Vacuum pump incorporating safety device and manufacturing method thereof

Abstract

A safety device for a vacuum pump, arranged to be associated with a duct putting the interior of the casing of the vacuum pump in communication with the outside environment, The safety device comprises a breakable member ( 3 ), which breaks when subjected to a pressure, which is at least equal to a predetermined threshold (p break ) chosen so that the member breaks in case when an overpressure could damage the pump, and remains unbroken at operating pressures during normal operation of pump.

1 . A safety device for a vacuum pump having a casing, a first gas inlet port, a second gas outlet port, one or more pumping stages pumping gas from the first port to the second port and a third port of a duct communicating the interior of the casing with the outside environment, the safety device, which associates with the third port comprising:
 a body ( 1 ) with an axial through-hole ( 1   c ) for putting the interior of the vacuum pump casing in communication with the outside environment; and   a breakable member ( 3 ) closing said axial through-hole ( 1   c ), which breaks when a predetermined pressure threshold (p break ) is exceeded.   
     
     
         2 . The safety device as claimed in  claim 1 , wherein said body is constructed so as to maintain its structural integrity up to a pressure higher than said threshold (p break ). 
     
     
         3 . The safety device as claimed in  claim 1 , wherein said predetermined threshold (p break ) is lower than the minimum pressure (p max ) at which the components of the vacuum pump become damaged. 
     
     
         4 . The safety device as claimed in  claim 3 , wherein said predetermined threshold (p break ) is lower than the maximum pressure (p min ) to which the components of the vacuum pump are subjected to storage, transportation, installation and normal operation. 
     
     
         5 . The safety device as claimed in  claim 4 , wherein said predetermined threshold (p break ) is in a range of 1.5 to 3.0 bars and preferably is about 2.0 bars. 
     
     
         6 . The safety device as claimed in  claim 1 , wherein said breakable member ( 3 ) is retained within said body ( 1 ) by a Seeger retaining ring ( 5 ), preferably with the interposition of a spacer ring ( 7 ). 
     
     
         7 . The safety device as claimed in  claim 1 , further comprising a gasket ensuring vacuum tightness of said safety device at pressures lower than said predetermined threshold (p break ). 
     
     
         8 . The safety device as claimed in  claim 7 , wherein said gasket is integrated into said breakable member ( 3 ). 
     
     
         9 . The safety device as claimed in  claim 1 , wherein said breakable member ( 3 ) is integrally formed with said body ( 1 ). 
     
     
         10 . The safety device as claimed in  claim 1 , wherein said breakable member comprises a membrane ( 3 ). 
     
     
         11 . The safety device as claimed in  claim 10 , wherein said membrane ( 3 ) comprises a thicker circumferential portion ( 3   a ) and a thinner central portion ( 3   c ), preferably connected by a peripheral portion ( 3   b ) of intermediate thickness. 
     
     
         12 . The safety device as claimed in  claim 11 , wherein said central portion ( 3   c ) of said membrane ( 3 ) has a thickness in the range of 0.01 to 0.2 mm, and preferably of about 0.1 mm. 
     
     
         13 . The safety device as claimed in  claim 8 , wherein said membrane has a substantially uniform thickness in the range of 0.01 to 0.2 mm and preferably of about 0.1 mm. 
     
     
         14 . The safety device as claimed in  claim 13 , wherein said membrane ( 3 ) has a diameter in the range 30 to 40 mm. 
     
     
         15 . The safety device as claimed in  claim 11 , wherein said membrane ( 3 ) has a diameter in the range 30 to 40 mm and said central portion ( 3   c ) of said membrane has a diameter in the range 12 to 17 mm. 
     
     
         16 . The safety device as claimed in  claim 15 , wherein said membrane ( 3 ) is made of Viton® or similar elastomeric material. 
     
     
         17 . A vacuum pumping system having a vacuum pump with at least one casing, a first inlet gas port, a second outlet gas port, one or more pumping stages for pumping the gas from the first port to the second port, and a third port of a duct communicating the interior of the casing with the outside environment, the system comprising:
 a safety device associated with the third port, said safety device comprising a body ( 1 ) with an axial through-hole ( 1   c ) communicating the interior of the vacuum pump casing with the outside environment; and   a breakable member ( 3 ) closing said axial through-hole ( 1   c ), which breaks when a predetermined pressure threshold (p break ) is exceeded.   
     
     
         18 . The vacuum pumping system as claimed in  claim 17 , wherein said predetermined threshold (p break ) is lower than the minimum pressure (p max ) at which the components of the vacuum pump become damaged. 
     
     
         19 . The vacuum pumping system as claimed in  claim 17 , wherein said body maintains its structural integrity up to a pressure higher than said threshold (p break ). 
     
     
         20 . The vacuum pumping system as claimed in  claim 17 , wherein said vacuum pump is an oil rotary vacuum pump ( 10 ) and said safety device is associated with the port ( 36 ) of an oil supply duct of said oil pump.