Patent Publication Number: US-2022212211-A1

Title: Jet cartridges for jetting fluid material, and related methods

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/730,522, filed Jun. 4, 2015, the disclosure of which is hereby incorporated by reference as if set forth in its entirety herein. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to fluid dispensers, and more particularly, to fluid dispensers for jetting fluid material. 
     BACKGROUND 
     Liquid dispensers for jetting fluid materials, such as epoxy, silicones, and other adhesives, are known in the art. Jet dispensers generally operate to dispense small volumes of fluid material to a substrate by rapidly impacting a valve seat with a valve member to create a distinct, high pressure pulse that ejects a small volume, or droplet, of fluid material from the nozzle of the dispenser, which flies from the nozzle through the air to impact a surface, or substrate, onto which the fluid material is being applied. Known jet cartridges used with jet dispensers include a cartridge body that houses the valve member and a nozzle, the cartridge body being adapted to couple to an actuator of the jet dispenser. 
     In applications for jetting heated fluid material, a heating element is coupled to the cartridge body, which then transfers heat to the fluid material as it flows through the internal passages of the jet cartridge. The viscosity of the fluid material may be temperature-dependent. Accordingly, the viscosity of the fluid material may be controlled by transferring heat to the fluid material as it flows through the jet cartridge, particularly in applications in which a low viscosity of the fluid material is desired. 
     In order to achieve uniform fluid flow characteristics and dispense weight repeatability, it is desirable to maintain a uniform, consistent temperature of the fluid material as it flows through the jet cartridge and into the nozzle for jetting. However, known heated jet cartridges fail to maintain a uniform temperature of the fluid material as the fluid material flows through the jet cartridge and into the nozzle. In particular, the fluid material is often exposed to heat for an insufficient length of time within the jet cartridge such that the fluid material experiences a drop in temperature (i.e., partially cools) by the time it reaches the nozzle. As a result, the fluid material flowing toward the nozzle experiences inconsistent temperatures and viscosities, thereby resulting in imprecise dispensing performance. 
     Known heated jet cartridges are further deficient in that many are not designed to be disassembled, and later reassembled, to fully expose the internal fluid passages for inspection and cleaning between uses. Alternatively, known heated jet cartridges that are disassembleable often require the assistance of an external tool, such as a wrench or a screw driver, for disengaging one or more tightened mechanical fasteners. Accordingly, exposure of the internal fluid passages of known jet cartridges for adequate inspection and cleaning is made difficult, if not impossible. In this regard, blind fluid paths and “dead zones” within jet cartridges, which may undesirably trap fluid during use and hinder fluid flow, may be insufficiently accessible for proper inspection and cleaning. 
     Therefore, a need exists for improvements to known jet cartridges for jet dispensers. 
     SUMMARY 
     In accordance with one embodiment, a jet cartridge for jetting fluid material includes a body adapted to receive fluid material, and a fluid passage defined within the body and extending along a longitudinal axis thereof. At least a portion of the fluid passage extends obliquely relative to the longitudinal axis. Additionally, the body is adapted to receive heat from a heating element and to transfer the heat to the fluid material flowing through the fluid passage. 
     In accordance with another embodiment, a method is provided for jetting fluid material with a jet dispenser including an actuator and a jet cartridge operatively coupled to the actuator and having a nozzle. The method includes receiving fluid material into the jet cartridge, and directing the fluid material through the jet cartridge along a longitudinal axis thereof and obliquely relative to the longitudinal axis, in a direction toward the nozzle. The method further includes heating the fluid material directed through the jet cartridge to a target temperature, and maintaining the target temperature as the fluid material enters the nozzle. The method further includes jetting the heated fluid material through the nozzle. 
     In accordance with another embodiment, a jet cartridge for jetting fluid material includes an outer body, a flow insert received within the outer body, a fluid passage defined between the outer body and the flow insert, and a frictional connection between the outer body and the flow insert. The frictional connection is facilitated by a releasable sealing element disposed between the outer body and the flow insert, and is adapted to be disengaged for exposing the fluid passage without use of an independent tool. Additionally, the outer body is adapted to receive heat from a heating element and to transfer the heat to the fluid material flowing through the fluid passage. 
     Various additional features and advantages of the invention will become more apparent to those of ordinary skill in the art upon review of the following detailed description of the illustrative embodiments taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a jet dispenser including a jet cartridge according to an embodiment of the invention. 
         FIG. 2  is a front perspective view of the jet cartridge of  FIG. 1 , including a cartridge body and a flow insert. 
         FIG. 3  is a front perspective similar to  FIG. 2 , showing the flow insert removed from the cartridge body. 
         FIG. 4  is a rear perspective view of the jet cartridge of  FIG. 1 , showing the flow insert removed from the cartridge body, and showing a cross-section of an extension portion of the flow insert. 
         FIG. 5  is a side cross-sectional view taken along line  5 - 5  of the jet cartridge of  FIG. 1  coupled to an actuator of the jet dispenser, showing flow of fluid material through the jet cartridge. 
         FIG. 6  is a side cross-sectional view similar to  FIG. 5 , showing the fluid material being jetted through a nozzle. 
         FIG. 7  is a schematic view of a fluid flow path, including a main fluid passage, of fluid material directed through the jet cartridge of  FIG. 1 . 
         FIG. 8  is a front cross-sectional view taken along line  8 - 8  of the jet cartridge of  FIG. 1 , showing details of a clamp coupling the jet cartridge to the actuator of the jet dispenser. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a jet dispenser  10  in accordance with an embodiment of the invention is shown. The jet dispenser  10  includes an actuator  12 , a jet cartridge  14  operatively coupled to the actuator  12 , and fluid reservoir  15  adapted to supply fluid material to the jet cartridge  14  through a fluid feed tube  16 . The fluid material may include various heat-sensitive fluid materials, such as epoxy, silicone, or other adhesives having a temperature-dependent viscosity. The jet dispenser  10  further includes a heating element  18 , shown in phantom, powered by a controllable power supply  19  for heating the jet cartridge  14  and fluid material flowing through the jet cartridge  14  to maintain an optimal temperature and viscosity of the fluid material during dispense. As described in greater detail below, the actuator  12  is operable to actuate a valve member within the jet cartridge  14  to “jet” or “eject” fluid material from the jet cartridge  14  onto a substrate. 
     Referring to  FIGS. 2-4 , detailed structural features of the jet cartridge  14  are shown. In general, the jet cartridge  14  includes an outer cartridge body  20  and a flow insert  22  removably received within the outer cartridge body  20 , such that the flow insert  22  and the outer cartridge body  20  define a fluid passage therebetween, as described in greater detail below in connection with  FIGS. 5-7 . The outer cartridge body  20  and flow insert  22  may be formed of any suitable heat-resistant material, such as  303  stainless steel for example. 
     The flow insert  22  includes an insert head  24  and an insert shaft  26  extending axially from the insert head  24 . The insert head  24  includes a planar upper surface  28  and an actuator socket  30  extending through the upper surface  28 . The actuator socket  30  is sized and shaped to receive a driving portion  32  of the actuator  12  having a drive pin  34 , as shown best in  FIGS. 5 and 6 . The actuator socket  30  may include a lead-in chamfer  36  at an upper edge thereof to assist in aligning the jet cartridge  14  with the actuator  12  during assembly. The insert head  24  further includes a contoured side surface  38  having a pair of diametrically opposed flat faces  40 , and extending radially outward to define an extension portion  44  of the insert head  24 . The extension portion  44  may include one or more radially extending fluid leak passages  46  that open to the actuator socket  30  at one end, and to an outer face  48  of the extension portion  44  at an opposite end. 
     The insert shaft  26  extends axially from a lower surface  50  of the insert head  24 , and includes a cylindrical shaft portion  52  and a tapered end  54 , as shown best in  FIGS. 5 and 6 . The cylindrical shaft portion  52  includes a fluid passage groove  56  extending circumferentially about a periphery of the cylindrical shaft portion  52  to at least partially define a main fluid passage  58 . As described below, the fluid passage groove  56  and resultant main fluid passage  58  may be helical in shape, for example. An upper sealing element  60 , such as an o-ring, may be received within a seal groove positioned between the lower surface  50  of the insert head  24  and the fluid passage groove  56 . 
     As shown in  FIGS. 3 and 4 , the fluid passage groove  56  includes an inlet end  62 , which may be rounded and chamfered, and may extend helically along a longitudinal axis of the flow insert  22  toward an outlet end  63  proximate the tapered end  54  of the insert shaft  26 . As shown, the longitudinal axis of the flow insert  22  is aligned coaxially with the longitudinal axis of the outer cartridge body  20 , thereby defining a single, common longitudinal axis for the jet cartridge  14 . The fluid passage groove  56  may extend for at least one full revolution (e.g., 360 degrees) about the longitudinal axis of the flow insert  22 . In alternative embodiments, the fluid passage groove  56  may extend for greater than one full revolution (e.g., greater than 360 degrees), for example a plurality of revolutions, or for less than one full revolution (e.g., less than 360 degrees), about the longitudinal axis. Additionally, the fluid passage groove  56  may alternatively be formed on the inner surfaces  76 ,  78  of the outer cartridge body  20  rather than on the flow insert  22 , or in combination with being formed on the flow insert  22 . 
     The helically-shaped fluid passage groove  56  may be formed with an axial width that remains substantially constant along an upper portion of the helical groove  56 , and which then tapers as the fluid passage groove  56  approaches the outlet end  63 . Additionally, the fluid passage groove  56  may be formed with a radial width that remains substantially constant along an entire length of the fluid passage groove  56 . It will be appreciated that the helically-shaped fluid passage groove  56  may be formed with any suitable axial width, radial depth, pitch, and quantity of helical revolutions to achieve optimal flow characteristics in any desired application. In one embodiment, the fluid passage groove  56  may be formed with a pitch of approximately 3.5 mm. 
     While the fluid passage groove  56  is shown and described herein as being helical in shape in connection with the illustrated exemplary embodiment, it will be appreciated that various alternative shapes of the fluid passage groove  56  may also be provided. For example, the fluid passage groove  56  may be formed with any suitable spiral shape that extends along (e.g., parallel to) and circumferentially about the longitudinal axis of the flow insert  22 . The one or more revolutions of such spiral shapes may define one or more angles relative to the longitudinal axis of the flow insert  22 , such that the spiral may be non-helical, and may define one or more diameters of the spiral about the longitudinal axis. In this regard, it will be understood that the term “spiral,” as used herein, encompasses any three-dimensional path extending parallel to and circumferentially about the longitudinal axis of the flow insert  22 . Furthermore, it will be understood that a “spiral” path is not limited in shape to a path defining a constant angle relative to the longitudinal axis, nor to a path defining a constant or uniformly changing diameter about the longitudinal axis. 
     More generally, the fluid passage groove  56  may be shaped so as to define any path that extends along (e.g., parallel to) the longitudinal axis of the flow insert  22 , as demonstrated by the helically-shaped fluid passage groove  56 , and having at least one portion that extends obliquely relative to the longitudinal axis. In other words, having at least one portion that extends obliquely relative to the longitudinal axis and having at last one portion of the fluid passage groove  56  that defines a directional path which traverses across the longitudinal axis and is neither directly parallel to nor directly perpendicular to the longitudinal axis in a plane spaced from the longitudinal axis (e.g., a plane tangent to the outer surface of the cylindrical shaft portion  52 ). For example, each revolution of the helically-shaped fluid passage groove  56 , when viewed head-on from a side view as shown in  FIGS. 3 and 5 , is obliquely angled relative to the longitudinal axis of the flow insert  22  such that the fluid passage groove  56  continuously advances along the longitudinal axis while simultaneously traversing across the longitudinal axis. As such, the oblique revolution is not confined to purely parallel and/or perpendicular directions relative to the longitudinal axis of the flow insert  22 . 
     It will be appreciated that the fluid passage groove  56  may be formed with various alternative shapes, other than helical and spiral, that extend along the longitudinal axis of the flow insert  22  and which include at least one portion that extends obliquely relative to the longitudinal axis, as understood in view of the description provided above. For example, though not shown, the fluid passage groove  56  may define a zig-zag-like pattern that weaves back and forth across the longitudinal axis to define one or more obliquely extending segments that are axially spaced from one another. Additionally, the fluid passage groove  56 , in whole or in part, may extend fully circumferentially about (i.e., at least 360 degrees) the longitudinal axis of the flow insert  22 , or only partially circumferentially about the longitudinal axis of the flow insert  22  (i.e., less than 360 degrees). 
     The outer cartridge body  20  is in the form of a heat-transferring shell having a planar upper surface  64  and an insert socket  66  extending through the upper surface  64  and being sized and shaped to receive the insert shaft  26  of the flow insert  22 . The outer cartridge body  20  includes a contoured side surface  68  having a pair of diametrically opposed flat faces  70 , and extending radially outward to define an extension portion  72  of the outer cartridge body  20 . As shown in  FIG. 2 , the side surface  38  and extension portion  44  of the flow insert  22  substantially align with the side surface  68  and extension portion  72  of the outer cartridge body  20  when the flow insert  22  and the outer cartridge body  20  are coupled together. A fluid fitting  74  may be coupled to the extension portion  72  for receiving a flow of fluid material from the fluid reservoir  15 , as described below. 
     Referring to  FIGS. 3-6 , additional structural features of the jet cartridge  14  will now be described. The insert socket  66  of the outer cartridge body  20  includes a cylindrical portion defined by an upper cylindrical face  76  and a lower cylindrical face  78  having a diameter slightly smaller than that of the upper cylindrical face  76 . An angled annular shoulder  80  is defined between the upper and lower cylindrical faces  76 ,  78 . The insert socket  66  further includes a tapered portion defined by a lower tapered face  82  extending from the lower cylindrical face  78 . The cartridge body  20  further includes a lower collar  84  that receives a nozzle hub  86 , for example through threaded engagement. The nozzle hub  86  houses a nozzle  88  that is secured in place by a nozzle retainer  90  positioned between an outer circumference of the nozzle  88  and inner circumference of the nozzle hub  86 . The retainer  90  may be comprised of epoxy that bonds and seals the nozzle  88  against the nozzle hub  86 , for example. 
     As shown best in  FIGS. 5 and 6 , the extension portion  72  of the outer cartridge body  20  includes a fluid inlet passage  92  extending radially through an outer face  94  thereof and opening to the insert socket  66 . The fluid inlet passage  92  includes a threaded bore for receiving the fluid fitting  74  in threaded engagement. The fluid fitting  74  defines a fluid inlet  98  that communicates with the fluid inlet passage  92 , and includes an outer thread  100  for coupling to the fluid feed tube  16  for directing fluid material from the fluid reservoir  15  into the jet cartridge  14  for jetting, as described in greater detail below. 
     The actuator socket  30  of the flow insert  22  extends through the insert head  24  and the cylindrical shaft portion  52  of the insert shaft  26 , as shown in  FIGS. 5 and 6 . The actuator socket  30  includes a cylindrical portion defined by a cylindrical face  102 , and a tapered portion defined by a tapered face  104 . The cylindrical portion is sized and shaped to receive the driving portion  32  of the actuator  12 . The flow insert  22  further includes a lower aperture  106  extending through the tapered end  54  of the insert shaft  26  and opening to the insert socket  66 . 
     A valve member  108  including a valve head  110  and a valve stem  112  having a stem tip  114  is supported by the flow insert  22  with a spring washer  116 . The spring washer  116  may be supported at an upper end of the tapered face  104  and includes a central aperture through which the valve stem  112  is received such that the valve head  110  abuts the spring washer  116 . The valve stem  112  extends through the lower aperture  106  of the flow insert  22  and is sealingly engaged by an annular valve seal  118 . As described in greater detail below, the valve member  108  may be rapidly actuated between an upward position and a downward position to eject material through the nozzle  88 . 
     During assembly, the flow insert  22  is aligned with the outer cartridge body  20  in the manner generally shown in  FIGS. 3 and 4 . In particular, the insert shaft  26  is aligned coaxially with the insert socket  66 , and the side surface  38  of the flow insert  22  is aligned with the side surface  68  of the cartridge body  20 . The insert shaft  26  is then removably received within the insert socket  66  in the manner shown in  FIGS. 1, 5, and 6 . In particular, the lower surface  50  of the flow insert  22  is supported by the upper surface  64  of the outer cartridge body  20 . Additionally, the upper sealing element  60  of the flow insert  22  sealingly and releasably engages the upper cylindrical face  76  of the cartridge body  20 , thereby establishing a frictional connection between the outer cartridge body  20  and the flow insert  22 . As shown in the illustrated exemplary embodiment, the flow insert  22  is not otherwise coupled to the outer cartridge body  20  with any mechanical fasteners, such as threaded fasteners. Thus, the flow insert  22  may be easily disassembled from the outer cartridge body  20  by simply disengaging the frictional connection by hand. As such, no independent tools (e.g., wrench or screwdriver) are required to disassemble the flow insert  22  from the cartridge body  20 . Consequently, and advantageously, the flow insert  22  is releasably, or removably, coupled to the cartridge body  20  such that these components may be quickly and easily disassembled by hand to thereby expose the confronting surfaces of the flow insert  22  and cartridge body  22  for inspection and cleaning purposes. 
     When the flow insert  22  is received by the outer cartridge body  20  as shown, the cylindrical shaft portion  52  of the insert shaft  26 , including the fluid passage groove  56 , confronts the upper and lower cylindrical faces  76 ,  78  of the insert socket  66 . In this manner, the fluid passage groove  56  and the upper and lower cylindrical faces  76 ,  78  collectively define the main fluid passage  58  between the flow insert  22  and the outer cartridge body  20 . As shown in the exemplary embodiment illustrated herein, the fluid passage groove  56  and main fluid passage  58  may be helical in shape. However, as described above, the fluid passage groove  56  may be formed with various alternative shapes to thereby define a variety of corresponding alternatively shaped main fluid passages  58 , such as a non-helical spiral fluid passage for example. The inlet end  62  of the fluid passage groove  56  is aligned directly with the fluid inlet passage  92  such that the fluid inlet passage  92  communicates with the main fluid passage fluid passage  58 . 
     The tapered end  54  of the insert shaft  26  is suspended above the lower tapered face  82  of the insert socket  66 , thereby defining an annular tapered fluid chamber  120  that communicates at an upper end with the main fluid passage  58  and at a lower end with a lower fluid chamber  122  defined by the nozzle hub  86 . As shown, the valve stem  112  extends into the lower fluid chamber  122  and is suspended above the nozzle  88 . 
     As indicated by the directional arrows in  FIG. 5 , the fluid inlet  98 , fluid inlet passage  92 , main fluid passage  58 , tapered fluid chamber  120 , and lower fluid chamber  122  collectively define a fluid flow path  124  through the jet cartridge  14 , along which fluid material is directed. Accordingly, during operation, the flow insert  22  functions as a baffle for directing fluid material, received through the fluid inlet passage  92 , toward the nozzle  88  for jetting. 
     The assembled jet cartridge  14  is coupled to the actuator  12  of the jet dispenser  10  such that the driving portion  32  is received within the actuator socket  30  and the drive pin  34  abuts the valve head  110 . As described below, the actuator  12  is operable to rapidly actuate the drive pin  34  downward (see  FIG. 6 ) and upward (see  FIG. 5 ) to thereby actuate the valve member  108  for ejecting fluid material through the nozzle  88 . 
     The heating element  18 , shown in phantom herein, is releasably coupled to and surrounds a periphery of the outer cartridge body  20 , such that the heating element  18  directly contacts at least a lower annular shoulder  126  of the outer cartridge body  20 . In alternative embodiments, the heating element  18  may directly contact other portions of the outer cartridge body  20  as well. As best shown in  FIG. 8 , the assembled jet cartridge  14  may be releasably coupled to the actuator  12  via the heating element  18  and a clamp  128  having arms that extend around and releasably engage an upper portion of the heating element  18  and a lower portion of the actuator  12 . In this manner, the clamp  128  may hold the heating element  18 , the outer cartridge body  20 , and the flow insert  22  in axial compression against the actuator  12 , and may be easily disengaged from the jet cartridge  14  by hand without use of an independent tool (e.g., wrench or screwdriver). In alternative embodiments, any other suitable mechanical fastening device may be used. 
     The heating element  18  is energized by power supply  19  to heat the outer cartridge body  20 , which then transfers heat to the fluid material flowing along the fluid flow path  124 , as described in greater detail below. The power supply  19  is controllable to provide the heating element  18  with a suitable degree of electrical power for achieving any desired heating effect of the cartridge body  20  and the fluid material flowing along the fluid path  124 . For example, the power supply  19  may be controlled dynamically during operation of the jet dispenser  10  to adjust a temperature, and thus a resultant viscosity, of the fluid material being jetted. The heating element  18  and/or the jet cartridge  14  may include one or more thermal sensors (not shown) for sensing a temperature of the outer cartridge body  20  and/or a temperature of the fluid material flowing along the fluid flow path  124 . The power supply  19  may then be selectively controlled in response to temperatures sensed by the thermal sensors in order to achieve or otherwise maintain a target temperature of the outer cartridge  20  and/or the fluid material flowing along the fluid flow path  124 . 
     Referring to  FIGS. 5-7 , operation of the jet dispenser  10 , including the jet cartridge  14 , will now be described in greater detail.  FIG. 5  shows the drive pin  34  and valve member  108  in upward positions. Fluid material is directed into the fluid inlet  98  of the fluid fitting  74  from the fluid reservoir  15  through the fluid feed tube  16 . The fluid material then passes through the fluid inlet passage  92  and into the main fluid passage  58  defined between the flow insert  22  and the outer cartridge body  20 . The releasable seal established between the flow insert  22  and the cartridge body  20  by the upper sealing element  60  aids in containing the fluid material within the main fluid passage  58 . The fluid material flows from the main fluid passage  58 , through the tapered fluid chamber  120 , and into the lower fluid chamber  122  in which the fluid material generally fills the region between the valve stem tip  114  and the nozzle  88 . As described below in connection with  FIG. 6 , the fluid material is then jetted out through the nozzle  88  by the valve stem tip  114 , as indicated by fluid ejection arrow  125 . 
       FIG. 7  shows a schematic representation of the fluid flow path  124 , including a helically-shaped main fluid passage  58 . The dot-dashed lines shown in  FIG. 7  demonstrate that the outer cartridge body  20  and the flow insert  22 , including the fluid passage groove  56 , may be formed with any suitable axial dimensions so as to define a main fluid passage  58  extending axially for any suitable length and having any suitable number of revolutions about the longitudinal axis of the flow insert  22 . 
     As the fluid material flows through the main fluid passage  58  and into the tapered fluid chamber  120  toward the nozzle  88 , the fluid material is forced into contact with the inner surfaces of the outer cartridge body  20 . Heat generated by the heating element  18  is transferred to the outer cartridge body  20  through the annular shoulder  126 , and from the outer cartridge body  20  to the fluid material flowing along the fluid flow path  124 . Accordingly, the outer cartridge body  20  functions as a heat exchanger. More specifically, heat is transferred through the upper and lower cylindrical faces  76 ,  78  of the outer cartridge body  20  to fluid material flowing through the main fluid passage  58 , and through the lower tapered face  82  to fluid material flowing through the tapered fluid chamber  120 . Heat from the heating element  18  may also be transferred through the lower collar  84  and through the nozzle hub  86  to fluid material within the lower fluid chamber  122 . In this manner, fluid material flowing through the jet cartridge  14  may be heated along substantially an entire portion of the fluid flow path  124 , including at least the main fluid passage  58  and the tapered fluid chamber  120 . As described above, the temperature to which the fluid material is heated may be selectively adjusted during dispensing operations via control of the power supply  19  that energizes the heating element  18 . 
     Referring to  FIG. 6 , the actuator  12  is operable to rapidly actuate the drive pin  34  and the valve member  108  into downward positions in which the valve stem tip  114  forcibly contacts a valve seat defined on the nozzle  88 , thereby forcing (i.e., jetting) heated fluid material out through the nozzle  88 , as indicated by fluid ejection arrow  125 . The drive pin  34  is then raised and the valve member  108  is returned to its upward position by a spring force provided by the spring washer  116 . Fluid material continues to flow along the heated fluid flow path  124  toward to the nozzle  88 , in the manner generally described above, and the valve member  108  may be rapidly actuated by the drive pin  34  between its upward and downward positions for further jetting. During jetting, any fluid material that seeps upward past the valve seal  118  into actuator socket  30  may is directed out through the fluid leak passages  46  in order to prevent fluid entry into the actuator  12 . 
     Advantageously, the main fluid passage  58 , whether helical, spiral, or otherwise in shape, contributes in defining a heated fluid path having a length sufficient to expose the fluid material to heat for a period of time sufficient to establish and substantially maintain a uniform target fluid temperature within the fluid cartridge  14 , including at the nozzle  88 . Consequently, a substantially consistent and uniform target viscosity of the fluid material may be maintained throughout the jet cartridge  14  as the fluid material flows toward and into the nozzle  88  for jetting. As a result, undesirable decreases in temperature of the fluid material at the nozzle  88  prior to and during jetting are substantially prevented, thereby improving dispense weight repeatability and enabling jetting with high fluid flow rates for high throughput applications. 
     Additional benefits are also provided by the configuration of the jet cartridge  14  shown and described herein. For example, the releasability of the fluid-tight seal established between the flow insert  22  and the outer cartridge body  20  by the upper sealing element  60  facilitates easy disassembly and reassembly of the flow insert  22  and the outer cartridge body  20  without use of an independent tool. Accordingly, all fluid-contacting portions of the outer cartridge body  20  and flow insert  22  may be quickly and easily exposed for comprehensive inspection, cleaning, and maintenance between uses. In particular, the fluid passage groove  56  formed on the flow insert  22  and the inner faces  76 ,  78 ,  82  of the outer cartridge body  20  are readily accessible upon disassembly, and thus may be easily inspected, cleaned, and maintained. Furthermore, the shape of the fluid passage groove  56  provides a single, continuous fluid passage  58  that enables a substantially constant and steady flow of fluid material toward the nozzle  88  without generating “dead flow zones” in which fluid flow would become hindered and form blockages, and without causing air entrapment along the fluid flow path  124 . 
     While the present invention has been illustrated by the description of specific embodiments thereof, and while the embodiments have been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such detail. The various features discussed herein may be used alone or in any combination. 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 of the general inventive concept.