GB2340208A - Fluid distributor device for a hydraulic remote-control system - Google Patents

Description

2340208 A fluid distributor device, in particular for a hydraulic

remote-control svstem The present invention relates to improvements made to fluid distributor devices, particularly for a hydraulic remote-control system, such as those referred to as "hydraulic manipulators", having at least one pressure reducing valve mounted in a body and a control member designed to modify the pressure setting of the reducer, said reducer having a plunger piston which is displaced by said control member in a cavity of the body which has, at the one end, a compartment in which a pressure - regulating spring of the reducer is arranged and, at the other end, a bore in which an active part of the plunger piston can be displaced as a means of reducing the fluid pressure, said plunger piston having a rod section mounted above said active part and extending substantially in said compartment, said rod section having at its free end an enlarged head defining a first shoulder and, at the end at which it adjoins said active part a second shoulder on which said pressureregulating spring is supported, the other end being supported on a valve spring washer which is coaxial with the section of rod and which is elastically biassed in support against said control member.

In conventional arrangements of a device such as that outlined above, the pressure-regulating spring is a conventional helical spring: a device of this type is described in documents FR 2 376 978 or FR 2 507 732, for example. The hydraulic pressure regulation curve obtained by known devices of this type is substantially linear and its slope is determined by the stiffness of the spring.

In certain fields of application, users have wanted

2 to be able to obtain more complex regulation curves with a variable slope (where the slope in the regulation curve is more pronounced towards the end of the control member's travel, for example). Accordingly, one distributor device has become known whose response curve has a double slope: a device of this type is illustrated in figure 1 of the appended drawings.

This known device consists of a body 1 (which may be formed by joining several parts in order to facilitate insertion of the internal components), having at least one pressure- reducing valve 2 arranged therein. This reducer comprises a plunger piston 3 which is displaced in a cavity 4 arranged in the body 1. This cavity 4 has, at the one end, a widened compartment 5 in which a pressure- setting spring 6 is arranged, being supported between a shoulder 7 of the plunger piston and a valve spring washer 8 which moves in the compartment 5 in the vicinity of the free end of the plunger piston and, at the other end, a bore 9 in which an active part 10 of the plunger piston can be,displaced as a means of reducing the pressure of the fluid which is fed via an inlet orifice (not visible) connected to the bore 9 via a passage 12 opening radially therein whilst an outlet orifice 13 is located at the end of the bore 9. The active part or piston 10 of the plunger has an axial recess 22 opening at the base of the piston 10 on the side of the outlet orifice 13 and a radial orifice 23 communicating with the axial recess 22.

The plunger 3 also has a rod section 14 mounted above the active part 10 and extending substantially in the cavity 5, being coaxially surrounded by the pressuresetting spring 6; this rod section 14 passes through the valve spring washer 8 terminating with an enlarged iead 3 defining a retaining shoulder 16 of the valve spring washer.

A return spring 17, coaxial with the rod 14, is interposed between the valve spring washer 8 and a shoulder defined in the body 1, so as to push the valve spring washer upwards, i.e. into its position defining a minimum pressure setting.

Mounted above the valve spring washer 8 is a movable push rod 18 sliding freely in a bore of the body and partially projecting out from the body so as to be in contact with a cam 19 which pivots about an axis under the action of an actuating member such as a handle 21.

The way in which this device operates is known and reference may be made to documents FR 2 376 978 or FR 2 507 732 cited above for more details.

In the known device described above, the regulating spring 6 is a standard helical spring, comprising a metal wire of homogeneous geometry, specifically being of constant section, helically coiled at a constant pitch and a constant diameter. As mentioned above, this linear regulating spring provides, alone, a linear regulating curve, the slope of which is determined by the stiffness of said spring.

If it is desirable to obtain a regulating curve with a double slope (two successive linear sections with different slopes), a known approach is to arrange a second spring, having different characteristics, adjoining the above-mentioned spring 6.

In view of the small amount of space available inside the pressure reducer, it has proved necessary to arrange the second regulating spring 24 inside the push rod 18, which is recessed for this purpose.

As illustrated in figure 1, the push rod 18 is 4 provided with an axial recess 25 extending across almost its entire length so that the second regulating spring 24 housed therein extends across only a part of the length of the recess 25 in its non-compressed state (the situation illustrated in figure 1), an empty gap remaining at the top of the recess.

At its bottom end, the second spring 24 is supported on an additional push rod 26 which is guided in the recess 25 and rests on the head 15 of the plunger 3. The additional push rod 26 is extended upwards by means of an axial finger 27, which acts as a guide for the spring surrounding it.

As the inclination of the cam 19 causes the push rod 18 to be pushed back downwards, only the regulating spring 6 is operating at the start of the travel of push rod 18 and is so until the second spring 24 comes into contact with the base of the compartment 25 hollowed into the push rod. The regulating curve is then linear, its slope being determined by the characteristics of the regulating spring 6.

As soon as the second spring 24 comes into contact with the base of the compartment 25, the regulating characteristic is determined by the two springs 6 and 24 which then act in series: the regulating curve continues to remain linear but with a slope that is determined by the characteristics of the two springs 6 and 24. An assembly of this type therefore meets all practical requirements and is satisfactory in terms of the result obtained. 30 However, the structure of the device is complicated since the push rod has to be machined in a special way (it is no longer a standard push rod) and it is also necessary to provide additional components (second spring 24, additional push rod 26). This makes the device more expensive.

Furthermore, whilst an arrangement of this type does enable a regulating curve with a double slope to be obtained whilst remaining relatively simple in terms of structure, it is nevertheless impossible, in practice, to construct means of this type in a manner that will produce a regulating curve having at least three linear segments or a gradually rising curvilinear regulating curve, should it be desirable.

It should be pointed out that the small dimensions of the component parts of the device (figure 1 is somewhat larger than the actual size) and the close proximity of the pressure reducing valves to one another within the body (four reducers arranged in a cross design and in opposing pairs) does not leave any room free to insert additional regulating springs. In practical terms, figure 1 illustrates the only feasible layout in a space as limited and as encumbered as this.

An underlying objective of the invention is to overcome or ameliorate one or more of the disadvantages outlined above. The inventor proposes an improved and economic layout that will enable a regulating curve of a desired pattern to be obtained without the need for additional components and/or without modifying the existing components (retaining in particular standard push rods which do not require additional machining). A further objective is to keep manufacturing costs as low as possible.

A fluid distributor device proposed by the invention is characterised in that each pressure reducing valve has only one pressure-regulating spring and it is a helical spring having a variable winding pitch, as a result of 6 which the fluid pressure regulating curve obtained when the control member is activated to cause at least a partial compression of the pressure-regulating spring will exhibit a variable slope.

In practical terms, therefore, the same number of components are needed as in the device of the prior art and this is a particularly important feature in view of the fact that it is very difficult, not to say impossible, to provide any extra free space in a radial direction inside the device.

In practice, users, requirements more often than not tend towards regulating curves with two successive linear sections having differing slopes. This being the case, the helical regulating spring will have at least two successive sections of different coil pitches.

However, the general conditions under which the invention is implemented make it possible, if necessary, in a simple manner and without modifying the environment inside the device, to meet requirements for more complex regulating curves having multiple linear segments of differing slopes or even a curvilinear contour or a combination of linear sections and curvilinear sections: to this end, it is proposed that the helical regulating spring have a winding pitch which is continuously variable over at least a part of its length so that the regulating curve is curvilinear across at least a part of its 'Length.

By virtue of the features of the invention, the desired regulating curve is obtained by using a single helical spring having turns wound in an appropriate manner, this spring simply being provided instead and in the place of the basic helical spring conventionally used. The other components of the device may remain 7 identical to those which have always been used and do not require any modification. In other words, all the remote control devices may be constructed in the same manner, with the same component parts and the regulating curve of each pressure-regulating valve is adapted solely by selecting the appropriate single spring.

This makes for a significant saving not only in manufacturing terms but also as regards assembly and maintenance.

The invention will be more readily understood from the detailed description below of various embodiments, given purely as illustrative examples.

Throughout the description, reference will be made to the appended drawings, of which:

- figure 2 is a simplified partial diagram, in section, of a distributor device with a layout as proposed by the invention; - figure 3 is a simplified view showing a helical spring wound in a double pitch enabling a regulating curve having two linear segments of differing slopes to be obtained; - figure 4 is an example of a regulating curve with two linear segments of. differing slopes which can be obtained by means of the spring illustrated in figure 3; 25 - figures SA and 5D are simplified views showing respectively two helical springs capable of producing complex regulating curves; and - figure 6 is a graph showing two complex regulating curves which can be obtained by the springs illustrated in figures 5A, 5B respectively.

Figure 2 illustrates, in section, a part of a distributor device constructed as proposed by the invention. The device in figure 2 differs from that illustrated in figure 1 by dint of the fact that in this instance, the regulating spring 6 of figure 1, of the helical type, has been replaced by a helical spring of a specific type 28, examples of which will be given b elow.

Since the single spring 28 is capable of producing the desired regulating curve alone, the second regulating spring 24 and the requisite corresponding layout (compartment 25 in the push rod, supporting head 26 and guide finger 27) are no longer necessary: the push rod 18 is therefore a standard, solid push rod, provided at its base with the requisite recess to allow the upper end of the rod 14 of piston 3 to be displaced freely.

This being the case, it may be noted that the regulating device illustrated in figure 2 is similar in structure to that of a conventional device as illustrated in the drawings accompanying documents FR 2 376 978 or FR 2 507 732; the regulating spring 28 is itself of essentially the same overall geometry (length, external diameter), having been modified in terms of its coil design only.

In order to produce a regulating curve with a double slope 29 such as that illustrated in figure 4 (load plotted on the ordinate, winding height of the spring plotted on the abscissa on an inverse, oriented axis with increasing values to the left), i.e. comprising, for example, a first linear sect-ion 30 with a predetermined slope corresponding to the greater part of the regulating path followed at the end section of the regulating path by a second linear section 31 having a steeper slope - a regulating spring 28 is used having a winding pitch which varies as illustrated in fig. 3: the spring 28A has a first section 33 with relatively close turns and a second section 34 in which the turns are relatively less close 9 together, all the turns being substantially of the same coil diameter and being made from the same metal wire, the composition and section being the same throughout.

When the spring 28A is initially compressed, only the first section 33 with relatively close turns, which is less stiff, is active in practical terms, producing a regulat4 on which varies linearly as shown in the first L section 30 of curve 29 in figure 4. Once all the turns of the first section 33 are edge to edge, the second section 34 with the turns spaced relatively farther apart, and hence of a higher stiffness, becomes active and produces a regulation as shown in the second section 31 of curve 29 in figure 4, having a steeper slope.

A spring with a double winding pitch as illustrated in figure 3A can be manufactured without any particular difficulty and at an acceptable cost. It is therefore possible to manufacture a regulating device at a cost that is no higher than that of a conventional device.

The features proposed by the invention may also be applied as a means of producing much more complex regulating curves, still retaining the simple structure illustrated in figure 2.

For example, the spring 28D illustrated in figure 5A extends the layout illustrated in figure 3 to a greater number of sections of different pitch (here, the pitch size increases and there are four such sections) 39, 40, 41 and 42 respectively. A spring of this type will produce a regulating curve 43 such as that illustrated in figure 6, which is made up of four successive linear sections 44, 45, 46 and 47, each having a different and more steeply rising slope.

As another example, the spring 28E illustrated in figure 5S is made from a wire of identical section, wound on a single diameter, with a gradually variable pitch. A spring of this type will produce a curvilinear regulating curve 48 (fig. 6) without a single point (continuous curvature).

Clearly, the features described above may be combined in order to produce any desired regulating curve (combination of linear and curvilinear section(s)).

I i i i i t

Claims (4)

1. A fluid distributor device, in particular for a hydraulic remotecontrol system, having at least one pressure -reducing valve (2) mounted in a body (1) and a control member (19) capable of modifying the pressure setting of the reducer, said reducer (2) having a plunger (3) which can be displaced by said control member in a cavity (4) of the body (1) which has, at one end, a compartment (5) in which a pressure-setting spring (28) of the reducer is arranged and, at the other end, a bore (9) in which an active part (10) of the plunger (3) can be displaced as a means of reducing fluid pressure, said plunger (3) having a rod section (14) mounted on said active part (10) and extending substantially in said compartment, said rod section (14) having, at its free end, an enlarged head (15) defining a first shoulder (16), said plunger having at the end of the rod section (14) where it adjoins said active part (10), a second shoulder (7) on which said pressure-setting spring (28) is supported, the other end of said pressure- setting spring being supported on a valve spring washer (8) coaxial with the rod section (14) and elastically biassed (17) in support against said washer, characterised in that each pressure-reducing valve has only one pressuresetting spring (28) and it is a helical spring with a varied winding pitch.

2. A device as claimed in claim 1, characterised in that the helical pressure- setting spring (28) has at least two successive sections (33, 34) of differing winding pitches, as a result of which the regulating curve (29) consists of at least two successive straight-line 12 segments (30, 31) of differing slopes.

3. A device as claimed in claim 1, characterised in that the helical pressure- setting spring (28E) has a continuously variable winding pitch across at least a part of its length, as a result of which the regulating curve (48) is curvilinear across at least a part of its length.

4. A fluid distributor device substantially as herein described and/or illustrated in any of Figures 2 10 to 6.