Sectional Forms For Concrete

Abstract

A sectional form or mold for concrete or like materials is constructed to permit easy detachment of the sections and removal of the form when the material has cured or hardened. The sections, which may be made of plastic, are united by a unique joint comprising interlocking male and female members, retained in interlocked relation by a rubber-like wedge or gasket in the form of an elongated strip, driven between the joint members. The wedge can easily be withdrawn to permit disengagement of the joint and removal of the form sections from the hardened material. The undamaged sections may then be reused.

Description

SUMMARY OF THE INVENTION

The present invention comprises a novel form into which concrete and like material can be poured and allowed to harden or cure. The form is made in sections secured together by interlocking joints, so that the sections can be disassembled and the form readily removed and reused.

It has been common practice heretofore to pour concrete into forms of fibrous material, such as multi-ply paper tubes, which are stripped from the hardened concrete. Such forms are destroyed in the stripping process and are not reusable. Furthermore when reinforcement such as metal bars or screen is used in a concrete column, beam, or other structural form of substantial length, and a continuous form is used, the form must be initially sleeved over the reinforcement. Often damage to the reinforcement, the form, or both results as the form is being positioned.

This invention avoids these and other problems by constructing the form in sections which are applied and removed laterally without damage to the sections or to any pre-positioned reinforcing elements.

The forms may be made of plastic, i.e. polymeric resins; I prefer to use a thermoplastic resin which may be extruded in sheet form. The joints between the sections may be integrally formed with the sections, or may be separately formed and secured to the sections by rivetting or bonding.

The joints between adjacent sections of the form preferably consist of interlocking male and female parts, either of plastic or extrudable metal such as aluminum, and are retained in interlocked relation by a rubber-like wedge driven between the parts to provide tightly engaged butt-joints at the inner faces of the interlocked sections. Wedges of synthetic elastomer are especially suitable.

Further objects and advantages of the invention will be evident from the following detailed description when read in conjunction with the accompanying drawing illustrative of the invention.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a view in perspective of a sectional form embodying the invention;

FIG. 2 is a transverse section through the joint between adjacent sections, showing the joint elements in interlocked relation;

FIG. 3 is a view corresponding to FIG. 2, but illustrating a modification in which the joint elements are formed separately from and secured to the respective form sections; and

FIG. 4 is an end elevation of a form of rectangular shape.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in detail, FIG. 1 shows a form 10 of generally oval shape and consisting of two sections 11 and 12, interlocked by joints 15. The sections are preferably identical, each section having a male joint element at one side and a female joint element at the other side to reduce manufacturing cost and inventory. The assembled form illustrated in FIG. 1 is open at both ends, the lower end seating on the base or support on which the concrete column is to be erected. The inner face of each section of the form is provided with a coating 16 of an anti-adhesive material to facilitate separation of the form from the cured concrete. The material sold under the trade name "Teflon" (polytetrafluoroethylene) is eminently suited for the purpose, being highly resistant to adhesion with the concrete and moisture resistant as well. A thin film normally suffices; the thickness of the coating 16 is exaggerated in the drawing.

The form sections are preferably made of synthetic plastic, such as a thermoplastic resin capable of extrusion in sheet form. When an extruded sheet is produced, the die may be so shaped as to form integrally with the sheet the interlocking members at each side. The sheet may then be further processed to give the assembled form the desired contour, i.e. the oval shape of FIG. 1, a circular or polygonal shape, or the rectangular shape of FIG. 4. Polystyrene, an expanded form of which has been used for load bearing walls in houses, is suitable for use in the fabrication of the sectional forms of the present invention, but many other plastic materials possess the necessary mechanical strength and are as readily fabricated, either by extrusion or other processing methods.

A preferred form of joint 15 is shown in FIG. 2. A female member on one section comprises an outer lip 20 and an inner protuberance 21, shaped as shown to provide a mouth in which is received a projection 24 on the adjacent section, constituting the male member of the joint. The rounded and enlarged head at the outer end of projection 24 passes freely into the mouth of the female member and is retained therein by wedge 25, which is driven into the space between lip 20 and projection 24 by a hammer or other suitable tool. When so driven, the wedge 25 forces the bulbous head of projection 24 into engagement with the sloping wall of protuberance 21 to draw the sections together into tight abutted relation, and offering high resistance to separation of the sections when the form is poured.

The wedge is preferably formed of an elastomer such as the synthetic rubber-like materials made by polymerization of chloroprene, sold under the name "Neoprene." Wedges made of such materials can readily be driven into position, serve to lock the joint effectively and to seal against leakage, and can readily be removed with pliers to disassemble the form.

In FIG. 3 is shown a joint 30 fabricated separately from the form sections 11 and 12 and secured thereto by rivets 31. The male and female members of joint 30 may be formed as shown in FIG. 2 and need not be again described. In lieu of rivetting, other methods such as bonding may be used to secure the joint members to the form sections. Other materials may be used; for instance, the joint members may be formed by extruding aluminum, and the form sections may be of materials other than plastic when provided with a suitable anti-adhesive coating 16 to ensure a smooth finish and facilitate removal of the form from the cured concrete. However, plastic form sections and joint members are preferred, whether made separately or bonded together.

In FIG. 4 is shown a rectangular form embodying the invention, the joints 35 being located adjacent corners of the rectangle to facilitate separation from the cured material.

Whatever the contour of the assembled form, more than two sections may be employed in one from if desired, but unless the column to be cast is unusually large, two sections suffice. In the event the column is of excessive height (or of excessive length in the case of horizontally cast beams or slabs), or to facilitate handling and transportation, two or more forms, each constructed as shown, may be stacked. In that event, suitable means, such as interengaging peripheral flanges or pin-and-socket devices are provided on adjacent ends of the stacked sections to prevent lateral relative displacement.

When the structure to be cast is large, imposing a heavy load on the form, the slope of the engaged surfaces of projection 24 and protuberance 21 should be more nearly radial to offer increased resistance to the peripheral force tending to release the joint. Also, the wedge 25 may be stiffened by suitable reinforcement to increase its resistance to compression and thus enabling the joint to resist the increased loading of the form.

It will be appreciated that plastic sectional forms afford many advantages over the conventional laminated paper forms, in addition to reuse. Thus, finishing of cast columns is minimized, for the form surface is smooth and there is little flash where the sections abut. Also, designs can be produced on the concrete by appropriate molding or processing of the inner surfaces of the forms.

Other advantages and uses of the invention will be apparent to those skilled in the art to which the invention relates.

Claims

What is claimed is:

1. A sectional form for concrete and like hardenable material, comprising at least two form sections capable of being interlocked to provide a continuous form,

each section having at each side thereof a joint member extending longitudinally of the section,

the joint member at one side of one section being a female member and the coacting joint member at the adjacent side of the contiguous section being a male member freely received within and removable from the said female member by relative lateral displacement of said coacting joint members,

and a removable elastic wedge member driven laterally between assembled coacting joint members to apply radial pressure therebetween to effect interlocking and sealing of said coacting joint members,

whereby said form may be assembled and removed laterally of the element to be formed and may be reused.

2. A sectional form as claimed in claim 1 in which the form sections are composed of a polymeric resin.

3. A sectional form as claimed in claim 1 in which the form sections are composed of a thermoplastic resin extruded in sheet form.

4. A sectional form as claimed in claim 3 in which the thermoplastic resin in polystyrene.

5. A sectional form as claimed in claim 1 in which said coacting joint members are formed to provide abutting sloping walls resisting disengagement of said joint members when said wedge member is driven home.

6. A sectional form as claimed in claim 1 in which said wedge is composed of a synthetic elastomer.

7. A sectional form as claimed in claim 6 in which said elastomer is a neoprene.

8. A sectional form as claimed in claim 1, in which each section is provided on its inner face with a coating of an anti-adhesive composition.

9. A sectional form as claimed in claim 8, in which said anti-adhesive composition is polytetrafluoroethylene.

10. A sectional form as claimed in claim 1 in which said form sections and said joints are integrally formed.

11. A sectional form as claimed in claim 3 in which said joints are formed integrally with said sections by extrusion.