The present invention relates to a filter bowl securing means for a fluid filter assembly and/or a lubricator assembly, and relates particularly, but not exclusively, to a double locking feature for retaining filter bowls on an apparatus for filtering and/or lubricating a stream of compressed air.

Compressed air is widely used throughout industry as a safe and reliable source of energy. However, the quality of the compressed air delivered directly from an air compressor is unsuitable for most uses without treatment to improve its purity. Treating compressed air generally involves filtering it, to remove oil and particulates, and drying it to remove moisture. Treatment may also involve controlled lubrication using a lubricator assembly. A typical example of a fluid filter assembly apparatus includes a head, which contains an inlet and an outlet, and a bowl like body, which engages with the head to form a sealed vessel, within which a filter element is contained. The filter element is typically a tube sealed at one end, the open end of the filter element is attached to the head and extends into the bowl of the body. A pair of fluid ducts integrally formed into the head direct air to and from the filter element. A first duct directs the air from the inlet into the centre of the filter element, the air flows through the tubular wall of the filter element, up the sides of the bowl of the filter body and then through a second duct, directing the air to the outlet. In this arrangement the air is flowing from the centre of the filter element to the outside but this flow can be reversed such that air flows from outside of the filter element to the core of the filter element and then to an outlet. A typical example of a lubrication assembly apparatus includes a head, which contains an inlet, an outlet and an atomiser, and a bowl like body, which engages with the head to form a sealed vessel. The bowl contains a reservoir of oil for providing lubrication, via the atomiser, to an air stream passing through the head.

Maintenance of fluid filter assemblies includes changing of the filter element. Maintenance of a lubricator assembly includes replenishing the oil reservoir. To change the filter element the body of the fluid filter assembly must be detached from the head of the fluid filter assembly. There are a number of methods of attaching the body of a fluid filter assembly to the head. For example a threaded connection means between the head and body, a twist lock arrangement wherein a key is provided on the body which engages with a corresponding keyway on the head or vice versa, or a latching mechanism which utilises a sprung pawl on the body to engage with a notch on the head or vice versa. Often fluid filter assemblies are located in confined spaces wherein the removal of the body by unscrewing the body from the head can be difficult. Furthermore, the body is often coated in a layer of oil due to the environment in which it operates making it difficult to unscrew. Additionally, the threaded engagement may be overtightened when fitting the body to the head which may inhibit later removal or damage the threads. The thread can also be under tightened i.e. not correctly engaging the body with the head, potentially causing leaks of compressed air out of the fluid filter assembly. With a threaded attachment there is no indication that the body is correctly engaged with the head and it is possible to disengage the head from the body when there is compressed air passing through the fluid filter assembly. A keyway attachment means only requires the body to be pressed toward the head and a slight rotation of the body relative to the head to disengage the body meaning that it easier to disengage in a confined space than a threaded attachment, but again there is no indication that the body is correctly engaged with the head. A latching mechanism provides a visual and/or audible confirmation that the body is correctly engaged with the head, however similarly to a threaded attachment means, a latching mechanism can be disengaged whilst there is compressed air flowing through the fluid filter assembly. Disengaging the body from the head whilst there is still pressurised fluid in the fluid filter can cause the sudden venting of compressed air to the environment. This could lead to oil and particulate matter spraying out of the compressed air system causing a mess.

Preferred embodiments of the invention seek to overcome the above described disadvantages of the prior art.

According to the present invention there is provided a fluid filter assembly or lubricator assembly comprising:- a head having an inlet and an outlet; a body defining a bowl; wherein the head and body are removably attachable; and the head is configured to close the body;

a first securing means for attaching said head to said body, the first securing means may include at least one key; and at least one keyway configured to receive the at least one key; a second securing means for locking said head to said body, the second securing means may comprise a latching mechanism.

The latching mechanism may include at least one notch; and at least one catch configured for engagement with the at least one notch.

The first securing means may require movement of the body towards the head in a first direction followed by movement away from the head in a second direction to engage. Movement of the body in the first direction when pressurised fluid is present in the fluid filter assembly may require a greater force than movement of the body in the first direction when pressurised air is not present in the fluid filter assembly.

The at least one key may be situated on the body and the at least one keyway may be positioned on the head. The at least one key may be situated on an outward facing surface the body and the at least one keyway may be positioned on an inward facing surface of the head. Alternatively, the at least one key may be situated on the head and the at least one keyway may be positioned on the body. The at least one key may be situated on an inward facing surface the body and the at least one keyway may be positioned on an outward facing surface of the head.

The at least one key may comprise a protrusion in the form of a raised profile.

The at least one catch may be positioned on the body, alternatively, the at least one catch may be positioned on the head. The at least one catch has a first position defined by the second securing means being in a locked state and a second position defined by the second securing means being in an unlocked state. The at least one catch may have a protrusion and when in the second position the first end may be received in the at least one notch.

The at least one catch may include a biasing spring for biasing the catch into the first position.

The second securing means may be configured to only be correctly engaged when the first securing means is correctly engaged.

The head and body may be configured to receive a pressurised fluid therethrough and the inlet is adapted for connection to a pressurised fluid line. The pressurised fluid may be air.

The second securing means may be unlocked when the pressurised fluid is present in the head and the body.

The body may be adapted to receive a filter element, preferably wherein the filter element is a replaceable filter cartridge.

Assembling the fluid filter assembly or lubricator assembly may include the steps of: attaching the first securing means; and locking the second securing means.

Attaching the first securing means may include the steps of:- biasing the body towards the head in the first direction; rotating the body relative to the head such that the at least one key engages with the at least one keyway.

The step of locking the second securing means may be a result of correctly attaching the first securing means. The second securing means may be configured to make an audible click when correctly locked.

Disassembling the fluid filter assembly or lubricator assembly may include the steps of - unlocking the second securing means; and detaching the first securing means.

The second securing means may be unlocked by depressing an end of the catch distal relative to the notch. Detaching the first securing means may include the steps of - biasing the body in the first direction towards the head; rotating the body relative to the head such that the at least one key disengages with the at least one keyway.

The body may be detached from the head by releasing the second securing means and next releasing the first securing means.

Preferred embodiments of the present invention will now be described, by way of example only, and not and in any limitative sense with reference to the accompanying drawings in which:-

Figure 1 is a side elevation of a fluid filter assembly of the present invention;

Figure 2a is a sectional view taken along line B-B of the fluid filter assembly of figure i ;

Figure 2b shows a simplified plan view of the body of Figure 1;

Figure 3 is a close up view of a portion of the fluid filter assembly of figure 1 ; Figure 4 is a further view of the fluid filter assembly of figure 1; and

Figure 5 is a further close up view of a portion of the fluid filter assembly of figure 1 with the key located in the keyway. Referring to figures 1 and 2, a fluid filter assembly is shown and this apparatus is used to filter a stream of gas. In particular, the assembly 10 is used to filter a stream of compressed air, this being typically undertaken prior to a drying step in a compressed air purification process.

The main components of the fluid filter assembly 10 are a head 12, a body 14, a first securing means 16 and a second securing means 18. The head 12 has an inlet 22 for receiving the stream of compressed air. The head 12 also has an outlet 20 through which the compressed air passes on to downstream apparatus (not shown). The head has a lower face 23. The lower face 23 having an opening 25. In use, the stream of compressed air passes to and from a filter assembly 24 via first and second ducts as is known in the art. The filter assembly 24 may be contained within the body 14.

The body 14 has a tubular wall 26 terminating in an aperture 28 through which a drain valve 30, for exhausting liquid water, is located. An O-ring seal 32 is provided in an annular recess 34 in the body 14 so that the head 12 and body 14 together form a vessel capable of retaining the compressed air at high pressure. The O-ring seal 32 is provided to seal against a seal seat 33. The seal seat 33 has a height Y. The body 14 is typically made from cast aluminium or injection moulded polymer. The head 12 is made from cast aluminium. The body 14 has an opening 36 at an end 38 distal to the aperture 28. The opening 36 is formed at an open end of the tubular wall 26 and is substantially circular in cross section about an axis X.

The tubular wall 26 has an outer face 27a and an inner face 27b.

As shown in Figure 2b, the body 14 is provided with a lug arrangement. The lug arrangement comprises a pair of plain lugs 41, a pair of detent lugs 42 and a pair of profiled lugs 43. The lugs 41, 42, 43 are arranged on the outer face 27a, adjacent the O-ring seal 32 and recess 34. The lugs 41, 42, 43 protrude radially from the outer face 27a of the body 14. The pair of plain lugs 41 are simple in form and arranged diametrically opposite one another. The pair of detent lugs 42 each include a downwardly extending axial detent 50 at a first end thereof 46.

The pair of profiled lugs 43 each include a downwardly extending axial profile 52 at a first end thereof 47.

The first end 46 of each detent lug 42 and the first end 47 of each profiled lug 43 face one another, and define a space therebetween 45.

The first securing means 16 includes a keyway 40 and a key. The key is provided by detent lug 42. The lower face 23 of the head 12 defines a tab 23a which co-operating with the space 45 between the detent lug 42 and profiled lug 43 so as to allow relative axial movement between the head 12 and the body 14.

The keyway 40 has an aperture 44. The aperture 44 is adjacent to the lower face 23 of the head 12. The keyway 40 has a cavity 41, the cavity 41 has a lower wall or floor (not shown) that is generally U- Shaped.

The aperture 44 of the keyway 40 is adapted to receive the key 42 therethrough. The second securing means includes a notch 60 and a catch 70. The notch 60 is formed in the lower surface 23 of the head 12.

The catch 70 has a chassis 71, a first end 72, a second end 74, a shoulder 75, a protrusion 76 (see figure 4), ridges 78 and a spring 80.

The protrusion 76 has a length L and is narrower than the width of the catch 70. The protrusion 76 extends from the chassis 70 at the shoulder 75. The catch 70 is slideably attached to the outer surface 27a of the tubular wall 26. The spring 80 is captive between the catch 70 and the outer surface 27a of the tubular wall 26. The spring 80 biases the catch 70 into a first position. The catch 70 can be slid downwards into a second position by compressing the spring 80.

The protrusion 76 extends from the first end of the catch 70. The spring 80 serves to bias the catch 70 towards the end 38 of the body 14. The ridges 78 are provided on the catch 70. The ridges 78 provide increased grip levels when compared with a smooth surface of a catch 70.

In use the head 12 is provided to close the opening 36 of the body 14. The first securing means 16 and the second securing means 18 ensure that the head 12 and the body 14 are held together whilst the fluid filter assembly 10 is in use.

To assemble the body 14 to the head 12, the body 14 is arranged to position the key 42 facing towards and in line with the aperture 44 of the keyway 40. The tab 23 a of the head 12 is aligned with the space 45 between the detent lug 42 and profiled lug 43. The body 14 is next pressed against the head 12 so that the raised profile 52 passes through the aperture 44 of the keyway 40. The shape of an internal cavity (not shown) of the keyway 40 is substantially a relief of the shape of the key 42. The protrusion 76 of the catch 70 simultaneously contacts the lower surface 23 of the head 12. The catch 70 and the key 42 are arranged such that the action of moving the body 14 towards the head 12 as the key 42 enters the aperture 44 of the keyway 40, the protrusion 76 contacts the lower surface 23. To further insert the key 42 through the aperture 44, the catch 70 must move downwards. The contact between the protrusion 76 and the lower surface 23 halts the relative movement between the catch 70 and the head 12. The key 42 continues to pass through the aperture 44 as the body 14 is moved towards the head 12. To accommodate this relative movement the, catch 70 slides down the body 14 to a second position, compressing the spring 80.

The opening 36 of the body 14 is received inside the head 12 until the key 42 has entirely passed through the aperture 44. In this position, the head 12 and the body 14 form a single unit but are not held together. That is if the body 14 is not held in this position, releasing the body 14 would cause the body 14 to become detached from the head 12 due to the force exerted on the head 12 by the compressed spring 80 acting on the latch 70. If the body 14 and head 12 are in an upright position i.e. the axis X is vertical, gravity would also act to cause the body 14 moving away from or drop out of engagement with the head 12.

To secure the body 14 to the head 12, the head and body must next be rotated relative to one another about the axis X.

The rotation of the body 14 relative to the head 12 causes the key 42 to move from a primary position where the raised profile 52 is wholly inside the cavity 41 and in line with the aperture 44, to a secondary position where the raised profile 52 is wholly inside the cavity 41 and to one side of the aperture 44.

The action of rotating the body 14 relative to the head 12 about the axis X also moves the protrusion 76 of the catch 70 of the body 14, along the lower face 23 of the head 12 towards the notch 60. The catch 70 and the key 42 are positioned axially about the axis X on the body 14 such that as the body 14 is rotated relative to the head 12, and consequently the key 42 moves out of alignment with the aperture 44, the protrusion 76 of the catch 70 begins moves towards being in alignment with the notch 60. The relative rotation is continued until the protrusion 76 is in complete alignment with the notch 60. Immediately as the protrusion 76 comes into alignment with the notch 60, the compression force held stored by the spring 8 is released as the spring 80 is now free to bias the catch 70 back into a third position. This can be achieved as the protrusion 76 is received into the notch 60 thereby facilitating the relative movement of the catch 70 sliding on the outer surface of the body 14. The spring 80 is prevented from moving the catch 70 to the first position where the spring is completely relaxed, by the shoulder 75 of the catch 70 abutting the lower surface 23 of the head 12 adjacent to the notch 60. In the third position the spring 80 is still compressed but less so than when the catch is in the second position. The force of the spring moving the catch from the second position to the third position causes the shoulder 75 to collide with the lower surface 23. This collision produces an audible click.

With the catch 70 in the third position, the raised profile 52 of the key 42 is not aligned with the aperture 44 of the key way 40. The detent 50 is now in alignment with the U-shaped floor of the cavity 41 but 50 is not in contact with the U-shaped floor.

The body 14 can now be released, i.e. the body 14 is no longer biased towards the head 12.

Releasing the bias, allows the body 14 to move away from the head 12. This movement is arrested by the detent 50 and/or a portion of the raised profile 52 coming into contact with the U-shaped floor of the cavity 41 of the keyway 40. This relative movement of the head 12 and the body 14 is sufficient to allow the spring 80 to bias the catch 70 into the first position.

The body 14 is now secured to the head 12.

The height Y of the seal seat 33 is such that the O-ring seal 32 is engaged with the seal seat 33 throughout the movement of the catch 70 from the first position, to the second and third positions. That is, the O-ring seal 32 is engaged with the seal seat 33 when the key 42 is within the cavity 41 of the keyway 40. The engagement of the O-ring seal 32 with the seal seat 33 provides a seal between the head 12 and the body 14. In operation, pressurised fluid enters the inlet 20, passes through the filter assembly 24 into the body 14. The pressurised fluid then exits the filter assembly 24 via the outlet 22. The action of the pressurised fluid passing through the chamber formed by the head 12 and the body 14 acts to try and separate the head 12 from the body 14. This separation is prevented by the engagement of the key 42 with the keyway 40.

To disassemble the body 14 from the head 12, the body 14 must first be urged towards the head 12. This action moves the catch 70 from the first position to the third position and moves the detent 50 out of engagement with the U-shaped floor of the cavity 41. To release the body 14, the body 14 must next be rotated relative to the head 12. The relative rotation of the head 12 and the body 14 about the axis X is prevented by the engagement of the protrusion 76 and the notch 60. As such, to rotate the body 14 relative to the head 12, the body 14 must first by urged towards the head 12 thereby moving the catch 70 from the first position to the third position and the detent 50 out of engagement with the U-shaped floor of the cavity 41, and the catch 70 must be manually actuated from the third position to the second position either concurrently or immediately following the urging together of the head 12 and the body 14. When the catch 70 is in the second position the body 14 is rotated relative to the head 12 until the key 42 is in line with the aperture 44. With the key 42 aligned with the aperture 44, the body 14 can be separated from the head 12 by moving the head 12 and the body 14 apart along the X axis. When the assembly 10 is in operation, the pressurised fluid acting on the chamber formed by the head 12 and body 14 prevents the body 14 and head 12 from being urged together. As this step cannot be completed, the body 14 cannot be separated from the head 12 when there is pressurised fluid in the assembly 10 because of the engagement of detent 52 against keyway 40 prevents rotation of the body 14 relative to the head 12. This prevents unsafe disconnection of the head 12 from the body 14.

The audible click made by the catch 70 when moving from the second position to its third position signals that the head 12 and the body 14 are correctly engaged and ready to receive pressurised fluid therethrough. This feature prevents incorrect or incomplete engagement of the body 14 and the head 12 which may lead to undesirable operation of the assembly 10.

The description has focussed on the example of a fluid filter assembly, however the skilled person will appreciate that the invention is equally applicable to a lubricator assembly.