GB2274323A

GB2274323A - Fluid cylinders

Info

Publication number: GB2274323A
Application number: GB9300717A
Authority: GB
Inventors: Ian Musson
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-01-14
Filing date: 1993-01-14
Publication date: 1994-07-20
Anticipated expiration: 2013-01-14
Also published as: GB9300717D0; GB2274323B

Abstract

A fluid piston-cylinder has a piston (7) mounted on a piston rod (9) and movable, by fluid pressure applied to its opposite ends, longitudinally in a cylinder (1). A square section rod (11) extends through an aperture in the piston (7) and into a longitudinally extending recess (13) in the piston (7). The square section rod (11) is not rotatable in the aperture in the piston and the piston rod (9) is thus not rotatable with respect to the cylinder (1) except by rotating a portion (23) of the square section rod which is located outside the cylinder (1), a bearing (27) and seals (29) being provided in an end cap (25) of the cylinder (1). <IMAGE>

Description

FLUID CYLINDERS This invention relates to fluid cylinders.

Fluid cylinders normally comprise a cylinder having thereon mounting means whereby it can be secured in a desired position on a piece of apparatus and a piston mounted on a piston rod and movable within the cylinder by fluid pressure applied to one end or the other of the cylinder to cause the piston rod to extend from or be retracted into the cylinder. The outer end of the piston rod normally has connection means whereby a lever or other mechanical device can be coupled thereto.Since the piston must form a sliding seal with the inside wall of the cylinder and the piston rod must exit a cylinder end wall through a sliding seal, it is impractical to provide either the piston or the piston rod of a non-circular section and accordingly very difficult, if it is so desired, to prevent the piston rod and piston from rotating about the longitudinal axis of the fluid cylinder except by external means.

According to the invention in a fluid cylinder a non-circular section member is provided to extend from an end wall of the cylinder, through the piston and into a longitudinally extending recess in the piston rod and is secured against rotation with respect to the piston rod such that by securing the elongate non-circular section member against rotation about its longitudinal axis the piston and piston rod can be restrained from rotating with respect to the cylinder about the longitudinal axis of the fluid cylinder.

Advantageously the elongate non-circular section member is restrained from rotation with respect to the cylinder by means engaging an extension of the elongate non-circular section member at a position outside the cylinder and such means are controllable such that the elongate non-circular section member can be rotated as desired about its longitudinal axis to effect consequent rotation of the piston rod with respect to the cylinder.

Preferably the elongate non-circular section member is a square section rod which, if it is merely desired to prevent rotation of the piston rod, can be secured against rotation by securing it, for example by welding, to the end wall of the cylinder. Preferably a member through which the square section rod passes in the piston rod to secure it against rotation with respect thereto is a bush with a sixteen sided aperture therein secured to the piston rod, the aperture in the bush cooperating such that midway along each flat face of the square section rod there is a triangular passageway to permit passage of fluid from the recess in the piston rod into the cylinder upon movement of the square section rod into and out of the recess in the piston rod.

Where external control of the angular position of the square section rod is required, the square section rod is advantageously secured to a member which extends through a thrust bearing and a seal in the end wall of the cylinder and has a non-circular section portion projecting externally of the cylinder which can be gripped by torque means, such as by providing the projecting portion of square section and providing a square section aperture in a lever such that angular movement of the lever will cause rotation of the member and of the square section rod within the cylinder.

The invention is diagrammatically illustrated by way of example in the accompanying drawings in which: Figure 1 is a perspective cut-away view of one end of a fluid cylinder according to the invention; Figures 2a and 2L are respectively an elevation and an end view of the cylinder of Figure 1; Figure 3 is a sectional view on line A-A of Figure 2k; Figure 4 is a corresponding end view; Figure 5 is a sectional view on line B-B of Figure 4; Figure 6 is a sectional view on line C-C of Figure 5; Figure 7 is a perspective part sectional view of a second embodiment of a fluid cylinder according to the invention; Figures 8a and 8k are respectively an elevation and an end view corresponding to Figure 7; Figure 9 is a sectional view on line A-A of Figure 8h; Figure 10 is a corresponding end view;; Figure 11 is a sectional view on line B-B of Figure 10; and Figure 12 is a sectional view on line C-C of Figure 11.

Referring to the drawings and firstly to Figures 1 to 6, a fluid cylinder 1 has a cylindrical wall 2, a cap end wall 3, a head end wall 4, a first fluid inlet 5 and a second fluid inlet 6.

Mounted within the cylinder 1 is a piston 7 with seals 8 to effect a seal with the inside face of the cylindrical wall 2 of the cylinder 1, a piston rod 9 which is secured to the piston 7 and extends through the head end wall 4 with the provision of seals 10 and a square section rod 11 which is secured to the centre of the cap end wall 3 of the cylinder 1 and extends through a matching non-circular section aperture 12 in the crown of the piston 7 into a longitudinally extending recess 13 in the piston rod 9. A space 14 between the cap end wall 3 and the piston 7, a space 15 between the piston 7 and the head end wall 4 and a space 16 within the recess 13 are at all times filled with fluid. By supplying fluid to the inlet 5 the piston rod 9 can be caused to extend from the cylinder 1 until the piston 7 is touching the head end wall 4.By supplying fluid to the inlet 6 the piston rod can be retracted into the cylinder 2 until the piston 7 is touching the cap end wall 3. At all times the square section rod 11 sliding in the aperture 12 in the crown of the piston 7 will prevent the piston rod 9 from rotating with respect to the cylinder 1 about the longitudinal axis of the cylinder 1. Mounting means (not shown) are provided on the cylinder 1 or it can be gripped in a clamp and mounting means (not shown) are provided on the end of the piston rod 9 projecting from the cylinder 1 or again it can be gripped in a clamp but it is not necessary to provide restraining means on the mounting means of the cylinder or the piston rod to prevent relative rotation thereof.

Referring to Figures 7 to 12, a cylinder 21 is shown which in almost all respects is similar to the cylinder 1 shown in Figures 1 to 6 and like reference numerals are used to denote parts which are the same in Figures 7 to 12 as in Figures 1 to 6 and such parts are not further described.

The significant difference between the cylinder 21 and the cylinder 1 is that in the cylinder 21 the square section rod 11 is not fixedly secured to the cap end wall 3 but rather is fixedly secured to a mushroom shaped member 22 having a stem 23 which extends through a bore 24 in a cap end wall 25 of the cylinder 21, which cap end wall 25 is considerably thicker than the cap end wall 3 of the embodiment of Figures 1 to 6. A thrust bearing 27 is provided between a head 28 of the mushroom shaped member 22 and the end wall 25 and seals 29 are provided in the bore 24 between the stem 23 and the end wall 25. An outer end part 30 of the stem 23 can be provided of non-circular section such that torque means not shown can be applied thereto to cause rotation of the mushroom shaped member 22 and hence the square section rod 11 and the piston rod 9 as desired.

The means provided at the free end of the mushroom shaped member 23 to cause rotation of the mushroom shaped member and thus of the square section rod 11 and the piston rod 9 could be provided as a rotary motor, for example a pneumatic motor or a hydraulic motor with a collet and drill bit provided on the free end of the piston rod 9 thereby forming a drilling machine which could safely be used in atmospheres where it would be hazardous to use an electric motor. Thus the cylinder 21 and such a rotary motor can together provide both rotary motion and axial feed.

A cylinder of the invention has many other applications, one of which could be for example as a pick and place robotic unit whereby with the cylinder 21 generally vertical and with an arm projecting horizontally from the upper end of the piston rod 9, the free end of the arm could collect a component to be placed and the piston rod could be rotated within the cylinder, before during or after extension or contraction of the cylinder to swing the arm through an arc to place the component down at a required position. A further application could be in the form of a lorry mounted crane, that is to say, a crane provided on a lorry to load and unload goods from the lorry.

Claims

1. A fluid piston-cylinder having a cylinder, a piston and a piston rod wherein an elongate non-circular section member is provided to extend from an end wall of the cylinder, through the piston and into a longitudinally extending recess in the piston rod and is secured against rotation with respect to the piston rod such that, by securing the elongate non-circular section member against rotation about its longitudinal axis, the piston and the piston rod can be restrained from rotating with respect to the cylinder about the longitudinal axis of the fluid piston-cylinder.

2. A fluid piston-cylinder according to claim 1, wherein the elongate non-circular section member is restrained from rotation with respect to the cylinder by means engaging an extension of the elongate non-circular section member at a position outside the cylinder and such means are controllable such that the elongate non-circular section member can be rotated as desired about its longitudinal axis to effect consequent rotation of the piston rod with respect to the cylinder.

3. A fluid piston-cylinder according to claim 1 or claim 2, wherein the elongate non-circular section member is a square section rod.

4. A fluid piston-cylinder according to claim 3, wherein the square section rod is secured against rotation by being secured to the end wall of the cylinder.

5. A fluid piston-cylinder according to claim 4, wherein the rod is secured to the end wall of the cylinder by welding.

6. A fluid piston-cylinder according to any one of claims 3 to 5, wherein a member through which the square section rod passes in the piston rod to secure it against rotation with respect thereto is a bush with a sixteen sided aperture therein secured to the piston rod and the aperture in the bush cooperates with the square section rod such that midway along each flat face of the square section rod a triangular passageway is formed to permit passage of fluid from the recess in the piston rod into the cylinder upon movement of the square section rod into and out of the recess in the piston rod.

7. A fluid piston-cylinder according to claim 3 when appendant to claim 2, wherein the square section rod is secured to a member which extends through a bearing and a seal in the end wall of the cylinder and has a non-circular section portion projecting externally of the cylinder to be gripped by torque means.

8. A fluid piston-cylinder according to claim 7, wherein the bearing is a thrust bearing.

9. A fluid piston-cylinder according to claim 7 or claim 8, wherein the projecting portion is of square section and a lever has a square section aperture therein to engage the portion of square section such that angular movement of the lever will cause rotation of the member and thus of the square section rod within the cylinder.

10. A fluid piston-cylinder substantially as hereinbefore described and illustrated with reference to the accompanying drawings.