WO1998043898A1

WO1998043898A1 - Lifting device for plate shaped objects

Info

Publication number: WO1998043898A1
Application number: PCT/DK1998/000106
Authority: WO
Inventors: Arndt Pedersen
Original assignee: Arndt Pedersen
Priority date: 1997-03-19
Filing date: 1998-03-19
Publication date: 1998-10-08
Also published as: AU6611798A

Abstract

In connection with construction work there is frequently practised manual lifting of heavy plate shaped objects in awkward working postures. During handling said objects it is also often difficult to obtain a sufficient hold. To relieve the above mentioned problems there is specified a lifting tool of the kind that comprises gripping means for clamping/gripping plate shaped objects during a lifting process, the gripping means comprising an activation grip (40) which will take an operative carrying hold/grip, when the gripping clamp in lateral position is inserted in regular engagement over a side edge area of said plate (56), and where the gripping means respectively comprise an adjustable retaining plate (20) and a transverse displaceable pressure plate (18) connected to an asymmetrical part (54) on a torsion shaft with an activation grip (60).

Description

Lifting Device for Plate-Shaped Objects

The present invention concerns a lifting device of the kind which comprises gripping means for clamping plate-shaped objects during a lifting process, and comprising a gripping clamp provided with an activation grip which assumes an operative carrying position when the gripping clamp in the lateral position is inserted in regular engagement over a side area of said plate. In connection with construction work, it is often required to handle and transport plate-shaped building materials of standard dimensions from trucks to a place of storage, and from here further to the site where the plate-shaped building materials are processed and erected. Said transport is very often effected manually and involves the lifting of heavy objects in awkward working postures. It is frequently also difficult to achieve a proper grip on the plate material, the surfaces of which are most often smooth, the result being that the only possibility of being able to effect a proper lift is to lift the plates at their lower sides. In addition to the above-mentioned disadvantages, this gives rise to problems with passage through door openings, which most often are not of sufficient height to allow passage of the plate material when this is carried by the lower edge.

The achieving of an optimally expedient lifting posture in connection with the manual lifting of plate materials is determined in a very individual manner, but it depends first and foremost on the height of the person who is required to carry out the lifting. If the lifting of larger plates is involved, where the lifting must be effected by two persons who are not of the same height, and where the transport also involves carrying the plate material up or down steps or stairs, there will be individual requirements to take into consideration in connection with lifting postures and lifting situations. It will be assumed that at some time or another it will be necessary to effect the lifting at the upright sides of the plate, where it is difficult to obtain and maintain a good lifting grip for longer periods of time.

A lifting tool for the execution of such a lift is known from US 1,982,225, this tool comprising a U- shaped carrying beam with webs with inner sides which are provided with countersunk pressure plates, the rear sides of which have pressure blocks which via openings in the webs stand in connection with spring-loaded pressure plates, the outer sides of which are in turn provided with wedge-shaped portions which, under the influence of a U- shaped activation grip which is pivotably mounted on the webs of the carrying beam are brought to an active position of use, will displace the pressure plates for the securing of a plate-shaped object when the tool is late- rally inserted in a regular engagement over a side edge of said plate. However, a disadvantage with said lifting tool is that the tool has limitations with regard to the thickness of the plates which are handled with the lifting tool, which is determined by the height of the wed- ge-shaped portions. Another disadvantage is that the position of the lifting tool's activation grip in relation to the lifting tool will vary with the plate thickness.

However, this problem is solved with the lifting tool disclosed in US 3,374,024, which comprises a U- shaped beam consisting of two angle profiles clamped together, where the distance between the webs is adjustable by means of slot-shaped holes in the one profile. The one angle profile which constitutes the U-shaped profile constitutes a retaining plate, and the other angle profile comprises a pressure plate with reversing spring mechanism, said pressure plate being connected with an activation grip extending from the angle profile, said activation grip consisting of a rectangularly-bent tube piece whose side nearest the angle profile is pivotably mounted on this, and where at the middle of said tube piece there is provided a pressure element which, upon operation of the activation grip, will displace the pressure plate for securing of a plate-shaped object when the tool is late- rally inserted in a regular engagement over a side edge of said plate. The disadvantage with this tool, however, is that the lifting gives rise to a turning-moment on the plate being handled by the lifting tool, the result being that the user must use the other hand to prevent the tip- ping of the plate. Moreover, the adjustment of the retaining plate will be troublesome and time-consuming, in that it is necessary to loosen and tighten two adjusting bolts. Moreover, neither of the two lifting tools will remain in the position of engagement in the plate's side area if the user releases the activation grip, which means that the lifting tool must be re-positioned after pauses in the lifting operations.

Furthermore, investigations and experience have shown that the loading of the wrist, the forearm and back of people who lift and carry burdens with the hands, is least providing that the burden can be lifted with an underhand grip similar to that which is employed when using a wheelbarrow.

It is the object of the invention to provide a lifting tool of the kind described in the preamble, which during the lifting of a plate-shaped object does not give rise to torque on the plate, and which can be used in connection with the lifting of plates of varying thickness, which is quickly adjustable for use in the lifting of a plate of a given thickness, and whose activation grip is disposed in such a manner that the load on the person who uses the lifting tool is reduced as much as possible . Such a lifting tool comprises a housing built up of two halves, the one end of which in the assembled state comprises a substantially U-shaped carrying beam with webs between which there are a retaining plate and a transversely-displaceable pressure plate for the gripping and securing of a plate-shaped object, characterized in that the retaining plate is transversely-displaceable, fixably mounted on a threaded bolt extending through the one web of the U-shaped carrying beam, said bolt cooperating with a threaded, rotatably-mounted bush in said web with a corresponding flange housed in a cut-out in the web on the side facing towards the retaining plate, the opposite end of said bush standing in connection with an operating knob which is similarly rotatably mounted on the external side of the web, and where said pressure- plate is mounted on a displaceable pin extending in a bush through the second web of the U-shaped carrying beam, and which near its free end is provided with a return spring supported by the external side of the web, and where in said external side of the web there is a slide bearing in which a torsion shaft is housed, the one end of said torsion shaft having an asymmetrical pressure area in the form of an arcuately- extending part, the opposite end of the shaft being provided with an arm which extends at the rear of the housing laterally in relation to the longitudinal axis of the torsion shaft, the free end of said arm being provided with an activation grip which extends parallel with the longitudinal axis of the torsion shaft . By placing examples of the lifting tool at a suitable lifting height on each upright end of a rectangular plate, and thereafter lifting at the activation grip, the torsion shaft will be turned in the slide bea- ring, and herewith the pressure area, so that the displaceable pressure pin and herewith the pressure-plate are pushed in towards the side of the plate, the other side of which is pressed against the retaining plate, hereby creating the friction necessary for the lifting of the plate-shaped object, while at the same time a good lifting grip on the lifting handle is achieved at a user- adapted lifting height.

With the special configuration of the lifting tool, as is the case with the already-mentioned known lifting tools, it is achieved that the tool can randomly be placed in an operative lifting position on the upright side edge of a plate-shaped object at a lifting and carrying height which is optimal for the carriers of the plate. Moreover, as a consequence of the quite special positioning of the activation grip in the operative carrying position of the lifting tool, where the activation grip is placed behind the tool's housing in extension of the plate-shaped object, it is achieved that the plate- shaped object is not influenced by a transverse moment, and moreover that when the lifting is effected, use can be made of the preferred underhand grip both during the normal lifting and during the transport of the plate. The manual transport is eased further in that the position of the activation grip creates a certain distance between the carriers and the plate-shaped object which is lifted. There is also achieved a considerable easing of the work in connection with the adjustment of the lifting tool for varying plate thicknesses, in that the adjustment can easily be effected by turning the adjustment knob on the outside of the lifting tool housing, whereby the retaining plate can be displaced for use of the lifting tool for the lifting of respectively thicker or thinner plate-shaped objects. For further easing of the adjustment of the lifting tool for a given plate thickness, the housing along the edge of the bottom of the U-shaped profile can comprise a scale which indicates the correct setting of the retaining plate for a given plate thickness, and said scale being placed in such a manner that compensation is made for the displacement of the pressure-plate in towards the plate-shaped object upon assumption of the carrying position, so that the activation grip at the operative carrying position is optimal for those executing the lift.

When the lifting tool is used, a moment will arise as a consequence of the distance between the activation grip and the pressure plate and retaining plate, which can give rise to a tilting of the lifting tool as a result of the turning of the plates around their bearing pins in the housing, so that the activation grip will form an upwardly- sloping angle in relation to the horizontal. This will give rise to a lifting grip which is inexpedient for those executing the lift, while at the same time the edge of the housing between the webs will lie up against the upright plate edge and possibly damage the edge. To prevent this, the pressure plate and the retaining plate in the side facing towards the housing are configured with an asymmetrical bottom shape which is matched by a corresponding shape of the adjacent housing side, whereby the turning of said plates and herewith the tilting of the lifting tool is prevented.

With the object of being able to use the lifting tool for lifting plate-shaped materials with varying roughness, the opposing sides of the retaining plate and the pressure plate respectively can be arranged so that they have replaceable surfaces.

When executing manual lifting and transport of plate-shaped objects, it will sometimes be necessary for those carrying out this work to take a rest. With the use of the known lifting tools, this will mean that these tools must be replaced by the users in order to continue with the lifting, with a consequent consumption of time, in that the return spring will draw the pressure plate away from the retaining plate when the activation grip is released.

With the object of maintaining the lifting tool in the operative carrying position during pauses in the lifting of plate-shaped objects, the torsion shaft can be provided with a locking lever on the outside of the housing which secures the torsion shaft and herewith the pressure plate in the operative carrying position, whereby the activation grip can be released by the user wit- hout the pressure plate being displaced away from its contact with the outer side of the plate-shaped object, and the lifting tool will thus remain sitting in the preferred position in which it was originally placed before the pause in the lifting.

The invention will now be described in more detail with reference to the drawing, where fig. 1 is a perspective view of a lifting tool according to the invention seen from below, fig. 2 is a top view of fig. 1, seen obliquely from the rear, fig. 3 is as fig. 1, but where the one half of the housing has been removed, fig. 4 is a section in the plane A in fig. 1, and fig. 5 is a side view of the lifting tool according to the invention inserted in the position of engagement over side areas on a plate-shaped object.

The lifting tool shown in figs. 1 and 2 comprises a housing consisting of two halves 4, 6, mutually connected by means of through-going bolts 8. Each half 4, 6 of the housing has projecting parts 10, 12 with arcuate front ends which together with the rest of the housing 2 form a forwardly-directed U-shaped opening 14, the bottom 16 of which is made up of the combined half parts 4, 6 of the housing. On the oppositely-facing sides 10, 12 of the U-shaped opening there is mounted a pressure plate 18 and a retaining plate 20 respectively. As will be seen, the pressure and retaining plates 18, 20 are configured so that these follow the arcuate forwards shape of the parts 10, 12, and also so that they follow the shape of the bottom 16 in the U-shaped opening, which has a depression 22. The effect of this configuration of the pressure and retaining plates and bottom 16 is that the pressure and retaining plates are not turned under the influence of torque.

In fig. 3, which is a view of the lifting tool according to the invention where the half 4 of the housing is removed, it will be seen that the pressure plate 18 is mounted on a smooth pin 24 which leads through a hole 26 in the part 10, cf. fig. 4, and ends in a cut-out 28 in the external side of said part, cf . fig. 1. A part of the projecting end 30 of the pin 24 is surrounded by a helical spring 32 having ends which lie up against the bottom of the cut-out 28 and a stop 34 which, in the e- xample embodiment shown, comprises a locking-ring fastened to the end 30 of the pin 24. The pin 24, and herewith the pressure plate 18, are displaceable in the transverse direction, i.e. in towards and away from the retaining plate 20.

As will be seen in fig. 4, the retaining plate 20 is mounted on a threaded stud 36 which is surrounded by a threaded bush 38 which is rotatably housed in a through-going hole 40 in the part 12. At the one end, the bush 38 has a collar 42 which is housed in a recess 44 in the internal side of the part 12 for the absorption of compressive forces on the retaining plate 20. The opposite end of the bush is connected with a rotatable adjustment knob 46, so that rotation of the adjustment knob will result in a displacement of the threaded stud 36 in the bush 38, and herewith a lateral displacement of the retaining plate 20. The bottom 16 of the U-shaped opening is provided with a graduated scale 39 which shows the setting of the retaining plate 20 for a given plate thickness.

On the outside of the part 10, in a longitudinal hole provided for this purpose, there is housed a torsion shaft 50 which is oriented in the part's longitidinal direction, cf. figs. 2, 3 and 4. At the free end, the tor- sion shaft 50 has a step 52 on which there is secured an arcuate pressure lever 54 which abuts against the projecting end 30 of the pin 24 housed in the cut-out 28. At the rear of the housing, the torsion shaft 50 is cranked to form an arm 56 which extends parallel with the re- ar of the housing 2, the free and of said arm 56 then extending at an angle to form the basis for an activation grip 60, the centreline 62 of which lies close to the centre of the housing 2. Near the rear end of the housing 2, the torsion shaft 50 is provided with a toggle-type locking arm 62 with a wedge-shaped slotted part housed in and co-operating with a recess 64 in the part 10, so that activation of the locking arm 62 results in a wedging- fast of the torsion shaft, whereby this and herewith also the pressure plate 18 remain in their position.

When using the lifting tool according to the invention for the lifting of a plate 66 , a lifting tool is placed at a convenient lifting height at the plate's upright ends, cf. fig. 5, so that the plate lies between the retaining plate 20 and the pressure plate 18. If necessary, the retaining plate 20 is adjusted for the desired plate thickness by turning the adjustment knob 46. With the lifting tools in the position described, the plate is now lifted by taking hold of the grip 60 and lifting, whereby a turning of the torsion shaft 50 occurs and herewith a displacement of the pressure lever 54 which is pressed in against the pin 24, which hereby presses the pressure plate 18 against the plate 66, the result being that the plate is clamped between the pres- sure plate 18 and the retaining plate 20. In an easy and convenient manner, it will now be possible for the relevant plate to be carried with the carriers assuming postures which are suitable for their individual heights. Upon arrival at the plate's destination, the plate is placed on an underlayer and the activation grip 60 is released, whereby the spring 32 pushes the pressure-plate 18 back to the start position and the lifting tools are free.

If a pause is held during the transport of the plate to its destination, or if it is desired that the lifting tool remains in its position, possibly with the object of being able to place the plate in its position later, the locking arm 62 is activated, whereby the torsion shaft 50 and herewith the pressure-plate 18 and the activation grip 60 remain in the operative position, but the plate 66 is clamped between the pressure-plate 18 and the retaining plate 20. It is hereby achieved that the transport/lifting of the plate 66 can directly recommence without the need to adjust the position of the lifting tools .

The above example embodiment of the lifting tool according to the invention is based primarily on the lifting of plates of a size and weight which require the ef- forts of at least two persons, i.e. one person lifting at each end of the plate with each their example of the plate lifter. The lifting tool in this embodiment is based on a turning of the torsion shaft 50 in the hole 48 by the gripping of and lifting with the activation grip 60, whereby the pressure-plate 18 is pressed in against the plate 66 which is thus securely held.

The opposing surfaces 68, 70 of the retaining plate and the pressure-plate respectively can be coated with a special friction-creating material which can be changed depending on the type of plate material to be lifted with the lifting tool. Examples of suitable materials can be rubber when the plate lifting tool is used for lifting plates of wood, possibly with a coating of carburundum for the lifting of non- greasy metal plates, rasped metal surfaces for the lifting of greasy metal plates etc. In order to ease the work involved in the changing of the surfaces, the replaceable surfaces can be fastened to the pressure-plate and retaining plate with Velcro . The use of the disclosed lifting tool according to the invention for the lifting of normally heavy and unwieldy objects, such as large plates etc., will serve to avoid industrial accidents and all-too-early wearing down of the persons who must effect the lifting of such objects in their daily work.

Claims

C L A I M S

1. Lifting tool (2) of the kind comprising gripping means (18, 20) for the clamping/gripping of plate- shaped objects (66) during the lifting of said objects, and comprising a gripping clamp (4, 6) configured with an activation grip (60) which will assume an operative carrying position when the gripping clamp in lateral position is inserted in regular engagement over a side edge area of said plate, where the gripping clamp is comprised of a housing in two halves (4, 6) which in combination constitute a substantially U-shaped carrying beam (4, 6), the webs of which have opposing sides which respectively comprise gripping means (18, 20) in the form of a retai- ning plate (20) and a transversely-displaceable pressure plate (18) for the gripping and securing of the plate (66) , c h a r a c t e r i z e d in that the retaining plate (20) is fixably mounted with locking means in a transversely-adjustable manner on the one web (12) of the U-shaped carrying beam (4, 6), and that the pressure plate (18) is mounted in a transversely-displaceable manner on a transversely-displaceable pressure pin (24) through the second web (10), and where in said web's external side there is provided a slide bearing in which is housed a torsion shaft (50) , the one end of which has an asymmetrical pressure area in the form of an arcuate projecting part (54) which lies up against the free end (30) of the pressure pin (24), the opposite end of said shaft being provided with an arm (56) extending behind the housing transversely in relation to the longitudinal axis of the torsion shaft, the free end of said arm being provided with an activation grip (60) extending parallel with the torsion shaft.

2. Lifting tool (2) according to claim 1, c h a r a c t e r i z e d in that the locking means for the retaining plate (20) are comprised of a threaded pin (36) extending through the one web (12) of the U-profile, in that said pin (36) co-operates with a threaded bush (38) housed in a rotatable manner in said web with a flange (42) provided in a co-operating recess (44) in the web on the side facing towards the retaining plate (20) , the opposite end of said bush standing in connection with an operating knob (46) mounted in a similarly rotatable manner on the outside of the web (12) .

3. Lifting tool (2) according to claim 1 or 2 , c h a r a c t e r i z e d in that near its free end

(30) , the pressure pin (24) is provided with a return spring (32) in abutment with the outside of the web and with a locking ring (34) on the pressure pin, so that the pressure plate (18) is pushed back to the start position in the inoperative position of the activation grip.

4. Lifting tool (2) according to one or more of the foregoing claims 1-3, c h a r a c t e r i z e d in that the housing (4, 6) , along the edge of the bottom of the U-profile, is provided with a measuring scale (39) which indicates the correct setting of the retaining plate (20) for a given plate thickness.

5. Lifting tool (2) according to claim 4, c h a r a c t e r i z e d in that the measuring scale (39) along the edge of the bottom of the U-profile is placed in such a manner that compensation is made for the displacement of the pressure plate towards the plate-shaped object upon assumption the carrying position, whereby in the operative carrying position the activation grip is in the optimum position for the person executing the lift.

6. Lifting tool (2) according to one or more of the claims 1-5, c h a r a c t e r i z e d in that at the side facing towards the bottom of the U-profile, the pressure and retaining plates (18, 20) are configured with an asymmetrical bottom shape which is matched by a corresponding shape of the adjacent side (16, 22) of the U-profile.

7. Lifting tool (2) according to one or more of the claims 1-6, c h a r a c t e r i z e d in that the opposing sides of the retaining plate (20) and the pressure plate (18) are arranged with replaceable surfaces.

8. Lifting tool (2) according to one or more of the claims 1-7, c h a r a c t e r i z e d in that the outer side of the housing (4, 6) has a locking lever (62; which, in the active position, clamps the torsion shaft (50) and herewith the pressure plate (18) in the operati- ve carrying position.