Plastic article or earthenware shaping or treating: apparatus – Distinct means to feed – support or manipulate preform stock... – And means to apply stress to preform and uniting in stressed...
Patent
1985-11-27
1988-01-12
Hoag, Willard E.
Plastic article or earthenware shaping or treating: apparatus
Distinct means to feed, support or manipulate preform stock...
And means to apply stress to preform and uniting in stressed...
249 83, 425122, 425223, B29C 3914, B29C 4526
Patent
active
047188391
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of producing a concrete product prestressed in at least two directions, according to which method
at least one prestressing wire is mounted in a zigzag-like manner between sides of a casting bed to extend in two crossing directions for forming of a net,
the wires are subjected to prestressing, and
concrete is fed in said bed to form a prestressed concrete blank.
It is previously known to arrange the prestressing wires of a reinforcement on a casting bed so that said wires extend between the sides of the casting bed in at least two crossing directions obliquely with respect to the main directions of the casting bed, e.g. the length and the width thereof. By tensioning the wires, a prestressed, netlike reinforcement is provided in the casting bed. A concrete product prestressed in this way is advantageous if the concrete is required to be extremely firm and possess high non-cleaving properties in different directions of the product.
USSR Inventor's Certificate No. 139,968 discloses a single mould for producing a prestressed concrete product. A four-side mould with fixed sides is provided with supporting studs pivoted on said mould for a prestressing wire. The wire is passed around the supporting studs to extend in a zigzag-like manner between the opposite sides so that a netlike structure is obtained. After the concrete has hardened, rods attached to the supporting studs are heated electrically so that the supporting studs turn inwards and are released from the prestressed wire.
A disadvantage of such mode of reinforcing is the complicated structure of the mould, because each of the four sides of the mould must be provided with pivotable supporting studs. When the wire is passed around the supporting studs, it must be tensioned in four different directions, before the reinforcing net is completed. In addition, the electrical use of such mould requires certain special measures to be taken. The suggested mode of prestressing cannot be applied in continuous casting of an endless concrete blank in order to provide prestressing in two directions, because an endless casting bed comprises two sides only.
SE Patent Specification No. 113,712 discloses a conical mould for producing a prestressed concrete mast. The mould comprises a stationary end plate and a movable end plate, prestressing wires passed between the plates in a zigzag-like manner to form a sleeve-like reinforcing net. The wires are tensioned by displacing the movable end plate away from the stationary end plate.
A disadvantage of such mode of reinforcing is that it mainly provides prestressing in the longitudinal direction of the mould only, whereas no prestressing is provided in the transversal direction of the conical mould. The suggested mode of prestressing cannot, either, be used for continuous casting of an endless concrete blank, because the sides of the casting bed, which support the wires extending there between, must be stationary.
The object of the present invention is to provide a method which avoids the aforementioned disadvantages and which enables a prestressing wire to be mounted in position as well as tensioned in a simpler manner. This object is achieved by means of a method according to the invention, which is characterized in that said prestressing wire is passed crosswise between at least two opposite stationary sides of the casting bed and is tensioned from a third side of the casting bed in parallel with said two sides.
The invention is based on the idea that when the prestressing wire or wires are arranged to extend mutually crosswise between at least two sides of the casting bed, a netlike structure is obtained which provides prestressing in two, almost perpendicular directions when tensioned from a third side of the casting bed. Therefore, two stationary sides are enough in the casting bed for mounting of the prestressing wire and, nevertheless, prestressing is provided essentially both in the longitudinal and transversal direction of the finished concrete product. Consequently, also a continu
REFERENCES:
patent: 1457999 (1923-06-01), Pedersen
patent: 2569231 (1951-09-01), Danhof
patent: 2607099 (1952-08-01), Schroder et al.
patent: 2950517 (1960-08-01), Brickman
patent: 3283385 (1966-11-01), Oakden
patent: 3694118 (1972-09-01), Crowder
patent: 4069285 (1978-01-01), Morgan
patent: 4321024 (1982-03-01), Terraillon
Hoag Willard E.
Oy Partek Ab
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