It will be appreciated that it is necessary to provide air filters within a motor vehicle in order to ensure that detrimental particle matter does not enter the engine or other vehicle systems in order to foul their operation.

By their nature, with filters there is a conflict between provision of sufficient air flow over an operational filter lifetime against the size of the filter required. Thus, it is typical for the filter unit to have a pleated or concertina configuration in order to enhance the available surface area for air transfer filtration. Nevertheless, air filter units are still bulky items.

There is an ever-increasing requirement to include additional functional systems such as power steering, air-conditioning, etc, within an engine compartment of a motor vehicle along with pressures to reduce vehicle profile and so improve drag coefficients, so that such bulky filter units are inconvenient.

As indicated above, increasingly motor vehicles are including quite sophisticated heating, ventilation and air-conditioning (HVAC) systems.

Such HVAC systems themselves requires a particulate filter but, generally

it will be appreciated, that the critical operational performance of such a filter is not so imperative as that with regard to the air supply for the engine. Thus, it is possible to locate such particulate filters in more confined areas within the motor vehicle. However, location and installation of such HVAC system particulate filters is difficult due to the inherent bulky nature of an operational filter as described above.

It is an objective of the present invention to provide a particulate filter which can substantially relieve the above-mentioned problems.

In accordance with the present invention, there is provided a filter unit for a motor vehicle, the filter unit comprising a filter element collapsible in a filter plane and said filter element associated with latch means arranged to have a first filter position and a second filter position with said filter element thereby resiliently held in respective distinct filter positions in said filter plane, said latch means being displaceable between said first filter position and said second filter position.

The first filter position will generally be with the-filter element substantially or completely collapsed and so in an inoperative state but easier to manipulate for installation whilst in said second filter position the filter element is deployed and so operational.

Typically, the filter element will be pleated or have a concertina profile.

Respective ends of the filter element may be secured in a U frame component, so that latch elements secured to one U frame component act upon reciprocal elements within the other U frame in order to resiliently hold that said filter element in said first filter position and said second filter position.

The latch means will typically be a longitudinal component with respective latch elements located at spaced positions therealong.

The latch means generally includes manipulation means, ie. a handle, whereby said filter unit can be installed whilst in said first filter position and thereat deployed into said second filter position by said manipulation means.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 illustrates a filter unit in a first filter, non-operational position; Figure 2 illustrates a filter unit in a second filter, operational position; and

Figure 3 illustrates basic stages a-d involved with filter unit installation.

Referring to Figures 1 and 2, it will be noted that a filter unit 1 comprises a filter element 2 secured within respective U frame ends 3,4.

The unit 1 also includes a latch component 5 having latch elements 6,7 arranged to engage a latch detent 8 secured in the U frame end 4. The filter element 2 is sealed within the U frame ends 3,4.

In Figure 1, the filter unit 1 is depicted in a first non-operative filter position. Thus, the detent 8 engages latch 6 and the filter element 2 is located in a collapsed configuration. Thus, essentially there is no filter surface available for easy transfer of air flow. It will be appreciated by those skilled in the art that transportation of the filter unit 1 in this condition is also more convenient in that the filter surface of the element 2 is less susceptible to damage.

In the first filter position shown in Figure 1, the U frame ends 3,4 are in a close relationship as depicted.

Figure 2 illustrates the filter unit 1 in a second operative filter position.

The detent 8 now engages the latch element 7 in the latch component 5.

Thus, the filter element 2 is expanded to present a filter surface between

the U frame ends 3,4. This expansion of the filter element 2 generally takes place in a filter plane parallel with the latch component 5.

Normally, the filter element 2 will have concertina profile or be pleated to allow an appropriate collapse or extension of the element 2.

Furthermore, by such a concertina arrangement, it will be appreciated that the filter element 2 retains some configurational strength. However, it will be normal to present the filter unit 2 within U-shaped side rails either side such that further configurable strength is provided by such rails and reinforced by the latch component 5. Thus, the latch component 5 will normally be arranged to be on the leeward side of the filter to provide such reinforcement. The side rails will also include sealing mechanisms to isolate one side of the filter component 2 from the other in order to effect the filtration function.

As indicated above, it is an object of the present invention to provide a filter unit 1 which allows installation within tight confined spaces or inconvenient locations. Thus, it will be appreciated that the compact configuration of the filter unit 1 in the first filter position shown in Figure 1 will allow easy manipulation of the filter unit 1 for installation. Whilst simple release of the detent 8 in latch element 6 allows expansion of the filter element 2 in the filter plane between, and guided by, any side rails, into the operational second filter position depicted in Figure 2 with the

detent element 8 secured in latch element 7. In order to create this expansion, it will be appreciated that the unit 1 may be mounted in an upwards direction in order that gravity can be utilised to expand the filter unit 2 or bespoke expansion means may be included such as a drawstring in order to achieve the appropriate expansion. If gravity is to be used to precipitate filter element to expansion, the lower end 4 may be weighted to enhance such expansion. Alternatively, the spring bias effect of a pleated or concertina filter element 2 may be utilise.

The latch component 5 is secured to one end of the filter element 2 whilst, as indicated above, the other end 4 includes a detent element 8 to engage respective latch elements 6,7 at spaced locations within the latch component 5. There may be a range of latch positions within the component 5 to achieve different expansions of the filter element 2. Thus, the filter unit 1 may accommodate or achieve different air flow rates as required or be flexible in order to allow installation in different systems. In such circumstances, the filter unit 1 is flexible in terms of performance and the range of original equipment to which it can be incorporated.

In Figure 3 the basic installation stages for the filter unit 1 are depicted. Similar nomenclature has been used in order to improve clarity with reference to Figures 1 and 2. In Figure 3a, the filter unit 1 is pushed upwards through side rail guides 11,12. These rails 11,12, as indicated

above, generally have a U-shaped channel form to allow sealing of the unit 1 sides. The next stage in the filter unit 1 installation is for the bottom end frame 4 to be engaged typically through a clip to the bottom of the rails 11, 12. Once the frame bottom end 4 is secured, the detent 8 is released from the latch element 6 such that the filter element 2 can be expanded by the latch component 5. Such expansion continues until a top end 3 of the filter unit 1 is adjacent or engaged by the top end of the rails 11,12. In such an expanded condition, the end 3 will be secured to the rails 11,12 and the detent 8 will engage the latch element 7 of the component 5. Thus, the filter element 2 is deployed in its expanded state. For withdrawal, the detent element 8 is withdrawn from the latch element 7 and so the filter element 2 collapsed. Once sufficiently collapsed the detent element 8 will again engage the latch element 6 of the latch component 5 and the filter unit can be withdrawn from the rails 11,12.

As depicted in Figure 3, generally the filter unit 1 will be used to filter an air flow through a conduit 14. Thus, the rails 11,12 will normally be perpendicular to this conduit 14 in order to present the filter unit 1 appropriately. By their nature, there may be a wide variety of conduit dimensions used in different application systems. Thus, rather than provide a bespoke filter unit for each such system, it will be appreciated that, in accordance with the present invention, a multitude of latch positions 6,7 could be provided in the latch component 5 to achieve a wide range of

operational filter positions for a filter unit 1 in accordance with the conduit dimensions present. However, it will be appreciated that the filter element 2 must be adequately deployed to allow required air flow otherwise the resultant flow attenuation may be unacceptable for associated functional system operations.

As indicated previously, the diminished dimensions of the filter unit 1 in the non-operational first filter position facilitates easier installation of the unit 1 within the conduit 14. It will be appreciated that typically the conduit 14 will be located within a motor vehicle in order to pass through the vehicle's bulk head between the engine compartment and the passenger compartment. Thus, it is most convenient for the filter unit 1 to be located within this conduit thereabout such a bulkhead. Unfortunately, and as will be appreciated, such location for the filter unit 1 creates installation problems due to confined space and indirect installation pathways. A reduced dimension filter unit 1 will be easier to install. Furthermore, it will be understood that the filter element 2 should as far as possible not be contaminated or clogged with oil prior to installation. Thus, by presenting a filter unit which can assume two filter positions, one operational and one not, it will be appreciated that, in the compacted non-operational position, cover panels are secured over the filter element 2 surfaces of the unit 1.

These cover panels would be located with fracturable seams, such as perforations, in the cover panel whereby upon displacement of the filter

element 2 between the first filter position and the second filter position the fracturable seams rupture and then become detached to expose the filter element 2 within the conduit 14. In any event, the compacted element 2 in the first filter position will present less filter area available for contamination with oil etc, both during storage and installation.

It will also be understood that, by collapsing the filter unit 1 to the first non-operational filter position after use, such filter unit 1 may be more readily removed that with regard to previous filter units. Furthermore, the pleating or concertina configuration of the filter element 2 is such that by a bellows action, ie. alternate compression and expansion of the element 2, it will be appreciated that a degree of decoking or removal of debris from the filter element 2 may be achieved so extending the operational life of the filter unit 1.

In order to more readily achieve the displacement of the filter element 2 between the first filter position denoted by latch element 6 and the second filter position denoted by latch element 7, it is generally necessary to provide a manipulation handle 15 resiliently attached to the latch component 5.

It is important in accordance with the present invention, that the filter element 2 is displaceable in a filter plane in order to vary the cross-sectional

area of the filter unit 1 and so the dimensions of that filter unit 1 to facilitate installation, etc. The filter plane will typically be parallel with the major axis of the latch component 5 in order to achieve, in use, convenient deployment of the filter element 2. However, it will be appreciated that it is engagement between the ends 3,4 with any rail or channel which defines the displacement filter plane. Thus, the filter plane may, to an acceptable degree, be curved or inclined in order to achieve the best operational filter deployment for the filter element 2 with regard to the conduit 14 presenting air flows.