GB2065253A - Tube for coupling between relatively movable parts - Google Patents

Abstract

A coupling between two relatively movable parts comprises a pipe of wrapped or solid drawn construction formed into two or three helical coils 24, 25 and 26 intermediate its ends with the axes of the coils parallel. By appropriately dimensioning, forming and positioning the pipe, and in particular the coils, the effect of vibrations to which the coupling is in use subjected due to relative movement of the parts and torsional forces can be minimised. <IMAGE>

Description

SPECIFICATION A fluid coupling The present invention relates to tubular couplings for use between relatively movable parts.

There are a number of known forms of such tubular couplings for correcting relatively movable fluid carrying pipes. In one form the coupling comprises a hose made from flexible material such as natural rubber or rubber substitute synthetic plastics material. The hose may, if desired, be reinforced. Common reinforcements are braiding or wire coils. Such hoses are liable to be sensitive to attack by certain fluids, by the environment (for example, sunlight) or by temperature effects. They are subject to manufacturing difficulties in monitoring control over the materials, and are usually in the form of a composite assembly of a number of items. Their durability and reliability standards are sometimes open to criticism, and this gives rise in some cases to the need to use more well tried materials.

Some of the problems encountered with hoses may be overcome by using metal pipes having flexibility derived from having a length greater than the distance between their end connections in the two parts having relative movement.

Such pipes are somteimes arranged to include bends so as to give them a "U" or "L" shape, but these are liable to occupy a disproportionate amount of space and to need vibration control.

Similar results can however, be obtained by introducing a coil in the pipe, for example arranged around an axis common to an axis about which two parts are required to describe relative torsional oscillation. However, pipes of this kind have limited life in service when asked to handle relatively high internal fluid pressures in combination with movements of various amplitudes in up to three planes, perhaps in addition to torsional or angular effects.

According to the presetn invention, there is provided a fluid coupling for coupling fluid carrying members on relatively movable parts comprising a pipe formed with two helical coils intermediate the two ends of the pipe.

A preferred embodiment of the invention may comprise any one or more of the following preferred features.

(a) The pipe is of wrapped construction, (b) The pipe is solid drawn pipe, (c) There are three helical coils intermediate the ends of the pipe, (d) the axes of the coils are parallel, (e) The diameter and number of turns in the coils and the relative disposition of the coils is chosen in dependence upon the frequency and magnitude of the vibrations to which the coupling will in use be subjected, (f) The ends of the pipe are provided with end fittings.

In order that the invention may be more clearly understood, one embodiment thereof will now be described, by way of example, with reference to the accompanying drawing in which:~ Figure 1 shows a diagrammatic front elevational view of a linkage system connecting an automobile engine block to the corresponding automobile chassis frame in such a way as to provide freedom for all relevant relative motion between them, Figure 2 shows a front elevational view of one form of pipe coupling developed from Fig. 1, Fig. 3 shows a plan view of the coupling shown in Figure 2, Figure 4 shows a side elevational view of the coupling shown in Figure 2 and Figure 3, Figures 5, 6 and 7 show views of another form of coupling respectively corresponding to Figures 2, 3 and 4, Figure 8 shows one form of end connection for the couplings shown in Figures 2 to 7, and Figures 9 and 10 show alternative forms of end connection to that shown in Figure 8.

Referring to Figure 1, a linkage system (representing a brake pipe coupling) is diagrammatically shown between the engine block and chassis of an automobile. The block is referenced 1, and chassis 2 and the linkage system generally 3. The linkage system has three pivot pins 4, 5 and 6 which will cater for relative movement between block 1 and chassis 2 which takes place in the plane of the drawing paper. In the case of a pipe coupling, it would be difficult to provide pivotal coupling joints at pivots 4, 5 and 6, and furthermore it would be even more difficult to arrange that these cater for relative movement between block 1 and chassis 2 in a fore-and-aft direction, that is at right angles to the plane of the paper. In order to overcome this problem, a helical coil is disposed in the pipe at each of the points 4, 5 and 6.

The coupling may then take the form shown in Figures 2, 3 and 4. This coupling is made entirely from about two feet of wrapped pipe having an outside diameter of 5/32 inch. The three helical coils shown, each having a mean coil diameter of 1.1/2 inches are respectively referenced 24, 25 and 26. The coils are disposed at the corners of an equilateral triangle. The distance between coil centres is 3.1/2 inches and the length of the pipe from the nearest coil to the end of each fixing is 1.3/4 inches. Coils 24 and 25 have two and coil 26 one full turn. All kinds of relative movements in the plane of the paper and of the order of 1/4 inch amplitude are within the capability of this coupling, whilst carrying internal hydraulic fluid pressurised to 2500 psi.Low natural frequencies in the coupling should be avoided: This means that the coupling should be as rigid as possible, that is with the minimum number of turns in each coil, consistent with the requirement to absorb relative motion between the engine and chassis. The relative flexibility of the coils themselves will be graded in dependence upon the modes and amplitudes of movement to which, in use, they will be subjected. The free ends of the coupling are provided with end connections or fixings 27 or 28 which will be described in more detail later.

An alternative form of coupling is shown in Figures 5, 6 and 7. The coupling again comprises three coils respectively referenced 54, 55 and 56, and the ends of the coupling are provided with end fixings 57 and 58 of an alternative form to those shown in Figures 2 to 4. In this coupling, as in the coupling described with reference to Figures 2 to 4, the coil furthest removed from the end fixings (coils 25 and 55) may be provided with a stabilizing rubber bung or cork.

The basic requirement of the end fixing or connection is to make the end encastre to take load off, or largely reduce the load on the flare at the pipe end which has to make the fluid tight joint. One arrangement which is virtually torsion proof is to clamp the pipe to the sleeve nut after making the joint. In this way bending is taken from the flare. Such an arrangement is illustrated in Figure 8. The flared end of the pipe is referenced 80 and abuts the similarly flared end 81 of the pipe on the engine block. A threaded sleeve 82 extends over the end of the pipe of the coupling and together with that end of the pipe extends into the engine block. This sleeve is clamped on the pipe by means of a locking ring 83 comprising an olive 84 against one end of the threaded sleeve.

The sleeve is fixed in position relative to the block by means of a further locking ring 85.

An alternative arrangement to the arrangement of Figure 8 is shown in figure 9. Here the free end of the pipe 90 of the coupling is bent at 91 and clamped at 92 to the engine block 93 outside the end fitting 94. A still further alternative is shown in Figure 10. Where the two pipes 100 and 101 to be connected are brazed into bores in a connection block 102. This connection block is provided with internal passage 103 connecting the bores.

It will be appreciated that the above embodiments have been described by way of example only and that many variations are possible within the scope of the invention. For example, the coupling may comprise only two coils if desired. The pipe of the coupling may be Kunifer 10 or solid drawn pipe.

By appropriate dimensioning, formation and positioning of the coupling the effect of the vibrations to which the coupling is in use subjected due to the relative movement about the three coordinate axes of the engine block and chassis and torsional forces can be minimised.

In the examples described above about two feet of 3/1 6 inch external diameter Bundy pipe suitably coiled will bridge the engine/subframe gap at an engine mounting carrying hydraulic fluid at 2,500 psi at +4 inch of movement without failure.

5/32 Bundy inch external diameter would be better in the same space. In this way, fluid coupling can be simply and inexpensively achieved. Fitting problems more usually associated with flexible hoses can be reduced or eliminated. In an automobile the gaps between engine/subframe/body/suspension member can be bridged in one or two stages as desired. In two stages the ends of each of the two pipes can be located close to mounting points where better control of dimensions can be expected. In one stage there will be saving in weight and cost, but some special arrangement may be needed to prevent installed stress due to variation between end positions.

Claims (8)

1. A fluid coupling for coupling fluid carrying members on relatively movable parts comprising a pipe formed with two helical coils intermediate the two ends of the pipe.

2. A fluid coupling as claimed in Claim 1 in which the pipe is of wrapped construction.

3. A fluid coupling as claimed in Claim 1, in which the pipe is solid drawn pipe.

4. A fluid coupling as claimed in Claims 1, 2 or 3, in which there are three helical coils intermediate the ends of the pipe.

5. A fluid coupling as claimed in any preceding claim, in which the axes of the coils are parallel.

6. A fluid coupling as claimed in any preceding claim, in which the diameter and number of turns in the coils and the relative disposition of the coils is chosen in dependence upon the frequency and magnitude of the vibrations to which the coupling will in use be subjected.

7. A fluid coupling as claimed in any preceding claim, in which, the ends of the pipe are provided with end fittings.

8. A fluid coupling substantially as hereinbefore described with reference to Figures 2, 3 and 4 or Figures 5, 6 and 7 with the modification shown in any of Figures 8, 9 or 10 of the accompanying drawings.