of Figure 1 on a girder in various stages of having a rope attached; and Figures 6a and b are front perspective and rear perspective views respectively of a further embodiment of a safety anchor in accordance with the present invention.

DETAILED DESCRIPTION

In the drawings, a safety anchor 10 according to the invention comprises a bracket 12 pivoted to a cam 14 about a clamp axis 16. A hook 18 is pivoted in the cam 14 about a hook axis 20.

The bracket 12 comprises a top leg 22 a rear leg 24 and a bottom leg 26. The bracket is constructed from two sheet metal, C-shaped elements 28 spot welded to an L shaped sheet metal intermediate element 30. A gusset 32 and pins 34 reinforce the construction. The parts are held together by spot welding, as at 36.

Cam 14 comprises a plastics moulding of, for example, nylon or other self lubricating polymer over-moulded onto a sheet metal skeleton 38 (see Figure 3a) to give strength.

Skeleton 38 has an eye 40 that coincides with clamp pivot axis 16. It is also provided with a recess 42 coinciding hook axis 20. Various notches 44 and eyes 46 lock the skeleton 38 firmly within it's over moulding. Apertures 48 permit pins (not shown) to support the skeleton 38 with in the mould (not shown). Within eye 40 a boss 87 is moulded in the cam 14; within recess 42, a notch 120 is moulded Cam 14 has two ends, a clamp end 50 and a tail end 52. The clamp end 50 is provided with a serrated edge 54. Intermediate the two ends, more or less on a line between them, are the clamp axis 16 and hook axis 20. The tail end 52 has a first flange 56 which is formed as an arc centered on the hinge axis 20. A second lugflange 58 is at a greater distance from the axis 20 than the first flange 56. Finally, a third stop-flange 60 is provided, as further explained below.

Hook 18 is a loop of steel whose ends are welded together. It can be considered as fabricated from a circular ring. Firstly folded about a diameter of the ring forming two semi-circles connected at their ends 64, 66. Next, the semi-circles are straightened, and then folded about an axis 62 intermediate the ends, so that the ends 64, 66 approach one another forming a mouth 68 of the hook 18. Thus the hook 18 comprises hinge-legs 72 extending from hinge end 64 of the hook 18, and lip-legs 74 adjacent the end 66, which forms a lip of the mouth 68. End 70 formed by the bend about axis 62 forms the base or cup of the hook 18. Lip-leg 74 is inclined towards hinge-leg 72, but is kinked outwardly at 75 near its end to flair mouth 68 and form a shepherd's crook shape for the hook 18.

The radius of curvature of the ends 64, 66 is arranged to be slightly larger than half the thickness of the cam 14. This ensures that there is room between the hook legs 72 for the tail end 52 of the cam to pass. Indeed, the hinge end 64 of the hook is a snap fit into the notch 120 formed around the notch 42 of the skeleton 38. When all assembled, the bracket 12, cam 14 and hook 18, all lie in a common swing plane (comprising the plane of the drawings shown in Figures 4 and 5) with the cam 14 being pivotable with respect to both the bracket and hook about said parallel axes 16, 20,both being orthogonal to the swing plane.

In order to retain the hook 18 in engagement with the notch 120, slots 122, 124 are formed in either side of the moulding 14, both above and below the notch 120. Two tabs 126 are a tight sliding fit in the slots 122, 124, the tabs 126 bridging the mouth of the notch 120 and preventing the hook from unintentionally escaping.

The pivot 16 is formed by a bolt 76 passing through holes (not visible in the drawings) in the bottom leg 26 of the bracket 12, and the boss 87. A nut 78 secures the connection.

However, a narrow slit 80 is formed on both sides of the bracket 12 and, in an annular space 82 on either side of the boss 87, a spring 86 (only one being shown in Figure 3c) is disposed. One end of the spring 86 is in one of four bores 88 through the boss 87 of the moulding 14, the other end being retained in the slit 80. As a consequence, the cam can be given a positional bias so that it is pressed towards the position shown in Figures I and 2. The degree of bias can be adjusted according to in which hole 88 around the boss 87 the end of each spring is retained. Pivoting the bracket clockwise with respect to the cam (in the orientation shown in the drawings) against the spring bias opens the mouth 100 formed between the serrated surface 54 of the cam 14 and the top leg 22 of the bracket 12.

In use, the anchor 10 is grasped in a pistol-grip type of hold by the user's hand, as shown in Figure 4a and b. The user's fore fingers encircling a scalloped recess 57 formed on the front edge of the cam 14. The heel of the user's hand abuts the tail end 52, while the thumb is positioned between pins 34. Here, a lever 90 is positioned to be actuated (against a spring bias, not shown) to disengage the lever from a series of ratchet-latches 92 formed on the cam 14. When disengaged, the bracket 12 can be pivoted clockwise by the user's thumb pressing on the lower pin 34 and pulling back on the scalloped area 57 of the cam 14. When released, the spring bias provided by spring 86 returns the bracket in an anti clockwise direction.

Thus, as shown in Figure 4a, when opened, the mouth 100 can be inserted over a bottom flange 102 of a girder 104. When the user's grip is released, the spring bias presses the serrated surface 54 into engagement with the lower surface of the girder flange 102.

Turning to Figures 5a, b and c, once connected as shown in Figure 4a, a rope 106 of a safety netting (not shown) maybe hooked over the tail end 52 of the cam 14 into a V- notch 101 between the back of the bracket 12 and the cam 14. In this arrangement, it is envisaged that the tension in the rope 106, and attached safety netting, is in the direction of the arrow X in Figure 5a. The tension in the rope 106 already pivots the cam 14 about axis 20. However, the hook 18 is, at this point, pivoted in an anti clockwise direction about the axis 20. Since the lip 66 is centered on the axis 20, it follows the profile of the first flange 56 of the tail end 52. Therefore, the mouth 68 of the hook 18 is closed.

However, when the hook is in the position shown in Figure 5a, the lip 66 abuts lug-flange 58, which inhibits further movement without deliberate action, deforming temporarily the hook 18. Once over the lug-flange 58, the hook 18 is freely pivotable until the lip 66 abuts the back of the bracket 12. Now, the rope 106 is pressed backwardly towards the mouth 68 and over retaining stop-lug 60 and into hook 18, moving in the direction of the arrowZin Figure5b.

Finally, once the rope is released in this position, it pivots the hook 18 back over the lug 58 pulling the whole arrangement taut as shown in Figure 5c. Here, the direction of pull on the hook 18, acting on the base of notch 120, pivots the cam 14 with maximum torque about axis 20, pressing tightly the serrated face 54 toward top leg 22, squeezing the girder flange 102 between them.

On the other hand, in the position shown in Figure 5b, in which the mouth 68 is relatively open, any pull on the hook 18 in the direction of the arrow Z serves, if anything, to open the mouth 100. Since it is not intended that this situation would ever be implemented, it is towards this orientation that the mouth 100 opens allowing rope 106 to be detached from the hook 18. Otherwise, the mouth 100 is permanently closed so that, even if by some chance the anchor 10 should become disconnected from the girder 104, the anchor 10 will be unlikely to become disconnected from the rope 106 and thus itself present a falling hazard.

Of course, should safety netting be required on both sides of the girder 104, it is simply a matter of attaching another anchor 10 on the other flange 105 of the girder 104. The second anchor should be at some distance along the girder form the first, so that they do not get in each other's way when ropes are hooked over their respective hooks.

Turning to Figures 6a and b, a preferred embodiment of a safety anchor 10' in accordance with the present invention is shown. Here, the bracket 12' is an aluminium casting in two, mirror image parts 12a,b, split along the swing plane of the cam 14' and hook 18 (see split line I 2c in Figure 6b). The two parts include mutually engaging lugs and slots (not shown) which interlock when the parts 12a,b are mated together. To create the single integral unit 12', therefore, it is only necessary to prevent the two parts from separating by the use of two bolts 13.

To protect the paintwork on girders, to which the anchor is attached, a rubber boot 175 is provided which is fitted over a flange 177 seen in the drawings protruding from the end of the boot 175. Notches (not shown) may be provided in the flange 177 (and corresponding lugs in the boot 175) to lock the boot on the flange and prevent it slipping off. The boot not only prevents metal-to-metal contact between the face (le top leg 22') of the bracket 12' and the girder 104, but it also extends around onto rear leg 24' protecting also the edge of the girder. This may be important where girders are assembled pre-painted and it is not intended to repaint them or otherwise provide further corrosion protection.

Finally, stop lugs 179 are provided on this embodiment of the cam 14', to prevent excessive swing of the hook 18. Excessive swing (in the clockwise direction of the drawings, could take the nose 66 of the hook 18 beyond the end of the wing 56, and thereby open the hook and allow what it retains to drop off.

Of course, both the bootl75 and stop lugs 179 could be provided in the embodiments of Figures 1 to 5 described above.

It is very much preferred, for the reasons described above, that the hook 18 be pivoted to the cam 14,14'; for example, this enables the hook to be opened and closed by its pivotal position. However, it should be understood that this pivoting is not necessarily essential. Instead, it would be feasible, without departing from the spirit of the present invention, to form the hook integrally with the cam 14,14'. Thus the present invention also provides an anchor comprising: a C-shaped bracket, having a top leg, a bottom leg and a back leg defining a swing plane, which swing plane is, in normal use of the anchor, arranged vertically; and a cam, pivoted at the end of the bottom leg about a clamp axis perpendicular the swing plane, which cam has a clamp-part and a hook-part, the clamp axis being between said parts, and the cam being spring biased about said clamp pivot to close a gap between the clamp-part and said top leg, a hook being formed on the hook-part of the cam.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", means "including but not limited to", and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

Claims

1. An anchor comprising: a C-shaped bracket, having a top leg, a bottom leg and a back leg defining a swing plane, which swing plane is, in normal use of the anchor, arranged vertically; a cam, pivoted at the end of the bottom leg about a clamp axis perpendicular the swing plane, which cam has a clamp-part and a hook-part, the clamp axis being between said parts, and the cam being spring biased about said clamp pivot to close a gap between the clamp-part and said top leg; and a hook, having a mouth and pivoted about a hook axis on said hook part of the cam.

2. An anchor as claimed in claim 1, in which the clamp-part is provided with a serrated surface.

3. An anchor as claimed in claim I or 2, in which the cam is a plastics moulding over a sheet metal skeleton.

4. An anchor as claimed in claim 3, in which the skeleton includes an eye around said clamp axis.

5. An anchor as claimed in claim 3 or 4, in which the skeleton includes a notch in its edge around said clamp axis, a corresponding notch also being formed in said moulding.

6. An anchor as claimed in claim 5, in which slots are formed in said moulding on either side of an open mouth of said notches, whereby tabs inserted in said slots close said notches.

7. An anchor as claimed in any preceding claim 1, in which said hook comprises a closed ring folded into a hook shape.

8. An anchor as claimed in claim 7, in which the ring is folded a first time about a first-fold axis comprising a diameter of said ring until two sides on either side of the fold are parallel, and a second fold intermediate the first fold about a second-fold axis orthogonal said first-fold axis.

9. An anchor as claimed in claim 8, in which said first fold forms a hinge and a lip of the hook, and said second fold forms a pair of hinge- legs and a pair of lip-legs of the hook, the radius of curvature of said first fold being more than half the thickness of said moulding so that, when said hinge is received in said notches, the hinge-legs depend on either side of said moulding, said hinge- and lip-legs being arranged parallel said swing plane.

10. An anchor as claimed in claim 9, in which the radius of curvature of the second fold is substantially the same as that of the first fold, said legs being inclined towards one another.

11. An anchor as claimed in claim 9 or 10, in which said lip-legs are kinked in said swing plane near the lip to open said mouth of the hook between said hinge and lip.

12. An anchor as claimed in any of claims 7 to 11, in which said hook comprises a bar that has been bent into shape and the ends welded to form a continuous ring.

13. An anchor as claimed in any preceding claim, in which said cam includes a tail extending beyond said hook axis, said lip defining an arc of rotation about said hook axis when the hook is pivoted about said axis, said tail including a first flange closing said mouth in most rotational positions of the hook with respect to the cam except in at least one open position.

14. An anchor as claimed in claim 13, in which said open position is where tension on the hook in a direction away from said hook axis applies a torque greater than zero on said cam about said clamp axis opposite to said spring bias.

15. An anchor as claimed in claim 14, in which a lug-flange is provided on the tail to engage said lip and resist rotation of the hook to said open position.

16. An anchor as claimed in any preceding claim, in which said cam and bottom leg define a V-notch between them to receive temporarily ropes of a safety net to be engaged with the anchor, said cam having a protrusionflange over which said ropes pass to enter said mouth of the hook.

17. An anchor as claimed in any preceding claim, in which, said bracket comprises at least first, second and third elements punched from sheet metal, said first and second elements forming side elements and said third element being between said side elements and connecting them together.

18. An anchor as claimed in claim 17, in which said first and second elements are parallel and said third element is orthogonal to said side elements.

19. An anchor as claimed in any of claims I to 16, in which said bracket comprises a casting, for example of aluminium.

20. An anchor as claimed in any preceding claim, in which a spring lever is mounted in said bracket to lock the cam in a rotational position, ratchet latches being formed on the cam and engaged by the lever permitting rotation of the cam to close said gap between the clamp-part and said top leg.

21. An anchor as claimed in claim 20, the anchor having front and rear sides, the front side being defined by said gap, wherein said lever is arranged to be accessible by a human thumb whose hand is grasping the anchor with fingers around the front side of said cam and thumb behind said bracket, whereby said gap may be opened by the thumb actuating said lever and the user squeezing said cam and bracket together to pivot them with respect to one another about said clamp axis.

22. An anchor comprising: a C-shaped bracket, having a top leg, a bottom leg and a back leg defining a swing plane, which swing plane is, in normal use of the anchor, arranged vertically; and a cam, pivoted at the end of the bottom leg about a clamp axis perpendicular the swing plane, which cam has a clamp-part and a hook-part, the clamp axis being between said parts, and the cam being spring biased about said clamp pivot to close a gap between the clamp-part and said top leg, a hook being formed on the hook-part of the cam.

23. A safety anchor for use with construction girders, substantially as hereinbefore described with reference to the accompanying drawings.