US2061105A - Method and device for reenforcing articles and structures made from concrete and the like - Google Patents

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METHOD AND DEVICE FOE REENFORCING ARTICLES AND STRUCTURES MADE FROM CONCRETE AND THE LIKE Filed Oct. 11, 1935 Nov. 11, 1936. B RUML 2,061,105

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11\unununnunnnn o Patented Nov. 17, 1936 METHOD AND DEVICE ARTICLES AND STRU PATENT OFFICE FOR REENFORCHWG CTURES MADE FROM CONCRETE AND THE LIKE Bohuslav Ruml, Prague, Czechoslovakia Application October 11,

1935, Serial No. 44,574

In Belgium October 11, 1934 7 Claims.

In the manufacture, according to usual processes, of articles and structures made from concrete reenforced by means of iron or steel and in which the iron or steel is subjected to tensile stress, the power of resistance of the reenforcing material to internal tensile stresses is not utilized to its maximum extent. This occurs for instance in reenforced concrete pipes subjected to a high internal pressure and in which the transverse reenforcement, generally of helical formation, and the wall of the tube are under tensile stress. Considering the small tensile strength of the concrete and the limited ability of the latter to elongation or extension, the articles made according to the known processes are not of quite safe structure.

To avoid this inconvenience, it has already been proposed to heat the reenforcement and to Wind it in a heated state on a resistant and rigid core of concrete or the like, forming part of the article to be manufactured, so as to produce in said reenforcement, after cooling, a permanent initial or preliminary tension which will exert a pressure on the said core, thus increasing the strength and tightness, especially as regards internal pressures, of the finished article.

According to my invention, the desired result is obtained in a more sure and perfect manner than hitherto, owing more particularly to the fact that the amount of initial tension produced in the reenforcement may be very accurately predetermined and that the said initial tension will yield a maximum efiect. Moreover, this result is obtained at the cost 'of a considerably smaller amount of energy than was necessary in the known processes.

To this end, the heated iron winding or reenforcement wire is wound on the core in such a manner that the temperature of the reenforcement remains constant for the whole duration of the winding process and until the reenforcement is definitively fixed to the core, to prevent contraction on cooling. Furthermore, said wire should be subjected while it is wound, to a tractive strain suiiicient to prevent any slackening of the wire and securing a close. contact between the latter and the core, without tending however to cause any noticeable elongation or extension of said wire. The reenforcement is subsequently embedded in concrete or the like. If it is helically wound, it may bev secured in a very simple way relative to the core by soldering each terminal winding so as to form an annular spire.

Thus, during the process of winding the reenforcementon the core, the length oi reenforcement having been wound on the core and having one end secured thereto will not be allowed to cool and, consequently, will not contract longitudinally. The reduction of initial tension due to such contraction which unavoidably occurs in 5 the known processes is thus prevented, so that the required power consumption is greatly reduced.' In practice, the application of the heat may, if desired, be limited to a portion of the length of wire having been wound on the core, 10 without causing a substantial reduction of initial tension, provided the friction between the core and the length of wire already wound be greater than the longitudinal contracting stress due to cooling. 15

Further, it is to be noted that, owing to the fact that the temperature of the wire is kept constant, the cooling will take place in a quite uniform manner, which will secure a uniform initial tension throughout the length of the wire and a 20 uniform strength of the finished article.

The temperature to which the reenforcement is to be heated may be predetermined by calculation or experiment, keeping in mind various factors such as the tensile strength of the re- 25 enforcement metal being used, the strength of the concrete and the amount of the desired initial tension. Inasmuch as the tractive strain exerted on the heated reenforcement wire does not tend to produce a noticeable elongation of the 30 wire, the method according to my invention al lows to attain a very high degree of initial tension, considering that merely the limit of elasticity of the metal when cold is to be taken in account and cannot be exceeded. 35

It is particularly desirable to apply the heat by passing an electrical current through the reenforcement wire. Inso proceeding,the temperature attained in the reenforcement wire may be readily adjustable with a veryhigh accuracy, so that 40 the amount of initial tension which will be obtained is exactly known. When the latter heating method is applied directly to the reenforcement while on the winding machine, the loss of heat by convection or radiation is reduced to a mini- 45 mum, inasmuch as unnecessary conveyance of heated wire is eliminated. The said winding machine is so designed as to produce a rotary movement of the previously prepared core about its axis and a relative longitudinal displacement be- 50 tween the core and the guide member for the reenforcement wire. The latter relative displacement is obtained by imparting either to the core or to the wire guide member a movement which, in either case, will be preferably uniform. The 66 combination of said relative movement and the said rotary movement of the core provides the helical winding of the reenforcement wire.

According to my invention, the electrical heating may be applied by means of a device whereby the current is supplied across two contact pieces, viz. a first sliding or brush contact piece upon which the wire about to be wound on the core is caused to slide, said contact piece being arranged at such a distance from the core as is necesary to allow to every particle of the metal suflicient time to be heated and to cause the loss of heat by convection and radiation to be compensated by the heat supply obtained from the electrical energy converted into heat by virtue of the Joule effect, and a second contact piece in contact with a point of the length of wire already wound on the core.

In order to keep the temperature of the reenforcement constant for the whole duration of the winding process, the said second contact piece will be connected to that end of the reenforcement wire which has been attached to the core at the beginning of the winding process. Considering that with this arrangement the length of wire to be heated increases progressively in proportion as the wire is being wound, it will be necesary,in order to secure a constant supply of electrical energy per unit of wire length,-to vary the intensity of the electric current proportionally to the increase of the length of wire having been wound on the core, said variation being for instance proportional to the rate of the relative longitudinal displacement occurring between the core and the wire guiding device, or proportional to the number of revolutions executed by the core. To this end use may be made of any convenient mechanism, such as operating a rheostat adapted to regulate the intensity of the electric current.

Where the application of heat is limited to a certain number of the turns already wound on the core, the said second contact piece may be made, for example, in form of a stationary sliding or brush contact piece upon which the wire already wound is caused to slide. Inasmuch as the length of wire being heated in the latter instance remains constant, there is no need for varying the intensity of electric current.

A constructional example of the invention will now be described, reference being made to the accompanying diagrammatic drawing, which shows a complete installation for the electric heating of a spirally wound reenforcing wire.

A resistant core i is supported at its ends by discsIJintheend-sofaxiallyalignedshafts 4,5 respectively which are rotated by any suitable means. A transmission device i causes rotation of a threaded but axially fixed shaft 1, which in turn imparts a longitudinal movement to a carriage 8 which guides the reenforcing wire 9 fed from a spool ll. Heating of the thread is eiIected by electric current supplied from a source ll through a contact member I! in engagement with the commencement of the wire and a movable contact member IS on the carriage 8 and connected by a sliding contact I with a conductor rail IS. The intensity of the current is adjusted proportionally to the increase in length of the wound wire between the contact I! and the carriage I by means of a slider l6 cooperating with a resistance II in the current circuit.

Transmission means it from shaft 4 causes rotation of the threaded shaft IS on which the slider I6 is mounted.

Should it be desired to heat only a predetermined constant portion of the wire wound on the core, the elements I6, l1, l8 and I9 may be dispensed with and the contact I2 may be displaced axially of the core and jointly with the carriage I and the contact i3.

What I claim is:

'1. A method for reenforcing hollow bodies,

' enforcement wire on a resistant core in close contact with the latter, securing both ends of the reenforcement wire in a fixed position relative to the core respectively before and after the winding of the reenforcement on the core, and applying a protective layer over the reenforcement, heating the reenforcement at a constant temperature for the duration of the process of winding the reenforcement on the core up to the moment it is flxed'in position relative to the core.

3. A method according to claim 2, including limiting the application of heat to the reenforcement to a portion of the length of wire which has been wound on the core, said portion being of such magnitude that the friction between the wire already wound and the core is higher than the longitudinal contraction stress, due to cooling. of the portion of the wire already wound on the core, the commencement of which is secured in a fixed position relative to the core and to which heat is no longer applied.

4. A method for reenforcing hollow bodies, comprising helically winding a heated metal reenforcement wire on a resistant core in close contact with the latter, securing both ends of the reenforcement wire in a fixed position relative to the core respectively before and after the winding of the reenforcement .on the core, and applying a protection layer over the reenforcement, heating the reenforcement at a constant temperature for the duration of the process of winding the reenforcement on the core up to the moment it is fixed in position relative to the core, by supplying electric current from a source of current to said wire by means of two contact pieces one of which is a brush contact arranged at a distance from said core for making sliding contact with the wire about to be wound on the core, while the second contact piece is in contact with the wire already wound on the core.

5. A method according to claim 4, including connecting the second contact piece to the front end of the wire already wound on the core and increasing the supply of electric energy to the wire to be heated proportionally with the increase of the length of the portion of wire comprised between the said two contact pieces.

6. In a device for heating a transverse metal reenforcement wire during its disposal on a rigid core for the construction of hollow reenforced bodies, a source of electric current, a first brush contact piece connected to the source of electric current and in sliding contact with the portion of the wire about to be wound on the'core, a second contact piece connected to the source oi electric current and to the portion 01' wire already wound on the core, and means for varying the supply of electric energy to the portion of wire comprised between the two contact pieces proportionally to the increase of the length of that portion of wire.

7, In a device for heating a transverse metal reenforcement wire during its helical winding on a resistant core for the construction of hollow reenforced bodies, means for supporting the core and for imparting theretoa rotary movement round its axis, means for guiding the reenforcement wire about to be wound on the core, means for producing relative longitudinal movement between said guiding means and the core, a source of electric current, a first contact piece supported by the said guiding means and in sliding contact with the reenforcement wire, a second contact piece connected to the front end of the wire already wound on the core, leads for connecting said contact pieces to the source of current, a rheostat in the electric circuit, a movable member whose displacements are proportional to the increase of the length of the part of wire comprised between the two contact pieces, and means for varying the resistance of the rheostat under the action of the displacements of said member for increasing the supply of electric energy to said part of wire proportionally to the increase of the length of that part of wire.

BOH'USLAV RUIML.

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