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AssigneeLeybold Durfrrit GmbH
InventorsPaul Heilmann, Peter Minarski, Friedrich Preisser
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In a vacuum heat treating oven operating with hydrogen under pressure as the cooling medium, especially for the quenching of greatly heated metal workpieces (5), a method is provided for the automatic control of the progress of the process and for monitoring safety of operation. The housing (4) of the heat treating oven is for this purpose connected to gas inlet lines (9 and 10), one for the admission of the cooling gas and one for the admission of the flushing gas (H.sub.2 and N.sub.2, respectively), and also to a vacuum line (17) and to a gas outlet line (11) into each of which gas sensors (24, 39, 42) are inserted, which during the quenching process signal the gas concentration to a central processing unit (41) which also is connected to pressure sensors (19, 20) and a gas sensor (21) which issue additional signals concerning the gas pressures prevailing in each instant in the interior of the housing (4) or gas inlet line (10) and concerning the gas concentration in the environment of the oven to the central processing unit (41), which then in turn, according to preset programs, actuates the gas inlet and gas outlet valves (25, 30, and 18, 28, respectively) and turns on or off the motor-blower unit (12, 13) and the heating unit (15, 15a, . . . ).
Apparatus for the independent monitoring of safety of operation and for controlling the progress of a process in a vacuum heat-treating oven operating with cooling gas under pressure, for the hardening of metal workpieces, with a housing enclosing the heating chamber for accommodating the charge of workpieces and connected to a vacuum pump, with gas inlet openings and gas outlet openings leading into the heating chamber, a motor blower unit whose impeller circulates the cooling gas, a cooling gas supply tank, a heating unit and with a heat exchanger in the cooling gas circuit, wherein a pressure sensor measuring the pressure in the housing of the oven, and at least one gas sensor disposed in the immediate environment of the oven are provided, each of which, in conjunction with a processing unit, upon failure to reach a given pressure in the interior of the housing and a gas concentration simultaneously establishing itself in the oven environment, initiates a safety program which produces an immediate closing of the cooling gas inlet valve, an opening of the gas outlet valve and an opening of a flushing gas inlet valve, which is inserted into a line which connects the one flushing gas tank with the interior of the oven housing and thus finally, in accordance with the cooling gas concentration at the gas outlet valve, registered by a gas sensor inserted into a branch line to the gas outlet line, produces the pressure equalization of housing interior and oven environment.
Apparatus for the automatic monitoring of the safety of operation and for the control of the progress of a process in a vacuum heat-treating oven operated with hydrogen gas as cooling gas under pressure for the hardening of metal workpieces, with a housing surrounding the heating chamber for the accommodation of the workpiece charge and connected to a vacuum pump, with gas inlet lines and gas outlet lines leading into the heating chamber, a motor blower unit whose impeller circulates the cooling gas stream, a cooling gas supply tank, a heating unit and with a heat exchanger in the cooling gas circuit, wherein an evacuating valve and at least one gas sensor are inserted into the vacuum line leading from the housing of the vacuum heat treating oven to the vacuum pump, and that a first pressure sensor detecting the pressure in the interior of the housing and a second pressure sensor detecting the pressure in the cooling gas inlet line are provided, and that at least one gas sensor testing the oven environment in the direct vicinity of the vacuum heat treating oven and one gas sensor inserted into the cooling gas outlet line are disposed, and, after the evacuating valve has been closed at the start of the quenching process, a first measurement of the two pressure sensors for the pressure in the interior of the housing and for the pressure in the cooling gas inlet line produces either the interruption of the quenching process or else produces the opening of the cooling gas inlet valve until the pressure in the housing has reached a given level, which is sensed by the first pressure sensor, or else leads to the interruption of the current quenching process if the gas sensor for the gas concentration in the environment fails to detect a given level, and finally, after the closing of the cooling gas inlet valve and an allowable gas concentration in the oven environment, the quenching procedure is ended and, after the housing has been relieved of pressure by opening the cooling gas outlet valve, a filling of the housing with flushing gas is performed by opening the flushing gas inlet valve, until the cooling gas concentration in the gas outlet line monitored by the gas sensor has become uncritical.
Dependencies are inferred from the claim text.