FR2664848A1 - METHOD AND DEVICE FOR THE INJECTION MOLDING OF RUBBER SOLE. - Google Patents

Abstract

Method and device for the injection molding of rubber soles, the unvulcanized raw rubber mass being injected by at least one injection unit and via a rubber dispensing device into at least two mold cavities superimposed in pairs and heatable between which the rubber dispensing device can be inserted and where it is at least prevulcanized. The unilaterally opened cavities (24, 25) are closed by the inserted rubber dispensing device (18), after which the raw rubber mass is injected through two injection groups (4, 5) into the cavities. thus formed, the raw rubber mass being maintained, throughout its path (19, 20) through the rubber distribution device, at a temperature which prevents premature vulcanization.

Description

Method and device for injection molding of insoles made of

  The invention relates to a method for the injection molding of rubber soles, the mass of unvulcanized raw rubber being injected by at least one group.

  injection and via a distribution device

  bution of rubber in at least two mold cavities superimposed in pairs and heatable between which can be inserted the rubber dispensing device and o

it is at least pre-vulcanized.

  The injection process was taken over from PVC and materials.

  thermoplastic materials Unlike these materials which are

  injected at a high temperature into the mold and hardened there

  feels under the effect of cooling, it's just the opposite

  for processing rubber The gross mass must be

  thrown into the mold at a temperature as low as pos-

  susceptible to prevent premature vulcanization Vulcani-

  sation then occurs in the mold under the action of cha-

their.

  However, this technique has so far only allowed

  that the manufacture of simple and uniform rubber soles

  colors, that is to say monolayers, since it has not been successful, as in the case of thermoplastics, to first inject a first layer into the mold, to open the mold further and then inject the second

  layer in the cavity thus created to thereby obtain se-

  two-color rubber beads during rubber injection molding, which takes place at pressures of around 2000

  bars, the mold should be closed all around and made of

  tal to be able to withstand high injection pressures. For example, to still be able to provide

  high-quality sports shoes with a rubber sole-

  bi or multicolored chouc, such soles have been manufactured

  so far by compression molding.

  When compression molding rubber articles

  chouc, it is however generally essential to use a quantity of material greater than that which is necessary for the filling of the volume of the mold Otherwise, a compression molding is impossible and a density

  suitable inside the item cannot be obtained.

  Since during compression molding the material ex-

  is automatically expelled to the outside by

  above the sealing edges of the mold, the proportion of

  is very large during the manufacture of these rubber soles The additional disposal costs are high accordingly In addition, in the case of compression molding, the sealing edges of the mold are subjected to

  permanent wear This means that, unlike

  Injection molding, it is not possible to work with an exact breaking edge and the soles must therefore be trimmed manually. This waste problem has so far played a role.

  also for injection molding of rubber soles

  Single layer chuck Indeed, a problem has hitherto arisen in the sense that it was necessary to prevent the material from vulcanizing already during injection and respectively into the supply device. The vulcanization process must be slowed down a little. , but it must then take place very quickly in the injection molding machine. Although some progress has already been made in this direction, it remains after the vulcanization of small carrots which

  must be removed by a touch-up operation.

  A process of the aforementioned kind is indicated in FR-A-

  94 673 However, the distribution device is not then used to close the cavities formed in the plates of the

  mold As is clear in particular from fig 3 of the publica-

  tion cited, this dispensing device comprises die bodies projecting outwardly which are connected to the injection ports of the respective molds In addition, in

  the case of this distribution system, it is not the whole

  ble of the intermediate body (distribution device) which is maintained at a temperature which prevents premature vulcanization of the rubber to be injected. Such maintenance of the temperature is only achieved in the region of the end caps.

  sector It cannot therefore be excluded that the mass of rubber

  raw cabbage already undergoes, on its way from the injection group

  in the cavities, a pre-vulcanization in the intermediate body.

  This results in blockages which must respectively be eliminated before a new molding operation, so that production must always be interrupted again. In addition, the device used for the well-known process is

  very expensive since on the one hand the device for

  tribution is relatively complicated and that on the other hand a complete mold is associated with each sector of the distribution device This complexity of the structure leads to a

  not insignificant sensitivity to disturbances which acts

  negatively negative on the well-known process But the process is also negatively influenced by the fact that, in the case of the well-known device, stop members are

  mounted in the distribution channels in order to allow

  be a cyclic molding The disadvantage lies here not only-

  lies in the fact that the shut-off members are stressed

  canonically by continual openings and closings, this

  which can lead to failures; stop devices can

  also be blocked and closed by the

  mass of rubber which already vulcanizes in the distribution channels

tribution.

  Another disadvantage of the well known and

  Pectively of the well known device is that this device does not allow to produce soles with two layers. The object of the invention is therefore to conduct procedures

  dice of the aforementioned kind so as to be able to manufacture

  simple rubber soles without significant waste

and at a rapid pace.

  According to the invention, this object is achieved with a pre-

  better variant by the fact that the open cavities one-sided

  are closed by the inserted rubber distribution device, after which the mass of raw rubber is injected by means of two injection groups into the cavities thus formed, the mass of raw rubber being maintained, throughout its course at through the rubber delivery device, at a temperature which prevents premature vulcanization; that, after a first heating time, the molds arranged face to face are separated and that the rubber distribution device is withdrawn between the molds after which the cavities placed opposite one of

  the other and filled with pre-vulcanized rubber

  and respectively form a single cavity, the vulcani-

  sation of soles composed of two layers being completed

  during a second heating time.

  Given the fact that the rubber dispensing device itself constitutes an element of the molds, the construction of the device according to the invention is simpler than that corresponding to the current state of the art, hence a sensitivity to disturbances less This results in a

  more reliable and above all faster control of the process

  on the one hand, the number of moving parts is reduced and

  on the other hand the conformation of these parts is simplified.

  Whereas in the case of the well-known method, it is first necessary to close the molds proper, then to introduce the dispensing device, these operations are carried out in the case of the method according to the invention in a single step. distribution is introduced and then ensures the closing of the molds Because the mass of raw rubber is maintained, throughout its journey through the distribution device, at a temperature which prevents premature vulcanization of the mass, it is certain that, during the following injection cycle, no blockage of the channels opposes the mass of raw rubber injected into the device;

positive distribution.

  Unlike the well-known process, the process according to

  the invention makes it possible for the first time to produce

  Simple way of the two-layer soles For this purpose, the

  positive distribution is removed between the molds and the two molds are brought together so that the pre-vulcanized sole elements can bond intimately during the

second heating time.

  The method according to the invention has the advantages

  already known from the injection molding process which results in

  smells by better quality, by greater yield and

  therefore by more economical production.

  Unlike the compression molding process,

  the molds have, in the case of the injection molding process

  junction, breaking edges so that the soles have

no need to be cropped.

  The decisive advantage of the present invention however lies in the use of an intermediate body which

  acts as a rubber distribution device The parti-

  regularity consists in that the intermediate body is main-

  held at a temperature so low that no vulcaniza-

  tion of the raw rubber mass does not occur in the intermediate body, so that said mass is injected by the shortest path into the cavities, which removes

  practically any waste Since the intermediate body

  diaire constitutes a delimitation of the cavities considered, two of which are respectively arranged one above the other,

  it is relatively easy to achieve by injection of se-

  two-layer and two-part rubber melles

colors.

  By means of the intermediate body, the mass of raw rubber of a respectively necessary color is injected simultaneously, using a double injection group, into the cavities separated by the intermediate body.

  and associated with each other After a first heating time

  during which the sole elements are pre-vulcanized

  sés, that is to say that the partial surfaces of the soles di-

  ribbed towards the intermediate body remain practically unvulcanized, the intermediate body is removed laterally from the machine The associated cavities are brought together and form

  a single cavity, so that the sole elements prevul-

  channeled now rest on each other with the surfaces

  "cold" In this position, the soles are now made

  killed in two layers undergo complete vulcanization at

  during a second heating time.

  The aim mentioned above is however

  also achieved by a process variant which is characterized

  that the unilaterally open cavities are closed

  driven by the rubber distribution device engaged,

  after which the mass of raw rubber is injected by the

  intermediate of two injection groups in the cavities thus formed, the mass of raw rubber being maintained, on

  all of its journey through the distribution system

  rubber consumption, at a temperature which prevents vul-

  premature piping and the surfaces of the dispensing device

  tribution of rubber directed towards the cavities having substantially the same temperature as the molds themselves, which results in a uniform vulcanization of the soles everywhere,

  after which the rubber dispensing device is

  lifted between the cavities and the finished monolayer soles

are withdrawn.

  As in the case of the first variant of the process, the dispensing device again forms, together with the cavities, the actual mold Unlike the

  first variant of the process, it is not a question here of the

  brication of two-layer soles but the manufacture of a double number of monolayer soles This is why the

  heating the filled mold also affects the surface of the

positive distribution.

  To prevent this despite pre-vulcanization

  inside the intermediate body, the heated area is ther-

  insulated from the rubber dispensing device

well said.

  As for the first variant of the process, the intermediate body being put in place, the mass of raw rubber is injected by means of the double injection group and of the distribution device in the respective cavities,

  so that rubber of the same color or also of different

  color annuities is introduced into the soles cavities

  arranged above and below the intermediate body.

  In this position, vulcani-

  complete position of the soles which are removed from the open mold at the end of the heating time, after removing the

intermediate body.

  The two variants of the process discussed above can be modified by detaching in the soles located

  in the different cavities and respectively in the elements

  pre-vulcanized sole elements of the segments which are then replaced by segments of a different color In the

  framework of the first variant of the process, the two cavities as-

  companies are therefore close together and the sole is subjected to complete vulcanization. In the context of the second variant of the process, the heating time is interrupted for example, the segments are detached which are replaced by segments of another color and we finish vulcanization Here too,

  the desired goal mentioned above is achieved.

  In this way, it is possible to perform se-

  multicolored rubber melles Since in each mold the cavities are provided in pairs, it is possible to

  make a pair of bi-soles at each injection cycle

  colored (according to the first variant of the process) or two pairs of single-colored soles (according to the second variant of the process), namely respectively with segments of a

other color.

  The invention allows the use of machines for

  injection molding at one or two stations.

  When working only with a machine at a station, the yield in two-color soles is around 25

  pairs per hour As a result, 50 pairs of single soles

colors are produced per hour.

  However, a person can also easily drive two and respectively four machines associated with each other, so as to consequently increase the

  production of two-color and one-color soles respectively.

  The invention also relates to a device for the implementation of the aforementioned methods The advantages compared to the device well known by the cited publication arise from the above The characteristic that the intermediate body serves as a heatable closure plate in the region of its surfaces for the cavities formed in the mold plates, indicates that the heating of the surfaces of the intermediate body plays a role only for the second

variant of the process.

  In detail, the device according to the invention is

  characterized in that the channels (19, 20) in the intermediate body

  diary (18, 18 ', 21, 22) intended to conduct the material to in-

  jecter can be balanced in temperature, the intermediate body (18, 18 ', 21, 22) serving as a heatable closure plate in the region of its surfaces for the cavities (24, 25) formed in the plates (13, 16 ) of the mold, and in the orifices of the channels (19, 20) on the mold side being provided nozzles (23) which are movable in the direction of their longitudinal axes and whose surface <29) oriented towards the cavity (24, 25 ) and surrounding the orifice of the nozzle is smaller than the opposite surface (28) supplied with material to be injected. Thanks to the conformation and the particular arrangement of the nozzles, it is possible that they are displaced only by the pressure of the material to be injected towards the mold, the nozzles being strongly applied with their edges against

  the separation surface between the cavity and the intermediate body

  diaire and thus ensuring sealing.

  As regards the molds, these are, as has already been said, molds arranged in pairs which can be taken up with slight modifications to the compression molding process. In the case of the two-layer process, the closure

  cavities is ensured by separating plates available

  on the upper faces of the intermediate body When

  the manufacture of single-colored soles, it is possible to use

  read two normal molds for the molding process

compression.

  The body temperature balancing system

  the intermediate is advantageously constituted by a system of channels drilled parallel to the rubber distribution system which is for example supplied by a pressurized water heating apparatus, which makes it possible to bring in and respectively to dissipate the heat in order to be able to maintain the

  rubber dispensing device at set temperature

  The temperature is regulated and stabilized by a system

  adjustment integrated in the machine control.

  For the manufacture of single-colored soles, the upper faces of the intermediate body are provided with heating plates which are thermally insulated with respect to the intermediate body. The heating is done for example by means of

  heating cartridges so that the heating plates

  leaves reach a temperature of around 2000 C, while

  the core channels of the rubber distribution device

  chouc are kept at a temperature of around 70 to 900 C.

  Thanks to the conformation and the particular arrangement

  nozzles, these can be pushed towards the separation plates so as to automatically seal on said separation plates which

are changed for each mold.

  Because each soleplate and each cavity respectively is equipped with more than one nozzle (in particular two), the flow paths in the mold become even shorter, and one can expect very low pressures at

  inside the mold which are necessary for the

puckering of the cavity.

  The low achievable internal pressures assu-

  also limit or remove burrs.

  The following description, next to the drawings

  annexed by way of nonlimiting examples, will allow a good understanding of how the invention can be put into practice. Figure 1 shows, partially in section, a top view of an injection molding machine; Figures 2 a to d show, schematically, the course of the process during the manufacture of two-layer rubber soles; Figure 3a shows, partially in section, a side view of an intermediate body for use in the process according to Figs 2 a to d; Figure 3b shows a top view of the intermediate body of Fig 3a; FIGS. 4 a and b show, diagrammatically, the course of the process during the manufacture of rubber soles with a single layer; Figure 5a shows, partially in section, a side view of an intermediate body for use in the process according to Figs 4a and b; FIG. 5 b represents a top view of the intermediate body of FIG 5 a; Figures 6 a and b show, schematically, the course of the process during the manufacture of soles

  monolayers with insertion segments.

  Fig 1 shows an injection molding machine

  tion used for the manufacture of rubber soles and generally bearing the reference 1 Next to the machine 1 is

  depicted the electric power supply installation

  sheet 2 The machine operates with a closing force of 1600 k N and has an injection volume of twice 350 cm 3

  for an injection pressure of 2000 bars The hydrau-

  for closing and opening the mold 3 which is indicated here only schematically, and for driving the injection groups 4 and 5 is marked 6 The groups 4 and 5 operating as group d double injection ends in an injection head 7 o open there outwards the channels 8 and 9 arranged vertically one above the other and leading the raw rubber masses of different colors It emerges from the fig 1 that the machine 1 is equipped with a demolding table 10 so that the lower element of the mold, the impression plate, can

be pulled out laterally.

  Figs 2 a to d show the schematic structure

  of the machine molding station 1 The reference 11

  signs the stationary upper fixing plate on which is mounted the upper heating plate 12 which brings to

  in turn the upper plate 13 of the mold.

  Similarly, the lower fixing plate

  mobile laughter on which the lower heating plate is mounted

  upper 15 which in turn carries the lower plate 16 of the

mold is designated by 14.

  Fig 2a shows the situation in which a se-

  two-color two-layer rubber melle 17 is removed from

the molding station.

  The two-channel injection head is indicated and

bears the reference 7.

  In fig 2 b, an intermediate body 18 is inserted between the upper plate 13 and the lower plate 16 of the mold. Inside the intermediate body 18 is provided a rubber distribution device with carrot channels 19 and 20 From on the side of the intermediate body 18 directed towards the injection head 7, these first of all lead horizontally towards the inside of the intermediate body 18 and then move at right angles to the plates 13 and 16 of the mold Between the surfaces of the intermediate body 18 and the plates 13 and 16 of the mold, the intermediate body 18 is

  provided with a separation plate 21 and 22 respectively.

  As is apparent in particular from FIGS. 3 and 5 and as described in detail below, the channels 19 and 20 ending at the separation plates 21 and 22 are fitted with nozzles 23 The figure represents the instant o respectively a

  color was injected into cavities 25 and 24 through the

channel 19 and 20.

  In FIG. 2 c, the injection head 7 has been moved aside after a first heating time, and the lower fixing plate 14 has moved away, with the lower mold, from the upper fixing plate 11 The intermediate body 18 which is no longer indicated only schematically is also removed. Then (fig 2 d), the mold elements (13, 16; 24, 25) are brought together During a second heating time, the two sole elements undergo complete vulcanization to

form the bicolor sole 17.

  FIG. 3 a shows an intermediate body 18 as it is used in the method according to FIGS. 2 a to d. The cores canals 19 and 20 are noted respectively. 22 are shown in section These holes widen towards the outside In these recesses 26 and 27 the nozzles 23 are mounted in a movable manner These are shaped so that the front face 28 supplied by the mass of rubber is larger that the front face 29 oriented towards the separation plate 21 and respectively 22 When

  the supply of the nozzles 23, these are pushed towards

  divider plate 21 and 22 respectively

  which they apply tightly.

  Channels designated by 30 are part of a system

  temperature balancing system that keeps the body

  diary 18 and especially the carrot channels 19, 20 at a constant temperature of around 800 C. As can be seen from FIG. 3 b which represents a top view of the intermediate body 18, the carrot channel 19 and respectively 20 branches out first of all at a right angle in the horizontal direction to branch again 900 in the same plane, so that respectively two orifices with the corresponding nozzles 23 are disposed on both sides of the channel 19 and respectively 20 coming from the head injection 7. Figs 4 a and b show a variant of the process

according to the invention.

  Here, we respectively make two pairs of se-

  single color, so that the upper and lower shelves

  lower 13 and 16 of the mold are shaped as a mirror image.

  The intermediate body 18 'used here differs from the inter-

  18 by the fact that, as can be seen in FIG. 5 a,

  the upper faces of the intermediate body are provided with

  one of a hot plate 31, 32 which are separated from the body

  intermediate 18 'by thermal insulation 33 and 34.

  The channels for the heating medium are designated

by 35.

  To reinforce the insulation, the nozzles 23 are mounted in inserts 36 and 37 which are in turn arranged in recesses 38 and 39 formed in the insulation 33, 34 and respectively in the heating plates 31, 32 Between

  the outer wall of the inserts 36, 37 and the heating plates

  leaves 31, 32 and insulations 33, 34 respectively

  left a ventilation slit 40 Furthermore, the body inter-

  18 'medial shown here does not differ from the intermediate body

  diary 18 Using this intermediate body 18 ', the

  injection molded plates are subjected to complete vulcanization in a manner analogous to that shown in the

fig 2 a and b (see also fig 4 b).

  For both the first and the second va-

  laughing at the process, it is possible to give certain

  sole regions different coloring This is illus-

  very using the example of fig 6 a and b.

  The soles and respectively the elements of se-

* pre-vulcanized melles (fig 2 b, fig 4 b) remain within

  molds Segments are removed from the molded material by

  jection and pre-vulcanized and replaced by congruent segments (41) of different coloring Next, the soles (fig 6 b) and respectively assembled sole elements

  (fig 2 d) are subjected to complete vulcanization.

Claims (9)

  1 Process for the injection molding of se-   rubber, the mass of unvulcanized crude rubber   being injected by at least one injection group and by means of a rubber distribution device into at least two mold cavities superimposed in pairs and heatable between which the device can be inserted   rubber distribution and where it is at least pre-   channeled, characteristic S that the unilaterally open cavities are closed by the inserted rubber distribution device, after which the mass of raw rubber is injected via two injection groups into the cavities thus formed , the mass of raw rubber being maintained, over its entire path through the rubber dispensing device, at a temperature which prevents premature vulcanization, that, after a first heating time, the molds arranged face to face are separated and that the rubber distribution device is removed between the molds, after which the cavities placed opposite one another and filled with pre-vulcanized rubber are brought together and respectively form a single cavity, the vulcanization of the soles composed of two   layers being finished during a second heating time fage.   2 Method for injection molding of se-   rubber, the mass of unvulcanized crude rubber   being injected by at least one injection group and by means of a rubber distribution device into at least two mold cavities superimposed in pairs and heatable between which the device can be inserted   rubber distribution and where it is at least pre-   channeled, characterized in that the one-sided open cavities   are closed by the inserted rubber distribution device, after which the mass of raw rubber is injected by means of two injection groups into the cavities thus formed, the mass of raw rubber being maintained, throughout its course at through the rubber delivery device at a temperature which prevents   premature vulcanization and the surfaces of the dis-   rubber tribution associated with cavities presenting   roughly the same temperature as the molds themselves, which results in uniform vulcanization of the soles everywhere,   after which the rubber dispensing device is re-   pulled between the cavities and the finished monolayer soles are removed.   3 Method according to one of claims 1 or 2,   characterized in that the sole and respectively of the elements   parts of pre-vulcanized soles are detached from the segments which are replaced by congruent segments of a coloring   different, after which the vulcanization of the soles is ter-   undermined. 4 Device for implementing the method   according to one of claims 1 to 3, comprising a tray   upper fixing plate and a lower fixing plate   which can be moved relative to each other, a first heatable mold tray can be mounted on the upper fixing plate and a second heatable plate   of the mold which can be mounted on the lower fixing plate   laughing, as well as an intermediate body insertable between the mold plates and serving as a device for distributing   rubber, in which are provided channels for the conduction   tion of the mass of raw rubber which open on the one hand into the cavities formed in the mold plates and on the other hand exit laterally from the intermediate body, at the   outlet of at least one injection group, c a r a c t e r i -   s e e N c e that the channels (19, 20) used to conduct the material to be injected can be temperature balanced in   the intermediate body (18, 18 ', 21, 22), the intermediate body   diary (18, 18 ', 21, 22) serving as a closing plate for the cavities (24, 25) formed in the plates (13, 16) of the mold and which can be heated in the region of its surface, and nozzles ( 23) being provided in the orifices of the channels (19,   ) on the mold side, which nozzles are movable in the di-   rection of their longitudinal axes, and whose surface (29) directed towards the cavity (24, 25) and surrounding the orifice of the nozzle is smaller than the opposite surface (28) supplied with material to be injected.   Device according to claim 4, characterized in that the surfaces of the intermediate body (18) closing the cavities (24, 25) consist respectively of a separation plate (21, 22).   6 Device according to one of claims 4 or   , characterized in that in the intermediate body (18, 18 ') there are provided, in the region of the channels (19, 20), conduits   (30) for conduction of a temperature equalizing fluid ture.   7 Device according to one of claims 5 and   6, characterized in that heating elements (35) are provided in the intermediate body (18 '), in the vicinity of the separation plates (21, 22).   8 Device according to claim 7, characterized in that the cooled region of the intermediate body (18 ') is respectively separated by an insulating layer (33, 34) of   heated regions (31, 32) of the intermediate body (18 ').   9 Device according to one of claims 7   or 8, characterized in that the heating elements consist of heated metal plates (31, 32) from the outside.   Device according to any one of the res-   dications 7 to 9, characterized in that the nozzles (23) are arranged in inserts (36, 37) which are provided in recesses made both in the insulating layer (33, 34) and in the heating plate (31, 32), the diameter of the recess provided in the insulating layer (33, 34) being more   larger than the diameter of the recesses in the heating plates   rims (31, 32) and inserts - (36, 37) passing with an edge   in the form of a flange under the shoulder located between the iso- layer   lante (33, 34) and the heating plate (31, 32).   11 Device according to claim 10, character-   rised in that a ventilation slot (40) is provided between the   serves (36, 37) and the heating plate (31, 32) and respective- the insulating layer (33, 34).   12 Device according to any one of the res-   dications 4 to 11, characterized in that the channels (19, 20) have for each cavity (24, 25) more than one orifice provided a nozzle (23).