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(11) | EP 0 211 809 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | A structure, adjustable in extension by means of an inner closed-circuit hydraulic device, particularly suitable as vertical rod structure for the seat rest of a chair |
| (57) In order to adjust the extension of a twin-section telescopic structure, normally
compression loaded, the sections themselves, forced to stretch by an inner coaxial
spring, are connected to each other by an inner structure that is also coaxial, can
be adjusted in extension and is made up of a cylinder-piston unit of a completely
oil filled equal section inner chambers type. One stem of such cylinder+ piston unit
is fixed to the free end of one of said sections, while the body of the cylinder -
piston unit is fixed to the free end of the other telescopic section with interposition
of bearings. A cylindrical box is fitted on or in proximity of the piston of the hydraulic
unit. This box intercepts special holes through which the pressure chambers of the
same unit can be interconnected. The box is forced to close by a spring and can be
remote controlled by means of a control rod that passes axially through the stem fixed
to one of the telescopic sections and sticks out of that section for the necessary
operation. |
[0001] The invention regards a telescopic structure, adjustable in extension, that can be made rotate around its own axis and can be efficaciously used as a structure of vertical rod for the seat rest of a chair. The structure at issue differs from the known structures used for the same purpose in that it is adjustable in extension by means of a closed circuit hydraulic device placed coaxially inside the structure and distinguished by a very simple design and very high technological reliability. This hydraulic device is normally closed and after having been opened, if left free, automatically returns to block position. The hydraulic adjustment device is also distinguished by the fact that it can be operated without appreciable physical effort even when the structure is stressed by the weight of the sitting person.
[0002] This and other characteristics and peculiarities of the structure at issue, together with the advantages resulting from it, will appear evident in the following description of a preferred realization form of it, illustrated merely as a non restrictive example in the figures of the two tables attached hereto, in which:
- figures 1 and 2 illustrate the lengthwise sectioned structure in the condition of maximum extension (adjustment control closed) and in the condition of maximum contraction (adjustment control open), respectively;
- figure 3 illustrates the adjustment control enlarged and lengthwise sectioned in closed condition, as per fig. 1.
[0003] With reference first to figure 1, you notice that the structure includes a round-section steel sheath 1 closed at the bottom by a bottom plate 101 and cone-shaped in the lower part of end 201 so that it can be coupled in the known manner with the base-structure of the chair. A guide bushing 2, made of nylon, for example, or of other suitable material with low friction coefficient, or even of a compound material, is snugly inserted in the upper part of sheath 1. This bushing is provided with an upper collar 102 resting on the top edge of sheath 1. Barrel 3, made of steel as well, is mounted telescopically in the sheath 1, fitted with bushing 2, and may slide axially and rotate round its own axis, as it is closed at the top end as indicated with 103 and as it is characterized by a conveniently cone-shaped upper part of end, as indicated with 203, so that it can be coupled in known manner with the seat structure of the chair.
[0004] One end of a tubular stem 4 is fixed to the cap 103 of barrel 3. This stem is placed coaxially inside the barrel and has at least externally a round and machined section and is fixed at the other end (see fig. 3) to a piston 5 that can slide with lateral tightness in a cylinder 6 closed at the ends by plugs 7-7' which are axially and with lateral tightness crossed respectively by the above mentioned stem 4 and by a tubular, round-section stem 8 axially aligned to parts 5-4 and having an external diameter equal to that of stem 4. Therefore, inside cylinder 6 there are two pressure chambers A and B, defined by the two faces of piston 5, that have a perfectly identical section. These chambers are completely filled with oil or other suitable liquid.
[0005] 9-9' indicate the ring gaskets that assure laterally tight connection of plugs 7-7' to cylinder 6 ends, while 10-10' indicate the ring gaskets assuring lateral tightness between the plugs themselves and stems 4-8.
[0006] It is understood that gaskets 9-9' can be combined or replaced with sealing agents or adhesives.
[0007] The stems 4-8 ends are preferably fixed to coaxial and opposed bar holds 105-105' with which piston 5 is enbloc and coaxially provided, such an assemblage 5-105-105' being provided with an axial hole 11, the diameter of which is equal to the inner diameter of stem 4, while it is inferior to that of stem 8, so that at the lower end of bar hold 105' there remains free a ring step 12 which will be dealt with later.
[0008] Laterally tight sliding of piston 5 in cylinder 6 is guaranteed for example by a ring gasket 13 preferably placed on the intermediate lateral part of the piston, so that the ends of this member can be properly tapered with a turning operation, as indicated with 205-205'.
[0009] Holes 14-14', preferably with similar characteristics, are radially cut at the tapered ends of the piston. These holes open into above mentioned hole 11 through which the hydraulic connection between pressure chambers A and B of the cylinder-piston unit can be realized.
[0010] A cylindrical round-section box 15 is fitted in hole 11 sufficiently snugly, but with the possibility to slide axially in it. The intermediate part of such box is equipped with a ring recess 16 of regular-symmetrical shape (see hereafter) being at least or substantially as long as the distance between centers of A/M holes 14-14'. Above and below such recess, box 15 is provided with ring gaskets 17-17' for laterally tight cooperation with the wall of hole 11. Gaskets 17' are more distant from ring recess 16 than gaskets 17, so that between parts 16-17' the box itself shows a section 115 of its pitch diameter.
[0011] Box 15 protrudes with its lower end inside stem 8 and at this end it bears enbloc a head 18 which beats against the above mentioned step 12 under the stress of an elastic device 19. In this rest position the section 115 of box 15 cooperates with a ring gasket 20 placed in a ring recess obtained in the intermediate part of hole 11 so that it appears equally distant from holes 14-14'.
[0012] Through the effect of such cooperation of parts 115-20 and 115-14 the hydraulic connection between chambers A-B and B-A is prevented, and the cylinder-piston unit 6-5 remains firmly blocked in the position in which it is in that particular time. The above mentioned elastic device 19 is a garter spring fitted on stem 8 and maintained in the appropriate calibration ratio by a spacing bar 21 fixed on stem 8 for example by means of centripetal bending of the lower end of such device, as indicated with 108. The spacing bar 21 is preferably axially hollow, as indicated with 121, in order to avoid forming of pressure or vacuum at the bottom of box 15, which could compromise the smooth working of this device.
[0013] Box 15 can be moved axially downwards, with a stroke of suitable length, by means of a rod 22 that axially crosses stem 4 and that protrudes from it and from barrel 3 with a section provided at the end with a head 122. Rod 22 can be structurally separated from box 15 or fastened to it or be enbloc with it. It is to be noticed that stems 4 and 8 must be refined only on the lateral outer surface which is meant to cooperate in tightness with plugs 7-7'. The inner surface of stems 4-8 can be unrefined instead as, for the purpose in question, only hole 11 together with box 15 need to be refined.
[0014] Stems 4 and 8 are of such length that they remain in the necessary lateral tightness condition with the relative plugs, when piston 5 beats against the plugs 7-7', as per figures 1 and 2. As an indication, it is pointed out that,when stem 4 is completely extended from cylinder 6, the unit 4-6 shows a length which is substantially equal to that of barrel 3.
[0015] In figure 1 you can also notice that the lower plug 7' protrudes from cylinder 6 for a length sufficient to allow fixing of a coaxial pipe 23 at the end. This pipe is smoothly connected to the thickened part 124 of the end of an axially hollow pin 24 closed at the bottom. The axial cavity 224 of pin 24 has a larger diameter than the outer diameter of stem 8, as it is to be engaged by the latter (see fig. 2).
[0016] A helical spring 25, with suitable characteristics, is fitted inside pipe 23 and the bottom end 123 of the pipe 23 is bent towards the center so that the pipe doesn't come out of the thickened part 124 of pin 24. This bottom part of the pin is equipped with a ring collar 224 weighing upon an axial thrust bearing 26 placed at the bottom of sheath 1. Pin 24 crosses this bearing, passes with clearance through a hole obtained at the bottom of sheath 1 and is constrained to the bottom 101, with sufficient clearance, by means of an elastic ring 27. Pipe 23 preferably presents an outside diameter equal or substantially equal to that of cylinder 6 and such as to leave between these parts and telescopic unit 1-3 a hollow space of such a width as to enable coaxial placing of a garter spring 28, with suitable characteristics, that with its upper end lies on a conical ring 29 centered on top of barrel 3, while with its bottom end the spring 28 lies on bearing 26.
[0017] It appears evident from figures 1 and 2 how all the springs of the unit turn out to be efficaciously guided, thanks to the solution herein described. In order to ensure silent operation of the contrivance, it is not excluded that at least springs 28 and 25 be covered with suitable plastic material.
[0018] The operation of the structure so conceived is simple and evident. When the structure is in rest position, box 15, with its part 115,obstructs hydraulic connection of chambers A and B, and in this condition stem 4 can be neither extended nor retracted from and in cylinder 6, therefore if unit 1-3 is axially stressed, the unit itself contracts only for the length allowed by the stroke of pipe 23 on pin 24, in contrast with the action of springs 25 and 28. Spring 25 therefore has such characteristics as to assure the necessary cushioning of telescopic unit 1-3. Thanks to the presence of bushing 2 and bearing 26, parts 1 and 3 can even rotate freely between them, thus permitting necessary rotation of seat.
[0019] By pushing rod 22 downwards, as per Fig. 2, the box moves with part 115 away from seal 20, till it makes recess 16 position as bridge between holes 14-14'.
[0020] It is to be noticed that the opening movement of box 15 is hindered only by the action of spring 19 and can take place easily even if chamber A is under pressure (owing to the weight of the person sitting in the chair equipped with the structure in question), as thanks to the symmetric and regular form of recess 16, the axial movement of box 14 doesn't appear to be affected by the pressure exerted by transfer oil between chambers A and B (or viceversa). When rod 12 is left free, spring 19 brings box 15 back to closed position and the system automatically returns to block position.
[0021] When box 15 is opened, as above described, in consequence of the reciprocal connection of holes 14-14' by means of ring recess 16, oil can pass from chamber A to B or viceversa and it is thus possible to modify length of unit 6-4 and then of unit 1-3 as wished. It is to be reminded that chambers A and B are of equal section and that the transfer of oil between them doesn't therefore create phenomena of pressure or vacuum that could cause blow-by of oil from cylinder 6. At this point, the semplicity of construction and high technological reliability of the described structure are evident.
[0022] It is understood that several mainly construction variants and changes can be made in the invention and they can refer for example to what follows.
[0023] The structure as described can be utilized also upside-down. Rod 22 can be partly threaded and screwed to a correspondingly threaded part of stem 4, so that the axial movement of box 15 takes place in consequence of a rotation given to rod 22. However elastic devices are provided for even in this case, wire springs for example, in order to bring rod 22 automatically back to rest position when left free, so as to permit automatic return of box 15 to block position. According to a further construction variant, box 15 can be supplied without thickening of head 18 and can be fitted in an upside-down version as compared to the solution shown in the drawings, so that it can be operated in opening, with axial movement upwards in contrast with the action of an outer spring that would tend to stress it downwards, in the condition of interception of holes 14-14'. In this case box 15 would be fastened or integral with control rod 22.
[0024] If the liquid placed in cylinder 6 can be subject to temperature changes and hence to variations in volume, a hydropneumatic compensator or any other kind of compensator normally used for the same purpose in hydraulic shock-absorbers can be installed inside at least one of the pressure chambers A-B. The system as described above is extremely reliable. This doesn't prevent, however, other suitable interception means from being integrated in piston 5, preferably in combination with those described, in order to further improve the reliability of the unit. Box 15, with its inclined-plane shaped parts, could for example be used as linear cam to open and close a small tap that controls the passage of liquid between chambers A and B, and closes automatically when the box itself is left free and returns to block position.
[0026] It is finally understood that holes 14-14' may be different in number and placed in a different manner on piston 5 or on parts close to it. Seal gaskets can also be different in number and of a quality different from those schematically shown in the drawings. These, as well as all those small modifications anyway easy to intuit by the experts of this field, are not beyond the scope of the invention as described ahove, as illustrated and as claimed hereinafter.
1) A structure particularly suitable as vertical rod for seat rest of a chair or destined
to any other use for which it appears suitable, a structure comprising a sheath (1)
in which a barrel (3) telescopically slides, with the interposition of one or more
low friction coefficient bushings (2), said barrel being stressed to retract during
the utilization in said sheath, in contrast with the action of a helical spring (27)
coaxially placed in the telescopic unit in question, together with a structure adjustable
in extension as wished by means of a control placed at either end of the telescopic
unit itself, being the whole characterized by the fact that the latter structure is
made up of a cylinder-piston unit (6-5) having inside it two pressure chambers (A-B)
of equal size and completely filled with oil or other liquid and being provided with
opposed stems (4-8), of equal section, one of which is fixed to the free end of barrel
(3) and is crossed by adjustment rod (22), while the cylinder is fixed to the free
end of the sheath (1) with the interposition of suitable means; arrangement is made
for any suitable valve and/or interception device to be fitted in the piston of this
unit or in its proximity; said valve and/or interception device can be operated by
means of the adjustment rod and normally seal ducts (14-14'-11) through which it is
possible to effect connection between pressure chambers (A-B) in order to adjust extension
of telescopic structure at issue, being it arranged that there are means wherefore
said valve or interception device can be operated without excessive physical effort
and being it also arranged that there are devices (18-19) wherefore the valve and/or
interception device returns automatically and accurately to block position as soon
as it's left free after each opening operation.
2) A structure, according to claim 1), in which said valve and/or interception device
is made up of a cylindrical box (15) stressed in closed position by a spring (19)
or by any other suitable pressure device.
3) A telescopic structure, adjustable in extension and capable of rotation round its
own longitudinal axis, particularly suitable as vertical rod for the seat rest of
a chair, a structure realized more in detail, in all or substantially, as described,
as illustrated in the figures of the two drawings enclosed and for the purposes stated
above.