Gas spring system having at least one gas spring

Abstract

The present invention relates to a gas spring system having at least one gas spring (1) with a piston device (3) displaceably arranged in a cylinder. The piston device (3) is designed as a directionally closed piston packet, the piston packet being designed in a springless manner and having at least one annular sealing element (12) for sealing between a holding area (10) of a cylinder (2) and the piston device (3) during the gas spring's (1) expulsion movement, the sealing element (12) being arranged in a radially outer annular space (23) of the piston packet and displaceable therein, such that the sealing element (12) can be pressed against the cylinder (2) with a first pressing force during the gas spring's (1) expulsion movement and with a second, lower pressing force during the gas spring's (1) expulsion movement.

Description

[Technical Field]

[0001] The present invention relates to a gas spring system having at least one gas spring, comprising: a cylinder having a closed first end; a piston device displaceably arranged in the cylinder, the piston device dividing the cylinder into a first working chamber near the first end and a second working chamber remote from the first end; and a piston rod arranged on one side of the piston device, the piston rod protruding through the second working chamber and leading out of the cylinder at a second end opposite the first end, the second end being sealed by a seal and a piston rod guide, concentrically with respect to the longitudinal axis of the cylinder. [Background technology]

[0002] Gas spring systems with gas springs are known. Gas springs are used, in particular, not only for force assistance but also for damping and locking. In addition to lifting, gas springs can also be used to suppress movement at a specifically defined speed. Gas spring systems are used, for example, in flap systems with two end positions, such as vehicle tailgates, which need to be easily adjusted from a closed position to an open position. Depending on the application, it may be desirable to limit or provide different flap opening angles.

[0003] Gas springs known for these applications typically have a directionally acting piston valve with a piston seal that is closed by spring force during the gas spring's self-extending movement and opens in the holding area due to a pressure-dependent force acting in the opening direction. This piston seal with a spring-loaded valve, known, for example, from German Patent No. 3301544 A1, has proven to be disadvantageous, particularly with regard to friction resistance and temperature dependency. Likewise, the use of a piston valve can be disadvantageous with regard to noise emissions.

[0004] For example, German Patent No. 2513302(A1) discloses a gas spring with a springless piston packet. High friction of the sealing element proves to be a disadvantage. Chinese Patent No. 103775552(B) discloses a gas spring whose piston has a groove and a sealing element disposed therein. The base of the groove has a cylindrical and conical groove portion. When a piston rod attached to the piston is retracted, the sealing element can be displaced into the conical groove portion, thereby enabling a fluid connection between the working chambers of the gas spring. Summary of the Invention

[0005] The object of the present invention is to propose an improved gas spring system having at least one simply constructed gas spring.

[0006] This object is achieved according to the present invention by a gas spring system as set forth in claim 1. The gas spring system according to the present invention includes at least one gas spring system comprising: a cylinder having a closed first end; a piston device displaceably disposed within the cylinder, the piston device dividing the cylinder into a first working chamber near the first end and a second working chamber remote from the first end; and a piston rod disposed on one side of the piston device, the piston rod protruding through the second working chamber and exiting the cylinder concentrically with respect to the longitudinal axis of the cylinder at a second end opposite the first end, the second end being sealed by a seal and a piston rod guide. The cylinder has at least one overflow channel that can be connected to a working space for automatic pushing movement of the gas spring. At least one holding area of ​​the cylinder blocking the overflow channel is provided to limit the stroke of the piston device, thereby preventing automatic pushing movement. The piston device is designed as a piston packet that closes depending on the direction. Furthermore, the piston packet is designed without a spring and has at least one annular sealing element provided for sealing between the holding area of ​​the cylinder and the piston device during the expulsion movement of the gas spring, the sealing element being arranged in the radially outer annular space of the piston packet and displaceable therein, so that the sealing element can be pressed against the cylinder with a first pressing force during the expulsion movement of the gas spring and with a second, lower pressing force during the retraction movement of the gas spring.

[0007] In this context, a directionally closing piston packet means that no additional force, such as a spring force, is required to close the piston packet during the pushing movement. By eliminating the valve spring, the design of the piston packet can be greatly simplified, which optimizes the cost of the gas spring system and reduces the design effort due to the greatly simplified design.

[0008] The gas spring system also has a low temperature dependency due to the elimination of the valve spring. In known gas springs with a valve spring, the holding force decreases with increasing temperature. To compensate for this, it is therefore necessary to use a stronger valve spring, which results in an increase in the adjusting force at intermediate temperatures, and especially at low temperatures.

[0009] In a gas spring with a piston packet according to the invention, the pushing force increases with increasing temperature, but at the same time the holding force of the piston packet also increases, so no compensation for this is necessary.

[0010] The reduction in the pressing force of the sealing element during the pushing movement also allows for a reduction in friction.

[0011] The system according to the invention therefore allows for improved ease of adjustment, especially in the medium and low temperature ranges, due to a smaller dispersion of adjustment forces.

[0012] The piston packet comprises a further sealing element provided for static sealing between the piston device and the piston rod.

[0013] These two annular sealing elements may allow for one-sided or two-sided static sealing as well as an airtight design of the piston packet, resulting in lower sealing element friction.

[0014] A particularly simple construction of the piston packet is achieved in that the piston packet has a piston and a stop disc, the piston abutting against the stop disc with the protrusion extending axially relative to the longitudinal axis in such a way that a radially outer annular space is formed.

[0015] The stop disc abuts against a shoulder of the piston rod and a piston rod extension projects through the piston packet to attach the piston packet to the piston rod.

[0016] The stop disc is preferably substantially cylindrical and has a radial collar which abuts against a shoulder of the piston rod and has at least one radially outer recess, the piston abutting against the side of the collar facing away from the piston rod.

[0017] Preferably, the piston has an annular recess for receiving a further annular sealing element for sealing the piston against the piston rod.

[0018] If, during the pushing movement, the piston packet reaches a holding area of ​​the cylinder that blocks at least one overflow channel, this easily ensures sealing between the piston and the piston rod or between the piston and the cylinder.

[0019] The protrusion is tapered on its outside, which ensures that during the pushing-out movement the sealing element is displaced towards the piston and comes into contact with the holding area of ​​the cylinder, blocking the overflow channel. During the pushing-in movement, the sealing element moves towards the collar of the stop disc, which can cause overflow. The tapered protrusion advantageously reduces the pressing force of the sealing element against the cylinder, and therefore the frictional forces.

[0020] Preferably, the collar has knob structures on the side facing away from the piston rod, over which it is easy to flow and which ensure the pre-positioning of the sealing element in the direction of the piston, while the flow through the recesses in the stop disc can be easily ensured.

[0021] According to an advantageous design of the present invention, at least one overflow channel is designed as an axial groove, the contour of which is provided for adapting a controllable stroke-dependent extrusion speed, for example to achieve a uniform start of the automatic extrusion movement of the gas spring.

[0022] Preferably, at least two overflow channels are provided, designed as axial grooves, and a retaining area for the cylinder blocking the overflow channels is provided to adjust the stroke limit, which allows the realization of several opening angles when used in a flap system.

[0023] According to an advantageous embodiment of the gas spring system, the gas spring system comprises a further gas spring. Depending on the application, the two gas springs may have identical or differently constructed piston packets or may differ in the design of their overflow channels.

[0024] The gas spring system according to the present invention can be preferably used in a flap system, particularly a tailgate system, but can also be used in a front hood system. [Brief explanation of the drawings]

[0025] Further advantages are shown in the following description of the drawings. Embodiments of the invention are shown in the drawings. The drawings, the description, and the claims include a number of feature combinations. Those skilled in the art can also conveniently consider these features individually and combine them to form advantageous further combinations.

[0026] In the following examples: [Figure 1] 1 shows a gas spring of a gas spring system according to the invention in longitudinal section; [Figure 2] The characteristics of the pushing force of the gas spring shown in Figure 1 are shown. DETAILED DESCRIPTION OF THE INVENTION

[0027] 1 shows a detail of a gas spring 1 of a gas spring system according to the invention in longitudinal section. The gas spring system can preferably be used in a flap system (not shown), in particular in a tailgate system. It can also be used in a front hood system.

[0028] The gas spring 1, shown in its fully inserted state, comprises a cylinder 2 with a closed first end (not shown) and a piston device 3 displaceably disposed within the cylinder 2, dividing the cylinder 2 into a first working chamber 5 near the first end and a second working chamber 6 away from the first end, both filled with compressed gas. A piston rod 7, located on one side of the piston device 3, protrudes through the second working chamber 6 and exits the cylinder 2 at a second end 4 opposite the first end, concentric with the longitudinal axis L of the cylinder 2 or the gas spring 1, sealed by a seal 8 and a piston rod guide (not shown in detail). The cylinder 2 has at least one overflow channel 9, connectable to the working chambers 5, 6 for automatic compression of the gas spring. When the piston device 3 is located in this region of the cylinder 2, the overflow provides dynamic damping of the compression movement. If, during the course of its movement, the piston device 3 reaches a holding area 10 of the cylinder 2 which blocks the overflow channel 9, the automatic pushing movement of the piston device 3 is prevented. In other words, the holding area 10 of the cylinder 2, the area of ​​which is illustrated by two dashed lines, is provided to limit the stroke of the piston device 3.

[0029] As shown, if a further overflow channel 21 is provided, during further progression of the pushing movement the holding area 10 is followed by a second area with automatic pushing movement.

[0030] The piston device 3 is designed as a directionally closing, springless piston packet. In this context, a directionally closing piston packet means that no additional force, such as a spring force, is required to close the piston packet during the extrusion movement. By eliminating the known valve spring, the design of the piston packet can be significantly simplified, which optimizes the cost of the gas spring system and reduces the design effort due to the significantly simplified design. Similarly, since the gas spring system is less temperature-dependent due to the elimination of the valve spring, improved overall adjustability can be achieved, especially in the medium and low temperature ranges, due to the smaller variance in the adjustment force.

[0031] As can be seen in Figure 1, the piston packet has an annular portion 12 as well as a further sealing element 11, which are provided during the pushing movement in the holding area 10 of the cylinder 2 blocking the overflow channels 9, 21 in order to seal between the cylinder 2 and the piston packet and between the piston packet and the piston rod 7. The piston packet comprises a piston 13 as well as a stop disc 14 which rests against a shoulder 15 of the piston rod 7 and a piston rod extension 16 which protrudes through the piston packet and additionally fixes the piston packet to the piston rod 7, for example by riveting. The piston rod 7 together with the piston device 3 form a piston-piston rod unit.

[0032] The piston 13 can advantageously be made of a plastic material.

[0033] 1, the stop disc 14 is substantially cylindrical and has a radial collar 17 which abuts against a shoulder 15 of the piston rod 7 and which has at least one radially outer recess 18. The piston 13 abuts on the side of the collar 17 facing away from the piston rod 7 with a protrusion 19 extending axially—with respect to the longitudinal axis L of the gas spring 1 or cylinder 2.

[0034] Furthermore, the piston 13 has a radially inner annular recess 20 for receiving a further annular sealing element 11 for sealing the piston 13 against the piston rod 7 or piston rod extension 16, which, together with its protrusion 19 and the collar 17 of the stop disc 14, forms a radially outer annular space 23 for receiving the annular sealing element 12. When, during the pushing-out movement, the piston packet reaches the holding area 10 of the cylinder 2 which blocks the overflow channels 9, 21, sealing between the piston 13 and the piston rod extension 16 or between the piston 13 and the cylinder 2 is thereby ensured in a simple manner.

[0035] The sealing element 12 is arranged in the radially outer annular space 23 and is displaceable therein, so that the sealing element can be pressed against the cylinder 2 with a first pressing force during the expulsion movement of the gas spring 1 and with a second, lower pressing force during the retraction movement of the gas spring 1. The first pressing force is very high, for example at least twice as high as the second pressing force.

[0036] For this purpose, the protrusion 19 is tapered on its outside, which ensures that during the pushing movement the sealing element 12 is displaced towards the piston 13 and comes into contact with the holding area 10 of the cylinder blocking the overflow channels 9, 21. As can be seen in Figure 1, the sealing element 12 abuts against the radial piston surface 24 and the axial piston surface 25 of the piston 13 with high contact pressure.

[0037] During the pushing movement, the sealing element 12 is displaced in the direction of the collar 17 of the stop disc 14 in such a way that gas can overflow from the working chamber 5 over the sealing element 12 in the direction of the working chamber 6. Since the sealing element 12 no longer sealingly abuts against the radially formed piston surface 24 and the axially formed piston surface 25, gas can now flow between the piston 3 and the sealing element 12 and enter the working chamber 6 via the recess 18.

[0038] The displacement of the sealing element 12 in the direction of the stop disc 14 results in a reduction in the pressing force of the sealing element 12 onto the cylinder 2, and therefore significantly lower friction there.

[0039] On the one hand, the flow can easily pass over the knob structure with the knob 22 on the side of the collar 17 facing away from the piston rod 7, which ensures pre-positioning of the sealing element 12 in the direction of the piston 13. In other words, the knob 22 prevents the sealing element 12 from being displaced too far in the direction of the stop disc 14. Sealing of the recess 18 can be reliably prevented.

[0040] In the illustrated embodiment, the overflow channels 9, 21 are designed as axial grooves, the groove path of which is provided to accommodate a controllable discharge speed depending on the stroke. This can, for example, ensure a uniform start of the self-expanding movement of the gas spring 1. Other groove profiles (not shown) are also conceivable within the scope of the invention. By providing two overflow channels 9, 21 with an intermediate retention area 10 blocking the overflow channels 9, 21, for example, two opening angles of the flap system can be realized.

[0041] FIG. 2 shows the characteristic curve of the thrust force of the gas spring 1. At the first point 1 on the characteristic curve, the piston rod 7 is pushed in by the piston packet, i.e., at the rightmost position in the drawing. In this state, for example, a tailgate hinged to the gas spring is closed. When the tailgate is opened, the piston packet is initially located in the area of ​​the first overflow channel 9, and gas flows from the second working chamber 6 to the first working chamber 5 across the groove of the first overflow channel 9. The filling pressure is selected to overcome the weight of the tailgate, automatically pushing out the gas spring 1. The thrust force Faus decreases linearly until the piston packet reaches the retention area 10 and the first opening angle of the tailgate. In this area, the piston packet is statically sealed, ensuring the tailgate's retention or stopping function. Due to gas compression, the thrust force Faus drops to a minimum.

[0042] If the tailgate is opened further, the gas spring 1 or its piston-piston rod unit can usually be manually guided into the area of ​​the two overflow channels 21 by means of an adjustable release force, so that the piston rod 7 is automatically pushed out again until it reaches the leftmost position indicated by point 2 in the figure, at which point the second opening angle of the tailgate is reached.

[0043] The gas spring 1, and therefore the gas spring system, exhibits significantly improved temperature behavior. To overcome the triggering force or overpressure, the piston-piston rod unit must be displaced against the build-up of a pressure cushion in the second working chamber 6 until the sealing element 12 reaches the area of ​​the second overflow channel 21 and is able to reduce the pressure cushion thereon.

[0044] As the piston packet moves, the second working chamber 6 in front of the piston packet becomes smaller, and the pressure continues to rise. This rise corresponds to the ratio of the volume at the end of the holding region 10 to the volume at the end of this region. If the starting pressure increases due to an increase in temperature, the increase in absolute pressure at the end will be greater than in the case of a lower starting pressure. This effect can be counteracted by increasing the extension force, which counteracts the decrease in overpressure at higher temperatures and neutralizes this undesirable effect.

[0045] A gas spring system according to the invention can comprise the described gas spring 1 as well as further gas springs. The further gas springs can be constructed similarly to gas spring 1. Alternatively, the further gas springs can be designed differently from gas spring 1, for example, they can have a non-static seal and / or a reduced groove cross-sectional area and / or only movement-dependent damping.

[0046] To improve the friction resistance, the gas spring can further have a piston packet with piston rings that have improved sliding properties. Here, for example, PTFE rings can be used. In this case, the retention function is ensured only by the gas spring 1 described above.

Claims

1. A gas spring system having at least one gas spring (1), comprising: a cylinder (2) having a closed first end; a piston device (3) displaceably arranged in the cylinder, the piston device dividing the cylinder (2) into a first working chamber (5) near the first end and a second working chamber (6) remote from the first end; and a piston rod (7) arranged on one side of the piston device (3), the piston rod protruding through the second working chamber (6) and leading out of the cylinder (2) concentrically with respect to the longitudinal axis (L) of the cylinder (2) at a second end (4) opposite the first end, the second end being sealed by a seal (8) and a piston rod guide, the cylinder (2) having at least one overflow channel (9) connectable to the working chambers (5, 6) for automatic pushing movement of the gas spring (1), and blocking the overflow channel (9).

1. A gas spring system comprising: at least one holding area (10) of the cylinder (2) for limiting the stroke of the piston device (3), wherein the automatic extrusion movement is prevented; the piston device (3) is designed as a directionally closed piston packet; the piston packet is designed in a spring-free manner and has at least one annular sealing element (12) for sealing between the holding area (10) of the cylinder (2) and the piston device (3) during the extrusion movement of the gas spring (1); the sealing element (12) is arranged in a radially outer annular space (23) of the piston packet and is displaceable therein, whereby the sealing element (12) can press against the cylinder (2) with a first pressing force during the extrusion movement of the gas spring (1) and with a second, lower pressing force during the retraction movement of the gas spring (1).

2. 2. The gas spring system according to claim 1, characterized in that the piston packet has a further annular sealing element (11) provided for static sealing between the piston device (3) and the piston rod (7).

3. 3. The gas spring system according to claim 2, wherein the piston packet comprises a piston (13) and a stop disc (14), the piston (13) abutting against the stop disc (14) with a protrusion (19) extending axially relative to the longitudinal axis (L) in such a way that the radially outer annular space (23) is formed.

4. 4. The gas spring system of claim 3, wherein the stop disc (14) abuts against a shoulder (15) of the piston rod (7), and a piston rod extension (16) protrudes through the piston packet and secures the piston packet to the piston rod (7).

5. 5. The gas spring system according to claim 4, wherein the stop disc (14) is substantially cylindrical and comprises a radial collar (17) abutting the shoulder (15) of the piston rod (7) and having at least one radially outer recess (18), the piston (13) abutting against the protrusion (19) on a side of the collar (17) facing away from the piston rod (7).

6. 6. A gas spring system according to claim 5, characterized in that the piston (13) has an annular recess (20) for receiving the further annular sealing element (11) for sealing the piston (13) against the piston rod (7).

7. 7. A gas spring system according to claim 6, characterized in that the collar (17) has a knob structure (22) on the side facing away from the piston rod (7).

8. 8. The gas spring system according to claim 7, characterized in that the at least one overflow channel (9) is designed as an axial groove, the contour of which is provided for adapting a controllable extrusion speed depending on the stroke.

9. 9. A gas spring system according to claim 8, characterized in that at least two overflow channels (9, 21) are provided and are designed as axial grooves, and the holding areas of the cylinder (2) blocking the overflow channels (9, 21) are provided for adjusting the stroke limit.

10. The gas spring system according to any one of claims 1 to 9, characterized in that the gas spring system comprises a further gas spring.

11. 11. The gas spring system according to claim 10, characterized in that the gas spring system comprises a further gas spring, the gas spring (1) having an identical or differently constructed piston packet.

12. 12. The gas spring system according to claim 10 or 11, characterized in that the gas spring system comprises a further gas spring, the gas spring (1) having a differently designed overflow channel (9, 21).

13. A gas spring system according to any one of claims 1 to 12 for use in a flap system, in particular a tailgate system.

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