GB1604686A

GB1604686A - Fluid pressure actuators

Info

Publication number: GB1604686A
Application number: GB1022678A
Authority: GB
Original assignee: Pilgrim Engineering Developments Ltd
Current assignee: Pilgrim Engineering Developments Ltd
Priority date: 1978-05-31
Filing date: 1978-05-31
Publication date: 1981-12-16

Description

(54) FLUID PRESSURE ACTIVATORS (71) We, PILGRIM ENGINEERING DEVELOPMENTS LIMITED, a British company of Beaufort House, St. Botolph Street, London EC3A 7DX, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to fluid pressure actuators. It is concerned especially with actuators in tensioning and gripping devices and with actuators in sealing arrangements.

Hydraulically expanded nuts are known that comprise an annular body with an annular groove in its end face and an annular piston fitted in the groove. An annular load cell in the form of annular tyre is located in the groove behind the piston and is connected by a stem pipe through the wall of the body to the exterior. Hydraulic fluid is pumped into the tyre to cause it to expand in the radial direction and force the piston outwardly from the body.

The present invention consists of forming the pressure cell in hydraulically expanded nuts and other actuator devices from a length of flexible tube formed e.g. by a continuous moulding process.

According to the present invention there is provided a fluid pressure actuator comprising a body with a recess in a surface of the body, a piston which is a close sliding fit in the recess, and a pressure cell in the recess behind the piston, the pressure cell being formed by a length of flexible tube laid in the recess, the ends of the tube passing through the body to the exterior, the piston and the recess together define a cavity, the crossaection of which in the rest position conforms to the cross-sectional profile of the tube, and the centre-line of the tube in the region that is in contact with the piston lying in a substantially flat plane.

The actuator can take various forms depending on the use envisaged. For example: (1) in the straight form i.e. with a straight groove, it may be used for lifting and clamping applications in heavy engineering and shipbuildingi.e. bar jacks; (2) in the annular form, i.e. with an annular groove in a flat surface,it may be used for applying axial loads in hydraulic jacking nuts or axial clamping devices or axial seals, and (3) in the curved form, i.e. with internal or external peripheral grooves for applying radial loads in clamping devides acting inwards or outwards and in flexible seals moved inwards or outwards onto their mating parts Embodiments of the invention will now be described by way of example with reference to the accompanying drawings of which: Figure 1 shows a cross-section of a straight linear actuator according to the invention; Figure 2 shows a plan view of the actuator of Figure 1; Figure 3 shows a cross-section on the line III-III of Figure 1; Figure 4 shows a plan view of an annular form of actuator in which the piston thereof moves axially; Figure 5 shows a section on the line VI-VI of Figure 4; Figure 6 shows a section of an annular form of actuator in which the piston thereof moves radially inwardly; Figure 7 shows a section on the line VIII-VIII of Figure 6; Figure 8 shows a section of an annular form of actuator in which the piston thereof moves radially outwardly; and Figure 9 shows a section on the line X-X of Figure 8.

A linear type of actuator or jacking device 10 is shown in Figures 1 to 3. An elongate piston 11 is housed in a groove 12 in a body 13.

The ends of the groove 12 line up with holes 14 in the body 13 parallel to the direction of movement. A flexible tube 15 of rubber of similar elastomer enters through one hole 14, is laid along the groove 12 and exits through the other hole 14. The flexible tube 15 is constrained inside the body by the walls of the groove and by the piston 11 and end fillet pieces 16. The outer ends of the tube where they emerge from the body 13 are terminated in fittings 17 which seal the tube and provide feed and vent connections 18. To prevent extrusion of the tube between the piston and the wall of the groove the piston is machined to a section with antiextrusion side fins 19 on the back face as shown in Figure 3.

When hydraulic fluid is pumped into one end of the tube through the fitting 18 air is vented at the other end and when the tube is completely filled the other end is closed so that the pressure of the fluid can be raised to expand the tube laterally and thus force the piston 11 outwardly of the flat end face 22 of the body 13.

An annular form of actuator is shown in Figures 4 and 5. In this form a flexible tube 30 is contained in an annular radiussed groove 31 in the end face of an annular body 32 behind an annular piston 33 which fits in the groove.

The annular piston has a finned cross section and is forced out of the end face of the body 32 when the flexible tube is presussurised with hydraulic fluid. The ends of the tube 30 are brought out of the groove through holes 34 parallel to the direction of movement and their ends can be arranged to be adjacent one another in contact side by side. A fillet piece 35 fills the gap between the bends of the tubes and the piston allowing the hydraulic pressure to act on the full periphery of the piston 33. The ends are terminated in fittings 36 that seal the tube and provide feed and vent connection 37.

This type of curved form could also be made in shorter segments if required. These loading devices could be used for jacking devices, such as self strained nuts or bolts, or for inflatable annular seals, where the piston is made from a suitable hard elastomer.

Other curved forms are shown in Figures 6 and 7 and 8 and 9 where the groove 40 is cut radially inwards Figures 6 and 7 or outwards Figures 8 and 9 in the body 41, so that the piston 42-in segmented forms forced inwards or outwards in a radial direction by the inflation of the tube 43. The groove may be an annulus, with terminating holes drilled radially as shown side by side. Fillet pieces 44 are fitted at the end bends and fishplates 45 are inserted between tube and segments at the segment joints to prevent extrusion of the elastomer.

The ends of the tube are terminated in fittings 46 that seal the bore of the tube and provide the feed and vent connections for inflation.

This arrangement could be used for radial clamping applications for fastening tubing from inside or outside, for swaging thin wall tubing, or for securing circular bar, all these altematives having applications in general engineering, marine engineering and shipbuilding and in off- shore engineering and pipeline applications.

Furthermore a variation having a continuous hard elastomer piston would provide a radial seal against fluid or gas leakage.

WHAT WE CLAIM IS: 1. A fluid pressure actuator comprising a body with a recess in a surface of the body, a piston which is a close sliding fit in the recess, and a pressure cell in the recess behind the piston, the pressure cell being formed by a length of flexible tube laid in the recess, the ends of the tube passing through the body to the exterior, the piston and the recess together define a cavity, the cross-section of which in the rest position conforms to the cross-sectional profile of the tube, and the centre-line of the tube in the region that is in contact with the piston lying in a substantially flat plane.

2. A fluid pressure actuator according to claim 1, in which the piston is made of an elastomeric material so that in use it may seal against a complementary surface.

3. A fluid pressure actuator according to claim 1 or 2, in which the recess comprises a recess in a flat surface of the body and the flexible tube lies along the recess.

4. A fluid pressure actuator according to claim 3, in which the recess is generally rectilinear.

5. A fluid pressure actuator according to claim 3, in which the recess is annular, the ends of the flexible tube passing out of the recess through the body at points adjacent one another.

6. A fluid actuator according to claim 1 or 2, in which the recess is an annular recess formed in a cylindrical surface of the body, the ends of the flexible tube being taken out of the recess through the body at points adjacent one another.

7. A fluid actuator according to any of the preceding claims in which the piston has fins projecting towards the bottom of the recess along both of its longitudinal edges.

8. A fluid actuator substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the wall of the groove the piston is machined to a section with antiextrusion side fins 19 on the back face as shown in Figure 3. When hydraulic fluid is pumped into one end of the tube through the fitting 18 air is vented at the other end and when the tube is completely filled the other end is closed so that the pressure of the fluid can be raised to expand the tube laterally and thus force the piston 11 outwardly of the flat end face 22 of the body 13. An annular form of actuator is shown in Figures 4 and 5. In this form a flexible tube 30 is contained in an annular radiussed groove 31 in the end face of an annular body 32 behind an annular piston 33 which fits in the groove. The annular piston has a finned cross section and is forced out of the end face of the body 32 when the flexible tube is presussurised with hydraulic fluid. The ends of the tube 30 are brought out of the groove through holes 34 parallel to the direction of movement and their ends can be arranged to be adjacent one another in contact side by side. A fillet piece 35 fills the gap between the bends of the tubes and the piston allowing the hydraulic pressure to act on the full periphery of the piston 33. The ends are terminated in fittings 36 that seal the tube and provide feed and vent connection 37. This type of curved form could also be made in shorter segments if required. These loading devices could be used for jacking devices, such as self strained nuts or bolts, or for inflatable annular seals, where the piston is made from a suitable hard elastomer. Other curved forms are shown in Figures 6 and 7 and 8 and 9 where the groove 40 is cut radially inwards Figures 6 and 7 or outwards Figures 8 and 9 in the body 41, so that the piston 42-in segmented forms forced inwards or outwards in a radial direction by the inflation of the tube 43. The groove may be an annulus, with terminating holes drilled radially as shown side by side. Fillet pieces 44 are fitted at the end bends and fishplates 45 are inserted between tube and segments at the segment joints to prevent extrusion of the elastomer. The ends of the tube are terminated in fittings 46 that seal the bore of the tube and provide the feed and vent connections for inflation. This arrangement could be used for radial clamping applications for fastening tubing from inside or outside, for swaging thin wall tubing, or for securing circular bar, all these altematives having applications in general engineering, marine engineering and shipbuilding and in off- shore engineering and pipeline applications. Furthermore a variation having a continuous hard elastomer piston would provide a radial seal against fluid or gas leakage. WHAT WE CLAIM IS:

1. A fluid pressure actuator comprising a body with a recess in a surface of the body, a piston which is a close sliding fit in the recess, and a pressure cell in the recess behind the piston, the pressure cell being formed by a length of flexible tube laid in the recess, the ends of the tube passing through the body to the exterior, the piston and the recess together define a cavity, the cross-section of which in the rest position conforms to the cross-sectional profile of the tube, and the centre-line of the tube in the region that is in contact with the piston lying in a substantially flat plane.