GB1600095A

GB1600095A - Apparatus and electronic components thereof for use in a pressurized environment

Info

Publication number: GB1600095A
Application number: GB20003/78A
Authority: GB
Original assignee: TRW Inc
Current assignee: Northrop Grumman Space and Mission Systems Corp
Priority date: 1978-03-06
Filing date: 1978-05-16
Publication date: 1981-10-14
Also published as: FR2419650A1; JPS54118100A; NO790729L

Description

(54) APPARATUS AND ELECTRONIC COMPONENTS THEREOF FOR USE IN A PRESSURIZED ENVIRONMENT (71) We, TRW, INc., a corporation of the State of Ohio, tunized States of America, of One Space Park, Redondo Beach, California, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to apparatus and electronic components thereof for use in a pressurized environment.

More particularly, but not exclusively, this invention concerns a pressure balanced subsea chamber having electrical and electronic components that are provided with individual pressure compensation systems that promote use of such electrical anc! electronic components in environments where temperatures and pressures might otherwise adversely affect proper operation thereof.

In the production of petroleum products, electronic control systems have been developed that tind effective use in automatically controlled and continuously monitored production. Electrohydraulic production systems have been developed wherein electrically controlled valves are utilized to control hydraulic fluid that in turn controls actuation of tile production flow control valves of wellhead assemblies.

Such control systems have found wide use in subsea production environments.

It is typically desirable from the standpoint of design to provide an enclosure for electronic components that has an internal chamber which is maintained under the pressure of one atmosphere. One of the advantages of a one atmosphere type protective enclosure is that all of the materials and components that are employed in the control system are maintained under ambient pressure. Additionally, the single atmosphere environment could be controlled, if desired, to achieve optimum component and circuit life.

Single atmosphere circuit enclosure en environments are disadvantageous in many cases. For example, the physical size of one atmosphere type electronic circuit enclosures is directly proportional to the pressure to which the outer protective envelope will be subjected. Such enclosures become extremely large as the pressure of an ocean environment approaches the hydrostatic pressure of the five hundred foot level. In deeper, higher pressure environments, design considerations encounter difficult problems if a pressure of one atmosphere is to be maintained within an enclosure. The physical size of the internal chamber o.fthe enclosure is reduced because of the necessity to provide thick, pressure resistant walls, thus limiting the physical size of the electronic package it can contain. Heat build-up within the enclosure also becomes a problem because the thick walled structure resists transfer of heat from the electronic package to the subsea environment. The electronic com ponents are then required to function in a hot environment which decreases the effective operating life of the components.

Where single atmosphere enclosures are utilized in high pressure environments, it is typically difficult to maintain an effective interiace for signal uow across the envelope defined by the enclosure. Special high pressure electrical connectors are necessary and these must, of necessity, be very large so as to resist high pressure. Moreover, large electrical connectors further reduce the available space within high pressure single atmosphere enclosures, further complicating the availability of space for the electronic package. The problems outlined above increase geometrically by orders of magnitude as the pressure of the environment increases.

The present invention, the scope of which is defined in the appended claims utilizes a pressure balancing concept whereby ambient pressure of a pressurized environment is transmitted to components of an electronic system and no pressure differential exists at any interface.

This pressure balancing concept affords an effective alternative to the single atmosphere type protective enclosures and provides advantages that promote the use of a subsea well production control system in extremely deep locations.

One of the advantages of employing a pressure balanced enclosure for an electronic control system is that no requirement exists for excessive superstructure strength to withstand pressure induced forces. The physical size and strength of the enclosure is not a function of pressure because no pressure differential will exist regardless of the water depth. The wall thickness and internal space of an enclosure may remain the same whether the enclosure is designed to withstand hydrostatic pressure of one hundred or five thousand feet of water.

Where pressure balanced enclosures are employed heat transfer problems are minimized. A dielectric fluid with excellent heat transfer capability may be selected to fill the enclosure and the wall structure of the enclosure can remain rather thin and thus will have excellent heat transfer capability.

Another advantage resides in the capability of providing a light-weight housing structure with simple, small and lightweight connection devices that provide for electrical connection through the envelope established by the enclosure. Virtually any type of suitable water-proof connector will suffice in view of the absence of pressure differential across the interface established by the enclosure envelope. There is no need to limit the design of the enclosure to specific pressure-resistant geometric shapes, such as spheres or cylinders as is required in one-atmosphere type enclosures.

Where subsea electronic control systems are protected by a pressure balanced enclosure, thus subjecting the interior of the enclosure to ambient pressure, the design criteria for such systems raises other problems from the standpoint of implementation. As a primary design consideration, all of the electronic components must be capable of withstanding the ambient pressure of the subsea environment. For example, where 5,000 psig is the hydrostatic (ambient) pressure at the level of installation of a control system, the electronic components of that control system must be capable of functioning at 5,000 psig.

From the standpoint of withstanding high pressure, the components of typical control systems can Ibe classified as inherently acceptable components, marginally acceptable components and unacceptable components. Inherently acceptable components such as manifolds, high-pressure tubing, valves and other rigid mechanical structures resist the forces of pressure quite readily.

Components that are marginally acceptable from the standpoint of pressure can be classified as parts or components that do not have substantially unlimited pressurewithstanding capabilities. Small bodied discrete electronic components can be classified as marginally acceptable. Parts or components that are unacceptable from the standpoint of pressure-withstanding capability, such as large bodied electronic components, for example, generally define a majority of the components of an electronic control system.

In order to promote the use of large bodied electronic components in high pressure ambient environments, such as at great ocean depths, it is desirable to modify these components and thus provide them with the capability of withstanding high pressure conditions. This can be accomplished by pressure balancing each of the individual electronic components through modification of the enclosures of the components. By so doing, these components are rendered effective for use in subsea environments and thus promote the use of subsea well production control systems at great ocean depths.

A preferred embodiment of the invention comprise a pressure balanced enclosure system is provided that is adapted to be located in a high pressure environment, such as a subsea environment having high hydrostatic pressure, and functions to provide protection for electrical and electronic components contained therein. The enclosure system is basically defined by inner and outer housing structures defining redundant variable volume chambers with these chambers being filled with a substantially incompressible protective fluid medium. The outer chamber is in communication with the hydrostatic pressure of the subsea environment by means of a third variable volume chamber defined by a fluid filled expansible enclosure comprising a flexible bladder. The bladder structure is contained within a bladder housing that is supported exteriorly of the outer housing. The pressure of the subsea environment enters the bladder housing through a pressure-transfer port and thus allows application of hydrostatic pressure directly on the expansible enclosure or bladder. This pressure is communicated from the bladder to the fluid environment within the outer housing structure.

Within the outer housing is located an inner housing defining a secondary chamber containing the electrical and electronic components, which chamber is also filled with a substantially incompressible fluid medium. The hydrostatic pressure of the sea water, communicated into the outer housing, is also communicated into the inner housing without allowing physical fluid interchange between the inner and outer housing structures. A portion of the wall structure of the inner housing is defined by an expansible section, such as a bellows, that allows variation in the volume of the inner or secondary chamber which, consequently, causes variation in the volume of the primary chamber defined between the inner and outer housings. The expansible bellows section is of rather thin construction and is protected by an external shroud that extends from the upper portion of the internal housing.

The inner housing structure is releasably maintained in sealed assembly with the outer housing structure by means of cooperating flanges maintained in assembly by means of clamp means.

To the housing or cover structure of encased electronic components there is connected an expansible pressure balancing housing having a filling tube attached thereto. The housing or cover of the electronic component will be formed to define an opening communicating the cavity of the electronic component with a variable volume chamber defined by the pressure balancing housing. The cavity of the electronic component and the variable volume chamber may then be filled with an inert and substantially incompressible fluid medium that transmits fluid pressure externally of the component into the cavity of the electronic component. After filling, the filling tube or opening is closed and sealed.

Fluid pressure acting externally of the expansible housing and electronic component will be transmitted to the protective fluid within the variable volume chamber and will then be transmitted into the electronic component cavity through the aperture formed in the housing or cover. Fluid pressure internally of the electronic component and expansible housing is thus balanced with external pressure at all times.

There is no tendency for the cover or any other portion of the electronic component to become deformed due to the application of pressure thereto.

The expansible housing structure may be attached to the cover or enclosure of the component by soldering or by an epoxy material such as an electrically insulating epoxy system designed for hermetic lid sealing.

The expansible housing structure may conveniently take the form of a bellows such as ,might be composed of metal or any other suitable material. The filling tube may be connected to the free end wall of the bellows by soldering or by any other suitable form of connection. The opening defined by the filling tube may be sealed in any suitable manner.

In order that the invention may be well understood, the preferred embodiment thereof, which is given by way of example only, will now be described in more detail, reference being had to the accompanying drawings, in which: Fig. 1 is a fragmentary sectional view in elevation depicting apparatus for use in a pressurized environment; Fig. 2 is a partial sectional view illustrating an inner housing of the same apparatus; Fig. 3 is a fragmentary sectional view illustrating a detail of the inner housing; Fig. 4 is a fragmentary sectional view illustrating another detail of the inner housing; Fig. 5 is a sectional view in elevation illustrating an electrical or electronic component comprising a semi conductor device housed in a casing and an expansible enclosure connected to the casing; Fig. 6 is an exploded view of the component of Fig. 5 as the parts appear prior to assemby; Fig. 7 is a sectional view illustrating another electronic component; Fig. 8 is a sectional view of a relatively large electronic component having a large flat cover encasing electronic circuitry elements to which cover is attached an expansible enclosure; and Fig. 9 is an isometric view of another electrical or electronic component.

Referring now to the drawings, and first to Fig. 1, there is illustrated an apparatus 10 which is adapted for use in a pressurized environment. The apparatus 10 is also adapted for location in a corrosive high pressure environment such as might be prevalent in the ocean. While use of the apparatus 10 is discussed herein with particular reference to subsea environments, it is to be understood that the apparatus has effective application in other high pressure fluid environments.

The apparatus 10 has an outer protective housing 12 defined by a generally cylindrical wall structure 14 that is connected to a base flange 16 by a suitable weld connection 18 or by any other suitable form of attachment. A generally circular closure 20 is welded to or formed integrally with the wall structure 14 and cooperates with the wall and base structures to define an internal chamber 22 which is referred to herein as the primary chamber. It should be borne in mind that the particular configuration of the wall structure, the closure and the base portion of the outer enclosure 12 is presented herewith only for purposes of illustration.

Communication of the hydrostatic pressure of the sea water or other fluid medium surrounding the outer housing 12 into the primary chamber 22 is accomplished by the outer housing 12 having at least one pressure transfer port 24 and a suitable conduit connection structure 26 which is connected externally of the wall structure 14 and surrounds the port 24. A fluid transfer conduit 28 extends from the connection 26 to provide support for an enclosure 30. The enclosure 30 is located externally of the housing 12 and is of a rigid construction to provide protection for an internal flexible bladder 32 whose internal chamber 34 is in fluid communication with a passage 36 defined by the support conduit 28. The bladder 32 is clamped to an internal sleeve 38 within the rigid enclosure 30. If desired, any suitable form of sealant material may be applied at the connection between the bladder and the sleeve 38 in order to ensure against any possibility that the fluid medium surrounding the bladder might enter the fluid transfer passage 36. A port 40 is defined in the rigid enclosure 30 in order to permit flow of sea water or other pressurized fluid medium into the rigid enclosure 30 and surrounding bladder 32.

With the primary chamber 22 filled with a substantially incompressible protective dielectric fluid, and with the bladder chamber 34 and passage 36 also filled with the dielectric fluid, hydrostatic pressure from the fluid medium, i.e. sea water, externally of the outer enclosure 12 will be communicated through port 40 into the rigid enclosure 30 and will thereby exert hydrostatic pressure on the bladder 32 and its contents. This hydrostatic pressure will therefore be communicated through the bladder and the fluid therein and through the passage 36 into the primary chamber 22.

Thus, the primary chamber and its contents will be subjected to the hydrostatic pressure of the sea water environment. The bladder 32 provides at an interface that positively separates the surrounding fluid, i.e. the sea water from the inert dielectric fluid contained within the chamber 34 while enabling instantaneous pressure equalization. The bladder 32 also functions to balance pressure within the primary chamber 22 with the pressure of the external environment in which the housing 12 is located. Although the dielectric fluid within the bladder chamber 34 and the primary chamber 22 is substantially incompressible, nevertheless, its volume can vary responsively to both pressure and temperature changes. Volumetric changes due to changes in temperature and pressure will be compensated for by the bladder 32 as its chamber 34 is of variable volume. By ensuring that the pressure within the primary chamber 22 remains balanced with the pressure of the external environment, the outer housing 12 may be contructed of relatively light-weight, lowcost materials, thereby enhancing the commercial feasibility of the apparatus 10.

The outer housing 12 provides protection for an electrohydraulic system which includes a plurality of electrically controlled valves 41 that control the flow of hydraulic fluid in a hydraulic system including hydraulic lines 43. The hydraulic lines communicate with hydraulically actuatable flow control valves of subsea wellheads, not shown.

The apparatus 10 is designed particularly for protection of all its internal components and is further designed to provide protection for such components over extremely long periods of time. Electrical and electronic components are located within an inner protective housing 42, which is located within the outer housing 12, The inner protective housing 42 is filled with a dielectric fluid and pressure balanced with respect to the pressure of the outside environment and, thus the pressure within the primary chamber 22. Such is conveniently and effectively accomplished by providing the inner protective housing 42 with a construction such as is illustrated in Figures 1 and 2. As shown in greater detail in Fig. 2, the inner protective housing 42 is formed by an expansible wall portion shown generally at 44 which includes upper and lower generally cylindrical portions 46 and 48, respectively, that are formed integrally with an intermediate expansible section 50 having a convoluted bellows-like structure. The expansible wall portion 44 is formed of a suitable metal of relatively thin cross-section or any other suitable material. The convolutions of the expansible section 50 allow the length of the expansible wall portion to vary substantially, thus allowing variation in the volume of the dielectric fluid within the housing 42 in response to pressure differentials between the interior and exterior of the housing 42. An upper closure element 52 is provided having an annular flange portion 54 that is suitably connected within the upper section 46 of the expansible wall portion. Connection between the flange 54 and the upper section 46 of the expansible wall portion may be accomplished by welding or efficient connection may be established in any other suitable manner, it being necessary that the connection between the upper portion 46 and the flange 54 be posi tively sealed. The connection between the upper section 46 and the flange 54 is illustrated in detail in Fig. 3.

As shown in Fig. 2, and in greater detail in Fig. 4, an annular releasable connection element 56 is provided defining a generally cylindrical connection portion 58 that is adapted to be connected within the annular lower portion 48 of the expansible wall portion 44 with such connection being established by any suitable means, such as welding. It is necessary that connection between the annular connection element 56 and the lower portion 48 of the expansible wall portion 44 be impervious to the dielectric fluid internally and externally of the housing 42. The releasable connection element 56 also has an external tapered or frusto-conical surface 60 defined by an annular flange 62 that is adapted for juxtaposition with an annular connection flange 64 of a lower closure element 66. The connection flange 64 is also formed to define a tapered or frusto-conical surface 68 which is engaged along with frusto-conical surface 60 by means of a clamp element 70 that serves to retain the flanges 62 and 64 in assembly. The clamp element 70 defines internal frusto-conical surfaces 72 and 74 that engage the mating tapered surfaces 60 and 68 of the flanges 62 and 64, respectively, and provide a camming action that positively urges the flanges 62 and 64 into tightly engaged assembly.

In order to provide against leakage at the joint between the flanges 62 and 64, the releasable connection element 56 defines an annular recess 76 that cooperates with a corresponding recess defined in a generally planar surface 78 to provide an annular seal chamber within which is located a sealing element 80 such as an elastomeric 0ring or other suitable form of seal. An extension portion 82 of the lower closure element 66 is adapted to project within the releasable connection element 56 so as to provide wall structure for encapsulating the sealing element 80 within its seal chamber The sealing element 80 is maintained under a degree of mechanical compression to provide a positive seal at the joint between flanges 62 and 64. The clamp element 70 may be in the form of clamp segments or a clamp ring and may be caused to urge the flanges 62 and 64 in assembly by means of bolts or other suitable mechanical securing devices. The lower closure element 66 may be connected to a plate structure defining an annular connection flange 84 through which bolts or studs (not shown) may extend for mechanical attachment of the closure structure to other structural elements of the apparatus.

Because the expansible wall portion 44 is of relatively light-weight construction and might possibly be subjected to damage during use or during handling operations, it is desirable to provide mechanical protection for its intermediate expansible section 50. This may be conveniently accomplished by providing a shroud element 86 having an upper reduced diameter connection flange 88 that is suitably connected to the outer surface 90 of the upper wall portion 46 with such connection being established by welding or by any other suitable means. The outer body portion of the shroud 86 is adapted to be disposed in spaced relation with the intermediate expansible section 50 and is of suitable length to completely enclose its convoluted bellows-like structure when extended to its maximum length. The lower annular section 48 of the expansible wall portion is of sufficient length to insure that the shroud does not contact other structural elements when the expansible section 50 is fully compressed.

With the clamped and sealed connection established between the expansible wall portion 44 and the lower closure element 66, the inner protective housing 42 effec- tively defines an internal variable volume chamber 92 within which may be located a suitable array of electrical and electronic components. As shown in Figs. 1 and 2, a plurality of structural support elements 94 are suitably connected to the lower closure plate 66 and these support elements provide support for a plurality of generally horizontal circuit boards 96 on which are located an array of electrical and electronic components.

The dielectric fluid in the internal variable volume chamber 92, which is referred to herein as the secondary pressure balancing chamber, is substantially incompressible and does not interfere with the activity of the electrical and electronic components.

Referring now to Figs. 5 and 6, there is shown at 100 an electrical or electronic component comprising a semi-conductor device. The component 100 has a base portion 112 that is usually formed of metal.

Through the base portion 112 extend a plurality of etectrical connector elements 114 through which electrical connection is established with internal circuits of the electronic component. In accordance with conventional practice, a housing or casing 116 is connected in a sealed manner to the base portion 112, thereby serving to encase the semi-conductor device and protect the internal circuit elements from contamination by the environment in which the component is located. In the structure shown in Fig. 5, the housing 116 is defined by a generally cylindrical wall portion 118 and a planar wall portion 120 that is integral therewith. The electrical or electronic com ponent thus described is of conventional nature. Typical examples are transistors.

In order to adapt the electrical or electronic component 110 for operation in a high pressure environment or an environment where temperature changes might cause development of pressure, it is desirable to provide a pressure balancing system that causes internal pressure within the fixed volume chamber 122 defined by the housing ill6 to remain balanced with external pressure at all times. This is conveniently accomplished by forming an aperture 124 in the housing 116 through which fluid pressure is communicated into the chamber 122. An expansible enclosure element or housing having a convoluted bellows-like structure is illustrated generally at 126. The expansible element 126 is secured to the electronic component in such manner as to define a sealed variable volume chamber 138 externally of the housing 116 and surrounding the aperture 124. As shown in Fig. 5, the expansible element 126 is provided with a generally cylindrical connector portion 128 disposed in close fitting relation about the cylindrical wall 118 of the housing 116. An hermetic seal may then be developed between the housing and the connector portion 128 in any desirable manner. One suitable seal may employ an impervious bonding agent, such as an epoxy material which is shown at 130, as establishing a bead at the lower portion of the cylindrical connector element 128. The bonding agent positively establishes a mechanical connection between the expansible element 126 and the housing 116, as well as developing a fluid impervious seal.

As shown in Fig 6 the bonding agent 130 is applied at the juncture between the base 120 and housing 116 of the component, after which the cylindrical connector portion 128 of the element 126 is assembled to the component. After curing of the bonding agent, the assembly is ready for filling with dielectric fluid.

At the upper extremity of the connector portion 128 the element 126 includes bellows-like convolutions 132 defining a flexible portion. The element 126 may also have a generally planar free end wall 134 to which is connected a filling tube 136. A high quality, incompressible, dielectric fluid is introduced through the filling tube 136 into the chamber 138 and through aperture 124, to the chamber 122 defined by the housing 116. After filling, the filling tube may be sealed thereby entrapping the fluid medium and preventing contaminance externally of the element 126 and housing 116 from causing possible damage to the internal circuit elements of the electronic component.

In the case of the same type of electronic component as shown generally at 110 in Fig. 7, an expansible element 140 having a bellows construction may be provided with a connector flange 142 that engages the upper portion of the housing 116 as shown.

A bonding agent, such as epoxy material, may be utilized in this case to establish a posltive connection and fluid tight seal between the housing 116 and the element 140.

In the alternative, the connection portion of the bellows may be secured to the housing structure by soldering or by any other suitable form of connection.

Referring now to Fig. 8, there is shown a relatively large electronic component 144 which comprises a body portion 146 through which extends a plurality of connector elements 147 for establishment of electrical connection with internal circuits.

A large protective cover, illustrated generally at 148, is connected to the body portion or case 146 by means of connection flanges 150 that may be bonded, soldered or otherwise sealed to the case 146.. The cover element defines a rather large planar portion 152 that, because of its surface area, would readily yield to the application of pressure. A pressure balancing expansible element 154 having a bellows construction is connected to the planar portion 152 of the cover 148 about an aperture 156 formed in the cover. A flat connection portion 158 of the element 154 may be bonded, or otherwise connected to the planar portion 152 of the cover. The bellows-like convolutions 160 of the element 154 begin immediately above the connector plate 158. The element 154 has an end wall structure 162 to which is connected a filling tube 164.

pressure balancing expansible element 174 is connected to the upper planar surface 172 of the cover 170 in substantially the same manner as shown in Fig. 8. A lower connection ring 176 may be connected to the planar surface 172 of the cover by bonding, soldering or by any other suitable means of connection. The structure of the expansible element 174 may be similar to that illustrated in Fig. 8.

The bladder 32 and the relatively large space within housing 12 may be filled with an economy grade dielectric fluid, such as transformer oil or the like. The housing 42, which contains the electronic circuit boards 96, is filled with a dielectric fluid of a higher dielectric constant such as that commonly used for filling high-voltage apparatus such as X-ray tube housings and the like. In contrast, a primary consideration in the design of the apparatus 10 is selection and preparation of the filling fluid for the relatively very small electronic component housings 126, 140 and 148. Some semi-conductor devices are highly vulnerable to corrosion and contamination by foreign materials while such components are electrically activated. Accordingly a substantially water-free incompressible dielectric fluid of a higher dielectric constant than that used to fill the housing 42 is used to fill the chambers of the electronic components. Thus, we prefer to fill the fixed and variable chambers of the electronic components with a silicone oil, such as that manufactured by the Dow-Corning Corporation and sold under trade designation DC200. Preferably, the DC200 silicone oil is prepared for vacuum filling of the components by first filtering the silicone oil to remove any solid contaminants and then heating tlle oil in a vacuum to remove any moisture.

The electronic components, including their bellows type expansible elements are assembled in a manner avoiding damage to the delicate internal electronic parts of the semi-conductor devices. Through use of a bonding agent, such as an epoxy system, a bond may be established that positively secures the miniature bellows in sealed and positively connected relationship with the casing or housing of the semiconductor device. Fluid interchange occurs through a small aperture in the cover of the semiconductor device.

In view of the foregoing, it will be seen that there has been provided electrical and electronic components with small individual pressure balancing systems that function to prevent the case, cover or body structure of such component from yielding due to the forces of hydrostatic pressure. The internal cavities of the components are maintained free from contamination by moisture or other foreign matter that might interfere with proper operation thereof.

Accoldingly, it is a primary feature of the embodiment to provide a novel pressure balancing system for encased electrical and electronic components such that no part of such components are caused to yield due to the hydrostatic pressure applied thereto.

It is also a feature of the embodiment to provide a pressure balanced housing structure incorporating internal and external pressure balanced chambers to provide superior protection for electrical and electronic components located within the internal chamber.

It is a further feature to provide external and internal housing structures for electrical and electronic components with the internal housing structure defining a variable volume chamber allowing hydrostatic pressure to be communicated from the outer housing structure into the inner housing.

It is also an important feature of the embodiment to provide a pressure balancing system for electrical and electronic components which effectively prevents moisture and other contaminants from entering the casing of such components and affecting the operation thereof.

Among the several features of the embodiment is a pressure balancing system for individual electrical and electronic components that provides an inert and substantially incompressible fluid medium within such components to insure optimum operation thereof under high pressure conditions.

It is also a feature of the embodiment to provide a pressure balancing system for encased individual electrical and electronic components whereby volumetric changes responsive to temperature changes as well as pressure changes are effectively accomodated without adversely affecting the operation of such components.

It is also an important feature of the embodiment to provide a pressure balancing system for encased electronic components that provides for simple and efficient modification of such components for pressure balancing without contaminating or damaging such components.

It is also a feature of the embodiment to achieve pressure balancing of a control system and individual electronic components within inner and outer cascaded protective enclosures through employment of a first dielectric fluid filling the inner protective enclosure and a second, higher grade dielectric fluid filling each of the individual electronic components and a third dielectric fluid of economy grade filling the outer protective enclosure.

It is also a feature of the embodiment to provide a pressure balancing system for encased electronic components that is of simple nature and is reliable in use.

WHAT WE CLAIM IS: 1. Apparatus for use in a pressurised environment and comprising electronic circuitry, including at least one semiconductor device; a first housing enclosing said circuitry and filled with a first dielectric fluid, said first housing being provided with means for allowing variation in the volume of said first dielectric fluid in response to pressure differentials between the housing interior and exterior; a second housing enclosing said semiconductor device, filled with a second dielectric fluid which is hermetically sealed off from said first fluid, said second housing being provided with a variable volume chamber which is in fluid communication with said second housing through an aperture therein to allow variation in the volume occupied by said second fluid in response to pressure differentials between the interior of said second housing and the space occupied by said first fluid.

2. Apparatus as claimed in claim 1, wherein said electronic circuitry includes a plurality of semiconductor devices each of which is enclosed within a respective protective housing which forms a said second housing, each of said second housings having a respective said variable volume chamber connected thereto.

3. Apparatus as claimed in claim 1 or 2, further comprising a third housing enclosing said first housing and defining a chamber around said first housing, which chamber is filled with a third dielectric fluid; a variable volume chamber in fluid communication with the chamber around the first housing for allowing variation in the volume of that chamber; and means communicating fluid pressure externally of said third housing into said chamber around said first housing.

4. Apparatus as claimed in claim 3, wherein said third housing is of rigid construction and said variable volume chamber in fluid communication with the chamber around the first housing is in fluid communication therewith through an aperture in said third housing.

5. Apparatus as claimed in claim 3 or 4, wherein said variable volume chamber in fluid communication with the chamber around the first housing is located externally of the third housing.

6. Apparatus as claimed in any one of the preceding claims. wherein said second dielectric fluid has a higher dielectric constant than said first dielectric fluid.

7. Apparatus as claimed in claim 3, 4 or 5, wherein said third dielectric fluid is of a lower dielectric constant than said first and second dielectric fluids, and said first dielectric fluid has a lower dielectric constant than said second dielectric fluid.

8. Apparatus as claimed in any one of the preceding claims, wherein said first housing comprises a convoluted bellowslike wall structure for allowing expansion and contraction of said first dielectric fluid.

9. Apparatus as claimed in claim 8, wherein shroud means is affixed to said first housing and surrounds said convoluted, bellows-like wall structure for providing protection therefor.

10. Apparatus as claimed in any one of the preceding claims, wherein the variable volume chamber connected to the or each second housing has a convoluted, bellowslike wall sucture for allowing expansion and contraction of said second dielectric Suid.

11. Apparatus for use under water comprising a plurality of valves for controlling fluid flow in a hydraulic system; electricallycontrolled devices for actuating each of said valves; electronic circuitry, including at least one semiconductor device, for controlling at least one of said electricallycontrolled devices in response to signals from a remote location; a first housing enclosing said circuitry, filled with a first dielectric fluid and comprising a bellowslike wall which allows variation in the volume of said first dielectric fluid in response to pressure differentials between the housing interior and exterior; a second housing enclosing the or each respective semiconductor device, filled with a second dielectric fluid which is hermetically sealed off from said first fluid; a variable volume chamber having a bellows-like wall which is affixed to the or each respective second housing about an aperture therein to allow variation in the volume occupied by said second fluid in response to pressure differentials between the interior of the or each second housing and the space occupied by said first fluid; a rigid housing enclosing said first housing and defining a pressure balancing chamber therearound; and a variable volume chamber adapted to be subjected to the pressure of the environment externally of said rigid housing for communicating said pressure into said pressure balancing chamber through an aperture in said rigid housing.

12. A method of pressure compensating a semiconductor device which is housed in a casing forming a fixed volume chamber about said semiconductor device and is to be subjected to fluid pressures, said method comprising forming at least one aperture in the casing; hermetically bonding means defining a variable volume chamber to said casing about said aperture; filling said chambers with a substantially water free dielectric fluid medium through a filling opening; and sealing said filling opening.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. encased electronic components that is of simple nature and is reliable in use. WHAT WE CLAIM IS:

1. Apparatus for use in a pressurised environment and comprising electronic circuitry, including at least one semiconductor device; a first housing enclosing said circuitry and filled with a first dielectric fluid, said first housing being provided with means for allowing variation in the volume of said first dielectric fluid in response to pressure differentials between the housing interior and exterior; a second housing enclosing said semiconductor device, filled with a second dielectric fluid which is hermetically sealed off from said first fluid, said second housing being provided with a variable volume chamber which is in fluid communication with said second housing through an aperture therein to allow variation in the volume occupied by said second fluid in response to pressure differentials between the interior of said second housing and the space occupied by said first fluid.

13. A method as claimed in claim 12,

further including the step of vacuum dehydrating said dielectric fluid medium prior to filling said chambers.

14. A method as claimed in claim 12 or 13, wherein said variable volume chamber has a bellows-like wall and said bonding thereof to said casing is accomplished by the method steps of: applying a quantity of bonding agent to at least one of the connection portions on said wall and casing; bringing said connection portions of said wall and casing in assembly whereby said bonding agent establishes a fluid impervious seal between said connection portions; and causing said bonding agent to cure to establish a mechanical bond between said connection portions.

15. In combination with or for a semiconductor device housed in a casing; an expansible enclosure element adapted to be connected to said casing so as to be in fluid communication with the interior of the casing, and provided with a filling opening to allow filling of said expansible enclosure element and casing with a fluid medium.

16. An enclosure element as claimed in claim 15, comprising a connector portion adapted to interfit with a portion of the casing.

17. An enclosure element as claimed in claim 16, wherein said connector portion is substantially cylindrical and adapted to receive a portion of said casing in close interfitting relation therein.

18. A pressure balanced semiconductor component comprising a casing defining a fixed volume chamber within which is located a semiconductor device, an expansible enclosure element hermetically bonded to said casing about an aperture in said casing such that said fixed volume chamber is in fluid communication with a variable volume chamber defined by said expansible enclosure element through said aperture; and a vacuum dehydrated dielectric fluid medium filling said chambers.

19. Apparatus including an electronic control system incorporating large bodied electronic component means and adapted for location in a high pressure subsea environment, said apparatus comprising: a first variable volume chamber means adapted for fluid pressure communication with said subsea environment in use, said first variable volume chamber means being filled with a first dielectric fluid medium: second variable volume chamber means located within said first variable volume chamber means and being in fluid pressure communication with said first dielectric fluid medium, said second variable volume chamber means being filled with a second dielectric fluid medium; and third variable volume chamber means located within said second variable volume chamber means and being adapted for fluid pressure communication with said second dielectric fluid medium, said third variable volume chamber means at least partially surrounding said large bodied electronic component means and being filled with a third dielectric fluid medium.

20. Apparatus as claimed in claim 19, wherein said second dielectric fluid medium has a higher dielectric constant than said first dielectric fluid medium; and said third dielectric fluid medium has a higher dielectric constant than said second dielectric fluid medium.

21. Apparatus as claimed in claim 19 or 20, comprising an outer housing, a pressure balancing housing connected to said outer housing and a flexible wall means which is located within said pressure balancing housing and divides said pressure balancing housing into inner and outer chambers, said inner chamber and the interior of said outer housing constituting said first variable volume chamber means and the pressure balancing housing having an opening such that in use said outer chamber is in communication with said subsea environment, said flexible wall means forming an impervious interface between said subsea environment and said first variable volume chamber means.

22. Apparatus as claimed in claim 19, 20 or 21, wherein said second variable volume chamber means is defined by a second housing a portion of which is capable of movement relative to a rigid portion thereof.

23. Apparatus as claimed in claim 22, wherein said portion comprises a convoluted bellows-like wall of the second housing.

24. Apparatus as claimed in claim 22 or 23, wherein a protective shroud at least partially encloses said movable portion of said second housing.

25. Apparatus as claimed in claim 24, wherein said protective shroud is supported by said movable portion of said second housing.

26. Apparatus as claimed in any one of claims 19 to 25, wherein said third variable volume chamber means is defined by a protective wall means of said large bodied electronic component means, said protective wall means being movable to vary the volume of said third variable volume chamber means.

27. Apparatus as claimed in claim 26, wherein said large bodied electronic component means includes wall means at least partially defining a housing containing electronic circuit means, said wall means having at least one aperture formed therein; and a bellows-like expansible element being connected to said wall means about said aperture to define with said housing containing said electronic circuit means said third variable volume chamber means.

28. Apparatus for use in a pressurised environment and substantially as herein described with reference to the accompanying drawings.

29. A method of pressure compensating a semiconductor device to be subjected to fluid pressures substantially as herein described with reference to Figures 5 to 9 of the accompanying drawings.

30. A pressure balanced semiconductor component substantially as herein described with reference to Figures 5, 7, 8 or 9 of the accompanying drawings,