Rough-vacuum pump of dry type

Abstract

A rough-vacuum pump of dry type includes a duct formed in the stator and of which an inlet orifice is intended to be connected to at least one source of purge gas and of which at least one outlet orifice communicates with the last pumping stage communicating with the delivery and a device for injecting a heated purge gas including a heating device to at least partly heat the purge gas injected into the duct to a temperature higher than 40° C.

1 .- 15 . (canceled) 
     
     
         16 . A rough vacuum pump of dry type, comprising:
 a stator comprising at least two pumping stages mounted in series between an intake and a delivery of the vacuum pump;   two rotors arranged in the at least two pumping stages, the rotors being borne by shafts configured to rotate synchronously in opposite directions in order to entrain a gas that is to be pumped between the intake and the delivery;   a duct formed in the stator and of which an inlet orifice is configured to be connected to at least one source of purge gas and of which at least one outlet orifice communicates with the last pumping stage communicating with the delivery; and   a device to inject a heated purge gas comprising a heating device configured to at least partly heat the purge gas injected into the duct to a temperature higher than 40° C.   
     
     
         17 . The vacuum pump according to  claim 16 , wherein the outlet orifice of the duct communicates with at least one shaft passage of the stator communicating with the last pumping stage via a clearance between the shaft and the shaft passage. 
     
     
         18 . The vacuum pump according to  claim 17 , wherein the duct communicates with the two shaft passages of the pumping stage. 
     
     
         19 . The vacuum pump according to  claim 18 , wherein the duct has a linear portion connected to the inlet orifice, the linear portion being interposed between the two shafts and communicating with two lune shaped cavities, each cavity communicating with a respective shaft passage. 
     
     
         20 . The vacuum pump according to  claim 17 , further comprising at least one sealing device interposed between a lubricated bearing of the vacuum pump and the pumping stage to seal the shaft passage, wherein the duct communicates with the shaft passage between the sealing device and the pumping stage. 
     
     
         21 . The vacuum pump according to  claim 16 , wherein the device to inject a heated purge gas further comprises:
 a temperature probe in fluidic communication with the purge gas heated by the heating device, and   a controller connected to a power supply of the heating device and to the temperature probe, to control the temperature of the purge gas.   
     
     
         22 . The vacuum pump according to  claim 16 , wherein the heating device comprises a heating cartridge comprising resistive heating elements arranged in a tube between an inlet and an outlet of the tube in which a purge gas is configured to circulate in order to become heated. 
     
     
         23 . The vacuum pump according to  claim 16 , wherein the device to inject a heated purge gas is configured so that the portion of the flow of purge gas that is heated is between 10% and 100% of the purge gas injected into the duct. 
     
     
         24 . The vacuum pump according to  claim 16 , wherein the device to inject a heated purge gas is configured so that the flow rate of the heated purge gas is greater than 33.8 Pa·m 3 /s. 
     
     
         25 . The vacuum pump according to  claim 16 , wherein the heating device is configured to heat the purge gas to a temperature lower than 200° C. 
     
     
         26 . The vacuum pump according to  claim 16 , further comprising a cooling circuit at least partially incorporated into the stator and surrounding the duct. 
     
     
         27 . The vacuum pump according to  claim 16 , further comprising a bearing purge duct formed in the stator, configured to be connected to a source of purge gas, and opening into at least one bearing of the vacuum pump. 
     
     
         28 . The vacuum pump according to  claim 16 , further comprising at least one stage purge duct formed in the stator, configured to be connected to a source of purge gas, and opening into an inter stage canal connecting the outlet of one pumping stage to an inlet of the following pumping stage. 
     
     
         29 . The vacuum pump according to  claim 16 , further comprising a distributor configured to be coupled to a source of purge gas and to the bearing purge duct, to the stage purge duct(s), to the duct and to a pipe connected to an outlet of the heating device. 
     
     
         30 . The vacuum pump according to  claim 29 , further comprising an additional heating device configured to heat at least part of the purge gas distributed by the distributor.