GB2039996A

GB2039996A - A compressed air cylinder provided with a damping arrangement

Info

Publication number: GB2039996A
Application number: GB7941691A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1979-01-05
Filing date: 1979-12-03
Publication date: 1980-08-20
Also published as: FR2445905A1; IT1126627B; IT7928260A0; DE2900281A1

Abstract

A compressed air or hydraulically operated cylinder (10-14) has an attached damping device which operates at the ends of the piston's stroke to brake the latter together with the piston rod 14 in a jerk-free manner and more positively than hitherto even with large masses and at high speed. The damping device consists of a sleeve (24) slidingly arranged on the piston rod for displacement by abutment discs (20, 22) thereon and provided with a piston (25) which is tightly slidingly guided in a damping chamber (26). The two sides of the damping chamber are connected to one another by a duct (43) and bores (37, 38) the cross-sectional area of which can be varied to a greater or lesser extent by means of throttle bolts (39, 40). During damping of the leftward stroke fluid flows from the left side of the chamber (26) to the right side through an annular space (51) between the sleeve (24), and the throttled bore (38), the duct (43), a chamber (30) and bores (29) controlled by non-return valves (33). <IMAGE>

Description

SPECIFICATION A compressed air cylinder provided with a damping arrangement State of the art The invention originates from a compressed air cylinder according to the type set forth in the main claim. With one known compressed air cylinder, a pneumatic limit position damping is provided in which the air compressed by the working piston is exhausted through a throttle in the end phase of the piston movement. Such a limit position damping is no longer sufficient at high piston speeds and with large moved masses. The limit position of the working piston is reached either in a jerky nonuniform movement or the piston strikes against the limit position which rapidly leads to damage.

Advantages of the invention As opposed to this, the compressed air cylinder in accordance with the invention comprising the characterising features of the main claim has the advantage that a completely jerk-free, more reliable braking is achieved even at high working speeds and with large masses.

Advantageous further developments and improvements of the working cylinder set forth in the main claim are made possible by the measures set forth in the sub-claims. The damping device in accordance with the invention is suitable not only for working cylinders operated by compressed air but also for working cylinders operated hydraulically.

Drawing An embodiment of the invention is illustrated in the drawing and is described in detail in the following specification. Figure 1 shows a longitudinal section through the working cylinder provided with a damping device, Figure 2 is a section along Il-Il in Figure 1.

Description ofthe embodiment Aworkingpiston 12istightlyslidinglyguided in a cylindrical tube 10 which is closed at one end by a cover 11. The piston is fixed to the end of a piston rod 14 by means of a screw 13. In the cover 11, a blind bore 15 is formed into which issues a transverse bore 16 which serves for the supply and discharge of compressed air. The other end of the cylindrical tube 10 is closed by a two-part housing 17 which accommodates a damping device. A longitudinal bore 18 is formed in the housing portion 17' which directly engages the cylindrical tube, a transverse bore 19, which likewise serves for the supply and discharge of compressed air, issues into the bore 18. Thus, the working cylinder is made doubleacting.

The piston rod 14 extends through the entire housing 17, an abutment disc 20 being fixed at its end with the aid of a screwthread 21. A similar abutment disc 22 is located at the opposite end of the piston rod where the piston is located. The disc 22 is urged against a shoulder 14' on the piston rod by the piston 12 and the screwthread 13.

In the region of the housing 17, an elongate sleeve 24 is tightly slidingly arranged on the piston rod 14.

A piston 25 which is tightly slidingly arranged in a damping chamber 26 is arranged on the central portion of the sleeve 24; sealing is provided by a sealing ring 27. Thus, where the piston 25 is mounted, the central portion of the sleeve 24 has a larger diameter; conical zones 24', 24" extend on either side of the said portion. A central longitudinal bore 51 formed in the housing portion 17" has the same diameter as the central portion of the sleeve 24. On the one hand, a plurality of stepped bores 29 lead from the damping chamber 26 to an annular chamber 30, on the other hand similar stepped bores 31 lead to an annular chamber 32. Plate-like nonreturn valves 13,34 the stroke of which is limited by safety rings 35, 36 are arranged in all the stepped bores. A bore 37,38 also leads from each annular chamber 30,32 to the damping chamber 26.An ajustable throttle valve 39,40 which consists of a bolt with a shank 41 or 42, projects into a respective one of the said bores 37 and 38. These shanks are preferably made conical. According to the extent of screwing in, the passage from the damping chamber 26 through the bores 37,38 to the annular chambers 30,32 is throttled to a greater or lesser extent. The annular chambers 30,32 are in communication with one anotherthrough a duct 43 shown dotted. This is shown dotted in Figure 1 since it is laterally displaced with respect to the throttle bolts 39,40 (see Figure 2). A housing bore 45 which leads to the annular chamber 32 issues into the duct 43. An annular chamber 46 in which is arranged a fluid store 47 is also connected to the annular space 32.A threaded sleeve 48 which projects out of the housing 17 is screwed onto the end of the sleeve 24 remote from the working cylinder.

The compressed air cylinder is actuated in known manner such that compressed air is either supplied to the bore 16 or to the bore 19 and is exhausted from the respective other bore. The pressure medium supplied to the bore 19 arrives in the cylindrical tube through the gap 50 formed between the sleeve 24 and the bore 18. It is assumed that the working piston is located in the illustrated left-hand limit position and that compressed air is supplied to the bore 19. Then, the working piston is moved towards the cover 11. When it arrives at the end of its stroke, the abutment disc 20 engages the threaded sleeve 48 whereupon the sleeve 24 is set in motion so that the piston 25 must compress fluid pressure medium contained in the damping chamber 26.This arrives, through the gap formed by the sleeve 24 and the bore 51 and the bore 37 restricted by the throttle 39, in the annular chamber 30 and from there arrives through the duct 43 in the annular chamber 32. The gap is increasingly reduced by the conical zone 24' so that during this procedure the working piston is braked jerk-free over a relatively short path by the narrowing gap and the action of the throttle 41.

Thus, the pressure medium located in the chamber 26 is compressed towards the annular chamber 32 in the manner described and from there arrives through the stepped bores 31 and the open nonreturn valve 34 to the other side of the damping chamber 26. In so doing, the non-return valve 33 abuts against the shoulders in the stepped bores 29 so that no pressure medium can arrive in the annular chamber 30 from the bores 29.

If compressed air is now supplied to the bore 16, then the piston 12 is moved towards the left and the abutment disc 22 engages the sleeve 24 at the end of its stroke whereupon the piston 25 is likewise urged towards the left and pressure medium is displaced into the bore 38. This is restricted by the throttle 40 and also by the gap in the bore 51 which is increasingly restricted so that the pressure medium can then only flow throttled into the annular chamber 32 and arrive from there through the duct 43 to the annular chamber 30. Moreover, the non-return valves 34 engage the shoulders in the stepped bore 31. From the annular space 30, the pressure medium flows through the stepped bores 29 and the open non-return valve 33 once again to the other side of the damping chamber 26. The damping device is filled with fluid pressure medium through the bore 45.

Claims

1. A compressed air cylinder provided with a device for damping the movement of the working piston at the ends of its stroke wherein pressure fluid is conveyed out of a damping chamberthrough a throttle, the device consisting of a separate unit built on to the working cylinder, the unit having a piston tightly sliding in a damping chamber and being a part of a sleeve slidingly arranged on the piston rod and at the ends of the stroke being movable longitudinally of the piston rod together with the sleeve and the damping chambers divided on both sides of the piston being connected to one another through a throttled connection.

2. A cylinder according to claim 1, wherein the throttled connection comprises a duct formed between the damping chamber and bores cooperating with annular chambers associated with the damping chamber.

3. A cylinder according to claim 2, wherein an adjustable throttle is provided in each of the said bores.

4. A cylinder according to claim 3, wherein each adjustable throttle is formed by a screw projecting into the respective bore.

5. A cylinder according to any one of claims 1 to 4, wherein the damping chambers on each side of the piston are each in communication with a respective annular chamber through stepped bores, a non-return valve being arranged in each of the stepped bores.

6. A cylinder according to any preceding claim, wherein abutment members which actuate the sleeve during a damping operation, are arranged in the vicinity of the ends of the piston rod.

7. A cylinder according to any preceding claim, wherein the device for damping has a 2-part housing, one part of which forms the closure at one end of the working cylinder the piston rod passes through the said housing and the sleeve is guided on the piston rod within the housing.

8. A cylinder according to any preceding claim, wherein the sleeve has the greatest diameter where the piston is located and regions extend away from both sides of the piston in which the diameter decreases continuously or discontinuously to a constant value.

9. A compressed air cylinder provided with a damping device substantially as herein described with reference to the accompanying drawings.