WO2011072749A1

WO2011072749A1 - Process and apparatus for vulcanizing a strand-like extrudate composed of rubber material

Info

Publication number: WO2011072749A1
Application number: PCT/EP2009/067489
Authority: WO
Inventors: Xavier Boland
Original assignee: Federal-Mogul S.A.
Priority date: 2009-12-18
Filing date: 2009-12-18
Publication date: 2011-06-23

Abstract

Process and apparatus (1) for producing a strand-like extrudate (4) composed of a rubber material which is vulcanized after extrusion, wherein the vulcanization is carried out in a bath (5) by means of a heat treatment mediu (6) present therein, with the special feature that the strand-like extrudate (4) is transported through the heat treatment medium (6) along an at least substantially L-shaped path inside the bath (5).

Description

PROCESS AND APPARATUS FOR VULCANIZING A STRAND-LIKE EXTRUDATE COMPOSED OF

RUBBER MATERIAL

The present invention relates to a process and an apparatus for producing a strand-like extrudate composed of a rubber material which is vulcanized after extrusion, wherein the vulcanization is carried out in a bath by means of a heat treatment medium present therein. Such a process and such an apparatus are widely known, particularly for manufacturing a wiping element for a wiper blade of a vehicle, such as described in German patent publication no. 10 2005 000 851 (Bosch) . Usually, a rubber material, such as a (whether or not reinforced) elastomer, is used for the strand-like extrudate. Normally,

vulcanization of the strand-like extrudate takes place after extrusion. After leaving the extruder, the strand-like extrudate is subsequently heated to enable vulcanization, wherein a bath containing a heating medium is used, for example.

International (PCT-) patent publication no. WO 2008/074622 (Bosch) discloses also a process and an apparatus for producing a strand-like extrudate composed of a rubber material which is vulcanized after extrusion, wherein the vulcanization is carried out in a bath by means of a heat treatment medium present therein. The strand-like extrudate is transported through the heat treatment medium in vertical direction, wherein use is made of a vertically extending channel which has openings for entry and exit of the strand^¬ like extrudate and is arranged so that the strand-like extrudate can be conveyed through it in vertical direction. A disadvantage of the process and the apparatus known from the above international (PCT-) patent publication is that they are complicated and cumbersome. For example, when the strand-like extrudate leaves the extruder, it is weak and therefore vulnerable for (high) forces guiding the strand^¬ like extrudate down into the vertical channel, all the more as buoyant forces have to be overcome. In this respect it is noted that the heating medium containing salts has a high density, so that the strand-like extrudate tends to float onto the heating medium. Further, providing a hole into the ground in order to be able to mount the vertical channel therein is intricate and therefore expensive. Further, in practice it appears that less space is available to mount a collecting device above the vertical channel having a small width in order to collect fumes and the like originating from the heating medium containing salts, wherein reference is made to figures 1 and 2 of this international (PCT-) patent publication. The extruder or the roll shown in these figures just stands in the way for such a collecting device.

It is the aim of the present invention to improve the prior art, more in particular to provide a simple and elegant process for producing a strand-like extrudate composed of a rubber material which is vulcanized after extrusion, wherein the above disadvantages are obviated.

In order to accomplish that objective a process of the type mentioned in the introduction is characterized according to the invention in that the strand-like extrudate is

transported through the heat treatment medium along an at least substantially L-shaped path inside the bath.

Preferably, the strand-like extrudate is transported through the heat treatment medium in an essentially vertical direction and subsequently in an essentially horizontal direction. In the alternative, the mechanical reversal is possible in the sense that the strand-like extrudate is transported through the heat treatment medium in an

essentially horizontal direction and subsequently in an essentially vertical direction. The combination of a vertical and a horizontal path, i.e. an L-shaped path, at the time of starting the process allows the relatively weak strand-like extrudate to be easily transported along the horizontal path only, thereby avoiding any damages thereof. After a certain period of time the strand-like extrudate can then be transported first along the vertical path and subsequently along the horizontal path, i.e. travelling along the entire L-shaped path. The use of the L-shaped path further makes it possible to make the vertical path thereof smaller in length (half the length, i.e. 5 meter instead 10 meter, for example) , so that it is less cumbersome to provide a hole into the ground for mounting the vertical path therein. Above the horizontal path there is enough space to mount a collecting device for collecting fumes and the like originating from the heating medium containing salts .

It is noted that the terms "essentially vertical" and

"essentially horizontal" encompass deviations between 0 and 25°.

In a preferred embodiment of a process in accordance with the invention the strand-like extrudate is transported through the heat treatment medium in downward direction, subsequently in upward direction and finally in horizontal direction . In a further preferred embodiment of a process according to the invention the strand-like extrudate is formed by a wiping element, particularly a wiping element for a wiper blade of a vehicle.

The present invention also relates to an apparatus for carrying out a process in accordance with the invention, comprising a bath containing a heat treatment medium, characterized in that the bath is in the form of a closed L- shaped channel provided with an inlet and an outlet for the strand-like extrudate, such that the strand-like extrudate can be transported through the heat treatment medium along an at least substantially L-shaped path inside the bath. The heat treatment medium particularly comprises a salt melt.

In a preferred embodiment of an apparatus according to the invention the apparatus comprises at least one guiding roll for the strand-like extrudate, wherein the guiding roll is movable in essentially vertical direction between an upward position above a downwardly extending part of the L-shaped channel and a downward position into the downwardly

extending part of the L-shaped channel. Particularly, the apparatus comprises further guiding rolls for the strand^¬ like extrudate, wherein the further guiding rolls are movable in essentially vertical direction between an upward position above a horizontally extending part of the L-shaped channel and a downward position into the horizontally extending part of the L-shaped channel. In a further preferred embodiment of an apparatus in

accordance with the invention the bath containing the heat treatment medium is directly connected to a working tool of an extruder, so that the strand-like extrudate can be directly vulcanized into the heat treatment medium.

In a further preferred embodiment of an apparatus according to the invention the apparatus comprises heating means for heating the bath containing the heat treatment medium. The temperature of the heating medium varies between 150 and 300 °C.

In a further preferred embodiment of an apparatus in

accordance with the invention the bath containing the heat treatment medium is thermally isolated from the environment. Hence, temperature losses to the environment are thereby minimized, resulting in a cost reduction.

In a further preferred embodiment of an apparatus according to the invention the L-shaped channel comprises a downwardly extending part and a horizontally extending part, wherein the ratio between the width of the downwardly extending part and the length of the horizontally extending part varies between 0,3 and 1.

The combination of a vertical and a horizontal path, i.e. an L-shaped path, in accordance with the invention has the following advantages over the use of a traditional

horizontal path only. First of all, due to the fact that the stand-like extrudate (partly) follows a vertical path, any deformation of the stand-like extrudate as a result of the force of gravity is minimized. Secondly, the L-shaped path is shorter in length, resulting in minor temperature losses of the heating medium to the environment, for example, and thus a more homogeneous temperature distribution over the entire length of the L-shaped path. The present invention will be explained further with the help of a preferred embodiment of the invention illustrated in a drawing, wherein - figures 1 and 2 schematically show an apparatus for

producing a strand-like extrudate formed by a wiping element for a wiper blade of a vehicle, wherein figure

1 refers to a start phase of the production and figure

2 relates to a running phase of the production.

The apparatus (1) in figures 1 and 2 comprises an extruder (2), wherein a rubber material, such as natural rubber or synthetic rubber (for example, polyurethane rubber or EPDM rubber or CR rubber) is plasticized. A working tool (3) of the extruder (2) subsequently transforms the rubber material from the extruder (2) into a strand-like extrudate (4) in the form and in the size of a wiping element for a wiper blade for a vehicle. After the extrusion, the strand-like extrudate (4) is vulcanized by transporting the strand-like extrudate (4) in a bath (5) comprising a heat treatment fluid (6) therein. The heat treatment fluid (6) is

particularly composed of a salt melt, wherein the salt may be a mixture of potassium nitrate, sodium nitrate and sodium nitrite or a mixture of lithium nitrite and potassium nitrate, for example. The salt melt is held at a temperature between 150 and 300 °C with the help of a heating device (not shown) .

As can be seen from figure 2, the strand-like extrudate (4) is transported through the heat treatment fluid (6) along a L-shaped path inside the bath (5) , wherein the strand-like extrudate (4) is transported through the heat treatment fluid (6) in the direction of the arrows (7), i.e. first in downward direction, subsequently in upward direction and finally in horizontal direction. In view of the fact that the strand-like extrudate (4) travels along the L-shaped path through the heat treatment fluid (6), the bath (5) is in the form of a closed L-shaped channel (8) provided with an inlet (9) and an outlet (10) for the strand-like

extrudate (4) . More in particular, the L-shaped channel (8) comprises a downwardly extending part or tube (11) filled with the heat treatment fluid (6), that is the salt melt, as well as horizontally extending part or chute (12) having a U-shaped cross-section. The downwardly extending part (11) and the horizontally extending part (12) are interconnected, wherein they are preferably in one piece of metal or

plastic. The horizontally extending part (12) is also filled with the salt melt. The vertically extending part (11) and the horizontally extending part (12) are both thermally isolated from the environment through a lining (13) on the outside thereof. Above the horizontally extending part (12) is a collecting device (14) for collecting ("sucking") fumes and the like originating from the salt melt.

With reference to figures 1 and 2, the apparatus (1)

comprises a driven guiding or transport roll (15) movable in vertical direction between an upward position above the downwardly extending part (11) of the L-shaped channel (8) (figure 1) and a downward position into the downwardly extending part (11) of the L-shaped channel (8) (figure 2) . During the start phase of the production of the strand-like extrudate (4) (figure 1), that is at the start up of the production, the strand-like extrudate (4) is transported from the working tool (3) of the extruder (2) by means of the roll (15) being in the upward position and a roll (16) located at the transition between the downwardly extending part (11) and the horizontally extending part (12) of the L- shaped channel (8) . In other words, the strand-like

extrudate (4) is transported between said rolls (15,16) towards the outlet (10) . Other driven guiding or transport rolls (17) located above the horizontally extending part (12) of the L-shaped channel (8) are not working in the start up of the production. In this respect it is noted that these further guiding rolls (17) are movable in vertical direction between an upward position above the horizontally extending part (12) of the L-shaped channel (8) (during the start phase of the production) and a downward position into the horizontally extending part (12) of the L-shaped channel (8) (during the running phase of the production) . At the start up of the production, the strand-like extrudate (4) is thus directly transported along the horizontally extending part (12) of the L-shaped channel (8), so that the

vertically extending part (11) of the L-shaped channel is left idle at the start up. However, during the running phase of the production (figure 2) the roll (15) is lowered in its downward position into the downwardly extending part (11) of the L-shaped channel (8), so that during that phase the strand-like extrudate (4) is transported along the entire L- shaped path, that is downwardly and subsequently upwardly in the downwardly extending part (11) of the L-shaped channel (8), and subsequently horizontally in the horizontally extending part (12) of the L-shaped channel (8) . The roll (15) and/or the rolls (17) are/is movable in vertical direction between an upward position and a downward position by means of hydraulic or pneumatic means. In the alternative electrical means take care thereof.

In figures 1 and 2 is further shown an inlet (18) for the salt melt near the bottom (19) of the downwardly extending part (11) of the L-shaped channel (8), as well as an

overflow (20) for the salt melt at the location of a free end of the horizontally extending part (12) of the L-shaped channel (8) . The overflow (20) is connected, via a collector

(21) , to a salt melt cleaner (not shown) . The salt melt cleaner pumps the salt melt in a closed circuit towards the inlet (18) . Ground level is indicated with reference number

(22) , whereas a reservoir for rinsing the strand-like extrudate (4) is given reference number (23) .

The present invention is not restricted to the embodiment shown in figures 1 and 2, but also extends to other

preferred embodiments falling within the scope of the appended claims.

Claims

Process for producing a strand-like extrudate (4) composed of a rubber material which is vulcanized after extrusion, wherein the vulcanization is carried out in a bath (5) by means of a heat treatment medium (6) present therein, characterized in that the strand-like extrudate (4) is transported through the heat treatment medium (6) along an at least substantially L-shaped path inside the bath (5) .

A process according to claim 1, wherein the strand-like extrudate (4) is transported through the heat treatment medium (6) in an essentially vertical direction and subsequently in an essentially horizontal direction.

Process according to claim 1, wherein the strand-like extrudate (4) is transported through the heat treatment medium (6) in downward direction, subsequently in upward direction and finally in horizontal direction.

Process according to claim 1, 2 or 3, wherein the strand-like extrudate (4) is formed by a wiping

element, particularly a wiping element for a wiper blade of a vehicle.

Apparatus (1) for carrying out a process according to any of the preceding claims 1 through 4, comprising a bath (5) containing a heat treatment medium (6),

characterized in that the bath (5) is in the form of a closed L-shaped channel (8) provided with an inlet (9) and an outlet (10) for the strand-like extrudate (4), such that the strand-like extrudate (4) can be transported through the heat treatment medium (6) along an at least substantially L-shaped path inside the bath (5) .

Apparatus (1) according to claim 5, wherein the

apparatus (1) comprises at least one guiding roll (15) for the strand-like extrudate (4), and wherein the guiding roll (15) is movable in essentially vertical direction between an upward position above a downwardly extending part (11) of the L-shaped channel (8) and a downward position into the downwardly extending part (11) of the L-shaped channel (8) .

Apparatus (1) according to claim 6, wherein the

apparatus (1) comprises further guiding rolls (17) for the strand-like extrudate (4), and wherein the further guiding rolls (17) are movable in essentially vertical direction between an upward position above a

horizontally extending part (12) of the L-shaped channel (8) and a downward position into the

horizontally extending part (12) of the L-shaped channel ( 8 ) .

Apparatus (1) according to claim 5, 6 or 7, wherein the bath (5) containing the heat treatment medium (6) is directly connected to a working tool (3) of an extruder (2), so that the strand-like extrudate (4) can be directly vulcanized into the heat treatment medium (6) .

Apparatus (1) according to any of the preceding claims 5 through 8, wherein the apparatus (1) comprises heating means for heating the bath (5) containing the heat treatment medium (6) .

10. Apparatus (1) according to any of the preceding claims 5 through 9, wherein the bath (5) containing the heat treatment medium (6) is thermally isolated from the environment .

11. Apparatus (1) according to any of the preceding claims 5 through 10, wherein the L-shaped channel (8)

comprises a downwardly extending part (11) and a horizontally extending part (12), and wherein the ratio between the width of the downwardly extending part (11) and the length of the horizontally extending part (12) varies between 0,3 and 1.

12. Apparatus (1) according to any of the preceding claims 5 through 11, wherein the heat treatment medium (6) is a salt melt.