NL1037570C2

NL1037570C2 - A device for dispensing a substance.

Info

Publication number: NL1037570C2
Application number: NL1037570A
Authority: NL
Inventors: Hendrikus Johannes Schellens; Bontko Witteveen
Original assignee: Heinmade B V
Priority date: 2009-12-18
Filing date: 2009-12-18
Publication date: 2011-06-21
Also published as: WO2011074970A1; EP2516838A1

Description

A device for dispensing a substance.

DESCRIPTION

The invention relates to a device for dispensing a substance, 5 comprising at least one nozzle for dispensing said substance, supply means for supplying said substance to said nozzle, comprising at least an outlet opening being in fluid communication with said nozzle and at least one actuator assembly for causing said substance being dispensed through said nozzle.

Known dispensing devices according to the above are arranged in 10 accommodating a liquid-like substance, such as ink in an inkjet printing device. For dispensing said substance in a droplet like fashion, the dispensing chamber is deformed by means of an actuator. The deformation causes the chamber volume to change (to decrease) causing the substance to be dispensed via the nozzle in droplets. For a further dispensing action the volume of the dispensing chamber 15 needs to return to its initial state, causing an under pressure in that chamber. The under pressure causes an intake of substance via the supplying means replenishing the amount of substance being dispensed through the nozzle.

However as the present day devices are operated at atmospheric pressure conditions the under pressure occurring the dispensing chamber also 20 causes the formation of vapor bubbles of the liquid substance once the pressure of the liquid falls below its vapor pressure. The presence of air or gas bubbles in the substance to be dispensed in adversely affects the performance of the dispensing device. In particular the presence of air bubbles in the substance in the dispensing chamber can prevent the substance from being dispensed through the nozzle.

25 The air bubbles need to dissolve back in the liquid substance and this degassing phenomenon in the substance will take some time.

The invention aims to provide an improved dispensing device according the above preamble, wherein the drawbacks of under pressure, the occurrence air bubbles and degassing is not present.

30 According to the invention said supply means are arranged for supplying substance under pressure to said nozzle, and wherein said actuator assembly being positioned between said supply means and said nozzle.

Herewith the substance to be dispensed always exhibits a pressure higher than the atmospheric pressure levels and the occurrence of any air bubbles in 1037570 2 the substance during operation is prevented.

More in particular the dispensing device is herewith capable of dispensing very small amounts of gas or liquid as herewith very small displacements can be achieved with the actuator assembly of the dispensing device, thereby 5 opening en closing the outlet opening for very short periods of time, thus dispensing (very) small amounts of substance at a time towards the nozzle. This allows the dispensing device to be operated at high frequencies, for example as a part of the combustion engine with fuel (diesel) injection. Herewith the combustion engine can be operated with a higher efficiency and reduced fuel consumption.

10 Further embodiments of the dispensing device according to the invention are mentioned in the dependent claims.

The invention will now be described with reference to a drawing which drawing discloses in:

Figures 1a-1b a first embodiment of a device according to the 15 invention;

Figures 2-10 further embodiments of a device according to the invention.

For the sake of clarity in the figurative description below all like parts are denoted with corresponding reference numerals.

20 In figures 1a and 1b a first embodiment of a dispensing device according to the invention is disclosed. The device, denoted with reference numeral 1, comprises a dispensing chamber 10 which accommodates a dispensing . space 10' for accommodating a certain amount of substance which substance is supplied via supply means 5. Supply means 5 comprises an inlet port or opening 5a 25 for the intake of said substance from a (not-depicted) buffer or reservoir through a supply channel towards an outlet port or opening 5b. The supply means 5 is in fluid communication with the dispensing chamber 10 via the outlet opening 5b.

Furthermore the dispensing chamber 10 is provided in its chamber wall section 10a with at least one nozzle 11 through which nozzle 11 the substance 30 accommodated in the dispensing chamber 10' can be ejected.

For the sake of clarity it is noted that in this application with ‘substance’ any type of gas or liquid is denoted, such as water, gasoline, oil, ink or any other substance depending on the application of the dispensing device according to the invention.

3

According to the invention the dispensing device 1 also comprises an actuator assembly 20 which during use causes the substance accommodated in the dispensing chamber 10' to be dispensed through said nozzle 11.

In the embodiments as shown in figures 1a and 1b the actuator 5 assembly 20 comprises a contact element 21 which is mounted to the dispensing chamber 10 near the wall sections 10a and 10b, thereby closing the dispensing chamber 10. The contact element also abuts against the circumferential edge 5c of the outlet opening 5b in such manner that the outlet opening 5b is closed.

In order to prevent any leakage of substance from the outlet 10 opening 5b across the circumferential edge 5c towards the dispensing chamber 10 (space 10') the supply means 5 are provided with one or more sealing members 6 which are mounted on or near the outlet opening 5b. Thus, in rest the contact element 21 abuts against the sealing members 6 near the outlet opening 5b, thereby obtaining a proper sealing functionality, and avoiding any unintentional leakage of 15 substance towards the dispensing chamber 10.

The actuator assembly 20 also comprises an actuating element 22 which - in this embodiment - is mounted to the contact element 21 as clearly depicted in figures 1a and 1b. The actuator element 22 is preferably an element made from a piezo-electric material, which piezo-electric material will undergo an 20 mechanical deformation once a voltage signal is applied to the piezo-electric material.

Figure 1a discloses the device in a resting position wherein the actuator assembly 20 closes the outlet opening 5b of the supply means 5, whereas in figure 1b the operational situation is disclosed wherein the piezo-electric material 25 of the actuator element 22 is being mechanically deformed due to a voltage signal applied thereto. The mechanical deformation of the piezo-electric material of the actuator element 22 results in a displacement of the actuator assembly (more in particular the contact element 21) away from the outlet opening, allowing fluid communication from the supply means 5 towards the nozzle 11.

30 According to the invention the supply means 5 are arranged in supplying the substance towards the nozzle 11 under pressure. Hereto the supply means 5 are provided (not depicted) with a reservoir wherein a sufficient amount of substance is present as well as means for supplying under pressure said substance from the reservoir via the inlet opening 5a towards the outlet opening 5b.

4

As long as the actuator assembly 20 is in its closed position as depicted in figure 1a the substance present in the supply means 5 under pressure cannot leak through the outlet opening 5b and across the contact element 21 towards the nozzle 11 as the pressure of the substance in the supply means 5 is 5 insufficient to urge the contact element 21 away from the outlet opening 5b.

In other words, the outlet opening 5b can only be opened when the actuator element 22 is properly energized by a voltage signal, thus resulting in a mechanical deformation, urging the contact element 21 away from the outlet opening 5b. This is shown in figure 1b where the substance under pressure being 10 accommodated in the supply means 5 is capable of entering the dispensing chamber 10 as depicted by the arrows due to the mechanical deformation of the contact element 21 (by means of the actuator element 22). Due to the pressurized behavior of the substance in the dispensing chamber 10, said substance is dispensed in droplets via the nozzle 11.

15 Unlike the known devices in the state of the art their drawbacks will not occur with the device according to the invention. The use of a substance (gas or liquid) under pressure being dispensed via the nozzle 11 once the outlet opening 5b is actively being opened by the actuator assembly 20 at a pressure level being higher than the atmospheric pressure, prevents the degassing phenomenon such as 20 the occurrence of gas bubbles in the substance (when a liquid as substance is being, dispensed) as with the known devices.

In figure 2 a second embodiment of the present invention is disclosed having nearly the same construction as the embodiment in figures 1a and 1b. In addition the dispensing device 1 in figure 2 is provided with additional 25 pressure performing means 40 which exhibit a pressure on the closure element 21 towards the outlet opening 5b.

The pressure performing means 40 comprises a support housing or bar 25 which is mounted to the dispensing device 1 with bar element 25a. Bar element 25b extends adjacent to the actuator assembly 20 being mounted to the 30 wall sections 10a and 10b of the dispensing chamber 10 and closing (in the rest position) the outlet opening 5b. Between the actuator assembly, more in particular the contact element 21 and the bar element 25b of the pressure performing means 40, a spring element 27 is accommodated. Spring element 27 has a certain spring tension which is exerted on the contact element 21, urging the contact element 21 5 against the outlet opening 5b and more in particular against the sealing members 6 present in the circumference 5c of the outlet opening 5b.

The sealing members 6 can be made from an elastic material, which is deformed once the contact element 21 is urged against the circumference 5c of 5 the outlet opening 5b. In order to avoid a degradation of the elastic material due to intense operation of the dispensing device it is desirable in certain applications where the dispensing device and in particular the opening and closure of the outlet opening 5b is performed at a high frequency (small intervals) to use a less elastic material, for example a sealing element 6 made from a stiff and durable material 10 such as a ceramic. Both types of material could be used as a sealing element 6 in either embodiment disclosed in the drawings.

With this embodiment wherein an extra pressure or tension is exerted on the contact element 21 urging it towards the outlet opening 5b a higher pressure in the substance (gas or liquid) is to be applied by the supply means 5 in 15 order to open the outlet opening 5b once the actuator element 22 is deformed due to a voltage signal being applied to the piezo-electric material.

In figure 3 yet another embodiment of the dispensing device according to the invention is disclosed wherein the dispensing chamber 10 is shaped as a block having bores 10' forming the dispensing space 10' for accommodating a 20 certain amount of substance (gas or liquid). The bores 10' are in fluid connection with the nozzle 11. The dispensing chamber 10 is provided with an end face 21 which serves as the contact element 21 of the actuator assembly 20. The contact element or end face 21 abuts against an end face 5c surrounding the outlet opening 5b of the supply means 5.

25 The dispensing chamber 10 is provided with a permanent sealing member 31, in particular being an O-ring sealing element which seals the dispensing chamber 10 and the end face 5c of the outlet opening 5b of the supply means 5 together in a permanent way. Furthermore, end face 5c is provided with an O-ring shaped sealing member 6 closing or sealing off the fluid connection between the 30 supply means 5 and the nozzle 11 once the contact element/end face 21 of the dispensing chamber 20 abuts against the circumferential end face 5c (and the sealing member 6) of the outlet opening 5b.

For a proper orientation of the contact element/end face 21 relative to the outlet opening 5b the contact element 21 is provided with a protruding notch 6 21' which extends with some play into the outlet opening 5b. A certain play between the protruding notch 21' and the outlet opening 5b is present allowing the passage of substance under pressure from the inlet opening 5a towards the outlet opening 5b along the protruding notch 21' towards the dispensing space 10' once the contact 5 element 21 is in an open position.

Hereto the actuator assembly also comprises actuator elements 22 which are mounted adjacent to the contact element 21 and the dispensing chamber 10 in a planar fashion. The actuator elements 22 are preferably made of a piezoelectric material as in the embodiments shown in figures 1a-1b and 2. The actuator 10 elements 22 are mounted to support elements 28a-28b which are connected with one end to the dispensing chamber 10 and with the other end to support housing 25 using connection means 29a-29b (bolts or screws). The housing elements 25 are mounted to the supply means 5 of the dispensing device 1.

A proper actuating of the piezo-electric actuating elements 22 will 15 result in a mechanical deformation of the piezo-electric material 22 urging the dispensing chamber 10 and the contact element 21 away from the end face 5c, the sealing members 6 and the outlet opening 5b. In this operational condition the outlet opening 5b is in fluid connection with the nozzle 11 via the dispensing space 10' and substance under pressure can be supplied via the inlet opening 5a towards the 20 nozzle 11, where it is dispensed in small droplets. De-energizing the actuator elements 22 will cause a closure of the outlet opening 5b as the dispensing chamber 10 and the contact element 21 will return to their initial resting position, wherein the contact element 21 will be urged against the sealing members 6 thereby closing the outlet opening 5b.

25 In figure 4 an embodiment more or less similar to the embodiment of figure 3 is disclosed. However, in the embodiment of figure 3 the actuator elements 22 are mounted in a planar orientation relative to the outlet opening 5b whereas in the embodiment of figure 4 the actuator elements 22 (for example made of a piezo-electric material) are cylindrical^ shaped and accommodated around the 30 outlet opening 5b. However, the operation of the dispensing device as shown in figure 4 is quite similar to that of the embodiment in figure 3.

In figure 5 yet another embodiment of a dispensing device according to the invention is disclosed wherein the contact element 21 of the actuator assembly 20 is accommodated inside the supply means 5. Here the contact 7 element 21 is provided with a cylinder-shaped plunger 210 which extends within the supply means 5 with a certain amount of play. More in particular the plunger body 210 is provided with grooves 212 which serve as a passage way for the substance (gas or liquid) being supplied via the inlet opening 5a under pressure towards the 5 outlet opening 5b.

Furthermore the plunger body 210 is at its other end (not being the end where the contact element 21 is situated) with a recess 211 for accommodating one end of a spiral-shaped spring 27. The spiral-shaped spring 27 is part of the pressure performing means 40 comprising a pressure plunger which can be 10 accommodated inside the supply means 5. The pressure plunger 40 is provided with a plunger part 40a around which the other end of the spring 27 is accommodated. The pressure plunger 40 is also provided with a second plunger element 40b which is provided with an outer screw thread 40b’. The inlet opening 5a is provided with an inner screw thread 5a which corresponds with the outer screw thread 40b’ of the 15 plunger part 40b.

Thus the plunger body 40 can be screwed inside the inlet opening 5a of the supply means 5, thereby pre-tensioning the spring 27 against the plunger body 210 of the contact element 21.

In this embodiment the actuator elements 22 are mounted against 20 the supply means 5, thereby - upon mechanical deformation of the piezo-electric material - urging the dispensing chamber 10 / dispensing space 10' / nozzle 11 away from the contact element 21. Due to the long response time of the contact element 21 to follow the displacement of the dispensing chamber 10 / nozzle 11 upon the mechanical deformation of the piezo-electric actuator elements 22 the outlet 25 opening 25 is in fluid communication with the nozzle for a brief period of time allowing substance under pressure being supplied from the inlet opening 5a towards the outlet opening 5b to enter the dispensing chamber 10 / dispensing space 10' and to be dispensed via the nozzle 11.

In figure 6 an embodiment is disclosed which resembles similarities 30 with the embodiment of figure 5, however here the actuator elements 22 are constructed as ring-shaped piezo-electric elements positioned around the outlet opening 5b whereas in the embodiment of figure 5 the piezo-electric actuator elements 22 are positioned in a parallel planar orientation relative to the longitudinal axis of the device.

8

It is observed that in the embodiments of figures 5 and 6 the closure elements 21 are provided with a hollow end face 21" surrounding the outlet opening 5b. This reduced the path of friction of the substance, when the closure element 21 is displaced over a very small distance leaving a very small passageway between 5 the contact element 21 and the circumference 5c of the supply means 5 for the substance being dispensed under pressure through this passageway towards the nozzle 11.

The device according to the invention is highly suitable for dispensing a gaseous or liquid substance, which substance is supplied under 10 pressure. In particular the device can be implemented in combustion engines for dispensing a combustion substance such as oil, gasoline or the like. As with the embodiments disclosed very small displacements can be achieved with the actuator assembly of the dispensing device, and thus the outlet opening is opened and closed for very short periods of time,(very) small amounts of substance at a time can 15 be dispensed towards the nozzle. This allows the dispensing device to be operated at high frequencies, for example as a part of the combustion engine with fuel (diesel) injection. Herewith the combustion engine can be operated with a higher efficiency and reduced fuel consumption.

In figure 7 another embodiment of a dispensing device according to 20 the invention is disclosed, wherein the actuator element 22 is accommodated inside the contact element 21. Hereto the contact element 21 comprises a hollow end face 21", which is covered or closed by a thin wall section 60. Actuator 22 is placed in direct contact against said thin wall section 60.

Upon energizing the actuator element 22 the thin wall section 69 will 25 be urged away from the outlet opening 5b creating a small passage way allowing fluid communication from the inlet port 5a towards the nozzle 11. Due to its symmetrical orientation around the longitudinal axis said substance can be applied under pressure from all sites across a relative large surface towards the outlet opening 5b and the nozzle 11.

30 In figures 8a-8c an other embodiment is disclosed of a dispensing device according to the invention having features quit similar to the embodiment of figure 7. In the embodiment of figures 8a-8c the contact element 21 is also provided with a hollow end face 21" which is closed by a thin wall section 60. When the device is in its closing position as is depicted in figure 8a the thin wall section 60 abuts 9 against the housing of the device and closes the outlet opening 5b.

Upon energizing the first actuator element 22 as in the embodiment of figure 7 the contact element 21 will be deformed thereby urging the thin wall section 60 away from the outlet opening 5b. Between the thin wall section 60 and the 5 outlet opening 5b a small passage way 61 is created. The passage way 61 will bring the inlet opening 5a and the nozzle 11 in fluid communication with each other allowing the substance being supplied under pressure to pass through the small passageway 61 towards the nozzle 5b. Due to the rotation symmetric orientation of the device relative to the outlet opening 5b the substance can flow towards the outlet 10 opening 5b from all sites around the contact element as the contact element (and the thin wall section 60) is urged away entirely from the outlet opening.

In Figure 8c the operational condition of the dispensing device according to the invention is depicted wherein the contact element 21 has been urged towards the outlet opening 5b by means of a proper energizing of the first 15 actuator element 22. In this situation a further actuator element 62 is accommodated in the hollow end face 21", which further actuator element 62 upon a proper energizing urges the thin wall section 60 away from the outlet opening 5b.

Herewith an additional dispensing action is realized of substance present in the space 10" between the outlet opening 5b and the thin wall section 60 20 being deformed by said further actuator element 62. With this embodiment it is possible to accurately dispense very small amounts of substance during very short time intervals.

The embodiment shown in figures 9a-9d is an enlarged view of the embodiment of for example figures 5 and 6. In this embodiment the follow end face 25 21" is covered or closed by a membrane 60, which is preferably made from a flexible (or elastic) material, such as a thin metal sheet. As shown in figure 9a the opening 5b (and nozzle 11) is closed by means of the contact element and more in particular by means of the cover membrane 60. Substance supplied under the pressure via inlet opening 5a of the supply means 5 will not leave the device via the nozzle 11.

30 By energizing the actuator assembly (for example the piezo electric element) the contact element 21 is urged away from the opening 5b as depicted in figure 9b. The displacement of the contact element 21 away from the opening 5b creates a small passageway (indicated with reference numeral 61) between the contact element 21, the cover membrane 60 and the circumference 5c around the 10 opening 5b. Due to its symmetrical construction around the longitudinal axis of the device the substance under pressure can flow from all sites towards the outlet opening 5b and the nozzle 11 through the passage way 61 created.

When the opening 5b is closed by means of the contact element 21 5 (see figure 9c) and due to the pressure of the substance being supplied the flexible cover membrane 60 is locally deformed in the hollow end face 21" of the contact element 21. The volume being present in the hollow end face 21" and being closed by the flexible cover membrane 60 decreases and the air in the hollow end face 21" is being compressed. After closure of the outlet opening 5b as shown in figure 9c the 10 deformed cover membrane 60 will return to its initial flat orientation as shown in figure 9a, which results in an additional dispensing of substance accommodated in the space 10' formed by the deformed cover membrane 60.

In figure 10 a further embodiment of a dispensing device according the invention is disclosed. Reference numeral 70 discloses an injection module for 15 use in a combustion engine for injecting fuel (gasoline) towards a combustion chamber of the engine. Hereto is the module 70 provided with an outer screw thread 71 allowing a proper and secure mounting of the module in the engine.

This embodiment has a similar configuration as the embodiment of figure 7 in combination with features of figure 9a-9d. Actuator element 22 and 20 contact element 21 forming the actuator assembly 20 are mounted inside the module 70 and connected to a block 72. Block 72 is fully accommodated against a spring 69 in module 70 in order to allow any thermal expansion of the block 72, as the module 70 is operated at relatively high temperatures in the combustion engine. The spring 69 interacts with block 72 and closure nut 73 which is screwed by means 25 of screw thread 73a in module 70 which is provided with an inner screw thread 70a. This allows the block 72 as well as the actuator assembly 20 being mounted with a pre-tension inside the module 70.

As in the embodiment of figure 9a-9d contact element 21 in figure 10 is provide with a hollow end face 21" which is shielded off by means of a thin wall 30 section 60 made from an elastic material or from a thin metal layer. Furthermore the actuator assembly 20 is shielded off from the supply means 5 by means of an shielding element 65. Shielding element 65 is completely surrounding the actuator assembly 20 creating a space 66 between the actuator assembly and the shielding element 65.

11

The dispensing device of figure 10 is furthermore provided with cooling means 67-68-65 for providing a coolant medium, for example oil towards the space 66 between the actuator assembly 20 and the shielding element 65. This allows a proper cooling of the actuator element 22 as the actuator assembly 20 is 5 operated at high temperatures in the combustion engine. The coolant medium reduces the operational temperature of the actuator assembly 20 increasing its life span and efficiency. The cooling means comprise a supply line 67 for supplying coolant medium towards the space 66 between the actuator assembly 20 and the shielding element 65 as well as a discharge line 68 for discharging said coolant 10 medium.

Between block 72 and the module housing 70 a sealing element 32, preferably an O-ring shaped sealing element 32 is present sealing the inner space of the module 70 when substance under pressure is supplied against leakage across block 72. Although block 72 is biased by means of a pre-tensioning spring 69 and a 15 nut 73 in the module housing 70 leakage will not occur as the O-shaped sealing ring 32 will be pressed between the block 72 and the module housing 70 due to the pressure exerted by the substance thereon (as shown by means of arrows 33).

During opening and closing of the outlet opening 5b by a proper energizing of the actuator element 22 an identical deformation of the thin wall 20 section 60 and the hollow end face 21" will occur as described with the embodiment of figure 9a-9d. Likewise a further actuator element 62 can be accommodated in the contact element 21 as depicted in the figures 8a-8c.

With the embodiment of figure 10 the opening and closing of the outlet opening 8b can be achieved at very short time intervals. Therefore the 25 dispensing device as shown in figure 10 can be used as an high frequency fuel injection device allowing an improved control of fuel injection of for example diesel engine significantly improving fuel consumption as well as enhancing the motor characteristics.

30 1037570

Claims

An apparatus for dispensing a substance comprising at least 5 - one nozzle for dispensing the substance; supply means for supplying the substance to the nozzle, comprising at least one outlet opening which is in fluid communication with the nozzle and at least one excitation assembly which ensures that the substance is dispensed, characterized in that the supply means are arranged for supplying the substance under pressure to the nozzle and wherein the excitation assembly is placed between the supply means and the nozzle and wherein the device further comprises a delivery chamber for receiving a certain amount of substance and wherein the at least one nozzle is included in a wall of the delivery room.

Device as claimed in claim 1, wherein the device comprises control means for controlling the actuation assembly.

3. Device as claimed in claim 1 or 2, wherein the actuating assembly comprises a closing element for opening and closing the exit opening of the supply means.

Device as claimed in any of the foregoing claims, wherein the excitation assembly comprises at least a first excitation element for displacing the closing element or the exit opening relative to each other.

Device as claimed in claim 4, wherein the at least first actuating element is mounted around the closing element.

Device as claimed in claim 4, wherein the at least first actuating element is attached to the closing element.

7. Device as claimed in any of the foregoing claims, wherein the device comprises at least one sealing element which is placed between or near the exit opening and the closing element.

Device as claimed in any of the foregoing claims, wherein the device comprises pressure exerting means for exerting a pressure on the closing element in the direction of the exit opening. 1037570

Device as claimed in claim 8, wherein the pressure applying means are adjustable pressure applying means.

Device as claimed in claim 8 or 9, wherein the pressure applying means comprise at least one spring.

Device as claimed in any of the claims 8 to 10, wherein the pressure applying means are included within the supply means.

12. Device as claimed in claim 11, wherein the pressure applying means also included a plunger element that is freely movable within the supply means.

Device as claimed in claim 12, wherein the plunger element is provided with at least one passage that allows the passage of the substance in the direction of the exit opening.

Device as claimed in any of the claims 8 to 10, wherein the pressure applying means are included outside the supply means.

Device as claimed in any of the claims 1 to 14, wherein the closing element comprises a centering cam which is directed inwards towards the exit opening.

Device as claimed in any of the claims 1 to 14, wherein the closing element comprises a hollow end surface that surrounds the exit opening.

17. Device as claimed in claim 16, wherein the closing element comprises a membrane which covers the hollow end face.

The device of claim 17, wherein the membrane is made of a flexible material.

19. Device as claimed in claim 17 or 18, wherein the membrane is made of a metal.

The device of any one of claims 16-19, wherein the excitation assembly comprises at least one further excitation element included in the hollow end face.

21. Device as claimed in claim 20, wherein the at least one further energizing element is placed on the membrane.

Device as claimed in any of the claims 6-21, wherein the excitation assembly is shielded from the supply means by means of a shielding element.

The device of claim 22, wherein the device comprises cooling means for supplying a cooling medium between the excitation assembly and the shielding element.

Device as claimed in any of the foregoing claims, wherein the first and the further energizing elements are piezo-electric actuators. 5 1 037 57 0