DEVICE FOR PRODUCING A MIXTURE OF AT LEAST ONE GAS AND AT LEAST ONE LIQUID PLASTIC COMPONENT

Description

[0001] The present invention relates to a device for producing a mixture of at least one gas and at least one liquid plastic component.

[0002] A known device is shown in Fig. 10 of EP 0 776 745 B1. There, the introduction device for the at least one gas is designed in the form of a gas cylinder. The delivery device for the at least one liquid plastic component is in the form of a pump. Piston pumps are also disclosed in other figures of this document. The at least one gas and the at least one liquid plastic component are mixed in the piston pumps themselves. The gas supply is carried out and regulated via a valve. As described in this document, it is difficult to introduce the correct amount of gas in the correct ratio into the liquid plastic component.

[0003] The object of the invention is to provide a device in which the problems described above are avoided.

[0004] This object is achieved by a device having the features of claim 1. Advantageous embodiments of the invention are defined in the dependent claims.

[0005] Documents FR 2 595 121 A1, EP 0 810 917 B1, WO 2014 / 195312 A1, DE 29 17 865 A1, and GB 1 503 648 A merely disclose devices of a different generic type. Although some of them depict piston pumps, they do not have a gas source and thus do not depict a device for producing a mixture of at least one gas and at least one liquid plastic component. In particular, the pumps in these documents do not alternately constitute an introduction device or a conveying device.

[0006] The use of piston pumps for both the at least one gas and the liquid plastic component allows for the precise metering of gas to the liquid plastic component. Assuming that the piston pump of the conveying device has a specific maximum fill volume for the liquid plastic component and that the piston pump of the introducing device has a specific maximum fill volume for the at least one gas (this can be the same as or different from the fill volume of the conveying device), the amount of gas supplied to the liquid plastic component can be influenced by the pressure with which the gas is filled into the introducing device. The solution according to the invention is more cost-effective, structurally simpler, and smaller.

[0007] In order to achieve a particularly simple and cost-effective design, it is provided that the piston of the insertion device and the piston of the conveying device are mechanically or electrically coupled.

[0008] There are two variants for this coupling. In a mechanically opposed coupling, the piston of the introduction device and the piston of the conveying device are coupled in such a way that when gas is discharged from the introduction device, liquid plastic component is introduced into the conveying device, and when liquid plastic component is discharged from the conveying device, gas is introduced into the introduction device. In contrast, in a parallel or mechanically synchronous coupling, the piston of the introduction device and the piston of the conveying device are coupled in such a way that when gas is discharged from the introduction device, liquid plastic component is discharged from the conveying device, and when gas is introduced into the introduction device, liquid plastic component is introduced into the conveying device.

[0009] Protection is also sought for a device for producing foamed plastic parts, in particular sealing beads, with a device according to the invention for producing a mixture of at least one gas and at least one liquid plastic component.

[0010] Embodiments are discussed with reference to the figures. They show: Fig. 1 schematically shows a device for producing foamed plastic parts, Fig. 2 a first embodiment of a piston pump in which the pistons are mechanically coupled in opposite directions, Fig. 3 a variant of the embodiment of the Fig. 2 , Fig. 4 an embodiment in which the pistons are mechanically synchronously coupled, Fig. 5 an embodiment in which the pistons are electrically coupled, Fig. 6 an embodiment of the invention, wherein one piston pump and the other piston pump are each alternately designed as an introduction device and as a conveying device, Fig. 7 in detail the buffer device and Fig. 8 an alternative variant of the buffer device.

[0011] Fig. 1 1 schematically shows, in its entirety, an apparatus 100 for producing foamed plastic parts, in particular sealing beads. This apparatus 100, in turn, comprises several essential subunits.

[0012] Such a subunit is formed by a device 16 for producing a mixture of at least one gas and at least one liquid plastic component. This device 16, in turn, has at least one mixing device 17, an introduction device 19 for the at least one gas, connected to the mixing device 17 via a first line 18, and a conveying device 21 for the at least one liquid plastic component, connected to the mixing device 17 via a second line 20. In addition, this device 16 has a container 53 for the plastic component and a gas source 54, in particular a compressed air generation device. Instead of the container 53, a conveying pump could also be provided.

[0013] In such a device 16, in contrast to the prior art, it is provided that the introduction device 19 and the conveying device 21 are designed as piston pumps 25 and 24 having pistons 22 and 23.

[0014] In this example, the piston 22 of the insertion device 19 (piston pump 25) and the piston 23 of the delivery device 21 (piston pump 24) are mechanically coupled in opposite directions via a pressure intensifier 26. This allows the use of a drive that operates at relatively low pressure (e.g., pneumatic), since the necessary force increase is achieved via the force transmission. Also visible are the inlet valves 27, 28 and the outlet valves 29, 30.

[0015] As in Fig. 2 As shown in more detail, these inlet valves 27, 28 and outlet valves 29, 30 are actuated by a control device 33 in accordance with the movement of the coupled pistons 22, 23. Also shown is a sensor 31 which is connected to the control device 33 via a signal line 32 for signal transmission. The sensor 31 serves to determine the position of the pressure intensifier 26. This also determines the position of the pistons 22, 23. The position of the pistons 22, 23 can also be determined directly via the sensor 31 (see the further exemplary embodiments). In general, leakage detection can be carried out with such a sensor 31, namely when the piston seals between the piston 23 and the cylinder 34 of the introduction device 19, the piston seals between the piston 22 and the cylinder 35 of the conveying device 21 and / or at least one of the valves 27 to 30 are worn. For leakage detection, for example,Inlet valve 28 and outlet valve 30 on the gas side are closed. Piston 22 compresses the gas volume between inlet valve 28 and outlet valve 30. If a leak is present, an irregular movement of pressure intensifier 26 occurs after compression, which is detected by sensor 31. It is also possible to check whether irregular gas components are present in the liquid plastic component, since these lead to a movement of piston 23 when inlet valve 27 and outlet valve 29 are closed, since the liquid plastic component is compressible due to the irregular gas components. This can be compensated for by control device 33 if necessary.

[0016] Fig. 3 shows a single piston pump, which simultaneously forms the piston pump 24 for the conveying device 21 and the piston pump 25 for the insertion device 19. In this variant, no separate pressure intensifier is provided, but rather a piston forms both the piston 23 of the piston pump 24 and the piston 22 of the piston pump 25. This system according to Fig. 3 works mechanically in reverse. This means that when gas is discharged via the feed device 19 (shown below), liquid plastic component is introduced into the conveying device 21, and vice versa.

[0017] In contrast, Fig. 4 a system in which the piston pumps 24 and 25 are mechanically coupled synchronously. Specifically, the piston 22 of the introduction device 19 and the piston 23 of the conveying device 21 are coupled via a coupling mechanism 63 such that when gas is discharged from the introduction device 19, liquid plastic component is discharged from the conveying device 21, and when gas is introduced into the introduction device 19, liquid plastic component is introduced into the conveying device 21.

[0018] Fig. 5 shows an electronic coupling of piston pumps 24 and 25. The movement of pistons 22 and 23 is controlled by a control device 64, which is connected via signaling to the drive devices of the two piston pumps 24 and 25. Pistons 22 and 23 can be moved in opposite directions or synchronously. This can be adjusted via control device 64.

[0019] Fig. 6 shows a piston pump 25 and a piston pump 24, which alternately form the introduction device 19 or the conveying device 21. One advantage here is that the seals on both sides are alternately lubricated by the liquid plastic component. A change is possible after a predefined number of cycles. The change is carried out via switching devices 65 and 66, which can either be switched manually or, preferably, via a control device 67, preferably regularly. In the first switching position, the liquid plastic component is conveyed from the container 53 via a first line 68 to the piston pump 24 (shown above), while the gas is conveyed from the gas source 54 via the second line 69 to the piston pump 25. In this respect, the entire system in this first switching position complies with the Fig. 1 and 2agree. In the second switching position, however, a diversion occurs. Specifically, in this second switching position, the liquid plastic component is conveyed from the container 53 via a third line 70 to the piston pump 25 (shown below), while the gas is conveyed from the gas source 54 via a fourth line 71 to the piston pump 24. In this second switching position - conversely to the first switching position - the piston pump 25 forms the conveying device 21 and the piston pump 24 forms the introduction device 19. Depending on the switching position, the liquid plastic component or the gas is then pumped on to the mixing device 17 via the first line 18 or the second line 20.

[0020] Returning to Fig. 1 A further subunit of the device 100 is formed by a device 36 providing a liquid plastic component, preferably mixed with gas, for a dosing device 38. This device 36 has a source 37 for at least one liquid plastic component. This source 37 is preferably formed by a line leading away from the previously mentioned mixing device 17. Furthermore, this device 36 has an intermittently operating forwarding device for the at least one liquid plastic component. This intermittently operating forwarding device is formed by the piston pumps 24, 25, but can also be any other device of any design suitable for intermittently forwarding the liquid plastic component. An intermittently operating source is understood not only to mean a source whose delivery rate drops to zero (e.g.a piston pump), but also a source whose flow rate is subject to fluctuations, especially pulsating ones (e.g. gear pump).

[0021] The device 36 further comprises a metering device 38, preferably a metering pump, for which the plastic component is provided by the forwarding device. Furthermore, the device 36 comprises a buffer device 39 arranged between the source 37 for the at least one liquid plastic component and the metering device 38, with a variable buffer volume 40, through which the liquid plastic component intermittently conveyed to the buffer device 39 is always made available in sufficient quantity with sufficient preload pressure for the metering device 38. After the metering device 38, the plastic component reaches a metering valve 60, after which the plastic component is fed directly (see nozzle 61 shown in dashed lines) - or as in Fig. 1 shown indirectly via a further mixing element 58 - via a nozzle 61 and foamed by the discharge and the associated pressure drop.

[0022] To enable the most consistent transfer possible, it is preferably provided that the pressure prevailing in the liquid plastic component between the buffer device 39 and the dosing device 38 can be controlled by the buffer device 39. The liquid plastic component flows from the source 37 into the buffer volume 40 of the buffer device 39 via an inlet opening 41. The buffer volume 40 is in turn connected to the dosing device 38 via an outlet opening 42. Fig. 1 the inlet opening 41 is formed in a wall of a housing 43 of the buffer device 39. This is also in Fig. 7 Alternatively, it can also be provided that the inlet opening 41 is formed in a piston rod 44 of the buffer device 39 which is connected to a piston 45 (see Fig. 8 ). Furthermore, an inlet valve 51 is arranged upstream of the inlet opening and an outlet valve 52 is arranged downstream of the outlet opening 42. In addition, a displacement sensor 72 can be provided, with which at least selected positions of the piston 45 in the housing 43 can be determined.

[0023] Furthermore, it is provided that a pressure sensor 46 is arranged on an output side of the dosing device 38. This pressure sensor 46 is connected to a control device 47 via a control line 48. The control device 47 controls the buffer device 39 such that the pressure present on the input side of the dosing device 38 tracks the pressure prevailing on the output side of the dosing device 38. Furthermore, the control device 47 can be designed to close both the inlet valve 51 and the outlet valve 52 and to compress the liquid plastic component located in the buffer volume 40. In addition, a sensor (not shown) can be provided, by which irregular compression of the buffer volume 40 can be detected.

[0024] Furthermore, the buffer device 39 is connected to a device 49 for pressurizing the buffer device 39. This device can be controlled either by the control device 47 (line shown in dashed lines) or by an independent control device 50.

[0025] In principle, the two devices 16 and 36 would suffice for the production of foamed plastic parts in the form of sealing beads. However, it can also preferably be provided that a second plastic component is foamed, preferably physically, parallel to the first plastic component or mixed with the first plastic component to form the plastic part. Therefore, a further subunit of the device 100 is formed by a device 62 for multi-component foaming (see again Fig. 1 ). This device 54 has a container 55 for a second plastic component, from which the second plastic component, preferably mixed with gas, is fed via a metering device 56 and a metering valve 57 to the mixing element 58. In this mixing element 58, this second plastic component is mixed with the first plastic component. This mixture is then dispensed via a schematically indicated nozzle 61 after a further metering valve 59, whereby the gas contained in the mixture foams. In other words, the dispensing causes a pressure drop; the gas causes the liquid plastic component to foam, and after the foamed plastic component has hardened, a porous plastic part is produced, for example in the form of a sealing bead 73.

[0026] In the metering valves 57 and / or 60, check valves can also be provided, as in the Fig. 1marked with the reference numerals 51 and 52 are used as inlet and outlet valves. List of reference symbols:

[0027] 16Device 17Mixing device 18First line 19Introduction device 20Second line 21Conveying device 22Piston 23Piston 24Piston pump 25Piston pump 26Pressure intensifier 27Inlet valve 28Inlet valve 29Outlet valve 30Outlet valve 31Sensor 32Signal line 33Control device 34Cylinder 35Cylinder 36Device for conveying a liquid plastic component 37Source 38Dosing device 39Buffer device 40Buffer volume 41Inlet opening 42Outlet opening 43Housing 44Piston rod 45Piston 46Pressure sensor 47Control device 48Control line 49Device for pressurizing 50Control device 51Inlet valve 52Outlet valve 53Container for plastic component 54Gas source 55Container for second plastic component 56Mixing device 57Dosing valve 58Mixing element 59Dosing valve 60Dosing valve 61Nozzle 62Device for multi-component foaming 63Coupling mechanism 64Control device 65Switching device 66Switching device 67Control device 68First line 69Second line70third line 71fourth line 72position sensor 73sealing bead 100device for producing foamed plastic parts

Claims

1. A device (16) for producing a mixture of at least one gas and at least one liquid plastics component, comprising a container (53) or a conveying pump for the at least one liquid plastics component, a gas source (54) and a mixing device (17) which is connected via a first line (18) to an introducing device (19) for the at least one gas and via a second line (20) to a conveying device (21) for the at least one liquid plastics component, wherein the introducing device (19) and the conveying device (21) are designed as piston pumps (25, 24) that comprise pistons (22, 23) and have inlet valves (27, 28) and outlet valves (29, 30), wherein the piston (22) of the introducing device (19) and the piston (23) of the conveying device (21) are mechanically or electrically coupled, wherein the inlet valves (27, 28) and outlet valves (29, 30) can be actuated in accordance with the movement of the coupled pistons (22, 23) by means of a controller (33), wherein the device (16) comprises a sensor (31) which is connected to the controller (33) via a signal line (32) for signal transmission and is used to determine the position of the pistons (22, 23), wherein the two piston pumps (24, 25) in each case alternately form the introducing device (19) or the conveying device (21).

2. The device (16) according to claim 1, wherein the piston (22) of the introducing device (19) and the piston (23) of the conveying device (21) are coupled in such a way that when gas is discharged from the introducing device (19), the liquid plastics component is introduced into the conveying device (21) and when the liquid plastics component is discharged from the conveying device (21), gas is introduced into the introducing device (19).

3. The device (16) according to claim 1, wherein the piston (22) of the introducing device (19) and the piston (23) of the conveying device (21) are coupled in such a way that when gas is discharged from the introducing device (19), the liquid plastics component is discharged from the conveying device (21) and when gas is introduced into the introducing device (19), the liquid plastics component is introduced into the conveying device (21).

4. A device (100) for producing foamed plastics parts, in particular sealing beads, comprising a device (16) according to one of claims 1 to 3.