High-pressure mixing device with one-piece delivery piping

Abstract

A high-pressure mixing device suitable for forming a polymer mixture by reacting two or more reactive liquid components or resins, comprising: a head body provided with a mixing chamber, the mixing chamber having an inner cylindrical surface with an inlet and an outlet for injecting and recirculating the reactive components; a pipe for conveying the mixture, which is connected to the mixing chamber; a valve body with a longitudinal recirculation groove, which slides in the mixing chamber between a rearward position that makes the inlet unobstructed and can mix the components and a forward position that connects the inlet and the outlet; a self-cleaning conveying pipe is a single-piece element that is removably fastened by a fixing tool and can be inserted into the hole of the mixing chamber; the diameter of the tubular element is larger than the diameter of the mixing chamber, which is used to compensate for alignment and mutual positioning errors and to avoid interference. A gap is defined between the tubular element and the through hole in the head body, so that the tubular element can be inserted and removed. The sealing tool prevents the polymer mixture and the lubricating liquid from leaking in the gap.

Description

Technical Field

[0001] The present invention relates to a device for mixing liquid polymer components or reactive resins under high pressure to form a reactive polymer mixture for casting or injection to produce various objects. The mixing device according to the invention is capable of processing polyurethane, epoxy resin, vinyl ester, polyester, silicone and phenolic resins. Background Art

[0002] Mixing devices are known in the art, in particular high-pressure, self-cleaning L-shaped mixing heads suitable for mixing polymer components, for example to obtain a reactive chemical mixture intended to be injected or delivered into a mold. The chemical mixture results from the impact of at least two jets within a cylindrical cavity of circular cross-section, known as the mixing chamber.

[0003] exist Figure 1 , a known "L-shaped" self-cleaning mixing head 100 is shown, some parts of which are also shown in FIG. Figure 1A , 2, 3, 4 and 5.

[0004] Before being fed into the mixing chamber 103 in the head 2, the polymer components are metered in stoichiometric ratios and under high pressure by volumetric meters, monitored in closed loop by suitable flow rate transducers.

[0005] Appropriately metered polymer components reach the mixing head where suitable injectors 130, which convert the pressure energy into kinetic energy of the jets, inject them into the mixing chamber 103 where mixing occurs by the impact of the respective jets and due to the resulting high turbulence.

[0006] The reaction mixture produced by mixing the jets then flows towards a cylindrical delivery duct 107 placed orthogonally with respect to the mixing chamber 103, which deflects the mixture flow and reduces its turbulence until the final outlet.

[0007] The term "L-shaped head" is generally used to denote this particular type of head, the construction of which is determined by the mutual spatial arrangement of two ducts, namely a mixing chamber 103 and a delivery chamber or delivery duct 107 extending orthogonally with respect to each other.

[0008] In each of the above chambers there is a slidable element adapted to scrape and spray the reactive resin, (respectively a valve member or mixing slide 109, and a cleaning member or rod 111, as Figure 2 , 3, as described below), for the delivery and subsequent discharge of the final volume of reaction resin, corresponding movements of the slidable elements must occur in sequence.

[0009] In the mixing chamber 103 having a circular cross-section, there are faced two or more injection holes 105 (associated with corresponding injectors 130), which are placed closer to the front area, that is, towards the part of the inflow delivery pipe 107, and through which the reactive resin is supplied; and two or more corresponding recirculation holes 106, which are placed at the rear and longitudinally on the axis with the above-mentioned more forwardly placed injection holes 105 and whose function is to allow the reactive resin to be recirculated towards the corresponding storage tank.

[0010] Inside the mixing chamber 103 , the aforementioned valve member or mixing slide 109 is slidingly movable, provided with longitudinal grooves 110 for separate recirculation of the resin and which also performs cleaning of the mixing chamber 103 during its advancement by ejecting residues of the mixed resin.

[0011] The valve member 109 , which is hydraulically controlled by a cylinder, reciprocates between a rearward open and mixing position and a forward closed and recirculation position.

[0012] When the valve member 109 is brought to the advanced closed position, its recirculation groove 110 faces the injector 130 and conveys the corresponding resin flow backwards towards the corresponding recirculation hole 106 formed in the body 102 of the head, wherein the resin flows back to the corresponding tank through a specific pipe, from which the resin is extracted and metered under pressure.

[0013] In the rearward or open position, the injection holes 105 are exposed and the resin jets flow into the mixing chamber where they may collide with each other or against the walls of the chamber to mix with each other through intense turbulence within milliseconds.

[0014] The valve member 109 thus acts as a hydraulic member which performs: a first step of recirculating the reactive resins through the recirculation groove 106 in order to keep them separated; a subsequent second step in which, when it is retracted to expose the injection orifice, the jets are allowed to collide with each other and against the walls of the mixing chamber 103, creating the necessary turbulent conditions for rapid and thorough mixing of the same resins; and a third step of interrupting the mixing, during which the valve member 109 is advanced again to return the groove at the jets, causing the resins to recirculate separately; at the same time, in its forward movement, the valve member ejects the volume of mixed resin from the mixing chamber 103 towards the delivery pipe 107, the latter also being called a "self-cleaning pipe" due to the presence of a cleaning member or rod 111 that can move back and forth therein.

[0015] Tank 110 thus performs the recirculation and keeps the reactive resins separated during the operating steps in which they cannot be mixed with one another, but on the contrary they must be metered under pressure and kept separate in order to set the metering parameters, i.e. the correct ratio between the reactive components, the pressure reached by the injectors, and maintain their recirculation pumping, thus stabilizing the essential parameters of the process, such as temperature, pressure, ratio and dispersion of possible charges or expansion agents.

[0016] The front portion of the valve slide 109 is cylindrical, solid and cavity-free, and is coupled to the mixing chamber with a gap of several microns therebetween to act as a scraper and ejector in the advanced closed position and not allow the resin to flow to the self-cleaning pipe 107 when the valve slide is closed for recirculation, as shown. Figure 1A shown.

[0017] Typically, the movement of the valve slide 109 is very rapid and its front solid cylindrical portion interrupts the jet of reactive components for a very short time as it passes in front of the injector while the valve slide retracts to achieve mixing; when the valve slide advances to switch from the mixing position to the recirculation position, the injection port is again "blinded" for a very short time.

[0018] During the recirculation step, the pump metering the reactive resin brings the different streams to flow regime without mixing the reactive resin between them, while the injector regulates the pressure through a hydraulic throttle valve usually made on the nozzle outlet orifice.

[0019] This prevents the different streams from not reaching the correct stoichiometric ratio during the first mixing and conveying step.

[0020] The reaction polymer mixture starts to polymerize while flowing out of the mixing chamber 103 and then through the transfer pipe 107, and a gradual reduction of the mixing turbulence along the aforementioned pipe 107 occurs.

[0021] If the loss of turbulence is sufficient, a viscous jet may flow out of the end of the delivery conduit 107, otherwise there remains a jet subject to rotational movement and turbulence events.

[0022] It is desirable to have an outlet bonding jet to ensure a correct process for foaming and filling the mold and to obtain a high quality product.

[0023] The above-mentioned cleaning and closing member, also called the self-cleaning rod 111, which is hydraulically controlled and slides along the conveying pipe 107, performs the closing of the mixing slide valve 109 in sequence to inject the reaction resin and keep the pipe properly clean, and when the slide valve 109 is fully advanced and flush with the inner surface of the conveying pipe 107, it scrapes off the resin residue in the conveying chamber and scrapes off the residue adhering to the front end of the slide valve 109.

[0024] The self-cleaning rod 111 may have a cylindrical shape and have a constant diameter ( Figure 2 or a cylindrical scraping head coupled to the delivery pipe with a reduced clearance, and the control rod portion has a portion having a smaller diameter than that of the scraping head so that it does not slide on the thin layer of reacted resin formed on the inner surface of the delivery pipe by pressure contact ( Figure 3 The above-mentioned scraping cylindrical parts are all connected to the conveying pipe with reduced clearance.

[0025] It is important to ensure high geometrical precision and very limited clearances in the connections between the various components, such as between the valve slide 109 and the mixing chamber 103, and between the head of the self-cleaning rod (cleaning member) and the delivery duct 107. This is intended to ensure the effectiveness of scraping off residual resin from the surfaces wetted by it; in fact, after each recycling cycle, the resin gradually accumulates in the form of a reactive adhesive thin layer that quickly polymerizes and hardens by bonding at the surfaces of the corresponding chamber.

[0026] The above-mentioned high-pressure mixing heads have the following disadvantages and limitations.

[0027] In particular, the problem involves the following three factors: the adhesive effect exerted by the reacted resin or reactive resins at the interface between the surface of the fixed wall and the surface of the movable element on which it is layered, the leakage of the resins (when still in the liquid phase whether they are mixed or unmixed or in the reactive phase) through the gaps in the pipes or elements used to separate and partition the resins, and the wear that affects the sealing elements during operation, which is now exacerbated by the frequent cycles and high speeds.

[0028] During use, in the mixing head 100, a thin layer or film of reacted resin forms in the gaps between the movable elements and the respective chambers in which they slide, i.e. between the slide valve 109 and the mixing chamber 103, but more significantly and continuously between the self-cleaning rod 111 and the delivery pipe 107. This thin layer of reactive resin, initially in a liquid state, polymerizes rapidly within a few tens of seconds and, after a few hundred delivery cycles, forms a well-adhesive layer with high adhesive power on the surface.

[0029] Layers of polymer resin tend to accumulate on the movable components and on the walls of the chambers they slide in. This occurs quickly and systematically in self-cleaning pipes, whereas in the case of mixing chambers, the accumulation and stratification of reactive resin is less rapid, as a result of the pressure differences between the recirculation tanks and the entry of jets of reactive components at high speed and pressure, the washing effect of the non-mixed resin sliding into the corresponding tanks during the recirculation process and the leakage of the non-mixed resin along the gap between the mixing slide and the chamber.

[0030] With particular reference to self-cleaning pipes, as long as the movable members are able to remove these hardened resin layers from the surface in the form of rolls, sheets, or strands through their own movement, there are no problems. However, the operation becomes more critical when these layers begin to accumulate on the surface, particularly on one side of the overlapping chambers. In this case, the movement of the movable scraping members is no longer able to uniformly remove the polymerized resin layer accumulated over the longitudinally extending area, and the strong pressure resulting from the scraping parts tends to completely scrape off the layer on the opposite side of the pipe surface sliding in metal-to-metal contact, with the resin gradually delaminating more and more. The strong pressure generated during sliding on both sides of the pipe causes such compression and friction that they generate intense heating, which then leads to damage due to surface seizure in the metal-to-metal contact area.

[0031] The phenomenon of stratification generally occurs on all surfaces associated with reciprocating motion, but with very different effects depending on the conduit with which the self-cleaning effect is being considered. For example, the resin layer deposited on the walls of mixing chamber 103 and on the cylindrical surface of slide valve 109, which is slidably connected thereto, is largely flushed away by the resin recirculation that occurs before and after each delivery cycle and by the passage of the front cylindrical portion of the slide valve in front of the injector. With respect to slide valve 109, a layer of reacted resin forms, primarily affecting its front portion, perpendicular to its longitudinal axis, which has a saddle-shaped geometry and faces self-cleaning delivery conduit 107. The formation of this layer of reacted resin has very little effect on the cylindrical surface of slide valve 109 (which is slidably connected to mixing chamber 103).

[0032] Typically, a layer of reacted resin forms on the cylindrical surface of the slide valve only after a long interruption in delivery, during which the slide valve itself remains in the closed position. However, during the working cycle, the resin layer is removed by the unmixed resin flow, which has a washing effect.

[0033] During the opening and closing movement of the slide valve 109 , the injector 130 is very close to the slide valve 109 , thereby compressing the resin jet in the inserted meatus causing a sudden and rapid washing action.

[0034] Similarly, on the surface between the recirculation grooves 110 of the slide valve 109, the layer is hardly formed and is flushed due to the action of the smaller amount of resin (usually the most viscous), where the above resin tends to flow to the groove 110 of the less viscous resin by virtue of the pressure difference between the two grooves 110.

[0035] Therefore, the polymer resin layer is rarely formed on the surface of the slide valve 109, and on the wall of the mixing chamber 103, the layer is formed only in the connecting ravine or in specific grooves or gaps and on the inner circumference of the hole 13 facing the self-cleaning pipe.

[0036] In contrast, the layer of reacted resin formed on the surface of the self-cleaning rod 111 and on the wall of the corresponding conveying chamber 107 is difficult to be completely removed by the scraping action of the self-cleaning rod 111 during its sliding movement.

[0037] During the opening and closing sliding operation, the pointed front portions of the self-cleaning rods 111 cannot completely remove the reacted resin by scraping the layer, but they remove a portion and press the remaining portion.

[0038] The scraping effect of the thickness of the resin that encounters the corners of the self-cleaning head 111 is formed by scraping off the surface layer or thin layer by a combination of mechanical actions. The resin layer is partially removed by a real shearing action of the surface of the reacted or reacting resin, while a certain thickness - above the gap defined between the self-cleaning head 111 and the conveying chamber 107 - is not sheared, but is first squeezed by the passage of the self-cleaning head 107 and then removed in the subsequent passage by compression and subsequent rolling, together with the removal of thin sheets of polymer compressed and dragged by the movement.

[0039] However, a thin layer of reacted resin remains adhered to the surface of the self-cleaning delivery tube 107; this thin layer, while it is still liquid, spreads along all its own surface, but it tends to remain bounded, accumulating only in some areas of main longitudinal extension and only in some angular positions relative to the radial extension.

[0040] During the passage of the scraping head of the self-cleaning rod, the thin layer of resin that remains adhered is strongly compressed and, as it adapts elastically-plastically, resists the scraping action, thus avoiding complete removal; at the same time, the compression force generated amplifies this force due to the friction against the sliding of the self-cleaning head.

[0041] It has been noted in various tests, and is further evidenced in the use of reactive resins that form hard compounds (low-density and high-density), that when polymerizing, while the "L-shaped" self-cleaning head 100 is in operation, and especially after tens of thousands of self-cleaning cycles, the resin begins to form a thicker layer on one side of the delivery pipe 107, and this layer exerts a strong force on the head of the self-cleaning member or rod 111 towards the opposite side. This phenomenon tends to be self-sustaining and increasingly intense; in fact, the gradual increase in the thickness of the reactive resin formed on one side simultaneously causes a similarly significant increase in the pressure exerted by the self-cleaning rod 111 on the opposite side, where the compressive force is able to remove the resin through the front sharp corners of the self-cleaning rod 111 and by scraping and subsequently rolling and / or separating the flakes of resin debris formed under the relative movement under strong friction and compression.

[0042] In other words, on the inner longitudinal strip of the self-cleaning duct 107, a strongly compressed thin layer of resin forms occupying all gaps between the rod and the duct, while on the other opposite longitudinal surface, high pressure and friction conditions hinder the formation of the resin layer and metal-to-metal contact occurs.

[0043] This problem has long been known and occurs during the operating life of several thousand transfers. However, this phenomenon is less obvious and prominent when the construction of the self-cleaning transfer chamber 107 consists of two separate and connected pieces and therefore has a geometric step-like discontinuity at the junction between the head body 102 and the portion 140 of the protruding transfer duct or the extension of the self-cleaning duct to which it is connected, as shown in FIG. Figure 4 , 5, 4A, 4B and 5A are schematically shown, which illustrate two possible structural configurations currently used in the prior art and two possible protrusion situations of the combined steps.

[0044] The formation and configuration of the steps depend on: the tolerances and machining errors of the two parts if they are machined separately; and the mutual sliding of the coupled parts during the working cycle caused by the intense and sudden heating and cooling generated by friction and by the passage of the resin, wherein the above-mentioned heating causes the parts to shift relative to each other even if the joined parts have been machined in a mutually assembled configuration.

[0045] In particular, Figure 4 The joining step is shown when the two parts of the conveying pipe have the same nominal diameter, that is, the hole in the head body has the same diameter as the hole existing in the extension (d1=d0), wherein one of the above two parts is integral with the head body 102 and the other part is a different extension 140A and is fixed to the bottom by a centering tool and screws.

[0046] On the contrary, Figure 5 , another configuration of a combined step resulting from a structural solution is shown, wherein the extension 140B is preferably configured with an inner bore of the extension having a diameter (d0) greater than the corresponding diameter (d1) of the bore in the head body (d0>d1). This solution is adopted to simplify alignment during assembly and avoid potential interference with the corners of the sliding self-cleaning rod 111. However, a step must be formed, which can also be centered relative to the axis of the pipe 107, but which generally moves during assembly of the two components and due to shear caused by thermal stresses.

[0047] The presence of small steps or misalignments higher than 5 microns is sufficient to cause non-uniformity and accumulation of resin mainly in the largest parts of the wall of the delivery conduit 107 .

[0048] Reference Figure 5A and Figure 4B, the abnormal accumulation of reacted resin can also depend on the inclination or lack of parallelism of the two combined parts (element 140 connected to the head body 102) that define the conveying pipe; when the self-cleaning head slides towards the lower part of the conveying pipe, the above situation causes different side pressures on the surface of the conveying pipe, where the reacted resin leaves and intensifies the accumulation of reacted resin on the side as mentioned above.

[0049] When the delivery pipe is made up of two parts and there is a step at the junction between them, the resin layer of reaction and compression tends to accumulate in the more likely delamination area of ​​the delivery pipe, that is, in the area of ​​the largest part overlooking the step. When the step has a larger protrusion thickness, the longitudinal strips of the accumulated resin layer are formed on the cylindrical inner surface of the self-cleaning pipe. At the same time, on the opposite side, the strong push given to the self-cleaning rod by the resin compressed on the opposite side causes the self-cleaning rod itself to completely scrape off the resin and produce metal-to-metal sliding. This phenomenon is self-sustaining as mentioned above, and due to the heat generated, direct friction between metal surfaces unfortunately causes undesirable scratches and seizing. Through the first stuck area, the self-cleaning rod needs to significantly increase its intensity to move along the delivery pipe.

[0050] Such a problem is very important because damage to the delivery pipes and self-cleaning valve stem surfaces due to sticking inevitably leads to the need to replace expensive and complex components such as mixing heads, which is economically disadvantageous due to the production line interruption lasting not less than several hours (necessary for the replacement operation).

[0051] Due to the prohibitively expensive assembly requirements, it is impossible, or in any case extremely difficult, to obtain a delivery pipe with a step-free area and perfect axial alignment. Due to the rapid assembly speed and low construction costs, the delivery pipe structure consisting of two joined parts is most often used in "L-shaped" mixing heads. However, the presence of the aforementioned joining area with the inevitable step and possible angular misalignment of the shaft relative to the bore contributes to the aforementioned problems. This is compounded by the fact that, over the life of the mixing head, the joined parts often become misaligned with each other. Therefore, even if the joint initially has a step of irrelevant dimensions, due to the misalignment (due to thermal shock expansion and mechanical stresses), the step itself will assume dimensions that are relevant to the aforementioned consequences.

[0052] In view of the above, we can therefore list below some limitations and disadvantages associated with the above-described mixing head 100:

[0053] It is impossible to avoid such joining areas in the conveying pipe: these inevitably lead to step areas which lead to or at least strongly promote the formation of uneven layers of hardened resin which adhere to the inner surface of the conveying pipe in an asymmetrical manner; these layers can cause jamming conditions which are detrimental to the self-cleaning rod and the conveying pipe;

[0054] - Difficulty in assembly operations: In order to minimize the aforementioned step area, machining tolerances are sometimes very tight, and the various components must be aligned with each other with high precision, significantly increasing costs and assembly time;

[0055] - The assembly costs and time are considerable, not only when constructing the self-cleaning head, but also during its service life, i.e. during the necessary regular interventions to replace damaged parts due to seizures (which are in any case unavoidable even under very tight operating tolerances).

[0056] Unfortunately, in the mixing heads described above and discussed above, it is impossible to foresee and prevent the asymmetric layers of hardened resin that can lead to scratching and seizures along the self-cleaning ducts, which can cause metal-to-metal contact. These phenomena subject the mixing heads to a state of severe wear during operation and inevitably necessitate the replacement of the components involved, in this case the head and the extension of the self-cleaning duct, with the consequent significant additional maintenance costs and unavoidable machine downtime, which is economically detrimental.

[0057] Many of the above problems are successfully overcome by a self-cleaning head solution which works very well and is disclosed in patent EP2767376 by the same applicant. Summary of the Invention

[0058] Although this latest solution has significant advantages compared to the above-mentioned devices, one object of the present invention is to provide a new and improved solution that overcomes all the disadvantages and problems previously mentioned and also achieves further advantages.

[0059] In particular, one object of the present invention is to provide a solution which, in addition to minimizing the above-mentioned destructive phenomena and thus significantly extending the service life of the high-pressure mixing device, makes it possible to simplify and make the construction, assembly and operation of the device itself more cost-effective, even with lubricant in the isolation chamber, and makes it possible to replace the conveying pipes and the self-cleaning members connected thereto easier, faster and cheaper, according to a configuration with reduced clearances and high geometrical precision.

[0060] In particular, the object of the present invention is to provide an "L-shaped" high-pressure mixing device, which is designed for special maintenance purposes of a conveying pipe that is already connected to the corresponding self-cleaning member with a suitable, uniform gap relative to the self-cleaning member, making it extremely simple and quick to assemble, remove and replace, and has a precise geometry throughout the entire extension of the conveying pipe, further facilitating the axial and longitudinal centering and angular orientation of the conveying pipe relative to the seat of the head that accommodates it and relative to the cylindrical bore of the mixing chamber, thereby easily compensating for possible working errors and dimensional inaccuracies.

[0061] Therefore, it is desirable to provide a technical solution, such as simplifying and making the construction of the device more cost-effective, realizing the entire conveying and self-cleaning pipe with high geometric accuracy and without joints, making it easier, faster and more cost-effective to connect it with the self-cleaning head with reduced clearance, and replacing only the conveying pipe and the self-cleaning member without having to replace the head body.

[0062] In particular, the object is to provide an "L-shaped" high-pressure mixing device that allows for very easy and rapid assembly and replacement, for special maintenance purposes, of a delivery conduit that is already coupled with corresponding self-cleaning elements with suitable, uniform spacing and in precise geometry. In particular, the object is to provide a structural solution that exhibits a high level of overall geometrical precision for the coupling of the delivery conduit and the cleaning elements, thanks to the increased dimensional and geometrical precision provided by the novel construction of the one-piece delivery conduit.

[0063] Another object is to provide a technical solution that allows the production and accommodation of the conveying pipe in a corresponding seat in the head body, so as to simplify the axial and longitudinal centering and angular orientation of the conveying pipe relative to the seat of the head body that accommodates it and relative to the cylindrical hole of the mixing chamber, making it easy to compensate for possible processing errors and dimensional inaccuracies.

[0064] Another object of the invention is to provide a solution which is further improved and which immediately after installation provides a sealing action preventing leakage of the reaction mixture and lubricating fluid along the walls of the bore housing the tubular element and along the front cylindrical surface of the mixing slide valve, wherein the compartment separating the hydraulic control cylinder of the self-cleaning rod from the head body is usually filled with said lubricating fluid and continuously allows it to flow out (flux) by means of a pump-type distributor.

[0065] As is clear from the description, the compartment serves to collect debris from the reacting resin. When opening towards it, the movement of the self-cleaning rod scrapes away this debris and transfers it into the compartment itself. When forced lubrication is applied, it removes this debris and further lubricates the self-cleaning pipe, reducing friction and delaying the reaction of the resin film, thus facilitating its operation for millions of cycles.

[0066] The introduction of lubricant liquid into the isolation chamber also inhibits reactive resin from forming in the portion coupling the bushing to the head body and entering the bore in the bushing extending the mixing chamber.This additional problem is solved by the seal provided by the present invention.

[0067] Another object of the present invention is to provide a solution which further improves the sealing effect against leakage of the reaction mixture between the delivery pipe and the header.

[0068] Another object of the present invention is to provide a solution that further improves and immediately provides a sealing effect to prevent leakage of the reaction mixture and the lubricating liquid (either fixedly present or forced into the isolation chamber for lubricating the self-cleaning rod, as will become clear from the following description), the lubricating liquid must be separated from the mixing chamber.

[0069] The above content can be obtained by the mixing device described in claim 1.

[0070] Thanks to the invention, all the intended objects are achieved.

[0071] The above objectives can be achieved thanks to:

[0072] a delivery duct made of a single piece and therefore of high dimensional and geometrical accuracy throughout its entire extension, of precise geometrical configuration, with uniform and precise clearances relative to the self-cleaning member and housed in its own seat in the head body with reduced clearance,

[0073] The diameter of the middle hole is larger than the diameter of the mixing chamber,

[0074] • Sealing tools are appropriately arranged between the joint interfaces of the various components.

[0075] All these features together enable immediate assembly of the various components, avoiding laborious adjustment operations and also expensive pre-resin sealing (or pre-application of hardening resin) of the mixing chamber extension both during initial installation and when replacing the tubular conveying element.

[0076] In particular, it is easier and faster to insert the single-piece delivery duct (defined in the transverse through-hole of the head body) in a position fully aligned longitudinally, transversely and angularly, significantly eliminating the complex and time-consuming pre-positioning operations and the subsequent necessary procedures for adjusting possible misalignments at the interface between the assembled parts. Most importantly, it is avoided to apply a preliminary sealing layer by means of a slow-reacting hardening resin in the groove of the hole extending the mixing chamber into the tubular element and in the gap between the latter and the head body.

[0077] Advantageously, sealing means on the intermediate hole (made on the delivery tube element) keep the front part of the valve member sealed and separated from the tubular delivery element, and sealing means on the cap (accommodated in a transverse hole placed directly opposite the mixing chamber in front of the valve member) advantageously seal and insulate the tubular element relative to the opposite part of the head body, thereby avoiding unwanted leakage of mixture and / or lubricant. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] All the features of the mixing device according to the invention will become more apparent from the following description and the accompanying drawings relating to some preferred embodiments.

[0079] Figure 1 A prior art "L-shaped" mixing head is shown;

[0080] Figure 1A is a planar cross-sectional view of the main body of an "L-shaped" mixing head of the prior art;

[0081] Figure 2 and Figure 3 Two different types of self-cleaning rods provided inside the mixing head are shown;

[0082] Figure 4 and 5 Schematically illustrating two different types of steps generated at the interface between the head body and the elongated protrusion that together define the delivery conduit;

[0083] Figure 4A and 4B Shown are known assembly configurations of conveying conduits that are affected by a first incorrect non-centering condition and a second incorrect misalignment condition, respectively, wherein the axis of the region of the elongated protrusion is tilted;

[0084] Figure 5A Schematically shows Figure 4 and Figure 5 solution, but suffers from misalignment errors that may occur in the combined delivery conduits of the prior art, where the axis is not parallel to the area of ​​the elongated protrusion;

[0085] Figure 6 、 7 8 and 9 show different configurations of the delivery pipes in the mixing device according to the present invention;

[0086] Figure 10 and 10A is a longitudinal cross-sectional view of a mixing device according to one form of the present invention having cleaning members respectively located in two different positions;

[0087] Figure 11 yes Figure 10 Magnified details;

[0088] Figure 12 An enlarged portion of one form of the device is shown;

[0089] Figure 12A yes Figure 12 a further enlarged detail of the head, in which the sealing means can be better seen, in particular the sealing element placed at the central hole in the tubular conveying element and the sealing element between the tubular conveying element and the through-seat in the head body;

[0090] Figure 12B and 12C is a schematic enlarged view of the interface area between the delivery conduit and the mixing chamber according to the present invention, in which the sealing elements not in contact with the valve member and in contact with the valve member, respectively, can be better seen;

[0091] Figure 13 and 14 The characteristics of the sealing element are shown, in particular its shape relative to the seat in which it is received in its undeformed state ( Figure 13 ) to work situation( Figure 14 ) variant, wherein, in the operating condition, the sealing element is inserted in an interference manner in the aforementioned seat;

[0092] Figure 15 and 16 is a schematic cross-sectional partial view of a mixing device according to two possible forms of sealing elements on the central hole;

[0093] Figure 17 and 18 are two perspective views of a sealing element according to the present invention having a saddle shape;

[0094] Figures 19 to 28 Other possible forms of sealing elements according to the invention are shown.

[0095] Figure 29 A form of tubular conveying element according to the invention is shown, which has a transverse central bore in which there is a seat made by a counter bore, configured to accommodate a saddle-shaped sealing element of constant cross-section;

[0096] Figure 30 Is a Figure 29 Enlarged detail of the hole of the seal seat;

[0097] Figure 31 yes Figure 29 Side view of a tubular element:

[0098] Figure 32 is based on Figure 31 A partial longitudinal sectional view of the plane in FIG;

[0099] Figure 33 yes Figure 32 An enlarged detail showing the transverse bore of a saddle-shaped sealing seat with constant cross-section in section.

[0100] Figure 34 A form of tubular conveying element is shown, having in its central bore a seat for an associated sealing element, which is saddle-shaped towards the outside, while the inner shoulder region has the shape of a flattened ring obtained by a countersink;

[0101] Figure 35 yes Figure 34 Enlarged detail of the hole with the seal seat;

[0102] Figure 36 yes Figure 34 One side of the tubular element;

[0103] Figure 37 It is along Figure 36 A longitudinal partial cross-sectional view of the plane ZZ of the tubular element in FIG;

[0104] Figures 38 to 41 is used to accommodate Figures 34 to 37 Several views of the sealing element in the sealing seat are shown;

[0105] Figure 42 A form of tubular conveying element according to the invention is shown, the seat for the sealing element on the central hole of which has a saddle-shaped configuration of constant cross-section and completely included in the thickness of the tubular element itself;

[0106] Figure 43 yes Figure 42 Enlarged detail of the hole with the seal seat;

[0107] Figure 44 yes Figure 42 A longitudinal partial cross-sectional view of a tubular element;

[0108] Figure 45 yes Figure 44 , showing a cross-sectional view of the transverse middle hole with the sealing seat. DETAILED DESCRIPTION

[0109] Refer to the attached Figures 6 to 45 The invention discloses an L-shaped high-pressure mixing device 1 configured to mix two or more liquid components or reactive resins with each other to form a reactive polymer mixture intended to be cast or injected to produce various articles. Polyurethane, vinyl ester, silicone and phenolic resins can be processed.

[0110] The mixing device 1 comprises a head body 2, which is provided with a mixing chamber 3 having an inner cylindrical surface 4, which is provided with an inlet or inlet hole 5 and a recirculation outlet or outlet hole 6 for introducing and recirculating liquid components or reactive resins, respectively; at the inlet 5 there is an injector, which generates a jet of two or more reactive resins, converting pressure energy into kinetic energy of the jet.

[0111] The injectors can be placed opposite each other or at various angles that converge on a single point in the jet.

[0112] The injector consists of a nozzle and may include a dividing pin with a settable position to create a suitable restriction of the fluid path, which generates pressure upstream of the injector from which the high kinetic energy jet originates.

[0113] Inside the mixing chamber 3 is housed a valve member 9 which is slidable along the longitudinal axis of the chamber 3 and provided with recirculation longitudinal slots 10. The valve member 9 is slidably movable in the mixing chamber 3 between a rearward position, in which it puts the inlet 5 and the component jets in communication, and an advanced position, in which each of the aforementioned recirculation longitudinal slots puts the corresponding inlet 5 in communication with the component jet via the corresponding outlet and recirculation opening 6 for recirculation of the corresponding reactive component towards a specific tank.

[0114] The mixing device 1 comprises a tubular element arranged transversely to the mixing chamber 3 for forming a conveying duct 7 along which the reaction mixture flows once it has emerged from the mixing chamber 3, for example to be discharged into a forming die. In particular, the conveying duct 7 extends orthogonally to the longitudinal extension of the mixing chamber 3.

[0115] The delivery conduit is composed of a single tubular element 7, made in one piece, having an open outlet end E1 and an opposite open end E2 at the compartment 18 'disclosed below. As better described below, the tubular element 7 is removably inserted into the head body 2 with a certain clearance; in other words, a suitable clearance I is defined between the tubular element 7 and the head body 2, which will be better specified later.

[0116] The tubular element 7, which has the axially symmetrical shape of a metal tube, is provided with a central transverse hole 13 which, in the assembled configuration, is aligned with the mixing chamber 3, except for tolerance deviations, and constitutes its extension, by an amount equal to the thickness of the tubular element 7 itself, up to the delivery chamber defined in the latter. The transverse hole 13, which will be described in more detail below, serves to establish fluid communication between the mixing chamber 3 and the delivery chamber defined in the delivery conduit 7.

[0117] The delivery conduit 7 has an internal cross-section greater than that of the mixing chamber 3. For example, it extends so as to project from the bottom relative to the head body 2 and longitudinally extend between the mixing chamber axis and the outlet E1, equal to or greater than three times the diameter of the delivery conduit itself. This characteristic serves to reduce mixing turbulence and ensures a laminar or cohesive flow of the delivered resin. In particular, it is useful for the delivery conduit to extend from the upper end of the mixing chamber to a length of at least four times its diameter.

[0118] The delivery conduit 7 has a cylindrical inner surface 8 in fluid communication with the mixing chamber 3 .

[0119] Thanks to the one-piece construction of the tubular element 7 , the onset of any type of step or error in the parallelism of the axis of the pipe is avoided, as there are no joining zones, thus preventing uneven accumulation of resin in the conveying pipe.

[0120] Due to the single-piece construction of the tubular element 7, which constitutes the conveying conduit, a high degree of geometrical precision is achieved; in other words, with this construction, the entire conveying conduit 7 is perfectly cylindrical, i.e., it is easier to avoid shape errors during its manufacture. This also allows the use of cleaning or self-cleaning elements, as described below, to be coupled thereto with greater precision.

[0121] There is provided a cleaning member or rod 11 (self-cleaning rod) which is slidably reciprocating inside this tubular element 7. The cleaning member or rod 11 has the function of ejecting the amount of mixture still contained in the tubular element 7 at the end of delivery and scraping off the adhered resin from the surface of the latter.

[0122] The delivery chamber and the opposing self-cleaning rod have a cylindrical shape and are mechanically coupled with a suitably precise and specific gap, which can vary between 8 and 60 mm depending on the size of the delivery portion.

[0123] The resin is scraped off the surface by the sliding of the self-cleaning rod 11, which can have a scraping length, that is, a cylindrical portion connected to the inner diameter of the conveying chamber with a precise gap, and the length is reduced relative to the extension of the chamber itself, and the self-cleaning rod 11 can have cavities or grooves or cuts of different shapes on the surface, which allow the cylindrical portion itself to be sealed relative to the conveying chamber by a sealing ring and / or by the accumulation of reacted resin, and at the same time reduce the surface of the reacted or reacting resin operating adhesion and surface friction between the self-cleaning rod 11 and the conveying chamber in the conveying pipe 7.

[0124] In the head body 2 and in the conveying tubular element 7, at a further position diametrically opposite and in front of the mixing chamber 3 (and the transverse hole 13 of the tubular element 7 itself) during normal operation, an additional through hole 52 is obtained, which during normal operation can be kept occupied and sealed by the cap 50.

[0125] Once the cap 50 is removed, the service hole 52 allows the application of a further valve element to the head body for the introduction of a washing or inerting liquid or gas. Thus, for example, a possible extended flexible pipe of a delivery line can be cleaned, or inerting gas can be injected into the mold cavity filled with reactive resin.

[0126] The cap 50 is centered and guided into the hole of the head body 2 and is housed in the hole obtained in the tubular element 7 with an increased clearance, similar to the clearance of the hole for the slide valve. In other words, a clearance III is defined between the surface of the cap 50 and the second hole 52 (allowing easier and faster centering and coupling between the cap 50 and the hole 52), and a suitable elastic or elasto-plastic seal 51 is inserted into the clearance III (suitable for avoiding any leakage of the fluid). Alternatively, in a similar manner, the cap 50 can be configured to have a reduced diameter in the area intended to penetrate the thickness of the tubular element 7, as in Figure 11 Can be seen better in.

[0127] For better operation, the cleaning member 11 can be continuously lubricated by a lubricating fluid, which can be stationary or forced to flow (by a pump), in a compartment 18 'defined above the delivery duct 7 (between the hydraulic control of the self-cleaning rod and the head 2) and also between its own delivery duct 7 and the rod portion of the cleaning member 11 with a reduced diameter, as can be seen in Figure 10 、 10A , 11, 15, 16 are better seen.

[0128] Advantageously, compartment 18' serves to collect debris of the reacted resin, which the cleaning member 11 scrapes during its sliding motion and conveys into compartment 18' during its opening movement. When forced lubrication is applied, it removes said debris and further feeds lubricant into the delivery pipe 7, thereby reducing friction, delaying the reaction of the thin layer of resin, and thus facilitating its operation over millions of cycles.

[0129] This lubrication, when applied, also has the effect of suppressing the reaction of the resin in the connection area between the tubular element 7 and the head body and in the transverse bore 13 extending the mixing chamber 3, thus promoting undesirable leakage of lubricant during the first steps of using the mixing device 1 (when the resin reacting in the various gaps has not yet formed a strong seal). However, due to the specific sealing construction and arrangement according to the present invention described below, the risk of lubricant leakage that could contaminate the reactive resin is successfully avoided. Specifically, any leakage of lubricant is effectively avoided in the interface between the delivery conduit 7 and the head body 2 and through the transverse bore 13 forming an extension of the mixing chamber 3.

[0130] The following description focuses mainly on the tubular element 7 .

[0131] The tubular element 7 can be removably inserted into a hole 12 obtained through the head body 2 and extending transversely relative to the mixing chamber 3 .

[0132] Once inserted, the tubular element 7 extends longitudinally throughout the bore 12 and transversely relative to the mixing chamber 3 .

[0133] It is also advantageous to make the conveying conduit a single piece and separate from the head body 2 (e.g. tubular element 7) since, regardless of the head body 2, it is possible to machine and improve the self-cleaning rod (cleaning member 11) and the conveying conduit itself with the necessary precision, connecting them to each other with the required clearance and geometric precision resulting from rotary machining (i.e. machining on a machine tool that rotates the part to be processed), making them interchangeable so that special maintenance of the parts can be carried out in the event of wear.

[0134] Different structural configurations of the tubular element 7 are possible.

[0135] In particular, the tubular element 7 is provided with an annular shoulder region 14 or portion arranged at a region remote from the transverse hole 13 , for example towards the conveying direction of the head 2 (at the bottom) or towards the compartment 18 ′ (at the top).

[0136] Different modes are also provided for detachably fixing the tubular element 7. In particular, fixing means (15; 15'; 16) will be described below, which are configured for rigidly and detachably fixing the annular shoulder region 14 to the upper or lower surface of the head body 2 in order to securely fasten the tubular element 7 in the transverse through hole 12.

[0137] A tolerance with a reduced clearance I is defined between the tubular element 7 and the transverse through-hole 12 of the head body 2. Such a tolerance is provided to facilitate insertion and removal of the tubular element 7 into and from the transverse through-hole 12.

[0138] Depending on the diameter, the gap clearance can vary between 12 and 80 microns, depending on the relevant head size.

[0139] The device 1 is also provided with a sealing gasket tool 20 on the through hole 12 transverse to the head body, which is positioned in the circumferential cavity above and below the holes 13 and 52 transverse to the conveying pipe; the sealing gasket tool 20 is configured to prevent the polymer mixture from leaking from the aforementioned gap toward the outside and toward the isolation chamber 18', and to prevent the lubricant liquid from leaking into the mixing chamber 3 through the above-mentioned gap I.

[0140] The gasket tool 20 comprises, in particular, an annular sealing element 20 .

[0141] The annular sealing element 20 is housed in a corresponding annular seat on the surface of the tubular element 7 and / or on the cylindrical surface of the aforementioned longitudinal through hole 12 and is placed near the transverse hole 13 extending the mixing chamber 3 as far as the conveying duct 7 .

[0142] The annular sealing element 20 may be provided directly above the intermediate hole 13 , ie at a height between the upper end E2 and the mixing chamber 3 , and / or directly below the intermediate hole 13 , ie at a height between the lower end E1 and the mixing chamber 3 .

[0143] Various possible forms of the high-pressure mixing device 1 will be described here, focusing on the configuration of the tubular element 7 and its removable fixing relative to the head body 2 .

[0144] according to Figure 6 In the form shown, an annular or flange-shaped shoulder zone 14A is arranged on the upper end E2 of the tubular element 7 and extends radially so that it can rest on the upper surface of the head 2 , in particular on the seat 17 .

[0145] The seat 17 , which may be obtained by a countersink, may be deep enough to completely house the shoulder region 14A, or only receive a portion thereof, the remainder of the shoulder region 14 remaining cantilevered upwards to be surrounded by other components (spacers).

[0146] exist Figure 6 In the form of, the fixing tool includes a threaded ring element 16, which is configured to engage with a threaded surface on the tubular element 7 at a position opposite the shoulder area 14A with respect to the head body 2 and is arranged to be placed on the lower surface of the head body 2 and apply pressure thereto.

[0147] By screwing the annular element 16 , the tubular element 7 is stretched downwards and blocked, thereby securing the shoulder or zone 14A against the lower opposite surface of the base body 2 .

[0148] In order to ensure the correct angular position of the tubular element 7 in the through hole 12, radial and angular centering means 19 are provided. These centering means may comprise a cavity 19 in the shoulder or area 14 and in the seat 17, designed to receive the latter, or two or more radial notches, also present on the tubular element 7 and the head 2, and into which a pin or a mutual centering key or another equivalent mechanical abutment is inserted; this tool ensures the mutual correct positioning, apart from the machining tolerances occurring at angles and transversely to the longitudinal axis of the hole 12 itself.

[0149] For this connection, it is necessary that the distance in the longitudinal direction of the intermediate hole 13 obtained transversely to the tubular element 7, measured from the contact surface of the head with the annular shoulder 14 of the tubular element 7 (delivery pipe), is sufficiently accurate, but without requiring, for example, special equipment, except those for machining made with modern tool machines.

[0150] Similarly, the accuracy of the radial positioning of the notches or of the radial centering notches does not require the use of special equipment, other than those machined with modern tool machines, thus significantly facilitating assembly operations and possible replacements.

[0151] Figure 7 The form of differs from the form just described in that the shoulder region 14 and the annular element 16 have inverted positions.

[0152] In this case, the shoulder region 14B extends radially from the middle region Z1 of the tubular element 7 in the shape of an annulus or flange and is configured to be placed on the lower surface of the head body 2 at a position opposite the upper end E2 of the tubular element 7. In contrast, the annular element 16 can be screwed onto the threaded region at the upper end E2 of the tubular element 7.

[0153] exist Figure 8 In the form of a head, a shoulder region 14C extends from the upper end E2 of the tubular element. The annular fixing element 16 is absent and the locking means comprises a specific screw 15 for fastening the shoulder region 14C directly in a seat 17 situated on the head body.

[0154] Figure 9 The form and Figure 8 , but differs in that it provides a shoulder area 14D having a locking screw 15 at the lower surface of the head body 2 in the aforementioned middle area ZI.

[0155] In accordance with Figure 7 , 8, 9, although not shown, radial and angular centering means (such as centering pins and keyways) are provided, similar to reference Figure 6 described and shown in the form of.

[0156] Figure 10 (and Figure 11 Another possible embodiment according to the invention is shown in the enlarged view of FIG. The shoulder region 14 is housed in the seat 17 and projects therefrom by a few hundredths of a millimeter. More precisely, depending on the size of the tubular delivery element 7, the upper surface of the bushing projects upward relative to the head body 2 by 3 to 9 percent of a millimeter.

[0157] Thus, it is tightened by pressure between the head body 2 and a spacer element 18, which is also fixed to the control cylinder of the cleaning member or rod 11, wherein the spacer element 18 forms the aforementioned compartment 18' and is also fixed to the control cylinder of the cleaning member or rod 11. In this case, the locking means include screw means 15', which are provided to fix the aforementioned spacer element 18 and compartment 18' to the head body 2. The upper surface of the shoulder area 14 protrudes slightly from the surrounding surface of the head body 2 and receives the tightening pressure through the elastically deformed spacer element 18.

[0158] In another possible form, as already mentioned, the shoulder region 14 is housed in a seat 17 partly on the head body 2 and partly in the lower surface of the spacing element 18 (compartment 18 ′), or almost entirely in the lower part of the latter.

[0159] The interface region between the mixing chamber 3 and the tubular element 7 will now be described in more detail, taking into account that the features described below must be considered to be present in all the forms described above.

[0160] The diameter D1 of the intermediate transverse hole 13 obtained on the tubular element 7 and extending the mixing chamber 3 is greater than the second diameter D2 of the mixing chamber 3 .

[0161] Due to this structural configuration, it is ensured that the diameter D1 of the hole 13 transverse to the conveying pipe 7 is sufficiently increased compared to the diameter D2 of the mixing chamber, so that even if there are radial and longitudinal misalignments caused by the processing and connection tolerances of the tubular element 7 and the head body 2, no protruding step will be formed within the diameter D2.

[0162] It is possible to compensate for possible alignment errors caused by processing and mutual positioning tolerances between the bore 13 of the tubular element 7 and the bore of the mixing chamber 3 during assembly, thereby avoiding the creation of internal protrusions in the end of the mixing chamber 3 in the head body 2 when the tubular element 7 is locked. Such a configuration makes it possible to avoid the creation of projecting steps in the mixing chamber and of interference areas that would hinder the movement of the valve member 9, both positively and laterally, when it is necessary to bring the valve member 9 into the fully advanced closed position.

[0163] Since the valve member 9 is usually coupled in the mixing chamber 3 with a very small clearance (from about 5 thousandths to about 25 thousandths of a millimeter), the larger diameter D1 of the transverse hole 13 makes it easy to couple the latter relative to the outlet of the mixing chamber 3, despite possible mutual positioning errors due to the tolerances and processing involved in the mutual coupling of the components.

[0164] The transverse hole 13 is thus configured as an extension of the mixing chamber 3 and can receive internally the front end of the valve member 9 in the advanced position.

[0165] The difference I between the first diameter D1 and the second diameter D2 i The diameter difference has a value between about 0.04 mm and about 0.3 mm. This diameter difference thus facilitates the assembly operation and avoids interference in the discontinuities of the surfaces, effectively ensuring the seal. It is also possible to compensate for misalignments and diameter differences, which could lead to friction, scratching and seizure of the mixing valve member or the slide 9 or damage the seal between the surfaces and cause leakage of resin or lubricant, by means of a specific sealing system as described below.

[0166] Similarly, the diameter of the hole 52 is larger than the diameter of the cap 50 by an amount of 0.1 to 0.3 mm to avoid interference of the cap with the inner diameter of the hole. The corresponding gap iii thus has a thickness or gap of up to 0.3 mm.

[0167] An annular seat 22 is obtained in the tubular element 7, which is arranged coaxially with the aforementioned intermediate transverse hole 13 and is configured to house an elastic or elasto-plastic sealing element 23, inserted by press-assembly and adapted to interact elastically with its seat and with the valve member 9 in an interfering manner so as to perform an effective sealing action and, in another configuration, a hydraulic sealing action on the surface of the hole 12 housing the tubular element 7.

[0168] This sealing system represents the most effective alternative to the solution of providing a small circular cavity on the cylindrical front part of the slide valve 9 and inserting therein a protruding resin seal which can easily break or wear at the corners of the above-mentioned discontinuous surfaces and the corners of the reactive resin inlet hole.

[0169] It also represents an alternative to resin sealing by applying a hardening resin or resin sealing the circular cavity obtained on the elongated hole 13 of the mixing chamber 3 in the self-cleaning cannula delivery duct, which resin sealing becomes less stable due to the presence of lubricants in the delivery duct itself.

[0170] With regard to these solutions, according to the invention, it is simpler and more convenient to obtain the annular seat 22 on the elongated hole 13 of the mixing chamber in the tubular element 7 housing a sealing element 23 made of elastic or elasto-plastic material.

[0171] The annular seat 22 and the elastic or elasto-plastic sealing element 23 can have different configurations.

[0172] According to an embodiment, the annular seat 22 may be obtained within the thickness of the tubular element 7 ; in this case, the annular seat 22 extends in a circle, has a uniform transverse section, ie has an annular shape, and contains laterally on both sides elastic or elasto-plastic sealing elements 23 . Figure 12A 、 12B , 12C, 13, 14, and 15 show examples of this configuration.

[0173] In other possible forms, the annular seat 22 can be obtained on the external surface of the tubular element 7 by countersinking and extending in the thickness of said tubular element 7 in the shape of an outer saddle, so as to be open on one side and facing the surface defining the transverse hole 13 obtained in the tubular element 7 and facing the surface of the through hole 12 of the head body 2 (extending transversely to the mixing chamber), and at the end of the mixing chamber 3, as Figure 16 and 29 to 33 as better shown.

[0174] exist Figure 12B A form of sealing ring 23 is schematically shown in FIG.

[0175] Thus, this elastic or elasto-plastic sealing element 23 is inserted and compressed in an interference manner in a constant cross-section annular seat 22, which may be flat or saddle-shaped (annular seat 22C, e.g. Figures 42 to 45 shown). Figure 13 and 14 Two different states of the sealing element 23 are shown, in particular compared to the seat 22 which accommodates it, from its unformed state ( Figure 13 ) to a shape change in the working situation, wherein, in the working situation, the sealing element is inserted in an interference manner into the aforementioned seat 22 and is compressed ( Figure 14 ).

[0176] Figure 12B The sealing element 23 shown in FIG has a cross-section characterized by having only one cusp 27 located on the inside of the annular seal (towards the axis of revolution) and two tip areas 26 located on the larger diameter outside the annulus, with an intermediate recessed area between the two tip areas 26 and with the two side bevel surfaces diverging inside the annulus to form a protruding corner. Once inserted in forced contact with the annular seat surface 22, the sealing element has a tip and a corner, which are pressed against the surface of the annular seat 22 and exert pressure by deformation, thereby ensuring the sealing effect. The tip 27 on the innermost diameter is intended to interact with the cylindrical surface of the valve member 9 (sliding valve) by squeezing during passage. The tip area is defined by the intersection of surfaces with different placement positions, in particular surfaces with opposite tapers between them.

[0177] Similar constructions can be found in Figure 19 , which has a similar annular extension.

[0178] In particular, the surface intended to interact with the valve member 9 has an inclined placement so as to act as a guide hole for the valve member 9 itself.

[0179] Figure 17, 18 is a cross-sectional and perspective view of the sealing element 23 in one of the possible "saddle" configurations. Figures 21 to 23 Further views (cross-sectional views) of the saddle-shaped sealing element are reported in and 25 to 28 .

[0180] Advantageously, the tip region 26 has the effect of increasing the coupling action with the annular seat 22 , compensating for possible dimensional irregularities or surface elevations.

[0181] When the sealing element is forced into its seat, the tips 26 are pressed against the surfaces to which they are coupled and they advantageously have the effect of increasing the specific pressure required to seal the coupled surfaces with the annular seat, adapting to possible dimensional irregularities or surface protrusions. Figure 20 ) has a portion with two beveled tip protrusions 26BIS, a middle portion with a groove on the outer surface having a larger diameter, and a portion with a groove between the two tips and the angled corners on the side surfaces on the inner surface. Elements 23A, 23B, 23D, and 23L have pointed tips.

[0182] Component 23C( Figure 21 )、23D( Figure 22 )、23E( Figure 23 )、23G( Figure 25 ) has a flat side, which is orthogonal to the circular extension axis and has a sharp corner; and an opposite saddle-shaped side, which has a sharp corner obtained by the intersection of two orthogonal cylinders with diameters corresponding to the outer surface of the mixing chamber 3 and the tubular element 7 and can be installed in the open cavity.

[0183] Component 23H( Figure 26 )、23I( Figure 27 )、23L( Figure 28 ) is provided with an annular saddle-shaped projection or shoulder, the shape resulting from the intersection of two orthogonal cylinders having a diameter corresponding to the external diameter of the projection, wherein the seat 22A of the projection is obtained outside the external thickness of the tubular element 7 (at Figures 29 to 33 (better visible in the).

[0184] Figure 17 and 18 is a perspective view of the sealing element 23 in one of the possible "saddle" geometric configurations.

[0185] When the sealing element is forced into its seat, the tip 26 or beveled tip 26BIS compresses the surface to which they are coupled by deformation and they advantageously increase the effect of the specific pressure required to seal with the annular seat 22 on the coupling surface, adapting to possible dimensional irregularities or surface roughnesses.

[0186] from Figure 12BAs can be clearly seen from the schematic diagram of FIG, the inner diameter D3 of the tip region 27 is smaller than the diameter D2 of the mixing chamber 3, and it is also smaller than the outer diameter of the valve member 9, and the surfaces of the outer corners and the tip of the sealing element are compressed and adapted to the surfaces against which they are pressed. As a result, the sealing element 23 interacts elastically with the valve member 9 (as Figure 12C and 14 as shown) and ensure hydraulic sealing to prevent leakage of reaction components and lubricants.

[0187] Thus, the tip region 27, which may have an inclined tip 26BIS, advantageously performs an effective sealing action on the cylindrical surface of the valve member 9 when the valve member 9 is present or when it is moved towards its advanced position.

[0188] Sealing element 23H( Figure 26 )、23I( Figure 27 )、23L( Figure 28 ) is provided with an annular peripheral relief 28 or "saddle" shoulder 28 which extends radially according to the intersection of two orthogonal cylinders whose diameter corresponds to the external diameter of the protrusion whose seat is in the external thickness of the tubular element.

[0189] The peripheral relief 28 ensures a more effective hydraulic seal in the open cavity in the area of ​​the connection between the outer surface of the tubular element 7 and the transverse hole 12 of the head body 2. Basically, the peripheral relief 28 is compressed between the counterbore located in the thickness of the tubular element 7 around the hole and the surface of the gap I between the tubular element 7 and the transverse hole 12 of the head body 2.

[0190] exist Figures 34 to 37 In FIG. 1 , a form of tubular conveying element 7 is shown, which has a seat 22B for a sealing element 23 in its central bore 13, made according to another possible geometric configuration. In this case, the seat 22B is used to accommodate a sealing element 23, such as Figures 38 to 41 The sealing element 23 of the configuration shown. This sealing element 23 comprises a relief 38 which is saddle-shaped on the outside but comprises a planar mating surface 34 on the inside.

[0191] The seat 22B also has externally a saddle shape while being internally delimited by a shoulder surface 35 of planar shape, obtained by a countersunk hole, suitable for receiving in abutment the planar matching surface 34 of the aforementioned sealing element 23 .

[0192] The planar shoulder surface 35 of the seat 22B serves to press the sealing element 23 against the surface defining the through hole 12 of the head body 2 .

[0193] Such a configuration enables the element 23 to exert a hydraulic seal at the interface between the intermediate transverse hole 13 and the slide valve 9 and at the interface between the outer surface of the tubular element 7 and the receiving surface of the through hole 12 (of the head body 2 ).

[0194] exist Figures 42 to 45 In a form shown, the annular seat 22C obtained at the intermediate hole 13 is suitable for a constant section and saddle-shaped sealing element entirely included in the thickness of the tubular element 7 .

[0195] The seat 22C, which has a constant cross section but has a saddle shape, is configured to accommodate a corresponding sealing element 23 of uniform cross section.

[0196] This configuration of the seat 22 can be realized, for example, on a double-interpolation CNC machine tool.

[0197] In summary, in its various forms, the sealing element 23 of elastic or elasto-plastic material is provided with a lip having a sharp or beveled angle, which ensures sealing in the compressed state. In fact, the sealing action is more reliable and effective if it is performed by a suitably compressed reduced annular extension surface, which operates at a high specific pressure and adapts by deformation to the roughness and geometrical tolerances of the surface that must be sealed. Figures 17 to 28 As shown, the sealing element can have an outer surface with one or more tip areas having sharp or oblique angles of a triangular or trapezoidal profile, or can have an inner surface with a tip area of ​​a triangular or trapezoidal profile, or can have an outer surface with four tip areas of a triangular or trapezoidal profile.

[0198] In general, due to the specific construction of the sealing ring 23 and the seat 22 in the various forms described above, the tubular element 7 (metal tube) can be manufactured without precise structural constraints, which would force it to be manufactured mechanically connected to the head body 2; therefore, advantageously, the two parts can be manufactured separately and simply connected by the various removable fixing solutions previously described (flange shoulder area, threaded ring, fastening by spacer 18, etc.).

[0199] Another technical advantage is achieved thanks to all of the aforementioned hydraulic sealing elements. Previously, reference was made to forced lubrication, by introducing a lubricant liquid into the compartment, to ensure the sliding of the cleaning member 11 within the tubular element 7. However, it was also noted that this lubrication inhibits the formation of reactive resin, which facilitates the sealing effect in the area of ​​the connection between the tubular element and the head body, as well as in the bore 13 extending the mixing chamber 3 toward the front cylindrical surface of the valve element or slide, thus potentially promoting or maintaining undesirable lubricant leakage during initial use of the mixing device 1. However, this risk is successfully avoided thanks to all of the aforementioned sealing elements, which effectively function at the interface between the single-piece delivery duct 7 and the head body 2, as well as at the interface between the transverse bore 13 of the duct 7 and the slide 9 in the recirculation forward position.

[0200] As is clear from what is disclosed and shown in the accompanying drawings, the mixing device 1 according to the invention successfully achieves all the intended objectives.

[0201] The solution according to the invention, in addition to significantly reducing the incidents of damage and thus extending the service life of the high-pressure mixing device 1, simplifies and makes the construction and assembly of the device 1 itself more cost-effective, thanks to the tubular element 7, the through hole 12 providing the gap I and the sealing means 20, and allows easier, faster and more cost-effective replacement of the conveying pipe 7.

[0202] The use of a single-piece tubular element 7 as the delivery conduit contributes to a significant increase in the average operating life of the cleaning member 11 and the delivery conduit 7 itself, and contributes to an overall improvement in the operating conditions of the entire mixing device 1 .

[0203] The disassembly and cleaning operations of the spacer element 18 are also facilitated.

[0204] Due to the larger diameter of the transverse hole 13 in the tubular element 7, together with the new sealing system provided by the aforementioned annular seat 22 and the sealing element 23, it is also very simple to axially center and angularly orient the conveying pipe relative to the seat of the head body 2 that accommodates it and relative to the mixing chamber, and it is quick and easy to compensate for geometric errors caused by manufacturing tolerances and possible geometric and dimensional inaccuracies.

[0205] In short, the delivery pipe 7 made in one piece, the gap I with the head body 2, the sealing tools 20, 23, 51 and the diameter of the intermediate hole 13 larger than the diameter of the mixing chamber 3, the diameter of the hole 52 larger than the diameter of the cap 50 work together to advantageously allow the delivery pipe 7 to be immediately inserted into the through longitudinal hole 12 of the head body 2 in a position that is fully aligned longitudinally, laterally and angularly so as to avoid interference with the front of the movable valve member, significantly eliminating the laborious and time-consuming positioning operations and the subsequent processing required to compensate for possible misalignment of the steps protruding at the interface between the assembled parts, and also avoiding the long and delicate operation of applying a hardening resin suitable for sealing, while connecting the gaps and voids between the tubular element and the hole 12 and the mixing slide valve and the hole 13.

[0206] Since the delivery pipe 7 is made in one piece and since sealing elements (20, 23) are active on the outer surface of the pipe 7 and in its transverse bore 13 (which is an extension of the mixing chamber 3), the risk of leakage of the mixture and lubricant liquid is avoided, which can occur in the prior art devices and must be sealed, for example, by applying a hardening resin, the polymerization and excess removal of which during the assembly and seal checking steps require additional working time. It is also known that the reactive resin that polymerizes in the delivery pipe delaminates significantly and unevenly on the surface of the delivery pipe, and in such delaminated areas, areas of strong compression against the cleaning member are determined, followed by strong metal-to-metal friction in the opposite areas. Even if lubrication delays and reduces the extent of this phenomenon, it cannot be interrupted. As mentioned in the introduction, this uneven behavior is more pronounced if the delivery pipe is combined and has steps or geometric errors, tilted axes or diameter variations, and therefore changes in the pipe and different accumulations caused by step protrusions, as occurs in the prior art devices.

[0207] The specific arrangement of the sealing elements (20, 23, 51) (made of elastic or elastoplastic material, such as elastomer or polytetrafluoroethylene), the construction of the single-piece delivery conduit 7 (avoiding any type of unevenness or steps that promote stagnation or accumulation of resin and enabling a very precise geometry to be obtained) work together to avoid the above-mentioned phenomenon and also avoid possible leakage of lubricant liquid (as mentioned above) that is more likely to occur during the first use of the mixing head.

[0208] Thanks to the one-piece construction of the tubular element 7 , it can also be coupled with the self-cleaning member with greater precision.

[0209] Depending on the intended application, the device 1 and its components may be configured and dimensioned as desired.

[0210] The materials may be appropriately selected according to the requirements claimed and in accordance with the state of the art, so long as they are compatible with the specific use for which they are intended.

[0211] Variations and / or additions may be made to what is described above and shown in the accompanying drawings without departing from the scope of what is claimed.

Claims

1. A high-pressure mixing device (1) suitable for forming a polymer mixture produced from a first chemically reactive liquid component and at least one second chemically reactive liquid component, the high-pressure mixing device (1) comprising: A head body (2) provided with a mixing chamber (3), said mixing chamber (3) having an inner cylindrical surface (4), said inner cylindrical surface (4) being provided with an inlet (5) and a recirculation outlet (6) for injecting and recirculating said chemically reactive liquid components, respectively; a delivery conduit for releasing and spraying the polymer mixture obtained, having a cylindrical inner surface in fluid communication with said mixing chamber (3) and inside which a cleaning member (11) is slidably movable, suitable for spraying said mixture once delivery is completed; a valve member (9) provided with longitudinal slots (10) for separately recirculating the chemically reactive liquid components and slidably movable in the mixing chamber (3) between a rearward position in which it exposes the inlets (5) and an advanced position in which each longitudinal slot (10) connects a respective inlet (5) with a respective recirculation outlet (6) for recirculating the respective chemically reactive liquid component, wherein the transport conduit is composed of a tubular element (7) made of a single, non-bonded piece having an open upper end (E2) communicating with the compartment (18') and an open lower end (E1) for transporting the reactive mixture; the cleaning member (11) being reciprocally movable in the tubular element (7) by hydraulic control between upper rearward positions, wherein in the upper rearward position it at least partially clears the outlet of the mixing chamber (3) into the delivery chamber defined in the tubular element (7) for enabling the reaction mixture to flow out; Sealing means configured to prevent leakage of the polymer mixture of the chemically reactive liquid components outside the mixing chamber (3) through the gap (I) and towards the compartment (18'), and to prevent any leakage of lubricating liquid from the compartment (18') through the gap (I) towards the mixing chamber (3), The tubular element (7) is a separate and separately processed piece from the head body (2) and can be detachably inserted into a through hole (12) of the head body (2) extending transversely relative to the mixing chamber (3). The tubular element (7) is arranged to extend transversely relative to the mixing chamber (3) and protrude longitudinally from the head body (2) along the axis of the through hole (12) at the bottom. wherein the tubular element (7) is provided with a central transverse hole (13) which, in the assembled configuration, is positioned to extend the mixing chamber (3) with an increasing diameter, so that the mixing chamber (3) extends upwards until it enters the inner chamber of the tubular element (7), wherein the intermediate transverse hole (13) has a first diameter (D1) and the mixing chamber (3) has a second diameter (D2), the first diameter (D1) being larger than the second diameter (D2) to compensate for mutual geometric positioning errors and tolerances due to machining tolerances during assembly, to avoid steps and areas interfering with the movement of the valve member (9) within the intermediate transverse hole (13), the intermediate transverse hole (13) being configured as an extension of the mixing chamber (3) and being adapted to receive the front cylindrical end of the valve member (9) internally in the advanced position, wherein the sealing means comprises an elastic or elastoplastic sealing element (23) having an annular seat on a surface defining the intermediate transverse hole (13) adapted to accommodate the elastic or elastoplastic sealing element (23), the elastic or elastoplastic sealing element (23) being accommodated and compressed in the annular seat by forced interference to perform a hydraulic sealing function, preventing the chemically reactive liquid components of the recirculated longitudinal groove (10) from leaking through the intermediate transverse hole (13) and the associated seat of the tubular element (7) when the front end of the valve member (9) is in the advanced position, and preventing the lubricating liquid from leaking from the gap defined between the control rod of the cleaning member (11) and the tubular element (7) toward the longitudinal groove (10), wherein the tubular element (7) is provided with an annular shoulder region (14), the annular shoulder region (14) being placed at a region remote from the central transverse hole (13); and fixing and centering means, which are arranged and configured for removably fixing the annular shoulder region (14) to a side surface of the head body (2) transverse to the through hole (12) in order to lock the tubular element (7) in the correct position in the through hole (12), A gap (I) is defined between the tubular element (7) and the through hole (12) and in the head body (2), which is configured to allow easy interchange of the tubular element (7) to facilitate insertion and removal of the tubular element (7) from the through hole (12).

2. The high-pressure mixing device (1) according to claim 1, wherein: The annular seat is coaxially arranged relative to the intermediate transverse hole (13), the at least one elastic or elastoplastic sealing element (23) protrudes toward the interior of the intermediate transverse hole (13) and is compressed in its annular seat for interacting with the valve member (9) in an interference manner, the annular seat having a constant cross-section and being completely contained in the thickness of the tubular element (7) without protruding on the outer cylindrical wall of the tubular element (7), and having a flat annular shape to contain the elastic or elastoplastic sealing element (23) forcibly accommodated on both sides, or the annular seat is saddle-shaped or externally saddle-shaped obtained by interpolation and has an annular or flat countersunk hole connected to or not coaxial with a countersunk hole of reduced diameter, the annular seat being open on one side and facing the surface defining the through hole (12).

3. The high-pressure mixing device (1) according to claim 1 or 2, wherein: The head body (2) and the conveying duct extend relative to each other according to an "L" configuration, wherein the conveying duct extends orthogonally relative to the longitudinal extension of the mixing chamber (3) and has a diameter section greater than the diameter section of the mixing chamber (3), and wherein the conveying duct extends so as to protrude relative to the head body (2) and extends longitudinally, measured from the axis of the mixing chamber (3) to the end outlet of the reaction mixture, at least three times higher than the diameter of the conveying duct.

4. The high-pressure mixing device (1) according to claim 1, wherein: The difference (Ii) between the first diameter (D1) and the second diameter (D2) has a variable value between 0.04 mm and 0.3 mm, and wherein the gap (I) has a variable value between 12 and 80 micrometers depending on the diameter of the mixing chamber (3).

5. The high-pressure mixing device (1) according to claim 1, wherein: The annular shoulder region (14) extends radially at the upper end (E2).

6. The high-pressure mixing device (1) according to claim 5, wherein: The annular shoulder area (14) having an annular or flange shape is fastened between the head body (2) and a spacing element (18) defining the compartment (18'), the compartment (18') being interposed between the control cylinder of the cleaning member (11) and the head body (2), wherein the fixing means comprise screw means (15') for fixing the spacing element (18) and therefore the compartment (18') to the head body (2), and wherein the annular shoulder area (14) is received in a seat (17) located on the head body (2) and / or the spacing element (18).

7. The high-pressure mixing device (1) according to claim 6, wherein: The seat (17) is completely on the head body (2) to completely accommodate the annular shoulder area (14), leaving the outer end surface of the annular shoulder area (14) exposed and suitable for receiving the tightening pressure of the spacer element (18) against the upper surface of the head body (2).

8. The high-pressure mixing device (1) according to claim 6, wherein: The seat (17) is partially on the head body (2) and partially on the lower end of the spacer element (18), so that the annular shoulder area (14) is partially housed in the head body (2) and protrudes therefrom to be partially contained in the spacer element (18), the annular shoulder area (14) thus spanning the interface surface between the head body (2) and the spacer element (18).

9. The high-pressure mixing device (1) according to claim 1, wherein: The annular shoulder region (14) extends radially from the middle region (ZI) of the tubular element (7) in an annular or flange shape and is configured to be placed on the surface of the head body (2) at a position opposite the upper end (E2).

10. The high-pressure mixing device (1) according to claim 1, wherein: The fixing means comprises a locking screw (15) arranged to engage directly with the annular shoulder region (14) to removably fix it to the head body (2).

11. The high-pressure mixing device (1) according to claim 1, wherein: The fixing tool comprises a threaded annular element (16) configured to engage with a threaded surface on an area of ​​the tubular element (7) opposite the annular shoulder area (14) and to abut against a surface of the head body (2).

12. The high-pressure mixing device (1) according to claim 1, further comprising a cavity (19) for radially centering the tubular element (7) by means of a pin or a key, said cavity (19) being in said annular shoulder region (14) and in a seat (17) arranged to receive said pin or key.

13. The high-pressure mixing device (1) according to claim 1, wherein: The sealing tool further comprises an annular sealing element (20) which is accommodated in a corresponding annular seat located on the surface of the tubular element (7) and / or on the cylindrical surface of the through hole (12) of the head body (2), the annular sealing element (20) being configured to prevent the polymer mixture and the chemically reactive liquid component from leaking from the mixing chamber (3) through the interface between the head body (2) and the tubular element (7) toward the compartment (18') and / or outward, and to prevent any leakage of lubricating liquid from the compartment (18') toward the mixing chamber (3).

14. The high-pressure mixing device (1) according to claim 1, wherein: In the intermediate transverse hole (13) provided on the tubular element (7), there is provided the annular seat or annular concentric double countersunk seat with a constant cross-section obtained by interpolation of the axis of the tool machine, or there is the annular seat coaxially provided with the intermediate transverse hole (13) on the outer surface of the tubular element (7), the annular seat extending in a saddle shape or a plane shape in the thickness of the tubular element (7) to be open on one side and facing the surface of the through hole (12) of the head body (2) for accommodating the tubular element (7), the elastic or elastoplastic sealing element (23) is suitable for interacting with the valve member (9) in an interference manner and being accommodated in an interference manner between the longitudinal surface of the through hole (12) and the surface of the annular seat in the shape of a saddle.

15. The high-pressure mixing device (1) according to claim 1, wherein: The elastic or elastoplastic sealing element (23) includes a recessed area and an escape area, which are configured to increase the specific contact and connection pressure with the annular seat, and increase the pressure and hydraulic sealing effect of the surface of the through hole (12) relative to the head body (2) and the hydraulic sealing effect of the surface of the annular seat that defines the elastic or elastoplastic sealing element (23), and increase the hydraulic sealing effect when interacting with the front cylindrical surface of the valve member (9).

16. The high-pressure mixing device (1) according to claim 1, wherein: The elastic or elastoplastic sealing element (23) includes a recessed area and an avoidance area on the outer surface, and has one or two or four tips, the tips having a triangular, triangular slope or trapezoidal shape, which is configured to increase the specific contact and connection pressure with the annular seat and increase the hydraulic sealing effect on the surface of the through hole (12) of the head body (2) and the hydraulic sealing effect on the surface accommodating the elastic or elastoplastic sealing element (23) and the hydraulic sealing effect when interacting with the cylindrical surface of the valve member (9), and wherein the outer surface of the elastic or elastoplastic sealing element (23) includes a transverse profile, which has one or two or four triangular or trapezoidal tips to increase the specific pressure on the surface of the cavity and better adapt to the roughness and tolerance of the surface receiving the elastic or elastoplastic sealing element (23) through deformation.

17. The high-pressure mixing device (1) according to claim 1, wherein: The outer surface of the elastic or elastoplastic sealing element (23) comprises a peripheral contour configured in a saddle shape, thereby ensuring a sealing effect even in the connection area between the outer surface of the tubular element (7) and the through hole (12) of the head body (2).

18. The high-pressure mixing device (1) according to claim 1, wherein: The elastic or elastoplastic sealing element (23) has an outer peripheral surface suitable for coupling with a cylindrical shape, and has one of the side surfaces configured to couple according to a saddle shape formed from the intersection between two cylindrical bodies of different radii, so as to exert a sealing effect at the annular seat having a counterbore surface in the coupling area between its outer surface and the surface defining the through hole (12) transverse to the head body (2).

19. The high-pressure mixing device (1) according to claim 1, wherein: The elastic or elastoplastic sealing element is provided with an annular peripheral relief (28) constructed according to a saddle shape obtained from the intersection between two orthogonal cylinders of different radii, in order to increase the surface and the sealing action even in the area of ​​the connection between the outer surface of the tubular element (7) and the surface of the through hole (12) defined in the head body (2), in the area of ​​the concentric double countersunk hole defining the annular seat.

20. The high-pressure mixing device (1) according to claim 1, wherein: In the head body (2), in the tubular element (7), at a position diametrically opposite and in front of the mixing chamber (3) and the intermediate transverse hole (13), there is a transverse further hole (52), which is occupied and sealed by the cap (50) during normal operation, and once the cap (50) is removed, the hole (52) allows the application of another valve element to the head body (2) for the introduction of a washing or inerting liquid or gas in order to clean the flexible extension of the conveying pipe or to inject inerting gas into the cavity of the mold injected with the polymer mixture, defining a corresponding gap (iii) between the surface of the cap (50) and the surface of the hole (52); the sealing means also include an elastic or elasto-plastic seal (51) inserted into the gap (iii) to avoid any leakage of the mixture or lubricating liquid towards the hole (52).

21. A method of manufacturing a high-pressure mixing device (1) according to any one of the preceding claims, the high-pressure mixing device (1) being suitable for forming a polymer mixture produced from a first chemically reactive liquid component and at least one second chemically reactive liquid component, wherein: The conveying conduit is configured as a tubular element (7) made in one piece, having an open upper end (E2) communicating with the compartment (18') and an open lower end (E1) for conveying the reactive mixture, and wherein the tubular element (7) can be machined separately from the head body (2) and inserted and removably fastened - to allow easy removal - in a through hole (12) in the head body (2), a central transverse hole (13) is obtained in the tubular element (7) before the tubular element (7) is inserted into the head body (2), the central transverse hole (13) being intended, in the assembled configuration, to extend the mixing chamber (3) with an increased diameter so that the mixing chamber (3) extends upwards until it enters the delivery chamber defined in the tubular element (7); The intermediate transverse hole (13) is configured to have a first diameter (D1), and the mixing chamber (3) has a second diameter (D2), the first diameter (D1) being larger than the second diameter (D2), so as to compensate for mutual geometric positioning errors caused by machining tolerances during assembly and to avoid the presence of steps and areas that interfere with the movement of the valve member (9), the intermediate transverse hole (13) being constructed as an extension of the mixing chamber (3) and being suitable for internally receiving the front end of the valve member (9) in the advanced position; On the cylindrical surface of the said intermediate transverse hole (13), in the thickness of the said tubular element (7), an annular seat is obtained, An elastic or elastoplastic sealing element (23) to be inserted in an interference manner and having an appropriate shape is forcibly accommodated in the annular seat and compressed toward all surfaces of the annular seat, thereby performing a hydraulic sealing function to prevent the chemically reactive liquid component from leaking from the longitudinal groove (10) toward the delivery pipe when the front end of the valve member (9) is in the advanced position, and to prevent the lubricating liquid from leaking from the gap defined between the control rod of the cleaning member (11) and the tubular element (7) toward the longitudinal groove (10); The tubular element (7) is provided with an annular shoulder region (14) located at a region remote from the central transverse hole (13), and The annular shoulder region (14) is detachably fixed to the side surface of the head body (2) by a fixing tool to lock the tubular element (7) in the correct position in the through hole (12), wherein a gap (I) is defined between the tubular element (7) and the through hole (12) of the head body (2) to limit the contact area and avoid sticking due to interference between the tubular element (7) and the head body (2), so as to facilitate insertion and easy removal of the tubular element (7) from the through hole (12); and Sealing means are provided which are configured to avoid leakage of the polymer mixture and the chemically reactive liquid component from the mixing chamber (3) to the interface between the head body (2) and the tubular element (7) and towards the compartment (18'), and to avoid any leakage of lubricating liquid from the compartment (18') to the mixing chamber (3).

22. The method according to claim 21, wherein The annular seat is located entirely within the thickness of the tubular element (7) in the cylindrical surface of the central transverse hole (13), the annular seat extending circularly entirely within the thickness of the tubular element (7) without protruding from one of the longitudinal cylindrical walls, in order to accommodate the elastic or elastoplastic sealing element (23) of annular and constant cross-section.

23. The method according to claim 21, wherein The invention provides a method for forcibly accommodating and compressing the elastic or elastoplastic sealing element (23) having an appropriate shape to be inserted in an interference manner toward all surfaces of the annular seat in the annular seat, thereby exerting a hydraulic sealing function, preventing the chemically reactive liquid component from leaking from the longitudinal groove (10) to the delivery pipe when the front cylindrical portion of the valve member (9) is in the advanced position, and preventing the lubricating liquid from leaking from the gap defined between the control rod of the cleaning member (11) and the tubular element (7) toward the longitudinal groove (10), wherein the annular seat is obtained by insertion in the surface defining the intermediate transverse hole (13) and toward the surface defining the through hole (12) so as to define a surface having a constant The invention relates to a saddle-shaped cross section or a counterbore or a saddle-shaped coaxial plane counterbore with a counterbore of reduced diameter, so that it is open on one side and faces the surface defining the through hole (12), and the annular seat is suitable for accommodating an elastic or elastoplastic sealing element (23) that is forcibly accommodated or compressed in its own annular seat, thereby performing a hydraulic sealing function, when the front end of the valve member (9) is in the advanced position, preventing the chemically reactive liquid component from leaking from the longitudinal groove (10) to the delivery pipe and toward the space (I) defined between the tubular element (7) and the through hole (12), and avoiding the lubricant liquid from leaking from the space defined between the control rod of the cleaning member (11) and the tubular element (7) toward the longitudinal groove (10).

Images