Device and method for the production of plastic parts with drying and dessicant feed devices

Abstract

A device (1) and method for the production of plastic parts (2), having a first plastic feed device (3a) for feeding a first liquid plastic starting component (K1); a second plastic feed device (3b) for feeding a second liquid plastic starting component (K2); a mixing device (5) with a mixing chamber (6), wherein in the mixing chamber the liquid plastic starting components that can be fed by the plastic feed devices can be mixed to form a plastic mixture (KG); a discharge nozzle (7) for discharging the plastic mixture; and a cooling device (8) for the mixing device, wherein a drying device (9) surrounding the mixing device at least in regions is provided, wherein the drying device has a separating device (10), a drying chamber (T) formed between the separating device and the mixing device, and a desiccant feeding device (11) opening into the drying chamber are disclosed.

Claims

1. A device (1) for producing plastics parts (2), comprising a first plastics feed device (3a) for feeding a first liquid plastics starting component (K1), a second plastics feed device (3b) for feeding a second liquid plastics starting component (K2), a mixing device (5) having a mixing chamber (6), the liquid plastics starting components (K1, K2) which can be fed by the plastics feed devices (3a, 3b) being mixable in the mixing chamber (6) to form a plastics mixture (KG) from the mixing device (5), a discharge nozzle (7) for discharging the plastics mixture (KG), and a cooling device (8) for the mixing device (5), characterized by a drying device (9) surrounding the mixing device (5) at least in regions, the drying device (9) comprising a separating device (10), a drying chamber (T) formed between the separating device (10) and the mixing device (5), and a desiccant feed device (11) for feeding a desiccant opening into the drying chamber (T), wherein the desiccant feed device (11) has a desiccant source (12), a compressed air generating device, and a tubular or pipe-shaped feed element (13) which is connected to the desiccant source (12), and the tubular or pipe-shaped feed element (13) is directed toward the discharge nozzle (7).

2. The device according to claim 1, characterized in that compressed air (L) is introduced continuously by the desiccant feed device (11).

3. The device according to claim 1, characterized in that the desiccant, in the form of compressed air (L) or in the form of a protective gas, has a dew point of below 10° C.

4. The device according to claim 1, characterized in that the separating device (10) has a base region (10a) that has an opening (10d) which is arranged centrally in the base region (10a), through which opening the discharge nozzle (7) projects.

5. The device according to claim 1, characterized in that the cooling device (8) has at least one cooling duct (14) which is undulating and formed in a housing (15) of the mixing device (5).

6. The device according to claim 1, characterized in that the separating device (10) is made of a fiber-reinforced plastics material or a rigid plastics material.

7. The device according to claim 6, characterized in that the fiber-reinforced plastics material or the rigid plastics material of the separating device (10) contains polyamide, polyethylene or polypropylene.

8. The device according to claim 1, characterized by a gas feed device (4) for feeding gas (G) to the first liquid plastics starting component (K1), to the second liquid plastics starting component (K2) or to the plastics mixture (KG).

9. A device (1) for producing plastics parts (2), comprising a first plastics feed device (3a) for feeding a first liquid plastics starting component (K1), a second plastics feed device (3b) for feeding a second liquid plastics starting component (K2), a mixing device (5) having a mixing chamber (6), the liquid plastics starting components (K1, K2) which can be fed by the plastics feed devices (3a, 3b) being mixable in the mixing chamber (6) to form a plastics mixture (KG) from the mixing device (5), a discharge nozzle (7) for discharging the plastics mixture (KG), and a cooling device (8) for the mixing device (5), wherein the device has a longitudinal axis (X); characterized by a drying device (9) surrounding the mixing device (5) at least in regions, the drying device (9) comprising a separating device (10), a drying chamber (T) formed between the separating device (10) and the mixing device (5), and a desiccant feed device (11) opening into the drying chamber (T), wherein the separating device (10) has a base region (10a) which separates the drying chamber (T) from a surrounding area (U) in the axial direction, and a lateral region (10b) connected to the base region (10a), which separates the drying chamber (T) from the surrounding area (U) in the radial direction and the separating device (10) is open to the surrounding area (U) in an opposing region (10c) facing away from the base region (10a), and the lateral region (10b) surrounds the mixing device (5) in the radial direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further details and embodiments of the present invention are explained in more detail below with reference to the description of the drawings and to the embodiments shown in the drawings, in which:

(2) FIG. 1 is a schematically shown cross section through the device,

(3) FIG. 2 is a perspective view of the mixing device without a separating device,

(4) FIG. 3 is a perspective view of the mixing device with a separating device, and

(5) FIG. 4 schematically shows a cross section through a device.

DETAILED DESCRIPTION OF THE INVENTION

(6) In FIG. 1, a device 1 for producing plastics parts 2 is shown in a schematic cross section. Specifically, the foamed plastics part 2 in this case is a sealing bead. The device 1 has the mixing device 5 as an essential component. The mixing device 5 has a, preferably metal, housing 15 in which a mixing chamber 6 is formed. A cooling duct 14 of the cooling device 8 is formed in the housing 15 of said mixing device 5. In the illustrated embodiment, the cooling duct 14 is helical (spiraled) around the longitudinal axis X. The cooling duct 14 can also be undulating. The cooling duct 14 is connected to a coolant source (not shown). A cooling liquid such as cooling water, oil, glycol-water mixture, alcohol or the like can be used as the coolant. A line 16 of the first plastics feed device 3a opens into the mixing chamber 6. The first plastics feed device 3a is connected to a source 17 for a first liquid plastics starting component K1. Gas G from a gas source 19 can be fed into the first plastics feed device 3a via a line 18 shown by a dashed line. The gas G can also be introduced directly into the mixing chamber 6, however. The line 18, together with the gas source 19, forms the gas feed device 4. The second plastics feed device 3b has a source 20 for a second liquid plastics starting component K2, and a line 21. The line 21 opens into the mixing chamber 6 of the mixing device 5. In the mixing chamber 6, the first liquid plastics starting component K1 mixes with the second liquid plastics starting component K2 to form the plastics mixture KG (gas G also possibly being contained). A discharge nozzle 7 is formed in the housing 15 of the mixing device 5. The plastics part 2 is produced by discharging the plastics mixture KG. When a plastics mixture KG (in the form of a mixture of plastics material and gas) is discharged from the discharge nozzle 7, the gas G foams up, resulting in a foamed plastics part 2. In general, dynamic mixing (with a stirrer), static mixing or high-pressure mixing can be carried out using the mixing device 5.

(7) When the introduced components are mixed, a chemical reaction occurs in which heat is released (in the case of dynamic mixing, a significant portion of the heat is generated by the stirring energy). In order to prevent an excessive and premature reaction from already taking place in the mixing chamber 6, the cooling device 8 which surrounds the mixing chamber 6 is provided. When the cooling device 8 cools the mixing device 5 (in particular the mixing head) to a temperature which is below the dew point temperature of the surroundings U, condensation forms on the surface of the mixing device 5. This condensation can drip onto the produced plastics part 2 and damage the plastics part 2 as a result.

(8) In order to prevent this, a drying device 9 is provided. Said drying device 9 has a separating device 10 (which is preferably substantially impermeable to gas), a desiccant feed device 11 (in the form of a feed element 13, including a desiccant source 12) and a drying chamber T between the separating device 10 and the surface of the mixing device 5. In the embodiment shown, the separating device 10 has a base region 10a axially defining the drying chamber T, and a lateral region 10b radially defining the drying chamber T. The desiccant source 12 is in the form of a compressed air generating device. Compressed air L is introduced by said compressed air generating device via the tubular feed element 13 into the drying chamber T enclosed by the separating device 10. In contrast to the view in FIG. 1, the outlet opening of the feed element 13 can also be arranged in the region of the upper opening of the separating device. In order to prevent the formation of condensation, it is sufficient if approx. 100 to 500 standard liters of compressed air L are introduced into the drying chamber T per hour. This results in a dew point temperature of approx. 5° C. in the drying chamber T. The introduced desiccant can gradually escape via the opposing region 10c which is open to the surroundings U (or via other openings). A central opening 10d is formed in the base region 10. The tip of the discharge nozzle 7 projects through said central opening 10d in the axial direction. The separating device 10 can consist of a rigid or solid plastics material. Alternatively, the separating device 10 can also consist of a relatively soft material, a film, metal, etc. The separating device 10 is preferably releasably connected to the mixing device 5. In the embodiment according to FIG. 1, the separating device 10 can be releasably connected to the mixing device 5 by being fitted on. This fitted connection (not shown) can be provided, for example, in the region of the discharge nozzle 7 or also in the region of the mixing device 5 that faces away from the nozzle.

(9) In FIG. 2, the device 1 is shown in a perspective view. The line 16 (supply) of the first plastics feed device 3a can be seen on the left-hand side. A corresponding return flow 24 is also provided. The line 21 (supply) of the second plastics feed device 3b is shown in the right-hand region. A corresponding return flow 25 is also provided. The feed line 22 (or the port thereof) of the cooling device 8 is shown in the right-hand region. Coolant is conducted into the cooling ducts 14 via a feed line 22 (not shown). The surface of the housing 15 of the mixing device 5 can also be seen. The feed element 13 of the desiccant feed device 11 is not shown. For example, an air duct can pass through the mixing head and exit, for example, on the underside thereof, which air duct then forms the feed element 13.

(10) FIG. 3 is the same perspective view of the device 1, in which the mixing device 5 is enclosed by the separating device 10 of the drying device 9. It can be seen that the separating device 10 is designed in the form of a dome. Said separating device 10 consists of a flexible plastics material. The separating device 10 of the drying device 9 is held on components of the device 1 by connecting elements (not shown), for example in the form of connecting straps or snap elements. The discharge nozzle 7 protrudes axially in the base region 10a of the separating device 10. In this case, the tubular feed element 13 leads from above into the drying chamber T.

(11) FIG. 4 schematically shows a cross section through a device 1 for producing plastics parts 2. In this embodiment, in addition to the mixing chamber 6 and the housing 15, the mixing device 5 also has a stirrer 26. A seal 27 is arranged between the stirrer 26 and the housing 15. FIG. 4 therefore shows a dynamic mixer. A valve 28 is arranged in each of the lines 16 and 21. Said valves 28 are designed to control the feed of the plastics starting components K1 and K2. The separating device 10 surrounds the mixing device 5. In this case, the separating device 10 is designed to follow the contour of the mixing device 5. This means that the distance between the separating device 10 and the surface of the mixing device 5 can (as in the case shown) be substantially constant. Due to the irregular surface of the mixing device 5, however, the separating device 10 is usually not spaced apart from the surface of the mixing device 5 uniformly throughout. Specifically, a gap which forms the drying chamber T is formed between the separating device 10 and the surface of the mixing device 5. Said gap can be between 0 mm and 100 mm, preferably between 0.3 mm and 5 mm, wide. The schematically indicated feed element 13 for the desiccant leads into the drying chamber T.

LIST OF REFERENCE SIGNS

(12) 1 device 2 plastics parts 3a first plastics feed device 3b second plastics feed device 4 gas feed device 5 mixing device 6 mixing chamber 7 discharge nozzle 8 cooling device 9 drying device 10 separating device 10a base region 10b lateral region 10c opposing region 10d opening 11 desiccant feed device 12 desiccant source 13 feed element 14 cooling duct 15 housing 16 line 17 source 18 line 19 gas source 20 source 21 line 24 return flow first component 25 return flow second component 26 stirrer 27 seal 28 valves K1 first liquid plastics starting component K2 second liquid plastics starting component G gas KG plastics mixture T drying chamber L compressed air X longitudinal axis U surroundings