BACKGROUND OF THE INVENTION
1. Field of the Invention
Headwall construction for drainage pipe and the like; reinforced concrete construction. Prefabricated forms for concrete and the like.
2. Description of the Prior Art
The usual headwall construction involves the manual preparation of forms made from wood, plywood and other materials built at the location and stripped away after construction. The form is primarily temporary and may be removed after construction. There is a certain amount of expense involved for carpentry and other trades in the manual construction of forms. A lot of time is consumed in preparing and constructing the form and completing the work. The typical steps are as follows:
1. WOODEN FORMS ARE CONSTRUCTED AND ASSEMBLED AROUND THE PIPE END WHICH HAS NOT BEEN COVERED WITH EARTH. Pieces of heavy wooden planks and plywood sections are nailed together to form a concrete mold;
2. THE FORMS ARE SHORED-UP WITH TIMBERS, BOARDS AND STAKES WHICH HAVE BEEN DRIVEN INTO THE GROUND;
3. PAPER OR SIMILAR SOFT MATERIAL IS STUFFED AROUND THE PIPE AND THE WOODEN FORM TO PREVENT CONCRETE SEEPAGE AND LOSS. There is a pronounced gap in this area as the wooden forms cannot accurately be fitted within the time and skill permitted. Also, there is a tolerance and variation in pipe diameter due to normal allowances in pipe standards;
4. THE FORMS ARE GREASED TO FACILITATE REMOVAL;
5. DURING POURING THE WET CONCRETE NEEDS TO BE VIBRATED TO REMOVE AIR VOIDS;
6. AFTER THE POURED CONCRETE HAS BECOME HARD, THE WOOD FORMS HAVE TO BE REMOVED SINCE WOOD WILL DETERIORATE. State road departments require the forms to be removed;
7. THE SURFACE OF THE POURED CONCRETE SHOULD BE SMOOTHED AND RUBBED TO REMOVE IMPERFECTIONS LEFT AFTER FORM REMOVAL;
8. ONLY AFTER STEP "6." ABOVE CAN THE BACKFILLING BE DONE TO COVER-UP THE REMAINING EXPOSED DRAINAGE PIPE TO THE HEADWALL;
The above noted operations require workmen to attend and leave the work site three times and the use of semi-skilled labor is costly. Concrete finishing is also costly;
The present method and apparatus permits the forming of head walls and filling of earth to be coordinated in an improved and more efficient manner and sequence. In some instances this method can eliminate the steps 2, 3, 4, 5, 6 and 7 previously mentioned. In the present headwall construction there is no manual building or preparation of forms but rather two identical prefabricated half-shells or molded sections are placed back-to-back to form a hollow headwall form which is filled with concrete from openings in the top after the pipe is inserted through a hole in the middle.
SUMMARY OF THE INVENTION
The purpose of the present headwall form is to provide a simple, easy and less expensive way of forming a concrete headwall around the end of a drainage pipe and to facilitate the pouring of concrete by controlling, directing and confining wet concrete to a predetermined configuration and shape. Two identical concave, prefabricated half-shells or form sections are combined simply by fastening together leaving an open base in communication with the ground. This eliminates all of the manual construction of concrete forms and furthermore installation can be done by ordinary day laborers instead of carpenters.
Some of the advantages and features of this headwall form, which can be made by relatively thin plastic sheets, is as follows:
1. By utilizing thin plastic sheets or the like to construct the two sections or half-shells the complete form is made in an inexpensive manner and is very lightweight and can be handcarried to the site.
2. Rigidity is obtained by transforming a thin sheet into an intricate shape of ribs, channels, flanges and tubes to create stiffness so that the unit can support wet concrete pressure and other forces while maintaining the desired shape. No shoring is required. The position, placement and size of the ribs, channels, flanges or tubes may be predetermined so as to minimize deflection wherever not wanted. Molded flanges may be bonded together.
3. The walls of the form sections may be made thinner or thicker wherever desired and in the area of a center hole where the drainage is inserted the shell may be made thin or even frangible to provide deflections for two reasons:
a. to provide ease of inserting the drainage into the mold prior to the pouring of concrete.
b. to allow significant deflections during and after the concrete is poured to provide for interlocking and securing. If a thin membrane is used the fluid pressure of the wet concrete will force the thin membrane shell around the circumference of the drainage pipe. If openings are used, then the wet concrete will run through the openings into contact with the pipe. In either case the center opening will be formed to the shape of the pipe and after the concrete is hardened a secure interlocking fit will have been made. The concrete flow is even and complete without tapping or vibrating.
4. Installation is quick and easy and does not materially delay back filling of earth which may be done as soon as the concrete has set and without removing the present form which may be left in place without deterioration. The mold is smooth and no finish is required.
5. It is possible to accommodate many different sizes of pipe with the same half sections because of the expansion possible in the center opening.
6. The mold is easily installed and there are openings whereby reinforcing rods may be inserted or for other purposes.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a typical molded plastic shell which is one half of the completed form made from two of these shells.
FIG. 2 is a perspective view of two of the half shells placed back-to-back to make the completed form which is receiving concrete through the top.
FIG. 3 is a cross-sectional view taken substantially along lines 3--3 in FIG. 2.
FIG. 4 is a cross-sectional view taken substantially along lines 4--4 in FIG. 3.
FIG. 5 is a cross-sectional view taken substantially along lines 5--5 in FIG. 3.
FIG. 6 is a cross-sectional view taken substantially along lines 6--6 in FIG. 3.
FIG. 7 is a partial perspective view of a modified form of the interior of the center opening.
FIG. 8 is a bottom view of the completed form shown in FIG. 2 with a portion thereof broken away.
DESCRIPTION OF A PREFERRED EMBODIMENT
The completed form is made up of two concave sections each designated generally by reference numeral 10 and each of which may be manufactured from thin plastic sheets that are molded and stretched to a specific configuration to produce the shell together with various integral stiffening means such as flanges, bulges and channels at certain predetermined locations. Each section 10 may be manufactured from any plastic having sufficient strength from its inherent quality as well as rigidity from design configuration to resist loads imposed upon it from inside by freshly poured concrete. For example, the plastic may be of the type ABS, polyethylene, polystyrene, or polypropelene which can be molded into any intricate shape to produce the desired shell. The shell or half form 10 may be manufactured by the well known thermoforming process, commonly known as vacuum forming, by forming a plastic sheet into the shell 10 which in turn is attached back-to-back to another identical shell.
In the drawing, the completed form is made up of two prefab half-forms, also called shells or half-sections 10, placed back-to-back in the manner shown in FIG. 2 into a completed mold used as a form and designated generally by reference numeral 12. The completed headwall form 12 includes a center pipe opening 14 through which a typical concrete pipe 41 or corrugated metal pipe is inserted.
Each shell 10 comprises a concave vertical section designated generally by reference numeral 16 having end walls 17 and a concave base or horizontal section designated generally by reference numeral 18 with end walls 19 which are integrally formed as one complete unit. A flat peripheral flange 20 extends all around the margin or edge of the shell 10. Thus, the peripheral flange 20 on one shell 10 in FIG. 2 is placed against and super-imposed on an identical flange 20 on the other identical back-to-back section 10 creating a complete substantially hollow form 12 which is hollow inside until filled with concrete 26 from a pouring spout 29 or any other source. The concrete 26 is poured through a top wall 27 having openings 28 created by matching cut-out openings 30 on one shell 10 with the identical cut-out sections 30 on the other identical shell 10.
The base 18 is molded with a plurality of longitudinal cavities 34 which create concrete ribs 35 in the base after the concrete 26 is poured therein. The ribs 35 thereby formed provide strengthening means in a concrete base 36 which is formed inside of the base 18 and the bulges 34 provide the ribs 35 in the shell 18 in such a way as to strengthen the mold and prevent abnormal deformation during pouring and the like.
The two mold sections 10 are placed back-to-back as mentioned previously and in the manner seen in FIG. 2 are attached by means of straps 38 of plastic or other material attached across the bottom from flange 20 on one side to flange 20 on the other. Straps 38 may be plastic strips which are attached in place by solvents, plastic adhesive, plastic welding or any other suitable means such as ethylene dichloride, epoxy glue, stapling or otherwise. In one form of the invention shown in FIG. 1, the center opening 14 has a peripheral thin-wall construction 40 which bulges under the pressure from the poured concrete 26 and tightly squeezes around a concrete pipe 41 placed therein. After the two sections 10 are assembled, the pipe is inserted in the opening 14 and concrete 26 is poured in place.
In another form shown in FIG. 7, the wall 42 of the form is formed with a series of interrupted projecting flanges 44 separated from each other by slits and openings 46 which allow the concrete 26 to drain around the pipe inserted in the opening. The flanges 44 occupy a position almost perpendicular to the wall 42 and are pushed and displaced by the drainage pipe to practically a horizontal position. Flanges 44 displaced by a pipe help align, center and retain the form 12 in place until after the concrete is poured and set.
In the event reinforcing rods (not shown) should be placed within the completed mold 12 prior to pouring the concrete 26, supporting flanges can be made as an integral part of the mold by the contouring and shaping of the bottom straps 38 and sides of the mold 10 or by horizontal projections or plastic pins (not shown) inserted where needed inside the mold on which the rods when placed are held in proper position and alignment. Additional plastic straps 38 may be placed and attached to the base wherever desired to prevent pronounced spreading and distortion of the base dimension. Such straps 38 will also serve the function of reducing the upper force of the wet concrete on the mold which would cause the mold base to separate from contact with the ground.
It is worthwhile to note that the thickness of the walls of the shell 10 can be controlled and governed by the mold process whereby stretching and distortion can be predetermined either to permit it to take place if desired or to prevent it from taking place if not desired. For example, as mentioned previously the wall 40 may be made thin so that it will bulge and stretch under the weight of the concrete to tightly squeeze around the concrete pipe.
In addition to the above noted construction, bleed holes 54 may be placed through the shell 10 at critical locations to allow possible and trapped air to escape and to give positive indication that all voids are filled with concrete. The positive indication will be in the form of the appearance of concrete at the bleed holes 54.
The shell configuration 10 is such that the placement of the ribs 34, channels and other tubes wherever needed in conjunction with large corner radius and fillets will control the flow and direction of the concrete during pour. This tends to minimize air entrapment thereby precluding the necessity of tapping and packing the mold or vibrating the wet concrete. It also helps to provide free concrete casting.
Further strength in the mold may be obtained by having the depressions 60 formed in the vertical section 16 by tapered walls 62 leading to a flat apex 64 whereby apexes 64 on one section 10 abutts the apexes on the other matching section 10 as seen in FIG. 3. The apexes are bonded to each other as are other parts of the sections 16 that touch.
While I have shown and described a particular embodiment of this invention together with at least one suggested modified form this is by way of illustration of known preferred embodiments and does not constitute any sort of limitation since there are various changes, alterations, eliminations, deviations, additions, subtractions, combinings, removals and departures which may be made in the forms disclosed and discussed without departing from the scope of my invention as defined only by a proper interpretation of the appended claims.