Well screen

A well screen is provided, for insertion into a well, for screening out sand and other particles from the well, and for connection at its upper end to a pipe for delivering water or other liquid up from the well, with the well screen having a skin with slits in it for passage of liquid therethrough, and with the skin having internal rigidifying supports. The skin is provided with a surface area increase in the form of undulations preferably of sawtooth configuration throughout its surface, and is preferably thinwalled. The screen is preferably of thermoplastic construction.

FIELD OF THE INVENTION 
This invention relates to devices for screening particulates from liquids, 
and most specifically to well screens. 
BACKGROUND OF THE INVENTION 
In drilling wells for water, oil, etc., or in otherwise making an extended 
hole in the ground, for the same purpose, it is known that one winds up 
with a hole of a certain depth, at the bottom of which is the liquid that 
is to be drawn up from the ground, preferably by placing a pump or other 
device in the well. 
It has become commonplace to provide a well screen at the bottom of the 
well, to screen out sand and other particulate material from the zone at 
the bottom of the well, so that a pump may be lowered into the well, to 
pump the liquid under conditions in which the pump will be free of 
particulate material that might otherwise be damaging. Even in those 
instances when a pump is not inserted into the bottom of the well, as for 
example when suction devices are used, it is still nevertheless desirable 
to have sand or other particulate material screened out of the liquid 
entering the hole. Accordingly, it has become commonplace to construct 
well screens and to place them at the bottom of the well. Frequently, such 
screens are generally cylindrical in shape, and usually have the lower end 
closed off, with an open upper end, for attachment of a pipe or similar 
conduit to the well screen at its upper end. Thereafter, a number of 
lengths of pipe may serially be connected together, as needed, to provide 
for delivery of liquid from the well screen, to a location generally above 
ground. 
In recent years, well screens have been constructed of synthetic polymeric 
materials, such as polyvinyl chloride (PVC), because of the corrosion 
resistant characteristics of such materials, as well as their bacteria 
resistant characteristics. 
Such well screens may be made in a single piece, or in multiple sections 
that are secured together, by heat sealing, solvent sealing, vibration 
sealing, or other forms of sealing or welding, as may be desired, some of 
which are discussed in U.S. Pat. No. 4,352,512, the entire disclosure of 
which is herein incorporated by reference. Also, fittings of various pipe 
sections together, and of the lower-most pipe section to a well screen, or 
of well screens one to the other, in serial fashion, may be made by any 
suitable technique, such as by the bayonet type locking arrangements 
integrally molded with the screens and pipe sections, such as is also 
disclosed in the above-mentioned patent, particularly when the screens are 
constructed of a molded polymeric material in which the protrusions and 
recesses of the bayonet type of locks may be readily integrally molded 
therewith. 
Additionally, when the well screens are constructed of moldable material, 
it is known to mold rigidifying supports, of both the radial or ring-like 
type, and of the upstanding, inwardly directed and axially or 
longitudinally extending type, as part of the well screen, integral 
therewith, for efficiency and economy in construction. In addition to the 
disclosure of the above-mentioned patent, reference is made in this regard 
to U.S. Pat. No. 4,262,744, the complete disclosure of which is also 
herein incorporated by reference. In this patent also, it is taught that a 
plurality of spaced slots may be formed in the skin extending therethrough 
with the slots disclosed in portions of the skin located between adjacent 
compression ribs, and with the slots extending essentially entirely around 
the periphery of a preferably tubular well screen, in order to maximize 
filtration over the surface of the well screen. 
THE PRESENT INVENTION 
The present invention is directed to further maximizing the slotted area on 
a given well screen to permit an increase in the open area through which 
the fluid can enter the screen. This is made possible by making the 
structure of the surface of the screen so that it has increased area, and 
is accomplished most specifically by providing it with preferably 
longitudinal undulations, to give it a fluted design, preferably of 
sawtooth cross section. This is particularly helpful when a multiple part 
well screen is utilized, as for example, as in U.S. Pat. No. 4,352,512. 
When a multiple part screen is utilized, those portions of the screen that 
are joined together, at the end of each arcuate part, result in a loss of 
screen area where the joints are effected. This occurs irrespective of the 
number of parts being joined together, whether two parts, three parts, 
etc. However, even in instances in which the screen may be molded as a 
single unit, the present invention effects an increase in screening area. 
SUMMARY OF THE INVENTION 
The present invention is directed toward increasing the screen area of a 
well screen by providing a fluted surface for the screen, while also 
maximizing the slotted area in the screen through which fluid may pass, 
and preferably doing so with a screen that is sufficiently thin-walled 
that the skin area undergoes a real increase. In instances in which the 
screen is constructed as a tubular member of a plurality of components, 
and especially wherein the presence of joints at connection zones prevents 
the slotting of the screen at those locations along the joints, the 
additional screening area provided by utilizing a fluted screen in 
accordance with this invention, at least compensates for the loss in 
slotted area along the joints. 
Accordingly, it is a primary object of this invention to provide a novel 
well screen. 
It is another object of this invention to provide a well screen having an 
enhanced or larger slotted skin area. 
It is a further object of this invention to provide a well screen having a 
fluted skin that, when slotted, at least compensates for loss in slotted 
area at joints, wherein the well screen is of the multiple-component 
molded type, having joints for connecting the components together. 
It is another object of this invention to provide a well screen having 
enhanced slotted screening area, wherein the skin of the screen is fluted 
on both the interior and exterior, and especially wherein supporting ribs 
are provided integral therewith. 
Other objects and advantages of the present invention will be readily 
apparent to those skilled in the art from a reading of the following brief 
descriptions of the drawing figures, detailed descriptions of the 
preferred embodiments and the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings in detail, reference is first made to FIG. 1, 
wherein a well screen is shown, generally designated by the numeral 10, as 
being a multiple component well screen of a type preferably formed of at 
least two components, of synthetic polymeric material, such as PVC, with 
the components each being integrally molded together and then joined along 
their vertical joints by suitable sealing or welding techniques as have 
been discussed above. 
The screen 10 has a suitable plastic pipe, conduit or the like 11 connected 
thereto at its upper end by any suitable connection means, such as by 
screw threads, by a bayonet connection, or the like. At the bottom of the 
well screen 10, there is provided a bottom closure plate (not shown). 
Referring now to FIG. 2, it will be seen that the skin 12 of the screen 10 
is provided with a plurality of transverse slits 13, extending through the 
wall of the skin. Behind the skin 12, there are provided a plurality of 
longitudinal or vertical ribs 14, molded integrally therewith. The ribs 14 
are also molded integrally with a plurality of vertically spaced-apart 
compression ribs 15 that extend around the interior of the screen. It will 
be noted that the skin 12 of the screen is substantially thin-walled, and 
is provided with the ring-like ribs 15 for lending stability thereto, and 
that the ribs 15 taper from a more outward portion to a more inward 
portion as shown in FIG. 4, in vertical cross-section, in order to allow 
free passage of water or other liquid therebetween from outside to inside, 
without substantially restricting the flow. It will also be noted that the 
vertical ribs 14 extend radially inwardly of the inward or leftward 
extension of the ribs 15 as viewed in FIG. 4, to allow for longitudinal 
placement of a pump or the like therein, without becoming encumbered on 
transverse ribs 15. 
With reference to FIGS. 3 and 4, in particular, it will be seen that the 
exterior 16 of the skin 12 is provided with vertical, or longitudinal 
flutes 17, comprised of alternating channels 18 and mounds 20, one after 
the other, substantially around the periphery of the skin 12. Similarly, 
the interior 21 of the skin 12 is provided with fluting 22, likewise 
comprised of alternating mounds 23 and channels 24 respectively disposed 
inside the outer respectively associated channels 18 and mounds 20, 
providing a sawtooth arrangement as illustrated in FIG. 3, with the mounds 
and channels being intersected by the slots 13. 
It will be seen that the slots 13 do not intersect the vertical ribs 14, 
but otherwise extend substantially completely around the periphery of the 
skin 12, with the exception of that portion of the periphery of the screen 
having joints 26. It will be understood that if a two component screen is 
utilized, such will be comprised of a pair of half tubular portions, each 
preferably having some mechanical joint structure, such as for example, a 
vertical protrusion 27 adapted to be received within a complementarily 
configured vertical recess in the half tubular portion to be disclosed 
thereagainst along a parting line 28, for solvent sealing, vibration 
welding, etc. of the two components together along such line. Therefore, 
at the location of each joint 26, it will be preferable not to provide a 
slot. However, if desired, the slot may extend completely around the 
periphery, but such would be a groove, ineffective for flow through the 
screen at joint locations 26. 
It will be noted that the interior mounds 23, collectively define a surface 
of revolution R.sub.i, and that the external mounds 20 collectively define 
a surface of revolution R.sub.o, and that the thickness of the skin, 
whether measured at its wall thickness, T.sub.1, or at the apex of a 
mound, T.sub.2, in either case, is of a lesser dimension than the 
difference between said radii R.sub.i and R.sub.o, and that this 
thin-walled feature for the skin 12 assures that the aggregate flow 
surface area is enhanced over and above the flow area that would be 
presented with a smooth-surfaced screen. For example, reference is made to 
FIG. 3, wherein arrows 28 and 30 demonstrate that flow may be across the 
thin-walled portions of the skin 12 along the paths of arrows 28 and 30, 
as well as generally radially inwardly along the paths of arrows 31 and 
32, for enhancing fluid flow. With such a corrugation for the skin 12, the 
wall thickness of the skin remains essentially uniform, notwithstanding 
the presence of the channels. It will also be noted, in order to maximize 
the number of slots 13, a slot is present between each compression rib 15, 
as can be seen with reference to FIG. 4. 
It will be seen from the foregoing that the well screen provided herewith 
is able to accomplish the ends of this invention. It will also be 
understood that various modifications may be made in the details of 
construction of this invention, all within the spirit and scope of the 
invention as defined in the appended claims. For example, while this 
invention is particularly adapted to offsetting a minor loss of flow 
surface area caused by the presence of joints when a multiple-component 
screen is utilized, it is likewise particularly adaptable to enhancing the 
flow surface area of a single component well screen. Also, while, for 
example, the slots are described as being transverse or substantially 
transverse, it will be understood that within such a definition, the slot 
would also be spiral or helical, in which case the circumferential ribs 
would likewise also preferably be spiral or helical, and that such a 
construction would remain within the scope of this invention. Other 
details of construction and variations will further be understood. It will 
be apparent that this invention is adapted for use with screens of various 
sizes and shapes, and with many variations of relationships between slot 
thickness S.sub.1 and slot spacing S.sub.2, all within the spirit and 
scope of this invention.