WO1990000152A1

WO1990000152A1 - A goods lifting and lowering arrangement

Info

Publication number: WO1990000152A1
Application number: PCT/SE1989/000364
Authority: WO
Inventors: Boh Gösta WESTERLUND
Original assignee: Helpher Ab
Priority date: 1988-06-29
Filing date: 1989-06-27
Publication date: 1990-01-11
Also published as: AU3843989A

Abstract

The invention relates to a goods lifting and lowering arrangement which utilizes a first lifting assembly (1), serving as a goods or load carrier (3), which is attached to a second lifting assembly (10). The second lifting assembly comprises one or more side member structures, where each side member structure includes three or more telescopic sections (10a, 10b, 10c). It is proposed that the first lifting assembly (1) comprises a frame structure (4) on which the goods supporting or carrying surface (3') of a load carrier is mounted, and that for each positional setting of the moveable sections (10b, 10c) of the second lifting assembly (10) the load carrier (3) of the first lifting assembly can be raised to a position (3b') located in the same plane, or essentially the same plane as the upper surface (4a) of the frame structure.

Description

TITLE OF THE INVENTION

A goods lifting and lowering arrangement

TECHNICAL FIELD

The present invention relates to a goods lifting and/or lowering arrangement and then particularly to such an arrangement which comprises a first lifting assembly, which acts as a goods or load carrier and which is connected to a second lifting assembly.

The second lifting assembly of the inventive arrangement comprises one or more side-wall structures, each of which comprises three or more sections which are move- able telescopically in relation to one another, and of which sections a first section is fixed in relation to a bearing structure forming part of the arrangement, whereas the two remaining sections are moveable relative to one another and in relation to the first section, through the intermediary of a lifting and lowering device which acts on one of said sections, and in which arrangement the side member sections are so connected to one another that the third section has twice the length of stroke or vertical movement of the second section and moves at twice the speed of said second section.

BACKGROUND PRIOR ART Arrangements operative in lifting and lowering goods which rest on a goods or load carrier are known to the art in many different forms and for many different fields of application. It is also known that particularly constructed lifting assemblies can be used in these arrangements.

For instance, the US Patent Specification 3,174,634, particularly Figures 9 and 10 of said patent specifica¬ tion, teaches an arrangement which includes a lifting assembly comprising two side member structures each of which includes three moveable sections which can be telescoped relative to one another and of which a first section is fixed in relation to a bearing structure forming part of the arrangement, whereas the two remain¬ ing sections are arranged for movement in relation to one another and in relation to the first section, through the intermediary of a lifting and lowering device which acts on one of these sections, and in which the two side member sections are so connected to one another that the third section has twice the length of stroke of the second section and will move at twice the speed of said second section.

In the case of this known arrangement, the goods or load carrier is fixedly connected to the third side member section.

The arrangement described and illustrated in Swedish published specification 446 852 also belongs to the prior standpoint of techniques.

SUMMARY OF THE INVENTION TECHNICAL PROBLEMS

When studying the prior standpoint of techniques as described in the aforesaid prior publications it will be seen that a technical problem is one of providing a lifting arrangement, with the aid of simple means, whose load carrier can be raised from principally ground level to a pre-determined height, for instance a height of about 1.0 meter, where the load carrier can comprise a simple load support table (load surface) which lacks projecting elements and therewith provide conditions which will enable this load surface to be raised to a further height of, for instance, about 2.0 meters.

A further technical problem is one of providing such a construction in which the load carrier can be raised and lowered for each selected positional setting of the vertically moveable sections of the second lifting assembly, and particularly raised to a position located in the same, or essentially the same plane as the upper¬ most surface of the frame structure, therewith to faci- litate the use of the load supporting or take-up surface of the load carrier.

Another technical problem is one of realizing the advantages afforded by the possibility of attaching to said frame structure or like structure a lower load carrier or load take-up device whose vertical lifting and lowering movements are activated solely by the second lifting assembly.

When considering the prior state of the art as illustra¬ ted and described above, it will be seen that a further technical problem is one of achieving mutual coaction between the two lifting assemblies such that their respective load supporting surfaces can be raised and lowered through the intermediary of their respective lifting and lowering devices, and to realize the advantages that are afforded when allowing at least a lower load supporting surface to be readily removed. In addition, a technical problem resides in the provi¬ sion of a load carrier which can be lowered to floor level and raised to a plane in register with or slightly above the upper surface of the frame structure, and therewith to enable the load carrier to be raised to a level which is at least twice the vertical dimension of the frame structure.

It will also be seen that a further technical problem resides in the provision of conditions which will enable a first load carrier on the first lifting assembly and a second load carrier on the second lifting assembly to be positioned in one and the same lower horizontal plane.

When the load carriers have the form of a substantially flat load supporting surface, it will be seen that a technical problem resides in the provision of conditions which will enable the first load carrier to be lowerable into the confines of the second load carrier, said load carriers being located in individual, closely adjacent horizontal planes.

A further technical problem resides in the provision of a construction which will enable respective load car- riers to be readily exchanged for alternative carriers, for instance carriers in the form of hooks, forks, gripping claws or like devices.

Another technical problem resides in the ability to use two mutually different load carriers mounted on indivi¬ dual lifting and lowering assemblies, these mutually different carriers being constructed to carry gripping claws and clamping devices or to co-act mutually to, for instance, control a remotely controlled loading/off- loading procedure, for instance by attaching a video camera to a first lifting assembly and a gripping claw to a second lifting assembly.

Another technical problem resides in the provision of a module system which will enable these lifting assemblies to be combined mutually, so as to achieve greater flexi¬ bility at low costs.

Still another technical problem resides in realizing that the technical effect obtained when attaching one lifting assembly to another lifting assembly is that the total lifting distance, from a bottom position to a top position, will exceed the total height of the frame structures of the two lifting assemblies, wherewith the possible lifting distance in the vertical direction will exceed the vertical extension of the tandem-construction in its lowered position.

When considering the state of the prior art as described above, it will be seen that a qualified technical prob¬ lem encountered with a goods lifting and lowering arran¬ gement provided with a goods or load carrier is one of realizing that the provision of unique co-action between a first lifting assembly and a second lifting assembly will afford significant simplifications and greater flexibility with respect to adapting the level of the goods to a pre-determined load plane or surface.

It will also be seen that a technical problem is one of realizing that in such cases the first lifting assembly needs to comprise a frame structure to which said goods supporting carrier provided with said load supporting surface shall be arranged, and also to realize the advantages which are afforded when the load carrier can be displaced along a frame part of said frame structure.

It will also be seen that a further technical problem is one of realizing that the frame structure, or frame part, of the first lifting assembly can be replaced with the third section of the three telescopically moveable sections of the second lifting assembly.

It will also be seen that a technical problem is one of providing a goods transporting carriage adapted to retail trade requirements and enabling goods to be lifted and lowered in a simple manner through the inter¬ mediary of two separately driven and separately actuable lifting and lowering arrangements.

It will also be seen that another technical problem is one of providing a goods lifting and lowering arrange¬ ment in which, for each positional setting of the moveable sections of the second lifting assembly, the load carrier of the first lifting assembly can be raised to a position located in the same plane, or essentially the same plane as the upper surface of said frame part, despite the necessary provision of the link wheels or guide wheels of a weight-supporting device beneath said uppermost part or surface.

It will also be seen that a technical problem is one of realizing the advantages that can be afforded by per¬ mitting a lifting and lowering device operative in driving the first lifting assembly, with the aid of a compact construction, to be separate from a lifting and lowering device which drives the second lifting assemb¬ ly, with said devices being adapted for individual drive, thereby enabling the lifting and lowering device of the first lifting assembly to satisfy requirements placed thereon and to adapt the second lifting and lowering device to the requirements placed on the second lifting assembly.

It will also be seen that a further technical problem is one of giving the first, second and third side member sections of suitable cross-sectional shape, so as to enable said sections to coact mutually within a res¬ tricted volumetric space, and to realize the advantages that are afforded when each of these sections comprises an extruded lightweight metal profile.

It will also be seen that a technical problem resides in forming these lightmetal profiles in a manner which will enable the ends of a belt, band or like device to be connected to the first section of each respective side member structures, said belt being connected to the third section over upper and lower rollers in the second section.

It will also be seen that a technical problem resides in the realization of the advantages that are afforded when the third side member section presents a space for accommodating flexible lifting means or weight take-up means of the lifting and lowering device of the one lifting assembly.

Finally, it will be seen that a further technical prob¬ lem is one of providing a construction in which the side member sections are so formed that the width and height dimensions of the lifting arrangement can be readily adapted to prevailing requirements in manufacture and that a space between the side member structures can be adapted to accommodate lift drive motors and batteries. SOLUTION For the purpose of solving one or more of the aforesaid technical problems, the present invention is based on a goods lifting and/or lowering arrangement which includes a first lifting assembly, which acts as a goods or load carrier, and a second lifting assembly connected to the first lifting assembly.

The second lifting assembly comprises at least one, normally two, although some times more lifting members (in the case of two lifting members referred to as side members), with each side member comprising three or more sections which are moveable telescopically in relation to one another and of which sections a first section is fixed in relation to a bearing or frame structure which forms part of the arrangement and optionally also a part of a moveable carriage, whereas the two remaining sec¬ tions can be moved relative to one another and relative to the first section through the intermediary of a lifting and lowering device which acts on one of the sections, the intermediate section, and in that the side member sections are so connected to one another that the third section will have twice the length of stroke of the second section and will move at twice the speed of said second section.

In accordance with one preferred embodiment of the invention, the first lifting assembly comprises a frame structure, or at least a frame part structure, on which said goods supporting or carrying surface or the like belonging to a load carrier is mounted.

The load carrier of the first lifting assembly is arranged for movement to a position located in the same plane or essentially the same plane as the uppermost surface of the frame part structure, for each positional setting of the moveable sections of the second lifting assembly.

According to one particularly advantageous embodiment of the invention, the load carrier is arranged for movement along a frame structure or frame part structure, and that said frame structure or frame part structure, is provided with means operative in co-acting with and holding a second load take-up device which is normally positionable beneath the surface of a first load carrier and which has the form of one or more load carriers.

The first load carrier shall be arranged such that it can be lowered into abutment with a floor surface and raised to the uppermost surface level of the frame structure by the first lifting assembly, whereas the second lifting assembly shall be capable of raising said load carrier to a level which will at least exceed twice the vertical extension of the frame structure.

In this respect, a first load carrier belonging to the first lifting assembly and a second load carrier belong¬ ing to the second lifting assembly can be arranged in a manner which will enable them to be positioned in one and the same lower plane, particularly when said car¬ riers operate in different vertical planes, such as forked carriers.

When the two load carriers have the form of planar load carrying surfaces, the arrangement may be such as to enable the first load carrier to be lowered down in channels provided in the second load carrier. According to one advantageous embodiment, the lifting assembly is provided with means which will enable a second load carrier, having a load supporting surface, to be positioned beneath said first load carrier with the aid of quick coupling means.

It is also proposed that for each positional setting of the moveable sections of the second lifting assembly, the load carrier of said first lifting assembly can be lowered to a position of the load supporting surface above the lowermost surface of the frame structure part of the first lifting assembly corresponding solely to the thickness of the load carrier.

It is also proposed that a lifting and lowering device which drives the first lifting assembly shall be sepa¬ rate from the lifting and lowering device which drives the second lifting assembly, and that these devices are preferably completely different devices.

Each of the three mutually co-acting and telescopically moveable sections of a side member structure may consist of an extruded lightmetal profile whose cross-sectional shape is different from either of the remaining sec- tions.

Connected to the first side member section, or frame structure part, is a belt or like device which is con¬ nected to the third side member section over at least one roller, normally two rollers, in the second side member section.

Finally, it is proposed that the lightmetal profile of the third section presents a space for accommodating components, e.g. flexible lifting elements or load take- up devices of the lifting and lowering device of the first lifting assembly, and that said space will also house the device used to attach a- lifting element to the load carrier.

ADVANTAGES The advantages primarily afforded by the inventive arrangement is that the load carrier of the first lift¬ ing assembly can be lowered principly to floor level and raised to a position located in the plane of the upper¬ most surface of the frame structure, whereafter this surface, comprising a single load support surface (table) can be further raised to a level which corres¬ ponds to or exceeds twice the vertical extension of the frame structure in a normal or lowermost position for the frame structure or moveable sections of the second lifting assembly.

Furthermore, the inventive arrangement enables a first lifting assembly to be mounted on or combined with a second lifting assembly in the form of a unit, with separate lifting and lowering drive devices, therewith affording greater flexibility with regard to the lifting and lowering of goods resting on the load support sur- face of a goods or load carrier, and therewith enabling stability and flexibility to be increased when the two lifting and lowering devices are intended for different lifting capacities, at the same time as the load carrier of the first lifting assembly can be brought to a posi- tion which is independent of the positional settings of the moveable sections of the second lifting assembly and the load carrier of said assembly, where the load car¬ rier is arranged in a manner which will enable it to be raised to a position located in the same plane or essen- tially the same plane as the uppermost surface of the frame structure part.

In addition, the invention provides two mutually co-acting lifting assemblies each having an individual load supporting surface or load carrier, so constructed that the upper can be lowered telescopically down into and over the lower so that their combined thickness will not be appreciably greater than their individual thicknesses.

The primary characteristic features of an arrangement according to the present invention are set forth in the characterizing clause of the following Claim 1.

BRIEF DESCRIPTION OF THE DRAWING

An exemplifying embodiment having features charac¬ teristic of the invention and being the preferred embodiment at this time will now be described in more detail with reference to the accompanying drawing, in which

Figure 1 is a sideview of an inventive arrangement comprising mutually connected first and second lifting assemblies and shows a load supporting surface on a load carrier on the first lifting assembly located in a position slightly above the lowermost sur¬ face of its frame structure part; Figure 2 is a view showing the load carrier of the first lifting assembly in its uppermost position and the second lifting assembly in an almost fully extended position with the load carrier mounted; and Figure 3 is a cross-sectional view of a proposed side member structure which comprises three lightmetal profiled sections, and also shows the elements and devices required for guiding relative movement of said sections.

DESCRIPTION OF A PREFERRED EMBODIMENT

Figures 1 and 2 are side views of a goods lifting and/or lowering arrangement which comprises a first, complete lifting assembly 1 and a second lifting assembly 10 connected to the first assembly 1.

The first lifting assembly is the subject of a Swedish (PCT) Patent Application which was filed on the same date as the present application, or document, and which relates to "Goods lifting and/or lowering assembly". Consequently, the first lifting assembly will not be described in detail here. However, the contents of the aforesaid conterminous patent application shall be understood to form part of the present application or document.

The second lifting assembly 10 comprises two side member structures, of which only one is shown in the side views of Figures 1 and 2. Each side member structure includes three mutually telescopic sections, of which a first section 10a is fixed relative to a bearing or foundation structure "A" which forms part of the inventive arrange¬ ment and which may advantageously be a lower stand or frame part of a moveable, wheeled carriage.

The remaining two sections 10b, 10c are moveable verti¬ cally in relation to one another and in relation to the first section 10a. It should be noted that one of the side member sections of the second lifting assembly, namely the third side member section 10c is identical with a frame structure 2, or rather a frame part struc¬ ture, of the first lifting assembly 1 and reference to this third section 10c in the following is accompanied with the reference (2).

In the Figure 1 and 2 illustration, the three side member sections 10a, 10b and 10c have been displaced laterally to some extent, for the purpose of illustra¬ tion. It will be seen from Figure 3, however, that these sections are preferably arranged in much more intimate relationship, with the sections 10b and 10c accommodated within the section 10a, which has an L-shaped cross- section to this end.

One of the side member sections, namely the second section 10b, is connected to a section raising and lowering device 11 (Figure 2), this device being equiva¬ lent to the corresponding device described and illus¬ trated in the aforesaid US patent specification.

It will be understood, however, that said device may alternatively have some other form, such as the form of a ball-screw arrangement and a piston-cylinder arrange¬ ment for example.

The sections 10a, 10b and 10c are interconnected in a manner such that the third section 10a (2) will have twice the length of stroke of the second section 10b and will move at twice the speed of said second section. This is achieved by connecting to the first section 10a, with the aid of a connector 12, a belt or chain 13 incorporated in the second section 10b, and by connect¬ ing the third section 10c to the belt or chain 13 by means of a further connector 14, said belt or chain 13 running over a lower belt wheel 15 and an upper belt wheel 16 .

Although the first lifting assembly 1 is described in detail in the aforesaid patent specification, it should be mentioned here that said first assembly 1 comprises a frame structure or frame structure part 2, which is intended to replace the third side member section 10c and along which a load carrier 3 having a load support surface 3' or some like support is vertically moveable.

This load carrier 3 can thus be moved along the frame structure 2 or frame structure part 4 to any selected intermediate position between a lower position 3a and an upper position 3b, by activating a section raising and lowering device related to the first lifting assembly 1 and being different to the device referenced 11 in the Figure 2 illustration. These devices can thus be ac¬ tuated separately.

This means that with each positional setting of the moveable sections 10b, 10c of the second lifting assem¬ bly, the load carrier 3 on the first lifting assembly can be raised to a position 3b which is located in the same plane, or essentially the same plane, as the upper- most surface of the frame structure, this surface con¬ stituting the uppermost part or surface of the lifting arrangement.

Furthermore, for each positional setting of the moveable sections 10c, 10b of the second lifting assembly 10, it is possible to lower the load carrier 3, and thus the load support surface 3' , of the first lifting assembly 1 to at least one position 3a located above the lowermost surface 4d of the frame structure part corresponding to the thickness of the load carrier. It should be noted that in the Figure 1 illustration, the third section 10c and the second section 10b can be lowered still further, into abutment with the bearing or foundation structure "A", or into abutment with the edge surface of a loading bay, platform or the like located beneath said foundation structure.

Consequently, the illustrated connector 14 shall be higher than the surface 4d.

The device by means of which the first lifting assembly 1 is raised and lowered, this device not being shown in the present document, is of different construction to the device by means of which the second assembly is raised and lowered, and the two devices may optionally be given mutually different lifting capacities. For stability reasons, it may be suitable to dimension the second device 11 for a lower lifting capacity than that of the lifting device driving the first assembly, so as to prevent loads of excessive weights from being raised to the highest level.

It also lies within the concept of the invention to provide more than three telescopically related sections, although it is believed that three such sections are more advantageous with respect to a desired height distance from the foundation structure "A" to the posi¬ tion 3b' and a suitable total lifting height of twice the vertical extension of the frame structure.

Figure 2 also shows a position 3a', a lowermost posi¬ tion, or the load carrier 3. The load support surface 3' of the load carrier 3 can be moved to any selected position between given terminal positions. It will also be seen from the Figures that in the case of the illustrated embodiment, the lowermost part of the section 10c (2) has provided thereon means 30, in this case screws, which hold a further or second load sup¬ porting device, or load carrier 31, this second load supporting device or load carrier being positionable beneath the load support surface 3' of the first men¬ tioned load carrier 3. The second load carrier 31 is driven by a lifting and lowering device 11 and accom¬ panies the up and down movement of the frame structure 2.

When the first and second load carriers 3, 31 have the form of lifting forks or tines, they can be positioned in mutually different vertical planes and are therewith able to adopt the same horizontal lower plane, or may also be operated independently of one another.

When the first and second load carriers 3, 31 have the form of continuous or planar load support surfaces, the upper surface 31' of the load carrier 31 may be provided with channels capable of receiving and enclosing at least the support bars of the load carrier 3, such that the latter can be lowered in the former.

Figure 3 illustrates a compact side wall construction, of which each of the three sections 10a, 10b and 10c comprise an extruded lightmetal profile, the cross- sectional shape of which is shown clearly in Figure 3.

Although not shown, the corresponding side member struc¬ ture has a corresponding configuration and form.

The first section 10a of respective side wall structure has a belt 13 connected thereto. It is suggested here that the two end parts of the belt or band are attached with the aid of a clamp device 20 positioned in the upper part of the first side member section lOa, using a bar 14.

The belt runs around an upper belt roller 16 and a lower belt roller 15. The location of the upper belt roller is referenced 21. The belt is attached to the lower part of the third side member section 10c in a manner similar to that achieved with the clamp device 20.

It should be noted that the positioning of the belt of the Figure 3 embodiment is alternative to the position¬ ing of the belt or chain 13 of the embodiment illustra- ted in Figures 1-3.

The third side member section 10c also presents a space 22 for accommodating a flexible lifting element or weight take-up element in the form of a chain 23 incor- porated in the first lifting assembly of the inventive lifting and lowering arrangement.

It will also be seen from Figure 3 that provided between the first section 10a and the second section 10b are wheels (or slide elements) 25,26 which are intended to facilitate relative movement between the first and second side member sections 10a and 10b and to ensure that such movement will be free from play.

Relative movement between the second and third side member sections 10b and 10c is similarly facilitated and guided by wheels (or slide elements) 27, 28.

It will also be seen that the third side member section 10c co-acts with the aforesaid frame structure part 4, which is in this case has the form of a round-section bar 4, through the intermediary of wheels 5, 6 which run against diametrically opposed surfaces and which co-act with the load carrier 3 in a manner described in more detail in the aforesaid conterminous patent document.

The illustrated embodiment has been shown to include a first load carrier 3 which is capable of vertical move¬ ment between the positions 3a and 3b in Figure 1 and between the positions 3a' and 3b' in Figure 2, and a second load carrier 31 which can be raised and lowered as a result of raising and lowering the third side member section 10c (2).

It lies within the scope of the invention, however, to replace one of the load carriers with a holder device for, e.g., a video-camera, which may be remotely con¬ trolled, and to replace the other load carrier with a gripping claw or corresponding device, which may also be remotely controlled.

Although the description of the illustrative and exemplifying embodiment has been made with reference to a goods support surface "supporting and carrying surface" it will be understood that within the scope of the invention this and similar expressions can also be taken to include the use of one or more hooks for lift¬ ing a hanging load, one or more gripping claws, prefer¬ ably remotely controlled, for holding and moving goods, and like devices. The same extensive interpretation can also be applied to such expressions as "load or weight take-up surface".

The invention is not therefore restricted to the descri¬ bed and illustrated embodiment and modifications can be made thereto within the scope of the invention as defi¬ ned in the following claims.

Claims

1. A goods lifting and lowering arrangement comprising a first lifting assembly, which acts as a goods or load carrier, and a second lifting assembly which is con¬ nected to the first lifting assembly and which includes one or more sidewall structures each of which comprises three or more sections which are moveable telescopically in relation to one another and of which sections a first section is fixed in relation to a foundation structure which forms part of the arrangement, whereas the two remaining sections are capable of being moved relative to one another and also relative to the first section through the intermediary of a section lifting and low- ering device which acts on one of said sections, and in which arrangement the side member sections are so con¬ nected to one another that the third section has twice the length of stroke of the second section and moves at twice the speed of said second section, characterized in that the first lifting assembly comprises a frame struc¬ ture on which said goods supporting or goods carrying surface is mounted, said surface forming part of a load carrier structure; and in that for each positional setting of the moveable sections of the second lifting assembly, the load carrier of the first lifting assembly can be raised to a position located in the same or essentially the same plane as the uppermost surface of said frame structure.

2. An arrangement according to Claim l , characterized in that the load carrier is arranged for movement along a frame part belonging to said frame structure; and in that said frame structure and/or frame structure part is provided with means for co-action with and holding a load support means capable of being positioned beneath the carrier surface of said load carrier.

3. An arrangement according to Claim 1 or 2, charac¬ terized in that the load carrier is arranged in a manner to enable said carrier to be lowered to floor level and to be raised to the level of the uppermost surface of the frame structure; and in that the second lifting assembly is constructed so as to be able to raise said load carrier to a level which at least exceeds twice the vertical dimension of the frame structure.

4. An arrangement according to Claim l or 2, charac¬ terized in that the first load carrier on the first lifting assembly and a second load carrier mounted on the second lifting assembly are so arranged that the first and the second load carriers can be moved to a position in one and the same, or essentially the same plane.

5. An arrangement according to Claim 1 or 2, charac¬ terized in that the first load carrier on the first lifting assembly and a second load carrier mounted on the second lifting assembly are coordinated in a manner such that the first load carrier can be lowered into the second load carrier.

6. An arrangement according to Claim l, characterized in that for each positional setting of the moveable sec¬ tions of the second lifting assembly, the load carrier of the first lifting assembly can be lowered to a posi¬ tion for the load supporting surface located above the lowermost surface of the frame structure corresponding to the thickness of the load carrier.

7. An arrangement according to Claim 1 or 6, charac¬ terized in that the device by means of which one lifting assembly is raised and lowered is different to the device used to raise and lower the other lifting assembly.

8. An arrangement according to Claim 1, characterized in that each of the three side member sections comprises an extruded lightmetal profile.

9. An arrangement according to Claim 1, characterized in that the first section of each respective side wall structure has attached thereto a belt or like device which is also attached to the third section, over at least one roller mounted in the second section.

10. An arrangement according to Claim 1 or 9, charac¬ terized in that the third side member section presents a space for accommodating components, such as flexible lifting elements, included in the lifting and lowering device of said first lifting assembly.