GB2303713A

GB2303713A - A load indicator device

Info

Publication number: GB2303713A
Application number: GB9515289A
Authority: GB
Inventors: Anthony Hemmings
Original assignee: DEEWELD Ltd
Current assignee: DEEWELD Ltd
Priority date: 1995-07-26
Filing date: 1995-07-26
Publication date: 1997-02-26
Anticipated expiration: 2015-07-26
Also published as: GB2303713B; GB9515289D0

Abstract

A load indicator device comprises a load transmitting member which transmits load applied thereto to a loadable member to be put under load via compressible or expandable resilient biasing means 22, indicator means 29,30 FIG4 moving with said biasing means and being displaceable such that when the biasing means is loaded and displaced to reach a predetermined load equivalent to that required for the loadable member and/or any device associated therewith, the indicator means reaches a fully loaded indicating position (FIG 5) whereat the user can readily visually and/or physically determine said fully loaded position has been reached. Two pairs of plates 3, FIG 2, form two jaws pivoted together with a force adjustable by a threaded rod 12. Rotation of the rod clamps the jaws with a predetermined pressure against a beam 8.

Description

A LOAD INDICATOR DEVICE The present invention relates to a load indicator device and particularly to a clamping device incorporating such indicator device or means for improved safety.

With many clamping devices wherein the jaws of the clamp are moved against an item to be clamped under the action of rotation of a threaded rod acting between the jaws, such as a "Screwlok" clamp as marked by Deeweld Ltd of Sealand Chester, which are designed to fit flanges of RSJ's and Universal beams as semi-permanent lifting points suitable for use with powered hoists, chain blocks etc. (as illustrated in Fig. 1), it is important that the clamp be tightened to the requisite amount. There is a danger that if a clamp is not tightened to the requisite amount, the clamp may appear at first sight to be correctly located in position but once a load is applied to the clamp it may release its grip on the item to which it should be securely clamped with the risk of resultant likely dangerous consequences.

It is an object of the present invention to provide simple and economic means whereby an operator can readily determine when clamping jaws such as of a clamp are clamped to the requisite load/tension or to a load indicator device per se.

According to the present invention there fts provided a load indicator device comprising a loadable load transmitting member which transmits load applied thereto to a member to be put under load via compressible or expandable resilient biasing means, indicator means moving with said biasing means and being displaceable such that when the biasing means reaches a predetermined load equivalent to that required for the loadable member and/or any device associated therewith, the indicator means reaches a fully loaded indicating position whereat the user can readily visually and/or physically determine said fully loaded position has been reached.

More specifically according to the present invention a clamping device with load indicator safety device for indicating when a predetermined load is reached, comprises at least one clamping jaw displaceable towards and away from another clamping surface by means of a rotatable threaded operating rod extending from said at least one jaw to another member, said rod acting through resilient means which flex or deform as the predetermined load is reached, and indicator means mounted to move upon deformation of said resilient means and to reach a readily determinable fully loaded indicating position when said predetermined load is reached.

Also according to the present invention there is provided a clamping device with tensioning indicator for indicating when a predetermined load is reached and comprises two clamping jaws displaceable towards and away from each other by means of a threaded operating rod extending between mounting members therefor on each jaw and rotatably retained in each, with one said mounting member having a load transmitting member non-rotatably displaceable with respect thereto and threadingly engaged with the threads of said operating rod so as to be displaceable upon rotation of said spindle, resilient means being located between said load transmitting member and retaining portion of said mounting member so as to be compressible (of expandable) by said load transmitting member as said predetermined load is reached, and indicator means on said load transmitting member and movable therewith upon deformation of said resilient means to reach a fully loaded indicating position when said predetermined load is reached.

Preferably the indicator means comprises at least one projection extending through or passed a reference surface in the normally unloaded position but displaceable to be retracted into the aperture in the surface or passed a reference surface when said fully loaded indicating position is reached. Preferably the indicator means will be specifically coloured and preferably differently coloured to the associated reference surface to facilitate visible determination when said fully loaded indicating position is reached.

It is of course possible that rather than retraction, extension to a fully loaded indicating position may alternatively be provided, for example, e.g. a different color emerging from or passed a surface or the indicator projection reaching an indicator surface or marking or other indicia.

Whilst the resilient means may comprise a compression or tension spring, it has been found particularly preferable for such to comprise a plurality of bevel washers especially since ordinary compression springs do not work particularly well and since problems are created by the large diameter thereof with respect to the loads supplied and space available.

Preferably a stop surface for limiting the movement of said load transmitting member against the resilient means will be provided to prevent overloading.

Preferably, the threaded operating rod or spindle will have two spaced apart opposite-hand threaded portions with each threaded portion threadedly and drivably engaging in an appropriately correspondingly threaded portion of the mounting member or the load transmitting member thereof as appropriate.

The invention will be described further, by way of example, with reference to the -accompanying drawings, in which: Fig. 1 is a perspective view of a "Screwlok" (Trade Mark of Deeweld Ltd) clamping device incorporating a safety tensioning indicator (not shown in Fig. 1) and shown clamped in position of use suspended from a beam; Fig. 2 is a longitudinal section through the centre of the clamping device of Fig. 1; Fig. 3 is an elevation of the clamping device of Fig. 1 in the direction of arrow A; Fig. 4 is an section on the line A-A of Fig. 3 showing the indicator device in normal other than fully loaded indicating position; and Fig. 5 is also an enlarged section on the line A-A of Fig. 3 but wherein the tensioning indicator is in the fully loaded indicating position and the bevel washers compressed together.

The clamping device shown in the drawings comprises first and second clamping jaws 1 and 2 each formed from a pair of hook-like shaped metal plates 3 with each pair being interconnected at their clamping end by cross bars 4 and with the two jaws 1 and 2 i.e. the two pairs of plates 3, being pivotally interconnected by a pivot pin 5 riveted over at its outer ends 5' to maintain the pairs of jaws together and to permit relative rotary displacement - similar to what has been provided in known manner. The pin 5 also acts as a mounting pin for connection shackle or eye 6 through the lugs of which pin 5 extends. The connecting cross-bars 4 are similarly riveted over or chamfered over at 4' to hold the ends of the pairs of plates 3 of the clamping jaws 1 and 2 together.The shaped end portions 7 of each of the jaw plates 3 are suitable for receiving the crosspiece 8' of a beam 8 (only shown in part of Fig. 2).

A first simple mounting member 9 is provided extending between the plates 3 of clamping jaw 2 and comprises a cylindrical bar extending through apertures in plates 3 with sufficient clearance to permit relative pivotal movement and preferably with shoulders on the inner side of each plate 3 to act as retention means. A tubular collar or sleeve 11 extends around rod 9 with clearance and with slight clearance between plates 3 so as to be in floating position relative thereto.

Transverse aligned apertures are provided in sleeve 11 and through which threaded rod 12 extends freely. The particular handed portion 12' of threaded rod 12 which extends through a threaded bore in mounting member 9 threadedly engages within threaded inner portion and mounting member 9.

Threaded rod 12 has another threaded portion 12" of opposite hand to portion 12' and has an enlarged diameter handle portion 13 with a cross or tommy bar 14 slidably extending thereto and held captive -by enlargements at the opposite ends thereof.

A second mounting member 10 which extends between plates 3 of first clamping jaw 1 comprises a bar 10' of rectangular cross section in the region between the plates 3 and having cylindrical end projections 10' 11 extending from opposite ends thereof and with slight clearance through aligned circular apertures in plates 3 to enable relative pivotal movement between mounting member 10 and plates 3 and to retain mounting member 10 between said plates 3.

It will be apparent from Fig. 2 that the pairs of plates 3 of each jaw are equally spaced with one pair being offset relative to the other.

The main body of the mounting part 10 has a central aperture 15 extending therethrough and through which threaded rod 12 extends. The aperture or through passage 15 comprises a large diameter portion 16 of a rectangular section and covered by a rectangular cover plate 17 securable by screws 18. Plate 17 has a circular aperture through which the threaded portion 12' of rod 12 extends with clearance. Threaded portion 12' also extends the other side of member 10 with clearance through aperture 19 which is of reduced diameter and forms a shoulder portion 20 of a larger cylindrical bore 21 in which there are located a plurality of bevel washers 22 forming resilient means which are deformable/flex when loaded.A load-transmitting member 23 has a central threaded through bore which threadingly engages with the threaded portion 12" of rod 12 and is displaceable in bore portion 16, 21 on rotation thereof.

The load transmitting member 23 has a cylindrical portion 24 slidable in bore 21 and has a stop shoulder 25 abuttable against shoulder 26 between bores 16 and 21 s the load transmitting member 25 moves into bore 21 to prevent overload of bevel washes 22. A larger portion 27 of load transmitting member 24 and associated portion 16 of the through bore is of rectangular section so as to prevent relative rotational movement but is such as to permit relative sliding movement. Two cylindrical projecting pins 29, 30 (only one in fact required) are located in apertures in portion 28 of the load transmitting and act as indicator means and extend through apertures 31 in plate 17 and are preferably distinctively coloured e.g. coloured red to indicate that such are safety indicators.

It will be appreciated that rotation of the rod 12 will cause the jaws 1 and 2 to move together or apart and when such are moved together and abut the cross piece 8' of a beam or other member, then as tightening continues, the increasing load is applied to the load transmitting member 23 which is then displaced in bore 15 against the action as resilient bevel washers 22 so as to compress such.Resilient washers 22 are such as to provide the necessary resistance against compression/flexing during normal movement of the jaws but are so selected with respect to the length of the indicator pins 29, 30 or the length of said pins selected relative to the compression/flexing amount, such that when the clamping device is applying the appropriate clamping pressure/load to the beam 8 the pins 29, 30 are retracted into the bore 15 such that the free ends of the pins lie flush with the outer surface of plate 17 or slightly within the apertures therein and in this position they indicate the fully loaded position and safety position of the clamping device.

It will be appreciated that only one indicating pin is necessary although two are preferably provided one each side of the spindle for increased visibility and safety.

It is also envisaged that instead of retracting pins into a space, such might be alternatively arranged to project outwardly to a requisite amount with or beyond suitable indicia means.

The "Screwlok Clamp" is primarily used as a temporary suspension device for supporting lifting equipment from the bottom flange of a standard rolled steel beam 8.

Turning the handle tommy bar 14 anti-clockwise such acts on pivoting left hand and right hand nuts or mounting member 9 and 10, this opens the clamp jaws 1 and 2. The clamp jaws can then be attached to the bottom flange 8' of the beam 8 and tightened into position by turning the handle 13, 14 clockwise. The clamp is fitted with the innovative tension indicator device which indicates to the operator that the clamp is securely attached to the beam flange.

The operator turns the handle 14 until the jaws 1 and 2 are touching either side of the beam flange 8'. The tensioning device will be in position as shown on section in Fig. 4 Further tightening of the clamp will cause the load transmitting member 23 to move laterally causing bevel washer 22 to compress.

Member 23 can move a lateral distance of for example, 6mm whereupon only then is the load transmitted through cross bar 10'. As the load transmitting member 23 moves laterally the 2 pins 29,30 painted "Red" are drawn into the bore of the cross plate 17. This visually indicates to the operator that a force has been applied to the clamp jaws 1,2, (NB. A 6mm movement of the indicator pins means a horizontal force of 85 kg has been applied).

The operator now knows the clamp is not loosely attached to the beam and this provides for considerably increased safety. Operating instructions will specify that when red indicator pins are to be flush with the cover plate 17 the operator should attempt to tighten further. The magnitude of this additional horizontal force will depend on the force applied by the operator to the handles of the tommy bar.

The "Screwlok Clamp" with tension indicating safety device is primarily intended for providing a suspension point although may also be used for attachment to loads (beams) that have to be lifted and handled. The operator must however, ensure that the clamp is attached to the point of centre of gravity of the load.

According to an alternative broad aspect of the invention a tension indicator for indicating a predetermined tension in a shaft or rod comprises an externally threaded shaft or rod extending through a bore through a housing, a load transmitting member having an internally threaded bore extending therethrough in threaded engagement and said shaft or rod and being axially displaceable within the housing and reversibly displaceable into increasing abutment with resilient or spring means also contained within said bore of the housing, an indicator projection or other indicator means carried by said load transmitting member and displaceable therewith, said resilient means being of such resistance or requiring such load to compress such as to yield to a sufficient extent when said predetermined load is applied, and said indicator means is provided so as to indicate when said extent of yielding has been reached and thus said predetermined load. Preferably, an apertured end plate closes one end of said throughbore in the housing and said indicator projection or extends therethrough until the predetermined load is reached.

Resiliently extendable means may be used instead of compression spring means. It is even envisaged that the indicator might be incorporated as a composite nut for a bolt which indicates when the requisite load is applied.

Instead of threaded drive and/or engagement, a ratchet-like interrelationship of the load transmitting member with its drive is also envisaged or even hydraulically or pneumatically powered sliding displacement means.

Claims

1. A load indicator device comprising a load transmitting member which transmits load applied thereto to a loadable member to be put under load via compressible or expandable resilient biasing means, indicator means moving with said biasing means and being displaceable such that when the biasing means is loaded and displaced to reach a predetermined load equivalent to that required for the loadable member and/or any device associated therewith, the indicator means reaches a fully loaded indicating position whereat the user can readily visually and/or physically determine said fully loaded position has been reached.

2. A clamping device with load indicator safety device for indicating when a predetermined load is reached, comprises at least one clamping jaw displaceable towards and away from another clamping surface by means of a rotatable threaded operating rod extending from said at least one jaw to another member, said rod acting through resilient means which flex or deform as the predetermined load is reached, and indicator means mounted to move upon deformation of said resilient means and to reach a readily determinable fully loaded indicating position when said predetermined load is reached.

3. A clamping device with tensioning indicator for indicating when a predetermined load is reached, comprises two clamping jaws displaceable towards and away from each other by means of a threaded operating rod extending between mounting members therefor on each jaw and rotatably retained in each, with one said mounting member having a load transmitting member non-rotatably displaceable with respect thereto and threadingly engaged with the threads of said operating rod so as to be displaceable upon rotation of said spindle, resilient means being located between said load transmitting member and retaining portion of said mounting member so as to be compressible of expandable by said load transmitting member as said predetermined load is reached, and indicator means on said load transmitting member and movable therewith upon deformation of said resilient means to reach a fully loaded indicating position when said predetermined load is reached.

4. A device as claimed in any of claims 1, 2 or 3, in which the indicator means comprises at least one projection extending through or passed a reference surface in the normally unloaded position and displaceable to be retracted into the aperture in the surface or passed a reference surface when said fully loaded indicating position is reached.

5. A device as claimed in claim 4, in which the indicator means is differently coloured relative to the associated reference surface to facilitate visible determination when said fully loaded indicating position is reached.

6. A device as claimed in any of claims 1 to 5, in which the resilient means comprises a plurality of bevel washers.

7. A device as claimed in any of claims 1 to 6, in which a stop surface for limiting the movement of said load transmitting member against the resilient means is provided to prevent overloading.

8. A device as claimed in any of claims 2 to 7, whenever dependent on claims 2 or 3, in which the threaded operating rod or spindle has two opposite-hand threaded portions with each threaded portion threadedly and drivably engaging in an appropriately correspondingly threaded portion of the mounting member or the load transmitting member thereof as appropriate.

9. A tension indicator for indicating a predetermined tension in a shaft or rod, comprises an externally threaded shaft or rod extending through a bore through a housing, a load transmitting member having an internally threaded bore extending therethrough in threaded engagement and said shaft or rod and being axially displaceable within the housing and reversibly displaceable into increasing abutment with resilient or spring means also contained within said bore of the housing, an indicator projection or other indicator means carried by said load transmitting member and displaceable therewith, said resilient means being of such resistance or requiring such load to compress such as to yield to a sufficient extent when said predetermined load is applied, and said indicator means is provided so as to indicate when said extent of yielding has been reached and thus said predetermined load.

10. An indicator as claimed in claim 9, in which an apertured end plate closes one end of said throughbore in the housing and said indicator projection or extends therethrough until the predetermined load is reached.

11. A composite nut for a bolt which indicates when the requisite load is applied by an externally threaded shaft or rod when extending therethrough, comprises a housing having a bore extending therethrough, a load transmitting member having an internally threaded bore extending through the housing and member for threaded engagement with said member which member is axially displaceable within the housing and reversibly displaceable into increasing abutment with resilient or spring means also contained within said bore of the housing, an indicator projection or other indicator means carried by said load transmitting member and displaceable therewith, said resilient means being of such resistance or requiring such load to compress such as to yield to a sufficient extent when said predetermined load is applied and said indicator means is provided such as to indicate when said extent of yielding has been reached and thus said predetermined load.

12. A load indicator device substantially as herein described with reference to the accompanying drawings.