US20050106051A1

US20050106051A1 - Metering pump

Info

Publication number: US20050106051A1
Application number: US10/957,643
Authority: US
Inventors: Willi Hempelmann
Original assignee: Micro Mechatronic Tech AG
Current assignee: Micro Mechatronic Tech AG
Priority date: 2003-10-06
Filing date: 2004-10-05
Publication date: 2005-05-19
Also published as: EP1522727A2; DE10346341A1; EP1522727A3

Abstract

A metering pump is disclosed which has a simple structure and in which conventional injectors can be used as pump elements. Injectors having different piston diameters can be inserted in a clamping means, and due to the arrangement of the elements of the metering pump on a base plate, a simple structure results.

Description

The invention relates to a metering pump, in particular for very small delivery quantities.
The invention is intended to propose a metering pump which has a simple structure and in which conventional injectors can be used as pump elements.
According to the invention, this is achieved by a metering pump according to claim 1. Injectors having different piston diameters can be inserted in the clamping means, and due to the arrangement of the elements of the metering pump on a base plate, a simple structure results.
An exemplary embodiment of the invention is explained in more detail below with reference to the drawing, in which
FIG. 1 shows a perspective front view of the metering pump,
FIG. 2 shows a view of the back of the base plate of the metering pump,
FIG. 3 shows a longitudinal section through the metering pump along the line A-A in FIG. 2,
FIG. 4 shows the control means in various views,
FIG. 5 shows a schematic representation of the cooperation between switching means and control means,
FIG. 6 shows a schematic representation of the control means with a de-aerating injector,
FIG. 7 shows a schematic representation of the function of the de-aerating injector, and
FIG. 8 shows a schematic view of the drive pan of the metering pump.
FIG. 1 shows a front view of the metering pump without the injectors inserted therein which are shown schematically in FIG. 1 a. On an approximately rectangular base plate 1 (FIGS. 2 and 3), there is fixedly mounted approximately in the middle a clamping means 2, on whose front side clamping screws 2 a are provided for injectors 3 to be inserted in the clamping means. In the embodiment shown, six clamping screws 2 a are provided for six injectors 3.
The approximately box-shaped clamping means 2 is open on both sides and has a side which abuts on the base plate 1, on which abutting side there are formed six V-shaped grooves 2 b, wherein an injection cylinder is laid in each of these V-shaped grooves 2 b. Opposite these grooves 2 b there is arranged an elongated clamping piece 2 c having a corresponding V-shaped groove and connected to the corresponding clamping screw 2 a, through which it can be moved back and forth in the direction of the V-groove 2 b to clamp in or release an injection cylinder 3 c, as shown in FIG. 1 a.
On two guide bars 4 and 4′ arranged parallel to one another on the base plate 1, two piston slides 5 and 5′ are displaceable and have a transverse groove 5 a and U-shaped holding prongs 5 b, wherein into the transverse groove 5 a a pressure plate 3 a of the piston rod 3 b of an injector 3 is inserted, as FIG. 1 a shows schematically. At 5 c, clamping screws are shown through which a pressure plate 3 a of a piston rod can be fixedly clamped without clearance in the transverse groove 5 a. In the embodiment shown, the piston rods of three injectors 3 are joined in this way to the piston slide 5 and three injectors 3 are joined to the piston slide 5′.
In FIG. 3, a preferably transparent housing part 1 b is shown, which covers the piston slide 5.
On the opposite side of the clamping means 2, a control means 6 is mounted on the base plate 1, to which the individual cylinders 3 c of the injectors 3 are connected by means of preferably flexible hose pipes 3 d, as FIG. 1 a shows. The control means 6 is preferably formed as a rotary vane control system as shown in FIG. 4. Into a semi-circular groove of a control block 6 a having connecting pipes 6 b, there is inserted a bar-shaped rotary vane 6 c, on whose circumference connecting passages 6 c′ are formed for connecting and interrupting the pipes 6 b. The bar-shaped rotary vane 6 c is held by a cover 6 d having a corresponding semi-circular groove connected by means of screws to the control block 6 a. At 6 e, a component part (FIG. 4 e) having a U-shaped cross-section is mounted on the control block 6 a, in which connecting bores 6 e′ for connecting pipes are formed, through which medium is sucked and pumped after the pumping process. At the rotary vane 6 c, there is fixed a control bracket 6 f having a prong at its free end which protrudes through a recess 6 d′ in the cover 6 d (FIGS. 4 a and 4 c). This control bracket 6 f protrudes through an opening in the base plate 1 and engages with a pin 9 e of a U-shaped switching bracket 9 which is explained in more detail below by means of FIGS. 2 and 3.
As FIG. 3 shows, the two piston slides 5 and 5′ are provided with a clamping jaw 5 c and 5 c′ which protrudes through an opening 1 a in the base plate 1 and is fixedly joined to a metal band 7 which is guided around two spaced rollers in the form of rolling bearings 7 a and 7 a′ which are supported in a recess on the back of the base plate 1 in roller holders 7 b, 7 b′. The roller holder 7 b is fixedly joined to the base plate 1 by a screw 7 c, while the roller holder 7 b′ is adjustable relative to the base plate 1 in the longitudinal direction of the metal band 7 by means of a screw 7 c′, so that the band 7 can be stretched tightly around the two rollers or rolling bearings 7 a and 7 a′. Instead of a metal band 7, a toothed belt or the like can also be provided.
FIG. 3 shows a section through the clamping jaw 5 c′ of the piston slide 5′, which is not shown in FIG. 3. In FIG. 2, this clamping jaw 5 c′ is fixed to the upper section of the band 7 which is guided around the two rollers 7 a, 7 a′, while the clamping jaw 5 c is fixed to the lower section of the band 7. The clamping jaw 5 c′ is provided with a pocket bore 5 d in which a drive pin 13 (FIG. 8) of a drive means engages, which moves the clamping jaw 5 c′ back and forth in the direction of the band 7. Due to the driving movement to the left of the clamping jaw 5 c′ in FIG. 3, simultaneously and synchronously the clamping jaw 5 c and thus the piston slide 5 is moved to the right. Due to the back-and-forth movement of the drive pin 13 engaging in the pocket bore 5 d, the two piston slides 5 and 5′ are moved back and forth counter to one another by the metal band 7, due to which the one group of three pistons carries out, for example, a pumping movement, while the other group of three pistons carries out a sucking movement.
The clamping jaw 5 c′ engages in an elongated hole 8 a of a connecting rod 8 which is guided on the rear side of the base plate 1 in a recess and connected at the opposite end with a slider 8 b which is guided displaceably on a guide rod 8 c which is fixedly arranged in a recess of the base plate 1. Fixedly connected to the slider 8 b is a traveller 8 d having at both ends a prong-shaped section with a sloping surface 8 e, which cooperates with a spring- biased catch 10 or 10 a such that during the displacement movement of the traveller 8 d in FIG. 3 to the right, the catch 10 a is pressed back and the leg 9 a of the control bracket 9 is released, which is biassed in a direction to the right by a spring 9 c′. Hereby, the control bracket 9 in FIG. 3 having the left leg 9 b and abutting on the base plate 1, is moved to the right, taking with it the control bracket 6 f, which engages with the pin 9 e of the switching bracket 9. In this way, by releasing the spring 9 c′, the rotary vane 6 c is rotated into a position in which switching is carried out from intake to delivery or vice versa.
The left leg 9 b of the switching bracket 9 in FIGS. 2 and 3 cooperates with an end switch 16, preferably in the form of an inductive sensor which determines two positions 16 a and 16 b of the leg 9 b. By means of electric wires 16 c, 16 c′, a corresponding signal is sent to a drive motor 13 f (FIG. 8), so that this reverses its direction of rotation, for carrying out a drive movement of the piston slide 5′ to the left in the Figures via the drive pin 13 engaging in the clamping jaw 5 c′, while simultaneously by means of the metal band 7 the piston slide 5 is moved to the night, for carrying out a pump stroke.
Hereby, the clamping jaw 5 c′ in FIGS. 2 and 3 is first moved to the left without the connecting rod 8 also being taken, because the clamping jaw 5 c′ moves in the elongated hole 8 a of the connecting rod 8. At a pre-determined distance in front of the left end position of the piston slide 5′, the clamping jaw 5 c′ driven by the drive motor comes to abut at the end of the elongated hole 8 a, so that the connecting rod 8 in FIGS. 2 and 3 is displaced to the left. In the preceding displacement of the switching bracket 9 to the night, the leg 9 b was displaced in front of the catch 10, so that this catch 10 holds the switching bracket 9 in the position on the right, and during the displacement movement of the slider 5 b to the left, first the spring 9 c is compressed and tensioned against the leg 9 b, while the right-hand spring 9 c′ remains released. As soon as the sloping surface 8 e of the slider 8 d reaches and presses back the catch 10 during the movement to the left, the left leg 9 b of the switching bracket 9 is released, so that the pre-stress of the spring 9 c presses the switching bracket 9 to the left, due to which by means of the pin 9 e the rotary, vane 6 c is rotated into another position.
FIGS. 5 and 5 a show schematically, using the reference numerals of FIGS. 2 and 3, the switching means and the control means. By means of the embodiment shown, a switching time of 2 ms results at the rotary vane 6 c, wherein simultaneously the direction of rotation of the drive motor 13 f is switched via the inductive sensor 16. In the schematic representation in FIG. 5, the sloping surfaces 8 e are formed directly onto the connecting rod 8. The drive pin 13 can also engage in the elongated hole 8 a, to directly trigger the switching movement.
FIG. 6 shows schematically the sucking stroke and pressure stroke of two pistons which are joined to the piston slide 5 and 5′ respectively and which belong to two injectors 3 and 3′, and the control mean 6 and the rotary vane 6 c. At 11 in FIG. 6, a blocked de-aerating rotary vane is shown, whose function is explained in more detail by means of FIG. 7.
In FIG. 6, the de-aerating rotary vane 11 is shown in its shut-off position. As FIG. 4 shows, the de-aerating rotary vane 11 is integrated into the control means 6 in the same way as the control rotary vane 6 c. It projects beyond an end of the control means 6 and is joined to a lever 11 a so that its position can be changed manually. In FIGS. 6 and 6 a, a de-aerating injector 12 is connected to a connecting pipe lib of the control means 6, in which the de-aerating rotary vane 11 is arranged. This connecting pipe 11 b is connected to the pipes 6 b leading to the injection cylinders 3 c, wherein in the schematic representation of FIGS. 6 and 7, in each case only one of the connecting pipes 11 b leading to the pipes 6 b is shown.
To de-aerate the metering pump before starting operation, the individual pistons of the injectors 3 in the vertical position of the metering pump according to FIG. 1, are pulled out one after the other at the top of the injection cylinder, as FIG. 7 shows schematically. To the injector 3 to be de-aerated, the de-aerating injector 12 is joined by switching the de-aerating rotary vane 11, while the rotary vane 6 c joins the outlet of the injector 3 to the delivery side. In this position, medium is pressed into the injector 3 through the de-aerating injector 12, wherein when the injector 3 is full, a cone M forms at its upper open end due to the surface tension of the medium. Simultaneously, air bubbles 3 o contained in the medium collect at the upper end of the injection cylinder 3 c, wherein knocking on the injection cylinder enables them to escape upwards. Hereupon, the piston is attached to the cone M of the medium and pushed into the injection cylinder such that no air bubbles are present any longer at the upper end of the injection cylinder. By further pushing in of the de-aerating injector 12, air bubbles 3 o located in the pipe 6 b of the control means 6 are pressed outwards to the delivery side, as indicated by an arrow in FIG. 7. For de-aerating the injector designated by 3′ in FIG. 7, the de-aerating injector 12 is joined to the injection cylinder 3 c′, while this is joined to the outlet or delivery side by means of the rotary vane 6 c. Hereupon, in the same way, the injection cylinder 3 c′ is filled by introducing medium through the de-aerating injector 12, wherein the piston is pulled out of the injection cylinder via the piston rod 3 b′, so that air bubbles 3 o can escape. Onto the cone M forming due to surface tension of the medium, the piston is attached and pushed into the injection cylinder such that in this area no more air bubbles are present. By further pushing in of medium through the de-aerating injector 12, air bubbles 3 o are transferred out of the pipe 6 b′ to the outside.
Due to the drive motor 13 f described below, the described metering pump functions pulsation-free and continuously, and can be used for various mediums up to 10 bar, wherein the respective medium is transported carefully and gently.
Due to the strength train of the metering pump being designed clearance-free and rigid, minimum delivery quantities can be delivered, wherein for example within one hour, a stroke of only approximately {fraction (2/10)} mm can be carried out. Due to the joining of the piston slides 5 and 5′ via clamping jaws 5 c to the metal band 7 which is guided free of clearance around the rolling bearings 7 a, in this area of the drive means an embodiment is achieved which is free from clearance. FIG. 8 shows such a drive of the drive pin 13 engaging in the clamping jaw 5 c′ in the embodiment shown. This drive pin 13 is mounted on a screw nut 13 a, which on one side is guided free of clearance on a guide rod 13 b, for example through a pre-stressed ball guide, and on the other side is driven by a precision spindle 13 c, wherein in the spindle nut, a re-adjustment means is provided. At 13 d, a bearing application of the precision spindle 13 c is shown, which is pre-stressed so as to be free of clearance and is connected to the drive motor 13 f via a compensating coupling 13 e, which is free of clearance and torsion-proof, the drive motor 13 f being preferably formed as an electronically commutated direct current servomotor having almost ideal sine generation for pulsation-free operation.
The drive motor produces a drive movement corresponding to a harmonious sine curve. This contributes considerably to the production of pulsation-free delivery. In addition, there is a clearance-free and rigid drive train having a clearance-free and torsion-proof coupling 13 e, a clearance-free and rigid bearing application 13 d, a precision spindle 13 c, a clearance-free spindle nut 13 a, and a clearance-free spindle nut guide 13 b (FIG. 8).
The obtainable delivery quantity of the metering pump results from the piston surface of the respective injectors 3 and the delivery speed of their pistons, wherein volumes of delivery are obtainable in the range of 80 nl/h to 10 l/h.
The metering pump as described, having three injectors per delivery- or intake stroke, can pump or mix up to three different fluids in a prescribed ratio. Even when the metering pump is designed for small delivery amounts, rinsing with another medium can be carried out at a higher delivery amount by increasing the stroke speed of the pistons.
As no valves are required for switching between sucking/intake and delivery/pumping stroke, switching can be achieved by the rotary vane in a range of less than 2 ms, wherein due to the rotary vane shaft, volume-neutral switching results.
FIG. 8 shows schematically the electric or electronic control system of the metering pump described, with motor electronics 14 having a performance unit 14 a, a controller 14 b and a control unit 14 c which receives the signals from the contact-free end-position-sensor 16 and sends them to the motor 13 f for switching the direction of rotation. At 15, an operating mode selection switch is shown which allows drive or desired value setting via a potentiometer P, an analog signal A or via an interface RS, due to which drive via a PC or corresponding software is possible. By means of software, free parameter setting of the delivery amount is possible.
The drive unit schematically shown in FIG. 8 can be housed in a separate, block-shaped component, from which merely the drive pin 13 protrudes which is coupled with the metering pump. For fast joining and releasing of drive unit and metering pump, tension brackets or similar connecting elements can be provided, preferably in connection with locating pins between pump unit and drive unit, so that the drive unit takes up a pre-set position relative to the metering pump.
The metering pump itself is so constructed that it can be easily disassembled for sterilizing and cleaning. For example, the clamping means 2 and the control means 6 can be fixed to the base plate 1 by means of screws.
Various modifications of the described structure are possible. For example, instead of the clamping means 2, the injectors 3 can also be provided fixedly mounted in such a way that they are inserted in one component which is screwed onto the base plate 1. In this way, this component can be easily removed with the injectors and handled separately for sterilizing and cleaning.
Instead of the described embodiment of the metering pump having two groups of three injectors 3, another grouping of injectors at the individual piston slides 5 can also be provided, to obtain a pre-determined multi-flow embodiment. The piston diameters of the injectors can be designed differently, to obtain a desired ratio of mixture in a pumping process.
As FIG. 1 shows, the metering pump is preferably mounted on an L-shaped support T, wherein the metering pump is inserted between two support plates Tp. Laterally on one of the support plates, there are provided the operating mode selection switch 15 and an adjusting button 20 for adjusting the piston speed and the like. The metering pump having relatively small dimensions can be positioned by means of the support T on a laboratory table or the like. The drive unit can hereby be mounted fixedly with the base plate 1 between the support plates Tp, while the control means 6 conducting medium is attached releasably, for example by means of screws, so that all the components which conduct medium can be quickly dismounted for cleaning and sterilizing. The injectors not shown in FIG. 1 are joined by means of pipes and plug connectors (not shown) to the corresponding bores in the control means 6. On the front side of the control means 6, bores are provided for the connecting pipes.
The vertical positioning of the metering pump on the support T having the piston rods 3 b lying on top facilitates the de-aerating of the individual injectors 3.
In the metering pump shown, two groups of three pistons are coupled to a precisely functioning, clearance-free linear drive system wherein all the pistons move synchronously to one another, without a difference in stroke occurring between the individual pistons. Conventional injectors having a diameter range of ca. 0.7 to 23 mm can be used.
Preferably, all the components of the metering pump which come into contact with medium are made of electrically insulating material or are electrically insulated, so that no electric potential of the medium can be carried off if, for example, ionized medium is transported.

Claims

1. Metering pump, comprising:

a base plate,

a clamping means, mounted on the base plate, for clamping injection cylinders of at least two injectors,

two actuating elements which are displaceable on the base plate and to which piston rods of the injectors are connectable,

a control means mounted on the base plate and joined by pipes to the injection cylinders of the injectors, wherein connecting pipes are connectable to the control means, and

a drive means which moves the actuating elements back and forth counter to one another and switches over the control means such that the pipes connected to the injection cylinders are connected to different connecting pipes.

2. Metering pump according to claim 1, wherein the actuating elements are each joined by a clamping jaw to a section of a band which is guided around two rollers and is moved back and forth by a drive motor.

3. Metering pump according to claim 1, wherein the drive means of the actuating elements is joined to a switching means having a switching bracket which is biased in opposite directions by springs, is joined to the control means, and is held by catch elements in end positions in which the switching bracket (9) is biased by one of the springs.

4. Metering pump according to claim 1, wherein at each of the actuating elements, which are synchronously displaceable relative to one another, a group of injectors is mountable, so that for each stroke movement, simultaneously both groups of injectors carry out an intake stroke or a delivery stroke.

5. Metering pump according to claim 4, wherein the group of injectors are joinable in different ways to the control means, to set a pre-determined volume flow combination.

6. Metering pump according to claim 1, wherein the strength train of the drive means of the injectors is formed rigid and clearance-free.

7. Metering pump according to claim 1, wherein in the control means a de-aerating valve is provided, by means of which the individual injectors can be de-aerated.

8. Metering pump according to claim 7, wherein the pump is positioned in a vertical position on a support (T) such that the pistons of the injectors lie on top, for facilitating de-aeration of the injectors.

9. Metering pump according to claim 1, wherein all the components of the pump which come into contact with medium are made of electrically insulating material or are electrically insulated.

10. Metering pump according to claim 1, wherein the drive motor is formed such that is produces a sine-shaped drive movement.