Storage Facility

Abstract

A mobile storage facility comprising three or more storage structures arranged successively along a track and each movable along the track, drive means operable to move the two end structures in mutually opposite directions between first positions in which all of the structures are closed onto one another and second positions which are spaced further apart than the first positions, and coupling means selectively to couple and uncouple each successive pair of structures to and from one another.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to storage facilities and more particularly to facilities providing what is commonly known as "mobile storage."

2. Description of Prior Art

Conventional mobile storage facilities comprise a number of storage structures mounted on a floor track such tat they can be moved together to form a block but such that an access aisle can be created between any pair of adjacent structures by moving selected structures along the track.

Many mobile storage facilities are provided with drive means in order to drive the storage structures along the track. Usually the drive means is in the form of a cable drive but there have been recent proposals to employ pneumatic or hydraulic rams to provide the drive. However, in all the previously known facilities having drive means, the drive means has operated to create a new access aisle simply by moving one or more of the storage structures in one direction to take up the previously existing aisle space. The present invention provides a novel arrangement which has advantages over all the known power driven facilities as will be apparent from the ensuing description.

SUMMARY OF THE INVENTION

According to the invention there is provided a mobile storage facility comprising three or more storage structures arranged successively along a track and each movable along the track, drive means operable to move the two end structures in mutually opposite directions between first positions which are so spaced that all of the structures are then in buff with one another and second positions which are spaced further apart than said first positions, and coupling means selectively to couple and uncouple each successive pair of structures together.

Preferably the drive means comprises a pair of double-acting pneumatic or hydraulic power cylinders connected one to each end structure.

Preferably further the strokes of the power cylinders are equal.

In order that the invention may be more fully explained some specific embodiments thereof will now be described in detail with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a plan of a pneumatically operable mobile storage facility constructed in accordance with the invention and shows the facility in a closed condition;

FIG. 2 is a further plan of a major part of the facility but shows the facility in an open condition;

FIG. 3 is a cross section on the line 3-3 in FIG. 2;

FIG. 4 is a cross section on the line 4-4 in FIG. 3;

FIG. 5 is a cross section on the line 5-5 in FIG. 3;

FIG. 6 is an enlargement of part of FIG. 4 and in particular shows a latching mechanism latching two mobile storage structures of the facility together;

FIG. 7 is a view similar to FIG. 6 but shows the latching mechanism in a released condition;

FIGS. 8A and 8B fit together to form a diagram of the pneumatic circuit of the facility;

FIG. 9 is a somewhat diagrammatic representation of certain components of the pneumatic circuit;

FIG. 10 shows an alternative means for actuating the latching mechanism of FIGS. 6 and 7;

FIG. 11 is a view similar to FIG. 3 showing an alternative arrangement for a main drive cylinder of the facility; and

FIGS. 12 and 13 are diagrammatic plans of a high density car parking system constructed in accordance with the invention and show the system in two differing conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The storage facility illustrated in FIGS. 1 to 7 comprises seven mobile storage structures (hereinafter termed "mobiles") arranged side by side to roll along a floor track extending between a pair of end walls 21, 22. The two end mobiles 23, 24 are half the width of the five intermediate mobiles 25, 26, 27, 28, 29. End mobiles 23, 24 are closed in at their outer side faces 31, 32 and are open on their inner side faces 33, 34 to provide access to storage shelves (not shown) spaced vertically within them. Each of the intermediate mobiles 25, 26, 27, 28, 29 is open on both side faces and is provided with a central vertical partition and vertically spaced shelving to each side of the partition.

The floor track is constituted by a pair of laterally spaced flat metal strips 36 which extend in parallel relationship between end walls 21, 22 and are embedded in a concrete floor 37 between the end walls so as to lie flush with the upper surface of the floor. The bases of the mobiles are provided adjacent their four corners with unflanged transport wheels 38 which run on the track strips 36. Laterally within the transport wheels 38, the mobiles are also fitted with vertical stub axles 39 which carry at their lower ends guide rollers 41. The latter rollers engage accurately machined inner side faces 42 of a pair of channel shaped guide tracks 43 which are also embedded in the floor 37 so as to be flush therewith.

End walls 21, 22, which may be structural walls of a building in which the facility is installed, are spaced apart by a distance which is somewhat greater than the combined widths of the mobiles and the two end mobiles 23, 24 can be moved along the floor track by operation of a pair of opposed double-acting pneumatic power cylinders PC1, PC2. FIGS. 3, 4 and 5 show the manner in which power cylinder PC1 drives end mobile 23 and power cylinder PC2 drives end mobile 24 in identical fashion. As shown in FIGS. 3, 4 and 5, power cylinder PC1 is housed within an elongate hollow housing 46 which is embedded in the concrete floor 37 midway between the track strips 36 so as to extend longitudinally centrally of the facility. The casing 47 of the power cylinder is fastened to the depending legs of a channel shaped metal bracket 49 welded to the base 23a of end mobile 23. The depending legs of bracket 49 project into housing 46 through a pair of laterally spaced longitudinally extending slots 51 cut in the upper wall of the housing which lies flush with floor 37. The end of the piston rod 52 of power cylinder PC1 is in the form of a clevis 53 and is connected by means of a pin 54 to a cleat 56 welded into the end of housing 46. FIG. 3 shows the cylinder in a retracted condition. Extension of the cylinder will cause casing 47 to move to the right within housing 46 and the end mobile 23 will also be drawn to the right by virtue of its connection to the casing by bracket 49.

Power cylinders PC1 and PC2 are connected into a pneumatic circuit (which will be described hereinafter) so that they can be operated simultaneously in opposed relationship. Extension of these cylinders moves the end mobiles 23, 24 into the positions shown in FIG. 1 in which they are spaced equally from the respective end walls 21, 22 and in which they are closed onto the five intermediate mobiles 25, 26, 27, 28, 29 so that all of the mobiles are in buff with one another whereas retraction of the rams draws the end mobiles outwardly from one another to the position shown in FIG. 2 in which they lie closely adjacent the end walls. The mobiles are fitted with resilient stops or pads 40 which engage one another when the mobiles are in buff.

Coupling means is provided to enable selective coupling and uncoupling between each of the six successive pairs of mobiles. The coupling means comprises latching mechanisms denoted generally as 57, 58, 59, 60, 61, 62 which provide selective coupling between the successive mobile pairs 23--25, 25--26, 26--27, 27--28, 28--29 and 29--24 respectively. The latching mechanisms are all of identical construction and the mechanism 57 is detailed in FIGS. 3, 4, 6 and 7. This mechanism comprises a pair of swingable caliper arms 63 mounted on the base 23a of end mobile 23 and a catch member 64 mounted on the base 25a of mobile 25. Caliper arms 63 are cranked at 66 and are pivotally mounted at their left-hand end on a common pivot pin 67 which is fixed to a lug 68 projecting inwardly from the peripheral skirt 50 of the mobile base 23a. When in their latching condition, arms 63 extend through a slot 69 in skirt 50 and a further slot 71 in the skirt 55 of mobile base 25a. Their free ends 70 are swingable toward and away from one another and have inturned teeth 72 defining abutments 73 which face back toward pivot pin 67.

At the locations 66 where they are cranked, caliper arms 63 are pivotally connected to a pair of links 74 extending back to a pin 76 which pivotally connects them together. Pivot pin 76 is movable toward and away from fixed pivot pin 67 by operation of a small single-acting and spring return pneumatic cylinder LC1 which is mounted on the mobile base 23a. The casing of cylinder LC1 is bolted to a structural member 76 of the mobile base 23a and the piston rod 79 is connected to pivot pin 76 by a yoke 81. When cylinder LC1 is retracted caliper arms 63 are swung away from one another and then open out to the condition shown in FIG. 7 in which their free ends 70 are retracted back through slot 69 into mobile base 23a. When cylinder LC1 is extended the caliper arms are swung toward one another.

Catch 64 comprises an externally screw-threaded stem 86 mounted in an internally threaded nut 87 which is fastened to a structural member 88 of the mobile base 25a. Catch stem 86 is longitudinally aligned in a vertical plane with pivot pins 67, 76 and it can be axially adjusted by rotation within nut 87. Its end nearest mobile 23 is provided with a conically pointed head 89 the rear side of which defines an annular shoulder 91 disposed around the stem and facing away from mobile 23.

When mobiles 23, 25 are separated and are to be pushed together by operation of the main power cylinders PC1 and PC2, the small latch cylinder LC1 is firstly extended so as to close caliper arms 63 toward one another. They then approach catch 64 with their free ends 70 in much the same relative disposition as shown in FIGS. 4 and 6. The leading edges of these ends are rounded at 92. The rounded edges firstly engage the conically pointed surface of catch head 89 and the free ends are thus wedged apart against the biasing force of cylinder LC1 until the ram abutments 73 reach the catch head shoulder 91 whereupon the arms ends 70 are forced inwardly so that their abutments engage the shoulder 91 as shown in FIGS. 4 and 6. Mobiles 23 and 25 are then latched against separation. However, the latch connection can be disrupted by retraction of cylinder LC1.

As will be more fully explained hereunder, the operation of latch mechanism 57 is controlled by switches carried on a control console 93 which is mounted on the front face of mobile 23. In case cylinder LC1 should fail to operate to release latch mechanism 57, a manual override device is also provided. This comprises a rod 94 which is pivotally connected at one end 96 to a triangular swinging plate 97 pivotally mounted at 98 on a structural member 99 of mobile base 23a and extends at its other end through an aperture in an arm 82 carried by the piston rod 79 of cylinder LC1. Rod 94 is slidable through the aperture in arm 82 and is fitted with an adjustable abutment in the form of a threaded nut 101. A flexible wire 102 is connected at one end to swing plate 97 and at its other end a knob 103 on console 93. By pulling outwardly on knob 103 wire 102 can be caused to swing plate 97 so as to draw rod 94 to the left. The engagement of abutment nut 101 with arm 82 then causes retraction of the ram to release the catch mechanism. During normal operation of the catch mechanism by retraction of cylinder LC1, rod 94 merely slides through the aperture in cross arm 82.

As mentioned above latch mechanisms 58, 59, 60, 61 and 62 are identical to mechanism 57. However, the caliper arms of mechanisms 58, 59 are both mounted on mobile 26 with the catches mounted on mobiles 25, 27 respectively and the caliper arms of mechanisms 60, 61 are similarly mounted on mobile 28 with the associated catches on mobiles 27, 29. This enables the operation of catch mechanisms 58, 59 to be controlled by switches on a single control console 104 on the front face of mobile 26 and the operation of catch mechanisms 60, 61 to be controlled by switches on a single console 106 on mobile 28. The operation of catch mechanism 62 is controlled by switches on a control console 107 mounted on the front face of mobile 24.

The pneumatic control circuit of the facility is shown in FIGS. 8A and 8B. These FIGS. show in diagrammatic form the mobiles 23, 25, 26, 27, 28, 29, 24, the main power cylinders PC1 and PC2, the latch control consoles 93, 104, 106, 107 for the respective mobiles and the latching cylinder LC1 of the latch mechanism 57. The latch cylinders of latch mechanisms 58, 59, 60, 61, 62 are designated LC2, LC3, LC4, LC5 and LC6 respectively. The control consoles carry three-port, pushbutton and spring return poppet valves OB1, OB2, OB3, OB4, OB5 and OB6 for initiating opening of the facility, similar push button poppet valves CB1, CB2, CB3 and CB4 for initiating closing of the facility and three-port, double pressure operated, piston valves PV1, PV2, PV3, PV4, PV5 and PV6.

The numeral 167 designates flexible tubular "bumpers" which are fitted to the sides of the mobiles which face one another, two of these bumpers being shown in FIGS. 3 and 4. These bumpers are mounted on the bases of the mobiles and extend from front to rear of the mobiles so that when any pair of mobiles are closing on to one another and there is an obstruction in the aisle at least one of the bumpers will be struck to generate a pressure signal in the control circuit. Numeral 108 designates similar tubular bumpers fitted to the outer faces of the two end mobiles 23, 24, one of these bumpers being shown in FIGS. 3 and 4.

CV1 and CV2 are five port, double pressure operated, piston valves and CV4, CV5 are diaphragm operated, three-port poppet valves. CV3 is a four port, midopen, diaphragm operated spool valve the construction and purpose of which will be described in detail hereunder. SCV1, SCV2, SCV3, SCV4, SCV5 and SCV6 are all air flow regulators and SV1 and SV2 are shuttle valves. BV1 and BV2 are bleed valves and 141, 142, 143, 144, 145, 146, 147, 148, 149, and 150 are nonreturn valves.

Pressurized air enters the circuit from an air supply via a line 111 after having passed through suitable filters and a pressure regulator (not shown). That part of the circuit falling within the dotted line 112 is mounted in a casing sunk into the floor at the front of the facility and midway between its two ends. This casing is indicated as 115 in FIG. 1. The air lines of the circuit leaving this casing may run along a gallery set into the floor along the front of the facility, the connections to the consoles being made via relatively short lengths of flexible tubing connected to the lines in the gallery.

Before describing the operation of the circuit in detail, its general functions will now be described briefly. With the mobiles in the closed up condition shown in FIG. 1, an operator selects and operates one of the opening buttons OB1 and OB6 which is appropriate to the aisle he desires to create. This causes the appropriate latch mechanism to release and the main power cylinders PC1 and PC2 to operate simultaneously to create the desired aisle. Upon reaching a fully open condition the power cylinders PC1 and PC2 stall and hold the mobiles in this condition. When the operator has finished using the aisle he presses the appropriate closing button CB1, CB2, CB3 or CB4 and the power cylinders PC1 and PC2 then operate to move the mobiles to the closed condition. The latch connection is reestablished and the power cylinders stall to hold the mobiles in the closed condition. Should some other operator endeavor to close the facility whilst someone or something is in the aisle space, at least one of the bumpers 167 is deflected to create a signal in the circuit which reverses the air supply to the power cylinders PC1, PC2 thereby causing them to move the mobiles to the open condition.

Deflection of either of bumpers 108 on the outer faces of mobiles 23, 24 will cause the power cylinders PC1 and PC2 to operate to move the mobiles to the closed condition. Signals produced by deflection of bumpers 167 will override signals produced by operation of the closing buttons CB1 to CB4 and signals produced by deflection of bumpers 108 will override signals produced by operation of opening buttons OB1 to OB6.

The manner in which the circuit operates to perform the above functions will now be described in some detail. When the facility is in a closed condition, valves CV1 and CV2 are conditioned so that compressed air is fed through them from a line 114 branching from line 111 to the piston ends 116, 117 of power cylinders PC1, PC2 and so that the other ends of the power cylinders exhaust to atmosphere through valves CV1, CV2, exhaust lines 118, 119, valve CV3 and air flow regulators SCV5 and SCV6. Thus the power cylinders PC1 and PC2 are stalled in their extended conditions to keep the facility closed. The following will then be normal sequence of operation.

1. Operation of one of the opening buttons OB1--OB6 will cause supply of air via the respective one of the valves PV1--PV6, to the appropriate one of the latch cylinders LC1--LC6 thereby operating that latch cylinder to release the appropriate latch. A pressure signal will also be transmitted via lines 121, 122, valve SV1 and lines 125 to the ends of control valves CV1, CV2 to move the pistons of the latter valves so as to reverse the connections to power cylinders PC1 and PC2. Air from line 114 is then supplied via valves CV1 and CV2 to the piston rod ends of cylinders PC1 and PC2 and the ends 116, 117 exhaust to atmosphere through valves CV1 and CV2, lines 118, 119, valve CV3, and flow regulators SCV5 and SCV6. Thus the power cylinders PC1 and PC2 operate to open the facility and create an aisle at the appropriate location. When the opening button is released the pressure in lines 125 is relieved by bleeding back through shuttle valve SV1 and to atmosphere via valve SCV1.

2. When the appropriate closing button is now depressed, it cuts off the supply of air to the extended latch cylinder which then retracts under the influence of its return spring to swing the caliper arms of the latch mechanism toward one another. A pressure signal also flows from the closing button along lines 123, 124, shuttle valve SV2 and lines 126, 127 to the pistons of control valves CV1, CV2 which then move to reestablish connections to power cylinders PC1, PC2 which cause them to extend thereby closing the facility. When the closing button is released pressure in lines 127, 126 is relieved by bleeding back through shuttle valve SV2 and via valve SCV2 to atmosphere. The power cylinders PC1, PC2 move to their extended conditions and stall to hold the mobiles closed and the circuit is then in its original condition.

3. If any of bumpers 167 is depressed, a pressure signal is generated in line 128 causing diaphragm operated valve CV4 to move such that pressurized air is supplied from line 114 and line 129 via the valve CV4, line 131 and shuttle valve SV1 into lines 125 thereby causing control valves CV1 and CV2 to move to the condition in which power cylinders PC1 and PC2 operate to open the facility. In similar fashion deflection of one of the extremity bumpers 108 will send a signal through line 130 to condition valve CV5 so that lines 126, 127 are pressurized to move valves CV1, CV2 to a condition in which the rams retract. Bleed valves BV1 and BV2 prevent build up of pressure in lines 128, 130 due to ambient temperature rise which could otherwise cause improper actuation of valves CV4 and CV5.

The diaphragm operated valve CV3 and the valves SCV5 and SCV6 are incorporated in the circuit in order to equalize the speeds of travel of power cylinders PC1 and PC2 even though these cylinders may be acting against widely differing loads. This part of the circuit is shown in more detail in FIG. 9. As shown in that FIG. the spool 131 of valve CV3 is connected via a rod 132 to a flexible diaphragm 133 which divides the interior of a hollow vessel 134 into two chambers 136, 137. The valves SCV5 and SCV6 are fitted to the exhaust lines 118, 119 downstream of valve CV3 and each produces at its upstream side a pressure rise which is indicative of the volumetric flow through the exhaust line. The two pressure rise regions of exhaust lines 118, 119 communicate via tubes 138, 139 with chambers 136, 137 respectively.

When the flows through exhaust lines 118, 119 are equal, the pressure rises produced by valves SCV5 and SCV6, and consequently the pressures in chambers 136, 137, will also be equal. Thus there is no pressure differential across diaphragm 133 and the diaphragm does not exert any force on spool 131. However, if the flow in one of lines 118, 119 tends to be greater than in the other, the pressure rise produced by its associated restrictor valve SCV5 or SCV6 will be greater than the pressure rise produced by the other flow restrictor valve and the resulting pressure difference across diaphragm 133 will cause the diaphragm to move spool 131 so as to increase the obstruction to flow through that line 118, or 119 and to decrease the obstruction to flow in the other line. Thus the loading of the power cylinder PC1 or PC2 which is tending to operate at a faster speed is effectively increased and the arrangement is such that under all conditions of load the cylinders will travel at equal speeds, although the actual speed of travel will vary under different operating conditions and will in particular depend on the position where the aisle is being created.

FIG. 10 shows a manually actuable device which could be employed for releasing the latch mechanisms as an alternative to a pneumatic cylinder. In this case the yoke 81 at the pivotally connected ends of the links 74 is carried by a short rod 170 which can be moved axially by swinging a lever 171 from a spring loaded neutral position 171a to a position in which it can be engaged with a latch 172 to hold the latch in an open condition. A bellows 173 is connected to the lever so as to generate pressure signals to initiate operation of the main power cylinders LC1 and LC2.

FIG. 11 shows an alternative method of mounting power cylinders PC1 and PC2 for moving the end mobiles 23, 24. In this case extension of the power cylinders causing opening of the facility and retraction causes closing and consequently the pneumatic connections to the cylinder must be reversed.

In the above-described facility, an aisle is opened at twice the speed of moving of the power cylinders and the mobiles. The choice of aisle opening speed in any powered facility is determined mainly by the problem of controlling the acceleration and deceleration of the loaded mobiles and providing sufficient strength to withstand the forces generated thereby. With the present arrangement it is possible safely to achieve aisle opening rates which would present extreme strength and control problems in conventional powered facilities. Because the stroke of each power cylinder LC1 and LC2 is only one-half of the full aisle width, the power cylinders can be of much lighter duty than would be necessary in a single power cylinder arrangement. However, the above-described facility has been advanced by way of example only and many modifications and adaptations may be made thereto. For example in that part of the circuit which equalizes the speeds of the power cylinders, the movement of the spool of valve CV3 could be effected by differences in pressure drops through Venturis in the cylinder exhaust valves 118, 119. In this case, the connections of tubes 138, 139 would have to be reversed. Instead of acting on a flexible diaphragm, the two signals could be caused to act directly on the two opposite ends of the valve spool 131. Furthermore the speed control valve connections could be incorporated on the inlet sides of the power cylinders to meter and control the inflow of fluid thereto rather than outflow. The exhaust side was chosen in this particular case since greater sensitivity could be achieved and because the apparatus is then much safer in operation. If the speed control means were incorporated on the inlet sides of the power cylinders then high pressures could be introduced into chambers 136, 137 and a blockage or break in one of the inlet lines could lead to damage of the diaphragm and the valve CV3.

The control buttons could be grouped together in a single console and it is envisaged that such a console could be located such that a forklift truck operator on a journey to the facility could initiate operation of the facility so that a required aisle space has been created when he arrives. A single control console could alternatively be located in a central control face. Remote radio control by forklift operators is also feasible.

A facility according to the invention may also be designed to provide high density car parking and such a facility is shown diagrammatically in FIGS. 12 and 13. As shown in those FIGS., the car parking facility comprises three rows 151, 152, 153 of mobiles 154. In this case the mobiles 154 are each designed to receive a motor vehicle and each row is mounted for movement between a pair of end walls 156 in similar fashion to the mobiles of the first described facility and is provided with a pair of power cylinders 157, 158. The mobiles are also fitted with latching mechanisms which may be similar to those already described above.

FIG. 12 shows the facility in a closed condition and FIG. 13 shows the facility opened to create an aisle 159 so that a motor vehicle in one of the mobiles 154a can be driven along the aisle to the front of the facility. Before operating the power cylinders to open the facility mobile 154a is unlatched from the mobile 154b immediately to its left so that on operation of the rams 157, 158 it will be drawn through half an aisle width to the right whereas the mobiles 154c, 154d in front of it are unlatched from the mobiles 154e, 154f to their right so that they are moved in unison one-half an aisle width to the left. The six power cylinders 157, 158 are then operated in unison so that a full aisle is created in direct alignment with the selected mobile 154a as shown in FIG. 13.

In order to enable full access to the end mobiles of rows 151 and 152 coupling means should be provided to enable selective coupling and uncoupling of the drive cylinders 157 and 158 of rows 152, 153 to and from their respective end mobiles. For example, upon uncoupling the drive cylinders 157 of rows 152 and 153 from their respective mobiles, all of the mobiles of rows 152 and 153 can be drawn to the right to create an aisle giving access to the left-hand end mobile of row 151 when the latter mobile is drawn to the left. The coupling means may comprise four further latch mechanisms similar to mechanism 158 but acting between the drive cylinders and the appropriate end mobiles. The catch member of each latch mechanism could be mounted on a bracket attached to the appropriate drive cylinder with the caliper arms and latch cylinder mounted on the respective end mobile.

Claims

I claim:

1. A mobile storage facility comprising a track, at least three storage structures arranged successively along the track and each movable along the track, drive means for simultaneously moving the two end structures in mutually opposite directions between first positions which are so spaced that all of the structures are then in buff with one another and second positions which are spaced further apart from the first positions, and coupling means for selectively coupling and uncoupling each successive pair of structures to and from one another.

2. A mobile storage facility as claimed in claim 1, further comprising a central circuit means for controlling operation of the drive means and pressure sensitive means for causing the drive means to position the structures in their second positions, wherein the storage structures are each provided with pressure sensitive means connected into the control circuit such that if any of the pressure sensitive means is struck the drive means operates to move the structures to their second positions.

3. A mobile storage facility as claimed in claim 1, wherein the coupling means comprises a plurality of latch mechanisms, there being one latch mechanism for each successive pair of storage structures, each latch mechanism comprising a pivot on one of the structures of the respective pair of structures, a pair of caliper arms swingable about said pivot and extending from that pivot toward the other structure of said pair to free ends having abutments extending inwardly toward one another and facing back toward said pivot, actuator means mounted on said one structure which means is operably connected to said caliper arms for imparting opening and closing movement thereto, and, mounted on said other structure, catch means which has abutment portions facing away from said one structure and which, on relative movement of said structures toward one another with the actuator means acting to close said arms, is engageable with said arms to force them apart until the arm abutments reach the catch abutment portions whereupon the actuator means forces the free ends toward one another so that the arm abutments and catch abutment portions interengage to prevent separation of said pair of structures, the latch connection thereby established being releasable by operation of said actuator means to open said arms.

4. A mobile storage facility as claimed in claim 3, wherein the actuator means comprises a single acting and spring return fluid operable cylinder.

5. A mobile storage facility as claimed in claim 4, wherein the drive means comprises a pair of fluid operable power cylinders extending longitudinally of the track and connected in opposed relationship one to each of the end structures.

6. A mobile storage facility as claimed in claim 5, wherein the said power cylinders have strokes of equal length.

7. A mobile storage facility as claimed in claim 1, wherein said drive means comprises a pair of fluid operable double acting power cylinders extending longitudinally of the track and connected in opposing relationship one to each of the end structures, and a fluid control circuit which controls operation of the power cylinders such that they operate together through opposed forward strokes and together through opposed return strokes.

8. A mobile storage facility as claimed in claim 7, wherein the coupling means comprises a plurality of latch mechanisms, there being one latch mechanism for each successive pair of storage structures, each latch mechanism comprising an actuator means operable to condition the mechanism to uncouple the respective pair of structures.

9. A mobile storage facility as claimed in claim 8, wherein the control circuit includes means which, on operation of the actuator means of any of the latch mechanisms to uncouple a pair of structures, causes the power cylinders to move the end structures to said second positions.

10. A mobile storage facility as claimed in claim 7, wherein the control circuit includes power cylinder speed control means which is effective substantially to equalize the speeds of operation of the power cylinders during both forward and return strokes.

11. A mobile storage facility as claimed in claim 10, wherein the control circuit includes two fluid flow ducts which serve as exhaust ducts for the respective power cylinders and said speed control means comprises valve means actuable to present variable obstruction to flow through the two ducts and control means to meter flows in the ducts and to actuate the valve means such that a substantially constant ratio between the flow rates in the two ducts is maintained.

12. A mobile storage facility as claimed in claim 1, wherein said drive means comprises a pair of fluid operable double-acting power cylinders extending longitudinally of the track and connected in opposing relationship one to each of the end structures, a fluid control circuit which controls operation of the power cylinders and which includes two fluid flow ducts serving as exhaust ducts for the power cylinders, a valve having a valve member movable to simultaneously increase resistance to fluid flow through one of the ducts and to decrease resistance to flow through the other duct and vice versa, first means to produce in one region of each duct a pressure which is dependent on the volumetric flow rate through that duct and second means to move the valve member in response to differences between the pressure in said one region of one duct and the pressure in said one region of the other duct.