MIXHEAD AND METHOD OF MANUFACTURING A MIXHEAD - Patent application

Abstract

The mixing head (100) includes a head portion (102) and a mixing chamber device (104) disposed within the head portion (102). The mixing chamber device (104) has a mixing chamber (108) with at least two inlets (120) for introducing raw materials into the mixing chamber (108) and one outlet (122) by which a mixture of the raw materials can be discharged from the mixing chamber (108). A control piston (114) is movably disposed within the mixing chamber (108). In this case, the mixing chamber device (104) is removably disposed within the head portion (102) to allow replacement, and a middle fit and / or clearance fit is formed between the head portion (102) and the mixing chamber device (104). A corresponding manufacturing method is further described and claimed.

Description

[Technical field]

[0001] The present invention relates to a mixhead including a head portion and a mixing chamber apparatus disposed within the head portion, as well as a method of assembling the mixhead. [Background technology]

[0002] Generally, mixing heads are known which are mostly used for processing reactive or polymeric components for producing thermosetting materials, in particular polyurethanes, in which at least two reactive raw materials are thoroughly mixed with one another in a mixing chamber and the mixture is then discharged from the mixing chamber.

[0003] Mixing heads according to the generic term are already known from the prior art. For example, DE 195 15 039 A1 discloses an apparatus for mixing at least two chemically reactive plastic components under high pressure, which comprises a cylindrical mixing chamber into which the components are injected, in which a reversible piston is arranged for discharging the residual plastic mixture. The apparatus also has a cylindrical stabilization chamber / outlet chamber / outlet channel which is connected to the mixing chamber and which preferably runs at an angle of 90° to the longitudinal axis of the mixing chamber, in which a reversible cleaning piston is arranged for discharging the reactive plastic mixture from the stabilization chamber. The cleaning piston forms a number of recesses in its cylindrical circumferential wall which are filled with a spacer material and which are arranged in a helical manner in the circumferential wall, so that the cleaning piston rotates when it moves axially. This causes interruptions of the circumferential surface during the axial movement of the piston and thus serves as a wear protection measure.

[0004] In the mixing chamber, a control piston is arranged in a known manner, which is accommodated in a reciprocating manner. In this case, the control piston is formed with a number of recirculation grooves, which serve in the inward switching position, in which the mixing chamber itself is closed, to ensure a recirculation for the raw materials, i.e. a backflow of the raw materials into the starting vessel (recirculation phase). Such recirculation via these recirculation grooves is also known and does not require further explanation. In the retreating switching position of the control piston, the mixing chamber is emptied, so that the raw materials can be mixed with one another and then discharged from the mixing chamber (discharge phase). Such a mixing head is known, for example, from EP 1 979 143 A1.

[0005] In the known mixer heads, the mixing chamber is either directly formed in the head part or alternatively is contracted by means of a bushing, which makes it impossible to simply replace the mixing chamber in the recirculating mixer head. If the mixing chamber no longer works properly due to wear, the mixer head must be completely replaced or at least dismantled and subjected to laborious mechanical reworking and then heat treatment, or a new bushing with a mixing chamber by means of contraction technology must be used and then precision machining and reshaping of the nozzle assembly space must be performed. Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to provide a mixing head which is easier to maintain and repair compared to known solutions while at the same time achieving time and cost savings. [Means for solving the problem]

[0007] This problem is solved by the subject matter of the independent claims. Advantageous refinements of the invention are set out in the dependent claims, the description and the accompanying drawings. In particular, an independent claim of one claim category may be refined in the same way as a dependent claim of another claim category.

[0008] The mixer head according to the invention comprises a head part and a mixing chamber device arranged in the head part. The mixing chamber device has at least one mixing chamber and at least two inlets for introducing the raw materials into the mixing chamber. The mixer head is intended for the production of reactive plastics. Furthermore, an outlet is provided through which the mixture of raw materials can be discharged from the mixing chamber, in which case a control piston is movably arranged. In this case, the mixing chamber device is removably arranged in the head part in order to be replaceable. In this case, a middle fit and additionally or alternatively a clearance fit are formed between the head part and the mixing chamber device.

[0009] Furthermore, the mixhead has at least two recirculation outlets, whereby one recirculation outlet is arranged corresponding to each inlet for introducing raw materials. The mixhead and in particular the control piston of the mixhead are shaped in such a way that in the closed position, a fluid connection is created between the inlets and the correspondingly arranged recirculation outlets, so that the raw materials that can be introduced via the inlets can be recirculated towards the correspondingly arranged recirculation outlet. That is to say, the mixhead has at least one recirculation outlet per inlet, which in the closed position of the control piston is connected to the respectively correspondingly arranged inlet for recirculation.

[0010] The mixhead may be a mixhead for a reactive casting machine for producing reactive plastics, i.e. a polyurethane foam installation arranged for producing reactive plastics such as polyurethane foams. Reactive plastics generally consist of two (reactive) components (base and hardener) and possibly other additives, which harden by chemical reaction with one another. In particular, the reactive components may mean the raw materials. Components of the surrounding atmosphere may also react together. In this case, mixing can only take place immediately before the action, and then hardening begins. The reactive plastics in a processable state before chemical hardening are called reactive resins. Reactive plastics may mean, for example, epoxy resins (EP), polyurethanes (PU / PUR), nylons or polyamides (thermoplastics - but produced as polyadducts in the mixhead), DPCD (dicyclopentadiene / polyesters) or unsaturated polyesters (UP).

[0011] In particular, the mixing head can be used for the production of polyurethanes (PUR). The basic components of which the PUR material is made are polyols and isocyanates, whereby, in particular on the polyol side, mixtures of different polyols can be used. The processing of such multi-component reactive systems can be called reactive casting. If the reactive mixture additionally contains a blowing agent and is therefore foamable, it can also be called reactive foam casting. The mixing head is based on the countercurrent injection principle and uses the mixing action of turbulent flows. The components fed can have a pressure of more than 50 bar, in particular between 100 bar and 250 bar.

[0012] In particular, a clearance fit may be important. A clearance fit generally means that the smallest dimension of the bore is always larger than the largest dimension of the shaft (in extreme cases they are the same size). Since it is not possible to adhere to the nominal dimensions of the mating parts, and it is not even worthwhile to do so, for example for economic reasons, there is always a tolerance zone between the bore and the shaft. In this case, the shaft represents the mixing chamber device or the outer contour of the mixing chamber device in this description. Correspondingly, the bore represents the reception of the mixing chamber device in the head part. The mixing chamber device is therefore sometimes also called a mixing chamber bushing.

[0013] In this case, the tolerance classes make it possible to comply with the various requirements for the fit. These requirements can in principle be distinguished into three variations in which the tolerance ranges of the bore and the shaft are related to one another. In detail, these are clearance fit, intermediate fit and interference fit. In DIN 7157, all three variations are specified for the unit bore, while the unit shaft is standardized only with clearance fit. The shaft may always have a play with respect to the bore, i.e. there may be a desired distance between the outer delimitation of the shaft and the inner delimitation of the bore. Of course, the prerequisite for this clearance fit is that the maximum dimension of the shaft is always smaller than the minimum dimension of the bore. In the case of a clearance fit, it is not assumed that the maximum dimension of the shaft is not reached at the same time as the minimum dimension of the bore, so that in rare cases both dimensions may be identical. Furthermore, it must be noted that for a clearance fit, the tolerance ranges are selected in such a way that the maximum play, i.e. the maximum distance between the minimum dimension of the shaft and the maximum dimension of the bore, meets the permissible value.

[0014] The raw materials may be reactive or polymeric components, such as a polyol (or a mixture of polyols) and an isocyanate.

[0015] The mixhead may be a linear mixhead or a variable direction mixhead.

[0016] In this case, at least two inlets and two outlets of the mixing chamber can already be molded into the mixing chamber device before it is joined to the head part. This means that, advantageously, after joining the mixing chamber device to the head part, costly rework can be avoided and the mixing head is, so to speak, immediately ready for use after joining. The advantage of this solution is that the mixing chamber device can be easily replaced and thus quickly replaced in the event of wear. This makes it possible to reduce or keep the downtime of the mixing head short. The recirculation outlet can also already be correspondingly molded and positioned, again without the need for rework.

[0017] The inlet and / or the recirculation outlet may be sealed between the head part and the mixing chamber. For this purpose, a seal or sealing device may be provided or alternatively or additionally this can be achieved by adhesive or face seal. The seal may be molded as an O-ring. Alternatively, the seal may be molded, for example, as an elastomeric sleeve, a trimmed elastomeric sleeve (so-called sealing socks), a variant of an elastomeric or plastic seal (glid ring, step seal, etc.) or as a seal preloaded by a spring element (shaft seal ring, stripper, etc.).

[0018] An outlet chamber may be arranged on the mixing chamber on the outlet side. The outlet chamber may be molded in one piece. The outlet chamber may be replaceable. The outlet chamber may also be called an outlet passage. In this case, a cleaning piston may be inserted into the outlet chamber. Thus, it may be a direction-changing mixhead.

[0019] The control piston may have at least two control grooves. In this case, the control grooves may be machined symmetrically to one another (especially in the case of an even number of control grooves) or alternatively, the control piston may have at least three control grooves arranged evenly distributed to one another on the circumferential surface of the control piston, which reduces wear. Such a regular arrangement of the control grooves reduces unavoidable wear. This allows the control piston to move more easily in the center of the mixing chamber. The control grooves are sometimes called recirculation grooves. The raw materials fed via the inlet, i.e. for example the reactive or polymeric components, can be guided to the recirculation outlet via the control or recirculation grooves in the control piston and may be circulated from the recirculation outlet while the control piston is arranged in the closed state of the mixing head. When the control piston moves away from the outlet, the inlet or inlets are temporarily closed, which then frees the connection leading from the inlet through the mixing chamber to the outlet.

[0020] The control piston may be formed from multiple parts. Alternatively, the control piston may be formed in one piece. In this way, the control piston can be easily manufactured and installed. Damage to the control piston can also be more easily prevented.

[0021] The mixing chamber may have at least one radial groove to create an axial seal. The near side radial groove formed in the mixing chamber allows a purely cylindrical play between the control piston and the mixing chamber. In this case, the near side does not need a narrow play, i.e. a dedicated fitting is not required. This allows interchangeability to be achieved. Thus, functionally, a self-forming seal can be formed. For example, a self-forming seal can create a scraping of the reaction material based on two radial grooves in the mixing chamber. In this case, a second radial groove or further radial grooves can make this effect even more effective. Alternatively, a rod seal, for example a vector seal, a scraping ring or a glide ring can be provided. A glide ring can mean a sealing element known in hydraulics that provides an outer seal for the piston.

[0022] The mixing chamber device can be designed with mirror symmetry, which allows the mixing chamber device to be manufactured particularly simply (essentially as a turned part with a hole). In this case, the mirror symmetry relates to the basic body. The mirror symmetry also allows wear to be reduced.

[0023] The mixing head can be provided with an outlet chamber device, also called an outlet pipe, arranged transversely to the direction of movement of the control piston, in which case the outlet pipe has a recess for the mixing chamber device. The recess can be formed as a hole. In this case, the recess can have a depth smaller than the radius of the outer diameter of the outlet pipe. In this way, an undercut configuration (of the mixing chamber device) can be dispensed with.

[0024] The mixing chamber device may have at least one notch in the cylindrical outer wall, which is machined as a groove for a strip. At least one groove or notch may be machined in the cylindrical inner wall of the head part. In this case, a strip may be arranged in the at least one notch, which engages in a groove in the cylindrical inner wall to ensure alignment of the mixing chamber device relative to the head part and additionally or alternatively to prevent rotation of the mixing chamber device. The notch, the groove and the strip may be collectively referred to as anti-rotation means.

[0025] The mixing chamber device may have at least one notch machined into the cylindrical outer wall as a groove or hole for a pin. The cylindrical inner wall of the head part may have at least one hole or notch machined into it. In this case, a pin may be arranged in the at least one notch, which engages in a groove or hole in the cylindrical inner wall to ensure alignment of the mixing chamber device relative to the head part and additionally or alternatively to prevent rotation of the mixing chamber device. The notch, hole / groove and pin may be collectively referred to as anti-rotation means.

[0026] The idea of ​​the invention can also be realized in a method for assembling a mixing head, which in this case has a head part and a mixing chamber device arranged in the head part, which has at least two inlets for introducing the raw materials and an outlet through which a mixture of the raw materials can be discharged from the mixing chamber. A control piston is arranged movably in the mixing chamber. In this case, the joining of the mixing chamber device into the head or the removal of the mixing chamber device from the head is carried out without the supply of thermal energy. This results in a simple repair method, since both the removal and the subsequent re-joining can be carried out with less effort than if the mixing chamber device were thermally joined as in the prior art.

[0027] In this case, the supply of thermal energy concerns that the head part and the mixing chamber device are each manufactured from materials having the same or similar temperature expansion coefficients, and thus the supply of thermal energy does not have a direct effect on the gap dimensions between the head part and the mixing chamber device. The mixing head can be completely immersed in a solvent or boiled in a solvent in order to melt the bonded plastics or to soften the bonded plastics by heating, thereby allowing the separation of the head part and the mixing chamber device.

[0028] This allows more freedom in the selection of materials, since thermal properties do not have to be taken into account for assembly and possibly also for disassembly. This means that the head part and the mixing chamber device can have the same or similar thermal expansion coefficients. In this case, without the supply of thermal energy can mean that, for example, during the joining of the mixing chamber device into the head part or during the removal of the mixing chamber device from the head part, the temperature of the mixing chamber device differs from that of the head part by less than 50° C. and / or the temperature of the mixing chamber device and / or the temperature of the head part differs from the ambient temperature by no more than 20° C. In this case, the temperature difference is to be understood as being due, for example, to the purely production run, since the processed materials are partly processed at high temperatures (for example in the range up to 220° C.). Typical processing temperatures of the components are often below 120° C., usually below 90° C. or below 45° C. Before disassembly, the mixing head is cooled. In this case, due to the construction, the temperatures of the individual components may differ from each other if they are cooled differently.

[0029] When the mixing chamber device is bonded into the head portion, the mixing chamber can be aligned relative to the head portion, i.e., ideally no post-operation is required after bonding.

[0030] After joining the mixing chamber device into the head portion, the at least two inlets, the at least two recirculation outlets, and the outlet of the mixing chamber device may be aligned to fit precisely, in particular they may be aligned to fit precisely without post-operation.

[0031] For assembly, the outlet pipe is first introduced into the head part, the outlet pipe being arranged transversely to the direction of movement of the control piston. In this case, the outlet pipe can have a recess (especially a hole) for the mixing chamber device, the recess having a depth smaller than the radius of the outlet pipe. Furthermore, in a subsequent work step, the mixing chamber can be joined to the head part, the plane of the recess of the outlet pipe being able to determine the position of the mixing chamber device in the direction of movement of the control piston as a stop.

[0032] For assembly, the outlet pipe is first introduced into the head part, the outlet pipe being arranged transversely to the direction of movement of the control piston. In this case, the outlet pipe can have a recess (especially a hole) for the mixing chamber device, the recess having a depth smaller than the radius of the outlet pipe. Furthermore, in a subsequent work step, the mixing chamber can be joined to the head part, the diameter projection on the outer diameter of the mixing chamber device defines the position of the mixing chamber device in the direction of movement of the control piston at the stop of the head part. At the stop in the region of the diameter projection, the head part and the mixing chamber device come into abutment, in such an embodiment, a small play remains between the outlet pipe and the mixing chamber device, the play being blocked or sealed off with the reactive material during the first injection.

[0033] The mixing chamber device can be fastened in the head portion by means of a sealing flange, which is easy to install and simple to manufacture.

[0034] In other words, the mixing chamber device, also called mixing chamber bush, is inserted in a precisely fitted manner into the head part by simple assembly without shrinking techniques. In this case, subsequent machining of the inlet, also called mixing chamber / mixing chamber device or nozzle installation space, is no longer required. This results in no restrictions on the material selection of the bush. This is achieved because no shrinking techniques are used. Corresponding sealing elements can be provided to prevent the components, also called raw materials, from moving to the outer diameter of the mixing chamber device. This advantageously reduces the time required for repairs of the mixing chamber to a minimum. A separate mixing chamber device or a mixing chamber device with a control piston has significant advantages over a complete mixhead: corresponding replacement parts, i.e. the mixing chamber device and / or the control piston, can be stocked near the machine for maintenance purposes.

[0035] The above statements regarding the method apply correspondingly to the apparatus and vice versa.

[0036] In the following, one advantageous embodiment of the invention will be described with reference to the accompanying drawings. [Brief description of the drawings]

[0037] [Figure 1] 1 is a cross-sectional view of a mixhead according to an embodiment of the present invention. [Diagram 2] 1 is a cross-sectional view of a mixhead according to an embodiment of the present invention. [Diagram 3] 1 is a cross-sectional view of a mixhead according to an embodiment of the present invention. [Figure 4] 1 is a cross-sectional view of a mixhead according to an embodiment of the present invention. [Diagram 5] 1 is a cross-sectional view of a mixhead according to an embodiment of the present invention. [Figure 6] FIG. 2 is an exploded view showing the attachment of an outlet chamber of a mixhead according to one embodiment of the present invention. [Figure 7] FIG. 2 is an exploded view showing installation and alignment of the mixing chamber bushings of a mixhead according to one embodiment of the present invention. [Figure 8]FIG. 2 is an exploded view showing installation and alignment of the mixing chamber bushings of a mixhead according to one embodiment of the present invention. [Figure 9] 4 is a flow chart of a method of assembling a mixhead according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] The drawings are merely schematic and are used only to illustrate the invention. Elements that are the same or have the same function are provided with the same reference numbers throughout.

[0039] The illustrated and below described example shows a variable-direction mixhead. This special embodiment of the mixhead (for high-pressure mixing), which allows for example direct coupling of the mixing mechanism to the mould, is a self-cleaning design of the mixhead. At the end of the injection, the residual mixture is discharged by a piston (cleaning piston or cleaning plunger in the outflow chamber). After a sufficient reaction time to prevent subsequent contamination of the mixing chamber, the piston retracts, freeing the outflow chamber for the next injection. In the case of a linear mixhead, the outflow chamber is omitted, the raw materials are mixed in the mixing chamber, the resulting reactive plastic (or the reactive mixture forming this reactive plastic) is discharged directly from the mixing chamber into the mould, and the residual mixture is discharged by a control piston.

[0040] Linear mixheads are usually small and compact, and therefore have a low weight. They are also advantageous in that they are often simple to manufacture and therefore inexpensive. Furthermore, hydraulic or electrical drive controls can be easily implemented. Linear mixheads may be sufficient for closed-cell applications (where the linear mixhead may be rigidly attached to the mold). Linear mixheads are ideally suited for RIM, RRIM of very fast reacting plastic systems, often based on polyurea (PUA).

[0041] The linear mixing head can be made relatively easily wear-resistant by means of a wear-resistant mixing chamber device, which can additionally be easily replaced in accordance with the concepts described herein, so that machine downtimes or breakdown times can be kept short or avoided.

[0042] FIG. 1 shows a mixing head 100 with a head part 102 and a mixing chamber device 104 arranged in the head part 102. The head part 102 is provided with a recess 106 for the mixing chamber device 104. In the illustrated embodiment, the base body of the mixing chamber device 104 is machined substantially rotationally symmetrically and can be compared to a bush. The recesses, holes, machined surfaces, nozzle installation spaces, etc. of the mixing chamber device are machined mirror-symmetrically in the illustrated embodiment, as is clear from the drawings. In this case, the mixing chamber device 104 has a mixing chamber 108, which is machined centrally along the axis of rotation of the mixing chamber device 104. In this case, the mixing chamber 108 can be machined as a hole in this embodiment. The mixing chamber device 104 is held in the recess 106 of the head part 102 by a sealing flange 110. The sealing flange 110 has a central through hole 112 through which a control piston 114 (first shown in FIG. 2) can be guided which is axially movable within the mixing chamber 108. In the assembled state, the control piston 114 extends through the through hole 112 into the mixing chamber 108.

[0043] A particularly integral outlet chamber 116 is machined transversely to the mixing chamber 108 or to the mixing chamber arrangement 104 in which the mixing chamber 108 is arranged. In the embodiment shown, the outlet chamber 116 is machined into an exchangeable outlet chamber arrangement 118. In one embodiment (not shown), a cleaning piston extends into the outlet chamber 116. The outlet chamber arrangement 118 is machined rotationally symmetrically in the embodiment shown, although this is not necessary (it is usually machined at least mirror symmetrically, with the exception of the opening into the mixing chamber 108 or the mixing chamber arrangement 104).

[0044] The mixing chamber 108 has an inlet 120. Moreover, the mixing chamber 108 has a second inlet 120' (not shown) arranged symmetrically with respect to the first inlet 120, the second inlet 120' so to speak extending from the drawing plane towards the viewer. Via the two inlets 120, the raw materials can be introduced into the mixing chamber 108, where they are mixed (under pressure) and then discharged from the mixing chamber 108 through an outlet 122 into the outflow chamber 116. The inlet 120 extends from the wall of the mixing chamber 108 through the mixing chamber device 104 to the outer surface of the mixing chamber device 104.

[0045] A mixing chamber recess 106 is machined into the head part 102. This can be machined, for example, as a hole, if the mixing chamber device 104 is rotationally symmetrical at least in its outer contour and has a cylindrical outer wall surface. Between the mixing chamber recess 106 and the mixing chamber device 104, in the present embodiment, a clearance fit 126 is machined, i.e. the diameter of the inner periphery of the mixing chamber recess 106 is larger than the corresponding diameter of the outer periphery of the mixing chamber device 104.

[0046] The mixing chamber 108 has a radial groove 128 at its end facing the outlet chamber 116 and two further radial grooves 128 in the direction away from the outlet chamber 116, which, as already indicated, allows a purely cylindrical play between the control piston 114 and the mixing chamber 108. The radial grooves 128 create a self-forming seal during operation.

[0047] Both the mixing chamber recess 106 and the outer peripheral wall surface of the mixing chamber device 104 each have a diameter projection 130. In one embodiment, this diameter projection 130 serves as a first stop 132, i.e. the diameter projection 130 at the outer diameter of the mixing chamber device 104 defines a first stop 132 for a corresponding stop 132 provided in the mixing chamber recess 106 of the head part 102. Via these two stop surfaces the position of the mixing chamber device 104 in the direction of movement of the control piston 114 is defined.

[0048] Alternatively, in another embodiment, a second stopper 134 is provided. In this case, it should be noted that the counting of the first stopper 132 and the second stopper 134 does not necessarily mean that two stoppers are realized in one embodiment. Rather, in such a case, the system would be overspecified, which could lead to problems. Thus, in this document, the statements of the first stopper 132 and the second stopper 134 only serve to distinguish these two options from each other. In a variant in which the second stopper 134 is used, a cutout 138 of the outflow chamber device 118, also called the outflow pipe, is provided with a plane 136, which, as the second stopper 134, defines the position of the mixing chamber device 104 in the direction of movement of the control piston 114.

[0049] The outflow chamber 116 is arranged transversely to the direction of movement of the control piston 114. The outflow chamber device 118, also called partly outflow pipe, is provided with a recess 138, preferably formed as a hole, for the mixing chamber device 104. In a preferred embodiment, the recess 138 has a depth smaller than the radius of the outside diameter of the outflow chamber device 118.

[0050] In FIG. 2, the mixing head 100 according to FIG. 1 is shown rotated by 90°. A control piston 114 is arranged in the mixing chamber 108. Two control grooves 140 are molded into the control piston. The control grooves 140 are arranged symmetrically to one another. In one embodiment (not shown), the mixing head 100 has an odd number of control grooves 140, for example three control grooves 140, which are arranged on the circumferential surface of the control piston 114, evenly distributed to one another. The control grooves 140 are also called recirculation grooves, because they allow the raw materials to be recirculated in the closed position of the control piston 114, i.e. back into the starting or storage vessel. In this way, it is advantageously possible to supply the raw materials at a defined temperature and at a defined pressure. As already explained at the beginning, the raw materials are reactive components or thermosetting materials for producing polyurethanes, for example polyols and isocyanates.

[0051] In the embodiment shown in FIG. 2, the control piston 114 is machined as a single piece.

[0052] In Fig. 2 the control piston 114 is arranged in an open position, and in Fig. 3 in a closed position. The control piston 114 is axially movable in the mixing chamber 108 and can be moved between an open position and a closed position. In Fig. 3 the function of the control groove 140 is clear. The raw material enters through the inlet 120 and is guided via the correspondingly arranged control groove 140 to the recirculation outlet 152. The flow of the raw material is shown as arrows in Fig. 4.

[0053] As can be seen in Figures 2-4, the inlet 120 and the recirculation outlet 152 are sealed between the head portion 102 and the mixing chamber 108, i.e. the raw material cannot penetrate into the clearance fit 126 between the head portion 102 and the mixing chamber arrangement 104. For this purpose, seals 154 are provided in corresponding radial grooves. In alternative embodiments (not shown), alternative sealing concepts are also used.

[0054] The anti-rotation means 150 of the mixing chamber device 104 in the head part 102, which will be described below, can be seen most clearly in the exploded views shown in Figures 6, 7 and 8. However, the strip 148 is already visible in Figures 2 and 3. The mixing chamber device 104 has a notch 146 in its cylindrical outer wall. At least one groove 142 is formed in the cylindrical inner wall 144 of the head part 102. A strip 148 is arranged in the notch 146, which engages in the groove 142 in the cylindrical inner wall 144, thereby ensuring the alignment of the mixing chamber device 104 with respect to the head part 102. This also prevents the mixing chamber device 104 from rotating. The groove 142 in the cylindrical inner wall 144, together with the notch 146 and the strip 148, thus forms the anti-rotation means 150. This is shown more clearly in figures 7 and 8, where the assembly (and the assembly sequence) can also be seen diagrammatically.

[0055] An alternative anti-rotation means (not shown) can be achieved by means of a pin instead of a strip. In this case, preferably the notch and the groove are replaced by a hole. In this case, the pin can be introduced transversely to the mixing chamber. In this case, the pin may furthermore have a device for preventing unintentional separation by selecting an intermediate fit between the hole and the pin or, for example, by an additional thread.

[0056] 9 shows a flow chart of a method of assembling a mix head according to one embodiment of the present invention. The method includes a joining step and additionally or alternatively a disassembly step. The mixing chamber device 104 is removably disposed within the head portion 102 to allow replacement. A clearance fit and / or clearance fit is formed between the head portion 102 and the mixing chamber device 104.

[0057] When the mixing chamber device 104 is joined into the head portion 102, the mixing chamber 108 is aligned with respect to the head portion 102. After joining the mixing chamber device into the head portion, the at least two inlets and the at least two recirculation outlets as well as the outlet of the mixing chamber device are aligned to fit precisely without any special post-operation.

[0058] For assembly, the outlet pipe is first introduced into the head part, with the outlet pipe being arranged transversely to the direction of movement of the control piston. The outlet pipe has a recess (preferably a hole) for the mixing chamber device, the recess having a depth smaller than the radius of the outlet pipe, and in a subsequent work step the mixing chamber is joined to the head part. The plane of the recess of the outlet pipe acts as a stop and determines the position of the mixing chamber device in the direction of movement of the control piston.

[0059] Alternatively, for assembly, the outlet pipe is first introduced into the head part, with the outlet pipe being arranged transversely to the direction of movement of the control piston, the outlet pipe having a recess (hole) for the mixing chamber device, the recess having a depth smaller than the radius of the outlet pipe, and in a subsequent work step, the mixing chamber is joined to the head part, with a diameter projection on the outer diameter of the mixing chamber device defining the position of the mixing chamber device at the stop of the head part in the direction of movement of the control piston. This shows two different possibilities for the configuration of the stop for the positioning of the mixing chamber device in the head part or (if an outlet pipe is provided) relative to the outlet pipe.

[0060] The mixing chamber device can be clamped within the head portion by a sealing flange. [Explanation of symbols]

[0061] 100 Mixing Head 102 Head part 104 Mixing chamber equipment 106 Notch, mixing chamber notch 108 Mixing room 110 Sealing flange, axial fixing means 112 Through hole (in sealing flange) 114 Control piston 116 Outflow chamber 118 Outflow chamber device, outflow pipe 120 Entrance 122 Exit 126 Gap Fitting 128 Radial grooves (before and / or after the mixing chamber) 130 diameter protrusion 132 (First) Stopper 134 (Second) Stopper 136 plane 138 Outflow chamber device notch 140 Control groove / recirculation groove 142 Notch, groove 144 Cylindrical inner wall 146 Notch 148 strips 150 Anti-rotation means 152 Recirculation outlet 154 Seal

Claims

1. A mixhead (100) for producing reactive plastics, comprising a head portion (102) and a mixing chamber device (104) disposed within the head portion (102), the mixing chamber device (104) having a mixing chamber (108), at least two inlets (120) for introducing raw materials into the mixing chamber (108), one outlet (122) for discharging a mixture of the raw materials from the mixing chamber (108), and at least one recirculation outlet (152) for each inlet (120), the recirculation outlets (152) being connected for recirculation to the corresponding inlets (120) in a closed position, and a control piston (114) movably disposed within the mixing chamber (108), The mixing head (100) is characterized in that the mixing chamber device (104) is removably arranged in the head portion (102) to enable replacement, and a clearance fit and / or a gap fit is formed between the head portion (102) and the mixing chamber device (104).

2. 2. The mix head (100) of claim 1, wherein the at least two inlets (120) and the outlet (122) of the mixing chamber (108) are already machined and molded into the mixing chamber apparatus (104) before being joined to the head portion (102).

3. The mix head (100) of claim 1 or 2, wherein the inlet (120) and the recirculation outlet (152) are sealed between the head portion (102) and the mixing chamber (108).

4. 2. The mixing head (100) according to claim 1, wherein the mixing chamber (108) has an outlet side, in particular an integral outlet chamber (116), and / or the outlet chamber (116) is replaceable.

5. 2. The mixhead (100) of claim 1, wherein the control piston (114) has at least two control grooves (140) so that raw material supplied through one inlet (120) can be guided to the recirculation outlet (152) through the correspondingly arranged control groove (140).

6. The mixhead (100) of any preceding claim, wherein the mixing chamber (108) has at least one radial groove (128) for providing an axial seal.

7. 2. The mix head (100) of claim 1, further comprising an outlet chamber device (118) arranged transversely to the direction of movement of the control piston (114), the outlet chamber device (118) having a notch (138) for the mixing chamber device (104), the notch (138) having a depth less than the radius of the outer diameter of the outlet chamber device (118).

8. 2. The mix head (100) of claim 1, wherein the mixing chamber device (104) has at least one notch (146) in its cylindrical outer wall, and the cylindrical inner wall (144) of the head portion has at least one groove (142) machined therein, and wherein the at least one notch (146) has a strip (148) or pin (148) arranged therein that engages in the groove (142) in the cylindrical inner wall (144), thereby ensuring alignment of the mixing chamber device (104) with respect to the head portion (102) and / or preventing rotation of the mixing chamber device (104).

9. 2. A method for assembling a mix head (100) for producing reactive plastics according to claim 1, the mix head (100) comprising a head portion (102) and a mixing chamber device (104) disposed within the head portion (102), the mixing chamber device (104) having at least two inlets (120) for introducing raw materials, one outlet (122) capable of discharging a mixture of the raw materials from a mixing chamber (108), and at least one recirculation outlet (152) for each of the inlets (120), the recirculation outlets (152) being connected for recirculation to the corresponding inlets (120) in a closed position, and a control piston (114) movably disposed within the mixing chamber (108); The method includes joining and / or removing the mixing chamber device (104) into and / or from the head portion (102) such that the mixing chamber device (104) is removably disposed within the head portion (102), thereby making the mixing chamber device (104) replaceable, and a clearance fit and / or a clearance fit (126) are formed between the head portion (102) and the mixing chamber device (104).

10. The method of claim 9, wherein the mixing chamber (108) is aligned with the head portion (102) when the mixing chamber device (104) is mated within the head portion (102).

11. 11. The method of claim 10, wherein after joining the mixing chamber device (104) into the head portion (102), the at least two inlets (120) and the at least two recirculation outlets (152) of the mixing chamber device (104) and the outlet (122) are aligned to fit precisely without any further work.

12. 12. The method according to claim 9, wherein for assembly, first an outlet chamber device (118) is introduced into the head part (102), the outlet chamber device (118) being arranged transversely to the direction of movement of the control piston (114), the outlet chamber device (118) having a recess (138) for the mixing chamber device (104), the recess (138) having a depth smaller than the radius of the outlet chamber device (118), and in a subsequent work step, the mixing chamber (108) is joined to the head part (102), the plane of the recess (138) of the outlet chamber device (118) acting as a stop (134) determining the position of the mixing chamber device (104) in the direction of movement of the control piston (114).

13. 10. The method according to claim 9, wherein for assembly, first an outlet chamber device (118) is introduced into the head part (102), the outlet chamber device (118) being arranged transversely to the direction of movement of the control piston (114), the outlet chamber device (118) having a recess (138) for the mixing chamber device (104), the recess (138) having a depth smaller than the radius of the outlet chamber device (118), and in a subsequent work step, the mixing chamber device (104) is joined to the head part (102), a diameter protrusion on the outer diameter of the mixing chamber device (104) determining the position of the mixing chamber device (104) at a stop (132) of the head part (102) in the direction of movement of the control piston (114).

14. The method of claim 13, wherein the mixing chamber device (104) is clamped within the head portion (102) using a sealing flange (110).

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