GB2180914A - Piston/cylinder assembly - Google Patents

Abstract

The external circumference of a piston/cylinder assembly is provided with at least one longitudinal strut (8) designed as a longitudinal guide (10) extending in the longitudinal direction of the cylinder tube. The longitudinal guide (10), as viewed in the circumferential direction of the cylinder tube (1), has a guide face (29) and a clamping face (30) lying opposite each other. There is further provided a mounting part (23) for a proximity switch (24) or the like, said mounting part sitting on the longitudinal guide (10) in the manner of a rider. For this purpose, the mounting part (23) is provided with a mounting groove (34) into which the longitudinal guide (10) is immersed. The first side wall (35) of the mounting groove (34) is capable of resting against the guide face (29), while the second side wall (36) faces the clamping face (30) at a distance. Between the clamping face (30) and the second groove side wall (36), a clamping device is provided to act against the clamping face (30) in order to secure the mounting part (23) on the cylinder tube (1). <IMAGE>

Description

SPECIFICATION Piston/cylinder assembly The invention relates to a piston/cylinder assembly comprising acylindertubeclosed by end coversat both ends and an axially movable piston arranged therein, said piston being connected to a piston rod extendingthrough at least one ofthe end covers whileforming a seal, at least one longitudinal strut extending outside the cylindertube and parallel to its longitudinal direction, and at least one mounting part for a proximity switch orthe like, which is likewise mounted ontheoutsideofthecylindertube.

In the case of piston/cylinder assemblies ofthe above type, the longitudinal strut, of which at least one is provided, is a tie rod, to each ofthe ends of which one ofthe end covers ofthe cylinder is detachablyfixed,thus permitting the tensioning oftheend coversagainstthecylindertube.Asa rule,fourtie rods are provided arranged at equal distances round the circumference ofthe cylindertube. Piston/ cylinder assemblies ofthis type are in particular used in applications where high internal pressures in the cylindertube are involved which necessitate special arrangements to secure the end covers against shooting off.If assemblies ofthistype are installed into machines, they often serve the purpose of triggering certain machine functions in dependence on the relative position ofthe piston in the cylindertube.

Forthis reason, proximity switches orthe like are externally mounted on the cylinder, which transmit an operative signal whenever the piston passes their location. These proximity switches or the like are usually rigidly mounted on the cylindertube by means of such parts as mounting bases or else bolted to the cylindertube. Since the threaded bores requiredforthis purpose have to be produced before the piston/cylinder assembly is installed on the cylindertube, itis latervirtuallyimpossibletoachievea precise adjustment ofthe response time ofthe proximity switches; the only possible solution is their graded positioning at certain points ofthe cylinder tube. Known assemblies are therefore not suitable for precise control functions.

There is the further disadvantage ofverytime- consuming assembly or removal ofthe proximity switches or mounting parts. Finally, retrofitting of commercially avaiiable cylinders with proximity switches is impossible in the conditions described.

The invention aims at creating a piston/cylinder assembly ofthe type described above, which would permitthe easy installation and removal of proximity switches while enabling their responsetimeto be precisely adjusted and being simple and costeffective in manufacture and construction.

This problem is solved by a assembly, wherein the longitudinal strut is a longitudinal guideforthe mounting partofthe proximity switch orthe like, having a guide face and a clamping face, the faces being arranged opposite each other on opposing sides alongside the longitudinal guide if viewed in the circumferential direction ofthe cylinder tube, and wherein the mounting part can be located with a mounting face on the longitudinal guide in the mannerofa rider and capable of movement inthe longitudinal direction ofthe cylindertube,the longitudinal guide being completely or almost com pletelyimmersed in a mounting groove formed in the mounting part on the side ofthe mounting face and extending over its entire length,thefirstside wall ofsaid mounting groove, which adjoinstheside, resting against the guide face ofthe longitudinal guide, while its second side wall extends opposite the clamping face at a distance therefrom and is provided with a clamping device consisting of at least one clamping element acting againstthe clamping face for secure, detachable location ofthe mounting part on the longitudinal guide. In this way, the mounting part carrying the proximity switch orthe like can be pushed on the longitudinal guide very simply and is continuously adjustable along its long itudinal dimension, so that it can be secured atany point. When the desired operating position is reached, the mounting part can be clamped in position by means ofthe clamping device.The longitudinal guide may directly be provided by a tie rod, offering the possibility of fitting a proximity switch to a conventional cylinderwithout additional machining. Since the mounting part surrounds the longitudinal guide on two sides, it can be securely clamped to is without accidentally sliding off. Since the distance between the two side walls ofthe mounting groove is greaterthan the width of the longitudinal guide, the dimensional accuracy requirements with regard to the longitudinal guide are relatively modest, and the mounting part can be securelyfitted to tie rods of differing diameters.

Advantageous further developments of the piston/ cylinder assembly according to the invention are described in the sub-claims.

The longitudinal strut or longitudinal guide may suitably be designed integrally as a profiled rail on the cylindertube,which would preferablyfulfil the additional function of a tie rod as described in Claim 3.

Inthefurtherdevelopmentdescribed in Claim 5, the guide face and the clamping face of the longitudinal guideconvergeconicallytowardsthecylin- dertube, the clamping element acting on the clamping face in the area ofthe external circumference of the cylindertubewhen the mounting part is installed.

If clamping element now acts againstthe clam- ping face, a tensile force biassing the mounting part towards the cylindertube is created in addition to the clamping force, resulting in an additional centring effect and a more secure attachment of the mounting part.

In thefurtherdevelopment described in Claim 6, the mounting part, and thus the proximity switch or the like, can be even more precisely located. In order to ensure an accurate response ofthe proximity switch, the distance between the proximity switch in question and the piston or magnet element attached to it, to which the proximity switch responds, must be precisely maintained at all times. In the further development according to Claim 6, the swivelling of the mounting partabouttheaxisofthelongitudinal guide is prevented, maintaining a constant distance ofthe proximity switch from the cylindertube even during or afterthe adjustment of the mounting part.

The further development described in Claim 10 is particularly simple and cost-effective to produce.

The further developments described in Claims 11 to 18 permitthetransmission ofthe clamping force fromtheclamping devicetotheclampingfaceofthe longitudinal guide over a large surface area, resulting in surface pressure ensuring excellent security.

Since the clamping action is no longer restricted to a point, damagetothe longitudinal guide is prevented; pointclamping may leave indentations inthe longitudinal guide, which may later make the precise adjustment ofthe mounting part more difficult. The advantageous further development described in Claim 16, for instance, is very simple to produce, essentially requiring one operation, such as injection moulding, only, while the further development described in Claim 17 permits easy renewal ofthethrust pad in the unlikely event of its detachment.

The further development described in Claim 19 is quickly and easily installed on or removed from the cylinder tube.

In the further development described in Claim 20, the point force supplied by the at least one clamping screw and acting on the thrust pad is transmitted to the clamping face of the longitudinal guide in an evenly distributed manner, resulting in a secure clamping action combined with protection ofthe clamping face against damage.

The invention is described in detail below with re ferenceto the embodiments illustrated in the drawing.

Figure 1 shows a first embodiment of the invention along line I-I of Figure 2, Figure2 is a side view of the arrangement illustrated in Figure 1, and Figures 3and 4showtwo embodimentsofthe mounting part.

The detailed description below initially refers to Figures 1 and 2. These show a piston/cylinder assembly comprising a cylindrical tube 1 closed and sealed at both ends by the end caps 2,3. This cylinder tube houses a piston not illustrated here, which divides the internal space of the cylinder into two pressure chambers and is capable of longitudinal move ment4inthe cylindertube 1. A coaxial piston rod 5 extends the piston, passing through the end cap 3 in a mannerto provide a seal. The part ofthe piston rod which protrudes from the cylinder tube may be attached to a powertake-off device.There are further provided two flow passages 6, 6' illustrated by broken lines, each one passing through one of the end covers; these serve as pressure medium inlets or outletsforthe pressure chambers, by which means the piston is moved in the cylinder.

On the outside of the cylindertube 1 ,four longitudinal struts 8 extending parallel to the cylinder axis 4 are provided, these being evenly distributed round the circumference of the cylindertube 1 . They are designed integral with the outside or outer sur face 7 of the cylindertube 1,forming profiled rails 14, 15, 16, 17 and representing a profiled tube 9 together withthecylindertube 1.

In the cross-section illustrated in Figure 1,the profiled rails 14-17 assumethe shape of eyes extending radially from the cylindertube.

The length ofthe profiled rails 14 - 17 equals that of the cylindertube 1,their axial end sections 18,19 being provided with axial blind threaded bores 20.

Coaxially aligned with the threaded bores 20, the corners of each end cap 2,3 are provided with a throughbore 21, through which a bolt can be inserted to be tightened in the threaded bore 20. The profiled rails 14- 17thus fulfil the function of tie rods securing the end caps, 2, to the cylindertube 1.

A proximity switch 24 only indicated in the drawing is mounted on the outside of the profiled tube 9 by means of a mounting part 23. This switch is det achablefrom the mounting part 23 and comprises a reed contact indicated by a broken lineforemitting a control signal via the signal lines 27 wheneverthe switch is passed by the piston guided inthecylinder, which is either of a magnetic design or contains a magnetic insert element.

The mounting part 23 is detachably mounted on one ofthe profiled rails 16forming a longitudinal guide 10 along which the mounting part 23 can be adjusted. The longitudinal guide 10 hasa guide face 29 and a clamping face 30 which face away from each other, being located at opposite sides ofthe longitudinal guide if viewed in the circumferential direction ofthe cylinder tube 1. The faces are preferably flat and directly adjoin the outer circumference 7 of the cylindertube 1 if viewed in the radial direction.

In the embodiment shown, the four profiled rails 14 - 17 are identical, offering the opportunity of mounting several proximity switches distributed round the circumference of the cylindertube 1. These would then not be in each other's way if one ofthem is axially adjusted. The guide and clamping faces 29, 30 of each profiled rail 14-17 could be arranged parallel and at a distance from each other- the distance approximately corresponding to the thickness or dia- meter of the profiled rail in question - so thatthey could extend at equal distances either side from a plane axially and radially oriented relative to the longitudinal axis 4 ofthe cylindertube 1. This embodiment is not illustrated in the drawing.A more advantageous alternative is the arrangement of the faces 29,30 on opposite sides, if viewed in the circumferential direction ofthe cylindertube 1, of a reference plane 31 axially and radially oriented relative to the longitudinal axis of the cylinder tu be, the planes 32,33 containing the faces 29,30 converging towards the cylindertube. The planes 32,33 enclose an acute angle, o, with the reference plane 31, the two angles o,(3 being preferably identical. The longitudinal axes of the profiled rails lie in the associated reference planes 31. This conical arrangement facing towards the external circumference 7 enhances the secure seat of the mounting part, which will be explained in detail in a later passage.

The single mounting part 23 illustrated in Figure 1 is mounted on the longitudinal guide 10 in the manner of a rider capable of adjustment along the axis 4 ofthe cylinder tube. The longitudinal guide 10 is virtually completely immersed in a mounting groove 34 of the mounting part 23, which is formed therein on the side of the mounting face 28 facing the cylinder tube 1. The mounting groove 34 has an es sentially rectangular cross-section with a U-shaped outline, its flat side wall 35 adjoining the mounting side 28,the shape of which complementsthat ofthe guide face 29, resting against the guide face 29.The width ofthe mounting groove 34, measured between this first side wall 35 and the opposite second side wall 36, is greaterthan the distance of the two faces ofthe longitudinal guide 10, providing for a distance between the second sidewall 36 and the clamping face 30.

The second side wall 36 is associated with a clamping device 37 acting against the clamping face 30 or biassed towards it or capable of being biassed towards it, this being provided for the secure but detachable mounting ofthe mounting part 23 on the longitudinal guide 10.

The mounting part 23 has a rocker-like shape with two legs 38,38' in V-arrangement enclosing an obtuse angle (see Figures 3 and 4). From the open side 39, which is identical to the mounting side 28, the mounting groove 34 is formed intheV-shaped mounting part 23, this groove being essentiallysym- metrical relative to the legs 38,38'. The mounting groove 34 preferably has an approximately rectangular or square cross-section, its outline, i.e. the arrangement of the groove walls, being U-shaped.

The two side walls 35,36 which lie opposite each other are preferably parallel to each other, each lying in oneplanewhich is parallel orapproximatelyparallel in relation to the longitudinal central plane 40 of the mounting part 23. The longitudinal central plane 40 extends in the longitudinal direction of the mounting groove 34 orthe longitudinal guide 10, thus in a way representing the imaginary plane of division for the legs 38,38' ofthe mounting part. As a result ofthe mounting groove, the cross-section of the mounting part 23 is vaguely U-shaped.

The depth of the mounting groove 34 essentially equalstheheightofthelongitudinal guide10as measured in the radial direction ofthe cylindertube 1,being preferably slightly greaterto enable the longitudinal guide 10 to be completely immersed in the mounting groove 34 when the mounting part 23 is installed. The sections 44,44' of the legs 38,38', which face towards the mounting side 28, rest against the external surface 7 on both sides ofthe longitudinal guide 10. In this way, any accidental swivelling ofthe mounting part 23 about the longitudinal guide 10 is prevented even while the mounting part is adjusted along the longitudinal guide (arrow 46).This ensures a constant distance 45 between the proximity switch 24 and the external surface 7 ofthe cylindertube 1, which is vital for the accurate function of the proximity switch. Any increase or decrease in this distance would result in a premature or delayed response of the proximity switch to the approaching piston or any magnetic device attached thereto; faults like this are avoided by the present invention.

The mounting groove may of course be radiussed in the area between the first groove side wall 35 and the base 47 (at 48), which may be done to comple mentthe external contours of the longitudinal guide 10. In this way, a close mutual fit between the guide face 29 and the side wall 35 is achieved, resulting in reliable longitudinal guidance.

The clamping device 37 is described in more detail below. With all embodiments, this device comprises athreaded bore 49 extending squarelythroughthe mounting leg 38' facing the clamping face 30 in rela tiontothe second sidewall 36. In this bore, a clamping screw, preferably in the form of a grubscrew50 can be screwed in either direction fortighteningtow- ardsthe clamping face 30 ofthe longitudinal guide 10 or loosening in the opposite direction. The longitudinal axis of the clamping screw is square orapp roximately squareto the clamping face 30.Afurther threaded bore 49 and a clamping screw 50' may suitably be provided, the two clamping screws being arranged at some distance from each other in the longitudinal direction 4 ofthe cylindertube 1, as illustrated by Figure 2.

Theclamping device 37 comprises at leastone clamping element supported between the mounting part 23 and the longitudinal guide 10 and capable of being biassed towards the clamping face 30. In the embodiment according to Figure 4, which is of a part icularlysimpleconstruction,theclampingelements 51 are represented by the clamping screws 50,50' themselves; they cross the free space between the second groove side wall 36 and the clamping face 30, their end faces 52 acting directly against the clamping face 30. If the clamping screws are thightened towards the clamping face 30, this results in contact be tween the guideface 29 andthefirstgroove side wall 35, thus clamping the mounting part 23 in position.In orderto adjustthe mounting part 23 along the longitudinal guide 10 (arrow 46), the clamping acrews 50, 50' are simply loosened slightly.

In the embodiment illustrated in Figures 1 and 3, the clamping element 53 is a plate-like thrust pad 54 arranged between the clamping face 30 and the second groove side wall 36 which faces it. Thisele- ment is attached to the mounting part 23 in the area ofthe base ofthe mounting groove 34 and projects into the mounting groove 34 in the manner of a tongue. The thrust pad 54 has an essentially rectangular plate shape, its plane 55 extending parallel or approximately parallel to the first side wall 35 of the mounting groove 34. The length ofthethrust pad 54 as measured in the longitudinal direction ofthe cylindertube equals the length of the mounting groove 34. The thrust pad 54 is preferably flexibly attached to the mounting part 23, which is best done near one of its longitudinal edges 56. There is no need for a joint or other articulated attachment, since flexibility may be achieved by appropriate selection ofthe material used for the manufacture ofthethrust pad 54, this being a flexible, elastic material. The thrust pad 54 is further relatively thin in relation to its width and length, this alone ensuring a certain degree of flexibility. The width of the thrust pad 54 as measured parallel to the second groove sidewall 36 is so chosen that it substantially corresponds to the depth of the mounting groove 34, its free longitudinal edge, when the mounting part 23 is installed on the longitudinal guide 10, contacting a pointofthe clamping face 30 which is close to the external sur face 7 of the cylindertube 1.

In the embodiment illustrated in Figure 1,the thrust pad 54 is integral with the mounting part 23, enabling the two components to be produced in one operation. In the further development illustrated in Figure 3, the thrust pad 54 is separate from the mounting part23, being an insert 58 located in a groove 57 extending in the longitudinal direction of the mounting groove 34. The insert groove 57 is a surface groove formed in the base 47 of the mounting groove 34, being narrow in the area of the groove base 47 (at 62) and subsequently becoming wider (at 63).Theshapeofthelongitudinal edgeofthethrust pad 54 complements this arrangement. The thrust pad 54 is inserted, preferably under pressure, from one ofthe end faces 64,64'ofthe mounting part 23 as viewed in the axial direction 4.This latterfurtherdevelopment offers the advantage that the thrust pad 54 may, if damaged or broken off, be replaced simply without necessitating the replacement of the whole mounting part 23.

The distance between the first groove side wall 35 of the mounting groove 34 and the adjoining clamping face 66 of the thrust pad 54 approximately equaisthe distance between the clamping and guide faces ofthe longitudinal guide as measured in the circumferential direction ofthe cylinder tube 1. In this way, the open side ofthe mounting part 39 can simply be pushed on the longitudinal guide 10, the first groove sidewall 35 resting against the guide face 29 and the clamping face 66 ofthe thrust pad 54 being in contact with the clamping face 30. If the clamping screw 50 is tightened towards the longitudinal guide 10, its end 52 presses against the thrust face 67 ofthe thrust pad 54, thus biassing ittowards the clamping face 30.

In this way, the point force exerted by the clamping screws 50,50' on the thrust pad 54 is distributed to become an areal clamping force transmitted from the clamping face 66to the clamping face 30. Thisarea contact between the clamping element 53 and the clamping face 30 protects the latter, so that even high clamping forces do not leave any indentations in the clamping face 30. This distribution ofthe clamping force further results in a much moresuitable mounting arrangement than any point force could achieve.

When the clamping screws 50,50' are loosened, the tongue-shaped clamping element 53 returns to its initial position, enabling the mounting part23to be removed from the longitudinal guide 10 or adjusted along its longitudinal direction (arrow 46) to be re-clamped in the desired position. When the clamping screws 50,50' act on the thrust pad 54, this is flexed nearthe point of attachment (Figure 3) or where it begins to project from the groove base 47 (Figure 1).By accurately matching the distance between the guide face 29 and the thrust pad 54to the width ofthe longitudinal guide 10, this flexing movement can, however, be made to be so insignificant thatthere is hardly anyflexural fatigue, so thatthe service life ofthe thrust pad 54 remains virtually unaffected.

In a further embodiment not illustrated in the drawing, there are no clamping screws 50,50', the clamping force being produced by the tongue-shaped clamping element 53 only. In this case, the distance between the first groove sidewall 35 and the clamping face 66 of the thrust pad 54 is suitably chosen to be less - when the mounting part is removed from the longitudinal guide 10-than the distance between the guideface 29 and the clamping face30 ofthe longitudinal guide. When the mounting part23 is pushed on the longitudinal guide 10, the thrust pad 54is flexed, resulting in a greater distance between itself andthefirst groove sidewall 35.The clamping action is in this case entirely dependent on the restoring force of the thrust pad 54, which has been bent towardsthe second groove sidewall 36. The clamping face 30 and the respective clamping side ofthethrust pad should in this case be so designed that the mounting part 23 can be clipped to the longitudinal guide 10.

As has been described above, the security of the mounting part 23 on the longitudinal guide 10 may be substantially enhanced by making the clamping face 30 and the guideface 29 enclose an angle a, (3 with the reference plane 31. Owing to the flexibility of the thrust pad 54, the first groove sidewall 35 and the clamping face 66 are in firm contact with the clamping face 30 and the guide face 29 respectively.

Since, however, the distance between the first groove side wall 35 and the clamping face 66 in the area of the external surface 7 of the cylindertube 1 is less than that near the groove base 47, a mechanical locking action is added to the clamping force which prevents the mounting part23from being pulled off the longitudinal guide 10.Thethrustpad54issuit- ably provided with a longitudinal rib 68 near its free edge and on the clamping face 66 for additional contact in the narrowed section ofthe longitudinal guide 10 near the external circumference 7 ofthe cylinder tube 1. Optimum transmission ofthe clamping force supplied by the clamping screws 50,50' is achieved if the end faces 52 ofthe clamping screws act on that part of the thrust face 67 which is opposite the longitudinal rib 68.

The proximity switch 24 is preferably attached to the mounting part 23 by means of a bolt 69 extending through the leg 38 of the mounting partwhich is op- posite the clamping device and projecting from its end face 70 facing the circumference of the cylinder tube 1,to be tightened in a mannerto permitsubse quentremoval in a corresponding threaded bore in the proximity switch 24.

As it is located in the plane ofthe leg, the bolt 69 is easily accessible. To securethe proximity switch 24 in position, a locating pin 71 is provided, this being inserted from the end face 70 into the mounting part 23 and projecting therefrom,the projecting section being designed for insertion an a corresponding bore of the proximity switch 24. The proximity switch can thus be removed and re-installed whenever required, and installation in the original position poses no problem.

When installed on the longitudinal guide 10,the cross-section of the mounting part 23 is approximately roof-shaped in relation to the longitudinal guide 10, the legs 38,38' starting radially outside the longitudinal guide 10 extending tangentially relative to and at a distance from the outer circumference 7 of the cylindertube 1. The legs 38,38' terminate near the longitudinal guide, and the proximity switch is located approximately opposite the apex of the cylin dertube between two profiled rails 15,16.

Claims (29)

1. A piston/cyl inder assem bly com prising acylin- dertube closed by end covers at both ends and an axially movable piston arranged therein, said piston being connected to a piston rod extending through at least one ofthe end covers while forming a seal, at least one longitudinal strut extending externally along the cylindertube and parallel to the longi tudinal direction thereof, and at least one mounting partfor a proximity switch orthe like, which is like wise mounted externally of the cylinder tube, the lon gitudinal strut being a longitudinal guideforthe mounting part ofthe proximity switch or the like, having a guideface and a clampingface,thefaces being arranged opposite each other along the longi tudinal guide, if viewed in the circumferential direc tion of the cylindertube, and the mounting part being located with a mounting face on the longitudinal guideformovementtherealong in the longitudinal direction of the cylinder tube, the longitudinal guide being substantially enclosed in a mounting groove formed in the mounting part on the side ofthe mounting face and extending along the length thereof, a first sidewall of said mounting groove, which adjoins the side, restingagainsttheguideface on the longitudinal guide while a second side wall extends oppositethe clamping face at a distance therefrom and is provided with clamping means comprising at least one clamping element acting againstthe clamping faceforsecure, detachable loc ation of the mounting part on the longitudinal guide.

2. A piston/cylinder assembly according to claim 1, wherein the or at least one longitudinal strut is a profiled rail integral with the cylindertube and rad ially extending from the outer surfacethereof,the rail forming a profiled tube with the cylindertube.

3. Apiston/cylinderassembly according to claim 2, wherein the length of the profiled rail corresponds tothelength ofthecylindertubeandwhereintwo end sections ofthe profiled rail have axial threaded bores for installing boltsto retain the end coversat the respective cylinder ends.

4. A piston/cylinder assembly according to any of claims 1 to 3, wherein both the clamping face and the guideface are flat, the two faces being in a spaced apart, parallel relation, at equal distances on respect ive sides of a reference plane axially and radially ori- ented relating to the longitudinal axis ofthe cylinder tube.

5. A piston/cylinder assembly according to any of Claims 1 to 3, wherein both the clamping face and the guide face are flat, the two faces, if viewed in the circumferential direction of the cylindertube, extending on opposite sides of a reference plane axially and radially oriented relative to the longitudinal axis of the cylindertube, the planes containing the faces converging towards the cylinder tube, and each enclosing an acute angle with the reference plane, and wherein the clamping element acts in particular on that part of the clamping face which is associated with the cylinder tube.

6. A piston/cylinder assembly according to claim 5, wherein each of the angles is 2".

7. A piston/cylinder assembly according to any of the preceding claims, wherein the mounting parten gages against the outer surface ofthe cylindertube with sections of the mounting face which are located one on either side of the mounting groove, if viewed in the circumferential direction ofthe cylindertube, thus preventing swivelling of the mounting part aboutthe longitudinal axis ofthe longitudinal guide, the depth of the mounting groove substantially equalling the height of the longitudinal guide.

8. A piston/cylinder assembly according to any of the preceding claims, wherein the cross-section of the mounting groove is defined by walls providing a U-shape, the walls which represent the legs of the U lying opposite the clamping face and the guide face respectively.

9. A piston/cylinder assembly according to any of the preceding claims, wherein the clamping device is provided with at least one threaded bore, one end thereof opening into the mounting groove atthe second side wall while the other end opens exter nallyofthemounting part, the bore extending through the section of the mounting part associated with the second sidewall of the mounting groove and being designed for a clamping screw capable of being tightened towards the clamping face of the lon gitudinal guide and loosened in the opposite direc tion.

10. A piston/cylinder assembly according to claim 8, wherein the longitudinal axis ofthe clam ping screw is substantially squaretothe clamping face.

11. A piston/cylinder assembly according to claim 9 or 10, wherein the clamping means is formed by at least one clamping screw capable of being tightened inthethreaded bore until being in contact with the clamping face and of being loosened in the opposite direction.

12. A piston/cylinder assembly according to any of claims 1 to 10, wherein the clamping element is a plate-like thrust pad located between the second side wall of the mounting groove and the clamping face and mounted on the mounting part in the area ofthe base ofthe mounting groove.

13. A piston/cylinder assembly according to claim 12, wherein the thrust pad has a substantially rectangular plate shape, the plane ofthe plate being substantially parallel to the second side wall ofthe mounting groove.

14. A piston/cylinder assembly according to claim 13, wherein the dimension of the thrust pad which is measured along the longitudinal direction ofthe cylindertube equals the length of the mount ing groove.

15. A piston/cylinder assembly according to any of claims 12 to 14, wherein the thrust pad is flexibly mounted on the mounting part.

16. A piston/cylinder assembly according to claim 15, wherein the thrust pad is made of a flexible elastic material.

17. A piston/cylinderassembly according to any of claims 12to 1 6, wherein the thrust pad is integral with the mounting part.

18. A piston/cylinder assembly according to any of claims 12 to 16, wherein the thrust pad is separate from the mounting part, being designed as a re placeableinsertina recess or groove formed in a side wail or in the base ofthe mounting groove.

19. A piston/cylinder assembly according to any of claims 12 to 18, wherein the distance between the first sidewall associated with the guide face ofthe longitudinal guide, and the clamping face ofthe thrust pad which is facing the clamping face is, when the mounting part is removed from the longitudinal guide, less than the distance between the guide face and the clamping face ofthe longitudinal guide, so thatthemounting part is clampedtothe longitudinal guide while the thrust pad is flexed towards the second sidewall when the mounting part is pushed on the longitudinal guide.

20. A piston/cylinder assembly according to claim 19, wherein the mounting part can be clipped to the longitudinal guide, this being suitably achieved bya longitudinal rib provided on the thrust pad in the area ofthe opening ofthe mounting groove engaging a recess in the clamping face.

21. A piston/cylinder assembly according to any of claims 12 to 20, wherein the clamping element is capable of being tightened towards the plate face of the thrust pad which forms the th rust face and lies opposite the clamping face in ordertotighten the place face of the thrust pad which forms the clamping face against the clamping face of the longitudinal guide, an end face ofthe element acting againstthethrustface.

22. A piston/cylinder assembly according to any ofthe preceding claims, wherein two clamping elements are arranged in sequence along the length of the mounting groove at a distance from each other.

23. A piston/cylinder assembly according to any ofthe preceding claims, wherein the mounting part may, if required, be adjusted longitudinally along the longitudinal guide after loosening the or each clamping element and clamped where required.

24. A piston/cylinder assembly according to any ofthe preceding claims, wherein a proximity switch orthe like may be detachably fitted to a section ofthe mounting part associated with the first sidewall of the mounting groove, the distance of said switch from the external circumference ofthe cylindertube remaining constantwhen being moved along the longitudinal guide.

25. A piston/cylinder assembly according to any ofclaims 1 to 10 or 12to 24, wherein the clamping element is pressed against the clamping face.

26. A piston/cylinder assembly according to any ofthe preceding claims, wherein the mounting part has a V-or U-shaped cross-section,the mounting groove being associated with the open sides oftheV or U,while a mounting section ofthe mounting part carrying the proximity switch or the like is associated with either of the legs ofthe V or U.

27. Apiston/cylinder assembly comprising at least one longitudinal guide provided externally on a cylinder and extending longitudinallytherealong, and at least one mounting part for a proximity switch orthe like, the guide having a guide face and a clamping face which are arranged on opposing sides of, and along, the guide, if viewed in the circumferential direction ofthe cylinder, and the mounting part being locatedwith a mounting face on the guidefor movementtherealong in the longitudinal direction of the cylinder, the longitudinal guide being substanti- ally enclosed in a mounting groove formed in the mounting face ofthe mounting part and extending along the length thereof, a first sidewall ofthe mounting groove engaging the guide face of the longitudinal guide and a second sidewall extending opposite the clamping face at a distance therefrom and being provided with clamping means comprising at least one clamping element acting againsttheclam- ping faceforsecure, detachable location ofthe mounting part on the longitudinal guide.

28. A piston/cylinder assembly substantially as hereinbefore described with reference to the accompanying drawings.

29. Any novel subject matter or combination including novel subject matter herein disclosed in the foregoing Specification or Claims and/or shown in the drawings, whether or not within the scope of or relating to the same invention as any of the preceding claims.