A lockable piston-cylinder unit having a cylinder that is closed at both ends and filled with pressurized fluid and in which a piston that is sealed relative to the inner wall of the cylinder is displaceably guided. The piston divides the interior of the cylinder into a first working chamber and a second working chamber. A piston rod is arranged at the piston and is guided out of the cylinder 1 through one of the working chambers and through a guiding and sealing unit which closes the one end of the cylinder.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a U.S. national stage of application No. PCT/EP2014/053118, filed on Feb. 18, 2014. Priority is claimed on German Application No. DE 102013101627.8, filed Feb. 19, 2013, the content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to a lockable piston-cylinder unit having a cylinder closed at both ends and filled with pressurized fluid in which a piston that is sealed relative to the inner wall of the cylinder is displaceably guided. The piston divides the interior of the cylinder into a first working chamber and a second working chamber and has a piston rod arranged at the piston and is guided out of the cylinder through one of the working chambers and through a guiding and sealing unit which closes the one end of the cylinder. An actuation rod is arranged to be axially displaceable, one end of the actuation rod projects out of the cylinder and can be acted upon by an actuation element so as to be movable in the push-in direction of the actuation rod, and a valve slide of a blocking valve which can be acted upon in closing direction by the pressure in the first working chamber can be acted upon by the other end of the actuation rod in opening direction of the blocking valve so as to be axially displaceable by a displacement between a closed neutral position and its open position, through which blocking valve the first working chamber can be connected to the second working chamber via a connection, wherein the actuation element is movable between an actuation position and a non-actuation position, and the actuation element contacts a stop in the non-actuation position.

2. Detailed Description of the Prior Art

In lockable piston-cylinder units of the type mentioned above, due to manufacturing tolerances, there is play between the actuation element and the actuation rod in the non-actuation position of the actuation element. Depending on the application, this play leads to rattling noises when these parts strike one another. To prevent a rattling noise of this kind, it is known to apply spring force to the actuation element in direction of the actuation rod so as to keep it permanently in contact with the actuation rod.

This arrangement is uneconomical and requires additional component parts and additional assembly effort.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a piston-cylinder unit of the type mentioned above that prevents rattling noise caused by the actuation element and actuation rod striking one another in a simple, easy-to-assemble construction.

According to one embodiment of the invention a valve slide in its closed neutral position without contacting a fixed stop is forced in closing direction by the pressure in the first working chamber and is permanently supported at the actuation element via the actuation rod.

As a result of this construction, no additional spring elements are required for holding the actuation element and actuation rod in contact with one another; rather, the pressure in the cylinder, which acts upon the closing member and which exists anyway, is utilized for this purpose. This also allows the piston-cylinder unit to have a small size.

A simple construction has the valve slide displaceably arranged in a through-opening extending coaxial to the cylinder in a valve body and a region of reduced diameter between a first region of greater diameter and a second region of greater diameter into which a connection opening formed in the valve body opens radially, this connection opening connecting the region of reduced diameter to the second working chamber. The first region of the valve slide that is at a greater distance from the first working chamber is displaceably guided in the through-opening to be sealed by a first seal, and the second region of greater diameter of the valve slide that is closer to the first working chamber is displaceably guided in the through-opening so as to be sealed by a second seal and projects partially into the first working chamber in its closed neutral position and projects at least approximately completely into the first working chamber in its open position.

The displacement of the valve slide between its closed neutral position and its open position is located within an axial preloading distance. During assembly, the actuation rod is brought into contact with the valve slide and, when the actuation element is installed, the actuation rod and, along with it, the valve slide are then displaced by the actuation element within the preloading distance in the opening direction against the pressure in the cylinder, without arriving in the open position. In this position, the actuation element is in its non-actuation position and contacts its fixed stop defining the non-actuation position. At the same time, the valve slide is still acted upon by the pressure in the cylinder and is supported at the stop via the actuation rod and actuation element.

In a simple construction, the first seal and/or the second seal can be a sealing ring arranged in the valve body and which tightly surrounds the valve slide.

In one embodiment the piston forms the valve body and the actuation rod is displaceably guided through a coaxial passage of the piston rod. In so doing, an actuation device having the actuation element can be arranged at the end of the piston rod that projects freely outward. In one embodiment, the valve body is fixedly arranged at the end of the cylinder remote of the piston rod so as to close the latter. In so doing, a guide element with a coaxial passage can be arranged at the valve body on the side remote of the piston, and the piston rod can be displaceably guided through this coaxial passage.

In a simple construction, the actuation element is a swiveling lever that is swivelable around a pivot extending transverse to the longitudinal extension of the actuation rod, the actuation rod contacting this swiveling lever at a distance from the pivot. In so doing, the actuation rod can contact the swiveling lever by its front end opposite the valve slide.

The valve slide can be acted upon in opening direction indirectly or directly by a preloaded spring element supported at the cylinder or at a component part which is fixedly connected to the cylinder, the preloading force of this spring element being smaller than the closing force acting on the valve slide through the pressure in the first working chamber.

As a result of this construction, only slightly more than the differential force between the closing force acting on the valve slide and the force of the spring element acting in the opposite direction on the valve slide need be applied for canceling the locking of the piston. This differential force can be very small. It need only ensure that when valve actuation force is not applied the valve slide moves securely into its closed position and is held there to cancel the locking of the valve slide. This also facilitates an actuation of the release tappet.

The valve slide can be acted upon so as to be movable from its closed position into its open position by an actuation rod which is guided axially out of the cylinder. In so doing, the valve slide can be drivable by an actuator, but also indirectly or directly manually, so as to be movable out of its closed position into its open position.

Only a small installation space is required when the spring element is a helical compression spring that surrounds the valve slide or the actuation rod at a distance and which is supported by its one end at a structural component part which is fixedly connected to the cylinder and acts on the valve slide or the actuation rod with its other end.

Accordingly, the entire piston-cylinder unit can also be constructed with a small size.

Further, a helical compression spring is a simple and inexpensive component.

To allow actuation manually or by an actuator transverse to the longitudinal axis of the cylinder, the front side of the end of the valve slide or of the actuation rod, which end projects out of the cylinder, can be acted upon by the first arm of a two-armed swiveling lever which is swivelable around a pivot which extends transverse to the longitudinal axis of the cylinder and which is fixedly connected to the cylinder, which swiveling lever is acted upon by the spring element so as to operate the first arm against the front side of the valve slide or of the actuation rod, and its second arm can be acted upon by the valve actuation force.

In this regard, the spring element can be a tension spring supported at the cylinder or at a structural component part connected to the cylinder and, in a simple construction, is a garter spring surrounding the second arm of the lever arm and the component part connected to the cylinder.

The valve can be either a poppet valve or a gate valve.

One construction consists in that the valve is arranged in a valve body closing the cylinder in an end area.

A piston-cylinder unit of this type is advantageously applicable in an object support column such as a chair column or table column for vertical adjustment of the seat surface or table surface.

In another construction, the valve can be arranged in the piston.

A construction of this type can advantageously be used preferably for locking heavy hatches and covers, but also for other applications which require holding in different positions.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The lockable piston-cylinder units shown inFIGS. 1 to 3have a cylinder1in which a piston2,2′ is guided so as to be axially displaceable, the interior of the cylinder1which is filled with a pressurized gas being divided by piston2,2′ into a first working chamber3,3′ and a second working chamber4,4′.

A piston rod5,5′ is fixedly arranged at the piston2,2′ at one side. The piston rod5,5′ is guided through second working chamber4inFIG. 1and through second working chamber4′ inFIG. 3and is guided outward so as to be sealed through a guiding and sealing unit6.

A blocking valve8is arranged in piston2inFIGS. 1 and 2and in a valve body7closing the cylinder1at its end remote of the piston rod inFIG. 3. The blocking valve8has a cylindrical valve slide10displaceably arranged in a through-opening9formed coaxially in the piston2or in the valve body8.

The valve slide10has in its center region11a reduced diameter, while the two outer regions12,12′ have a larger diameter corresponding to the through-opening9.

The outer region12is surrounded by a first sealing ring18that seals the through-opening9from the region11of smaller diameter of the valve slide10to an actuation rod13. This seal is maintained in every axial position of the valve slide10.

Outer region12′ is surrounded by a second sealing ring19that seals the through-opening9from the region11of smaller diameter of the valve slide10to the first working chamber3,3′ in the closed neutral position shown in the drawing.

At its end facing the first working chamber3,3′, the valve slide10is permanently acted upon by the pressure in the first working chamber3,3′.

An actuation rod13that is guided so as to be displaceable coaxial to the valve slide10contacts and is supported at the front end of the valve slide10remote of the first working chamber3,3′ by its one end and contacts and is supported at a swiveling lever14swivelable around a pivot15at a distance from the pivot15by its other end.

In the embodiment example inFIGS. 1 and 2, the actuation rod13is displaceably guided through a coaxial passage24in the piston rod5, and in the embodiment example inFIG. 3through a coaxial passage24in a guide element25arranged at the valve body7.

In the non-actuation position shown in the drawing, the swiveling lever14contacts a stop16.

Engaging at the end region of the swiveling lever14opposite the pivot15is the core of a Bowden cable17which can be put into tension manually or by motor and can accordingly swivel the swiveling lever14so as to lift off from the stop16. Accordingly, the valve slide10is also displaced by a displacement20. At the end of the displacement20, the region11of smaller diameter of the valve slide10is in the open position, a position overlapping the second sealing ring19, so that the first working chamber3,3′ can flow around the second sealing ring19through the region11of smaller diameter. This is the open position of the valve slide10.

The region11of smaller diameter is then also configured to overlap with a connection opening21which is formed radially in the piston2or valve body7and which leads into the through-opening9.

InFIGS. 1 and 2, the connection opening21leads directly to the second working chamber4.

InFIG. 3, the connection opening21leads to an outwardly closed annular gap22between cylinder1and an outer cylinder23enclosing the cylinder at a distance. The annular gap22is connected to the second working chamber4′ at its end opposite the valve body7.

As a result of this swiveling movement of the swiveling lever14, the actuation rod13is displaced toward the blocking valve8and also displaces the valve slide10farther into the first working chamber3,3′.

Accordingly, in both embodiment examples, the first working chamber3,3′ is connected to the second working chamber4,4′ as a result of the valve slide10achieving the open position.

During assembly of the piston-cylinder unit, the actuation rod13is inserted into the passage24after installing the blocking valve8and filling the cylinder1with pressurized gas.

The arrangement of the swiveling lever14is then carried out. Because of the length of the actuation rod13, this actuation rod13must be displaced to a certain extent in opening direction so that the swiveling lever14can reach its installed position abutting the stop16. In so doing, the valve slide10is also displaced in the opening direction by the same amount against the pressure in the first working chamber3,3′, but only far enough that the region12′ of larger diameter is still enclosed by the second sealing ring19and the through-opening9accordingly remains closed. The valve slide10is now located in its closed neutral position. Since the valve slide10continues to be acted upon by the pressure in the first working chamber3,3′, it is forced by this pressure against the actuation rod13, and the actuation rod13in turn presses the swiveling lever14firmly in contact with the stop16so that regardless of manufacturing tolerances there is no play between the valve slide10and stop16which could cause rattling noise.

However, in contrast to the prior art, no additional component parts are required for this purpose; rather, only the pressure which is present anyway in the cylinder1is utilized.

The lockable piston-cylinder units shown inFIGS. 4 to 7have an outer cylinder23in which a cylinder1is coaxially arranged. Because of the different diameters, an annular gap22forming a flow path is formed between the annular cylinder23and cylinder1.

A piston2′ is arranged in the cylinder1so as to be axially displaceable and divides the cylinder1into a first working chamber3′ and a second working chamber4′.

A piston rod5′ which is connected by its one end to the piston2′ is guided through the second working chamber4′ and outward through guiding and sealing units6so as to be sealed.

In the end region of cylinder1near the guiding and sealing unit6, the second working chamber4′ is connected to the annular gap22via a radial opening26.

A valve body7is inserted into the end of the cylinder1opposite the guiding and sealing unit6, and the end of the valve body7projecting out of the cylinder1sealingly contacts the inner wall of the outer cylinder23.

A spacer27is located between the valve body7and the upper end of the outer cylinder23and is enclosed at its end opposite the valve body7by a bead of the end of the outer cylinder.

A stepped coaxial guide bore29is formed in the spacer27, the large step28thereof facing the valve body7. An actuation rod13is displaceably guided in the small step30of the guide bore29, one end of which actuation rod13projects outward from the guide bore29and can be acted upon by an axially inwardly directed valve actuation force.

A retaining washer31is arranged at the actuation rod13(FIG. 4). This retaining washer31facilitates correct and reliable assembly.

Alternatively, the actuation rod13has a radially protruding tab32with the same function (FIG. 5).

At its end directed toward the valve body7, the actuation rod13abuts a valve slide10of a blocking valve8, this valve slide10forming a closing member.

The valve slide10is displaceably arranged in an axially continuous through-opening9of the valve body7opening into the first working chamber3′ and has at its end facing the first working chamber3′ a flange-like widening33which can make contact in the moving-out direction at a second sealing ring19forming a valve seat arranged at the valve body7.

Inside the valve body7, the valve slide10has a region of smaller diameter11. The through-opening9in the region overlapped by the region11of smaller diameter is connected to the annular gap22by a radial connection opening21in the valve body7.

As shown inFIG. 6, at the region of the spacer27projecting out of the outer cylinder23a two-armed swiveling lever14is mounted so as to be swivelable around a pivot15extending transverse to the longitudinal axis34of the cylinder1.

The first arm35of the two-armed swiveling lever14contacts the outer front side of the actuation rod13, while the second arm36extends approximately parallel to the longitudinal axis34and has at its free end a connection piece37to which a valve actuation force can be applied transverse to the longitudinal axis34.

Using a preloaded garter spring39, which encircles the second arm36and a part38of the spacer27extending parallel to the longitudinal axis34, the first arm35contacts the actuation rod13under corresponding preloading and acts upon the valve slide10via the actuation rod13in lift-off direction of the flange-like widening33from the second sealing ring19.

As shown inFIGS. 4 and 5, the actuation rod13is surrounded in the region of the large step28of the guide bore29by a preloaded helical compression spring40which is supported by its one end at the shoulder between the large step28and the small step30of the guide bore29and by its other end at the flange-like widening41of the actuation rod13and acts upon the valve slide10via the actuation rod13in lift-off direction of the flange-like widening33from the second sealing ring19without opening the valve.

The two working chambers3′ and4′ are filled with a pressurized gas. Gas pressure of the first working chamber3′ also acts on the flange-like widening33of the valve slide10and presses it against the second sealing ring19. In this way, a flow passage from the first working chamber3′ through the through-opening9, radial bore21, annular gap22and radial opening26to the second working chamber4is held closed.

The force of the garter spring39(FIG. 6) or helical compression spring40(FIG. 7) acting on the actuation rod13in valve closing direction is smaller than the force exerted on the valve slide10in valve closing direction by the gas pressure in the first working chamber3′.

The flange-like widening13is accordingly held in contact at the second sealing ring19, and the valve passage9is therefore held closed.

The valve slide10is not displaced and the valve passage is not opened until the actuation rod13is acted upon in valve opening direction by an additional valve actuation force which, added to the force acting on the actuation rod13by the garter spring39or helical compression spring40, is greater than the force acting upon the valve slide10in closing direction.

The piston2and, along with it, the piston rod5can accordingly be displaced in the cylinder1.

When the valve actuation force ceases to be applied, the valve passage is closed again and the piston2is locked in the position occupied by it.

The example inFIG. 7has substantially the same construction as the embodiment examples inFIGS. 4 to 6and is correspondingly provided with the same reference numerals.

In contrast toFIGS. 4 to 6, the blocking valve8is not arranged in a valve body, but rather in the piston2.

When the valve passage is open, the first working chamber3′ is connected to the second working chamber4′ via through-opening9and radial connection opening21.

The actuation rod13is guided through the guide bore29in the piston rod5.