WO2003051604A1

WO2003051604A1 - Check valve with wear-resistant coating and method for the production thereof

Info

Publication number: WO2003051604A1
Application number: PCT/EP2002/014153
Authority: WO
Inventors: Paul-Eberhard Kortmann; Bernhard PÖLTL
Original assignee: Mannesmann Plastics Machinery Gmbh
Priority date: 2001-12-14
Filing date: 2002-12-12
Publication date: 2003-06-26

Abstract

Disclosed is a check valve (9) with a base body (1) comprising a top part (2) provided with wings (6) and a shank part (3), and an axially moveable check ring (10). The forward stop face (15) of the check ring (10) engages with the base of the top part (2) in the open position, and the rearward stop face (14) engages with a thrust collar (5) in the closed position. Each surface (7, 8, 14, 15) of the check ring (10), the top part (2), and the thrust collar (5) entering in contact with each other are provided with different layers (A, B, C, D) of a wear-resistant coating such that said wear-resistant coating is optimally adapted to the wear to which each surface is subjected. Different strips A, B, C, and D containing the respective desired coating material are fixed to the surfaces that are to be coated and are thermally treated.

Description

Non-return valve with wear protection layer and process for its manufacture

description

The invention relates to a non-return valve according to the preamble of patent claim 1 and a method for its production according to the preamble of the independent patent claim 9.

In the injection molding of thermoplastic materials, screws are used that can be axially displaced in plasticizing cylinders and rotated in a defined direction. The plastic granulate is melted by the friction occurring here and by additional heating strips placed on the outside of the plasticizing cylinder. The screw is used as a piston to inject the plastic compound into the cavity of a mold and is moved axially in the plasticizing cylinder. In order to prevent melted plastic from flowing back during this injection process, i.e. when the non-rotating screw moves forward, non-return valves are used.

Non-return valves are known from the prior art (WO 00/23248), which have a locking sleeve or a locking ring at the front end of the screw. During injection, this locking ring is pressed against a pressure ring surface of a base body arranged at the head of the screw. When dosing, i.e. when the rotating screw returns, the locking ring is lifted off the pressure and stop surface and pressed against the stop surfaces by wings or the like arranged on the head of the base body. The locking ring is freely movable with respect to the screw and does not rotate at all or only at a low speed when dispensing due to the friction on the wall of the plasticizing cylinder. This results in a rubbing process between the locking ring and the contact surfaces of the wings.

In order to increase the service life of non-return valves, the abutting surfaces are provided with wear protection layers. From EP 0 853 541 B1 a method for producing a coating on the surface of a non-return valve is known, in which a metallic, hard metal or ceramic edge layer is produced by means of laser beam remelting. A disadvantage of the laser beam remelting process is that the process is expensive and lengthy. From DE 3943 344 C1 it is known to provide a plasticizing screw with a wear protection layer by winding a winding tape consisting of a wear-resistant metallic material onto the top of the web of the screw webs and fixing it there.

The invention is based on the object of specifying a non-return valve which has a long service life and of specifying a method for its production which enables a rapid production process to be carried out at low cost.

These objects are achieved by a non-return valve with the features of claim 1 and by a method with the features of the independent claim 7.

The main advantage of the non-return valve according to the invention is that the friction pairings can be optimally coordinated with one another by using different wear protection layers. In this way, the

Wear protection coating can be optimally adapted to the respective wear. This advantage can also be achieved by varying the chemical composition of the belt and thus taking into account the different types of wear.

In the method for producing a wear protection coating on the surface of a non-return valve constructed from a screw tip, a pressure ring and a blocking ring for a plasticizing unit of a plastic machine, a tape containing a coating material is applied to the areas of the non-return valve that are subject to increased wear, different tapes are used for different surface areas. It proves to be a great advantage that the respective tape can be cut in the simplest manner to the appropriate shape of the surface to be coated. The strip sections are then thermally treated, so that a wear-protected surface is created in said areas, the surfaces corresponding to one another having different wear protection layers. The belts can be applied and thermally treated at any processing stage of the non-return valve of the plasticizing, mixing or conveying screw, provided that only the surfaces on which the belt sections are applied have already been machined during machining. Another advantage is that the belts can also be used to repair a non-return valve that is already in use. In one embodiment of the invention, the band is applied and tempered on an annular sealing and / or friction surface of the screw tip and / or of the pressure ring and / or of the locking ring directed in the conveying direction and / or counter to the conveying direction of the plasticizing unit. These axially directed surfaces meet during the operation of the non-return valve. The end face of the screw tip directed against the conveying direction meets a surface of the locking ring pointing in the conveying direction. An end face of the locking ring directed against the conveying direction meets an end face of the pressure ring directed in the conveying direction. The surfaces hit each other and rub against each other. These surfaces are therefore subject to high wear during operation of the non-return valve. A wear protection coating according to the method of the invention therefore proves to be particularly advantageous here.

The band sections are advantageously applied to at least one end face of a pressure ring and / or locking ring. Preferably, all the surfaces that meet, the annular sealing or friction surface of the screw tip, both end surfaces of the locking ring and the end surface of the pressure ring pointing in the conveying direction are armored with a wear protection layer.

The tapes are preferably glued onto the non-return valve. This is the easiest and cheapest way of fastening.

In an advantageous variant of this, the strips are fixed on the non-return valve by a ceramic support device or a wire mesh, so that it cannot slip during the subsequent thermal treatment. Compared to gluing the tape, the glue is not required in this variant. This does not cause problems with the adhesive's combustion residues during the heat treatment of the tape.

The thermal treatment is preferably a soldering process or a sintering process. The belt is firmly bonded to the non-return valve without it being distorted by excessive thermal stress. This thermal treatment preferably takes place in a vacuum oven. This avoids oxidation processes on atmospheric oxygen.

In an alternative embodiment of the invention, the thermal treatment takes place by means of an induction coil. This is a quick and space-saving alternative to the vacuum furnace. In order to avoid oxidation processes on atmospheric oxygen, the thermal treatment by means of the induction coil is preferably carried out with a blanket of inert gas. In a further alternative to this, the thermal treatment is carried out using a flame. This is a very inexpensive variant.

In a further development of the invention, a tape containing a coating material is applied to a worn area of the non-return valve after its mechanical pretreatment for repair purposes. The strip is then thermally treated, so that a wear-protected surface is created in said area. The surface is preferably machined. As a result, a non-ready-to-use non-return valve can be put back into use at low cost.

An embodiment of the invention is shown in a drawing.

A non-return valve 9 has a base body 1, which consists of a head part 2 tapering towards the front, a cylindrical shaft part 3 and an end piece 4. On the head part 2 wings 6 are provided, on the end faces 7 of the locking ring 10 in the open position of the non-return valve. At the front end of the end piece 4, a pressure ring 5 is provided, while the rear end of the end piece 4 has a thread (not shown here) in order to be able to fasten the non-return valve in the plasticizing screw.

On the shaft part 3, the locking ring 10 is freely movable in a certain area on the base body 1 between the end faces 7 of the wings 6 as a stop surface and a stop surface 8 of the pressure ring 5. Between the inner wall of the locking ring 10 and the shaft part 3, an annular gap 12 is formed, through which the plastic melt can flow into the antechamber in the open position of the non-return valve. The axially directed surfaces meet one another during operation of the non-return valve 9. In the closed position of the non-return valve, the locking ring 10 rests with its rear stop surface 14 close to the stop surface 8 of the pressure ring 5, while in the open position the locking ring 10 with its front stop surface 15 bears against the stop surfaces 7 of the wing 6.

The end faces 6 of the vanes 7 directed counter to the conveying direction 11 meet the front stop face 15 of the locking ring 10 pointing in the conveying direction 11. The rear stop face 14 of the locking ring 10 directed counter to the conveying direction 11 meets an end stop facing in the conveying direction 11 End face 8 of the pressure ring 5. Here hit the surfaces against each other and rub against each other. These surfaces are therefore subject to high wear during operation of the non-return valve 9. To protect them, these surfaces are therefore provided with anti-wear coatings AD.

To produce the wear protection coatings, a first band A containing a coating material is applied to the friction surfaces 7 of the vanes 6, which are directed against the conveying direction 11 of the plasticizing unit. Furthermore, a second, different band B is applied to the front stop surface 15 and a third band C to the rear stop surface 16 in the locking ring 10. In addition, a fourth band D is applied to the end face 8 of the pressure ring 5 pointing in the conveying direction 11. To do this, tapes A, B, C and D are cut to the appropriate shape beforehand. The inside of the tapes are provided with an adhesive and therefore adhere independently to the previously mentioned surfaces to be coated. Bands A - D are optimized depending on the type of wear that occurs. In an advantageous version, these strips are sintered onto the areas of the wings 6, the locking ring 10 and the pressure ring 5 to be coated in a vacuum furnace, not shown. The adhesive burns on the inside of the tapes. The tapes melt and form an intimate connection with their respective base. The surfaces of the wings 6, the locking ring 10 and the pressure ring 5 which are intimately connected to the band 1 are now armored by different and optimally coordinated wear protection coatings.

One or more of the following materials are used as coating materials in the strips: Al, B, Co, Cr, Mo, Nb, Ni, Si, Ti, W, AlO-ZrO, AL-TiO, Co-Cr, Co-Ni, CO- Mo-Cr, CrC-NiCr, CrC-Ni, Cr-Ni, CrO, NiCrAI, NiCrMo, TiC-CrNi, VC-CrNi, WC-CrC-Ni, WC- CrC-NiCr, WC-Co, WC- Co-Cr, WC-Co-NiCr, WC-Ni, WC-VC-Ni, ZrO-AlO, ZrO-MgO. For the selection of the material combination, the material to be processed on the plastics machine can be a determining factor.

The following friction partners have proven themselves:

- toilet co,

- WC-Ni

- WSC

- Cr C

- Cr O where the proportion of hard phases in the strip alloys can vary between 5 and 50% by weight. The friction partners should have a different composition if possible, for example when using alloys with the hard phase WC-Co the proportion in the contact surfaces of the wings is 50% by weight and 30% by weight in the corresponding front stop surface of the locking ring.

Bezυgszeichenliste

Claims

claims

1. non-return valve (9) for a plasticizing and injection screw of an injection molding machine, with a base body (1) which has a head part (2) which preferably tapers towards the front and an area (3) adjoining the head part (2) towards the rear has a smaller diameter than the base of the head part (2), with an axially movable locking ring (10) which is arranged behind the head part (2) of the base body (1) in the area (3) with the smaller diameter and in this area forms a gap (12) with the base body (1), the front stop surface (15) of the locking ring (10) in the open position at the base of the head part (2) and the rear stop surface (14) in the closed position at one of the Base body (1) located pressure ring (5), and the surfaces of the locking ring (10), head part (2) and pressure ring (5) that come into contact with one another are at least partially provided with a wear protection layer, characterized calibrates that the surfaces (7, 8, 14, 15) that come into contact with each other are different

Have wear protection layers (A, B, C, D).

2. Non-return valve according to claim 1, characterized in that the wear protection layers (A, B, C, D) vary in their chemical composition.

3. non-return valve according to claim 1 or 2, characterized in that the wear protection layer (B) on the front stop surface (15) of the locking ring (10) and the wear protection layer (A) of the contacting surface (7) at the base of the Head part (2) contains one or more of the following materials: AI, B, Co, Cr, Mo, Nb, Ni, Si, Ti, W, AlO-ZrO, AL-TiO, Co-Cr, Co-Ni, CO- Mo-Cr, CrC-NiCr, CrC-Ni, Cr-Ni, CrO, NiCrAI, NiCrMo, TiC-CrNi, VC- CrNi, WC-CrC-Ni, WC-CrC-NiCr, WC-Co, WC-Co- Cr, WC-Co-NiCr, WC-Ni, WC-VC-Ni, ZrO-AlO, ZrO-MgO, whereby in one wear protection layer (A) a different material or a different material combination than in the other wear protection layer (B) is provided is.

, Non-return valve according to claim 1 or 2, characterized in that the wear protection layer (B) on the front stop surface (15) of the locking ring (10) and the wear protection layer (A) of the surface (7) coming into contact with it at the base of the head part ( 2) contains one or more of the following materials: AI, B, Co, Cr, Mo, Nb, Ni, Si, Ti, W, AlO-ZrO, AL-TiO, Co-Cr, Co-Ni, CO-Mo- Cr, CrC-NiCr, CrC-Ni, Cr-Ni, CrO, NiCrAI, NiCrMo, TiC-CrNi, VC- CrNi, WC-CrC-Ni, WC-CrC-NiCr, WC-Co, WC-Co-Cr, WC-Co-NiCr, WC-Ni, WC-VC-Ni, ZrO-AlO, ZrO-MgO, the same material or the same material combination being provided in different concentrations in both wear protection layers (A, B).

5. Non-return valve according to one of claims 1 to 4, characterized in that the wear protection layer (C) on the rear stop surface (14) of the locking ring (10) and the wear protection layer (D) on the stop surface (8) coming into contact therewith Pressure ring (5) contains one or more of the following materials: AI, B, Co, Cr, Mo, Nb, Ni, Si, Ti, W, AlO-ZrO, AL-TiO, Co-Cr, Co-Ni, CO- Mo-Cr, CrC-NiCr, CrC-Ni, Cr-Ni, CrO, NiCrAI, NiCrMo, TiC-CrNi, VC-CrNi, WC-CrC- Ni, WC-CrC-NiCr, WC-Co, WC-Co- Cr, WC-Co-NiCr, WC-Ni, WC-VC-Ni, ZrO-AlO, ZrO-MgO, whereby in one wear protection layer (C) a different material or a different material combination than in the other wear protection layer (D) is provided is.

6. Non-return valve according to one of claims 1 to 4, characterized in that the wear protection layer (C) on the rear stop surface (14) of the locking ring (10) and the wear protection layer (D) on the stop surface (8) coming into contact therewith Pressure ring (5) contains one or more of the following materials: AI, B, Co, Cr, Mo, Nb, Ni, Si, Ti, W, AlO-ZrO, AL-TiO, Co-Cr, Co-Ni, CO- Mo-Cr, CrC-NiCr, CrC-Ni, Cr-Ni, CrO, NiCrAI, NiCrMo, TiC-CrNi, VC-CrNi, WC-CrC- Ni, WC-CrC-NiCr, WC-Co, WC-Co- Cr, WC-Co-NiCr, WC-Ni, WC-VC-Ni, ZrO-AlO, ZrO-MgO, whereby in both wear protection layers (C, D) the same material or same material combination is provided in different concentrations.

7. non-return valve according to one of claims 1 to 6, characterized in that at the base of the head part (2) three or more wings (6) are provided, between which the head part (2) has recesses (16) and that the wings ( 6) have stop surfaces (7) directed counter to the conveying direction (11).

8. Non-return valve according to one of claims 1 to 7, characterized in that the stop surfaces (14, 15) of the locking ring (10) and / or the parts of the base body (1) interacting with these surfaces have ceramic and / or hard metal inserts

9. A method for producing a wear protection layer on a non-return valve according to one of claims 1 to 8, characterized in that different strip materials (A, B, C, D) on the areas to be coated

(7, 8, 14, 15) of the non-return valve (9) are applied.

10. The method according to claim 9, characterized in that tapes (A, B, C, D) are provided with different coating materials, which are applied to the areas to be coated (7, 8, 14, 15), and that the tapes ( A, B, C, D) are then thermally treated, so that surfaces with different wear protection layers are created in said areas (7, 8, 14, 15).

11. The method according to claim 9 or 10, characterized in that a strip material B for the front stop surface of the locking ring and a surface (7) of the head part (2) corresponding to this surface in the open position Tape material A with a chemical composition different from tape material B can be used.

12. The method according to any one of claims 9 to 10, characterized in that for the rear stop surface (14) of the locking ring (10) a strip material C and for the stop surface (8) of the pressure ring (5) corresponding to this surface in the closed position Tape material D with a chemical composition different from tape material C can be used.

13. The method according to any one of claims 9 to 12, characterized in that the strips (A, B, C, D) are each fixed on the areas of the non-return valve (9) to be coated by a ceramic support device or a wire mesh.

14. The method according to any one of claims 9 to 13, characterized in that the thermal treatment is a soldering process or a sintering process.

15. The method according to any one of claims 9 to 14, characterized in that the thermal treatment takes place in a vacuum oven.

16. The method according to any one of claims 9 to 15, characterized in that the thermal treatment is carried out by means of an induction coil.

17. The method according to any one of claims 9 to 16, characterized in that the thermal treatment is carried out by means of a flame.

18. The method according to any one of claims 9 to 17, characterized in that the strips contain one or more of the following materials: AI, B, Co, Cr, Mo, Nb, Ni, Si, Ti, W, AlO-ZrO, AL-TiO, Co-Cr, Co-Ni, CO-Mo -Cr, CrC-NiCr, CrC-Ni, Cr-Ni, CrO, NiCrAI, NiCrMo, TiC-CrNi, VC-CrNi, WC-CrC-Ni, WC-CrC-NiCr, WC-Co, WC-Co-Cr , WC-Co-NiCr, WC-Ni, WC-VC-Ni, ZrO-AlO, ZrO-MgO, whereby different materials or material combinations or the same materials or material combinations are contained in different concentrations in bands that come into contact with one another.

19. A method for regenerating a worn area of a non-return valve, characterized in that, after mechanical pretreatment of this area, a strip material containing a coating material is applied and the strip material is then thermally treated, so that a wear-protected surface is created in said area.