US2378584A - Prestressing reinforcing device for concrete - Google Patents

Description

June 19, 1945. H. SCHORER PRESTRESSING REINFORCING DEVICE FOR CONCRETE Filed May 5, 1943 2 Sheets-Sheet l INVENTOR. HER/W /v SCHO/E'EE.

BY /1 4 W ATTO'RNEK June H. SCHORER ,37

PRESTRESSING REINFORCING DEVICE FOR CONCRETE Filed May 5, 1945 2 Sheets-Sheet 2 Ev fl 8a i -y INVENTOR. HERMAN JCHOEE/F.

BY MW Patented June 19, 1945 PRESTRESSING REINFORCING DEVICE FOR CONCRETE Herman Schorer, Valhalla, N. Y., assignor to Schorer Corporation, New York, N. Y., a corporation of New York I Application May 5, 1943, Serial No. 485,703

11 Claims.

This invention relates to a prestressing. reinforcing device for concrete and a method of its manufacture.

The present application is a continuation in part of my copending application jSer. No.

406,806, filed August 14, 1941.

An object of the invention is .the provision of a prestressing reinforcing unit for concrete comprising a central compression member, a plurality of wire-like tension members disposed therearound and spaced therefrom by means of a plurality of spacer members, an operable mechanism disposed at one end of said unit for stretching said tension members and for transmitting the tension force'reaction to said compression member and comprising a member to which all tension members are rigidly connected and with which they form an integral part, and a device disposed at the other end of said unit for transmitting the tension reaction force from said tension members to said compression member and also comprising a member to which the other ends of all said tension members are rigidly connected and with which they form an integral part.

An object of the present invention is the provision of a simplified design of the member to which the tension members are connected, whereby the connection is made by means of welding, preferably resistance welding.

A further object of my invention is the provision of a unit as characterized above in which the units or mechanisms disposed at the ends of the unit have substantially the same outside diameter as the rest of the unit whereby insertion of the unit into the mold for the concrete mass, and also assembly of the unit, for example by a machine similar to that used for stranding or braiding of wire rope and the like, are greatly facilitated.

An object of the invention is the provision of a simplified mechanism for tensioning the tension members, whereby application and release of the stretching force is facilitated and whereby relatively long prestress units, such as required in bridge construction, can easily be stretched. The new stretching mechanism comprises a ram member which can be long, thin and light because it is enclosed in, and guided by a tubular member which is tensioned at the same time the ram member is compressed.

Due to the inexpensive and much simplified construction of the device at one end of the unit for connection of the tension members and the stay member, this device may be left embedded in the concrete in case of inaccessible locations. The stretching and release mechanism at the other end of the unit, of course, must be accessible which does not present any practical difilculties.

A further object of my invention is the provision of improved sheath means for enveloping the compression member and preventing contact thereof with the concrete mortar and facilitating removal of the compression member after it has done its duty, said sheath means being rigid against forces acting in a radial direction and being somewhat resilient or expansible in the longitudinal direction.

An object of the invention is the provision of an improved spacer member for holding the tension members at a desired distance from the compression member which spacer member is of such design as to facilitate its manufacture, increase its strength, facilitate connection thereto of the sheath members, and improve and simplify support of the tension members, and flatten the curvature of the latter in longitudinal direction adjacent to the spacer members.

An object of my invention is the provision of a prestressing reinforcing unit of the type specified in which the number of parts is greatly reduced and the individual parts are of simplified design whereby the cost of manufacture is reduced, and in which the size and weight of and the material requirements for said parts are minimized.

Further and other objects of the present invention will be hereinafter set forth in the accompanying specification and claims and shown in the drawings which, by way of illustration, show What I now consider to be preferred embodiments of my invention.

In the drawings:

Fig. 1 is a longitudinal part sectional view of the prestressing reinforcing unit according to the present invention.

Fig. 21s a part cross sectional view of a stretching force reaction transmitting device used at the ends of the unit according to the invention, taken along line 2-2 of Fig. 1.

Fig. 3 is a part longitudinal sectional view of an alternative stretching force reaction transmitting device according to the invention.

Fig. 4 is an end view of a spacer member according to the invention.

Fig. 5 is a part sectional view of the spacer member shown in Fig. 4 taken along line 5-5 of said figure.

Fig. 6 is an end view of a modified spacer according to the invention.

Fig. 7 is a part sectional view of the spacer shown in Fig. 6 taken along line 'I-I in said figure.

Fig. 8 is a longitudinal part sectional view of a mechanism for operating the stretching and tension force transmitting mechanism according to the invention.

Fig. 9 is a part sectional view of a further mitting device according to the invention. Like parts are designated by like numerals in all figures in the drawings.

Referring more particularly to the drawings, I designates the tension wires, 2 the spacer supports or spacers, and 3 the compression member which, in the embodiment of the invention shown. is a rod.

The compression member 3 is surrounded by tubular corrugated sheath members 4 having threads rolled thereon and forming the corrugations, similar to the screws and sockets of electric lamp bases. These members may be made of metal or plastic or -of other suitable material of a similar nature. The corrugations provide rigidity against forces acting in radial direction so as to effectively resist the fluid pressure of the concrete mortar. At the same time they permit a desired elongation in longitudinal direction when the wires I are stretched. The ends 'of the corrugated tubular members are screwed into threaded extensions of members 2, as shown in Fig. 5. or into interiorly threaded portions at the ends of members 5. as shown in Fig. 1, which members are parts of the devices provided at the ends of the prestressing reinforcing unit.

The ends of the sheath members may also be cylindrical and pushed over correspondingly shaped portions of members 2 and 5 as shown in Figs. 7 and 3.

The end devices of t e unit comprise the aforementioned member 5 which may be termed a nut member into which, at one of the outer ends of the prestressing unit, a hollow longitudinal guide member 8a is screwed. and. in the case of the device at the other end of the prestress ng unit, an end bolt me ber 8b is screwed. A holding member or welding head 6 extends around the outer end of member 5 having an interior shoulder I6 abutting. through the intermediary of an electrically insulating filler member 'I, the end surface of member 5. Member 6 has a substantially cup-shaped configuration with recessses extend ng from the rim thereof and leaving teeth or prongs I2. To the ends of these prongs the ends of tension wires I are ri idly connected preferably by welding and particularly by flash welding. The recesses forming prongs may be omitted. In the embodiment of the invention illustrated. always two tension wires are connected to the end of one prong. One of said wires belongs to a set of Wires spacedly wound in long helices in one direction about the compression member 3 and theother wire belongs to a set of wires similarly wound in opposite direction about the compression member. Circumferen tial grooves or recesses I1 are provided on members 5 to facilitate welding and accommodating the welds.

The strength of the welded connection depends to a large extent on the carbon'content and subsequent heat treatment of the composite materials. The fiash welding process is adapted to produce a maximum strength of the welded joint.

modification of a stretching force reaction trans- The welding sleeve 8 may be modified as shown in Fig. 3 to suit special conditions. In case of cold drawn, high carbon tension wires, it may be advantageous to substitute hair pin shaped members 25 made of the same wire, instead of teeth or prongs I2, and to position members 25 on part 6a by inserting them in suitable grooves provided on part 6a and holding them therein by means of a cup or cage member 25 push-fitted over part 6a- For low carbon wires a simple ridge welded connection, as shown in Fig. 9 will develop the desired strength. In this case, member 5a which is otherwise the equivalent to member 5, is provided, on the outside, with a coarse thread or annular grooves and the wires I are ridge-welded directly thereto.

During manufacture of the prestressing unit according to the invention the tension wires I are held in correct position and clamped to member 5 by means of screws I4 and washers I5, the latter 'being individually interposed between the heads of bolts I5 and the wires I and pressing the latter to the surface of member 5 the clamping area of which may be roughened or knurled to provide an increased friction effect. For assuring correct position and pairing of wires I wire guides I3 are provided near the inner end of member 5. The wire positioning means or guides I3 preferably consist of a stamping having prong portions extending between the wires to be separated. Members I4 and I5 are for the purpose of temporarily connecting the tension wires to part 5 while the unit is pulled through a machine similar to that used for stranding or braiding of wire rope or the like and while the wires are wound around the compression member in steep helices. After winding of a unit is completed, the wires are cut, for example. adjacent to groove I1 and the unit can be removed from the winding machine for making way for the next unit to be wound. Sufficient length of wire is left between clamp screws I4 and'the end of the wires to apply an electrode of the welding machine. Another electrode is connected with the welding head 6 or 6a and a flash weld connection I8 is produced between the ends of prongs I2 or hair pin members 25 and of wires I. Member i provides the necessary insulation between parts 5 and =6 for the welding operation. After completion of the weld the temporary clamping devices I4 and I5 may be removed. I do not wish to limit myself to the particular temporary clamping devices shown. Other temporary clamping devices may be provided for this purpose without depart ng from the present invention.

For tensio-ning the unit, a threaded rod II having an end abutting an end of compression member 3 is inserted in the guide member 8a. A nut member ID is screwed to rod I I and is provided with an exterior collar I9 adapted to engage an interior shoulder provided on cap member 9 which is connected with the outer end of guide tube 8a. Member III, by means of shoulder I9 and through cap nut 9 pulls on member 8a and through member 5, shoulder I6, and member 5, on wires I, while the tension force reaction is transmitted through the interior threads on member III to rod I I and therefrom to compression member 3.

Fig. 1 shows the parts in position when the unit is in tensioned condition. Fig. 8 shows the mechanism which may be used for tensioning the unit. A yoke 20 abuts collar 2I of member 8a. This yoke is part of a hydraulic jack having a ram 98 which pushes on rod II through the intermediary of a nut 22 and a tubular spacer 23. A limited longitudinal movement of collar I9 inside cap member 9 is possible and is effected whenever pressure is applied through ram 93 whereby a mill is exerted on wires I, and yoke 20 and thereby members 9a and 9 are moved downward as seen in Figs. 5 and 8. Nut III can then easily be turned until its collar I9 abuts shoulder 29 of member 9. While the load is held by this engagement, nut 22 can be turned and moved down and the ram be brought in position for a renewed push. These operations are repeated until the desired tension of wires I is obtained as observed by means of a pressure gage 94 connected to the pressure fluid supply conduit for the ram 93. Rod II is thereby gradually worked from the position shown in Fig. 8,to the position shown in Fig. 1. It is to be noted that during the tensioning process member 8a is tensioned and is thus well adapted to prevent buckling or warping of member II which is compressed. Furthermore, the distance between nuts I and 22 need only be slightly greater than the stroke of shoulder I9 permitted by the clearance inside member '9 which is small. The free carrying length of member II is thus small and a com-' paratively thin rod can be used. The stretching mechanism of the type described is particularly well adapted to stretch relatively long units. Members II and 8a can be long without any danger of buckling because tubular member 8a is always under a tension which is equal to the compression acting on rod I I For releasing the tension on wires I and transferring it to the concrete surrounding said wires at the desired moment, the operations described in the paragraph next above are reversed.

The tensioning head shown in Fig. 1 is outside of the mold 21 and is removed after the concrete has hardened by cutting wires I. The wires can then be accurately severed from the welding head 9 and the unit can be used again. The unit shown on the top of Fig. 1 may be placed outside of mold 21 if there is accessible space and may also be removed by cutting the wires after the concrete has hardened. This unit, when made according to the present invention, is inexpensive and may be left embedded in the concrete if it can not be placed in an accessible position.

In order to assure correct spacing of the tension members I from the compression or stay member 9, spacers 2 are provided. These are composed of a sleeve part 28 which may have a thread for screwing sheath members 4 thereto as shown in Fig. 5 or may be cylindrical asthe sleeves 28a shown in Fig. '7. Members 28 or 28a carry a perforated disc-like spacer member proper 29 which has radial recesses 30 accommodating the tension members I. In the construction shown, always two tension members extend through the same recess and one is on top and outside of the other. One of the tension members in the same recess belongs to a set of tension members wound in the same direction and the other belongs to the set of tension members wound in opposite direction. The bottom of recesses 90 is provided with an embossed or coined lip to lengthen the contact of the wires with the spacer disc and prevent sharp kinks. In the construction shown in Figs. 4 and 5, the spacer disc 29 is held to sleeve 28 between two rings 3| which are press-fitted to the sleeve. The outside diameter of rings 3| is preferably the same as the lips on member 29' crete of the type comprising 'a longitudinal stay member, a plurality of wire-like reinforcing prestressing members disposed therearound in spaced relation thereto, and stress reaction transmitting means interposed between always one end of said wire-like members and one end of said stay member, a single holding member forming part of said reaction transmitting means and being welded to the ends of said wire-like members and forming an integral unit therewith.

2. In a prestressing reinforcing device for concrete of the type comprising a longitudinal stay member, a plurality of wire-like reinforcing prestressing members disposed therearound in spaced relation thereto, and stress reaction transmitting means interposed between always one end of said wire-like members and one end of said stay member, said reaction transmitting means comprising a holding member having an outside surface provided with substantially circumferential grooves and ridges, always one end portion of said wire-like members being positioned at a. substantially right angle to said grooves and ridges and being ridge-welded to the outside surface of one of said holding member 3. In a prestressing reinlrcing device for concrete of the type comprising a longitudinal stay member, a plurality of wire-like reinforcing and prestressing members disposed therearound in spaced relation thereto, a holding member disposed at each endof said device and having substantially cup-shaped configuration to the rim of which one end of said wire-like members is rigidly connected by means of welding, and stress reaction transmitting means interposed between always one of said holding members and one end of said stay member and comprising a member surrounding the end portion of said stay member and being surrounded by said wire-like members and extending inside said cup-shaped holdingmember.

4. In a prestressing device for concrete as set forth in claim 3, said holding members having recesses extending from saidrim between the points at which said wire-like members are welded thereto.

5. In a prestressing reinforcing unit for con-- crete of the type comprising a longitudinal compression member and a plurality of wire-like reinforcing and prestressing members disposed therearound in spaced relation thereto, a holding means disposed at each end of said device, and stress reaction transmitting means interposed between always one of said holding means and one end of said compression member, said holding means comprising looped members and said wirelike members being welded to said looped membars.

6. In a prestressing reinforcing device for concrete of the type comprising a longitudinal stay member, a plurality of wire-like reinforcing and prestressing members disposed therearound in spaced relation thereto, and stress reaction transmitting means individually interposed between the ends of said compression member and the neighboring ends of said wire-like members, a holding means disposed at each end of said device 5 and forming part of said transmitting means and having the ends of said wire-like members welded thereto in pairs individually consisting of two parallel and tangent ends of said wire-like members and being spaced from other pairs of ends of said wire-like members.

7. In a prestressing reinforcing device for concrete of the type comprising a longitudinal stay member, a plurality of wire-like reinforcing tension members disposed therearound in spaced re- 16 lation thereto, a holding member disposed at each end of said device and connected to the respective ends of said tension members, and stress reaction transmitting means interposed between always one of said holding members and one end 20 of said stay member, an adjustable stretching mechanism forming part of one of said stress reaction transmitting means and being adapted to stretch said tension members and transmit the stretching force reaction to said stay member, said mechanism comprising longitudinal hollow means having an inner end portion axially abuttingly engaging said holding member and hav-- ing an outer end portion provided with an interior cavity and an interiorly projecting shoul- 3Q der at one end of said cavity, a threaded member axially slidably disposed within said hollow means and having an end abutting one end of said stay member, a nut member screwed to the other end of said threaded member and having a portion extending into said cavity and havin a collar engaging said shoulder, said nut member, when turned to move outward on said threaded member, pulling through said collar and shoulder on said hollow means and through said holding member on said tension members and pushing said threaded member against said stay member.

8. In a prestressing reinforcing device for concrete of the type comprising a longitudinal stay member and a plurality of wire-like reinforcing and prestressing members disposed therearound/ in spaced relation thereto, a holding member disposed at each end of said device and having one end of said wire-like members connected thereto by means of welding, stress reaction transmitting means interposed between always one end of said holding members and one end of said stay member, said stress reaction transmitting means comprising an intermediary member havmg a portion extending inside said holding member and having a surface portion abutting said wire-like members from the inside of the unit formed thereby, and clamp means removably connected with said intermediary member and temporarily clamping said wire-like members thereto .while the weld connection is made.

9. In a prestressing reinforcing device for concrete of the type comprising a longitudinal stay member and a plurality of wire-like reinforcing and prestressing members disposed therearound in spaced relation thereto, stress reaction transmitting means interposed between always one end of said tension members and one end of said stay member and comprising a single holding member having said wire-like members welded thereto, and positioning means disposed adjacent said holding meansand having portions extending between said wire-like member and maintliaining said wire-like members in desired posit on.

10. A prestressing reinforcing device for concrete comprising a longitudinal stay member, a set of wire-like reinforcing tension members wound therearound in spaced relation thereto and in steep helices, another set of wire-like reinforcing tension members wound in opposite direction to said first set around said stay member in spaced relation thereto and in steep helices, a holding member disposed at each end of said device and connected to the respective ends of said tension members, stress reaction transmitting means interposed between always one of said holding members and one end of said stay member, and spacer means disposed in axially spaced relation on said stay member and maintaining the desired radial distance of said tension members from said stay member, said spacer means comprising a sleeve part surrounding said stay member, and a spacer member proper radially extending from said sleeve part and having substantially radially extending recesses accommodating said tension members in pairs consisting of a tension member of one of said sets and a tension member of the other set.

11. A prestressing reinforcing device for concrete comprising a longitudinal stay member, a plurality of wire-like reinforcing tension members disposed therearound in spaced relation thereto, stress reaction transmitting means interposed between always one end of said tension members and one end of said stay member, and substantially tubular sheath means having corrugations substantially transverse to their longitudinal extension disposed around said stay member and preventing binding of the concrete therewith.

HERMAN SCHORER

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