ES2988844A1 - HEAT EXCHANGER FOR ADHESIVE APPLICATOR - Google Patents

Abstract

Heat exchanger (100), for a hot melt adhesive applicator, of the type comprising a body (101) with at least one adhesive inlet (120) towards a circuit comprising heating means such that they heat a corresponding sheet-shaped adhesive flow running through an annular space existing between said heating means and the inner walls of the circuit, the adhesive exiting through at least one outlet (130) to which an adhesive applicator device can be connected for its application, in which the heating means are a single heating cartridge (140) insertable into a through hole in said body (101), the through hole having a continuous section geometry forming a channel (110) that forms the annular space between the channel (110) and the heating cartridge (140) through which the sheet-shaped adhesive flow circulates to at least one outlet (130). (Machine-translation by Google Translate, not legally binding)

Description

DESCRIPTION

HEAT EXCHANGER FOR ADHESIVE APPLICATOR

Technical sector

The present invention relates to the technical sector of adhesive applicators. More specifically, it relates to hot-melt adhesive applicators in which said adhesive must be brought to a suitable working temperature moments before its application.

State of the art

In the hot melt adhesive sector, it is known that these have a temperature or temperature range suitable for their application and in which said product is in a fluid state appropriate to travel through the internal circuit of the applicator, until reaching the corresponding nozzle and without substantially losing its adhesive and durability properties. In this sense, one of the drawbacks lies in the fact that, at these working temperatures, and in certain applications, residues are generated - called thread or angel hair in the technique - that remain hanging from the application nozzle with the consequent interruptions of service or actions by operators for cleaning or maintenance. The most common way to overcome this problem is to reduce the viscosity of the adhesive (increase its fluidity) so as not to give the product time to create these threads. This reduction in viscosity can be achieved by increasing the temperature applied to the adhesive flow at some point in the circuit traveled by it inside the applicator.

One of the known solutions (which is disclosed, for example, in patent ES2900485T3) consists of creating a sheet-shaped adhesive flow in which, by the principle of drag of the viscous boundary layer, a fairly homogeneous heating of the entire flow occurs. This sheet-shaped flow must be formed by a remarkably thin layer of adhesive that is made to run over a heated surface which communicates this heat to the passing flow. In the aforementioned patent, the creation of this thin layer of adhesive is achieved by means of a section of tubular circuit that houses two heating cartridges in two perforations of the applicator. These cartridges are tubular, but with a diameter slightly smaller than the perforations that house them, in such a way that the adhesive is forced to move through the generally cylindrical space that remains between the inner surface of each tubular perforation and the outer surface of its corresponding heating cartridge. The tubular section is defined in the body of the heat exchange device having an inlet that receives a flow of liquid adhesive material and an outlet configured to provide the liquid adhesive material to a dispensing device for adhesive bonding application. The heat exchange device comprises an adhesive material inlet with a fluid passage that splits and recombines to several outlet orifices with equal pressure and flow rate for a plurality of dispensing devices connected to the heat exchange device. Said tubular section connects the adhesive inlet and outlets, creating a thin slot section in an annular space between the perforations and the heating cartridges that produce said sheet-like flow. The drawback of this solution (and similar ones) is that, under these operating conditions (with the sheet-like flow formed and its subsequent heating), the adhesive degrades and particles of burnt or carbonized adhesive are generated that can clog components of the applicator circuit such as, for example, the outlet nozzles. This obviously has consequences on the productivity of the system, since cleaning and maintenance actions are necessary, during which the application devices must be stopped, opened, the aforementioned heating cartridges must be removed (in the case of the previous patent, two for each application device) and these must be cleaned, as well as their tubular housings.

Therefore, one of the objectives of the present invention is to provide a hot melt adhesive applicator that facilitates maintenance and cleaning operations particularly in relation to the heating cartridges of said device, while maintaining the same (or similar) features with respect to laminar heating and subsequent dosing of the adhesive. As will be seen from the description and successive claims, an applicator device is achieved that has a heating cartridge system with improved structural, assembly and/or manufacturing characteristics, or at least alternatives to those of the prior art.

Object of the invention

Therefore, considering the purpose set forth in the previous section, the object of the present invention is a hot-melt adhesive applicator of the type that includes at least one adhesive inlet towards a circuit comprising heating means such that they heat a flow of adhesive in the form of a corresponding sheet that runs through an annular space existing between said heating means and the inner walls of the circuit, the adhesive exiting through at least one outlet to which an adhesive applicator device can be connected for its application. The heat exchanger in which the heating means are a single heating cartridge insertable into a through hole with a continuous section geometry that forms a channel that forms the annular space between the channel and the heating cartridge through which the flow of adhesive in the form of a sheet circulates to the outlets.

The channel cross-section must be such that, in combination with the built-in heating cartridge, it achieves a sheet-like flow, as is known in the art; i.e. tolerance variations are permissible provided that the necessary technical effect of sheet-like flow between the heating cartridge and the channel of the heat exchanger body is achieved.

Thanks to this configuration, the heating cartridge, which forms a single rigid element, can be inserted and replaced more easily than in the state of the art, where it was necessary to remove one cartridge on each side of the heat exchanger. With this configuration, the inner channel can also be cleaned more easily in one go, as a cleaning system can be passed from one side of the channel to the other. Maintenance times are therefore reduced and the manufacturing process is more efficient, thereby achieving improved competitiveness.

Additionally, since it is a rigid element (it is contemplated that there may be several screwable elements that form a single rigid cartridge) the supports of the cartridge in the channel are made at the ends, not requiring additional elements to center the cartridge inside the channel as in the state of the art in which protrusions were used on the outer surface of the cartridge to support the inner end of each cartridge. The manufacture of the cartridge will therefore be simpler and, in addition, will not include extra supports that interrupt the flow of the adhesive.

In one embodiment, the heating cartridge may be inserted interchangeably through either side of the channel for installation.

According to a characteristic of the heat exchanger, the preferably central part of the single heating cartridge, which is located at the branch corresponding to the adhesive inlet, has a narrowing for better distribution and distribution of the adhesive towards the area of creation of the sheet-shaped flow. This narrowing will be sized so that the resistance of the cartridge in this area is not weakened and a bending can be caused, which produces adhesive jams in the annular space created between the cartridge and the channel.

Alternatively or in combination with the previous feature of the narrowing of the cartridge, the invention contemplates a heat exchanger with a body comprising a recess around the channel in correspondence with the adhesive inlet. This configuration allows for better distribution and allocation of the adhesive towards the area of creation of the flow in the form of a sheet, dispensing with the narrowing of the cartridge so as not to weaken the resistance of the cartridge, and also making the manufacture of the heated cartridge itself simpler.

Preferably, the length of the heating cartridge is equal to or less than the length of the channel in which it is housed, so that the heat exchange surface for heating the adhesive is increased.

According to another feature of the invention, the heating cartridge achieves the effect of heating the adhesive by means of at least one elongated heating resistor that can be inserted laterally into the heating cartridge.

For the production of two elongated resistors, said resistors will have substantially the same length, to thermally cover the entire desired heat application length of the cartridge.

In a variant of this embodiment of the invention, the elongated resistors may be composed of a metal cylinder with a resistive wire wound along it and, in another more specific variant, the resistive wire winding is embedded, at least partially, within the metal cylinder. The metal cylinder has a uniform diameter along the entire resistor, having a minimum tolerance in its insertion into the heating cartridge so that it makes good thermal contact along its entire surface, since if there were not good diffusion of heat to the heating cartridge the resistor would break, since it can reach very high temperatures (up to more than 1,000 °C) in a few seconds.

According to one feature of the invention, the longitudinal hole for housing the resistors is blind or pluggable. That is, for a single resistor it can only be inserted through one of the sides of the heating cartridge, and in the case of two resistors the hole of each resistor will end in the middle part of the heating cartridge.

Preferably, for a single resistor, the longitudinal hole for housing the resistor will be through so as to avoid the vacuum caused by introducing the resistor.

Preferably, for the production of two resistors, there is a drill that connects both longitudinal holes, in order to avoid vacuum during the positioning of the resistors in the heating cartridge.

According to another feature of the invention, the cross section of the heating cartridge comprises interconnected rectilinear and/or curved segments that form a closed perimeter in correspondence with the section geometry of the channel. Preferably, the cross section is elliptical, or polygonal, with the cross section geometry of the channel being in correspondence, creating the aforementioned annular space that allows the sheet-like flow of the adhesive.

According to another characteristic of the invention corresponding to the embodiment in which the heating cartridge has an elliptical cross section, two longitudinal through or blind holes are formed in each of the foci of the ellipse, and said through holes house the desired heating resistors for better heat distribution.

According to another feature of the invention, one of the ends of the heating cartridge comprises a peripheral narrowing in correspondence with a narrowing of the channel. In this way, taking into account that a sealing gasket will be installed at the ends of the heater to prevent the adhesive from escaping, it is avoided that the gasket is damaged when inserting and removing the heating cartridge, since, if the end were of the same diameter, the gasket would interact with the adhesive inlet, being very likely to break or weaken, possibly generating leaks of hot adhesive.

In this case, it will be necessary to use retaining elements such as auxiliary flanges to prevent the cartridge from being expelled from the body due to the difference in pressure at each end. Therefore, the option of a heating cartridge with ends of the same section in which the forces are compensated is also contemplated, but the option of ends of different sections is preferred because it is a safer embodiment. In this respect, in relation to the embodiment of the invention with a recess in the body corresponding to the adhesive inlet, it would avoid having to make a narrowing at the end of the cartridge, since in this case, when the sealing gasket of the ends passes through the interior of the channel, it does not interact with the adhesive inlet.

Finally, another feature of the invention relates to housings for sealing gaskets included in the ends of the heating cartridge.

All of these features make maintenance easy, allowing maintenance to be carried out by unqualified technicians without damaging the head and minimising the possibility of an accident or leak occurring.

Description of the figures

The attached drawings illustrate, by way of non-limiting example, embodiments of the adhesive applicator of the invention and some of its components. In said drawings:

Figure 1 is a perspective view of the hot melt adhesive applicator of the invention.

Figure 2 is another perspective view of the adhesive applicator of the invention, showing the holes made in the applicator block.

Figure 3 is a sectional view of part of the adhesive applicator of the present invention without resistors for better visualization.

Figure 4 is another perspective view of the adhesive applicator of the present invention, with transparencies of some of its components to explain the flow of adhesive in said applicator.

Figure 5 is a sectional view of one of the heating cartridges of an applicator of the present invention.

Figure 6 is a sectional view of another of the heating cartridges of an applicator of the present invention, in which the resistors positioned within the cartridge are schematically represented.

Figure 7 is views of three different embodiments of the heating cartridge that forms part of the adhesive applicator of the present invention.

Figure 8 is a sectional view for a cartridge with a single resistor.

Figure 9 is a sectional view of part of the adhesive applicator of one embodiment of the present invention with a recess in the body.

Figure 10 is a perspective view of the adhesive applicator of the present invention, with transparencies of some of its components and arrows to explain the flow of adhesive in said applicator according to the embodiment of Figure 9.

Figure 11 is a perspective view of a heating cartridge for an exchanger according to the practical embodiment of Figure 9.

Detailed description of the invention

A detailed description of the invention will now be provided, emphasizing some details not presented so far.

Figure 1 shows a perspective view of a heat exchanger (100) for an adhesive applicator of the present invention that will serve to have a general idea of the operation of this type of device, showing an adhesive applicator block that will be installed in a hot adhesive supply machine. Figure 2 shows another perspective view of the same heat exchanger (100) in which the holes made in the applicator block are shown in order to better show the internal adhesive circuit of the apparatus.

First, the adhesive inlet (120) can be seen, where the adhesive circuit of the applicator (100) starts; then, the adhesive passes through a section (150) (figure 2) which ends in a "T" fork where the product is distributed to the left and right in a channel (110), the channel (110) being a through hole made in the body (101) of the heat exchanger (100).

To facilitate the understanding of the specification and the interpretation of the claims, the section (150) corresponds to the vertical side of the "T" and the channel (110) to the horizontal side. In areas close to the ends of the left and right sections of the horizontal side of the T (the channel (110)) there are openings through which the fluid exits said channel (110) until it reaches the outlets (130) of the applicator (100); in these outlets (130) the adhesive can be applied directly to the desired surface by means of, for example, nozzles or application devices. These sections of the circuit can be better seen by referring to figure 4, where arrows have been representatively drawn indicating the path of the adhesive flow from its entry at (120) to its exit at (130).

Furthermore, as explained above in the background section, this type of heat exchanger (100) has heating cartridges that are located in each of the sections of the channel (110), and with a small separation between its outer surface and the inner surface of the channel (110), so that an annular space is formed through which a flow of adhesive is created in the form of a sheet, around the heating cartridges, for better heating of the product.

The present invention replaces the two independent heating cartridges mentioned above with a single heating cartridge (140) which is housed in the channel (110) preferably occupying the entire length of the latter (Figures 3 and 4). In this way, when it is necessary to change the heating cartridge (140), because the adhesive (under these conditions of sheet-like flow and high temperature) has a certain tendency to form carbonized or overburned residues that can clog the circuit, it is sufficient to simply open the channel (110) on one of its sides and remove the cartridge (140) housed there. To this end, one of the characteristics of the invention is that the cross section of the channel (110) is continuous or constant throughout its length, whereby the heating cartridge (140) can be inserted throughout the channel, for example, a cylindrical configuration of the heating cartridge (140) in correspondence with a cylindrical configuration of the channel (100).

For reasons of design or for a possible better distribution of the adhesive, preferably the cross section comprises a narrowing (142) such that the mouth (112) of the section (150) of the circuit spills into a relatively open space with a view to the cylindrical distribution of the fluid adhesive through the sheet-shaped flow gap existing between the cartridge (140) and the inner surface of the channel (110); this distribution of the fluid can be better seen with the arrows in figure 4.

Said narrowing (142) can adopt any suitable form that allows the passage of the adhesive around it and towards the cylindrical interstices between the cartridge (140) and the channel (110). In the figures, a narrowing (142) has been represented with angled shapes but the contour of the same could be smooth, without angles, or with a greater number of angles (sections) to avoid the concentration of residues in these nooks.

With such a configuration, the assembly and disassembly of the heating cartridge (140) with respect to the applicator (100) is facilitated, as well as the cleaning or maintenance thereof, since the cross section (at least constant, although it could be greater in the central area) of the channel (110) favors the introduction of any tool or utensil for such purpose. In addition, the central support points corresponding to the two cartridges of the prior art, in the area of the channel (110) close to the mouth (112), and which were required to center each of the two cartridges so that the sheet-shaped flow-generating gap remained constant, are not necessary; in our case, since the heating cartridge (140) is made of a single piece, only supports are required at the ends thereof.

Since the use of sealing gaskets is necessary to prevent adhesive leaks, these gaskets will be installed at the ends of the heating cartridge (140), however, if both ends are of the same cross section, the gasket could be damaged when passing through the mouth (112), the contour of the mouth (112) can cause damage to the sealing gaskets placed at the ends of the cartridge (140). The internal adhesive circuit is usually obtained by drilling on initial pieces of aluminum which causes sharp corners or angles, as could be the case of the mouth (112) in the channel (110). On the other hand, the characteristics of such an applicator (100) are such (sheet-like flow) that the heating cartridge (140) fits very tightly inside the channel (110), i.e. with a very small gap between the two, which could lead to contact between these sharp angles and the sealing gaskets when inserting and removing the cartridge (140) from its channel (110), with the consequent risk of damage or breakage of the latter. Therefore, said peripheral narrowing (144) is preferably located at the end of the cartridge (140) that first enters the channel (110) in the assembly operation.

The shape of this narrowing (144) has been illustrated as a step (figure 5, for example) but, as can be deduced from what is expressed in the claims, this shape could be any other as long as it fulfills the function of reducing the outer contour of the cartridge (140) to avoid damage to the seals. Therefore, as can be seen in figure 5, at one of the ends there is a peripheral narrowing (144) that will rest on a complementary flange (114) included in the corresponding end of the channel (110), in which (144) the sealing gasket will be installed.

It is also contemplated to include a small enlargement (145) at the opposite end of the cartridge (140) to facilitate support of the heater cartridge (140) at that end. As is apparent from the sheet-like flow functionality, the dimensions of these support elements will be such as to provide that close and constant separation between the cartridge (140) and the channel (110) in the sheet-like flow creation areas.

In another embodiment, the ends of the heating cartridge (140) may comprise respective housings (143, 143') to house the corresponding sealing gaskets in order to prevent the passage of fluid adhesive (Figure 6).

In said figure 6, peripheral slots (147) can also be seen, the purpose of which will be to house the adhesive to facilitate its exit through the outlets (130) located at the same height.

The heating transmitted by the heating cartridge (140) to the adhesive is achieved by means of at least one heating resistor (160) housed therein. Advantageously, in the preferred embodiment, as can be seen in Figure 6, the heating cartridge (140) comprises two elongated heating resistors (160) each of which heats a part (preferably half) of the length of said heating cartridge (140). With this arrangement, a more homogeneous distribution of the heat is obtained, which is very important with a view to a homogeneous fluidization of the adhesive.

The number of heating resistors (160) could be greater or less than two depending on the factors considered in the design, such as the ease of assembly and disassembly of the cartridge (140), the productivity in its manufacture or the aforementioned homogeneity in the distribution of heat. In the preferred embodiment, the housing or housings for the heating resistors (160) consist of a through hole (141) to facilitate the introduction of said resistors (160) so that a vacuum effect is not generated that makes their extraction or insertion difficult. An alternative example of a cartridge (140) with a single resistor (160) can be seen in Figure 8. This through hole (141) could have the same cross section throughout its length or, for example, it could be somewhat narrower in the central area that corresponds approximately to the location of the narrowing (142), such as a drill or hole (146) made for the communication of the sections that house the resistors (160). Being narrower right in that area would cushion the weakening effect of the thinner walls due to the narrowing (142) and, in addition, it could serve to provide stops in order to correctly position the resistors (160) (cross sections of figures 5 and 6 for example).

In another preferred embodiment, the heating resistors (160) comprise a metal cylinder with a resistive wire wound around it. This wire is preferably embedded in the aforementioned cylinder and the manufacturing tolerances of the cylinder, resistive wire and the corresponding inner housings of the cartridge (140) are such as to guarantee good thermal contact substantially on all the surfaces facing the cylinder with the walls of the inner housing. That is, the heating resistors (160) are mounted tightly within these housings in order to generate a thermal bridge as extensive as possible and thus, on the one hand, better communicate the heat generated by the resistive wire, and, on the other, avoid concentrations of energy that could break the resistor (in relation to this it should be noted that said element can reach temperatures of up to 1,000 °C in a few seconds).

Although the preferred embodiment of the heating cartridge (140) is cylindrical, as can be seen in Figures 1 to 6, other shapes are also envisaged and are illustratively shown in Figure 7. The cross section of the cartridge (140) could be, for example, elliptical (Figures 7(a) and (b)) and, in this case, the cartridge (140) could comprise a single resistor (160) with its corresponding housing hole - Figure 7(a), or two resistors (160), each in a hole (141', 141'') at each focus of the ellipse, in order to generate a more homogeneous temperature distribution.

Another of the shapes provided by the present invention for the heating cartridge (140) is a polygonal outline (figure 7(c), octagonal in this case) in which the sides of the polygon may or may not be equal to each other. Obviously, whatever the shape of the cartridge (140), the channel (110) must have an inner section that corresponds to said shape in order to comply with the sheet-shaped flow creation characteristic claimed for this type of device (100). Furthermore, it is provided that for this embodiment of cartridge (140) with a polygonal section, or other similar ones, the cartridge (140) comprises longitudinal holes preferably close to the flat faces so that the material distance to the thermal source is similar to that of the corners.

According to another practical embodiment of the invention, as can be seen in Figures 9 and 10, instead of making a narrowing (142) in the heating cartridge (140) for the distribution of the adhesive from the inlet (120), it is provided to make a recess (121) in the body (101) around the channel (110) in correspondence with the adhesive inlet (120). In this way, it is avoided having to make said narrowing (142) of the cartridge (140) that could weaken it. Therefore, the cartridge (140) could equally have said narrowing (142) or have a uniform surface as can be seen in Figure 11.

For this embodiment, the peripheral narrowing (144) could be dispensed with since when removing the cartridge (140) it would not interfere with the entry of adhesive (120) by having a recess (121) in the body (101).

The present adhesive applicator (100) may comprise any of the technical features described above individually or in combination as set forth in the claims.

Claims (14)

1. Heat exchanger (100), for a hot melt adhesive applicator, of the type comprising a body (101) with at least one adhesive inlet (120) towards a circuit comprising heating means such that they heat a corresponding sheet-shaped adhesive flow running through an annular space existing between said heating means and the inner walls of the circuit, the adhesive exiting through at least one outlet (130) to which an adhesive applicator device can be connected for its application, characterized in that the heating means are a single heating cartridge (140) insertable into a through hole in said body (101), the through hole having a continuous section geometry forming a channel (110) that forms the annular space between the channel (110) and the heating cartridge (140) through which the sheet-shaped adhesive flow circulates to at least one outlet (130). 2. Heat exchanger (100) according to claim 1, wherein the heating cartridge (140) comprises a narrowing (142) in correspondence with the adhesive inlet (120). 3. Heat exchanger (100) according to claim 1 or 2, wherein the body (101) comprises a recess (121) around the channel (110) in correspondence with the adhesive inlet (120). 4. Adhesive heat exchanger (100) according to any of the preceding claims, wherein the length of the heating cartridge (140) is equal to the length of the channel (110). 5. Heat exchanger (100) according to any of the preceding claims, wherein the heating cartridge (140) used for heat diffusion comprises, inside it, at least one elongated heating resistor (160) insertable laterally into the cartridge (140). 6. Heat exchanger (100) according to the preceding claim, wherein the elongated heating resistor (160) comprises a metal cylinder with at least one winding of resistive wire along it, fitable into a longitudinal hole (141) of the heating cartridge (140). 7. Heat exchanger (100) according to claim 5 or 6, wherein the longitudinal hole (141) for housing the resistance(s) (160) is blind or pluggable. 8. Heat exchanger (100) according to claim 5 or 6, comprising at least two resistors (160) aligned in respective longitudinal holes (141) comprising a drill (146) communicating both longitudinal holes (141). 9. Heat exchanger (100) according to claim 5 or 6, comprising at least one resistor (160) with a length equal to or less than the length of the heating cartridge (140), the longitudinal hole (141) where said resistor (160) is housed being through. 10. Heat exchanger (100) according to any of the preceding claims, wherein the cross section of the heating cartridge (140) comprises interconnected rectilinear and/or curved segments that form a closed perimeter in correspondence with the section geometry of the channel (110). 11. Heat exchanger (100) according to any of the preceding claims, wherein the heating cartridge (140) comprises at least one longitudinal heat distribution hole. 12. Heat exchanger (100) according to claim 9, wherein the heating cartridge (140) comprises a longitudinal hole (141', 141'') for housing a resistance (160) at each focus of an ellipse formed by the cross section of said cartridge (140). 13. Heat exchanger (100) according to any of the preceding claims, wherein one of the ends of the heating cartridge (140) comprises a peripheral narrowing (144) in correspondence with a narrowing of the channel (110). 14. Heat exchanger (100) according to any of the preceding claims, wherein one of the ends of the heating cartridge (140) comprises a peripheral widening (145) in correspondence with a widening of the channel (110).