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(11) | EP 1 018 483 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Gas-thight solenoid valve coupling |
| (57) A fuel pump unit comprises a first space (1) containing a fuel duct (15) and mechanical
equipment for controlling a fuel flow in the duct (15), a second space (2) which is
free of inflammable liquids and contains electric equipment (18). A barrier (20) separates
the first space (1) from the second space (2), and a valve assembly (3), which has
a valve means (5) arranged in the fuel duct (15), and an electric unit (4) for controlling
the valve means (5). The fuel pump unit comprises a casing (7) surrounding the control
unit (4) in the first space (1) and extending through the barrier (20) to the second
space (2) to form a connection (8) which is enclosed therein and extends between the
control unit (4) and the second space (2). |
Field of the Invention
[0001] The present invention relates to a fuel pump unit of the type stated in the preamble to appended claim 1. Moreover, the invention concerns a method of manufacturing a fuel pump unit according to the preamble to claim 10.
Background Art
[0002] There are very strict rules and regulations governing the design of electric equipment that is used for the handling of inflammable liquids. Fuel pump units comprise such equipment as must meet rigid demands in respect of safety and explosion proofness so as to prevent accidents. It is very important for inflammable liquids in a fuel pump unit not to come into contact with a spark, electric arc, high temperature or the like and cause ignition or explosion. Fuel pump units of the type mentioned by way of introduction are usually designed to guarantee safe handling of inflammable liquids without any risk of accidents.
[0003] Fuel pump units of the type mentioned above often have a first zone for inflammable liquids and a second zone for electric equipment. A partitioning barrier separates the two zones. By separating the electric equipment from the fuel, a safe fuel pump unit is obtained. In the cases where electric equipment is arranged in the hazardous zone, a special design and securing of the equipment is necessary to prevent ignition and explosion. For instance, coils and electric cables used in the explosive zone are made explosive-proof by special encapsulations or by being intrinsically safe. The connections between the electric cables and other equipment in the explosive environment must also meet high demands for safety.
[0004] Intrinsically safe coils which have been specifically made for use in explosive environment are purpose-made and expensive. Electric cables contain a sealing compound to achieve explosion proofness. Connections between electric cables and intrinsically safe coils are complicated and time-consuming to produce. First the cables must, even if they are intrinsically safe, be peeled and then connected to the safe coil according to industry standard and safe-guarding according to Eexd or Eexm classes. The reason for the stringent requirements placed on connections of cables in the first zone is the risk of liquid moving in the cables owing to capillary action. It has also been found difficult and expensive to obtain an adequate gas-tight seal between cables connecting the two zones and the barrier.
[0005] US 4,986,445 discloses a fuel pump unit of the type stated by way of introduction. The fuel pump unit has in prior-art manner been divided into a first zone for mechanical equipment, which contains inflammable liquids, and a second zone for electric equipment. A gas-tight barrier consisting of two walls which define an air gap has been arranged between the first and the second zone. A valve assembly having a mechanical part and an electric part is arranged in the fuel pump unit to control the fuel flow in the first zone. The mechanical valve part comprises a movable valve means for controlling a fuel flow and is arranged in the fuel flow and controls the same in the first zone. The electric part in the form of a coil is arranged in the second zone. The movable valve means has an elongate piston element extending through the barrier in an elongate sleeve for cooperation with the coil in the second zone. When the coil is actuated, a magnetic field forms and actuates the piston element and, thus, the valve means in the first zone.
[0006] The piston element in this construction is in itself considerably longer than is usual in such valve assemblies. Therefore this and also other parts of the valve assembly must be specially made for the purpose. Since the piston element is especially long and, consequently, heavier, the control properties are deteriorated, inter alia, owing to the great inertia causing slow motions.
[0007] A further drawback of prior-art valve assemblies of the type described above is that they are relatively complicated and time-consuming to mount in the manufacture of a fuel pump unit.
Summary of the Invention
[0008] An object of the present invention is to provide a fuel pump unit which is improved relative to the technique described above and which has great explosion proofness, and in particular to provide an improved valve assembly in such a fuel pump unit.
[0010] According to the invention, these and other objects that will appear from the following specification are achieved by a fuel pump unit and a method, which are of the types stated by way of introduction and which besides have the features defined in the characterising clause of claims 1 and 10, respectively.
[0011] According to the invention, an electric control unit belonging to a valve assembly is encapsulated in a surrounding casing and arranged in a first space containing inflammable and explosive liquids. From there the casing extends through a gas-tight barrier to a second space, which is intended for electric equipment and is free of inflammable liquids. Thus there forms a connection through the barrier between the control unit and other electric equipment in the second space. Since the casing extends through the barrier, an excellent seal between the casing and the barrier is easily obtained. The casing surrounds both the control unit and its electric connections and connects the control unit to electric equipment in the first space while at the same time the explosive environment in the first space is locked out. The need for explosion-proof connections is obviated. This implies that the control unit in itself does not require any further adaptation to explosion proofness requirements. At the same time the control unit can be arranged in the first space adjacent to the valve means of the valve assembly, which results in a simple construction. The valve means can be designed freely to obtain good controlling properties. This also makes it possible to use standard components. The construction consists of but a few parts, which besides yields a low manufacturing cost.
[0013] In addition to the above-mentioned advantages, the encapsulation of the casing implies that the valve assembly can easily be installed in the first space of the fuel pump unit. No connection between the control unit and electric cables must be made on site in the first space.
[0015] In a preferred embodiment, the casing is gas-tight, which prevents gas from the first space from penetrating into the casing.
[0016] In a further embodiment, the casing is made of rigid plastic. This makes it possible to work the casing, for instance, provide it with threads and shoulders, and affords firm abutment against the barrier.
[0017] In a special embodiment, the casing is moulded. The control unit, the electric cables and their connection are arranged in the casing during moulding. This eliminates the need for these components to be arranged in the fuel pump on site.
[0018] In another embodiment, the casing is made in one piece, which results in good explosion proofness and easy mounting.
[0019] A special embodiment has a casing which is made of rigid plastic in one piece, is gas-tight and moulded to produce the above-mentioned advantages.
[0020] Preferably, the barrier is designed as two gas-tight walls with an intermediate air gap. The air gap of the barrier means that vapours and gases that possibly would pass through one of the walls can quickly and easily be entrained. Moreover, the barrier with two walls yields twofold explosion proofness.
Brief Description of the Drawings
[0021] The invention will now be described in more detail with reference to the accompanying drawing, which for the purpose of exemplification illustrates a currently preferred embodiment.
Description of the Preferred Embodiments
[0023] The Figure shows part of a fuel pump unit which has a first space 1, where mechanical equipment is arranged in contact with inflammable liquids, and a second space 2, which is free of inflammable liquids and in which electric equipment generally designated 18 is arranged. A gas-tight barrier 20 separates the first space 1 from the second space 2. In the first space 1, a valve assembly 3 is arranged to control a fuel flow. The valve assembly 3 comprises a control unit 4 and a valve means 5. The control unit 4 consists of a coil 6 which is encapsulated in a casing 7.
[0024] The casing 7 extends through an opening in the gas-tight barrier 20 and defines a connection 8 between the control unit 4 and the second space 2. The casing 7 is well sealed against the environment in the first space 1. In the connection 8, an electric cable 9 extends from the control unit 4 through the barrier 20 to the second space 2. The electric cable 9 establishes an electric connection through the barrier 20 from the control unit 4 to the electric equipment 18 arranged in the second space 2. The connection between the control unit 4 and the electric cable 9 is surrounded by the casing 7 and, thus, is explosion-proof. The explosion proofness of the casing is achieved by a thickness of the casing in the range of 1-5 mm, preferably about 3 mm, to prevent contact between a possible spark and the inflammable liquid. It is also important that there be no air in the encapsulation of the casing 7, according to explosion proofness regulations such as SSEN 50015 and SSEN 50018.
[0025] The barrier comprises a gas-tight wall 21 facing the first space 1 and a gas-tight wall 22 facing the second space 2. Between the walls 21 and 22 there is an air gap 23 for entraining any inflammable liquids that may have passed the wall 21. The air gap between the walls 21 and 22 is about 25 mm and leads to a safe zone outside said spaces 1 and 2.
[0026] The casing 7 is secured to the barrier 21 in a gas-tight manner by means of a threaded engaging device 10. The casing 7 is advantageously moulded of plastic round the coil 6 and the cable 9 and is preferably made in one piece, but may also consist of a plurality of closely joined parts. Sealing nuts 11 abut against the barrier 20 and the outside of the casing 7 to seal the transitions therebetween in an explosion-proof manner. It is an easy and reliable measure to produce adequate tightness between the rigid casing 7 and the barrier 20. In one embodiment, a sealing nut 11 is arranged on each side of the wall 21. Moreover, the casing 7 has a shoulder 14 abutting against the wall 22. Owing to the shoulder, the casing 7 abuts correctly against the barrier and a close abutment is obtained. A sealing nut 11 is arranged against the wall 22 from the side of the second space 2 to ensure a good seal between the wall 22 and the casing 7. The sealing nuts 11 also connect the casing 7 to the barrier 20.
[0027] Ducts 15 are formed in the first space 1 to conduct inflammable liquids to and from the valve assembly 3. The valve assembly 3 comprises a solenoid valve, in which the coil 6 of the control unit 4 is made explosion-proof by means of the casing 7 alone, or in combination with a sleeve 19 arranged in the centre of the coil 6.
[0028] The valve means 5 has an elongate portion 12 extending from the body 13 of the valve means 5 into the centre of the coil 6. In the elongate portion 12, a piston element 16 is slidably arranged to control the fuel flow in corporation with a seat means 17. By electrically transmitting a signal through the barrier 20 to the coil 6, the fuel flow in the first space 1 is controlled. The coil 6 actuates a magnetic field which moves the piston element 16 away from the seat means 17 to allow the fuel to flow through the valve means 5. When the magnetic field ceases to work, the liquid returns the piston element 16 to close abutment against the seat means 17.
[0029] Manufacturing a fuel pump unit with a valve assembly 3 arranged in the gas-tight barrier 20 is extremely easy in the shown embodiment of the invention. The casing 7 is formed so as to surround the control unit 4 of the valve assembly 3. The valve assembly 3 is placed in such a manner that the casing 7 extends through the gas-tight barrier 20 and encloses a connection 8. The barrier 20 separates the first space 1, which contains a fuel duct 15 and mechanical equipment for controlling a fuel flow in the duct 15, from the second space 2, which is free of inflammable liquids and encloses electric equipment 18. The casing 7 is secured in the gas-tight barrier 20.
[0030] The valve assembly 3 can quickly and easily be positioned from one side of the barrier 20, preferably from the first space, and obtain gas proofness between the casing 7 and the barrier 20. This facilitates the manufacture of a fuel pump unit and results in saving of labour in the manufacture.
[0031] It will be appreciated that a great number of modifications of the above embodiment of the invention are feasible within the scope of the invention as defined in the appended claims. For instance, the separating barrier may consist of a single wall which separates the first space from the second space. The engaging devices of the casing can, for instance, engage the barrier in a snap or press fit, such that mounting, dismounting, repair and maintenance may be carried out rapidly and effectively. Moreover, the casing can be made of a plurality of different materials, such as rubber or the like, as long as satisfactory explosion proofness is achieved.
1. A fuel pump unit comprising
a first space (1) containing a fuel duct (15) and mechanical equipment for controlling a fuel flow in the duct (15),
a second space (2) which is free of inflammable liquids and encloses electric equipment (18),
a barrier (20) which separates the first space (1) from the second space (2), and
a valve assembly (3), which has a valve means (5) arranged in the fuel duct (15), and
an electric unit (4) for controlling the valve means (5), characterised in that
a casing (7) surrounds the control unit (4) in the first space (1) and extends through the barrier (20) to the second space (2) to form a connection (8) which is enclosed therein and extends between the control unit (4) and the second space (2).
2. A fuel pump unit as claimed in claim 1, wherein the casing (7) separates in a gas-tight
manner the control unit (4) and the connection (8) from the inflammable liquids in
the first space (1).
3. A fuel pump unit as claimed in claim 1 or 2, wherein an electric cable (9), which
is connected to the control unit (4) on the inside of the casing (7), extends in the
casing (7) from the control unit (4) in the first space (1) through the barrier (20)
to the second space (2).
4. A fuel pump unit as claimed in claim 1, 2 or 3, wherein the casing (7) has a thickness
in the range of 1-5 mm and preferably about 3 mm.
5. A fuel pump unit as claimed in any one of the preceding claims, wherein the casing
(7) is made of rigid plastic.
6. A fuel pump unit as claimed in any one of the preceding claims, wherein the casing
(7) is moulded.
7. A fuel pump unit as claimed in any one of the preceding claims, wherein the casing
(7) is made in one piece.
8. A fuel pump unit as claimed in any one of the preceding claims, wherein the barrier
(20) consists of a first gas-tight wall (21) facing the first space (1) and a second
gas-tight wall (22) facing the second space (2), an air gap (23) forming between the
first (21) and the second (22) wall.
9. A fuel pump unit as claimed in any one of the preceding claims, wherein the casing
(7) on its outside is connected in a gas-tight manner to the barrier (20) by means
of engaging devices (10).
10. A method of manufacturing a fuel pump unit,
characterised by the steps of:
characterised by the steps of:
forming a casing (7) which surrounds an electric control unit (4) belonging to a valve assembly (3),
arranging the valve assembly (3) such that the casing (7) extends through and encloses a connection (8) through a gas-tight barrier (20), which separates a first space (1), which contains a fuel duct (15) and mechanical equipment for controlling a fuel flow in the duct (15), from a second space (2), which is free of inflammable liquids and encloses electric equipment (18), and
securing the casing (7) in the gas-tight barrier (20).
11. A method of manufacturing a fuel pump unit as claimed in claim 10, characterised by the step of
inserting the casing (7) from the first space (1) through the barrier (20), and connecting the casing (7) with the barrier (20) in a gas-tight manner.
inserting the casing (7) from the first space (1) through the barrier (20), and connecting the casing (7) with the barrier (20) in a gas-tight manner.