Fluid pump and cartridge

RELATED APPLICATIONS

0001This application claims the benefit of U.S. Provisional Application No. 60/186,763, filed Mar. 3, 2000 and U.S. Provisional Application No. 60/163,952, filed Nov. 8, 1999 the contents of which are incorporated herein by reference, in their entirety.

BACKGROUND OF THE INVENTION

0002Contemporary 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.

0003Contemporary dispensing pumps comprise a syringe, a feed tube, a dispense cartridge, and 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, 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.

0004A 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 continuously-running motor drives the feed screw via a rotary clutch, which is selectively actuated to engage the feed screw and thereby effect dispensing. A bellows linkage between the motor and cartridge allows for flexibility in system alignment.

0005Pump 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.

0006Such conventional pump systems suffer from several limitations. The motor and rotary clutch mechanisms are bulky and heavy, and are therefore limited in application for modern dispensing applications requiring increasingly precise, efficient, and fast operation. The excessive weight limits use for those applications that require contact of the pump with the substrate, and limits system speed and accuracy, attributed to the high g-forces required for quick movement of the system. The mechanical clutch is difficult to control, and coasts to a stop when disengaged, resulting in deposit of excess fluid. Clutch coasting can be mitigated by a longitudinal spring mounted about the body of the feed screw and urged against the chamber end to offer rotational resistance. However, the spring adds to the length of the cartridge, and contributes to system complexity.

0007The inlet neck feeds directly into the side of the feed screw or “auger”. Consequently, as the auger collects material from the small and circular inlet port, high pressure is required for driving the material into the auger body, because the auger threads periodically pass in front of the feed opening, preventing material from entering. This leads to inconsistent material flow. Additionally, the inlet neck is commonly perpendicular to the auger screw, requiring the fluid to make a 90 degree turn upon entering the pump. This further limits material flow and can contribute to material “balling” and clogging.

0008Overnight storage of dispensed fluids often requires refrigeration of the fluid and cleaning of the system. The syringe is typically mounted directly to a mounting bracket on the pump body such that the output port of the syringe passes through a aperture on the mounting bracket. The feed tube is then coupled to the output port on the opposite face of the bracket. Since the tube and bracket are on opposite sides of the bracket, removal of the syringe from the pump body requires dismantling of the tube and syringe, which can contaminate fluid material positioned at the interface during disassembly. Further, since the syringe and cartridge can not be removed and stored together as a unit, disassembly and cleaning of the cartridge is required. Additionally, the inlet neck is narrow and therefore difficult to clean.

SUMMARY OF THE INVENTION

0009The present invention is directed to a fluid group and cartridge system that overcomes the limitations of conventional systems set forth above.

0010In a first aspect, the present invention is directed to a cartridge adapted for use with a fluid pump. The cartridge includes a material inlet port, a material outlet port, a feed screw, and a reservoir. The feed screw is disposed longitudinally through the body of the cartridge for delivering fluid provided at the inlet port to the outlet port. The inlet port takes the form of an elongated port provided at a side portion of the feed screw proximal to allow for fluid provided at the inlet port. This elongated configuration promotes even distribution of fluid during transport by the feed screw, and lowers system pressure, thereby reducing the likelihood of “balling-up” and/or clogging of fluid.

0011The inlet port is preferably provided through the cartridge body at an acute angle relative to the reservoir to allow for gravity-assisted fluid delivery. The inner portion of the cartridge may be lined with a carbide or plastic (for example Teflon, torlon, or tercite) liner having an aperture aligned with the inlet port to enhance ease of cleaning. The elongated port of the cartridge may be provided in a wall of the carbide liner.

0012In another aspect, the present invention is directed to a release bracket for mounting the syringe and cartridge to the body of the pump. In this manner, the syringe, feed tube, and cartridge can be dismantled from the pump body as a unit, allowing for joint storage of the syringe, feed tube and cartridge, while minimizing risk of contamination of the material. Additionally, once the system is initially purged of extraneous gas during initialization, the purged system can be stored as a unit without the need for re-initialization prior to its next use.

0013In another aspect, the present invention is directed to a fluid pump assembly that employs an electronically-operated servo-motor assembly. A closed-loop servo motor having a rotary encoder is adapted for controlling rotation and position of the feed screw with heightened accuracy, as compared to those of conventional clutch-driven assemblies. For example, in a preferred embodiment, a rotary encoder capable of 8000 counts in a 360 degree range may be employed to achieve dispensing resolution to a degree that is orders of magnitude greater than conventional systems. Servo-motor-based systems further confer the advantages of small, lightweight systems well-suited for high-performance operation. Electronic control allows for complete determination of the acceleration/deceleration of feed screw rotation, allowing for application-specific flow profiles. An orbital gear transmission unit may be provided between the motor and the pump feed screw for providing further accuracy in controlling the feed screw.

0014In another aspect, the present invention is directed to a pump assembly that is compatible with both floating-z and fixed-z cartridges and dispensing tips. A quick-release pin, which may be spring-biased, is provided on the side of the cartridge body to allow for removal/insertion of cartridges. A fixed-z cartridge includes a hole for receiving the quick-release pin in a fixed relationship. A floating-z cartridge includes a longitudinal groove to permit longitudinal travel of the pin in the groove, and thus allow for floating-z operation.

0015In another aspect, the present invention is directed to a quick-release mount assembly for mounting a pump to a dispensing frame. The pump body includes a tab feature on its surface for mating with a hole on a mounting plate attached to the dispensing frame. The mounting plate includes a lever for securing the tab when inserted. Guide features may be provided for aligning and guiding the pump body relative to the mounting plate.

0016In another aspect, the present invention is directed to an apparatus and method for drawing entrapped air from the material supply during a dispensing operation, thereby purging the system of entrapped air. A vacuum is drawn from the material supply, for example by a vacuum tube with needle inserted into a material feed tube, in a direction parallel to material flow through the feed tube. In this manner, air is withdrawn from the dispensed material, leading to an improvement in dispensing consistency, especially at small tolerances.

0017In another aspect, the present invention is directed to a vacuum purge configuration for removing air entrapped in the body of the cartridge during initialization of a dispensing operation. A first purge interface is placed on the end of the feed tube, and a vacuum is drawn, thereby purging the feed tube of entrapped gas. A second purge interface is then placed on the cartridge body outlet while the feed screw is rotated slowly until material presents itself at the outlet. A vacuum is drawn to eliminate entrapped gas from the cartridge. A third purge interface is then placed on the needle assembly and a vacuum is drawn to eliminate entrapped air from the needle body. Entrapped air is thus substantially removed from the feed tube, auger screw and dispensing needle. Normal dispensing can commence following removal of the purge interface.

0018In another aspect, the present invention is directed to a bellows means inserted at the piston end of, and replacing the piston of, a dispensing syringe. The bellows is pressurized from within and expands, thereby exerting pressure on the underlying material, forcing material flow. In this manner, material can be driven with minimal pressure, and with minimal air migration into the material, as compared to plunger-style drivers. In a preferred embodiment, the bellows comprises a latex film applied about the lip of the syringe top. The syringe top is preferably vented to allow for expansion of the bellows.

0019In another aspect, the present invention is directed to a pump cartridge having a material feed aperture that is elongated with respect to the primary axis of the feed screw. In this manner, a larger portion of the feed screw threads are exposed to the material supply, leading to improvement in dispensing consistency. In a preferred embodiment, a carbide cartridge liner is inserted in the cartridge cavity between the cartridge body and the feed screw, and the elongated aperture is provided in the body of the carbide insert to provide increased material supply exposure.

BRIEF DESCRIPTION OF THE DRAWINGS

0020The 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.

0021<figref idref="DRAWINGS">FIGS. 1A and 1B</figref> are an exploded perspective view and an assembled perspective view respectively of a pump assembly configured in accordance with the present invention.

0022<figref idref="DRAWINGS">FIGS. 2A and 2B</figref> are an exploded perspective view and an assembled perspective view respectively of a fixed-z-type cartridge assembly in accordance with the present invention.

0023<figref idref="DRAWINGS">FIGS. 3A and 3B</figref> are an exploded perspective view and an assembled perspective view respectively of a floating-z-type cartridge assembly in accordance with the present invention

0024<figref idref="DRAWINGS">FIGS. 4A</figref>, <b>4</b>B and <b>4</b>C are side views of a cartridge opening illustrating the conventional embodiment having a small, circular opening, and first and second embodiments of the present invention having elongated openings respectively.

0025<figref idref="DRAWINGS">FIG. 5A</figref> is a cutaway side view of a cartridge feed mechanism employing a carbide liner including an elongated slot at the inlet to allow for increased capturing of input material at the feed screw inlet, in order to promote consistency in material flow at a reduced pressure, in accordance with the present invention.

0026<figref idref="DRAWINGS">FIG. 5B</figref> is a perspective view of the liner having an elongated slot, in accordance with the present invention.

0027<figref idref="DRAWINGS">FIGS. 6A and 6B</figref> illustrate operation of the syringe and cartridge quick release mechanisms, in accordance with the present invention.

0028<figref idref="DRAWINGS">FIGS. 7A and 7B</figref> illustrate a side view and front view respectively of a quick-release mounting plate, for mounting the pump to a pump dispensing frame, in accordance with the present invention.

0029<figref idref="DRAWINGS">FIG. 8</figref> is a illustration of an improved dispensing configuration employing a vacuum tube inserted into the material feed tube, in accordance with the present invention.

0030<figref idref="DRAWINGS">FIG. 9</figref> is an illustration of an air purge configuration wherein a purge vacuum is applied to the needle assembly for initially purging the material flow of air pockets, to prime the system for dispensing, in accordance with the present invention.

0031<figref idref="DRAWINGS">FIG. 10</figref> is an illustration of a bellows configuration for application to the top of a material feed syringe, allowing for use of minimal pressure to drive material flow with mitigation or elimination of air migration into the material, in accordance with the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

0032<figref idref="DRAWINGS">FIGS. 1A and 1B</figref> are an exploded perspective view and an assembled perspective view respectively of a pump assembly configured in accordance with the present invention. With reference to <figref idref="DRAWINGS">FIGS. 1A and 1B</figref>, an embodiment of the dispensing pump <b>18</b> comprises a motor <b>42</b>, an optional transmission box <b>44</b>, a pump housing <b>52</b>, and a cartridge <b>58</b>.

0033The motor <b>42</b> preferably comprises a closed-loop servo motor with an independent motion controller <b>43</b>. The motion controller <b>43</b> may be provided by the host dispensing platform, and may comprise, for example, a Delta Tau controller, Northbridge, Calif., USA. The closed-loop servo motor may comprise, for example, a Sigma Mini Series motor, produced by Yaskawa Electric Corp., Japan. Feedback is preferably provided by a rotary encoder, for example providing 8192 discrete counts over 360 degree rotation. The motor <b>42</b> includes an axle <b>41</b> which operates to drive the feed screw in the cartridge assembly <b>58</b> (described below). In this manner, high-performance control is maintained over material dispensing. For example, rotary position, rotational velocity, and acceleration/deceleration of the feed screw can be readily controlled by the closed-loop servo motor, and is easily programmed at the controller <b>43</b>. This is compared to conventional embodiments that rely on timed open-loop coasting of a mechanical clutch for control over the feed screw. Additionally, the closed-loop servo-motor is generally a compact system that is small, lightweight, and designed for high-performance operation; as compared to the bulky, inefficient, and inaccurate conventional motor pump systems.

0034An optional planetary-gear transmission box <b>44</b> may be provided to step down the available motor positions, thereby providing even more enhanced control over angular position of the feed screw. For example, step-down transmissions offering 7:1, 25:1, and 48:1 step-down ratios are available for increasing the number of angular steps from 8,192 to 57,344, 204,800 and 393,216 respectively, depending on the application. Such transmission boxes are also available in compact units that match well in size and weight with the closed-loop servo motor <b>42</b>.

0035The pump housing <b>52</b> comprises a machined or die cast body having an opening <b>49</b> at a top portion for receiving the motor drive axle <b>41</b> or optional transmission box <b>44</b> drive axle (not shown). The interior of the housing <b>52</b> is hollow for receiving a cartridge <b>58</b> that extends through the housing <b>52</b> from an opening <b>51</b> at a bottom portion, upward to the top portion, and interfaces with the motor drive axle or transmission box drive axle. The motor <b>42</b> and transmission box <b>44</b> are mounted to each other, and to the housing <b>52</b>, by bolts <b>46</b>, and screws <b>24</b>, <b>28</b>, and <b>30</b>. Cavities <b>53</b> are preferably provided in the walls of the housing <b>52</b>, in order to reduce weight.

0036A cartridge release lever <b>34</b> is rotatably mounted to the housing <b>52</b> by bolt <b>38</b>. When rotated, the cartridge release lever <b>34</b> engages an actuator pin <b>56</b>, biased by spring <b>54</b> to remain in a released position. With reference to <figref idref="DRAWINGS">FIGS. 6A and 6B</figref>, the actuator pin <b>56</b> extends into the body of the housing <b>52</b> and engages an actuator pin capture <b>62</b> (see <figref idref="DRAWINGS">FIG. 2B</figref>) or elongated actuator pin capture (see <figref idref="DRAWINGS">FIG. 3B</figref>) formed in the cartridge body <b>60</b>. In this manner the cartridge release lever is operable to remove/insert a cartridge <b>58</b> at the underside of the housing <b>52</b> as indicated by arrow <b>95</b> (see FIG. <b>1</b>B).

0037A syringe <b>22</b> and feed tube <b>40</b> are releasibly coupled to a side wall of the housing, as shown. The syringe <b>22</b> includes a syringe holder <b>20</b>, a syringe body <b>22</b>, and a syringe outlet <b>32</b>. The feed tube <b>40</b> is preferably formed of a flexible material, a first end of which elastically deforms to fit over the end of the syringe outlet <b>32</b> to form a tight seal. The second end of the feed tube <b>40</b> inserts into a feed aperture <b>64</b> (see <figref idref="DRAWINGS">FIGS. 2B and 3B</figref>) formed in the cartridge body <b>60</b>.

0038With reference again to <figref idref="DRAWINGS">FIGS. 6A and 6B</figref>, the syringe <b>22</b> is likewise preferably configured to be readily separable from the pump housing <b>52</b>, along with the cartridge <b>58</b>. To accommodate this feature, a syringe quick-release arm <b>48</b> extends from a side wall of the pump housing <b>52</b>, and includes a slot for map-capturing a neck portion <b>33</b> of the syringe outlet. The quick release arm preferably elastically deforms to receive the neck <b>33</b>, and to fix the syringe <b>22</b> in position during a dispensing operation. In this manner, the cartridge release lever <b>34</b> operates in conjunction with the syringe quick release arm to allow for easy removal and storage of the cartridge mechanism <b>58</b> and syringe <b>22</b> as a unit. This is especially helpful in situations where overnight refrigeration of the dispensing material is required, since the entire material pathway can be removed and stored as a unit, without the need for disassembly and cleaning of the individual components, as required by conventional pump configurations.

0039A release bracket <b>50</b> is mounted to a side wall of the housing <b>52</b> by bolts <b>36</b>. With reference to <figref idref="DRAWINGS">FIGS. 7A and 7B</figref>, the release bracket <b>50</b> includes first and second alignment pins <b>110</b> and a central lock pin <b>114</b>, including a body <b>11</b> and retaining head <b>112</b>, extending outwardly from its surface. A corresponding release bracket plate <b>124</b> is mounted to a dispensing frame <b>122</b>, and includes alignment pin captures <b>116</b>, a lock pin capture <b>118</b> and a spring-loaded lever <b>120</b>. When operated, the lever, engages/disengages a clasp within the lock pin capture <b>118</b>, that, in turn, clasps the retaining head <b>112</b> of the release bracket, when inserted and properly aligned with the plate <b>124</b>. In this manner, the pump <b>18</b> can be readily attached/detached from the pump dispensing frame for maintenance and inspection.

0040<figref idref="DRAWINGS">FIGS. 2A and 2B</figref> are an exploded perspective view and an assembled perspective view respectively of a fixed-z-type cartridge <b>58</b> assembly in accordance with the present invention. The cartridge assembly includes an elongated cartridge body <b>60</b>, a first end of which is adapted to receive a fixed-z-type dispensing needle, for example Laser™-style needle <b>68</b>. An opening at a second end of the cartridge receives an auger screw, or feed screw <b>74</b> having threads <b>75</b> at a first end, and having an indexed shaft <b>66</b> at an opposite end, adapted to register with the motor axle <b>41</b>, or transmission axle. The auger screw <b>74</b> includes a collar <b>78</b>, the height of which is adjustable by set screw <b>76</b>. Washer <b>72</b> ensures a tight seal. A cap nut <b>80</b> contains the various cartridge components within the cartridge body <b>60</b>. As explained above, an inlet port <b>64</b> is formed in the body <b>60</b> of the cartridge for receiving an end of the feed tube, for the delivery of material toward the feed screw threads <b>75</b>. An actuator pin capture <b>62</b> engages the cartridge release pin <b>56</b>, as described above. In the fixed-z embodiment of <figref idref="DRAWINGS">FIGS. 2A and 2B</figref>, the actuator pin capture <b>62</b> is the size of the release pin, to prevent longitudinal travel of the pump.

0041<figref idref="DRAWINGS">FIGS. 3A and 3B</figref> are an exploded perspective view and an assembled perspective view respectively of a floating-z-type cartridge <b>58</b> assembly in accordance with the present invention. In this embodiment, the feed screw mechanism is similar to that of <figref idref="DRAWINGS">FIGS. 2A and 2B</figref>; however, the cartridge is adapted for receiving a floating-z-type dispensing needle <b>82</b>. The needle body <b>82</b> registers with locator <b>88</b> at the cartridge outlet, and is fixed in place by needle nut <b>84</b>. For the floating-z-type cartridge assembly, an elongated actuator pin capture <b>86</b> is provided to allow for longitudinal travel of the cartridge <b>58</b> relative to the pump housing <b>52</b> during a dispensing operation.

0042<figref idref="DRAWINGS">FIGS. 4A</figref> of a inlet port for a conventional cartridge <b>108</b> embodiment having a small, circular port opening <b>106</b>. In this embodiment, it can be seen that the pressurized material entering the port opening <b>106</b> periodically confronts a major diameter of the feed screw thread <b>102</b>, which periodically inhibits flow of material into the feed screw cavity formed between the minor diameter portion <b>104</b> of the thread and the interior wall of the cartridge body <b>108</b>. As much as ⅓ to ½ of the port opening can be periodically blocked by the major diameter of the feed screw thread <b>102</b> at any given time. The blockage fluctuates as a function of the rotational position of the feed screw which can cause inconsistency in material dispensing, especially at small tolerances. The blockage further increases the likelihood of material stagnation and drying at the inlet port, in turn causing system contamination.

0043The present invention overcomes this limitation by providing an elongated cartridge inlet port. With reference to <figref idref="DRAWINGS">FIGS. 4B and 4C</figref>, the elongated inlet port <b>100</b> of the present invention is preferably elongated in a longitudinal direction, with respect to the longitudinal axis of the feed screw <b>74</b>. In this manner, dispensing material is presented to a larger portion of the feed screw cavity formed between the minor diameter portion <b>104</b> and the inner wall of the cartridge <b>70</b>. This configuration reduces pressure requirements for material delivery through the system, and enhances consistency in material flow, as the dependency on material flow rate as a function of the feed screw thread position is mitigated or eliminated. In general, a longer inlet port as shown in <figref idref="DRAWINGS">FIG. 3</figref> is preferred, as compared to the relatively shorter inlet port <b>100</b> shown in <figref idref="DRAWINGS">FIG. 4B</figref>; however, the inlet port <b>100</b> should not be so long as to provide an opportunity for pooling of dormant material in the inlet port <b>100</b> prior to flow through the feed screw <b>74</b>.

0044<figref idref="DRAWINGS">FIG. 5A</figref> is a cutaway side view of a cartridge feed mechanism employing a carbide liner <b>70</b> including an elongated slot <b>100</b> at the inlet port to allow for increased capturing of input material at the feed screw inlet, in order to promote consistency in material flow at a reduced pressure, in accordance with the present invention. <figref idref="DRAWINGS">FIG. 5B</figref> is a perspective view of the liner having an elongated slot, in accordance with the present invention.

0045In this embodiment, the elongated inlet port is provided by a slot <b>100</b> formed in a side wall of a cylindrical carbide liner <b>70</b> inserted in the cartridge body <b>60</b> about the feed screw <b>74</b>. The cartridge inlet port <b>64</b> comprises a standard circular bore formed in the cartridge body <b>60</b>, preferably at an acute angle relative to the feed screw <b>74</b>, to allow gravity to assist in material flow. An elongated chamber, or pocket <b>101</b>, is formed within the slot <b>100</b>, between the feed screw <b>74</b> and the inner wall <b>103</b> of the cartridge body, in a region proximal to the inlet port <b>64</b>. The elongated pocket <b>101</b> allows for dispensing fluid to migrate in a downward direction, and is captured by the feed screw threads over a larger surface area, conferring the various advantages outlined above.

0046<figref idref="DRAWINGS">FIG. 8</figref> is a illustration of an improved dispensing configuration employing a vacuum tube inserted into the material feed tube. In this embodiment, entrapped gas impurities, such as air microbubbles, are drawn from the material supply during a dispensing operation, thereby purging the system of entrapped air. A vacuum unit <b>126</b> draws a vacuum from the material supply tube <b>40</b>, for example by a vacuum tube <b>127</b> with needle <b>128</b> inserted into the material feed tube <b>40</b>, along the direction of material flow, as shown. In this manner, air is withdrawn from the dispensed material, leading to an improvement in dispensing consistency, especially at small tolerances.

0047<figref idref="DRAWINGS">FIG. 9</figref> is an illustration of an air purge configuration wherein a purge vacuum is applied to the needle assembly for initially purging the material flow of air pockets, to prime the system for dispensing. In this process a first purge interface <b>134</b> is placed on the end of the feed tube, and a vacuum is drawn by vacuum unit <b>126</b>, thereby purging the feed tube <b>40</b> of entrapped gas. A second purge interface <b>134</b> is then placed on the cartridge body outlet <b>133</b> while the feed screw is rotated slowly until material presents itself at the outlet <b>133</b>. A vacuum is drawn by vacuum unit <b>126</b> to eliminate entrapped gas from the cartridge. A third purge interface <b>134</b> is then placed on the needle assembly <b>82</b> and a vacuum is drawn by vacuum unit <b>126</b> to eliminate entrapped air from the needle body. Entrapped air is thus substantially removed from the feed tube, auger screw and dispensing needle. Normal dispensing can commence following removal of the purge interface. Note that the first, second and third purge interfaces <b>126</b> may require different interface configurations for the different components undergoing purging.

0048<figref idref="DRAWINGS">FIG. 10</figref> is an illustration of a bellows configuration for application to the top of a material feed syringe, allowing for use of minimal pressure to drive material flow with mitigation or elimination of air migration into the material. In this configuration, a bellows means <b>130</b>, for example comprising an air-tight, flexible material, is inserted at the piston end of, and replaces the piston of, a dispensing syringe <b>22</b>. The bellows is pressurized by air pressure unit <b>132</b> from within and expands, thereby exerting pressure on the underlying material <b>135</b>, forcing material flow through the outlet <b>32</b>. In this manner, material can be driven with minimal pressure, and with minimal air migration into the material, as compared to plunger-style drivers. In a preferred embodiment, the bellows comprises a latex film applied about the lip of the syringe top. The flexible latex film serves to conform to the inner walls of the syringe during expansion, pushing the underlying material in a downward direction The syringe top is preferably vented to allow for expansion of the bellows.

0049In this manner a high-performance, lightweight pump configuration is provided. The pump is operable in both fixed-z and floating-z mode. Quick release mechanisms provide for storage of the syringe and cartridge as a single unit, without the need for component disassembly. The components themselves are relatively easy to clean and maintain. The elongated inlet port provides for enhanced dispensing consistency at a lower material pressure, while the various purging and priming techniques allow for removal of entrapped gases, further improving dispensing consistency.

0050While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

0051For example, the enhanced control over material flow offered by the various configurations of the present invention make the pump system of the present invention especially amenable to use with dispense needles having a flat dispensing surface with a cross pattern formed in the dispensing surface for dispensing a cross patternspattern for providing a filletsfillet for bodingbonding a dyedie to a substrate. Particularly, since the closed-loop servo motor pump of the present invention offers control over both position and velocity of the feed screw, the delivery of fluid through the needle to the cross pattern can be controlled to a level of precision previously unattainable. Cross-pattern-style fillets can be achieved at a level of accuracy orders of magnitude beyond those currently achieved.