GB2091116A - Mixing head for reactive chemical substances - Google Patents

Abstract

A mixing head (1) for reactive chemical components, comprises a mixing chamber (5) in which a cleaning member (3) slides, injectors (8, 9) for feeding the individual components into the mixing chamber (5) and respective similar recycling valves (21a, 21b), with a needle (27) fitted onto a control member (28), on one side of which the feeding pressure for the chemical component is exerted, whereas on the opposite side the control fluid pressure is exerted, for balancing the thrust of the chemical component. The control sides (29) of each injector (8, 9) and of the corresponding recycling valve (21a, 21b) are connected in parallel to an adjustable source of fluid with constant pressure. <IMAGE>

Description

SPECIFICATION Mixing head for reactive chemical substances, with remote-controlled injectors This invention refers to a mixing head for reactive chemical components to be fed into a mould.

There are known heads for pressure-feeding, into a mould, a mixture of reactive chemical components, in which the individual components are fed into a mixing chamber th rough individual injecting devices; each of the components, before each mixing phase, is, moreover, made to recycle at a pressure value equal or similar to the feeding pressure for mixing, through a duct comprising a recycling valve wholly similar to the injector device.

With mixing heads of the type mentioned above, there is the problem of initial adjustment and setting of all the injectors and all the recycling valves of the head, in orderto ensure the regular feeding of the chemical components, at the desired stiochiometri cal ratios. In the heads of the known type, both the injectors and also the recycling valves are adjusted manually, therefore the setting of the entire head proves to be extremely complicated and tiresome inasmuch as separate adjusting operations must bs carried out before achieving the right setting of the injectors and of the valves.This involves an enormous waste of time, loss of material due to the numerous preliminary operating tests required, and furthermore, the non-perfect setting of a recycling valve, with respect to the corresponding injecting device, can give rise to situations of nonhomogeneous feeding of one of the components and, consequently, the forming of defects in the end product, a thing which is highly undesirable and to be avoided in high-quality products.

The aim of this invention isto provide a mixing head of the type mentioned, which is capable of simplifying the initial setting of the head, and of enabling the simultaneous and wholly identical adjusting of the injector and of the recycling valve for each component; it is thus possible to easily and accurately achieve recycling conditions substantially identical to those of the injection of each component.

A further aim of this invention is to provide a mixing head as defined above, in which the adjustment of the various injectors and of the individual recycling valves of the components, can be carried out by a remote control, without operating directly and manually on the head itself.

According to this invention, a mixing head for reactive chemical substances is provided, comprising a mixing chamber within which a cleaning member can slide between a forward position in which it closes the inlet apertures for the components and the outlet aperture for the mixture and, respectively, a backward position in which it opens the aforementioned apertures, the head comprising moreover, injecting devices in correspondence with the inlet apertures for the components into the mixing chamber, and control valves each of which can be opened in order to connect the inlet for one component to a feeding injector, respectively with an outlet through a first recycling path, for recycling at a first pressure value and respectively through a second recycling path comprising a recycling valve for a recycling at a second pressure value higher than the previous value, in which both the injector and the recycling valve for each component are of the type comprising a needle connected to a positive hydraulic control member on one side of which the feeding pressure for the component is exerted, and on the opposite side of which the pressure of a control fluid is exerted, for balancing the component feeding pressure, and in which the control-fluid feeding sides of the injector and the respective recycling valve are connected to the same source of constant pressure control fluid.The source of control fluid may be either shared by the two component injector and recycling valve units or each unit may have its own individual source in order to allow the individual components to be fed in with different pressure values.

A preferred embodiment of a mixing head with remote-controlled recycling valves and injectors, according to this invention, will be described with reference to the accompanying drawings, in which Figure 1 shows a longitudinal section of the head; and Figure 2 is a cross-section along the line 2-2 of Figure 1.

The drawings show a mixing head 1, comprising a cylindrical chamber 2 for mixing at Beast two chemical components capable of reacting together according to pre-established stoichiometric ratios. Sliding inside the mixing chamber 2 is a cleaning member in the form of a pin 3 connected to the shank of a positive hydraulic control c-/clinder 4; the cleaning pin 3 is therefore movable between a forward position in which it closes the outlet aperture 5 of the mixing chamber and the inlet apertures 6 and 7 for the chemical components, and a backward position in which it opens the aforementioned outlet 5 and inlets 6 and 7.

As shown in the Figures, the mixing head 1 comprises two injecting devices 8 and 9, the nozzles of which communicate with the respective opposing apertures 6 and 7 of the mixing chamber 2 and are connected respectively with the inlets 11 and 12 for each component, through corresponding multipleway control valves 13, 14. The valves 13, 14 are operated simultaneously in order to direct the flow of each chemical component towards its respective injector 8,9 and the mixing chamber 2, that is to say, towards a first recycling path along which the component is made to recycle at a first pressure value and, respectively, towards a second recycling path along which the component is made to recycle at a higher pressure value than the previous value, equal or substantially similar to the pressure value for feeding the component during a mixing phase.

In particular, each control valve 13 or 14 is composed of a cylindrical plug having an axial passage iso or 15bathe lower end of which communicates with the inlet 11 or 12 for the compGnei at which, in turn, is connected to a tank 32a or 32b for feeding the reactive component th rough a filter 33a or 33b and by means of a metering pump 34a or 34b, as shown schematically; the pump is capable of supplying metered quantities of the reactive component at a delivery pressure equal to or above 100/200 atmospheres, according to working requirements.During the recycling, the component is conveyed back to the tank32a or 32b through a recirculating line 36a or 96O. The axial passage 1 spa or P 15b of each control salve 13 or 14 can also communicate directly with a irstrecycling path 16a or 16btowards an outlet 17a or 17b through lateral aperture 18a or 18b in the lower part of the cylindrical plug. The passage 15a or 15b of the valve can, lastly, communicate with a second recycling path 19a or 19b, branching off or in parallel to the previous one, through a second lateral aperture 20a or 20b in the upper part of the plug, which aperture is annularly displaced with respect to the lower aperture 18a or 18b.The second recycling path 119a or 19b in turn, communicates with the outlet 17a or 17b through a recycling valve 21 a 21 b cap- able of being adjusted to supply a recirculating pressure for a chemical component, equivalent to or subseantialiy equal to that of the feeding into the mixing chamber 2 through the injector 8,9; therefore both the injectors 8,9 and the recycling valves 21a, 21b are of similarconstruction.

The two control valves 13, 14 are operated simultaneously with the movement of the cleaning pin 3, for example, by means of an operative connection comprising a rack 22, connected to the rod of the piston 4, having lateral cogs which engage with respective cogged wheels 22a, 22b at the upper end of the plugs of the control valves 13, 14.

As mentioned previously, according to the invention, each injector 8,9 and the respective recycling valve 21a or21 bare of identical construction and their setting may be carried out simultaneously, by a remote control, without having to act on the mixing head directly. In orderto simplify the description, reference will be made herebelowto the structure of the injector 9, that of the injector 8 and of the two recycling valves 21a, 21 b being wholly similar.In fact, each injector and each recycling valve comprises a body 23 tightly screwed into the head 1; this body 23 defines a cylindrical chamber 24, which communicates with the mixing chamber 2 through the nozzle 26 of the injector (respectively with the outlet 17b for the recycling valves) and with the inlet 11 of the component through the control valve 14.

Inside the chamber 24 is a needle 27, axially supported by a positive control member in the form of a piston 28 sliding within a chamber 29, formed to the rear of the body 23 and connected to a source 302 (301 for injector 8) of constant pressure control fluid.

Hence, the pressure of the chemical component itself is exerted on one side of the piston 28, that is to say, the side facing the needle 27, whereas the constant pressure of the control fluid is exerted upon the opposite side, which serves to provide the proper thrust for balancing the needle 27. As shown schematically, in Figure 2, the control sides of each injector 8,9 and of the relative recycling valve 21 a or 21 bare connected in parallel to the source 301 or 302 of control fluid, fed ate constant pressure, through a regulating device 30a or 30b for each injector and recycling valve unit. it isthmus possible to operate and adjust, by remote control, all the injectors and recycling valves of the head, achieving homogeneous feeding and recycling conditions for each component.The source of control fluid may either be shared by the two component injector and recycling valve units or each unit may have its own individual source.

The head operates according to the following description: Starting from the position shown in the drawings, which represents the low-pressure recycling conditions, each chemical component is fed in through the inlet 11 or 12 and the controlvalve 13 or 14towards the outlet 17a or 17b through the aperture 18a or 18b of the control valve 13 or 14 and made to recycle to the tank 32a or 32b through the line 36a or 36b.

As it is now necessary to mix the components, a first recycling phase is carried out at high pressure through the branched duct comprising the recycling valve 21 a or 21 bin this connection, the cylinder 4 is operated, making it carry out a first pre-established length of its control stroke so that the rack 22 causes the plugs of the control valves 21 a, 21 b to rotate by 90" until the apertures 20a, 20b communicate with the respective recycling ducts 19a, 19b; at the same time the control valves 13, 14 close the direct communication between the respective inlets 11, 12 and the respective outlets 17a, l7bforthe components.

Upon completion of the high-pressure recycling phase, the control cylinder 4 is operated again until it has carried out its entire backward stroke, rotating the plugs of the control valves by a further 90" in this way, the inlet 11 or 12 for each component is connected to its respective injector 8 or 9 as the aperture 20a or 20b of the control valve now coincides with the duct 31 a or 31 b. The individual components are then fed into the mixing chamber 2 of the head from where the mixture is delivered through the aperture 5, into a mould, not shown.

Upon completion of the mixing and mould-filling phase, the control cylinder 4 is operated once more in order to move the pin 2 forward which empties and cleans the chamber 2 of any remaining mixture, returning the control valves 13, 14 to the lowpressure recycling condition shown in the Figures.

Claims (5)

1. Mixing head for reactive chemical components, comprising a mixing chamber in which a cleaning member slides between a forward position in which it closes the inlet apertures for the components and the outlet aperture for the mixture and respectively a backward position in which it opens the aforementioned apertures, the head also comprising injecting devices in correspondence with the inlet apertures for the components and control valves each one of which can be operated in order to connectthe inlet for one component with an injector and the mixing chamber, respectively with an outlet through a first recycling path for a recycling at a first pressure value, and respectively through a second recycling path, comprising a recycling valve for recycling at a second pressure value higher than the first, in which both the injector and the recycling valve for each component are of the type comprising a needle connected to a positive hydraulic control member on one side of which the component feed- ing pressure is exerted, and upon the opposite side of which the control fluid pressure is exerted in order to balance the component-feeding pressure, and in which the control fluid feeding sides of the injector and the respective recycling valve are connected to the same source of constant-pressure control fluid.

2. Mixing head as claimed in Claim 1, in which each injector and respective recycling valve are connected to the source of a control fluid, at constant pressure, through a pressure regulating device.

3. Mixing head as claimed in Claim 1 or Claim 2, in which the source of fluid under pressure for controlling the injector and the recycling valve consists of a single source of fluid under pressure common to the injectors and the recycling valves for both the components.

4. Mixing head as claimed in Claim 1 or Claim 2, in which the control sides of the injector and of the recycling valve for one component are connected to a source of control fluid separate from that of the injector and of the recycling valvefortheothercom- ponent.

5. Mixing head substantially as hereinbefore described with reference to the accompanying drawings.