Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
DEVICE AT A PRESSURE FLUID CYLINDER WITHOUT PISTON ROD
Document Type and Number:
WIPO Patent Application WO/1983/002306
Kind Code:
A1
Abstract:
A pressure fluid cylinder without a piston rod and of the kind having a slotted cylinder tube (1) and a piston displaceable therein, said piston being connected to a movement transfer device, which extends radially through the slot. The slot is sealed axially on each side of the piston by means of internal and external sealing strips (31, 32) consisting of a flexible sealing band (37, 38) as well as retention means (44, 45) extending into the slot and securing a releasable mechanical engagement with each other or, by friction, with the side walls of the slot.

Inventors:
HOEGLUND INGOLF (SE)
Application Number:
PCT/SE1982/000433
Publication Date:
July 07, 1983
Filing Date:
December 20, 1982
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
MECMAN AB (SE)
International Classes:
F15B15/08; F15B15/14; F16J10/00; F16J10/02; (IPC1-7): F15B15/08
Foreign References:
DE3124878C11982-12-09
DE3124915A11983-01-13
SE343467B1972-03-13
US2665467A1954-01-12
US2978769A1961-04-11
US3428272A1969-02-18
US3893378A1975-07-08
US4164893A1979-08-21
US4252285A1981-02-24
EP0033541A11981-08-12
EP0068088A11983-01-05
EP0069199A11983-01-12
Download PDF:
Claims:
_ λlC L A I M S
1. A device at a pressure fluid cylinder without a piston rod and of the kind comprising a cylinder tube (1) closed at its ends by means of end covers (2) and a piston (3) be¬ ing axially movable therein and operable by pressurized fluid and being connected to a movement transfer device (19), which extends substantially radially outwards through a longitudinal slot (4) i the cylinder tube, an internal an preferably also an external flexible sealing strip (31,32; 31' ,32') being arranged to seal the slot from the inside and from the outside, respectively, axially on each side of the piston '(3), c h a r a c t e r i z e d in that at least said internal sealing strip (31; 31') consists of a flexible sealing band (37) , which is wider than the slot (4) and engages with its edge portions (62,63) sealingly against the cylinder tube (1) at each transversal side of the slot, as well as retention means (44; 73,74; 75,76) connected to the sealing band (37) and extending into the slot (4) between the side walls (71,72) thereof and being in releasable mechanical engagement with said side walls (71,72) or with corresponding retention means (45) of the opposite sealing strip (32) .
2. A device as defined in claim 1, c h a r a c t e r i z e. in that said retention means comprise elements (75,76) distributed longitudinally along the sealing strip (37) .
3. A device as defined in claim 1, c h a r a c t e r i z e in that said retention means comprise a continuous profile element (44; 73,74,77).
4. A device as defined in anyone of claims 13, c h a r a c t e r i z e d in that said retention means (73,74; 75;76) are arranged to engage with bias against the side walls (71,72) of the slot so as to exert a retaining frictional grip. _ ... _. 12 .
5. A device as defined in claim 4, c h a r a c t e r i z e in that the external sealing strip (32*)is divided length¬ wise at the middle,wherein each strip half (67,68) is secured to the outside'of the cylinder tube at its outer edge (67',68*), whereas the inner edge portions (67",68") of the strip halves engage sealingly against each other or against the movement transfer device (19) connected to the piston (3) .
6. A device as defined in anyone of claims 13, c h a r a c t e r i z e d in that said retention means comprise mutuall cooperating zipperlike hook elements (44,45) on the internal as well as the external sealing strip (31,32).
7. A device as defined in claim 6, c h a r a c t e r i z e in that said hook elements (44,45) consists of a wear resistant elastic material having low friction and a low module of elasticity, e.g. nitrile rubber or polyurethan.
8. A device as defined in claim 6 or claim 7, c h a r a c t e r i z e d in that the mutual mechanical engagement of the hook elements (44,45) is resilient in the direction towards each other in such a way that, axially on each side of the piston (3) , the sealing band (38) of the external sealing strip (32) engages sealingly against the outside (61,61) of the cylinder tube (1) .
9. A device as defined in anyone of the preceding claims, c h a r a c t e r i z e d in that the edge portions (62,63 of the sealing band (37) of the internal sealing strip (31) are bevelled (64) into a sharp edge (65) on the side of the sealing band (37) facing the slot (4) of the cylinder tube.
10. A device as defined in anyone of the preceding claims, c h a r a c t e r i z e d in that said retention means (44,45; 73,74,77; 75,76) are glued or vulcanized onto the sealing band (37,38).
11. A device as defined in anyone of the preceding claims, c h a r a c t e r i z e d in that said sealing band (37,38 consists of a flexible, wear resistant and corrosion resistant metallic material, e.g. rustproof steel or beryllium bronze. C. FI.
Description:
Device at. a Pressure Fluid Cylinder without Piston Rod

The invention relates to a device at a pressure fluid cyli

» without a piston rod an of the kind defined in the preamb of claim 1.

Such pressure fluid cylinders without a piston rod with at least one internal sealing strip are known e.g. from US 4 164 893 (Granbom) and EP 0033541 (Tol-0-Matic) , wherein the internal sealing strip is retained in a position sealin the slot by magnetic attraction between the strip and the cylinder tube wall or permanent magnets inserted therein.

The object of the present invention is to achieve a reliabl retention, guiding and engagement of at least the internal sealing strip in relation to the slot of the cylinder tube axially on each side of the piston, without the use of mag¬ netic elements. The latter are unsuitable in many cases, i.- in environments containing airborne magnetic particles, e.g. of ferromagnetic material. Such particles can be attracted by the magnets of the pressure fluid cylinder and cause operational disturbances. Other objects of the inventi are to enable a simple design and manufacture o the slotte cylinder tube and to ensure a satisfactory sealing of the slot of the cylinder tube even under pressure build-up. '■

These and other objects are fulfilled by the device defined principally in claim 1, according to which at least the in¬ ternal sealing strip consists of a flexible sealing band, which is wider than the slot and engages with its edge por¬ tions sealingly against the cylinder tube at each transver¬ sal side of the slot, as well as retention means connected to the sealing band and extending into the slot between the side walls thereof and being in releaseable mechanical en- gagement with said side walls or with corresponding re¬ tention mean ' s of the opposite external or internal sealing strip. Hereby, a secure retention of the internal sealing

strip against the inside of the cylinder tube adjacent the slot is obtained, so that the sealing result is effecti even under pressure build-up. As stated in claim 6, the re- leaseable mechanical engagement is preferably achieved by means of zipper-like, mutually co-operating hook members on the two sealing strips. Other developments and detailed embodiments of the inventive idea are given as examples in claims 2 - 5- and 7 - 11.

The invention will be explained further below with referenc to the appended drawings, illustrating three embodiments.

Fig.l shows a longitudinal section through a pressure fluid cylinder with a device according to the invention;

Fig. 2 shows a cross-section along the line II-II in Fig.l;

Fig. 3 shows in a larger scale a partial cross-section of the cylinder tube adjacent the slot with coupled internal and external sealing strips;

Fig. 4 shows the corresponding section as in Fig. 3 in an even larger scale, wherein the right half illustrates the sealing strips in a non-loaded state, i.e. without the infl ence of an internal fluid pressure, whereas the left half illustrates the sealing strips under the influence of an in ternal fluid pressure;

Fig. 5 is a view corresponding to Fig. 4 of a second embodi ment of the two sealing strips; and

Fig. 6 is a view corresponding to Figs.4 and 5 of a third embodiment of the two sealing strips.

In Fig. 1 there is shown in a longitudinal section one end portion of a working cylinder without a piston rod and con¬ sisting of a cylinder tube 1 with an upper longitudinal slo

(in the sectional plane) , an end cover 2 at each end of th cylinder tube 1 (only the left one is shown in Fig. 1) and a movable piston 3, which is operable by pressurized fluid along the cylinder tube between the end covers. As appears from Fig. 2, the wall thickness of the cylinder tube 1 is largest at the bottom of the figure and is gradually reduce on each side up to the slot 4 situated at the top. Hereby, in a manner known per se, it is achieved at the resistance to bending sideways varies uniformly with the bending momentum.

The end cover 2 is fastened by means of circumferentially distributed screw fasteners 5 against a holding ring 6, which is secured axially with an inner flange 7 against a locking ring 8 inserted in a groove in the external surface of the cylinder tube 1. The end cover 2 has a central cylin drical portion 9, which projects somewhat inwardly inside the end of the cylinder tube 1 and is sealed against the inside thereof by means of an O-ring 11 inserted into a cir cumferential groove 10. A connection port 12 for pressurize fluid formed in the end cover 2 communicates with a tubular sleeve 13 disposed centrally and extending along the axis of the cylinder tube 1 a portion inwardly from the end sur¬ face of the endcover 2 , the tubular sleeve being dimensione so as to extend, when the piston 3 is located in its corre¬ sponding end position, into a central bore 14 (and 14*, res tively) in the corresponding end portion of the piston 3. Externally on the tubular sleeve 13, a lip sealing ring 15 serving as a check valve is inserted into an annular groov 16 adjacent to the free end of the tubular sleeve 13. By co-operation between the tubular sleeve 13 with the lip sealing ring 15, on the one hand, and the bore 14 of the piston 3,on the other hand, an end position damping of the piston movement is obtained by pressure build-up in the cy- linder room outside the tubular sleeve 13 between the end cover 2 and the piston 3, which is sealed against the insid

of the cylinder tube 1 by means of conventional piston seals 17, 17*. If desired, the damping effect can be set by an adjustable throttle in a connection channel (in the end cove between the cylinder room and the connection port 12.

As mentioned above, the piston 3 is axially displaceable be¬ tween the end covers 2 under the influence of pressurized fluid at either side. The piston 3 is guided against the in¬ side of the cylinder tube by means of piston support rings 1 18' of thermoplastic material,_ e.g. polyamide, disposed adja cent to the piston seals 17, 17' and providing a sliding fit with low friction.

Between its ends (see also Fig. 2), the piston 3 has a radia outwardly through the slot 4 of the cylinder tube extending portion 19, which serves .as a movement transfer device, i.e. for transfer of movement and force between the piston 3 and an external, driven or driving element of some kind (not sho Tha radially extending portion 19 consists of an elongated body having an inner, substantially half-cylindrical portion 20, which is fastened to the mid portion of the piston by means of screws 21 in a cut away part of the cy¬ lindrical piston body 3, an elongated narrow portion 22 di¬ mensioned to extend through the slot 4 of the cylinder tube 1 and an outer, in section fork-like portion 23, the fo branches 24, 25 of which embracing a coupling member 26. The latter has transversal through holes 27,28,29,30, which also extend through the fork branches 24, 25 and permit a releasa connection of the driven or driving element, e.g. by means o screw fasteners.

The arrangement described so far is substantially previously known, e.g. from the EP 0033541 (Tol-0-Matic) mentioned abov According to the present invention, however, the slot 4 of t cylinder tube 1 is sealed axially at each side of the piston in a novel and advantageous way. This is achieved, at the

_

embodiment according to Figs.1-4, by means of flexible inne and outer sealing strips 31 and 32, respectively, which are in releasable mechanical engagement with each other in the slot 4 axially on each side of the piston 3. In the region the piston 3 , the' sealing strips 31,32 are guided in a way known per se by means of longitudinal recesses 36 and 36*, respectively,in the inner and outer portions 20 and 23, re¬ spectively, of the movement transfer device 19. Adjacent t the ends of the piston 3, i.e. somewhat inside the respecti piston seal 17, 17' the two sealing strips 31, 32 are guided and compressed into mutual engagement by means of outer guides 33, 33' secured to the ends of the coupling member 26 and produced by thermoplastic material and provided with scraper lips 34, 34', as well as inner guides or guide shoes 35,35' forming a part of the respective piston support rings 18, 18'. Axially inside these guides 33,33", 35,35* the sealing strips 31, 32 are separated wedge-like from each other in the longitudinal recesses 36,36' in the movement transfer device 19. The sealing strips are held longitudinal ly stretched in that they are secured in each cylinder end cover 2 . Thus, ribbon-like portions 37 and 38, respectively, of the sealing strips 31, 32 extend through a recess 39 form for this purpose in the holding ring 6 and further into a co responding recess 40 in the end cover 2. A first locking scr 41 clamps the ribbon-like portion 37 of the inner sealing strip 31 against the end cover 2, and a second locking screw 42 clamps the outer ribbon-like portion 38 of the outer sea¬ ling strip 32 against an intermediate piece 43 inserted into the recess 40.-

As shown in figs 3 and 4, the sealing strips 31,32 comprise mutually releaseably connectable hook elements 44 and 45, respectively, in a zipper-like manner, the hook elements en¬ gaging mechanically with each other axially at each side' of the piston 3 in the slot 4. These hook elements 44, 45 can possibly be made in one piece with the wider, band-like

OMPI

portions 37 and 38, respectively, engaging internally and externally against the cylinder tube 1, but preferably they consist of separate members which are secured, e.g. by vul¬ canization, glueing or by some other method, to the respec- ' tive ribbon-like portion 37,38 (denoted sealing bands37,38 below). These sealing bands 37,38 are preferably made of a flexible, wear resistant and corrosion resistant metallic material, e.g. rustproof steel or beryllium bronze,whereas the hook elements 44,45 preferably consist of wear resistant elastic material with low friction and low modulus of elas¬ ticity, e.g. nitrile rubber or polyurethane. The hook elements 44, 45 can consist either of separate,along the length of the respective sealing band distributed members or hook profile elements extending continuously inthe longi- tudinal direction. In the embodiment according to Figs 1-4, the latter alternative is chosen. The lower hook profile element 44 constitutes a male part with a base portion 46 and an upwardly directed, central bead 47, (seeFig. 4, the part to the right). From the base portion 46, the bead 47 is widened substantially rectilinearly 48 in cross-section to a point 49, from which the bead tapers off, likwise sub¬ stantially rectilinearly 50, up to an upper, planar portion 51. The upper hook profile element 45 constitutes a female part and has approximately a complementary cross section as compared to the male part. From a base portion 52 (see also the left half of Fig. 4) two legs 53, 54 extend symme¬ trically on each side of the bead 47 of the lower hook profi element 45. Next to an inner, rounded part 55, there follows insection, a substantially rectilinear part 56 down to a point 57, from which each leg tapers off likewise substan¬ tially rectilinearly 58 obliquely down to a planar lower surface 59.

The widest portion of the bead 47, e.g. at level with the - point 49, is somewhat wider than the distance between the legs 53,54 at the level of the point 57. The bead 47, howeve

ι τ

can be inserted between the legs 53,54 in that the latter are resiliently bent apart from each other when the obliqu surfaces 50 Of the bead 47 engage the likewise oblique sur faces 58. When the point 49 passes the point 57, the bead will be brought further inwards somewhat because the legs 54 will move resiliently back towards each other, whereas the points 57 (in the section according to Fig. 4) on each leg will move downwards along the parts 48 of the bead. To the right in Fig. 4, there is shown the relative positio taken without influence of any overpressure within the cy¬ linder tube 1, whereas the . left half of Fig. 4 shows how the lower sealing strip 31, under the influence of the over pressure of the pressurized fluid inside the cylinder tube is bent slightly upwards, while the upper sealing strip 32 remains in its position because the upper surface 51 of the bead 47 has a slight play to the base portion 52 of the up¬ per hook profile element 45 (as does the base portion 46 of the lower hook profile element 44 relative to the lower surfaces 59 of the legs 53,54) and because the legs 53,54 has such resiliency and are so dimensioned in relation to the bead 47 that the legs 53,54 engage the bead 47 " with som bias in the absence of a fluid pressure (the position to th right in Fig. 4) and move towards each other when an inter¬ nal fluid pressure bends up the sealing band 37 to the posi tion shown in the left half of Fig. 4. This means that the two hook profile elements 44,45 will come closer to each other, so that the upper sealing band 38 tends to retain its sealing engagement with the planar surfaces 60,61 of the cylinder tube externally at each side of the slot 4.

The described arrangement will ensure that the lower sealin band 37 constantly engages with its edge portions 62,63 against the internal cylindrical surface of the cylinder tube 1 adjacent the slot 4. The edge portions 62,63 are bevelled obliquely on the side facing the slot 4 (the upper side in Figs. 3 and 4), and the bevelled edge surface 64

(see the right part of Fig. 4) will form an outer sharp edg 65. This edge 65 engages the internal cylinder surface 66 of the cylinder tube in the absence of an internal fluid pressure. Hereby, it is ensured that the lower sealing band 5 37 will seal the slot 4 already at the start when a working pressure is to be built up internally in the cylinder tube for actuating the piston 3. When the pressure increases, th sealing band 37 is bent upwardly and a gradually larger por tion of the obliquely bevelled edge surface 64 will get in

10 contact from the outside and inwardly, since the tapered portion closestto the the sharp edge has less resistance to bending than the rest of the band 37 which is uniformly thick. At full* orking pressure, the whole edge surface 64 will be bent so as to contact sealingly the cylinder surfac

15 66, as appears from the left half of Fig. 4.

The two embodiments shown in Fig. 5 and 6 differ f__om the preceding one in that the internal and external sealing strips are not directly coupled to each other. The uoper 20 sealing strip 32' is divided lengthwise at the middle and thus consists of two strip halves 67,68 of elastic material and arranged in parallel next to each other. The outer edge portion 67 * , 68 ' of each strip half is pressed down into a groove 69 and 70, respectively, at the outside of the cylin

25 tube 1 at the side of the slot 4, whereas the inner edge po tions 67", 68" engage sealingly againsteach other centrally above the slot 4. When the piston 3 with the movement trans member 19 passes, the strip halves 67,68 are bent away from each other to the position shown in Figs.5 and 6 with dash-

30 dotted lines.

The internal sealing strip 31' comprises, as in the precedi embodiment, a rather stiff but flexible sealing band 37 of metallic material. However, the retention elements secured " thereto are not designed as hook elements, but as frictiona ly engaging elements 73,74 (Fig. 5) and 75,76 (Fig. 6) , res tively, pressing sideways against the side walls 71,72 of

O F

of the slot 4. In the embodiment of Fig. 5, these friction ly engaging elements are made in one piece with a longi-. tudinally continuous profile element having two legs 73,74 extending obliquely outwardly (upwards in Fig. 5) from a common base portion 77, which is secured to one side (the ' upper side in Fig. 5) of the sealing band. The profile ele ment 73,74, 77 is preferably made of a wear resistant elastic material having a substantial friction against the cylinder tube material (normally aluminum) , ^.g. rubbe some synthetic elastomeriσ material with similar frictiona * qualities. The legs 73,74 are so dimensioned that upon be¬ ing inserted into the slot 4 they engage with the side wal 71,72 with a. certain bias, so that a desired frictional gr is obtained. Furthermore, they are provided with bevelled edges 78,79 at their free ends so as to facilitate the ins tion into slot 4 (by means of the guides 35,35' of the pis 3 shown in Fig. 1) .

According to Fig. 6, the friction engaging elements are instead made of longitudinally distributed, separate clamp elements 75,76 of a stiff, resilient band material, e.g. steel. These elements are secured in pairs on the sealing band 37 on the side facing the slot 4 and dimensioned to engage with a certain bias with a rounded, in section ac- cording to Fig. 6/substantially arcuate portion 80 and 81, respectively,against the respective side wall 71,72 of the slot. The bias ensures that a frictional engagement is retained even when the slot 4 is slightly widened under the influence of the pressure inside the cylinder tube 1. The same is true for the embodiment according to Fig. 5. More¬ over, the engagement is facilitated in that the sealing ban 37 is bent into archuate form in cross section, so that the elements 73,74 and 75,76, respectively,are swung outwartly sideways.

In the embodiments according to Figs 5 and 6, the lower sea ling strip 31' extends through the longitudinal recess 36 o piston 3 (see Fig. 2) . The upper, divided sealing strip 3 _!_

however, is held outside the movement transfer member 19, and in this case no longitudinal recess 36' is needed.

The inventive device has many advantages. The absence of magnetic retaining means for the sealing strips will elimin the risk of magnetically attractedparticles being collected in and adjacent to the slot of the cylinder tube with accom panying operational disturbances. The mechanical retention according to the invention will also permit lower productio costs in that special recesses for magnets are unneccessary Likewise, the assembly work is facilitated. The cylinder tu can be made with a uniform, cylindrical internal surface without radial differences, and a slot can be formed with straight side walls. The material of the sealing band can be chosen at will, since it does not have to posses mag¬ netic qualities.

By forming at least the internal sealing strip with a rela¬ tively wide sealing band and retention members secured ther to and extending in between the side walls of the slot, an excellent sealing between the edge portions of the sealinq band and the cylinder surface as well as a secure reten¬ tion and guiding of the retention members inside the slot are obtained. This is of great importance in those cases where the cylinder is exposed to vibration or other move¬ ments which may displace the sealing strips from their sealing positions. The embodiment according to Fiσs. 1-4 with zipper-like, mutually engaging hook elements provides f especially good retention.

Q"?




 
Previous Patent: THERMAL ENGINE

Next Patent: ACCESSORY DRIVE ARRANGEMENT