GB2333821A

GB2333821A - Adjustable coil spring assembly

Info

Publication number: GB2333821A
Application number: GB9801806A
Authority: GB
Inventors: Stephen Francis Wood
Original assignee: AUDIENCE SYSTEMS Ltd
Current assignee: AUDIENCE SYSTEMS Ltd
Priority date: 1998-01-28
Filing date: 1998-01-28
Publication date: 1999-08-04
Also published as: GB9801806D0

Abstract

An adjustable coil spring assembly (2)comprises an inner member (6), a coil spring (24) and an outer member (4), the coil spring (24) applying a pre-tension between the inner (6) member and the outer member (4). The coil spring (24) is wound about a central axis and has a radially inner end (22) connected to the inner member (6) and a radially outer end (26) releasably connected to one of the plurality of fixing points (28). The fixing points (28) are formed on the outer member (4) and are spaced apart in a circumferential direction of the coil spring (24). The pre-tension between the inner (6) and outer (4) members is set by selecting to which of the fixing points (28) the outer end (26) of the spring (24) is fixed. A tool (48) is provided for adjusting the pre-tension in the spring (24) and a method of adjusting the pre-tension is also described herein.

Description

ADJUSTABLE COIL SPRING ASSEMBLY This invention relates to an adjustable coil spring assembly and particularly, although not exclusively, relates to an assembly comprising an adjustable tension drum joint in an auditorium seat.

Conventional auditorium seats comprise a frame fixed to the auditorium structure and a tipping seat squab mounted to the frame on its back edge by means of two adjustable tension drum joints. In an unloaded condition, pre-tension in the drum joints causes the seat squab to lift up, so that the seat rows are Wept clear unless the seat is in use.

To improve the comfort and general ease of use of the seat, it is desirable that just sufficient pretension is applied by the drum joints to ensure that the seat squab will raise when the user of the seat stands up. As there is no facility for adjusting the spring pre-tension in the assembled drum joints, the only way of reducing the raising force on the seat squab is to remove the spring from one of the drum joints. This requires the complete disassembly of the drum joint.

However, for smoothness of operation, it is important that the spring pre-tension is the same in both drum joints. Consequently, in order to overcome manufacturing variations and on site variations in orientation and possible distortion of the seat frame, it is desirable for there to be adjustability in at least one of the drum joints in each seat assembly.

According to the present invention there is provided an adjustable coil spring assembly comprising an inner member, a coil spring and an outer member, the coil spring applying a pre-tension between the inner member and the outer member, in which assembly the coil spring is wound about a central axis and has a radially inner end connected to the inner member and a radially outer end releasably connected to one of a plurality of fixing points which are formed on the outer member and are spaced apart in a circumferential direction of the coil spring, the pre-tension between the inner and outer members being set by selecting to which of the said fixing points the outer end of the spring is fixed.

Preferably, the fixing points comprise openings formed through the outer member. Preferably, the openings are interconnected. This interconnection may be provided by a continuous slot which is substantially aligned with the circumferential direction of the coil spring.

Preferably, the coil spring is flat in section and the openings are elongate and extend substantially parallel to central axis. Conventional drum joints use round section coil springs which when under load must be held in place with a support washer. As these springs are partially wound and unwound in service, the coils bear against the washer, causing unwanted friction and wear in the drum joint. The use of a flat spring removes the need for a support washer because the force in the loaded spring is purely radial.

Preferably, the adjustable coil spring assembly further comprises an adjustment tool comprising a handle fixed to a shaft, the free end of the shaft being biforcated, the respective prongs of the biforcated end defining a notch which is adapted to receive the outer end of the coil spring. Preferably, the prongs are accommodated in the slot when the outer end of the coil spring is received in the notch.

Preferably, the outer member is fixed to a supporting structure. Preferably, the supporting structure comprises a chair frame and the inner member is fixed to a tipping seat squab. Preferably, the outer member comprises a tubular housing disposed about a longitudinal axis, the coil spring being located in the housing such that the central axis of the coil spring is substantially aligned with the longitudinal axis of the housing. Preferably, the inner member comprises an end plate which at least partially closes off a side of the housing.

Preferably, the adjustable coil spring assembly comprises an adjustable tension drum joint of an auditorium seat.

According to a further aspect of the present invention there is provided a method of adjusting the pre-tension between the inner member and the outer member of an adjustable coil spring assembly as hereinbefore described, the method comprising the steps of: applying a force on the outer end of the coil spring in a direction towards the central axis, thereby to release the said outer end from a respective one of the said fixing points; sliding the outer end of the coil spring in a circumferential direction relative to the outer member until the outer end is aligned with another of the said fixing points; releasing the force on the outer end to engage the outer end with the said fixing point.

Embodiments in accordance with the present invention provide enormous improvements over current methods used in the industry. The principal advantages are as follows. i) On site adjustments can easily be made to take into account varying site conditions such as uneven floors and surface conditions. Installation time can be greatly reduced as no chair dismantling is necessary to adjust spring tension, thus giving a substantial reduction in labour costs. ii) Manufacturing efficiency is improved as a single design of drum joint will suit a full range of chair products. iii) There is a considerable improvement in wastage and human resource. This is the result of streamlined manufacturing and less installation resource needed for site installation. An improvement in production line efficiency will also result from the ease of adjustment. iv) There is a significant improvement in product quality due to the ease at which a consistent seat tipping action can be achieved. v) The design enables spring tension to be adjusted from outside the spring housing by use of a specially designed tool. This enables seat squabs of varying weights/widths and sizes to use a standard design of drum joint. The spring can be adjusted to suit any need by simply altering the spring tension. vi) As the adjustment of the tension drum joint can only be achieved by use of an appropriate tool, the tension drum joint is resistant to tampering.

For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1A is an exploded perspective view of an ajustable coil spring assembly comprising an adjustable tension drum joint for a seat; Figure 1B is an exploded side view of the joint of Figure 1; Figure 1C is a view of the drum and intergral bracket of the drum joint of Figure 1B, viewed on arrow C; Figure 2 is a plan view of an auditorium seat in which the seat squab is connected to the frame by means of a pair of adjustable tension drum joints; Figure 3 is a side view of the seat squab of Figure 2 shown in the lowered and raised position; Figure 4 is an enlarged plan view of an adjustable tension drum joint; Figure 5 is an enlarged side view of a tension drum joint; Figure 6 is an enlarged side view of the tension drum joint of Figure 5, with the seat squab in the raised position; Figure 7 is an illustration of how the tension drum joint is adjusted by means of a hand tool; and Figure 8 is a further illustration of adjustment of the tension drum joint viewed from the side of an auditorium chair.

Figures 1A, 1B and 1C show an adjustable coil spring assembly embodied as a tension drum joint 2 of an auditorium seat. The drum joint 2 comprises a housing or drum 4 to which is fitted an end cap 6. The drum 4 is fitted with a bracket 8 which is fixed to one side of the back edge of an auditorium seat squab (not shown) and the end cap 6 is bolted directly to a frame 10 of the auditorium seat.

A drive shaft 12 and limit stops 14, 16 are fixed to an inside surface 18 of the end cap 6 and project from the end cap 6 substantially at right angles to the inside surface 18. At least one of the limit stops 14,16 is provided with a resilient buffer such as a rubber or neoprene sleeve or ferrule (not shown).

The free end of the drive shaft 12 is provided with a slot 20 which is adapted to receive a radially inner end 22 of a flat section coil spring 24. A radially outer end 26 of the coil spring 22 is bent radially outwardly from the main body of the coil spring and is shaped to engage any one of a plurality of interconnected openings 28 formed in a circumferential wall 30 of the drum 4.

As best seen in Figure 1C, the end wall 32 of the drum 4 is provided with a central opening 34 and is cut away at both sides, so that the end wall 32 is in the form of a bar which is wasted at upper and lower regions 36, 38 to provide abutments 40, 41, 42, 43 for the limit stops 14, 16.

In the assembled condition of the tension drum joint 2, the end plate 6 closes off the end of the drum 4, and the drive shaft 12 is supported in the central opening 34 in the end wall 32 of the drum 4 by means of a bush 44. The coil spring 24 is located within the drum 4 such that the central axis about which the coil spring is wound is substantially aligned with a longitudinal axis A of the drum 4. The inner end 22 of the coil spring 24 is located in the slot 20 in the drive shaft 12 and the outer end 26 of the coil spring is located in one of the openings 28 in the circumferential surface 30 of the drum 4.

Figure 2 shows an auditorium chair in which a seat squab 46 is fitted to the frame 10 by means of a pair of tension drum joints 2 bolted to respective sides of the rear edge of the seat cushion 46.

Figure 3 is a side view of the arrangement of Figure 2 showing the seat squab 46 in both the lowered and raised positions.

Figures 4, 5 and 6 are enlarged views of the tension drum joint 2 in service and clearly illustrates the disposition of the various components of the joint.

In particular, it is possible to see the interaction between the end wall 32 of the drum 4 and the limit stops 14 and 16, which determine the position of the seat squab 46 in the lowered (Figure 5) and the raised (Figure 6) positions. As will readily be appreciated, the two limit positions are determined by abutment of respective abutments 40, 41, 42, 43 which are formed on the end wall 32 against respective limit stops 14, 16.

If resilient buffers are provided, they serve to damp the deceleration of the seat as the respective limit positions are reached.

When an auditorium seat has been installed, it is necessary to adjust the spring tension in the tension drum joints such that the least possible tipping force is applied to the seat squab 46 which still ensures reliable tipping of the seat squab 46 when the seat is vacated. Figure 7 shows how adjustment of the pretension in a tension drum joint 2 is achieved. As described above, the outer end 26 of the coil spring 24 is located in one of the openings 28 formed in the circumferential wall 30 of the drum 4. In the arrangement illustrated in Figure 7, the outer end 26 of the coil spring 24 is located in the uppermost opening 28 and consequently the relative position of the outer end 26 to the inner end 22 of the coil spring 24 are such that the pre-tension is at a minimum. If the outer end 26 is moved into a lower slot, the coil spring is wound tighter and hence the spring pretension is increased. Thus, a desired spring pretension can be achieved by locating the outer end 26 of the coil spring 24 in the appropriate opening 28.

In order to facilitate movement of the outer end 26 of the spring 24 into successive openings 28, a hand tool 48 is provided. The hand tool 48 comprises a handle 50 and a shank or shaft 52. The free end of the shaft 52 is biforcated and comprises a pair of prongs 54, 56 which together define a notch 58.

In use of the handle 48, the prongs 54, 56 are engaged on opposite sides of the outer end 26 of the coil spring 24 and force is applied in a radial direction towards the centre of the coil spring 24 causing it to deflect radially inwardly and enabling the outer end 26 to drop out of the opening 28 in which it is located. A force is then applied on the handle 48 in a circumferential direction of the coil spring 24 causing the prongs 54, 56 to travel along the slot which interconnects the openings 28, until the outer end 26 is aligned with another more appropriate opening 28.

The other tension drum joint 2 on the opposite side of the seat squab 46 is then adjusted in a similar manner until the required smoothness and precision of operation is achieved in the tipping action of the seat squab 46. As the adjustment of the respective tension drum joints 2 is so straightforward and quick, the time and cost of installation of the auditorium seat is reduced.

Although in the illustrated embodiment, the end cap 6 is attached to the seat frame 10 and the drum 4 is attached to the seat squab 46, the tension drum joint 2 may be modified, such that the drum 4 is attached to the seat frame 10 and the end cap 6 is attached to the seat squab 46.

Claims

1. An adjustable coil spring assembly comprising an inner member, a coil spring and an outer member, the coil spring applying a pre-tension between the inner member and the outer member, in which assembly the coil spring is wound about a central axis and has a radially inner end connected to the inner member and a radially outer end releasably connected to one of a plurality of fixing points which are formed on the outer member and are spaced apart in a circumferential direction of the coil spring, the pre-tension between the inner and outer members being set by selecting to which of the said fixing points the outer end of the spring is fixed.

2. An adjustable coil spring assembly as claimed in claim 1, in which the fixing points comprise openings formed through the outer member.

3. An adjustable coil spring assembly as claimed in claim 2, in which the openings are interconnected.

4. An adjustable coil spring assembly as claimed in claim 3, in which the interconnection between the openings is provided by a continuous slot which is formed through the outer member and extends in the circumferential direction of the coil spring.

5. An adjustable coil spring assembly as claimed in any one of claims 2 to 4, in which the openings are elongate and extend substantially parallel to the central axis of the coil spring.

6. An assembly comprising an adjustable coil spring assembly and an adjustment tool, the adjustment tool comprising a handle fixed to a shaft, the free end of the shaft being bifocated, the respective prongs of the bifocated end defining a notch which is adapted to receive the outer end of the coil spring.

7. An adjustable coil spring assembly as claimed in any one of the preceding claims, in which the outer member is fixed to a supporting structure.

8. An adjustable coil spring assembly as claimed in claim 7, in which the supporting structure comprises a chair frame and the inner member is fixed to a tipping seat squab.

9. An adjustable coil spring assembly as claimed in any one of the preceding claims in which the outer member comprises a tubular housing which extends along a longitudinal axis, the coil spring being located in the housing such that the central axis of the coil spring is substantially aligned with the longitudinal axis of the housing.

10. An adjustable coil spring assembly as claimed in claim 9, in which the inner member comprises an end plate which at least partially closes off the side of the housing.

11. An method of adjusting the pre-tension between the inner member and the outer member of an adjustable coil spring assembly as claimed in any one of the preceding claims, the method comprising the steps of: applying a force on the outer end of the coil spring in a direction towards the central axis, thereby to release the said outer end from a respective one of the said fixing points; sliding the outer end of the coil spring in a circumferential direction relative to the outer member until the outer end is aligned with another of the said fixing points; releasing the force on the outer end to engage the outer end with the said other fixing point.

12. An adjustable coil spring assembly substantially as described herein, with reference to and as shown in the accompanying drawings.