GB2040390A - Improvements in or relating to compression springs - Google Patents

Abstract

In order to avoid premature abutment between the end convolution (4) (which in use is supported on a plate along 0.75 of a convolution) and the adjacent resilient convolution of a linear, cylindrical helical compression spring, with consequent possible surface damage to those convolutions consequent upon relative sliding movement between them, the end convolution (4) is spread or opened out axially to produce in the spread region, a convolution pitch which is approximately 1.6 times as great as the pitch of the remaining convolutions (1) in the spring when fully compressed. <IMAGE>

Description

SPECIFICATION Improvements in or relating to compression springs This invention concerns linear, cylindrical helical compression springs.

Linear, cylindrical helical compression springs are amongst the most widely used mechanical components. They are mass-produced and are used inter alia, as suspension springs for supporting the body of a motor vehicle. They are made from cylindrical wire which is coiled around the axis of the intended helical spring with a constant pitch in the entire effective region of resilience and with a constant diameter of the spring convolutions. All of the resilient convolutions of a linear, cylindrical helical compression spring contribute uniformly to the total spring travel, since, owing to the uniform pitch, and thus the uniform axial spacing of the convolutions, they remain fully effective up to the stage when they all become fully compressed, that is to say, they do not before that time come into mutual contact.In addition to the effective or resilient convolutions, such springs also have ineffective or dead convolutions at their ends, these end convolutions being intended to transmit the external load from the associated spring abutment plates to the effective turns as centrally as possible, that is to say, with the line of action coincident with the axis of the helical spring. For this purpose, approximately 0.75 convolutions are usually provided at each end of the spring, so that the abutment surfaces of the end convolutions in each case are of a circular extent of approximately 270". These end convolutions are normally flattened, that is to say, they have, for example, a pitch equal to the wire diameter when in a non-loaded fitted state, while the effective (resilient) convolutions of course, have a greater pitch.

Thus, the first resilient convolution in each case slides on the dead end convolution upon deflection of the helical spring, whereby the surfaces of the convolutions which ride upon one another are damaged, so that such damaged locations can be increasingly attacked by corrosion with corresponding consequential damage. Furthermore, rattling sounds can occur. In order to avoid mutual contact between the convolutions before the spring is fully compressed (fully deflected helical spring), it is known either to draw in the ineffective dead end convolution to a smaller diameter orto widen it to a larger diameter, so that the adjacent convolution can remain resilient.Whilst the end convolutions of a helical spring usually cannot be widened for spatial reasons, manufacturing difficulties and consequential higher costs preclude the drawing-in of both ends of the spring, since one of the two end convolutions has to be rolled-in in an additional working operation, a helical spring which is drawn-in at both ends being impossible to remove from the coiling mandrel.

It is also known to slip protective sheaths of plastics material onto each ofthe end convolutions of linear, cylindrical helical compression springs, in order to prevent the end convolutions from coming into direct abutment against one another during normal deflection of the springs.

The object of the invention is to construct linear, cylindrical helical compression springs of the type discussed above, without changing the average diameter of the spring convolutions and without using protective sheaths of plastics material, such that freedom of contact is ensured between the ineffective or dead end convolutions and the adjacent first effective or resilient convolution over the whole or su bstantia I Iy the whole travel of the spring.

In accordance with the invention, this object is achieved by the characterising features of the patent claim.

Thus, at least one end of the spring (both ends of the spring if necessary) is spread to a considerable extent, so that the pitch of this dead end winding is made considerably larger than is otherwise customary.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a linear, cylindrical helical compression spring in accordance with the prior art, and Fig. 2 shows a similar spring embodying the invention.

The effective or resilient convolutions of the spring in Fig. 1 are generally designated 1, and the top end of the spring which abuts against the top spring abutment plate (not illustrated) is designated 2. As shown in Fig. 1, this top end of the spring has been drawn-in to a smaller diameter than that of the remaining convolutions. The bottom, ineffective or dead end convolution 3 of the spring amounts to approximately 0.75 turns and thus has a circular extent of approximately 270 . The pitch of the end convolution corresponds to the pitch when the spring is fully compressed, that is to say, it has approximately a pitch equal to the magnitude of the diameter of the wire when in its illustrated nonloaded state. The pitch of the effective, resilient convolutions 1 is clearly greater.The central axis of the helical compression spring is shown by dash-dot lines and is designated 0.

With the exception of the bottom end, the cylindrical helical spring which is constructed in accordance with the invention and which is illustrated in Fig. 2 is identical to the spring illustrated in Fig. 1. The ineffective or dead end convolution 4 of the spring rests on a bottom spring abutment plate (not illustrated) and, in comparison to Fig. 1, is spread or opened out to a considerable extent in an axial direction. This spread is chosen such that the end convolution 4 cannot lift or slide over the entire spring travel. This is the case when the pitch of the convolution in this region, approximately along the last 0.75 of a convolution, is approximately 1.6 times as great as the pitch of the convolutions of a helical spring which has been fully compressed, that is to say, in which the individual resilient convolutions have come in to abutment against one another. It is therefore important that the pitch of the associated bottom spring abutment plate is the same as that of the opened-out end convolution of the spring.

As a result of the spreading or opening out of the bottom convolution 4 of the spring, the convolution adjacent to it cannot come prematurely into abutment against the dead end convolution, so that rattling sounds, damage to the spring surfaces and damage consequent thereto are largely avoided.

It will be appreciated that the top end of the spring may be of different design from that illustrated and, for example, can be diametrically widened or can be spread or opened out like the bottom convolution.

Claims (2)

1. A linear, cylindrical helical compression spring, particularly for the spring suspension of a motor vehicle body, said spring having end convolutions which, in the fitted state, are each supported on a spring abutment plate along at least approximately 0.75 of a convolution, characterised in that at least one end convolution of the spring is axially spread or opened out along the said 0.75 of said convolution to the extent that there exists in this region a convolution pitch which is approximately 1.6 times as great as the convolution pitch of a helical spring which is fully compressed, and that the associated spring abutment plate has the same pitch.

2. A linear, cylindrical helical compression spring constructed and arranged substantially as hereinbefore described with reference to and as illustrated in Fig. 2 of the accompanying drawings.