WO1999032799A1

WO1999032799A1 - Spring element

Info

Publication number: WO1999032799A1
Application number: PCT/EP1998/008188
Authority: WO
Inventors: Hermann Krautkrämer
Original assignee: Krautkraemer Hermann
Priority date: 1997-12-18
Filing date: 1998-12-14
Publication date: 1999-07-01
Also published as: DE19881964D2; AU1968299A; DE29880118U1; EP1040282A1

Abstract

The invention relates to an enhanced spring element i.e. an improved gas spring or hydraulic spring. The invention is characterised in that the spring element is embodied as a multi-tube spring. At least two tubes (4, 6) are provided to embody the inventive spring. The tubes of the spring are arranged in a substantially concentric manner. At least two of the tubes define at least two volume areas (22, 24) that communicate with each other by means of a control device (20).

Description

Spring element

The present invention relates to a spring element, in particular a gas spring or a hydraulic spring, and the production thereof.

A gas spring is a hydropneumatic adjustment element with a self-contained gas and oil system as an energy store. The spring force is generated by a compressed filling medium. The principle of gas springs is based on the compressibility of a gas volume enclosed in a container.

Gas springs can be designed both as gas pressure springs and as gas tension springs. The structure of a conventional gas spring is described below using an example of a conventional gas pressure spring. These consist essentially of a cylindrical pressure tube, which is sealed gas-tight on one side with a cover and on the opposite side by a sealing and guide package. A piston rod is axially movably guided by the seal and guide package, at the end of which a piston is fastened inside the pressure tube and at the same time limits the extension of the piston rod. The outer end of the piston rod and the pressure pipe end are each provided with a fastener adapted to the application.

The desired spring insertion and extension force of the piston rod of a gas spring is achieved by introducing a certain excess gas pressure into the cylindrical pressure tube. Furthermore, the cross-sectional area of the piston, on which the pressure in the cylindrical pressure tube acts, is important for determining the desired spring insertion and extension force. When the piston rod and the piston of a gas spring are pushed in or out, the volume space of the gas is reduced and an increase in pressure, which is a measure of the increase in the potential energy for the respective position, is brought about. The piston in the interior of the gas spring has the function of enabling a specific extension speed, effecting damping adapted to the application, serving as a guide element and limiting the extension width of the piston rod.

Piston designs are known in which the piston is provided with one or more small nozzle bores or with a labyrinth system. When using such a piston, a targeted damping when pushing the piston rod in and out can be achieved by the overflow of gas.

To lubricate gas springs, there is a certain amount of oil in the cylindrical pressure chamber, which can also be used as position-dependent hydraulic end position damping. Further end position damping is known from coil springs or rubber end stops.

The spring characteristic of a conventional gas spring is shown in the force-displacement diagram (F-s diagram). The force curves follow approximately a straight line and have a slight increase in force over the spring travel compared to coil springs. The breakaway force, which characterizes the force with which the piston rod must be released at the beginning of a movement, is usually not shown in the F-s diagram. This breakaway force is usually a multiple of the initial insertion or extension force.

The spring characteristic of the conventional gas spring can be changed, for example, by introducing oil. An increased oil quantity inside the gas spring causes increased insertion and extension forces. Furthermore, the spring characteristic can be varied by changing the dimensions of the pressure pipe and the piston rod. A further possibility for influencing the spring characteristic is to provide a spring element in the volume space, whereby the spring characteristic of the gas spring is superimposed on that of the spring element.

The production of such gas springs, in particular the piston rod, requires a considerable amount of production work, since the surface is a sealing surface. The piston rod must be hardened and have a maximum roughness depth of approximately 1 to 3 μm. To do this, it is conventionally ground, surface hardened and chrome-plated.

Another method that can be used as an alternative to chrome plating is a salt bath hardening method. The piston rods are placed in a salt bath on e.g. Heated to 580 ° C and remain in it for a certain time. This process is an ascent hardening process that also provides rust protection for the surface of the piston rod. After the piston rods are removed from the salt bath, they have to be processed on a polishing machine in order to obtain the required surface quality.

The known gas springs and methods for their production have the particular disadvantages that their characteristic cannot be changed arbitrarily, the functionality of the gas spring is no longer guaranteed with the slightest damage to the piston rod or the tube, and high system pressures in the gas spring are required, as a result of which at elevated temperatures, for example in the event of vehicle fires, there is a considerable risk potential. Further disadvantages are the high breakaway force of the piston rod, the complex manufacturing process of the piston rod and the associated environmental problems. In particular, environmentally harmful residues caused by the salt bath hardening process are problematic, as well as grinding and polishing residues or sludges, which as highly toxic special waste have to be disposed of in a very complex and expensive manner.

Another major disadvantage of conventional gas springs is that they are not suitable for many applications because e.g. their characteristic curves do not meet the requirements, the gas springs cannot be adequately protected from contamination at the respective places of use or excessive pressures in the gas springs would be required. In such applications, hydraulic systems are often used, which are significantly more expensive, require more space and have a lower life expectancy. Furthermore, hydraulic systems have the considerable disadvantage that leakage problems often arise, i.e. Oil leaks, e.g. Dirt adheres, which affects not only the functionality of the entire system, but also the aesthetics.

In the case of a hydraulic spring, the hydraulic medium, which is hardly or preferably not compressible, serves as the transmission medium. Normally, therefore, a pressure or energy store must be provided for storing energy. With conventional hydraulic springs, this is external, e.g. arranged in the form of a pressure vessel.

A specific application of hydraulic systems is e.g. to find on industrial robots. There the hydraulic system is used to absorb deceleration forces when moving the robot arms. Due to the leakage problem of these hydraulic systems, use in many areas is not possible or only possible through complex, additional measures, such as in food production and processing or in pharmaceutical processing.

The present invention is therefore based on the object of an improved spring element, in particular an improved one To provide gas spring and an improved hydraulic spring and a corresponding manufacturing process. This object is achieved with the features of the claims.

The invention has the advantage that the spring can be designed as a multi-tube spring with at least one piston such that the sliding surfaces of the spring are safe from damage and the spring remains operational even in the event of external damage.

A compression spring according to the invention has, for example, an inner tube and an outer tube, preferably arranged concentrically around it, and a piston with a piston rod provided in the inner tube. The two tubes define two volume spaces that are connected or connectable to one another via a control unit.

At least two tubes, preferably three tubes, are to be provided for executing a tension spring according to the invention. The tubes of the tension spring are advantageously arranged essentially concentrically. At least two pipes define at least two volume spaces communicating with one another via a control device. In the case of a gas tension spring according to the invention, the inner volume space preferably has a constant volume, while the volume of the outer volume space, in which an annular piston is guided, is variable in accordance with the piston position. In a hydraulic tension spring according to the invention, the volumes of both volume spaces are variable. The third tube is preferably arranged outside the tube defining the outer volume space in order to protect all sliding surfaces from contamination. Consequently, three volume spaces are formed, two of which are provided for the actual function of the spring in order to form the two volume spaces filled with fluid. The third volume space is a protective space to protect the spring from damage. The spring of the present invention thus has the particular advantages that damage to components of the spring according to the invention which are accessible from the outside do not result in any functional impairment, their filling pressure can be reduced by up to 50% compared to conventional springs, their characteristic curve can be designed variably and the extension or the insertion speed of the piston can be set as desired. Furthermore, the springs according to the invention can be produced in an environmentally friendly manner since their components do not have to be subjected to any special processes in which environmentally harmful substances are produced. The spring can furthermore have variable fastening means, have a clamping device for fixing the piston in any axial position and have means for damping the end position.

Another advantage is the low breakaway force of the piston and its versatility due to its high passive safety. Furthermore, the springs according to the invention can be inexpensively, e.g. are manufactured from commercially available components, thereby achieving a further reduction in manufacturing costs and enabling use as a mass product. The springs according to the invention can be used without problems even in heavily soiled or soiling systems. Leakage of oil, e.g. in conventional hydraulic systems, on the one hand by gas as the filling medium and on the other hand by using a closed hydraulic system, i.e. without hydraulic pressure accumulator, can be excluded, whereby the spring according to the invention also e.g. in places with high to highest demands on purity, e.g. can be used in the food, pharmaceutical or chemical industry, as well as in clean rooms.

Preferred embodiments of the gas spring according to the invention are described below by way of example with reference to the drawings. The drawings show: Fig. 1 shows a first embodiment of an inventive

Two-pipe gas spring; Fig. 2 shows a second embodiment of the invention

Two-pipe gas spring; Fig. 3 shows a third embodiment of the invention

Two-pipe gas spring; Fig. 4 shows a fourth embodiment of the invention

Two-pipe gas spring; Fig. 5 shows a first embodiment of an inventive

Three-pipe gas spring; Fig. 6 shows a second embodiment of the invention

Three-pipe gas spring; and FIG. 7 shows an embodiment of a hydraulic tension spring according to the invention.

The two-tube gas pressure spring 2 of the present invention, as shown in FIGS. 1 to 4, essentially has an inner tube 4 and an outer tube 6 arranged essentially coaxially therewith. In the inner tube 4 there is a piston 8 which is slidably mounted in the inner tube 4. The piston 8 is connected to a piston rod 10, for example by a thread, but preferably by a crimp or crimp connection. To guide the piston rod 10, a guide element 14 is provided on a first end 12 of the tubes 4 and 6, which guides the piston rod 10, preferably simultaneously seals the inner tube 4 with respect to the outer tube 6 and has means 16 against the ingress of dirt from the outside. The opposite end 18 is closed by a control unit 20. The inner tube 4, the piston 8 and the control unit 20 thus form a first volume space 22. The annular space between the inner tube 4 and the outer tube 6 forms together with the guide element 14 and the control unit 20 a second volume space 24. The two volume spaces 22 and 24 are connected or connectable by the control unit 20 by the control unit 20 having a control slot 26, which is preferably communicates with an annular channel 28. The dimensions of the control slot 26 and the annular channel 28 define the extension speed of the piston rod 10. By varying the size of the volume spaces 22 and 24, ie by varying the tube diameter and length, any pressure ratios can be set, so that the characteristic of the two-tube gas pressure spring can be adjusted in the Fs diagram depending on the application.

The volume spaces 22 and 24 are filled with gas, preferably with nitrogen, through a radial gas filling hole 30. Both volume spaces 22 and 24 are thus subjected to the same gas pressure. The gas filling bore 30 is closed with a closure 32, which also acts as a burst protection for the two-pipe gas pressure spring 2. The closure 32 is preferably in the form of an annular elastic element e.g. made of rubber, which is arranged within the gas filling bore 30, so that when the two-tube gas pressure spring 2 is filled, the closure 32 is pressed inwards, while the pressure of the gas then presses the closure 32 onto the gas filling bore 30 and seals. If the pressure inside the spring increases excessively, e.g. by heating in the event of a fire, the rubber sealing element 32 is pressed through the gas filling opening 30, as a result of which an enlarged volume space is created or the gas pressure can finally escape. It is therefore impossible that the piston rod becomes a projectile if the internal pressure of the gas spring increases beyond a permissible maximum.

The piston 8 of the two-pipe gas pressure spring 2 is provided with a groove-ring sleeve 34, which has a V-shaped groove, as a result of which the system pressure in the first volume space 22 acts on the groove-ring sleeve 34 and the sealing effect is intensified . Preferably, the groove-ring sleeve 34, as shown in FIG. 4, is firmly connected to the piston 8 by means of a retaining washer 35 and a support ring 37, for example by riveting, screwing, gluing or other known fastening measures. This has the effect that the groove-ring sleeve 34 seals the piston 8 tightly against the inner tube 4. In this context, the term “firmly seated” means in particular that relative rotations are not possible between the piston 8 and the groove-ring sleeve 34, or only by applying large forces.

The piston rod 10 is provided at one end opposite the piston 8 with a connecting element 36, which can be designed differently depending on the application. Likewise, the outer tube 6 or the control unit 20 has a connecting element 38, which can be designed flexibly depending on the application.

To operate the two-pipe gas pressure spring 2, the two volume spaces 22 and 24 are acted upon by the same system pressure via the gas filling opening 30. The piston 8 and the piston rod 10 are brought into an extended basic position by the system pressure. If the piston rod 10 is pushed in, the piston 8 moves in the inner tube 4 in the direction of the control unit 20 and thus reduces the volume of the first volume space 22. As a result, the gas flows from the first volume space 22 through the control unit 20 into the second volume space 24 and is preloaded . When the piston rod is relieved, it is pushed out by the prestressed gas pressure in the second volume space 24 at a precisely defined extension speed. This extension speed is defined by the cross section of the ring channel 28 and the control slot 26.

There is a small amount of lubricating oil in the volume spaces 22 and 24 for lubricating the gas spring.

Gas pressure springs are used in particular in driving and aircraft, chairs and any machines. A typical one Application examples can be found on tailgates, bonnets or seats in motor vehicles.

O-rings are preferably used to seal the two volume spaces 22 and 24 against one another on the guide element 14 and on the control unit 20. Against the ingress of dirt from the outside along the piston rod 10, the sealing means 16 is also preferably designed as an O-ring. Another O-ring is provided on the piston 8 for the same purpose.

The two-tube gas spring 2 shown in Figure 2 shows a second embodiment of the invention. In a departure from the first embodiment, the connecting element 38 is not located on the control unit 20 but on the outer tube 6 of the two-tube gas pressure spring 2. Furthermore, the connection between the first volume space 22 and the second volume space 24 is in the control unit 20 by a spiral control slot 40 and the annular channel 28 bound. A spring element 44 in the form of a helical compression spring is located in an annular space 42 between the guide element 14 and the piston 8 in order to dampen the piston rod 10. However, any other compressible medium for damping could be used instead of the coil spring.

The third embodiment of the two-tube gas pressure spring 2 of the invention shown in FIG. 3 essentially corresponds to the gas spring described in FIGS. 1 and 2. However, the piston 8 is provided with a quad ring 46 as a dynamic seal. The guide element 14 is also designed to receive a clamping device 48. This clamping device 48 consists of an annular clamping wedge 50, an annular pressure piece 52 and a nut 54 which can be screwed onto the guide element 14 and thus clamps the annular clamping wedge 50, whereby the piston rod 10 is clamped. In addition to this embodiment of the clamping device, all other known embodiments of clamping devices for fixing the piston rod 10 to the springs according to the invention can also be provided. Any damage to the piston rod or the outer tube 6 of the two-tube gas pressure spring according to the invention does not impair the operation in the slightest, since the surface quality of the piston rod and the nature of the outer tube 6 are unimportant for the function and no gas-sealing effect is achieved on them or by them.

Fig. 4 shows a further embodiment of the gas spring according to the invention. The fastening of the groove-ring sleeve 34 by means of the retaining disc 35 and the support ring 37 is shown. Furthermore, in this embodiment, the piston rod 10 is connected to the piston 8 by a crimp or crimp connection 56 in order to obtain an inexpensive connection.

Furthermore, the control device 20 is modified in such a way that an overflow bore 58 is provided in the ring channel 28, which is sealed with a preferably circumferential sealant 60, e.g. a flat sealing ring, is sealable. As a result, when the piston rod 10 is pushed in, the gas can additionally flow through the overflow bore 58 by the pressure lifting off the sealant 60. When the insertion process has ended, the sealing means 60 rests on the overflow bore 58 and seals it, so that the extension characteristic, as with respect to the above embodiments, e.g. is predetermined by the ring channel 28 and / or control slot 26.

Furthermore, a further sealing element 62 is provided between the inner tube 4 and the control device 20 in order to seal the two volume spaces 22 and 24 in a gas-tight manner. In the embodiment according to FIG. 4, the spring element 44 is held in the guide element 14, preferably under prestress, for damping the end position of the spring 2. For this purpose, a retaining ring 64 is provided in the guide element 14, which fixes the inner tube 4 and at the same time carries a support disk 66, on which the spring element 44 acts. If the piston 8 is moved near its end position when it is pushed out, it strikes the support disk 66 and lifts it against the spring force of the spring element 44 from the retaining ring 64, so that it moves in a damped manner to its end position. Preferably, a brake ring 68 is additionally provided between the support disk 66 and the spring element 44 in order to move the piston 8 braked into the end position. A further support disk 70 is then preferably provided between the brake ring 68 and the spring element 44. The brake ring 68 is preferably made of plastic, such as rubber, and is installed dry.

The two-pipe gas springs shown in the various embodiments are gas pressure springs. However, the idea on which the invention is based can also be used for gas tension springs. For this, e.g. the guide element 14 can simultaneously be designed as a control unit and the annular space 42 represents the first volume space.

The guide element 14 of the two-tube gas spring only serves to better guide the piston rod 10, but is not a mandatory component. In the case of two-pipe gas pressure springs of the invention, instead of the guide element 14, the second volume space 24 can only be closed, e.g. through an annular lid.

The control unit 20 can instead of the control slot 26 and the annular channel 28 also be formed by a valve with which the passage cross section can be varied.

A gas spring according to the invention can also have further volume spaces by providing additional tubes. Their precise design should then be carried out, for example, in accordance with what has been described above, as shown in FIGS.

A three tube gas tension spring 102 of the present invention is shown in Figures 5 and 6. It essentially has an inner tube 104, a middle tube 106 and an outer tube 108. The tubes 104, 106 and 108 are arranged essentially coaxially to one another with respect to a central axis 110. The tubes 104, 106 and 108 are preferably cylindrical tubes, the wall thickness of which can vary according to the application. The wall thickness of the inner tube 104 and the middle tube 106 are, for example, between 0.1 and 10 mm, preferably between 0.5 and 5 mm. The inner tube 104 is connected at its first axial end to a terminating element 112 in a gas-tight manner. This connection can be, for example, a screw connection with a corresponding seal or an adhesive, but the inner tube 104 and the end element 112 are preferably connected to one another by friction welding. The closure element 112 has a gas filling bore 114 which opens into the interior of the inner tube 104. A closure device 116 is provided at the second axial end opposite the first axial end of the inner tube 104. The closure element 116 is connected to the inner tube 104 in a gas-tight manner by suitable sealing means 118. The inner tube 104 thus forms a first volume space 120 with a constant volume through the closure element 112 and the closure device 116. The volume space 120 is connected to a second volume space 124 by a control device 122, which is preferably formed in the form of at least one gas transfer hole. The second volume space 124 is defined by the inner tube 104, the middle tube 106, an annular element 126 arranged at the second end of the inner tube 104 and by an annular piston 128. The ring element 126 and the ring piston 128 are sealed gas-tight against the adjacent tubes 104 and 106 by means of sealing elements 130 and 132, respectively. The center tube 106 of the throttle cable according to the invention the connection to the ring piston 128 thus simultaneously represents the piston rod.

As already explained above, the two volume spaces 120 and 124 are connected or connectable to one another by the control device 122, in that the control device 122 has at least one gas transfer hole or a gas transfer slot. The insertion and removal speed of the piston rod can be defined by changing the dimensions of the control device. By varying the size of volume spaces 120 and 124, i.e. by varying the pipe diameter and length, any pressure ratios can be set, so that the characteristic curve of the gas spring according to the invention in the F-s diagram can be adapted depending on the application.

The volume spaces 120 and 124 are filled with gas, preferably with nitrogen, as already explained above with reference to FIGS. 1 to 4, through the gas filling bore 114. Both volume spaces 120 and 124 are connected to the same by means of the control device 122 Gas pressure applied. The gas filling bore 114 is closed with a closure 134 (only shown schematically), which at the same time acts as a burst protection for the gas tension spring according to the invention. The closure 134 is preferably realized in the form of an annular elastic element, for example made of rubber, which is arranged within the gas filling bore 114, so that when the three-pipe throttle cable is filled, the closure 134 is pressed inwards, while the pressure thereafter of the gas presses the closure 134 onto the gas filling bore and seals it. If the pressure inside the gas spring increases excessively, for example due to heating in the event of a fire, the closure element 134 is pressed through the gas filling opening 114, as a result of which an enlarged volume space is created or the gas pressure can finally escape completely. It is therefore impossible for the piston to become a projectile if the Internal pressure of the gas spring 102 increases beyond a permissible maximum.

The sealing means 130 and 132 provided on the ring element 126 and ring piston 128 are preferably groove-ring sleeves which have a V-shaped groove, as a result of which the system pressure in the second, outer volume space 124 acts on the groove-ring sleeve, and the sealing effect is reinforced.

Furthermore, the sealants 130 and 132 preferably contain or consist entirely of polytetrafluoroethylene (PTFE). This material is highly anti-adhesive, has a low sliding and static friction coefficient and therefore no "stick-slip" effect. Furthermore, PTFE is in a wide temperature range, i.e. Can be used from around -200 to + 270 ° C and has the highest chemical resistance.

5, the ring element 126 and the closure device 116 are formed as two parts, these could also be integral, i.e. be provided in one piece.

A mounting device 136 is provided on the middle tube 106 serving as a piston at its end opposite the annular piston 128, by means of which the gas tension spring 102 according to the invention can be connected to various connecting elements that are specific to the application. The terminating element 112 is also designed to be able to be coupled to various connecting elements.

The outer tube 108 of the gas spring according to the invention is arranged concentrically with the two inner tubes 104 and 106 by means of the closure element 112. The outer tube 108 is preferably connected to the end element 112 by friction welding. At the end element 112 Above the end of the outer tube 108, a stripping device 138 is provided, with which dirt particles which are attached or adhering to the center tube 106 can be stripped off. The scraper device 138 also has a device 140 against penetration of fine dirt particles or liquids. The device 140 is preferably a sealant, such as an O-ring or felt ring. For the same purpose, at least one further device 142 or 144 against the ingress of dirt and liquids is preferably provided on the annular piston 128 and on the ring element 126 in order to ensure the operability of the gas tension spring 102 in accordance with the invention. The arrangement of the outer tube 108 with the scraper device 138 and the devices 140, 142 and 144 ensures that the gas tension spring 102 according to the invention is protected against contamination on all sliding surfaces, so that it can be used even in dirty or heavily polluting systems and still has a long service life.

To operate the three-tube gas spring 102 according to the invention, the two volume spaces 120 and 124 are acted upon by the same system pressure via the gas filling opening 114. Due to the system pressure, the annular piston 128 and thus the central tube 106 representing the piston rod are brought into a retracted basic position. If the piston rod 106 is pulled out, the annular piston 128 moves between the inner tube 104 and the central tube 106 in the direction of the control device 122 and thus reduces the volume of the second volume space 124. As a result, the gas flows from the second volume space 124 through the control device 122 into the first Volume space 120 and is further biased. When the piston rod 108 is relieved, it is pushed in by the increased gas pressure in the first volume space 120 at a precisely defined insertion speed. This speed is defined by the opening, ie by the control device 122. In cases where the gas spring is to be inserted and removed as quickly as possible, the control unit can tion 122 should be designed so that it does not represent too high a flow resistance to avoid heating. That means that in such a case the control device 122 should have at least one, but preferably a plurality of gas transfer bores or openings with a relatively large diameter.

There is preferably a small amount in the volume spaces 120 and 124 for lubricating the gas tension spring 102

"3

Lubricating oil, e.g. 1 to 8 cm, e.g. can be introduced into the volume spaces 120 and 124 together with the gas or is introduced during assembly of the gas tension spring.

A modified embodiment of the gas tension spring 102 according to the invention is shown in FIG. 6. The basic structure of the gas tension spring 102 is essentially identical to that previously described according to FIG. 5. The gas tension spring 102 according to FIG. 6 differs, however, in that a piston 146 is provided in the first volume space 120, with which the volume of the volume space 120 can be varied. The piston 146 is preferably guided so as to be axially movably adjustable via at least one threaded rod 148 with a screw head 150 in a thread in the end element 112. The piston 146 is provided with sealing means (not shown) in order to seal the first volume space 120 from the annular space 152. As already explained above, the F-s characteristic curve of the gas spring can be varied by means of a variable volume space 120. The gas tension spring 102 shown in FIG. 6 can thus be used even more flexibly.

The gas tension spring 102 shown in FIG. 6 also has a connecting element 154 or 156 provided on the one hand on the terminating element 112 and on the other hand on the mounting element 136. In the embodiment shown here, the connecting elements 154 and 156 are each mounted on the end element 112 or the mounting element 136 with the aid of a thread 158 or 160. The thread 158 of the connection Element 154 is provided in a through hole so that the head 150 of the threaded rod 148 is easily accessible for adjusting the piston 146. The thread 160 of the connecting element 156 on the opposite side is also provided in a through hole, so that a space 162 communicates with the surroundings via an opening 164. The closure device 116 of the inner tube 104 is designed to be axially movable in the ring element 126 by means of a fine thread, so that it covers the control device 122 or its openings when the axial position is shifted in such a way that different flow cross sections and thus different flow speeds between the two volume spaces 120 and 124 cause can be. The locking device 116 is adjusted through the bore 164 in the mounting element 136, through which a tool can be guided in order to engage a head 166 of the locking device 116 and to move the locking element 116 axially. By varying the flow cross section of the control device 122, the Fs characteristic of the gas tension spring or the insertion and extension speeds can be made more flexible.

The connection elements 154 and 156 are only shown by way of example. They can also be designed differently depending on the application or installation requirements. In the present case, transverse bores 168 and 170 are provided on the connecting elements 154 and 156 in order to mount the gas tension spring with a bolt in a machine (not shown). Instead of the screw connections between the connecting elements 154 and 156 and the closing element 112 or mounting element 136, any other conventional type of connection can also be provided. In particular, it can be preferred to form these elements in one piece or to produce them by welding individual parts, for example by friction welding. According to a further embodiment of the invention, which is not shown with respect to the gas tension spring 102, an end stop means is provided in an annular space 172 formed between the inner tube 104 and outer tube 108 for damping the end position of the annular piston 128. This end stop means is preferably a helical compression spring. However, any other compressible damping medium, such as an elastic rubber element, could be used instead of the coil spring. Such an end stop means can also be provided in the second volume space 124, for example on the piston 128 or on the ring element 126.

According to a further embodiment, not shown, the gas tension spring shown in FIG. 5 or 6 is further modified in that the outer tube 108 and also any other suitable component is designed to accommodate a clamping device (not shown). This clamping device is similar to that described above with reference to Figures 1 to 4 and consists e.g. from an annular clamping wedge, an annular pressure piece and a nut which can be screwed onto the outer tube 108 and thus clamps the annular clamping wedge, whereby the piston rod or the central tube 106 is clamped. In addition to this embodiment of the clamping device, all other known embodiments of clamping devices can also be provided for fixing the piston rod 106 to the gas tension spring 102. Any damage to the center tube 106 or the outer tube 108 of the three-tube gas tension spring 102 according to the invention does not affect the operation in the slightest, since the surface quality on the outside of the center tube 106 and the nature of the outer tube 108 are unimportant for the function and on them or by them no gas sealing effect is achieved.

The three-tube gas springs shown in the various embodiments are gas tension springs. However, the idea on which these embodiments of the invention are based can also apply by reversing the principle for gas pressure springs.

In addition to the openings, the control device 122 can also be formed by a valve with which the passage cross section can be varied. A gas spring according to the invention can also have further volume spaces by providing additional tubes. Their exact training should then be carried out in accordance with the previously described. Furthermore, at least one pressure measuring device (not shown), which is connected to one of the volume spaces 120 and / or 124, can be provided in order to monitor the gas pressure or to feed it as a control input parameter. The pressure measuring device can also be designed as a pressure switch. Such a pressure monitoring device is also possible for the embodiments described in FIGS. 1 to 4.

To produce the three-pipe gas tension spring according to the invention, first the inner tube 104 is joined to the end element 112 and then the outer tube 108 is also mounted on the end element 112. This can be done either by screwing threaded connections, by gluing, welding or other known, gas-sealing connection methods. The inner tube 104 and the outer tube 108 are preferably welded to the end element 112 by friction welding. The stripping device 138 can already be preassembled on the outer tube 108 or can be installed at a later time. The piston rod or the center tube 106 is then mounted with the piston 128 and inserted into the annular space 172 between the inner tube 104 and the outer tube 108. The closure device 116 and the ring element 126 are then mounted so that the two volume spaces 120 and 124 are sealed gas-tight from the environment. In the following, the mounting element 136 is mounted on the center tube 106. To provide a functional gas spring, the volume spaces 120 and 124 can be filled with a gas pressure in accordance with the requirements for the gas spring. This method has already been explained above.

It is pointed out that the sliding parts required for the gas spring according to the invention, namely the inner tube 104 and middle tube 106 and the annular piston 126 can be produced from commercially available raw parts. The surfaces of the sliding elements preferably have a roughness depth of 0.5 to 5 μm, but in particular a roughness depth of 1 to 3 μm is preferred.

FIG. 7 shows a further embodiment of a spring element according to the invention in the form of a hydraulic tension spring 202. The structure of the hydraulic tension spring 202 essentially corresponds to the three-tube gas tension spring 102 described above with reference to FIGS. 5 and 6. This hydraulic tension spring as well Three-tube tension spring 202 has an inner tube 204, a middle tube 206 and an outer tube 208. These tubes are preferably arranged essentially coaxially with one another with respect to a central axis 210. The tubes 204, 206 and 208 are preferably cylindrical tubes, the wall thickness of which varies according to the application. The wall thickness of the inner tube 204 and the middle tube 206 are, for example, between 0.1 and 10 mm, preferably between 0.5 and 5 mm. The inner tube 204 is connected at its first axial end to a sealing element 212 in a fluid-tight manner. The connection can be, for example, a screw connection with a corresponding seal, an adhesive or preferably a friction weld connection. A closure device 214 for the inner tube 204 is provided at the second axial end opposite the first axial end of the inner tube 204. The closure device 214 is connected to the inner tube 204 in a fluid-tight manner by means of suitable sealing means and / or a corresponding connection; the closure device 214 has an oil fill opening 216, which is preferably designed as an oil fill valve. In addition, is preferably in the Closing device 214, a vent valve 218 is provided in order to be able to discharge existing air when the hydraulic gas spring 202 is filled with hydraulic fluid. A piston 220 is provided in the inner tube 204 so as to be axially movable. The piston 220 has a stop projection 222 which bears against the closure device 214 when the hydraulic three-tube tension spring 202 according to the invention is in the inserted, ie relaxed, state. Thus, the inner tube 204 with the closure element 214 and the piston 220 form a first annular volume space 224 formed around the stop projection 222. On the side of the piston 220 opposite the first volume space 224, a helical compression spring 226 is provided between the closure element 212 and the piston 220 which presses the stop projection 222 of the piston 220 against the closure device 214. A guide pin 228 is preferably provided on the piston for fixing the coil spring 226.

Coil spring 226 may be a cylindrical helical compression spring as shown. However, it is also possible not only to provide a helical spring, but also to provide a plurality of nested helical compression springs with opposite coils. Furthermore, coil springs with changing wire cross-section and / or conical coil compression springs can also be provided. It is also possible to provide a gas pressure spring instead of the coil spring. When choosing the appropriate spring means 226 it is only important that it be able to absorb kinetic energy e.g. by storing or compressing a gas.

The first volume space 224 is connected to a second volume space 232 by a control device 230, which is preferably designed in the form of at least one fluid transition bore. The second volume space 232 is defined by the inner tube 204, the middle tube 206, the closure device 214 and by an annular piston 234. The Ver- Closing device 214 and the annular piston 234 are sealed in a fluid-tight manner with respect to the adjacent tubes 204 and 206 by means of sealing elements 236 and 238, respectively. The central tube 206 of the hydraulic three-tube tension spring 202 according to the invention thus simultaneously represents the piston rod due to the connection to the annular piston 234.

As already explained above, the two volume spaces 224 and 232 are connected or connectable to one another by the control device 230 in that the control device 230 has at least one gas transfer hole or a gas transfer slot. The insertion and removal speed of the piston rod can be defined by changing the dimensions of the control device 230. By varying the size of volume spaces 224 and 232, i.e. by varying the pipe diameter and length, any pressure ratios can be set, so that the characteristic curve of the spring according to the invention can be adapted in the F-s diagram depending on the application.

As already explained with reference to the preceding embodiments of the invention, the sealing means 236 and 238 provided on the annular piston 234 and on the closure device 214 are preferably groove-ring sleeves which have a V-shaped groove and are therefore superimposed by the system pressure in the second volume space 232 be so that the sealing effect is enhanced. As also explained above, the groove-ring sleeves are non-rotatably on their respective seats. Furthermore, the sealants 236 and 238 preferably have or consist entirely of polytetrafluoroethylene (PTFE).

On the middle tube 206 serving as the piston, a mounting device 240 is provided at its end opposite the annular piston 234, by means of which the spring 202 according to the invention can be connected to various connecting elements that are specific to the application. Furthermore, on the Closing element 212 such a connecting device can be provided.

The outer tube 208 of the hydraulic three-tube tension spring according to the invention is arranged concentrically with the two inner tubes 204 and 206 by means of the closing element 212. The outer tube 208 is preferably connected to the connecting element 212 by friction welding. At the end of the outer tube 208 opposite the end element 212, a stripping device 242 is provided, with which dirt particles which are attached or adhered to the center tube 206 can be stripped off. The wiping device 242 also has a device 244 against the penetration of fine dirt particles or liquids. This means 244 is preferably a sealant such as e.g. an o-ring or felt ring. For the same purpose, at least one further device 246 or 248 against the ingress of dirt and liquids is preferably provided on the annular piston 234 and on the closure device 214 in order to ensure the operability of the hydraulic tension spring 202 according to the invention. The arrangement of the outer tube 208 with the stripping device 242 and the devices 244, 246 and 248 ensures that the hydraulic tension spring 202 according to the invention is protected against contamination on all sliding surfaces, so that it can be used even in dirty or heavily soiled systems and nevertheless has a long service life.

When the hydraulic three-tube tension spring 202 according to the invention is installed horizontally, an oil pan 250 provided on the outer tube 208 is also preferably provided in order to catch any hydraulic fluid that may escape and thus keep the environment clean. For this purpose, at least one through hole 252 is provided in the outer tube 208.

The possibilities described with reference to the embodiments explained above in accordance with FIGS. The further development of the spring elements according to the invention, such as the provision of a pressure measuring device, end position damping or a locking device, can all also be applied to the hydraulic tension spring 202 described above.

To operate the hydraulic three-tube tension spring 202 according to the invention, the two volume spaces 224 and 232 are acted upon by a hydraulic fluid under the same system pressure via the oil fill opening or the oil fill valve 216. Due to the system pressure, the annular piston 234 and thus the central tube 206 representing the piston rod are brought into a retracted basic position. If the piston rod 206 is pulled out, the annular piston 234 moves in the direction of the control device 230 and thus reduces the volume of the second volume space 232. As a result, the hydraulic fluid flows from the second volume space 234 through the control device 230 into the first volume space 224 and displaces the piston 220 the spring force of the spring element 226 due to its incompressibility. The applied movement work is stored by the prestressing of the spring means 226, so that when the piston rod 208 is relieved, the hydraulic fluid is conveyed back from the now decreasing first volume space 224 into the second volume space 232. The dimensioning of the control device 230 maintains a precisely defined insertion speed. In cases in which the hydraulic tension spring is to be pushed in and out as quickly as possible, the control device 230 can be designed in such a way that it does not represent too high a flow resistance in order to avoid heating, i.e. the control device 230 should at least in such a case have one, but preferably a plurality of fluid transition bores or openings with a relatively large diameter.

With regard to the hydraulic three-tube tension spring, the possibility explained above with reference to FIG. speed of changing the cross-section of the control device can be used. In addition, the length of the space containing the spring means can also be varied by means of an axially adjustable piston according to the explanations corresponding to FIG. 6.

Although the hydraulic spring element has been shown as a hydraulic tension spring, the basic principles explained above also apply to a hydraulic compression spring using a multi-tube arrangement.

The piston 220 is sealed in a fluid-tight manner in the inner tube 204 by a groove-ring collar 254 and is preferably guided by a guide and sealing element 256.

Claims

Patent claims

1. Spring element which is designed as a multi-tube spring.

2. Spring element according to claim 1, wherein it is a two-tube gas spring (2) and an inner tube (4), an outer tube (6) arranged around it, a piston (8), a piston rod (10) and a control unit (20 ), a first volume space (22) and a second volume space

(24) is formed, which can be connected to one another by the control unit (20).

3. Spring element according to claim 2, wherein the control unit (20) is formed by an axial (26) and / or spiral control slot (40) and / or an annular channel (28).

4. Spring element according to claim 3, wherein from the annular channel (28) an overflow bore (58) in the second volume space

(24) opens and the overflow bore (58) is sealed by a sealing ring (60) in the second volume space (24) when the piston rod (10) is not inserted.

5. Spring element according to one of claims 2 to 4, wherein it further comprises sealing means which seal the two volume spaces (22, 24) against each other and the environment.

6. Spring element according to claim 5, wherein the sealing means which seals the first volume space (22) on the piston (8) from the environment, a groove-ring sleeve (34) which is acted upon by the gas pressure in the first volume space (22), or is a quad ring (46).

7. Spring element according to one of claims 1 to 6, wherein it further comprises a guide element (14) which guides the piston rod (10).

8. Spring element according to one of claims 1 to 7, wherein it further has a filling opening (30), a closure and / or a burst protection (32) for the filling opening (30).

9. Spring element according to claim 8, wherein the filling opening (30) is a radial bore in the outer tube (6), which is closed by a closure (32) in the form of an elastic element, which simultaneously represents the burst protection.

10. Spring element according to one of claims 1 to 9, wherein it further comprises means (44) for cushioning the piston rod (10) and the piston (8).

11. Spring element according to one of claims 1 to 10, wherein it further comprises means for blocking (48) the piston rod (10) in any axial position.

12. Spring element according to claim 11, wherein the means for blocking (48) the piston rod (10) are formed by an annular clamping wedge (50) which can be clamped between the piston rod (10) and the guide element (14).

13. Spring element according to one of claims 2 to 12, wherein a sealing element (62) is provided between the end of the inner tube (4) and the control device (20).

14. Spring element according to one of claims 6 to 13, wherein the groove-ring sleeve (34) by a support ring (37) and a retaining ring (35) with the piston (8) is rotatably connected and the retaining ring (35) on the piston (8) is riveted.

15. Spring element according to one of claims 10 to 14, wherein it has a helical compression spring (44) in the guide element (14) for end position damping, which is located on a supports the retaining ring (64) provided for fixing the inner tube (4) under pretension.

16. Spring element according to claim 15, wherein between the retaining ring (64) and the spring (44) two support disks

(66, 70) and a brake ring (68) provided between them.

17. Spring element according to one of claims 2 to 16, wherein the piston (8) on the piston rod (10) is crumpled.

18. Spring element according to one of claims 1 to 17, wherein it is designed as a gas pressure spring.

19. A method for producing a spring element, in particular according to one of the preceding claims, with the following method steps:

(a) forming an inner tube (4) into an outer tube (6);

(b) inserting a piston (8) with a piston rod

(10) in the inner tube (4);

(c) forming a control unit (20) on the two tubes (4, 6);

(d) closing the open ends of the tubes (4, 6); and

(e) filling the gas spring with gas and / or lubricating oil through a filling opening (30)

20. The method according to claim 19, wherein for filling the gas spring a filling opening (30) is formed by radially boring the outer tube (6), which is sealed by an elastic element as a closure (32).

21. Spring element according to claim 1, wherein it is designed as a three-tube spring (102; 202) and has an annular piston (128; 234).

22. Spring element according to claim 21, wherein it has an inner tube (104; 204), a concentrically arranged central tube (106; 206) and a likewise concentrically arranged outer tube (108; 208), the annular piston (128; 234) with the Center tube (106; 206) represents a unit forming the piston rod of the spring (102; 202) and a first volume space (120; 224) and a second volume space (124; 232) is formed, which are together by a control device (122; 230) are connected or connectable.

23. Spring element according to claim 22, wherein the control device (122; 230) through at least one radial bore and / or slots in the inner tube (104; 204) of the spring

(102; 202) is formed.

24. Spring element according to claim 22 or 23, wherein the outer tube (108; 208) a stripping device (138; 242) and / or a device (140; 244) against the ingress of contaminants into a between the inner tube

(104; 204) and the outer tube (108; 208) formed annular space (172).

25. Spring element according to one of claims 22 to 24, wherein it further comprises sealing means (118, 130, 132; 236, 238, 254) which seal the two volume spaces (120, 124; 224, 232) against each other and the environment.

26. Spring element according to claim 25, wherein the sealing means

(130, 132; 236, 238, 254), seal the sliding surfaces on the inner tube (104; 204) and center tube (106; 206), are ring seals with a gas groove (124; 232) acted upon by V-groove.

27. Spring element according to one of claims 21 to 26, wherein it further comprises a filling opening (114), a closure and / or has a burst protection (134) for the filling opening (114).

28. Spring element according to claim 27, wherein the filling opening (114) is a flow channel provided in a closure element (112), which can be closed by the closure (134).

29. Spring element according to claim 27 or 28, wherein the closure (134) is an elastic element which can be introduced into the filling opening (114) and at the same time represents a burst protection.

30. Spring element according to one of claims 21 to 26, wherein it further has a filling opening (216) in a closing element (214) closing the inner tube (204).

31. Spring element according to claim 30, wherein the filling opening (216) is a self-closing pressure valve.

32. Spring element according to claim 30 or 31, wherein a vent opening (218) is provided in the closure element (214).

33. Spring element according to one of claims 26 to 32, wherein at least one device (142, 144; 246, 248, 256) is provided against the ingress of contaminants on the sliding surfaces.

34. Spring element according to one of claims 23 to 33, wherein the control device (122; 230) is designed such that the flow cross section of the bores or slots is adjustable by a closure device (116; 216) arranged axially positionable on the inner tube (104; 204) .

35. Spring element according to claim 34, wherein the positioning of the closure device (116; 216) takes place by means of a head (166) formed thereon, on which means for engaging with a tool are provided.

36. Spring element according to one of claims 22 to 35, wherein a movable piston (146) is provided in the first volume space (120; 224), with the aid of which the volume of the first volume space (120; 224) can be varied.

37. Spring element according to claim 36, wherein the piston (146) is adjustable by means of a threaded rod (148) with a screw head (150).

38. Spring element according to one of claims 21 to 37, wherein it further comprises means for end position damping of the central tube forming the piston rod (106; 206) and / or the annular piston (128; 234).

39. A spring element according to any one of claims 21 to 39, further comprising means for blocking the central tube (106; 206) forming the piston rod in any axial position.

40. Spring element according to claim 39, wherein the means for blocking the central tube (106; 206) are formed by an annular clamping wedge, which between the central tube (106; 206) and the outer tube (108; 208) or its stripping device (138; 242) can be clamped.

41. Spring element according to one of claims 25 to 40, wherein the sealing means for sealing the sliding surfaces comprise polytetrafluoroethylene.

42. Spring element according to one of claims 21 to 41, wherein it is designed as a gas-tension spring (102).

43. Spring element according to one of claims 21 to 41, wherein it is designed as a hydraulic tension spring (202).

44. Spring element according to claim 43, wherein in the inner tube (204) an axially movable piston (220) is provided, which is pressed by means of a spring element (226) with a stop projection (222) provided thereon against the closure device (214), the the first volume space (224) is variable in order to receive displaced fluid therein when the spring element (202) is pulled out of the second volume space (232) and to store the work done in the spring means (226).

45. Spring element according to claim 43, or 44, wherein further an oil pan (250) is provided in order to catch any escaping fluid.

46. The spring element according to claim 45, wherein the oil pan (250) is provided in a substantially horizontal installation position of the spring element (202) along a circumferential section and in the axial direction on the outer tube (208), with leaked fluid through openings (252) in the oil pan ( 250) can reach.

47. Method for producing a spring element, in particular according to one of claims 21 to 46, with the following method steps:

(a) forming an inner tube (104; 204) with a control device (122; 230) on a closure element (112; 212);

(b) threading an annular piston (128; 234) onto an outer sliding surface of the inner tube (104; 204), the annular piston (128; 234) being connected to a central tube (106; 206) serving as a piston rod;

(c) closing the end of the inner tube (104; 204) opposite the end element (112, 212); (d) Introducing a ring element (126) and / or closure element serving as a guide and sealing element

(116; 214) on the inner tube (104; 204) and in the center tube (106; 206);

(e) filling the spring (102; 202) through a filling opening

(114; 216).

48. The method of claim 47, wherein on the end element

(112; 212) an outer tube (108; 208) is arranged concentrically to the inner tube (104; 204) and center tube (106; 206), which a stripping device (138; 242) and / or a device (140; 244) against Penetration of dirt.

49. The method of claim 47 or 48, wherein an axially movable piston (146) is arranged in the inner tube (104; 204).

50. The method according to any one of claims 47 to 49, wherein a flow channel is provided in the closure element (112) which forms a filling opening (114) for filling the spring (102), the filling opening (114) by an elastic element as a closure (134) is sealed.

51. The method according to any one of claims 47 to 50, wherein the formation of the inner tube (104; 204) on the closure element

(112; 212) by friction welding.

52. The method according to any one of claims 48 to 51, wherein the formation of the outer tube (108; 208) on the closure element

(112; 212) by friction welding.

53. The method according to any one of claims 47 to 52, wherein a connecting element (154) is provided on the closing element (112) or the closing element (112) is simultaneously formed as a connecting element.

54. The method according to any one of claims 47 to 53, wherein a connecting element (156) is provided on the central tube (106) serving as the piston rod.

55. The method according to any one of claims 47 to 54, wherein the spring (102) is filled with nitrogen and / or oil as a lubricant.

56. The method according to any one of claims 47 to 54, wherein the spring (202) is filled with hydraulic fluid.

57. The method of claim 56, wherein a piston (220) with a spring element (226) is provided in the inner tube (204) before the closure device (216) for closing the inner tube (204) is applied.