EP0255858B1 - Working cylinder with a length elastic power transmission - Google Patents

Description

The invention relates to an actuating cylinder according to the preamble of claim 1.

Actuating cylinders of the generic type (construction sheet SZ 1000-K 16 / spring-loaded cylinder SZ 111. Stand 1/79) have a wide range of uses; They are required, among other things, in motor vehicle construction for the actuation of injection pump regulators on diesel engines. Here, a pulling working stroke on the actuating cylinder serves to adjust the control lever of the fuel control pump, whereas in a certain driving condition an opposite stroke on the pull rod of such an actuating cylinder is required if, in the case of a vented actuating cylinder, the control lever counteracts the movement of the first-mentioned stroke. The elastic length compensation required for the lever is accomplished by pulling out the pull rod of the actuating cylinder relative to a cylinder tube guiding the pull rod. In the known actuating cylinders, the tie rod is supported on the inside of the cylinder tube by means of a compression spring, in such a way that the required elastic length compensation is possible by compressing the compression spring when the cylinder tube and the tie rod are displaced. When the cylinder tube is moved inside the housing of the actuating cylinder, so-called secondary space can be contaminated, in which the storage spring which presses the cylinder tube into its initial position is located. The space in the interior of the cylinder tube accommodating the pull rod is also exposed to the known dangers of soiling and contamination and thus increased corrosion as a result of the free access to the secondary space.

Proceeding from this, the object of the invention is to design an actuating cylinder of the generic type in such a way that a properly functioning internal ventilation of the secondary space with air from the primary space can be achieved, although a large number of relative positions are possible between the cylinder tube and the tie rod. It should be ensured absolutely effectively that the penetration of dirt particles and moisture is avoided. At the same time, a secure guidance of the pull rod in the cylinder tube and an effective sealing of the secondary space are to be achieved if the primary space of the actuating cylinder is ventilated when the actuating cylinder is actuated.

The features according to the characterizing part of claim 1 serve to solve this problem.

The actuating cylinder is extremely effective with regard to the sealing against the secondary space by means of the ventilation device acting between the tie rod and the cylinder tube, due to the path-dependent function. This has a check valve of any design known per se in the housing of the actuating cylinder in order to be able to blow the air out of the secondary space when the primary space is ventilated and the cylinder tube is displaced. In reverse order, i.e. when the primary space is vented, the ventilation device which is effective when there is a relative displacement between the cylinder tube and the tie rod is effective in a very simple manner in order to be able to ventilate the secondary space by means of the air from the primary space. With such ventilation, the primary room is in a depressurized state, i.e. it is connected to outside air via valve devices known per se, which is supplied in the cleaned state. A particular advantage can also be seen in the fact that the elastic support acting between the tie rod and the cylinder tube, which enables length compensation, is designed as a pneumatic spring.

By appropriate ring surface dimensioning on the tie rod, it is in any case m: -, h that allow us to exert forces to move the tie rod. D, _'ie draw rod in the manner of a piston within the L .n-derrohres is performed, there is also the advantage of a very good guide, that is, a misalignment of the pull rod is not possible even when the pull rod with actuated cylinder tube relative to this is fully extended.

In another known actuating cylinder (GB-C 2 072 265), the pull rod is guided within a cylinder tube and, together with this, can be displaced when pressurized, the pull rod being able to compensate for the length directly against the cylinder tube against spring force. However, the secondary space of such actuating cylinders is directly connected to the atmosphere, i.e. heavy pollution must be accepted. In a compressed air-driven working cylinder (DE-A 2 904 805) of likewise known construction, an aeration device is provided on a piston which closes against compressed spring force by compressed air, which opens when the primary space is vented and brings about the ventilation of the secondary space. There is no provision for an additional tie rod, which is effective in relation to the piston in the sense of length compensation; the ventilation valve in the piston works depending on the pressure, i.e. if the primary room is slowly ventilated, it cannot always be completely closed.

Even in the case of an actuating device with spring arrangements connected in series in a housing (DE-A 3 125 127), length compensation of the desired type is not possible, since the pull rod is connected directly to the piston of the actuating cylinder. In other known cylinder-piston drives (US-C 3 390 616), valve systems are used which are arranged in the piston and are relatively complex, pressure-dependent closing or opening, in order to bring about pressure compensation between two cylinder spaces; however, such arrangements are not suitable for length compensation between a cylinder tube guided in a cylinder and an additional pull rod guided in the cylinder tube.

Advantageous refinements and developments are listed in further patent claims.

• Fig.1 ist eine Längsschnittansicht des Betätigungszylinders im unbetätigten Zustand;
• Fig.2 ist eine der Fig.l entsprechende Längsschnittansicht im betätigten Zustand, in welchem sich das Zylinderrohr und die Zugstange in Anschlagposition am Gehäuse des Betätigungszylinders befinden;
• Fig.3 ist eine stark vergrößerte Teilschnittansicht der Belüftungseinrichtung des Betätigungszylinders nach der Erfindung; und
• Fig.4 ist eine Draufsicht der Darstellung von Fig.3.

The invention is explained below using an exemplary embodiment with reference to the accompanying drawing.

• Fig.1 is a longitudinal sectional view of the operating cylinder in the unactuated state;
• Fig.2 is a Fig.l corresponding longitudinal sectional view in the actuated state, in which the cylinder tube and the pull rod are in the stop position on the housing of the actuating cylinder;
• 3 is a greatly enlarged partial sectional view of the ventilation device of the actuating cylinder according to the invention; and
• Figure 4 is a top view of the illustration of Figure 3.

The actuating cylinder shown in Fig.l and 2 has a housing I, in which a cylinder tube 3 is slidably guided. The cylinder tube 3 is sealed off from the inner wall of the housing I by means of a seal 5. The cylinder tube 3 divides the interior of the housing into a primary space 7 and a secondary space 9 by means of the seal 5; A compressed air connection II opens into the primary space 7, into which compressed air is introduced in the manner described below in order to shift the cylinder tube 3 to the right as shown in FIG. Within the secondary space 9 there is a compression spring 11 which is supported with its left end (according to FIGS. 1 and 2) on the cylinder tube 3 and with its right end on the inside of the housing I. A protective sleeve 13 can be provided for the compression spring II, which serves to guide the compression spring and also to protect the inner wall of the housing. The housing I of the actuating cylinder has a seal 15 at the left end according to FIGS. 1 and 2, while at the end of the housing shown on the right there is a check valve 17 of any design known per se. If the cylinder tube 3 moves from the position shown in FIG. 1 to the right into the position shown in FIG. 2, then the air located in the secondary space is blown out via the check valve 17.

Within the cylinder tube 13 there is a pull rod 19 in coaxial extension, which is designed as a piston, i.e. it is sealed off from the inner wall of the cylinder tube 3 by means of a sealing ring 21. The pull rod can be displaced relative to the cylinder tube in the manner described below, the sealing ring 21 acting as a component of a ventilation device 23 in order to vent the secondary chamber 9 via the primary chamber 7, which is kept depressurized during this time, when the cylinder tube is moved to the left . As shown in Figs. 1 and 2, the tie rod has a smaller diameter area, i.e. an annular surface 25 is formed on the pull rod; this annular surface is acted upon in the manner described below when compressed air is introduced into the compressed air connection 10 by the compressed air, in such a way that the pull rod 19 can be moved to the right.

An important component of the actuating cylinder is the aforementioned ventilation device 23. The ventilation device 23 serves for internal ventilation of the secondary space 9 while simultaneously relieving pressure in the primary space 7. According to the enlarged partial sectional view according to FIGS. 3 and 4, the sealing ring 21 is located in a groove 27 of the pull rod 19 ; the sealing ring is guided on the fly, i.e. it has play between the two flanks of the groove 27 and is at the same time radially outwards, i.e. biased towards the inner wall of the cylinder tube 3. This allows air to pass between the groove base and the sealing ring. The width of the groove in the pull rod is greater than the width of the sealing ring 21, so that it always has play to one of the two groove flanks, that is to say is guided overhung and thus allows air to pass through there (FIG. 3). The groove 27 in the pull rod 19 is provided on the flank closest to the primary space 7 with at least one notch 31, which is shown as a cut transverse bore. The sealing ring 21 can consequently flow around the notch 31 when it is in contact with the flank 29 (FIG. 3). The cylinder tube is provided at the right end in the illustration according to FIGS. 1 and 2 with a stop collar 33, against which the end of the pull rod 19 is able to rest. The pull rod penetrates by means of a shoulder 35 the stop collar 33, that is to say that when the pull rod and the cylinder tube move to the right, a relative movement takes place between the two parts when the stop collar 33 in the position shown in FIG. 2 on the inside of the right hand side Housing I strikes. During this relative movement between the positions shown in FIGS. 1 and 2, the sealing ring 21 moves with respect to an overflow channel 37 which extends in the stop collar 33 and opens into the secondary space 9. Instead of an overflow channel, several such channels can also be provided. The length of the overflow channel 37 is designed such that, in the abovementioned system of the pull rod on the stop collar 33 of the piston, the overflow channel is connected to the primary space of the cylinder via the outer circumference of the pull rod. Fig.l shows this position in which there is a connection between the primary space and the secondary space via the overflow channel or several such channels. In the event of a slight stroke of the pull rod from this end position, the connection between primary space 7 and secondary space 9 is interrupted by passing over the channel end. The cylinder tube with the overflow channel, the tie rod and the sealing ring 21 thus form the ventilation valve 23 to the secondary space due to the aforementioned structural assignment.

The operation of the actuating cylinder and the ventilation device used in it is as follows:

In the non-ventilated state of the actuating cylinder, the pull rod 19 according to FIG. 1 is in the retracted position (position 0), the cylinder tube 3 pointing to the left as shown in the illustration when the primary space is depressurized by the compression spring II tet is clamped and by means of the stop collar 33 has taken the pull rod 19 in the stop position. When the actuating cylinder is ventilated via the compressed air connection 10, the cylinder tube 3 and the pull rod 19 carry out a working stroke (in the direction I). The cylinder tube 3 is acted upon on the annular surface between the inner wall of the housing I and the outer wall of the tie rod 19 on its larger diameter with compressed air, while the tie rod 19 is in turn acted upon by the compressed air on the annular surface 25, so that the two parts shown in their Relative position make the rightward movement. During the ventilation of the primary space and the movement of the cylinder tube and tie rod to the right, some air can escape through the ventilation device 23, since the seal 21 is in overlap with the overflow channel 37 (FIG. 1) and compressed air consequently along this overflow channel in the secondary space 9 can escape. This air and the air displaced when the volume of the secondary space is reduced are blown out of the secondary space via the check valve 17. Finally, if the shoulder 35 of the pull rod lies against the inner end of the housing on the right (FIG. 2), then the cylinder tube 3 moves relative to the pull rod until the stop collar 33 is also applied to the inner end of the housing. In this position there is no overlap between the sealing ring 21 and the overflow channel, ie the ventilation device 23 is blocked.

When using the actuating cylinder on an injection pump regulator of a diesel engine, a counterforce in direction II can come into effect on the pull rod 19. This is the case when driving downhill if the engine speed increases and the lever of the speed controller is moved in the direction of the idle position due to the characteristics of the same. the pull rod 19 is pulled out of the housing I against the force of the pneumatic spring acting on the annular surface 25. When the primary space is ventilated, length compensation takes place between the tie rod and the cylinder barrel. The pneumatic spring can be adapted to the working conditions of the drawbar by appropriate dimensioning of the annular surface 25. During the above-described relative displacement of the pull rod with respect to the cylinder tube, the ventilation device 23 is in the closed position, since there is no overlap between the seal 21 and the overflow channel 37.

The action of the counterforce on the pull rod 19 can also be present at the same time when the primary space is ventilated, in which case the cylinder tube 3 is moved to the right in accordance with FIGS. 1 and 2, while the pull rod 19 is either relative to the housing in the case of a counterforce that overcomes the pull rod force stops or performs the above-mentioned movement to the left. In any case, there is a relative movement between the cylinder tube and the tie rod, i.e. an elastic length compensation between the two components takes place. If the counterforce acting on the pull rod is equal to or greater than the pull rod force generated by the application of the annular surface 25, the ventilation device 23 is closed immediately in any case due to the relative displacement between the pull rod and the cylinder tube, i.e. blowing out a very small volume of the compressed air in the primary room is only extremely short-term.

The special task of the ventilation device 23 is to prevent dirt from penetrating into the secondary space when the primary space is vented and the volume of the secondary space increases accordingly when the cylinder tube and the pull rod are retracted. When the primary room is vented, i.e. when pressure is released at the compressed air connection 10, the compression spring 11 moves the cylinder tube from the position shown in FIG. 2 in the direction of the position shown in FIG. If the pull rod is in the position shown in FIG. 2 at the beginning of the venting, then an overlap between the sealing ring 21 and the overflow channel 37 takes place within a short time. In this relative position of the pull rod and cylinder tube, with simultaneous return of the same, air can reach the secondary space 9 from the primary space, which is now kept at atmospheric pressure, along the outer circumference of the pull rod and via the overflow channel 37, i.e. the secondary room is ventilated with air from the primary room at atmospheric pressure. This prevents the penetration of dirt particles from the ambient air via the check valve 17. The secondary room therefore remains free of coordinating influences, which can be caused by dirt and moisture.

When the primary rod begins to be vented, the pull rod 19 is in a relative position in which the pull rod is pulled out of the housing I as a result of an opposing force, i.e. If the relative position of the pull rod and cylinder tube shown in FIG. 3, ventilation of the secondary space from the primary space is nevertheless possible. As illustrated in FIG. 3, when the cylinder tube is displaced to the left relative to the tie rod, a force in the direction of the arrow is exerted on the sealing ring 21, with the result that the sealing ring rests on the flank 29. This releases a connection which exists between the outer circumference of the tie rod, the notch 31, the groove base, the flank 30 opposite the flank 29 and the secondary space. Air can consequently follow the arrow representation in FIG. 3 from the primary space into the secondary space. The ventilation of the secondary room is therefore possible in any case, regardless of the starting relative position of the cylinder tube and tie rod.

Reference symbol list

• I housing
• 3 cylinder tube
• 5 seal
• 7 primary room
• 9 secondary room
• 10 compressed air connection
• 11 compression spring
• 13 protective sleeve
• 15 seal
• 17 check valve
• 19 tie rod
• 21 sealing ring
• 23 ventilation device
• 25 ring surface
• 27 groove
• 29 flank
• 30 flank
• 31 notch
• 33 stop collar
• 35 approach
• 37 overflow channel

Claims (3)

1. Actuating cylinder with longitudinally resilient power transmission, with a cylinder tube (3) guided in a housing (1) and sealed against the inner wall of the latter that is pneumatically moveable against the force of a compression spring (11) with a traction rod (19) extending concentrically inside the cylinder tube (3) that projects, in relation to the support of the compression spring (11) on the housing side at the opposite end of the housing (1) of the actuating cylinder out of the latter and that is able to extend, under the action of external traction forces, in relation to the cylinder tube (3) against a resilient support from the housing (1), such as to permit an elastic linkage extension between the traction rod (19) and the cylinder tube (3), wherein the traction rod (19) is guided as a piston within the cylinder tube (3), with an annular surface (25) fashioned at the traction rod (19) that can be pneumatically pressurized in the same way as an annular surface provided on the cylinder tube (3) and facing the primary space (7), such that the cylinder tube (3) and the traction rod (19) are jointly moveable, and wherein a ventilation device (23) mounted at the end of the traction rod (19) and the cylinder tube (3) that projects into the secondary space (9) features a sealing ring (21) that is guided in a groove (27) of the traction rod (19) with radial pretension, with an overflow channel (37) located at the end of the inner circumference of the cylinder tube (3) acting with respect to the sealing ring (21) towards opening the connection between the primary space (7) and the secondary space (9) when the sealing ring (21) comes to overlap with the overflow channel (37) as the relative displacement between the traction rod (19) and the cylinder tube (3) takes place and wherein the resilient support is generated by a pneumatic spring acting with respect to the annular surface (25) of the traction rod (19) by means of which the traction rod (19) is supported in relation to the bottom of the housing (1) with the primary space pressurized.

2. Actuating cylinder according to Claim 1, wherein the sealing ring (21) is guided in a floating way between the two flanks (29, 30) of the groove (27) with at least one indentation (31) being provided in the groove of the flank (29) opposite the end of the traction rod that establishes a communication between the primary space, the groove bottom and the secondary space that passes through the indentation (31) as the sealing ring (21) applies against the flank (29), when the traction rod and the cylinder tube are in a relative position in which the sealing ring (21) does not overlap with the overflow channel (37).

3. Actuating cylinder according to one of the aforementioned claims, wherein the end of the cylinder tube (3) turned to the secondary space features a stop collar (33) for the traction rod that can be shifted within the cylinder tube, in which the overflow channel (37) discharges into the stop collar and wherein the traction rod extends via a shoulder (35) through a centrical opening of the stop collar, such that there is a relative displacement between the traction rod and the cylinder tube as the shoulder (35) applies against the inside end of the housing turned to this shoulder while the ventilation device (23) is shut off.

Images