Patent Publication Number: US-6702434-B2

Title: Fluidic interconnect structures

Description:
BACKGROUND OF THE DISCLOSURE 
     Needle septum fluid interconnects have been employed in inkjet printing systems. These interconnects have used a molded elastomeric septum placed below a rigid chamber in which are placed a small metallic ball and a helical compression spring. A slit in the septum forms an opening for a side-hole needle to penetrate. A crimp sleeve held the septum in place. 
     Slitting the septum causes micro-tearing in the septum material, causing high stress when the septum is penetrated by the needle. When the needle is engaged, the ink can contact the septum, and can attack the high stress areas of the septum, leading to possible material property degradation and material set. Slitting the septum can result in jagged coarse surfaces. As the needle engages the septum, it can scrape septum material away, introducing small particles into the ink and thus contaminating the ink. 
     SUMMARY OF THE DISCLOSURE 
     A septum structure includes a septum body structure fabricated of a resilient material. The body structure includes an opening formed there through and a first seal surface circumscribing the opening to engage against a needle when inserted into the opening. The body structure further includes a second seal surface for engaging against a stopper structure assembled with the seal septum when the needle is not inserted into the opening. The septum structure can be over-molded on a rigid host part, or fabricated as a separate structure from the host part, and pressed in to place. Other embodiments are disclosed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     These and other features and advantages of the present invention will become more apparent from the following detailed description of an exemplary embodiment thereof, as illustrated in the accompanying drawings, in which: 
     FIG. 1 is a cutaway view of an embodiment of a glandular septum structure, showing a needle in an engaged state with a seal element in the septum. 
     FIG. 2 is a cutaway view similar to FIG. 1, but showing the needle in a disengaged state. 
     FIG. 3 is an enlarged view of a portion of the septum structure of FIG. 1, showing exemplary forms of a seal element surface and a gland seal surface. 
     FIG. 4 is a cross-sectional diagrammatic depiction of an exemplary fluid supply employing the septum structure of FIG.  1 . 
     FIG. 5 is a cutaway view of an embodiment of a glandular septum structure having a double gland seal structure for sealing an engaged needle. 
     FIG. 6 is a cutaway view of an alternate embodiment of a septum structure. 
     FIG. 7 is a cutaway view similar to FIG. 6, but showing the needle in an engaged state. 
     FIG. 8 is an enlarged view of a portion of the septum structure of FIG.  6 . 
     FIG. 9 is a cutaway isometric view of an embodiment of an over-molded septa structure. 
     FIG. 10 is a cutaway isometric view of the septa structure of FIG. 9 after it has been mated to a host part. 
     FIG. 11 is a cutaway isometric view of another embodiment of an over-molded septa structure, employing a slit in a continuous membrane at the base of the stopper receptacle to create the needle entry point and seal, illustrating the structure in a needle disengaged condition. 
     FIG. 12 is a view similar to FIG. 11, but showing the needle in an engaged condition. 
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     An embodiment of a septum structure  20  is shown in FIGS. 1-3. The structure  20  forms a glandular septum pressed into a host part  10 , e.g. an ink supply body. A ball  30  is urged against a top sealing surface  22  of the septum by a helical spring  32 . The helical spring  32  has one end in contact with the ball, and a second end (not shown in FIGS. 1-3) which engages against a stop surface of the host part. The septum is adapted to engage with a hollow needle  40  having a side opening  42  formed therein. 
     The septum structure  20  provides two seals, each suitable for a different mode of operation. The first seal is a glandular seal , similar to an o-ring seal. This seal is the primary seal while the needle is engaged. This type of seal is particularly useful for use during engagement because it is a low stress seal, i.e. the material does not undergo extreme local deformations. This is in contrast to traditional slit septum designs that endure extreme local deformations while in the presence of ink. The second seal is a stopper seal that is created between the ball and the funnel shaped face of the septum. This type of seal is optimized to provide the reseal function after the needle and the septum are disengaged. 
     FIG. 1 is a cutaway view, illustrating the needle and septum in an engaged state. FIG. 2 is a similar view, but showing the disengaged state. FIG. 3 is an enlarged view of a portion of the septum  20 , illustrating the seal surfaces. In this exemplary embodiment, the septum structure  20  is a unitary one-piece structure, injection molded of an elastomeric material such as liquid injection molded (LIM) silicon, EPDM or isoprene. The septum structure in this exemplary embodiment has a circular symmetry about its longitudinal axis. An opening  24  is formed in the septum, through which the needle can be inserted. The opening is defined by a half-toroidal-shaped gland seal surface  26  of the septum. In this exemplary embodiment, the inner diameter of the gland seal surface (analogous to the minor diameter of an o-ring) is sized relative to the outer diameter of the needle to present a 20% diametrical interference with the needle. The surface  26  engages against the needle while it is inserted to form a gland seal. 
     The septum  20  further includes a funnel-shaped seal surface  22  which is inclined from the longitudinal axis. The ball  30  seats against the surface  22  in the absence of the needle, under the spring bias. The seal surface  22  is at the base of a ball receptacle  28  defined by the structure  20 . The receptacle  28  has a slightly larger diameter than the ball  30 , and thus the ball slides up and down within the receptacle as the needle is inserted through the opening  24 . 
     The outer surface of the septum structure  20  has a double barbed shape to fit into a complimentary shape defined in the host part  10 , to secure the septum structure in place within the host part. Of course, other shapes or securing means could alternatively be employed such as adhesives. The use of a feature on the outer surface of the septum allows the septum to be secured in place without the need for adhesives or crimping structures in this embodiment. 
     FIG. 4 illustrates an exemplary structure employing the septum structure  20 . In this example, the host part  10  is a fluid supply, having a housing  12  enclosing a fluid reservoir  11 . The septum structure  20  is positioning in the output port for the supply, to provide an interconnect permitting fluid to pass from reservoir  11  in the direction of arrows  13 , when the stopper  30  is engaged by a needle (not shown in FIG. 4) and pushed against the bias of spring  32 . 
     FIG. 5 illustrates in a cutaway view an alternate embodiment of a gland seal septum structure  20 ′, wherein multiple gland seal surfaces  26 A,  26 B are provided to enhance the sealing of the needle when in the engaged position. In other respects, the structure  20 ′ is similar to the septum structure  20  of FIGS. 1-3. 
     Another embodiment of a septum structure in accordance with the invention is illustrated in FIGS. 6-8. This alternate septum structure  100  employs a slit to create the needle path through the septum structure and also employs a low stress glandular seal. This structure has a molded continuous slit membrane  102  that is slit from the bottom side, or lanced from either side, to create a slit or opening  104 . Above the slit membrane  102 , a gland seal feature  110  is created. This gland seal acts as a redundant seal to ensure proper seal integrity when the needle  40  is engaged, even if the septum has been in contact with ink for a long duration, and also helps to center and guide the needle before it comes into contact with the slit. 
     As with the septum structure  20  of FIGS. 1-3, the septum structure further includes a ball receptacle  106  into which the ball  30  is received when the interconnect needle is in a disengaged state (FIG.  6 ). A biasing member such as a helical spring  32  urges the ball  30  into the receptacle, sealing against the funnel face  106 A to prevent fluid flow through the slit  104 . When the needle  40  is positioned in the engaged state (FIG.  7 ), the tip  40 B of the needle is inserted through the gland seal  110  and through the slit seal  104 , to expose the side hole  40 A formed in the needle tip  40 B and allow fluid to flow through the hollow needle through the fluid interconnect. 
     The septum  100  in this exemplary embodiment is press fit into the host part  120 , as in the embodiment of FIGS. 1-3. The outer surface of the septum structure  100  has a double barbed shape to fit into a complimentary shape defined in the host part  120 , to secure the septum structure in place within the host part. The host part is fabricated of a rigid material such as an injection-molded engineering plastic, in an exemplary embodiment. 
     In another embodiment, the septum structure is over-molded onto a rigid substrate, the host part. The rigid substrate is produced in a first mold cavity, using injection molding techniques. This substrate is then transferred to a second mold cavity, wherein a single septum or a plurality of septa are over-molded onto the substrate to create a single part, in which case a single part, multiple-fluid interconnect structure is produced. 
     FIG. 9 is a cutaway isometric view of an over-molded septa structure  130 . This exemplary embodiment provides a ganged set of four septa, although in general the structure can include a single over-molded septum or many septa. The rigid substrate  132  defines a plurality of through openings, one for each septum. For example opening  132 A is defined by a peripheral wall  132 B, which terminates at an upper ridged lip portion  132 C. An elastomeric structure  136  is over-molded over the rigid substrate to define the individual septa  138 A- 138 D. The elastomeric structure  136  defines, for each septum, a glandular seal and a stopper seal surface for sealing against a stopper member. Septum  138 A, for example, has a glandular seal  138 A- 1  and a funnel-shaped stopper seal surface  138 A- 2 . The glandular seal and the stopper seal surface for the over-molded septa structures are similar to those described above with respect to the embodiment of FIGS. 1-3. The gland seal is similar to an o-ring structure, and is the primary seal while the fluid interconnect needle is engaged. The stopper seal surface with the stopper provides a seal function when the needle and septum are not engaged. 
     Each septum also is molded with an externally facing second glandular seal at the top of the rigid substrate wall surface for providing a seal to a host part. For example, septum  138 A is formed with a glandular seal  138 A- 3 . 
     Exemplary suitable materials for the rigid substrate include LCP, PPS, NORYL (TM), and high heat thermoplastics. Exemplary suitable materials for the over-molded structure include EPDM, LIM silicon, and Isoprene. 
     An advantage of this exemplary embodiment of an over-molded septa structure is that the septa geometry can be created during a single over-mold operation, and allows for a simple, single action mold tool without slides to create the septa features. 
     FIG. 10 is a cutaway isometric view of the septa structure  130  after it has been mated to a host part  140 . The host part includes a plurality of cylindrical bosses, e.g. boss  142 , which define fluid chambers, e.g. chamber  144 . The distal ends of the bosses engage the externally facing glandular seals formed on the septa structure to provide a fluid seal between the host part  140  and the septa structure  130 . For example, the distal end  142 A of boss  142  engages in a compressive relationship with seal  138 A- 3 . 
     The host part  140  in this exemplary embodiment includes a top plate portion which is part of a unitary host part structure, injection molded to form the top plate portion and the bosses. The host part  140  further includes a downwardly extending pin for each chamber, e.g. pin  146  in chamber  144 . The pins hold in position respective helical springs, e.g. spring  148 , which bias the respective stopper elements, e.g. ball  150 , for each chamber. 
     FIG. 10 shows a hollow needle  160  with its distal end  160 A inserted into the septum  138 A, to provide a fluid interconnect through the hollow needle, its side opening  160 B inserted past the glandular seal  138 A 1 . The needle tip has pushed the stopper ball  150  back and out of engagement with the funnel shaped seal surface  138 A- 2 . Thus, fluid can flow between the hollow needle and the chamber  144 . The adjacent chamber  152  is illustrated in FIG. 10 with the stopper  154  urged into a compressive face seal between the funnel shaped stopper seal surface  138 B- 2  and the stopper  154  by spring  158 , i.e. with no needle inserted into the septum  138 B. 
     The host part  140  in this exemplary embodiment is part of a larger assembly, e.g. a fluid manifold or a fluid supply structure, and the needle is connected to another assembly, e.g. a print cartridge. Other types of structures can employ the fluid septa  130  in other applications. 
     FIGS. 11 and 12 illustrate another embodiment of an over-molded septa structure  180 , which is assembled to the host part  140 . Structure  180  is similar to structure  130  of FIGS. 9-10, except that it employs a slit  182  in a continuous membrane  184  at the base of the stopper receptacle to create the needle entry point and seal. FIG. 11 illustrates the structure in the needle disengaged condition, and FIG. 12 the needle engaged condition. Thus, in FIG. 11, the stopper ball  150  is in engagement with the stopper seal surface  138 A- 2 , similar to the embodiment of FIGS. 9-10. In FIG. 12, the needle  160  is pressed through the slit  182 . The slit surface deforms upon needle entry, creating a radial seal around the needle. The needle opening is above the membrane, allowing fluid flow through the needle. 
     It is understood that the above-described embodiments are merely illustrative of the possible specific embodiments which may represent principles of the present invention. Other arrangements may readily be devised in accordance with these principles by those skilled in the art without departing from the scope and spirit of the invention.