Fractionator modules having lip seals

A module, utilizing a spirally wound membrane envelope, and adapted to be fitted into a containment tube of a fractionator, has a lip seal between the module and the containment tube, there being small apertures in the lip of the seal arranged and directed so as to allow a small controlled flow to continually bypass the module and thus prevent the product from becoming stagnant behind the seal.

BACKGROUND OF THE INVENTION AND DESCRIPTION OF THE PRIOR ART 
A fractionator is a machine that utilizes the ultra-filtration or reverse 
osmosis technique of membrane separation for food products and 
by-products. 
One typical use for the machine of the present invention is to separate the 
protein out of cheese whey, as disclosed in U.S. Pat. No. 3,880,755, 
although it is not restricted to this use. The embodiment disclosed in the 
present invention utilizes a spiral wound element which consists of a 
sealed envelope of membrane material resembling a plastic bag, the neck of 
which is attached to a hollow tube, the latter having a series of holes 
running longitudinally. These holes communicate with the neck of the bag 
so that material that passes through the membrane will migrate to the neck 
of the bag, enter the hollow tube through the holes therein, and be drawn 
off. The plastic-like bag is wound up in a spiral manner much like a 
window shade, and the entire outside is covered with a wrapping. These 
elements or modules are then placed end to end in long tubes, usually six 
to a tube, and conncted together with special interconnectors as shown in 
U.S. Pat. No. 3,880,755. U.S. Pat. Nos. 3,367,504 and 3,933,646 also 
disclose spirally wound membrane envelopes. 
In this general type of apparatus there is an annular space between the 
outer surface of the module and the inner surface of the tube in which 
product might flow and bypass the module. To prevent this, U.S. Pat. No. 
3,880,755 discloses a one directional lip-type seal attached to the 
outside of the module so that, in forward flow, the product is forced to 
flow through the module. 
In water purification systems, the above described arrangement is very 
desirable, but in food product applications, and in particular where the 
food is intended for human consumption, the lip seal has presented a 
serious problem. The modules are customarily 39 inches long, and the lip 
seal is close to the leading edge. Thus the product can then get back to 
the seal from the backside and become stagnant. To prevent this, health 
authorities have required that the machine be stopped every 30 minutes, 
that the valves be adjusted, and that the pumps be restarted so that flow 
is established in the reverse direction for one minute. The purpose of 
this is to force the stagnant product past the lip seal by collapsing it 
and, thereby, replacing it with fresh product. This method was acceptable 
but required complex programming of switches, required extra controls, and 
caused undue wear and tear on the modules, and lost production time. 
SUMMARY OF THE INVENTION 
In the device disclosed, a cylindrical fractionating module is utilized 
within a containment tube, there being an annular space between the module 
and the tube, and there being an annular lip seal for sealing said annular 
space. With the present invention, small aperture means is provided 
through the lip of the lip seal, which aperture means is arranged to allow 
a small controlled flow to continually bypass the module through the 
annular space, and prevent stagnation of the product behind the seal. 
A general object of the invention is to provide an improved module having a 
lip seal which has a simple means for preventing stagnation of the product 
behind the seal, thereby eliminating the extra controls heretofore 
required for reversing the flow, greatly reducing the wear and tear on the 
delicate membrane, increasing production, and providing a more sanitary 
method of preventing stagnation, and insuring a superior finished product. 
A further object of the invention is to provide an improved arrangement 
wherein a jet stream action is created which, in addition to preventing 
stagnation behind the seal, is also effective in setting up turbulent flow 
patterns that tend to clean and keep clean the exterior surface of the 
module, both in front of and behind the lip seal. 
With the above and other objects in view, the invention consists of the 
improved fractionator modules having lip seals, and all of the parts and 
combinations as set forth in the claims, and all equivalents thereof.

DETAILED DESCRIPTION OF THE INVENTION 
Referring more particularly to the drawings, the improved modules are 
designed for use in a machine such as that fully described in U.S. Pat. 
No. 3,880,755, issued Apr. 29, 1975. In this patent, however, complicated 
valves and controls are required for reversing the flow periodically to 
prevent stagnation of the product behind the lip seal. The feature of the 
present invention eliminates the necessity for such arrangement. 
In the illustrated embodiment, a containment tube 10, forming part of a 
fractionator of the general type shown in U.S. Pat. No. 3,880,755, has a 
module 11 therein, there being an annular space 12 between the module and 
the interior of the containment tube. As described in U.S. Pat. No. 
3,880,755, the module 11 is a spirally wound element which consists of a 
sealed envelope 13 of membrane material resembling a plastic bag and a 
feed spacer, the envelope and spacer being spirally wound around a hollow 
tube 14 which has a series of holes 15 therein extending for substantially 
the length of the module. As has been heretofore taught by the prior art, 
the neck of the plastic bag 13 is so attached to the tube 14 that the 
holes 15 communicate with the interior of the bag so that any material 
which passes through the membrane material into the spirally wound bag 
will migrate spirally to the neck of the bag, enter the hollow tube 
through the holes 15, and then be drawn off through the tube. 
The membrane material is wound up in a spiral manner, much like a window 
shade, and the entire outside is covered with a wrapping 16. The end edges 
of the spirally wound membrane envelope, which appear at the ends of the 
module, are sealed together. A number of modules are placed end to end in 
relatively long containment tubes and are connected together with special 
interconnectors, as illustrated in U.S. Pat. No. 3,880,755. 
In use of this type of device, the components of whey are separated by 
causing them to flow axially under pressure between layers of the spirally 
wound module, with the low molecular weight materials passing through the 
membrane material into the interior of the spirally wound bag. These 
membranes having a very high percent of retention of lactalbumin, the 
soluble milk protein. This protein concentrate accounts for 14% by volume 
of the whey and is removed by the fractionator. The remainder of the whey 
solution is permeate, and this is drawn off through the tube 14. 
Heretofore the whey was an unproductive by-product, presenting a disposal 
problem. With the use of fractionators of the type disclosed in the 
present invention, the protein recovery presents an important source of 
profit. With the present invention the lost time and expense heretofor 
encountered in periodically reversing the flow to prevent stagnation has 
been eliminated. With the present invention it has been found that by the 
use of a small number of holes or apertures, a controlled amount of flow 
through the annular space 12 may be provided which prevents the product 
from becoming stagnant behind the lip seal 17. This lip seal is otherwise 
similar to that disclosed at 46 in U.S. Pat. No. 3,880,755. These lip 
seals are formed of suitable material, such as rubber or plastic, and 
include lips 18 which resiliently bear against the inner side of the wall 
of the containment tube 10. 
With the flow in the direction indicated by the arrows in FIGS. 1 and 2, a 
controlled amount of the product passes into the V of the lip seal and 
through holes 19 at the juncture between the lip 18 and the base of the 
lip seal, the holes providing elongated bypass ducts 19. These holes or 
ducts 19 allow a small controlled amount of flow to continually bypass the 
module into the annular space 12 and prevent the product from becoming 
stagnant behind the seal. While the number of holes, the size of the 
holes, and the orientation may be varied considerably, it has been found 
that the arrangement illustrated is particularly effective. Here three of 
the holes 19 are employed, 120.degree. apart. Normally this type of 
machine operates with a differential pressure across each module of from 5 
- 10 psi, the flow being between 10 and 20 gpm, 7 psi and 15 gpm being the 
norm. The present invention, however, is not limited to these values. 
Tests show that a 7 psi differential pressure, and at 14 gpm total flow, 
0.7 gpm will pass through three equally spaced 1/16 inch diameter holes 
19. 
In order to make the arrangement still more effective, it has been found 
desirable to have the center line 20 (FIG. 2) of each bypass duct at a 
30.degree. angle with respect to the center line of the module. This gives 
a superior spiral motion to the product as it passes over the exterior of 
the module. However, satisfactory results can be obtained at other angles 
or when the center line of the holes is parallel to the center line or 
axis of the module. 
It has also been determined that by having the center line 20 angled 
outwardly at a small angle, as shown in FIG. 4, that this causes the jet 
stream created by the elongated bypass ducts to be directed toward the 
wall of the containment tube 10 instead of against the covering 16 of the 
module where erosion might occur. The angle 20 shown in FIG. 4 is 
preferably about 5.degree., but the angle may be varied. 
Dye tests have shown that the features of the present invention have 
resulted in a complete change of the product behind the seal every 45 - 60 
seconds. This is thirty times more often than is obtained with the forward 
flow-reverse flow method of the prior art. 
It is also found that with the present invention the jet stream action is 
effective in setting up turbulent flow patterns which tend to clean and 
keep the exterior surfaces of the module clean, both in front of and 
behind the lip seal. This is much more effective than the corresponding 
cleaning resulting from the backflush method. 
Various changes and modification may be made without departing from the 
spirit of the invention, and all of such changes are contemplated as may 
come within the scope of the claims.