GB2118919A - An articulated telescopic boom assembly - Google Patents

Abstract

An articulated telescopic boom assembly is mounted on a base member via a turntable (4) and a support member (8). The assembly comprises an outer boom (11), an inner telescopic boom (12) and a third pivotal boom which carries a work platform (14). A hydraulic cylinder (19) drives a carriage (18) which is attached to and extends second boom (12). Continuous levelling cables (42, 42') extend through the booms to maintain the work platform (14) level, pulleys (45, 46) taking up slack when the booms retract. A movable carrier (60) protected by housing member (61) travels along rail (21) to take up slack in a continuous supply conduit (50) which extends from a main control box 52 on the support member (8) through the booms to a control box (51) on the working platform (14). <IMAGE>

Description

SPECIFICATION An articulated telescopic boom assembly This invention concerns an articulated telescopic boom assembly, particularly, though not exclusively of the kind to be mounted on a vehicle chassis and carrying at its outermost end a work platform to be raised above the ground to provide access to an elevated position for the purpose of carrying out work or to permit escape of personnel, for example, from a burning building.

Apparatus of this kind usually includes control means which may be operated from the base of the structure, i.e. close to the ground, and from the work platform which may be elevated therefrom.

Therefore it is necessary for the control conduits including the hydraulic fluid hoses which supply the hydraulic motors which in turn drive the assembly, to pass from the base of the structure to the outermost end thereof. In cases where the boom assembly comprises, for example, a first boom containing a second boom which is telescopically extendible relative thereto, it is necessary for the control conduits to pass along the boom system and around means to take up the slack during extension and retraction.

Similarly, the work platform must be maintained at a levei attitude irrespective of the configuration of the boom assembly, and for this purpose a continuous cable usually extends from the base support member to the work platform, passing around a plurality of pulleys such that during elevation and lowering of the boom assembly the levelling cable unwraps from one pulley whilst wrapping onto another. In this way the cable maintains a constant taut length.

Many systems have been devised to carry the conduits along the boom assembly. In some cases the conduits travel along the outside of the booms where they are exposed to damage, whilst in another example they are contained internally therewithin and a system of pulleys is also located within the booms to enable the slack to be taken up during telescoping movements.

For the system taking up the slack to be contained within the booms it is usual for a complex pulley system to be installed within a restricted space, and should the system malfunction, access to the pulleys to rectify the problem is restricted if not wholly prevented short of dismantling the whole boom assembly.

An object of the present invention is to provide a system of the kind generally referred to above wherein the aforementioned disadvantages are substantially avoided.

According to the present invention there is provided an articulated telescopic boom assembly comprising a first hollow boom pivotally mounted about a horizontal axis on a support member, a second hollow boom longitudinally slidable within the first boom and carrying a pivotable work platform, drive means for elevating the boom assembly about its horizontal axis, drive means for telescoping the second boom relative to the first, at least one continuous levelling cable extending internally through the booms from the support member to the work platform and around at least one movable pulley means within the first boom to take up slack when the second boom retracts, and at least one continuous control conduit extending internally through the booms from the support member to the work platform and around means outside of booms to take up slack when the second boom retracts, said means being at least partially encased for protection of said conduit.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is an elevation of an articulated telescopic boom assembly incorporating the features of the invention; and Fig. 2 is a schematic section taken on line Il-Il of Fig. 1.

The assembly comprises a base member or chassis 1 normally mounted on a vehicle (not shown) and incorporating ground-engaging jacks 2 which stabilise the apparatus by being brought into contact with the ground when the assembly is to be elevated. A turntable 4 carries a support member 8 for rotation about a vertical axis.

The booms which are pivotally attached to the support member 8 at 9 comprise a first boom 11 within which is slidably and telescopically mounted a second boom 12. The booms 11, 12 may be elevated aboutthe horizontal axis 9 by means of a hydraulic cylinder 10 attached to the support member 8 and the boom 11.

Pivotally attached at 1 5 to the outer end of boom 12 is a third boom 13 which carries at its outermost end a work platform 14 mounted for pivotal movement about a horizontal axis 5. A hydraulic cylinder 1 7 and links 1 7a are extendibie to elevate the boom 13 relative to the boom 12.

A carriage 18 movable inside boom 11 is adapted to be driven by a hydraulic cylinder 19, longitudinally within boom 11. A pair of chains 20 pass around sprockets 41 on carriage 18, and the ends of each chain are attached respectively to the outer boom 11 and the inner boom 12.

Extension of the cylinder 1 9 to drive the carriage 18 thus causes the boom 12 to be driven (by the chains) by a distance which is twice that moved by the carriage.

A cage levelling cable 42 is anchored to the upper end of the support member 8 as indicated at 43. The cable passes around a first pulley 44, a second pulley 45 rotatably mounted on the carriage 18, a third pulley 46 rotatably mountd on the inner end of boom 12, a fourth pulley 47 at the outermost end of boom 1 2, a fifth pulley 48 at the innermost end of boom 13, and is anchored to the base of the work platform at 49. A cage restraint cable 42' which prevents the cage from tipping backwards passes in the reverse direction around smaller diameter pulleys 44', 4s', 46';47' and 48' mounted on the same shafts as the pulleys around which the levelling cable 42 passes. The smaller pulleys are freely rotatable on the shafts and in operation rotate in the opposite direction to their associated larger pulleys.

At least one hydraulic fluid hose 50 extends from a control box 51 on the work platform 14 to the main control unit 52 on the support member 8. The or each hose, after passing around drums 53 and 54 at the joint between booms 12 and 13 extends straight through the boom system internally thereof and emerges at the root of boom 11 to pass around drum 56 and outside the booms to a drum 57 from which it extends around further drums 58 and 59 before passing to the control box 52. Drum 57 is mounted on a carrier 60 below boom 11 which travels along a rail 21 to vary the distance between drums 57 and 58. The carrier 60 is attached by a hose-tensioning cable 29 to the carriage 1 8 and thus moves half the distance of the boom 12 during telescopic movement thereof to maintain a constant taut hose length.Thus, as carriage 1 8 moves to the right during extension of the booms, carrier 60 moves to the left permitting the hose or hoses to extend accordingly. Reverse movement of the carriage 1 8 and carrier 60 causes the slack in the hose or hoses to be taken sup as the booms retract.

Since carriage 1 8 travels outside boom 12, and pulley 46 directs levelling cable 42 through boom 12, it is necessary for the rotational axis of pulley 46 to be slightly inclined to enable the levelling cable 42 to pass outside the side wall of the boom 12 towards pulley 45.

The carrier 60 and rail 21 are encased by a housing member 61 to protect them from damage as the boom assembly rotates on turntable 4 in use.

However, since drums 57 and 58 and carrier 60 are disposed outside of the booms, the system for taking up the hoses is readily accessible without dismantling the boom assembly. Housing member 61 may be made readily removable for this purpose.

Although, in an attempt to keep this description and the drawings as simple as possible, the system has been described as including a single hydraulic hose or other control conduit, it will be appreciated that a plurality of conduits, and, if required, one or more flexible electrical conductors, i.e. a complete control system for the machine, can extend from the base of the structure to the working platform in the manner described.

In some cases, the third boom 13 may be omitted and the work platform 14 mounted directly on the end of boom 12.

Additional equipment may be required at the outermost end of the boom structure, such as a water jet nozzle for fire fighting purposes. In this case, the water supply hoses may extend throughout the boom structure in a manner similar to that described in relation to the control conduits.

For practical purposes and to balance the system, carriage 18, levelling cables 42 and 42 and their associated chains and pulleys are preferably provided in duplex and mounted sideby-side symmetrically about the longitudinal centre line of the boom assembly, as can be seen from Fig. 2.

In another embodiment, there may be three or more relatively telescopic booms, in which case the carriage 18 is substituted by the second or third boom.

In yet another embodiment, the telescopic boom assembly generally as described, may be mounted pivotally at the free end of a lowermost boom which itself is pivotally mounted on the support member 8.

Claims (16)

1. An articulated telescopic boom assembly comprising a first hollow boom pivotally mounted about a horizontal axis on a support member, a second hollow boom longitudinally slidable within the first boom and carrying a pivotable work platform, drive means for elevating the boom assembly about its horizontal axis, drive means for telescoping the second boom relative to the first, at least one continuous levelling cable extending internally through the booms from the support member to the work platform and around at least one movable pulley means within the first boom to take up slack when the second boom retracts, and at least one continuous control conduit extending internally through the booms from the support member to the wqrk platform and around means outside of the booms to take up slack when the second boom retracts, said means being at least partially encased for protection of said conduit.

2. An articulated telescopic boom assembly according to Claim 1, wherein said continuous levelling cable is anchored at one end to the support member, forms a loop around a pair of spaced pulleys and extends therefrom through the booms and is anchored to said work platform such that for any configuration of the boom assembly the levelling cable is maintained in a taut condition and the work platform is maintained at a level attitude.

3. An articulated telescopic boom assembly according to Claim 2, wherein one of said pair of pulleys is mounted at the innermost end of the second hollow boom, and the other of said pair of pulleys is mounted on a carriage movable longitudinally of the boom assembly between the two booms.

4. An articulated telescopic boom assembly according to Claim 1 including a carriage movable longitudinally of the boom assembly and connected by continuous drive members to the two booms respectively in such a way that movement of the carriage in one direction causes simultaneous movement in the same direction of said second boom relative to said first boom, the distance travelled by said second boom being twice the distance travelled by said carriage.

5. An articulated telescopic boom assembly according to Claim 4, wherein said drive means for telescoping the second boom relative to the first boom, comprises a hydraulic cylinder attached to said first boom and to said carriage, to drive the carriage and thus said second boom relative to said first boom.

6. An articulated telescopic boom assembly according to any preceding claim, including at least one further continuous levelling cable extending internally through the booms from the support member to the work platform and adapted to prevent the work platform from tilting in a direction opposite to that in which the platform is prevented from tilting by said first continuous levelling cable.

7. An articulated telescopic boom assembly according to any preceding claim, including a plurality of control conduits extending intemally through the booms from the support member to the work platform and around said means outside of the booms.

8. An articulated telescopic boom assembly according to any preceding claim, inclucing a supply hose for a water jet nozzle mounted adjacent the work platform, the supply hose extending internally through the booms from the support member to the work platform and around said means outside of the booms.

9. An articulated telescopic boom assembly according to Claim 4, wherein said means outside of the booms to take up slack in the control conduits when the second boom retracts comprises a carrier movable on a rail longitudinally with respect to the boom assembly by a distance equal to that travelled by the carriage, to which it is connected.

10. An articulated telescopic boom assembly according to Claim 9, wherein said carrier includes a pulley or drum around which the or each said control conduit passes, there being a second pulley or drum around which said conduit passes, at a fixed position with respect to said booms.

11. An articulated telescopic boom assembly according to Claim 9 or Claim 10 when dependent upon Claim 4 or Claim 5, wherein said carrier is connected by a continuous flexible member to said carriage such that the carriage and the carrier move simultaneously in opposite directions.

12. An articulated telescopic boom assembly according to Claim 4 or Claim 5, in which said carriage and the associated levelling cable or cables are provided in duplex and mounted sideby-side symmetrically about the longitudinal centre line of the boom assembly between said first and second booms.

13. An articulated telescopic boom assembly according to Claim 9 or Claim 10, wherein said carrier and the rail upon which it travels are at least partially encased by a housing member which protects them from damage in use, said housing member being readily removable for access to the control conduits, without dismantling the boom assembly.

14. An articulated telescopic boom assembly, according to any preceding claim, wherein a third boom is~pivotally attached to the outermost end of the second boom, and carries at its free end, said wqrk platform.

15. An articulated telescopic boom assembly, according to any preceding claim, wherein said first and second hollow booms are mounted pivotally at the free end of a lowermost boom which itself is pivotally mounted on the support member.

16. An articulated telescopic boom assembly, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.