AU1132799A - Chair back height adjust mechanism - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

4 4 4 4 BE COMPLETED BY APPLICANT *4*p Actual Inventor: DARRYL BURPEE Address for Service: A.P.T. Patent and Trade Mark Attorneys GPO Box 772, Adelaide, SA 5001 Invention Title: CHAIR BACK HEIGHT ADJUST MECHANISM Details of Associated Provisional Application No. PP1345 dated 15th January 1998 The following statement is a full description of this invention, including the best method of performing it known to us:- This invention relates to a mechanism for height adjustment of the back of a chair.

BACKGROUND TO THE INVENTION Chairs are made with a number of component parts including a seat, which is supported on a base, and a chair back which supports the back of a person seated on the chair.

The chair back is supported on an elongate chair back support member which might take the form of a steel flat bar, or a tubular member. The chair back is usually pivoted relative to the chair back support member. The height of the back is adjustable by either movement of the chair back relative to the chair back support member or where the chair back is fixed vertically in relation to the chair back support member then the chair back support member may slide vertically relative to the base of the chair.

The height adjustment has, until recently, been achieved by reason of a screw threaded or cam operated clamp bearing against the chair back support member, the path of the clamp is dictated by the dimensions of a slot in the support member. More recently, however, ranges of chairs have become available where the adjustment has been to 15 discrete vertical positions by reason of engagement of a detent with a slot or ridge, and activation has been by operation of a spring biased lever or button. There are a number of different configurations of this type of height adjustment but all have a relatively complex operating mechanism with a higher cost of assembly, and parts, and this has usually necessitated the use of non-standard covers for the chair back support element 20 and height adjust mechanism.

"A preferred feature of such a mechanism is that it requires the detent to be manually disengaged whilst the chair back is shifted downwards, but that shifting of the chair back upwards can be achieved without manually disengaging the detent. This then requires what might be termed a ratchet mechanism to operate.

OBJECT OF THE INVENTION It is an object of the present invention to provide a chair back height adjust mechanism that obviates or minimises any one of the above problems or at least provides the public with a useful choice.

SUMMARY OF THE INVENTION It has been found that a good ratchet mechanism can be provided by punching a plurality of vertically aligned and inwardly sloping tabs in a tubular chair back support member to form a plurality of apertures engagable by a detent of a locking mechanism of a chair, the detent being biased for engagement with each of the apertures and which detent is able to ride out of the aperture by reason of riding on the tab. The provision of a tab greatly facilitates the manufacture of the mechanism and allows for the ratchet action.

The invention, in one form, might be said to reside in a height adjustment mechanism for a chair back, said adjustment mechanism including: a chair back support member to which at an upper portion the chair back is to be attached; a locking means operable at a lower portion of the chair back support member and connectable with a base or a seat of a chair; and, the chair back support member being vertically slidable within a support member pathway relative to the locking means, tubular and having a plurality of vertically spaced tabs; V0 the tabs being punched inwardly into an internal channel of the tube resulting in a 1. plurality of apertures, each aperture having a free downwardly facing edge, and the tabs 15 extending upwardly and sloping inwardly into the internal channel of the chair back support member; the locking means including: detent means slidable between an extended position in the support member pathway and a retracted position away from the support member pathway; 20 biasing means to bias the detent means to the extended position; and, actuation means to retract the detent means to the retracted position against the S•bias of the biasing means which when retracted allows for downward movement of the chair back support member relative to the locking means; and, said detent means when in use and in the extended position being biased into one of said apertures and the free downwardly facing edge of the said one of the apertures bearing down on said detent to engage the chair back support member in position to prevent downwards movement of the chair back but permitting upward movement of the chair back whereby the detent is progressively retracted by riding over the respective tab into a lower aperture..

In another form the invention may be said to reside in a height adjustment mechanism for a chair back, said adjustment mechanism including: a chair back support member adapted at a location for attachment of the chair back, said chair back support member being elongate and tubular and having a plurality of aligned spaced punched apertures along at least a portion of its length, each aperture having a free facing edge facing away from the location of the chair back attachment, and for each aperture a tab extending and sloping inwardly into the chair back support member and generally directed towards the location of the chair back attachment; locking means within which the chair back support member is slidably supported along a support member pathway, the locking means being adapted to connect with a base or a seat of a chair, and the locking means including: detent means slidable between an extended position in the support member pathway and a retracted position away from the support member pathway; biasing means to bias the detent means to the extended position; and, 15 actuation means to retract the detent means to the retracted position against the bias of the biasing means which when retracted allows for movement of the chair back support member away from the location of the chair back attachment; and, when in use said detent means being biased in the extended position into one of said S 20 apertures and the free facing edge of the said one of the apertures bearing on said detent to engage the chair back support member in position to prevent movement of the chair back away from the location of the chair back attachment but permitting movement of the chair back support member towards the location of the chair back attachment whereby the detent is progressively retracted by riding over the respective tab into an 25 adjacent aperture.

The tubular chair back support member is preferably made of a closed tube, which configuration of tube gives greater structural strength, and the tube can be made of thinner metal than otherwise. In one form the chair back support member is elongate in cross section, having opposed wide sides and opposed narrow sides with the plurality of apertures preferably being formed in one of the opposed wide sides. The narrow sides may be arcuate. This placement allows for a far simpler actuation means, and allows for example the use of a biased lever to operate the detent. However it is considerably more difficult to be made because the flat portion is far more susceptible to deformation than an arcuate thin side. The use of a three part mandrel to support the tube has been found to provide adequate support for the tube to allow punching of the tabs to occur with any deformation limited to a degree that does not interfere with normal sliding action required of the chair back support member.

The plurality of apertures are preferably substantially rectangular or rectilinear in plan, whereby the detent can move substantially over a length of the aperture. The apertures may be unifiormaly spaced along the chair back support member.

The adjustment mechanism preferably includes guide means to guide the vertical sliding of the chair back support member in position relative to the locking means in a support member pathway.

It will be understood that the invention might also reside in a chair incorporating a height adjustment mechanism as defined above or described herein.

It will also be understood that the invention might also reside in a chair adjustment mechanism incorporating a height adjustment mechanism as defined above or described herein.

In one form, each tab has proximal to its free end a land substantially parallel to the surface of the chair back support member through which the respective aperture was punched, and said land being adapted to limit insertion of the detent within the chair back support member. The land may also provide a more positive registering of the detent within an aperture.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding, the invention will now be described with reference to one S illustrated embodiment wherein: Figure 1 is a schematic side view of a height adjustment mechanism for "adjusting the height of the back of a chair, with the chair back supporting member in the lowest position; Figure 2 is a schematic side view of the height adjustment mechanism shown in Figure 1, with the chair back supporting member in the highest position; Figure 3 is a schematic side view of the height adjustment mechanism shown in Figure 1 with the chair back supporting member in a retracted position; Figure 4 is a schematic plan view showing more detail of the locking mechanism associated with adjustment mechanism shown in Figure 1, with the detent in the extended position; Figure 5 is a schematic plan view of the locking mechanism as in Figure 4 with the detent in the retracted position; and, Figure 6 is a perspective view showing greater detail of the tubular chair back support member.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

Dimensions of certain of the parts as shown in the drawings may have been modified and/or exaggerated for the purposes of clarity of illustration.

The illustrated embodiment shows a height adjustment mechanism for a chair back which includes a tubular chair back support member an upper end of which is attached to a chair back, and a locking means which is attached to a chair control shown partially at The chair control is rigidly connected to a seat support which •rigidly supports the seat of the chair.

The chair back support member is constructed from a tube and includes a plurality of 15 vertically spaced apart tabs which are punched inwardly into an internal channel of the tube. The inwards punching of each of the tabs forms a respective aperture and thus the chair back support member includes a plurality of spaced apart apertures.

Each of the apertures includes a free edge which in use is downwardly facing.

The chair back support member is vertically slidable relative to the locking means in a support member pathway defined by the movement of the chair back support member.

The locking means includes a detent (10) slidable between an extended position, which is in the support member pathway as is shown in Figures 1, 2, and 4, and a retracted position which can be seen in Figures 3 and 5. A biasing means is in the form of a wire torsion spring (11) which biases the detent into the extended position, so that when the detent and one of the apertures are aligned the detent will extend into the aperture, and respective free downwardly facing edge will bear down on the detent to engage the chair back support member in position to thereby lock the chair back into position.

The tabs extend upwardly into the aperture and slope inwardly, so that lifting the chair back support member is possible, because the detent is urged progressively into the retracted position by the action of the sloping part of the tab. The height adjustment arrangement can thus be seen as acting as a ratchet arrangement, allowing movement of the chair back upwards but not downwards. The detent can be released by an actuation means (15) which in this illustrated embodiment is a lever that can be pushed against the torsion spring (11) to retract the detent, and permit movement of the chair back upwards.

This then described the illustrated chair back adjustment mechanism in general terms.

Now turning to a more detailed description.

The chair back support member can be constructed of tubular steel of an industry standard, and thus might be 32 mm or 50 mm in longest diameter The tubular member is thus elongate in cross section, with two wider sides (16) and two thinner sides The thinner sides are arcuate and the wider sides are substantially parallel.

An upper end (not shown) of the chair back support member is in use attached to the chair back, and in accordance with usual practice has welded thereon a lateral pin which can be used to pivot about two brackets fixed to the chair back so that the chair back can pivot about a generally horizontal axis.

A lower portion of the chair back support member is generally left open, as illustrated, but is covered with a plastics sleeve and is not readily visible.

15 Several tabs are formed in a lower portion of the support member. During manufacture the tube of the chair back support member is supported by a mandrel, which includes three portions, two side portions on either side of the apertures, to support the sides, and a central elongate portion, which is lower than the side portions.

A punch with a lower edge shaped to the desired profile is used to punch each of the 20 tabs out of one of the two wider sides. Seven punches would be operated in the one time to form all of the apertures at the same time. The mandrel is then retracted. The tool involved in this process is generally referred to as a floating horn press tool.

It can be seen that the tabs are not entirely straight, but include a land (18) which is substantially parallel with the wider side of the tubular chair back support member and 25 a sloping portion (19) which slopes to meet a lower edge of the aperture The land (18) can act to limit the extent to which the detent can extend into the aperture, and is also formed so that the detent registers positively in place. The number and spacing of these apertures can be varied in accordance with the degree of variation of back rest positions that is desired.

It can be seen that the apertures are substantially rectangular in plan view. This is a convenient shape and allows for the detent to ride through the entire length of the aperture.

The locking mechanism is housed within a U shaped locking housing (30),which is conventional for other cam-operated or screw threaded clamp operated height adjust mechanism. Accordingly this is a substantial advantage in so far as it fits in with 8 standard industry fittings. The housing includes two pairs of apertures (20, 21) the first is to accommodate a housing pin (22) which passes through similar apertures within the control housing. The control housing (23) is in the form a U shaped channel member.

The second of the two pairs of apertures (21) is to accommodate a pin (24) for holding a series of plates which are used in the mechanism for control the tilt of the seat. A tilt spring (25) which biases the tilt of the chair is also shown in the illustrations.

A collar (31) is fitted in the U shaped locking housing. The collar is held in place by two pins which fit through two pairs of collar holding apertures (32, 33). The collar has an external shape which fits into the U shaped locking housing, and has an internal aperture defining a support member pathway (34) through which the chair back support member passes. The internal aperture defining the support member pathway fit relatively closely to an external surface of the support member.

The actuation means (15) to operate the detent (10) is in the form of a lever which is pivoted at a first end on an edge (35) of a small slot (36) of one side of the U shaped S. 15 housing, a second end of the lever extends through an elongate slot (37) to form a o. handle (38) which is readily accessible to the fingers of a user. The detent (10) is formed as a protrusion extending from a middle part of the lever, and is aligned with the plurality of apertures. A wire torsion spring (11) is coiled around a spring pin which pin is held in place by the housing and a first arm of the torsion spring bears 20 against an underside of housing pin and also against the lever at cut out to O bias the detent to engage with one of the apertures, as shown in Figure 2, and Figure 4.

Finger pressure against the handle opposes the bias of the torsion spring to retract the detent from the aperture.

It can be seen especially from Figure 1 and Figure 2, that the detent in the extended position extends into the chair back support member passageway, and with the back support present will tend to extend through one of the apertures The land (18) limits the extent to which the detent can extend through the aperture, as does the size of slot A free downwardly facing edge of the aperture bears down on the detent by reason of the weight of the chair back and the support member and accordingly the chair back cannot be pushed further down. The chair back can however be lifted without the lever (15) being operated by handle. As the chair back is lifted the detent rides up on the sloping portion (19) of the tab, until it is clear of the aperture as is shown in Figure 3, it can cross over into the aperture below that in which it was first engaged, and then engage the free edge of that aperture, or continue until the desired height of the chair back is reached to then engage with a suitably positioned aperture.

This configuration of chair back height adjustment mechanism uses an arrangement within the usual size constraints of standard height adjust mechanisms.

Various features of the invention have been particularly shown and described in connection with the exemplified embodiment of the invention, however, it must be understood that these particular arrangements merely illustrate and that the invention is not limited thereto and can include various modifications falling within the spirit and scope of the invention.

Claims (11)

1. A height adjustment mechanism for a chair back, said adjustment mechanism including: a chair back support member to which at an upper portion the chair back is to be attached; a locking means operable at a lower portion of the chair back support member and connectable with a base or a seat of a chair; and, the chair back support member being vertically slidable within a support member pathway relative to the locking means, tubular and having a plurality of vertically spaced tabs; the tabs being punched inwardly into an internal channel of the tube resulting in a oplurality of apertures, each aperture having a free downwardly facing edge, and the tabs 1 pextending upwardly and sloping inwardly into the internal channel of the chair back support member; 9*9**9 15 the locking means including: 99*999 detent means slidable between an extended position in the support member pathway and a retracted position away from the support member pathway; biasing means to bias the detent means to the extended position; and, actuation means to retract the detent means to the retracted position against the S 20 bias of the biasing means which when retracted allows for downward movement of the chair back support member relative to the locking means; and, said detent means when in use and in the extended position being biased into one of said apertures and the free downwardly facing edge of the said one of the apertures bearing down on said detent to engage the chair back support member in position to prevent downwards movement of the chair back but permitting upward movement of the chair back whereby the detent is progressively retracted by riding over the respectivetab iWU a iUwri apiLLure.

2. A height adjustment mechanism for a chair back, said adjustment mechanism including: a chair back support member adapted at a location forattachment of the chair back, said chair back support member being elongate and tubular and having a plurality of aligned spaced punched apertures along at least a portion of its length, each aperture having a free facing edge facing away from the location of the chair back attachment, and for each aperture a tab extending and sloping inwardly into the chair back support member and generally directed towards the location of the chair back attachment; locking means within which the chair back support member is slidably supported along a support member pathway, the locking means being adapted to connect with a base or a seat of a chair, and the locking means including: detent means slidable between an extended position in the support member pathway and a retracted position away from the support member pathway; biasing means to bias the detent means to the extended position; and, actuation means to retract the detent means to the retracted position S•against the bias of the biasing means which when retracted allows for 1. :movement of the chair back support member away from the location of the chair back attachment; and, when in use said detent means being biased in the extended position into one of said apertures and the free facing edge of the said one of the apertures bearing on said detent to engage the chair back support member in position to prevent movement of the chair back away from the location of the chair back attachment but permitting movement of S 20 the chair back support member towards the location of the chair back attachment od: whereby the detent is progressively retracted by riding over the respective tab into an adjacent aperture. 4

3. A height adjustment mechanism for a chair back as in either Claim 1 or Claim 2 wherein the apertures are uniformly spaced.

4. A height adjustment mechanism for a chair back as in any one of the preceding claims wherein each aperture is rectilinear.

A height adjustment mechanism for a chair back as in any one of the preceding claims wherein the chair back support member is manufactured of tubing having in cross section two substantially parallel spaced wide sides and spaced arcuate joining sides with the apertures being punched in one of the wide sides.

6. A height adjustment mechanism for a chair back as in any one of the preceding claims wherein each tab has proximal to its free end a land substantially parallel to the surface of the chair back support member through which the respective aperture was 12 punched, and said land being adapted to limit insertion of the detent within the chair back support member.

7. A height adjustment mechanism for a chair back as in any one of the preceding claims wherein the locking means includes guide means adapted to guide sliding movement of the chair back support member within the support member pathway.

8. A height adjustment mechanism for a chair back as in any one of the preceding claims wherein the biasing means includes a torsion spring.

9. A height adjustment mechanism for a chair back as in any one of the preceding claims wherein the locking means supports the actuation means, the detent is a projecting part of the actuation means, and the actuation means has at a first end a handle projecting from the locking means and at a second end a portion to bear against the locking means and act as a pivot where the actuation means being adapted to pivot about the aforementioned pivot under the influence of manual pressure applied to the handle against the biasing means. SS :V.6 15

10. A height adjustment mechanism for a chair back as in any one of the preceding claims incorporated into a chair.

11. A height adjustment mechanism for a chair back substantially as described herein with reference to the accompanying figures. 20 Dated this 14th day of January 1999 •ol•• 1, BOS SEATING SYSTEMS (AUST) PTY LTD o..i By their Patent Attorneys, A. P. T. Patent and Trade Mark Attorneys