In a flow meter, especially for liquid cooling media in injection
molds, comprising a housing with an inlet and outlet conduit and
inside the housing a piston that is slidable against the force of
an axially acting spring by the pressure of the fluid flowing through
the housing in such a way that the displacement of the piston takes
place in dependence upon the flow rate and is indicated through
a window, provision is made, to attain a high measuring accuracy
with a simple construction, for a helical spring (22) that is guided
in extension of the inlet conduit (2) in an axial direction to be
disposed in such a way that the entering fluid is transported around
the centrically disposed helical spring (22).
What is claimed is:
1. A flow meter, especially for liquid cooling media in injection
molds, comprising, a housing with an inlet and outlet conduit, a
piston slidable inside the housing against a force of an axially
acting spring caused by pressure from a fluid flowing through the
housing, a displacement of the piston being dependent upon a flow
rate of the fluid and indicated through a window; wherein a helical
spring is arranged in an extension of the inlet conduit in an axial
direction so that entering fluid is transported around the centrically
disposed helical spring, wherein the piston (24) is formed conically
and disposed in a conical recess (25), wherein the fluid, after
passing an interspace between the recess (25) and the piston (24),
flows into an expansion chamber which has a cross-section greater
than that of the recess (25).
2. A flow meter according to claim 1 wherein the expansion chamber
(26) is encompassed at least partly by a window (5).
3. A flow meter according to claim 1 wherein the outlet conduit
(3) is disposed in an axial extension of the helical spring (22).
4. A flow meter according to claim 3 wherein a counter bearing
or guide element (15) for the helical spring (22) is disposed on
a shoulder of the outlet conduit (3), said shoulder being provided
with radial openings (19) so that the fluid can enter from the expansion
chamber (26) into the outlet conduit (3).
5. A flow meter according to claim 1 wherein a center housing
part (4) is threaded so that the flow meter can be screwed directly
onto a manifold (31).
6. A flow meter according to claim 1 wherein the outlet conduit
(3) has a flow adjustment valve (28 33) disposed downstream from
7. A flow meter according to claim 6 wherein the adjustment valve
is a ball valve (28).
8. A flow meter according to claim 7 wherein the adjustment valve
is a plug valve.
9. A flow meter according to claim 8 wherein the plug valve (33)
has a valve seat (34) and a valve lifter (35) SO that the valve
lifter (35) is axially movable relative to the valve seat (34) by
an external knurled nut (38).
10. A flow meter according to claim 1 wherein the piston has an
assigned electro-optical position reading device.
11. A flow meter according to claim 10 wherein the electro-optical
position reading device is formed by a luminous source or luminous
source field and a photoelectric cell or photoelectric cell field.
12. A flow meter according to claim 1 wherein the helical spring
(22) is arranged in an extension (21), which is slidably engaged
in the conical piston (24).
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a flow meter, especially for
liquid cooling media in injection molds, comprising a housing with
an inlet and outlet conduit and inside the housing a piston that
is slidable against the force of an axially acting spring by the
pressure of the fluid flowing through the housing in such a way
that the displacement of the piston takes place in dependence upon
the flow rate and is indicated through a window.
2. Background Art
A flow meter according to the preamble is known from U.S. Pat.
No. 3979955 wherein the flowing fluid compresses a spring, which
shifts a plate, the deflection of which is readable on a scale.
U.S. Pat. No. 3805611 also describes a flow meter wherein a piston
is displaced against the force of a spring. Disposed on the piston
is a conical measuring piece, the position of which is changed proportionally
to the flow rate.
From U.S. Pat. Nos. 4389901 and 5343763 flow meters are known
with a hollow conical insert through which the fluid flows. The
housing is transparent and provided with a scale so that the degree
of shifting of a piston against the force of a spring that is caused
by the flowing fluid can be seen or read.
From U.S. Pat. No. 4945771 a measuring device for determining
the flow rate is known that comprises a compression spring mounted
on a piston and an air flow controlling cone.
U.S. Pat. No. 4497202 describes a flow meter having radial slots
to permit a laminar flow. These radial slots are formed in an annular
Further flow meters are known from U.S. Pat. Nos. 828108 2244552
3218853 3408865 3889535 4524616 5044199 and 5554805.
In known systems of this type the medium flows through the interior
of the helical screw. A design of this type is expensive to construct
and unsatisfactory regarding its measuring accuracy.
SUMMARY OF THE INVENTION
With this as the starting point, the invention has as its object
to further develop a flow meter of the above type in such a way
that it can be implemented in the most simple and cost effective
manner possible while providing a high degree of measuring accuracy.
This object is met according to the invention with a helical spring
that is guided in extension of the inlet conduit in an axial direction
and disposed in such a way that the entering fluid is transported
around the centrally disposed helical spring. This centrical position
of the helical spring serves to attain particularly simple geometric
conditions that permit the use of a minimum of components with an
A further design of the invention provides for the entering fluid
to flow into an expansion chamber with an enlarged cross section
after passing the piston. An expansion chamber of this type prevents
turbulence from forming in the outlet area, which could cause the
piston to oscillate with an alternating laminar and turbulent flow
and accordingly impact the accuracy and readability of the indicator.
For a direct visibility and display of the piston position, the
expansion chamber may be encompassed at least partly by a window,
which may have a scale that is readable from the outside.
The outlet conduit is advantageously disposed in an axial extension
of the helical spring, and a counter bearing or guide element for
the helical spring may be disposed on a shoulder of the outlet conduit,
said shoulder being provided with radial openings in such a way
that the fluid can enter from the expansion chamber into the outlet
conduit. This provides for an advantageous construction that ensures
a laminar discharge of the fluid.
Provision is advantageously made for the inlet conduit to have
an exterior thread in such a way that the flow meter can be screwed
directly into a manifold. A manifold of this type is known from
DE 40 32 562 C2. In this manner an extraordinarily compact unit
is attained and it is possible to read the flow rate in multiple
cooling fluid cycles more or less simultaneously.
A flow adjusting valve, which may be formed by a ball valve or
plug valve, may be disposed downstream from the outlet conduit.
In the latter embodiment, provision is preferably made for the
ball valve to have a valve seat and a valve lifter in such a way
that the valve lifter is axially moveable via an external knurled
nut or the like.
Provision is preferably made for the piston position to be measured
by an electro-optical measuring device. It may be formed, for example,
by a row of light-emitting diodes on one side of the piston and
a corresponding row of photoelectric cells on the other side of
the piston so that a certain number of photoelectric cells is illuminated
or darkened, depending on the displacement of the piston, and an
electronic position measuring signal can be formed accordingly.
The invention will be described in further detail below based on
preferred embodiments in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a longitudinal section through a first embodiment,
FIG. 2 through a further embodiment with a ball valve, and
FIG. 3 an embodiment that is screwed onto a manifold.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
An inventive flow meter that is shown in the drawing comprises
a housing 1 with an inlet conduit 2 and an outlet conduit 3 which
are each designed as a tube connection.
A central housing section 4 with a window 5 is screwed by means
of an inside thread 6 onto an exterior thread 7 of a base-like widening
8 of the inlet conduit 2 with the window 5 designed as an opening,
thus providing free view onto a sleeve element 11 of transparent
plastic that is held in place by seals 9 10.
The outlet conduit 3 also has a base-like shoulder 12 with an external
thread 13 onto which an inside thread 14 of the housing center part
4 is screwed. This also creates a counter bearing or guide element
15 via a sealing ring 16 against the sleeve element 11.
The counter bearing or guide element 15 has, in extension of the
outlet conduit 3 a through-opening 17 in the extension of which
axial webs 18 are formed, between which through-slots 19 are provided.
The webs 18 carry a counter bearing 20 and the extensions 21 of
the webs 18 form a guide section for a helical spring 22 that actuates,
via an annular shoulder 23 a piston 24 that is axially displaceable
in the inlet line 2 and conically widens towards the top and sits
in a corresponding conical recess 25 of the base 8. The recess 25
connects to the expansion chamber 26 which is bounded by the sleeve
If fluid enters through the inlet conduit 2 in the direction of
the arrow 27 the piston 24 is displaced upward in the drawing against
the force of the helical spring 22 and accordingly unblocks a passage
region relative to the recess 25 so that the fluid enters into the
expansion chamber 26 and can expand there. Through the slots 19
the fluid then enters into the through-opening 17 and into the outlet
The degree of deflection of the piston 24 is proportional to the
flow rate, with the deflection of the piston being readable on the
sleeve element 11 via the window 5 based on a scale not shown in
The embodiment shown in FIG. 2 corresponds, in its basic construction,
to the embodiment according to FIG. 1 except that the part 12'
has a ball-type through-valve 28 through which the fluid must pass
before it enters into the outlet conduit 3.
In the embodiment shown in FIG. 3 the inside thread 6 of the center
housing part 4 is screwed onto the exterior thread 29 on a neck-like
projection 30 of a manifold 31 which has a manifold conduit 32
extending perpendicular to the drawing plane in FIG. 3.
Furthermore, a plug valve 33 is connected to the center housing
part 4 in the embodiment according to FIG. 3 the valve seat 34
of which is formed in the part 12". The valve plug 35 with
a sealing ring 36 sits in a groove 37 of a knurled nut 38 which,
with its inside thread 39 acts together with an external thread
40 on the part 12" so that the valve cone 35 may be moved up
or down by actuating the knurled nut 38 and the flow rate becomes
adjustable in this manner.