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Title:
HYDRAULIC FITTING
Document Type and Number:
WIPO Patent Application WO/2015/136450
Kind Code:
A1
Abstract:
Hydraulic fitting including: - a housing connectable to one of a male/female self-sealing hydraulic connector; - said housing having a passage therethrough at least part of which is internally screw-threaded; - a plunger dimensioned to fit within said passage; - an external screw thread provided on at least part of said plunger, said external screw thread being engageable with said internal screw thread; - said plunger being rotatable relative to said passage between a first position in which the end of the plunger in use does not engage a valve of a self-sealing hydraulic connector connected to said the housing, and a second position in which the plunger in use engages a valve of said self-sealing hydraulic connector; such that the plunger opens said valve; - fluid relief means arranged to permit the passage of hydraulic fluid through an outlet provided on the housing.

Inventors:
DILLON, John William (129 Dillon Road, PahiaR.D., Riverton 9881, NZ)
Application Number:
IB2015/051750
Publication Date:
September 17, 2015
Filing Date:
March 11, 2015
Export Citation:
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Assignee:
DILLON HOLDINGS LIMITED (Cargill Chambers128 Spey Stree, Invercargill 9810, NZ)
International Classes:
F16K31/50; F16L37/32; F16L37/50
Domestic Patent References:
WO2004005788A12004-01-15
Foreign References:
US5623959A1997-04-29
US2739612A1956-03-27
US4921013A1990-05-01
Attorney, Agent or Firm:
BUCHANAN, Elspeth Victoria (15B Byron Street, Sydenha, Christchurch 8023, NZ)
Download PDF:
Claims:
Claims

1 . A hydraulic fitting which includes:

- a housing providing a first end and a second end, said first end being adapted to connect with one of:

- a male self-sealing hydraulic connector;

- a female self-sealing hydraulic connector;

- said housing having a passage therethrough at least part of which is internally screw-threaded;

- a plunger which is dimensioned to fit within said passage and to extend from said second end of said housing to said first end of said housing;

- an external screw thread provided on at least part of said plunger, said external screw thread being dimensioned and arranged to engage said internal screw thread in said passage;

- said plunger being rotatable relative to said passage so as to be moveable between a first position in which the end of the plunger adjacent said first end of the housing in use does not engage a valve of a self-sealing hydraulic connector connected to said first end of the housing, and a second position in which said end of the plunger in use engages a valve of a self-sealing hydraulic connector connected to said first end of said housing, such that the plunger opens said valve;

- fluid relief means arranged to permit the passage of hydraulic fluid from said first end of the fitting to an outlet provided on the housing.

2. The fitting as claimed in claim 1 wherein said plunger is rotatable by means selected from the group:

a handle; means for engagement with a wrench or spanner.

3. The fitting as claimed in claim 1 or claim 2 wherein said fluid relief means is selected from one or more of the group consisting of:

passages formed in the housing;

passages formed in the plunger;

passages formed in both the housing and the plunger;

increased-diameter portion formed in the housing;

reduced-diameter portion formed in the plunger.

4. The fitting as claimed in any one of the preceding claims wherein said plunger is provided with a seal adjacent said second end of the housing, to seal between the exterior of said plunger and the interior of said housing.

5. The fitting as claimed in any one of the preceding claims wherein said outlet is adapted to connect to a hydraulic hose.

6. The fitting as claimed in any one of the preceding claims wherein the plunger provides a reduced-diameter potion adjacent said end of the plunger which is adjacent said first end of the housing in use.

7. The fitting as claimed in claim 6, wherein said end of said plunger which is adjacent said first end of the housing in use includes a tip dimensioned to engage a valve of a self-sealing hydraulic connector connected to said first end of the housing, and a grooved portion between said tip and said reduced- diameter portion; said grooved portion being formed with a plurality of spaced grooves extending along the length of the plunger.

Description:
HYDRAULIC FITTING

Technical Field

The present invention relates to a hydraulic fitting for use with self sealing hydraulic couplings.

The fitting of the present invention could be used with pneumatic self-sealing couplings, but the problem overcome by the present invention is not common in relation to pneumatic fittings.

Background of the Invention

Self sealing hydraulic couplings are very widely used, for connecting a hydraulic supply unit to equipment requiring hydraulic power. For example, the hydraulic supply unit may be a farm tractor, which needs to be coupled to a hydraulically driven post- driver to be mounted on the tractor.

For this type of application, the hydraulic couplings frequently need to be connected and disconnected, and it is important that this can be done rapidly and without loss of hydraulic fluid. The problem of making a rapid and reliable hydraulic connection was solved many years ago by the invention of the "self sealing" hydraulic connection, in which both the male and female connectors are fitted with spring operated valves which are arranged to shut off automatically when the connectors are disconnected. When the connectors are connected, the arrangement in both parts of the coupling is such that the spring-loaded valves in the male and female connectors contact each other and push each other off the corresponding valve seats, allowing hydraulic fluid to flow through the joint.

Self sealing hydraulic couplings of this type are available in a number of different designs, but the basic principle is as described above. All references in this specification to 'hydraulic couplings' refer to self-sealing hydraulic couplings of the type described above.

The above described self sealing hydraulic coupling has the drawback that if for any reason the pressure on the valve on either side of the connection is too great, the valve cannot be moved off its seat by the valve in the opposing part of the connection, and the two connectors simply cannot be connected. For example, this problem can arise if the connectors are disconnected when the ambient temperature is cool, but by the time the connectors are reconnected, the ambient temperature has risen, causing expansion of the hydraulic fluid and thus increasing the pressure on the valve.

It is sometimes possible to release a stuck valve by hitting it, but obviously this is not good for the connector, and also results in the user being splashed with hydraulic fluid as the valve comes away from the seat. In extreme cases, it may be necessary to remove the whole hydraulic fitting from the end of the hydraulic hose, to release the pressure on the valve; this inevitably causes an unwanted release of hydraulic fluid.

Disclosure of Invention

An object of the present invention is the provision of a hydraulic fitting which enables the rapid and easy release of excessive pressure on a hydraulic valve in either a male or a female hydraulic connector, without spillage of hydraulic fluid.

A further object of the invention is the provision of a hydraulic fitting for the above purpose, which does not need to be permanently 'plumbed in' to a hydraulic system, but is readily portable.

The present invention provides a hydraulic fitting which includes:

- a housing providing a first end and a second end, said first end being adapted to connect with one of:

a male self-sealing hydraulic connector;

a female self-sealing hydraulic connector;

- said housing having a passage therethrough at least part of which is internally screw-threaded;

- a plunger which is dimensioned to fit within said passage and to extend from said second end of said housing to said first end of said housing;

- an external screw thread provided on at least part of said plunger, said external screw thread being dimensioned and arranged to engage said internal screw thread in said passage;

- said plunger being rotatable relative to said passage so as to be moveable between a first position in which the end of the plunger adjacent said first end of the housing in use does not engage a valve of a self-sealing hydraulic connector connected to said first end of the housing, and a second position in which said end of the plunger in use engages a valve of a self-sealing hydraulic connector connected to said first end of said housing, such that the plunger opens said valve;

- fluid relief means arranged to permit the passage of hydraulic fluid from said first end of the fitting to an outlet provided on the housing.

Preferably, said fluid relief means is selected from the group consisting of:

passages formed in the housing;

passages formed in the plunger;

passages formed in both the housing and the plunger;

increased-diameter portion formed in the housing;

reduced-diameter portion formed in the plunger.

The plunger may be rotatable by any suitable means e.g. a handle or a shaped surface for engagement with a wrench or spanner.

Preferably, said plunger is provided with a seal adjacent said second end of the housing, to seal between the exterior of said plunger and the interior of said housing.

Preferably also, the plunger provides a reduced-diameter portion adjacent said end of the plunger which is adjacent said first end of the housing in use.

Most preferably, said end of said plunger which is adjacent said first end of the housing in use includes a tip dimensioned to engage a valve of a self-sealing hydraulic connector connected to said first end of the housing, and a grooved portion between said tip and said reduced-diameter portion, said grooved portion being formed with a plurality of spaced grooves extending along the length of the plunger.

Brief Description of Drawings

By way of example only, a preferred embodiment of the present invention is described in detail, with reference to the accompanying drawings, in which :-

Figure 1 is a side view of an assembled male fitting in accordance with a first embodiment of the present invention;

Figure 2 is an exploded view of the fitting shown in Figure 1 ;

Figure 3 is a partly sectioned view of the fitting of Figures 1 and 2; Figure 4 is a side view of an assembled female fitting in accordance with a first embodiment of the present invention;

Figure 5 is an exploded view of the fitting of Figure 4;

Figure 6 is a partly sectioned view of the fitting of Figures 4 and 5;

Figure 7 is a sectioned view of a standard female hydraulic fitting;

Figure 8 is a sectioned view of a standard male hydraulic fitting;

Figure 9 is a partly sectioned view of a male fitting in accordance with a first embodiment of the present invention, engaged with a standard female hydraulic fitting;

Figure 10 is a partly sectioned view of a female fitting in accordance with a first embodiment of the present invention, engaged with a standard male hydraulic fitting;

Figure 1 1 is a side view of a fitting in accordance with a second embodiment of the present invention;

Figure 12 is a partly sectioned view of the fitting of Figure 1 1 , with the plunger removed;

Figure 13 is a side view of the plunger;

Figure 14 is a view of the end of the plunger taken in the direction of arrow X;

Figure 15 is a partly sectioned view of a variant of Figure 1 1 , with the plunger removed; and

Figure 16 is a side view of the plunger. Best Mode for Carrying out the Invention

As described above, a hydraulic coupling is made in two parts, with corresponding male and female connectors. The fitting of the present invention therefore is made in two variants, one of which is designed to interact with a male hydraulic connector, and the other of which is designed to interact with a female hydraulic connector.

Figures 7 and 8 show, respectively, female and male connectors which are typical examples of a known type of hydraulic fitting. Since both of these designs are well- known equipment, the description below covers only the major features.

Referring to Figure 7, a female connector 10 includes a housing 1 1 formed with an internal passage 12 through which hydraulic fluid can flow. One end 1 1 a of the housing is connected to a hydraulic hose (not shown) by any suitable means, (e.g. swaging); the other end 1 1 b of the housing is constructed to engage with a male connector of the type shown in Figure 8. The internal passage 12 is formed to provide a valve seat 13 against which a spring biased valve 14 seats. The valve 14 is suspended in the passage 12 by a spider 15 with a coil spring 16 arranged between the spider 15 and the head 14a of the valve, such that the coil spring 16 biases the head 14a of the valve into firm engagement with the valve seat 13, thus closing off the flow of fluid through the valve. The head 14a of the valve is fitted with a seal 17 in known manner.

The head 14a of the valve 14 is shaped such that when the valve is in sealing engagement with the valve seat 13, the end 14b of the head 14a of the valve projects beyond the valve seat 13, as depicted in Figure 7.

In use, the valve 14 can be opened to allow flow of hydraulic fluid through the passage 12 by pressure in the direction of arrow A, which presses the valve 14 back against the bias of the coil spring 16, moving the head 14a of the valve 14 out of engagement with the seat 13, and allowing fluid to flow through the passage. However, unless pressure is applied in the direction of arrow A, the valve is automatically moved to the sealed position not only by the spring 16, but also by the pressure of hydraulic fluid in the direction of arrow P.

The wall of the housing 1 1 adjacent the end 1 1 b of the housing is formed with a series of equidistantly spaced apertures 20 each of which carries a ball bearing 21 . The size of each aperture 20 is such that the ball bearing can project into the passage 12 or can move outwards to partially clear the passage 12.

A spring-loaded retaining collar 22 is a tight sliding fit over the exterior of the housing adjacent the end 1 1 b of the housing. In the position shown in Figure 7, the collar 22 overlies the apertures 20 and the ballbearings 21 , pushing the ball bearings 21 partially into the passage 12. The collar 22 can be manually slid over the housing against the force of the biasing spring 23 (i.e. in the direction of arrow A) to expose the apertures 20; this allows the ballbearings 21 to be moved partly out of the passage 12.

The corresponding male connector 30 is shown in Figure 8. The connector 30 includes a housing 31 which is formed with a passage 32 through which hydraulic fluid can pass. A spider 33 mounts a spring-loaded valve 34 having a valve head 35 in the passage 32. The valve head 35 is arranged to engage a valve seat 36 formed in the interior of the passage 32. The valve head 35 is shaped such that when the valve is in sealing engagement with the valve seat 36, the end 37 of the head 35 of the valve projects beyond the valve seat 36, as depicted in Figure 8.

The exterior of the housing 31 surrounding the valve 32 is sized to be a sliding fit within the end 12a of the passage 12 of the female connector 10. To fit the two couplings together, the spring-loaded retaining collar 22 on the female connector 10 is slid against the biasing spring (i.e. in the direction of arrow A) until the collar is clear of the apertures 20; this allows the ballbearings 21 to move outwards away from the passage 12. The male connector 30 is then slid into the end 12a of the passage 12 of the female connector 10, until the ballbearings 21 ride over the ridge 37 formed around the exterior of the housing 31 , and engage the groove 38. The collar 22 is then allowed to slide back towards the end 12a of the connector 10, to the position shown in Figure 7 in which the collar 22 overlies the holes 20 and urges the ballbearings 21 into engagement with the groove 38. In this position, the two connectors are locked together, since the ballbearings 21 cannot move out of engagement with the groove 38.

When the two connectors 10, 30 are locked together, the ends 37, 14b of the respective valves engage each other with sufficient force that both of the valves are pushed away from the valve seats, against the pressure of the biasing springs 16, 16a. This means that hydraulic fluid can flow through the joined connectors.

The passage 12 of the connector 10 is fitted with an internal seal 40 which engages the exterior of the male coupling 30 when the two connectors are engaged, and prevents leakage around the outside of the male coupling. A hydraulic hose (not shown) is secured to the end 31 a of the housing in known manner.

The male and female connectors 30, 10, are disconnected by sliding the spring-loaded collar 22 in the direction of arrow A, so that it ceases to overlie the holes 20, and allows the ballbearings 21 to disengage from the groove 38 on the male coupling 30. When the couplings are disengaged, the ends 37, 14b of the two valves 14, 32, cease to press against each other, and each valve is automatically moved to the closed position by the corresponding spring 16, 16a. This movement is assisted by the pressure of any hydraulic fluid in the line. If either valve 14/34 of the female or the male connector is jammed against the corresponding valve seat by excessive pressure in the direction of arrow P, so that the corresponding connector cannot be reconnected because the valve will not move, then one of the fittings of the present invention is used to release the valve and to run off any excess hydraulic fluid.

Referring to Figures 1 - 3 and 9, a hydraulic fitting 50 in accordance with the present invention, for use with a female hydraulic connector 10, includes a first part-housing 51 , a second part-housing 52 and a plunger 53. The first part-housing 51 is similar to the housing of the male connector described with reference to Figure 8, except that the valve 34, spider 33 and associated components have been removed. The first part-housing 51 has a through-passage 54.

The second part-housing 52 has a through-passage 55 which is arranged to communicate with the passage 54 to form a single passage when the first and second part-housings 51 , 52 are assembled together as shown in Figure 3 to form a single housing. The first and second part-housings 51 , 52 are assembled together by engaging an external screw thread 60 on the exterior of the second part-housing 52 with an internal screw thread 61 on the interior of the adjacent part of the first part- housing 51 ; a washer 62 is inserted between the first and second housings to ensure a fluid tight fit when the part-housings are assembled together to form a single housing.

The second part-housing 52 includes an increased diameter portion 56 which provides a housing outlet 59, incorporating an internally threaded seating for a hose coupling 57, the base of which has a corresponding screw thread to enable the hose coupling to be screwed into the portion 56. The hose coupling 57 is formed with an internal fluid passage; a hose can be connected to the hose coupling 57 simply as a press fit over the exterior of the hose coupling.

A fluid gallery 58 extends from the end of the second part-housing 52 which engages the first part-housing 51 , to the housing outlet 59 which receives one end of a hose coupling 57.

The plunger 53 is generally T-shaped, with a handle 53a rigidly secured to one end of a shaft 64, with a longitudinal axis of the handle 53a perpendicular to the longitudinal axis of the shaft 64. The shaft 64 provides a larger diameter portion 65 adjacent to the handle 53, and externally screw threaded portion 66 adjacent the portion 65, and one or two reduced diameter portions 67, 68 at the end of the plunger opposite to the handle. The external diameter of the portion 68 is such that the portion 68 can pass through the end 54a of the passage 54, at the end of the fitting remote from the handle when the components are assembled together (see figure 1 ). Depending upon the strength of the material used, the portion 67 may be formed with the same diameter as the portion 68.

The larger diameter portion 65 of the handle 53 is dimensioned to be a sliding fit within the interior of the first part 55a of the passage 55. The portion 65 is fitted with an CD- ring seal 70 to seal against the interior wall of the passage 55a, and ensure that no hydraulic fluid leaks past the plunger in use.

The external screw thread on the portion 66 is dimensioned to engage with a screw thread 71 formed on the interior wall of the second part 55b of the passage 55. The fluid gallery 58 forms part of the fluid-relief means and ensures that fluid can travel along the passage 54 to the inlet 59, and thus leave the fitting through the hose coupling 57.

The above described fitting is used as follows: to release the excessive pressure in the hydraulic fluid holding the valve shut in a female hydraulic connector (as shown in Figures 7 and 9), the part-housings 51 and 52 are screwed together as described above, to form a single housing, with the passages 54, 55 combined to form a single passage through said housing. The part-housing 51 (which has the external shape of a male connector) is fitted into the female connector by sliding back the spring-loaded retaining collar 22, and pushing the part-housing 51 into the connector 10 until the ballbearings 21 engage in the groove 73 formed around the exterior of the part- housing 51 . This groove is equivalent to the groove 38 formed on the exterior of a standard male connector.

Once the fitting 50 has been connected into the female connector 10 as described above, the plunger 53 is inserted into the second end of the housing, down the passage formed by the aligned passages 54, 55, until the externally screw threaded portion 66 engages the screw thread 71 on the interior wall of the second part 55b of the passage 55. Once the screw threads are engaged, the handle 53a is used to rotate the plunger 53 and move the shaft 64 of the plunger down the aligned passages 54, 55 until the end of the portion 68 of the plunger reaches the first end 54a of the fitting. At this position, the end 68 of the plunger comes into contact with the end 14b of the valve 14 of the female connector, and a further rotation of the handle 53 a drives the valve 14 in the direction of arrow B (Figure 9), thus opening the valve 14 and allowing the pressurised hydraulic fluid in the passage 12 of the female connector to flow past the valve 14 into the fluid-relief means formed by the reduced diameter parts 68, 67 of the plunger, and the gallery 58, to reach the housing outlet 59 and pass into the hose coupling 57. The hose coupling may be arranged to vent direct into a container, or a hose may be connected to the hose coupling, to take the hydraulic fluid through to a suitable container.

Once the excess pressure of hydraulic fluid in the female connector has been relieved, the plunger handle 53a is rotated in the opposite direction, to withdraw the end 68 of the plunger; this allows the valve 14 to be closed by the spring 16 in the usual way. The spring-loaded retaining collar 22 is then slid back to release the pressure of the ballbearings 21 on the groove 73, and the fitting 50 is withdrawn from the female connector. Now that the excess fluid pressure has been removed from the female connector, only the relatively light pressure of the spring 16 holds the valve 14 closed, and a normal connection with a male connector can be made in the usual way.

Referring now to Figures 4, 5, 6 and 10, a hydraulic fitting 80 in accordance with the present invention, for use with a male hydraulic connector 30 (Figure 8) includes a first part-housing 81 , a second part-housing 82 and a plunger 83.

The first part-housing 81 resembles the female connector described above with reference to Figure 7, except that the valve 14, spider 15 and associated components have been removed, and a screw threaded outlet 84 has been formed in the side of the housing 81 , to accommodate an externally threaded hose coupling 85 which is screwed into a screw thread 86 formed around the outlet 84. The valve seat 13 is formed as a narrowing of the passage through the housing, as described with reference to Figure 7.

A spring-loaded collar 22 and ballbearings 21 are arranged in exactly the same manner as described with reference to Figure 7 and the internal passage 87 of the first housing 81 is fitted with an internal seal 40 as described with reference to Figure 7. The end of the first part-housing 81 remote from the collar 22 is internally screw threaded with a screw thread 88, which is dimensioned to engage with a complimentary screw thread 89 formed on the exterior of the adjacent end of the second part-housing 82. When the first and second part-housings are connected together to form a single housing, a washer 90 is used to give a fluid tight seal to the joint.

A portion of the internal wall of the second part-housing 82 is formed with a screw thread 91 , which is dimensioned to engage with a screw thread 66 on the plunger 53, as described below. The second part-housing 82 is formed with a through-passage 92 which aligns with the passage 87 in the part-housing 81 when the part-housings are connected together, to form a single passage through the single housing formed by the combined part-housings.

The plunger 53 is identical to the plunger 53 described with reference to Figures 1 - 3, and the same reference numerals are used.

The above described fitting is used as follows: to release excessive pressure in the hydraulic fluid holding the valve shut in a male hydraulic connector (as shown in Figures 8 and 10) the first and second part-housings 81 , 82 are screwed together by engaging the screw threads 88, 89, with the washer 90 sandwiched between the housings, to form a single housing. The fitting is then engaged with the male connector 30 by sliding back the spring-loaded collar 22 mounted on the first part- housing 81 and sliding the male connector into the passage 87 of the part-housing 81 until the ballbearings 21 engage the groove 38 formed around the outside of the male connector 30. The collar 22 is then released to lock the fitting to the male connector.

The plunger 53 is then inserted into the second end of the combined housings 81/82 and engaged with the passage 87/92 which extends down the length of the combined part-housings 81 /82. The external screw thread 66 on the plunger 53 is engaged with the internal screw thread 91 in the passage 92 and the handle 53a of the plunger is rotated to wind the plunger down through the interior of the joined part-housings 81 /82 towards the first end of the housing, until the end 68 of the plunger extends through the valve seat 13 in the part-housing 81 and contacts the end 37 of the valve 34 of the male connector 30. Further rotation of the plunger pushes the end 37 of the valve in the direction of arrow B (Figure 10), forcing the valve 34 away from the corresponding valve seat 36, and thus opening the valve and allowing hydraulic fluid to flow past the valve, through the fluid-relief means formed by the passage 87 and the reduced- diameter portions 68, 67 of the plunger 53, and out through the outlet 84 and into the hose coupling 85. The fluid can be collected directly from the hose coupling 85 or via a hose connected to the hose coupling.

Once the excess pressure on the valve 34 has been released, the plunger 53 can be rotated in the opposite direction to allow the valve 34 to close normally, under the pressure of the spring 16a. The fitting is then removed from the male coupling 30 by sliding the spring-loaded collar 22 to release the engagement between the ballbearings 21 and the groove 38. The male connector can then be engaged with a female connector in the usual way.

In the above described embodiments, the fittings are described as being made from modified parts of standard hydraulic connectors. This reduces the cost of manufacture, because ready-made components can be adapted. However, it is perfectly possible to manufacture the fittings without using existing components, and in this case it is unnecessary to use two part-housings for each of the fittings:- if the fittings are custom-made, then they are made as single housings.

A second embodiment of the present invention is shown in Figures 1 1 -14, in which a fitting 100 in accordance with the present invention includes a housing 101 a first end 102 of which is fitted with a standard hydraulic fitting, and the other end 103 of which is apertured to receive a plunger 104. A passage 101 a is formed along the interior of the housing 101 , between the ends 102/103. Between the ends 102, 103 of the housing 101 , a connecting pipe 105 is connected into an outlet in the wall of the housing 101. The other end of the connecting pipe 105 is fitted with a standard hydraulic fitting 106.

The hydraulic fittings 102 and 106 are shown as standard female and male fittings respectively, but these fittings may be either male or female fittings, depending upon the particular application intended. Figures 15 and 16 show the version where fitting 102 is a male fitting 202.

Referring to Figures 13 and 14, the plunger 104 consists of a handle 107 secured to one end of a shaft 108, the other end of which is fitted with a grooved head portion 109. The handle 107 is used for rotating the plunger, and may, if preferred, be replaced by a shaped outer surface for engagement with a spanner or wrench.

The outer end of the head portion 109 is "bullet shaped", i.e. provides a convex outer surface 1 10 with a central tip 1 1 1 . The remainder of the head is formed with deep longitudinal grooves 1 12 (as shown in Figure 14) which extend parallel to the length of the head and to the length of the shaft 108.

Adjacent the handle 107, the shaft 108 is formed with an increased diameter portion 1 13 which is formed with a circumferential groove which receives a sealing O-ring 1 14. The adjacent portion of the shaft 108 is somewhat smaller in diameter than the portion 1 13, and is formed with an external screw thread 1 15.

The internal diameter of the housing 101 is such that the head portion 109 and shaft 108 can slide freely down the interior of the housing. The end 103 of the housing 101 is formed with an internal screw thread 1 16 which is dimensioned and arranged to engage the screw threaded 1 15 on the exterior of the plunger, and an increased diameter portion 1 17 which accommodates the O-ring 1 14 as a firm sliding seal. The end 102 of the housing 101 is formed with a reduced diameter portion 1 18 which is shaped and dimensioned to receive the head portion 109 as a sliding fit therein, but keep the head 109 centred inside the housing 101 .

The above described fitting is used as follows: if an item of hydraulic equipment has been disconnected from a hydraulic supply unit, with the equipment in such a condition that the pressure in the hydraulic hoses is too high to permit easy re- connection (for example the jib of a crane has been left in the raised position) then the hydraulic fitting 106 is connected to the inlet of a suitable hydraulic supply unit in known manner, and the hydraulic hose from the equipment is engaged with the fitting 102 on the end of the housing 101 . The hydraulic hose is fitted with a male hydraulic connector, in known manner.

The plunger 104 is pushed down the inside of the housing 101 until the screw threads 1 15/1 16 engage and the head 109 enters the reduced diameter portion 1 18 of the housing. The plunger 104 is then rotated to force the head 109 forward until the tip 1 1 1 engages the valve head (not shown) of the hydraulic connector on the end of the equipment hose, and further rotation of the plunger causes the tip 1 1 1 of the head 109 to push the valve head back, releasing the hydraulic fluid under pressure. The hydraulic fluid travels past the head 109, through the fluid relief means formed by the combination of the grooves 1 12, and the reduced-diameter shaft 108, to travel up the pipe 105, where it can be discharged into the hydraulic supply unit.

A variant of the second embodiment of the present invention is shown in Figures 15- 16, in which a fitting 200 in accordance with the present invention includes a housing 201 the first end 202 of which is fitted with a standard male hydraulic fitting, and the other end 203 of which is apertured to receive a plunger 204. A passage 201 a is formed along the interior of the housing 201 , between the ends 202/203. Between the ends 202, 203 of the housing 201 , a connecting pipe 205 is connected into an outlet in the wall of the housing 201 . The other end of the connecting pipe 205 is fitted with a standard hydraulic fitting 206.

The hydraulic fitting 206 is shown as standard male fittings, but this fitting may be a female fitting 206a (as shown in broken lines), depending upon the particular application intended.

Referring to Figures 15 and 16, the plunger 204 consists of a handle 207 secured to one end of a shaft 208, the other end of which is fitted with a grooved head portion 209. The handle 207 is used for rotating the plunger, and may, if preferred, be replaced by a shaped outer surface for engagement with a spanner or wrench.

The outer end of the head portion 209 is formed with a protruding central tip 21 1 . The remainder of the head is of increased diameter and is formed with deep longitudinal grooves 212 (as shown in Figure 16) which extend parallel to the length of the head and to the length of the shaft 208.

Adjacent the handle 207, the shaft 208 is formed with an increased diameter portion 213 which is formed with a circumferential groove which receives a sealing O-ring 214. The adjacent portion of the shaft 208 is somewhat smaller in diameter than the portion 213, and is formed with an external screw thread 215. The internal diameter of the housing 201 is such that the head portion 209 and shaft

208 can slide freely down the interior of the housing. The end 203 of the housing 201 is formed with an internal screw thread 216 which is dimensioned and arranged to engage the screw threaded 215 on the exterior of the plunger, and an increased diameter portion 217 which accommodates the O-ring 214 as a firm sliding seal. The end 202 of the housing 201 is formed with a portion 218 which is shaped and dimensioned to receive the head portion 209 as a sliding fit therein, but keep the head

209 centred inside the housing 201 .

The above described fitting is used as follows: if an item of hydraulic equipment has been disconnected from a hydraulic supply unit, with the equipment in such a condition that the pressure in the hydraulic hoses is too high to permit easy re- connection (for example the jib of a crane has been left in the raised position) then the hydraulic fitting 206 is connected to the inlet of a suitable hydraulic supply unit in known manner, and the hydraulic hose from the equipment is engaged with the fitting 202 on the end of the housing 201 . The hydraulic hose is fitted with a female hydraulic connector, in known manner.

The plunger 204 is pushed down the inside of the housing 201 until the screw threads 215/216 engage and the head 209 enters the portion 218 of the housing.

The plunger 204 is then rotated to force the head 209 forward until the tip 21 1 protrudes through the aperture 220 at the end 202 of the housing and engages the valve head (not shown) of the hydraulic connector on the end of the equipment hose, and further rotation of the plunger causes the tip 21 1 of the head 209 to push the valve head back, releasing the hydraulic fluid under pressure. The hydraulic fluid travels past the head 209 through the fluid relief means formed by the combination of the grooves 212 and the reduced-diameter portion 208, to travel up the pipe 205, where it can be discharged into the hydraulic supply unit.

As described above, the fluid relief means is provided by passages in the housing and a reduced-diameter portion on the plunger. However, the fluid relief means may in fact be provided by any one of the following, alone or in combination with the other features:

- passages (grooves) formed in the housing;

- passages (grooves) formed in the plunger; one or more increased-diameter portions formed in the interior wall of the housing;

one or more reduced diameter portions formed in the plunger.

The only essential requirement for the fluid relief means is that it provides a passage for hydraulic fluid from the first end of the fitting to the outlet.

It will be appreciated that the above described fitting is readily portable, and can be made in any range of sizes, to suit the hydraulic connectors with which they are to be used. The fittings may be made of any suitable material.