Volume Compensated Housing

Abstract

This invention relates to a housing containing oil which has means to compensate for variations in the volume of oil in the housing, such means comprising a cartridge having a rigid shell in which a deformable partition is positioned defining a gas chamber and an oil chamber on opposed sides thereof respectively, the gas chamber being charged through a charging fitting rigidly secured to one end of the shell, with the other end of the shell having a relatively large opening in communication with the housing through a perforated disc extending across the opening, the cartridge being totally immersed in the housing.

Description

It is among the object of the invention to provide a housing for a liquid such as oil, which housing has a cartridge therein adapted to be completely immersed in such oil and which will serve to compensate for changes in the volume of oil in the housing due to thermal expansion and contraction of the oil or to the extension or withdrawal of the piston rod of a hydraulic actuator operatively connected to said housing, which cartridge need be of relatively low cost, light weight construction.

Another object is to provide a housing for a liquid such as oil, which housing has a cartridge therein adapted to be completely immersed in such oil and which will maintain the hydraulic system with which it is used, including the feed line and the return line above ambient pressure to prevent the entry of foreign matter into the system.

According to the invention, the housing is substantially sealed and contains a cartridge which is adapted to be completely immersed in the oil in the housing. The cartridge is a pressure vessel, having a shell of impermeable material which has a gas port at one end and an oil port at its opposed end. A deformable partition such as a bladder, the interior of which defines a gas chamber, is positioned in said shell, said bladder having a mouth connected by a charging fitting to the gas port so that the bladder may be filled with gas under pressure. The oil port has a perforated plate extending thereacross which permits the oil in the housing which is under pressure, to flow into and out of the portion of the shell exteriorily of the bladder which defines an oil chamber, to compensate for variations in the volume of the oil in the housing.

In the accompanying drawings in which is shown one or more of various possible embodiments of the several features of the invention;

FIG. 1 is a diagrammatic view of a hydraulic system incorporating a volume compensated liquid housing according to one embodiment of the invention,

FIG. 2 is a detailed view on a larger scale of the liquid volume compensating cartridge, and

FIG. 3 is a diagrammatic view of a hydraulic system according to another embodiment of the invention.

Referring now to the drawings, as shown in FIG. 1, a housing 11 is provided having an opening 12 in the top wall 13 thereof which is closed by means of a cover plate 14 secured to the top wall 13 by means of a plurality of screws 15. A suitable gasket 16 is positioned between the periphery of the cover plate 14 and the periphery of the opening 12 to provide a seal.

The housing 11 has a port 17 which may be connected to a hydraulic system including a pump P, a reversing valve V and a hydraulic actuator A, the return line R of the system being connected to port 17'.

Positioned in the housing 11 is a volume compensating cartridge 21 which, as clearly shown in FIG. 2, comprises a rigid shell 22 substantially cylindrical as shown, said shell being of any suitable material such as steel and having an impermeable wall surface.

The upper end 23 of the shell has a gas port 24 in which a suitable charging fitting 25 is mounted. Positioned in the shell is a deformable impermeable partition, illustratively a bladder 26, preferably of elastic material such as rubber or the like, which defines a variable volume chamber, the bladder having a mouth at one end (not shown) which is secured to the charging fitting 25 and being closed at its other end 27.

The lower end 28 of the shell 22 which forms the oil port 29 has positioned therein a closure member 32. As is shown in FIG. 2, the closure member comprises a perforated disc 33 having secured to its inner surface 34 adjacent its periphery, an annular fillet 35 preferably of resilient material such as rubber. The fillet 35 is substantially in the form of a right angle triangle in cross section, having its side wall 36 secured to the inner surface 34 of disc 33 adjacent its periphery; its side wall 37 being adapted to press against the inner surface of the shell at its lower end 28 and its hypotenuse 38 extending inwardly and defining an inclined supporting surface for the side wall 40 of the bladder 26 adjacent the end 27 thereof.

Although the closure member 32 may be retained in position in any suitable manner, in the embodiment shown, a removable snap ring 41 is positioned in an annular groove 42 formed in the inner surface of the shell 28 adjacent its lower end, releasably to retain the closure member in position.

The cartridge 21 is preferably mounted on the cover member 14. In the embodiment shown, a plurality of straps 43 are provided, each having an outwardly extending leg 44 at one end and an inwardly extending leg 45 at the other. The straps 43 are secured as by screws 46 extending through openings in each of the legs 44 to the undersurface of cover 14 so as to depend therefrom in equally spaced relationship.

The side wall of the shell 22 has a plurality of lugs 47 illustratively three in number, extending outwardly therefrom, each of the lugs having an opening therethrough to which the leg 45 of an associated strap 43 is secured as by bolts 48. Thus, the cartridge will be suspended in the housing 11 so that when the latter is filled with oil the cartridge will be completely immersed in such oil.

In operation, the cartridge is charged with gas under pressure through the gas fitting 25 which will cause the bladder 26 to expand to substantially fill the interior of the shell 22, the lower end 27 of the bladder being supported by the perforated disc 33 and the side wall 40 by the hypotenuse 38 of the fillet 35. The perforations 49 in disc 33 are of sufficiently small size to preclude extrusion of the bladder.

The cartridge 21 mounted to the cover member 14 is then positioned through the opening 12 in the housing which is charged with oil, and the cover member 14 is then secured in place and sealed by screws 15. Thus, a closed hydraulic system is provided.

In the event that there are variations in the volume of oil in the hydraulic system due, for example, to thermal changes or movement of the piston and piston rod of actuator A, the bladder 26 will expand or contract as necessary to compensate for such volume changes.

In the embodiment diagrammatically shown in FIG. 3, the invention is incorporated in a hydraulically controlled variable pitch propeller system.

In such a system the housing 11 is defined by a hollow propeller hub 51 which is completely charged with oil under pressure through a filling port 52. The hub 51 mounts a plurality of propeller blades 53 only one of which is shown. Illustratively the shaft 54 of each propeller 53 extends into the hub 51 through a bearing 55 which also defines a seal. The inner end of the shaft 54 mounts a pinion 56 which is engaged by a rack conformation 57 at the end of the piston rod 58. The piston rod 58 is secured to a piston 59 slidably mounted in the cylinder of an actuator A', the latter being suitably supported in the hub.

The cylinder has a discharge port 61 in communication with the interior of the hub 51 and a control port 62 connected by line 63 to a rotary seal 64 which is connected by line 65 to the pressure port 66 of reversing valve V'. The hub is rotated by a shaft 68 in conventional manner.

As the variable pitch propeller and the control mechanism therefor is well known in the art, the foregoing description thereof is merely intended to illustrate the invention.

Mounted in the hub 51 is a cartridge 21' which is of the type shown in FIG. 2 and which is precharged with gas under pressure before the hub 51 is filled with oil.

The valve V' has a pair of control ports 69, 71. The port 69 is connected through motor driven pump 72 to a reservoir 73 which has a conventional breather 74 and the port 71 defines an outlet port connected to reservoir 73.

With the propeller in the position shown, the piston 59 and piston rod 58 are retracted. When the valve V' is actuated to connect ports 66, 69, oil under pressure will be forced by pump 72 through the rotary seal 64 into port 62 of the actuator A' to move the piston 59 and piston rod 58 outwardly. As a result, the shaft 54 will be turned to change the pitch of the propeller 53.

When the piston is initially moved outwardly, it will force the oil from the cylinder out of port 61. As the hub 51 is fully charged with oil, the additional oil forced into the hub plus the oil displaced by the extension of piston rod 58 will cause the pressure on the oil in the hub to increase and as a result, such additional volume of oil will be forced into the cartridge 21' to compress the bladder 26 and the gas contained in the bladder.

When the pitch of the propeller is to be restored to its original position for example, the valve V' is actuated to connect ports 66, 71. As a result of the increased pressure of the gas in bladder 26, oil in the cartridge will be forced outwardly therefrom into the hub. As such increased volume of oil is under pressure, it will be forced into port 61 of the actuator to retract the piston rod 58 and piston 59 to change the pitch of the propeller.

The oil in the actuator A' at the back of the piston will be forced through port 62, rotating seal 64, line 65 through valve V' into the reservoir 73 which, as above noted, has a bleeder to atmosphere.

In the absence of liquid, there is no sealing problem with respect to the gas charging valve of the cartridge as the precharge pressure in the bladder is relatively low.

As the cartridge 21 is totally immersed in the oil in the housing 11, 11', it is apparent that the differential pressure to which the cartridge is subjected cannot exceed the value of the precharge pressure in the bladder 26 even when the pumps are actuated.

As a result, the cartridge may be made of relatively thin wall stock of sufficient strength to retain its integrity based only on the precharge pressure in the bladder and hence can be light in weight and relatively inexpensive in cost.

With the arrangement above described, a relatively simple pressure housing is provided which will take up pulsations and pressure surges and compensate for volume variations of liquid in a hydraulic system.

Claims

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A volume compensated rigid housing for liquid, a rigid cartridge of impermeable material in said housing and positioned to be immersed in the liquid therein, said cartridge having a deformable partition positioned therein defining a gas chamber and a liquid chamber on opposed sides thereof, said cartridge having aligned ports on opposite ends thereof, one of said ports defining a gas port, a charging fitting secured in said gas port and in communication with said gas chamber to charge the latter, the other port defining a liquid port, said liquid port having a perforated disc extending substantially completely thereacross, said liquid port being directly in communication with the interior of said housing, said housing having means to connect the hydraulic system thereto.

2. A hydraulic system comprising a rigid housing for liquid, a rigid cartridge of impermeable material in said housing and positioned to be immersed in the liquid therein and, said cartridge having a deformable partition positioned therein defining a gas chamber and a liquid chamber on opposed sides thereof, said cartridge having a charging port in communication with said gas chamber and a liquid port in communication with said liquid chamber and the interior of said housing, means to prevent extrusion of said partition from said liquid port, a hydraulic actuator in said housing having a piston slidably mounted therein and a piston rod operatively connected to said piston and extending from said actuator, said actuator having a pair of control ports on opposite sides of said piston, means on one of said control ports defining an outlet port and the other of said control ports defining a pressure port, means connecting said outlet port to discharge directly into said rigid housing whereby upon extension of said piston rod and discharge of oil from said actuator into said housing, said partition of said cartridge will be deformed to compensate for such additional volume of oil.