NZ556103A - Adjustable work surface with slippable belt drive - Google Patents

Abstract

The position of the working surface of a work desk or table is adjustable by one or more adjusting arrangements which are driven via a belt transmission by a drive mechanism. The belt transmission includes a preferably toothed belt 28 connecting a drive gear or pulley 21 receiving power from the drive mechanism and one or more adjustment gears and/or pulleys 30, 31, 32 of the adjustment mechanism. The belt is configured to slip on at least one of the gears and/or pulleys, preferably on the drive gear 21, when overloaded so that the mechanisms are not damaged. The tension of the belt can be adjusted by a tensioning arrangement such as being able to move the position of the idler pulleys.

Description

556103 OurRef: AGL002NZ Patents Form No, 5 PATENTS ACT 1953 Complete after Provisional No. 556103 dated 22 June 2007 COMPLETE SPECIFICATION ADJUSTABLE FURNITURE We, Dexion Commercial (New Zealand) Limited, a New Zealand company of CARussell Mcveagh, Level 30, Vero Centre, 48 Shortland Street, Auckland, New Zealand do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: 556103 FIELD OF THE INVENTION The invention relates to adjustable furniture, particularly but not exclusively to height adjustable furniture such as desks, tables and the like.

BACKGROUND TO THE INVENTION Adjustable furniture is well known. For example, height-adjustable desks are available. These generally have two or more legs and an adjustment means for extending or decreasing the lengths of the legs to adjust the height of the desk work surface.

However, adjustable furniture is often somewhat delicate. The adjustment means can degrade and are particularly vulnerable to misuse. For example, attempts to adjust the height of an adjustable desk while the desk bears a large weight (such as a person sitting on the desk) often leads to damage or failure of the adjustment means.

Also, some adjustment means are bulky or generally in the way of the user, or are difficult to access should repair be necessary.

It is an object of the invention to provide improved adjustable furniture or at least to provide the public with a useful choice.

SUMMARY OF THE INVENTION In a first aspect the invention provides an article of furniture including: a working surface having an adjustable position; a drive mechanism; one or more adjustment arrangements for adjusting the position of the working surface; and 2 556103 a transmission connecting the drive mechanism to the adjustment arrangements; wherein the transmission is configured to slip when driven under an overload so as to prevent damage.

In the context of the present invention the term "working surface"' means a surface of an article of furniture which performs a function other than simply supporting the furniture itself. For example, a desktop surface provides the function of supporting a user's work, computer, telephone etc. A tabletop surface performs a similar function. A bookcase surface performs the function of supporting books or other objects. The article of furniture may be a desk, table, shelf, bench, bookcase, chair or the like.

Preferably the transmission includes a belt connecting a drive gear or pulley receiving power from the drive mechanism and one or more adjustment gears and/or pulleys, the belt being configured to slip on at least one of the gears and/or pulleys under an overload. Preferably the belt slips on the drive gear or pulley under an overload.

Preferably the transmission includes one or more idler wheels configured to guide the belt on its path. Preferably at least some of the idler wheels are positioned to increase the contact area between the belt and the gears and/or pulleys.

Preferably the transmission includes a tensioning arrangement allowing the belt tension to be adjusted. Preferably the tensioning arrangement includes an idler pulley with an adjustable position.

Preferably the belt is a toothed belt.

Preferably the article of furniture includes two or more adjustment arrangements, together configured to adjust the lengths of supports so as to adjust the height of the working surface. Preferably the transmission includes a single belt which drives all 3 556103 of the two or more adjustment arrangements. Preferably each adjustment arrangement includes a threaded lead screw which is driven to adjust the length of a support.

Preferably each support includes an inner and outer component configured to slide over each other when the length of the support is adjusted. Preferably the inner and outer components are formed as extrusions.

Preferably the drive mechanism is a hand-operated crank.

Preferably the hand-operated crank drives a 90 degree gearbox.

Preferably the hand-operated crank sits flush with the underside of a desktop in a stowed position.

Preferably the article of furniture is a height-adjustable table or desk.

In a second aspect the invention provides an article of furniture including: a working surface having an adjustable position; a drive mechanism; one or more adjustment arrangements for adjusting the adjustable position of the working surface; and a toothed belt connecting the drive mechanism to the adjustment arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described by way of example only, with reference to the accompanying drawings, in which: 4 556103 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 DETAILED DESCRIPTION Figure 1 shows a height-adjustable desk framework 1. The framework includes a number of supports (e.g. legs) 2, 3, 4 and an upper section 5 which supports a desk surface (not shown). Each support is adjustable in length, allowing the height of the desk surface to be adjusted. A user adjusts this height by operating a drive mechanism 6. Power is carried by a transmission from the drive mechanism to adjustment arrangements in each support 2, 3, 4. Preferred drive mechanism, transmission and adjustment arrangements are described below.

The framework 1 may also include structural members 7 and feet 8 for rigidity and stability. Similarly, the framework 1 may include large attachment surfaces 9 for stable and strong attachment of a desk surface to the framework 1. The transmission is a perspective view of a height-adjustable desk, without the desk surface; is a top plan view of the desk of Figure 1; is a perspective view of a 90 degree gearbox; is an exploded view of the gearbox of Figure 3; shows the handle, handle housing and mounting bracket of the drive mechanism; is an exploded view of the handle assembly; is a cross-section of the handle assembly; is a perspective view of a support; is a first vertical cross-section of the support and adjustment arrangement; is a second vertical cross-section of the support and adjustment arrangement; and is a horizontal cross-section of the support and adjustment arrangement. 556103 is preferably contained in one or more trays 10, with the top of the trays closed by the desktop in an assembled desk.

Figure 2 is a top plan view of the drive mechanism and transmission. The drive mechanism 6 includes a hand-operated crank 20 which feeds a drive gear or pulley 21 via a 90 degree gearbox such as that shown in Figures 3 and 4.

Figure 3 shows a gearbox 22 having a keyed input shaft 23 for engaging with the shaft 24 of the hand crank 20. The output shaft 25 of the gearbox 22 is at 90 degrees to the input shaft 23, changing the rotation around a horizontal axis of the hand crank 20 into a rotation around a vertical axis of the drive gear or pulley 21.

Figure 4 is an exploded view of the gearbox, showing the input shaft 23 and output shaft 25 with their respective gears 26, 27.

Returning to Figure 2, the drive gear or pulley 21 drives a toothed belt 28. This belt forms a single loop to drive adjustment of the three supports 2, 3, 4 in unison. The belt path is defined by one adjustment gear or pulley 30, 31, 32 per support 2, 3, 4 and by a number of idler pulleys 33, 34, 35, 36. The idler pulleys may be arranged to increase the area of contact between the belt and one of the gears or pulleys. For example, idler pulleys 35, 36 act to increase the contact area between the belt and the drive gear or pulley 21.

One or more of the idler pulleys may have adjustable positions in order to lengthen or shorten the length of the path followed by the toothed belt 28. This enables adjustment of the belt tension, either to allow for belt stretch or following installation of the belt 28. 6 556103 The belt 28 may be a T5 profile timing belt, having 200 teeth per metre and a width of 10mm. The belt may be formed from polyurethane reinforced with stainless steel. Many other types of belt may be suitable.

The use of a toothed belt 28 provides an advantageous compromise between driving capacity and slippage. Where a chain or drive rod or similar system is used, the transmission is generally permanently engaged. If the transmission is driven under overload (for example if someone sits on a desk while its height is adjusted) this may result in failure of the system, through stripping of teeth from a gear, or snapping of the chain or other equipment failure. In contrast, a toothed belt such as used in the Applicant's system will slip on the drive gear or pulley 21 when it is driven under an overload. This results in no, or at least minimal, damage to the system. As the slipping occurs at the drive gear or pulley 21, the supports 2, 3, 4 remain of equal length throughout.

On the other hand, when the transmission is driven under a normal load, the toothed belt 28 provides sufficient power to the adjustment gears or pulleys 30, 31, 32 to adjust the lengths of the supports 2, 3, 4 and the height of the desk.

Other forms of transmission which slip under an overload may be suitable.

The toothed belt transmission described above is advantageous because it is made from readily available parts and is relatively easy and cheap to manufacture. The system is reliable and allows many different configurations to be used, including configurations suitable for straight desks and corner desks (as in Figures 1 and 2) with different corner angles. The system is also compact, so that the drive, transmission and adjustment arrangement together form a low-profile, discreet system. The mechanism is also very quiet. 7 556103 A V-Belt, double V-belt, flat belt or other type of belt could be used. However, the toothed belt is expected to have superior performance.

The crank handle assembly is shown in detail in Figures 5, 6 and 7. The handle 20 drives a shaft 24 which is formed in two telescoping sections 41, 42. The shaft is keyed at its end 43 to cooperate with the input shaft of the gearbox shown in Figures 3 and 4.

The shaft rides in a housing 44 which is mounted to the underside of the desktop using a bracket 45. The telescoping nature of the shaft 24 allows the handle to be pulled out from under the desk into an operating position to drive the height adjustment, then pushed back into a stowed position under the desk when the height has been adjusted.

In order to ensure that the handle lies flat against the underside of the desktop in the stowed position, the front edge 46 of the housing 44 is angled, as shown in Figure 5. When the handle is pushed home, part 47 of the handle 20 rides up on the angle 46, forcing the handle 20 to rotate to sit against the underside of the desktop. This keeps the handle out of the way of a desk user.

Figure 6 is an exploded view of the handle assembly, showing the keyed internal shape 48 of the outside section 42 of the shaft 24. A toothed bush 49 is driven by the end 50 of the internal section 41 and engages with the keyed shape 48 to drive the external section 42. The toothed bush 49 rides freely along the external section 42, allowing the shaft 24 to telescope.

Figure 7 is a cross-section of the handle assembly in the stowed position. The external section 42 of the shaft 24 is fixed between the housing 44 and the end 43 which engages with the gearbox but is free to rotate. The internal section 41 and the handle 20 can be pulled outwards into an operating position by a user. 8 556103 Each support 2, 3, 4 includes telescoping internal and external extrusions 60, 61 as shown in Figure 8. This allows the length of the support to be adjusted but maintains an attractive external surface at all lengths.

Each support includes an adjustment arrangement, as shown in detail in Figures 9 to 11. Figures 9 and 10 are vertical cross-sections and Figure 11 is a horizontal cross-section of the support 2, 3, 4 and adjustment arrangement.

The adjustment arrangement includes a threaded lead screw 62 which is driven at its top end 63 by the corresponding adjustment gear or pulley 30, 31, 32. A lead screw tower 64 sits at its lower end 65 at the bottom end of the support 2, 3, 4. At its top end, the lead screw tower supports a lead screw nut 66 which engages with the thread on the lead screw 62. The lead screw tower 64 and lead screw nut 66 remain stationary. Thus, when the lead screw is driven and rotates, the length of the combined lead screw 62 and lead screw tower 64 increases or decreases (depending on the direction of rotation of the lead screw 62).

Thus the height of the desk can be increased or decreased by rotating the crank handle 20 in the appropriate direction.

The outer (i.e. lower) extrusion includes channels 67 for attachment of structural members 7. The channels are shaped and dimensioned to accept M6 flanged nuts, which slide in the channel to the appropriate position. A structural member 7 can then be attached using an M6 bolt. Screw channels 68 are also provided for attaching the extrusion to feet 8.

The inner (top) extrusion includes recesses 69 for receiving a height scale. Ribs 70 accurately locate the bearing 71. Screw channels 72 are provided for attaching the extrusion to the upper section 5 of the desk framework. 9 556103 Bushes 73 operate to ensure accurate sliding of the extrusions with respect to each other. The bushes are retained in the correct position with respect to the outer extrusion by ribs 74.

The materials of the belt have been described above. The other components may be formed from the following materials. The drive, adjustment and idler gears or pulleys may be formed from injection moulded plastic (ABS or Class Filled ABS), or aluminium. The trays for enclosing the transmission may be formed from mild steel, preferably with a powder coated finish. The gearbox housing and the gears may be formed from injections moulded, glass-filled nylon; while the gearbox bearing components may be formed from a combination of bronze, steel and PTFE. The gearbox shafts may be formed from mild steel. The extrusions 60, 61 may be formed from aluminium.

Although described with reference to a desk, the invention may also apply to other adjustable furniture such as tables, shelving etc. Similarly, the advantageous transmission may be used with a motor-driven rather than hand-driven system.

The Applicant's system lessens damage to adjustable furniture through overload. The system is flexible, being suitable for a variety of furniture configurations. The system provides accurate adjustment, with little slop in adjustment. The transmission may be contained in a tray under a desk surface, making it easily accessible by removing the desk surface, should repair be necessary. The drive, transmission and adjustment arrangement require no ongoing lubrication. The system is easy to use and requires little maintenance.

While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the 556103 appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of the Applicant's general inventive concept. 11 RECEIVED at IPONZ on 04 December 2009 556103

Claims (17)

What is claimed is:

1. An article of furniture including: i. a working surface having an adjustable position; ii. a drive mechanism; iii. one or more adjustment arrangements for adjusting the position of the working surface; and iv. a transmission connecting the drive mechanism to the adjustment arrangements; wherein the transmission includes a belt connecting a drive gear or pulley receiving power from the drive mechanism and one or more adjustment gears and/or pulleys, the belt being configured to slip on at least one of the gears and/or pulleys when placed under an overload so as to prevent damage, and wherein the transmission includes a tensioning arrangement allowing the belt tension to be adjusted.

2. An article of furniture as claimed in claim 1 wherein the belt slips on the drive gear or pulley under an overload.

3. An article of furniture as claimed in claim 1 or 2 wherein the transmission includes one or more idler wheels configured to guide the belt on its path.

4. An article of furniture as claimed in claim 3 wherein at least some of the idler wheels are positioned to increase the contact area between the belt and the gears and/or pulleys.

5. An article of furniture as claimed in claim 1 wherein the tensioning arrangement includes an idler pulley with an adjustable position.

6. An article of furniture as claimed in any one of claims 1 to 5 wherein the belt is a toothed belt. 12 556103 RECEIVED at IPONZ on 04 December 2009

7. An article of furniture as claimed in any preceding claim including two or more adjustment arrangements, together configured to adjust the lengths of supports so as to adjust the height of the working surface.

8. An article of furniture as claimed in claim 7 wherein the transmission includes a single belt which drives all of the two or more adjustment arrangements.

9. An article of furniture as claimed in claim 7 or 8 wherein each adjustment arrangement includes a threaded lead screw which is driven to adjust the length of a support.

10. An article of furniture as claimed in any preceding claim wherein each support includes an inner and outer component configured to slide over each other when the length of the support is adjusted.

11. An article of furniture as claimed in claim 10 wherein the inner and outer components are formed as extrusions.

12.An article of furniture as claimed in any preceding claim wherein the drive mechanism is a hand-operated crank.

13. An article of furniture as claimed in claim 12 wherein the hand-operated crank drives a 90 degree gearbox.

14. An article of furniture as claimed in claim 12 or 13 wherein the hand-operated crank sits flush with the underside of a desktop in a stowed position.

15.An article of furniture as claimed in any preceding claim, being a height-adjustable table or desk. 13 RECEIVED at IPONZ on 04 December 2009 556103

16. An article of furniture as claimed in claim 1 substantially as herein described.

17. An article of furniture substantially as herein described with reference to the accompanying drawings. DEXION COMMERCIAL (NEW ZEALAND) LIMITED By Their Attorneys ELLIS TERRY 14