Heater for billets

Claim 2

In a method of heating a length of material to an elevated temperature, the steps of providing a source of primary gas at a temperature at least that to which the material is to heated; providing a source of pressurized secondary gas at a temperature below that to which the material is to be heated; discharging said secondary gas through an opening against the material, the opening being of a type to create a high velocity jet-like stream; passing said jet-like stream first through a zone containing said primary gas and then through a restricted aspirating throat for entraining and accelerating quantities of said primary gas to heat the material by heat transfer to the material from a mixture of primary and secondary gases impinged upon the materials's surface.

Claim 3

In the method described in claim 1 pressurizing the gas of the primary source to a pressure greater than the gases on the discharge side of the aspirating throat.

Claim 4

In a method of heating a billet of metal to a temperature suitable for extrusion, the steps of providing a source of heated primary gas; providing a source of pressurized secondary heated gas; discharging said secondary gas through a plurality of jet openings against the billet in jet-like streams; passing said jet-like streams first through a zone containing said primary gas and then through a restricted aspirating throat for entraining and accelerating quantities of said primary gas to heat the billet by heat transfer to the billet from a mixture of primary and secondary gases impinged upon the billet's surface.

Claim 5

In a method of heating a billet of metal to a temperature suitable for extrusion, the steps of providing a source of heated primary gas; providing a source of pressurized secondary heated gas; discharging said secondary gas through a plurality of jet openings against the billet in jet-like streams; passing said jet-like streams first through a zone containing said primary gas and then through a restricted aspirating throat for entraining and accelerating quantities of said primary gas to heat the billet by heat transfer to the billet from a mixture of primary and secondary gases impinged upon the billet's surface.

Claim 6

In the method described in claim 3 discharing the secondary gas at several locations spaced circumferentially of the billet, directing the jet-like stream of gas at each location through a separate aspirating throat for surrounding the billet with impinging gas.

Claim 7

In the method described in claim 3 heating said primary air to a temperature substantially higher than the temperature of said secondary air.

Claim 8

In a method of heating a billet of aluminum to a temperature suitable for extrusion, the steps of providing a source of primary gas, heating said primary gas at a point remote from the billet to a temperature at least that to which the billet is to be heated; providing a source of pressurized secondary gas at a temperature below that to which the billet is to be heated; discharging said secondary gas through a plurality of jet openings against the billet in jet-like streams; passing said jet-like streams first through a zone containing said primary gas and then through a restricted aspirating throat for entraining and accelerating quantities of said primary gas to heat the billet by heat transfer to the billet from a mixture of primary and secondary gases impinged upon the billet's surface.

Claim 9

In a method of heating a billet of aluminum to a temperature suitable for extrusion, the steps of providing a source of primary gas, heating said primary gas at a point remote from the billet to a temperature at least that to which the billet is to be heated; providing a source of pressurized secondary gas at a temperature below that to which the billet is to be heated; discharging said secondary gas through a plurality of jet openings against the billet in jet-like streams; passing said jet-like streams first through a zone containing said primary gas and then through a restricted aspirating throat for entraining and accelerating quantities of said primary gas to heat the billet by heat transfer to the billet from a mixture of primary and secondary gases impinged upon the billet's surface.

Claim 10

The method described in claim 6 wherein the temperature of the primary gas is 1000°-1500° F. and the temperature of the secondary gas is 400°-700° F.

Claim 11

In the method described in claim 7 pressurizing the primary gas to a pressure exceeding that of the gas on the discharge side of the aspirating throat.

Claim 12

In a method of heating a billet of aluminum to a temperature suitable for extrusion, the steps of passing the billet in sequence through a preheating zone and at least one main heating zone; in the main zone providing a source of primary gas at a temperature at least that to which the billet is to be heated; providing a source of pressurized secondary gas at a temperature below that to which the billet is to be heated; discharging said secondary gas through a plurality of jet openings against the billet in jet-like streams; passing said jet-like streams first through a zone containing said primary gas and then through a restricted aspirating throat for entraining and accelerating quantities of said primary gas to heat the billet by heat transfer to the billet from a mixture of primary and secondary gases impinged upon the billet's surface, withdrawing the gas mixture after its impingement, discharging a portion of the withdrawn gas mixture into the peheating zone and impinging it on an entering billet; utilizing the gas in the preheating zone after its impingement on the entering billet as the gas supply for said source of secondary gas.

Claim 13

In a method of heating a billet of aluminum to a temperature suitable for extrusion, the steps of passing the billet in sequence through a preheating zone and at least one main heating zone; in the main zone providing a source of primary gas at a temperature at least that to which the billet is to be heated; providing a source of pressurized secondary gas at a temperature below that to which the billet is to be heated; discharging said secondary gas through a plurality of jet openings against the billet in jet-like streams; passing said jet-like streams first through a zone containing said primary gas and then through a restricted aspirating throat for entraining and accelerating quantities of said primary gas to heat the billet by heat transfer to the billet from a mixture of primary and secondary gases impinged upon the billet's surface, withdrawing the gas mixture after its impingement, discharging a portion of the withdrawn gas mixture into the peheating zone and impinging it on an entering billet; utilizing the gas in the preheating zone after its impingement on the entering billet as the gas supply for said source of secondary gas.

Claim 14

In the method described in claim 9 recirculating and heating the remaining portion of the withdrawn gas to provide a supply of gas for said source of primary gas.

Claim 15

In a method of heating a billet of aluminum to a temperature suitable for extrusion in a closed cycle system, the steps of passing the billet in sequence through a preheating zone and at least one main heating zone; in the main zone providing a source of primary gas at a point remote from the billet, heating the gas to a temperature at least that to which the billet is to be heated; providing a source of pressurized secondary gas at a temperature below that to which the billet is to be heated; discharging said secondary gas through a plurality of jet openings against the billet in jet-like streams; passing said jet-like streams first through a zone containing said primary gas and then through a restricted, aspirating throat for entraining and accelerating quantities of said primary gas to heat the billet by heat transfer to the billet from a mixture of primary and secondary gases impinged upon the billet's surface, withdrawing the gas mixture after its impingement, discharging a portion of the withdrawn gas mixture into the preheating zone and impinging it on an entering billet; as the gas supply for said source of secondary gas returning the remaining portion of the withdrawn gas to the primary gas source and reheating it for reuse as primary gas.

Claim 16

In a method of heating a billet of aluminum to a temperature suitable for extrusion in a closed cycle system, the steps of passing the billet in sequence through a preheating zone and at least one main heating zone; in the main zone providing a source of primary gas at a point remote from the billet, heating the gas to a temperature at least that to which the billet is to be heated; providing a source of pressurized secondary gas at a temperature below that to which the billet is to be heated; discharging said secondary gas through a plurality of jet openings against the billet in jet-like streams; passing said jet-like streams first through a zone containing said primary gas and then through a restricted, aspirating throat for entraining and accelerating quantities of said primary gas to heat the billet by heat transfer to the billet from a mixture of primary and secondary gases impinged upon the billet's surface, withdrawing the gas mixture after its impingement, discharging a portion of the withdrawn gas mixture into the preheating zone and impinging it on an entering billet; as the gas supply for said source of secondary gas returning the remaining portion of the withdrawn gas to the primary gas source and reheating it for reuse as primary gas.