US2689999A - Apparatus for manufacturing prestressed concrete structural units - Google Patents

Description

p 28, 1954 R. P. PETERSEN 2,689,999

APPARATUS FOR MANUFACTURING PRESTRESSED CONCRETE STRUCTURAL UNITS Filed May 26, 1950 2 Sheets-Sheet 1 p 28, 1954 R. P. PETERSEN 2,539,999

APPARATUS FOR MANUFACTURING PRESTRESSED CONCRETE STRUCTURAL UNITS Filed May 26, 1950 2 Sheets-Sheet 2 '1 P I 1:. 5 I

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INVENTOR.

Faber! PPe/ery-ew Patented Sept. 28, 1954 UNITED STATES PATENT OFFICE APPARATUS FOR MANUFACTURING PRESTRESSED CONCRETE STRUC- TURAL UNITS Vania Application May 26, 1950, Serial No. 164,341

2 Claims.

The present invention relates to certain novel apparatus which is designed primarily for the manufacture of pre-stressed concrete structural units.

In the co-pending application of Robert P.

Petersen, Serial Number 164,342, filed May 26, 1950, and entitled Prestressed Concrete Structural Unit and Method of Producing Same there is illustrated and described a prestressed concrete structural unit together with a method of producing such a structural unit. The present invention has in view as its foremost objective the provision of apparatus for carrying out this method.

In a prestressed concrete structural unit of the type provided by the invention of said co-pend ing application, stressing elements in the form of wires are placed under tension prior to thepouring of the concrete. The concrete is then cast about the stressing wires and the tension on the latter maintained until the concrete is fully set. The setting of the concrete creates a bond between the tension wires and concrete throughout their entire length, so that when the tension on the wires is relieved at their free extremities, the tension still remains and is effective throughout the main body portion of the wires which are embedded in the concrete.

An important object of the present invention is to provide, in a concrete form, a bed which includes end elements and which end elements are provided with means for applying a predetermined degree of tension to wire elements which are supported thereby. This means preferably takes the form of one or more jacks which are associated with one of the end elements.

Still another object of the invention is to provide, in a concrete form, a bed having end elements which are peculiarly constructed and designed to have two layers of tension wires supported thereby in spaced relation above the inner surface of the bed. Each of these end elements is formed with a row of openings through which tension wires are adapted to be threaded, and a row of notches along its upper edge with each notch being adapted to receive a tension wire.

Another object of the invention is to provide in a concrete form of the type indicated, a bed which includes a pair of end members at opposite ends, and which members are adapted to receive and support two layers of tension wires. One end member i provided with means for operatively supporting a jack which is so assembled relative to the end member that a predetermined preliminary tension may be applied to a pair of tension wires held thereby, after which the jack may be operated to achieve a predetermined degree of elongation in the wires and thereby set up a predetermined tension therein.

Various other more detailed objects and advantages of the invention, such as arise in connection with carrying out the above noted ideas in a practical embodiment, will in part become apparent and in part be hereinafter stated as the description of the invention proceeds.

The invention therefore comprises apparatus for manufacturing prestressed concrete structural units, and which apparatus consists essentially of a concrete form having a bed provided with end members which are adapted to receiwe in a supported position a plurality of tension wires. A plurality of jacks are carried by one of the end members for placing these wires under a predetermined degree of tension.

For a full and more complete understanding of the invention, reference may be had to the following description and accompanying drawings, wherein:

Figure 1 is a top plan view of the bed of the concrete form which is designed in accordance with the precepts of this invention;

Figure 2 is a view in side elevation of the bed shown in Figure 1;

Figure 3 is an end view, partially in elevation and partially in section, of the bed, with the side walls of the form shown in broken outline;

Figure 4 is a side view of the bed'with parts broken away, showing a tension wire applied thereto; and

Figure 5 is a detailed perspective of one of the jack members.

Referring now to the drawings wherein like characters of reference denote corresponding parts, the bed of the concrete form is referred to in its entirety by the reference character B.

The bed B is intended to support a pair of removable side walls which are depicted in broken outline at It and H, and also a pair of end walls for the form, not illustrated. The present invention is not particularly concerned with the side walls Ill and It, nor with the end walls, as these are simply now well-known form elements. The novel features of the form which are provided by the present invention are embodied in the bed B. Y

The bed B includes a bottom made up of bottom end plates I2, side channel members I3, intermediate I-beams I 4, with vacuum holes about 8" O. C. in the upper flange engaging the angle iron noted later, and concrete [5 which is cast about the reinforcing beams [4 between the side channel members l3. The bed B also includes a pair of end members [6 and [1 which rest on the bottom end plates l2 in abutting engagement with the end faces of the concrete l5. This concrete [5 presents a bottom surface at I8 which is adapted to rest on any appropriate support such as a factory floor, and an upper surface H) which constitutes the working surface of the bed, or rather, the bottom surface of the form.

A pair of angle irons such as represented at as are welded to I-beam 14 in equidistantly spaced relation with respect to and on opposite sides of a short tube 2| which is disposed at a lower level than the angles 20. This tube 2| extends through a hole in the end member l6 as shown in Figures 1, 2 and 4 and projects beyond this end member.

A pair of inclined pipes 22 connect the angles 20 with the inner end of the tube 21. These elements 20, 2! and 22 are imbedded in the concrete l5 and serve to provide a channel for extracting of water from the concrete by vacuum.

Extending outwardly from the side channel members I3 are screw bolts 23 which constitute a means for securing the side walls It in position on the bed B. The headed portion of the bolts are imbedded in the concrete, as represented by the broken lines in Figure 3.

The end member 16 of the bed B has a portion which extends above the top working surface 19 of the bed. This projecting portion is formed with a plurality of openings 24 that are arranged in a row spaced above and parallel to the surface Is. The upper edge of the end member I6 is formed with a series of notches 25, with each notch 25 being positioned above one of the openings 24.

The end member l'l also has a portion projecting above the working surface [9, and this projecting portion is also formed with a row of openings 24 and notches 25 in its upper free edge. The relation of the openings '24 and notches 25 in the end member I! is exactly the same as that in the end member l6.

At this point it is well to note that Figures 1 and 3 depict a certain arrangement or grouping of the openings 24 and notches 25. It is these openings and notches which determine the position of the tension wires in the finished structural unit. Obviously, the particular arrangement illustrated may be varied without parting from the spirit of the invention, as it is not intended as a limitation thereon.

Mounted on the outer face of the end member I! is a bracket 26 which supports a plurality of jacks, each of which is referred to in its entirety by the reference character J. Each jack J includes a block 2'! that is slidably positioned on the bracket 26 and a pair of screw stems 28 which are threaded through openings 29 in the block 21. Each of these screw stems 28 is provided with a tool engaging shank 38 at its outer free end, while its inner end is formed as a rounded nose 3! which is received in and bears against a complemental depression formed in the outer face of the end member IT.

The block 21 is formed with a plurality of openings 32 which are intended to align with the openings 24 of the end member H. The upper edge of block 21 is also formed with a plurality of recesses 33 which are in alignment with the notches 25 in the end member [1.

Secured to the outer face of the end member I6, such as by screws shown at 34 in Figure 4, is

a wire anchor member 35 which extends along the entire outer face of the end member H; between the openings 24 and notches 25.

Figure 4 illustrates how the above-described apparatus is used. A tension Wire which is represented at 36 with anchorage 38 attached to one end is threaded through an opening 32 in the jack block '21 and then through an opening 22 in the end member 11. It is then extended across the bed B above the working surface I!) thereof and threaded through the opening 2 4 in the end member Hi. It is then passed around the anchor member 35 in the manner depicted in Figure 4 and returned back across the bed B in spaced relation above the lower ply thereof. As it is so returned it is received in the notches 25 in the end members It and l! and also in one of the recesses 33 of the jack block 21.

The two plies of the wire 38 are now placed under a preliminary tension of a predetermined degree, say for example five hundred pounds, after which a second end anchorage, such as shown at 37, is applied thereto. These anchorages 3'! securely grip the end portions of the wire 36 and bear against the outer face of the jack block 21. 1

At this point it is well to note that the tension wires 36 are multistranded, helically-twisted wires which are susceptible of being elongated to set up tension therein.

After a plurality of the wires 35 have been positioned in the manner above described and all of them placed under the same preliminary tension, an appropriate tool such as a wrench is applied to the end portions 30 of the screw stems 28 and rotated to operate jacks J. These jacks are operated so as to move the jack blocks 21 a predetermined distance relative to the end member I1. Thus each wire 36 is elongated to a predetermined degree. This elongation also is accompanied by a reduction in the cross-sectional area of the wire. Moreover, this elongation places each wire under a required predetermined tension.

Concrete is now poured into the form of the bed B and completely encompasses both plies of the wire 36. This concrete will enter the interstices and helical grooves of the wire 35 so that when it sets it will be thoroughly bonded to the wires.

After the concrete is thoroughly set the sides of the form are removed and the end portions of the wires 36 which project beyond the end members It and Il cut to permit the structural unit which has been formed to be stripped from the form. Even though the wires 36 are now relieved of the effects of the anchor 35 and jacks J they will still be under tension because of their being confined by the concrete and bonded thereto. Thus the concrete unit is placed under a compressive stress which materially enhances the structural characteristics thereof.

While a preferred specific embodiment of the invention is hereinbefore set forth, it is to be clearly understood that the invention is not to be limited to the exact construction, mechanisms and devices illustrated and described because various modifications of these details may be provided in putting the invention into practice within the purview of the appended claims.

What is claimed is:

1. In apparatus for manufacturing prestressed concrete structural units, a concrete form having a bed, said bed comprising a pair of bottom end plates, side channel members and reinforcing members extending between said end plates with a concrete body cast about said reinforcing members between said channels and presenting an inner working surface, a pair of end members positioned on said end plates and having portions extending above said working surface, each of said end members being formed With a series of openings spaced above said working surface with the upper edge of each end member being formed with a series of notches corresponding in number and position to said openings, a wire anchor on the outer face of one of said end members between said openings and notches, a bracket mounted on the outer face of the other of said end members, and a plurality of jacks operatively supported by said bracket, each of said jacks comprising a block that is slidably positioned on said bracket and which block is formed with openings in alignment with the openings in the end members and notches in its upper edge in alignment with the notches in the said end members, each of said blocks being formed with a pair of threaded openings and a screw stem in each of said threaded openings, each of said screw stems having a rounded nose engaging the adjacent end member and wrench-engaging means at its opposite end.

2. In apparatus for manufacturing prestressed concrete structural units, a bed having an upper working surface and end members extending above said working surface, each of said members being formed with a series of openings spaced above said working surface with the upper edge of each end member being formed with a series of notches corresponding in number and position to said openings, a wire anchor on the outer face of one of said members between said openings and notches, a bracket mounted on the outer face of the other of said members, and a plurality of jacks operatively supported by said bracket, each of said jacks comprising a block that is slidably positioned on said bracket and which block is formed with openings in alignment with the openings in the end members and notches in its upper edge in alignment with the notches in said end members, and screw means associated with each of said blocks for moving said block relative to the end member on which it is mounted.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 465,169 Eckley Dec. 15, 1891 791,041 Myers May 30, 1905 852,898 Owens et al. May 7, 1907 937,793 Haas Oct. 26, 1909 1,186,554 Crisenberry June 13, 1916 1,334,881 Bennett Mar. 23, 1920 2,075,239 Strange -1 Mar. 30, 1937 2,171,120 Bullard Aug. 20, 1939 2,397,728 Dowsett et a1. Apr. 2, 1946 2,408,149 Miller et a1 Sept. 24, 1946 2,511,761 Barber June 13, 1950 2,516,453 Dobell July 25, 1950 FOREIGN PATENTS Number Country Date 641,590 Germany Jan. 28, 1937

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