Patent Application
20230321874
The invention relates to a device and a method for mixing at least two chemically reactive plastics components under pressure, having a cylindrical mixing chamber into which the plastics components are injected in each case by way of a component-feeding opening, wherein a reversible control piston is arranged for opening and closing the component-feeding openings and for discharging plastics mixture remaining within the mixing chamber.
Generic mixing heads are already known from the prior art. For example, DE 195 1 039 A1 discloses a device for mixing at least two chemically reactive plastics components under high pressure, having a cylindrical mixing chamber into which the components are injected, wherein a reversible piston is arranged for discharging plastics mixture remaining within the mixing chamber. The device also has a cylindrical outlet chamber, also designated as a settling chamber or outlet channel, which adjoins the mixing chamber and runs at an angle of preferably 90° to the longitudinal axis of the mixing chamber, wherein in the settling chamber a reversible cleaning piston is arranged for discharging the reactive plastics mixture from the settling chamber. The cleaning piston has depressions, formed on its cylindrical outer surface, which depressions are filled with spacing material and are arranged in a spiral-shaped manner on the outer surface, so that on an axial movement of the cleaning piston this is set in rotation.
DE 36 29 042 C1 describes a mixing head for producing a chemically reacting mixture of at least two components, in particular of a mixture of isocyanate and polyol reacting out to polyurethane, which has a bore with an axially displaceable tappet and, in the wall of the bore, for the formation of a mixing chamber, two nozzles for the feeding of the components. The tappet conveys the produced mixture out of the bore. The axially displaceable tappet has a cylindrical cross-section and is coupled with a rotary drive. The axially displaceable tappet can also be coupled with a drive oscillating about its axis. If the axially displaceable tappet has a prismatic cross-section, it is coupled with a drive oscillating in axial direction of the tappet.
Both the control piston and also the cleaning piston are hydraulically driven in the known solutions. These can thus be easily moved into a predefined end position, wherein each change of the end position causes a modification on the machine. The hydraulics also require additional components, in order to build up and maintain the necessary hydraulic pressure.
It is an object of the present invention to create a solution by which a flexible manufacture with reactive plastics components is enabled and which solves or improves the known challenges.
The problem is solved by the subjects of the independent claims. Advantageous further developments of the invention are indicated in the dependent claims, the description and the accompanying figures. In particular, the independent claims of one claim category can also be further developed in an analogous manner to the dependent claims of another claim category.
A device according to the invention for mixing at least two chemically reactive plastics components under pressure has a cylindrical mixing chamber, into which the plastics components are injected in each case by way of a component-feeding opening. A reversible control piston is arranged within the mixing chamber for opening and closing the component-feeding openings and for discharging remaining plastics mixture. The control piston is—mechanically—connected to an electric drive. A movement of the electric drive thus brings about a movement of the control piston.
A component-feeding opening can also be understood as a component nozzle or an inoculation bore. A first chemically reactive plastics component is fed under pressure to the mixing chamber through a first component-feeding opening, a second chemically reactive plastics component is fed under pressure to the mixing chamber through a second component-feeding opening. The two plastics components, fed under pressure, intermix in the mixing chamber. The control piston is set up to close the two component-feeding openings and, at the same time, to open them, so that the two plastics components (can) flow into the mixing chamber. The control piston moves in the mixing chamber in a linear manner. The electric drive can be, for example, an electric motor, an electro-magnetic drive or a linear motor.
The control piston is coupled with the electric drive, for example directly (direct drive), via a gearing, a belt drive (belt or chain), bevel gear and/or via a coupling. The motor shaft can optionally also be formed in one piece with the downstream coupling elements such as a spindle.
The mixing chamber is formed in such a way that the control piston can be moved linearly therein. The inner contour of the mixing chamber thus corresponds to an outer contour of the control piston. A cylindrical mixing chamber is to be understood as a shape corresponding to a general cylinder, therefore not only a circular cylinder with a circle as base area. Other geometric shapes such as a rectangle or polygons, but also free closed curves are also conceivable as surrounding the base area.
Through the use of an electric drive, the activation of the device can be simplified and thus changes in the production can be reacted to more easily.
The electric drive can be configured here to generate a rotational movement. The electric drive can be connected to the control piston via a coupling device. Thus, the coupling device can therefore couple the electric drive with the control piston, wherein the electric drive carries out a rotational movement and the control piston carries out a linear movement. The coupling device is configured to convert the rotational movement of the electric drive into a linear movement of the control piston. The coupling device can have a spindle or a rack. A widely available electric motor can thus be used as electric drive for driving the linearly moving control piston.
The coupling device can be configured as a spindle-nut combination with or without self-locking. The relative movement of the control piston to the device can take place through a relative rotation of spindle and spindle nut. Here, either the spindle or the spindle nut can be rotatably driven by the electric drive.
By a spindle-nut combination, or respectively spindle-spindle nut combination, being used, in particular when this has a self-locking, a very good control is provided over all movements of the control piston. In contrast to hydraulically driven control pistons, there does not have to be any fear of an overhasty action of the control piston in the case of a decreasing counter force. Rather, the electrically operated control piston continues its path in a controlled manner independent of force. By the relative rotation of spindle and spindle nut, a rotational movement of the electric drive is converted into a linear movement—of the control piston.
A gearing can be arranged between the electric drive and the motor-driven part of the spindle-nut combination. With such a gearing, the application of force onto the control piston can be produced in a desired range according to the drive performance of the electric drive.
Here, the electric drive can be configured as a servo motor or stepping motor. The electric drive can be connected to a spindle via a coupling, and can set the spindle into a rotational movement. The spindle can drive a spindle nut. The spindle nut can be moved (linearly) along the spindle by a rotational movement. The rotation direction thus influences the movement direction of the spindle nut. The spindle nut can be connected to the control piston via a thrust tube. The spindle nut can thus be coupled with the thrust tube and the thrust tube can be coupled with the control piston.
A bearing device can support the spindle. The bearing device can be arranged between the coupling and the spindle nut. The bearing device can be formed as an angular ball bearing. The bearing device can support axially and additionally or alternatively can support radially. The bearing device can thus have axial bearings, radial bearings, radiaxial bearings and/or linear bearings. The bearing device can have a number of bearings such as sliding bearings or roller bearings, in particular with balls, cylinder, needles, barrels or cones as rolling bodies, therefore ball bearings, rolling bearings, roll bearings, needle bearings.
Alternatively, the spindle can be formed as an inverted spindle. The electric drive can be connected here via a coupling to a spindle nut, which drives the spindle. The spindle can be connected to a thrust tube which is coupled to the control piston.
A bearing device can be provided which supports the spindle nut. The bearing device supporting the spindle nut can be formed as an angular ball bearing. The bearing device can support axially and, additionally or alternatively, can support radially. The bearing device can thus have axial bearings, radial bearings, radiaxial bearings and/or linear bearings. The bearing device can have a number of bearings such as sliding bearings or roller bearings, in particular with balls, cylinder, needles, barrels or cones as rolling bodies, therefore ball bearings, rolling bearings, roll bearings, needle bearings.
The device can also be configured as a transfer mixing head. Here, additionally, a cleaning piston is provided. A cylindrical outlet chamber adjoins the mixing chamber. In the outlet chamber, partly also designated as settling chamber, the reversible cleaning piston is arranged for discharging the reactive plastics mixture from the outlet chamber. The control piston and the cleaning piston are preferably arranged transversely with respect to one another, in particular when the outlet chamber runs at an angle of 90° to the longitudinal axis of the mixing chamber. The arrangement at right-angles, or respectively transversely to one another, constitutes an arrangement which is proven in practice. A Y-arrangement or an arrangement in an angle range of +/−30° to the right angle constitute possible arrangements.
Analogously or alternatively to the control piston, the cleaning piston can be driven electrically, as is already presented above for the control piston. The cleaning piston can thus be coupled with a—further—electric drive. The cleaning piston is set up to carry out a linear movement in the outlet chamber. A further spindle-nut combination can thus be provided, via which the cleaning piston is driven by the further electric drive. A (first) thrust tube can thus be coupled with the control piston, and a further (second) thrust tube can be coupled with the cleaning piston. As described in detail above, a rotation direction of the electric drive respectively brings about a linear movement direction of the control piston or respectively of the cleaning piston. The embodiments for connecting and bearing the control piston are also applicable or respectively able to be used in an analogous manner accordingly for the cleaning piston. The inventive idea can be implemented when only the cleaning piston or only the control piston, or when both pistons, are driven electrically.
The thrust tube, associated with the control piston, can be equipped with an anti-rotation device, which prevents a co-rotating of the thrust tube with the spindle. Likewise, the (further) thrust tube, associated with the cleaning piston, can be equipped with an anti-rotation device, which prevents a co-rotating of the thrust tube with the spindle.
The inventive idea can also be implemented in a method for mixing at least two plastics components. The at least two chemically reactive plastics components are injected under pressure into a cylindrical mixing chamber in each case by way of a component-feeding opening. A reversible control piston is arranged within the mixing chamber for opening and closing the component-feeding openings and for discharging remaining plastics mixture. The control piston is connected to an electric drive and is driven by the latter.
Furthermore, a cleaning piston can be provided, having an outlet chamber which adjoins the mixing chamber, wherein in the outlet chamber the cleaning piston is arranged for discharging the reactive plastics mixture from the outlet chamber. The cleaning piston is moveable reversibly or in other words linearly in the outlet chamber. The cleaning piston is connected to an electric drive and is driven by the latter.
A current position of the cleaning piston and additionally or alternatively a current position of the control piston can be determined, and thus a controlling of the cleaning piston and/or of the control piston can take place using the respective determined current position. Through the use of the determined position, a position control (closed loop) can take place. Thereby, a very precise approach of the desired position is possible, as a target position can be compared with the actual position (i.e. the determined position) at any time. For position determining, a measurement value can be detected which represents the current position.
Depending on the design of the spindle-nut combination in connection with the electric drive (electric motor), the force-path course can be controlled very finely on movement of the control piston and/or of the cleaning piston. Also, all movement parameters can be established in a functionally accurate manner and maintained accurately during operation by high-resolution path measurement devices in connection with the currently available electric servo motor technology.
A control device can be provided which actuates the electric drives and is set up to carry out steps of the method which is presented here. The control device can be set up to emit control signals for actuating the electric drive or the electric drives. Furthermore, it can be set up to receive and process measurement values for determining position.
A throttle position of the cleaning piston can be varied via an activation of the electric drive which is associated with the cleaning piston. The activation can take place directly from the control device of the cleaning piston or respectively of the electric drive, and a manual re-measuring of the throttle position is no longer necessary.
A speed profile of the cleaning piston and/or a speed profile of the control piston can be varied as a function of the produced part.
The electric drive associated with the control piston can be actuated in such a way that the control piston approaches an intermediate position, in order to flush rerouting grooves in the control piston. The rerouting grooves are also designated as recirculation grooves. The rerouting grooves serve to direct the plastics component from the component-feeding opening to a return, in order to be able to move the plastics component under pressure in the system, so that on opening of the component-feeding opening, the plastics component flows into the mixing chamber without dead time with the desired and set pressure. In the intermediate position, regions can now be flushed which otherwise are only rarely flowed through with material.
A torque and/or a rotation speed and/or an electric current consumption of the electric drive of the cleaning piston and/or of the electric drive of the control piston or electric signals representing these can be monitored. Using the rotation speed and/or the torque and/or the electric current consumption, a wear parameter can be determined for prospective maintenance. The electric signal(s), which represent the torque and/or the rotation speed and/or the electric current consumption of the electric drive, can be monitored for maintaining a threshold value, and on exceeding (or falling below) the predefined threshold value, an alarm signal can be emitted. This can be implemented for example simply by means of a comparator. Alternatively, an AI system can be taught-in and used in order to obtain information for prospective maintenance.
The above explanations concerning the method apply to the device accordingly and vice versa. The control device for controlling the electric drives can be embodied in one component or distributed in several components. Furthermore, the control device can be integrated into an ASIC or a comparable integrated circuit (mC, FPGA, . . . 0). The control device can generally also be understood as a control apparatus. The control device which is mentioned here can be embodied in particular as a processor unit and/or an at least partially hardwired or logic switching arrangement for the metrological steps and steps for actuating the electric drives of the described method. Said control device can be or comprise any type of processor or calculator or computer with correspondingly necessary periphery (memory, input/output interfaces, input-output devices, etc.).
Such a device and such a method for mixing at least two chemically reactive plastics components are to be described more closely in the following with reference to the figures. The following description is, however, to be regarded as purely by way of example. The invention is determined solely through the subject of the claims. An advantageous example embodiment of the invention is explained below with reference to the accompanying figures. There are shown:
The figures are only schematic illustrations and serve only to explain the invention. Elements which are identical or equivalent are provided with the same reference numbers throughout.
The device 100 is set up for mixing at least two chemically reactive plastics components. The two different plastics components are injected under pressure into the substantially cylindrical mixing chamber 124 via two component-feeding openings 126, 126′ which are not illustrated in
In the example embodiment, the electric drive 122 is formed as a servo motor 128. The latter generates a rotation movement. The servo motor 128 is connected to the control piston 101 via a coupling device 130 and moves the latter linearly on a rotation movement of the servo motor 128. The coupling device 130 is therefore configured to convert the rotation movement of the electric drive 122 into a linear movement of the control piston 101. A direction reversal of the rotation brings about a direction reversal of the linear movement. For this, the coupling device 130 comprises the spindle 104 and spindle nut 106 acting together in a spindle-nut combination. The servo motor 128 is connected to the spindle 104 via the coupling 108. In an example embodiment which is not illustrated, a gearing is additionally arranged between spindle 104 and servo motor 128. By the rotation of the spindle 104, brought about by the servo motor 128, the non-rotating spindle nut 106 is moved linearly relative to the spindle 104. The spindle nut 106 is coupled to the control piston 101 via the thrust tube 114.
The bearing device 110, supporting the spindle 104, is arranged between the coupling 108 and the spindle nut 106. In the example embodiment, the bearing device 110 is configured as an angular ball bearing receiving both axial and also radial forces. Depending on the length of the spindle, the number of bearings can be increased. Thus, in the illustrated example embodiment, two bearings are used.
The sealing flange 112 is arranged on the outer circumference of the thrust tube, which sealing flange seals towards the housing 120.
The mixing chamber 124, in which the control piston 101 is arranged in a reversible manner, is arranged in a head piece 132. The example embodiment illustrated in
The structure of the cleaning piston 102 is completed by a (second) spindle 144, a (second) spindle nut 146, a (second) coupling 148, a (second) bearing device 150, a (second) sealing flange 152, a (second) thrust tube 154, a (second) anti-rotation device 156 and a (second) housing 160. Furthermore, this part of the device has a (second) electric drive 162. The structure of the further, or respectively second, elements associated with the cleaning piston 102 is analogous to the control piston 101, as already described above.
The cleaning piston 102 also serves for the discharging of remaining plastics mixture from the outlet chamber 136. The cleaning piston 102 is linearly movable within the outlet chamber 136. For this, the cleaning piston 102 is connected to the further or second electric drive 162.
In the example embodiment, the electric drive 162 is configured as a servo motor 164. The latter generates a rotation movement. The servo motor 164 is connected via a coupling device 166 to the cleaning piston 102 and moves the latter linearly on a rotation movement of the servo motor 164. The coupling device 166 is therefore configured to convert the rotation movement of the electric drive 162 into a linear movement of the cleaning piston 102. A direction reversal of the rotation brings about a direction reversal of the linear movement. For this, the coupling device 166 comprises the spindle 144 and spindle nut 146, acting together in a spindle-nut combination. The servo motor 164 is connected via the coupling 148 with that of the spindle 144. In an example embodiment which is not illustrated, a gearing is additionally arranged between spindle 144 and servo motor 164. By the rotation of the spindle 144 brought about by the servo motor 164, the non-rotating spindle nut 146 is moved linearly relative to the spindle 144. The spindle nut 146 is coupled to the cleaning piston 102 via the thrust tube 154.
The bearing device 150, supporting the spindle 144, is arranged between the coupling 148 and the spindle nut 146. In the example embodiment, the bearing device 150 is configured as an angular ball bearing receiving both axial and also radial forces.
On the outer circumference of the anti-rotation device 156, the sealing flange 152 is arranged, which seals towards the housing 160.
A mixing head outlet 168 is formed at the end of the outlet chamber 136.
The configuration of the rerouting grooves 474,474′ can be seen better in the detail enlargement of this region in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 123 521.6 | Sep 2020 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/070896 | 7/26/2021 | WO |
