TECHNICAL FIELD The present invention relates to a materials or goods lifting and/or lowering assembly, and then particularly, but not exclusively, to an assembly comprising a frame structure, a load carrier, a materials supporting or carrying surface on said load carrier, drive means operative in raising and lowering the load carrier via oppositely located wheels or rollers along a part of the frame structure, and devices for taking-up the weight of the materials, or goods, and the load carrier, said devices being intended to co-act with the load carrier at a distance from said frame structure.

The invention also relates to assemblies of this kind in which the weight take-up device has the form of a flexi¬ ble element, such as a chain, which is fixedly attached to the load carrier and which passes upwardly through the frame structure and over one or more wheels or pulleys mounted on and positioned closely adjacent to the upper part of the frame structure or frame structure part.

Although the proposed assembly is intended for both lifting and lowering materials or goods placed on the load carrier, the assembly will be referred to herein¬ after simply as the "lift assembly", for simplicity reasons.

BACKGROUND PRIOR ART

A lifting assembly of the aforesaid kind is described and illustrated in German Patent Specification 409 597, in which a platform is arranged to rest on a carrier

device (or forks) , positioned horisontally and extending beyond a frame part.

Two carriers each having a horizontally extending part and a vertically, upwardly directed arm are positioned on the outside of a frame structure part. The upper free ends of the arms co-act with a shaft on which upper rollers are mounted, these rollers being intended to support against one side of the frame structure part and to roll along said part when the carriers are raised or lowered.

The horizontal carriers also co-act with lower rollers, located beneath the load supporting surface of the carrier, and also rest against one side of the frame structure part, but then against its opposite side.

The upper and lower rollers are arranged so as to hold the platform supported by the carriers in a horizontal position, while moving the platform up and down along the frame section part. The upper ends of two load- supporting chains are attached to the upper shaft, on the rear side of the frame section part via a respective spring means. Each of the chains extends over a bottom, driven sprocket or chain wheel, and passes from said wheel upwards and over a corresponding sprocket or chain wheel mounted on the upper end of the frame structure, from where the chains pass down to the platform and are attached to the centre part of respective vertical arms.

The chains are attached to the vertically extending arm between the wheels, as seen in the vertical extension, and a line extending through the rotational axes of the wheels or rollers forms an angle of about 60° with the horizontal.

The torgue generated by the combined weight of the goods and load carrier is taken-up by the wheels and the frame section part, whereas the weight itself is taken- up by the chains.

The ratio of the length of the -load carrier to the vertical distance between the wheel axes is in the order of slightly less than 3.

A lifting assembly of principally corresponding con¬ struction is described and illustrated in the German Patent Specification 566 326. In the case of the assembly known from the German Patent Specification, however, a weight supporting or take-up device, in the form of a lifting line, co-acts with the load carrier at a point insignificantly outside two wheels or rollers intended for taking-up occurrent torque. The lifting lines co-act with an upper line drum.

The arrangement illustrated and described in German Offenlegungsschrift 3 300 018 also forms part of the prior art. This publication teaches an arrangement in which a load is suspended from two weight-supporting devices in the form of lines and the arrangement com¬ prises two rollers in which a line which passes through the rotational axes of the rollers extends horizontally. The rollers control the lifting or lowering of a load along a vertically extending frame structure part with- out being able to take-up torque.

SUMMARY OF THE PRESENT INVENTION

TECHNICAL PROBLEMS When studying the present state of this art, as descri- bed above, it will be seen that in the case of an arran-

gement of the kind defined in the introduction a techni¬ cal problem resides in realizing that a quite particular construction is required in order to enable the load carrying surface of the. load carrier to be raised to a level adjacent the upper part or upper surface of the frame or frame part notwithstanding the obstructive presence of pulleys or wheels positioned beneath said uppermost part or surface and co-acting with the weight take-up device, and therewith provide a practical struc- ture with respect to the dimensioning of the attachment points of said device.

When considering the aforesaid circumstances and the solution to the aforesaid technical problem, it will be seen that a further technical problem is one of provid¬ ing a structure in which the load carrier can be moved to a position adjacent the surface on which the lifting assembly is supported, while giving the load carrier a thickness of only 5-10% of the length of the load carrier.

Another technical problem is further of providing an assembly in which the ratio of load carrier length to the horizontal distance between wheel axes can be grea- ter than that aforementioned, so as to enable the load carrier to be given a low height dimension while still being able to take-up the forces generated by Jhe load carrier between the wheels and the frame part.

A still more complicated technical problem in this regard is to provide an assembly in which the load carrier can be located in the same plane as the lower¬ most part or surface of said frame part.

In addition hereto, a technical problem resides in providing an assembly in which the free end of the load carrier can be tipped towards the assembly supporting surface solely by making simple modifications to the assembly.

It will also be seen that a technical problem resides in the ability to take-up the torque generated by the goods or load with the aid of wheels or rollers which are mounted on the load carrier and which run along tracks on the frame part, with said wheels or rollers located close together in the vertical direction but nevertheless being capable of overcoming oσcurrent forces by the virtue of a chosen configuration of the frame part and the peripheral surface of the wheels.

It will also be seen that a further technical problem is one of providing a lifting assembly in which the verti¬ cal distance between the wheel axes divided by the roller diameter at the point of contact results in a factor smaller than four and still enables occurrent high forces and loads to be mastered.

Another technical problem is one of mastering occurrent forces, by suitably dimensioning the wheel axles and bearings of the assembly.

When considering the earlier standpoint of techniques as described above, and with a view to the large normal forces acting between the wheels or rollers and the frame part and generated by a loaded load-carrier, a qualified technical problem resides in being able to pass a line through the rotational axes of the wheels at a small angle to the horizontal plane.

Another technical problem is one of proposing in prac¬ tice a particular range within the length extension of the load carrier within which the weight take-up device can work, so as to counteract occurrent normal forces instead of amplifying said forces.

When considering one or more of the aforesaid technical problems, it will be seen that a further technical problem resides in achieving optimal dimensioning of the assembly components, taken from a loading aspect, while still ensuring, at the same time, optimal dimensioning of the components from the aspect of the space avail¬ able.

A further technical problem associated with the afore¬ mentioned weight take-up device resides in the provision of a well defined attachment of said device to the load carrier, while taking into account the space require¬ ments of the frame part, the wheels and the guide pul- leys.

When taking the aforegoing into account, it will be seen that a technical problem resides in the provision of a lifting assembly, and preferably an assembly which can be moved along a floor surface, which is capable of being used, inter alia, in department stores, general retail stores etc. such as to enable large quantities of light weight goods to be moved horizontally between mutually different storage locations and also in those circumstances where it is desirable to move a load carrying surface on a load carrier to mutually different vertical levels.

SOLUTION For the purpose of solving one or more of the aforesaid* technical problems, the present invention relates to a goods lifting and lowering assembly comprising a frame structure, a goods supporting or carrying surface, a drive means intended for co-action with a load carrier such as to enable said carrier to be raised or lowered along a part of said frame structure with the aid of mutually opposing wheels or rollers, and which includes a device for taking up the weight of the goods and the load carrier and which cooperates with the load carrier at a distance from said frame part.

In accordance with the invention, the weight take-up device has the form of a flexible element, such as a chain, which extends upwardly from the load carrier and passes over at least one chain guide wheel or pulley positioned beneath and attached to the upper part of the frame or frame part.

In accordance with the present invention it is proposed that the weight take-up device of this known arrangement is adapted to co-act with the load carrier at a distance beneath the load supporting surface thereof such as to enable said surface to be raised to a level adjacent to or somewhat higher than the upper surface of the frame or frame part.

In accordance with the embodiments at present proposed within the scope of the inventive concept, it is sug¬ gested that said distance will at least correspond to or exceed the radius of the direction changing wheel or pulley.

Furthermore, it is suggested that the length of the load carrier divided by a vertical distance between the rotational centres of the opposing wheels or rollers will result in a factor greater than 5, preferably a factor between 10 and 30.

It is further proposed that a vertical centre distance between the wheel axes divided by a roller diameter at the point or surface of contact with the frame part will result in a factor smaller than four, preferably a factor between one and three.

In this respect, it is possible for the load carrier to take a position in which the load carrying surface is located at a distance above the lowermost part of the frame or frame part which corresponds to the thickness of the load carrier.

In accordance with one particular embodiment of the invention, the total thickness of the load carrier will be less than 10% of the length of the load carrier, preferably between 5 and 8% of said length.

Attached to the upper part of the frame is at least one, normally two horizontally spaced pulleys intended for co-action with a flexible element, in the form of a chain, which runs upwardly, over the pulley, or pulleys, and from there down to a driven pulley or wheel, and then upwards to the frame-related edge part of the load carrier, where the chain is attached.

The two opposing wheels or rollers on the frame part are mounted close together, such that a line passing through the rotational axes of the wheels will form an angle to the horizontal larger than 20° and smaller than 50°,

preferably about 40°.

Further the wheels or rollers will co-act with the running surface of the frame structure part in such a manner that they will take up the whole or the main part of the torque from the load and its load carrier.

The weight take-up device is intended to act on the load carrier with an upwardly directed force close to the frame part, from a space aspect, and normally within a range of 5-20% of the length of the load carrier, located between the frame part and the outer surface of the load carrier or some corresponding surface.

In accordance with one advantageous embodiment of the inventive assembly, the drive means comprises a common drive machine and at least two power transmission mem¬ bers, each of which is located in the vicinity of a respectively two wheels or rollers co-acting with a respective frame part.

When the power transmission members have the form of an element which will not be stretched or flexed by tensile forces, the drive machinery may be attached to the frame in a manner which will enable the vertical position of the machinery to be adjusted, therewith to enable the tension to be maintained in respective power transmis¬ sion members and to lock said members in the position in which the drive machine stops.

For the purpose of enabling another adjustment to be made, it is proposed that at least one end of one member is arranged to co-act with the load carrier over a length adjusting element.

According to one preferred embodiment, the frame part is constructed from hardened round rod and the peripheral surfaces of the wheels have a shape which conforms to the peripheral form of the round rod, so as to be able to take-up occurrent forces, particularly torque.

It is also proposed that the inventive lifting assembly is provided with means which enable additional vertical movement to be made. Accordingly, the frame part may be stationarily related to a telescopic lifting unit as in load carrier.

Load carriers in the form of a flat platform or in the form of lifting tines or forks have an outwardly narrow- ing cross-sectional shape. The lowermost part of the frame structure part is bevelled or curved, wherein at least one of the wheels is arranged to run along said bevel or curve, such as to tip the free end of the load carrier down towards the floor surface or like founda- tion, during terminal movement of the load carrier.

ADVANTAGES Those advantages primarily associated with an inventive lifting assembly according to the present invention reside in the provision of a load carrier of low con¬ struction height which can be moved along a frame struc¬ ture part, and in which assembly a load carrying or load bearing surface on the load carrier can be raised to a position level with or slightly higher than the upper- most end of the frame structure part, notwithstanding the presence on said uppermost frame part of two wheels or pulleys which receive a load take-up chain located beneath the uppermost end of said frame part.

The load carrier has a limited thickness and can there¬ fore be lowered to a position level with the lower surface of the frame part, such as to enable the load carrier to be brought adjacent an assembly supporting surface, e.g. a floor surface.

It has been found that the inventive lifting assembly can be utilized to particular advantage in connection with transport trolleys, carriages etc. within the retail industry and storage industry, such as to enable large quantities of lightweight goods to be moved horiz¬ ontally between mutually different storage locations and/or moved vertically to mutually different vertical levels.

The primary characteristic features of an inventive lifting assembly are set forth in the characterizing clause of the following Claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in more detail with reference to an exemplifying embodiment thereof at present preferred and with reference to the accompanying drawings, in which Figure 1 is a schematic side view of a lifting assembly constructed in accordance with the invention; and Figure 2 is a schematic side view of a lifting unit in which the load carrier is intended to co-act with a frame part or a frame structure forming part of the assembly illustrated in Figure 1, thereby enabling the unit to be lifted to a high level.

DESCRIPTION OF A PREFERRED EMBODIMENT

The inventive lifting assembly is primarily intended to be mounted on or form part of a carriage, or trolley, of the kind normally used for the purpose of moving goods as before indicated, e.g. such as a transport trolley provided with caster wheels. Since the trolley, carriage or similar device used to support the lifting assembly does not constitute a significant part of the invention, solely the lifting assembly and the various components thereof will be described in the following.

The invention relates to a materials or goods lifting and/or lowering assembly, hereinafter referred to solely as as lifting assembly.

Figure 1 illustrates the principle of a "low-lift" unit 1, i.e. a lift arrangement in which a load is lifted from essentially floor level to a comfortable working height, e.g. a height of lm. Naturally, the load sup¬ porting surface is lowered to the same extent.

The low-load lift assembly 1 comprises a vertically extending frame structure 2, a load carrier 3, a verti¬ cally extending frame part or guide column 4, two guide and bearing wheels or rollers 5 and 6 mounted on the load carrier 3, a drive motor 7 and a drive chain 8.

As will be understood, a practical design of the assembly 1 may include one, although normally two guide columns 4, each provided with two guide wheels or roll- ers 5, 6, which in this case are mounted on a common load carrier (load supporting surface) or each pair of wheels mounted on a respective load carrier, which load carriers, optionally in the form of lifting tines or forks, is adapted to support a load either directly or through the intermediary of a load supporting surface.

In the case of the illustrated embodiment, the vertical guide column or post 4 has a round cross-section and is so mounted in relation to the frame structure 2 that the inner, frame-related end or edge part 3b remote from the load-carrying end 3a of the load carrier 3 can extend past the guide column 4, and such that the guide rollers 5 and 6 journalled on the load carrier at a distance from the inner end thereof are in active, guiding enga- gement with the guide column. Although not shown, the peripheral surfaces of the guide rollers 5 and 6 will conform totally or partially with the peripheral shape of the guide column.

In the case of the illustrated embodiment, the drive motor 7 is a reversible worm gear motor, which is moun¬ ted adjustably at the bottom of the frame structure 2, by schematically illustrated means 9a, and drives a chain wheel 10 via a gear 9, one such chain wheel being provided for each chain. The vertical position of the drive motor 7 can be adjusted in a known manner with the aid of the aforesaid means 9a, such as to hold the chain 8 in tension.

The gear 9 is an reversible, self-braking gear and is dimensioned to hold the load carrier 3, when carrying a load, in a latched position, with the aid of no other means other than not activating the motor 7. Alterna¬ tively, the gear can be arranged to cooperate with an electrical, deactivating brake.

For the sake of simplicity, an embodiment will now be described which comprises solely one frame part 4 or guide column, although two mutually parallel guide columns or posts are to be preferred.

Extending around the chain wheel drive 10 is a flexible elemnt in the form of a chain 8, a first end 11 of which is attached to the inner end, or frame-related edge part 3b of the load carrier 3, at a location adjacent the upper surface 3' of the load carrier, and the other or second end 12 of which is attached to the load carrier 3, via two pulley or guide wheels 13 and 14 mounted at the top of the frame structure 2, outwardly of both the guide column 4 and the guide roller 6. The first end 11 of the chain is suitably attached to the load carrier 3 at a location which is spaced at a shorter distance from the guide column 4 than the second chain end 12. This_ latter feature is primarily occasioned because of reέT- sons of space.

As will be seen from Figure 1, each of the guide rollers 5 and 6 is mounted on a respective side of the guide column 4, wherein the rotational axes of the first guide roller 5, which is the rear guide roller, and the point of contact of the guide roller with the guide column 4 are located at a higher level than the rotational axis of the forward, second guide roller 6 and its point of contact with the guide column 4. This arrangement is operative to balance the torque generated by the load carrier 3. It should be observed in this respect that the chain attachment point 12 will primarily be sub¬ jected to a force which corresponds to the weight of the load, and that the bending movement around the frame part 4 is taken up by the rollers 5, 6.

It will be understood from this that the roller journals must be dimensioned accordingly.

In practice, the attachment 12 is able to compensate for and to take-up part of the torque generated, by reducing the normal forces and therewith the frictional forces in the rollers 5 and 6.

When raising and lowering the load carrier 3, the motor 7 is activated, such as to cause the chain drive 10 to rotate either in an anti-clockwise or a clockwise direc¬ tion as seen in Figure 1. When the chain drive 10 is rotated in an anti-clockwise direction, the part 8' of the chain located between the drive 10 and the pulley wheel 13 is pulled downwards, resulting in the applic¬ ation of an upwardly acting force, via the pulley wheels 13 and 14, on the chain part 8" located between the pulley wheel 14 and the chain end 12, causing the chain part 8" to move upwards. At the same time, the chain part 8"' located between the chain drive 10 and the first chain end 11 is extended to a corresponding ex¬ tent, i.e. the chain end 11 moves upwards and holds the chain part 8 ' ' ' suspended.

The vertical guide column 4 is mounted between the wheels 5, 6. The first wheel or roller 5 mounted on the load carrier 3 is intended to run along a first roller surface or track 4b provided on the guide column and facing away from the load carrying surface, whereas the second wheel or roller 6 mounted on the load carrier is intended to run on a second running surface or track 4c facing towards the load carrying surface, the first wheel 5 being located slightly higher than the second wheel 6, so that the peripheral surfaces of respective wheels are located slightly beneath the load supporting surface 3' and slightly above the lower surface 3".

The two wheels are intended to co-act with respective running surfaces 4b, 4c on the frame part such that the wheel attachments mounted on reinforcements in the load carrier 3 adjacent the frame part or column 4 will take up the whole, or essentially the whole of the torque generated by the weight of the goods and the weight of the load carrier.

As illustrated in Figure 1, the second chain end 12 is attached to the load carrier 3 at a location slightly beneath the load supporting surface 3' of the load carrier 3, whereas the first chain end 11 is attached to the load supporting surfaer ^" 3 ^" * or immediately there- beneath. Consequently, it is possible to lower the load carrier 3 to some considerable extent, i.e. in principle such that the surface 3' will be level with the rota¬ tional axis of the chain drive 10. As a result, the lower surface 3" of the load carrier 3, and then par¬ ticularly its frame-related part, will be located level with or slightly beneath the lowermost part 4d of the frame part 4.

Furthermore, the bottom edge surface of the frame part or column 4 is bevelled, as shown at 4e, or alter- natively the guide column 4 is curved, so that the load supporting surface 3' of the load carrier 3 can be caused to tip downwards, such as to bring the under- surface 3" in parallel abutment with the supporting surface A. This will enable the pointed part 3a of the load carrier to be brought flat against the supporting or floor surface A.

According to the invention, the two wheels 5, 6 are located close to one another, and a line 30 extends through the rotational axes or journal axles of the

wheels such as to form a small angle "a" with the hori¬ zontal plane "B", this angle being greater than 20° and less than 50°, preferably about 40°.

The chain part 8" is intended to operate with an upward¬ ly directed lifting force in the near vicinity of the guide column 4, although externally off said column, although in practice the force will act within a region of 5-20% of the load carrier length, calculated from the guide column 4 and to the outer edge 3a of the load carrier. The lower value will preferably exceed the diameter of the wheel 6 and the diameter of the pulley 14.

The chain part 8" is also intended to co-act with the load carrier 3 at a distance beneath the load supporting surface 3' of said carrier, this location being referen¬ ced 12 and the distance being selected such that the load supporting surface 3' can be located in a plane level with the uppermost surface 4a of the guide column or frame part 4, or slightly above said surface. Conse¬ quently, in practice, this distance should be equal to the radius of the caster wheel 14 or slightly greater than said radius. The attachment 12 can be located adjacent the undersurface 3" of the load carrier 3.

When two chains are used, at least one of the chain parts 8" should be arranged to co-act with the load carrier via a length adjusting device.

It should be ensured that the attachment 12 is not located at such a distance from the frame 2 and the guide column 4 as to cause the gravitational centre of the load carrier 3 to lie between the frame 2 and the attachment 12.

In the aforegoing it has been said that the torque generated by the weight of the load is taken-up by the wheels 5, 6, and that the forces acting between the wheels 5, 6 and the frame part 4 are high.

Since, for practical reasons, the vertical distance "c" should be very small, and since the stresses acting between the wheels and the frame part can therefore be expected to be very high, it is proposed that the verti¬ cal distance "c" between the wheel axes divided with the roll diameter "d" for one of the wheels at its point of engagement results in a factor of less than 4. For practical reasons, however, this factor cannot readily be permitted to lie beneath 1. A suggested range in this respect is between 1 and 3, preferably between 1 and 2.

In order to enable an integrated lifting assembly to achieve higher lifting heights than those achieved solely by a low lift assembly 1, while still enabling the load carrier and load to be lowered to floor level and to be raised to a level corresponding to the upper surface of the frame, the frame 2 of the lifting assemb¬ ly 1 can be combined with a high lift assembly 15, illustrated schematically in Figure 2, thereby enabling the load plane to be raised above the normal vertical extension of the frame.

The high lift assembly 15 comprises two, normally three guided profile sections which can be telescoped relative to one another, i.e. an outer or rear profiled section 16, an intermediate profiled section 17 and an inner or forward profiled section 2. The outer section 16 is intended to be attached, for instance, to a trolley or carriage "A". The intermediate section 17 carries a

pulley or guide wheel 19 around which there extends an endless belt, wire, chain or like element 21.

The endless element 21 extends freely around pulley wheels or guide wheels 19 and 20 and is attached ad¬ jacent the top (at 22) to the outer section 16 and adjacent the bottom (at 23) to the inner section 2. A power generated device (not shown) such as a pneumati¬ cally or hydraulicly operated cylinder- and piston arrangement or an electromechaniσ positioning device as an electrical linear actuator is mounted between the fixed outer section (or a trolley or some like machine on which the outer section is__rigidly mounted) and is intended to urge the intermediate section 17 upwards. This will cause the inner part 23 of the endless element 21, attached to the inner section 2, to move upwards at a speed which is twice the speed of the intermediate section 17 and through a distance which is twice the length of stroke of said section.

The assembly illustrated in Figure 2 is described and illustrated in more detail in a conterminus patent application relating to "A goods lifting and lowering arrangement comprising mutually connected first and second lifting assemblies".

It should be noted in particular that in the description of the exemplifying embodiment reference has been made to a materials or goods support surface. It will be understood that the expression "supporting or carrying surface" will also include the use of one or more hooks for lifting a hanging load, one or more gripping claws, preferably remotely controlled, for holding and moving goods or the like, or to some corresponding device.

The same extensive interpretation shall also be applied to the expression "load supporting surface".

It will be understood that the invention is not restric¬ ted to the aforedescribed and illustrated exemplifying embodiment, and that modifications can be made within the scope of the following claims.