CH666731A5 - PISTON, ESPECIALLY FOR HYDRAULIC OR PNEUMATIC WORKING CYLINDERS. - Google Patents

Description

DESCRIPTION

The invention relates to a piston which can be used in particular for hydraulic or pneumatic working cylinders.

Pistons for working cylinders are known in a variety of embodiments. The present invention has for its object to provide a piston which is particularly inexpensive to construct, inexpensive to manufacture and easy to assemble.

This object is achieved by the features according to claim 1. The piston according to the invention therefore consists of two piston half-parts which can be mounted on a piston rod in a mirror-symmetrical arrangement. Each of the two piston half-parts is made up of a metallic insert and a plastic envelope molded onto this insert. The insert is provided with a radially projecting anchoring part, which is embedded in the plastic when sprayed on and ensures a permanent, form-fitting connection between the insert and the envelope.

The construction of the piston according to the invention from two identical half-parts simplifies manufacture and storage. You can combine two half parts to form a piston for a double-acting cylinder and also use the half parts as pistons of a single-acting cylinder. Furthermore, it is possible to implement multiple piston arrangements with the piston half part as a construction module. The construction of the piston half-part as a composite body with a metallic core and a sheathing made of plastic optimally satisfies the loads that occur during operation. The core gives the piston body a high degree of stability and it absorbs the axial forces acting on the piston. The plastic material of the sheathing provides low-friction guidance, and it is suitable for absorbing the transverse forces and moments that occur during operation. Plastic is also characterized by low material costs, and it can be shaped precisely in an uncomplicated manner. The composite created by spraying is durable and highly resilient, and the plastic injection molding technology used is characterized by low production costs.

Preferred developments of the invention are characterized in subordinate claims.

The design according to claims 2 and 3 creates a particularly solid connection between the metallic core and the sheathing made of plastic.

The non-rotatable contact position between the piston half-parts characterized in claims 5 and 6 brings with it an operating behavior which corresponds entirely to that of a one-piece piston. Seals provided on the piston half-parts are not burdened by an additional degree of freedom of rotation. The rotationally fixed connection between the piston half-parts can be realized in a simple manner by means of latching means which are formed on the plastic casing and work on the principle of tongue and groove.

In the design according to claim 7, the plastic

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A buffer sleeve is injection molded onto the jacket of the piston half-parts, which serves to dampen the end position of the piston. In this way, a combined guidance and damping function is achieved in a structurally uncomplicated manner.

According to claim 9, the molded plastic sheathing can directly take over the guidance of the piston according to the invention. So you can on separate sliding guide rings or the like. forego and thus achieve savings. The development according to claim 10 ensures low-friction running of the piston according to the invention.

According to claim 13, it is possible to provide the piston according to the invention with a position transmitter ring which is detected by an electromagnetic unit for measuring the piston position in an uncomplicated, assembly-friendly manner. The positioner ring is simply inserted into an annular groove between the piston parts.

In the development according to claim 14, this annular groove can also serve as a storage volume for a lubricant if no position detection of the piston is provided and the annular groove is accordingly not occupied by a position transmitter ring.

Further advantages of the invention result from the following description of an exemplary embodiment with reference to the drawings. Show it:

1 shows a longitudinal section through a double-acting working cylinder which is equipped with the piston according to the invention.

2 shows a section through a half of the piston along the line II-II of Fig. 3.

3 shows an end view of the piston half-part with a view in the direction III from FIG. 2;

4 shows a plan view of the edge of the piston half-part with a view in the direction IV of FIG. 2;

5 shows a metal insert of the piston half-part in an end view with a view in the direction III of FIG. 2.

Referring first to FIG. 1, a double-acting hydraulic or pneumatic working cylinder 2 is shown as an application example of the piston 1 according to the invention. This consists of a cylinder liner 3 and two cylinder lids 4, 5 closing the cylinder liner 3 at the ends, each of which is provided with connections 6 for a pressure medium. The cylinder covers 4, 5 have axial bores 7 which communicate with the connections 6. The axial bore 7 in one of the cylinder covers 4 is designed as a through bore. It receives a piston rod 8, which emerges from the end of the cylinder cover 4 and is mounted in the axial bore 7 of the cylinder cover 4 with the interposition of a slide bush 9 and piston rod seal 10. The axial bore 7 in the other cylinder cover 5 is designed as a blind bore. In the case of both cylinder covers 4, 5, the wall 11 of the axial bore 7 runs towards the inside 12 of the working cylinder 2 at a distance from the piston rod 8. In the wall 11, a circumferential annular groove 13 is provided which receives a buffer seal 14; the latter is part of a device for damping the end position of the piston 1, which is described in more detail.

The piston 1 consists of two piston parts 15, which are designed completely identical. The piston half-parts 15 abut one another at their one axial end, their contact surface 16 extending transversely to the longitudinal direction of the piston, i.e. extends radially. The piston half-parts 15 are arranged mirror-symmetrically with respect to this contact surface 16. They represent modular components which, according to FIG. 1, are fitted together on one and the same piston rod 8 in order to build up the piston 1 of a double-acting working cylinder. However, it should be noted that the piston half-parts 15 can also be used individually as pistons (not shown), preferably in single-acting working cylinders.

Each of the piston half-parts 15 has a metallic insert 17 with an essentially circular cylindrical plan. The insert 17 is provided with an axial through hole 18, by means of which the piston half-parts 15 can be pulled onto a centering pin 19 on the piston rod 8. This pin 19 forms an axial extension of the piston rod 18 and it is tapered in diameter compared to this. The transition between the piston rod 8 and the pin 19 is formed by an annular step 20 with which the insert 17 of one of the two piston half-parts 15 mounted on the pin 19 comes to rest on the end face. The ring step 20 thus forms a stop which limits the depth of the piston half-parts 15 to the pin 19. The outside diameter of the insert 17 in the abutting area on the ring step 20 essentially corresponds to that of the piston rod 8.

The pin 19 protrudes through the through hole 18 of both piston half-parts, and it projects axially with a threaded end 21 from the second piston half-part 15. A cylindrical threaded bushing 22 is screwed onto this threaded end 21 and acts on the end face of the insert 17 of the second piston half-part 15. The outer diameter of the threaded bushing 22 corresponds to that of the insert 17, i.e. approximately the diameter of the piston rod 8. The free end of the threaded bushing 22 facing away from the piston 1 is designed for the engagement of a screwing tool, and it can in particular be provided with an internal hexagon. To assemble the piston 1 according to the invention, the piston half-parts 15 are threaded axially one behind the other on the pin 19 of the piston rod 8, whereupon the threaded bushing 22 is screwed on and tightened. The piston half-parts 15 are thereby clamped against one another and non-rotatably and captively fixed on the piston rod 8 in the axial direction.

The inserts 17 of the piston half-parts 15 are encapsulated in an enveloping body 23 which surrounds the inserts 17 in a form-fitting manner on their radial outer side. The enveloping body 23 is made of plastic and it is sprayed onto the inserts 17. In order to achieve a captive connection, a radially protruding anchoring part 24 is formed on the inserts 17, which may have the shape of a circumferential flange, for example. The anchoring part 24 according to FIG. 1 is located in the axial central region of the insert 17. Between the contact surface 16 and the anchoring part 24, the outer jacket of the insert 17 runs essentially circular-cylindrical, whereas it tapers slightly conically in the region beyond the anchoring part 24. The insert 17 is embedded in the enveloping body 23 over its full axial length. The latter closes at the contact surface 16 of the piston half-parts 15 at the same height with the metallic insert 17.

5, the anchoring part 24 can be provided with openings 25 which allow material to pass through when the plastic is sprayed on. A particularly intimate bond between the insert 17 and the enveloping body 23 is created by means of these openings 25. The openings 25 have an elongated shape in the embodiment shown. They are arranged concentrically with respect to the axis of the piston half-part 15 and are delimited by corresponding circular arcs. In particular, eight such elongated holes can be provided, each one

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Circumferential angle of e.g. Take approx. 33 °, while webs with a circumferential extension of approx. 12 ° remain between them.

With reference to FIGS. 2 to 4, complementary latching means can be formed on the contact surface 16 of the half parts 15, by means of which the piston half parts 15 can be fixed to one another in a non-rotatable manner. It is advisable to mold the latching means on the plastic envelope 23, which is particularly simple in terms of production technology. By way of example, a pin 26 can be seen in FIG. 2, which is molded onto the periphery of the enveloping body 23 and protrudes axially from the contact surface 16. A complementary fitting hole 27 is provided diametrically opposite the pin 26 (see FIG. 3). When assembling two piston half-parts 15, which are completely identical in their construction, the pin 26 of one piston half-part 15 engages in the fitting hole 27 of the other, and vice versa, as a result of which a non-rotatable contact position is achieved. Instead of one pin 26 and fitting hole 27 each, there can of course also be several, and other locking devices that work on the tongue and groove principle are also possible.

Returning to FIG. 1, the piston half-parts 15 with the enveloping body 23 are guided on the inner jacket of the cylinder liner 3. For this purpose, the enveloping body 23 itself is designed as a guide surface 28 over part of its axial length. So there are no sliding guide rings or similar. Special parts for the piston 1 according to the invention, which greatly simplifies its construction. In the exemplary embodiment shown, the part of the piston half-parts 15 that directly adjoins the contact surface 16 serves as the guide surface 28. The piston 1, which is composed of two piston half-parts 15, is guided in its axial central region. A circumferential groove 29 of the piston half-part 15 adjoins the guide surface 28 in the axial direction, in which an annular piston seal 30 is received. In the case of a piston 1 for a double-acting working cylinder 2, preferably both piston half-parts 15 each carry a piston seal 30. The piston seals 30 in the exemplary embodiment shown are C-shaped double lip seals in cross section, with their C opening facing away from one another and away from the contact surface 16 are directed. A sealing lip of the piston seals 30 which is longer in the axial direction comes to rest on the base of the circumferential groove 29, while a sealing lip which is shorter in the axial direction works on the cylinder liner 3.

The circumferential grooves 29 for the piston seals 30 are each located in the axial central region of the enveloping body 23, i.e. they lie radially opposite the anchoring part 24 of the insert 17. As already mentioned, the jacket part of the enveloping body 23 forms a guide section 28 between the circumferential groove 29 and the contact surface 16, with which the piston 1 slides on the cylinder liner 3. In contrast, the outer diameter of the enveloping body 23 is reduced in the area 31 facing away from the contact surface 16 beyond the circumferential groove 29. The enveloping body 23 has no guiding function here, but serves exclusively to hold the piston seal 30.

The piston 1 according to FIG. 1 is provided with a transmitter ring 32, which is used for the electromagnetic position and / or speed and / or acceleration measurement. The corresponding data of the piston movement can be recorded magnetically or inductively, for example. The donor ring 32 is stretched in the area of the contact surface 16 between the piston half-parts 15. For this purpose, the piston half-parts 15 each have an annular groove 33 on the contact surface 16 in a concentric arrangement with respect to the piston axis, which groove is suitable for receiving a half side of the sensor ring 32.

In the exemplary embodiment shown, the annular grooves 33 have a rectangular cross section. You vote in

Profile and diameter match, and they are opposite each other in mirror symmetry in such a way that a continuous ring opening for receiving the encoder ring 32 is created.

In order to ensure low-friction running of the piston 1, suitable peripheral recesses 34, so-called grease pockets, can be arranged in the region of the guide surface 28 for receiving a lubricant for permanent lubrication. Referring to FIGS. 2 to 4, one can see an arrangement which is particularly simple in construction, in which the recesses 34 are open towards the contact surface 16 of the piston half-parts 15. The recesses 34 are provided in the form of circular sector-shaped cutouts between the annular groove 33 receiving the transmitter ring and the outer jacket of the enveloping body 23. The axial depth of the cutouts is less than the depth of the annular grooves 33. The cutouts are distributed over the circumference of the piston half-parts 15 in such a way that they lie opposite one another in the assembled state and form double lubrication openings in cross section. For example, eight, each with a circumferential angle of e.g. Provide recesses 34 which take approximately 15 ° and are separated by intermediate webs which extend over approximately 30 °.

If an electromagnetic detection of the piston position is provided, the annular groove 33 is covered with a transmitter ring 32 and a lubricant filling is only introduced into the peripheral recesses 33. If, on the other hand, a donor ring 32 is not required, the annular groove 33 can moreover be filled with lubricant which gradually emerges through the recesses 34. This is a major advantage of lubricant recesses 34 that meet the annular groove 33.

Returning to FIG. 1, the piston half-parts 15 clamped against one another are sealed against one another at their contact surface 16. The sealing is preferably carried out in the area of the metallic insert 17, which lies radially on the inside and can be processed in a simple manner to form a high-quality sealing surface. A sealing ring 35 is placed around the pin 19 of the piston rod 8 as a sealant. The through-bore 18 of the piston half-parts 15 receiving the pin 19 is widened in the area of the contact surface 16, so that a half-groove 36 is formed on each of the piston half-parts 15, which serves to receive the sealing ring 35. When the piston half-parts 15 are clamped together, the sealing ring 35 is pressed, as a result of which a seal is made towards the piston rod 8.

The piston half-parts 15 are provided with buffer sleeves 37, which serve to damp the end position of the piston 1. The buffer sleeves 37 are integrally formed on the plastic envelope body 23. They stand axially beyond the end position 17 on the side of the piston half-parts 15 facing away from the contact surface 16. Their inside diameter corresponds to the outside diameter of the piston rod 8, so that they are suitable for receiving a section of the piston rod 8 or threaded bushing 22. The buffer sleeves 37 of the piston 1 dip into the axial bores 7 which are provided in the cylinder covers 4, 5. In their area facing the interior 12 of the working cylinder 2, the axial bores 7 form an annular space around the piston rod 8, into which the buffer sleeves 37 fit. As already mentioned, a buffer seal 14 is received in an annular groove 13 on the periphery of this annular space. When the buffer sleeve 37 is immersed in the annular space, the buffer seal 14 lies sealingly around the jacket of the buffer sleeve 37, the run-up movement being facilitated by a conical bevel 38 at the free end of the buffer sleeve.

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The piston 1 is shown in FIG. 1 at the end of its stroke in the left cylinder cover 5. The piston stroke is limited in that a radial end face 39 of the enveloping body 23 strikes the end face of the cylinder cover 5. In order to carry out a return stroke of the piston 1, a pressure medium is placed on the connection 6 in the left cylinder cover 5, while the connection 6 of the right cylinder cover 4 is relieved of pressure. During the return movement of the piston 1, the medium contained in the interior 12 of the working cylinder 2 can initially flow out over the full cross section of the axial bore 7. This flow path

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is blocked when the buffer sleeve 37 dips into the axial bore 7 and comes into contact with the buffer seal 14. As a result, a pressure cushion can be built up in front of the cylinder cover 4 that is approached, which dampens the piston movement shortly 5 before it reaches its end position. The buffer seal 14 is a special 3-lip seal. It opens a throttled flow path through the annular groove 13, through which the pressure cushion is reduced. This limits the possible back pressure of the pressure cushion and the io piston 1 reaches its stop position on the cylinder cover 4.

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1 sheet of drawings

Claims (16)

666 731 1. Piston (1), consisting of two piston half-parts (15) which can be pulled up in a mirror-symmetrical arrangement on a piston rod (8), each of which consists of a metallic insert (17) with a radially projecting anchoring part (24) and an envelope (23) sprayed onto the insert (17) are made of plastic. 2. Piston according to claim 1, characterized in that that the anchoring part (24) is flange-shaped and is arranged in the axial central region of the insert (17). 2nd PATENT CLAIMS 3. Piston according to claim 1 or 2, characterized in that the anchoring part (24) is provided with openings (25) which allow material to pass through when the plastic is sprayed on. 4. Piston according to one of claims 1 to 3, characterized in that the piston half-parts (15) with an essentially transversely to the piston-longitudinal direction-kendende end face (16) are in contact with each other. 5. Piston according to claim 4, characterized in that complementary locking means are formed on the contact surface (16), by means of which the piston half-parts (15) can be fixed to one another in a non-rotatable manner. 6. Piston according to claim 5, characterized in that the locking means on the envelope body (23) are formed, for. B. in the form of an axially projecting pin (26) and a diametrically opposite, complementary fitting hole (27). 7. Piston according to one of claims 1 to 6, characterized in that an axially over the insert (17) projecting buffer sleeve (37) is integrally formed on the end of the envelope body (23) facing away from the contact surface (16). 8. Piston according to one of claims 1 to 7, characterized in that the piston half-parts (15) each carry a piston seal (30) which is arranged in a circumferential groove (29) on the outer jacket of the envelope body (23). 9. Piston according to one of claims 1 to 8, characterized in that the outer jacket of the enveloping body (23) is formed on at least part of its axial length as a guide surface (28). 10. Piston according to claim 9, characterized in that the envelope body (23) in the region of the guide surface (28) is provided with peripheral recesses (34) suitable for receiving a lubricant. 11. Piston according to claim 10, characterized in that the recesses (34) for the lubricant to the contact surface (16) of the piston half-parts (15) are open. 12. Piston according to one of claims 1 to 11, characterized in that the circumferential groove (29) for the piston seal (30) is located in the axial central region of the enveloping body (23) and that the jacket portion of the enveloping body (23) between the circumferential groove (29 ) and the contact surface (16) of the piston half-parts (15) serves as a guide surface (28), while the outer diameter of the enveloping body (23) is reduced in the area (31) facing away from the contact surface beyond the circumferential groove (29). 13. Piston according to one of claims 1 to 12, characterized in that the enveloping body (23) on the contact surface (16) of the piston half-parts (15) have annular grooves (33) which are suitable for receiving one half side of a sensor ring (32) . 14. Piston according to one of claims 1 to 13, characterized in that the recesses (34) for the lubricant in the form of sector-shaped cutouts are provided between the annular groove (33) and the outer jacket of the envelope body (23). 15. Piston according to one of claims 1 to 14, characterized in that the piston half-parts (15) on it Contact surface (16) are sealed against each other, preferably in the area of the metallic insert (17). 16. Piston according to one of claims 1 to 15, characterized in that the inserts (17) are provided with an axial through-bore (18) which is located on the contact surface (16) in the form of a half-groove (36) for receiving a sealing ring ( 35) expanded.