An air-flow meter for milking machines, comprising an enclosed
housing with a connection to a line that is to be tested for flow
and pressure and with an air-intake mechanism with a variable cross-section.
The air-intake mechanism is an air intake with a slot-shaped cross-section.
A rotating cylinder is accommodated inside the housing and operates
in conjunction with the slotted intake. The cylinder has a breach
that tapers out along a considerable length of its circumference.
The longitudinal axis of the intake parallels the axis the cylinder
rotates around, the free cross-section of the intake is only a fraction
of length of the breach along the circumference of the cylinder,
and any area of the breach can be aligned with the air intake by
rotating the cylinder.
1. An air-flow meter for milking machines, comprising a housing
with a connection to a line to be tested for flow and pressure of
the line and air-intake means comprising an air intake with a slot-shaped
cross-section, a rotatable cylindrical slide valve disposed inside
the housing and rotatable about an axis, wherein the slide valve
has a gradually enlarging opening extending along a length of its
circumference, wherein a longitudinal axis of the intake is parallel
to the axis of rotation of the slide valve, and wherein the slide
valve is movable relative to the intake to position any portion
of the opening in alignment with the intake to define an effective
free cross-section of the intake which varies from a minimum to
a maximum portion thereof.
2. The air-flow meter as in claim 1 wherein the air intake is
radially movable relative to the housing.
3. The air-flow meter as in claim 2 further comprising springs
for biasing the intake toward the slide valve.
4. The air-flow meter as in claim 1 further comprising a transmission
coupled to the slide valve.
5. The air-flow meter as in claim 4 further comprising a drive
motor coupled to the transmission.
6. The air-flow meter as in claim 1 further comprising a first
angular position sensor associated with the slide valve.
7. The air-flow meter as in claim 6 further comprising a second
angular position sensor associated with the motor.
BACKGROUND OF THE INVENTION
The invention concerns an air-flow meter for milking machines.
The meter comprises an enclosed housing with a connection to a line
that is to be tested for flow and pressure. The housing has an air-intake
mechanism with a variable cross-section.
A milk-flow meter of this type is known from German OS 1 757 838.
It measures the output of a vacuum pump, a component of the machine,
subject to various operating conditions. These measures must be
repeated at various intervals, and their results must comply with
domestic regulations in various countries.
The air-intake mechanism in the known meter consists of calibrated
bores and of rotating disks that block them off. Since the disks
are subject to considerable pressure, they are difficult to rotate.
Furthermore, only discontinuous adjustments can be carried out,
and no interpolations are possible. Finally, the bores can clog
up and contaminate the results.
SUMMARY OF THE INVENTION
The object of the present invention is accordingly an air-flow
meter for milking machines wherein the flow of air can be adjusted
easily and continuously.
This object is attained in accordance with the present invention
in a milking machine of the aforesaid type by the characteristics
now described. The air-intake mechanism is an air intake with a
slot-shaped cross-section. A rotating slide valve is accommodated
inside the housing and operates in conjunction with the slotted
intake. The slide valve has an opening that tapers out as it extends
along its circumference. The longitudinal axis of the intake parallels
the axis the slide valve rotates around. The free cross-section
of the intake is only a fraction of the length of the opening along
the circumference of the slide valve. Any area of the opening can
be aligned with the air intake by rotating the slide valve.
Since there is little friction between the rotating slide valve
and the air intake, the amount of air flowing through the machine
can be precisely and rapidly adjusted. The tapering opening makes
it possible to continuously vary the width of the port by rotating
the slide valve. Since the air-intake mechanism will not clog up,
the results will not be contaminated.
The air intake in one practical embodiment of the invention is
positioned radially movable with respect to the housing. The slot
is accordingly positioned free of clearance in relation to the rotating
The seal is created between the air intake and the rotating slide
valve in one embodiment because springs force the intake toward
the slide valve. This system also maintains the surface of the slide
The rotating slide valve in another advantageous embodiment is
coupled to a transmission. This design enables even more precise
and easier adjustment.
The transmission in another advantageous embodiment is coupled
to a motor. The procedure can be automated by providing the motor
with controls. Since the meter is so easy to adjust, the motor can
be small and use little electricity. This feature is a particular
advantage because it is usually difficult to supply electricity
to the site from outside, and the motor must be battery-powered.
The battery can be accommodated in the meter's controls for example.
The controls can be integrated into the housing along with the battery
An angular position sensor can be associated with the rotating
slide valve and another with the motor.
One embodiment of the invention will now be specified with reference
to the drawing, wherein
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a section through the air-flow meter,
FIG. 2 is a section along the line II--II in FIG. 1 and
FIG. 3 is a view of the area X in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
The housing 1 illustrated in FIG. 1 has a line connection 2 and
an air-intake mechanism 3. Air-intake mechanism 3 comprises an air
intake 4 on the outside of housing 1 and a rotating slide valve
5 accommodated in the housing and associated with the intake. The
circumference of the slide valve is interrupted by an opening 6.
Opening 6 tapers out as it extends along the circumference of the
slide valve. Any area of the opening can be aligned with air intake
4 by rotating slide valve 5. Springs 12 can force the intake toward
the slide valve. Slide valve 5 can, as will be evident from FIG.
2 be rotated by a motor 7 by way of a transmission 8. A sensor
9 communicates the instant angle of rotation of slide valve 5 to
unillustrated controls. The controls accommodate a battery that
powers motor 7. Associated with motor 7 is another angular position
sensor 10 that mediates fine adjustment of slide valve 5. Associated
with line connection 2 is a sampling connection 11. An unillustrated
vacuum gauge communicates with sampling connection 11 and transmits
pressure data to the controls.
As will be evident from FIG. 3 the free cross-section of air intake
4 along the circumference of rotating slide valve 5 is only a fraction
of the length of opening 6. Slide valve 5 can accordingly be rotated
to various angles to align any area of opening 6 with air intake
4. The continuous taper of opening 6 along so much of the circumference
of slide valve 5 allows very fine adjustment of the flow of air.
Associated with each instantaneous angle of rotating slide valve
5 is a specific level of air flow and difference in pressure. The
associated data are entered in the controls. The level of the vacuum
at sampling connection 11 is also processed in the controls, and
slide valve 5 rotated to establish a prescribed level. A program
for the entire measurement sequence is stored in the controls, and
the procedure can be entirely automatic. The results can be displayed
and filed. Since there is no human intervention, the results will
be free of any errors deriving from manual control.