Measuring and testing – Volume or rate of flow – Expansible chamber
Reexamination Certificate
1999-03-08
2001-06-26
Patel, Harshad (Department: 2855)
Measuring and testing
Volume or rate of flow
Expansible chamber
C073S253000, C073S861770
Reexamination Certificate
active
06250151
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a flow meter, particularly for liquid fuels in petrol pumps, with at least two inter-engaging screw spindles through which liquid can flow in the axial direction and which are mounted at their ends in a housing so as to rotate, wherein the housing includes a measuring chamber through which liquid can flow and in which an exciter disc, which is rigidly connected to one of the spindle, can rotate in order to cooperate with a detector at the housing end.
A generic flow meter is known from EP 05 72 621. The flow meter disclosed therein is used in petrol pumps for liquid fuels, such as Petrol, Diesel or similar. High levels of accuracy are demanded from such measuring arrangements, the device must be able to be calibrated and, in addition, a device of this type must be relatively inexpensive in manufacture and have a long service life. The measuring device described contains a case, in which two intermeshing screw spindles are arranged. The screw spindles are mounted at each end, so as to rotate with easy action. The outer flanks of the screw spindles rotate very closely to the inner case wall in corresponding bores. From one of the axial directions the fluid to be measured flows into the spindle arrangement where the rate of its flow causes the spindles to rotate. The fluid leaves the spindle arrangement at the opposite axial direction and passes through a measuring chamber, in which an exciter disc, which is rigidly connected to one of the spindles, is allowed to rotate. The exciter disc, rotating in the flow of the fluid, co-operates with a detector at the housing end, which receives information on rotational speed transmitted by the exciter disc and which feeds this to an electronic evaluation circuit to convert the measured pulses into values of volume. From DE 42 08 869 a device is also known to determine the volumetric flow in a fuel line. In that case a steel pole wheel is fitted to the end of a spindle which co-operates with an inductive proximity switch. To enable identification of the direction of rotation of the spindles, two proximity switches are provided and screwed into the housing, opposite but offset to each other, and reaching into the fluid flow within the measuring chamber. The disadvantage of such proximity switches is their complex method of assembly, since they have to be screwed into appropriately tapped holes in the measuring chamber and are then directly positioned within the flameproofed section of the measuring arrangement. In addition, proximity switches require a large cross section of the measuring chamber flow channel.
Correct operation of a generic flow meter assumes, that the spindles are allowed to rotate with a minimum application of force. This requires, that the braking action caused by an exciter disc, rotating within the fluid, is minimised.
SUMMARY OF THE INVENTION
It is a object of the invention to improve manufacturing techniques and operational functions of such a generic device.
Such purpose is met by the invention wherein there is provided a device for measuring fluid volume output by a pump, comprising: a meter housing having an inlet and an outlet through which the fluid flows; at least two inter-engaging screw spindles rotatably mounted within the meter housing and being rotatable in response to fluid flow through the housing; an exciter disc arranged in the fluid flow in the meter housing and connected to one of the at least two inter-engaging screw spindles for rotation therewith, the exciter disc having at least one substantially planar surface and a plurality of magnets arranged thereon with their fields in an axial direction relative to the exciter disc, wherein the meter housing is configured to form a gap and the exciter disc penetrates the gap whereby a region of the meter housing is in close proximity to and extends over a portion of the planar surface of the exciter disc; and at least two magnetic-sensitive detectors disposed in said region of the meter housing, proximate to and spaced from the exciter disc, for cooperating with the magnets of the exciter disc for producing a signal representing rotation of the exciter disc.
Because of the configuration of the invention, the exciter disc rotates in a partially screened area, having the shape of a gap. This produces minimum braking action by the exciter disc on the flowing medium. The effect is further enhanced by the smooth edging of the disc, whereby a “paddlewheel effect”, as is possible in devices according the current state of the art, is prevented. The gap formation allows the scanning of the exciter disc from its flat surface. For this purpose, at least two detectors are provided in the region of the wall gap, which respond to magnetic fields. The disc carries two magnets or has two magnetic areas which act in an axial direction whereby the magnetic flux lines pass virtually across the gap wall. For preference, Hall effect sensors are used as detectors for the magnetic field. Such Hall effect sensors are preferably fitted into a detector chamber, which is accessible from outside and which is separated from the measuring chamber by an aluminium wall so that the sensors are no longer within the flameproof area of the flow meter. Such measures significantly reduce the demands that have to be made on the sensors. Assembly too is simplified, since the screwing of the sensors into threads contained in the housing may now be omitted. For preference, the detector chamber is assigned to a part of the housing, which is mounted onto the screw spindle chamber. This simplifies assembly, since the separation level is in the region of the gap. For preference the exciter disc comprises eight magnets, which are uniformly disposed in a circle on the disc. The magnets may be oriented either in parallel or, alternating, in antiparallel. The gap wall facing the spindle housing is partly formed in a further advantageous development of the invention by a screen covering one of the spindle bearings and having an aperture, through which the liquid may flow in an axial direction. The detector housing reaches into the measuring chamber approximately up to the axis of the spindle, respectively of the exciter disc, so that about one half of the disc penetrates the gap. This reduces the forces acting upon the disc by the flow of the fluids. In addition, the disc is very flat; its thickness is many times smaller than its diameter, thereby reducing its moment of inertia. This reduces non-linear errors.
The invention prevents the projection of components into the D-shaped measuring chamber. Electrical components, when contained in the separate detector chamber, may be easily screened, both from external magnetic or electric influences and from the measured fluid medium. At least two Hall effect sensors, arranged in the detector chamber, may be positioned exactly so as to obtain information on phase angles and, thereby, providing information on the direction of rotation of the disc. The magnetic disc segments, which act by their faces, consist of soft and small magnetic formations, arranged in a circle around the disc centre. The measuring chamber cross section in the region of the exciter disc is greater than or equal to the smallest cross section of the path of the fluid. This arrangement limits fluid accelerations in the region of the exciter disc to within the tolerable range.
REFERENCES:
patent: 3969940 (1976-07-01), Butcher
patent: 4224015 (1980-09-01), Nagata
patent: 4295369 (1981-10-01), Wendelboe
patent: 4641522 (1987-02-01), Lopresti
patent: 4872352 (1989-10-01), Alden et al.
patent: 4878454 (1989-11-01), Cann
patent: 4911010 (1990-03-01), Foran et al.
patent: 4996888 (1991-03-01), Foran, Jr. et al.
patent: 5251149 (1993-10-01), Williams et al.
patent: 5252824 (1993-10-01), Picanyol
patent: 5325715 (1994-07-01), Foran et al.
patent: 5447062 (1995-09-01), Köpl et al.
patent: 5559288 (1996-09-01), Schumacher
patent: 5594173 (1997-01-01), Frey et al.
patent: 4042397 (1992-07-01), None
patent: 4208869 (1993-09-01), None
patent: 4423461
Harding Alfons
Kopl Manfred
Miller Willi
Tingleff Michael
Frank Robert J.
Kinberg Robert
Marconi Commerce Systems GmbH & Co. KG
Patel Harshad
Venable
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