Abstract:
A heated dispense pump overcomes the limitations of conventional systems providing for reliable and efficient heating of the dispensed material in a system that is compact, lightweight, and accurate. A pump housing and cartridge body are formed of a thermally conductive material such as copper, aluminum, or an alloy combination thereof. A heater element is applied directly to the body of the pump housing, and a thermocouple is included to provide for closed-loop controllability. The material flows though the cartridge body and is heated prior to release at the dispense tip. The heated elements, including the pump housing and cartridge body, are thermally insulated from the pump motor and pump gantry to prevent the escape of heat from the system and to protect those adjacent components from heat damage. An optional syringe heater is provided for heating the material in the syringe, and for controlling the temperature of the material, in closed-loop fashion. In this manner, the temperature of the material in the syringe and the temperature of the material in the pump can be controlled independently of each other.

Description:
RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/546,886, filed Feb. 23, 2004 and U.S. Provisional Patent Application Ser. No. 60/458,528, filed Mar. 28, 2003, the contents of which are incorporated herein by reference, in their entirety. 
   This application is related to U.S. patent application Ser. No. 10/424,273, filed Apr. 28, 2003, now U.S. Pat. No. 6,983,867; U.S. patent application Ser. No. 10/295,730, filed Nov. 15, 2002, now U.S. Pat. No. 6,851,923; U.S. patent application Ser. No. 10/054,084, filed Jan. 22, 2002, now U.S. Pat. No. 6,892,959; U.S. patent application Ser. No. 10/038,381, filed Jan. 4, 2002, now U.S. Pat. No. 6,957,783; and U.S. patent application Ser. No. 09/702,522, filed Oct. 31, 2000, now U.S. Pat. No. 6,511,301, the contents of each being incorporated herein by reference, in their entirety. 

   BACKGROUND OF THE INVENTION 
   Contemporary fluid dispense systems are well suited for dispensing precise amounts of fluid at precise positions on a substrate. A pump transports the fluid to a dispense tip, also referred to as a “pin” or “needle”, which is positioned over the substrate by a micropositioner, thereby providing patterns of fluid on the substrate as needed. As an example application, fluid delivery systems can be utilized for depositing precise volumes of adhesives, for example, glue, resin, or paste, during a circuit board assembly process, in the form of dots for high-speed applications, or in the form of lines for providing underfill or encapsulation. 
   Contemporary dispensing pumps comprise a syringe, a feed tube, a dispense cartridge, and a pump drive mechanism. The syringe contains fluid for dispensing, and has an opening at its distal end at which a feed tube is connected. The feed tube is a flexible, or rigid, hollow tube for delivering the fluid to the cartridge. The cartridge is hollow and cylindrical and includes an inlet neck at which the opposite end of the feed tube is connected. The inlet neck directs the fluid into the hollow, central cartridge chamber. 
   A feed screw disposed longitudinally through the center of the cylindrical chamber transports the fluid in Archimedes principle fashion from the inlet to a dispensing needle attached to the chamber outlet. A motor drives the feed screw via a rotary clutch, which is selectively actuated to engage the feed screw and thereby effect dispensing. Alternatively, a closed loop servomotor may be employed for providing precise control over the angular position, velocity and acceleration of the rotation of the feed screw during a dispensing operation, as described in U.S. Pat. No. 6,511,301, incorporated herein by reference above. A bellows linkage between the motor and cartridge allows for flexibility in system alignment. 
   Pump systems can be characterized generally as “fixed-z” or “floating-z” (floating-z is also referred to as “compliant-z”). Fixed-z systems are adapted for applications that do not require contact between the dispense tip and the substrate during dispensing. In fixed-z applications, the dispense tip is positioned and suspended above the substrate by a predetermined distance, and the fluid is dropped onto the substrate from above. In floating-z applications, the tip is provided with a standoff, or “foot”, designed to contact the substrate as fluid is delivered by the pump through the tip. Such floating-z systems allow for tip travel, relative to the pump body, such that the entire weight of the pump does not bear down on the substrate. 
   In certain applications, the material being dispensed is heated in order to lessen its viscosity. Heating of the material also allows for improved control over process temperature, for example in environments where ambient temperature can vary greatly over the course of a day, or over the course of a year. 
   The heating of material flow has been accomplished in a number of ways. In one approach, a heated reservoir is placed in line with the feed tube such that the material enters the pump already heated. However, this approach leads to a more complicated configuration that is difficult to clean. 
   In another approach, hot air is generated and circulated down the fluid path. However, this approach is mechanically complex, and involves the movement of air above components, which can affect the reliability of the dispensing operation. 
   In another approach, resistive heaters are formed in the shape of cylindrical cartridges that are mounted to the pump body. In such heaters, referred to in the industry as “cartridge” heaters, a cylindrical metal jacket encases a resistive winding. In these embodiments, the heat tends to be localized to the region of the cylinder. In addition, due to the tolerances of the cylinder, air gaps can form between the inner circumference of the cylinder and the body of the pump, leading to inaccurate and inefficient heating. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a heated dispense pump that overcomes the limitations of the conventional systems set forth above. In particular, the present invention provides for a reliable and efficient heating of the material in a system that is compact, lightweight, and accurate. 
   The present invention includes a pump housing and cartridge body that are formed of a thermally conductive material such as copper, aluminum, or an alloy combination thereof. A heater element is applied directly to the body of the pump housing, and a thermocouple is included to provide for closed-loop controllability. The material flows though the cartridge body and is heated prior to release at the dispense tip. The heated elements, including the pump housing and cartridge body, are thermally insulated from the pump motor and pump gantry to prevent the escape of heat from the system and to protect those components from heat damage. 
   In another embodiment, an optional syringe heater and thermocouple are provided for heating the material in the syringe, and for controlling the temperature of the material in the syringe in closed-loop fashion. An independent controller and heater element are provided for the syringe so that the temperature of the material in the syringe and the temperature of the material in the pump can be controlled independently of each other. The interface between the syringe and pump body is insulated, so that heat does not flow between the respective bodies, maintaining the independence of their respective heating systems. 
   In one aspect, the present invention is directed to a material dispense pump. A pump body is formed of thermally conductive material. A motor includes an output axle. A pump cartridge is formed of thermally conductive material, the pump cartridge having an auger screw driven by the output axle of the motor for dispensing material, the pump cartridge being in thermal communication with the pump body. A motor mount mounts the motor to the pump body, the motor mount comprising a thermally insulating material that thermally insulates the motor from the pump body. A pump body heater is in thermal communication with the pump body for applying heat to the pump body and cartridge. 
   In one embodiment, the cartridge comprises a material selected from the group consisting of aluminum, copper, aluminum alloy, copper alloy, and aluminum-copper alloy. 
   In another embodiment, an auger coupler couples the motor axle to the auger screw, the auger coupler comprising thermally insulating material, for example Ultem™, that thermally insulates the motor axle and auger screw. 
   In another embodiment, the pump body heater comprises a heater and a temperature monitoring device. The pump further includes a pump body heater controller for controlling the temperature of the pump body in response to a signal received from the temperature monitoring device. The pump body heater comprises a resistive heater and the temperature monitoring device comprises a thermocouple. The pump body heater controller, the pump body heater, and the temperature monitoring device are configured as a closed loop heat control system for controlling the temperature of the pump body. 
   In another embodiment, a pump body heater plate that abuts a surface of the pump body, the pump body heater plate comprising a thermally insulating material, for example Ultem®, wherein the pump body heater is seated at an outer surface the pump body heater plate to interface with the surface of the pump body. The pump body heater plate further comprises a compression mechanism that urges the pump body heater toward physical contact with the surface of the pump body. A quick release mounting plate mates with a latch plate for mounting the material dispense pump to a base, the quick release mounting plate being coupled to the pump body heater plate such that the quick release mounting plate is thermally insulated from the pump body. 
   In another embodiment, cartridge retention screws retain the pump cartridge in the pump body, an outer surface of the cartridge retention screws comprising thermally insulating material. A dispense tip retention nut is further included for mounting a dispense tip to the pump cartridge, an outer surface of the dispense tip retention nut comprising thermally insulating material. The thermally insulating material comprises Ultem™. 
   In another embodiment, the motor comprises a closed-loop servo motor having indexed rotational positions. 
   In another embodiment, the material dispense pump further comprises a material reservoir heater for heating material contained in a material reservoir to be dispensed by the pump cartridge. The material reservoir heater comprises a heater and a temperature monitoring device and a material reservoir heater controller is further included for controlling the temperature of the material in response to a signal received from the temperature monitoring device. The material reservoir heater comprises, for example, a resistive heater and the temperature monitoring device comprises a thermocouple. A heat distribution body comprising heat conductive material is in thermal communication with the material reservoir heater that houses the material reservoir and heats material contained in the reservoir. In one example, the material reservoir comprises a material syringe, and the heat distribution body is cylindrical in shape. A reservoir support mount supports the heat distribution body and the material reservoir, wherein the reservoir support mount is formed of thermally insulating material such as Ultem™ that thermally insulates the heat distribution body from the pump body. The material reservoir heater controller, the material reservoir heater, and the temperature monitoring device are configured as a closed loop heat control system for controlling the temperature of the material reservoir. 
   In another aspect, the present invention is directed to a material dispense pump. A pump body is formed of thermally conductive material. A motor has an output axle. A pump cartridge is formed of thermally conductive material, the pump cartridge having an auger screw driven by the output axle of the motor for dispensing material, the pump cartridge being in thermal communication with the pump body. A pump body heater is in thermal communication with the pump body for applying heat to the pump body and cartridge. A material reservoir heater is in thermal communication with a material reservoir containing material to be dispensed for applying heat to the material, wherein the material reservoir heater and pump body heater operate independently to control the temperature of the pump body and cartridge and the temperature of the material. 
   In one embodiment, a motor mount mounts the motor to the pump body, the motor mount comprising a thermally insulating material such as Ultem™ that thermally insulates the motor from the pump body. 
   In another aspect, the present invention is directed to a method for controlling a material dispense pump. The temperature of a pump body is controlled, the pump body formed of thermally conductive material and having a pump cartridge formed of thermally conductive material, the pump cartridge having an auger screw driven by a motor for dispensing material, the pump cartridge being in thermal communication with the pump body. The temperature of a material reservoir containing material to be dispensed by the pump cartridge is also controlled. Control of the temperature of the pump body and control of the temperature of a material reservoir are independent. 
   In one embodiment, controlling the temperature of the pump body comprises monitoring the temperature of the pump body, and applying heat to the pump body in response to monitored temperature. Controlling the temperature of the material reservoir comprises monitoring the temperature of the material reservoir, and applying heat to the material reservoir in response to monitored temperature. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects, features and advantages of the invention will be apparent from the more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
       FIG. 1  is a perspective view of a heated fluid dispense pump assembly configured in accordance with the present invention. 
       FIG. 2A  is an exploded top and side view of the heated fluid dispense pump assembly of  FIG. 1  in accordance with the present invention.  FIG. 2B  is a top view of the pump body heater of  FIG. 2A , in accordance with the present invention. 
       FIG. 3  is a perspective view of heated fluid dispense pump assembly further including a syringe heater, in accordance with the present invention. 
       FIGS. 4A and 4B  are first and second side views, respectively, of the heated pump assembly of  FIG. 3 , in accordance with the present invention. 
       FIG. 5  is a cross-sectional view of the syringe heater of the heated pump assembly of  FIG. 3 , in accordance with the present invention. 
       FIG. 6  is an exploded perspective view of the heated pump assembly of  FIG. 3 , in accordance with the present invention. 
       FIG. 7  is an exploded side view of the syringe heater of the heated pump assembly of  FIG. 3 , in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a perspective view of a heated fluid dispense pump assembly configured in accordance with the present invention.  FIG. 2A  is an exploded top side view of the heated fluid dispense pump assembly of  FIG. 1  in accordance with the present invention.  FIG. 2B  is a side view of the pump body heater of  FIG. 2A , in accordance with the present invention. 
   The components and operation of the dispense pump depicted in  FIGS. 1 and 2  are similar in form and purpose to those disclosed in the embodiments of the patent applications referenced above, and incorporated herein by reference. The dispense pump includes a pump housing or body  34 , a motor  54 , and a cartridge assembly  40 . A coupling  60  includes a first opening  60 A that interfaces with an axle of the motor  54  and includes a second opening  60 B that interfaces with a top portion  46 A of the auger screw  46 . The motor  54  and cartridge assembly  40  are mounted to the pump housing  34  and communicate via the coupling  60  such that rotational movement of the motor axle induces rotational movement of the auger screw  46  in the cartridge assembly  40 , as described in the referenced patent applications. 
   In the embodiment of the present invention as shown in  FIGS. 1 and 2 , a heater element  30  is disposed at an outer surface of a heater plate  32 . The heater plate  32  is mounted to the pump housing  34 , for example via machine screws  32 A such that the heater element  30  is in direct thermal contact with the pump housing  34 . A foam insulator insert  36 , for example comprising silicone foam rubber, is seated in the heater plate  32  beneath the heater element  30 , in a cavity formed in the heater plate  32 , and is under compression when mounted in order to outwardly urge the heater element  30  against the body of the pump housing  34 . A quick-release mount plate  38  is mounted to the heater plate  32  opposite the pump housing  34 . As described in the referenced patent applications, the quick-release mount plate  38  allows the pump to be removably secured to a pump positioning gantry or other pumping system base. A mating latch plate  39  includes a button release mechanism  39 A for mounting the dispense pump to a gantry, as described in U.S. Pat. No. 6,511,301, incorporated herein by reference above. 
   With reference to  FIG. 2B , the heater element  30  comprises, for example, a resistive heating element with a high degree of temperature control and reliability, for example a 24 Volt, 40 Watt Kapton™ heater unit, available from High-Heat industries, Lewistown, Mont., U.S.A. The heater element  30  preferably includes a thermocouple unit  70 , for example, a 100 ohm RTD thermocouple, for monitoring the temperature at the junction of the heater element  30  and the pump housing  34 , at the point closest to the location of material flow. The heater element  30  preferably contacts the pump housing  34  over a wide area, so as to distribute the applied heat evenly across the body of the housing  34 . 
   The temperature of the heater element  30  is preferably controlled by a digital controller  62  (see  FIG. 4B , below), for example a Eurotherm™ digital controller, available from Eurotherm Controls, Inc., Louisbourg, Va., U.S.A. The digital controller  62  is coupled to both the heater element  30  and thermocouple  70  at connector  72  via wires  30 A and  70 A respectively (see  FIG. 2B ). The signals from wires  30 A,  70 A are exchanged with the digital controller  62  via connector  72  and cable  72 A. In this manner, the combined operation of the heater element  30  and thermocouple  70  provide for desirable closed-loop control of the heater element  30  by the controller, with knowledge of the temperature in the heated environment. Other types of controllers, including analog controllers, that ensure closed-loop operation, are also applicable to the present invention. 
   A cartridge assembly  40 , including cartridge  42 , washer  44 , O-ring  45 , auger  46  and spanner nut  48 , is disposed within the pump housing  34 . The cartridge assembly  40  operates in a manner similar to that disclosed in the referenced applications, and is secured in place in the pump housing  34  using thumb lock knobs and screws  50 . The thumb lock knobs and screws  50  mate with an indentation  42 A in the cartridge body, for fixing the cartridge in place in a fixed-z application, or mate with a groove formed in the cartridge body to allow the cartridge to move longitudinally, in a floating-z application. In a preferred embodiment, the fluid enters the auger region at an elongated chamber or slot along the side of the auger threads, as described in U.S. Pat. No. 6,511,301. 
   A motor mount  52  secures a motor  54  to the pump housing  34 . The motor mount  52  is secured to the pump housing by machine screws  53 , and the motor is likewise mounted to the motor mount by machine screws (not shown). The motor  54  comprises, for example, a closed-loop servo motor having indexed rotational positions to allow for accurate control over the angular position, velocity, and acceleration of the auger screw during a dispensing operation, as disclosed in U.S. Pat. No. 6,511,301. The motor axle  56  is coupled to the auger  46  by axle coupling  60 . 
   A dispense tip nut  66  secures a dispense tip  68  to the body of the cartridge  40 . The dispense tip may comprise, for example, a dispense tip of the type disclosed in U.S. Pat. No. 6,547,167, the content of which is incorporated herein by reference. 
   The pump housing  34  and cartridge body  42  are preferably formed of a thermally conductive material such as copper, or aluminum, or an alloy combination thereof. In this manner, the pump housing  34  conducts the heat provided by the heater element  30  into the path of material flow through the cartridge body. 
   During dispensing of material from the dispense tip  68 , heat is drawn into the material flow as it passes through the cartridge from the cartridge body  42  and pump housing  34 . As heat is drawn, the thermocouple  70  embedded in the heater element  30  senses a reduction in temperature in the pump body  34 , and the controller  62  responds by providing additional heat at heater element  30 . In this manner, the system operates in closed-loop fashion and provides for reliable heating of the material flow at a predictable temperature. 
   The heater plate  32 , motor mount  52 , and coupling  60  are preferably formed of a thermally insulative material, for example Ultem™, a polymer available from Beodeker Plastics, Shiner, Tex., U.S.A. In this manner, the heated pump housing  34  and cartridge body  40  are thermally insulated from the motor  54  by the insulative coupling  60  and the insulative motor mount  52  in order to minimize heat exchange between the respective bodies. In addition, the heated pump housing  34  and cartridge body  40  are thermally insulated from the latch plate  39  and gantry, or other body to which the dispense pump is mounted, by the insulative heater plate  32 , in order to minimize heat exchange between the dispense pump body and gantry. In addition, the dispense tip nut  66  and thumb lock screws  50  may additionally be formed of a thermally insulative material such as Ultem™, in order to retain heat and in order to remain cool to the touch for handling purposes. 
   An optional insulative shroud (not shown) for example formed of silicone rubber or plastic may be applied over the pump housing and cartridge, to further insulate the heated dispense pump from ambient temperatures and to provide for a more controlled thermal environment. 
   In another embodiment, a syringe heater is provided for heating material contained in a dispensing syringe that is mounted to the pump. As shown in the assembled perspective view of  FIG. 3  and in the exploded perspective view of  FIG. 6 , the syringe heater system of the present invention includes a cylindrical hollow tube  110  or other chamber of a geometry suitable for retaining a material reservoir such as a syringe, for example formed of aluminum, or other heat-conductive material. The tube includes a flange  111  on which an inserted syringe head rests. An insulative sleeve  120  insulates the heated tube  110 . The cylindrical tube  110  is mounted to a mounting plate  122 , which is, in turn mounted to the pump housing  34 , for example via machine screws (not shown). 
     FIGS. 4A and 4B  are first and second side views, respectively, of the heated pump assembly of  FIG. 3 , including a syringe heater  102 , in accordance with the present invention. With reference to  FIGS. 4A and 4B , the syringe  112  includes an inlet for the application of pressurized air  104 , a plunger (not shown) within the body of the syringe, and an outlet  106  at which material is released from the syringe. The pressurized air is applied to the region above the plunger for driving the plunger in a downward direction, thereby serving as a control mechanism for controlling the rate of introduction of material to the pump. The outlet of the syringe  106  communicates with a feed tube  108 , in turn communicating with the cartridge inlet neck  119 , for introducing material to the dispense pump at the cartridge. 
   A second control unit  162 , for example similar in wattage and control features to those of the digital controller  62  described above in connection with the pump body heater, controls the temperature of the material in the syringe. In this manner, the temperature of the material is stabilized over the course of the day, irrespective of fluctuations in ambient room temperature where the pump is in operation. In addition, the material viscosity can be controlled by elevating the temperature of the material past room temperature in order to increase its viscosity and provide for more regular flow. 
   With additional reference to  FIG. 7  and the cutaway side view of  FIG. 5 , the syringe heating system  102  includes a tubular heat distribution body  110  configured to house a syringe body  112 . The heat distribution body  110  is preferably formed of a thermally conductive material such as aluminum in order to distribute applied heat throughout its body. In one example, the syringe body  112  comprises a plastic body. The heat distribution body  110  includes a flange  111  at a first end that rests against the syringe head retention mechanism  114  that couples the pressurized air source to the syringe body. A heater element  118  is in direct contact with the aluminum tube, and is formed, for example, of a flexible, embossed Kapton™ material. A thermocouple  119 , for example of type described above, is also provided at, or proximal to, the heater element  118 , in order to allow the second controller  162  to take periodic temperature readings. In this manner, the syringe heating system operates in closed-loop fashion, with continuous knowledge of the temperature in the heated environment. A mounting sleeve  116 , for example formed of silicone material, retains the heater element  118  in place against the heat distribution body  110 . An insulative sleeve  120 , for example comprising a rubber tube, encompasses the aluminum tube and heater, providing an insulated environment for the aluminum tube, while physically protecting the heater element. 
   The syringe and heating apparatus is mounted to the pump body using a mounting plate  122  including a large aperture  128  that receives the aluminum tube  110 . The large aperture includes an extension  128 A to provide space for passage of the control wires  180  for the heater element  118  and associated thermocouple  119 . The mounting plate  122  also includes a small aperture  130  that serves as a mount for connector  172 , that transfers signals passed between the controller  162  and the heater  118  and thermocouple  119 . The mounting plate  122  is preferably formed of a thermally insulating material, such as Ultem™, or plastic, such that heat generated by the syringe heater system  102  does not migrate to, or otherwise influence, the pump heater  30 , and such that heat generated by the pump heater  30  does not influence the syringe heater apparatus. In addition, the second control unit  162  preferably operates independently of the first control unit  62 . In this manner, the temperature of the material in the syringe, and the temperature of the material in the pump, can be independently controlled and managed. For example, the temperature of the material in the syringe can be set to 100 F, while the temperature of the material in the pump can be set to 130 F. 
   While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made herein without departing from the spirit and scope of the invention as defined by the appended claims.