WO1988003609A1

WO1988003609A1 - Pneumatic or hydraulic cylinder with built-in velocity control

Info

Publication number: WO1988003609A1
Application number: PCT/SE1987/000525
Authority: WO
Inventors: Sören Robert KÖRMARK
Original assignee: Hydro-Pneumatic Ab
Priority date: 1986-11-10
Filing date: 1987-11-10
Publication date: 1988-05-19
Also published as: EP0362201A1; FI892218A; FI892218A0; SE463884B; SE8604813L; AU8271287A; SE8604813D0

Abstract

A pneumatic or hydraulic cylinder with built-in velocity control has a connection port (1) for intake and removal of working medium to and from the respective cylinder chamber (3). A first inner part of said connection port facing towards the cylinder chamber is provided with a non-return valve means (2, 4, 5, 14), which is constructed such that on one hand it permits working medium inflow with small flow losses to the cylinder chamber from an outer part of the connection port situated outside said non-return valve means, and, on the other hand, it blocks outflow of the working medium from the cylinder chamber to said outer part of the connection port. A second inner part of said connection port, similarly facing towards the cylinder chamber, is provided with an adjustable constriction valve means (6, 6a), which is constructed to enable a variable degree of working medium outflow from the cylinder chamber to said outer part of the connection port depending on the desired working velocity of the cylinder.

Description

Pneumatic or hydraul ic cyl i nder with bui l t-i n vel oci ty control

Technical Field

The present invention relates to a pneumatic or hydraulic cylinder with built-in velocity control, and more particularly to a cylinder having a connection port for intake and removal of working medium to and from the respective cylinder chamber.

When it is a question of controlling the speed of a pneumatic or hydraulic cylinder, it has been found that the best result is obtained by restricting the medium flow when the medium flows out from the respective cylinder chamber. Since it is not desirable to restrict the flow to the cylinder chamber, a restricting and non-return function is requi ed in the respective cylinder cap. When the medium flows into the respective cylinder chamber, this shall take place with small flow losses, which means that cylinders are made without built-in flow control so that the connection port leads straight into the respective cylinder chamber. For obtaining velocity regulation in the cylinder, flow must be prevented in the opposite direction in the connection port so that the medium is compelled to depart from the cylinder chamber via a constriction at the respective cap. State of the Art In an embodiment known from the patent application EP 0097 751, this is achieved by forming the connection port as a bottom hole, which is then connected by an outer duct in which there is placed a non-return val e, comprising a spring with a ball co-acting with a valve seat. This outer duct must be plugged to prevent leakage to the outside. In addition, it cannot be die cast without extra core-making work. To make it possible for the medium to reach the cylinder chamber, the other side of the ball must be connected by a further duct to the chamber. Summary of the Invention

The object of the present invention is to achieve a simplified solution for a pneumatic or hydraulic cylinder with built-in velocity control, which permits more rational manufacture and thereby lower manufacturing costs than for the solutions known up to now. This object is primarily achieved by bringing the working medium to pass directly into the cylinder chamber via a non-return function built in the connection port in the respective cylinder cap, and more specifically with a cylinder of the kind defined in the introduction, where a first inner part of said connection port facing towards the cylinder chamber is provided with a non-return valve means, which is constructed such that, on the one hand, it permits inflow of the working medium with small flow losses from an outer part of the connection port situated outside said non-return valve means into the cylinder chamber, and in that on the other hand it blocks the outflow of working medium from the cylinder chamber to said outer part of the connection port, and in that a second inner part of said connection port, similarly facing towards the cylinder chamber, is provided with an adjustable constriction valve means which is constructed to enable a variable degree of working medium outflow from the cylinder chamber to said outer part of the connection port depending on the desired working velocity of the cylinder. Description of Figures

Presently preferred embodiments of the invention are described fn more detail in the following with reference to the accompanying drawings, where

Figure 1 is a side view of a first embodiment of the pneumatic or hydraulic cylinder in accordance with the invention,

Figure 2 is a cross section through the axial plane A-A of the embodiment according to Figure 1, Figure 3 is a cross section through the plane B-B in Figure 2 of the embodiment according to Figure 1, with certain details removed for the purpose of clarification,

Figure 4 is a cross section of the embodiment according to Figure 1 through the plane C-C in Figure 2 with certain details removed for the purpose of clar fication,

Figure 5a is a detailed view of the non-return valve in the embodiment according to Figure 1 through the plane D in Figure 2,

Figures 5b and 5c are cross sections of the non-return valve in the embodiment according to Figure 1 in closed and open position respectively, Figure 5d is a top view of the non-return valve in Figure 2, and Figures 6a-c illustrate an alternative embodiment of the non-return valve in the cylinder according to the invention in views corresponding to those in Figures 5b, 5c and 5d. Description of Preferred Embodiments

As appears most clearly in Figure 2, the connection port 1 is made in the respective head of the cylinder, in the presently preferred embodiment of the invention with its cylindrical part la so far down that there is only one or a few millimeters thickness of material 2 remaining down to the respective cylinder chamber 3, where a junction takes place (in the thin material 2) through a plurality, e.g. four small holes 2a-2d cf Figure 5a, or by some suitable alternative configuration for the passage of medium, which prevents the ball 4 included in the non-return function from passing out into the cylinder chamber 3, but still gives th possibility for the medium to pass out into the cylinder chamber. The ball

4 included in the respective connection port 1 prevents the medium from passing in the opposite direction when the ball seals against a valve sea

5 screwed into the connection port, see Figures 5b and 5c.

Since working cylinders are strictly standardized with regard to-' the exterior size of the cyl nder caps only a very limited space is afforded for constructing a non-return function directly in the connection port of the respective cylinder cap.

There is achieved with the cylinder in accordance with the present invention the non-return function without the ball 4 being acted on by a spring, as is the case in previously known solutions, which is possible in accordance with the invention by screwing the valve seat 5 for the ball 4 down into a fixed position, so that the movement of the ball will be so small that it seals rapidly and with a reliable function against the seat without the need to bias the ball by a spring, irrespective of how the cylinder is mounted.

A comparatively small ball 4 is used and the difference between the ball diameter and the diameter of the hole 5a in the valve seat 5 is small to give as large a flow area as possible, cf Figure 5b. The ball is preferably made of a suitable plastics material so that it will not pass through the hole in the valve seat 5 (taking into account the above- mentioned small diameter difference) and so that the ball will be sufficiently light to rapidly move upwards and reliably close the medium passage by its bearing against the valve seat.

The connection port 1 in the respective cylinder cap is constructed such that its cylindrical portion la goes right down until there remains only one or a few millimeters thickness of the material 2 to the cylinder chamber 3, where the passage takes place by a plurality, in this case four small holes 2a-2d, see Figure 5a (any other number is of course possible as well), or by some other suitable configuration which prevents the ball 4 from passing out into the cylinder chamber 3, but simultaneously give the medium the possibility of passing out into the cylinder chamber.

Further advantages with the cylinder in accordance with the invention with the non-return function of the cylinder built into the connection port itself in the respective cylinder head are that no separate plugging is required for this purpose, and that a smaller number of ducts is requi ed.

When the medium flows out of the respective cylinder chamber 3, the flow shall pass a constriction which is adjustable for enabling adjustment of the cylinder piston velocity. As mentioned, in embodiments known up to now this is achieved by placing a throttle screw in an outer duct to the cylinder chamber, and connecting the other side of the constriction to the connection port by a further outer duct which must be plugged. In the velocity controlled pneumatic or hydraul c cylinder, in accordance with the present invention the connection from the cylinder chamber 3 after the constriction 6, here also in the form of a throttle screw 6a, to the connection port 1 is formed of an inner duct 7, which is so designed that it is easy to die cast without an extra core. The necessary sealing of this duct 7 against the cylinder chamber 3 at the respective cylinder head preferably takes place by a projecting part 8a on a washer 8, fitted into the opening of the duct 7 facing towards the piston, said washer being preferably extruded in plastics, and apart from the mentioned seal ng function also having additional functions in the cylinder, such as sealing between respective cylinder cap 9 and cylinder barrel 10, guiding the cylinder barrel 10 in the respective cap 9, forming a stop for the conventionally included damping seal ng 11 in the cylinder at the respective cylinder head from passing out into the cylinder chamber 3, and also serving as mechanical damping of the piston 12 in its end positions.

In the views according to Figures 3 and 4 the washer 8 and damping sealing 11 are removed from Figure 3, and the washer 8, the damping sealing 11 and the piston 12 are removed from Figure 4 for the purpose of making the figures more clear.

A conventionally arranged adjusting screw 13 is indicated in the figures for completeness, and it is intended for adjusting suitable damping in the cylinder, this function having no relevance in respect of the present invention.

Figures 6a-6c illustrate an alternative embodiment of the non-return function built into the connection port in the cylinder in accordance with the invention, wherein instead of the previously shown ball 4 and the holes 2a-2d a conical valve body 14 is used co-acting with the valve seat 5. This valve body is provided with a pin-like projecting, central part 14a, which at its free end is rigidly attached to a portion of a plurality. here four, perpendicularly to the central axis of the valve body disposed legs. In this case these legs 14b-14e are arranged radially in a cross, and when they engage the valve seat 5, when the medium flows into the connection port 1, passage of the medium into the cylinder chamber 3 is permitted between said legs 14b-14e, see Figure 6b, said portion thus retaining the valve body 14 by engagement against the "rear side" of the valve seat 5 so that the valve body is not urged by the medium into the cylinder chamber 3 in the cylinder. The present invention is not limited to the embodiments described above and illustrated on the drawings, but a plurality of other variations are possible within the scope of the inventive concept.

Claims

1. Pneumatic or hydraulic cylinder with built-in velocity control, having a connection port (1) for intake and removal of working medium into and out of the respective cylinder chamber (3), characterized in that a first inner part of said connection port facing towards the cylinder chamber is provided with a non-return valve means (2,4,5,14), which is constructed such that, on the one hand, it permits inflow of the working medium with small flow losses into the cylinder chamber from an outer part of the connection port situated outwards of said non-return valve means, and in that, on the other hand, it blocks the outflow of working medium from the cylinder chamber to said outer part of the connection port, and in that a second inner part of said connection port, similarly facing towards the cylinder chamber, is provided with an adjustable constriction valve means (6,6a), which is constructed to enable a variable degree of working medium outflow from the cylinder chamber to said outer part of the connection port depending on the desired working velocity of the cyl nder.

2. Pneumatic or hydraulic cylinder as -claimed in claim 1, characterized in that said non-return valve means comprises a ball (4), which, when the medium flows into the cylinder chamber (3) and as a result of the action of the medium, co-acts with a first wall (2) forming a junction between said first inner part of the connection port (1) and the cylinder chamber, this wall being formed such that, on the one hand, it prevents the ball from passing out into the cylinder chamber, and, on the other hand, it allows inflow of working medium with small flow losses to the cylinder chamber, while the bal co-acts with a second wall (5) forming a ball valve seat, when the medium flows out of the cylinder chamber, as a consequence of the action of the medium, said second wall (5) being situated between said first inner part and said outer part of the connection port, for blocking the outflow of working medium through this passage.

3. Pneumatic or hydraulic cylinder as claimed in claim 2, charac¬ terized in that the distance between the first and the second wall (2 and 5) only slightly exceeds the diameter of the ball (4) for minimizing, the necessary movement of the ball between both its working positions.

4. Pneumatic or hydraulic cylinder as claimed in any one of the preceding claims, characterized in that the first wall (5) exhibits a number of small holes (2a-2d), each of which has a diameter considerably less than that of the ball (4).

5. Pneumatic or hydraulic cylinder as claimed in any one of the preceding claims, characterized in that said second inner part of the connection port (1), in which the adjustable constriction valve means (6,6a) is arranged to function, communicates with the outer part of the connection port (2) through an internal duct (7) extending substantially in the longitudinal direction of the cylinder in the respective cylinder cap, the opening of this duct facing towards the respective cylinder chamber (3) in the direction towards the piston (12) is sealed by a seal ng body (8a) fitted into said opening.

6. Pneumatic or hydraulic cylinder as claimed in claim 5, charac- terized in that said sealing body (8a) comprises a projecting portion of a washer means, known per se, disposed in the junction between the respective cylinder cap (9) and the cylinder barrel (10), said washer means conventionally having additional functions in the cylinder, e.g. mechanical damping of the piston (12) in its' end positions.

7. Pneumatic or hyraulic cylinder as claimed in claim 1, characterized in that the non-return valve means includes a conically shaped valve body (14) connected to a stop means (14a-e), which allows the used working medium to pass, and in the open position of the valve means engages a seat (5) for the valve body to limit its opening movement.

8. Pneumatic or hydraulic cylinder as claimed in claim 7, characterized in that said stop means includes a pin portion (14a) extending from the minor end surface of the valve body (14) through the valve opening, and having at its end legs (14b-e) perpendicular to the pin portion said legs being formed as a cross and being intended to limit the movement of the valve body by engaging the valve seat (5).