Apparatus and method for a liquid cooled shield for improved piercing performance

Patent metadata

Field	Value
Publication number	US-9789561-B2
Application number	US-201414496872-A
Country	US
Kind code	B2
Filing date	Sep 25, 2014
Priority date	Mar 12, 2008
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

A shield for a plasma arc torch is configured to protect consumable components of the plasma arc torch from splattering molten metal. The shield includes a generally conical unitary body defining (i) an interior surface to form a gas flow path with an outer surface of an adjacent nozzle of the plasma arc torch, and (ii) an exterior surface. The body includes (i) a distal first portion defining an exit orifice; and (ii) a proximal second portion formed of a flange sharing a common surface with the distal first portion. The shield also includes a seal assembly disposed on the common surface to retain the liquid coolant flow along the proximal second portion.

First claim

The invention claimed is:

1. A shield for a plasma arc torch that pierces and cuts a metallic workpiece producing a splattering of molten metal directed toward the torch, the shield configured to cover and protect at least a nozzle and a nozzle retaining cap of the plasma arc torch from the splattering molten metal and to be replaced independently of the nozzle, the shield comprising:
a generally conical unitary body defining an interior surface to form a gas flow path with an outer surface of an adjacent nozzle of the plasma arc torch and an exterior surface, the body comprising:
a distal first portion defining an exit orifice and having: i) a substantially conical exterior surface region exposed to the molten metal and formed along the exterior surface of the body, and ii) an interior surface region to be contacted by a cooling shield gas flow within the gas flow path along the interior surface of the body to cool the nozzle and the shield; and
a proximal second portion formed of a flange sharing a common surface with the distal first portion having one or more surface regions to be directly cooled by a liquid coolant flow along the common surface shared with at least one of the exterior surface of the body or the interior surface of the body,
the exterior surface region of the distal first portion being conductively cooled by the direct liquid cooling of the flange along a thermally conductive path formed through a continuous conductively cooled region so as to limit the molten metal splatter from bonding to the exterior surface of the distal first portion, at least a portion of the conductively cooled region disposed adjacent the flange; and

a seal assembly disposed on the common surface shared between the flange of the proximal second portion and the distal first portion along the unitary body to retain the liquid coolant flow along the proximal second portion, to limit leakage of the liquid coolant flow from the plasma arc torch, and limit the liquid coolant flow from contacting the nozzle.

2. The shield of claim 1 , wherein the unitary body is formed of a consistent thermal medium.

3. The shield of claim 1 wherein at least a portion of the surface region to be directly cooled by the liquid coolant flow is an outer exterior surface of the flange.

4. The shield of claim 1 wherein the body defines one or more exit ports formed through the distal first portion.

5. The shield of claim 1 wherein the one or more surface regions to be directly cooled by a liquid coolant reduces molten splatter material from accumulating on the shield during use of the torch.

6. The shield of claim 1 wherein the cooling shield gas flow convectively cools the interior surface of the body.

7. The shield of claim 1 wherein the liquid coolant flow convectively cools the one or more surface regions of the flange.

8. The shield of claim 1 wherein the seal assembly is in mechanical communication with a retaining cap that attaches the shield to the plasma arc torch.

9. The shield of claim 1 wherein the continuous conductively cooled region comprises a temperature gradient across the region.

10. The shield of claim 1 wherein the liquid coolant flow comprises a liquid chilled to less than about 60 degrees Fahrenheit.

11. The shield of claim 1 wherein the exterior surface region exposed to the molten metal is chilled to less than about 60 degrees Fahrenheit during use of the plasma arc torch.

12. The shield of claim 1 further comprising a channel in the body between the distal first portion and the proximal second portion, the channel configured to accept the seal assembly that retains the liquid coolant flow along the proximal second portion.

13. The shield of claim 1 wherein the exterior surface region exposed to the molten metal and formed along the exterior surface of the body is sufficiently large to intercept substantially all of the molten metal splatter.

14. The shield of claim 1 wherein the seal assembly comprises at least one of an o-ring, an epoxy seal, or a metal-to-metal contact seal.

15. The shield of claim 1 wherein the shield is attachable to the plasma arc torch, the shield configured to surround a nozzle of the plasma arc torch.

16. The shield of claim 1 wherein the unitary body is a single piece.

17. The shield of claim 1 wherein the direct liquid cooling prevents strengthening of a bond between the molten metal splatter and the exterior surface region of the distal first portion.

18. The shield of claim 1 wherein the shield is configured to be rapidly cooled such that the shield stays at substantially the same temperature during piercing as before piercing by extracting heat from the molten metal that is in contact with the exterior surface region of the distal first portion.

19. The shield of claim 1 wherein the shield is configured to be cooled to operate below ambient temperature.

20. The shield of claim 1 wherein the direct liquid cooling includes a constant liquid flow around the proximal second portion of the body.

21. The shield of claim 1 further including a cooling device configured to provide a cooling medium, wherein the cooling device is a chiller.

22. The shield of claim 1 wherein the unitary body is a one-piece solid body.

23. The shield of claim 1 wherein the distal first portion has a substantially consistent thickness between the exterior surface region and the interior surface region.

24. The shield of claim 1 wherein a length of the distal portion is greater than a length of the proximal portion.

25. The shield of claim 4 wherein a distance between the exit orifice and the one or more exit ports is greater than a distance between the one or more exit ports and the seal assembly.

Assignees

• Hypertherm Inc

Inventors

• Liebold Stephen M
• Lindsay Jon W

Classifications

• H05H1/34

  Details, e.g. electrodes, nozzles · CPC title

• F28F3/12

  Elements constructed in the shape of a hollow panel, e.g. with channels {(F28D1/02, F28D1/03 take precedence)} · CPC title

• B23K10/00 Primary

  Welding or cutting by means of a plasma · CPC title

• H05H2001/3457

  Electricity · mapped topic

• B23K9/296

  using non-consumable electrodes · CPC title