Gas spring with a pressurized lubricant reservoir

Abstract

Gas spring (1) comprising: - a housing (10) with a longitudinal axis (15) and a cylindrical bore (17) extending in the longitudinal axis (15) with a wall (19), and - a piston (30) which is displaceable in the cylinder bore (17) along the longitudinal axis (15), - wherein the piston (30) has an outer surface (31) comprising a lateral surface (32), a pressure side (33) and an end face (34), - wherein a gas compression chamber (20) is formed between the piston (30) and the housing (10), - wherein the piston (30) has at least one lubricant reservoir (40) for a lubricant (4), - wherein at least one lubricant reservoir (40) is connected to the outside (31) by at least one lubricant line (42), - wherein the at least one lubricant reservoir (40) has at least one pre-tensioning means by which the lubricant (4) can be pressurized, and - wherein the at least one lubricant reservoir (40) comprises a movable lubricant piston (50) which can be pressurized by means of the preloading means, characterized in that - that the preloading device is a compression spring (52), - that at least one lubricant reservoir (40) has an insertion opening (46), wherein the insertion opening (46) is arranged on the pressure side (33) and is closed with a cover (48), and - that the compression spring (52) is supported on the one hand by the lubricant piston (50) and on the other hand by the cover (48), so that the spring force of the compression spring (52) pressurizes the lubricant (4) stored in the lubricant reservoir.

Description

[0001] The present invention relates to a gas spring having the features of claim 1 with improved properties and an extended service life due to effective lubrication of a piston.

[0002] Gas springs are known in various designs from the prior art and typically comprise a housing with a cylinder bore and a longitudinal axis. A piston is movably arranged in the cylinder bore along the longitudinal axis. The piston forms a gas compression chamber in the cylinder bore with the housing, in which a gas, preferably a gas with a large molecular size, for example nitrogen, is enclosed. Such gas springs are well known from the prior art and are used in a variety of ways in tools and machines. They are characterized by their high reliability. It has been shown that the service life is reduced due to inadequate lubrication or a lack of continuous relubrication of the piston in the cylinder bore.In particular, it has been shown that due to insufficient lubrication of the piston in the cylinder bore, the seals used wear out and therefore gas can escape from the gas compression chamber.

[0003] FR 2 672 355 A1 discloses a gas spring having the features of the preamble of claim 1. Further gas springs are disclosed in DE 10 2011 119 011 A1, US 3 204 536 A, DE 26 08 441 B2, US 5 339 932 A, DE 33 18 840 C2, US 4 583 722 A, and US 5 318 281 A.

[0004] It is therefore the object of the present invention to provide a gas spring that features improved lubrication of the piston in the cylinder bore of the housing and is cost-effective to manufacture. Furthermore, the gas spring according to the invention should have an unchanged external geometry compared to conventional gas springs, allowing gas springs to be replaced with the improved gas spring according to the invention in the event of wear or a defect, without requiring additional structural modifications to the tool or machine.

[0005] According to the invention, these objects are achieved by a gas pressure spring having the features of claim 1.

[0006] Advantageous embodiments and further developments of the invention are specified in the appended claims.

[0007] The gas spring according to the invention comprises a housing with a longitudinal axis and a cylinder bore extending along the longitudinal axis, having a wall, and a piston that is displaceable in the cylinder bore along the longitudinal axis. The piston has an outer side comprising a circumferential surface, a pressure side, and an end face, with a gas compression chamber formed between the piston and the housing. The gas compression chamber is thus enclosed by the housing and the piston, or rather its pressure side, with the circumferential surface of the piston interacting with the wall of the cylinder bore and providing a gas-tight sliding bearing for the piston in the cylinder bore.Furthermore, the piston comprises at least one lubricant reservoir for a lubricant, wherein the at least one lubricant reservoir is connected to the outside of the piston by at least one lubricant line with at least one lubricant opening, and wherein the at least one lubricant reservoir has at least one preloading means by which the lubricant can be pressurized. The preloading means applies pressure to the lubricant in the at least one lubricant reservoir and the at least one lubricant line, thus displacing the lubricant from the at least one lubricant reservoir by means of the at least one lubricant line. The lubricant emerging from the lubricant opening ensures that the surfaces adjacent to the lubricant opening are wetted with the lubricant.The lubricant can be a viscous medium, for example an oil or a grease, which has a sufficiently high viscosity in the permissible temperature range of the gas spring.

[0008] According to the invention, the at least one lubricant reservoir comprises a movable lubricant piston. Furthermore, according to the invention, the preloading means, by means of the lubricant piston, applies pressure, preferably an overpressure, to the lubricant stored in the at least one lubricant reservoir. The lubricant piston is further preferably designed to completely displace the lubricant from the lubricant reservoir in order to ensure efficient utilization of the lubricant stored in the lubricant reservoir.

[0009] According to the invention, the preloading means is a compression spring, which enables constant pressure to be applied to the lubricant stored in the lubricant reservoir. Compression springs are both cost-effective and particularly reliable.

[0010] Furthermore, it has proven advantageous if the at least one lubricant reservoir is arranged along an axis, in particular along an axis parallel to the longitudinal axis of the housing. The lubricant reservoir can have any shape, for example, a cylindrical, polygonal, or elliptical shape. Particularly preferably, the lubricant reservoir has a constant cross-section along the axis, which allows a lubricant piston to dispense the lubricant stored in the lubricant reservoir in a fluid-tight manner.

[0011] The invention provides that the at least one lubricant reservoir has an insertion opening on the pressure side of the piston. The insertion opening forms physical access to the lubricant reservoir in the piston and, during the manufacture of the gas spring according to the invention, enables the insertion of the preloading means into the lubricant reservoir. It is further particularly preferred if a cross-sectional area of ​​the insertion opening corresponds to at least one cross-sectional area of ​​the lubricant reservoir, so that the preloading means, in particular the lubricant piston and the compression spring, can be inserted into the lubricant reservoir through the insertion opening. Furthermore, the lubricant can be introduced into the lubricant reservoir through the insertion opening after or before the preloading means is inserted into the lubricant reservoir.

[0012] According to the invention, the insertion opening is arranged on the pressure side of the piston and closed with a pressure-tight cover. The arrangement of the cover on the pressure side of the piston does not restrict the fastening of the component to be actuated on the front side of the piston, particularly when replacing a conventional gas spring with a gas spring according to the invention.

[0013] Advantageously, the at least one lubricant line opens into the outer surface between the pressure side and the end face. Furthermore, the piston can be provided with a radial groove in the area of ​​the lubricant opening, which allows the lubricant to be distributed over the circumference of the piston. The lubricant displaced from the lubricant reservoir is thus guided directly into the area between the outer surface of the piston and the wall of the cylinder bore of the housing, thus reaching the areas requiring lubrication.

[0014] Furthermore, it is particularly advantageous if at least one piston seal is arranged between the lubricant opening and the pressure side of the piston, sealing the gas compression chamber on the piston side and the cylinder wall in the area of ​​the piston. Furthermore, the piston seal prevents the gas pressure of the gas compression chamber from acting on the lubricant stored in the lubricant reservoir. The lubricant in the lubricant reservoir is thus not exposed to a pressure change when the gas spring is actuated, which could potentially cause lubricant to be forced back into the lubricant reservoir or leak out in an uncontrolled manner.

[0015] Furthermore, it is further advantageous if a lubricant seal is provided between the end face and the lubricant opening on the lateral surface, which prevents uncontrolled leakage of the lubricant.

[0016] Furthermore, it is advantageous if a guide ring is provided between the pressure side and the end face on the outer surface, which ensures concentric, sliding-bearing guidance of the piston in the cylinder bore. The guide ring can be formed in one or more parts and can be wrapped around the piston as a band.

[0017] In particular, it has proven advantageous if a lubricant-absorbent lubricating film body is arranged on the outside of the piston and is in contact with the wall. The lubricant-absorbent lubricating film body can preferably be made of a material or a material mixture that is capable of transporting the lubricant using the capillary effect. Suitable materials include felt or fleece, for example. The lubricating film body can store the lubricant and distributes it evenly over the wall of the housing, thereby ensuring, in particular, uniform wetting of the wall over the entire circumference. Furthermore, the lubricating film body absorbs excess lubricant and thus contributes to the effective and economical use of lubricant, whereby the lubricant stored in the lubricant reservoir is sufficient for a long time and protects the gas spring according to the invention from wear.

[0018] The lubricating film body is preferably arranged in a recess, with the at least one lubricant line particularly preferably opening into the recess. The recess can be designed such that it contributes volume-wise to the storage of the lubricant and impregnates the lubricating film body. More preferably, the recess is a radial groove, which even more preferably extends over the entire circumference of the lateral surface.

[0019] A further advantageous embodiment of the present invention provides that at least one filling line is provided, and that the at least one filling line opens into the at least one lubricant line or the at least one lubricant reservoir. Particularly preferably, the lubricant can be refilled from the end face of the piston into the lubricant reservoir through the filling line, whereby the service life of a gas spring according to the invention can be extended many times over by refilling with additional lubricant. When refilling the lubricant, the preloading means, for example the piston and the compression spring, are returned to their original starting position in the lubricant reservoir, and the refilled lubricant is pressurized.

[0020] It is particularly advantageous if the filler opening of the filler line is located on the end face of the piston or on a tappet mounted on the piston, thus ensuring easy handling when refilling the lubricant. It is particularly preferred if the filler opening is closed with a valve.

[0021] Furthermore, it is advantageous if the cylinder bore has an undercut at one end of the cylinder head. Excess lubricant, old and / or contaminated lubricant, and its components can accumulate in the undercut without affecting the tribological system between the wall and the piston. Furthermore, the undercut can offer both manufacturing and design advantages, for example, in reducing stress peaks.

[0022] A further advantageous embodiment of the present invention provides that the housing has at least one vent hole. It is particularly preferred if the at least one vent hole is provided to remove excess lubricant, as well as old and / or contaminated lubricant, from the cylinder bore, in particular from the undercut.

[0023] It is advantageous if the gas compression chamber is filled with nitrogen. Nitrogen is a cost-effective and safe gas that does not react with the materials used in the gas spring or with the lubricant.

[0024] A further preferred embodiment according to the invention provides that the cylinder bore or the housing is closed with a cover or with a tank plate.

[0025] Below, three exemplary embodiments of a gas spring according to the invention are explained in detail with reference to the accompanying figures. They show: Fig. 1: a sectional view of a first embodiment of a gas pressure spring according to the invention with a lubricant reservoir arranged in the piston, in which a lubricant is pressurized by at least one preloading means, Fig. 2: a sectional view of a second embodiment of the invention, Fig. 3: a sectional view of a third embodiment of the invention.

[0026] The following are based on the Fig. 1, Fig. 2 and Fig. 3 three preferred embodiments of a gas pressure spring 1 according to the invention are described in detail, wherein functionally identical parts are provided with the same reference numerals.

[0027] Fig. 1 shows a sectional view of a first exemplary embodiment of a gas spring 1 according to the invention. The gas spring 1 has a housing 10 and a piston 30 and can be further closed by a cover (not shown). The cover can be formed, for example, by a housing cover or a tank plate. In the exemplary embodiment shown, the housing 10 is a substantially rotationally symmetrical body which is formed along a longitudinal axis 15 and has a circular-cylindrical cylinder bore 17 with a wall 19 which is machined or formed into the housing 10 coaxially to the longitudinal axis 15. The housing 10 also has a base part 21 with an opening 22, wherein the base part 21 has a cylinder base 18 on the side facing the cylinder bore 17.

[0028] The piston 30 is movably mounted in the cylinder bore 17 along the longitudinal axis 15 and comprises an outer side 31 formed by a pressure side 33, a circumferential surface 32, and an end face 34. The shape of the piston 30 corresponds to the shape of the cylinder bore 17, with the piston 30 comprising a tappet 70 on the end face 34, which extends through the opening 22 in the base part 21. The piston 30 and the tappet 70 can be formed as one piece or in multiple parts.

[0029] In the cylinder bore 17, the piston 30 and the wall 19, together with the cover (not shown), form a gas compression chamber 20 in which a gas, for example, nitrogen, is disposed. The gas is compressed when the piston 30 moves along the longitudinal axis 15, so that pressure builds up in the gas compression chamber 20. This pressure generates a restoring force that acts against the pressure side 33 of the piston 30. Such gas springs 1 are used in particular in tools or machines and the like.

[0030] To seal the gas compression chamber 20, the piston 30 includes a piston seal 36, which is inserted into a radial groove. The radial groove is machined into the outer surface 32 of the piston 30, directly adjacent to the pressure side 33. The piston seal 36 is formed in said radial groove to provide a gas-tight seal for the gas compression chamber 20. To this end, the pressure prevailing in the gas compression chamber 20 presses the piston seal 36 against the wall 19 of the housing 10 on the one hand and against the piston 30 on the other.

[0031] A dirt wiper 74 is arranged in the opening 22, which closes the opening 22 against the plunger 70 so that no foreign bodies can penetrate into the gas spring 1.

[0032] In addition, Fig. 1 shows that a guide ring 38, 72 is arranged both on the outer surface 32 of the piston 30 and in the opening 22, which guide ring enables a sliding mounting of the piston 30 in the cylinder bore 17 and a sliding mounting of the tappet 70 in the opening 22.

[0033] The guide ring 38 is inserted into a radial groove on the outer surface 32 of the piston 30 and is fixedly arranged there, while the guide ring 72 is arranged in a radial groove in the opening 22 of the base part 21 of the housing 10. The guide rings 38, 72 can be made of a metallic material or a plastic.

[0034] A lubricant reservoir 40 is machined or formed into the piston 30 and is designed to hold a lubricant 4. In the illustrated embodiment, the lubricant reservoir 40 is a circular cylindrical recess machined or formed into the piston 30 coaxially with an axis 45. The axis 45 is further aligned coaxially with the longitudinal axis 15. The circular cylindrical recess of the lubricant reservoir 40 is machined into the piston 30 from the pressure side 33 and has an insertion opening 46 on the pressure side 33, which is closed with a cover 48, for example by means of a screw connection, during operation of the gas spring 1.

[0035] Arranged in the lubricant reservoir 40 is a preloading means for pressurizing the lubricant 4 stored in the lubricant reservoir 40. This preloading means comprises a lubricant piston 50 and a compression spring 52. According to the invention, the compression spring 52 is supported on the one hand by the lubricant piston 50 and on the other hand by the cover 48. The spring force of the compression spring 52 pressurizes the lubricant 4 stored in the lubricant reservoir 40.

[0036] The insertion opening 46 provides physical access to the lubricant reservoir 40 and is required during the manufacture of the gas spring 1 for mounting the preloading means in the lubricant reservoir 40. For this purpose, the insertion opening 46 has a cross-sectional area that is larger than a cross-sectional area of ​​the lubricant reservoir 40 or the preloading means transverse to the axis 45. The cover 48 for closing the insertion opening 46 can then be sealed gas- and liquid-tight using sealing means.

[0037] The lubricant reservoir 40 is connected to the outer surface 32 of the piston 30 by at least two lubricant lines 42, in the present embodiment, exactly two, arranged symmetrically to the longitudinal axis 15. The lubricant 4 can exit on the outer surface 32 through a lubricant opening 43 into an annular space between the piston 30 and the wall 19. To achieve improved distribution of the lubricant 4 over the circumference of the piston 30 or the wall 19, a radial groove can be incorporated into the piston 30 in the region of the lubricant opening 43.

[0038] The two lubricant lines 42 open into the lubricant reservoir 40 on the side of the lubricant reservoir 40 facing away from the cover 48 and can guide the lubricant 4 displaced from the lubricant reservoir 40 by the lubricant piston 50 to the outer surface 32 and the surfaces adjacent there, and in particular wet the outer surface 32 and the wall 19 with lubricant 4.

[0039] In addition, there is a lubricant seal 37 between the end face 34 and the lubricant opening 43, which seal, together with the piston seal 36, closes off an annular space, whereby the lubricant 4 cannot freely leave the annular space between the outer surface 32 of the piston 30 and the wall 19 of the cylinder bore 18.

[0040] The lubricant piston 50 can be provided with a seal which seals a gap between the lubricant piston 50 and a wall of the lubricant reservoir 40 on a jacket surface of the lubricant piston 50.

[0041] Lubricant 4 can be refilled into the lubricant reservoir 40 via a filling line 60. The filling line 60 extends from a free end of the tappet 70 on the side of the piston 30 facing the end face 34, from a filling opening 62 to the lubricant reservoir 40. The filling line 60 is aligned coaxially with the axis 45 and the longitudinal axis 15 and opens centrally into the lubricant reservoir 40. The filling opening 62 can be closed with a valve, in particular a one-way or check valve.

[0042] In the transition area between the wall 19 and the cylinder base 18, a relief groove 24 is arranged in the housing 10. The relief groove 24 is a local cross-sectional expansion in the cylinder bore 17, which allows excess, old, and / or contaminated lubricant 4 to settle. The relief groove 24 allows lubricant to settle and accumulate without affecting the functionality of the gas spring 1. The relief groove 24 can also provide manufacturing and design advantages. The relief groove 24 can be connected to a vent hole 25, which extends through the housing 10 as a through hole and can be closed with a plug or a valve.

[0043] Fig. 2 shows a longitudinal section through a second embodiment of the gas pressure spring 1, wherein the embodiments in the Fig. 1 and Fig. 2 differ in the design of the lubricant reservoir 40 and the filling line 60.

[0044] The lubricant reservoir 40 in Fig. 2 is machined into the piston 30 as a blind hole from the pressure side 33. The lubricant reservoir 40 is essentially circular-cylindrical along the axis 45. The axis 45 is arranged parallel to and spaced from the longitudinal axis 15 of the housing 10. Furthermore, Fig. 2 that the lubricant reservoir 40 has a substantially constant cross-section along the axis 45. On the pressure side 33, the lubricant reservoir 40 is closed by the cover 48.

[0045] The preloading means, which in turn consists of a compression spring 52 and a lubricant piston 50, is arranged in the lubricant reservoir 40. The compression spring 52 is supported at one end on the end of the blind bore and at the other end on the lubricant piston 50. Accordingly, the lubricant piston 50 is preloaded along the axis 45, with the effective direction of the compression spring 52 and the lubricant piston 50 being directed toward the cover 48 and the lubricant line 42, respectively.

[0046] The gas pressure spring 1 also has Fig. 2 has a filling line 60 for refilling, which is machined or molded into the tappet 70 at a distance from the longitudinal axis 15 and the lubricant reservoir 40. The filling line 60 is designed as a blind hole and extends from the end face of the tappet 70 into the lubricant line 42, where it opens. The filling opening 62 of the filling line 60 is closed by a valve.

[0047] The longitudinal section in Fig. 2 shows two lubricant lines 42, whereby in principle one lubricant line 42 is sufficient to supply the outer surface 32 of the piston 30 with the lubricant 4. However, it has proven advantageous if several lubricant lines 42 are arranged, in particular symmetrically around the longitudinal axis 15, whereby on the one hand a uniform lubricant distribution is achieved over the circumference and on the other hand no radial force is applied between the wall 19 and the piston 30 by the preloading means, which could possibly displace the piston 30 eccentrically in the cylinder bore 17.

[0048] Fig. 3 shows a longitudinal section through a third embodiment of the gas pressure spring 1. The third embodiment differs from the first two embodiments according to Fig. 1 and Fig.2 in that the piston 30 has a lubricating film body 35 on the outer side 31 at the mouth of the lubricant line 42.

[0049] The lubricating film body 35 is made of a lubricant-absorbent material capable of capillary transport of the lubricant 4. In the illustrated embodiment, the lubricating film body 35 is a felt ring that protrudes from a recess 39 on the outer surface 32 of the piston 30 and contacts the wall 19 of the housing 10. The recess 39 can be machined or formed into the outer surface 32 as a radial groove. The lubricant line 42 opens into the recess, whereby the recess 39 can increase the amount of lubricant 4 stored in the piston 30 through an appropriate design.

[0050] The capillary forces in the lubricating film body 35 distribute the lubricant 4 over the entire circumference of the lateral surface 32. Furthermore, the lubricating film body 35 limits and promotes the controlled and resource-saving use of the lubricant 4.

[0051] In all three described embodiments, both the lubricant reservoir 40 and the filling line 60 can be arranged arbitrarily in the piston 30. The preloading means can also be designed and / or arranged in a variety of ways, for example, in the cover 48. Furthermore, the insertion opening 46 can be arranged on the end face 34 of the piston 30 or on the end face of the plunger 70. It is also conceivable for both the insertion opening 46 and the filling opening 62 to be arranged on a lateral surface of the plunger 70 or the cover 48. List of reference symbols 1 gas spring 4 Lubricants 10 housings 15 Longitudinal axis 17 cylinder bore 18 Cylinder base 19 Wall 20 Gas compression chamber 21 Base part 22 Opening 24 undercut 25 vent hole 30 pistons 31 Outside 32 lateral surface 33 printed pages 34 front side 35 lubricating film bodies 36 Piston seal 37 Lubricant seal 38 Guide ring 39 recess 40 Lubricant reservoir 42 Lubricant line 43 Lubricant opening 45 Axis 46 insertion opening 48 lids 50 lubricant pistons 52 compression spring 60 filling line 62 Filling opening 70 pestles 72 guide ring 74 dirt wipers

Claims

[1] Gas spring (1) comprising: - a housing (10) with a longitudinal axis (15) and a cylinder bore (17) extending in the longitudinal axis (15) with a wall (19), and - a piston (30) which is displaceable in the cylinder bore (17) along the longitudinal axis (15), - wherein the piston (30) has an outer side (31) comprising a jacket surface (32), a pressure side (33) and an end face (34), - wherein a gas compression chamber (20) is formed between the piston (30) and the housing (10), - wherein the piston (30) has at least one lubricant reservoir (40) for a lubricant (4), - wherein the at least one lubricant reservoir (40) is connected to the outside (31) by at least one lubricant line (42), - wherein the at least one lubricant reservoir (40) has at least one preloading means by which the lubricant (4) can be pressurized, and - wherein the at least one lubricant reservoir (40) comprises a movable lubricant piston (50) which can be pressurized by means of the prestressing means, characterized by , - that the pretensioning means is a compression spring (52), - that the at least one lubricant reservoir (40) has an insertion opening (46), wherein the insertion opening (46) is arranged on the pressure side (33) and is closed with a cover (48), and - that the compression spring (52) is supported on the one hand on the lubricant piston (50) and on the other hand on the cover (48), so that the spring force of the compression spring (52) pressurizes the lubricant (4) stored in the lubricant reservoir. [2] Gas pressure spring (1) according to claim 1, characterized bythat the at least one lubricant reservoir (40) is arranged along an axis (45), in particular that the at least one lubricant reservoir (40) is arranged along an axis (45) parallel to the longitudinal axis (15). [3] Gas pressure spring (1) according to claim 2, characterized by that the at least one lubricant reservoir (40) has a constant cross-section along the axis (45). [4] Gas pressure spring (1) according to one of claims 1 to 3, characterized by that a cross-sectional area of ​​the insertion opening (46) corresponds to at least one cross-sectional area of ​​the at least one lubricant reservoir (40). [5] Gas pressure spring (1) according to one of the preceding claims, characterized by that the at least one lubricant line (42) opens onto the lateral surface (32) between the pressure side (33) and the end face (34). [6] Gas pressure spring (1) according to one of the preceding claims, characterized bythat at least one piston seal (36) is arranged between the pressure side (33) and the end face (34) on the outer surface (32). [7] Gas pressure spring (1) according to one of the preceding claims, characterized by that at least one guide ring (38) is provided between the pressure side (33) and the end face (34) on the lateral surface (32). [8] Gas pressure spring (1) according to one of the preceding claims, characterized by that at least one lubricant-absorbent lubricating film body (35) is provided which is in contact with the wall (19) of the housing (10). [9] Gas pressure spring (1) according to claim 8, characterized by that the at least one lubricating film body (35) is arranged in a recess (39) on the outer side (31) of the piston (30) and that the at least one lubricant line (42) opens into the recess (39). [10] Gas pressure spring (1) according to one of the preceding claims, characterized bythat at least one filling line (60) is provided for refilling the lubricant (4), and that the filling line (60) opens into the at least one lubricant line (42) or the at least one lubricant reservoir (40). [11] Gas pressure spring (1) according to one of the preceding claims, characterized by that the at least one filling line (60) has a filling opening (62) on the end face (34) of the piston (30). [12] Gas pressure spring (1) according to one of the preceding claims, characterized by that the cylinder bore (17) has a relief cut (24) in the region of a cylinder base (18). [13] Gas pressure spring (1) according to one of the preceding claims, characterized by that the housing (10) has at least one vent hole (25). [14] Gas pressure spring (1) according to one of the preceding claims, characterized by that the gas compression chamber (20) can be filled with nitrogen. [15] Gas pressure spring (1) according to one of the preceding claims, characterized by that the cylinder bore (17) is closed with a cover.

Images