Patent ID: 12208409

DETAILED DESCRIPTION

In this patent specification, the following terms should be understood as indicated:

‘Flexible’ refers to the ability of a structure to bend without breaking, and particularly to bend easily; i.e. relatively little force need be applied to cause bending. As will be apparent from the disclosure below, a relevant property of a flexible structure in the context of the invention is that it causes relatively little damping of vibrations generated by a vibrating mechanism such as a transducer.

A ‘fluid excitation device’ is understood to encompass any device that seeks to generate excitations in a fluid. The excitations may themselves be the usable output of the device, as in the case of an ultrasonic bath for cleaning, for example, or the excitations may cause some other effect such as droplet generation at an interface between the fluid and air, as in the case of an atomiser, for example.

A ‘head for a fluid excitation device’ refers to the portion of the fluid excitation device that operates to generate excitations in the fluid. The fluid excitation device will comprise the head and typically at least some form of fluid reservoir.

FIG.1provides a cross-sectional view of a head for a fluid excitation device100according to a first embodiment.FIG.2shows portion B ofFIG.1in greater detail, andFIG.3shows portion C ofFIG.1in greater detail.

Head100includes a transducer105that includes an upper vibration generation portion110a, a lower vibration generation portion110band a fluid excitation portion115. Upper vibration generation portion110aand lower vibration generation portion110bmay be referred to collectively herein as ‘the vibration generation portion’. In this embodiment the vibration generation portion is formed of a piezoelectric material and fluid excitation portion115is formed of a ceramic sheet or a metal sheet. These components are purely exemplary and the invention is not limited to any particular form of transducer so long as the transducer is capable of generating vibrations.

Head100is suitable for use in a fluid excitation device in which the objective is to generate waves within the fluid, e.g. an ultrasonic bath. The upper face of the fluid excitation portion115can be arranged in contact with fluid in a reservoir (not shown inFIG.1) that is mounted above head100. Vibrations are transmitted from the vibration generation portion to fluid excitation portion115and subsequently into the fluid where they manifest as waves within the fluid.

Fluid excitation portion115is secured to the vibration generation portion in a manner that enables vibrations to be transmitted from vibration generation portion110to fluid excitation portion115. In the illustrated embodiment fluid excitation portion115is sandwiched between upper vibration generation portion110aand lower vibration generation portion110b. This arrangement secures the fluid excitation portion115between the two pieces of the vibration generation portion in a stable and robust manner. This arrangement also ensures that the fluid excitation portion115is in good physical contact with the vibration generation portion so as to enable good transmission of vibrations generated by the vibration generation portion to fluid excitation portion115.

The invention is however not limited to the sandwiched arrangement shown inFIG.1and instead encompasses any securing mechanism that allows good vibrational transmission from the vibration generation portion to fluid excitation portion115. For example the securing mechanism could comprise an adhesive layer that is positioned between an edge of the fluid excitation portion and an edge of the vibration generation portion so as to adhere these respective edges to one another. Other variants will be apparent to the skilled person having the benefit of the present disclosure.

Head100also includes a flexible substrate125. In the illustrated embodiment flexible substrate125is a flexible printed circuit board, but this is not essential as the flexible substrate125can be any flexible sheet or other such flexible structure of material. An example of a suitable material for flexible substrate125is a polyamide plastic or polyimide plastic. Flexible substrate125can be of the order of tens of microns thick, e.g. in the range of 1 to 100 microns, or 1 to 500 microns. A preferred thickness for the flexible substrate is 20 microns. Thicknesses in the micron range have been found to offer desirable levels of flexibility that do not cause significant damping of vibrations generated by the vibration generation portion. However, the invention is not limited in this regard and any thickness of flexible substrate125is within the scope of the invention. For example, it is envisaged that the substrate could be significantly thicker, e.g. in the range of 500 microns to 10 mm thick.

Transducer105is secured to flexible substrate125via an adhesive layer130that is positioned between the substrate125and lower vibration generation portion110bof the transducer105(seeFIG.2). Adhesive layer130can be formed from any suitable adhesive such as a glue or solder. Adhesive layer130is typically relatively thin, e.g. of the order of tens of microns thick, perhaps in the range of 1 to 100 microns thick. A preferred thickness for the adhesive layer is 20 microns but the invention is not limited in this regard and any thickness of adhesive layer130is within the scope of the invention. Adhesive layer130may be electrically conductive, e.g. in the case where the flexible substrate is a printed circuit board.

Referring specifically toFIG.3, flexible substrate125is shown in greater detail. In the illustrated embodiment flexible substrate125is a flexible printed circuit board that comprises three layers—a lower flexible layer135a, an electrically conductive middle layer135band an upper flexible layer135c. That is, middle layer130bis sandwiched between lower and upper layers135a,135c. The total thickness of the three layers in this embodiment is approximately 20 microns, with each layer being approximately 7 microns thick. Lower and upper flexible layers135a,135ccan each be formed from a polyamide plastic or polyimide plastic. Middle layer135bcan comprise copper printed circuit board traces.

Optionally one or both of lower flexible layer135aand upper flexible layer135cmay include a gap or hole that exposes electrically conductive middle layer135bto fluid. If a coverlay is present on either or both of layers135a,135c, it will be appreciated that a corresponding gap or hole should be provided in the coverlay at the same place as the gap or hole in the flexible layer(s). The exposed part of electrically conductive middle layer135bcan be used as a sensor to sense properties of the fluid. Sensing can include: concentration sensing, pH sensing, pressure sensing, temperature sensing, and the like.

One or more fluid interaction components can be built into flexible substrate125to enable the component(s) to interact with the fluid in some manner. One example of a suitable component is a transducer that can be used to heat the fluid. Another example is a strain gauge that can be used as a pressure sensor. These and other components can be formed using appropriate shaped circuit traces in flexible substrate125.

A membrane may be provided between the fluid and the sensor(s) and/or fluid interaction component(s) so as to protect the sensor(s) and/or fluid interaction component(s) from fluid if needed. The membrane can be made of any material that provides fluid protection whilst enabling the component that it protects to perform its function.

As these sensors and/or fluid interaction components are integral to flexible substrate125advantageously they can be electrically coupled directly to middle later135bto provide power in a convenient manner. Additionally, the manufacture and assembly of the sensor(s) and/or fluid interaction component(s) is relatively simple as they are integrated into flexible substrate125. Furthermore, the sensor and/or fluid interaction components and can be located very closely to the fluid. This allows highly accurate readings to be taken in the case of sensors and efficient operation in the case of fluid interaction components.

Advantageously the use of a flexible PCB means that power can be supplied to the vibration generation portion relatively easily and simply. Referring back toFIGS.1and2, an optional first electrically conductive layer145can be provided between the flexible PCB and the lower vibration generation portion110b. First electrically conductive layer145can be formed of any material that exhibits good electrical conduction at room temperature. A preferred material for first electrically conductive layer145is silver, but other materials such as copper can alternatively be used. First electrically conductive layer145electrically couples middle layer135bof the flexible PCB to lower vibration generation portion110b—to assist with this coupling, adhesive layer130is preferably also electrically conductive.

Optionally, as best shown inFIG.2a second electrically conductive layer150can be provided above upper vibration generation portion110a. When both layers are present, the first and second electrically conductive layers sandwich the vibration generation portion as best shown inFIG.2. Second electrically conductive layer can be formed of any material that exhibits good electrical conduction at room temperature. A preferred material for second electrically conductive layer150is silver, but other materials such as copper can alternatively be used.

Second electrically conductive layer150can be electrically coupled to an optional second flexible PCB155as shown inFIG.2. Alternatively, a wire (not shown) can be used to electrically couple layer155to middle layer130b. These electrical coupling arrangements are purely exemplary and alternative couplings such as one or more wires in place of layer145and/or150can alternatively be used.

Advantageously, the illustrated electrical coupling arrangement is compact, reliable and relatively simple to manufacture. This arrangement also avoids having significant length wires or leads which can be difficult to secure effectively, particularly in environments in which head100is envisaged for use where electrical circuitry must be insulated against fluid ingress.

Transducer105can optionally also include first and/or second protective layers160,165to prevent corrosion of first and/or second conductive layers145,150as may be caused by exposure to the atmosphere and/or fluid. If present, first protective layer160is positioned between first conductive layer145and adhesive later130. If present, second protective layer165is positioned above second conductive layer150to act as a cap for transducer105. Second protective layer165may also cover at least a portion of second PCB155if present, as is shown inFIG.2. The or each protective layer160,165can be made of any material that affords protection against corrosion, with enamel being a suitable and preferred material.

In the case where flexible substrate125is a PCB, transducer105can optionally also include a coverlay170that is located between the adhesive layer130and the flexible PCB. Coverlays per se are known in the art and therefore coverlay170is not described in detail here. It is sufficient to understand that coverlay170provides a protective layer for the PCB and specifically the circuitry of the PCB. A coverlay may additionally or alternatively be provided on the lower face of lower flexible layer135a.

As can be best seen inFIG.1, fluid excitation portion115includes a fluid contact region175that is exposed or open, i.e. it is not covered by any part of the vibration generation portion or flexible substrate125. This fluid contact region175is the region in which fluid excitation occurs as, in use, the fluid contact region175is in contact with fluid and thus is capable of causing excitations in the fluid.

In known arrangements that involve clamping or other such mechanically-based securing techniques, significant damping is experienced across a relatively large part of the total area of the equivalent of fluid contact region175. This significantly reduces the total useful output of the fluid contact region in known arrangements.

In contrast, in the case of the invention the use of flexible substrate125and adhesive layer130means that vibrations in the fluid contact region175are of sufficient amplitude to generate useful fluid excitations across a large fraction of the total area of fluid contact region175, e.g. 80%, 85%, 90%, 95% or more of the total area of fluid contact region175. Here, useful fluid excitations are excitations that result in a desired output, e.g. waves in the fluid that are capable of effecting cleaning in the case of an ultrasonic bath, or droplets in the case of an atomiser. In this way the efficiency of the invention is greater than known clamping-type arrangements. In some cases known clamping-type arrangements can be precisely tuned such that they may have an efficiency approaching that of the invention. However, the tuning process is time-consuming and complicated and also places significant limitations on design freedom. In such cases the invention provides at least equivalent efficiency, if not greater efficiency, with significantly reduced manufacturing complexity and improved design freedom.

Additionally, since the invention puts a greater proportion of the total area of fluid contact region175to useful effect, the amount of useful output per unit time can be correspondingly increased. For example, the invention may be able to generate significantly more fluid excitations per unit time than known clamping arrangements. This can result in equivalent cleaning levels in a shorter time in the case of an ultrasonic bath, or a greater droplet generation rate in the case of an atomiser.

Transducer105can take any shape, but it is preferred that the vibration generation portion is ring-shaped and fluid excitation portion115is shaped so as to fit within a central hole of the ring. Here, ‘ring-shaped’ includes both circular and elliptical cross-sections. This produces an arrangement with a circular or elliptical fluid contact region175. The invention is however not limited in this regard and fluid contact region175can alternatively be any other shape, e.g. rectangular, square, etc.

In the illustrated embodiment flexible substrate125includes an optional fluid test hole140in its structure. The fluid test hole140enables a testing apparatus, e.g. a probe, to be guided through the substrate125and into a fluid reservoir (not shown inFIG.1,2or3) to enable testing of the fluid within the reservoir. The testing can include performance of any desirable test, e.g. pH testing, concentration testing, temperature testing, and the like, and any combination thereof. Advantageously, fluid test hole140enables testing to be performed without detaching the substrate from the fluid reservoir.

As shown, the fluid test hole140is located beyond an outer edge of the transducer105. This location is preferred such that hole140does not interfere in the operation of transducer105. The location of hole140is however not limited to this and hole140can be located anywhere in substrate125. Hole140is sized to enable a testing apparatus to gain access to fluid in the fluid reservoir, such that the size of the hole will vary in dependence on the nature of the testing apparatus. For example, in the case of a testing apparatus having a probe, hole140can have a width that is slightly greater than the width of the probe.

Although only a single fluid test hole is shown inFIGS.1and3, the invention is not limited in this regard and multiple fluid test holes can be present. Each hole may be suitable for use in combination with a different one of a set of test apparatuses, e.g. with complimentary dimensions and/or positioning in substrate125.

Referring now toFIG.4, a head200for a fluid excitation device in accordance with a second embodiment is shown in cross-section. Details B and C are identical to that of the first embodiment and therefore reference can be made toFIGS.2and3, respectively. Elements ofFIG.4are identical to elements of the first embodiment except as set out below. Corresponding elements between the two embodiments have the same suffix to enable easy cross-referencing.

The difference between head100and head200is that fluid excitation portion215of head200includes a plurality of holes in fluid contact region275, e.g. by forming a mesh in fluid contact region275. Head200is thus suitable for use in a fluid excitation device in which the objective is to generate droplets of fluid, e.g. an atomisation device, as the plurality holes in fluid excitation portion275can enable fluid from a reservoir (not shown inFIG.4) to pass through fluid contact region275(e.g. via pumping, or via capillary action if a wick is present) and generate droplets via the vibrations transmitted to the fluid excitation portion215.

In this case, the reservoir would tend to be located below head200in fluid-tight contact with flexible substrate215. The fluid excitation portion may be a micro-porous mesh in this embodiment.

Preferably the plurality of holes in fluid contact region275extend across at least a substantial portion of the width of fluid contact region275, e.g. holes are provided having positions lying across at least 80%, 85%, 90%, 95% of the width of fluid contact region275. Distributing holes across a significant fraction of the width of fluid contact region can advantageously increase the total amount of droplets generated per unit time. This is made possible by the use of flexible substrate225and adhesive130, which together minimise damping that would otherwise be present in a known clamping arrangement and which allow vibrations of an amplitude that is capable of generating droplets to persist across at least a large fraction of the width of fluid contact region275.

The size and shape of each hole and the spacing between adjacent holes is not essential to the working of the invention and can be selected according to the specifics of the design at hand. It will be appreciated that the shape and dimensions of each hole will affect the size of droplets that are generated. The spacing between adjacent holes will affect the hole density in fluid contact region275, with a corresponding change in the amount of droplets generated per unit time.

In known arrangements the o-ring or other clamping component (seeFIG.5, right-hand side) create a trap that tends to retain bubbles created during operation of the transducer close to the fluid contact region. This is undesirable as it can disrupt fluid flow through the holes in the fluid contact portion.

As can be seen fromFIGS.4and8, there is little or no protrusion of the fluid excitation portion215into the fluid, particularly in fluid contact region275. This means that any bubbles that are generated in the fluid during operation of the transducer are easily removed from fluid contact region275via fluid flow.

Disruption of fluid flow through the holes in fluid contact region275is therefore advantageously at least reduced if not virtually eliminated.

FIG.5provides an illustration of a distinction between the invention and known injection heads that make use of clamps or an equivalent mechanical forcing arrangement. The invention is shown on the left ofFIG.5and it can be seen that the amplitude of vibrations in the fluid excitation portion is relatively high (i.e. large enough to be usable to generate useful excitations in a fluid) across a large fraction of the width of the fluid contact region. In contrast, in the known arrangement shown on the right which employs clamps (shown as dark circles), the amplitude of vibrations in expected to vary significantly across the width of the fluid contact region. Specifically, vibration amplitude is expected to reduce significantly as distance to the clamps decreases. This makes the outer regions of the fluid excitation portion of the prior art unusable for generation of fluid excitations, whereas the invention can make use of a greater fraction of the width of the fluid contact region for useful excitation generation.

WhileFIG.5shows only head100, it will be appreciated that the illustration ofFIG.5applies equally well to head200. The amplitude vs. position graphs shown inFIG.5are purely illustrative and in practice the exact relationship between position and amplitude may take a different form than that shown. What is consistent across all implementations of the invention is that useful levels of excitation are produced across more of the area of the fluid excitation region than in known arrangements.

FIG.6shows in cross-section a fluid excitation device600that comprises the head100of the first embodiment and a reservoir605. Reservoir605is essentially a container capable of retaining a fluid610. Reservoir605can be made of any material capable of retaining fluid610and resisting any damaging effects that fluid610may have, e.g. corrosion, warping, etc. Typically reservoir605is made of plastic or metal. Fluid610can be any fluid that is of interest in the intended use for fluid excitation device600, including but not limited to: a disinfecting fluid such as hydrogen peroxide solution, water, a lubricant, a solvent for cleaning, and others.

Head100is mounted to reservoir605by a mounting layer615. The mounting layer can be formed of an adhesive material such as glue or solder and can create a fluid-tight seal between head100and reservoir605. If fluid testing hole140is present as shown, a corresponding hole can be formed in mounting layer615. A cap or other such fluid-tight sealing member may be provided to plug the hole in mounting layer615when fluid testing is not being performed.

Fluid excitation device600is suitable for use as either an atomiser or a cleaning unit, e.g. an ultrasonic bath. The primary function of fluid excitation device600is dictated by the height of fluid610that is maintained above the fluid contact region175of head100.

Within a certain range of heights, excitations in the fluid caused by head100will have sufficient energy when reaching fluid-atmosphere interface620to generate droplets of fluid at this interface. The droplets are ejected from fluid610into the air directly above. Air can be blown across the surface of fluid620to capture these ejected droplets and transport them to a desired location, e.g. a surrounding room in the case of disinfection or humidification, or a pipe or similar in the case of lubrication. In this case a fluid inlet (not shown) may be provided to top up fluid610as it is depleted via droplet generation so as to maintain the height h approximately constant over time.

In the case where the fluid height h exceeds the range for droplet generation, excitations in the fluid caused by head100will not have sufficient energy when reaching fluid-atmosphere interface620to generate droplets of fluid. However, the excitations in the fluid themselves can be used to clean objects placed within reservoir605, and in this case fluid excitation device600functions as an ultrasonic bath. Ultrasonic baths per se are known and so further description of an ultrasonic bath is not necessary here.

In addition to the fluid height h, other parameters may be adjusted to alter the operation of fluid excitation device600. An example of such a parameter is the frequency and/or amplitude at which the vibration generation portion is driven. Control circuity (not shown) can be provided to generate a control signal that drives the vibration generation portion and adjust such parameters as required.

Another fluid excitation device700according to the invention is shown inFIG.7. Fluid excitation device700is an atomisation device that is capable of maintaining a constant height h between the fluid excitation portion of head100and the atmosphere-fluid interface720without continual replenishment of fluid lost due to droplet production. This advantageously means that real time or near real time control of fluid levels in reservoir705is not needed; instead, reservoir705need only be filled from time to time. The constant height means that droplet production is reliable in terms of rate of generation and/or average droplet size.

In the embodiment ofFIG.7a flotation device is provided to suspend head100within fluid710at a constant height h with respect to the atmosphere-fluid interface720. The flotation device can take many forms and in the illustrated embodiment the flotation device comprises a ring725and first and second anchoring lines730a,730bthat secure the ring725to the flexible substrate of head100. Ring725can be formed of any material that floats on the surface of fluid710and should be dimensioned such that it is capable of floating when supporting the weight of head100. An exemplary material for ring725is polyethylene foam, but the invention is not limited in this respect and many other suitable materials for ring725will be apparent to the skilled person having the benefit of the present disclosure.

Anchoring lines730a,730bcan be formed of any material that is capable of reliably and robustly attaching the flexible substrate of head100to ring725. An exemplary material is a monofilament synthetic fibre such as monofilament nylon, but the invention is not limited in this respect and many other suitable materials for anchoring lines730a,730bwill be apparent to the skilled person having the benefit of the present disclosure. It will also be appreciated that fewer or more anchoring lines than two can be provided, e.g. one anchoring line, three anchoring lines, four anchoring lines, etc. The length of the or each anchoring line is set such that the height h between head100and interface720is constant as droplets are produced and the level of fluid710correspondingly drops.

An adjustment mechanism (not shown) may be provided to enable the length of anchoring lines730a,730bto be altered so as to change height h. This enables fine tuning of the fluid excitation mechanism and may be particularly useful where the fluid excitation device700is used as an atomiser.

It will be appreciated that after some time of use, the level of fluid710will drop sufficiently that either head100comes into contact with the bottom of reservoir705or the distance between the topmost part of the sides of reservoir705and interface720is too great for droplets to be effectively caught by air blown across the surface of fluid710. At this point fluid710can be topped up, e.g. via a fluid inlet (not shown). A sensor (not shown) may be provided to detect the current position of head100and cause fluid710to be topped up as needed and based on the detected positon of head100.

Advantageously head100and the flotation device can be provided as a single unit that is capable of being placed in any reservoir. This provides flexibility in deployment as existing reservoirs can be used without modification. Head100and the flotation device can also be easily removed from reservoir705to enable repairs or modifications to the components of head100to be carried out easily. Reservoir705can also be cleaned whilst the head100is removed.

FIG.8shows another fluid excitation device800according to an embodiment of the invention. Fluid excitation device800makes use of head200and is suitable for use as an atomiser. Unlike devices600and700, fluid excitation device800has a reservoir805that is located beneath head200. Fluid is moved from reservoir805via the holes in the fluid excitation portion of head200, e.g. directly via the pumping action of the fluid excitation portion of head200or via a capillary if a wick is present. Droplets are thus generated in the region above the fluid contact region, and can be transported from this region to any desirable location by directing an air flow across the upper surface of head200.

A fluid inlet (not shown) can be provided in reservoir805to enable topping up of reservoir805with additional fluid to compensate for fluid lost from reservoir805as droplets.

Flexible membrane225can also function as a fluid-tight seal between head200and reservoir805. This may be achieved by providing an adhesive sealing layer between the walls of reservoir805and the lower surface of flexible membrane225. This arrangement advantageously prevents fluid leakage without significant damping of vibrations in the fluid excitation portion of head200.

Numerous modifications and adaptations to the embodiments disclosed herein will be apparent to a skilled person having the benefit of the present disclosure. All such modifications and adaptations are also within the scope of the invention as defined by the appended claims.