GB2388200A - A stability test rig for vacuum cleaners - Google Patents

Abstract

A stability test rig for vacuum cleaners, the rig comprising a rigid wood or compressed fibre board 5 which forms a positive reference plane for measurement of the vertical height H; an inclinable board 3 which is laid to form a fulcrum at A with the angle of inclination being set by a jack 6. The angle of inclination 0 of the board 3 is gradually increased by operation of the jack 6 until the vacuum cleaner 2 topples and the angle of inclination at tis point is then calculated using the formula 0 = sin' (H/AB). The interface 4 between the vacuum cleaner 2 and the inclinable board 3 consists of a typical domestic carpet of a thickness of approximately 8 mm which is stuck to the board 3 using a suitable adhesive.

Description

1 2388200

STABILITY TEST FOR VACUUM CLEANERS

The disconnection of a vacuum cleaner from the electrical mains supply socket has resulted in sufficient disturbance of the cable entry as to cause the cleaner to overturn or "topple" from its rest or upright state whilst freestanding on a carpet.

The injuries caused by one particular accident were severe enough to warrant a thorough investigation into the mechanical stability of the cleaner in the context of topple. The results are best described by the accompanying drawing in which: Figure 1 illustrates the cleaner at the point of topple on the carpet after cleaning Figure 2 shows the same cleaner at the point of topple on a carpeted inclined plane.

Figure 3 shows the same cleaner at the point of topple on a smooth uncarpeted inclined plane with the addition of spring loaded chocks at the wheels and as used for acceptance testing for or on behalf of the cleaner manufacturers.

Figure 1 is a reference diagram which defines the essential details which must be reflected in any testing equipment for the evaluation of topple.

The cleaner 2 is shown at rest on the carpet 1 and the accident situation is reproduced by pulling at the cable outlet C in the direction of the arrow thus causing the cleaner to tilt through an angle until topple is imminent. Topple occurs about P' the contact line of wheels and carpet, when the degree of tilt is such that the centre of gravity of the cleaner now lies on the vertical axis from fulcrum P. Topple occurs when the angle of tilt is approximately 7 degrees and the force at C is approximately 6.5 ounces. The greater the topple angle the more stable the cleaner is deemed to be.

When this cleaner is placed on a smooth surface the tension at C induces the wheels to rotate and the cleaner to roll. Thus the cleaner cannot topple in the absence of carpet resistance.

The cleaner manufacturers quote the use of an inclined plane for the measurement of topple angle which exceeds by far that obtained in the "upright" state.

A test rig using an inclinable plane built and modelled on figure I is juxtaposed in figure 2 for easy comparison to ensure that all relevant features are included, and no intrusive forces are present. Topple at angle in figure I is precipitated by a tension applied at cable entry C while the same angle of inclination board in figure 2 induces exactly the same geometrical configuration with respect to gravity.

A carpet interface 4 between cleaner 2 and inclinable board 3 is included as an essential feature to complete the reproduction of the accident model in figure 1 and presents itself as a more accurate and practical industrial acceptance test.

The topple angle of 6 degrees is within 1 degree of the approximate measurement of the upright" test in figure 1 and the imbalance force and angle of board inclination is exclusively due to the the cleaner imbalance.

The rig in figure 2 has been designed to be simple and basic, easily set up and dismantled. The assembly consists of a rigid wood or compressed fibre board 5 checked and adjusted as necessary to be horizontal and to fonn a positive reference plane for measurement of the vertical height H. The inclinable board 3 is similar but shorter and is laid to form a point or fulcrum at A and the angle of inclination is set by handwheel operation of the jack 6. The angle of board inclination = sin '(H/AB) where AB is the length of the inclinable board 3.

The interface 4 is ordinary domestic carpet typically 8mrn thick. Material of carpet composition and orientation of nap make no difference to the measured topple angle. Very thin carpet or carpet tiles with little or no nap are unsuitable. The carpet may be roughly

secured to the inclinable board using suitable adhesive.

It is finally necessary to examine the test rig used for topple testing by the manufacturers.

Figure 3 illustrates such a test rig. The cleaner 2 rests on an inclinable board which is smooth and not covered by a carpet.

Spring loaded chocks 7 are adjusted to prevent the cleaner from rolling or sliding down the inclined plane and the angle of inclination at which topple occurs is 12 degrees i.e. twice the angle found when using the carpeted inclined plane shown in figure 2 for the same cleaner model. The omission of the carpet environment is fundamentally wrong in basic concept since the carpet is a vitally important component in the balance system.

The null balance nature of the chosen system demands that all the known forces must be represented, no external forces must be allowed to intrude and that a balance should be made so that the clockwise and counterclockvse moments are equal in the equilibrium state at the point of imminent topple.

The intrusive force applied by means of the chocks to prevent rolling is probably about 6.5 ounces as measured at C in figure 1. This force translates to 6 degrees inclination of the board.

The topple angle shown in figure 2 is 6 degrees, exclusively due to the cleaner imbalance.

For null balance as at figure 3, Total Angle of inclination = Angle for cleaner only + Angle for intrusive force = 6 + 6 degrees = 12 degrees.. This angle of 12 degrees is shown to be 100% in error when assumed to be exclusively due to the cleaner only and all cleaners tested on this balance should have been rejected as toppling at 6 degrees.

Claims (1)

1. A stability test rig including a rigid board pivoted or hinged at one end to provide and measure its angular movement with reference to gravity on application of an upward force at the other end, such board may be covered with a common domestic carpet to provide an interface between it and the appliance to complete the accident environment and thus avoid inevitable gross error by its omission.