Assemblies of conjoined parts

In a screw mounting arrangement for a plastics moulded filter or a coalescer element end cap to a base the base is provided with a serrated track which a locating member is engageable with when the filter or coalescer element is screwed onto the base such as to prevent loosening thereof due to vibration.

This invention relates to assemblies of conjoined parts and related 
especially but not exclusively to screw threaded assembly of a filter 
cartridge or filter and coalescer cartridge to a mounting and connecting 
part. 
BACKGROUND OF THE INVENTION 
In large filter/separator installations subjected to vibration such as in 
marine applications and in mobile and static installation also subject to 
vibration it is proposed to mount replaceable fuel or lubricating oil 
filter cartridges on screw-mounting and connecting parts provided within a 
cylindrical enclosure whereby fluid can flow radially inwardly or 
outwardly through a generally cylindrical filter element the interior and 
exterior of which are mutually sealed for fluid flow except through the 
filter element itself. In such an installation it is important to ensure 
that vibration does not result in loosening of the filter cartridge on its 
screw base since such loosening can result in a seal between the interior 
and the exterior of the element being bypassed by flow other than through 
the element itself. The present invention seeks to prevent such loosening 
even in cases where a mounting spigot with a screw thread is formed of 
relatively soft material such as moulded plastics. 
According to the present invention there is provided an assembly of 
conjoined parts comprising a mounting part and a mountable part said parts 
having complimentary means operable to conjoin them by relative rotation 
of the parts wherein one said part is provided with at least one 
resiliently deflectable locating member engageable with a locating track 
of the other part to resist relative rotation. 
In a preferred embodiment of the invention the second mountable part 
carries the locating member and the mounting part carries the locating 
track the locating track extending arcuately around and concentric with a 
screw-threaded portion such that upon screwing the parts together the 
locating member moves increasingly into engagement with the track. 
The locating track may be arranged to extend in an axial direction such 
that substantial engagement between the locating member and the track is 
maintained over a range of relative axial positions of the parts or it may 
be arranged to extend radially to be met by axial movement of the locating 
member.

DETAILED DESCRIPTION 
Referring to FIG. 1, the mounting part comprises a generally circular 
flange denoted by reference 1 with an upwardly extending generally 
cylindrical spigot denoted by reference 2 which is screw-threaded at 3 and 
the flange 1 is provided with a serrated track 4 with approximately 
symetrical saw tooth shaped serrations. The mounting part 1 is moulded of 
plastics material and is provided with an upward narrow section 5 for 
sealing engagement with a rubber gaskt 23 to be referred to below and a 
concentric axial bore 6 to receive a mounting bolt. The aperture 6 is 
surrounded further by a plurality of passages 7 providing for fluid flow 
to the interior of a filter element mounted thereon. 
Referring to FIG. 2, a filter element for mounting on the mounting part 1 
of FIG. 1 is provided with a moulded, generally annular plastics end cap 
11 within an upper annular recess 12 of which the annular and lower end of 
a generally cylindrical filter element 14 is sealed by a sealing compound 
at 13. The interior of the filter element is provided with an inner metal 
supporting sleeve 15 having a large number of holes 16 through which 
unrestricted fluid flow can take place. The outer surface 17 is similarly 
provided with a constraining metal mesh for containing filtering material 
18. This material may be felt, fine mesh or pleated paper or a combination 
of these for filtering and or coalescing. The lower end of the moulded end 
cap is provided with a downwardly extending annular skirt 19 which is 
moulded of similar plastics material to the part 1 and provided with an 
internal helical thread 20 which is complimentary to the thread 3 of the 
mounting part 1 of FIG. 1. Additionally, radially outwardly of the skirt 
19 there are provided diametrically oppositely located downwardly 
extending but circumferentially deflectable locating members 21. The lower 
ends 22 of these locating members are provided with a shape which is 
suitably engageable with the saw-tooth serrations of the track 4 when the 
member is screwed home to such a sufficient extent that the upper edge 5 
of the part 1 is sealingly engageable with the resilient rubber annular 
sealing gasket 23 retained within the moulded end cap as shown. 
The upper end of the generally cylindrical filter element is closed by a 
further moulded end cap (not shown) which can be of any suitable form but 
may if desired incorporate typically a hexagon to receive a tool for 
tightening the filter element into engagement with the mounting part by 
means of a tool only accessible from the end thereof before attachment of 
a closure member for closing of the filter chamber. 
Referring to FIG. 3, in the part sectional view of the assembly shown 
therein it is seen that the mounting part 1 is mounted to a machine base 
plate 24 by means of a central mounting bolt 25, permitting access through 
a number of apertures such as 26 to the lower ends of passages 7 as seen 
in FIG. 1. The part 1 is sealed against effective fluid pressure against 
the plate 24 by an annular gasket 27 and becomes part of the machine 
itself, whereas the filter element is a replaceable component. The part 1 
is normally mounted at the lower end of a generally cylindrical filter 
chamber access to which is gained from an opposite outer end which end, is 
normally closeable by a bolted-on closure plate. With the closure plate 
removed, the filter element can be screwed by rotation onto the mounting 
part 1 until engagement occurs between the upper edge 5 of the mounting 
part and the gasket 23. Before full engagement occurs appreciable 
resistence to rotation will be encountered by virtue of a prior engagement 
of the ends 22 locating members 21 with the serrations of the track 4 and 
further turning through a certain distance against increasing resistance 
will ensure that sealing engagement takes place between 5 and 23 and a 
substantial resisting force will be exerted by the resistance to bending 
of the locating members 21 which is necessary to permit unscrewing. 
Accordingly, when the filter is properly assembled, machine vibration is 
prevented from causing undesired unscrewing of the element even though the 
threaded portions of the filter and the mounting part are formed of a 
relatively soft plastic material. In the above described specific 
embodiment of the invention the locating member moves into closer 
proximity of the locating track as the screw threaded part is being 
screwed into its installation position and this introduces progressively 
increasing resistance to screwing together of the parts. This is because 
the track axially faces an approaching location part. In an altenative it 
may be arranged that the locating part faces the track in a radial 
direction rather than having such axial relationship. 
In one alternative arrangement the locating track could be arranged to face 
radially outward around a cylindrical surface beneath the threaded portion 
of the mounting part to be engageable by a radially inwardly projecting 
locating member. In this case the resistance to relative unscrewing of the 
parts would not appreciably change at least whilst the locating part is 
engaging the track. 
Alternatively, as shown in FIGS. 4 and 5, a locating track could be 
arranged to face radially inward around a cylindrical surface upstanding 
from the mounting part to be engageable by one or more radially outwardly 
pointing locating members of the mountable part. In FIG. 4. the mounting 
part again comprises a generally circular flange denoted by reference 41 
with an upwardly extending generally cylindrical spigot 42 carrying a 
screw thread 43. The moulding is again of plastics and has an upward 
narrow sealing edge 45 and an aperture 46 and flow passages 47 as before. 
However, a locating track 44 is now provided on the inner surface of an 
upwardly extending cylindrical portion 48. 
In FIG. 5 the mountable filter element 54 is substantially identical to 
that of FIG. 2 sealed at 55 into moulded lower mounting cap 50 with a 
downwardly extending annular skirt 51 moulded with an internal helical 
thread 52 which is complimentary to the thread 43 of the mounting part 41 
of FIG. 4. Pointing radially outward of the skirt 51 are a pair of 
diametrically opposite deflectable locating members 53 the length of which 
is such as to enable positive engagement with the saw-tooth serrations 44 
during the last revolution or so of the screwing thereof before full 
sealing engagement of the two parts. 
It will be understood that above specific examples of the invention are 
capable of modiciation whereby the locating track may be provided on the 
mountable part and the locating member may be provided on the mounting 
part. Again, in either example more than two suitably spaced locating 
members may be provided each being engageable with the locating track. 
By virtue of the invention the locating member or members are made 
sufficiently stiff as to prevent loosening of the mountable part on the 
mounting part due to operational vibrations.