GB2096080A - Improvement relating to load- carrying carriages which run on tracks - Google Patents

Abstract

The carriage (which is suitable for a mobile storage unit or for an overhead travelling crane) has its body 1 supported on wheels 2 between which and the body relative vertical movement is allowed. The wheels are normally urged downwards relative to the body by means of resilient pads 20 of rubber or plastics material located between fixed supports on the body and rigid plates 19 resting on non- rotatable axes 3 of the wheels. In the form shown each plate 19 and pad 20 is flat. In an alternative form each compression pad is of angle section disposed centrally over the respective axle with its flanges tangentially straddling the axle. Either a resilient pad of complementary angle section is located to engage with the two flanges of the compression pad, or there are separate resilient pads for the flanges. <IMAGE>

Description

SPECIFICATION Improvement relating to load-carrying carriages which run on tracks This invention relates to load-carrying carriages which run on tracks and are of the kind which support or are suitable for supporting, for example, mobile storage units of warehouse or like storage systems, or overhead travelling cranes.

Unevenness in the level of tracks on which such carriages run, produced by the positioning or form of the tracks, can seriously alter the load distribution on the wheels of the carriages during use. It-is usual for carriages to have four wheels and the loading on these wheels can be altered by unevenness in the track on which they run because not all four wheels are properly in contact with the tracks.

The problem becomes particularly acute when, in order to reduce the load which each wheel is intended to support, and keep down the size of the wheels, it is necessary for a carriage to have six or more wheels. When any of the wheels are out of contact, or not properly in contact, with the track the portion of the load which should be supported by those wheels has to be shared by the other wheels which increases the load on them and is undesirable.

The present invention consists in a loadcarrying carriage adapted to run on a track, comprising a body supported on wheels by resilient bearer means which permit relative vertical movement between the body and wheels, each wheel having a non-rotatable axis located with respect to the body by locating means allowing relative vertical movement between the body and the wheel, and the resilient bearer means comprising adjacent each wheel a rigid compression pad which rests on the axle and is urged downwardly, thereby urging the axle and wheel downwardly relative to the body, by a resilient pad of rubber or plastics material located between the compression pad and a support therefor fixed on the body.

The resilient bearer means allows controlled vertical relative movement between the body and the wheels which enables variations in the evenness of the track on which the carriage runs in use to be compensated for. Thus each wheel retains proper contact with the track and maintains support of its portion of the load on the carriage. Normally any unevenness of the track will be relatively small, perhaps deviating from the true level by only a few millimetres, and accordingly the relative movement which the resilient means has to allow is normally equally small.

The extent of the relative vertical movement allowed by the resilient bearer means is variable by appropriate selection of the thickness of the resilient pads. The thicker the resilient pads are the greater is the movement which is possible. As the thickness is reduced the area of contact between a resilient pad and its associated compression pad may be increased to increase its load supporting capacity.

Each resilient pad may be of unitary or composite construction.

Conveniently the respective compression pads and resilient pads are not physically connected together, and neither are the resilient pads and the fixed supports physically connected together, the compression pads and resilient pads being held in position by the compressive loads exerted on them through the wheel axles and supports. A compression pad and its associated resilient pad may be slid into and out of the operative position when the compressive loads are reduced or removed, for example by jacking up the body relative to the respective wheel.

Each compression pad may be in the form of a flat plate, preferably of steel, which is balanced horizontally centrally on the respective axle. In another form each compression pad may be of angle section disposed with its flanges tangential to the respective axle at opposite sides of the vertical plane containing the central longitudinal axis of the axle. There may be one resilient pad of angle section located on the two flanges of the compression pad, or there may be a separate resilient pad, or pads, for each flange. This alternative form has the advantage that it doubles the contact between the compression pad and the axle and thereby enables the area of contact between the resilient pad or pads and the compression pad to be made less for a given load to be supported than is required when the compression pad is in the form of a flat plate.

Thus space can be saved in the accommodation of the resilient bearer means on the carriage.

The relative vertical movement between the wheel axles and the body may be allowed for by locating the axles in apertures which are vertically elongated.

Preferably the support associated with each wheel comprises a housing fixed on the body in which the resilient and compression pads are accommodated. The housing may be of square or rectangular box shape disposed on its side with the axle extending centrally, or near centrally, into it. Where the compression pad is a flat plate disposed horizontally on the axle the box-shaped housing is conveniently arranged in an upright position on the body, that is to say with two opposite side walls vertically disposed and the other side walls horizontal. The compression pad and housing are relatively dimensioned such that the pad can be arranged as a free sliding fit between the vertical side walls, which then serve to guide the compression pad in its vertical movement and to position it centrally on the axle.Where the compression pad is of angle section the box-shaped housing is best arranged obliquely with one of its diagonals disposed vertically so that the resilient pad or pads can then seat against the two uppermost side wails of the housing.

For the construction of load-carrying carriages which support, or are suitable for supporting, mobile storage units of warehouse storage systems there are standard sized wheels readily available which are suitable for carrying loads of up to about 10 tons. For carrying heavier loads the wheels are not so readily available and may have to be purpose made; consequently they are more expensive.

Furthermore the carriages may have to be constructed differently to take the heavier load-carrying wheels. The present invention makes it possible for the standard sized wheels to be used if required, because the carriage can be arranged to run satisfactorily on more then four wheels if necessary so that the portion of the overall load which each wheel is to support is kept within the acceptable working limits for such wheels. The body construction may be of a known form modified to receive the resilient bearer means, and the resilient bearer means may be adapted to keep to a minimum the modifications required for them to be accommodated on the body.

Hence manufacture of carriages in accordance with the present invention is facilitated.

An additional advantage of the present invention is that the carriage may be quieter running than known carriages because of the resilient bearer means. This may be particularly beneficial when the carriage supports an overhead travelling crane indoors.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which, Figure 1 is a fragmentary side view of a load-carrying carriage in accordance with the invention showing a wheel and the associated resilient bearer means, Figure 2 is a section on line 2-2 of Fig. 1, and Figure 3 is a fragmentary side view of a load-carrying carriage showing a wheel and a further form of associated resilient bearer means.

Referring to Figs. 1 and 2 of the accompanying drawings, the carriage comprises a rectangular body 1 constructed from channel section, L-section and plate frame members rigidly secured together and braced by a diagonal member or members against distortion from the rectangular shape. The frame members in combination present a substantially planar top surface of the carriage. Wheels 2 support the body.

The carriage is suitable for use in supporting a mobile storage unit in a storage system of the kind in which three or more storage units disposed in a row are movable along the row such that any adjajcent two of the storage units in the row can be spaced apart to provide a gangway in the storage system for ready access to the units, possibly with a fork, or like, lifting truck. The wheels of the carriage run on a track in the storage system, usually at floor level.

Each wheel 2 is rotatably mounted by suitable bearings on a non-rotatable axle 3 which extends between two parallel frame members 4, 5 of the body of similar channel section.

The frame members 4, 5, as shown in Fig. 2, are disposed with the web walls 6 of the channels vertical and towards one another, and the side walls 7 of each channel extending horizontally in directions away from the other channel. Opposite ends of the axle 3 extend through vertically elongated apertures 8 in the web walls 6 and centrally into housings 9 accomodated within the channels of the frame members 4, 5. Each of the housings 9 is of square box-shape disposed on its side and is fabricated from steel plate.

The housing is welded at rear edges of its four side walls to a front face of a circular steel plate locator 10 which is secured by screws 11 in a complementary recess 1 2 in a rectangular steel seating member 1 3 welded against the inside face of the web wall 6. The locator 10 and seating member 1 3 both have elongated apertures 14 and 15 respectively of similar shape to and in register with the elongated aperture 8 in the web wall.

The opposite ends of the elongated apertures 8, 14 and 1 5 are of complementary diameter to the axle. Typically the apertures are extended vertically by not more than 5mm from a true circular shape, and on the average the extension is 3mm.

In this embodiment each housing 9 is mounted in the channel with two of its opposite side walls 16 disposed vertically and its other two side walls 1 7 disposed horizontally parallel to the side walls 7 of the frame member.

Below the axle in each housing an antirotation plate 1 8 is welded to the axle which extends horizontally between, and is a sliding fit between, the vertical side walls 1 6 of the housing, and serves to prevent the axle from turning whilst allowing it to move vertically in the apertures 8, 14 and 15.

Above the axle in each housing a steel plate compression pad 19 is balanced horizontally on the axle, and a resilient pad 20 of high density rubber is sandwiched between the compression pad and the top side wall 1 7 of the housing. The compression pad and resilient pad are slid into position in the housing and are fully contained within the housing.

The resilient pad, acting through the compression pad 19, urges the axle towards the bottoms of the apertures 8, 14 and 1 5. The clearance in the apertures above the axle then permits vertical movement of the axle and the wheel it carries in the case of any unevenness of the track on which the wheel runs when the carriage is in use. The vertical side walls 1 6 of the housing locate the compression pad and resilient pad against lateral movement on the axle.

As previously mentioned the relative vertical movement allowed between the body and the wheels under given loads carried by the carriage in use is determined by the thickness of the resilient pads and the area of contact between those pads and the compression pads. The resilient pads can be readily removed and replaced by others of different sizes and thicknesses if the load-carrying requirements of the carriage should need to be altered. The resilient and compression pads can also be readily replaced should they become worn.

A cover plate 21 is secured over the front of each housing to enclose the resilient and compression pads, and the axle end, in the housing. The cover plate may be retained in position by a screw 22 passed through a hole in the plate and screwed into a tapped axial hole in the end of the axle, or in any other suitable manner.

In the alterantive form shown in Fig. 3 each wheel is mounted on the body in a manner similar to that described above, and the housing 9 is secured in similar manner to the frame member 4,5 of the body. However, the housing is fixed obliquely to the locator 10 so that in its secured position on the frame member one of its diagonals is vertical and the other is horizontal. In this case a compression pad 23 of steel angle section is positioned longitudinally on the axle in the housing so that its two flanges 24 are tangential to the axle symmetrically at opposite sides of the vertical plane containing the central longitudinal axis of the axle. An angle-section resilient pad 25, again of high density rubber, is located on the compression pad and sandwiched between that pad and the two uppermost side walls of the housing.The resilient pad 25, through the two areas of contact which the compression pad has with the axle, urges the axle towards the bottom ends of the vertically elongated apertures in the web wall of the frame member, the seating member and locator.

In either of the forms described above the body may have four, six, or more, wheels depending upon the load required to be carried by the carriage in use. Where six or more wheels are provided they will normally be evenly spaced along the body. This helps not only to spread the load on the carriage as evenly as possible between the wheels but also to spread the points at which loads are applied to the tracks through the wheels, which is desirable in a storage system as described when several storage units may be grouped together along the tracks.

It will be appreciated that where suitable a carriage substantially as described with reference to either Figs. 1 and 2 or Fig. 3 may be used for supporting an overhead travelling crane.

Claims (1)

1. A load-carrying carriage adapted to run on a track, comprising a body supported on wheels by resilient bearer means which permit relative vertical movement between the body and wheels, each wheel having a non-rotable axle located with respect to the body by locating means allowing realtive vertical movement between the body and the wheel, and the resilient bearer means comprising adjacent each wheel a rigid compression pad which rests on the axle and is urged downwardly, thereby urging the axle and wheel downwardly relative to the body, by a resilient pad of rubber or plastics material located between the compression pad and a support therefor fixed on the body.

2. A load-carrying carriage according to claim 1 wherein each resilient pad is of unitary construction.

3. A load-carrying carriage according to claim 1 wherein each resilient pad is of composite construction.

4. A load-carrying carriage according to any preceding claim wherein the compression pads and resilient pads are retained in position relative to the wheel axles and supports by compressive loads exerted on them through the wheel axles and supports.

5. A load-carrying carriage according to any preceding claim wherein each compression pad comprises a flat plate balanced horizontatly centrally on the respective axle.

6. A load-carrying carriage according to any of claims 1 to 4 wherein each compression pad is of angle section disposed with its flanges tangential to the respective axle at opposite sides of the vertical plane containing the central longitudinal axis of the axle.

7. A load-carrying carriage according to claim 6 wherein each resilient pad is of angle section and is located to engage with the two flanges of the angle section compression pad.

8. A load-carrying carriage according to claim 6 wherein there is a separate said resilient pad for each of the flanges of the angle section compression pad.

9. A load-carrying carriage according to any preceding claim wherein the locating means comprise vertically elongated apertures in the body, or parts fixed relative thereto, in which elongated apertures the axles are recieved.

10. A load-carrying carriage according to any preceding claim wherein the support associated with each wheel comprises a housing fixed on the body in which the compression and resilient pads are accommodated.

11. A load-carrying carriage according to claim 10 wherein the housing is of square or rectangular box shape disposed on its side with the axle extending centrally, or near centrally, into it.

1 2. A load-carrying carriage according to claims 5 and 11 wherein the housing is arranged with one pair of opposite side walls vertically disposed and the other pair of opposite side walls horizontally disposed, and the compression pad and housing are relatively dimensioned such that the pad is a free sliding fit between the vertical side walls which guide the compression pad in its vertical movement and position it on the axle.

1 3. A load-carrying carriage according to claim 11 and any of claims 6 to 8 wherein the housing is arranged obliquely with one of its diagonals disposed vertically so that the resilient pad or pads seat against the two up;'r-most side walls of the housing.

4. A ioad-carrying carriage according to any of claims 11 to 1 3 wherein the housing is fixed at edges of its four side walls to a face of a circular locator which is secured in a complementary recess in a seating member fixed to a frame member of the body.

1 5. A load-carrying carriage according to any of claims 10 to 14 wherein the axle of each wheel is restrained from rotation by means of a plate secured to and projecting transverseiy from the axle towards opposed walls of the housing which prevent the plate, and thereby the axle, from rotating in the housing.

16. A mobile storage unit including a load-carrying carriage as claimed in any preceding claim.

1 7. A storage system comprising a track, three or more storage units supported on the track by load-carrying carriages as claimed in any of claims 1 to 1 5 running on the track, the carriages and storage units being disposed in a row along the track and the storage units being movable along the track on the carriages such that any adjacent two of the storage units in the row can be spaced apart to provide a gangway between them.

1 8. An overhead travelling crane including a load-carrying carriage as claimed in any of claims 1 to 1 5.

1 9. A load-carrying carriage substantially as described herein with reference to and as illustrated by the accompanying drawings.