WO2001089698A1

WO2001089698A1 - Droplet dosing device and droplet dosing installation equipped therewith

Info

Publication number: WO2001089698A1
Application number: PCT/NL2001/000400
Authority: WO
Inventors: Rudolf Johannes Gerardus Antonius Van Der Hoorn
Original assignee: Cats Beheer B.V.
Priority date: 2000-05-23
Filing date: 2001-05-23
Publication date: 2001-11-29
Also published as: AU2001260799A1; NL1015280C2

Abstract

The invention relates to a droplet dosing device, with a source (2) of a medium for spraying, a spray nozzle (5), a channel (4) connecting the source to the spray nozzle, pumping means (6) for carrying the medium for spraying from the source to the spray nozzle, and means for damping a pressure pulse generated by the pumping means, which damping means (10) are operably connected to the pumping means. The pumping means can comprise a member displaceable by a drive element and the damping means can be arranged between the drive element and the displaceable member or between the drive element and a fixed part of the pumping means. The droplet dosing device can further be provided with spring means which are operably connected to the pumping means and which can also be arranged between the drive element and the displaceable member or between the drive element and a fixed part of the pumping means. When the pumping means comprises a displaceable member driven by a piezo-element, the device can be provided with means connected to the piezo-element for amplifying the operation thereof. The invention finally also relates to a droplet dosing installation which consists of a number of droplet dosing devices as described above arranged on a carrier in a determined pattern.

Description

DROPLET DOSING DEVICE AND DROPLET DOSING INSTALLATION EQUIPPED THEREWITH

The invention relates to a droplet dosing device, comprising at least one source of a medium for spraying, at least one spray nozzle, at least one channel connecting the source to the spray nozzle, pumping means for carrying the medium for spraying from the source to the spray nozzle. Such a droplet dosing device is known, and- is applied for instance in printer heads of printers for use in computers. A number of droplet dosing devices can herein be arranged in a determined pattern on a movable carrier or head which is guided along a sheet of - paper for printing. A desired pattern, for instance a line of text or an image is thus formed on the paper by operating the droplet dosing devices under the control of the computer. Printer heads of the above described type are not only used in computer printers, but are increasingly finding application for preparing test plates for large- scale research into biological or chemical properties of substances, for instance using so-called 'dot blots' or DNA chips. By means of the droplet dosing devices determined quantities of all kinds of substances can be dosed accurately onto a base, whereby mixtures of a determined composition can be formed very quickly or substances can be brought into mutual contact in order to evaluate their reactions.

For all these applications it is of great importance that the quantity of liquid dosed by the droplet dosing device can be very precisely controlled. Problems which occur here are, among others, the occurrence of so-called satellite droplets, small droplets which escape from the spray nozzle due to resonance in the liquid channel, which is in turn the result of the sudden pressure build-up in the channel during the dosing of a determined quantity of liquid. An additional problem is that in order to achieve an optimal spraying behaviour complicated and relatively large devices are often required, which are therefore also relatively costly.

The invention now has for its object to provide a droplet dosing device of the above described type, which has an improved dosing behaviour relative to conventional droplet dosing devices, and wherein particularly the occurrence of satellite droplets can be avoided. The invention further has for its object to achieve this improved spraying behaviour using a relatively simple, compact droplet dosing device which can be manufactured at low cost . According to a first aspect of the invention this objective is achieved in a droplet dosing device of this type by means for damping a pressure pulse generated by the pumping means, which damping means are operably connected to the pumping means . Owing to the presence of these damping means a pressure pulse generated in the channel is damped before resonances can occur, thereby preventing satellite droplets being pressed out of the channel .

The pumping means preferably comprise at least one member displaceable by a drive element and the damping means are arranged between the drive element and the displaceable member. According to another embodiment the damping means can also be arranged between the drive element and a fixed part of the pumping means. A simple embodiment is obtained when the damping means comprise an elastomer material. The at least one displaceable member can herein comprise a membrane and the elastomer material can lie against the membrane . According to a second aspect the invention provides for the purpose of achieving the above stated objectives a droplet dosing device of the above described type which is provided with spring means operably connected to the pumping means . The response behaviour of the pumping means is "cushioned" slightly by such spring means, whereby the occurrence of vibrations in the channel is further reduced. The spring means can herein advantageously be arranged between the drive element and the displaceable member, but it is likewise conceivable for them to be arranged between the drive element and a fixed part of the pumping means . The spring means and the damping means are otherwise preferably connected to each other. A particularly effective construction is hereby obtained which displays a very good dosing behaviour.

When the droplet dosing device is provided with pumping means which comprise at least one displaceable member driven by a piezo-element, according to a third aspect of the invention the device has means connected to the piezo-element for amplifying the operation thereof. Owing to such amplifying means it is possible to suffice with a relatively small piezo-element, which can furthermore be operated with a relatively small voltage.

According to a first variant the amplifying means herein comprise a number of additional piezo- elements connected to the piezo-element to form a multi- layer structure.

A simple construction with a low energy consumption is obtained when the amplifying means comprise a lever arranged between the piezo-element and the displaceable member. The lever herein advantageously also takes a resiliently flexible form and forms part of the spring means . The functions of the spring-mounting and the amplifying are thus combined in a single component. The damping means are then preferably also connected to the lever, for instance in that the lever is at least partially covered with the elastomer material, whereby even three functions are combined in the lever.

The invention also relates to a droplet dosing installation provided with a number of droplet dosing devices of the above described type arranged on a carrier in a determined pattern. In such a droplet dosing installation the carrier is preferably manufactured from a chemically resistant material, in particular glass. A very compact installation with a large number of droplet dosing devices can herein be obtained when the carrier is plate-like and the droplet dosing devices are formed therein by etching.

The invention is now elucidated on the basis of a number of embodiments, wherein reference is made to the annexed drawing, in which corresponding components are designated with the same reference numerals, and in which:

Fig. 1 is a schematic perspective view of a part of a droplet dosing device according to a first embodiment of the invention, etched into a glass plate,

Fig. 2 shows a view corresponding with fig. 1 of a number of droplet dosing devices according to the invention combined to form a droplet dosing installation, Fig. 3 is a schematic view of the most important components of the droplet dosing device and their mutual relation,

Fig. 4 is a view corresponding with fig. 3 of a slightly modified embodiment of the invention, Fig. 5 is a schematic view of amplifying means in the form of a lever for application in the pump of a droplet dosing device according to yet another embodiment of the invention,

Fig. 6 shows a detail on enlarged scale according to arrow VI in fig. 5,

Fig. 7 is a schematic view of amplifying means in the form of a multi-layer piezo-element, and

Fig. 8 shows a diagram in which the excitation of the drive element, the displacement of the pumping member resulting therefrom and the thus dosed quantity of liquid are shown for both a conventional droplet dosing device and a droplet dosing device according to the invention. OJ ω CO DO M H>

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connected to pump 6. The rising flank of the pressure pulse is flattened by such spring means 14, whereby a more gradual pressure build-up thus takes place, and the occurrence of parasitic vibrations can be avoided as far as possible. In the shown embodiment the spring means 14 are shown schematically as a coil spring arranged between piezo-element 12 and the fixed part 13 of pump housing 9, but it will be apparent that any other appropriate type of spring will in principle be suitable for the purpose. In an alternative embodiment of the droplet dosing device (fig. 4) the damping means 10 and spring means 14 can be combined. These combined spring and damping means can then be formed by a layer of elastomer material, which is arranged here between piezo-element 12 and membrane 11.

Damping means 10 are otherwise preferably chosen such that the system formed by drive element 12, membrane 11 and medium 3 in droplet dosing device 1 is critically damped, i.e. the vibration in the system is damped after a single period.

In order to enable a good operation of droplet dosing device 1 to be combined with a compact embodiment thereof, there are also preferably connected to piezo- element 12 means 15 for amplifying the operation thereof. In a possible embodiment of droplet dosing device 1 these amplifying means 15 are formed by a lever 16 which is arranged between piezo-element 12 and membrane 11, and whereby the relatively small deformations of piezo- element 12 are converted into larger movements of membrane 11 (fig. 5) . In the embodiment shown schematically here, an outer end 17 of lever 16 is fastened to a fixed part of droplet dosing device 1, for instance a wall of pump housing 9 , and the free outer end 18 thereof engages on membrane 11. Piezo-element 12 engages on lever 16 between these two ends 17,18, wherein the amplification achieved thus depends on the location of element 12 between these ends. In this embodiment the spring means 14 and damping means 10 are integrated with amplifying means 15 in that lever 16 is covered with a thin layer of elastomer material 19 (fig. 6), also takes a slightly resiliently flexible form, and thus functions as spring means .

A number of additional piezo-elements 12A, 12B, 12C ... 12N can also function as amplifying means, which elements are integrated with drive element 12 to form a multi-layer piezo-structure (fig. 7) .

The effect of damping means 10 and spring means 14 is shown in the graphs of fig. 8 where the behaviour of droplet dosing device 1 according to the invention is shown in full lines, while the behaviour of a conventional droplet dosing device is shown with the broken lines. In the case of an excitation in pulse form 10 of piezo-element 12 the membrane 11 is deformed, wherein the ascending flank 21 of the deformation curve rises relatively slowly as a result of the presence of spring means 14. This implies that the pressure in the medium is increased relatively slowly, whereby the chance of parasitic vibrations occurring is reduced. When the excitation pulse 20 falls away, the piezo-element 12 returns to its initial form, whereby membrane 11 does likewise and the pressure of medium 3 in pump 6 and channel 4 therefore decreases once again. The presence of damping means 10 herein prevents membrane 11, element 12 and medium 3 continuing to vibrate. The result hereof is that only one droplet 7 is dosed instead of several smaller droplets 22 as according to the prior art.

The droplet dosing device 1 can form part of a larger droplet dosing installation 23, which consists of a number of droplet dosing devices 1A, IB, 1C, ... , IN, arranged in a regular pattern on a carrier 24. Carrier 24 can herein be manufactured from a chemically resistant material such as glass, in which parts of the droplet dosing devices 1, particularly the source or the buffer 2, pump housing 9, channel 4 and spray nozzle 5 are formed by means of etching. The other components of droplet dosing devices 1, in particular the pump 6 and the connections (not shown) for control of the droplet dosing devices can be mounted in the etched parts, the thus formed devices of which are closed by a second plate .

Claims

1. Droplet dosing device, comprising at least one source of a medium for spraying, at least one spray nozzle, at least one channel connecting the source to the spray nozzle, pumping means for carrying the medium for spraying from the source to the spray nozzle, characterized by means for damping a pressure pulse generated by the pumping means, which damping means are operably connected to the pumping mean .

2. Droplet dosing device as claimed in claim 1, characterized in that the pumping means comprise at least one member displaceable by a drive element and the damping means are arranged between the drive element and the displaceable member.

3. Droplet dosing device as claimed in claim 1 or 2 , characterized in that the pumping means comprise at least one member displaceable by a drive element and the damping means are arranged between the drive element and a fixed part of the pumping means.

4. Droplet dosing device as claimed in any of the foregoing claims, characterized in that the damping means comprise an elastomer material .

5. Droplet dosing device as claimed in claims 2 and 4, characterized in that the at least one displaceable member comprises a membrane and the elastomer material lies against the membrane.

6. Droplet dosing device as claimed in any of the foregoing claims or as according to the preamble of claim 1, characterized by spring means operably connected to the pumping means .

7. Droplet dosing device as claimed in claim 2 or 3 and 6, characterized in that the spring means are arranged between the drive element and the displaceable member .

8. Droplet dosing device as claimed in claims 3 and 6 or 7, characterized in that the spring means are arranged between the drive element and a fixed part of the pumping means .

9. Droplet dosing device as claimed in any of the foregoing claims, characterized in that the spring means and the damping means are connected to each other.

10. Droplet dosing device as claimed in any of the foregoing claims or as according to the preamble of claim 1, wherein the pumping means comprise at least one displaceable member driven by a piezo-element, characterized by means connected to the piezo-element for amplifying the operation thereof.

11. Droplet dosing device as claimed in claim 10, characterized in that the amplifying means comprise a number of additional piezo-elements connected to the piezo-element to form a multi-layer structure.

12. Droplet dosing device as claimed in claim 10 or 11, characterized in that the amplifying means comprise a lever arranged between the piezo-element and the displaceable member.

13. Droplet dosing device as claimed in claims

7 and 12, characterized in that the lever takes a resiliently flexible form and forms part of the spring means .

14. Droplet dosing device as claimed in claims 9 and 13 , characterized in that the damping means are connected to the lever.

15. Droplet dosing device as claimed in claims 4 and 14, characterized in that the lever is at least partially covered with the elastomer material.

16. Droplet dosing installation comprising a number of droplet dosing devices as claimed in any of the foregoing claims arranged on a carrier in a determined pattern.

17. Droplet dosing installation as claimed in claim 16, characterized in that the carrier is manufactured from a chemically resistant material, in particular glass.

18. Droplet dosing installation as claimed in claim 17, characterized in that the carrier is plate-like and the droplet dosing devices are formed therein by etching.