HYDRAULIC POWER UNIT

Abstract: A hydraulic power unit comprising a reservoir for hydraulic fluid, a hydraulic pump for circulating hydraulic fluid under pressure through a hydraulically operated device to be driven by the power unit, wherein said reservoir is of annular constructions surrounding a chamber through which cooling air is passed.

Description: HYDRAULIC POWER UNIT This invention concerns a hydraulic power unit of the kind (hereinafter termed "a hydraulic power unit of the kind referred to") comprising a reservoir for hydraulic fluid, a hydraulic pump for circulating hydraulic fluid under pressure through a hydraulicaUy operated device to be driven by the power unit. The invention is particularly, though not exclusively, applicable to portable power units readily transportable to a desired site. In power units of the kind referred to it is necessary to maintain the temperature of the hydraulic fluid within acceptable limits and this has necessitated the provision of a heat exchanger through which the hydraulic fluid is passed. In our prior patent GB 2 114 235 B, there is described an arrangement wherein a portion of cooling air delivered to the heat exchanger is caused to flow over a wall of the reservoir to provide additional surface area for heat exchange. The present invention is based on an appreciation of the possibility of extending this principle whereby the entire heat exchange surface is provided by the walls of the reservoir enabling the provision of more compact and lightweight hydraulic power units of the kind referred to. According to the present invention, there is provided a hydraulic power unit of the kind referred to wherein said reservoir is of annular construction surrounding a chamber through which cooling air is passed. A fan may be located within said chamber and driven by a shaft extending from a prime mover to the hydraulic pump. Axially spaced radially extending annular fins may extend from the inner wall of the reservoir into the chamber. Axially spaced radially extending annular fins may extend from the inner wall of the reservoir into the interior of the reservoir. Fins extending into the chamber and into the interior of the reservoir may lie in common axially spaced planes. The invention will be further apparent from the following description with reference to the several figures of the accompanying drawings, which show, by way of example only, one form of hydraulic power unit embodying same. Of the drawings :- Figure 1 shows a perspective view of the power unit from the front; Figure 2 shows a perspective view of the power unit from the rear; Figure 3 shows a rear elevation of the power unit; and Figure 4 shows a cross-section through the power unit on the line IV-IV of Figure 3. Referring now to Figures 1 to 4 of the drawings, it will be seen that the hydraulic power unit comprises a prime mover, in this example a petrol driven internal combustion engine 10 mounted on a base plate 11 by means of which the unit may be secured within a wheeled chassis (not shown). A drive shaft 12 extends forwardly from the engine 10 and connects with a hydraulic pump 13 by means of a flexible drive coupling 14. Surrounding the drive shaft 12 between the engine 10 and pump 13 is an annular hydraulic fluid reservoir 15 defining a chamber 16 therewithin. Connected with the drive shaft 12 and within the chamber 16 is a fan 17 which draws air in through apertures 18 in an interface mounting plate 19 for the pump for passage through the chamber and over the inner wall of the reservoir 15 before being expelled through an air outlet 20 at the rear of the chamber 16. The radial depth of the reservoir 15 varies around its periphery, being at a minimum in the region of the air outlet 20. Axially spaced radially extending annular fins 21 extend into the chamber 16 from the inner wall of the reservoir 15. Additional axially spaced radially extending annular fins 22 extend into the reservoir 15 from the inner wall thereof. The fins 21 and 22 lie in common axially spaced planes. Hydraulic fluid is drawn from a suction outlet 23 by the pump 13 for passage through a hydraulicaUy operated device (not shown) before return to the reservoir 15 through an inlet 24. The outlet 23 and inlet 24 are diametrically opposed ensuring maximum contact of the fluid with the fins 22. The fins 21 provide an extended surface for heat exchange ensuring effective and efficient cooling of the fluid, notwithstanding the close proximity of the reservoir 15 and engine 10. Figures 5 and 6 show a petrol engine 51, an annular hydraulic tank 52 with an internal fan 53 coupled to the engine 51 by a drive shaft 54, with an intervening spacer 55. The tank 52 has a filler cap 56 and a sight gauge 57. A drive coupling 58 connects to a gear pump 59 secured in the annulus of the tank 52 by a flange 61. A suction filter 62 fits into the tank 52 as does a valve block 63 with a filter 64 and a pressure regulator cartridge 65. It will be understood that the units are extremely compact and does not require protective guards for the heat exchange arrangements which are of robust construction and located within the confines of the reservoir. It will be appreciated that it is not intended to limit the invention to the above example only, many variations, such as might readily occur to one skilled in the art, being possible, without departing from the scope thereof. Thus, the tank can be fabricated in metal or moulded.

Claims: CLAIMS 1. A hydraulic power unit comprising a reservoir for hydraulic fluid, a hydraulic pump for circulating hydraulic fluid under pressure through a hydraulicaUy operated device to be driven by the power unit, wherein said reservoir is of annular construction surrounding a chamber through which cooling air is passed. 2. A unit according to claim 1, comprising a fan located within the chamber. 3. A unit according to claim 2, in which the fan is driven by a shaft extending from a prime mover to the hydraulic pump. 4. A unit according to any one of claims 1 to 3, in which first cooling fins extend from the inner wall of the annular reservoir into the chamber. 5. A unit according to claim 4, in which said fins are axially spaced, radially extending fins. 6. A unit according to any one of claims 1 to 5, in which second cooling fins extend from the inner wall of the annular reservoir into the interior of the reservoir. 7. A unit according to claim 6, in which said second cooling fins are axially spaced, radially extending fins. 8. A unit according to claim 7 as appended to claim 5, in which said first and said second axially spaced, radially extending fins lie in common planes. 9. A hydraulic power unit substantially as herein described with reference to the accompanying drawings.

Inventors: FLETCHER STEPHEN JOHN, FLETCHER, STEPHEN, JOHN
Applicants: BELLE ENGINEERING SHEEN LTD, FLETCHER STEPHEN JOHN, BELLE ENGINEERING (SHEEN) LIMITED, FLETCHER, STEPHEN, JOHN
Application year: 2000
Main classification: F04B23
IPC codes: F04B23, F04B53