Sealed furnace

Patent metadata

Field	Value
Publication number	US-12420337-B2
Application number	US-202017429763-A
Country	US
Kind code	B2
Filing date	Feb 11, 2020
Priority date	Feb 11, 2019
Publication date	Sep 23, 2025
Grant date	Sep 23, 2025

Abstract

A furnace may include an outer wall defining a chamber, the chamber including an internal cavity configured to receive one or more parts, at least one heater positioned within the chamber, the at least one heater being configured to generate temperatures of at least about 800 degrees Celsius within the internal cavity, and a vacuum pump configured to apply a vacuum to at least a portion of the chamber. The furnace may also include at least one layer of inner insulation and at least one layer of outer insulation disposed outward of the inner insulation with respect to the chamber, the at least one layer of outer insulation being sealed with respect to the at least one layer of inner insulation.

First claim

What is claimed is:

1. A high-temperature high-purity vacuum furnace for heating parts over a range of high furnace temperatures, comprising:
an arrangement of furnace insulation with furnace heaters disposed therein, that when heating parts define a hot zone therein that is heated by the furnace heaters to a temperature that exceeds 800C for at least a portion of a furnace heating cycle,
an openable and closeable sealed vacuum retort that while closed is contained during the furnace heating cycle within the hot zone and is surrounded by an outside ambient air originating from outside the vacuum furnace, and is composed of a material that is:
(i) non-porous and thus impervious to diffusion of outside gases, and
(ii) capable of withstanding vacuum pressure throughout the furnace heating cycle;
wherein the sealed vacuum retort while closed defines an inner volume as a hollow interior in fluid communication with an inlet tube for injecting process gas therein and an outlet tube for applying vacuum thereto;
wherein each of the inlet tube and the outlet tube extends from the hot zone, towards an exterior of the furnace, through at least a portion of the arrangement of furnace insulation; and
wherein when the retort is closed the inner volume is vacuum sealed from the outside ambient air by a main retort seal that is within the hot zone that blocks contamination, of the process gas within the inner volume, by leakage of outside ambient air into the inner volume, to a sufficient degree to prevent adverse effects on parts quality by the outside ambient air.

2. The vacuum furnace of claim 1 wherein at least a portion of the arrangement of furnace insulation is moveable to allow access to the inner volume of the sealed vacuum retort between furnace cycles.

3. The vacuum furnace of claim 1 wherein, during operation with the sealed vacuum retort closed, the main retort seal blocks contamination, of the process gas within the inner volume, by leakage of outside ambient air into the inner volume, to a sufficient degree such that contamination in the inner volume is equal to or less than one air molecule from the outside ambient air for every million molecules of process gas.

4. The vacuum furnace of claim 1 wherein, during operation with the sealed vacuum retort closed, a first process gas purity in the inner volume is comparable to a second process gas purity achieved in commercial ultra-high vacuum systems.

5. The vacuum furnace of claim 1 wherein the main retort seal divides the sealed vacuum retort into a retort base and a retort body, wherein at least one of the retort body and the retort base is removable to provide an open, unsealed, position for loading parts into the sealed vacuum retort, and replaceable to provide a closed, sealed, position, in which the sealed vacuum retort can be vacuum sealed by the main retort seal; and
Wherein, during operation with the sealed vacuum retort in the closed position, the retort base and retort body are each surrounded by the arrangement of furnace insulation and thereby contained within the hot zone.

6. The vacuum furnace of claim 5 wherein a portion of the arrangement of insulation can support at least one of the retort body and retort base, for motion therewith.

7. The vacuum furnace of claim 5 wherein a portion of the arrangement of insulation can be connected to the retort body for movement therewith therewith when opening the sealed vacuum retort.

8. The vacuum furnace of claim 5 wherein the main retort seal includes an inner seal that employs a somewhat permeable, non-hermetic, vacuum gasket formed of a refractory material that can withstand a temperature range of the furnace heating cycle and the vacuum gasket exhibits a gasket leak, at least in part due to the permeability, and the outer seal acts as an additional seal that surrounds the inner seal and isolates the gasket leak from the outside ambient air.

9. The vacuum furnace of claim 8 wherein the vacuum gasket is a graphoil gasket.

10. The vacuum furnace of claim 9 wherein the outer seal is a peclet seal.

11. The vacuum furnace of claim 10 wherein the furnace system has no vacuum chamber outside of the sealed vacuum retort and therefore no vacuum can be applied outside of the sealed vacuum retort such that an outer exterior of the peclet seal remains at approximately atmospheric pressure.

12. The vacuum furnace of claim 10 wherein the arrangement of insulation is at least partially surrounded by a unsealed protective cover that permits a flow of outside ambient air therethrough.

13. The vacuum furnace of claim 10 wherein one of the retort base and the retort body includes a circumferentially extending sweep gas groove that is disposed between the inner gasket seal and the peclet seal and is configured to receive sweep gas from a sweep gas tube, that is in fluid communication with the sweep gas groove, such that the sweep gas surrounds the inner seal and a majority of the sweep gas flows into and through the peclet seal at a velocity sufficient to suppress diffusion of outside air towards the inner volume.

14. The vacuum furnace of claim 13 wherein the sweep gas tube extends through at least a portion of the arrangement of furnace insulation and is in non-separably hermetically sealed to the sealed vacuum retort.

15. The vacuum furnace of claim 13 wherein the sweep gas flows through the peclet seal at a rate of between and inclusive of 0.1 to 2.0 standard liters per minute (SLM).

16. The vacuum furnace of claim 13 wherein the sweep gas flows through the peclet seal at a rate of between and inclusive of 0.1 to 1.0 SLM.

17. The vacuum furnace of claim 13 wherein the sweep gas is an inert gas.

18. The vacuum furnace of claim 17 wherein the sweep gas is Argon.

19. The vacuum furnace of claim 13 wherein the sweep gas is a pure, laboratory grade, inert gas with a purity better than 1 ppm.

20. The vacuum furnace of claim 13 wherein the peclet seal includes (i) a peclet channel having a peclet channel length extending from the sweep gas groove to the exterior outside ambient air; and the peclet channel is delimited by (ii) a peclet gap extending between confronting faces of the retort body and the retort base such that the sweep gas flows from the sweep gas groove to the outside ambient air.

21. The vacuum furnace of claim 20 wherein the peclet gap is between or equal to one of 0.001 inches to 0.010 inches.

22. The vacuum furnace of claim 20 wherein the peclet gap is between or equal to one of 0.002 inches to about 0.005 inches.

23. The vacuum furnace of 20 wherein the sweep gas groove has a sufficiently large width and a depth such that a fluidic conductance of the channel is greater than 10 times a fluidic conductance of the peclet gap.

24. The vacuum furnace of claim 13 wherein the peclet seal provides suppression sufficient such that any sweep gas in the sweep gas groove that leaks into the sealed vacuum retort through the gasket leak is contaminated with outside ambient air only by an amount that is lower than 1 part per million (ppm).

25. The vacuum furnace of claim 24 wherein the amount of contamination is lower than 100 part per billion (ppb).

26. The vacuum furnace of claim 24 wherein the amount of contamination is lower than 10 ppb.

27. The vacuum furnace of claim 24 wherein the amount of contamination is lower than 1 ppb.

28. The vacuum furn

Assignees

• Desktop Metal Inc

Inventors

• Woodard Nathan
• Myerberg Jonah Samuel
• Sachs Emanuel M
• Fontana Richard Remo
• Weiss Robert Edward
• Chiang Yet-Ming
• Dipietro Stephen
• Bandiera Nicholas Graham

Classifications

• Y02P10/25

  Process efficiency · CPC title

• F27D99/0073

  Seals · CPC title

• F27D1/0033

  Linings or walls comprising heat shields, e.g. heat shields · CPC title

• F27B5/18

  Arrangement of controlling, monitoring, alarm or like devices · CPC title

• F27B5/08

  Arrangements of linings · CPC title