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Motor-driven metering pumpRelated Patent Categories: Pumps, With Signal, Indicator, Or Inspection MeansMotor-driven metering pump description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070041845, Motor-driven metering pump. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The invention relates to a motor-driven metering pump with a rotary drive motor and an oscillating piston. Rotary motion of a drive motor is transformed into an oscillatory motion of a connecting rod by means of a gear arrangement, so that a displacement means, e.g. a piston or diaphragm, actuated thereby executes an oscillating linear motion on continuous rotation of the drive motor that results in transfer of a medium to be metered in a metering head arranged in the longitudinal axis of the connecting rod cooperating alternately with an outlet and an inlet valve to produce a pump stroke (pressure stroke) and a priming stroke. [0002] Motor-driven metering pumps of that type are generally known and are matched to requirements by add-ons. They operate volumetrically, wherein metering is carried out by transporting a closed volume through a displacement means. The metering volume per stroke thus corresponds to the difference in volume on movement of the displacement means. [0003] In general, such motor-driven metering pumps convert the continuous rotary motion of a drive motor via a conversion means, e.g. a gear unit, (all such conversion means being referred to herein as a gear unit for convenience) into an oscillating linear motion of the displacement means. The rotary speed and torque of the motor may be reduced in the conversion unit and matched to speed and power requirements of the displacement means. A take-off shaft of the gear may drive a deflection device for converting the rotary motion into a lateral deflection, i.e. at right angles to the rotary axis, such as a spring/cog or cam drive. The lateral deflection actuates a connecting rod that may be slidably guided in bearings in the direction of the deflection. This transfers the motion and power to the displacement means that, in a metering head arranged in the longitudinal axis of the connecting rod, cooperating alternately with an outlet and inlet valve, produces a pump stroke (pressure stroke) and priming stroke and thus results in movement of the medium to be metered. [0004] The various embodiments may differ firstly in the type of motor. Such motors may usually be asynchronous motors, synchronous motors and step motors, that are mounted outside or inside the actual pump housing. The individual metering pump types also differ in the type of gear unit, e.g. a worm gear, a spur gear, a belt drive or a chain drive. The drive for the connecting rod via the deflection device can be force-guided or with positive locking only on forward motion of the deflection device. The connecting rod is usually driven in the pressure stroke by the deflection device, but in the latter case on priming, it may be driven by a recuperating spring, that places it close to the reversing of the deflection device. The recuperating spring is compressed on the pressure stroke and is dimensioned to provide the required force required upon priming. The various types of pump may also differ in form of the type of power coupling from the connecting rod to a diaphragm or piston as the displacement means either via a rigid linkage or a hydraulic intermediate circuit. Since hydraulic fluid, usually oil, is not compressible, a hydraulic coupling operates like a rigid coupling. In addition to the system described here with a metering head, pump constructions are also known that operate with two or more metering heads driven by a common drive. In one example, two opposing connecting rods may be arranged on either side of a cam in a common longitudinal axis that are driven in opposite directions and each has a metering head with its own displacement means. In another example, it is also known to operate with multiple metering heads with an extended cam shaft that carries several jointly driven cams each of which drive a unit formed by a connecting rod arranged across the cam axis and a metering head with a displacement means lying in the direction of the connecting rod axis. [0005] In the simplest case, all moving parts are mounted in ball bearings or friction bearings in a common pump housing; in other cases, the individual functional groups are collected in further housings or mountings some of which may be filled with oil and are mounted as modules. An example of this case would be a unit mounted outside the pump housing formed by the motor and reduction gear with a mounting flange and a ready mounted take-off shaft. [0006] In the simplest case, the drive motor is on continuously for continuous metering or for a particular period for individual metering strokes. Other types control the drive motor via a frequency converter in accordance with a predetermined time profile, whereby the motor rotary speed and thus the metering power is more reproducible and independent of electrical parameters such as the frequency or actual level of the mains. [0007] The motor rotary speed is predetermined by the electrical frequency of the motor drive and, together with the gear reduction and the gear characteristics that is sinusoidal with a cam gear, determines the period of each stroke. When continuously driven, the period per stroke is given by the effective motor rotary speed under load and the gear reduction. When in on/off operation, where single strokes or sets of strokes are carried out, between which the motor itself is stopped, for example at the priming dead centre, is stopped, startup and slowdown times must be considered and the period per stroke is correspondingly extended. In continuous operation, the stroke frequency is provided by the period per stroke and in on/off operation it is determined by the repetition rate for motor switching, that naturally cannot be faster than the time necessary for carrying out a stroke. [0008] The stroke length can be adjusted by limiting the lateral deflection. This may be carried out by adjusting an eccentric, for example using wobble cylinders, that operate on the basis of two inclined planes that are rotatable in opposite directions. A further possibility is an adjustable buffer that can be used with unforced deflection systems. This buffer, in the form of a mechanically adjustable spindle, when adjusted limits the reverse motion of the connecting rod on priming to an adjustable position before reaching the rear dead centre of the deflection device. The buffer provides the start point for the stroke motion; the end position is the completed deflection movement. In one possible embodiment, a stroke adjustment pin is screwed into a thread in the pump housing and has a calibrated knob accessible from the outside, that constitutes the buffer for the connecting rod on priming. With hydraulic systems, stroke adjustment is, for example, carried out by means of a slidable sleeve the position of which can be adjusted by means of a calibrated knob accessible by the operator, that is screwed into a thread in the pump housing. The sleeve covers a by pass bore in the connecting rod that, after moving a certain distance, opens a shunt in the oil circuit and increases the power coupling from the connecting rod to the diaphragm. [0009] The motion of the displacement means occurs by a combination of the gear and other mechanical components. During the forward motion, the drive operates against the recuperating spring force operating on the connecting rod via the displacement means. During the reverse motion, with forced displacement systems, the connecting rod is drawn back by the drive, and with one sided actuation, the recuperating spring pushes the connecting rod back and thus produces the power for priming the medium for metering. The motion of the connecting rod thus follows the characteristic of the deflection device; with a cam, for example, this is sinusoidal, lying between the two dead centres of the cam stroke for a full stroke length. In operation with a reduced stroke length, the motion on adjusting a cam is still purely sinusoidal with a reduced amplitude, with rigidly coupled systems with an adjustable buffer or hydraulic systems with a bypass bore, the original motion and the amplitude of the deflection device are maintained, but no longer carried out completely; moreover, the connecting rod motion is intersecting, depending on the adjusted stroke length and the coupling system, at the start or end regions (phase cut-off). The forward motion to carry out the pressure stroke is carried out during a time period which is rather less than one second (for example about 200 ms) depending on the drive of the motor. The priming stroke is carried out as set by the deflection device over a period that is similar to that for the pressure stroke. This results in relatively high instantaneous speeds for the metering medium in both stroke phases; for an eccentric drive, the maximum is about half way through the motion. [0010] With embodiments constituted by several units consisting of connecting rod and metering head driven by a common cam shaft operating with several cams, then those cams may be arranged on the shaft in a phase displaced manner in order to distribute the peak power requirement for the individual metering heads around a full rotation of the cam shaft and thus to optimize the use of the available power of the motor. [0011] Particular embodiments, so-called diaphragm metering pumps, use a partially flexible diaphragm as the displacement means. This is not rigid, but deforms elastically by a particular amount in the flexing region when the pressure of the metering medium operates thereon. The amount of deformation, incurred in a first part of the stroke motion that is not used for metering, is lost to the effective stroke motion and the result is that with increasing operational pressure, the metered amount reduces. This drop-off characteristic is much more prominent in normal use than allowed by the metering accuracy. Thus, motor-driven metering pumps normally cannot be adjusted over a wide range of operating pressures with the desired accuracy; moreover, the errors that arise by a calibration are exacerbated as they are included in further calculations. However, the calibration measurement must be carried out in use under actual operating conditions and particularly when using aggressive chemicals, is a step that is extremely difficult. [0012] Current motor-driven metering pumps in general use are efficient and for many processes have good metering properties, but suffer from disadvantages as regards the hydraulic properties of the metering process compared with the ideal position. Examples that may be mentioned are the relatively strong dependency of the metered amounts on the operating pressure of the metering circuit and disadvantages such as noisy flow or pressure drops due to the high instantaneous flow speeds of the metering medium. BRIEF DESCRIPTION OF THE DRAWINGS [0013] The drawings show: [0014] FIG. 1 shows a cross section through a motor-driven metering pump with positional sensor; [0015] FIG. 2 shows an exploded view of the positional sensor (enlargement of section X in FIG. 1); [0016] FIG. 3 shows components of positional control circuit; [0017] FIG. 4 shows components of speed control circuit; [0018] FIG. 5 shows a top view of positional sensor in axial direction; [0019] FIG. 6 shows a side view of positional sensor at right angles to axis; [0020] FIG. 7 shows an illustration of shadow region of positional sensor; [0021] FIG. 8 shows brightness values for pixels in a real shadow; [0022] FIG. 9 shows an illustration of positional sensor measurements on the basis of geometrical arrangement; Continue reading about Motor-driven metering pump... Full patent description for Motor-driven metering pump Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Motor-driven metering pump patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Motor-driven metering pump or other areas of interest. ### Previous Patent Application: Monitoring system for dispensing service fluids Next Patent Application: Turbomachine for low temperature applications Industry Class: Pumps ### FreshPatents.com Support Thank you for viewing the Motor-driven metering pump patent info. 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