GB2065575A - A levelling valve for pneumatic suspensions in vehicles - Google Patents

Abstract

In a levelling valve (1) for a vehicle suspension of pneumatic type, a drive shaft (13), connected to the vehicle wheel axle (3) by means of a linkage (4, 5), operates a control plunger or piston (9) of the inlet valve (11) by means of an eccentric pin (12). An angularly adjustable eccentric bush or sleeve (22) is mounted between said shaft (13) and bearing (21) for the drive shaft. Adjustment of the inlet or exhaust start to or from the pneumatic suspension can be obtained by rotating the sleeve by means of a tool engaging in notches (29). <IMAGE>

Description

SPECIFICATION A levelling valve for pneumatic suspensions in vehicles This invention relates to a levelling valve for pneumatic suspensions in vehicles, and particularly to a levelling valve provided with adjusting device for the position of inlet or exhaust start ofthe inlet valve.

As well known, levelling valves perform the function of maintaining constant the level or height of the vehicle frame from ground, independently of the load acting on the vehicle.

To this end, such valves are mounted on the vehicle frame, which is maintained at a determined distance from ground by means of pneumatic suspensions eg compressed air bellows interposed between said frame and the wheel axle.

The valve provides for pressure adjustment at said suspensions under control of an operating lever connected through a tie rod to said wheel axle.

At each change in load on the vehicle, a corresponding angular change in said level will occur with resulting operation of the levelling valve which, by causing the feed or exhaust of the suspensions, will restore the predetermined initial level conditions of the frame.

Under certain use conditions of the vehicle, it is required to adjust the position for inlet or exhaust start of the inlet valve controlling the bellows feed or supply.

Levelling valves are known as provided with inside devices allowing such adjustments.

According to a known embodiment, as shown in the German Patent Specification DAS No. 1,966,106, a levelling valve essentially comprises a cylindrical case or body having a plunger or piston sliding therein for the operation of a perforated stem controlling the inlet valve to provide the supply of compressed air to the pneumatic suspensions, of the exhaust or vent from the latter, which plunger or piston is moved in said case or body under the control of a pin eccentrically connected to a drive shaft rotatably driven by the operating lever.

In such a valve, the adjustment device is provided by means of an axial screw carried by the plunger or piston which by means of a cap is effective on said stem.

Besides being quite complicated and subjected to unscrewings due to vibrations, such a known device is difficult to assemble and handle because of being implemented within the cylindrical housing of the valve.

The present invention has been made from a consideration of the above-described difficulties of prior levelling values.

In accordance with the present invention there is provided a levelling valve for a pneumatic suspension of a vehicle, including a piston slidable within a housing for controlling the valve to admit or exhaust fiuid from the suspension; a rotatable drive shaft for the piston connected at one end to a wheel axle of the vehicle by a linkage for effecting rotation of the drive shaft in response to changes in the load on the vehicle, the drive shaft being connected at its other end to the piston by means of a connector eccentrically mounted with respect to the axis of rotation of the drive shaft whereby rotational movement of the drive shaft effects sliding movement of the piston; and an eccentric sleeve mounted between said drive shaft and a bearing therefor and being angularly adjustable within said bearing with respect to said drive shaft whereby to alter the disposition of said drive shaft axis relative to said piston housing and thereby displace the position of said piston within said housing for a given load on the vehicle.

In accordance with the present invention it is possible to provide a levelling valve provided with a very simple and precise adjustment device not affecting the internal structure of the valve and which is readily accessible from the outside for adjustment operations by an operator.

According to a preferred aspect of the invention, the eccentric sleeve circumferentially has a series of radial slots with which a clamping member cooperates to secure said bush or sleeve once the operator has completed such an adjustment operation.

The further features and details of the invention will become more apparent from the following description with reference to the accompanying drawings, in which: Figure 1 is a sectional view showing the levelling valve as fitted with an adjustment device according to the invention; Figure 2 is a sectional view of the valve taken along line A-A; and Figure 3 is a view showing a variation or modified form for the adjustment device.

Referring to Fig. 1, reference numeral 1 designates a levelling valve as mounted on a vehicle frame 2 and connected to the wheel axle 3 by means of a linkage comprising an operating lever 4 and tie rod 5.

Reference numerals 6 and 7 designate the pneumatic suspensions of the vehicle as implemented by means of bellows.

The apparatus casing or body 8 houses a plunger or piston 9 controlling by means of a perforated stem 10 an inlet valve 11. Such a plunger or piston slides within said casing or body upon operation of an eccentric pin 1 2 rigidly connected to a drive shaft 13, the latter being rotably driven by the operating lever 4. Thus, as a result of an increase in load on the vehicle, the pressure air from reservoir 14 will reach said bellows 6 and 7 through line 15, check valve 16, chamber 17, inlet valve 11 and iines 1 8 and 19, respectively.

Similarly, as a result of a reduction in load, the pressure air will vent to atmosphere from said bellows 6 and 7 through said lines 1 8 and 1 9 and the inner passage 20 in said stem-piston assembly 9, 10.

According to the invention, between said drive shaft 13 and associated bearing 21 there is freely mounted an eccentric bush or sleeve 22 provided, as shown in Fig. 2, by an increase in its thickness limitedly to an arc of circle, so that the outer and inner circular surfaces 23 and 24 of such a bush or sleeve are respectively coincident with the inner surface of said bearing 21 and the outer surface of said drive shaft 1 3. As a result, the axis of bearing 21 is not coincident with the axis of shaft 13, the respective outlines or traces of which are respectively designated by C and c'.

The particular shape of bush or sleeve 22 enables at each rotation thereof a translation in the direction of the valve axis for said drive shaft 1 3 and relative eccentrical pin 12, which causes a corresponding displacement of said piston-stem assembly 9, 10.

Still referring to Fig. 2, it will be seen that said bush or sleeve 22 circumferentially has a series of radial holes Al, A2, A3..., for receiving a pin 25 comprising the clamp member for said bush or sleeve once the adjustment operation has been carried out.

in order to provide for such a clamping, said pin 25 passes through a passage 26 formed in said bearing 21 of shaft 13, and is held in place by the closure plug 27 of the exhaust or vent connection 28. Said bush or sleeve 22 also has at the outer front side notches or similar means for the operation thereof by the operator by means of a tool.

Said eccentrical bush or sleeve 22 and pin 25 make up the above mentioned adjustment device controlling through said pin 12, plunger or piston 9 and stem thereof the inlet or exhaust of compressed air to or from the pneumatic suspensions.

Instead of radial holes, said bush or sleeve 22 is shown in Fig. 3 as provided with axial millings F1, F2, F3..., for engagement with said clamping pin 25.

The above described adjustment device enables a ready operability by an operator because of not being implemented within the levelling valve.

Moreover, a simplification can be made to the inner movable element, which comes down to a single piece, that is to say plunger or piston 9 integral with said perforated stem 10.

By means of a device according to the invention, it is also possible to provide a highly precise adjustment of inlet or exhaust start, just depending on the high number of radial apertures that can be circumferentially formed on the bush or sleeve.

Thus, by rotating said bush or sleeve through an angle equal to that separating one aperture (hole or milling) from the other, a very small translation is provided for said piston-stem assembly 9, 10, which may correspond to even fractions of a millimeter, thus assuring a highly precise and micrometrical adjustment.

Claims (8)

1. A levelling valve for pneumatic suspensions in vehicles, substantially comprising a casing or body having a plunger or piston sliding therein for the control of the inlet valve through its stem and which is operated by a pin eccentrically connected to the drive shaft rotably driven by a lever connected to the vehicle wheel axle by a tie rod, characterized in that an eccentric bush or sleeve (22) is freely mounted between said drive shaft (13) and bearing (21) thereof, so that at each rotation of said shaft there will correspond a translation in the direction of the valve axis of said drive shaft (1 3) with its relative pin (12) and accordingly a corresponding displacement of the piston-stem assembly (9, 10).

2. A levelling valve for pneumatic suspensions in vehicles according to Claim 1, characterized in that said eccentric bush or sleeve (22) is implemented by a radial increase in its thickness limitedly to an arc of circle, so that the outer and inner circular surfaces (23, 24) of the bush or sleeve respectively coincide with the inner surface of said bearing (21) and the outer surface of said drive shaft (13).

3. A levelling valve for pneumatic suspensions in vehicles according to Claims 1 and 2, characterized in that said bush or sleeve (22) circumferentially has a series of radial apertures for receiving a clamping member for said bush or sleeve once the adjustment operation has been completed.

4. A levelling valve for pneumatic suspensions in vehicles according to Claim 3, characterized in that said radial apertures comprise through holes.

5. A levelling valve for pneumatic suspensions in vehicles according to Claim 3, characterized in that said radial apertures comprise axial millings.

6. A levelling valve for pneumatic suspensions in vehicles according to Claims 3 to 5, characterized in that said clamping member comprises a pin (25) engaging with a hole or milling of said bush ar sleeve through a passage (26) formed in said bearing (21) of the drive shaft (13) and which is held in place by a closure plug (27) for the exhaust connection (28) of the levelling valve.

7. A levelling valve for pneumatic suspensions in vehicles according to the preceding claims, characterized in that said bush or sleeve (22) has on the outer front side notches (29) or the like for engagement with an operating tool.

8. A levelling valve for pneumatic suspensions in vehicles according to the preceding claims, characterized in that the moving element sliding within said casing or body (8) comprises a plunger or piston (9) which is integral with the stem (10) provided with axial hole (20) for the exhaust or vent of the bellows (6, 7).