GB2352482A

GB2352482A - Vibration damping mounting arrangement for a hydraulic unit

Info

Publication number: GB2352482A
Application number: GB0014914A
Authority: GB
Inventors: Anthony Roger Davies
Original assignee: Smiths Group PLC
Current assignee: Smiths Group PLC
Priority date: 1999-07-21
Filing date: 2000-06-19
Publication date: 2001-01-31
Also published as: SE0002721D0; GB9916947D0; IT1318185B1; SE521281C2; ITMI20001621A0; GB0014914D0; SE0002721L; DE10033870A1; ITMI20001621A1

Abstract

An hydraulic unit including an assembly 5 of a pump 10, a motor 9 and a valve block 11 is mounted on a tank 1 of hydraulic fluid 2 with the pump 10 extending through an aperture 4 into the tank. A hollow resilient tube formed into a ring 22 is compressed between the upper surface of the tank 1 and the lower surface of the valve block 11. Three studs 16 project upwardly from the tank 1 at locations radially outwardly of the ring 22 and extend in apertures 12 in the valve block 11. Resilient grommets 13 embrace the studs 16 in the apertures 12 so that there is no direct metal-to-metal contact of the assembly 5 with the tank 1, so that it is acoustically isolated from the tank.

Description

2352482 HYDRAULIC UNITS This invention relates to hydraulic units.

The invention is more particularly concerned with hydraulic units comprising an hydraulic pump, an electric motor, a tank of hydraulic fluid and a mount of the pump and motor with the tank.

Conventional hydraulic units often include a pump and an electric motor connected with the pump by means of a valve block, the pump being located within a tank of hydraulic fluid and the valve block providing a mount for the pump and motor on the tank. The valve block is bolted to the roof of the tank with the pump projecting down through an aperture in the roof. An O-ring seal between the underside of the valve block and the upper surface of the tank roof prevents leakage of hydraulic fluid. Because the motor and pump are bolted directly on the tank, vibration and noise produced in the motor and pump can pass to the tank, which acts as a sounding board, causing amplification. The noise can be further amplified by any housing attached with the tank, or if the unit is attached to a vehicle panel or the wall of a building. Noise produced by hydraulic. units can add significantly to environmental noise.

It is an object of the present invention to provide an alternative hydraulic unit.

According to the present invention there is provided an hydraulic unit including a tank for hydraulic fluid and an assembly of an hydraulic pump, a motor and a mount, the tank having an aperture in a face thereof through which the pump extends into the tank, the unit 2 including a resilient mounting ring extending around the aperture between the face of the tank and a surface of the mount, and a securing member attached with one of the mount and the tank for securing the mount with the tank with the mounting ring compressed, and the unit including additional resilient means interposed between the securing member and the other of the mount and the tank such that the mount is substantially acoustically isolated from the tank by the resilient mounting ring and by the additional resilient means.

The securing member is preferably a stud, the additional resilient means being an annular member extending around the stud. The stud may be secured with the tank. The unit preferably includes three studs spaced around the unit, each stud having a respective additional resilient means. The resilient mounting ring is preferably an annular hollow tube. The mount may be provided by a valve block. The resilient mounting ring preferably provides a fluid seal preventing escape of hydraulic fluid between the mount and the tank. The resilient mounting ring is preferably located radially inwardly of the securing member. The securing member may include spacing means that defines a spacing between the mount and the tank. The securing means preferably includes a stud, the spacing means being a sleeve embracing the stud.

An hydraulic unit according to the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a side elevation view of the unit; 3 Figure 2 is a cross-sectional side elevation view showing a part of the unit in greater detail; and Figure 3 is a cross-sectional side elevation view of a part of an alternative unit.

With reference first to Figures I and 2, the hydraulic unit has a rectangular metal tank I at its lower end containing an hydraulic fluid 2. The roof or upper face 3 of the tank I has a circular aperture 4 located substantially centrally.

Mounted on the roof 3 of the tank I is an assembly 5 of an hydraulic pump 10, a valve block I I and an electric motor 9 coupled to drive the pump in the conventional manner. The valve block I I is of circular section and has three vertical apertures 12 (only one of which is shown) spaced equally around it, close to its edge. The upper and lower end of each aperture 12 contains a rubber, or rubber-like, resilient elastomeric grommet 13 having a tubular stem 14 extending within the aperture, and a flange 15 projecting radially outwardly at an end of the aperture. Each aperture 12 receives a respective metal stud 16 secured to and projecting vertically from the roof 3 of the tank 1. The studs 16 project through the stems 14 of the grommets 13 and project a short distance above the upper end of the aperture 12, where the stud is threaded to receive a locking nut 17. The nut 17 bears on washers 18 interposed between the nut and the flange 15 of the upper grommet 13. The studs 16 provide a relatively stiff mounting against twisting motion of the assembly 5 about a vertical axis of the kind that can be produced when the motor 9 is energized initially.

4 The underside 20 of the valve block 11 has an annular channel 21 located radially inwardly of the apertures 12. A resilient mounting ring 22 is located in the channel 21, the ring being formed of a hollow tube of a neoprene rubber, or a similar rubber-like resilient elastomeric material having a Shore hardness between about 60 and 70. The tube is cut to length and opposite ends are joined together using an adhesive so that a volume of air is trapped within the bore 23 of the ring 22. This gives the ring 22 the necessary elastic properties. The diameter of the channel 21 and ring 22 are selected to be slightly larger than that of the aperture 4 in the roof 3 of the tank I so that the ring bears against the upper surface of the tank roof just outside the aperture. The thickness of the ring 22 is chosen so that, when it is compressed, it spaces the underside 20 of the valve block I I from the upper surface of the roof 3 of the tank 1.

The assembly 5 is secured on the tank I by threading the three studs 16 through respective ones of the apertures 12 and lowering the assembly onto the roof 3 of the tank so as to trap the ring 22 in position. A spacer shim (not shown) of defined thickness is then slipped between the lower surface 20 of the valve block 11 and the roof 3 of the tank 1. The locking nuts 17 are then tightened to pull the assembly 5 down onto the tank I and to compress the ring 22, until the gap between the valve block 11 and the tank roof 3 is equal to that of the spacer. The spacer is then removed.

In this state it can be seen that there is no direct metal-to-metal contact between the tank I and the pump/motor assembly 5, since the assembly is resiliently isolated by the ring 22 and by the grommets 13 in each aperture 12. Vibration and noise produced in the motor 9 and pump 10 are, therefore, substantially absorbed by the ring 22 and the grommets 13 so that they are not transmitted from the structure of the assembly 5 to the tank 1. The valve block 11 acts as a mount for the assembly 5 on the tank 1.

It can be seen that the ring 22 serves a dual fimction since, in addition to damping transmission of vibration and noise, it acts as a seal to prevent leakage of hydraulic fluid 2 from the tank 1.

The hydraulic unit could be modified in various ways, such as shown, for example, in Figure 3 where items similar to those in the arrangement of Figures 1 and 2 are given the same reference numbers with the addition of a prime'. In this arrangement, the valve block I V has a cylindrical collar 3 0 attached to its lower surface and extending down a short distance around the pump 10', the external diameter of the collar being slightly less than the diameter of the aperture 4' in the roof 3' of the tank 1'. An annular flange 31 welded to the outside of the collar 30 towards its lower end projects radially outwardly, being stepped down by a distance approximately equal to the thickness of the flange about midway along its length. This divides the Ran e 31 into an inner, upper region 32 and an outer, lower region 10- 9 33. The outer region 33 of the flange 31 has three holes 34 formed through it, only one of which is shown, equally spaced around the flange. In each hole 34 there is retained a resilient rubber, or rubber-like grommet 3 5 with a short, tubular metal spacer sleeve 3 6 gripped within the bore through the grommet. The holes 34 align with three short metal studs 16'welded to the upper surface of the roof 3' of the tank 1. The studs 16' carry a lower washer 3 7 between the roof 3' and the lower end of the sleeve 3 6, and an upper washer 3 8 between the upper end of the sleeve 3 6 and a locking nut 17'. A tubular resilient ring 22' is located between the upper surface of the roof 3' and the lower surface of the inner region 32 of the flange 31 just outside 6 the aperture 4'. When the locking nut 17' is fully tightened, the sleeve 36 is firmly gripped and defines the spacing between the flange 31 and the roof 3', which is selected to compress the ring 22'to the desired extent. Any vibration passing through the flange 31 is isolated from the tank P by the grom.met 3 5 and the ring 22'. Since there is, therefore, no direct, metal-tometal contact between the tank V and the motor or the pump 10', the noise levels of the unit are minimized.

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Claims

1. An hydraulic unit including a tank for hydraulic fluid and an assembly of an hydraulic pump, a motor and a mount, the tank having an aperture in a face thereof through which the pump extends into the tank, wherein the unit includes a resilient mounting ring extending around the aperture between the face of the tank and a surface of the mount, and a securing member attached with one of the mount and the tank for securing the mount with the tank with the mounting ring compressed, and wherein the unit includes additional resilient means interposed between the securing member and the other of the mount and the tank such that the mount is substantially acoustically isolated from the tank by the resilient mounting ring and by the additional resilient means.

2. An hydraulic unit according to Claim 1, wherein the securing member is a stud, and wherein the additional resilient means is an annular member extending around the stud.

3. An hydraulic unit according to Claim 2, wherein the stud is secured with the tank.

4. An hydraulic unit according to Claim 2 or 3, including three studs spaced around the unit, and wherein each stud has a respective additional resilient means.

5. An hydraulic unit according to any one of the preceding claims, wherein the resilient mounting ring is an annular hollow tube.

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6. An hydraulic unit according to any one of the preceding claims, wherein the mount is provided by a valve block.

7. An hydraulic unit according to any one of the preceding claims, wherein the resilient mounting ring provides a fluid seal preventing escape of hydraulic fluid between the mount and the tank.

8. An hydraulic unit according to any one of the preceding claims, wherein the resilient mounting ring is located radially inwardly of the securing member.

9. An hydraulic unit according to any one of the preceding claims, wherein the securing member includes spacing means that defines a spacing between the mount and the tank.

10. An hydraulic unit according to Claim 9, wherein the securing means includes a stud, and wherein the spacing means is a sleeve embracing the stud.

11. An hydraulic unit substantially as hereinbefore described with reference to Figures I and 2 of the accompanying drawings.

12. An hydraulic unit substantially as hereinbefore described with reference to Figures 1 and 2 as modified by Figure 3 to the accompanying drawings.

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13. Any novel and inventive feature or combination of features as hereinbefore described.