Device and method for delivering a fluid, in particular hot-melt adhesive

A device and a method for delivering a fluid, in particular hot-melt adhesive. The device includes a base member having an inlet opening for receiving the fluid from a fluid source and an outlet opening for delivering the fluid to a nozzle arrangement. The nozzle arrangement has a discharge passage with a discharge opening for delivery of the fluid. A heat transfer member heats or cools the fluid and includes a heat transfer passage through which the fluid can flow. The heat transfer passage is of a flow cross-section which changes in the flow direction.

The present application claims the priority of German Patent Application No. 102007048046.8 filed Oct. 5, 2007 under 35 U.S.C. §119, the disclosure of which is hereby fully incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a device and method for delivering a fluid, such as hot-melt adhesive.

BACKGROUND

In many industrial applications, free-flowing materials (fluids) are delivered with the aid of fluid delivery devices and placed or dispensed onto substrates. The fluids may be adhesives, paints, sealing materials or gases, for example, and the substrates may be sanitary articles, plastic films, furniture or machine parts and the like. Depending on the specific application, the fluids may be delivered in the form of beads, strips or films, for example, or the material may be sprayed, if necessary, with the aid of a gaseous stream that influences the fluid. The fluid delivery devices are connected to a fluid source, for example a container for adhesives, and the fluid is transported with the aid of a pump to a discharge opening that is circular or slot-shaped, for example.

In some applications, it is advantageous or necessary that the fluid be heated before it is delivered. In the case of spraying methods, it may be advantageous to heat a gas that affects a liquid to be delivered. In many applications, it may be necessary to heat a liquid to be delivered, in particular a fluid hot-melt adhesive prior to delivery and application to a substrate or material. A fluid delivery device with an integrated heat transfer chamber is known from the applicant's patent EP 1 419 826 A2, for example, in which it was proposed that a structure with cavities, made in particular of a sintering material, be disposed in a heat transfer chamber in order to influence the transfer of heat in an advantageous manner.

There is a need for further improvement of fluid delivery devices which have a heat transfer member. There is therefore a need to optimize the fluid mechanics of heat transfer member for heating or also for cooling a fluid, so that they can be better adapted to changing viscosities of the fluid, for example. There is also a need to reduce the geometrical dimensions of the fluid delivery device as a whole. In many cases, it is also necessary to process and apply temperature-sensitive fluids, particularly hot-melt adhesives or thermoplastic materials which must be gently heated, without causing temporary local overheating and hence detrimental impacts on the properties of the material.

The object of the present invention is to specify a device and a method for delivering a fluid, and a heat transfer member for a fluid delivery device, which take up relatively little installation space and/or which are suitable for processing temperature-sensitive fluids, particularly hot-melt adhesives, and/or are fluidically optimized, especially with regard to changing viscosities of the fluids.

SUMMARY

The invention achieves this object, according to a first aspect of the invention, with a device of the kind specified at the outset, in which the heat transfer passage is of a flow cross-section which changes in the flow direction.

A heat transfer member is fluidically optimized due to the flow cross-section of the heat transfer passage changing in the flow direction of the fluid. Depending on the respective fluid temperature, the viscosity of the fluid changes during heating or cooling. As a result of such change, there is also a change in the flow resistances, flow speeds and shearing forces within the fluid. By virtue of the heat transfer passage having a flow cross-section that changes and is adapted to the respective application conditions, the flow speed and/or shearing forces or other parameters can be adapted or positively affected, depending on the specific application, so that the fluid is gently heated or cooled.

In one particularly preferred embodiment in which, for example, hot-melt adhesive or other fluid or gases are to be delivered, it is proposed that the heat transfer passage has a flow cross-section which decreases, at least in sections thereof, in the direction of fluid flow. In this way, consideration is given to the fact that the viscosity usually decreases with increasing fluid temperature. Flow cross-sections which decrease in this manner result in a substantially uniform flow resistance and possibly also in uniform flow speed and shearing forces in the fluid.

Another embodiment of the invention is characterized in that the heat transfer passage is defined by heat transfer surfaces which are arranged in substantially mutually parallel relationship, and the mutual spacing of which decreases in the direction of the intended preferred flow of material. A decreasing flow cross-section is therefore realized with this relatively simple design measure.

According to another aspect or embodiment of the invention, the heat transfer passage is of a substantially meander-shaped configuration, at least in portions thereof. By means of such a meander-shaped configuration, the design and production of a fluid delivery device can be made especially compact.

In one embodiment, it is proposed that the heat transfer member comprise a base member through which the heat transfer passage defined by the heat transfer surfaces extends along a curved path disposed between two closure elements. The base member is configured with at least one closure element to receive a heating or cooling element. The fluid thus flows in a meandering manner along a curved path, thus achieving efficient heat transfer within a small installation space. It is advantageous when at least one closure element of the base member, or the base member itself, is adapted to receive a sealing element.

According to a further aspect, the invention achieves its object in a device of the kind specified at the outset, and/or is advantageously developed, in that the heat transfer member has a plurality of plates which each have at least one respective contact face and are so arranged that the contact faces of two adjacent plates are respectively connected to each other, wherein a continuous heat transfer passage extends through the entirety of the plates in their connected state, and the plates have apertures, in particular through openings, for receiving heating elements.

Due to the plurality of plates, the heat transfer member has a sandwich construction which provides advantages in production engineering, especially. If so required, the size and thermal capacity of the heat transfer member can be adapted in a simple manner by selecting the appropriate number of plates.

According to the embodiment of the invention with a meander-shaped configuration of the flow passage, it is proposed that, on at least one face, the plates have an aperture which does not extend completely through the thickness of a plate, and that the apertures have at least one through opening in an end portion of an aperture, which through opening is adapted for the through flow of fluid from one aperture into the aperture in an adjacent plate, so that the entire heat transfer passage is embodied by coupling the apertures. It is advantageous when the plates are adapted with at least one contact face to receive a sealing element. The outer plates of an assembly of plates can preferably be closed by means of closure elements.

According to one other aspect of the invention, the heat transfer surfaces of the heat transfer member are configured so that a reference output temperature of the fluid can be set, and that the heat transfer surfaces of the heat transfer member are designed with a surface area of such magnitude as to permit the attainment of the reference temperature by a heating temperature of the heat transfer surfaces, which is substantially equal to the reference temperature of the fluid.

According to an exemplary method of the invention, the reference temperature of the fluid is reached when the fluid flows over the heat transfer surfaces of the heat transfer member, and a heating temperature is substantially equal to the reference temperature of the fluid obtains at heat transfer surfaces.

By dimensioning the heat transfer passage in the manner of the invention such that, when the fluid is flowing through or has finished flowing through the heat transfer member, the actual or reference temperature of the fluid is substantially equal to the heating temperature of the heat transfer surfaces, i.e., the fluid has reached their surface temperature; particularly gentle heating (or cooling) of the fluid can thus be achieved, which is advantageous in the case of temperature-sensitive fluids, and particularly of thermoplastic adhesives, and any local damage due to overheating is prevented. In other words, by dimensioning the passage in the manner described, the selected surface temperature is so low that overheating or excessive temperature gradients in the fluid are effectively prevented.

According to one embodiment of the invention, it is proposed that the heat transfer member is essentially produced from a strongly heat-conducting material, such as copper or aluminum. It is particularly advantageous for the production process when the heat transfer passage is produced by wire erosion.

DETAILED DESCRIPTION

FIG. 1shows a device1according to an embodiment of the invention for delivering fluid. Device1may also be referred to as dispensing head1. Fluid, in particular a liquid hot-melt adhesive, is supplied to device1through an inlet opening2. The fluid flows through a heat transfer member3which is fixed to a base member5with fasteners4. In the embodiment shown, screw connections are provided as fasteners4, but other, preferably releasable connections, such as plug connections or the sliding of parts into one another by means of rails, can likewise be considered advantageous. In heat transfer member3, the fluid flowing therethrough is brought to a desired, and in particular a selectable reference temperature which is substantially identical to the discharge temperature of the fluid. A control unit6is likewise fixed to base member5. Control unit6cooperates with a valve mechanism and controls the selectably intermittent or continuous delivery of fluid and application of the fluid to a substrate.

A nozzle arrangement7is also fixed to base member5. Fluid is received by nozzle arrangement7from base member5and dispensed through a discharge opening9. Nozzle arrangement7also has a mouthpiece holder10and a mouthpiece11, which is fixed to mouthpiece holder10with fasteners8. Discharge opening9may be wholly or partially embodied in mouthpiece holder10or in mouthpiece11.

FIG. 2shows a plan view from below of device1inFIG. 1. It shows inlet opening2through which fluid is supplied to device1, heat transfer member3, base member5and nozzle arrangement7mounted on base member5. Mouthpiece holder10is connected to base member5by fasteners13. The discharge opening9of nozzle arrangement7is configured as a slot nozzle9′. Mouthpiece11extends along the entire length of mouthpiece holder10. A cross-sectional plane A-A is positioned substantially symmetrical through device1, such that inlet opening2, heat transfer member3, base member5, control unit6and nozzle arrangement7are shown in cross-section.

FIG. 3shows a cross-section of device1through sectional plane A-A. The path taken by the fluid until it is delivered to the substrate can readily be seen from theFIG. 3. After entering through inlet opening2, the fluid is fed to heat transfer member3. Heat transfer member3has a heat transfer passage14which has a plurality of parallel subsections in the form of generally planar passage portions40defined by two opposite heat transfer surfaces15,16. In the embodiment shown, heat transfer passage14has a meander-shaped configuration which is also shown inFIG. 5to aid understanding. In this regard,FIG. 5shows that each planar passage portion40is connected at a first end40ato a U-shaped passage portion42leading to the previous planar passage portion40, and connected at a second end40bto a U-shaped passage portion40leading to the next planar passage portion40. The flow cross-section of the heat transfer passage is not constant. Due to the changing distance between the heat transfer surfaces, the flow cross-section decreases in the direction of flow.

Heat transfer member3is closed on one side by a closure element17and on the opposite side abuts base member5. Heat transfer member3has apertures18on the surfaces which are in contact with closure element17and base member5. The apertures18are configured to receive sealing elements or a sealing material.

The fluid is fed from heat transfer passage14to a through-channel19in base member5, and passes through the channel19to control unit6. Control unit6has a valve mechanism20which is configured to move a valve piston21. In the selected orientation of device1, valve piston21performs a vertical movement and causes closure or opening of a through opening23. When valve piston21is in the open position, fluid is fed to a discharge passage25. Through discharge passage25, which in the chosen embodiment is partially disposed in mouthpiece holder10and in mouthpiece11, fluid is fed to a discharge opening9and delivered therethrough onto the substrate.

Valve mechanism20is connected to base member5and partially extends into the interior of base member5. Sealing elements22are provided in apertures and prevent the discharge of fluid at those locations. The nozzle arrangement likewise has apertures24which are configured to receive sealing elements or sealing material.

FIG. 4shows an alternative embodiment of a heat transfer member3, which is connected in an appropriate manner to a base member5as shown inFIG. 3, and which also cooperates functionally with the components thereof. This embodiment has a plurality of individual plates26with longitudinal apertures14′ that are embodied in a first end surface46of the plates26and which form a heat transfer passage—in sandwich construction—in that a transverse through opening27extending from the first end surface46through the thickness of plate26to a second end surface48is provided in a portion of each plate, thus forming a passage for the fluid from one longitudinal aperture14′ to the next. To this end, each of the longitudinal apertures46includes a first end46acommunicating with a transverse through opening48of a plate26located adjacent the first end surface46, and a second end46bcommunicating through the transverse through opening48of the plate26, thereby collectively defining a meandering back-and-forth flow path. Heat transfer member3is closed on one side by a closure element17′. The closure element17′ also delivers fluid from an inlet opening2′ to the heat transfer member3. In the chosen embodiment, a second closure element28configured to receive a filter arrangement20′ is provided on the opposite side. Filter arrangement20′ partially extends into the interior of second closure element28. A filter element21′ extends in the vertical direction in the heat transfer member3oriented as shown. A through opening23′ through which fluid can pass after filtration is connected to a through passage19, which is not shown here but corresponds to the one shown inFIG. 3.

Plates26each have apertures18′ on a contact surface29for receiving a sealing element. The second closure element28likewise has an aperture18′ for receiving a sealing element. Filter arrangement20′ likewise has an aperture22′ for a sealing element.

FIG. 5shows a perspective view of an integral embodiment of a heat transfer member3as shown inFIG. 3. Flow channel14is disposed inside heat transfer member3and has a meander-shaped configuration. The flow cross-section decreases in the direction of flow—which runs from bottom to top when the heat transfer member3is oriented as shown inFIG. 5. The fluid enters the heat transfer member3through an opening31. The fluid leaves heat transfer member3through an opening32. Aperture18for receiving a sealing element is embodied in the form of a circumferential groove. Heat transfer member3also has through bores30through which fasteners4(not shown) extend.

The arrangement of heating elements is shown by way of example inFIG. 6for an embodiment comprising a plurality of individual plates26. In a cross-sectional plane parallel to and in the vicinity of the lateral surfaces of the heat transfer member3, plates26and second closure element28have bores33configured to receive fasteners. Closure element17′ has threaded bores35in which screws for fixing plates26and closure elements17′,28can engage with each other. The second closure element28and plates26also have bores34which are configured to receive substantially cylindrical heating elements. Plates26are arranged in relation to each other in such a way that bores33,34of the respective plates are coaxial to each other, with the result that the screws and inserted heating elements can extend through the plates.

While the present invention has been illustrated by a description of various illustrative embodiments and while these embodiments have been described in some detail, it is not the intention of the Applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The various features discussed herein may be used alone or in any combination depending on the needs and preferences of the user. This has been a description of illustrative aspects and embodiments the present invention, along with the preferred methods of practicing the present invention as currently known. However, the invention itself should only be defined by the appended claims.