GB2316715A

GB2316715A - An actuator and a method of moving one body relative to another body

Info

Publication number: GB2316715A
Application number: GB9617579A
Authority: GB
Inventors: Alan George Andrew M Armstrong
Original assignee: Elscint Ltd
Current assignee: Elscint Ltd
Priority date: 1996-08-22
Filing date: 1996-08-22
Publication date: 1998-03-04
Also published as: GB9617579D0

Abstract

An actuator (4) for causing relative movement between two bodies contacting each other at an interface and which are biased towards each other by a force having a component normal to the plane or their interface; the actuator being connected, in use, to a first one of the bodies, and comprising a rigid frame (4) containing a fluid-containing driving sac (2), means (1,3) for moving the driving sac (2) within the frame in a first plane which, in use, is parallel to the interface, and means for varying, in use, the fluid pressure of the driving sac (2) to cause it to expand or contract in a direction normal to the first plane whereby, in use, drivingly to engage with or disengage from the second one of the bodies at the interface. There may be an array of such actuators, and they may form part of a ground-engaging vehicle, to propel it, or they may form part of a conveyor system for supporting and conveying articles or they may form part of a system for positioning machinery.

Description

kN ACTUATOR A'D A METHOD OF MOVING ONE BODY RELATIVE TO ANOTHER BODY This invention relates to an actuator for causing relative movement between two bodies, and to a method of moving one body relative to another body with which it is in contact at an interface.

The invention is particularly useful for vehicle propulsion at low speeds over soft terrain, and in the installation of heavy plant, with accurate location of the plant. It can also be used, differently orientated, in a conveyor system for moving a succession of objects along a path.

The invention provides an actuator for causing relative movement between two bodies contacting each other at an interface and which are biased towards each other by a force having a component normal to the plane of their interface; the actuator being connected, in use, to a first one of the bodies, and comprising a rigid frame containing a fluid-containing driving sac, means for moving the driving sac within the frame in a first plane which, in use, is parallel to the interface, and means for vaning, in use, the fluid pressure of the driving sac to cause it to expand or contract in a direction normal to the first plane whereby, in use, drivingly to engage with or disengage from the second one of the bodies at the interface. In the case of a vehicle, the first body would be the vehicle body. the second body the ground, and the force the weight of the vehicle.

The invention also provides a method of moving one body relative to another body with which it is in contact at an interface, the bodies being biased together with a force having a component normal to the plane of their interface, by using an actuator comprising a fluid-containing driving sac housed in a frame connected to a first one of the bodies, the method comprising increasing the fluid pressure of the driving sac so that an outer region of the sac is moved into frictional driving engagement at the interface with the second of the bodies, and moving the driving sac within the frame in a direction parallel to the interface thereby to cause the relative movement of the first and second bodies. Repeated movement may be achieved by then decreasing the fluid pressure of the driving sac so as to retract the outer region of the driving sac from its frictional engagement at the interface, returning the driving sac to its original position within the frame by moving it in a direction parallel to the interface, and repeating the above reciprocating cycle to cause step-wise relative motion.

The invention enables loads to be moved and carefully positioned, smoothly and accurately without the need for rotating parts. Low ground clearance, in confined spaces, is possible. Propulsion and conveying machinery embodying the invention can be made more cheaply, reliably and simply and lighter in weight, than with previous machinery.

In order that the invention may better understood, preferred embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a vertical cross-section through an actuator embodying the invention; and Figures (a) to 2(d) are sequential diagrams showing the operation of the embodiment of Figure 1.

A vehicle propulsion system embodying the invention consists of a set of modules, one of which is shown in Figure 1. For this use of the actuator, it would be inverted from the position shown in Figure 1, and allowed to engage the ground.

The invention may also be used in a conveyor system, again using a set of modules, each of which includes the actuator of Figure 1, and arranged in the orientation shown in Figure 1.

The actuator of Figure 1 consists of three closed, flexible sacs 1, 2, 3 which are contiguous and are held together in a row within a rigid casing 4 constituting a frame.

End walls of the frame engage the outer sacs 1, 3. The stiff casing 4 is, in this example, box-shaped, with an open face 5 as shown in Figure 2(a). Each sac is supplied with a working fluid, liquid or gas, from a pressure control module. In the example of a vehicle, a fluid compressor and the pressure control module are carried by the vehicle, but for short range duty, such as plant installation, the actuator would be connected through a flexible hose to an adjacent stationary compressed-air outlet or used with bottled gas.

The flexible sacs 1, 2 and 3 are capable of changing shape, under control of the pressure control module, in order to achieve propulsion or conveyance. In this example, the middle sac 2 is the driving sac, and the outer sacs 1, 3 have the function of moving the middle sac 2 from side to side. The sequence of motion is cyclic, and this reciprocating motion is shown diagrammatically in Figure 2.

Each of the outer sacs 1, 3 expands or contracts sideways, i.e. in a direction parallel to the open face 5. The outer sacs 1, 3 stay wholly within the casing 4, and their height changes very little. In contrast, the middle sac or driving sac 2 is arranged to expand or contract in a direction normal to the open face 5, so that it selectively projects from the casing 4.

At the point of the reciprocating cycle shown in Figure 2(a), the driving sac 2 is moved leftwards by causing the right hand outer sac 3 to expand and the left hand outer sac 1 to contract. As shown in Figure 2(b), the driving sac 2 is then expanded so that the upper portion of its surface projects from the casing 4. At this position, the driving sac 2 engages the ground, in the case of vehicle propulsion, or engages the body which is to be conveyed, in the case of a conveyor system. The driving sac 2 exerts normal pressure on the ground or the body being conveyed, and thus engages with it frictionally.

As shown in Figure 2(c), whilst maintaining the frictional engagement between the driving sac 2 and the ground or the body being conveyed, the driving sac 2 is moved towards the right, by expanding the left-hand outer sac 1 and contracting the right hand outer sac 3. As shown in Figure 2(d) the driving sac 2 is then retracted to its position within the casing 4, disengaging drive.

The cycle of Figure 2 thus represents reciprocating motion of the actuator relative to the ground or to the body being conveyed, the relative driving engagement occurring at the interface which coincides with the open face 5 of the casing A.

The number of actuators constituting the set of modules may be any number, depending upon the load and size.

The actuators are arranged so as to cooperate with one another. Generally, they would all be arranged so that their interfaces 5 are all in a common plane. For example, a vehicle may comprise eight actuators arranged in a 4 x 2 array, the row of 4 actuators arranged longitudinally of the vehicle In the case of a conveyor system, with the opposite vertical orientation, there may for example be a single row of ten or twenty actuators, so that the can convey a sequence of bodies along a line through each of the interfaces 5. The bodies being conveyed may be of a similar length to one actuator, or several actuators.

It will be appreciated that the array of actuators may be used for accurate positioning of a vehicle or plant machinery, by static adjustment of the pressures within at least the driving sacs 2. Thus for example one corner of a vehicle might be raised by increasing the pressure in the driving sac 2 of the actuator closest to that corner, and optionally by increasing, to a corresponding lesser degree, the pressure in the driving sacs 2 of actuators more remote from that corner. In the case of a conveyor system in which the actuators are orientated as shown in Figure 1, corresponding static adjustment is possible, in order to give fine control of the orientation or position of the body being supported on the conveyor system.

In a second embodiment of the invention, each actuator comprises at least five fluid-containing sacs at least two extra outer sacs (not shown) are disposed within the casing 4, touching the middle, driving sac 2. There is thus a ring of at least 4 sacs around the middle, driving sac 2. With appropriate control of pressures from the control module, motion of the driving sac 2 can be provided selectively in any direction in a plane parallel to the open face 5. Generally, this motion would be reciprocating motion in a direction which can be preselected, but other types of cyclic motion, such as circular or elliptical motion, would be possible with appropriate control.

In the first embodiment, shown in Figure 1, the sacs 1 to 3 are elongate, prolatespheroidal (sausage shaped). The casing 4, in this example, would be elongate in the plane of Figure 1. In the second embodiment, however, the casing 4 could be square, and each of the sacs could be spherical.

It will be understood that the invention may be embodied in other ways. For example, the outer sacs 1, 3 could be replaced by other means. for example mechanical actuators, for moving the central, driving sac 2 from side to side. Also, where there are three or more sacs, they may be formed integrally, for example as separately-controlled compartments of a single component. Further, it will be appreciated that the basic actuator unit could be employed in a wide variety of applications, where it is desired to move one body relative to another body or surface, simply by connecting the actuator to one of the bodies, or forming it integrally with that body. Also, vertical orientation of the actuator is not necessary in all examples, and neither is it necessary that the interface between the bodies is planar: there could be a series of actuators together defining an arcuate interface, for example.

The means for controlling pressure could be manual, by appropriate control of the opening and closing of valves. Alternatively, or in addition, there could be an automatic control system, arranged to provide the sequence typified by that of Figures 2(a) to 2(d), and giving rise to stepwise relative movement at the interface. In the case of a vehicle, two rows of actuators could be controlled in the manner of a track-laying vehicle, that is by separately controlling the speed of propulsion of each side of the vehicle.

Claims

CLAIMS:

1. An actuator for causing relative movement between two bodies contacting each other at an interface and which are biased towards each other by a force having a component normal to the plane or their interface; the actuator being connected, in use, to a first one of the bodies, and comprising a rigid frame containing a fluid-containing driving sac, means for moving the driving sac within the frame in a first plane which, in use, is parallel to the interface, and means for varying, in use, the fluid pressure of the driving sac to cause it to expand or contract in a direction normal to the first plane whereby, in use, drivingly to engage with or disengage from the second one of the bodies at the interface.

2. An actuator according to claim 1, in which the means for moving the driving sac comprise at least two outer fluid-containing sacs disposed contiguously with and on either side of the said fluid-containing driving sac within the frame and the moving means comprise means for changing the volume of each of the outer fluid-containing sacs, the outer fluid-containing sacs being such as to expand or contract in a direction towards and away from the driving sac so as to cooperate to move the intermediate driving sac in the first plane.

3. An actuator according to claim 1 or claim 2, comprising control means for controlling the fluid pressure-varying means to cause cyclic driving motion, in each cycle of which the driving sac is caused to expand normal to the first plane, it is then driven by the moving means in the first plane, it is then caused to retract in a direction normal to the first plane and into the frame, and it is then moved in the first plane back to its original position.

4. An actuator according to any preceding claim, in which the moving means comprise means for moving the driving sac within the frame, in the first plane, selectively in either of two relatively-inclined directions.

5. .kn actuator according to claim 4 as appendent to claim 2, in which the number of outer fluid-containing sacs is at least 4, disposed contiguously around the driving sac, and in which the pressure-varying means operates selectively on each of the outer sacs to cause the said movement of the driving sac.

6. .kn actuator according to claim 2 or any preceding claim dependent on claim 2, in which the frame comprises a housing having end walls engaging the outer sacs and an opee side face through which any of the sacs are free to project and which, in use, constitutes the interface.

7. A conveyor system for a body, comprising an actuator according to any preceding claim arranged to support the body at the interface.

8. x conveyor system according to claim 7, comprising a plurality of actuators according to any of claims 1 to 6 disposed adjacent one another and having a common interface with the body to be conveyed.

9. A method of moving one body relative to another body with which it is in contact at an interface, the bodies being biased together with a force having a compo-ent normal to the plane of their interface, by using an actuator comprising a fluid-containing driving sac housed in a frame connected to a first one of the bodies, the method comprising increasing the fluid pressure of the driving sac so that an outer region of the sac is moved into frictional driving engagement at the interface with the second of the bodies, and moving the driving sac within the frame in a direction parallel to the interface thereby to cause the relative movement of the first and second bodies.

10. A method according to claim 9, further comprising then decreasing the fluid press of the driving sac so as to retract the outer region of the driving sac from its frictional engagement at the interface, returning the driving sac to its original position within the frame by moving it in a direction parallel to the interface, and repeating the above reciprocating cycle to cause step-wise relative motion.

11. A method according to claim 9 or 10, in which the actuator comprises at least two outer fluid-containing sacs disposed contiguously with and on either side of the said driving sac within the frame, and the steps causing movement of the driving sac comprise increasing the volume of one of the outer sacs relative to the volume of the other one, the outer sacs being such as to expand and contract in a direction parallel to the said interface, so that they cooperate to move the intermediate driving sac in that direction.

12. A method according to claim 9, 10 or 11, in which the driving sac and the outer sacs are separately-formed sacs.

13. A method according to claim 9, 10 or 11, in which the driving sac and the outer sacs are joined integrally.

14. A method according to any of claims 9 to 13, comprising moving the driving sac within the frame, parallel to the interface, selectively in any direction.

15. A method according to claim 14, in which the means for moving the driving sac comprise at least four outer fluid-containing sacs disposed contiguously with and around the said driving sac within the frame.

16. A method according to any of claims 9 to 15, comprising effecting static adjustment of the relative positions of the two bodies in a direction normal to their interface, by adjusting the fluid pressure of the driving sac and/or of any outer fluidcontaining sacs.

17. A method of conveying an article in accordance with any of claims 9 to 16, using a conveyor constituted by the first one of the bodies, arranged to support the weight of the said article at the said interface.

18. A method of conveying an article according to claim 17 using a plurality of such actuators in line.

19. A method of propulsion of a vehicle or of plant, according to any of claims 9 to 16, using a plurality of such actuators connected to the vehicle or plant and arranged to engage the ground.

20. An actuator substantially as described herein with reference to the accompanying drawings.

21. A conveyor system substantially as described herein with reference to the accompanying drawings.

22. A method of moving one body relative to another, substantially as described herein with reference to the accompanying drawings.

23. A method of conveying, substantially as described herein with reference to the accompanying drawings.