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. 1a. 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 2a are provided for injectors 3 to be inserted in the clamping means. In the embodiment shown, six clamping screws 2a 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 2b, wherein an injection cylinder is laid in each of these V-shaped grooves 2b. Opposite these grooves 2b there is arranged an elongated clamping piece 2c having a corresponding V-shaped groove and connected to the corresponding clamping screw 2a, through which it can be moved back and forth in the direction of the V-groove 2b to clamp in or release an injection cylinder 3c, as shown in FIG. 1a.
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 5a and U-shaped holding prongs 5b, wherein into the transverse groove 5a a pressure plate 3a of the piston rod 3b of an injector 3 is inserted, as FIG. 1a shows schematically. At 5c, clamping screws are shown through which a pressure plate 3a of a piston rod can be fixedly clamped without clearance in the transverse groove 5a. 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 1b 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 3c of the injectors 3 are connected by means of preferably flexible hose pipes 3d, as FIG. 1a 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 6a having connecting pipes 6b, there is inserted a bar-shaped rotary vane 6c, on whose circumference connecting passages 6c′ are formed for connecting and interrupting the pipes 6b. The bar-shaped rotary vane 6c is held by a cover 6d having a corresponding semi-circular groove connected by means of screws to the control block 6a. At 6e, a component part (FIG. 4e) having a U-shaped cross-section is mounted on the control block 6a, in which connecting bores 6e′ for connecting pipes are formed, through which medium is sucked and pumped after the pumping process. At the rotary vane 6c, there is fixed a control bracket 6f having a prong at its free end which protrudes through a recess 6d′ in the cover 6d (FIGS. 4a and 4c). This control bracket 6f protrudes through an opening in the base plate 1 and engages with a pin 9e 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 5c and 5c′ which protrudes through an opening 1a 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 7a and 7a′ which are supported in a recess on the back of the base plate 1 in roller holders 7b, 7b′. The roller holder 7b is fixedly joined to the base plate 1 by a screw 7c, while the roller holder 7b′ is adjustable relative to the base plate 1 in the longitudinal direction of the metal band 7 by means of a screw 7c′, so that the band 7 can be stretched tightly around the two rollers or rolling bearings 7a and 7a′. 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 5c′ of the piston slide 5′, which is not shown in FIG. 3. In FIG. 2, this clamping jaw 5c′ is fixed to the upper section of the band 7 which is guided around the two rollers 7a, 7a′, while the clamping jaw 5c is fixed to the lower section of the band 7. The clamping jaw 5c′ is provided with a pocket bore 5d in which a drive pin 13 (FIG. 8) of a drive means engages, which moves the clamping jaw 5c′ back and forth in the direction of the band 7. Due to the driving movement to the left of the clamping jaw 5c′ in FIG. 3, simultaneously and synchronously the clamping jaw 5c 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 5d, 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 5c′ engages in an elongated hole 8a 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 8b which is guided displaceably on a guide rod 8c which is fixedly arranged in a recess of the base plate 1. Fixedly connected to the slider 8b is a traveller 8d having at both ends a prong-shaped section with a sloping surface 8e, which cooperates with a spring-biased catch 10 or 10a such that during the displacement movement of the traveller 8d in FIG. 3 to the right, the catch 10a is pressed back and the leg 9a of the control bracket 9 is released, which is biassed in a direction to the right by a spring 9c′. Hereby, the control bracket 9 in FIG. 3 having the left leg 9b and abutting on the base plate 1, is moved to the right, taking with it the control bracket 6f, which engages with the pin 9e of the switching bracket 9. In this way, by releasing the spring 9c′, the rotary vane 6c is rotated into a position in which switching is carried out from intake to delivery or vice versa.
The left leg 9b 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 16a and 16b of the leg 9b. By means of electric wires 16c, 16c′, a corresponding signal is sent to a drive motor 13f (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 5c′, 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 5c′ in FIGS. 2 and 3 is first moved to the left without the connecting rod 8 also being taken, because the clamping jaw 5c′ moves in the elongated hole 8a 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 5c′ driven by the drive motor comes to abut at the end of the elongated hole 8a, 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 9b 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 5b to the left, first the spring 9c is compressed and tensioned against the leg 9b, while the right-hand spring 9c′ remains released. As soon as the sloping surface 8e of the slider 8d reaches and presses back the catch 10 during the movement to the left, the left leg 9b of the switching bracket 9 is released, so that the pre-stress of the spring 9c presses the switching bracket 9 to the left, due to which by means of the pin 9e the rotary, vane 6c 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 6c, wherein simultaneously the direction of rotation of the drive motor 13f is switched via the inductive sensor 16. In the schematic representation in FIG. 5, the sloping surfaces 8e are formed directly onto the connecting rod 8. The drive pin 13 can also engage in the elongated hole 8a, 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 6c. 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 6c. It projects beyond an end of the control means 6 and is joined to a lever 11a so that its position can be changed manually. In FIGS. 6 and 6a, 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 11b is connected to the pipes 6b leading to the injection cylinders 3c, wherein in the schematic representation of FIGS. 6 and 7, in each case only one of the connecting pipes 11b leading to the pipes 6b 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 6c 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 3o contained in the medium collect at the upper end of the injection cylinder 3c, 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 3o located in the pipe 6b 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 3c′, while this is joined to the outlet or delivery side by means of the rotary vane 6c. Hereupon, in the same way, the injection cylinder 3c′ 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 3b′, so that air bubbles 3o 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 3o are transferred out of the pipe 6b′ to the outside.
Due to the drive motor 13f 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 5c to the metal band 7 which is guided free of clearance around the rolling bearings 7a, 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 5c′ in the embodiment shown. This drive pin 13 is mounted on a screw nut 13a, which on one side is guided free of clearance on a guide rod 13b, for example through a pre-stressed ball guide, and on the other side is driven by a precision spindle 13c, wherein in the spindle nut, a re-adjustment means is provided. At 13d, a bearing application of the precision spindle 13c is shown, which is pre-stressed so as to be free of clearance and is connected to the drive motor 13f via a compensating coupling 13e, which is free of clearance and torsion-proof, the drive motor 13f 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 13e, a clearance-free and rigid bearing application 13d, a precision spindle 13c, a clearance-free spindle nut 13a, and a clearance-free spindle nut guide 13b (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 14a, a controller 14b and a control unit 14c which receives the signals from the contact-free end-position-sensor 16 and sends them to the motor 13f 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 3b 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.
Patent Application
20050106051
