FR2710872A3 - Method for obtaining cardboard tubes with leaktight inner lining, particularly for shuttering (formwork), and devices for implementing it - Google Patents

Abstract

According to the method, a tube (2) is produced by spirally winding up strips of cardboard and the inner face of the tube (2) is coated with an impermeable product, then the helical furrow which results from the space remaining between the turns of the first wound-up strip is filled with impermeable product so as to obtain an inner surface which is perfectly uniform and a wall which is entirely protected from the moisture in the concrete. The devices for implementing the method comprise a circular smoothing member (7) and means (7a, 9) permitting the translational displacement of this member (7) in the tube (2).

Description

PROCESS FOR OBTAINING TUBE8 IN CARDBOARD
WITH WATERPROOF INTERNAL COATING, ESPECIALLY
OF FORMWORK8, AND DI8PO8ITIF8 OF MI8E IN WORK
The present invention relates to a process for obtaining cardboard tubes with a sealed internal coating, in particular formwork, and devices for its implementation.

 It is known, for example from patent FR N 1 513 315, to use cardboard tubes to form studs, posts, pillars or the like in poured concrete.

 In the case where the part to be obtained has a circular cross section, the formwork consists of a simple cardboard tube into which the concrete is directly poured. The internal face of the tube is coated with a layer of impermeable product so that the mechanical resistance of the wall is not affected by the humidity of the concrete.

 In the case where the part to be obtained is of polygonal section, the formwork is generally constituted by an outer tube in which is placed an inner envelope with polygonal section, with interposition of shims made of weakly compressible material.

 These cardboard tubes are obtained, by means of a suitable machine known as a "spiraling machine", by gluing strips of cardboard of relatively small thickness and spirally winding them on a mandrel. The first strip receives said waterproof product and is wound on the mandrel. The other strips are then glued and wound on this first strip.

 It is found, in practice, that the cylindrical parts obtained by these cardboard tubes have a helical thread projecting from their wall, bordered by zones comprising surface defects and underlined by a lightening of the concrete.

 This defect affects the finished appearance of the parts obtained.

 To solve this problem, it has been envisaged to cover the inside of the tube with a sheet of impermeable material, cut to the appropriate dimensions. Cutting the sheet, putting it in place and fixing it to the tube are long and tedious operations, which considerably increase the manufacturing time and increase the cost price of these tubes. In addition, the space which remains between the longitudinal edges of the sheet generates a longitudinal mark on the molded part, also altering its finished appearance.

 The present invention aims to remedy these drawbacks, by a new process for obtaining such tubular formwork eliminating any risk of marking of the formwork, without significantly affecting the manufacturing time of these tubes and their cost price.

 The method according to the invention, in which, in a known manner, a tube is produced by spiral winding of cardboard strips and the inner face of the tube is coated with an impermeable product, consists in filling the helical groove with impermeable product. which results from the space remaining between the turns of the first wound strip, so as to obtain a perfectly uniform interior surface and a wall entirely protected from the moisture of the concrete.

 Indeed, it appeared that the water contained in the concrete is absorbed under the layer of impermeable product by the edges of the first strip of cardboard wound, at the aforementioned space existing between the turns of this strip, these edges being devoid of waterproof product.

 The cardboard swells and leaves its imprint hollow on the wall of the molded part, on either side of the helical thread generated by this space.

 In addition, the water content of the concrete at this space decreases due to infiltration in the cardboard, which causes the concrete to lighten, highlighting this surface defect.

 The method according to the invention overcomes these drawbacks by making it possible to obtain cardboard tubes having both a completely impermeable wall and a perfectly uniform surface, therefore making it possible to obtain parts with the perfect finished appearance.

 According to one possibility of implementing this method, the impermeable product is deposited on the first strip before winding or on the internal face of the tube once the latter has been formed, then this product is smoothed while it is at 'plastic state, to make it flow in the aforementioned helical groove.

 The waterproof product is deposited in sufficient quantity to allow filling of the helical groove of the tube while retaining the nominal thickness of product necessary for waterproofing the wall.

 According to another possibility of implementing this process, the impermeable product is deposited and smoothed only in said groove before or after deposition of this impermeable product on the first strip before winding or on the internal face of the tube once it constituted.

 Advantageously, the method also consists in cutting the longitudinal edges of the first strip wound at an angle with respect to the plane of the strip and parallel to one another, so that the strip has, in cross section, the form of a parallelogram.

 It is thus possible to wind the first strip with almost contiguous turns, without the risk of overlapping its edges. The helical groove resulting from the space between the turns remains but has a narrower width than that existing with straight edges. The filling of the throat with waterproof product is therefore facilitated and the quantity of product required is less.

 The invention also relates to devices for implementing this method.

 In general, these devices comprise a circular smoothing member, with an outside diameter corresponding to the inside diameter of the tube and means allowing the translational movement of this member in the tube.

 According to a first embodiment, this device is mounted in the extension of the free end of the mandrel used for winding the strips of cardboard, and comprises a circular member for smoothing the internal wall of the tube as well as means allowing the rotation of this member at the same speed and in the same direction as the movement of the tube on the mandrel.

 This device allows the smoothing of the pre-coated wall of the tube in order to make the impermeable product flow in the groove, according to a movement of translation of the tube relative to the smoothing member.

The smoothing-creep operation is thus carried out under conditions which prove to be optimal for obtaining an internal wall of perfectly uniform surface.

 According to another embodiment, the device is independent of the mandrel and comprises a circular member for smoothing the internal wall of the tube which is moved inside the latter by means of a cable or the like.

 The cable allows a displacement in translation of said member relative to the tube to perform the smoothing-creep operation of the impermeable product.

After having traversed the whole of the tube, the member is detached from the cable to allow the withdrawal of the tube.

 This smoothing can advantageously be exercised vertically, which allows a descent of the smoothing member by simple gravity, and is exercised according to a back-and-forth movement of the smoothing member from a tube to the other, which allows a relatively fast cadence.

 Insofar as the impermeable product is of the thermoplastic type, the device further comprises means for heating the wall of the tube and / or the smoothing member, of any suitable type. Means for cooling the product after smoothing can also, if necessary, be provided.

 For its proper understanding, the invention will be described again below with reference to the appended schematic drawing representing, by way of nonlimiting examples, two embodiments of a device for implementing the method which it relates .

 Figures 1 and 2 are side views and in longitudinal section of this device, according to these two embodiments.

 FIG. 1 represents the mandrel 1 of a machine, known as a "spiraling machine", allowing the manufacture of cardboard tubes 2 by winding in spirals and superimposing strips of small thickness.

 The strips, previously glued, are at the height of the upper generatrix of the mandrel 1, are gripped by a belt which is engaged around the mandrel 1 and which is driven by dolls located on either side of the mandrel 1, and are wound in spirals on the latter without overlapping the turns to obtain an internal face of the tube 2 as smooth as possible. The tube 2 is thus manufactured continuously as the bands are wound up and advances by turning around the mandrel 1. It is then cut downstream of the latter to the desired length.

 This technique being known per se, the above-mentioned bands, belts and dolls are not shown in FIG. 1.

 The cardboard tubes obtained are intended to be used to form studs, posts, pillars or the like in poured concrete. In order not to have the resistance of their wall affected by the humidity of the concrete, the internal face of the tubes is coated with a layer of impermeable product, generally thermoplastic, which can be deposited on the first strip before winding or directly on said face. internal once the tubes are formed.

 The mandrel 1 is supported by a tube 3 fixed on a base 4 resting on a base 5. The mandrel 1 and the tube 3 are traversed right through by a tube 6 which is coaxial with them and which comprises, on the side of the free end of the mandrel 1, a circular member 7, coaxial with the mandrel 1, and a device 8 for heating the member 7 and / or the wall of the tube 2. The member 7 has a hub 7a, mounted on a bearing 9 which is engaged on the tube 6, and a circular skirt 7b scraping against the wall of the tube 2.

 The heating device 8 is fixed to the tube 6 by one or more radial arms 10 and can be of any suitable type, in particular of the infrared or microwave type.

 A disc 11, mounted on the end of the tube 6, closes the space delimited internally by the smoothing member 7, which is heated by the device 8.

 During its advancement beyond the free end of the mandrel 1, the tube 2 engages on the member 7. The skirt 7b of the latter smooths the impermeable product, made plastic thanks to the heating device 8, and make it flow in the helical groove which results from the space remaining between the turns of the first wound band.

 This process makes it possible to obtain a perfectly uniform interior surface and a wall entirely protected from the humidity of the concrete and, therefore, to obtain shuttered parts with the perfect finished appearance.

 The member 7, thanks to the fact that it is mounted rotating on the tube 6, follows the rotation of the tube 2 when the skirt 7b scrapes against the internal wall of the tube 2. Thus, the smoothing-creep operation is carried out according to a translational movement of the tube 2 relative to the member 7, that is to say under conditions which prove optimal for obtaining an inner wall of perfectly uniform surface.

 The tube 6 allows the passage of the electrical supply cables of the device 8 as well as, if necessary, the blowing through it of cooling air downstream of the member 7 and of the device 8.

 FIG. 2 represents another embodiment of a device for implementing this method, in which the device is independent of the spiraling machine.

 The tube 2, after manufacture and cutting to the desired dimensions, is erected vertically against a gantry 15 by means of a clamp 16, a cable 17 and a winch 18 mounted to slide along a rail 19.

 The circular smoothing member 20 is here suspended from the cable 21 of a winch 22, also movable along the rail 19 so that it can be positioned in the axis of the tube 2, and descends into the tube 2 by simple gravity.

 After having traversed the whole of the tube 2, the member 20 is detached from the cable 21 to allow the withdrawal of the tube 2.

 The member 20 houses or is associated with an appropriate device for heating the wall of the tube and / or the skirt 20b, supplied by the electric wire 23.

 The smoothing-creeping operation can be carried out according to a back-and-forth movement of the smoothing member 20 from one tube 2 to the other (descent for one tube, assembly for the next tube and so on. ), which makes it possible to obtain a high rate. This can also be done not vertically but horizontally.

Claims (9)

CLAIMB  1 - Process for obtaining cardboard tubes with waterproof internal coating, in particular formwork, during which a tube is produced by spiral winding of cardboard strips and the internal face of the tube is coated with an impermeable product, characterized in what it consists of filling with impermeable product the helical groove which results from the space remaining between the turns of the first wound strip, so as to obtain a perfectly uniform interior surface and a wall entirely protected from the moisture of the concrete.  2 - Method according to claim 1, characterized in that the impermeable product is deposited on the first strip before winding or on the internal face of the tube (2) once it has been formed, then in that one comes smooth this product, while it is in a plastic state, to make it flow in the above-mentioned helical groove.  3 - Method according to claim 1, characterized in that one comes to deposit and smooth the waterproof product only in said groove before or after deposition of this waterproof product on the first strip before winding thereof or on the inner face of the tube (2) once it has been formed.  4 - Method according to one of claims 1 to 3, characterized in that it further comprises cutting the longitudinal edges of the first strip wound at an angle with respect to the plane of the strip and in parallel with one to the other, so that the strip has, in cross section, the shape of a parallelogram.  5 - Device for implementing the method according to one of claims 1 to 4, characterized in that it comprises a circular member (7,20) of smoothing, of outside diameter corresponding to the inside diameter of the tube (2) and means (7a, 9,19,21,22) allowing the displacement in translation of this member (7,20) in the tube (2).  6 - Device according to claim 5, characterized in that it is mounted in the extension of the free end of the mandrel (1) used for winding the cardboard strips, and in that it comprises a circular member ( 7) for smoothing the internal wall of the tube (2) as well as means (7a, 9) allowing the rotation of this member at the same speed and in the same direction as the movement of the tube (2) on the mandrel (1 ).  7 - Device according to claim 5, characterized in that it is independent of the mandrel (1) and in that it comprises a circular member (20) for smoothing the internal wall of the tube (2) which is moved to the inside thereof by means of a cable (21) or the like.  8 - Device according to one of claims 5 to 7, characterized in that it comprises heating means (8) of the wall of the tube (2) and / or of the smoothing member (7,20).  9 - Device according to one of claims 5 to 8, characterized in that it comprises means for cooling the waterproof product after smoothing.