FR2526707A1 - Continuous prodn. line for sheet rubber - incorporating integrated heating, calendering, dusting, curing, washing and cutting units - Google Patents

Abstract

Prodn. line for continuous sheet made from natural rubber incorporates a continuous ribbon granulator (2) supplying a heated extruder (4) from which the output is transferred to a multiple roll calender (6). The product from the calender passes through a thickness gauge (8), a dispenser (9) for a superficial parting agent, such as talc, and a continuous vulcanisation tunnel (10) where the sheet is cured. The cured sheet then passes through a further thickness gauge (12), a wet wash (13) and a cooling bath (19) prior to collection (16) in lengths pref. controlled by an automatic cutter (15). More efficient overall than discontinuous processes where heating, calendering and curing are effected as batch processes.

Description

CONTINUOUS MANUFACTURING PLANT
NATURAL RUBBER SHEETS
The present invention relates to the field of the manufacture of natural rubber sheets, and it relates, more particularly, to an installation allowing the continuous manufacture of natural rubber sheets.

Currently, the manufacture of natural rubber sheets, which can be used to obtain elastic ribbons or threads after cutting, is done batchwise, in particular by implementing the method recalled below.
After a rubber mixture has been produced, a mixture comprising one or more kinds of natural rubber and various ingredients, the mixture is taken up in two-cylinder mixers. Heavy mixing of this mixture changes its temperature and viscosity.

 When these characteristics are suitable, the mixture can be introduced between the cylinders of the calender. I1 leaves a sheet of which we check the thickness before winding it on a drum. The rubber is not yet vulcanized at this stage, is sticky, and an anti-adhesive treatment is provided, in general by talc powdering, before this winding.

 This drum carrying its rubber sheet is then placed in an oven to vulcanize it which will develop all the specific properties of the rubber.

 At the end of vulcanization, other unwinding, washing and various checks or treatments must be carried out.

 This succession of manufacturing operations is obviously a complex implementation, costly in labor, and a low yield.

 The present invention overcomes these drawbacks by providing an installation allowing the continuous and perfectly controlled industrial production of natural rubber sheets, this in a fully automatic manner, except for the interventions necessary for feeding the installation. in rubber mixture, and for the evacuation of the sheets finally obtained.

The installation according to the invention essentially comprises, from upstream to downstream
- a continuous strip cutter receiving the rubber mixture,
- an extruder-heater,
- a grille,
- a first thickness gauge,
- a non-stick treatment device, such as talcage,
- a vulcanization oven,
- a second thickness gauge,
- a washing bath,
- A cooling bath, automatic conveyor means being provided between the preceding stations and / or inside these stations.

 The installation is therefore characterized by a combination of means which ensure all the necessary manufacturing operations, as well as transfers between the different stations and the essential thickness, temperature and speed checks.

 At the entrance to the installation, the cutter which performs the first manufacturing operation is advantageously designed to be supplied with a rubber mixture from a mobile transport container. This cutter automatically feeds the extruder-heater, placed upstream of the calender. Preferably, the conveyor means provided between the extruder and the calender consist of a conveyor belt with transverse oscillations, making it possible to distribute the material leaving the extruder over the entire width of the cylinders of the calender.

 According to another characteristic of the invention, the vulcanization oven is a multi-stage oven, with a plurality of superimposed conveyor belts.

 The installation according to the invention may also comprise, at its outlet, a transverse cutting device, for cutting the rubber sheet obtained, which is continuous, into sections of length corresponding to the capacity of the evacuation means used, such as receiving carts.

 In any case, the invention will be better understood with the aid of the description which follows, with reference to the single figure in the appended diagrammatic drawing representing, by way of nonlimiting example, an embodiment of this installation for continuous production of natural rubber sheets.

 The installation, shown in the drawing in two separate sections taking into account its length, will be described dtamont downstream, if one refers to the direction of progression of the treated materials.

 At the "upstream" end of the installation, the mixes to be cut are brought into a mobile transport tank (1), making it possible to feed a cutter into a confined band, (2), with a device for output automatic feed (3) for passage through a heating extruder (4). At the exit of this extruder, the material in strips reaches an oscillating lifting belt (5), whose transverse oscillations make it possible to feed a calender (6) with four cylinders (6a), (6b), (6c) and (6d), by distributing the material over the entire width of the cylinders. The ply obtained at the outlet of the calender (6) is brought, by a conveyor belt (7), to a thickness gauge (8) followed by 'a non-stick treatment device (9), for example a talcizing device, then it enters a vulcanization oven (10) with several stages, which it traverses on a plurality of superimposed conveyor belts (11), entrained in alternating directions. At the outlet of the vulcanization oven (10), the continuous rubber sheet obtained is checked by means of a thickness gauge (12), then it passes successively into a washing bath (13) and into a cooling bath (14). Finally, the sheet passes through a transverse cutting device (15), before falling into a receiving carriage (16), the device (15) cutting lengths of rubber sheet which correspond to the capacity of the carriage (16) used for evacuation.

 It goes without saying that the invention is not limited to the sole embodiment of this installation for the continuous manufacture of sheets of natural rubber which has been described above, by way of example; on the contrary, it embraces all variants of it, whatever the constructive details or the complementary arrangements.

Claims (6)

 1.- Installation for the continuous production of natural rubber sheets1 characterized in that it essentially comprises, from upstream to downstream  - a continuous strip cutter (2) receiving the Rubber compound,  - an extruder-heater (4),  - a grille (6),  - a first thickness gauge (8),  - a non-stick treatment device, such as talcage (9),  - a vulcanization oven (10),  - a second thickness gauge (12),  - a washing bath (13),  - A cooling bath (14), automatic conveyor means (3, 5, 7, 11) being provided between the preceding stations and / or inside these stations.  2.- Installation according to claim 1, characterized in that the cutter (2) is designed to be supplied with rubber mixture to be cut from a mobile transport container (1).  3.- Installation according to claim 1 or 2, characterized in that the aforementioned conveyor means are constituted between the extruder (4) and the calender (6), by a conveyor belt (5) with transverse oscillations.  4.- Installation according to any one of claims 1 to 3, characterized in that the grille (6) comprises at least three cylinders (6a, 6b, 6c, 6d).  5.- Installation according to any one of claims 1 to 4, characterized in that the vulcanization oven (10) is multistage, with a plurality of stacked conveyor belts (11).  6.- Installation according to any one of claims 1 to 5, characterized in that it also comprises, & s outlet, a transverse cutting device (15), for cutting the rubber sheet obtained into sections of corresponding length the capacity of the evacuation means (16) used.