A height-adjustable chair column includes a vertical post axially extending along a longitudinal axis, a bottom plate, a guide cylinder bushing permanently inserted into the upper end area of the vertical post, and a guide tube inserted in the guide cylinder bushing so that it is guided with freedom of axial movement and secured against rotation in the guide cylinder bushing. Further, the chair column includes a lockable gas spring assembly with a pressure cylinder, which is installed coaxially in the guide tube such that it is secured against axial displacement relative to the guide tube and it is free to rotate about the longitudinal axis, and with a piston installed in the pressure cylinder with freedom of sliding axially. The piston is connected to a piston rod which is fastened to the bottom plate and supported there with freedom of rotation about the longitudinal axis. Moreover, a height-adjustable foot rest is attached to the upper end region of the guide tube.

BACKGROUND OF THE INVENTION

The invention pertains to a height-adjustable chair column with a vertical post, a height-adjustable foot rest, and a lockable gas spring assembly, which is installed coaxially in the vertical post with freedom to slide up and down and to rotate about its longitudinal axis.

In these types of chair columns, it is known that the foot rest can be fastened at the desired height to a clip encircling the vertical post. This means that, every time the height of the chair column is adjusted, it is also necessary to make a separate height adjustment to the foot rest. This is inconvenient.

SUMMARY OF THE INVENTION

It is an object of the invention to create a height-adjustable chair column in which the height of both the chair column and the high load-bearing foot rest can be adjusted in a single step.

In a preferred embodiment of the invention, the height-adjustable chair column comprises a vertical post axially extending along a longitudinal axis, the vertical post having a first upper end area and a second lower end area; a bottom plate mounted in the second lower end area of the vertical post; a guide cylinder bushing permanently inserted into the first upper end area of the vertical post; a guide tube inserted in the guide cylinder bushing so as to be guided with freedom of axial movement, while being secured against rotation in the guide cylinder bushing, the guide tube having an upper end region projecting out from the guide cylinder bushing; a lockable gas spring assembly including a pressure cylinder having a first closed end portion projecting out from the first upper end area of the vertical post, and a second end portion arranged within the vertical post, the pressure cylinder being installed coaxially in the guide tube so as to be secured against axial displacement relative to the guide tube, while being free to rotate about the longitudinal axis, and a piston installed in the pressure cylinder with freedom of sliding axially, the piston being connected to a piston rod which passes out in a sealed manner through the second end of the pressure cylinder, wherein the piston rod comprises a lower end which is fastened to the bottom plate and supported there with freedom of rotation about the longitudinal axis; and a height-adjustable foot rest which is attached to the upper end region of the guide tube. The arrangement of the gas spring assembly in the guide tube and the ability of the guide tube to slide in the guide cylinder bushing of the vertical post ensures a high load-bearing capacity, whereas the mounting of the foot rest on the guide tube ensures that, when the gas spring assembly moves, the foot rest is adjusted at the same time.

One or more radially inward projecting guide blocks can be permanently attached to a first upper end area of the vertical post. These blocks engage in corresponding axial guide grooves in the radially surrounding lateral surface of the guide tube.

The number of parts can be reduced and the simplicity and ease of installation can be increased by providing the guide blocks on a guide ring, which can be tightly inserted into the first upper end area of the vertical post.

An especially high load-bearing capacity is obtained by making the guide tube out of a metal material, especially steel.

To easily rotate the gas spring assembly about the longitudinal axis, one or more guide bushings can be permanently installed in the guide tube. The pressure cylinder is then installed in these guide bushings so that it is free to rotate about the longitudinal axis.

The guide bushings are preferably made of a material with low frictional resistance such as a plastic suitable for bearing applications.

To secure the gas spring assembly axially to the guide tube in a way which is both simple and compact, at the lower end portion of the pressure cylinder, i.e., at the end at which the piston rod emerges, a radially projecting collar can be arranged. This collar is gripped on both axial sides by first and second stops on the guide tube and is able to rotate relative to the guide tube about the longitudinal axis between the stops.

The collar can be attached easily yet permanently by providing the collar on a cylindrical insert, which is inserted tightly into the pressure cylinder of the gas spring assembly. The insert is then permanently connected to the pressure cylinder, especially by dimpling.

Assembly can also be made easier by providing the second stop axially facing the guide tube on a sleeve, which can be permanently inserted into the guide tube.

To reduce the number of components, the sleeve can be one of the guide bushings and thus serve a double function.

One of the end surfaces of the guide bushing can also serve a double function by forming the first stop on the guide tube side, i.e., the side against which the collar rests axially.

To strengthen the support, the collar is preferably supported axially against the second stop, which is facing the guide tube, by a support washer. The load can be distributed uniformly around the entire circumference by providing the axial stop facing the guide tube in the form of a closed or split stop ring.

To reduce the number of components and thus to facilitate assembly, the guide bushing and the second axial stop facing the guide tube can be designed as a single part.

Assembly is also facilitated by bringing the collar or the support washer into axial contact with the second stop by way of a lock washer.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The chair column shown inFIGS. 1 and 2has a vertical post1, which is designed with a cone2at the bottom for the attachment of a chair base (not shown).

A bottom plate3is mounted in the bottom end of the vertical post1. The free end of a piston rod4is attached to this plate3and is supported there so that it is free to rotate about its longitudinal axis5.

The piston rod4extends into the pressure cylinder6of a lockable gas spring7, which is installed coaxially in the vertical post1. The end of the piston rod4projecting into the pressure cylinder6is connected to a piston25, which slides back and forth in the pressure cylinder6.

The cylindrical lateral surface of the pressure cylinder6is supported inside a guide tube8so that the pressure cylinder6can rotate inside the guide tube8. Guide bushings9and9′ (FIGS. 3 and 4) are permanently attached to the end areas of the guide tube8to guide the rotation of the pressure cylinder6.

The upper end of the guide tube8projects from the vertical post1, and its lateral, circumferential surface has axial guide grooves10, uniformly distributed around the circumference, into which radially inward directed guide blocks11, located on a guide ring12(FIGS. 7 and 8), project.

The guide ring12is permanently inserted into the upper end area of the vertical post1.

Axially adjoining the guide ring, a guide cylinder bushing13is firmly inserted into the vertical post1. The guide tube8is guided with freedom to slide back and forth inside this bushing13, but it cannot rotate due to the engagement of guide blocks11and guide grooves10.

The guide bushings9and9′ are connected to the guide tube8by spring dowel pins14. These pins14are inserted permanently into bores, which extend through the guide tube8and the guide bushings9,9′ in a direction transverse to the longitudinal axis5.

The upper end of the pressure cylinder6projects out of the guide tube8and has a cone15, to which a seat (not shown) of the chair can be attached.

The end surface of an actuating plunger24projects out from the upper end of the pressure cylinder6. This plunger24is used to release the locking of the gas spring7and thus to allow the height of the chair column to be adjusted.

The lower guide bushing9′ projects slightly from the guide tube8and carries as an integral part a split stop ring16, which is located a certain distance away from the lower end surface of the guide bushing9′. This stop ring16is concentric to the longitudinal axis5and has an inside diameter which is slightly larger than the outside diameter of the pressure cylinder6. The lower end surface of the guide bushing9′ forms a first stop17, and the side of the stop ring16opposite the first stop17and a certain distance away from it forms a second stop18.

A cylindrical insert19(FIGS. 5 and 6) is installed in the lower end of the pressure cylinder6and is permanently connected to the pressure cylinder6, for example by a catch or dimpling on at least one of the two opposing surfaces of the cylindrical insert19and the pressure cylinder6. The piston rod4passes through a cylindrical opening in the insert19.

A flange-like, radially projecting, circumferential collar20is formed as an integral part of the insert19, namely, on the end of the insert19which projects from the pressure cylinder6. One side of this collar20rests axially against the first stop17.

The collar20is also supported axially against the second stop18by way of a support washer21, which rests against the side of the insert19and of the collar20facing away from the guide tube8, and by way of a lock washer22(FIGS. 9 and 10), which is inserted between the support washer21and the second stop18. The piston rod4also passes through the center opening in the support washer21.

Thus the gas spring7is secured against axial displacement relative to the guide tube8.

Nevertheless, the gas spring7is still free to rotate about the longitudinal axis5relative to the guide tube8.

A radially oriented foot rest23with a stepped bore is mounted on the end of the guide tube8which projects from the vertical post1. The foot rest23can be designed as a foot ring.

Because the foot rest23is attached to the guide tube8, the height of the foot rest23will also be adjusted when the height of the chair column is changed.