Apparatus for generating droplets of fluid

Details Apparatus for generating droplets of fluid Apparatus for generating droplets of fluid

1995-09-28

1998-11-17

Tso, Edward

Incremental printing of symbolic information

Ink jet

Ejector mechanism

B41J 2045

Patent

active

058383506

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention relates to apparatus and methods for the production of droplets by means of an electromechanical actuator.
A number of processes exist for the generation of droplets using electromechanical actuation. For many of these systems, the overall size of the equipment is considerable, with diameters of 20 mm or above (see Toda EP-A-0 480 615, Maehara EP-A-0 049 636 & EP-A-0 077 636).
There are a number of applications where such a large size makes the product unsuitable or inconvenient. For example when dispensing drugs intra-nasally it is desirable that the generator can fit inside the nostril. In the related area of hand-held droplet generators, for example ink-jet pens, air brushes, eye droppers and perfume dispensers, it is desirable to have a light and compact structure that can be easily manipulated and stored by the user.
It is an object of this invention to provide a droplet generation apparatus that can be made compact and of relatively low overall diameter.
It is a further object of this invention to provide an apparatus that generates a well defined droplet pattern with relatively high electrical efficiency.
It is a further object of this invention to provide an apparatus that may be driven from a compact electrical circuit and power source.


SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a device for generating droplets of fluid, the device comprising
a fluid supply means;
an electromechanical transducer having electrodes arranged so as to cause expansion or contraction of the transducer in a dimension perpendicular to the applied electric field; and
an element coupled for movement with the expansion/contraction of the transducer in the direction of the given dimension and positioned for contact with fluid from the supply means.
According to a second aspect of the invention there is provided a device for generating droplets of fluid, the device comprising
an electromechanical transducer;
a fluid supply means; and
an element coupled for movement with the transducer and positioned for contact with fluid from the supply means;
wherein the movable element is removably mounted relative to the transducer.
The movable element may be a perforate plate, but may alternatively be imperforate and have, for example, a profiled surface.
Preferably, the dimension in which the transducer is expandable or contractible is much greater than at least one other dimension of the transducer.
In one type of device, the transducer may be tubular and is expandable or contractible in the direction of its central axis. This (and other constructions in accordance with the invention) enable a uniform electric field to be provided in the thickness or radial direction so as to provide a strain that is largely independent of thickness. Thus the transducer or actuator is caused to operate in an extensional mode.
Alternatively, the transducer may be disc-shaped or annular and is expandable or contractible in the radial direction.
The supply means is advantageously in the form of a collapsible thin-walled structure partially bounding the fluid and may comprise a fluid reservoir.
The movable element is preferably connected with the fluid supply means and/or reservoir to form a replaceable sub-assembly or fluid cartridge assembly.
The fluid reservoir may be in the form of a collapsible thin-walled structure.
The present invention provides a relatively compact device which generates a defined droplet pattern on demand.
A suitable power source will be provided for the actuator/transducer including whatever means are needed, e.g. electronics and electrical circuitry, to produce the desired electrical drive for the actuator.
A manually operated switch can be provided for actuating the electronics. The switch may be mechanical or electronic. Such an electronic switch may be actuated by a timer or by a sensor or by other means.
The devices of the invention may have the transducer electrodes disposed across those two surfaces which give the shortest in

REFERENCES:
patent: 3683212 (1972-08-01), Zoltan
patent: 3804329 (1974-04-01), Martner
patent: 4294407 (1981-10-01), Reichl et al.
patent: 5124716 (1992-06-01), Roy et al.
patent: 5502472 (1996-03-01), Suzuki
patent: 5505364 (1996-04-01), Plesinger
patent: 5563634 (1996-10-01), Fujii et al.

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