US3127821A - Fluid-flow grating - Google Patents

Description

United States Patent C) 3,127,821 FLUD-FLW GRATIN G Francis Leliaron, Jr., Commercial Yard and E. Union St., Brockton, Mass. Filed Apr. 29, 1960, Ser. No. 25,587 8 Claims. (Cl. 94-33) The present invention relates to fluid-flow gratings, and, more particularly, to catch-basin gratings and the like.

Numerous types of grates have been employed throughout the years for such purposes as covering street catch basins and similar openings, in order to permit the flow of water or other fluid into the basins or openings together with small Waste objects, such as stones and other debris, while protecting pedestrians and vehicles from communication with the openings. As an illustration, substantially horizontal planar gratings have been constructed with substantially parallel horizontal bars of circular or rectangular cross section that permit some part, at least, of an on-coming horizontally-directed stream of water or the like to become deilected and to pass into the catch basin together with some of the debris carried thereby. Such prior-art and present-day gratings, however, have generally been constructed to meet the requirements of a satisfactory cover, and not with the end in view of taking maximum advantage of hydraulic fluid-flow principles, as well, in order more efficiently to direct water or the like and debris into the catch basin. In presentday constructions, indeed, the converting of the iiuid ilow from the horizontal direction to the downward vertical direction into the catch basin, upon striking the grating bars, is abrupt. It is accompanied by appreciable loss of energy and violent turbulence as the water splashes part downward and part upward over the bars; both of which factors result in much of the fluid and the debris owing over and beyond the grating and not down into the catch basin. This is particularly serious in periods of heavy rainfall. Yet, it is the best that the art has heretofore developed.

An object of the present invention, accordingly, is to provide a new and improved grating and the like, that shall not be subject to these disadvantages but that, to the contrary, shall efficiently and without substantial turbulence turn the horizontally flowing water or other fluid from the horizontal direction to the downward vertical direction. This end is achieved through the employment of properly curved and oriented grating vanes.

A further object is to provide such a grating in which advantage is taken of the fact that the amount and speed of the fluid iiow varies from vane to vane.

An additional object is to provide a novel grate of more general utility, also.

Other and further objects will be explained hereinafter and will be more particularly pointed out in connection with the appended claims.

The invention will now be described in connection with the accompanying drawing, FIG. 1 of which is a perspective view of a preferred embodiment of the invention;

FlG. 2 is a longitudinal section taken along the line 2-2 of FiG. l, looking in the direction of the arrows; and

FlG. 3 is a view similar to FIG. 2 of a modification.

In accordance with the present invention, the vanes 1 of the grating are cast from cast iron or similar material to extend along a first direction transversely between integral longitudinally extending, preferably substantially parallel, planar side members 2. The side members 2 are illustrated as provided with preferred substantially straightline bottom edges. The vanes 1 are spaced in a second direction, orthogonal to the said first direction and are shown formed in arcuate fashion, curving, in vertical section, in a plane orthogonal to the horizontal plane of the 3,127,821 Patented Apr. 7, 1964 ICC top of the grating, defined by the rst and second directions, downward at both forward and rearward surfaces thereof from their upper preferably rounded free edges 3. The tangent to the cuve at the upper end 3 makes an acute angle 0, say 10 to l5 degrees, more or less, with the horizontal plane, indicated by the arrow V; the angle 0 approaching the actual entry angle of thefluid stream. This presents little disturbing effect to the flowing fluid. The fluid flow is thus smoothly and arcuately guided in the space 4 between adjacent vanes 1 from the horizontal direction V to the downward orthogonal vertical direction into the catch basin or the like there-below, not shown.

From a pure hydraulic point of view, the ow passage area 4 should decrease from the free edges 3 down to the bottom edges 7 of the vanes 1 in order to conform with the acceleration of fluid flow under the influence of gravity, and thereby avoid turbulence and losses. If this is done, however, the grating can easily become clogged with debris, as will later be made evident. It has been found preferable, however, to taper the vanes 1 so that the bottom edges thereof are of somewhat greater thickness than the upper free edges 3. Not only is a substantially free-falling parabolic flow curve thereby approximated, but, the flow passage area D normal to the intial @-ilow direction of fluid flow, between the upper free edge 3 of a vane and the backside of the forward adjacent vane 1, will be less than the ow area (shown as H in FIG. 2) presented to the substantially vertically-directed iiow between the bottom edges 7 of the vanes 1. The vanes 1, therefore, increase in thickness from top to bottom and the ow area therebetween ranges from D to a slightly larger value H. Debris and particles that succeed in passing between the upper edges 3 can thus continue through the grating. Further to aid in providing 'the required area and gravity head for fluid ilow between all portions of the vanes 1, the top edges of the side members 2 follow the curved vanes at 2; and, at 2', diverge, preferably concaveiy, from the free edges 3 of the corresponding vanes 1, downward to meet an intermediate point P of the next adjacent vane 1. The tapered vane construction, furthermore, enables ready removal of the cast grating from the sand mold, and, in addition, by virtue of the thicker base regions 7, takes advantage of the greater strength of cast iron in compression than in. tension. The side members 2, moveover, may also be slightly tapered from the `bottom edge upward for easy removal from the mold.

The overlapping or almost overlapping arcuate construction, moreover, obviates the necessity for longitudinal grating bars orthogonal to the transverse vanes and parallel to the direction of flow, that have been heretofore employed in some gratings to protect the pedestrian or vehicle.

A comparison of the experimental results obtainable wit-h the `grating of FIGS. l -and 2 with those obtainable with a convention-al present-day catch-basin grating compris/ing horizontally disposed bars having flat planar top sur-faces Iand Iof substantially rect-angular cross-section, though slightly downwardly converging, demonstrates the tremendous improvement of the present invention. For an `approach velocity of about 8 -to l0 feet per second and a water ilow of 'about 3 cubic `feet per second, las `an illustration, only about fifty percent of the incident water drops through the grating into the catch basin; the remainder spashing on, las before-described. Well over ninety percent of the incident water, on the other hand, passes through the grating of FIGS. l and 2, under the same conditions, the water entering with comparatively slight change of llow direction at angle 0, and leaving the grating in `substantially a vertical direction, with the greatest Vof velocity Voff the iiuid at successive vanes becomes successively larger; so that the successive vanes should have lesser amounts of curvature, with the angle of each successive vane correspondingly approaching closer to the vertical. In order to use the water-ow energy to optimum advantage, it has been determined that the angle should have the following approximate relationship:

where L is the dimension shown in FIG. 2 -for the second vane, namely, the distance to a vane from the right-hand or forward ed-ge of the grating, V1 is the fluid approach velocity and qlq is the angle of attack of the iluid at which the vane functions without separating the tlow or creating any turbulence at the back side or the vane-usually about For the case of a 10 foot-per-second velocity V1, and 1an `initial distance L of about 4 inches, the successively increasing values of qb indicated in FIG. 3 may be employed, ranging from about to about 40. For an approach velocity half as great, angles 05 of from about 21 to about 617 may be used. The vanes 1 of FIG. 3 are, for purposes of illustrating the versatility of the invention, shown of slightly different divergingly tapered configuration than those of FIG. 2, in which the lower portions of the vanes are more abruptly vertically directed.

'Ilhough a cast structure is `obviously preferred, the -grating may also be fabricated from separate parts. Further modiiications will also occur to those skilled in the art, and -all such .are considered to fall within the spirit and scope of the invention las deined in the appended claims.

What is claimed is:

1. For use in directing owing ground water or the like to a catch basin or the like, a grating comprising a plurality of vanes extending longitudinally along a rst, generally horizontal direction and spaced from one another in a row along a second, generally horizontal direction substantially orthogonal to said iirst direction, the iirst and second directions deiining a iirst plane, each vane having a cross-section in a second, generally vertical plane substantially orthogonal to said rst plane, that is curved, with the v-ane increasing in thickness from the top toward the bottom, each vane having la concave forward surface and a :convex rearward surface, the rearward surface of each vane intersecting said first plane at an acute angle at the top of the vane and being substantially orthogonal to said tirst plane at the bottom of the vane, the space between adjacent vanes normal to the direction of ilow therebetween increasing along the direction of ilow from the top toward the bottom of said vanes.

2. The grating of claim 1, said surfaces being substantially parabolic.

3. The lgrating of claim l, said acute angle for each vane being progressively greater from the forward-most vane to the rearwardnlost vane.

4. The grating o-f .claim 1, said vanes being supported at their opposite ends by substantially parallel plates.

5. rIhe `grating of claim 4, said plates having generally horizontal bottom edges and having serrated top edges following, in part, the convex curvature of said rearward surfaces lof t-he vanes and, in part, concave curvature between said vanes.

6. For use in directing flowing ground water or the like to a catch basin or the like, a grating comprising a plurality of vanes extending longitudinally along a lirst, generally horizontal direction and spaced trom one another in a row along a second, generally horizontal direction substantially orthogonal to said yfirst direction, the iirst and second directions defining a lirst plane, each vane having 'a crossasection in a second, lgenerally vertical plane substantially orthogonal to said rst plane, that is curved, each vane having la concave forward surface and a convex rearward surface, the rearward surface of each vane intersecting said rst plane at an acute angle at the top of the vane, said acute angle for each vane being progressively greater from the Vforward-most vane to the rearwardmost vane and being given substantially by the equation:

where L is the distance between the top of the vane and the yforward edge of the grating, V1 is the approach velocity of the liquid flow and gbl is an yangle of the order of substantially 10.

7. The grating of claim 6, said angles ranging from substantially 15 to substantially 40.

8. The grating of claim 6, said angles ranging vfrom substantially 21 to substantially 67.

References Cited in the file of this patent UNITED STATES PATENTS 408,235 Haskell i Aug. 6, 1889 2,158,413 Feinberg May 16, 1939 2,220,833 Young Nov. 5, 1940 2,303,812 Barber Dec. 1, 1942 FOREIGN PATENTS 24,397 Great Britain Oct. 23, 1909

Claims (1)

1. FOR USE IN DIRECTING FLOWING GROUND WATER OR THE LIKE TO A CATCH BASIN OR THE LIKE, A GRATING COMPRISING A PLURALITY OF VANES EXTENDING LONGITUDINALLY ALONG A FIRST, GENERALLY HORIZONTAL DIRECTION AND SPACED FROM ONE ANOTHER IN A ROW ALONG A SECOND, GENERALLY HORIZONTAL DIRECTION SUBSTANTIALLY ORTHOGONAL TO SAID FIRST DIRECTION, THE FIRST AND SECOND DIRECTIONS DEFINING A FIRST PLANE, EACH VANE HAVING A CROSS-SECTION IN A SECOND, GENERALLY VERTICAL PLANE SUBSTANTIALLY ORTHOGONAL TO SAID FIRST PLANE, THAT IS CURVED, WITH THE VANE INCREASING IN THICKNESS FROM THE TOP TOWARD THE BOTTOM, EACH VANE HAVING A CONCAVE FORWARD SURFACE AND A CONVEX REARWARD SURFACE, THE REARWARD SURFACE OF EACH VANE INTERSECTING SAID FIRST PLANE AT AN ACUTE ANGLE AT THE TOP OF THE VANE AND BEING SUBSTANTIALLY ORTHOGONAL TO

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