WO2004072480A2

WO2004072480A2 - Reciprocating pump for liquid and pasty media

Info

Publication number: WO2004072480A2
Application number: PCT/DE2004/000174
Authority: WO
Inventors: Erich SCHÜRMANN
Original assignee: Microcell Polymer Technology Gmbh
Priority date: 2003-02-14
Filing date: 2004-02-03
Publication date: 2004-08-26
Also published as: DE10306476B3; WO2004072480A3

Abstract

Disclosed is a reciprocating pump for liquid and pasty media, especially molten plastic materials, essentially comprising a cylindrical tube and a piston that is movable therein at least in an axial direction and is provided with at least one flow duct (18) which encompasses a check valve. The aim of the invention is to create a reciprocating pump that can be integrated as easily as possible into a mixing device. Said aim is achieved by means of the characteristics described in claim 1, according to which the front of the piston is provided with a piston-sealing area, the front being in relation to the direction of flow. The piston-sealing area is bridged in the direction of flow by means of the at least one flow duct including the check valve and is provided with a forced mixing area at the rear between the piston and the cylindrical tube, the rear being in relation to the direction of flow. The forced mixing area is formed by spaced-apart hollow spaces which extend outward within the cylindrical tube, at least in the axial range of movement of the piston, and spaced-apart hollow spaces that face inward inside the piston.

Description

Piston pump for liquid and pasty media

The invention first relates to a piston pump for liquid and pasty media, in particular plastic melts, consisting essentially of a cylinder tube and a piston which can be moved at least axially therein, the piston having at least one flow channel which is provided with a check valve.

Such a piston pump is generally known from the prior art which cannot be documented in printed form. Such pumps are often provided with additional mixing devices for different liquid or pasty media, since gaseous, liquid or solid additives have to be mixed into the medium to be pumped. In such devices, it is considered disadvantageous that two separate devices are required for pumping and mixing.

The object of the invention is to create a piston pump in which a mixing device is integrated in the simplest possible way.

The solution to the problem results from the features of claim 1, in particular the characterizing features, according to which the piston has a piston sealing area in the flow direction at the front, which is bridged with the at least one flow channel including check valve in the flow direction, and in the flow direction at the back between the piston and the cylinder tube a forced mixing area is provided, which is at least in the axial movement range of the piston on the one hand in the cylinder tube facing outward and spaced cavities and on the other hand, inwardly directed, also spaced cavities are formed.

Such a piston pump according to the invention first of all has the essential advantage that, without enlarging the design, it takes on an additional mixing function, so that separate mixing devices are unnecessary.

In addition, such a piston pump is versatile for all flowable and pasty media in which gaseous, liquid or solid additives have to be mixed. In particular in the case of the pasty and liquid media provided with gaseous foaming agents, it is particularly advantageous to move the mixing process into the piston pump in order to obtain a particularly finely divided foam. Solution and nucleation processes, which can be controlled in the piston pump according to the invention via the pump pressure, are responsible for an improved foam quality.

An extruder mixer is known from EP 0 048 590 and US 4,419,014, respectively, which has a hollow cylindrical stator and a cylindrical rotor mounted inside the stator for its rotation, the mutually facing cylindrical surfaces of the rotor and the stator each having a multiplicity of parallel ones , have circumferential rows of cavities. However, this is a non-generic state of the art.

In one embodiment of the piston pump according to the invention, the cavities in the cylinder tube and on the piston are concave.

In a further exemplary embodiment, the piston sealing region is reduced as an axially and circumferentially extending region Diameter formed in which an axially movable piston sealing ring is arranged, which in its forward position in the flow direction releases at least one flow channel lying between the piston skirt surface and the inner surface of the piston seal ring, while it blocks the flow path in its rear position in the flow direction.

In this embodiment, it is advantageously not necessary to provide the sealing area with internal flow channels and a check valve, since the piston has an area with a reduced diameter in which flow channels and sealing surfaces are arranged on the outer circumference, which can cooperate with the movable piston sealing ring.

In principle, in all of the aforementioned embodiments, the opposing cavities in the cylinder and in the piston can be dimensioned differently. It is also conceivable that the cavities in the cylinder and / or the cavities in the piston are dimensioned differently.

In addition to the aforementioned embodiments, a device for feeding an additive can be arranged in the forced mixing area of the piston pump according to the invention, which then advantageously results in a fine distribution of the additive in the medium to be pumped.

In a preferred embodiment of the invention it is also possible for the piston to be driven in rotation in addition to its axial movement. This results in an additional improvement of the mixing process, regardless of the pumping process.

The invention further relates to the use of a piston pump according to claim 7 in an injection unit of an injection molding machine. There is also an injection molding machine for injection units according to

State of the art the above-mentioned problem that, in addition to a device for conveying and injecting the melt, a separate mixing device is necessary for gaseous, liquid or solid

Being able to mix additives into the melt in finely divided form.

The object of the invention is therefore also to integrate a mixing device in a simple manner in an injection unit of an injection molding machine.

The solution to the problem results from the features of the claim

8, in particular the features of the identification part, according to which the piston of the

Pump / mixing device is arranged in the flow direction at the front on a screw conveyor rotating and axially movable in the housing of the injection unit.

The use according to the invention of a piston pump in an injection unit of an injection molding machine has the essential advantage that in connection with the supply of a gaseous, liquid or solid additive, an expensive separate mixing device is no longer necessary. As a result, the design of an injection unit of an injection molding machine is significantly simplified, which results in significant cost savings in connection with the manufacture, assembly and also maintenance.

Further advantages of the invention result from the following description of the exemplary embodiments. Show it:

Fig. 1 is a partial perspective view of a piston pump in

View, 2 is a partial view according to FIG. 1 in a partially sectioned view,

3 shows a longitudinal section through the injection unit of an injection molding machine after the melt has been ejected,

FIG. 4 shows a longitudinal section through the injection unit according to FIG. 3 during the filling of the collecting space for the melt and

Fig. 5 shows a longitudinal section through the piston of an injection molding machine.

In the drawings, a pump / mixer device is generally designated by the reference number 10.

1 and 2, the pumping / mixing device 10 of a piston pump can be seen in perspective and in a partial sectional view. The pumping / mixing device 10 has a cylinder tube 11, in which a piston 12 is arranged so as to be axially and rotatably movable. The piston 12 is provided with a sealing area 13 and a positive mixing area 14. The positive mixing area 14 of the piston 12 is provided with inwardly spaced, concave cavities 15. In addition, an inner peripheral surface 17 of the cylinder 11 also has such cavities 16.

2 that the sealing area 13 of the piston 12 has internal flow channels 18 which are brought together in a central flow area 19 in which a check valve 20 is arranged. In a pumping / mixing device 10 according to FIGS. 1 and 2, the piston 12 moves in the axial direction in the cylinder tube 11. The check valve 20 leaves the medium to be pumped when the piston 12 moves in the y-direction on the front side of the sealing area 13 flow in the x direction. When the piston 12 moves in the x direction, the check valve 20 prevents the medium from flowing back. If a gaseous, liquid or solid additive is supplied to the medium to be pumped in the compulsory mixing area 14 in a manner not shown, there is a uniform distribution of the additive in the medium to be pumped. This is done by the axial relative movement of the piston 12 and cylinder tube 11. Here, the medium to be mixed, which is located in the opposite cavities (calottes) 15, 16, is divided again and again and brought together with other divided volumes and thus mixed.

The cavities 15, 16 are arranged such that the remaining inner circumferential surface 17 of the cylinder tube 11 presents itself as a coherent surface which, together with a coherent outer circumferential surface 21 of the piston 12, enables a seal between the two surfaces 17 and 21 in the forced mixing area 14. Regardless of this, mutually overlapping cavities 15, 16 result in a continuous flow path somewhere in each position of the cylinder tube 11 relative to the piston 20. Thus, while in the forced mixing area 14 between the inner circumferential surface 17 of the cylinder tube 11 and the outer circumferential surface 21 of the piston 12 when the piston 12 is axially moved, the medium is transported and mixed in the flow direction S, an outer circumferential surface 22 of the sealing region 13, which has no cavities 15, forms in the Interact with the inner peripheral surface 17 a fluidic barrier. Due to the flow channels 18 and the check valve 20 described above, however, the medium can move in front of the piston 12 when the piston 12 moves in the y direction Flow sealing area 13. When the piston moves in the x direction, however, the check valve 20 blocks the flow channels 18.

3 and 4, an injection unit 23 j of an injection molding machine is shown in longitudinal section. The injection unit 23 has a screw conveyor 25 which is rotatable and axially displaceable and which is arranged in a housing 24 and is provided with a non-return valve 26 at the front in the flow direction S. A further housing 27 is fastened to the housing 24, in which a piston 28 of a pumping and mixing device 10 w is arranged. This is motionally connected to the screw conveyor 25 via a component 29. Finally, a component 30 is also attached to the housing 27, which has a nozzle bore 31 through which the melt located in a collecting space 32 can be introduced into an injection mold, not shown, which is arranged upstream of the component 30.

15

In the housing 27 there is also a device 33 for additive feed, with which the additives can be added to the melt. The housing 27 has mutually arranged in its inner peripheral surface 34, facing outward

20 spaced concave cavities 35. The piston 28 arranged in the housing 27 is also divided into a forced mixing area 36 and a sealing area 37. The sealing area 37 has, as shown for example in FIG. 2, flow channels 18 and a check valve 20. The forced mixing area 36 is also in its outer peripheral surface

25 38 provided with inwardly facing, spaced concave cavities 39.

During the plasticizing process of the injection unit 23, the screw conveys

25 the melt in the flow direction S to the front and moves in the process

30 rotating in the y direction. The additive feed, in particular that

Adding a physical foaming agent is preferred in Flow direction S take place before the forced mixing area 36. The mixture of melt and foaming agent flows through the compulsory mixing area

36 and is - as described above - mixed during the superimposed axial and rotational movement. Then it flows over the sealing area

37 arranged flow channels 18 in front of the piston 28 in the melt chamber 32. Ultimately, the piston 28 presses the melt in the injection process (movement in the x direction) into the injection mold, not shown, the foam formation only starting there due to the reduction in pressure.

3 shows the front position of the pumping and mixing device 10 of the injection unit 23 after the injection process, while in FIG. 4 the pumping and mixing device 10 including the screw 25 is in the rearward position in which the melt chamber 32 is filled. The injection process takes place in the next step.

Ultimately, FIG. 5 shows a partial longitudinal section of an injection unit 23 with a special design of a sealing area 40. Here, the piston 28 has a reduced cross section in the sealing area 40, an axially movable piston sealing ring 41 being arranged there, which is at least in its forward position in the flow direction S releases a flow channel 44 lying between a piston jacket surface 42 and a piston sealing ring inner surface 43. The piston sealing ring 41, which has the function of a check valve, is shown in its open position in region I below the longitudinal center line M of FIG. 5. It can be seen from this position that the piston sealing ring 41 has a sealing surface 45 which lies opposite a sealing surface 46 of the piston 28. With the axial and rotational movement of the piston 28 in the y direction, the melt, which was mixed in the compulsory mixing area 36, can now flow into the melt chamber 32 via the flow channel 44 in front of the piston 28. In contrast, the piston sealing ring 41 moves during the injection process

(Movement in the x direction) against the flow direction S until the sealing surface 45 bears against the sealing surface 46 of the piston 28. This is shown in area I of FIG. 5. The sealing region 39 of the piston 28 now has a completely sealing function.

Claims

Expectations

1. Piston pump for liquid and pasty media, in particular plastic melts, consisting essentially of a cylinder tube and a piston which can be moved at least axially therein, the piston having at least one flow channel which is provided with a check valve, characterized in that the piston (12) has a piston sealing region (13) in the flow direction at the front, which is bridged with the at least one flow channel (18) including check valve (20) in the flow direction (S), and in the flow direction (S) at the rear between the piston (12) and the cylinder tube (11) a forced mixing area (14) is provided which is formed by at least in the axial movement area of the piston (12) on the one hand in the cylinder tube (11) facing outward, spaced cavities (16) and on the other hand in the piston (12) pointing inward, also spaced cavities ( 15) is formed.

2. Piston pump according to claim 1, characterized in that the cavities (16, 15) in the cylinder tube (11) and in the piston (12) are concave.

3. Piston pump according to claim 1 or 2, characterized in that the piston sealing area (13) is designed as an axially and circumferentially extending area with a reduced diameter, in which an axially movable piston sealing ring (41) is arranged, which is arranged in its flow direction (S) at the front position releases at least one flow channel (44) lying between the piston jacket surface (42) and the sealing ring inner surface (43), while in its rearward direction in the flow direction (S) it blocks the flow path.

4. Piston pump according to one of claims to 3, characterized in that the opposite cavities (16, 15) in the cylinder (11) and in the piston (12) are dimensioned differently.

5. Piston pump according to one of the preceding claims, characterized in that the cavities (16) in the cylinder (11) and / or the cavities (15) in the piston (12) are dimensioned differently.

6. Piston pump according to one of claims 1 to 5, that a device for feeding an additive (33) is arranged in the forced mixing area (14).

7. Piston pump according to one of claims 1 to 6, characterized in that the piston (12) is additionally driven in rotation.

8. Use of a piston pump according to claim 7 in an injection unit of an injection molding machine, characterized in that the piston (12) of the pumping / mixing device (10) in the flow direction (S) at the front on a rotating in the housing (27) of the injection unit (23) and axially movable screw conveyor (25) is arranged.