EP1662152A2

EP1662152A2 - Locking unit for a linear pressure cylinder

Info

Publication number: EP1662152A2
Application number: EP05111432A
Authority: EP
Inventors: Bo Disbo
Original assignee: Bosch Rexroth Teknik AB
Current assignee: Bosch Rexroth Teknik AB
Priority date: 2004-11-30
Filing date: 2005-11-29
Publication date: 2006-05-31
Also published as: DE102004057581A1; EP1662152A3; DE102004057581B4

Abstract

Locking unit (1), in particular for a linear pressure cylinder (6), arranged inside and/or at the end of the linear pressure cylinder (6), comprising at least one lock ring element (2) for clamping a piston rod (3), whereby the piston rod (3) is guided through the locking unit (1), comprising a spring member (7) biasing the lock ring element (2) into a clamping position and a pressure chamber (4), connected to at least one releasing means (12) for a pressurising medium and/or a mechanical releasing device, configured for moving the lock ring element (2) into a releasing position, whereby the at least one lock ring element (2) is in an unadjusted floating position, whereby a centring of the lock ring element (2) relative to the piston rod (3) is ensured by at least one sealing element (10, 11). By this invention the objective can be reached, to provide a locking unit, which offers a simple construction and provides a blocking effect in both directions of the piston rod movement.

Description

Locking unit, in particular for a linear pressure cylinder, arranged inside and/or at the end of the linear pressure cylinder, comprising a lock ring element for clamping a piston rod, whereby the piston rod is guided through the locking unit, comprising a spring member biasing the lock ring element into a clamping position and a pressure chamber, connected to at least one port for a pressurising medium and/or a mechanical releasing device, configured for moving the annular lock ring element into a releasing position.
Usually a locking unit is used in combination with a pressure cylinder, in order to block the movement of a piston rod, so as to fix the piston respectively the piston rod against the pressure cylinder. During the operation of pressure cylinders the piston rod is free movable by pressurising the corresponding chambers of the cylinder, but in case of an inactive condition of the cylinder in many applications the piston has to be blocked, in order to keep an unchanged position of the piston and the corresponding mechanism to be moved.
In other cases a cycle of repetitive movements of pressure cylinders comprising at least one stop position as a part of a duty cycle, it is necessitated to provide a piston rod clamping mechanism, which can easily be controlled to clamp and to release the piston rod either by a pressure fluid, connected to the system or manually by activating a releasing screw or similar. Often such locking units are installed in order to increase the security of mechanical systems where pressure cylinders are used as linear drives, for example during maintenance or when a operator is on the system.
The blocking effect can not be realised by the fluid system supplying the pressure cylinder, because the resilience of the fluid is to high. Therefore a direct mechanical locking system is necessary.
Another security feature is the clamping position of the locking unit in a bleed status of the pressure chamber, which is normally connected to the central pressure medium supply, because in case of a system breakdown the piston rod is blocked and no further, uncontrolled movement of the linear system is possible. The clamping effect of the lock ring element shows a self- energising effect, so that by an increased holding force the clamping force increases likewise and is independent on the spring force.
According to the state of the art in the publication US 6308613 B1 is disclosed a fluid pressure cylinder, which has a lock mechanism. The lock mechanism to be assembled to a body of a cylinder includes a fulcrum pin for immovably supporting a lock ring element in its axial direction. A spring member biases the lock ring element in its tilting direction around the fulcrum pin. A returning pressure chamber is provided on the side in which the lock ring element is tilted by the biasing spring member and applies a fluid pressure to the lock ring element against a force of the biasing spring member by supplying a pressurized fluid. A sleeve is fitted over a piston rod of the cylinder for forming an inner peripheral wall of the returning pressure chamber. A pressure receiving member for air- tightly sealing a space between the lock ring element and an outer peripheral surface of the sleeve and between the lock ring element and an inner peripheral surface of the returning pressure chamber is mounted to the lock ring element closer to the returning pressure chamber.
Under the terms of the prior art different problems rise regarding the construction and the function of the disclosed locking unit. The construction is complex, whereby in particular a fulcrum pin has to be applied to immovably support the lock ring element in its axial direction. The fulcrum pin has to be mounted from the outside of the locking unit body. Moreover the pin must offer the possibility of tilting the lock ring element, whereby the fulcrum pin is used as the centre of rotation of the lock ring element. Regarding the surface quality due to the air- tightly sealing with the sealing element an extensive processing of the sealing surface of the sleeve is necessary.
Another disadvantage is the fact, that the lock ring element offers a blocking function in only one direction. If the piston rod moves in the opposite direction of the spring member, no clamping effect appears and the rod runs through the locking unit unaffected.
Therewith it is the objective of the present invention, to provide a locking unit, which offers a simple construction with a low mounting effort.
The problem can be solved basing on a locking unit, in particular for a linear pressure cylinder, according to claim 1 in conjunction to the representative features. Advantageous embodiments of the invention are given in the pending claims.
This object is achieved in the locking unit of claim 1. The invention discloses, that the at least one lock ring element is in an unadjusted floating position, whereby the body of the locking unit features at least one guide edge for guiding the tilting movement of the at least one lock ring element.
This lock ring arrangement provides a simple construction of the lock ring element, because no fulcrum pin, fulcrum ball or the like is necessary. Therewith the mounting technique is simplified, because the lock ring element only has to be put on the piston rod, and no further mounting and adjustment step of a fulcrum element is necessary. In order to ensure a tilting movement in a centre of rotation, instead of a fulcrum element a guide edge is performed. In case of only one lock ring element the guide edge is performed in the inner shape of the body of the locking unit, in case of two lock ring elements the rings are arranged closed to each other, therefore the guide edge is built by an inner edge in the shape of the lock ring element.
According to an advantageous embodiment, within the body of the locking unit two lock ring elements in opposite directions are arranged, whereby the lock ring elements are tilting in order to clamp the piston rod in both directions of the piston rod movement in at least one guide edge 13. In this embodiment the piston rod can be blocked in both directions of movement. Each lock ring element clamps the piston rod in one corresponding direction, whereby both lock rings elements are tilted in their clamping position simultaneously so as to obtain an absolutely rigid system in each direction.
Advantageously, the two lock ring elements are pressurised by one common pressure chamber, in order to tilt the at least one lock ring element in an releasing position. Due to the arrangement of two lock ring elements in their opposite directions the pressure chamber is bounded by both the left lock ring element and the right lock ring element, therewith both lock ring elements are pressurised by the pressure medium of only one inner pressure chamber. In that arrangement it is ensured, that by pressurizing of only one pressure chamber on the one hand both directions of movement are released and on the other hand both directions of movement are blocked, if the single pressure port is in a vented state.
It is an advantage of the invention, that a centring of the said lock ring element relative to the piston rod is ensured by at least one sealing element. With the invented solution it is offered the advantage, that the centring of the lock ring element relative to the piston rod is ensured by the inner sealing element and the peripheral sealing element, which is sufficient regarding the centring admeasurement. Lip seals in particular are a advantageously sealing solution coupled with the feature of centring the lock ring element, because the shape of the sealing guarantees a tight contact to the sealing surface due to its high spring member displacement.
According to an advantageous embodiment, at least one spring member tilts the lock ring element in a clamping position, whereby the at least one spring member is preferably performed as a compression spring member, and according to the case of two lock ring elements a tension spring member between at least two lock ring elements tilt the lock ring elements in a clamping position. The spring members are performed as coil springs, and in particular in the case of two lock ring elements the compression springs can be saved by applying one tension spring member in between the two lock ring elements, whereas the tension spring member is tilting both lock ring elements into their locking position.
Advantageously, the holding force for both directions of the rod movement amounts at least 500N. Depending on the size of the pressure cylinder a minimum holding force of 500N is necessary. Likewise in the most cases of linear drives performed as pressure cylinders the security holding force in a switched off system should be in the range of at least 500N.
It is an advantage of the invention, that the pressure of the pressurising medium for pressurising the pressure chamber amounts maximum 1 bar. Depending on the pressurised surface size of the locking ring element and the necessary holding force a pressure of 1 bar should be sufficient, because in some cases no higher system pressure is available. Due to the connection of the releasing pressure port to the pressure supply of the pressure cylinder, which features a system pressure of 1 bar, the clamping system should work absolutely reliable and no extra pressure supply is needed.
According to an advantageous embodiment, the body of the locking unit features two releasing means, whereby one releasing means is usable as a port for a pressurised medium and another releasing means is usable for a mechanical releasing device in order to release the locking unit manually. Alternatively to the releasing system, which is exclusively based on pressurising a chamber next to the locking ring element and between two lock ring elements respectively, a mechanical releasing system can be applied instead of the pressure system or additionally to it. The construction of the mechanical releasing system can be based on a screw, which presses the at least one lock ring element into a perpendicular position, using a tapered end section of the screw. If the screw is screwed in, the locking unit releases the piston rod, and if the screw is not in contact to the locking ring elements, the piston rod is clamped by at least one locking ring.
Advantageously, the body of the locking unit is removable mounted to the end face of the pressure cylinder. This embodiment offers a modular construction, and the locking unit can be mounted on different cylinders at the end face of the pressure cylinder body. As an alternative the locking unit is contained within the body of the pressure cylinder, in particular in the piston rod end side of the cylinder body for a smaller need of space and an easier construction, whereas this solution does not offer a modular locking system.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the enclosed drawings.

Fig. 1: shows a view of the locking unit with one lock ring element for clamping the piston rod in only one direction; and
Fig. 2: shows a view of the locking unit with two lock ring elements in opposite directions for clamping the piston rod in both directions.

In Fig. 1 is shown a view of the locking unit 1. The locking unit 1 is placed at the end of a pressure cylinder 6. In this embodiment only one lock ring element 2 is applied for clamping the piston rod 3 in one direction. In a vented state of the pressure chamber 4 the pressure face 5 of the lock ring element 2 is not pressurised, and the lock ring element 2 is tilted in a clamping position by a spring member 7. The spring member 7 tilts the lock ring element 2 round a guide edge 8, which is featured in the inner shape of the locking unit body 9. The lock ring element 2 tilts only a small amount, and the articulated joint is provided by the guide edge 8.
In this state the lock ring element 2 is under an angle less than 90° related to the piston rod 3, and an angular contact line similar to a screw thread rises between the lock ring element 2 and the piston rod 3. By this screw thread contact a clamping effect rises by a leverage effect and the force flow is guided from the piston rod 3 into the lock ring element 2, whereby a holding effect of the piston rod 3 against the cylinder is ensured in one direction of the piston rod force.
The lock ring element 2 can be transferred in a releasing position by a releasing means 12. In the present embodiment the releasing means 12 is carried out as a screw, which can be used for tilting the lock ring element 2 in a perpendicular position relating to the piston rod 3. The screw hole also can be used as a pressure medium port for pressurising the pressure chamber 4, in order to pressurise the face 5 of the lock ring element 2. In both cases the lock ring element 2 is tilted against the force of the spring member 7 and keeps in a vertical position.
The lock ring element 2 features an inner sealing element 10 and a peripheral sealing element 11. Both sealing elements 10, 11 are used for an air- tightly sealing of the pressure chamber 4. Furthermore the sealing elements 10, 11 are used for centring the lock ring element 2 relative to the piston rod. In particular a centred position of the lock ring element 2 is necessary in the released position, when the lock ring element 2 is perpendicular in relation to the piston rod 3.
The embodiment in Fig. 2 shows a view of the locking unit 1 with two lock ring elements 2 in opposite directions for clamping the piston rod 3 in both directions of movement. Due to the arrangement of the lock ring elements 2 the pressure chamber 4 is bounded by their pressure faces, whereas both lock ring elements 2 are tilted in a releasing position by one pressurised chamber 4 and a mechanical releasing means 12 respectively.
In the clamping position the lock ring elements 2 are tilting in a position less than 90° relative to the piston rod 3, whereby the articulated joint is provided by the guide edge 13, which features the articulated joint for the tilting movement. In this position both directions of the movement of the piston rod 3 are blocked, because both locking ring elements 2 contact the piston rod by a screw thread line.
The present invention is not limited by the embodiment described above, which is represented as an example only and can be modified in various ways within the scope of protection defined by the appended patent claims. Thus the invention is also applicable to different locking units.

Reference Numbers

1: locking unit
2: lock ring element
3: piston rod
4: pressure chamber
5: pressure face
6: pressure cylinder
7: spring member
8: guide edge
9: locking unit body
10: inner sealing element
11: peripheral sealing element
12: releasing means
13: guide edge

Claims

Locking unit (1), in particular for a linear pressure cylinder (6), arranged inside and/or at the end of the linear pressure cylinder (6), comprising at least one lock ring element (2) for clamping a piston rod (3), whereby the piston rod (3) is guided through the locking unit (1), comprising a spring member (7) biasing the lock ring element (2) into a clamping position and a pressure chamber (4), connected to at least one releasing means (12) for a pressurising medium and/or a mechanical releasing device, configured for moving the lock ring element (2) into a releasing position,
characterised in that the at least one lock ring element (2) is in an unadjusted floating position, whereas the body of the locking unit (1) features at least one guide edge (8) for guiding the tilting movement of the at least one lock ring element (2).
Locking unit (1) according to claim 1,
characterised in that within the body (9) of the locking unit two lock ring elements (2) in opposite directions are arranged, whereby the lock ring elements (2) are tilting in order to clamp the piston rod (3) in both directions of the piston rod movement in at least one guide edge (13).
Locking unit (1) according to claim 2,
characterised in that two lock ring elements (2) are pressurised by one common pressure chamber (4), in order to tilt the at least one lock ring element (2) in an releasing position.
Locking unit (1) according to claim 1,
characterised in that a centring of the said lock ring element (2) relative to the piston rod (3) is ensured by at least one sealing element (10,11).
Locking unit (1) according to claim 1,
characterised in that at least one spring element (7) tilts the lock ring element (2) in a clamping position, whereby the at least one spring element (7) is preferably performed as a compression spring.
Locking unit (1) according to claim 5,
characterised in that a tension spring between at least two lock ring elements (2) tilt the lock ring elements in a clamping position.
Locking unit (1) according to claim 1,
characterised in that the holding force for both directions of the rod movement amounts at least 500N.
Locking unit (1) according to claim 1,
characterised in that the pressure of the pressurising medium für pressurising the pressure chamber (4) amounts maximum 1 bar.
Locking unit (1) according to claim 1,
characterised in that the body (9) of the locking unit (1) features two releasing means (12), whereby one releasing means (12) is usable as a port for a pressurised medium and another releasing means (12) is usable for a mechanical releasing device in order to release the locking unit (1) manually.
Locking unit (1) according to claim 1,
characterised in that the body (9) of the locking unit (1) is removable mounted to the end face of the pressure cylinder (6).