FR2534845A2 - DEVICE FOR DIRECTING A MIXTURE OF PLASTIC MATERIAL TOWARDS A MOLD PARTICULARLY TO CAUSE A CHEMICAL REACTION - Google Patents

Abstract

THE INVENTION RELATES TO A DEVICE FOR DIRECTING TO A MOLD A MIXTURE OF PLASTIC MATERIAL LIKELY IN PARTICULAR TO CAUSE A CHEMICAL REACTION. IN THIS DEVICE, A 25A STOP MAY BE MOVED AT INTERVALS WHILE A MIXING HEAD IS IN OPERATION. THIS STOP 25A IS IN EFFECTIVE CONNECTION WITH A CYLINDER 25, 23A, 28 ACTUATED BY A PRESSURIZED FLUID. THIS STOP 25A IS CONSTITUTED BY THE END OF A PISTON 25 OF THE CYLINDER. THIS PISTON HOSTS A TAIL 27 THAT CAN BE LONGITUDINALLY BLOCKED IN THE HOUSING 18, 19, 23 OF A CLEANING BLOCK 14. RESPECTIVELY POST AND ANTERIOR POSITIONS OF THIS BLOCK 14 AND OF A RETAINER 15 ARE DETERMINED BY A COLLAR 28 AND BY AN EXTREME 30 SIDE, RESPECTIVELY. APPLICATION IN PARTICULAR TO THE MIXING OF REACTIVE MATERIALS.

Description

The present addition relates to a device for

  direct to a mold a plastic generating mixture that can

  especially to enter a chemical reaction.

  In a high-pressure mixing head for plastics resulting from a chemical reaction, according to DE-C-2 327 269, a channel developed downstream of the mixing chamber serves to tranquilize the turbulent mixture of the generator components. plastic material exiting said mixing chamber, before this mixture reaches the mold A cleaning block cleans the channel after each mixing phase It is known to equip mixing heads of mobile storage members in order to control the pressure which prevails in the mixing chamber and to obtain a good dosage even in the presence of small amounts spilled (a few grams for each phase of mixing), by arranging these accumulation members in the mixing chamber itself (DE-C documents 2,065,841 and DE-B-2,612,812), or behind

  said chamber in a casting channel (DE-U-2,544,749).

  These known arrangements have the disadvantage of being

  difficult to construct, to be cumbersome and to

  complicated and / or expensive control mechanisms.

  Patent Application DE-A-3 040 922 has already proposed a mixing head in which the cleaning block takes a posterior position such that the outlet orifice of

  the mixing chamber is partially closed and allows

  Thus, an adjustable throttling of the mixture of the reactive plastic components exiting from said chamber is also affected. Another disadvantage is that mixing residues are deposited on the part of the cleaning unit located in front of the outlet of the mixing chamber, arrive immediately or later in the cavity of the mold (having already more or less hardened) and harm to

  the quality of the object resulting from the molding.

  According to the main patent, this disadvantage is overcome by the fact that there is provided, between the cleaning block and the pilot piston of the latter, a displacement device which can be

  arbitrarily operated, functioning by reciprocal action and by means of

  which the throttling position of the cleaning block can be suppressed.

  Thus, the main patent describes a device of the mixing head type des-

  designed to direct to a mold a mixture (plastic generator

  comprising at least two components and in particular able to enter chemically

  in response), the device comprising a mixing chamber

  in which there is a dispenser member having a piston and

  reciprocating from a rear position disengaging the component introduction ports to a forward position in the region of the outlet of said mixing chamber; as well as a channel which

  preferably connecting immediately to said outlet of the chamber

  blending and opening into the molding tool either directly or through other supply ducts, is deflected in particular at right angles to the axis of said chamber and wherein a cleaning block can being actuated by a pilot piston can perform reciprocating movements between a rear position near the outlet orifice of the mixing chamber, and a forward position, said cleaning block being made so that it can be stopped so that its front end partially overlaps the exit port of the chamber

  of mixing by acting as a restraining member causing a choke

  however, that said pilot piston or cleaning block is applied

  in its retracted position against an abutment which is movable for adjustment of different throttling positions, a device being

  further provided by which the outlet of said mixing chamber

  This addition is intended to provide an even simpler device than this known device. Starting from a mixing head of the aforementioned type, this object is achieved by the fact that the device allows a mobility at intervals of the stop at the

  mixing head This results in a solution for

  The cleaning unit and the pilot piston are rigidly connected to each other, and an adjustable stop is provided. In order to achieve the rear position (throttling position) of the block of

  cleaning and at the position of this rearmost block (with sup-

  pressure of the throttling position), the pilot piston is urged by a fluid under pressure on its side facing the cleaning block and is moved to the stop In the most retracted position, the adjustable stop occupying its position extreme, or a fixed stop on the shoemaker

can come into action.

  Conveniently, the adjustable stop can be operated by means of a

  pressurized fluid and it can be effectively connected to an actuating jack

  In addition, one end of the piston of said cylinder can serve as an abutment; this actuator actuated by the pressurized fluid thus constitutes, strictly speaking, the movable stopper. In a particularly simple embodiment for obtaining the throttling position, the piston of said jack may consist of

  in an annular piston in the annular bore of which a rod is

  it can be stopped in different longitudinal positions W inside the housing of the cleaning block, for example by means of a threaded member placed on a threaded region, said rod may have a collar which determines the anterior position of the retaining member , while another fixed stop located on the housing of said cleaning block can determine the most retracted position of the latter (in which it releases the outlet orifice

of the mixing chamber).

  The invention will now be described in more detail with reference to two non-limiting examples of embodiment with reference to the accompanying drawing in which FIG. 1 is a longitudinal section showing a chamber of

  mix perpendicular to which a canal of tranquility is

  mixing; and FIG. 2 is a fragmentary longitudinal section of another

embodiment of said channel.

  In FIG. 1, a dispensing member 2 is movable along the axis of a mixing chamber 1 intended to produce, starting from

  two components, a polyurethane-generating mixture.

  bution 2, taking at the right end the shape of a piston 3, is actuated

  by a jack 4, which is placed on the side of said member 2 and a body 6 of the chamber

  mixing chamber opposite an outlet port 5 of said chamber In its extreme rear position (illustrated position), the piston 3 releases at its end face 7 the orifice opening 8 and 9 of the material generating components In its extreme forward position (on the right), this piston 3 closes said orifices 8 and 9 and prevents them from communicating with the chamber 1 and the outlet orifice 5 thereof. 22 or discharge, formed in the casing of the piston 3, communicate, when the piston 3 occupies its extreme forward position, the introduction ports 8 and 9 with reintroduction conduits and 11 separated one of the other and passing through the body 6 of the mixing chamber. At an angle of 90 to the longitudinal direction of the mixing chamber 1 and immediately behind the outlet port 5 of

  the latter, is a channel 12 of tranquilization of the general mixture.

  The channel 12, having a substantially semicircular cross-section, terminates freely (in a manner not shown in detail) above the cavity of a plastics chamber generated in said chamber 1 and penetrating into said channel 12. , mold open, so not yet closed, or else it ei

  connected to the cavity of a closed mold, or even to a feed duct de-

  plugging in a mold The end face 7 of the piston 3 is adapted to the confi

guration of the channel wall 12.

  In the channel 12, a cleaning block 14 is movable longitudinally.

  such that its lower end releases integrally or partially the outlet orifice 5 of the chamber while said channel 12 is otherwise clear, or it closes said orifice by running to reach a outlet port 17 of the channel Because the piston 3 and the cleaning block 14 can, in their extreme forward positions, take a position in which they are at least flush with the orifice 5 or 17, a residence residues of mixture in chamber 1 and in channel 12 is prevented after each mixing and

filling.

  The cleaning block 14 is actuated, by means of a connecting piece 16 of circular section, by a pilot piston 13-which is movable in a cylindrical casing 19 via a part 18 of the body, this housing 19 is clamped on the body 20 housing the cleaning block 14 The upper region of this housing 19 is closed by a cover 23 which, fixed by means of screws 24, receives in a lower cylindrical portion 23 has a

  annular piston 25 having a stop 25 a and houses, in its upper part

  The threaded region 26 is extended downwardly by a shank or shank 27 terminating in a collar 28. This collar 28 limits the ability of a threaded region 26 to be threaded and held in place by means of a counter nut 29. of movement, downwards, of the piston 25 provided with a stop, the latter being applied, in its highest position, against an end face 30 of the cover 23 between this end face 30 and the upper end face of the piston 25 equipped with the stop; there is a pressure chamber 31 which can be filled with a fluid under pressure by a bore 32, in which case the piston 25 can be moved downwards until it comes

abut the collar 28.

  The pilot piston 13 is moved downwards by a pressurized fluid delivered through a bore 33 and is moved upwardly by a pressurized fluid penetrating through a bore 34. With this bore 34, the pilot piston 13 is displaced upwardly from its position shown in FIG. 1 (which it has taken after a mixing process and in which the mixture residues have been expelled channel 12 from top to bottom), until it comes to bear against the piston 25 serving as an abutment and that the lower end of the cleaning block 14 (retaining member 15) partially closes the orifice of output 5 of the mixing chamber, and when said piston 3 occupies - pa position shown on the file l, the mixing head

  is ready for the next mixing process, this process

  The mixing is initiated by a high-pressure inlet of the plastic generating components into the chamber 1. These components are intimately mixed in said chamber. Through the outlet orifice 5 of the mixing chamber, strangled by the retaining member 15, the flow of the mixture penetrates, being deflected 90, in the channel 12 in which occurs first of all possibly a further improvement of the mixture, but in all cases a stabilization of the turbulent flow, this which causes the mixture to come out of the outlet port 17 of the

  channel according to a laminar flow.

  When it is necessary to put an end to the mixing process, the piston 3 is moved to the right by the jack 4. As a result, the action produced can be of three types: a) the connection between the introduction orifices 8 9 and the mixing chamber 1 is interrupted; flows

  components are then brought back by the channels of over-

  full 21 and 22 in the reintroduction ducts 10 and 11,

  then to unrepresented tanks (re-circulation)

  tion); b) the mixture in chamber 1 is expelled; and c) the walls of said chamber 1 are cleaned of their mixing residues Concomitantly with the movement of the piston 3, the retaining member 15 is moved upward until it fully secures the outlet orifice In this case, not only the above-mentioned operating phases b) and c) are facilitated, but in particular scraping removal of the mixing residues which have accumulated on the surface of the mixture is facilitated.

left of the retaining member 15.

  The highest (most rearward) position of the accumulation member 15 is obtained by a suppression in the pressure chamber 31 of the pressure which, during the mixing process, kept the stop piston 25 in its position. illustrated position although it was applied against the pilot piston 13 As a result, the piston 25 reaches its upper extreme position (in which it stops against

  the end face 30) and, correspondingly, the piston

  your pilot 13 can continue upwards, so that the outlet orifice 5 of the mixing chamber

is completely cleared.

  The extent of the overlap of the outlet orifice 5 of the mixing chamber when the retaining member 15

  occupies its throttling position is determined by the posi-

  The threaded region 26, and therefore the collar 28, is thus formed. A stroke length h is formed which determines the position

throttle.

  It is conceivable to foresee in the room of

  31 a pressure spring (spring Belleville type) which bears against the end face 30 and pushes down the stop piston 25 When, moreover, it develops in the pressure chamber constant pressure

  above the pilot piston 13 (inlet of the fluid under pres-

  through the bore 33), the three positions of the cleaning block 14 can be achieved by a simple variation of the pressure of the fluid admitted via

drilling 34.

  Like FIG. 1, FIG. 2 shows a mixing chamber 41 (which this time is smaller) a piston 43, an outlet orifice 35 of said chamber, a body 36 of the latter, the orifices of FIG. 8 and 9, as well as the portion 18 of said pierced body with a circular recess for receiving a cleaning block 38. In this embodiment, this block is of circular configuration, the diameter of a channel 39 formed by a portion 42 of the body for tranquilizing the mixture, being greater than the diameter of said mixing chamber 41 -Figure 2 represents a possible position allowing the throttling of the mixture flow which enters the channel 39 at the outlet

  41 In this throttling position, the end

  lower portion of the cleaning block 38 (i.e. a retainer 40) substantially covers more than half

  of the outlet port 35 of the mixing chamber.

  It goes without saying that many modifications can be made to the device described and shown, without leaving

of the scope of the invention.

Claims (4)

  1 device of the mixing head type for directing to a mold a mixture (plastic generator comprising at least two components and capable in particular to enter chemically reaction), this device com Dortant a room   in which there is a dispensing member   having a piston and being reciprocable from a rear position disengaging the component introduction ports to a forward position in the region of the outlet of said mixing chamber; as well as a channel which, preferably   at the outlet of the mixing chamber and   edge in the molding tool either directly or through other conduits -d'alimentation, is deviated in particular at right angles to the axis of said chamber and wherein a cleaning block can be actuated by a pilot piston can perform reciprocating movements between a rear position near the outlet of the mixing chamber, and a forward position, said cleaning block being made so that it can be stopped   so that its anterior end overlaps partially   the outlet of the mixing chamber   as a restraining member causing a constriction, while said pilot piston or said cleaning block is applied, in its retracted position, against an abutment which is movable for adjustment of different throttle positions, a device further provided by which the outlet of said mixing chamber can be completely disengaged, according to claim 1 of the main patent, characterized in that said displacement device at intervals allows a movement of the stopper (25a). ) during operation of the mixing head. 2 Device according to claim 1, characterized in that the movable stop (25 a) is in effective connection with a jack (25, 23 a, 28) actuated by a fluid under   pressure, preferably with hydraulic oil.   3 Device according to claim 2, characterized in that one end of the piston (25) of the cylinder serves stop (25 a).   4 Device according to one of claims 2 and 3,   characterized in that the piston (25) of the cylinder is   in the form of an annular piston in the annular bore   which is a shank or tail (27) which may be   blocked in different longitudinal positions within the   body or housing (18, 19, 23) of the cleaning block (14), for example by means of a threaded member placed on a threaded region (26); and in that the tail has a collar (28) which determines the anterior position of the retaining member (15), while another fixed stop (end face 30) on the housing of said cleaning block determines the position the most remote of the latter (with clearance   the outlet (5; 35) of the mixing chamber).