GB2099591A

GB2099591A - Furniture-testing apparatus

Info

Publication number: GB2099591A
Application number: GB8114952A
Authority: GB
Original assignee: FURNITURE IND RES ASS
Current assignee: FURNITURE IND RES ASS
Priority date: 1981-05-15
Filing date: 1981-05-15
Publication date: 1982-12-08
Also published as: GB2099591B

Abstract

Furniture-testing apparatus comprises a framework 1, 3 on which is pivotally mounted at 15 an assembly for applying a load to, for example, the seat of a chair. The assembly comprises a pair of arms 15, 17, one of which carries a movable weight 19 and the other of which carries an indentor pad 21 for contacting the article of furniture. The weight biasses the indentor pad against the article of furniture, which may then be unloaded by e.g. a pneumatic ram 23 arranged to oppose the bias of the weight 19. A second loading assembly may be provided for loading the back of a chair comprising arms 27, 29, weight 31, indentor 33 and unloading ram 35. The load applied depends only on the geometry of the apparatus and the need for calibration of pneumatic rams etc. is avoided. <IMAGE>

Description

SPECIFICATION Furniture-testing apparatus This invention relates to apparatus for testing articles of furniture, particularly chairs, for their ability to withstand repeated loads.

Conventionally, apparatus for testing furniture consists of a framework which supports one or more hydraulic or pneumatic rams for applying forces to the article of furniture to be tested. It is, of course, necessary that the forces applied by such rams are carefully controlled, in order that the correct test conditions are achieved. To this end it is usual to provide strain gauges to measure the forces applied by the rams, and to arrange that electrical signals generated by the gauges are used to control the application of power to the rams.

In the apparatus of the present invention, the loads applied are determined by the geometry of the apparatus, which may be variable to cater for varying requirements. Accordingly, the present invention avoids the expense of servo-controlled rams and the need for continual recalibration of the strain gauges, which is otherwise necessary if accuracy is to be maintained.

According to the present invention, there is provided apparatus for load-testing articles of furniture, particularly chairs, comprising a support member, a loading assembly pivotally attached to the support member, a weight attached to the loading assembly for biassing the load assembly against an article of furniture to be tested, and means for opposing the bias of the weight whereby to unload the article of furniture.

Preferably, the support member is movable relative to the surface on which the article of furniture is positioned during testing. For example, the article of furniture may be positioned on a platform, and the support member may be mounted for limited pivotal movement relative to the platform. By this means, it may be arranged that the loading assembly is movable not only in a direction substantially parallel to the line of action of the force applied by the loading assembly, but also in a direction substantially perpendicular to that line. This feature is of particular advantage in the testing of chairs, when it is frequently desired to apply loads not only to the seats, but also to the backs. The application of a load to the back of a chair may have the effect of moving the seat backwards.A movable support member for the seat loading assembly has the advantage that it is able to accommodate such lateral movement of the seat, while leaving the operation of the seat loading assembly unaffected.

The loading assembly may comprise a first arm to which the weight is attached, and a second arm (rigidly attached to the first arm) to which an indentor pad may be attached. The position of the weight on the first arm may be adjustable, so that the moment of the weight about the pivotal attachment to the support member may be varied. In this way, the force applied by the indentor pad may be varied. Usually, the distance between the weight and the loading assembly pivot will be substantially larger than the distance between the indentor pad and the same pivot. By this means, comparatively large loads may be applied by the indentor pad without the need for large weights.

If it is desired to apply a force approximately vertically (e.g. to the seat of a chair), the two arms of the loading assembly will be roughly parallel to each other, and on the same side of the loading assembly pivot. In this way, the gravitational pull on the weight will be translated by the rigid connection between the two arms into a downward force on the indentor pad.

If, on the other hand, it is desired to apply a force approximately at right angles to the back of a chair, the two arms will consequently be disposed approximately at right angles, in the form of a bell crank. In this way, the gravitational pull on the weight is translated into a horizontal force on the indentor pad.

Apparatus according to the present invention preferably comprises two loading assemblies; one for applying a load to the seat of the chair, and the other for applying a load to the back of a chair.

The means for opposing the bias of the weight is preferably a fluid-operated ram, for example a pneumatic ram.

Furniture-testing apparatus according to the present invention is now described, by way of example, with reference to the accompanying drawings, in which; Fig. 1 is a side elevation of the apparatus, Fig. 2 is a rear elevation of the apparatus of Fig.

1 with some parts omitted for clarity and, Fig. 3 is a view of the same apparatus from above.

Referring to the drawings, the apparatus comprises a base 1, on which is mounted a platform 3 of adjustable height. Also mounted on the base 1 are a pair of Plummer blocks 5, between which is located a base pivot bar 7.

Fixed to the bar 7 are a pair of seat loading assembly supports 9, which at their free ends are joined by a loading assembly pivot bar 11 (Fig.

2). The lower ends of the seat loading assembly supports 9 are so shaped as to abut against the base 1 when the supports 9 are disposed at a comparatively small angle (e.g. about 50) from verticality. The supports 9 are therefore capable of restricted pivotal movement relative to the base 1.

A cross member 13 is mounted along a major portion of the length of the pivot bar 11, providing a support for the pivotal attachment of a seat loading assembly to the pivot bar. The seat loading assembly comprises a first arm 1 5 and a second arm 1 7 rigidly connected to opposite ends of the cross member 13, in substantially parallel relationship. The first arm 1 5 carries a weight 1 9 which is movable along its length and fixable at any desired point. The second arm 17 has pivotally attached at its free end an indentor pad 21.

Extending between the first arm 1 5 and the base 1 is a first pneumatic ram 23, by means of which the first arm 1 5 may be raised against the bias of the weight 19.

The base 1 is also provided with a pair of back loading assembly supports 25. These supports are rigidly fixed perpendicular to the base, on a line parallel to the base pivot bar 7, and set back towards the rear of the base. Pivotally mounted between the free ends of the back loading assembly supports 25 is a chair back loading assembly, comprising a first back loading arm 27 and a second back loading arm 29. These first and second arms are rigidly connected at approximately 900 to each other. The first back loading arm 27 carries a movable weight 31. The second back loading arm 29 has fixed at its free end and a third arm 32, disposed perpendicularly to both the first and second back loading arms i.e.

parallel to the base pviot bar 7. A back indentor pad 33 is pivotally mounted at the free end of the third arm 32.

A second pneumatic ram 35 extends between the first back loading arm 27 and the base 1, whereby the arm may be raised against the bias of the weight 31.

The operation of the apparatus in load-testing a chair is as follows: a chair (shown in the Figures as a broken line) is placed on the platform 3. It is convenient to have the platform provided with a stop 35, against which the rear legs of the chair may be positioned, so as to prevent movement of the legs of the chair during testing. The height of the platform 3 is adjusted so that the seat of the chair is just in contact with the seat indentor pad 21 when the seat loading arms are horizontal. It will be appreciated that the seat loading arms should be approximately horizontal during application of the desired load to the seat, so that slight arcuate motion of the arms during testing (in response to distortion of the chair) should have as small an effect as possible on'the size of the load being applied.

An operating cycle may now be begun. The first pneumatic ram 23 is lowered allowing the seat indentor 21 to bear against the seat of the chair, with a load which is dictated by the geometry of the seat loading assembly. When the seat is fully loaded, the second pneumatic ram 35 is lowered allowing the back indentor 33 to bear against the back of the chain After a short time, the second pneumatic ram 35 is raised, thus unloading the back of the chain Then the first pneumatic ram 23 is raised, thereby unloading the seat. The operating cycle may be repeated as often as desired. For the purposes of fatigue testing, it is convenient to have the pneumatic rams 23 and 35 operate automatically to produce the operating cycle.

In conventional furniture-testing apparatus, distortion of a chair during loading may give rise to inaccuracies in the measurement of the applied loads. For example, loading the back of a chair commonly has two effects. Firstly, distortion of the joints between the seat and the legs allows the seat to be displaced backwards. Secondly, the back itself may flex, independently of the distortion of the remainder of the chain In the illustrated embodiment of the present invention no difficultly is caused by these two effects. Firstly, pivotting of the seat loading assembly supports 9 allows the seat indentor 21 to follow front to back motion of the chair seat.

Since the geometry of the seat loading assembly remains the same, however, the load applied to the seat is affected to only a negligible degree.

Secondly, the back loading assembly pivot is so positioned as to be in the approximate vicinity of the point about which the back of the seat flexes.

Consequently, the load applied by the back indentor 33 remains approximately normal to the back of the chair, even during substantial flexing of the chair back. During such substantial flexing, however, the weight of the arms 29 and 32, and the back indentor pad 33 may effect the load applied to the seat back, because the load is applied other than horizontally. For this reason it is convenient to have the second back loading arm 29 counterbalanced so that the arms 29 and 32 and the back indentor pad 33 have a net zero moment about the seat loading assembly pivot.

It will be appreciated that the apparatus of the present invention is simpler, and may therefore be made more cheaply, than existing furnituretesting apparatus. If desired, it could also be built to be of adjustable geometry, so as to cater for the shapes of many different designs of chain If it is desired to vary the loads applied by the apparatus, the weights 19 and 31 may be moved to achieve greater or lesser degrees of leverage, as mentioned above. If it is desired to apply very large loads, the arms 1 5 and 27 may be fitted with extensions to achieve yet greater leverage.

Claims

1 Apparatus for load-testing articles of furniture said apparatus comprising a support member, a loading assembly pivotally attached to the support member, a weight attached to the loading assembly for biassing the load assembly against an article of furniture to be tested, and means for opposing the bias of the weight whereby to unload the article of furniture.

2. Apparatus according to claim 1 wherein the support member is movable relative to the surface on which the article of furniture is positioned during testing.

3. Apparatus according to claim 2 wherein the support member is mounted for limited pivotal movement relative to said surface.

4. Apparatus according to any preceding claim wherein the loading assembly comprises a first arm to which the weight is attached, and a second arm, rigidly attached to the first arm.

5. Apparatus according to claim 4 wherein an indentor pad is directly or indirectly attached to the second arm.

6. Apparatus according to claim 4 or claim 5 wherein the position of the weight on the first arm is adjustable.

7. Apparatus according to any of claims 4 to 6 wherein the two arms of the loading assembly are substantially parallel to each other, and on the same side of the loading assembly pivot.

8. Apparatus according to any of claims 4 to 6 wherein the two arms of the loading assembly are substantially- at right angles to each other in the form of a bell crank.

9. Apparatus according to claim 7 for loadtesting the seat of a chair, further comprising a loading assembly as described in claim 8 for loadtesting the back of the chair.

10. Apparatus according to any preceding claim wherein the means for opposing the bias of the weight is a pneumatic ram.

11. Apparatus for load-testing articles of furniture, substantially as hereinbefore described with reference to the accompanying drawings.