Patent Publication Number: US-6712365-B2

Title: Over-molded gland seal

Description:
RELATED APPLICATION 
     This application is continuation of U.S. patent application No. 09/662,693, OVERMOLDED GLAND SEAL, filed Sep. 15, 2000, now abandoned, assigned to the assignee of the present invention. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to gasket seals for fluids and, more particularly, the present invention has application in creating fluidic seals in the ink delivery systems for ink jet printing systems. 
     BACKGROUND OF THE INVENTION 
     In general there are two types of gasket seals in use today to seal fluids within mechanical systems—compressive seals and gland seals. A compressive seal is a flat gasket that is compressed between two mechanical parts. These seals are physically “sandwiched” between the parts by a mechanical joint and typically use face seals between the gasket and each of the parts. A common example of a compressive seal is the head gasket on an internal combustion engine. On the other hand, a gland seal, such as an O-ring, is a seal that utilizes a mismatch in the size of two parts to create a compressive force for sealing. An example of a gland seal is an O-ring placed on a cylinder that is pressed into a hole. The mismatch between the diameter of the cylinder plus the annular thickness of the O-ring and the inside diameter of the hole compresses the O-ring and produces a seal. 
     The disadvantages of compressive seals are well known. Compressive seals must be continuously subjected to a compressive force, i.e., continuous loading. Further, the gasket itself over time takes on a “compression set” which, in turn, causes the mechanical joints to loosen up. In addition, relaxation of the compressive force can cause the seal to leak. 
     Gland seals, as well, have their disadvantages. They are very difficult to incorporate into applications other than circular shapes. For any complex geometrical shape or for an elongate shape, i.e., a shape with a large aspect ratio, a compressive seal is typically used. Also, during the assembly of parts, gland seals are difficult to handle and since one gasket is required for each seal, the part counts are high. 
     Over-molding is a well known, two step, fabrication process in which a rigid substrate is first formed, typically by injection molding. Thereafter, in a second step a layer of elastomer is molded onto the substrate typically by thermoset or thermoplastic injection molding. 
     Two overmolding methods are commonly used. The first is used for overmolding onto rigid thermoplastics. In this process, a ridge thermoplastic piece is molded. A thermoplastic elastomer is then overmolded after a section of movable coring is retracted. The thermoplastic part may be required to endure high mold temperatures during the second step of this process. 
     The second method of overmolding is used to overmold thermoset elastomer onto either a rigid thermoset or thermoplastic piece. In this process, a rigid piece (thermoset or thermoplastic) is molded using traditional injection molding techniques. The part is then transferred to a second mold cavity wherein the thermoset elastomer is injected onto it. Again, the rigid piece may endure high mold temperatures during the overmold process. 
     In the past shaped layers of elastomer with under cuts and overhangs have been uncommon because when the part is removed, the mold either tears the elastomer overhang off the elastomer layer or tears the entire elastomer layer off the substrate. Secondly, it has been found that if the elastomer overhang is compressed during assembly, there has been difficulty in supporting it and preventing it from being squashed by the mechanical joint. 
     There is also a continuing need in manufacturing for parts that are lower cost, easier to handle, and require fewer critical tolerances. Further, there is a need for assembled components that have lower part counts and are easier to assemble. Lastly, there is an ongoing need for robust fluidic seals and ink conduits for the ink delivery systems in ink jet printing systems. In these printing systems the seals serve as both mechanical bonds for holding assemblies together and seals for containing ink. 
     Thus, it will be apparent from the foregoing that although there are some well known fluid sealing techniques and fluid conduit systems, there is still a need for an approach that combines the beneficial aspects of both gland seals and compressive seals. 
     SUMMARY OF THE INVENTION 
     Briefly and in general terms, an apparatus for producing a fluidic seal according to the present invention includes a rigid substrate having an elastomeric layer over-molded thereon and an elastomeric gland seal molded into the over-molded layer. Another aspect of the apparatus according to the invention includes a rigid host-part having a raised wall thereon, said host-part receives the elastomeric gland seal and compresses the gland seal with the raised wall. 
     Further, an apparatus for producing a fluid conduit according to the present invention comprises a rigid substrate having an elastomeric layer over-molded thereon; an elastomeric gland seal molded into the over-molded layer for producing a fluidic seal; and a rigid host-part having a raised wall thereon, said host-part receives the elastomeric gland seal and compresses the gland seal with the raised wall. The substrate, the gland seal, and the host-part define an enclosed region. The apparatus also includes a fluid inlet port and a fluid outlet port that communicate with the enclosed region. 
     Other aspects of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a rigid substrate of an apparatus for producing a fluidic seal embodying the principles of the invention. 
     FIG. 2 is a perspective view of the rigid substrate of FIG. 1 with an elastomeric layer over-molded thereon and with an elastomeric gland seal molded into the over-molded layer. 
     FIG. 3 is a perspective view of a rigid host-part that receives the apparatus of FIG.  2 . 
     FIG. 4 is an end elevational view, in section and partially cut away, of the apparatus of FIG. 2 taken along lines  4 — 4  in FIGS. 1 and 2. 
     FIG. 5 is an end elevational view, in section and partially cut away, of the apparatus of FIG. 2 taken along lines  5 — 5  in FIGS. 1 and 2. 
     FIG. 6 is an end elevational view, in section and partially cut away, of the apparatus of FIG. 2 taken along lines  6 — 6  in FIGS. 1 and 2 and the host-part of FIG. 3 after the apparatus and host-part have been mated together. 
     FIG. 7 is an end elevational view, in section and partially cut away, of the apparatus of FIG. 2 taken along lines  7 — 7  in FIGS. 1 and 2 and the host-part of FIG. 3 after the apparatus and host-part have been mated together. 
     FIG. 8 is an end elevational view, in section and partially cut away, of an alternative apparatus for producing a fluidic seal embodying the principles of the invention. 
     FIG. 9 is a perspective view of a second alternative apparatus for producing a fluidic seal embodying the principles of the invention. 
     FIG. 10 is a perspective view of a host-part for the apparatus of FIG.  9 . 
     FIG. 11 is a perspective view, in section and partially cut away, of the apparatus of FIG. 9 taken along line  11 — 11  and the host-part of FIG. 10 taken along line  11 — 11  after the apparatus and host-part have been mated together. 
     FIG. 12 is a perspective view of a third alternative apparatus for producing a fluidic seal embodying the principles of the invention. 
     FIG. 13 is a perspective view of a host-part for the apparatus of FIG.  12 . 
     FIG. 14 is a perspective view of a fourth alternative apparatus for producing a fluidic seal embodying the principles of the invention. 
     FIG. 15 is a perspective view of a host-part for the apparatus of FIG.  14 . 
     FIG. 16 is an end elevational view, in section and partially cut away, of a fifth alternative apparatus for producing a fluidic seal embodying the principles of the invention. 
     FIG. 17 is an end elevational view, in section and partially cut array, of a sixth alternative apparatus for producing a fluidic seal embodying the principles of the invention. 
     FIG. 18 is perspective view, partially cut away, of seventh alternative apparatus for producing a fluidic seal embodying the principles of the invention. 
     FIG. 19 is an end elevational view, in section and partially cut away, of an eight alternative apparatus for producing a fluidic seal embodying the principles of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in the drawings for the purposes of illustration, the invention is embodied in an over-molded gland seal that can produce both a fluidic seal and a fluid conduit. 
     Referring to FIG. 1, reference numeral  20  indicates a substrate that is rigid and formed from a polymer material such as liquid-crystal polymer (LCP) available from Ticona, Inc. of Summit, N.J. The substrate is formed by conventional injection molding techniques. Located in the wall of the substrate is an inlet port  22  for the fluid that flows through the apparatus after assembly and during operation. The inlet port  22  communicates with a fluid channel  23  formed by a raised wall  25  on the substrate. The raised wall partially defines the fluid channel which is elongate, having more length than width, i.e., a large aspect ratio. 
     In FIG. 1, located around the outside surface of the raised wall  25  is a plurality of castellations  27  molded into the substrate  20 . Each castellation has the shape of a regular parallelepiped and has an upper shoulder surface  28 . The upper shoulder surface  28  supports the gland seal, prevents the gland seal from being squashed down during mating, and holds it in position during operation. Further, located between each of the castellations  27  is an aperture  29 . Each aperture penetrates completely through the substrate  20  and anchors the gland seal in position. 
     Referring to FIGS. 2,  4 , and  5 , reference numeral  31  generally indicates an over-molded layer of elastomer. The over-molded layer is molded onto the substrate  20  by conventional molding processes. In the preferred embodiment the layer is fabricated from silicone rubber. The over-molded layer includes a planer portion  32  and an elongated toroidal portion that forms a gland seal  33 . As illustrated in FIGS. 4 and 5, the toroidal portion  33  has a circular cross section and, as illustrated in FIG. 2, completely surrounds the raised wall  25 , FIG. 1 in an elongated, closed curve. As illustrated in FIG. 4, the gland seal  33  is supported vertically by the shoulder surface  28  of each castellation  27 . The shoulder surfaces also prevent the gland seal from being squashed down onto the planer portion  32  of the over-molded layer  31  when the parts are assembled. The side walls  34  of each castellation  27  support the gland seal  33 , prevent horizontal motion of the gland seal  33  (as illustrated in FIG. 4) when the parts are assembled and provide increased surface area onto which the over-molded layer can adhere. 
     Referring to FIG. 5, located below the substrate  20  and over-molded thereon is a second elastomeric layer  35 . The second over-molded layer  35  is fabricated from the same material and is molded in the same manner and at the same time as the upper over-molded layer  31 . The two over-molded layers  31 ,  35  are seamlessly connected together through the apertures  29  by a plurality of webs  36  of elastomeric material. The two over-molded layers  31 ,  35  and the webs  36  form a plurality of integral anchors around the substrate  20  through the apertures  29 . As illustrated in FIG. 5, the second over-molded layer  35  extends beyond the margins of the apertures  29 , and the anchors have the shape of and function like flanges. Orthogonal to the view illustrated in FIG. 5, the anchors are cinctures and completely encircle the substrate  20  through the adjacent apertures  29 . If the parts are separated from each other after being mated, the second over-molded layer  35  anchors the gland seal  33  in place, operates as either a flange or a cincture, and prevents the gland seal  33  from being pulled away from or separated from the substrate  20 . 
     It should be appreciated that for clarity the over-molded sidewalls  37  of the part are not illustrated in FIGS. 2,  9 , 12  and  18  although they are illustrated in FIGS. 4-7 inclusive and are present in all embodiments where there is a second over-molded layer. 
     Referring to FIG. 5, the gland seal  33  has a circular cross section that over hangs the web  36 . In other words, the gland seal extends horizontally (as illustrated in FIG. 5) beyond the vertical external surface of the web, thereby forming an under cut. To prevent the mold, not shown, that forms the gland seal  33  and the web  36  from either tearing the gland seal off the web or tearing the entire upper elastomer layer off the substrate  20  when the part is removed after fabrication of the over-molded layer  31 , the diameter of the gland seal, the horizontal dimension of the web, the compressibility of the gland seal, the number of apertures and the extent that the second over-molded layer  35  extends beyond the margins of the apertures  29  are each empirically adjusted. 
     In one over-molded gland seal actually constructed, the critical parameters and dimensions were: 
     Material: Silicone rubber 
     Durometer: 70 shore A 
     Diameter of gland seal: 0.93 mm 
     Horizontal dimension of the web: 0.60 mm 
     Compressibility of the gland seal: 29% diametral compression 
     In FIG. 3 reference numeral  40  indicates a host-part that mates with the over-molded layer  31  and substrate  20  illustrated in FIG.  2 . The host-part is rigid and formed from a polymer material such as LCP. The host-part is formed by conventional injection molding techniques. The host-part has a raised wall  41  on its surface and a outlet port  42  that communicates with the fluid channel  23  defined by the raised wall  25  on the substrate  20  after the parts have been assembled. The inside surface of the raised wall has a bevel  43  that facilitates assembly of the two parts. 
     Referring to FIGS. 6 and 7, when the host-part  40  is slipped over the raised wall  25  of the over-molded part, the bevel  43  progressively compresses the gland seal  33 . Next, the gland seal  33  is compressed between the outside surface  45  of the raised wall  25  of the substrate  20  and the inside surface  46  of the raised wall  41  of the host-part  40 . This compression occurs because of the mis-match between the diameter of the gland seal and the gap between the outside surface  45  of the raised wall  25  and the inside surface  46  of the raised wall  41  of the host-part  40 . The fluidic seal is made at the two surfaces indicated by reference numerals  48 ,  48 ′. 
     The two opposed sealing surfaces  48  illustrated in FIGS. 6 and 7 are loaded in a radial or “in-plane” manner so that the loads are mutually opposed in the plane of the seal. In other words, after assembly, the resultant seal forces are not trying to force the parts to separate; rather, there is a net resultant force of zero orthogonal to the plane of the sealing surface. 
     In operation, after the parts have been mated as illustrated in FIGS. 6 and 7, fluid enters the apparatus through the inlet port  22 , flows through the fluid channel  23 , and exits the apparatus through the outlet port  42 . The fluid channel is an enclosed region defined by the substrate  20 , the gland seal  33 , and the host-part  40 . The sealing surface of the enclosed region is the surface indicated by reference numeral  48 . 
     It should be appreciated that the inlet port and the outlet port to the apparatus can be in either part as well as both being on the same part. The only requirement is that both ports must communicate with the fluid channel  23 . 
     Further, it is contemplated that a substrate with a continuous shoulder or a ledge around the outside wall of the raised wall  25 , FIG. 1, can be used to support the gland seal, and the apertures and castellations can be eliminated. 
     Referring to FIG. 8, reference numeral  50  generally indicates a gland seal apparatus that incorporates no shoulders, no castellations, no apertures and no anchoring with another surface. The web  52  is sufficiently thick and the gland seal  51  sufficiently compressible to mate and seal with a host-part such as the one described above. If the parts are intended to be disassembled and reassembled, then the over-molded layer must have sufficient adhesion to the substrate both to survive ejection from the mold and to avoid being separated from it upon disassembly. 
     Referring to FIGS. 9,  10 , and  11 , reference numeral  55  generally indicates a gland seal apparatus having an elongate arcuate shape, elongate meaning having more length than width. The apparatus  55  includes a rigid substrate  54  that is fabricated from LCP by conventional injection molding techniques. Located on the substrate  54  is a raised wall  56  that can be either continuous or castellated depending on the need to reduce the wall thickness of the substrate. Like the other raised wall  25 , FIG. 4, this raised wall  56  supports the gland seal  59  and prevents the gland seal from being squashed down during mating. In addition, located on both sides of the raised wall  56  is a plurality of apertures  57  that penetrate through the substrate  54 . 
     Referring to FIGS. 9 and 11, reference numeral  61  indicates an over-molded layer of elastomer. The over-molded layer is molded onto the substrate  54 , is fabricated from the same material as described above, and is molded in the same manner. The over-molded layer includes a planer portion  62  and an arcuate portion that forms a gland seal  59 . The arcuate portion  59  has a circular cross section but is not a closed surface like the elongated toroid described above. As illustrated in FIG. 11, the gland seal  59  is supported vertically by the raised wall  56  in the same manner as described above. 
     Referring to FIG. 11, located below the substrate  54  and over-molded thereon is a second elastomeric layer  64 . The two over-molded layers  61 ,  64  are seamlessly connected together through the apertures  57  by a plurality of webs  63  of elastomeric material to form a plurality of integral cinctures around the substrate  54  through the apertures  57 . It should be appreciated from FIG. 11 that the two webs  63 ,  63 ′ are seamlessly connected together by the second elastomeric layer  64  so that a secure anchor completely encircling the raised wall  56  is formed for the gland seal  59 . In other words, a cincture. This cincture is in addition to the cinctures formed between the adjacent apertures on one side of the raised wall  56  and on the other side. 
     In FIGS. 10 and 11, reference numeral  66  indicates a host-part that mates with the elongate arcuate gland seal illustrated in FIG.  9 . This host-part is manufactured from the same materials as described above and in the same manner. The host-part  66  has a raised wall  67  on its surface, an inlet port  70 , and an outlet port  71 . The inside surface of the raised wall has a bevel  72  that facilitates assembly of the parts. 
     Referring to FIG. 11, when the host-part  66  is slipped over the gland seal  59 , the two inside, opposing surfaces of the raised wall  67  compress the gland seal. The fluidic seal is made at the surfaces indicated by reference numeral  74 . 
     In operation, after the parts have been mated as illustrated in FIG. 11, fluid enters the apparatus through the inlet port  70 , flows through a fluid channel  75 , and exits the apparatus through the outlet port  71 . The fluid channel is an enclosed region defined by the gland seal  59  and the host-part  66 . In contrast to the fluid channel  23 , FIGS. 6 and 7, the fluid channel  75  is defined in part by the surface of the gland seal  59  located between the two sealing surfaces  74  acting as a principal wall of the fluid channel. 
     Although the elongate fluid conduit described immediately above is arcuate with an arcuate longitudinal axis, other configurations are contemplated to be within the scope of the invention including S-shapes, Z-shapes, U-shapes, and straight /-shapes. 
     In contrast to the embodiments described above which are all planer or two dimensional, the embodiment illustrated in FIGS. 12 and 13 is multi-planer or three dimensional. Reference numeral  78  indicates a multi-planer gland seal apparatus having a substrate  81  and an over-molded gland seal  82 . Reference numeral  79  indicates a host-part for the gland seal apparatus  78 , and the host-part  79  has a raised wall  84 . Aside from the complex geometry of this embodiment, these parts  78 ,  79  are fabricated from the same materials and in the same manner and are mated and function in the same manner as the parts described above. 
     After the gland seal apparatus  78 , FIG.  12  and the host-part  79 , FIG. 13 are mated, the resulting configuration defines an enclosed region that can operate as a fluid channel or conduit. The direction of flow is indicated by an arrow  85 . In FIG. 12 the inlet and outlet ports are not shown because they are obscured by the walls of the gland seal. The fluid channel includes an inlet portion  86 , a medial portion  87 , and an outlet portion  88  which are all continuous, uninterrupted conduits forming the fluid channel. The plane of fluid flow in the inlet portion  86  of the enclosed region is displaced with respect to the plane of fluid flow in the outlet portion  88  of the enclosed region. In other words the enclosed region has a plurality of portions and the portion of the enclosed region having the inlet port is non-coplanar with the portion of the enclosed region having the outlet port. It is contemplated that the physical displacement between the planes in these portions can be either horizontal, vertical, axial or along any axis in the three dimensions in between. The planes of fluid flow can be either parallel, non-parallel, co-planer or non-coplanar. 
     The embodiment illustrated in FIGS. 14 and 15 is a fluid conduit formed by an over-molded gland seal that provides an enclosed region having a complex shape with portions having varying volumes. Reference numeral  90  indicates a gland seal apparatus having a substrate  91  and an over-molded gland seal  89 . Reference numeral  92  indicates a host-part for the apparatus  90 . These parts  90 ,  92  are fabricated from the same materials and in the same manner and are mated and function in the same manner as the parts described above. 
     After the gland seal apparatus  90 , FIG.  14  and the host-part  92 , FIG. 15 are mated, the resulting configuration defines an enclosed region that can operate as a fluid channel or conduit. The gland seal  89  defines one principal wall of the fluid channel. The fluid channel includes an elongate portion  93  and a plenum portion  94 . The elongate portion  93  is constructed and operates in the same manner as the embodiment illustrated in FIGS. 9,  10 , and  11 . The plenum portion  94  seals in the same manner as illustrated in FIG.  11  and provides an enclosed region having decreased fluid flow velocity and lower pressure. The direction of fluid flow is indicated by an arrow  96 ; however, the flow can go in either direction. In FIG. 15 the inlet port is obscured by the host-part  92 . In FIG. 14 the outlet port is indicated by reference numeral  95  and communicates through the gland seal  89 . 
     Referring to FIG. 16, reference numeral  110  generally indicates an over-molded gland seal that does not require either a web or a flange to secure the seal in place. The apparatus includes a rigid substrate  111  that is fabricated from the same material and in the same manner as described above. The substrate is illustrated with two apertures  112  that penetrate through the substrate although in practice a plurality of apertures is formed in the substrate. The apparatus  110  further includes an over-molded elastomeric layer  113  that is fabricated from the same material and in the same manner as described above. An elastomeric gland seal  114  is molded into the over-molded layer  113  as described above. Each aperture  112  inwardly tapers or narrows down in the direction of the gland seal  114 . In other words, the apertures  112  in the substrate  111  are molded with an under cut and are filled with the same elastomer that forms the gland seal  114 . If the gland seal  114  is pulled away from the substrate  111 , i.e., upward as illustrated in FIG. 16, the elastomer in the under cut secures the seal in place. 
     It should be appreciated, however, that the apparatus  110 , FIG. 16, could also be molded with either a web or a flange operatively connected to a second over-molded layer in the manner described above. Such an addition would provide even more support for the gland seal  114 . 
     Referring to FIG. 17, reference numeral  116  generally indicates an apparatus with an internal gland seal  117 . The apparatus includes a substrate  118  having an opening  119  with an interior wall  120 . Located in the interior wall  120  is an annular wall  121  that supports the gland seal  117 . The gland seal is over-molded on the interior wall  120  along with an over-molded layer  122  on the substrate  118 . The gland seal  117 , the substrate  118 , and the over-molded layer  122  are fabricated from the same materials and in the same manner as described above. Reference numeral  124 , indicates a host piece that, when inserted into the opening  119  in the apparatus  116 , compresses the gland seal  117  and produces a fluidic seal. The annular wall  121  supports the gland seal during the process of insertion of the host piece  124 . 
     It should be appreciated that the opening  119 , FIG. 17, in the apparatus  116  may be circular, elliptical, rectangular, triangular, or any other geometrical shape as long as the host piece  124  is received in the opening and forms a fluidic seal with the gland seal  117 . 
     Referring to FIG. 18, reference numeral  127  generally indicates an apparatus for producing a fluidic seal with an O-ring shaped seal  130 . The apparatus includes a rigid substrate  128  on which is over-molded an elastomeric layer  129 . The seal  130  is in the shape of a conventional O-ring and is molded into the elastomeric layer  129 . The apparatus is fabricated from the same materials and in the same manner as described above. Likewise, the operation of the apparatus with a host piece is as described above. 
     Referring to FIG. 19, reference numeral  133  generally indicates an apparatus for producing a fluidic seal in orifices, holes, and openings. The apparatus includes a rigid substrate  134  on which is over-molded an elastomeric layer  135 . The seal  136  has the shape of sphere and is supported by a raised wall  137 . The apparatus is fabricated from the same materials and in the same manner as described above. In operation the apparatus plugs openings in host pieces. 
     The apparatus described herein offers multiple advantages. The apparatus inherently reduces part count. The gland seal is attached to the part directly, and the part arrives at the assembly line with the gland seal securely in position on the part prior to assembly. The apparatus can be used to form both complex geometric seals and elongate seals with very large aspect ratios while still using a gland-like structure. Over-molding allows for multiple seals to be formed on a single substrate where in the past each seal required a separate part. The cost of a single over-molded part, in most cases, is less than the sum of the costs of the individual components. Because the seal is created using a molding process, closer position tolerances for the sealing surfaces are achievable. Assembly tolerances from gasket loading and placement are eliminated. Since the sealing surfaces are created by a mold, the positions of the sealing-surfaces are not affected by dimensional variations in the host part. Further, since the apparatus produces seals between parts, more alternative mechanical joining techniques for the parts are available. The seals are loaded in a radial or “in-plane” manner so the loads are mutually opposing in the plane of the seal. In other words, after assembly, the resultant seal forces are not trying to force the assembly apart; rather, there is a net resultant force of zero orthogonal to the plane of the sealing surface. Also, because the seal is created by an elastomeric material, the design of the seal and the design of the substrate can each be optimized for their different functions. That is to say, the over-mold material can be optimized for sealing and over-molding and the substrate can be optimized for mechanical joining. Lastly, the apparatus permits the over-molded part and the host part to be assembled and disassembled without degrading the efficacy of the seal. 
     Although specific embodiments of the invention have been described and illustrated, the invention is not to be limited to the specific forms or arrangement of parts so described and illustrated. The invention is limited only by the claims.