GB2212125A

GB2212125A - Vehicle mounted turntable

Info

Publication number: GB2212125A
Application number: GB8726560A
Authority: GB
Inventors: Bryce Ernest Randall
Original assignee: Permanent Way Equipment Co Ltd
Current assignee: Permanent Way Equipment Co Ltd
Priority date: 1987-11-12
Filing date: 1987-11-12
Publication date: 1989-07-19
Also published as: GB8726560D0

Abstract

An underslung vehicle lifting turntable has its slewing ring frame equipped with a number of lifting actuators 3 and 4 which may be of different sizes in order to lift offset loads on or in the vehicle and are constrained to extend at identical rates to prevent the turntable frame twisting by constantly monitoring actuator extension and adjusting control means 7,9. <IMAGE>

Description

IMPROV < .ENTS TO VEFIICLV MOUNTS TURNTABLE.

This invention relates to vehicles having a built in turntable to enable them to be elevated slightly and rotated to change direction of motion when lowered again.

It is well known that vehicles of this category are used on railway systems to provide permanent way and overhead maintenance.

Turn tables on this type of machine are traditionally mounted with their centres as near as possible to the vertical line passing through the vehicles centre of gravity in both mutually perpendicular planes. Such traditional turn tables are usually powered by a central vertical hydraulic or similar actuator or via a "scissors" type mechanism. In the former case it follows that such an actuator must be extremely strong and thus heavy and expensive if it is to carry the loads (which ax sometimes offset) imposed during lifting and rotating unless separate guides or similar structures are added again increasing weight and cost.Similarly, because at start of lift the "scissor" arms are heavily stressed and at maximum lift the active points are close together and not able to offer the stiffness such a mounting may demand, external and separate elements are often added. Both types would be addionally loaded and thus stressed if the turn table is required to lift its carrying vehicle when athwart sloping (canted) track or offset to the line of the centre of gravity of the vehicle.

According to this invention there is provided a turntable comprising a track or similar roadway mounting frame attached to a rotatable anchor frame having a multiplicity (normally 3 or 4) of actuators which are so formed and positioned as to at as vertical structural members between said turntable and its carrying vehicle.

As it may be difficult to position a turntable within an existing vehicle chassis in the most advantageous position relative to its centre of gravity, this invention provides for two or more actuators to be of larger proportions than the others and thus capable of carrying higher or offset loads with for example, the same hydraulic lifting pressure.

A specific embodiment of this invention will now be described by way of example with reference to the accompanying drawings: wig. 1 shows a side view of the carrying vehicle with the 2.

turntable raised and stowed.

Fig. 2 shows a side view of the carrying vehicle with turntable lowered and engaged into a railway track Fig. 3 shows a plan view of the carrying vehicle athwart tne railway track.

Fig. 4 shows an end view of vehicle athwart the railway track.

referring to the drawing Fig 2 the track engaging frame is attacned to or integral with a turntable slewing ring 2 which carries upon i secure anchor points for the moving portion of the actuators large 3 and smaller 4. The upper or non-moving end of the actuators 5 is anchored into the carr#'ing vehicle chassis ó in suct. a manner as to prevent displacement or deflection from vertical alig'trnent.

In order to prevent the actuators from extending at varying rates and thus tending to twist the assembly any one of a number of methods of control dependent upon actuator type, power source and proportion can be used to constantly monitor the rate of extension and thus trigger remedial action if requIred. One suggested control systems is to use a programmable logic controller (PLC) 7 to constantly examine a transmission of signals from the extension sensing device 8 and to cause the actuator extension control mechanism 9 to take the necessary corrective action. If for examp e, the actuators 3 and 4 are hydraulic cylinders then the control mechanism 9 might be a directional control valve electro-solenoid operated. If now referring to Fig. 3 the extension sersing device 8 is caused to compare the condition at position 3 with 3A and 4 with 4A i.e. from side to side or across the vehicle 10 and at the same time compare n with 4 i.e. from front to rear of vehicle 10 constant correction may be achieved.

Such correction is particularly important wr.en the lowering 3.

turntable contacts the track 11 and begins to lift the load of the vehicle 10. Extension sensing devices may be of the following types, rotary encoder, linear potentiometer, rotary potentiometer, linear variable displacement transducer, fibre optic systems or any of a variety. Similarly the actuators may be of the electrical linear form, and controlled directly by the P.L.C. 7.

Claims

CLAIMS.

What we claim is: 1. A vehicular mounted lifting turntable comprising a track engaging sub-frame securely attached to or integral with (and in the same plane of operation) a slewing ring having formed integrally with it, the anchor mountings for the extending portions of a multiplicity of small actuators whose line of action is perpendicular to the plane of rotation of the slewing ring, such actuators having their upper or non extending portions securely attached to the chassis of the carrying vehicle in such a manner as to prevent displacement or deflection of their line of action from that which is perpendicular to the track upon which the lowered turntable reacts or to change their positional relationship one with another.Due to the secure method of attachment of the actuators upper end to the chassis and lower to turntable such actuators become structural members of the lifting assembly, avoiding additional structures.
2. A turntable largely as in Claim 1 wherein the actuator extension is constantly monitored and corrected by separate means to guarantee the line of action of each actuator is mutually perpendicular to the plane of slewing of the turntable and the track with which it engages at all times.
3. A turntable largely as in Claims 1 and 2 wherein constant monitoring and corrective adjustment may be executed via onboard P.L.C. by means of any one of a number of control devices depending upon the power sources available and the type of actuator, i.e. hydraulic, electric, electro hydraulic, pneumatic etc.
4. A turntable as in Claims 1-3 wherein the lifting actuators may be of different sizes and thus, lifting capacity in order to cater for imposed loading which may be offset to the vertical line through the centre of gravity of the carrying vehicle, but 2.

at the same time using a common system pressure if of the hydraulic variety.
5. A turntable as in Claims 1-4 wherein the extension sensing device may be based upon a multiplicity of proximity switches co-acting with a number of holes in or projections from a vertical rod attached to the moving anchor of the actuator but displaced slightly to one side of it.
6. A turntable lifting assembly as in Claims 1-5 wherein the stroke of its actuator is such as to permit the carrying vehicle to be lifted clear of local obstructions such as a railway track and rotated manually or under power about the vertical centre line of the turntable slewing ring.
7. A turn table as in Claims 1-6 and as depicted in the accompanying drawings.

7. A turntable as in Claims 1-5 and largely as shown in the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS 1. A vehicle mounted lifting turntable equipped with a plurality of extensible lifting actuators (ideally 3 or 4) each having its upper end securely attached to the vehicle chassis in such a manner so they become structural members of the lifting system and its lower end attached to the ground or rail engaging element of an integral slewing ring equipped turntable, said actuators being controlled by in-built means to extend at a rate to maintain a correct attitude of the carrying vehicle and perpendicularity between turn table and actuators and actuators and chassis at all times during the extending operation irrespective of out of balance loads imposed upon said actuators by overhanging or offset loads.

2. A turntable largely as in Claim 1 wherein the actuators via their anchorage to chassis and turntable constitute the sole structural strength of said lifting system.

3. A turntable largely as in Claims 1 and 2 wherein constant monitoring and associated corrective adjustment to the extension of said actuators may be executed via an on-board P.L.C. (programmable logic controller) by any one of a number of control devices depending upon the power source used by the carrying vehicle and the type of actuators i.e. hydraulic, electric, electro hydraulic or pneumatic etc.

4. A turntable as in Claims 1-3 wherein the actuators.#y be of differing sizes and lifting capacity in order to better match any increase in local loading due to offset or overhanging loads whilst at the same time enabling said actuators to use a common system pressure if of the hydraulic variety or common voltage if electric etc.

5. A turntable as in Claims 1-4 wherein the extension sensing device may be based upon a multiplicity of proximity or limit switches co-acting with a series of holes in or projections from a rod or similar element moving in line with and parallel to the moving element of said actuators so as to accurately indicate an instantaneous position for each of said actuator's extension.

6. A turntable lifting device largely as in Claims 1-5 wherein the extension of its actuators is sufficient to permit the carrying vehicle to be lifted clear of local obstructions (such as a railway track) and rotated manually or mechanically about the vertical centre line through said slewing ring.