US 3901801 A
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[ Aug. 26, 1975 1 1 INDUSTRIAL SCREEN  Inventor: Leon C. Bixby, Clark's Green, Pa.
 Assignee: Hendrick Manufacturing Company,
 Filed; June 17, 1974  Appl. No.: 480,010
 U.S. Cl 209/395; 209/352  Int. Cl. B07B 1/12  Field 01 Search 209/393, 395, 98, 99, 352,
3,381,355 5/1968 Bixby 29/160 3,729,096 4/1973 Fitzner 209/393 FOREIGN PATENTS OR APPLICATIONS 1,912,870 10/1969 Germany 209/397 Primary Examiner-Frank W. Lutter Assistant Examiner-Greg0ry N. Clements Attorney, Agent, or Firm-Dybvig & Dybvig 5 7 ABSTRACT An industrial screen such as used to process coal, ore and the like comprises elongate plastic profile bars having depending flanges clad by metal sheaths which reinforce the profile bars. The clad profile bars are pressed into notches located in metal support members which support the bars in spaced apart parallel relationship. Metal rods which pass under the support members and transversely through the flanges as well as their reinforcing sheaths secure the profile bars to the support members. In some of the embodiments disclosed, means such as teeth project inwardly from the reinforcing sheaths to assist the rods in retaining the profile bars in their sheaths.
9 Claims, 8 Drawing Figures INDUSTRIAL SCREEN BACKGROUND OF THE INVENTION trial screens to assemble metal bars upon support members which are notched to receive the bars and to locate the bars in an accurately spaced apart relationship. An example of such a screen appears in U.S. Pat. No. l,769,l28. Screens of the nature shown in the aforementioned patent are ordinarily made of a metal such as steel so as to have good abrasion resistance. A consequent difficulty is that the screen is rather massive and for this reason is not well suited to many industrial processes such as those which require vibration of the screen.
With the development of modern plastics such as high molecular weight polyethylenes, plastics having an abrasion resistance far exceeding that available from steel have become available. While such plastics offer great promise for use in the construction of industrial screens the application of such plastics in this area has been delayed by reason of the fact that the plastics have tensile strengths which are relatively low in relation to steel and are not capable of retaining the intended screen dimensions when subjected to loads, vibratory stresses and the like.
SUMMARY OF THE INVENTION The obvious desirability of plastic having high abrasion resistance for use in industrial screen processes has generated efforts to mold entire industrial screens out of the plastic but such efforts have proved generally unsuccessful because the plastic screens do not have the requisite tensile strength for supporting loads and for maintaining their designed dimensions. The latter problem is particularly evident in screens of the slotted opening type which require that slender profile members assembled in a parallel grid accurately maintain the spaces therebetween. As a means for strengthening slender profile members of plastic composition, efforts have been made to mold the plastic around reinforcing supports, typically of steel composition, but such techniques are not known to have been successful because the plastic which thermally expands and contracts at a rate different than that of the reinforcing metal, easily breaks loose of the reinforcing metal and the screen loses its structural integrity.
The present invention circumvents these problems by retaining a conventional supporting structure heretofore used in steel screens and mechanically cladding or sheathing plastic profile bars with structurally adequate metal sheaths. The sheaths are so designed with respect to the plastic profile bars that they do not interfere with the design dimensions of the resulting screen.
An object of the present invention is to provide a new and improved screen construction.
Another object of the present invention is to provide an improved industrial screen in which plastic profiles are used in those areas of the screen which are most susceptible to wear.
Still another object of the present invention is to utilize mechanically retained metal sheaths for reinforcing plastic profiles assembled into industrial screens.
Other objects and advantages reside in the construction of parts, the combination thereof, the method of manufacture and the mode of operation, as will become more apparent from the following description.
DESCRIPTION OF THE DRAWINGS In the drawings:
FIG. 1 is a perspective view, with portions exploded to reveal construction details, of a screen constructed in accordance with the present invention.
FIG. 2 is an enlarged fragmentary side elevation view of the screen of FIG. 1.
FIG. 3 is a section view, with portions broken away, taken substantially along the line 33 of FIG. 1.
FIGS. 4, 5, and 6 are section views analogous to FIG. 2 and illustrating modifications.
FIG. 7 is an enlarged fragmentary elevation view, with portions broken away of the modification illustrated in FIG. 4.
FIG. 8 is an enlarged fragmentary elevation view of the screen of FIG. 7 after the screen has been utilized in the processing of an ore or coal in an aqueous environment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The screen illustrated in FIG. 1 is assembled upon spaced support members 10 each comprising a sheet of a relatively rigid metal such as steel bent about a longitudinal center line so as to have an arcuate crest l2. Depending upon the manner in which the screen is to be mounted and used the members 10 may have a generally V-shape as appears in the drawing or may be bent to other shapes such as a generally U-shape.
At spaced intervals along the crests 12, the members 10 have cutouts or perforations which extend transversely across the crests 12 so as to form notches l4 shaped to receive profile bars shown generally at 16.
The profile bars 16 comprise extruded plastic rods each having an upper profile section 18 from which extends a depending flange 20. Each of the depending flanges 20 of each of the profile bars 16 is clad by a generally U-shaped sheath 22. The sheaths 22 comprise a metal such as steel which is sufficiently thin to be bendable or formable for reasons to be described later. After the sheaths 22 have been assembled upon the flanges 20, the sheaths as well as the flanges are drilled transversely so as to provide apertures 27 which extend transversely through both the sheaths and the flanges 20. The spacing between the apertures 27 corresponds to the desired spacing between the support members 10.
At spaced intervals along the outer sides thereof the sheaths 22 are also swaged with a sharp instrument, not shown, to produce inwardly directed dimples 24. Due to the swaging, the sheaths 22 have teeth 26 along the interior walls thereof which are pressed into the flanges 20 by the swaging force. The teeth 26 thus closely fit the deformation of the flanges which results from the swaging.
In the assembly of a screen, the sheathed profile bars are pressed into the notches 14 of the members 10 which, by reason of a close fit, press the bendable sheaths 22 firmly against the flanges 20. As the sheaths are pressed into the notches l4 care is taken to assure that the apertures 27 are aligned with the crests 12 and become exposed under the crests 12. Care is also taken to maintain an axial alignment between the apertures 27 in successive profile bars assembled to the support members so that axially straight metallic rods 28 can be passed through the several apertures 27 located under the crests 12 of the support members 10. The rods 28 are sized to closely fit the apertures 27 and thus receive support from the sheaths 22. The ends of the rods 28 are preferably upset as shown at 29 to be assured that the rods 28 are retained in the screen assembly.
The screen described with reference to FIGS. 1, 2, and 3 can be seen to offer a number of advantages particularly in the utilization of plastic profile members. The support members 10, the sheaths 22 and the rods 28 form a self-supporting metallic frame which does not require the presence of the plastic profile members for structural integrity. Thus the profile members are not required to make any contribution to the structural strength of the screen. The sheaths 22 are also sufficiently buttressed by the support members 10 that the plastic profile members are not permitted to bend transversely thus disturbing the designed slot dimensions. Inasmuch as the sheaths provide a continuous and uninterrupted bed for supporting the profile members, the profile members are protected against breakage over their entire length. This feature is particularly desirable for vibratory screen applications.
As known, plastics have a much greater coefficient of thermal expansion than do metals. To protect the plastic profiles against disturbance by forces resulting from thermal expansion, the teeth 26 cooperate with the rods 28 to resist a tendency of the rods to bend upwardly out of the sheaths as the environmental temper ature changes.
Referring particularly to FIG. 3 it can be noted that the profile section 18 diverges outwardly in progressing upwardly from the sheath 22 to a width which is at least as great as the width of the flange 20 together with its sheath 22. It can also be noted that the profile section 18 continues diverging to its uppermost surface. Accordingly, when particulate matter passing over the screen has a size which the screen has been dimensioned to accept, the particulate matter will enter between adjacently positioned profile bars and there encounter a downwardly divergent space which permits the accepted particles to fall freely between the profile bars. Because the sheaths 22 lie laterally inside the cross sectional range of the profile bars, the free fall of particles passing through the screen is not obstructed by the sheaths 22. It will be further noted that the projective heights of the sheaths 22 within the notches I4 is just sufficient to reach the crests 12, the result being that particles passing between the profile bars will not tend to accumulate on a sharp shoulder produced by a misfit between the sheath 22 and the support member 10.
It is to be understood that the screen illustrated in FIG. 1 has been sized for convenient illustration in the drawings. In actual practice the screen may be several feet long and several feet wide and accordingly may comprise several more support members 10 and many more profile bars 16 than are illustrated in the drawmgs.
In the preferred construction, the plastic utilized in the profile bars is an ultra high molecular weight polyolefin such as a high density polyethylene, however, the benefits which result from the reduction in the weight of the screen in applications which require that the screen be vibrated are of sufficient importance in and of themselves that the abrasion resistance available from high molecular weight polyolefins is not always a primary consideration. Accordingly, other plastics such as polyurethanes and in general many types of plastic well known to those skilled in the art are suitable for use in the present invention.
Depending on the nature of the ore or coal being processed, particularly when the material is wet and the fines have a tendency to aggregate in clumps, it becomes important that precautions be taken to avoid accumulations of the material in the slots between adjacent profile bars. This problem is most important in screens designed with a very narrow slot width whereby accumulations against the sides of the sheaths for the profile bars readily form bridges between adjacent profile bars and thus blind" the screen.
One device for minimizing this problem is illustrated in the modification of FIG. 4. In this modification the upper profile section 18a has been made much wider with respect to the sheath 220 than was the case in the deferred embodiment. Further, the upper profile section 18a has been sized with respect to the sheath 22a to abut the upper edges of the sheath 22a. The lowermost surfaces of the profile section 18a thus bottom against the crests of the support members 10. Due to such construction, fines being processed are afforded little opportunity to accumulate on the sheaths 22a.
The modification of FIG. 4 also illustrates teeth 260 which have been more sharply swaged so as to more securely engage the flange 20a and thereby minimize distortion of the profile section 18a due to changing temperature conditions.
In the modification of FIG. 5 the sheath 22b has been formed with re-entrant flanges or teeth 26b along the upper edges thereof. The re-entrant flanges extend along the entire length of the sheath 22b. At the time the plastic profile member is formed, as by extrusion, longitudinal grooves 32 are formed in the sides thereof to accommodate the re-entrant flanges 26b. The flange 20b which depends from the profile section 18b is sized with the sheath 22b to require a slight pressed fit into the notch of the underlying support member 10. Accordingly, several support members 10 for a screen utilizing the modification of FIG. 5 cooperate to retain the re-entrant flanges 26b firmly in their accommodating grooves 32.
It will also be noted in FIG. 5 that the flange 20b has been formed with a downward convergence which causes the sheath 22b when pressed securely against the flange 20b to assume a downward convergence which extends the downward convergence of the profile section l8b. This construction allows fine particles being processed to pass downwardly between adjacent profile bars with a minimum opportunity for agglomeration on the sides of the profile bars.
In the modification of FIG. 6 the depending flange 20c has been tapered parallel to the tapering of the profile section l8c. The construction is such that when the sheath 22c is assembled about the flange 20c, the upper edges of the sheath firmly abut the profile section so as to minimize the opportunity for fine particles to agglomerate against the side surfaces of the profile bars. It will also be noted in the modification of FIG. 6 that the notches formed in the support member are also tapered to assure a uniform fit of profile bars into the notches of the support members.
FIGS. 7 and 8 are enlargements of the screen illustrated in FIG. 4. FIG. 7 illustrates the screen before any usage has commenced, and FIG. 8 illustrates the manner in which the screen will wear through prolonged use in an aqueous environment. A typical operation occuring in an aqueous environment concerns the washing and draining of coal which is passed longitudinally over the screen so that the wash water can drain through the screen. As evident in FIG. 8, an operation of this sort will ultimately round off the uppermost corners of the profiles 18a.
A consequence of this rounding, one would expect, is that progressively larger particles of coal are being permitted to pass through the screen with the wash water. A characteristic of all plastics when contacted to water for prolonged periods is that there is at least some moisture absorption. Along with this, there is at least some swelling of the plastic which is proportionate to the extent of moisture absorption. In the present invention this characteristic is utilized to maximum benefit by supporting the plastic profiles in a metallic frame which does not swell and does not change dimension during ordinary use. This means that any swelling of the plastic that may occur due to moisture absorption always tends to offset the wear that occurs during the usage of the screen. Thus, in contrast to metal profiles as heretofore utilized in industrial screens, there is at least a threefold advantage:
First, by proper selection of plastics such as high molecular weight polyolefins, the abrasion resistance can be increased by many orders of magnitude;
Second, by use of plastic profiles the overall weight of the screen is substantially reduced and the screen is rendered more suitable for use in vibratory screen applications;
Third, the use of plastic profiles supported by a metal frame in an aqueous environment always works to offset the changes in slot dimension occasioned by wear.
Although the preferred embodiments of this invention have been described, it will be understood that various changes may be made within the scope of the appended claim.
Having thus described our invention, we claim:
1. In an industrial screen of the type comprising a plurality of elongate plastic profile bars and support means for securing said profile bars in relative arrangement to one another, the improvements wherein said profile bars each comprise an elongate profile section, each profile section having flange means depending therefrom, each profile bar further including metalic sheath means for reinforcing said flange means, said sheath means embracing said flange means, said support means comprising support members having notches receiving said flange means and said sheath means.
2. The screen of claim 1 wherein said profile sections comprise a high molecular weight polyolefin.
3. The screen of claim 1 in which said support members comprise sheet means arched to a crest, said notches defined by perforations through said crests, said sheath means and said flange means projecting into said notches to positions lower than said crests, said sheath means and said flange means having apertures therethrough, said apertures lower than said crests, said support means further including a plurality of metallic rods, one for each support member, said rods disposed under the crests of their respective support members and passing through the apertures in the sheath means and the flange means supported by their respective support members.
4. The screen of claim 3 in which the ends of said rods have means thereon resisting removal of said rods from said sheath means and said flange means.
5. The screen of claim 1 wherein said sheaths are generally U-shaped and confront opposite sides of said depending flange means, and wherein the sides of said sheaths confronting the sides of said flange means have tooth portions projecting against the sides of said flange means.
6. The screen of claim 5 in which said tooth portions are spaced apart along the length of said sheaths.
7. The screen of claim 5 in which said flange means have longitudinally extending grooves recessed in the opposite sides thereof, said tooth portions comprising re-entrant flanges of said sheaths entering said grooves.
8. The screen of claim 1 in which said profile sections have a thickness transverse to the length of said profile bars which is at least as great as the thickness of said sheath means and said flange means in the same direction.
9. The screen of claim 8 in which said profile sections have transverse thicknesses greater than the transverse thicknesses of said sheathed flange means and contact said support members adjacent the notches therein.