Patent Application
20050236430
The present invention relates generally to liquid material dispensing systems, and more particularly to applicators for dispensing controlled patterns of thermoplastic material to a substrate.
Dispensing systems for supplying liquid material and filaments in other forms are conventionally used to apply thermoplastic materials, such as hot melt adhesives, to various substrates during the manufacture of diapers, sanitary napkins, surgical drapes, and other substrates. Typically, liquid material and pressurized air are supplied to the dispenser where they are heated and distributed to one or more dispensing modules for application to the substrate. The heated liquid material is discharged from the dispensing module while pressurized air is directed toward the dispensed liquid to attenuate or draw down the dispensed liquid material and to control the pattern of the liquid material as it is applied to the substrate.
Conventionally, liquid material dispensing systems have utilized separate manifolds for heating and supplying the pressurized air and liquid material to the dispensing modules. Accordingly, the separate air and liquid material manifolds use separate heaters specifically dedicated to heat the respective air and liquid material. Generally, the requirements for heating the liquid and air are different, therefore, different types of heating elements are typically used for each heater and the heating elements are separately controlled. This in turn contributes to increased manufacturing costs and the need to stock multiple service parts. Having separate air and liquid material manifolds also inhibits making the dispensers compact in size. Because the air and liquid material heaters are separately controlled, heat generated from one heater can interfere with the temperature control of the other material. For example, the heater for heating the air may be turned off by a controller in an effort to reduce the temperature of the pressurized air, but heat generated by the liquid material heater may continue to heat the air, thereby effectively contravening efforts to control the air temperature with the air heater. Finally, a dispenser having separate manifolds increases manufacturing time due to the need to couple together the individual manifolds to produce the adhesive dispenser.
Adhesive dispensing systems generally have manifolds configured to accommodate a fixed number of adhesive dispensing modules. Often, however, it is desirable to have an adhesive dispenser of a modular configuration which permits manifolds of the dispenser to be joined together or separated to permit flexibility in increasing or decreasing the number of modules which can be used in a given application. Such modular adhesive dispensers present unique challenges such as maintaining uniform heating across all modules so that liquid material is uniformly dispensed to the substrate, particularly from dispensing modules located at the ends of each manifold where less heat from the manifold heaters is transferred to the liquid material due to heat losses through the ends of the manifold.
A need therefore exists for an improved liquid material dispensing system which addresses various drawbacks of prior dispensing systems, such as those described above.
The present invention provides an integrated manifold for a dispensing system, as well as a dispenser incorporating the manifold, preferably used to dispense hot melt adhesives in an air assisted manner. The dispenser dispenses liquid material and process air from at least one dispensing module coupled to the manifold. The manifold of this invention integrates a process air distribution portion and a liquid distribution portion into a common, integral manifold body or block, which is preferably an aluminum extrusion. Unlike conventional hot melt adhesive systems, the power requirements for heating the process air are shared between a heater specifically designed to heat the incoming process air and at least one additional heater which heats both the liquid material and the process air.
More specifically, an integrally formed manifold body is configured to receive one or more of the dispensing modules thereon and includes an internal air heater passage. Liquid and process air supply passages are provided in the manifold body. A plurality of liquid passages in the manifold body communicate with the liquid supply passage to provide the liquid material to the module(s). A plurality of process air passages in the manifold body communicate with the process air supply passage to provide process air to the module(s). A first heating member is positioned within the internal air heater passage and a gap is formed between the first heating member and the manifold body. The gap forms a portion of the process air supply passage. A second heating member is operatively coupled to the manifold body proximate the liquid passages and supplies heat to the liquid material in the liquid passages and also supplies heat the process air in the gap and the process air passages.
A first temperature sensor is positioned in the manifold body at a location such that the first temperature sensor senses a temperature approximating the temperature of the process air provided to the modules from the process air passages, while minimizing the thermal effects of the second heating member on the first temperature sensor. A second temperature sensor is positioned in the manifold body at a location such that the second temperature sensor senses a temperature approximating the temperature of the liquid material provided to the modules from the liquid passages, while minimizing the thermal effects of the first heating member on the second temperature sensor. Advantageously, the first and second heating members are comprised of identical heating elements. First and second embodiments are disclosed in which the first and second heating members respectively extend substantially parallel to and transverse to the longitudinal extent of the manifold body. The manifold body further includes first and second ends each having fastening elements for coupling the manifold body to another manifold body, in side-by-side relation, to expand the number of dispensing modules of the dispensing system. This feature is especially adapted for the embodiment having transversely extending heating members.
The first heating member or process air heating member preferably further comprises an elongate cylindrical member. The cylindrical member may be a cartridge style heating element of an appropriate diameter, but in the preferred embodiment, the elongate cylindrical member includes a lengthwise extending central passage and an elongate, electrically operated variable heating element is positioned within the central passage. A groove is located on an outer surface of the cylindrical member and extends at least substantially around the circumference of the elongate cylindrical member. The groove is configured to receive process air to be heated by the elongate cylindrical member and communicates with the gap. The process air is heated by the manifold block on one side of the gap and by the first heating member on the opposite side of the gap. Since the manifold block is directly heated by the second heating member, the load for heating the process air is shared between the first and second heating members. Also, since the first heating member, e.g., the elongate cylindrical member, is spaced from the manifold block by the aforementioned gap, the heat supplied to the process air is effectively carried away by the process air moving through the gap. This minimizes the effect of variations in the heat supplied to the process air by the first heating member on the liquid sections of the manifold body. Thus, the set point temperature of the liquid may be more precisely maintained as the process air temperature is varied by controlling the power to the first heating member.
The features and various advantages of the inventive aspects will become more readily apparent to those of ordinary skill in the art upon further review of the detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.
Referring to
Several liquid dispensing modules 30 are secured to the front surface 14 of the manifold body 12 by fasteners 32. The dispensing modules 30 may be on/off-type modules with internal valve structure for selectively dispensing liquid material in the form of one or more filaments. An exemplary module of this type is disclosed in U.S. Pat. No. 6,089,413, commonly assigned to the assignee of the present invention and incorporated herein by reference in its entirety.
Liquid material, such as hot melt adhesive, and pressurized process air is supplied to the individual modules 30 through the manifold body 12 to thereby dispense beads or filaments of the liquid material to a substrate. The dispenser 10 further includes first, process air heating members 34a, 34b and second, liquid material heating members 36a, 36b for heating the air and liquid material, as will be described more fully below. Filters 38a, 38b are installed in the manifold body 12 to filter out contaminants from the liquid material supplied to the modules 30, and temperature sensors 40a, 40b and 42a, 42b are provided to measure the temperature of the liquid material and process air. Signals from the temperature sensors 40a, 40b, 42a, 42b are supplied to a controller (not shown) which controls the air and liquid heaters 34a, 34b and 36a, 36b to regulate the temperature of the air and adhesive dispensed from the modules 30. Each of the components described above is mounted to the unitary manifold body 12 as shown and described herein. In the description that follows, the dispenser of
Referring now to
A first, vertical bore 54 is formed through the top surface 18 of the manifold body 12 and extends downwardly through the manifold body 12 to intersect an air supply passage 56. The first bore 54 also communicates with the air inlet port 50 and is sized to receive the first heating member 34a for heating the incoming process air. In the embodiment shown, the first heating member 34a includes an elongate cylindrical member 60 that is received within the first bore 54 and spaced from the sidewalls of the first bore 54 to provide a clearance gap 62 along the length of the cylindrical member 60. In one embodiment, the clearance gap 62 is approximately 0.015 inch to 0.025 inch and process air is provided through the manifold body at a rate of approximately 0.5 to 2 SCFM (standard cubic-feet-per-minute) per module. The cylindrical member 60 is shown more clearly in
Referring to
The cylindrical member 60 is formed from a conductive material, such as metal, and has a central passage 72 extending along a longitudinal axis from the first end 70 toward the air supply passage 56. A first heating element 74 is disposed within the central passage 72 and is connected by an electrical lead 76, protected by conduit 77, to an appropriate power source (not shown). The heating element 74 and cylindrical member 60 are secured to the upper surface 18 of the manifold body by a clamp 75 and threaded fastener 79. In the embodiment shown, the heating element 74 is a cartridge heater, but it will be recognized that the heating element 74 may alternatively be other types of heating elements, as known in the art. Accordingly, when current is supplied to the heating element 74 through the electrical lead 76, the heating element 74 heats the cylindrical member 60 which, in turn, heats process air flowing through the inlet port 50 and along the gap 62 toward the air supply passage 56. The configuration of the first heating member 34a provides an efficient way to transfer heat to the process air. Specifically, the cylindrical member 60 is substantially enveloped in the process air such that heat from the cylindrical member must pass through the process air, except at the first end 70 where the cylindrical member 60 is sealed to the manifold body 12.
As shown in
With continued reference to
As shown in
Referring now to
As shown in
Liquid material enters the filter 38b through circumferentially spaced inlets 100 and circulates through the filter 38b whereafter filtered liquid material exits toward the bottom 102 of the filter cavity 94. Thereafter, the liquid material enters an adhesive distribution passage 104 communicating with the filter cavity 94 and extending longitudinally along the manifold body 12, adjacent the bank of liquid dispensing modules 30 and parallel to the process air distribution passage 80 and the inlet supply passage 96. As shown in
With continued reference to
As depicted in
Because both the first and second heating members 34a, 34b and 36a, 36b are mounted directly within the manifold body 12, and because the liquid and adhesive passages are formed through the unitary manifold body 12, it will be recognized that heat emanating from the second heating members 36a, 36b is conducted through the manifold body 12 to heat not only the liquid material, but also the process air flowing through the process air passages. Specifically, heat conducted through the manifold body 12 from the second heating members 36a, 36b provides heat to portions of the manifold body 12 surrounding the first bore 54 to cooperate with the first heating members 34a, 34b to heat process air flowing through the clearance gap 62 and other air passages 50, 54, 56. However, heat from the first heating members 34a, 34b is substantially isolated from the rest of the manifold body 12 by the process air flowing through the clearance gap 62 and therefore does not significantly affect the temperature of the liquid material flowing through the manifold body 12. This arrangement, in conjunction with the configuration of the first heating members 34a, 34b discussed above, provides a robust and efficient mechanism for heating the process air and minimizes heat loss between the first heating members 34a, 34b and the process air. Because heat loss from the first heating members 34a, 34b is minimized, the heating elements 74 of the first heating members 34a, 34b do not have to be overdesigned to obtain a desired temperature rise in the process air.
Referring again to
While the liquid dispenser 10 has been shown and described herein as having two sets of first and second heating members, filters, and associated air and liquid passages, it will be recognized that a liquid dispenser could alternatively be provided with only a single set of heaters, filters and associated air and liquid passages, or alternatively more than two sets of heaters, filters, and passages, as may be required for a particular application. Moreover, the vertical arrangement of heaters and filters facilitates adding additional manifold segments to accommodate a greater number of liquid dispensing modules 30, or alternatively providing additional heaters, filters, and associated flow passages into a common manifold.
Referring now to
Referring now to
The first heating members 152a, 152b comprise elongate cylindrical members 186 having central passages 188 for receiving heating elements 190, as described above. In the embodiment shown, the heating elements 190 are cartridge heaters with electrical wiring for coupling the cartridge heaters to appropriate power sources. The cylindrical members are spaced from the bore 184 to provide annular gaps 192a, 192b which extend along the lengths of the cylindrical members 186. The air inlet ports 180a, 180b are in fluid communication with the first bore 184 whereby air from the source is directed through the inlet ports 180a, 180b to the first bore 184 and along the gaps 192a, 192b between the cylindrical members 186 and the first bore 184. As the air travels through the gaps 192a, 192b, it is heated by the heating members 152a, 152b, as discussed above with respect to
With continued reference to
First temperature sensors 203a, 203b are coupled to the manifold body 160 through longitudinal cavities formed through the longitudinal ends 170, 172 thereof, adjacent the first bore 156, and extending toward the center of the manifold body 160. In this embodiment, the temperature sensors are located at positions to sense temperatures that closely correspond to the temperature of the process air moving through the air passages and discharged from the dispensing modules 30.
Referring now to
As shown most clearly in
The multiple liquid inlet ports 220a, 220b and 222a, 222b (collectively referred to herein as 220, 222) on the manifold body 160 facilitate convenient routing of liquid supply hoses (not shown) to the dispenser 150. The liquid inlet ports 220, 222 are in fluid communication with first and second filter cavities 228a, 228b by a liquid material inlet supply passage 230 extending longitudinally through the manifold body 160, whereby liquid material supplied to the manifold body 160 from appropriate liquid sources (not shown) is routed through the filters 174a, 174b and exit toward the bottoms of the filter cavities 228a, 228b, as previously described with respect to
A liquid distribution passage 232 extends longitudinally along the manifold body 160, similar to the liquid distribution passage 104 of
As depicted in
Advantageously, the locations of the second temperature sensors 240a, 240b are selected so that the sensed temperatures are very close to that of the liquid material flowing through the liquid distribution passage 232 and provided to the modules 30. In another embodiment, the locations of the first and second temperature sensors 203a, 203b and 240a, 240b are selected to minimize the effects of the heater associated with the other temperature sensor, to approximate a thermally decoupled system. This permits the controller to more accurately control the heating members to heat the liquid material and the process air to desired temperature ranges. Moreover, the second heating members 154a, 154b cooperate with the first heating members 152a, 152b to heat the process air flowing through clearance gaps 192a, 192b and other air passages 184, 200, 202a-202c, but the first heating members 152a, 152b do not affect the temperature of the liquid material, as discussed above.
The manifold bodies of the embodiments described herein lend themselves to fabrication by extrusion methods. Specifically, the uniform profile of the upper and lower surfaces and the front and rear surfaces of the manifold bodies facilitate forming the manifold bodies by extrusion in the longitudinal direction. After extrusion, various other features, such as screw threads and the various bores and cavities which do not extend in the longitudinal direction, may be machined into the manifold body. Furthermore, it will be appreciated that cavities and bores which extend in the longitudinal direction may be formed in the manifold body during extrusion. For example, the liquid inlet supply passage 96 and the liquid distribution passage 104 of the embodiment of
While the present invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended 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 invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of Applicant's general inventive concept.
