Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
:~04~L37~
This invention relates to a piston pump comprising a
cylinder, a first piston reciprocable in the cylinder from one
end thereof and arranged to shut off an inlet in the cylinder
by means of its movement, a second piston preferably resiliently
connected to the other end of the cylinder to be reciprocable
in the cylinder and arranged to shut o~f an outlet by means of `
its movement.
Object of the invention is to show a pump which is
especially fit for pumping concrete. The pumping of concrete
presents a number of particular problems. In the first place ~
concrete is difficult to pump on account of the heavy consistency. ;
Secondly there are always lumps in concrete, which easily
cause clogging up o~ pumps and pipes. Finally the setting of
the concrete presents special problems in connection with
concrete remaining in the pump system after it has been in
operation.
In the known technique of transporting concrete by
. I .
pumping are used rotating wing or centrifugal pumps, the
rotors of which are of extremely simple and regular construction,
and the individual rotor does not fill up all of the surrounding
pump housing so that some of the pumped material will pass the
rotor without having been in contact with it, cf. the technique
known from slurry pumps or mud pumps. As a rule pumping takes
place through rigid pipes having a relatively large internal
space, and it is common to clean the pipe and pumping system
after use by pumping water and perhaps sponges through the
pipes. These known pumps cannot achieve a very great pressure
height because of the construction of the rotor, and therefore
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~4~37~
it is impossibl~ to pump up the concrete higher than to the
- third floor with these pumps.
It is also known to use pis-ton pumps with valves
: for the pumping of concrete. If such pumps are used for
pumping of concrete the valves will cause problems when
:: cleaning the pumps. It will thus be difficult to pump
. sponges through the pumps. Furthermore, these known pumps
~ .
. work with a very big length of stroke which means that the
:. pumps are rather awkward.to handle and will therefore have
to be mounted on a truck. The pumps work with a very big
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length of stroke because they, on account of difficulties
i with tightening, are provided with rubber pistons which
~ only stand slow piston velocities, and which pistons have
;j to have a relatively small diameter in order to avoid de-
:~ for~ation.
~! `
.. ~ From the description of British Patent No.
. 301610 to Olaf Aage Ernst Jacobsen dated October 26, 1927,
l is known a pump of the mentioned kind, which, however, has
.::i the disadvantage that the second piston has a limited
'~
:5 motion.
According to the invention there is provided a .
1 piston pump comprising a cylinder having a side wall and
.~ opposite end walls, a first piston reciprocable in the
.1 cylinder from one end thereof and arranged to open and close an
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```.. ~l inlet in the side wall of the cylinder during its movement, .~
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4 37~
and a second piston reciprocable in the cylinder and arranged
to open and close an ou-tlet in the side wall of the-cylinder.
Resilient means is provided coupling the second piston
with the adjacent end wall of the cylinder and is adapted to
extend to allow the second piston to be moved beyond said
outlet by suction to a position in which the inner end of
the second piston is at least flush with said inlet.
The pump according to the invention is highly
suitable for pumping of high viscose mediums, like for
instance concrete. When thus the second piston follows
the first piston in the movement towards the inlet under
pre-stressing, then the second piston will yield a power-
ful suction the moment that the inlet is opened. The pump
is of simple construction and has no valves, and it is
therefore easy to clean. Furthermore it is possible in
the pump to apply non-deformable pistons, which means that
it will be possible to pump the concrete up to big heights,
for example, to the tenth floor. It is further possible to
design such a pump with considerably smaller dimensions than
those~of the known piston pumps, as the relation between
bore and length of stroke may be within the scale 1:1.
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~)4~37~
:- In -the cons-truction accordin~ to British Pa-tent
No. 301610 the second piston cannot follow the first piston
with the two pis-ton heads abutting each other all the way
to that spot where the abutting surface will be placed
on a level with the inlet or a part of it. Consequently,
. no essential suction can be achieved in connection with
"T the retrograde movement of the second piston.
An embodiment of the present invention will now
be described by way of example, with reference to the
;~ accompanying drawings, in which
fig. 1 illustrates a pump according to the in-
.. , vention, as viewed partly in section and
'.! schematically,
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.~ fig. 2 the same with both pistons in one of the
:. . extreme positions, and
fig. 3 the same with the pistons in the other
'':! ' extreme position.
In fig. 1 is illustrated a pump cylinder 1 with apiston 2, which is operated reciprocatingly by means of a piston
rod 3. The bottom is thus to the left and the top to the right
l in the drawing. In the top of the cylinder is embedded an
!,1 axially movable opposed piston 4, which through a compression
. and tension spring 5 is attached to the top cover 6 of the cylinder,
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~)4137C~
in which there is a vent hole 7. In the cylinder 1 there is
otheLwise designed an inlet 8 and an outlet 9, cf. the arrows.
The pump operates in the following manner. When the
piston 2 is moved towards the top of the cy~Linder, the flowable
material which is between the piston heads, and which may be
air, slurry etc., will be pressed out through the outlet 9
under compression o~ the spring 5. The extreme position is
shown in fig. 2. When the piston 2 is then moved back towards
the bottom position, the opposed piston 4 will follow on account
of the compression spring power, until the outlet 9 is shut off. ;
In the continued movement a negative pressure in the space
. :,
~ between the piston heads will result, whereby the opposed
... . .
piston 4 will be drawn out besides its neutral position, i.e.
the position in which the spring is tensionless. Hereby one
could be tempted to believe, that it is a necessary condition,
that the opposed piston 4 must in this neutral position shut
off for the outlet 9, but this is still not quite the case,
because the piston possesses a certain inertia. The piston
2 will cause a downwards directed power on the opposed piston
4 as long as the space between the pistons is shut off.
When the inlet 8 is opened by the downward movement of the
piston 2, material will flow into the pump compartment 10
between the pistons, where there is a negative pressure. The
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i extreme position is shown in fig 3. The opposed piston 4 will
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;i now be under influence of a tension towards the top by the
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j spring 5, whereby the opposed piston will contribute to material
being sucked into the pump ¢ompartment 10. When the piston
2 is then moving towards the top there may in principle be a
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~04137~
risk, that some ma-terial will be pressed back through the inlet
8, i.e. out of the pump compar-tment 1~, be~ore the inlet 8 is
shut off by the piston 2. However, i-t has proved to be possible
to dimension the single parts in such a manner, that both pistons
have in this situation nearly the same speed towards the right,
i.e. towards the top of the cylinder, and in this manner a good
efficiency of the pump has successfully been attained. The
pump shown in-the drawing has proportions correspondlng to a
prototype, which has proved excellent pumping properties in
pumping concrete.
The piston 2 may through the piston rod be operated
by a pneumatic, double-actiny compression cylinder, which may be
controlled by a known control equipment and furthermore be
provided with safety valves. It may likewise be advantageous,
if this control equipment is arranged for modification of the
frequency, which may then be adapted to the material having to
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be pumped.
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