FR2497686A1 - DEVICE FOR MIXING CHEMICAL COMPONENTS, PARTICULARLY REACTIVE, PROVIDED WITH MOBILE INJECTORS - Google Patents

Abstract

THE INVENTION RELATES TO A DEVICE FOR MIXING REACTIVE CHEMICAL COMPONENTS TO BE FEED IN A FORMING MOLD AND TO BE RECYCLED BEFORE EACH MIXING OPERATION. THE MIXING HEAD 1 IS PROVIDED WITH INFECTORS 6, 7 FOR THE SUPPLY OF EACH COMPONENT, WHICH ARE SUPPORTED TO BE AXIAL MOVABLE AND HYDRAULICALLY CONTROLLED, BETWEEN AN ADVANCED POSITION, IN WHICH THE INJECTION TAKES PLACE INTO THE MIXING CHAMBER, AND A RECOVERED POSITION, IN WHICH THE RECYCLING OF EACH COMPONENT TAKES PLACE BY MEANS OF THE INJECTORS.

Description

Device for mixing chemical components, especially reactive,

provided

mobile injectors.

  The present invention relates to a device for

  mixing - and distributing - chemical components

  including, but not limited to, components

  chemical reagents, specially designed for compounds

  sants reacting at a very high speed to provide

synthetic resin.

  There are known skimming devices provided with a head for mixing chemical components.

  reagents, to form a mixture of synthetic resin

  tick to feed in the hollow or recess of a mold.

  The head generally comprises a cylindrical mixing chamber provided with an inlet opening in which the injection injection convergers are placed.

  each component: each reactive component is supplied

  tee under high pressures, for example from 100 to 120 atmospheres, to obtain the required degree of nebulization or atomization, in order to ensure a mixture having

  correct stoichiometric relationships between the

  chemical layers, before the mixture formed is

  fed into a mold. Before each metering operation

  diaper and molding, these devices must be effective

  kill a recycling phase of each chemical component

  that, under a high pressure corresponding, or almost, to the value of the feed for the mixture: it has indeed been found that, to have a correct control of the stoichiometric ratios between the chemical components, it is necessary to feed the components during

  of the mixture as well as during recycling in use

  reading fundamentally consistent pressure values

  aunts and equal to each other. This pressure control is particularly critical in the transition conditions, that is to say at the time of the transition from a recycling phase to a mixing phase. During

  this transition phase, which lasts an infinite time-

  simal, can create, in fact, conditions for

  functioning capable of causing large variations

  aunt and uncontrolled supply pressures of the reactive components and each variation of the supply pressure of the components, at the beginning of their mixing, can produce defects, sometimes very serious, of the

resulting stamped part.

  Currently known devices include

  different types of compound recycling systems

  sants, comprising recycling valves separate from the injectors, i.e. recycling valves

  placed on the same line as the injectors,

  managing, for example, separate conduits for com-

  posing in a control device associated with the

  or inside the mixing chamber.

  The use of separate recycling valves does not allow

  that it is difficult to obtain feeding conditions

  tion of components that are homogeneous to each other, that is to say to recycle the components at supply pressures of the components equal to or almost equal to those of the mixing phase. The use of recycling pipes on the same line as the injectors, in control devices associated with the

  mixture or inside the latter does not

  co.e allowed to adequately solve the problem, especially for transitional switching periods

  between one phase and the next phase.

  Indeed, given that the transverse dimensions

  dirty mixing chambers are reduced it is im-

  possible to fit the control device inside

  room and provide recycling ducts

  key for the passage of components having a wide

  section and therefore not introducing additional overpressures

  tional; moreover, the possibility of formation of impurities along the recycling conduits, after the injectors, as well as at the level of the injection convergers, may modify the recycling conditions, with respect to the supply conditions during 'a mixing phase. These variations increase particularly during the transition from a recycling phase to the subsequent mixing phase due to a phenomenon linked to

  elastic behavior of the tubes which connect generally-

  the mixing head to the circulation pumps of each component. In fact, in installations of the aforementioned type, it is necessary to be able to move the mixing heads along the same mold, which means that we have to move them towards the molds which move along the molding line or else bring them to a remote position; the junction tubes must therefore be flexible, that is to say that they must follow the head during its movements. Since these systems are generally formed by rubber tubes, suitably reinforced, that is to say that they can expand at high operating pressures,

  and since the metering pumps supplying the components

  sants are of the constant flow type, it follows that a variation in the supply pressure of the reactive component upstream of the injector produces a variation in the volume of the tubes, that is to say a variation in their capacity which implies a modification of the stoichiometric ratios between the components. All this is particularly serious when switching from a recycling phase to a mixing phase, since everything

  uncontrolled overcharging occurs at the start

  bles, even if they have a very short duration. This incon-

  is strongly accentuated if, at the time of the deviation

  tion of the fluid from the recycling circuit to the chamber

  there is also a variation in feed

tation of the reactive component.

  To reduce the aforementioned drawbacks, the par-

  recycling course for each component should therefore have the same characteristics as the course

  supply to the mixing chamber, to allow

  put that feed during mixing and the

  components can be circulated again

  kill under basically constant aggression.

  This could be achieved, for example, by circulating the components, also during recycling

  although during mixing, always using the

  supply jets in the mixing chamber and preparing recycling conduits having large passage sections, so as to have pressures

  substantially equal feed.

  According to the invention, mobile injectors are therefore provided in an axial direction in order to be able to supply - in an advanced position, the components, directly through the openings, in the mixing chamber, and,

  - in a remote position, the openings of the cham-

  With the mixture closed, the reactive components, separately along their respective recycling conduits.

  However, the power of the components, through

  to the injectors in question, during both the mixing and recycling phases, is not sufficient

  alone, to guarantee feed pressures

  always equal to each other and to reduce fundamentally

  The phenomena linked to variations in the capacity

  cited tubes at the transition from an operating phase to the next phase. Indeed, so that the mixture of the components is correct, as regards the ratios

  desired stoichiometric values, from the start of the switching

  tion, the injectors must be moved simultaneously, in a controlled manner and at high speeds, that is to say in a switching time of a fraction

second.

  The subject of the present invention is therefore a provision

  sitive with a mixing head of the genus sus-

  which can avoid the above-mentioned drawbacks and which make it possible to obtain supply conditions, during the recycling of each reactive component, equal or substantially equal to the conditions which arise during a mixing phase and at the same time allowing paage from an operating phase to the next phase in a very short time and in a strictly controlled manner for all components, so as to ensure a correct stoichiometric ratio

  for mixing components from the start of mixing.

  A device for mixing chi-

  reagents capable of satisfying these com-

  takes a mixing head with a mixing chamber which has opposite inlet openings for each component and a mixture distribution opening, injectors for each component through the respective inlet openings in the mixing chamber, and at the minus a control device connected

  to an actuating device, this device for

  sliding hole along the mixing chamber between a first advanced position in which it closes

  the aforementioned openings and a second position received

  lée behind said openings, said device being characterized in that each injector is movable in an axial and transverse direction relative to the mixing chamber, between a position

  advanced, in which the common injection convergent

  fuck directly with the respective entrance opening

  of the component in the mixing chamber, and a posi-

  remote position, in which the openings of the cham-

  Since the mixture is closed, the injection convergent communicates directly with a recycling conduit,

  and in that the injectors are connected to devices

  respective control devices, actuated by a source of pressurized fluid, in a manner coordinated with the actuation device of the control device

  sliding in the mixing chamber.

  According to a preferred embodiment of the invention, the control devices consist of cylinders advantageously connected to the source of fluid which is under high pressure so that their actuation is rapid and simultaneous in order to ensure the best conditions operating from

start of mixing.

  The invention will be described below in more detail with reference to an embodiment

  a mixing head of particular shape not limited to

  tive, illustrated in the drawings, in which: - Figure 1 shows, in cross section, the mixing head, along line 1-1 of Figure 2, with the injectors in an advanced position; - Figure 2 is a longitudinal section of the mixing head; and - Figure 3 shows a partial sectional view of the head of Figure 2, with the injector

in a remote position.

  Figures 1 and 2 illustrate a mixing head 1 for reactive chemicals to be mixed and fed into a mold (not shown); the head 1, in the example shown, comprises a mixing chamber, in the shape of an "L", defined by a first part of chamber 2, of reduced length and diameter, and a second part of chamber 3, of diameter and larger in length, forming an angle with the first

  part of room 2; however, it is evident that the

  general idea and characteristics of this

  invention can also be used with other

  very shapes and other types of mixing chamber.

  The illustrated mixing chamber comprises lateral openings 4 and 5, diametrically opposite, in a part of its lateral surface, for example in the part of chamber 2 with reduced dimensions, to allow the supply, under high pressure, of at least minus two chemical components to be mixed

  diapers and fed in a mold in which they

  chemically slip to form a soft part

plastic material.

  References 6 and 7 indicate two devices

  of reactive components, more simply called

  injectors and of which only injector 6 is shown

  felt in section in Figure 1, the converging information

  jection can communicate with admissions openings

  sion 4 and 5 of the mixing chamber.

  Inside the room part 2 slides

  a first control device in the form of a gou-

  pile 8 powered by a hydraulic device

  nant a piston 9, short stroke, to quickly move the pin 8 between an advanced position, in which it closes at the same time the openings 3 and 4 of the components admission and the outlet 2 'of the chamber part 2 , at the same time emptying the chamber part 2 at the end of each mixing operation, and a retracted position, behind openings 3, 4,

  which it releases the aforementioned openings 3 and 4 of ad-

  components mission and issue 2, at the start of each mixing phase. In the embodiment shown, the head 1 comprises a second discharge device 10, in the form of a pin controlled by a second

  piston 11, long stroke; in this case too, the gou-

  pill 10 is movable in a longitudinal direction in part 3 of the mixing chamber, between an advanced position, in which it closes the opening 12 for output of the mixture towards a mold, as well as the outlet 2 of the part of chamber 2, and simultaneously carries out the evacuation of the part of chamber 3, and a retracted position, in which it clears the opening 12 for outlet of the mixture as well as

  outlet 2 ', as shown in Figure 2.

  We will now give a more detailed description.

  cut from the structure of the injector 6 (the other injector, having the same structure as can be seen in the figures); the injector 6 comprises a body 13 in which a needle valve 14 is placed, ending in a conical point which is introduced into the injection convergent 15 aligned with the opening 4

  of the chemical component. The body 13 of the injector

  tor has a cylindrical shape and it slides in an axial and transverse direction relative to the

  part 2 of the mixing chamber, by means of a device

  control device consisting of a double-acting cylinder, described below, supplied by a source of

  fluid under appropriate pressure.

  The sliding coros 13 of the injector defines, at its anterior end, an interior chamber 16 which is provided, at one of its ends, with the injection convergent 15 and has lateral openings 16a constantly in communication with the conduit d entry 17 of the component through a radial passage 18 and an annular part 19 into the interior surface of the body

  20 defining the cylinder for actuating the injection

  tor. Consequently, the reactive component contained in the reservoir 32 can be continuously supplied by the filter 33, the metering pump 34 and the flexible tubes, in the injector 6, whatever the position of

  this last. Reference 21 indicates an outlet duct.

  tie of the component which can be connected to the injector 6 in the manner described below, when each chemical component must be recycled in the reservoir 32, by the flexible conduit 36, while basically maintaining the supply pressure of the component upstream of

the injector 6.

  In the embodiment shown, the body 13 of the injector is screwed into a part 23a formed by a piston 23 sliding, in an axial direction, in a cylindrical chamber of the body 20 which constitutes the hydraulic control device, of the cylinder type. double-acting. As shown schematically in Figure 3, the anterior chamber, that is to say the one facing the mixing chamber, of each control cylinder of the injectors 6 and 7 and, correspondingly , the rear chamber of the cylinder 9a for actuating the pin 8 are connected,

  by flexible conduits 24, 25 and 26 and by a support

  switching valve 27, at a source 28 of a pressurized fluid or respectively at the discharge outlet,

  while the rear chamber of the

  injectors 6, 7 and the inside of the cylinder

  control of pin 8 are connected to the outlet

  cuation or respectively at the source 28 of a pressurized fluid, by flexible conduits 29, 30 and 31; consequently, the injectors 6 and 7 advance in a synchronous and coordinated manner at the retreat of the pin

8 and vice versa.

  The operation of the mixing head described is in summary as follows: assuming that the mixing phase of the chemical components has ended, that the pins 8 and 10 are in an advanced position and the injectors 6 and 7 in a remote position, the openings 4 and 5 of the mixing chamber are closed by the pin 8 and the body 13 of the injector 6, 7 opens the radial passage 22 as shown in FIG. 3, by putting the component inlet conduit 17 in communication with the outlet conduit 27, through the passage 18, 19, the chamber 16, the injection convergent

  and passage 22 to carry out a new circulation

  tion of the component to the tank. We can therefore recy-

  each component by supplying it with a supply pressure equal to that of the mixing phase, since this pressure is always determined by the same

  injector 6 and 7, the setting of which has not varied. Indeed-

  fet, the recycling conduits directly formed in the body 1 of the mixing head make it possible to maintain

  component passage sections, downstream of the

  jets 6 and 7, sufficiently large and very superior

  res to those of the injection convergent; in this way,

  we do not introduce any cause that could cause

  so many variations in the supply pressure of the

posants during recycling.

  At the end of the component recycling phase, to carry out the mixing phase, the pin is put in a retracted position, according to the execution instructions, and the injectors 6 and 7 are advanced, the pin is also placed 2 in a remote position

  completely clearing the mixing chamber and the

  component entry and entry vertices 4 and 5; since it is possible to use high pressures for controlling the hydraulic cylinders of the injectors, also providing for the use of appropriate pressure accumulators, and since the stroke of the injectors in question is very

  short, it is possible to obtain con-

  control of the flow of reactive components in extremely short times. In addition, no additional cause of pressure increase is introduced, since the thrusts of the reactive component, acting in both directions on the body of each injector, are

  fundamentally balanced between them. Since each

  that chemical component continues to be supplied by the

  same injector, it follows that the supply pressure

  tation basically does not vary during the mixing phase and is equal to that of the recycling phase. In this way, the disadvantages due, during the transient periods in the switching of two phases of the functioning, are avoided or minimized due to the phenomena which, as already said previously, cause an elastic dilation of the

  capacities of the flexible junction tubes of the head.

  A strict control of the stoichiometric relationships between the components is thus obtained from the start,

  therefore, a very good quality of mixture.

  At the end of the mixing phase, the injectors 6, 7 are returned to the retracted position (see FIG. 3), for the recycling of the components, and the pins 8 and 10 are advanced successively for closing and for evacuating the mixing chamber of the residual mixture. As it goes without saying, and as it results from elsewhere

  already from the above, the invention is not limited to

  ment to those of its embodiments and application

  which have been more particularly envisaged; she takes it

  brews, on the contrary, all variants.

Claims (4)

  1. Device for mixing chi-   Reagent mics comprising: a mixing head with a mixing chamber, which has opposite inlet openings for each component and a mixture distribution opening, injectors for each component through the respective inlet openings in the mixing chamber, and at least one   control device connected to an action device-   In addition, this control device slides along the mixing chamber between a first advanced position in which it closes the aforementioned openings.   and a second position moved back behind said or   vertices, said device being characterized in that each injector is movable in one direction   axial and transverse with respect to the meteor chamber   diaper between an advanced position, in which the   injection worm communicates directly with the opener   respective ture of entry of the component into the mixing chamber, and a retracted position, in which the   inlet openings of the mixing chamber being closed   mées, the injection converge communicates directly   with a recycling duct, and in that the injec-   torers are connected to respective device   control, actuated by a source of pressurized fluid   sion, in a coordinated way with the action mechanism-   sliding control device in the mixing chamber.   2. Device according to claim 1, character-   laughed at by the fact that said control devices   are represented by hydraulic cylinders.   3. Device according to claim 1 or 2, ca-   characterized by the fact that each injector is carried interchangeably by a part formed by   a piston of the hydraulic control cylinder.   4. Device according to claim 3, character-   laughed at by the fact that the injector comprises a cy-   lindrique sliding in an anterior extension of the body of the hydraulic control cylinder and by the fact that in this extension are formed side passages for supplying and recycling the component chemical through the injector.