Mold assembly for injection molding of a plastic pipe fitting and injection molded pipe fitting made of plastics

Patent metadata

Field	Value
Publication number	US-11577436-B2
Application number	US-201916967611-A
Country	US
Kind code	B2
Filing date	Feb 5, 2019
Priority date	Feb 6, 2018
Publication date	Feb 14, 2023
Grant date	Feb 14, 2023

Abstract

A mold assembly ( 1 ) for injection molding of a plastic pipe fitting ( 2, 3 ). The pipe fitting comprises an elbow-shaped or a tee-shaped internal flow channel ( 4 ). At least one of the first core member ( 14 ) and the second core member ( 15 ) of the core package ( 12, 13 ) comprises a built-in cooling arrangement ( 20 ) for cooling of the core package ( 12, 13 ), the cooling arrangement ( 20 ) extending longitudinally inside said core member over a substantial length of said core member. The pipe fitting ( 2, 3 ) comprises an elbow-shaped or tee-shaped internal flow channel ( 4 ) comprising at least two channel parts ( 5, 6, 7 ) arranged at a first angle (α) in relation to each other, the channel parts ( 5, 6, 7 ) each having a circular cross-section and a smoothly radiused inner corner face ( 8 ) between each two channel parts being at said first angle in relation to each other, the at least one of the channel parts having an inner diameter D, a length L from central corner point to the end of the channel part, the inner corner face having a rounding radius R. The ratio (D/R) of the inner diameter D and the rounding radius R is in the range 2 to 5, and the ratio (L/D) of the length L and inner diameter D is in the range 8 to 3.

First claim

The invention claimed is:

1. A mold assembly ( 1 ) for injection molding of a plastic pipe fitting ( 2 , 3 ), the pipe fitting comprising an elbow-shaped or tee-shaped internal flow channel ( 4 ) comprising at least two channel parts ( 5 , 6 , 7 ) arranged at a first angle (a) in relation to each other, the channel parts ( 5 , 6 , 7 ) each having a circular cross-section and a smoothly radiused inner corner face ( 8 ) between each two channel parts being at said first angle in relation to each other,
the mold assembly ( 1 ) comprising
a pair of mold members ( 9 , 10 ) adapted for movement between an open position and a closed position to define a mold cavity ( 11 ) having a shape conforming to the exterior geometry of the pipe fitting ( 2 , 3 ) to be molded,
a pair of retractable core packages ( 12 , 13 ) each comprising a first core member ( 14 ) and a second core member ( 15 ), each core package ( 12 , 13 ) being movable between an advanced position (I) protruding into said mold cavity ( 11 ) and cooperating with each other to define the internal flow channel ( 4 ) in the pipe fitting ( 2 , 3 ) to be molded, and a retracted position (II) substantially withdrawn from said mold cavity ( 11 ), the first core member ( 14 ) and the second core member ( 15 ) having distal ends (E) with end faces ( 16 , 17 ) for abutting engagement with each other when said first core member ( 14 ) and second core member ( 15 ) are in advanced positions (I) to define the internal flow channel ( 4 ) with said channel parts ( 5 , 6 , 7 ) at the first angle (a) in relation to each other, the first core member ( 14 ) defining an outer portion of the internal flow channel ( 4 ) and including an inclined guide member ( 18 ) extending longitudinally and at a second angle (( 3 ) in relation to a longitudinal axis, and the second core member ( 15 ) defining an inner portion of the internal flow channel ( 4 ), the second core member ( 15 ) being movably slidable along said inclined guide member ( 18 ) and including a curved inner edge ( 19 ) disposed generally at a distal end thereof, wherein said curved inner edges ( 19 ) of the second core member ( 15 ) cooperatively define the smoothly radiused inner corner face ( 8 ) of the internal flow channel ( 4 ); and wherein the second core member ( 15 ) is movable along the inclined guide member ( 18 ) on the first core member ( 14 ) upon movement of the core package ( 12 , 13 ) toward said retracted position subsequent to molding of the pipe fitting ( 2 , 3 ) within the mold cavity ( 11 ) to shift the second core member ( 15 ) towards a center axis (x) of the internal flow channel ( 4 ) for withdrawal of the core package ( 12 , 13 ) from the mold cavity ( 11 ) and the pipe fitting ( 2 , 3 ) molded therein, characterized in that at least one of the first core member ( 14 ) and the second core member ( 15 ) of the core package ( 12 , 13 ) comprises a built-in cooling arrangement ( 20 ) for cooling of the core package ( 12 , 13 ), the cooling arrangement ( 20 ) extending longitudinally inside said core member over a substantial length of said core member.

2. The mold assembly according to claim 1 , characterized in that the cooling arrangement ( 20 ) comprises an elongated blind hole ( 21 ) extending a substantial length of the core member between a support end ( 22 ) of the core member ( 14 , 15 ) and the distal end (E).

3. The mold assembly according to claim 2 , characterized in that the cooling arrangement ( 20 ) comprises a heat conductor element ( 23 ) having high thermal conductivity, the heat conductor element ( 23 ) being inserted in the blind hole ( 21 ).

4. The mold assembly according to claim 3 , characterized in that the cooling arrangement ( 20 ) comprises a cooling fluid channel ( 24 ) for circulating cooling fluid inside the core member ( 14 , 15 ).

5. The mold assembly according to claim 4 , characterized in that the heat conductor element ( 23 ) is partly arranged to extend inside the cooling fluid channel ( 24 ) to be flushed by the cooling fluid.

6. The mold assembly according to claim 4 , characterized in that the cooling fluid is water.

7. The mold assembly according to claim 4 characterized in that the cooling fluid is carbon dioxide (CO 2 ).

8. The mold assembly according to claim 4 , characterized in that the cooling arrangement ( 20 ) comprises a bubbler ( 25 ) comprising a narrow tube ( 26 ) arranged inside the cooling fluid channel ( 24 ) so that a gap ( 27 ) is formed between the tube and the wall of the cooling fluid channel ( 24 ), whereby the cooling fluid is capable to flow via the tube ( 26 ) to fountain from the end of the tube and to flow out via the gap ( 27 ).

9. The mold assembly according to claim 8 , characterized in that the heat conductor element ( 23 ) is partly arranged inside the tube ( 26 ) for cooling the heat conductor element with the cooling fluid.

10. The mold assembly according to claim 3 , characterized in that the heat conductor element ( 23 ) is a pin made of solid material having high thermal conductivity.

11. The mold assembly according to claim 9 , characterized in that the heat conductor element ( 23 ) is made of beryllium copper alloy.

12. The mold assembly according to claim 3 , characterized in that the heat conductor element ( 23 ) is a thermal pin which is a sealed cylinder filled with a fluid which is vaporized as it draws heat from the core member, and condenses as it releases heat to the cooling fluid.

13. The mold assembly according to claim 1 , characterized in that the first core member ( 14 ) is made of tool steel.

14. The mold assembly according to claim 1 , characterized in that the first core member ( 14 ) is made of beryllium copper alloy.

15. The mold assembly according to claim 13 , characterized in that the first core member ( 14 ) comprises a diamond-like carbon (DLC) coating.

16. The mold assembly according to claim 1 , characterized in that the second core member ( 15 ) is made of tool steel.

17. The mold assembly according to claim 1 , characterized in that the second core member ( 15 ) is made of beryllium copper alloy.

18. The mold assembly according to claim 16 , characterized in that the second core member ( 15 ) comprises a diamond-like carbon (DLC) coating.

19. The mold assembly according to claim 1 , characterized in that the first angle (α) is 30°-120 °.

20. The mold assembly according to claim 1 , characterized in that the first angle (α) is 90 °.

21. The mold assembly according to claim 1 , characterized in that the second angle (β) is in the range of 1° to 12°.

22. The mold assembly according to claim 1 , characterized in that the mold cavity ( 11 ) formed by the mold members ( 9 , 10 ) and the core packages ( 12 , 13 ) are configured to form a pipe fitting ( 2 , 3 ) wherein at least one of the channel parts ( 5 , 6 , 7 ) has an inner diameter D, a length L from central corner point to the end of the channel part, the inner corner face having a rounding radius R, and wherein the ratio (D/R) of the inner diameter D and the rounding radius R is in the range 2 to 5, and the ratio (L/D) of the length L and inner diameter D is in the range 8 to 3.

23. An injection molded pipe fitting ( 2 , 3 ) made of plastics by a mold assembly ( 1 ) according to claim 1 , the pipe fitting ( 2 , 3 ) comprising an elbow-shaped or tee-shaped internal flow channel ( 4 ) comprising at least two channel parts ( 5 , 6 , 7 ) arranged at a first angle (a) in relation t

Assignees

• Uponor Innovation Ab

Inventors

• Smahl Jarmo

Classifications

• B29L2031/246

  T-joints · CPC title

• B29C45/7337

  using gas or steam (B29C45/7331 takes precedence) · CPC title

• B29K2907/04

  Carbon · CPC title

• B29C45/73 Primary

  of the mould {(B29C45/2642 and B29C45/2737 take precedence)} · CPC title

• B29L2031/243

  Elbows · CPC title