Gas spring with separating piston, method for manufacturing the gas spring

Abstract

Gas spring (100) comprising a. a pressure chamber filled with a gas in a pressure tube (110); b. a working piston (120) which is movable in the pressure chamber along a stroke axis (HA), c. a piston rod (140) attached to the working piston (120) and guided out of the pressure tube (110) along the stroke axis (HA) by a guide-sealing device (130), and d. a separating piston (150) arranged on the side of the working piston (120) facing away from the guide-sealing device (130) and displaceable along the stroke axis (HA) relative to the pressure tube (110) and relative to the working piston (120), e. wherein the separating piston (150) divides the pressure chamber gas-tight into a working chamber (112) containing the working piston (120) and a support chamber (113), characterized in that f. the gas spring (100) comprises a holding device (160), g. wherein the holding device (160) holds the separating piston (150) in a fixed position on the pressure tube (110) as long as a positive pressure difference between a support pressure of the gas in the support chamber (113) and a working pressure of the gas in the working chamber (112) is less than a predefined switching differential, and h. wherein the holding device (160) is designed so that a switching force caused by the pressure difference acting on the separating piston (150) releases the separating piston (150) from the pressure tube (110) as soon as the pressure difference reaches the switching difference, so that the separating piston (150) is movable onto the working piston (120).

Description

Technical field

[0001] The invention relates to a gas spring comprising a gas-filled pressure chamber in a pressure tube, a working piston displaceable in the pressure chamber along a stroke axis, a piston rod attached to the working piston and guided out of the pressure tube along the stroke axis by a guide-seal device, and a separating piston arranged on the side of the working piston facing away from the guide-seal device and displaceable along the stroke axis. The separating piston divides the pressure chamber gas-tight into a working chamber containing the working piston and a support chamber.

[0002] The invention also relates to methods for manufacturing the gas spring. State of the art

[0003] Gas springs known from the prior art are used, for example, to support components such as flaps, especially vehicle flaps, and height-adjustable furniture parts against their own weight. If the gas pressure in such a gas spring decreases, for example due to a leak, the spring force of the gas spring diminishes and, below a certain gas pressure, is no longer sufficient to support the component. As a result, the component can fall and injure people or damage objects.

[0004] German patent application DE 31 37 193 C2 describes a gas spring which, as an insertion safety device, features a movable partition located inside the cylinder and sealed against the cylinder's inner wall. If the pressure in the gas chamber of the gas spring, divided by the piston, drops, the partition moves towards the piston until the pressure on both sides of the partition is equalized. When the piston rod of the gas spring is inserted into the cylinder, the piston comes into contact with the partition, so that with further insertion of the piston rod, the insertion force increases significantly, thus preventing an uncontrolled drop of a component supported by the gas spring.

[0005] A disadvantage of the solution described in DE 31 37 193 C2 is that pressure fluctuations occurring in the gas chamber during normal operation, for example due to the insertion and withdrawal of the piston rod, cause movement of the partition. This can lead to undesirable noises, or a partition seal between the partition and the cylinder can wear out, thus limiting the service life of the gas spring. Technical task

[0006] The object of the invention is to create a cost-effective, easy-to-manufacture, and durable gas spring with a locking mechanism in case of pressure loss, which does not impair the function of the gas spring. Technical solution

[0007] The present invention provides a gas spring according to claim 1, which solves the technical problem. The problem is also solved by the methods for manufacturing the gas spring according to claims 14 and 15. Advantageous embodiments are the subject of the dependent claims.

[0008] A gas spring according to the invention comprises a pressure chamber filled with gas within a pressure tube, which is, for example, hollow and cylindrical in shape. The gas is, for example, an inert gas, in particular nitrogen.

[0009] The gas spring comprises a working piston that is movable along a stroke axis within the pressure chamber and a piston rod attached to the working piston. This piston rod extends from the pressure tube along the stroke axis via a guide-seal device. The guide-seal device guides the piston rod along the stroke axis and seals the pressure chamber gas-tight.

[0010] The gas spring comprises a separating piston arranged on the side of the working piston facing away from the guide-seal device and displaceable along the stroke axis. The separating piston divides the pressure chamber gas-tight into a working chamber containing the working piston and a support chamber. The working chamber is located between the guide-seal device and the separating piston, and the support chamber is located between the separating piston and the base of the pressure tube. The separating piston fulfills the same function as the partition of the gas spring according to DE 31 37 193 C2 and thus forms an insertion lock in the event of pressure loss. The separating piston is, for example, essentially cylindrical in shape and / or arranged coaxially with the stroke axis.

[0011] The gas spring comprises a holding device, the holding device holding the separating piston in a fixed position on the pressure tube as long as the pressure difference between a support pressure of the gas in the support chamber and a working pressure of the gas in the working chamber is less than a predefined switching differential. The support pressure is, for example, 100 bar to 200 bar, particularly approximately 150 bar. During normal operation of the gas spring, the working pressure deviates only slightly from the support pressure due to the extension or retraction of the piston rod, for example by 1 bar to 10 bar. The switching differential is, for example, 10 bar to 20 bar, particularly approximately 15 bar.

[0012] The holding device is designed so that a switching force caused by the pressure difference acting on the separating piston releases the separating piston from the pressure tube as soon as the pressure difference reaches the switching difference. Beneficial effects

[0013] The retaining device ensures that the separating piston does not move during normal operation of the gas spring. Therefore, the service life and function of the gas spring are not affected by the insertion lock.

[0014] Because the separating piston can detach from the pressure tube as soon as the pressure differential reaches the switching differential, it is ensured that the separating piston moves towards the working piston in the event of a pressure loss in the working chamber. As soon as the separating piston comes into contact with the working piston, the pressure differential causes the separating piston to exert a force on the working piston, which inhibits further insertion of the piston rod into the pressure tube.

[0015] The surface area of ​​the separating piston, on which the pressure differential acts, can be significantly larger than the surface area of ​​the piston rod, which defines the spring force of the gas spring during normal operation. Thus, even when the support pressure resulting from the displacement of the separating piston towards the working piston is lower than the normal working pressure of the gas spring, the separating piston can exert a force on the working piston that corresponds to the normal spring force of the gas spring. Consequently, even in the event of a pressure loss, particularly a complete loss, in the working chamber, the gas spring can prevent the component supported by the gas spring from falling.

[0016] Typically, a pressure loss in a gas spring is caused by a leak in the guide-seal device. By positioning the separating piston on the side of the working piston facing away from the guide-seal device, it is ensured that the support chamber does not experience a pressure loss even when the separating piston moves towards the working piston. Description of the execution types

[0017] The holding device preferably comprises a detent receptacle attached to the pressure tube and a detent projection attached to the separating piston, wherein the detent projection is engaged in the detent receptacle as long as the pressure difference is smaller than the switching difference, and wherein the detent projection is designed to disengage from the detent receptacle by the switching force, preferably reversibly, as soon as the pressure difference reaches the switching difference.

[0018] A latching connection allows for a simple and precisely defined switching differential. Furthermore, the latching connection can be designed to be reversible, enabling the latching element to be re-engaged into the latching recess after a pressure loss, allowing the gas spring to be refilled and resealed, and thus enabling its continued use after the pressure loss.

[0019] The locking mechanism is preferably positively engaged, ideally between two circumferential grooves of the pressure tube. A positive-locking attachment ensures a particularly secure hold of the locking mechanism on the pressure tube. The two circumferential grooves make this positive-locking attachment particularly easy to achieve.

[0020] The detent receptacle preferably comprises a retaining disc, preferably having at least one slot for receiving the detent element. This allows the detent receptacle to be manufactured particularly easily.

[0021] The detent projection preferably comprises a detent pin aligned along the stroke axis, preferably tapering conically in sections. Such a detent pin can be easily manufactured and inserted into the detent receptacle, where it securely engages.

[0022] The holding device preferably includes a predetermined breaking point in the connection between the separating piston and the pressure tube, designed to break under the switching force as soon as the pressure differential reaches the switching differential. The predetermined breaking point preferably comprises an adhesive bond, a welded joint, or a soldered joint connecting the separating piston to the pressure tube. The predetermined breaking point allows for particularly easy implementation of a precisely defined switching differential.

[0023] The holding device preferably comprises a clamping connection and / or a magnetic connection that connects the separating piston to the pressure tube and is designed to release under the switching force as soon as the pressure differential reaches the switching differential. A clamping connection or magnetic connection can be designed particularly easily to be reversibly detachable, so that the gas spring can continue to be used after a pressure loss.

[0024] The separating piston preferably comprises a sealing element, preferably a lip seal, which provides a gas-tight seal between the separating piston and the pressure tube, the sealing element forming a gas-permeable check valve from the working chamber to the support chamber. When the working chamber is filled with gas, the gas can thus simultaneously fill the support chamber via the check valve. Consequently, the gas spring can be filled particularly quickly and easily, and a separate filling valve for filling the support chamber is not required. Since, both during normal operation and in the event of a pressure loss in the working chamber, the support pressure in the support chamber is at least as high as the working pressure in the working chamber, the check valve remains closed in both cases and therefore does not impair either the normal operation of the gas spring or the insertion safety mechanism provided by the separating piston.

[0025] The separating piston can include a check valve separate from the sealing element, which is gas-permeable from the working chamber to the support chamber and can be designed, for example, as described in the publication DE 31 37 193 C2.

[0026] The support chamber can be gas-conducted, for example through at least one opening, to an annular chamber located between the pressure tube and an outer tube that encloses the pressure tube around its stroke axis. The opening is located, for example, in a shell wall of the pressure tube near its base or in the base itself. This allows a sufficiently large gas volume to be provided in the support chamber and the annular chamber, even with a short gas spring length along the stroke axis, to exert a force sufficient on the separating piston and the working piston to ensure reliable insertion protection.

[0027] The separating piston preferably comprises a conduit, more preferably a piston groove, a channel and / or a porous area that connects the support chamber to the working chamber via a gas-conducting connection. Additionally or alternatively, the pressure tube can have at least one wall groove on an inner side of the pressure tube's outer wall, which connects the support chamber to the working chamber via a gas-conducting connection when the separating piston is moved from a starting position, in which the separating piston is held by the holding device, along the stroke axis towards the guide-sealing device.

[0028] Due to the conduit and / or the groove in the wall, the gas spring is not blocked by the support pressure acting on the separating piston after a pressure loss in the working chamber. Instead, the piston rod, along with the working piston and the separating piston, can be slowly pushed in, allowing gas to escape from the support chamber into the working chamber through the conduit. This enables, for example, a gas spring-assisted flap on a vehicle to be manually closed, allowing the vehicle to be driven to a workshop for replacement or repair of the gas spring.

[0029] Preferably, the flow resistance of the line for the gas is chosen to be so large or the cross-sectional area of ​​the line so small that the amount of gas escaping from the support chamber through the line in the event of a pressure loss in the working chamber does not impair the function of the insertion safety device.

[0030] The separating piston preferably includes a sealing element that gas-tightly closes the line as long as the separating piston is held stationary against the pressure tube, wherein the sealing element is designed to release the line as soon as the separating piston is moved relative to the pressure tube. Particularly in the case of a slow pressure loss in the working chamber, gas escaping through the line from the support chamber into the working chamber could prevent the pressure differential from reaching the switching differential, even though the operating pressure in the working chamber is no longer sufficient for the safe operation of the gas spring. This risk is eliminated by the sealing element.

[0031] The closure element can, for example, comprise a valve, in particular a crash valve, which is closed as long as the separating piston is in its initial position, and has a switching element that opens the valve as soon as the separating piston comes into contact with the working piston by a displacement of the separating piston along the stroke axis towards the guide-seal device. The switching element can, for example, comprise a pin, a needle and / or a cannula that pierces a diaphragm of the valve as soon as the separating piston comes into contact with the working piston.

[0032] The sealing element can, for example, be attached to the pressure pipe in such a way that it seals the pipe against the separating piston as long as the separating piston is in its initial position. Additionally, the sealing element can be detachably attached to the separating piston, for example, by means of a tear-off mechanism, to ensure a reliable seal of the pipe. Furthermore, the sealing element can include a sealing element for closing the pipe.

[0033] The wall groove runs, for example, along the stroke axis and / or between the starting position of the separating piston, in particular the sealing element of the separating piston, and the guide-seal device of the gas spring. In embodiments of the gas spring with the wall groove, the sealing element of the separating piston is preferably designed as a rectangular ring, because a rectangular ring penetrates the wall groove less deeply than, for example, an O-ring or a lip seal. The rectangular ring thus reduces the risk of the sealing element clogging the wall groove.

[0034] The gas spring preferably includes a guide device for guiding the separating piston in the pressure chamber along the stroke axis. The guide device prevents the separating piston from tilting in the pressure tube when it is moved towards the working piston, which could impair the function of the insertion safety device.

[0035] The guide device can, for example, comprise a guide sleeve, in particular a hollow cylindrical one, which is attached to the separating piston and rests against an inside of the pressure tube.

[0036] The holding device preferably comprises a cartridge arranged in the pressure chamber and attached to the pressure tube, wherein the cartridge holds the separating piston and at least partially encloses the support chamber. The cartridge allows for particularly simple manufacturing of the gas spring because the separating piston can be pre-assembled separately from the gas spring on the cartridge and then only needs to be inserted into the pressure chamber and secured there. The cartridge is, for example, essentially hollow-cylindrical in shape, arranged coaxially to the stroke axis and / or positioned against an inner surface of the pressure tube.

[0037] The cartridge can be designed, for example, so that when the separating piston is correctly positioned in the pressure chamber, it rests against the bottom of the pressure tube. This makes it particularly easy to position the separating piston in the pressure chamber and to attach the cartridge to the pressure tube in the correct position.

[0038] The cartridge is preferably positively attached to the pressure tube. This allows the cartridge to be held easily and securely on the pressure tube. The positive attachment can be achieved, for example, by at least one deformation of the pressure tube towards the cartridge, in particular by at least one circumferential groove in the pressure tube around the stroke axis.

[0039] The cartridge is preferably held between two beads of the pressure tube circumferentially around the stroke axis or between a bead of the pressure tube circumferentially around the stroke axis and a base of the pressure tube.

[0040] A method according to the invention for manufacturing a gas spring according to the invention, wherein the separating piston of the gas spring comprises a check valve permeable to gas from the working chamber to the support chamber, includes simultaneously filling the working chamber and the support chamber with gas through the check valve. In this way, the gas spring can be manufactured particularly easily and quickly.

[0041] A method according to the invention for manufacturing a gas spring according to the invention, wherein the holding device of the gas spring comprises a cartridge arranged in the pressure chamber and attached to the pressure tube, wherein the cartridge holds the separating piston and at least partially encloses the support chamber, comprises the steps: a. Pre-assembling the separating piston on the cartridge, b. Inserting the cartridge into the pressure chamber after pre-assembly and c. Attaching the cartridge to the pressure tube after insertion.

[0042] This makes manufacturing the gas spring particularly easy and quick. Brief description of the drawings

[0043] Further advantages, objectives and features of the invention are explained with reference to the following description and accompanying drawings, in which exemplary objects according to the invention are shown. Fig. Figure 1 shows a schematic longitudinal section of a gas spring according to the invention. Fig. Figure 2 shows a schematic top view of a latching device of a holding device of a gas spring according to the invention. Fig. Figure 3 shows a schematic longitudinal section of another gas spring according to the invention. Fig. 1

[0044] Fig. Figure 1 shows a schematic longitudinal section along the stroke axis HA of a gas spring 100 according to the invention.

[0045] The gas spring 100 shown comprises a gas-filled pressure chamber in a pressure tube 110, a working piston 120 displaceable in the pressure chamber along the stroke axis HA, a piston rod 140 attached to the working piston 120 and guided out of the pressure tube 110 along the stroke axis HA by a guide-seal device 130, and a separating piston 150 arranged on the side of the working piston 120 facing away from the guide-seal device 130 and displaceable along the stroke axis HA. The separating piston 150 is thus arranged between the working piston 120 and a base 115 of the pressure tube 110.

[0046] The separating piston 150 shown divides the pressure chamber gas-tight into a working chamber 112 containing the working piston 120 and a support chamber 113. The separating piston 150 comprises a sealing element 151, preferably a lip seal, which seals the separating piston 150 gas-tight to the pressure tube 110, wherein the sealing element 151 preferably forms a check valve that allows gas to pass from the working chamber 112 to the support chamber 113.

[0047] The gas spring 100 shown comprises a holding device 160, wherein the holding device 160 holds the separating piston 150 in a fixed position on the pressure tube 110 as long as the pressure difference between a support pressure of the gas in the support chamber 113 and a working pressure of the gas in the working chamber 112 is less than a predefined switching differential. The holding device 160 is designed such that a switching force caused by the pressure differential acting on the separating piston 150 releases the separating piston 150 from the pressure tube 110 as soon as the pressure differential reaches the switching differential.

[0048] The holding device 160 shown comprises a detent receptacle 161 attached to the pressure tube 110 and a detent projection 162 attached to the separating piston 150, wherein the detent projection 162 is engaged in the detent receptacle 161 as long as the pressure difference is less than the switching differential, and wherein the detent projection 162 is designed to disengage from the detent receptacle 161 by the switching force, preferably reversibly, as soon as the pressure difference reaches the switching differential.

[0049] The detent receptacle 161 shown is positively locked between two beads 114 of the pressure tube 110 which circumferentially surround the lifting axis HA and is attached to the pressure tube 110, wherein the detent receptacle 161 is designed as a retaining disc.

[0050] The detent projection 162 shown is designed as a detent pin aligned along the lifting axis HA, tapering conically in sections. Fig. 2

[0051] Fig. Figure 2 shows a schematic top view along the stroke axis of a detent receptacle 161 of a holding device 160 of a gas spring 100 according to the invention. The detent receptacle 161 shown is designed as a retaining disc which, for example, has two crossed slots 163 for receiving the detent projection 162. Fig. 3

[0052] Fig. Figure 3 shows a schematic longitudinal section along the stroke axis HA of another gas spring 100 according to the invention.

[0053] The in Fig. The gas spring shown in Figure 3 (100) differs from the one in Figure 3. Fig. 1 gas spring shown, wherein the holding device 160 comprises a cartridge 164 arranged in the pressure chamber and attached to the pressure tube 110, which holds the separating piston 150 and partially encloses the support chamber 113.

[0054] The cartridge 164 shown rests against the base 115 of the pressure tube 110 and is positively locked to the pressure tube 110 by a groove 114 circumferential around the stroke axis HA of the pressure tube 110.

[0055] The holding device 160 shown comprises a detent receptacle 161 fixed in the cartridge 164 and a detent projection 162 attached to the separating piston 150, wherein the detent projection 162 is engaged in the detent receptacle 161 as long as the pressure difference is less than the switching differential, and wherein the detent projection 162 is designed to disengage from the detent receptacle 161 by the switching force, preferably reversibly, as soon as the pressure difference reaches the switching differential. List of reference symbols 100 gas springs 110 pressure pipe 112 Chamber of Labour 113 Support chamber 114 groove 115 floor 120 working pistons 130 Guide-seal device 140 piston rod 150 separating pistons 151 Sealing element 160 Holding device 161 Rastaufnahme 162 Rastvorsprung 163 slots 164 cartridges HA lifting axle

Claims

[1] Gas spring (100) comprising a. a pressure chamber filled with a gas in a pressure tube (110); b. a working piston (120) which is movable in the pressure chamber along a stroke axis (HA), c. a piston rod (140) attached to the working piston (120) and guided out of the pressure tube (110) along the stroke axis (HA) by a guide-sealing device (130), and d. a separating piston (150) arranged on the side of the working piston (120) facing away from the guide-sealing device (130) and displaceable along the stroke axis (HA) relative to the pressure tube (110) and relative to the working piston (120), e. wherein the separating piston (150) divides the pressure chamber gas-tight into a working chamber (112) containing the working piston (120) and a support chamber (113), characterized by , that f. the gas spring (100) comprises a holding device (160), g. wherein the holding device (160) holds the separating piston (150) in a fixed position on the pressure tube (110) as long as a positive pressure difference between a support pressure of the gas in the support chamber (113) and a working pressure of the gas in the working chamber (112) is less than a predefined switching differential, and h. wherein the holding device (160) is designed so that a switching force caused by the pressure difference acting on the separating piston (150) releases the separating piston (150) from the pressure tube (110) as soon as the pressure difference reaches the switching difference, so that the separating piston (150) is movable onto the working piston (120). [2] Gas spring (100) according to claim 1, a. wherein the holding device (160) comprises a detent receptacle (161) attached to the pressure tube (110) and a detent projection (162) attached to the separating piston (150), b. wherein the detent projection (162) is engaged in the detent receptacle (161) as long as the pressure difference is less than the switching difference, and c. wherein the detent projection (162) is designed to disengage from the detent receptacle (161) by the switching force, preferably reversibly, as soon as the pressure difference reaches the switching difference. [3] Gas spring (100) according to claim 2, a. wherein the locking receptacle (161) is positively locked, preferably between two beads (114) of the pressure tube (110) circumferential around the stroke axis (HA), and / or b. wherein the detent receptacle (161) comprises a retaining disk which has at least one slot (163) for receiving the detent projection (162). [4] Gas spring (100) according to claim 2 or 3, wherein the detent projection (162) comprises a detent pin aligned along the stroke axis (HA), preferably tapering in sections. [5] Gas spring (100) according to one of claims 1 to 4, a. wherein the holding device (160) comprises a predetermined breaking point in a connection between the separating piston (150) and the pressure tube (110), which is designed to break under the switching force as soon as the pressure difference reaches the switching differential, b. wherein the predetermined breaking point preferably comprises an adhesive joint, a welded joint or a soldered joint connecting the separating piston (150) to the pressure tube (110). [6] Gas spring (100) according to any one of claims 1 to 5, wherein the holding device (160) comprises a clamping connection and / or a magnetic connection which connects the separating piston (150) to the pressure tube (110) and is designed to release itself by the switching force as soon as the pressure difference reaches the switching differential. [7] Gas spring (100) according to any one of claims 1 to 6, a. wherein the separating piston (150) comprises a sealing element (151), preferably a lip seal, which seals the separating piston (150) to the pressure tube (110) in a gas-tight manner, b. wherein the sealing element (151) forms a gas-permeable check valve from the working chamber (112) to the support chamber (113). [8] Gas spring (100) according to any one of claims 1 to 7, wherein the separating piston (150) comprises a conduit, preferably a piston groove, a channel and / or a porous area, which connects the support chamber (113) to the working chamber (112) in a gas-conducting manner. [9] Gas spring (100) according to one of claim 8, a. wherein the separating piston (150) comprises a sealing element that seals the line gas-tight as long as the separating piston (150) is held stationary on the pressure tube (110), b. wherein the closure element is designed to release the line as soon as the separating piston (150) is moved relative to the pressure tube (110). [10] Gas spring (100) according to one of claims 1 to 9, wherein the pressure tube (110) has at least one wall groove on an inside of a shell wall of the pressure tube (110) which connects the support chamber (113) to the working chamber (112) in a gas-conducting manner when the separating piston (150) is displaced from a starting position in which the separating piston (150) is held by the holding device (160) along the stroke axis (HA) towards the guide-sealing device (130). [11] Gas spring (100) according to any one of claims 1 to 10, wherein the gas spring (100) comprises a guide device for guiding the separating piston (100) in the pressure chamber along the stroke axis (HA). [12] Gas spring (100) according to any one of claims 1 to 11, a. wherein the holding device (160) comprises a cartridge (164) arranged in the pressure chamber and attached to the pressure tube (110), b. wherein the cartridge (164) holds the separating piston (150) and at least partially encloses the support chamber (113). [13] Gas spring (100) according to claim 12, wherein the cartridge (164) is positively attached to the pressure tube (110) by at least one deformation of the pressure tube (110) towards the cartridge (164), preferably by at least one groove (114) circumferential around the stroke axis (HA). [14] Method for manufacturing a gas spring (100) according to any one of claims 1 to 13, wherein the separating piston (150) of the gas spring (100) comprises a check valve permeable to gas from the working chamber (112) to the support chamber (113), the method comprising simultaneously filling the working chamber (112) and the support chamber (113) with gas through the check valve. [15] Method for manufacturing a gas spring (100) according to any one of claims 1 to 13, wherein the holding device (160) of the gas spring (100) comprises a cartridge (164) arranged in the pressure chamber and attached to the pressure tube (110), wherein the cartridge (164) holds the separating piston (150) and at least partially encloses the support chamber (113), the method comprising the steps: a. Pre-assembling the separating piston (150) on the cartridge (164), b. Inserting the cartridge (164) into the pressure chamber after pre-assembly and c. Attaching the cartridge (164) to the pressure tube (110) after insertion.

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