- Email: [email protected]
Cold traps for vacuum systems
VACUUM Classified A b s t r a c t s
II ~
Vacuum
Apparatus
and
Auxiliaries
--
II
Contd.
t h a t causes t h e r m a l shock in m a m m a l i a n spermatozoa. T r e a t m e n t w i t h lecithin can reduce the effect of both. The effect is a t t r i b u t e d to some physical change in the cell m e m b r a n e at low t e m p e r a t u r e and a t e n t a t i v e e x p l a n a t i o n of the probable m e c h a n i s m is given. Sommaire : Les effects de milieux c o n t e n a n t du glyc6rol sur certaines cellules v i v a n t e s pr~servdes h l'dtat gel6, s o n t discutds.
28
--
APPARATUS
COMPONENTS
--
Abstract ~'o. and References
Article by J. E. Lovelock Nature I73, 10.4.]95,t 659-661
28
Techniques Useful in Evacuating and Pressurising Metal Chambers
119/II
See A b s t r a c t No. : 163/I
Seal-Off Valve for Vacuum Systems
O
120/II
United States. Details are given of a small seal-off valve which m a y be employed w i t h a d v a n t a g e where the use of a conventional valve is undesirable because of its bulkiness, and pinched-off metal t u b i n g is n o t practicable because a new piece of t u b i n g has to be soldered on to the s y s t e m each time it is evacuated. The m a i n p a r t s of the new valve are a handle and stem, b o d y and seat, and a removable b o n n e t enclosing the seat a s s e m b l y and adjacent end of the stem. The moveable seat has six p u m p i n g ports, t h r o u g h which the s y s t e m is evacuated. On completion of the p u m p i n g the stem, fitted w i t h pins engaging in t w o of the p u m p i n g ports, is used to close the valve. The b o n n e t is t h e n removed, leaving only the seat assembly in position on the pipe. To open the valve, the procedure is reversed. Sommaire : Description d ' u n e v a n n e de fermeture d o n t la poignde et l'axe p e u v e n t etre facilement enlev6s laissant seulenrent le syst~me de fermeture sur l'appareil vid6.
Use of Toggle Valves and Teflon in Hydrocarbon Analysis
Report by Anon. N BS Summary Tech. Rep. No. 1858 May 1954
121/II
See A b s t r a c t No. : l l 7 / I I
A Three-Way V a c u u m Valve United States. A t h r e e - w a y v a c u u m valve employing sliding O - r i n g seals is described. The valve has a hollow, cylindrical b o d y w i t h t w o peripheral O - r i n g s set inside it, to divide the b o d y into three equal sections. The O - r i n g s act as seals against a central piston which is slightly longer t h a n the distance between the rings. Positive seating is provided at each end of the piston stroke. The v a c u u m connections are on either side of, and in between, the O - r i n g s in the body. The s h a f t and the b o d y are extended b e y o n d the distance between t h e seals. A pin in t h e shaft engages in a helical slot in the cylinder so t h a t r o t a t i o n of the s h a f t m o v e s the piston in the axial direction. Sommaire : Description d ' u n e v a n n e a vide ~t trois passages e m p l o y a n t des j o i n ~ mobiles du t y p e ' O - r i n g ' .
O
A Magnetic Mercury Cut-Off
122/II
Note by F. S. Stein Rev. Sci. Instrum. zS, May 1954 515-516
123/II
United Kingdom. A m e r c u r y cut-off is described, in which a glass cylinder closed at b o t h ends, containing an iron bar, floats on m e r c u r y in a vertical t u b e and can be d r a w n b e n e a t h the surface by an electromagnet. The m e r c u r y displaced b y the s u b m e r g e d glass cylinder rises in the t u b e and seals off a side arm. The cut-off will seal efficiently against a 2 cm. H g pressure difference. Sommaire : Description d ' u n systbme de Iermeture a mercure p o u v a n t tenir une difference de pression de deux centim~tres de mercure,
Cold Traps for V a c u u m Systems
Note by F. W. Thompson J. Sci. Instrum. 3x, April 1954 145 124/II
United Kingdom. The U - t u b e t y p e of cold trap, i m m e r s e d in a cooling m e d i u m such as liquid air, c o m m o n l y used in v a c u u m p u m p i n g s y s t e m s to p r e v e n t v a p o u r s from diffusing back into the vessel p u m p e d , is n o t suitable in p l a n t operating at high p u m p i n g speeds. T r a p s included in such p l a n t should offer m i n i m u m o b s t r u c t i o n to the flow of the gases coupled with the m a x i m u m p r o b a b i l i t y of condensing all v a p o u r molecules reaching the trap. I n addition, t h e y should be easily cleaned and degassed, and capable of being cooled rapidly. The design of a trap, claimed to meet these requirements, is described. I t essentially consists of baffles situated in the p u m p ing line which are cooled b y conduction along a metal rod, one end of which acts as the s u p p o r t of the baffles, the other, projecting outside the pipe, being immersed in a vessel holding the cooling medium. The baffle s y s t e m consists of a series of semi-circular sheets arranged in such a m a n n e r t h a t the gases p a s s i n g t h r o u g h the pipe can no longer move along a s t r a i g h t p a t h b u t are subjected to t o r t u o u s tlow. The baffle a s s e m b l y is fitted into a flanged section of pipe which gives a clearance of 1-2 ram. all r o u n d the baffles, the pipe section being connected directly into the p u m p i n g line. The internal walls of the pipe should be polished to minimise h e a t radiation to the baffles. By w a y of example the following dimensions are given: D i a m e t e r of the pipe s e c t i o n - -
July, 1954
Vacuum Vol. I V No. 3
376
VACUUM Classified A b s t r a c t s
II - -
Vacuum
Apparatus
and
Auxiliaries
--
II
Abstract No. and References
Contd.
3 inch., thickness of the baffles--0.028-l).030 inch. A t r a p of these dinlensions has been found to have a conductance for air of 48 litres per second and the pressures measured directly above the t r a p were less t h a n 10-7 ram. Hg. The cooling m e d i u m , in t h a t instance, was liquid air. Sommaire : Un donne des d6tails sur u n pi6ge compos6 de baffles refroidds par conduction ie long d ' u n e tige de mdtal, les baffles 4 t a n t disposals dans la t u b u l u r e r61iant le systbme "t la p o m p e h vide.
O
Apparatus for Stirring a Reaction Mixture Through a Vapour-Tight Seal United States. Agitation of a liquid in a totally enclosed reaction vessel can be effected by a magnetic stirrer or, where this is inadequate, b y a mechanically driven stirrer, in which case a seal of some kind is required for the driving shaft. A k n o w n form of seal of this kind, frequently used where tile reaction vessel is kept at a reduced pressure, consists of a spherical glass joint, one p a r t of which is s t a t i o n a r y and the other r o t a t e s a b o u t the axis of tile stirrer shaft, to which it is attached. The a u t h o r describes an i m p r o v e d design of the latter type of seal which ensures s y m m e t r i c a l wearing of the seal. I n the new design the stirring rod is sealed to the joint as before, or is a t t a c h e d b y m e a n s of a r u b b e r sleeve to allow for a d j u s t m e n t or replacement. The rod is free to t u r n a b o u t its own axis b u t is held in a counter-balanced a r m of a drive which revolves it a b o u t a centre of r o t a t i o n lying on an axis of the spherical joint. As a result, inside the flask, the stirring rod in action describes a cone. "the zone of the reaction vessel covered b y the action of the rod depends on the length of the driving a r m and its height above the seal. Suitable speeds are 50-300 r.p.m. Units of this kind have operated successfully at pressures of l).05 ram. H g in the reaction vessel for long periods. The seals should be lubricated w i t h a suitable lut)ricant. Sommaire : Description d ' u n nouvel agitateur employ6 particulibrement p o u r aider des rdactions se faisant dans des syst6mes c o m p l 6 t e m e n t ferm6s.
125/II
Note by J. R. Skidmm Analyt. Chem. 26, April 1954 789-790
Experiments Jn the Design of Ceramic Electron Tubes See A b s t r a c t N o . : l l 6 / I I
126/II
Fused Vacuum-Tight, Metal-to-Ceramic, Ceramic-to-Glass, Metal-to-Glass and Metal-to-Mica Sealing by Powdered Glass Techniques See A b s t r a c t No. : 6 2 / I V
127/II
2 9 --
MISCELLANEOUS
APPARATUS
--
29
Improvements in Manostat
O
J. Poilar4 & Nat. Res. Dev. Corp. Brit. Pat 709fl19
128/1I
United Sh~.tes. A m a n o s t a t is described whic'h is capable of mcmorising, after a rest period, a pressure to which it was set in an operation, i.e. if an operation in a s y s t e m was carried out at a set pressure and discoiltinued, the m a n o s t a t will r e t u r n the s y s t e m to the previous pressure w h e n operations have been s t a r t e d again. The instrum e n t consists essentially of a cylindrical housing containing a bell-shaped float w i t h its open end dipping in mercury. The u p p e r end of the float carries sealing discs of rubber-like material which, if the float rises high enough, will seal off a nozzle projecting downwards. The nozzle c o m m u n i c a t e s v i a channels in the u p p e r p o r t i o n of the i n s t r u m e n t h o u s i n g w i t h a v a c u u m p u m p on one side and the s y s t e m to be p u m p e d on the other. On the other hand, if the float sinks down low enough, the sealing discs at its u p p e r end will close off a nozzle projecting u p w a r d s from a s t a t i o n a r y t u b e of smaller diameter t h a n the tloat and situated inside tile float. This t u b e is connected to the s y s t e m to be p u m p e d via a valve. D u r i n g initial p u m p i n g of the s y s t e m the gases p u m p e d from the s y s t e m p a s s t h r o u g h the t o p p o r t i o n of the i n s t r u m e n t housing and reach the p u m p via the nozzle projecting d o w n w a r d s . W h e n the pressure has been reached at which the m a n o s t a t is to be set the position of tile u p p e r nozzle is adjusted in such a m a n n e r t h a t the sealing disc of the float and the u p p e r nozzle come in contact. The aforementioned valve connectipg the space u n d e r n e a t h the bell is t h e n closed and t h u s t r a p s an a m o u n t of gas in t h a t space which acts as the memorising control gas. The i n s t r u m e n t is then p e r m a n e n t l y set. W h e n the s y s t e m is s h u t d o w n and opened to a t m o s p h e r i c pressure, the bell is forced down and the sealing disc, m o v i n g a w a y from the u p p e r nozzle, is pressed against the lower nozzle t h u s t r a p p i n g the control gas. On r e s t a r t i n g p u m p i n g , c o m m u n i c a t i o n between the s y s t e m and the v a c u u m p m n p will remain open until, t h r o u g h the action of the control gas, the u p p e r nozzle is closed at the set pressure value. Various e m b o d i m e n t s of the w o r k i n g principle are described. Sommaire : U n m a n o s t a t , capable de se rappeler une pression r6duite particuli6re a 6t6 d6velopp6 ; le m a n o s t a t rdadjuste le syst6me remis en marche, k la pression, ~ laquelle il a 6t6 pr6alablement r6g16.
Economical Use of a Leak Detector Spectrometer See A b s t r a c t N o . : 141/I
July, 1954
Emil Greiner Co. Brit. Pat. 706,777
129/II
Vacuum Vol. I V No. 3
377
II ~
Vacuum
Apparatus
and
Auxiliaries
--
II
Contd.
t h a t causes t h e r m a l shock in m a m m a l i a n spermatozoa. T r e a t m e n t w i t h lecithin can reduce the effect of both. The effect is a t t r i b u t e d to some physical change in the cell m e m b r a n e at low t e m p e r a t u r e and a t e n t a t i v e e x p l a n a t i o n of the probable m e c h a n i s m is given. Sommaire : Les effects de milieux c o n t e n a n t du glyc6rol sur certaines cellules v i v a n t e s pr~servdes h l'dtat gel6, s o n t discutds.
28
--
APPARATUS
COMPONENTS
--
Abstract ~'o. and References
Article by J. E. Lovelock Nature I73, 10.4.]95,t 659-661
28
Techniques Useful in Evacuating and Pressurising Metal Chambers
119/II
See A b s t r a c t No. : 163/I
Seal-Off Valve for Vacuum Systems
O
120/II
United States. Details are given of a small seal-off valve which m a y be employed w i t h a d v a n t a g e where the use of a conventional valve is undesirable because of its bulkiness, and pinched-off metal t u b i n g is n o t practicable because a new piece of t u b i n g has to be soldered on to the s y s t e m each time it is evacuated. The m a i n p a r t s of the new valve are a handle and stem, b o d y and seat, and a removable b o n n e t enclosing the seat a s s e m b l y and adjacent end of the stem. The moveable seat has six p u m p i n g ports, t h r o u g h which the s y s t e m is evacuated. On completion of the p u m p i n g the stem, fitted w i t h pins engaging in t w o of the p u m p i n g ports, is used to close the valve. The b o n n e t is t h e n removed, leaving only the seat assembly in position on the pipe. To open the valve, the procedure is reversed. Sommaire : Description d ' u n e v a n n e de fermeture d o n t la poignde et l'axe p e u v e n t etre facilement enlev6s laissant seulenrent le syst~me de fermeture sur l'appareil vid6.
Use of Toggle Valves and Teflon in Hydrocarbon Analysis
Report by Anon. N BS Summary Tech. Rep. No. 1858 May 1954
121/II
See A b s t r a c t No. : l l 7 / I I
A Three-Way V a c u u m Valve United States. A t h r e e - w a y v a c u u m valve employing sliding O - r i n g seals is described. The valve has a hollow, cylindrical b o d y w i t h t w o peripheral O - r i n g s set inside it, to divide the b o d y into three equal sections. The O - r i n g s act as seals against a central piston which is slightly longer t h a n the distance between the rings. Positive seating is provided at each end of the piston stroke. The v a c u u m connections are on either side of, and in between, the O - r i n g s in the body. The s h a f t and the b o d y are extended b e y o n d the distance between t h e seals. A pin in t h e shaft engages in a helical slot in the cylinder so t h a t r o t a t i o n of the s h a f t m o v e s the piston in the axial direction. Sommaire : Description d ' u n e v a n n e a vide ~t trois passages e m p l o y a n t des j o i n ~ mobiles du t y p e ' O - r i n g ' .
O
A Magnetic Mercury Cut-Off
122/II
Note by F. S. Stein Rev. Sci. Instrum. zS, May 1954 515-516
123/II
United Kingdom. A m e r c u r y cut-off is described, in which a glass cylinder closed at b o t h ends, containing an iron bar, floats on m e r c u r y in a vertical t u b e and can be d r a w n b e n e a t h the surface by an electromagnet. The m e r c u r y displaced b y the s u b m e r g e d glass cylinder rises in the t u b e and seals off a side arm. The cut-off will seal efficiently against a 2 cm. H g pressure difference. Sommaire : Description d ' u n systbme de Iermeture a mercure p o u v a n t tenir une difference de pression de deux centim~tres de mercure,
Cold Traps for V a c u u m Systems
Note by F. W. Thompson J. Sci. Instrum. 3x, April 1954 145 124/II
United Kingdom. The U - t u b e t y p e of cold trap, i m m e r s e d in a cooling m e d i u m such as liquid air, c o m m o n l y used in v a c u u m p u m p i n g s y s t e m s to p r e v e n t v a p o u r s from diffusing back into the vessel p u m p e d , is n o t suitable in p l a n t operating at high p u m p i n g speeds. T r a p s included in such p l a n t should offer m i n i m u m o b s t r u c t i o n to the flow of the gases coupled with the m a x i m u m p r o b a b i l i t y of condensing all v a p o u r molecules reaching the trap. I n addition, t h e y should be easily cleaned and degassed, and capable of being cooled rapidly. The design of a trap, claimed to meet these requirements, is described. I t essentially consists of baffles situated in the p u m p ing line which are cooled b y conduction along a metal rod, one end of which acts as the s u p p o r t of the baffles, the other, projecting outside the pipe, being immersed in a vessel holding the cooling medium. The baffle s y s t e m consists of a series of semi-circular sheets arranged in such a m a n n e r t h a t the gases p a s s i n g t h r o u g h the pipe can no longer move along a s t r a i g h t p a t h b u t are subjected to t o r t u o u s tlow. The baffle a s s e m b l y is fitted into a flanged section of pipe which gives a clearance of 1-2 ram. all r o u n d the baffles, the pipe section being connected directly into the p u m p i n g line. The internal walls of the pipe should be polished to minimise h e a t radiation to the baffles. By w a y of example the following dimensions are given: D i a m e t e r of the pipe s e c t i o n - -
July, 1954
Vacuum Vol. I V No. 3
376
VACUUM Classified A b s t r a c t s
II - -
Vacuum
Apparatus
and
Auxiliaries
--
II
Abstract No. and References
Contd.
3 inch., thickness of the baffles--0.028-l).030 inch. A t r a p of these dinlensions has been found to have a conductance for air of 48 litres per second and the pressures measured directly above the t r a p were less t h a n 10-7 ram. Hg. The cooling m e d i u m , in t h a t instance, was liquid air. Sommaire : Un donne des d6tails sur u n pi6ge compos6 de baffles refroidds par conduction ie long d ' u n e tige de mdtal, les baffles 4 t a n t disposals dans la t u b u l u r e r61iant le systbme "t la p o m p e h vide.
O
Apparatus for Stirring a Reaction Mixture Through a Vapour-Tight Seal United States. Agitation of a liquid in a totally enclosed reaction vessel can be effected by a magnetic stirrer or, where this is inadequate, b y a mechanically driven stirrer, in which case a seal of some kind is required for the driving shaft. A k n o w n form of seal of this kind, frequently used where tile reaction vessel is kept at a reduced pressure, consists of a spherical glass joint, one p a r t of which is s t a t i o n a r y and the other r o t a t e s a b o u t the axis of tile stirrer shaft, to which it is attached. The a u t h o r describes an i m p r o v e d design of the latter type of seal which ensures s y m m e t r i c a l wearing of the seal. I n the new design the stirring rod is sealed to the joint as before, or is a t t a c h e d b y m e a n s of a r u b b e r sleeve to allow for a d j u s t m e n t or replacement. The rod is free to t u r n a b o u t its own axis b u t is held in a counter-balanced a r m of a drive which revolves it a b o u t a centre of r o t a t i o n lying on an axis of the spherical joint. As a result, inside the flask, the stirring rod in action describes a cone. "the zone of the reaction vessel covered b y the action of the rod depends on the length of the driving a r m and its height above the seal. Suitable speeds are 50-300 r.p.m. Units of this kind have operated successfully at pressures of l).05 ram. H g in the reaction vessel for long periods. The seals should be lubricated w i t h a suitable lut)ricant. Sommaire : Description d ' u n nouvel agitateur employ6 particulibrement p o u r aider des rdactions se faisant dans des syst6mes c o m p l 6 t e m e n t ferm6s.
125/II
Note by J. R. Skidmm Analyt. Chem. 26, April 1954 789-790
Experiments Jn the Design of Ceramic Electron Tubes See A b s t r a c t N o . : l l 6 / I I
126/II
Fused Vacuum-Tight, Metal-to-Ceramic, Ceramic-to-Glass, Metal-to-Glass and Metal-to-Mica Sealing by Powdered Glass Techniques See A b s t r a c t No. : 6 2 / I V
127/II
2 9 --
MISCELLANEOUS
APPARATUS
--
29
Improvements in Manostat
O
J. Poilar4 & Nat. Res. Dev. Corp. Brit. Pat 709fl19
128/1I
United Sh~.tes. A m a n o s t a t is described whic'h is capable of mcmorising, after a rest period, a pressure to which it was set in an operation, i.e. if an operation in a s y s t e m was carried out at a set pressure and discoiltinued, the m a n o s t a t will r e t u r n the s y s t e m to the previous pressure w h e n operations have been s t a r t e d again. The instrum e n t consists essentially of a cylindrical housing containing a bell-shaped float w i t h its open end dipping in mercury. The u p p e r end of the float carries sealing discs of rubber-like material which, if the float rises high enough, will seal off a nozzle projecting downwards. The nozzle c o m m u n i c a t e s v i a channels in the u p p e r p o r t i o n of the i n s t r u m e n t h o u s i n g w i t h a v a c u u m p u m p on one side and the s y s t e m to be p u m p e d on the other. On the other hand, if the float sinks down low enough, the sealing discs at its u p p e r end will close off a nozzle projecting u p w a r d s from a s t a t i o n a r y t u b e of smaller diameter t h a n the tloat and situated inside tile float. This t u b e is connected to the s y s t e m to be p u m p e d via a valve. D u r i n g initial p u m p i n g of the s y s t e m the gases p u m p e d from the s y s t e m p a s s t h r o u g h the t o p p o r t i o n of the i n s t r u m e n t housing and reach the p u m p via the nozzle projecting d o w n w a r d s . W h e n the pressure has been reached at which the m a n o s t a t is to be set the position of tile u p p e r nozzle is adjusted in such a m a n n e r t h a t the sealing disc of the float and the u p p e r nozzle come in contact. The aforementioned valve connectipg the space u n d e r n e a t h the bell is t h e n closed and t h u s t r a p s an a m o u n t of gas in t h a t space which acts as the memorising control gas. The i n s t r u m e n t is then p e r m a n e n t l y set. W h e n the s y s t e m is s h u t d o w n and opened to a t m o s p h e r i c pressure, the bell is forced down and the sealing disc, m o v i n g a w a y from the u p p e r nozzle, is pressed against the lower nozzle t h u s t r a p p i n g the control gas. On r e s t a r t i n g p u m p i n g , c o m m u n i c a t i o n between the s y s t e m and the v a c u u m p m n p will remain open until, t h r o u g h the action of the control gas, the u p p e r nozzle is closed at the set pressure value. Various e m b o d i m e n t s of the w o r k i n g principle are described. Sommaire : U n m a n o s t a t , capable de se rappeler une pression r6duite particuli6re a 6t6 d6velopp6 ; le m a n o s t a t rdadjuste le syst6me remis en marche, k la pression, ~ laquelle il a 6t6 pr6alablement r6g16.
Economical Use of a Leak Detector Spectrometer See A b s t r a c t N o . : 141/I
July, 1954
Emil Greiner Co. Brit. Pat. 706,777
129/II
Vacuum Vol. I V No. 3
377