and Regulating Appliance for Apparatus for Compressing Vapours of Ammonia and other Volatile Liquids.
Year: 1897

page_text: Date of Application, 12th Jan., 1397-Accepted, 27th Feb., 1897
COMPLETE SPECIFICATION.
Safety and Regulating Appliance for Apparatus for Compressing
Vapours of Ammonia and other Volatile Liquids.
I, THOMAS BELL LIGHTFOOT, of 35 Queen Victoria Street, in the City of
London, Engineer, do hereby declare the nature of this invention (as communicated
to me from abroad by Gesellschaft für Lindes Eismaschinen, of Wiesbaden,
Germany) and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement :-
In compressors for compressing vapours of ammonia and other volatile liquids,
such as are used in refrigerating apparatus, safety valves are provided for preventing
excessive pressure by allowing a portion of the vapour to escape when the pressure
attains a certain maximum degree.
The present invention has for its object to obviate the loss of volatile fluid which
occurs by such escape through the safety valve. For this purpose, the dead space
of the compressing cylinder is made to communicate with a closed chamber
containing a safety valve opening outwards, which is covered by a body of
non-volatile liquid, such as oil, so that when the pressure in the cylinder exceeds
the prescribed limit, such pressure in acting upon the said liquid will force open
the safety valve thus causing a portion of the liquid to escape, while preventing the
escape of the volatile liquid.
The same apparatus can also be employed for regulating the work performed by
the compressor by varying the quantity of liquid in the chamber, as will be
presently explained.
The communication between the compressor and the chamber is provided with a
cock or valve by which the said communication can be cut off.
If this cock or valve is closed, the compressor will work in the ordinary manner;
if on the other hand the cock is open the dead space of the cylinder is increased by
the space in the chamber which space can be varied by introducing more or less
liquid by this means the degree of compression and consequently the duty
performed by the compressor can be varied, and the degree of compression can be
reduced to such an extent that the compressor though still in motion would not
perform any useful work.
The accompanying drawing shews a part section of a compressing cylinder A
with the said invention applied thereto.
B is the closed vessel, connected to the cylinder by a pipe C containing a shut
off cock C; in the bottom of the vessel is provided a safety valve D closed by a
spring regulated by a screw so to allow the valve to open when the maximum limit
of pressure is attained. The vessel is filled to any required extent with liquid
through a branch pipe E provided with a stop cock.
The outer casing F of the safety valve is put in communication with the suction
valve chamber G of the compressor.
On the maximum prescribed compression being exceeded in the cylinder A, the
valve D will be forced open and a portion of the liquid will escape, the pressure
being reduced in proportion to the resulting enlargement of the part of the
capacity of B above the liquid.
The escaping liquid will pass into the valve chamber G and will be drawn into
the cylinder again at the following suction stroke and will flow thence back into
the vessel B.

page_text: If the device is to be used for regulating the duty performed by the compressor,
liquid is introduced into or discharged from the vessel B so as to vary the capacity
of the dead space as before described. If the regulation be only required to the
extent that the compressor shall either perform full duty, or work idle, no safety
valve and liquid are required in the vessel B, such regulation being effected by
either opening the cock C₁ in the one case, or closing it in the other.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
;-
1. The combination with a compressor of a closed vessel or chamber containing
a safety valve that is covered by a body of liquid, so that on a certain pressure
being exceeded in the compressor such pressure in acting on the liquid is made to
force the valve open and allow the liquid to escape more or less through the same,
while preventing the escape of the vapour of volatile fluid that is being compressed,
substantially as described.
2. The combination with a compressor of a closed vessel or chamber commu-
nicating with the dead space of the compressor, and whose capacity can be varied
by introducing more or less liquid, so as to vary the capacity of the said dead
space substantially as and for the purpose described.
3. The combination with a compressor of a closed vessel or chamber commu-
nicating with the dead space by a passage provided with a shut off valve, by
closing or opening which the compressor is caused either to work with full duty, or
to work idle, substantially as described.
Dated th: 10 1
ABEL & IMRAY,
Agents for the Applicant.