US2966717A

US2966717A - Apparatus for casting concrete elements

Info

Publication number: US2966717A
Application number: US611119A
Authority: US
Inventors: Wilford C Fuller; Oliver Crawford Percy
Original assignee: NORTHERN VIRGINIA CONSTRUCTION
Current assignee: NORTHERN VIRGINIA CONSTRUCTION; NORTHERN VIRGINIA CONSTRUCTION COMPANY Inc
Priority date: 1956-09-21
Filing date: 1956-09-21
Publication date: 1961-01-03
Anticipated expiration: 1978-01-03

Description

Jan. 3, 1961 W. c. FULLER EI'AL 2,966,717

APPARATUS FOR CASTING CONCRETE ELEMENTS Filed Sept. 21, 1956 WILFORD C. FULLER C. PERCY OLIVER ATTORNEY United States Patent APPARATUS FOR CASTING CONCRETE ELEMENTS Wilford C. Fuller, Silver Spring, Md., and Crawford Percy Oliver, Arlington, Va., assignors, by mesne assignments, to Northern Virginia Construction Company, Incorporated, Alexandria, Va., a corporation of Virginia Filed Sept. 21, 1956, Ser. No. 611,119

2 Claims. (Cl. 25-121) This invention relates to a device for casting lightweight ,prestre'ssed concrete beams to be used in making a decking for a bridge or afloor for a building.

An object of this invention is to provide a device for producing a series of accurate precast prestressed concrete beam-like units which will accurately fit together side by side to form a solid deckfor a bridge structure (or the floor of a building). This .is accomplished by providing direct contact areas between the units at spaced diaphragms and at 'end blocks as shown in my copending application Serial No. 611,121, new Patent No. 2,885,882, in which the beam-like elements are shown as being channelshaped.

A further object. of the inventon is to provide a mould in which such a beam, or similar element, may be cast and in which the accuracy of thedimensions of .such element may be heldto very close tolerances.

A .yet further object of the invention is to provide a casting bed for the-casting ofaccurately dimensioned concrete elements.

Other and further objectsandadvantages of the present invention will appearfrom the following'description taken with the accompanying drawingin which like reference characters designatelike parts in the several views and in which:

Fig. 1 is a fragmentary perspective view of the casting bed showing a mould in p'lacere'ady for the insertion of the reinforcements and showing =a-mould with the reinforcementsstressed and the concretepoured.

As-seen in Fig. 1, the casting bed may bemade of concrete and comprises a base :and at least two abutments or curbs 11. If a large number of elements are to'be made it would, of coursegbe ecouomicalvto provide more curbs so that several elements could be made simultaneously.

The material of the base and curbs is preferably of concrete but is not critical other than to provide adequate strength and rigidity.

Leveling bolts 12 are screwed into inserts in the base and are adjusted with a precision leveling instrument to a true elevation. This can, of course, be done to a very high degree of accuracy.

Slate slabs 13, which are obtained under a tolerance specification of plus or minus inch both as to planeness of surface and thickness are placed on the leveling bolts 12 so that each leveling bolt bears on the slate. It will be seen, then, that the bed on which the concrete element is to be cast is prepared to an accuracy of plus or minus inch or better. The back of the channelshaped beam-like element is cast against this bed surface to give the degree of accuracy required to assure accurate face to face contact between elements when assembled.

The next important consideration is the faces of the beam-like elements that will be in contact with the back of the adjacent beam. These surfaces too must be held within a small tolerance. To accomplish this, the side and are, at all points, the same distance apart.

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:forms are made with :faces 14 of plywood or other vsuitable material and .angle iron tops 15 and bottoms 16. These elements are bolted together so that the top and bottom angles are straight lines, parallel to each other These side forms may be made in short sections for retention of shape and for-ease of handling.

The beam-like element, is of channel shape but is formed with end blocks filling the space between the flanges and web at the ends of the element and with one 'or more diaphragm blocks similar to the end blocks spaced along the length of the channel. These diaphragm blocks and end blocks are formed by provision of a core 17 between the side forms so that the hollow portions of the channel between the flanges and the diaphragm blocks and end blocks are left in casting the element. These cores may conveniently be rectangular ,boxes of plywood or other flat rigid material with angle iron or other bracing in the inside corners.

In the inner surfaces of cores 17 are angle iron clips .18 flush with the top edge of the core.

Cores .17 are supported by hangers 19 of angle iron resting on the side forms. These hangers are secured to the cores and side forms by means of a quick-release clamping device not shown).

The side forms 14 are held in proper position by means of adjustable hooks 25. One end of the hook.en gages a hole through .a continuous angle iron .26 fastened to concrete curb .11 while the other end engages a hole in the clip angle 27 which is secured'to the side form 14. Once 'theseihooksare adjusted for the correct side form position, the side forms are either removed from or replaced on the slat by disengaging the hooks from the clip angle .27 or by the reverse process. For the sake of-rigidity these hooks ,may be placed at angles to the curb and to -the. mold and should not beparallel.

-At.each diaphragm and end block .two sleeve elements .must be cast into the concrete to form holes completely :through the-beam. When.the beams (or units) are placed .in-the final; position ,to form thefinished deck, these holes .must be in 'alignmentso that the lateral post-tensioning (cables described, in the copending application, .can be threaded from -.one ,side of the deck to the other.

Asthe beam .is cast on .its side these sleeves 28 are in .verticalposition at the time of casting. They mustbe held in a true ;.-v,ertical position. This .is accomplished by .;means -of a sleeve holding device which is easily removable. The leg of the sleeve holder 29 is slipped through the sleeve 28. This combination is then placed in casting position by dropping the other sleeve-holder leg 29 which must be parallel with leg 29, through a hole in bracket 32 mounted on upper angle iron 26. A similar bracket is fastened to the bottom curb angle 26 and the lower end of the sleeve-holder leg 2? goes through a hole in the bottom bracket. These two holes are set in a true vertical position which will in turn maintain the leg 29 in its true vertical position. It can be seen that after the concrete is cast around the sleeve, the sleeve holder can be picked up, leaving the sleeve 28 in the concrete.

Beam ends are formed by inserting bulkheads 35 between the side forms. These bulkheads 35 are provided with holes 36 to accommodate the passage of prestressing reinforcing wires to reach to and through stressing plates 37.

The prestressing steel is stressed by means of equipment as shown in the left-hand casting bed. One type of prestressing steel that may be used is a high tensile strength seven-wire strand. Use of such strand is described herein. Individual strands are placed through holes 36 in bulkheads 35, through corresponding holes in stressing plates 37 and suitably anchored at 38. The number of strands and the pattern in which they are arranged is in accordance with individual design. The stressing plate 37 is duplicated at the opposite end of the casting beds. Each individual strand is then stressed to a predetermined tension by any convenient means. The hydraulic rams 39 are activated, thereby forcing jacking head 40 outwardly. The stressing plate 37 follows this outward movement due to the connecting bolts 41 thereby stressing all the strands simultaneously and equally. The resulting pressure at the hydraulic ram bases is transferred to the concrete casting bed curbs 11 through the bucking head 42. After desired tension is achieved by this method the hydraulic rams may be replaced by steel struts so that the hydraulic rams may be used elsewhere. In order that the stressing plate 37 may have absolute rigidity, a plurality of strengthening webs 37 are secured ot the back side of the stressing plate and holes are provided around the margin at the edges in order to provide the passages for the prestressing steel which pass through these holes and are anchored by means 38. Means 38 may be any conventional anchoring means.

Lifting bolts may be placed in two of the diaphragms during casting to facilitate lifting the cured beam from the casting bed.

In using this device it is of course necessary first to set up the casting bed slates 13 and to erect on these casting slates the side forms 14 which are placed into position by books 25 and on which the core boxes 17 are supported and secured by angle bars 19, accurately located by pins and secured in place by clips. Sleeves 28 are secured in place. Prestressing steel is threaded through apertures 36 in bulkheads 35 and through holes in stressing plates 37. Each strand is stressed to a predetermined tension in any conventional manner, and anchored by any convenient anchoring means 38. Hydraulic rams 39 are then actuated to simultaneously stress all of the prestressing steel strands to the desired degree and the concrete is poured in the mold around the prestressed strands and around the sleeves 28 and is brought up level with the top edges of mold sides 14, core box 17, and bulkhead 35. The ends of core boxes 17 and bulkheads 35 may be slightly higher than the sides of the core box and the side forms 14 in order that the surfaces at the end blocks and at the diaphragms -may extend slightly beyond the edges of the flanges in the finished beam element for reasons explained in the copending application referred to above.

The above description is of a preferred form and other exemplifications of the invention and of the several features of the invention may be used in other combinations, and changes and modifications in design, structure and details may be made within the scope of the appended claims without departing from the spirit of this invention.

What is claimed is:

1. In a molding device for molding concrete elements, such as beams or the like, of the type in which vertical mold elements having accurately formed top and bottom edges are removably supported on a bed; a bed substantially longer than the elements to be cast, said bed being formed with a bottom portion and two parallel upstanding curbs aligned with said bottom portion extending the length of the bed, whereby stressing means abutting the ends of said curbs may be used to prestress longitudinal reinforcements to be cast into a beam, leveling bolts mounted for vertical adjustment with respect to said bottom portion, and an accurate surface comprising at least one sheet of slate supported by said leveling bolts.

2. In a molding device for molding concrete elements, such as beams or the like, of the type in which vertical mold elements having accurately formed top and bottom edges are removably supported on a bed; a bed substantially longer than the elements to be cast, said bed being formed with a bottom portion, leveling bolts mounted for vertical adjustment with respect to said bottom portion, and an accurate bed surface comprising at least one sheet of slate supported by said leveling bolts.

References Cited in the file of this patent UNITED STATES PATENTS 761,255 Rowell et al May 31, 1904 832,594 Collier Oct. 9, 1906 883,439 Wittbold Mar. 31, 1908 1,050,946 Jensen Jan. 21, 1913 1,457,991 Moore June 5, 1923 2,153,741 Cobi Apr. 11, 1939 2,306,107 Henderson Dec. 22, 1942 2,315,634 McCall Apr. 6, 1943 2,495,100 Henderson Jan. 17, 1950 2,510,810 Furst June 6, 1950 FOREIGN PATENTS 151,075 Australia Apr. 24, 1953 379,316 France Sept. 5, 1907 649,035 Great Britain June 17, 1951 712,892 Great Britain Aug. 4, 1954 711,203 Great Britain June 30, 1954 749,124 Great Britain May 16, 19 56