Resilient Column

Abstract

The single column supporting the seat of a stool or chair consists of two telescoping tubes and a pneumatic spring in the communicating bores of the tubes, the cylinder of the spring being secured to the tube attached to the seat and the piston rod being secured to the tube attached to the base of the chair by a spring washer. A circumferential groove near the free end of the piston rod is engaged by tongs extending into the central opening of the spring washer so that the piston rod may be pulled loose of the base and the associated tube by manual tension. The cylinder may be attached to the seat by a variety of fasteners which either respond to axial tension in the manner of the afore-described spring washer or may be removed manually without the use of tools.

Description

This invention relates to resilient columns including a pneumatic spring interposed between a tubular element and a load carrier element, as in a resilient leg for a chair or table, and particularly to a column whose pneumatic spring may be readily removed and installed for maintenance or replacement.

It is known to mount chair seats on single tubular columns in which a pneumatic spring is interposed between the base of the column and a load carrier element such as the seat of the chair. The pneumatic springs employed are similar in structure to automotive shock absorbers of the cylinder-and-piston type. Like shock absorbers, the pneumatic springs are usually welded shut, and also like shock absorbers, they need to be removed from time to time to replenish their compressed gas filling or to replace them altogether. While the useful life of a pneumatic spring in a chair of the type described is normally longer than that of an automotive shock absorber, the life of the other chair structure is usually much longer, making it worthwhile to replace the pneumatic spring rather then to discard the chair.

It is the primary object of the invention, therefore, to provide a column suitable for use in a chair or similar piece of furniture rendered resilient by a built-in pneumatic spring of the piston-and-cylinder type, from which the pneumatic spring may be removed readily, and preferably without the use of tools, and in which the repaired spring or a replacement spring may be installed in an equally simple manner.

With this object and others in view, the invention provides a resilient column comprising an elongated tubular element having a longitudinal axis, a load carrier element, and a pneumatic spring partly received in the tubular element. The cylinder of the spring is elongated axially of the tubular element and bounds an internal cavity which encloses a body of gas under a pressure higher than atmospheric pressure. A piston in the cavity slides axially in sealing engagement with the cylinder walls. A piston rod fastened to the piston for joint movement partly projects from the cylinder in an axial direction. First and second fastening means respectively secure the cylinder and the piston rod to the afore-mentioned two elements, and at least one of the fastening means includes a yieldably resilient catch mechanism which responds to manual tension applied to the elements in an axial direction for releasing the cylinder or piston rod from the element fastened thereto.

Other features, additional objects, and many of the attendant advantages of this invention will readily be appreciated as the same becomes better understood by reference to the following detailed description of preferred embodiments when considered in connection with the appended drawings in which:

FIG. 1 is a fragmentary, elevational view of a chair including a resilient column of the invention in section on the upright axis of the column;

FIG. 2 shows a catch member of the column in FIG. 1 in plan view;

FIG. 3 shows a modification of the top portion of the chair of FIG. 1 in a corresponding view;

FIG. 4 illustrates another modification of the same chair portion in the manner of FIG. 3;

FIG. 5 shows an element of the column of FIG. 4 in plan view;

FIG. 6 is a fragmentary, elevational section of yet another modification of the top portion of the chair in FIG. 1;

FIG. 7 shows an element of the column of FIG. 6 in plan view; and

FIG. 8 shows the pneumatic spring substantially common to the several embodiments of the invention in elevational section on its axis.

Referring now to the drawing in detail, and initially to FIG. 1, there is illustrated a stool whose seat 1 is shown without the upholstered cushion normally fastened on the horizontal, load-receiving, upper face of the illustrated load carrier structure. A tubular portion 2 of the load carrier structure depends from the center of the seat to which it is welded, and is coaxially slidable in a plastic sleeve 3 in a tubular element 5. The element 5 is held upright by a base 6 consisting of three legs equiangularly arranged about the common axis of the element 5, the sleeve 3, and the tubular portion 2, only parts of two legs being seen in FIG. 1.

The bottom end of the tubular element 5 is closed by a radial wall 7 which is centrally dished so as to define a recess or receptacle 8 for the abutting lower end 18 of a piston rod 10. The rod is cylindrical and has a circumferential groove 9 at the base of the end 18 which tapers approximately hemispherically toward the wall 7. A spring washer or apertured disc 11, better seen in FIG. 2, has a peripheral portion which is axially confined between a rigid washer 15 and the wall 7 and is surrounded by an annular gap 25. An annular corrugation 12 of the tubular element 5 and an annular welded seam 16 attaching the circumference of the wall 7 to the element 5 axially secure the spring washer 11. Radial tongs or catches 14 project from the continuous peripheral portion of the washer 11 into the central aperture 13 of the washer 11, the dimensions of the aperture 13 and the tongs 14 being chosen so that the tapering end 18 can be pushed through the aperture 13, bending the tongs 14, until the latter are seated in the groove 9 while the end 18 abuts against the wall 7.

The piston rod 10 is one of the two externally visible members of a pneumatic spring, the other member being a cylinder 17 which is received with some clearance in the tubular portion 2 of the seat structure. The upper end of the tubular portion 2 is lined by a bushing 19 having an inner wall of stepped, cylindrical shape. An axial slot 20 in the thicker wall portion of the bushing 19 movably receives the shorter arm of a valve operating lever 21 fulcrumed for movement about a horizontal axis in a bracket 22 on the underside of the seat 1. The lever 21 acts on a slide valve 23 in the cylinder 17 as will presently be explained with reference to FIG. 8.

A shoulder 24 on the bushing 19 between its thicker and thinnner wall portions provides an annular, radial abutment face for the top wall of the cylinder 17. The cylinder is releasably fastened to the tubular portion 2 of the seat 1 by circumferentially distributed spherical locking or catch members 4 biased by helical compression springs 27 in pockets 40 in the heavy top wall 41 of the cylinder 17 into engagement with recesses 28 in the bushing 19.

As is seen in FIG. 8, the pneumatic spring, whose basic features are common to the several embodiments of the invention, has a piston 47 fixedly fastened to the inner end of the piston rod 10. The piston sealingly engages the inner wall of the cylinder 17 and divides the cylinder cavity into two compartments 17a, 17b. The valve 23 is generally rod-shaped, but its inner end is enlarged and normally held against the top wall 41 of the cylinder 17 by the pressure of compressed nitrogen which fills the cylinder 17. A by-pass duct 46 connects the valve 23 to the compartment 17b, and is opened for flow of gas between the compartments 17a, 17b when the valve 23 is depressed by the lever 21 against the restraint of the gas in the cylinder cavity and of a non-illustrated valve spring. An annular notch 48 in the valve rod 23 is wide enough to bridge the wall separating the duct 46 from the compartment 17a.

When the valve 23 is opened manually while the seat 1 is not occupied, the gas pressure in the cylinder 17 expels the piston rod 10, and the resulting increase in the effective length of the pneumatic spring causes outward telescoping movement of the tubular portion 2 from the tubular element 5, and a raising of the seat 1 relative to the base 6. When the valve 23 is opened while the seat 1 is occupied by a person of average weight, the pneumatic spring is shortened by the compressive forces applied to the element 5 and the seat 1, as the piston rod 10 is driven inward of the cylinder 17. When the valve 23 is closed by releasing the lever 21, the gas in the upper compartment 17a is resiliently compressed by the weight of the person occupying the seat 1, and the seat 1 moves slightly up and down as the effectively applied weight is shifted, reduced, or increased. The pneumatic spring shown in FIG. 8 and its mode of operation are known in themselves, for example, from German Pat. No. 1,208,557.

As the frictionally engaged surfaces of the piston 47 and the cylinder 17 wear, the seat 1 tends to sink under an applied load even when the valve 23 is closed, and opening of the valve 23 does not cause spontaneous rising of the unoccupied seat. The pneumatic spring must be repaired or replaced, the latter operation being normally more economical.

When tension is applied manually or otherwise to the seat 1 and the base 6 or otherwise to the tubular element 5 and the carrier structure, such as the tubular portion 2, while the piston is fixed in the cylinder 17 by the gas in the cylinder or by abutment against the annular bottom wall of the cylinder, the spherical locking members 4 are readily displaced inward of the recesses 28, and the cylinder 17 slips out of the tubular seat portion 2. The exposed cylinder 17 may then be grasped and pulled axially out of the tubular element 5, the resilient tongs 14 of the spring washer 11 being flexed by the applied tensional forces until they slip out of the groove 9.

Another pneumatic spring may then be inserted by reversing the steps described above. The piston rod 10 is first anchored in the spring washer 11, and the seat structure is thereafter slipped over the cylinder 17 until the locking members 4 drop into the recesses 28. The edges of the pockets 40 in the cylinder 17 receiving the spherical members 4 are preferably peened over in a known manner, not shown, to prevent release of the locking elements under the pressure of the springs 27 in the absence of the tubular portion 2.

The modified embodiments of the invention illustrated in FIGS. 3 to 7 differ from that described above with reference to FIG. 1 in the load carrier structure and its cooperation with the pneumatic spring only. The fastening arrangement employed for securing the piston rod 10 to the base structure is unchanged in the devices partly illustrated in FIGS. 3 to 7, and will not again be described.

The spring-loaded, spherical locking elements 4 are replaced in the modified structure of FIG. 3 by rubber plugs 31, and the tubular portion 2' of the seat 1 is correspondingly modified to provide radial bores 34 axially aligned with a circumferential groove 26 in the spring cylinder 17', not otherwise significantly different from the afore-described cylinder 17.

Each plug 31 has a head 42 large enough not to pass through an associated bore 34. A reduced neck 43 between the head 42 and the larger, but compressible body 44 of the plug is received in the bore 34, while the conically tapering small end 45 of the plug enters the groove 26. The plugs 31 may permit the cylinder 17 to be pulled manually from the seat 1 as described above with reference to FIG. 1, but the plugs may also be withdrawn manually by grasping their heads 42 before disassembling the chair. The bushing 19' is axially shorter than the bushing 19 shown in FIG. 1 and of uniform wall thickness over its entire length. The annular abutment face 24 engaging the top wall of the cylinder 17' thus is an end face of the bushing.

The plugs 31 arranged in a common radial plane in the apparatus of FIG. 3 are replaced in the further modified chair partly seen in FIG. 4 by two wire springs 29, circularly arcuate in the relaxed condition shown in FIG. 5, except for one longitudinal end portion 30 which is bent radially inward. Two axially offset grooves 35 in the outer cylindrical face of the tubular seat portion 2", not otherwise different from that described with reference to FIGS. 1 and 3, receive the arcuate portions of the wire springs 29, while the radial end portions 30 pass through respective radial bores 34' in the tubular portion 2" into respective narrow, circumferential grooves 26a, 26b in the cylinder 17" which is otherwise the structural and functional equivalent of the afore-described cylinders.

It is not normally practical to pull the cylinder 17" from the seat 1 against the restraint of the springs 29, but the springs are readily removed without the use of tools.

The chair partly illustrated in FIG. 6 differs from that seen in FIG. 3 by the provision of locking elements 33 which are metallic plugs extending through diametrically opposite radial bores 34 in the tubular seat portion 2 into a groove 26 of the spring cylinder 17'. The rigid plugs 33 are held in position by an approximately semicircular leaf spring 32, and are readily withdrawn from the bores 34 and the groove 26 when it is desired to replace the pneumatic spring, and returned to their operative position shown in FIG. 6 after insertion of a new pneumatic spring, the proper position of the cylinder being determined by abutting engagement with the radial face 24 of the sleeve 19'.

It should be understood, of course, that the foregoing disclosure relates only to preferred embodiments of the invention, and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the invention set forth in the appended claims.

Claims

What is claimed is:

1. A resilient column comprising, in combination:

a. an elongated tubular element having a longitudinal axis;

b. a load carrier element;

c. a pneumatic spring partly received in said tubular element, said spring including

1. a cylinder member elongated in the direction of said axis and bounding a cavity therein,

2. a body of gas under a pressure higher than atmospheric pressure in said cavity,

3. a piston slidable in said cavity in said direction in sealing engagement with said cylinder member, and

4. a piston rod member fastened to said piston for joint movement, a portion of said piston rod member projecting from said cylinder member in said direction;

d. first fastening means securing said cylinder member to one of said elements; and

e. second fastening means securing said piston rod member to the other element,

1. at least one of said fastening means including yieldably resilient catch means responsive to manual tension applied to said elements in said direction for releasing one of said members from the element fastened thereto by said one fastening means.

2. A column as set forth in claim 1, wherein said one element is said load carrier element.

3. A column as set forth in claim 2, wherein said load carrier element has a tubular portion enveloping said cylinder member in telescoping engagement with said tubular element.

4. A column as set forth in claim 3, further comprising base means fastened to said tubular element for holding said axis upright when said base means is set on a horizontal surface.

5. A column as set forth in claim 4, wherein said load carrier element has a load receiving face extending from said axis in all radial directions and substantially horizontal when said axis is upright.

6. A column as set forth in claim 1, wherein said one fastening means secures said piston rod member to said tubular element, and said catch means includes a centrally apertured spring disc having a plurality of integral tong portions projecting into the central aperture thereof, and securing means axially securing said spring disc in said tubular element, said piston rod member being formed with at least one recess receiving said tong portions when said piston rod member is fastened to said tubular element.

7. A column as set forth in claim 6, wherein said piston rod member tapers from said at least one recess in a direction away from said piston for facilitating insertion of said piston rod member into said central aperture.

8. A column as set forth in claim 6, further comprising abutment means on said tubular element preventing axial movement of said piston rod member under compressive forces applied to said elements beyond a position of engagement of said recess in said piston rod member by said tongs.

9. A column as set forth in claim 8, wherein said abutment means include an abutment member, said securing means jointly securing said abutment member and said spring disc in said tubular element.

10. A column as set forth in claim 1, wherein said one fastening means secures said cylinder member to said load carrier element, said cylinder member and said load carrier element constituting a pair of releasably fastened members, one member of said pair being formed with a recess transverse to said axis, and said catch means being mounted on the other member of the pair and extending into said recess of the one member of the pair when fastening the members of said pair to each other.

11. A column as set forth in claim 10, wherein said catch means include a catch member and yieldably resilient means biasing said catch member inward of the recess in said one member of said pair.

12. A column as set forth in claim 1, wherein said one fastening means secures said piston rod member to said tubular element, said catch means being operatively interposed between said piston rod member and said tubular element, said first fastening means including manually releasable means for securing said cylinder member to said load carrier element.

13. A column as set forth in claim 12, wherein said load carrier element has a tubular portion enveloping said cylinder member in telescoping engagement with said tubular element, said tubular portion being formed with a radial bore, said cylinder member being formed with a recess aligned with said bore, and said manually releasable means include a locking member accessible from outside said tubular portion and passing through said bore into the recess of said cylinder member.

14. A column as set forth in claim 13, further comprising yieldably releasable means outside said tubular portion and biasing said locking member inward of said bore and of said recess.

15. A column as set forth in claim 13, further comprising abutment means on said load carrier element preventing axial movement of said cylinder member under compressive forces applied to said element beyond a position of engagement of said recess in said cylinder by said locking member.

16. A column as set forth in claim 1, wherein said piston separates two compartments in the cavity of said cylinder member, and said pneumatic spring further includes by-pass valve means operable for connecting said compartments and for sealing the same.