HOLDING DEVICE FOR PISTON POSITION DETECTOR

Abstract: Holding device (5) for a piston position detector, contained in a casing (9) and being displaceably mounted on the outside of a fluid pressure cylinder. The holding device consists essentially of a U-shaped yoke (6) being displaceable along two mutually parallel guides (4a, 4b) and being lockable in a desired axial position. The yoke (6) is locked by means of a first fastening screw (10), whereas the casing (9) is insertable between the shanks (7, 8) of the yoke and is lockable in inserted position by means of a second fastening screw (15). The casing (9) is protected by the yoke (6) and is detachable from the latter, also when the yoke is locked to the guides (4a, 4b).

Description: HOLDING DEVICE FOR PISTON POSITION DETECTOR ■ * The invention concerns a holding device, which is displaceably mounted on the outside of a fluid pressure cylinder, of the kind * 5 defined in the preamble of claim 1. Such a holding device is previously known from DE-C-3 516 346 (Daimler-Benz AG) . This previously known device comprises a bracket like holder with two hook shaped clamping elements, 10 which are jointly displaceable along a tension rod associated with the fluid pressure cylinder. One of the clamping elements is provided with a radially extending holding plate, to which a casing incorporating a piston position detector is detachably mounted by means of two screws, while the other clamping ele- 15 ment, which is pivotable relative to the first one, is provided, on the one hand, with a fastening screw for application against the tension rod and, on the other hand, with a clamping screw effective between the clamping elements and, upon tightening, causing the two clamping elements to pivot in opposite direc- 20 tions, so that the casing and a protruding tongue element of the second clamping element is pressed against the exterior of the cylinder tube under clamping action. On the basis of the above mentioned prior art and other similar 25 arrangements (US-A-4 230 023, EP-A-0 125 992 and EP-A-0 309 304) the present invention mainly aims to achieve a simple and reliable holding device, which - includes the least possible number of screws or similar 30 fastening elements; * * - enables simple detachment of the casing of the piston position detector also when the holder is positioned * and fastened in the desired position; and - protects the casing (and thereby the piston position 35 detector) against external influences. Further objects are to assure a fixation without play of the casing to the holding device with reproducable precision, so that the casing, and thereby the piston position detector, is placed in exactly the same position after detachment and remoun- ting, and to faciliate a protected placing of a signal cable which is connected to the piston position detector, so that the latter is also protected against external influences. The above stated objects of the invention are achieved by the features given in claim 1. Thus, the holder consists of a U-shaped yoke, into which the casing is at least partly insert- able, whereby the casing together with a piston position detector contained therein is protected by the surrounding yoke. Further, only two fastening means are needed, namely a first fastening means for the fixation of the two shank ends of the yoke to the mutually parallel guides and a second fastening means for the fixation of the casing in the inserted position in the yoke. It is essential that the casing can be detached from and remounted into the yoke, also when the latter is held in a fixed position by the first fastening means. Other suitable features are stated in the claims 2 - 12. Accor¬ ding to a preferred embodiment (cf. claims 5-11) of the inven¬ tion, the second fastening means includes a (second) fastening screw, which upon insertion of the casing between the shanks of the yoke is inserted transversally between the shanks, and which by means of an elastic sleeve (which is compressed axially and thereby expanded radially) engages between two stop means arranged at a longitudinal distance from each other on the casing . The invention will be explained in greater detail below with reference to the accompanying drawing. Fig. 1 shows in a perspective view a cylinder tube (the end plates and the piston of the fluid pressure cylinder are not shown) with a holding device according to the invention dis- * • placeably arranged on the outside thereof, the holding device being partly cut away to show a casing for a piston position ' 5 detector inserted therein; Fig. 2 shows, likewise in a perspective view, said piston position detector casing; 10 Fig. 3 shows a cross-section through the holding device in a vertical plane and through a fastening screw for fastening said casing; and Fig. 4 shows a cross-section corresponding to the one shown in 15 Fig. 3 of a modified embodiment. In Fig. 1 is thus shown a cylinder tube 1 of a fluid pressure cylinder, where the cylinder end plates at the ends of the cylinder tube and a piston with an associated piston rod move- 20 able therein are not shown in the figure. The cylinder tube 1 is preferably manufactured from a light metal alloy and has, on the one hand, longitudinal beads 2 with through holes 3 therein for fastening screws (not shown) for the end plates and, on the other hand, a dovetail-shaped longitudinal bead 4, which at its 25 longitudinal edges form undercut, mutually parallel guide slots 4a, 4b for a holding device 5 according to the invention dis¬ placeable along the cylinder tube. The holding device 5 for a piston position detector includes a 30 U-shaped yoke 6, the shanks 7 and 8 of which at their ends are * formed with inwardly projecting gripping edges 7a, 8a, which engage with the guide slots 4a, 4b. The yoke 6 may be made of i metal but is preferably produced out of a rigid plastic material rendering the yoke a certain dimensional flexibility as well as 35 good sliding properties relative to the guide slots 4a, 4b. The dimensional flexibility, which is also increased by the longitu¬ dinal weakenings 6a, 6b in the web portion 6c of the yoke adjacent to the respektive shank, is utilized for the detachable fastening of a casing 9 incorporating a piston position detector at the inside of the yoke 6 between its shanks 7, 8. At one end, as seen lengthwise, the shanks are provided with bevels or recesses 7b, 8b in the respective corner area to enable the displacement of the yoke all the way to the associated cylinder end plate. The yoke 6, serving as holder, is thus displacable along the whole length of the cylinder tube 1 (for the posi¬ tioning close to the second end plate, the yoke can be snapped out of the guide slots 4a, 4b and turned 180°, so that the bevelled corner portions 7b, 8b abut said second plate) and may be positioned and fixed in a desired position by means of a transverse fastening screw 10, which when tightened presses the shanks 7, 8 of the yoke towards each other in the area of the fastening screw 10, i.e. near one end of the yoke 6 close to the gripping edges 7a, 8a, so that the latter will frictionally engage the guide slots 4a, 4b and thereby fix the yoke 6 in a well-defined position. The head 10a of the fastening screw 10 is countersunk in a corresponding conical recess in the shank 8, while the threaded end portion (not visible in the figures) is in threaded engagement with a nut, which is non-rotatably guided in a recess at the outside of the opposite shank 7 (in the same way as the fastening screw shown in Fig. 3). The casing 9, which contains a piston position detector (not shown) connected to a signal cable 11, is essentially box-shaped and dimensioned to fit into the yoke with its mutually parallel side surfaces between the shanks 7, 8. On the upper side of the casing it is provided with two transverse ridges 12, 13 serving as stop means forming therebetween a rectangular channel. Before inserting the casing 9 into the position shown in Fig. 1; a sleeve of a relatively stiff elastic material is placed in the rektangular channel between the ridges 12, 13. Upon placing the casing 9 in position, a second transverse fastening screw 15 can be inserted through a hole in the shank 8 and through the "* • central hole of the sleeve 14 to an opposite hole in the shank 7, where a nut 16 is non-rotatably arranged in a recess in the 4 5 outside of the shank 7 for threaded engagement with the fastening screw 15. When the fastening screw 15 is tightened, the shanks 7, 8 are pressed together, so that they will be mutually parallel along the full length of the yoke 6 (by tightening of only the fastening screw 10 the shanks will 10 diverge somewhat in the direction towards the rear opening through which the casing 9 is inserted) . At the same time, the engagement of the gripping edges 7a, 8a to the guide slots 4a, 4b will increase, and the elastic sleeve will be compressed axially, so that it is somewhat deformed radially, thereby 15 eliminating the play against the associated fastening screw 15. Thus, the casing 9 is fixed effectively without play in the inserted position inside the yoke 6. Instead of placing the nut 16 in a recess in the shank 7, the 20 nut 16' (see Fig. 4) may be non-rotatably arranged in the rectangular slot between the ridges 12, 13, so that the nut 16' engages directly with the end of the sleeve 14' (and not via the shank wall) . Hereby, a great deformation of the sleeve 14' is assured. The free end portion 15'a of the fastening screw 15', 25 formed as a guiding pin, is guided with a close fit in a corres¬ ponding circular hole in the shank 7. To achieve the best possible fastening action, the nut 16' is of square section, so that it will fit well into the rectangular slot between the ridges 12 and 13. 30 <• ) It is obvious that the second fastening screw 15 or 15' can be loosened easily, so that the casing 9 can be withdrawn from the yoke 6, also when the latter is locked in a well-defined - position by means of the first fastening screw 10. If desired, the signal cable 11 may be protected by a covering strip (not shown) , which is cut into a desired length (corresponding to the distance between the rear end of the casing 9 and the rear end plate) and snapped onto the dovetailed bead 4. At the same time, the casing 9, with the piston position detector contained therein, will be protected by the entirely or partly surrounding yoke 6. The second fastening screw 15 may cooperate with the casing 9 in another way, e.g. without the intermediary of the sleeve 14 by direct cooperation with a transverse recess or hole in the casing. Alternatively, the ridges 12, 13 may be replaced by a number of upward projections distributed transversally in a suitable manner for the forming of " stop means on both sides of the second fastening screw 15 (with or without a sleeve) or by fastening means formed in some other way. Further, the mutually parallel guide slots 4a, 4b may be formed differently and do not have to be made in one piece with the cylinder tube. They may, e.g. , be formed in a separate longitu¬ dinal rail or consist of two separate guide strips. The yoke 6 may likewise be modified, e.g. consisting of two parts with a longitudinal joint in the web portion. It should, however, be of sufficient length to contain a substantial part of the casing 9. Also, the latter may have a different external shape provided that it is entirely or partly insertable between the shanks of the yoke and is lockable in a well-defined position by means of the second fastening means. These second means may, e.g. , consist of a fence bar, arresting pins or the like, being movable into locking engagement with the casing from the web portion 6c of the yoke.

Claims: C L A I M S "* 1. Holding device (5) for a piston position detector being displaceably mounted on the outside of a fluid pressure T 5 cylinder, comprising a holder (6) being displaceable along and lockable in any desired position at a longitudinal guide (4) on the outside of the cylinder tube, the piston position detector being disposed in a casing (9) detachably mounted at the holder (6), c h a r a c t e r i z e d in that the displaceable holder 10 consists of an essentially U-shaped yoke (6), the shank ends (7a, 8a) of which being guided along two mutually parallel guides (4a, 4b) and being fixable thereto by first fastening means (10), being effective between the shanks (7,8) of the yoke (6) and bringing the shank ends into frictional contact with the guides 15 (4a, 4b), and that the casing (9) of the piston position detector is at least partly insertable between the two shanks (7,8) of the yoke and fixable to the yoke (6) in an inserted, well- defined position by second fastening means (15), also when the yoke (6) is fixed to said guides (4a, 4b). 20 2. Holding device according to claim 1, c h a r a c t e r ¬ i z e d in that said first fastening means comprises a first fastening screw (10) . 25 3. Holding device according to claim 2, c h a r a c t e r ¬ i z e d in that the first fastening screw (10) is arranged at one end of the yoke (6), as seen in the longitudinal direction of the cylinder and the guides, and that said casing (9) is entirely or partly insertable through the other end of the yoke. 30 ^ 4. Holding device according to claim 3, c h a r a c t e r ¬ i z e d in that the first fastening screw (10) is located near ϊ the shank ends (7a, 8a), where the latter engage with the guides (4a, b) . 35 5. Holding device according to any one of the claims 1-4, c h a r a c t e r i z e d in that said second fastening means comprises a second fastening screw (15) extending transversally between the shanks (7,8) of the yoke (6), which screw (15) is inserted in its position upon insertion of the casing (9) bet¬ ween the shanks of the yoke and which screw (15), when tightened, locks the casing (9) against displacement in the longitudinal direction of the cylinder and the guides. 6. Holding device according to claim 5, c h a r a c t e r ¬ i z e d in that the casing (9) is provided with two stop means (12,13) arranged at a distance from one another, as seen in the longitudinal direction, between which the second transverse fastening screw (15) extends in the " inserted position. 7. Holding device according to claim 6, c h a r a c t e r ¬ i z e d in that said stop means consist of transverse ridges (12,13), recess walls or transversally distributed projections. 8. Holding device according to claim 5 or 6, c h a r a c t e r ¬ i z e d in that a sleeve (14'), consisting of an elastic material, is insertable transversally, between the stop means (12,13), and is provided with a through hole for the second fastening screw (15), said sleeve (14') being caused to expand radially upon tightening of the fastening screw for positioning the casing (9) without play. 9. Holding device according to claim 8, c h a r a c t e r ¬ i z e d in that the second fastening screw (15), upon being tightened, is arranged to bring the shanks (7,8) closer to one another and thereby expand the sleeve (14') radially when the inner sides of the shanks (7,8) compress the sleeve axially. 10. Holding device according to claim 8, c h a r a c t e r - i z e d in that the second fastening screw (15') acts between one of the shanks and a nut being non-rotatably guided by the casing (9), whereby the sleeve (14') is compressed axially between said shank (8) and said nut (16'). 11. Holding device according to claim 10, c h a r a c t e r ¬ i z e d in that the free end of the fastening screw forms a guiding pin (15 'a), being guided in a hole in the other shank (7) essentially without play. 12. Holding device according to any one of the preceding claims, c h a r a c t e r i z e d in that said two guides are constitu¬ ted by dovetail slots (4a, 4b) formed on the outside of the cylinder tube (1), the shank ends being provided with gripping edges (7a, 8a) engaging with said dovetail slots.

Inventors: PIRHADI EBRAHIM, PIRHADI, EBRAHIM
Applicants: MECMAN AB, AB MECMAN
Application year: 1990
Main classification: F15B15
IPC codes: F15B15