ADJUSTABLE GAS SPRING

Abstract: The invention relates to a gas spring (1), comprising a cylinder (2) filled with gas, a piston (3) that is axially movable in the cylinder and sealing it, the piston being provided with a narrow passage (12) and having a piston rod (5) extending outside the cylinder coaxially with it and sealing it, at the end of which rod is arranged an attachment element (6), and a second attachment element (7) arranged on the other side of the cylinder. The invention has for its purpose to make a gas spring of the type described in a form such that it is adjustable with simple means over a certain range so that the desired slide force, that is the minimum force for the mutual displacement of the attachment means, can be selected within a broad temperature range. In this respect the invention provides a gas spring which is characterized by a second piston (11) movable axially in the cylinder (2) and sealing it, and having a position which can be adjusted for setting the active volume of the cylinder, and thereby the slide force.

Description: The invention relates to a gas spring, comprising a cylinder filled with gas, a piston that is axially movable in the cylinder and sealing it, the piston being provided with a narrow passage and having a piston rod extending outside the cylinder coaxially with it and sealing it, at the end of which rod is arranged an attachment element, and a second attachment element arranged on the other side of the cylinder. Such a gas spring is known. It forms a combination of a spring on the basis of compression of gas and friction occurring during the displacement of the ends of the spring, so that deceleration of more rapid movements results. In view of the fact that the gas in the gas spring has a temperature related pressure the spring properties of the gas spring are dependent on the surrounding temperature and therefore the operating temperature of the gas spring. The invention has for its purpose to make a gas spring of the type described in a form such that it is adjustable with simple means over a certain range so that the desired slide force, that is the minimum force for the mutual displacement of the attachment means, can be selected within a broad temperature range. In this respect the invention provides a gas spring which is characterized by a second piston movable axially in the cylinder and sealing it, and having a position which can be adjusted for setting the active volume of the cylinder, and thereby the slide force. In a practical embodiment this gas spring can display the feature that the rod is provided with screw-thread, runs through an end wall of the cylinder provided with a corresponding threaded aperture and is connected with the second piston such that by rotation of the threaded rod relative to the cylinder the axial position of the second piston can be adjusted. A very simple embodiment is one in which the second piston is connected solely with the rod, since as a result of the pressure of the gas the piston is pressed against the free outer end thereof. In a particularly elegant embodiment, the gas spring according to the invention displays the feature that the free end of the rod is provided with the same thread which co-operates with a corresponding thread aperture in a second attachment element such that with rotation of the rod relative to the cylinder and the attachment member the interval between the first and the second attachment member remains unaltered. The rod can, for example, carry a contact member in the area of the transition between the one thread and the other thread to apply, if necessary using a tool, a turning moment to the rod. The invention will now be elucidated on the basis of a drawing of a random embodiment, in which: Fig. 1 shows a cross section through a preferred embodiment; and Fig. 2 shows a perspective view of a device in which the gas spring according to the invention is applied. Fig. 1 shows a gas spring 1, comprising a cylinder 2 filled with gas, a piston 3 that is axially movable in the cylinder and sealing it, the piston being provided with a narrow passage 12 and having a piston rod 5 extending outside cylinder 2 coaxially with it and sealing it by means of sealing rings 4, at the end of which rod a fixing eye 6 is arranged, and a rod 7 extending on the other side outside cylinder 2 and coaxially with it. This rod 7 is provided with thread 8. It runs through an end wall 10 of cylinder 2 provided with a corresponding threaded aperture 9 and rests against a second piston 11 such that, as a result of rotation of rod 7 relative to cylinder 2, the axial position of the second piston 11 can be adjusted. Once the second piston 11 is fixed in a selected position, the first piston 3 can then be moved axially between two extreme positions, namely, a compressed position, in which the faces 13 and 14 directed towards each other of respectively the first piston 3 and the second piston 11 lie against each other, and a position in which gas spring 1 has its greatest length, and in which the faces 16 and 17 directed towards each other of respectively the first piston 3 and the second end wall 18 lie against each other. By adjusting the axial position of the second piston 11 the active volume, i.e. the space that is bounded by end surfaces 14 and 17 and the inner surface of cylinder 2, can be determined. The free end of rod 7 is provided with screw-thread 19, which has the same pitch as screw-thread 8. Screw-thread 19 co-operates with a corresponding threaded aperture 20 in a second fixing eye 21 such that, with rotation of rod 7, the interval between the first fixing eye 6 and the second fixing eye 21 remains unaltered. In the area of transition between screw-thread 8 and screw-thread 19 rod 7 carries a nut 22 for applying, with the aid of an open-ended spanner or other tool, a turning moment to rod 7 for adjustment of the axial position of the second piston 11 and thereby of the spring characteristic of gas spring 1. Fig. 2 shows a device 23, namely an application of the gas spring 1 according to the invention within the framework of a sunbed. This device comprises a fixed table 25 supported by legs 24. A frame 27 bears an upper plate 26 that can pivot round a hinge 28 relative to a horizontal axis, in which plate radiation sources generating ultraviolet rays are present, this plate 26 being movable between two extreme positions, namely, a raised position and a lowered position or operating position. Plate 26 on the hinge is supported by two arms 29. One of these arms 29 is coupled with frame 27 by means of gas spring 1 as according to fig. 1. The position shown in fig. 2, the operating position, is now determined by the equilibrium of force between the weight of plate 26 and the spring characteristic of gas spring 1, particularly its slide force. This can be adapted to the weight of plate 26 by rotating nut 22 as required.

Claims: 1. Gas spring comprising a cylinder filled with gas, a piston that is axially movable in said cylinder and sealing it, said piston being provided with a narrow passage and having a piston rod extending outside said cylinder coaxial­ ly with it and sealing it, at the end of which rod is arranged an attachment element, and a second attachment element arranged on the other side of said cylinder, charac­ terized by a second piston movable axially in said cylinder and sealing it having a position which can be adjusted for setting the active volume of said cylinder, and thereby the slide force. 2. Gas spring as claimed in claim 1, characterized in that the second attachment element is arranged on a rod extending coaxially with and outside the cylinder, said rod being provided with screw-thread, running through an end wall of said cylinder provided with a corresponding threaded aperture and being connected with the second piston such that by rotation of said rod relative to said cylinder the axial position of said second piston can be adjusted. 3. Gas spring as claimed in claim 2, characterized inthat the second piston is connected solely with the rod, since as a result of the pressure of the gas said piston is pressed against the free outer end thereof. 4. Gas spring as claimed in claim 2 or 3, charac­ terized in that the free end of the rod is provided with the same thread which co-operates with a corresponding thread aperture in a second attachment element such that, with rotation of said rod relative to the cylinder and said attachment element the interval between the first and the second attachment element remains unaltered. 5. Gas spring as claimed in claim 4, characterized in that, in the area of the transition between the one thread and the other thread, the rod carries a contact member to apply, if necessary using a tool, a turning moment to said rod.

Inventors: TIEHUIS, JOSEPH HERMANUS MARIA
Applicants: HOLLAND HELLAS HYDRAULIEK & PNEUMATIEK B.V.
Application year: 1986
Main classification: F16F9
IPC codes: A61B6, F16F9