Improvements in Air Compressors.
Year: 1898

page_text: Date of Application, 10th Feb., 1898
Complete Specification Left, 22nd Oct., 1898-Accepted, 3rd Dec., 1898
Improvements in Air Compressors.
I, MAX KAUFHOLD, of 65, Worringerstrasse, Düsseldorf, in the German Empire,
Engineer, do hereby declare the nature of this invention to be as follows:-
This invention relates to improvements in air compressors.
Air compressors wherein the escape of the compressed air is effected through
back pressure or check valves, possess the disadvantage that they only work satis-
factorily at moderate speeds as the valves when the machines are working at a high
speed have not returned to their seats in consequence of inertia when the piston
starts its return stroke and are thus suddenly forced back by the back pressure of
the air. The speed of such compressors must, therefore, be confined within
moderate limits if rapid wear of the valves is to be obviated.
Now, the object of this invention is to avoid the back pressure action and to this
end the communication between the check valves and the interior of the cylinder
is interrupted by the piston when the said valves must close and this interruption
is continued until the valves have been returned to their normal position. With
this arrangement the machines can work quietly at a higher velocity than hereto-
fore.
In carrying out my invention I advantageously arrange a number of back pres-
sure or check valves in the path of the piston and at each end of the cylinder in
such a manner that they are one after the other cut off from communication with
the interior of the cylinder by the piston. A common pressure chamber with an
outlet pipe is arranged between the valves at the two ends of the cylinder.
If, now, it be assumed that the piston has arrived at the end of its stroke to the
right, and that the cylinder has been thereby filled with air either through the
medium of piston valves, rotary valves, etc., when the piston makes its return stroke
to the left, the air drawn into the cylinder is compressed. As soon as the pressure
in the cylinder becomes slightly greater than that in the pressure chamber, the
valves open, and each valve remains open until the piston begins to cut off com-
munication between it and the cylinder; it is then returned to its seat by its spring.
By these means the valves are closed before the piston commences its return stroke.
In consequence of the position of the valves at the ends of the cylinder they
are closed for long periods with relatively short piston strokes.
Instead of the step-like arrangement of the valves for effecting their successive
closing, the said valves can be arranged in a row so as to be simultaneously closed.
By making the length of the piston sufficient, two rows of valves arranged one
behind the other can be employed at each end of the cylinder.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.

page_text: I, MAX KAUFHOLD, of 65, Worringerstrasse, Düsseldorf, in the German Empire,
Engineer, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement:-
This invention relates to improvements in air compressors.
Air compressors wherein the escape of the compressed air is effected through
back pressure or check valves, possess the disadvantage that they only work satis-
factorily at moderate speeds as the valves when the machines are working at a high
speed have not returned to their seats in consequence of inertia when the piston
starts its return stroke and are thus suddenly forced back by the back pressure of
the air. The speed of such compressors must, therefore, be confined within
moderate limits if rapid wear of the valves is to be obviated.
Now, the object of this invention is to avoid the back pressure action and to this
end the communication between the check valves and the interior of the cylinder
is interrupted by the piston when the said valves must close and this interruption
is continued until the valves have been returned to their normal position. With
this arrangement the machines can work quietly at a higher velocity than hereto-
fore.
In the accompanying drawing :-
Figure 1 is a longitudinal vertical section of the upper part of an air compressor
having my improvements applied thereto.
Figure 2 is a diagrammatic view illustrating the relative positions of the valves,
and
Figure 3 is a diagram shewing a part of the path of the crank pin and illustrat-
ing the intervals of time during which the valves are cut off from communication
with the cylinder.
The edge of the piston K which works in the compressor cylinder I is indicated
by the broken line in the diagrammatic view, Figure 2; a number of back
pressure or check valves A, B, C are arranged side by side transversely to the
longitudinal axis of the cylinder in the path of the piston K and at each end of
the cylinder in such a manner that they are one after the other cut off from com-
munication with the interior of the cylinder I by the piston. A common pressure
chamber with an outlet pipe d is arranged between the valves at at the two ends of
the cylinder (in Figure 1 only one valve is shewn at each end of the cylinder
although it will be obvious that any desired number can be employed).
If, now, it be assumed that the piston K has arrived at the end of its stroke to
the left (as shewn in Figure 1) and that the cylinder has been thereby filled with
air either through the medium of piston valves, rotary valves, etc., then when the
piston makes its return stroke to the right the air drawn into the cylinder is com-
pressed. As soon as the pressure in the cylinder becomes slightly greater than that
in the pressure chamber 1, the valves A, B, C open, and each valve remains open
until the piston begins to cut off communication between it and the cylinder; it is
then returned to its seat by its spring. By these means the valves are closed
before the piston commences its return stroke. This operation is illustrated
diagrammatically in Figure 2 from which it will be seen that the edge -b of the
piston first reaches the valve A so that the valve is closed by its spring as soon as
its opening is contracted by the piston. The valves B and C are similarly closed in
succession. The valve C is however only cut off as described for a length of time
sufficient to effect its closing whilst the others are cut off as described for intervals
of time corresponding to their positions.

page_text: In consequence of the position of the valves at the ends of the cylinder I they
are closed for long periods with relatively short piston strokes as is clearly shewn
in Figure 3 where the line o, o indicates the path of the crank pin and the periods
during which the valves A, B, C, are cut off are indicated by the lengths of the
lines A, B, C respectively.
Instead of the step-like arrangement of the valves for effecting their successive
closing, the said valves can be arranged in a row so as to be simultaneously closed.
By making the length of the piston sufficient, two rows of valves arranged one
behind the other can be employed at each end of the cylinder.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is;-
An air compressor wherein the pressure valves are so arranged in the path of the
piston working in the compressor cylinder that they are cut off from the inside of
the said cylinder by the piston towards the end of its compression stroke, the said
valves being thereby closed independently of the air above them and in the cylinder,
substantially as hereinbefore described.
dow of Databov 1800
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.