DE3404095A1 - PISTON - Google Patents

Description

31. J.nu.r3Äfl4095

D 9243 - no

Festo KG, 7300 Essiingen, Germany.

Pistons

The invention relates to a piston that is used in particular for hydraulic or pneumatic working cylinders Application can come.

Pistons for working cylinders come in a variety of forms known. The present invention is based on the object of a particularly inexpensive structure, To create inexpensive to manufacture and easy to assemble pistons.

This object is achieved by the features according to claim 1. The piston according to the invention accordingly consists of two Piston half parts that are in a mirror-symmetrical arrangement can be pulled up on a piston rod. Each of the two piston halves is made of a metallic insert and an enveloping body made of plastic that is sprayed onto this insert built up. The insert is provided with a radially protruding anchoring part which, when sprayed on, becomes in the plastic is embedded and for a permanent, form-fitting connection between the insert and the enveloping body cares.

The structure of the piston according to the invention consists of two identical ones Half-parts simplify production and storage. You can make two halves into one Combine pistons for a double-acting working cylinder and also use the half-parts on their own as pistons of a single-acting working cylinder. It is also possible · with the piston half-part as a construction module Realize multiple piston arrangements. The construction of the piston half part as a composite body with a metallic core and a sheath made of plastic is optimally sufficient for the loads occurring during operation. The core gives the piston body a high degree of stability, and it takes the acting on the piston Axial forces. The plastic material of the sheath provides a low-friction guide, and it is suitable for the transverse forces and moments that occur during operation el astisch 'to record. Plastic also stands out cost by low material, and it can be in less expensive Shape precisely. The composite created by spraying is durable and highly resilient, and the one used Plastic injection technology is characterized by low production costs the end.

Preferred developments of the invention are in subordinate Claims.

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

The non-rotatable contact position between the piston half-parts, which is characterized in claims 5 and 6, brings a Operating behavior with itself that is completely that of a one-piece Piston corresponds. Provided on the piston halves Seals are not protected by an additional freedom of rotation degree burdened. The non-rotatable connection between the piston half-parts can be easily carried out on the plastic casing Realize shaped, working on the principle of tongue and groove locking means.

In the design according to claim 7 is on the plastic sheathing a buffer sleeve is molded onto the piston half-parts, which serves to cushion the piston in its end position. One achieves thus a combined guidance and damping function in a structurally uncomplicated way.

According to claim 9, the molded plastic sheath directly take over the leadership of the piston according to the invention. So you can use separate sliding guide rings renounce the above and thus achieve savings. The further training according to claim 10 ensures a low-friction Run of the piston according to the invention.

According to claim 13, it is possible to the invention Pistons in a simple, easy-to-assemble way to be provided with a position transmitter ring, which is supported by a electromagnetic unit for measuring the piston position is detected. The position transmitter ring is simply inserted into an annular groove between the piston half-parts.

In the development according to claim 14, this annular groove at the same time serve as a storage volume for a lubricant if no position detection of the piston is provided and the ring groove accordingly not with a position transmitter ring occupied i st.

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

Fig. 1 is a longitudinal section through a double-acting working cylinder, which with the invention Piston is equipped;

FIG. 2 shows a section through a half part of the piston along the line II-II of FIG. 3;

3 shows an end view of the piston half part with View in direction III of 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;

Fig. 5 shows a metal insert of the piston half part in

front view looking in direction III of FIG. 2.

Referring initially to FIG. 1, the piston 1 according to the invention is an example of application of a double-acting one

hydraulic or pneumatic working cylinder 2 shown. This consists of a cylinder liner 3 and two the cylinder liner 3 at the ends closing the cylinder covers 4, 5, which are each 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 as Through hole formed. It receives a piston rod 8 which protrudes from the cylinder cover 4 on the front side and with the interposition of a sliding bush 9 and piston rod seal 10 in the axial bore 7 of the cylinder cover 4 is stored. The axial bore 7 in the other cylinder cover 5 is designed as a blind bore. With both cylinder covers 4, 5, the wall 11 of the axial bore 7 extends towards the interior 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; latter is part of a device for end position damping of piston 1, which will be described in more detail.

The piston 1 consists of two piston half parts 15, which are designed completely identically. The piston half parts 15 butt against one another at one axial end, with their contact surface 16 extending transversely to the longitudinal direction of the piston, d. H. extends radially. The piston half parts 15 are arranged mirror-symmetrically with respect to this contact surface 16. They represent modular components which, as shown in FIG. 1, are drawn together onto one and the same piston rod 8 are to the piston 1 of a double-acting working cylinder

build up. It should be noted, however, that the piston halves 15 can also be used individually as a piston (not shown), preferably in single-acting Change working cylinders.

Each of the piston half parts 15 has a metallic insert 17 with a substantially circular cylindrical plan. the Insert 17 is provided with an axial through hole 18, by means of which the piston half-parts 15 are located a centering pin 19 can be pulled up on the piston rod 8. This pin 19 forms an axial extension the piston rod 18, and it is tapered in relation to this in diameter. 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, on the pin 19 raised piston half-parts 15 on the face side to the plant comes. The ring step 20 thus forms a stop which the depth of pushing the piston half-parts 15 onto the pin 19 limited. The outer diameter of the insert 17 in the joint area on the ring step 20 corresponds essentially to that of Piston rod 8.

The pin 19 protrudes through the through bores 18 of both Piston halves through, and he is with a threaded end 21 axially out of the second piston half part 15. On this threaded end 21, a cylindrical threaded bushing 22 is screwed, which the insert 17 of the second Piston half part 15 acted on the front side. The outside diameter the threaded bushing 22 corresponds to the joint area

the insert 17, d. H. approximately the same diameter as the piston rod 8. The free end of the threaded bushing facing away from the piston 1 22 is designed for the attack of a screwing tool, and it can in particular with a hexagon socket be provided. To assemble the piston 1 according to the invention, the piston half-parts 15 are axially one behind the other threaded the pin 19 of the piston rod 8, whereupon the threaded bushing 22 is screwed and tightened. the Piston half parts 15 are thereby clamped against one another and fixed on the piston rod 8 so that it cannot rotate and cannot be lost in the axial direction.

The inserts 17 of the piston half parts 15 are in a HIi 11 body 23 encapsulated, which surrounds the inserts 17 on their radial outer side in a form-fitting manner. The enveloping body 23 consists made of plastic, and it is injected onto the inserts 17. In order to achieve a captive connection, is on the inserts 17 a radially protruding anchoring part 24 formed, for example, the shape of a circumferential Can have flanges. The anchoring part 24 according to FIG. 1 is located in the axial central area of the insert 17. Between the contact surface 16 and the anchoring part 24, the outer jacket of the insert 17 is essentially circular-cylindrical, while it extends in the area beyond the Anchoring part 24 tapers slightly conically. The insert 17 is in the enveloping body 23 over its full axial length embedded. The latter closes at the contact surface 16 of the piston half-parts 15 at the same height as the metallic one Insert 17.

Referring to Fig. 5, the anchoring part 24 can with Breakthroughs 25 may be provided, which enable material to pass through when the plastic is sprayed on. Means these openings 25 form a particularly close bond created between the insert 17 and the enveloping body 23. The openings 25 have in the illustrated embodiment an oblong shape. They are concentric arranged with respect to the axis of the piston half part 15, and they are delimited by corresponding arcs.

In particular, eight such elongated holes can be provided

E.g. be approx. each occupying a circumferential angle of / 33,

while between them webs with a circumferential extension stop at about 12 °.

Referring to FIGS. 2 to 4, complementary latching means 15 can be formed on the contact surface 16 of the half-parts 15 by means of which the piston half-parts 15 Let them be fixed to one another so that they cannot be rotated. It is recommended that the locking means on the existing plastic Shaping enveloping body 23, which is particularly manufacturing technology is easy. As an 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. The pin 26 diametrically opposite (see. Fig. 3) is a complementary fitting hole 27 is provided. When assembling two piston half-parts that are completely identical in structure 15 engages the pin 26 of one piston half part 15 into the fitting hole 27 of the other, and vice versa, whereby a non-rotatable contact position is achieved. Instead of

Each of a pin 26 and fitting hole 27 can of course there may also be several, and other locking devices operating on the tongue and groove principle are also possible.

Returning to Fig. 1, the piston half parts 15 are with the enveloping body 23 on the inner surface of the cylinder liner 3 led. 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 other special parts for the piston 1 according to the invention use, which greatly simplifies its structure. The guide surface 28 in FIG the illustrated embodiment which extends in the axial direction directly adjoining the contact surface 16 part of the piston half parts 15. The one made up of two piston half parts 15 composite piston 1 is thereby guided in its axial central area. The guide surface 28 closes A circumferential groove 29 of the piston half part extends in the axial direction 15, in which an annular piston seal 30 is received. In the case of a piston 1 for a double acting Working cylinders 2 preferably carry both piston half-parts 15 each one piston seal 30. The piston seals 30 in the illustrated embodiment are in cross section C-shaped double lip seals with their C-opening facing away from each other and facing away from the contact surface 16. A sealing lip of the piston seals that is longer in the axial direction 30 comes to rest on the bottom of the circumferential groove 29, while a sealing lip which is shorter in the axial direction is working on the cylinder barrel 3.

The circumferential grooves 29 for the piston seals 30 are each located in the axial central area of the enveloping body 23, ie they are located 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 region 31 facing away from the contact surface 16 on the other side of the circumferential groove 29. The enveloping body 23 has no guiding function here, but rather serves exclusively to hold the piston seal 30.

The piston 1 according to FIG. 1 is provided with an encoder ring 32, which is used for electromagnetic position and / or speed and / or acceleration measurement is used. The corresponding data of the piston movement can, for example, be magnetic or be detected inductively. The transmitter ring 32 is clamped between the piston half-parts 15 in the area of the contact surface 16. For this purpose, the piston half-parts 15 point on the contact surface 16 in a concentric arrangement with respect to the piston axis each have an annular groove 33 which is suitable for a half-side of the encoder ring 32. In the exemplary embodiment shown, the annular grooves 33 are rectangular Cross-section. They match in profile and diameter, and they are mirror-symmetrically opposite one another in such a way that that a continuous ring opening for receiving the encoder ring 32 is created.

- 11 -

To ensure low-friction running of the piston 1, can be used for permanent lubrication in the area of the guide surface 28 suitable for receiving a lubricant, peripheral Recesses 34 - so-called fat pockets - be arranged. Referring to FIGS. 2 to 4, one recognizes an im Structure of a particularly simple arrangement in which the recesses 34 open to the contact surface 16 of the piston half-parts 15 are. The recesses 34 are in the shape of a sector of a circle Cutouts are provided between the annular groove 33 receiving the encoder 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 about the Perimeter of the piston half parts 15 distributed that they each other opposite in the assembled state and in cross-section form doubled lubrication openings. One can

e.g. ₀ approx.

for example eight, each occupying a circumferential angle of / 15 Provide recesses 34 which are separated by webs extending over / 3u in between.

If one sees an electromagnetic detection of the piston position before, the annular groove 33 is with a donor ring

32 occupied and a lubricant filling only in the peripheral Recesses 33 introduced. If, on the other hand, a transmitter ring 32 is not required, the annular groove 33 be filled with lubricant which gradually emerges through the recesses 34. This is an essential one Advantage of lubricant recesses 34 that form the annular groove

33 meet.

Returning to FIG. 1, the piston half-parts 15 clamped against one another are against one another at their contact surface 16 sealed. 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. As a sealing agent T. a sealing ring is placed around the pin 19 of the piston rod 8. The through hole receiving the pin 19 18 of the piston half-parts 15 is in the area of the contact surface 16 expanded so that at each of the sub-halves 15 one Half-groove 36 is formed, which serves to receive the sealing ring 35. When clamping together the piston half parts 15 is the sealing ring 35 is pressed, as a result of which a seal with respect to the piston rod 8 takes place.

The piston half-parts 15 are provided with buffer sleeves 37, which serve to cushion the piston 1 in its end position. The buffer sleeves 37 are integrally formed on the envelope body 23 made of plastic. You stand on the touch surface 16 facing away from the side of the piston half parts 15 axially beyond the insert 17. Their inner diameter corresponds to the outer diameter of the piston rod 8, so that they are suitable are to accommodate a portion of the piston rod 8 or threaded bushing 22 in itself. The buffer sleeves 37 of the piston 1 dip into the axial bores 7 provided in the cylinder covers 4, 5. The axial holes 7 form in their interior 12 of the working cylinder 2 facing Area of an annular space around the piston rod 8, into which the buffer sleeves 37 fit. As mentioned earlier, the

Periphery of this annular space in an annular groove 13 is a buffer seal 14 added. When the buffer sleeve 37 is immersed in the annular space, the buffer seal 14 lies down in a sealing manner around the jacket of the buffer sleeve 37, the Auf 1 moving up through a conical bevel 38 at the free end of the buffer sleeve 37 is facilitated.

The piston 1 is in Fig. 1 at the end of its stroke in the left Cylinder cover 5 shown. The piston stroke is thereby limited stop that a radial end surface 39 of the enveloping body 23 meets the end face of the cylinder cover 5. In order to perform a return stroke of the piston 1, a pressure medium is applied to the connection 6 in the left cylinder cover 5, while connection 6 of the right cylinder cover 4 is relieved of pressure. During the return movement of the piston 1, that contained in the interior 12 of the working cylinder 2 can First flow off the medium over the full cross section of the axial bore 7. This flow path is blocked when the Buffer sleeve 37 dips into axial bore 7 and comes into contact with buffer seal 14. This can A pressure pad in front of the approached cylinder cover 4 build up that the piston movement just before reaching its end position damps. The buffer seal 14 is a special 3-lip seal. It opens via the annular groove 13 a restricted flow path through which the pressure cushion is reduced. The possible counter pressure of the pressure pad is limited as a result, and the piston 1 reaches its stop position on the cylinder cover 4.

The invention is not based on one of two piston half-parts 15 constructed piston 1 limited. Rather, there is the possibility of the piston half part 15 also on its own to be used as a piston, especially in a single-acting cylinder.

List of Reference Numbers 3404095 1 Pistons 2 Working cylinder 3 Cylinder liner 4.5 Cylinder cover 6th Connection 7th Axial bore 8th Piston rod 9 Sliding bush 10 Piston rod seal 11th Wall 12th Interior 13th Ring groove 14th Buffer seal 15th Piston half part 16 Berlihrf pool 17th inlay 18th Through hole 19th Cones 20th Ring stage 21 Thread end 22nd Threaded bushing 23 HUl! Body 24 Anchoring part 25th Breakthrough 26th Pen 27 Pass hole 28 Guide surface 29 Circumferential groove 30th Piston seal 31 Smaller diameter area 32 Encoder ring 33 Ri ngnut 34 Recess 35 Sealing ring 36 Half groove 37 Buffer sleeve 38 Bevel 39 radial end face

Claims (17)

F e s t ο KG, 7300 Essiingen piston claims 1. Piston (1), consisting of two in mirror symmetry Arrangement of piston half-parts (15) which can be pulled onto a piston rod (8) and each consists of a metallic Insert (17) with a radially protruding anchoring part (24) and one sprayed onto the insert (17) Enveloping body (23) are constructed from plastic. 2. Piston according to claim 1, characterized in that the anchoring part (24) is designed and flange-like is arranged in the axial central region of the insert (17). 3. Piston according to claim 1 or 2, characterized in that the anchoring part (24) with openings (25) is provided, which allow a material to pass 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 one is essentially transverse to the piston longitudinal direction extending, frontal contact surface (16) are in contact with one another. 5. Piston according to claim 4, characterized in that on the contact surface (16) complementary latching means are formed by means of which the piston half-parts (15) can be fixed to one another so that they cannot rotate. 6. Piston according to claim 5, characterized in that that the locking means are formed on the enveloping body (23), for. B. in the form of an axially protruding pin (26) and one diametrically opposite, complementary Fitting hole (27). 7. Piston according to one of claims 1 to 6, characterized in that the contact surface (16) A buffer sleeve (37) projecting axially beyond the insert (17) is integrally formed on the opposite end of the enveloping body (23) is. 8. Piston according to one of claims 1 to 7, characterized in that the piston half parts (15) each wear a piston seal (30) which is arranged in a circumferential groove (29) on the outer surface of the enveloping body (23) is. 9. Piston according to one of claims 1 to 8, characterized in that the outer jacket of the enveloping body (23) is designed as a guide surface (28) over at least part of its axial length. 10. Piston according to claim 9, characterized in that the enveloping body (23) in the region of the guide surface (28) with peripheral, for receiving a lubricant suitable recesses (34) is provided. 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) in the axial central area of the enveloping body (23) is located, and that the jacket part of the enveloping body (23) between the circumferential groove (29) and the contact surface (16) of the piston half parts (15) as a guide surface (28) is used while the outer diameter of the enveloping body (23) is reduced in the area (31) facing away from the contact surface on the other side of 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) annular grooves (33) which are suitable for each half-side of an encoder rings (32) to be included. 14. Piston according to one of claims 1 to 13, characterized in that the recesses (34) for the Lubricant in the form of cutouts in the shape of a sector of a circle are provided between the annular groove (33) and the outer jacket of the enveloping body (23). 15. Piston according to one of claims 1 to 14, characterized in that the piston half parts (15) on their 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) with a axial through hole (18) are provided, which on the contact surface (16) in the form of a half-groove (36) for receiving a sealing ring (35). 17. Piston half part (15) according to one of the claims 1 to 16, in particular for use as a piston for one single-acting working cylinder.