WO1992007199A1

WO1992007199A1 - Safety lifting hook

Info

Publication number: WO1992007199A1
Application number: PCT/SE1991/000687
Authority: WO
Inventors: Rolf BERGSTRÖM
Original assignee: Gunnebo Lifting Ab
Priority date: 1990-10-12
Filing date: 1991-10-11
Publication date: 1992-04-30
Also published as: SE9003268D0

Abstract

The present invention relates to a lifting hook having a locking mechanism which functions to latch a barrier arm (16) in a position in which the arm closes the hook opening. According to the invention, the safety hook includes an additional latching element (34) which functions to lock the locking mechanism (20) in its locking state.

Description

SAFETY LIFTING HOOK

The present invention relates to a safety-lifting hook of the kind which includes a hook element provided with an opening, a two-arm lever element which is connected pivotally to the hook element by means of a pivot shaft in a manner such that when the lifting hook is subjected to load, one arm of the lever element forms a barrier which automatically closes the opening of said hook element while the other arm forms a suspension element by means of which the hook can be coupled to a hook supporting device, such as rope, chain or the like, and further includes a locking element which is journalled on the hook element and which is biased towards a posi¬ tion in which it is in locking engagement with the lever element so as to lock the barrier arm in its hook- opening closing position.

Lifting hooks of this kind are known to the art and, because of their self-locking function when subjected to load and because of the locking mechanism which holds the barrier arm locked in its closed position irrespec¬ tive of whether the load is then relieved or not, afford a high degree of safety in the event of unintentional release of load-carrying lines or lifting chains from the hook, such unintentional release being liable to cause accident or injury to those in the vicinity. Despite this positive safety function, however, there is a risk, although a very small risk, in certain extreme situations that the locking mechanism may be uninten¬ tionally released with subsequent opening of the barrier arm, so as to enable the load-carrying line to move out of engagement with the hook. This may occur, for in- stance, when the hook is temporarily relieved of load during a lifting operation and adopts an unfavourable

SUBSTITUTE SHEET ISA/SE position while, at the same time, the release part of the lock mechanism is struck by an external object in a manner which causes the barrier arm to swing-out and expose the hook opening, with the possible release of the load-carrying line as a result.

An object of the present invention is to eliminate such risk situations, or to render such situations almost impossible. In its widest aspect, the present invention solves this problem by coordinating with the locking element a latching element which, in a first position, functions to prevent the locking element from leaving its position of locking engagement with the lever ele¬ ment, and in a second position functions to permit the locking element to move to a free position in which the barrier arm is able to expose the opening in the hook element when the lifting hook is relieved of load. Thus, in accordance with the concept of this solution, it is proposed that the barrier arm which in one posi- tion latches the locking element has, in turn, a latch¬ ing element which is so constructed as to necessitate first moving the latching element away from its first, latching position to its second, non-latching position before it is possible to bring the locking element to a position in which the barrier arm can be released.

In the case of a lifting hook in which the locking element has the form of a catch which is pivotally mounted in a groove in the hook element and has engage- ment means for engagement with a complementary engage¬ ment means on the lever element, and an operating part onto which a force can be applied so as to pivot the catch away from its position of engagement with the lever element against the action of a spring force, the latching element, in accordance with one suitable em¬ bodiment of the invention, has the form of a pin which can be moved axially generally parallel with the pivot shaft about which the catch pivots, so as to engage the hook element in said first position in a manner to prevent pivotal movement of the catch. This requires the latching element to be moved generally perpendicular to the pivotal plane of the locking catch. This mini¬ mizes the risk of unintentional release of the locking catch.

The pin is preferably spring-biased towards its first, catch-locking position, in which it abuts an outer wall of the hook element. In its second, catch-release position, one end surface of the pin will suitable abut one side wall of the groove.

Similarly, in the case of a lifting hook in which the locking element has the form of a catch which is pivot- ally mounted in a groove provided in the hook element and has engagement means for engaging a complementary engagement means on the lever element and an operating part onto which a force can be applied so as to swing the catch away from its position of engagement with the lever element against the action of a spring force, the latching element, in accordance with another embodiment of the invention, has a part which, in the first posi¬ tion of said latching element, fills a space between the catch and a bottom wall of the groove, wherein at least this part of the latching element can be moved to the second position of said latching element generally parallel with the shaft about which the catch pivots.

In the case of this embodiment, the latching element is preferably supported on a pivot shaft on which the catch is pivotally mounted. This enables the latching element to be integrated with the locking element and to be con- structed as an additional part which can be readily fitted to an existing lifting hook which includes a locking catch which lacks a latching element. In this case, the latching element may suitably have the form of a blade-like arm or may comprise a wire spring having a round-coiled outer end which substantially fills the space between the catch and the bottom wall of the groove, said catch having a recess which, when the latching element is in said second position, accommo¬ dates at least the space-filling part of the latching element when the catch is swung away from its position of locking engagement with the lever element, therewith enabling the barrier arm to be swung away from the opening in the hook element when the lifting hook is relieved of load.

Further features of the invention are described in more detail herebelow with reference to the accompanying drawings, in which Figure 1 is a side view of a first preferred embodiment of an inventive safety hook; Figure 2 illustrates an opening phase of the hook, in which the latching element is activated to release the locking mechanism from its position of locking action with the barrier arm; Figure 3 is a view taken on the line III-III in Figure l; Figure 4 is a side view of a second embodiment of an inventive lifting hook; Figure 4a illustrates the locking catch in a latched position, the view being taken according to the arrows A-A in Figure 4; Figure 4b is a view similar to Figure 4a, but shows the locking catch in a non-latching position; Figure 5 is a side view of a lifting hook in which the latching element has an alternative construction; and Figures 5a and 5b are views of the Figure 5 embodiment corresponding to Figures 4a and 4b.

Figure 1 illustrates a lifting hook which comprises a hook part 10, whose upper end is pivotally connected to a two-arm lever element 12 by means of a pivot shaft 14. The one lever arm of the lever element 12 forms, in a known manner, a clapper or barrier 16, which is intended to close the opening of the hook part 10 during load- lifting operations. Accordingly, the outer end of the barrier arm is configured for complementary engagement with the outer end of the hook part 10, so as to be able to share the load placed on said hook part. The other arm of the lever element 12 forms a suspension part 18 which is intended to be coupled to a lifting line, lifting chain or the like (not shown) that extends from a crane for instance. The centre of the pivot shaft 14 is displaced to the right of the load symmetry line B of the hook, so that the barrier arm 16 will be brought automatically to its closing position when the hook is subjected to load.

The hook includes a locking mechanism which functions to hold the barrier arm 16 latched in its hook-closing position independently of the load on the hook, so as to prevent a load-carrying line suspended from the hook from being released unintentionally from said hook when the load thereon is relieved.

The locking mechanisms includes a locking catch 20 which is pivotally mounted on a pivot shaft 22 in a groove 24 provided in the upper part of the hook part 10. The locking catch 20 includes a nib or tip 26 which is intended to engage a corresponding recess 28 in the lever element 12. The catch 20 is biased towards its position of engagement with the lever element 12 by means of a torsion spring 30. When the nib 26 of the catch 20 engages the recess 28 in the lever element 12, the barrier arm 16 is latched in its hook-closing posi¬ tion.

The catch 20 also includes an operating part 32 which projects slightly from the upper side of the hook part 10. In order to release the catch 20 from its locking position, and therewith enable the barrier arm 16 to be swung to a hook-open position, it is necessary to apply pressure to the operating part 32 in the direction of the arrow C, so as to rotate the catch 20 anti-clockwise in Figure 1 against the action of the spring 30, until the nib 26 leaves the recess 28.

In order to prevent unintentional release of the catch 20, for instance in the event of the catch being struck by some object or other during a lifting operation, particularly when the hook is temporarily relieved of load during some phase of the lifting operation, such as to terminate the self-closing function of the barrier arm 16, there is provided in accordance with the present invention an additional safety device which when occupy¬ ing a first, normal position functions to prevent the locking catch 20 from rotating in a hook-releasing direction, and which when occupying a second position functions to permit the locking catch to move to a free position. In the case of a particularly preferred first embodiment of the invention, this additional safety device comprises a latching element which is arranged in the operating part 32 of the locking catch 20. The latching element has the form of a latching pin 34 which can be moved axially, parallel with the pivot shaft 22, between a normal, outwardly projecting position in which one side surface of the latching pin 34 abuts the upper, outer side 35 of the hook part 10, or a recess provided in said hook part (Figures 1 and 3) , so as to prevent pivotal movement of the catch 20, and a second position in which the latching pin 34 is located in the catch 20 so as to enable the catch to pivot in a manner to re- lease the barrier arm 16, as illustrated in Figure 2. The latching pin 34 is biased towards its first, latch¬ ing position by means of a spring 36, as illustrated in Figure 3.

In order to enable the barrier arm 16 to be released and swung up from its position in Figure 1, in which it closes the hook opening, the pin 34 is thus depressed in the direction of the arrow D in Figure 3, and the lock¬ ing catch 20 is then pressed down by exerting a pressure on the operating part 32 in the direction of the arrow C in Figure 2. The end surface of the pin 34 will then slide on the side wall of the hole 24, at the same time as the nib 26 of the locking catch 20 leaves the recess 28 in the lever element 12, so as to enable the lever element to be swung anti-clockwise, as shown in Figure 2, until the nib snaps into a recess 38 provided in the upper part 18 of the lever element, therewith holding the hook open.

According to an alternative embodiment illustrated in Figure 4, the latching element of the locking catch 20 has the form of an extension 31 of the torsion spring 30. The outer end 40 of the spring extension is thick¬ ened by means of a round-winding so that said outer end will generally fill the space defined between the under¬ side of the operating part 32 and the bottom wall of the groove 24. This prevents the catch 20 from being swung down to a release position, as shown in Figure 4a. In order to enable the catch 20 to be released, and there- with enable the barrier arm 16 to open, when the hook is not subjected to load, the outer end 40 of the spring can be moved manually in a direction parallel with the axis of the pivot pin 22, as shown by the arrow E in Figure 4a, to a central position in a recess 44. It is not until the catch 20 is located in this position that the catch 20 can be pressed downwards in the direction of the arrow C in Figures 4 and 4b, so as to free the barrier arm 16. The aforedescribed spring latching means 30, 40 is preferably biased towards the position in which it latches the catch 20, shown in Figure 4a.

Figure 5 illustrates an alternative embodiment of the latching element which differs from the torsion spring 30 and has the form of a blade-like arm 46 which is journalled on the pivot pin 20 and has an enlarged outer end 48, similar to the spring latches 30, 40. The arm 46 is also preferably biased towards the position in which it latches the catch 20, shown in Figure 5a, and can be moved to a catch release position, by applying a finger pressure in the direction indicated by the arrow E, as shown in Figure 5b.

In both of the embodiments illustrated in Figures 4 and 5, the respective latching elements 30, 40 and 44 are constructed to enable them to be subsequently fitted to existing lifting hooks provided with a barrier-arm lock¬ ing mechanism without need to modify the hook part 10.

Claims

1. A safety-lifting hook which comprises a hook ele- ment (10) provided with an opening, a two-arm lever element (12) which is pivotally connected to the hook element by means of a pivot shaft (14) such that when the hook is subjected to load one lever arm of said lever element will form a barrier arm (16) which auto- matically closes the hook element opening, while the other arm of said lever element forms a suspension element (18) by means of which the hook is coupled to a hook-supporting and load-lifting device, such as a rope, chain or like line, and further comprises a locking element (20) which is journalled to the hook element and which is biased towards a position in which it is in locking engagement with said lever element (12) there¬ with to lock the barrier arm (16) in the position in which it closes the hook element opening, c h a r - a c t e r i z e d in that the locking element (20) is coordinated with a latching element (34; 31; 46) which in. a first position functions to prevent the locking element (20) from leaving the position in which it is in locking engagement with the lever element (12) and which in a second position functions to permit the locking element (12) to move to a free position in which the barrier arm (16) is able to expose the opening in the hook element (10) when the hook is relieved of load.

2. A hook according to Claim 1, in which the locking element has the form of a catch (20) which is pivotally mounted in a groove (24) in the hook element (10) and which includes an engagement device (26) for engagement with a complementary engagement device (28) on the lever element (12), and an operating part (32) on which a force can be applied to swing the catch (20) away from its position of engagement with the lever element, against the action of a spring force, c h a r a c ¬ t e r i z e d in that the latching element has the form of a pin (34) which can be moved axially generally parallel with the pivot shaft (22) on which the catch

(20) is pivotal, so as in said first position to engage the hook element (10) such as to prevent pivotal move¬ ment of the catch (20).

3. A hook according to Claim 2, c h a r a c ¬ t e r i z e d in that the pin (34) is biased towards its first, catch latching position.

4. A hook according to Claim 3, c h a r a c - t e r i z e d in that in its first position, the pin (34) abuts an outer wall (35) of the hook element (10).

5. A hook according to Claim 3 or 4, c h a r a c ¬ t e r i z e d in that in its second position, the pin (34) abuts one end surface of one side wall of the groove (24).

6. A hook according to any one of Claims 2-5, c h a r a c t e r i z e d in that the pin (34) is journalled in the operating part (32) of said catch (20).

7. A hook according to Claim 1, in which the locking element has the form of a catch (20) which is pivotally mounted in a groove (24) provided in the hook element

(10) and which has an engagement device (26) for engage¬ ment with a complementary engagement device (28) on the lever element (12), and an operating part (32) on which a force can be applied so as to pivot the catch (20) away from its position of engagement with the lever element, against the action of a spring force, c h a r a c t e r i z e d in that the latching element (31; 46) has a part (40; 48) which in the first position of said latching element essentially fills a space between the catch (20) and a bottom wall (42) of the groove (24); and in that at least said part (40; 48) of the latching element (31; 46) can be moved to said second position generally parallel with the pivot shaft (2) around which the catch (20) can be pivoted.

8. A hook according to Claim 7, c h a r a c ¬ t e r i z e d in that the latching element (31; 46) is carried on a pivot shaft (22) on which the catch is pivotally mounted.

9. A hook according to Claim 7 or 8, c h a r a c ¬ t e r i z e d in that the latching element has the form of a wire spring (31) having an outer end (40) which is formed in a manner to essentially fill the space between the catch (20) and the bottom wall (42) of the groove (24).

10. A hook according to Claim 9, c h a r a c ¬ t e r i z e d in that the spring-like latching element is in the form of an extension (31) of a spring (30) which biases the catch (20) to its position of locking engagement with the lever element (12).

11. A hook according to Claim 8, c h a r a c ¬ t e r i z e d in that the latching element has the form of a blade-like arm (46).

12. A hook according to any one of Claims 7-11, c h a r a c t e r i z e d in that the latching element (31; 46) is biased towards its said first position, in which it latches the catch (20).

13. A hook according to any one of Claims 7-12, c h a r a c t e r i z e d in that the catch (20) has a recess (44) which is intended to accommodate at least that part (40; 48) of the latching element (31; 46) which fills said space when the catch (20) is swung away from its position of locking engagement with the lever element (12), thereby enable the barrier arm (16) to be swung away from the hook element opening when the hook is relieved of load.