GB2201942A

GB2201942A - Apparatus for interlocking telescopic members, such as a telescopic jib

Info

Publication number: GB2201942A
Application number: GB08802234A
Authority: GB
Inventors: Harry Hellwig; Lothar Schandert
Original assignee: MAN Takraf Fordertechnik GmbH
Current assignee: Takraf GmbH
Priority date: 1987-03-12
Filing date: 1988-02-02
Publication date: 1988-09-14
Anticipated expiration: 2008-02-02
Also published as: GB8802234D0; DD258409A1; DE3744393A1; GB2201942B

Description

1 1 APPARATUS FOR INTERLOCKING TELESCOPIC MEMBERS, SUCH AS A TELESCOPIC

JIB 2 '2' 0 19 4 z"l.

This invention relates to apparatus for interlocking telescopic members, particularly, but not exclusively, the telescopic parts of a telescopic jib, where it is important to achieve interlocking of the telescopic parts.

FR-2 236 771 discloses a securing device with which telescopic parts can be braced with respect to one another by a frictional locking action. For producing the pressure applied by the braking elements, a force is used which is created by the payload or the inherent weight of the telescopic parts. Thus, the securing force varies in proportion to the payload applied to the telescopic parts. This securing arrangement has the disadvantage that for every loading on the telescopic parts in a axial direction, a securing force is created which means that the telescoping process when under load is possible only if the driving arrangement is so dimensioned that the additional friction forces are overcome.

According to the present invention there is provided apparatus for interlocking telescopic members, comprising brake members provided on one telescopic part, a rail provided on another telescopic part, means for moving the brake members into gripping engagement with the rail, and switching means for controlling operation of said means for moving the brake members.

The locking apparatus of the present invention, at least in the preferred embodiments shown, makes it possible to improve the load carrying capacity of the telescopic members in the various telescopic positions and so enhance the usefulness of the telescopic device, and to avoid overloading of the drive means. In the case of a hydraulically or pneumatically operated drive means operated by a fixed pressure hydraulic or pnematic pressure fluid, this fluid is branched off in order to actuate the brake members. This branched pressurised fluid is fed via a combined pressure switch and valve to operate piston and cylinder devices which apply brake segments to the brake rail. The brake segments are disposed opposite one another so as to grip the rail by friction so that they can accommodate 2 t the full load of the telescopic portions in the supporting direction. The drive means for moving the telescopic parts is thus relieved of the load and the working cylinders of the drive means are pressureless. Upon actuation of the drive means in the extension direction, the brake segments become disengaged from the brake rail when the pressure of the working medium is not at or above a predetermined value. Springs urge the brake segments to the disengaged position.

In the case of a mechanically operated driving means, a resiliently loaded pivotably mounted beam disposed at the point of application of the drive means to said one telescopic part actuates a switching device which provides the signal to operate the brake members. When this happens, the brake segments are applied to the rail by an electromagnet which overcomes the pressure of the return springs. At the same time, via a signal from the switching device, the drive means is relieved after a time lag so that the deformation of the supporting beam is cancelled out and the electromagnet of the supporting arrangement becomes currentless.

Two embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a diagram of a locking apparatus according to one embodiment of the invention; Figure 2 is a view of the closed brake segments of the apparatus of Figure 1; Figure 3 is a view of the open brake segments of the apparatus of Figure 1, and Figure 4 is a diagram of a mechanical alternative embodiment.

As shown in Figure 2, a base or fixed part 1 of a telescopic member, such as a telescopic jib, is connected to a telescopic part 2 via a piston and cylinder drive means 3. Fluid connection to the drive means 3 is effected via feed conduits 4 which are connected to a driving or control assembly not illustrated or described. The drive means 3 is so constructed that it is possible to convey the driving force produced by the working fluid medium to a point of connection 5 of the drive means to the telescopic part 2. A connecting conduit 6 in communication with the extension-side cylinder space of the drive means 3, when a predetermined pressure at the pressure switch of a combined pressure switch and valve 7 is exceeded, conveys the working fluid, via the pressure switch and valve combination 7, to the piston p 1 I,z 3 "I and cylinder devices 8 of a locking means 9 which is articulatingly mounted on the telescopic portion 2. Thus, via a lever system 10, the piston and cylinder devices 8 of the locking means 9 apply brake segments 11 which are movably mounted on the telescopic portion 2 against brake rails 12 fixed on the base part 1 of the telescopic member, as shown in Figure 2. The force applied by the cylinders 8 overcomes the force of springs 13. When the telescopic part 2 is loaded in the retraction direction, the brake segments 11 grip the brake rails 12 and take over the conveying of axial forces from the telescopic part 2 to the base part I of the telescopic member. The drive means 3 is thus relieved of such axial forces. When the pressure of the working fluid drops below the predetermined pressure the combined switch and valve 7 switches the connection of the piston and cylinder devices 8 of the locking means 9 to return conduit 14. When the drive means 3 is actuated in the extension direction, and when the pressure of the working fluid is less than the predetermined value, the brake segments 11 are released from the brake rails 12 and the springs 13 maintain the brake segments 11 in the open position, a shown in Figure 3. Figure 4 shows a mechanical alternative embodiment. The base part 1 of the telescopic member is connected by a drive means 3 to the telescopic part 2. The drive means 3 is connected to the telescopic part 2 via a resiliently loaded pivotable beam 15. For a preset travel of a spring element 16, a switching arrangement 17 is actuated via which electrical current is supplied to an electromagnet 18 which sets the locking means 9 in operation.

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Claims

1. Apparatus for interlocking telescopic members, comprising brake members provided on one telescopic part, a rail provided on another telescopic part, means for moving the brake members into gripping engagement with the rail, and switching means for controlling operation of said means for moving the brake members.

2. Apparatus as claimed in claim 1, in which said switching means comprises a combined pressure switch and valve and said means for moving the brake members comprises a piston and cylinder device arranged to be supplied with pressure fluid from drive means for moving said one telescopic part relative to said one to said another telescopic part via said pressure switch and valve, said piston and cylinder device being connected to said brake means via a lever system.

3. Apparatus as claimed in claim 1, in which said means for moving the brake members comprises an electromagnet and said switching means comprises an electrical switch actuated by a resiliently loaded pivotable member aranged to be moved by drive means for moving said one telescopic part relative to said another telescopic part.

4. Apparatus for interlocking telescopic members, substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 3 or Figure 4 of the accompanying drawings.

5. Telescopic members provided with apparatus as claimed in any preceding claim.

6. A telescopic jib provided with apparatus as claimed in any one of claims 1 to 4.

1 Published 1988 at The Patent Offlce, State House, 68171 High Holborn, London WClR 4TP. Purther copies may be obtained from The Patent Ofnee, Wes Branch, St Mary Cray, Orpington, Kent BR5 3F.D. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Con. 1/87.

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