Device for assembling stacked annular filtering elements, under constant pressure

The invention relates to a device for assembling stacked annular filtering elements under constant pressure. The device comprises a support which provides an abutment for one end of the stack of filtering elements, a presser member which provides an abutment for the other end of the stack, and a calibrated spring which biases the presser member towards the support while trapping the stack of elements between the two abutments. The device is useful for the manufacture of filters used particularly for the filtration of oils.

The present invention relates to a device for the assembly of stacked 
annular filtering elements, under constant pressure. 
Prior art already exists relating to devices for assembling filtering 
elements constituted by annular plates made from paper or any other 
suitable material. 
Devices of this type comprise a support providing an abutment for one end 
of the stack of elements, a presser member providing an abutment for the 
other end of the stack of elements and a calibrated spring acting to bias 
the presser member towards the support such that said abutments are pushed 
one towards the other, trapping the stack of elements therebetween. 
Thus, for example, French Pat. No. 1,151,362 describes an assembly device 
of this type, in which the spring is a spring where the coils are touching 
and which is in tension and is located downstream of the filter 
constituted by the filtering elements. This spring may become a source of 
pollution, in view of the fact that the manufacturing impurities of the 
spring tend to remain attached between the coils and to be released during 
tensioning of the spring. 
The object of the present invention is to avoid such drawbacks by proposing 
an assembly device of the aforesaid type, which is characterised by the 
fact that the spring is located upstream of the filtering elements with 
respect to the direction of filtration. 
According to another feature of the invention, the spring is housed inside 
a tube whereof one end is connected to the presser member and whereof the 
other end is mounted to slide in a sealed manner on a securing member 
connected to the support.

The device illustrated in FIG. 1 comprises a support 10 screwed or fixed in 
any other manner to a filter-support plate 12. The support 10 provides an 
abutment for one end of a stack 14 of filtering elements each constituted 
by an annular plate made from paper or any other suitable material. 
The device also comprises a presser member 16 in the shape of a cup which 
provides an abutment for the other end of the stack 14 and which is biased 
towards the support 10 by means of a calibrated spring 18 such that the 
two abutments are pushed one towards the other thus trapping the stack 14 
of filtering elements therebetween. 
The spring 18 is threaded on a rod 20 which is connected to the support 10 
by means of a securing member 22 which is retained on the support by means 
of a cotter pin 24. The rod 20 may be made in one piece with the member 22 
or may be secured to the latter by screwing or any other suitable securing 
method. The spring 18 bears firstly on a retaining member located at the 
free end of the rod 20 and constituted by a washer 26 retained by a nut 28 
screwed to a screw-threaded part 30 of the rod and secondly on a washer 
32. This washer 32 co-operates with the shoulder 34 constituted by a 
contraction of a hollow tube 36 which constitutes a sealed chamber for the 
spring 18. The upper end of the tube 36 slides in a sealed manner on the 
securing member 22, the seal being ensured by an annular gasket 38 located 
in a groove provided in said member 22. The lower end of the tube 36 is 
rolled outwards in order to bias the presser member 16 in the direction of 
the support 10 and to form an annular groove 40 in which a gasket 42 is 
housed. 
The device also comprises a centering member constituted by a bent tube 44 
of substantially triangular section which is located in the annular part 
provided between the tube 36 and the inside of the stack 14, such that 
each of the three sides of the centering member 44 is in contact with the 
tube 36 and that each of the three tops of the centering member 44 is in 
contact with the inside of the stack (c.f. FIG. 4). This centering member 
may have a different shape and may for example have a square section. 
In the variation of FIG. 2, the washer 26 and nut 28 of FIG. 1 have been 
replaced by a grooved nut 48 provided with a gasket 50 and screwed onto 
the screw-threaded part 30 of the rod 20, such that the spring 18 is 
located in a sealed chamber 
Furthermore, it is possible both in the device of FIG. 1 and in that of 
FIG. 2, to place a stopper 46 at the lower part of the tube 36 (c.f. FIG. 
3). This stopper 46 ensures that the spring of the device of FIG. 1 is 
placed in a sealed chamber and constitutes an additional precaution in the 
case of the device of FIG. 2. 
The filter constituted by the filtering elements assembled by means of the 
device of the invention is used in a conventional manner. For this, it is 
sufficient to immerse the filter in the liquid to be purified and to 
provide a pressure difference between the inside and outside of the filter 
by connecting a vacuum pump to the support 10 of the device. 
To this end, the support 10 is provided with at least one opening, such as 
52, which allows the passage of the purified liquid. 
FIG. 5 is a partial section of a device constructed according to a second 
embodiment. 
This device comprises a stack 54 of filtering elements trapped between a 
support (not shown) indentical to that of FIG. 1 and a presser member 56 
in the shape of a cup. The presser member is biased towards the support by 
means of a spring 58 in tension, whereof one end is connected to the 
support by means of a securing member 60 and whereof the other end is 
connected to the presser member by means of a support member 62. The 
spring 58 is fixed to the securing member 60 and to the support member 62 
by being screwed with force onto screw-threaded parts, whereof the pitch 
is equal to the diameter of the wire from which the spring is made. 
The spring 58 is housed in a tube 64, whereof one end slides in a sealed 
manner on the securing member 60, the latter being provided with a gasket 
66 and whereof the other end is mounted on the cup by gripping or any 
other means. The support member 62 is provided with an orifice 68 to 
facilitate counterbalancing of the pressure in the tube. 
At its upper part, the tube 64 comprises a shoulder 70 in order to prevent 
the tube from escaping from the securing member in the case of accidental 
fracture of the spring. 
The device illustrated in FIG. 5 may also comprise a centering member as 
indicated above and it is used in the same way as the device illustrated 
in FIGS. 1 to 4. 
The device of the invention will therefore find an application in the 
production of filters for various industries and in particular in the 
chemical industry for the filtration of oils. 
Naturally the invention is not limited to the embodiments described and it 
also extends to variations in accordance with its spirit.