Water Intake Screen

Abstract

A traveling intake water screen installation for removing debris and fish from a flowing stream of water includes a screen movable through a vertically closed loop. The screen is suspended from a pair of dual material head sprockets and comprises multiple screen trays interconnected by endless dual material side chains. Each screen tray has flexible end closure plates for preventing passage of debris around the sides of the screen.

Description

BACKGROUND OF THE INVENTION

1. Field of the Disclosure

The present invention relates to fish and trash removal devices generally known as traveling water screens. More particularly, the invention concerns improvements in the sprockets and chains which support the screen sections and improvements in closure members between the screen sections and side walls of a water channel.

2. Description of the Prior Art

Traveling water intake screens are described in the U.S. Pat. No. 2,804,209 issued to Carlton et al. and U.S. Pat. No. 2,851,162 issued to Bleyer. Water screens of the above type generally comprise a head portion that includes a pair of driven head sprockets which vertically support a hanging traveling screen. The traveling screen is comprised of multiple rectangular screen trays transversely mounted between a pair of endless roller link chains. A pair of uprights on the channel sides forms closures with the screen and supports the upstream run of the screen against deflection from water pressure.

Traveling water screens of this type may be operated in either a continuous or intermittent mode. In the intermittent mode the water screen is operated only when sufficient trash is collected on the upstream surface of the screen to provide a substantial increase in water resistance passing through the screen. The screen is then advanced sufficiently to remove the trash from the water and to present a screen with a clean surface area in the water channel zone in which screening is accomplished. In the continuous mode, the continuously moving screens continuously remove trash and debris from the channel. In either operating mode, corrosion is a very important factor in the operating life of the water screen and particularly with respect to the sprockets and side chains which are used to support and move the water screen.

Another important aspect is wear of the chain rollers and sprockets and, in particular wear of the sprocket saddles which engage the chain rollers. These sprocket saddles are comparable to what is generally referred to as a sprocket tooth pocket and are located in the zone between two adjacent sprocket teeth where they are normally engaged by the chain rollers. The wear problem is particularly acute for the head sprockets due to the usual presence of sand and other abrasive contaminants which are carried up to the sprocket on the chain rollers.

Due to the substantial size of the sprockets, with for example, a diameter of 4 feet, the sprockets are usually of the fabricated type rather than being a one-piece forging or the like to reduce production costs.

One attempt to solve the combined wear and corrosion problem was the provision of stainless steel inserts within the sprocket tooth pocket or saddle area. This solution has not proved entirely satisfactory for two reasons. The first reason is that stainless steels do not exhibit satisfactory wear properties unless hardened. By way of example, for a traveling water screen of approximately a 10 foot width and a 51 foot distance between upper and lower sprocket centers, the estimated deadweight of the chain and screen trays is in the order of 19,000 pounds. When the chain and screen trays are advanced, a single chain pull of as high as 8,700 pounds can be expected and result in loading in the order of 7,200 pounds against an insert for each chain. For such an installation it has been found that the insert must have a hardness in the order of 410 Brinell. It has also been found that when an exact matching of such a hardened insert and the corresponding sprocket tooth pocket or saddle is not achieved rapid failure of the insert occurs due to the brittleness of the hardened stainless steel. The cost of machining both the sprocket and insert with sufficient accuracy was considered excessive.

The second reason the inserts have proved unsatisfactory is that if the insert failure is not immediately detected, the unhardened sprocket material wears relatively rapidly and thereafter a stainless steel replacement insert cannot be fitted. Consequently, an entire new sprocket assembly must be installed.

Engstrom, in the U.S. Pat. No. 1,870,801, describes a sprocket construction in which rubber is vulcanized into recesses in the tooth pocket areas, on and between the sprocket teeth which are engaged by rollers of a chain driven by the sprocket. Although such a sprocket might prove helpful in some limited light load applications which are not subject to the elements and atmosphere, the use of rubber as an anticorrosion or wear element in the present environment is unsatisfactory for the following reasons. Rubber in general does not exhibit satisfactory wear characteristics for the employment in high load, long life applications. Furthermore, rubber compounds are subject to serious ozone degradation and hardening. Additionally, sand or other debris would lodge in the rubber, forming a matrix structure, subject to rapid failure.

Another serious problem enocuntered in the use of the type of screens mentioned above, and particularly in the type of screen described by Carlton et al., is the problem of jamming. In this type of construction, each separate screen tray is suspended between pairs of side chains and incorporates an end closure plate located at both sides of the screen tray. These end closure plates prevent passage of debris (but not water) around the ends of the trays and between the upright support members.

The most serious problem occurs when the water screen is operated on an intermittent basis and substantial amounts of debris are allowed to collect against the screen. This often causes substantial amounts of material to collect in the boat area and some material is wedged between the end closure plates and the upright support and barrier members as well as articulation points between the separate screen trays. Consequently, upon start up of the chain, if substantial material has become so lodged, typical end closure plates, made of metal, tend to jam and may result in serious damage to the end closure plates and overload of the driving motor.

Damage to the end closure plates also results from impact by logs or other objects, often submerged and undetectable. The end plates must then be replaced or straightened. Such repairs may require partial disassembly of the water screen and the use of a diver.

SUMMARY OF THE INVENTION

In general, the purpose of the invention is to provide an improved traveling water screen installation that exhibits longer life and reduced maintenance costs to the user without a substantial increase in cost of manufacture.

Accordingly, one of the objects of the invention is to provide a dual material sprocket with superior strength, wear and corrosion resistant properties.

Another object of the invention is to provide a sprocket with contact portions that may be employed in tooth pockets formed to broad tolerances and may be used as replacements for tooth pocket portions which have failed, even if the sprocket material has become worn in an irregular manner.

A further object of the invention is to provide a long life chain and sprocket combination for use in an environment of water mixed with abrasives, subject to high loading.

The above objects are achieved by the use of contact portion made of a molded thermosetting plastic material which is attached to, and backed by, a steel material.

Yet another object of the present invention is to provide an improved end closure plate for traveling water screen trays that eliminates jamming and obviates the need for replacing or straightening the end closure plate.

Other objects of the invention will become apparent during the description of the drawings and the preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, partly broken away, of a traveling water screen embodying the present invention.

FIG. 2 is an enlarged fragmentary central sectional view taken through the upstream run of the traveling screen.

FIG. 3 is an enlarged partial front elevational view.

FIG. 4 is a cross-sectional view taken on line 4--4 of FIG. 2.

FIG. 5 is a side elevation of the head sprocket and side chain having portions broken away.

FIG. 6 is a cross-sectional view of the sprocket taken on line 6--6 of FIG. 5.

FIG. 7 is an enlarged view of a sprocket saddle and contact element.

FIG. 8 is an enlarged view of a portion of a side chain.

FIG. 9 is a cross-sectional view taken on line 9--9 of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the drawings, and particularly referring to FIG. 1, reference character 10 designates in its entirety a channel in which the traveling water intake screen is located to remove various types of refuse from water flowing through the channel. It will be appreciated that the water enters the channel 10 from any convenient natural source, such as a river, a large stream or lake, and flows through the channel in the direction indicated by the arrow 12 in FIG. 1.

Extending vertically along opposite sides of the channel 10 are parallel uprights 14, the bottom portions of which are connected to a boot 16 that extends laterally across the channel to prevent refuse from passing beneath a traveling screen 17. These uprights are secured to the sides of, and terminate at the top of, the water channel 10. A foot shaft 18 and foot sprockets 20 guide the lower end of the traveling screen, as will be described in more detail hereinafter. Channel beams 22 extend longitudinally along each side of the channel 10 adjacent the upper ends of the uprights 14 to form a supporting base for a head portion, which is designated in its entirety by the reference character 24.

Extending vertically upward from the beams 22 on each side of the channel 10 are a pair of vertical side frame members 26, which are spaced longitudinally of the beam 22, receiving thereon a take-up mechanism 28. Each of the take-up mechanisms 28 include a bearing (not shown). Journaled in these bearings is a head shaft 30 upon which are mounted the head sprockets 32, which lie in the same vertical plane as the foot sprockets 20, at each side of the channel 10. Drive sprocket 34 is mounted on shaft 30 between one of the sprockets 32 and the adjacent side frame members 26. A glass fiber reinforced plastic housing 36, of any suitable construction, functions to substantially enclose the head shaft 30, head sprockets 32 and drive sprocket 34. The upstream portion of the housing 36 has a refuse trough 38 which extends transversely across the channel adjacent the vertically rising upstream run of the traveling screen structure.

Mounted on the top of the housing 36 is a motor 40 which is suitably connected through a speed reducing unit 42 to a sprocket 44 over which is trained a drive chain, indicated at 46, for rotating the drive sprocket 34.

The traveling screen structure 17 comprises two endless chains 48 which are trained over the aligned sets of head and foot sprockets 32 and 20, respectively, for movement through a closed loop, to provide an active or upstream run through which the chains 48 move upwardly and a return run through which the chains move downwardly as indicated by arrows 50 and 52.

Connected to, and extending transversely of, the channel between aligned pitches of the two chains 48, are a plurality of screen trays 54. As best illustrated in FIG. 2, top and bottom edges 56 of the screen trays are offset so that the screen trays present screening surfaces that face slightly upwardly as the trays are moved along their active run. Nozzles 57, supplied with water under pressure through feed pipe 58, spray water through the screening surface of the upstream run of the screen trays 54 to dislodge and wash the collected refuse off the screening surface and into the refuse trough 38 as indicated in FIG. 1.

Referring now to FIGS. 2, 3 and 4, it can be seen that each of the screen trays 54 has a rectangular frame comprised of a pair of transverse angle members 59 joined to a pair of vertical side bars 60. A panel of wire cloth 62 is secured to the framework by means of backing strips 64 and bolts 65.

It should be noted (see FIG. 2) that on the upstream run, the tilted screens are in overlapping relationship, with the front of the upper edge of each screen frame close to the rear of the bottom edge of the screen directly thereabove. This arrangement prevents refuse from passing between the adjacent edges of the trays as they are moved through their active upward run.

Since the head sprockets 32 substantially support the entire hanging weight of the traveling water screen and further carry the additional loads produced by driving the screen, the sprockets must be of a rather substantial construction. Referring now to FIG. 5, a head sprocket 32 is shown comprising a central hub 66 which is mounted on the head shaft 30 by means of a key 68 and a set screw indicated at 70. A steel disc 72 is attached to the hub in a suitable manner such as by welding and is further reinforced by means of radially extending tapered webs 74. Around the periphery of the disc 72 are mounted multiple equally angularly spaced steel saddles 76 which are normally welded to the disc. On the disc 72 are a number of mounting bosses indicated at 78 to which the previously mentioned drive gear 34 is attached, as best shown in FIG. 6.

Referring now to FIG. 7, in which one of the aforementioned saddles 76 is shown, it can be seen that the base surface of the saddle indicated at 80 is curved to conform to the diameter of the disc 72. The upper surface of the saddle indicated at 82 is in the form of a concave cutout having a round bottom 83 and tangentially straight extending side portions 84. The exterior side portions of the saddle generally indicated at 86 are recessed to form projections 88 having a flat surface 90 parallel to the previously described surface 84. The saddle is made to the shape by the process known as flame cutting, allowing only a broad tolerance of approximately .+-.1/32 of an inch to be maintained with respect to the surfaces 83 and 84.

Mounted on the concave upper saddle surface 82 is a molded thermosetting type plastic contact portion or element 92. This element is approximately 1/2 inch thick and has a width of 1 3/8 inches. The lower surface of the contact element conforms generally to the upper surfaces 83 and 84 of the saddle while the upper surface of the element 92 is molded to conform to the diameter of the rollers of the chains 48. The contact portion or element 92 is attached to the saddle 76 by means of a bolt 94 which extends through the ear portions 88. This bolt has a head 96 counter sunk in the element 92, and is secured by a nut 98 engaging the previously described surface 90 on the opposite side of the ear 88.

In addition to bolting the contact element 92 to the saddles, other methods of attachment such as riveting or bonding may be employed to attach the element.

The materials which may be used for the contact element are thermosetting type plastics such as epoxy, phenolic, polyurethane or isocyanate resins. The preferred materials are poly tetra methylene glycol based urethanes reacted with toluenedisocyanate and methylene bisorthochloaniline with a glass fiber filler and are sold under the trade names Prothane -146-30 and Prothane -326-20 by Prothane Limited, 66 Six Point Road, Toronto 18, Canada. Preferably, the contact element material should have a Shore Scale D durometer hardness of approximately 75 but durometers in the Scale D range of 60-90 are acceptable.

Another important property of the contact element material is elasticity. This property enables the contact element to deform under load of a chain roller until it fully engages the upper saddle surfaces 83 and 84. The contact element is then backed and supported by the steel saddle or sprocket tooth pocket. This can best be illustrated by reference to FIG. 7. If the upper saddle surface is formed at maximum tolerance as indicated by a dashed line 82', a clearance 100 exists between the saddle surface 82' and the contact element lower surface 92a when the contact element is in an unloaded condition. When the contact element 92 is subjected to a load, such as by a chain roller, the element 92 will deform until its lower surface 92a engages and is backed and supportd by the tooth pocket or upper saddle surface 82'.

As a result, the contact element can be employed with more broadly toleranced sprocket saddles to reduce the manufacturing cost, or can be employed as a replacement element in saddles or tooth pockets in which the insert has broken and the backing or supporting surface has been worn.

In addition, the contact element material exhibits excellent wear properties and is not subject to significant cold flow or degradation if its properties due to high loads or effects of the environment.

Where the sprockets and contact elements are not required to be compatible with existing installations, the element thickness can be decreased to approximately one-sixteenth inch. In such an application, the glass fiber filler may be omitted in the preferred materials.

The screen tray supporting chains 48 will now be described with reference to FIGS. 8 and 9. Each side chain 48 generally comprises multiple identical links comprising steel chain side bars 102 which are held in a spaced apart relationship by means of hollow steel spacer bushings 104 that extend through the side bars and are flared at their outer ends as indicated at 106. The chain side bars 102 are stepped inwardly near one end as indicated at 108 at the right side of FIG. 8 such that the side bars of this end of the chain link pass inside the left end of the next adjacent chain link side bar members indicated at 102'.

As best seen in FIG. 9, a roller 110 is supported for free rotational motion on a steel bushing 112. The bushing 112 is press-fitted into holes 114 adjacent the stepped down end of the side bars 102. The roller 110 is made of a thermosetting type plastic material as described in connection with the sprocket contact elements.

Adjacent chain links are joined by means of pins 116 such as shown in FIG. 9. The pins 116 are press fitted into the normally spaced end portions of the side bars 102' which overlie the stepped down side bar ends of the side bars 102. A free rotating fit is maintained between the outer diameter of the pins 116 and the inner diameter of the bushings 112 thereby providing articulation between adjacent chain links. The steel pins 116 and bushings 112 act as a backing for the rollers 110 which may be considered as contact elements.

In order to prevent rotational frictional forces or other loads from loosening the pins 116, each of the pins has a flat 118 upon its end portion 120 which extends through one of the side bars 102. This flat 118 is engaged by a lock tab 122 welded to the side bar and thereby prevents any possible rotation of the pin 116.

Referring now to FIGS. 2, 3 and 4, it can be seen that each screen tray 54 is secured to a single link of each of the side chains 48 by means of bolts 124. These bolts pass through the vertical side bar 60, an end closure plate 126, chain side bars 102, hollow spacer bushings 104, and are secured by means of nuts 128.

In addition to an inwardly facing debris blocking barrier portion 130, each of the upright support members 14 at the sides of the water channel further includes a vertically extending angle 132. This angle 132 is supported by means of brackets 134 and in conjunction with the leg portion 130 forms a channel like guide for the rollers 110 of the side chains 48. The angle 132 serves to prevent the upstream run of the side chains 48 and screen trays 54 from being bowed due to water pressure exerted in the direction indicated by arrow 12.

In order to permit free articulation of the side chains 48 and screen trays 54 around the sprockets 20 and 32 and still form a substantially continuous closure during the upstream run to prevent passage of debris between adjacent end closure plates, each end closure plate 126 has a circular recess 136 on its upper end and a circular projection 138 on its lower end. As best seen in FIG. 4, the side end closure plates 126 are positioned in close proximity to the inner edge of the debris blocking barrier portion 130 to prevent passage of debris around the sides of the screen trays 54.

In order to prevent jamming of the traveling screen 17 due to severe permanent deformation of the end closure plates 126 by impact with large pieces of debris, or passage of debris around the closure plates when the deformation is less severe, the end closure plates are made of a flexible material. The material must be stiff enough to retain its position against normal accumulations of fine debris and water pressure yet be able to deflect, or flex, under the impact of heavy objects and return to its normal position.

It will be realized that a wide range of flexible materials such as rubber, plastics and the like may be employed. Furthermore, the degree of flexibility or stiffness required may vary substantially with the size of the installation and the type of debris encountered. For general applications, a polyurethane type plastic having a Shore Scale D durometer hardness of approximately 60 and a thickness of three-sixteenth inch has given excellent results. One material conforming to this specification is Prothane -104 commercially available from Prothane Limited, 66 Six Point Road, Toronto 18, Canada.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.

Claims

We claim:

1. In a traveling water intake screen for removing debris from a flowing stream of water in a channel, said screen being of the type comprising an endless series of screen trays movable through a closed vertical loop, a pair of head sprockets supported on a shaft, a pair of chains trained around said sprockets to move and to support said screen trays, a pair of upright support members on opposite sides of the water channel for supporting said chains and said screen trays against water pressure exerted against them, each of said upright support members including a debris blocking barrier, and a laterally extending curved boot plate connecting the upright support members at their bottom portions to prevent debris from passing beneath the movable screen trays, the combination comprising:

a. polyurethane type plastic end closure plate members on each side of said screen trays connected between the sides of the trays to the chains, said end closure plate members forming a substantially continuous closure with the boot plate and with the barrier portion of the upright support members to prevent passage of debris around the sides of the screen trays, said end closure plate members being able to flex without permanent deformation so as to prevent jamming of the screen trays; and

b. said pair of head sprockets being of the dual material type each comprising a steel disc having multiple tooth pockets formed on the disc's periphery with a broadly toleranced concave backing surface, a polyurethane type plastic contact portion engaging the backing surface of the tooth pockets, and fastening means for attaching said contact portion to said backing surface, said polyurethane contact portions being sufficiently elastic to deform into said broadly toleranced concave backing surface of the tooth pockets when engaged by said chain under load to provide sprockets having longer life and reduced maintenance costs under the existing abrasive and corrosive conditions.

2. The traveling water intake screen of claim 1 wherein the polyurethane type plastic contact portions of the head sprockets are molded thermosetting polyurethane resins with a glass fiber filler having a Shore Scale D durometer hardness in the range of 60-90.

3. The traveling water intake screen of claim 1 wherein said pair of chains are of the dual material type comprising pairs of multiple steel links with an offset end portion connected by a steel bushing, steel pins joining adjacent pairs of links for articulation and elastic thermosetting type plastic chain rollers supported for rotation on said bushings for engaging said polyurethane contact portions of the sprocket tooth pockets to provide increased resistance to wear and corrosion while maintaining a high load capacity.

4. The traveling water intake screen of claim 3 wherein the plastic chain rollers are molded polyurethane resins with a glass fiber filler having a Shore Scale D durometer hardness in the range of 60-90.