Patent Application
20130048900
The present invention relates generally to seal mechanisms, and more particularly to a hydraulic seal assembly for use within a hot melt adhesive or other thermoplastic material dispensing valve assembly.
In conventional liquid dispensing systems, such as, for example, those systems outputting or discharging hot melt adhesives or other thermoplastic materials, a dispensing valve assembly, comprising a reciprocally moving valve stem having a valve member fixedly disposed thereon and operatively associated with a valve seat, is usually employed so as to in fact permit the dispensing of the hot melt adhesive or other thermoplastic material when the valve member is disposed at its UNSEATED or OPENED position with respect to the valve seat, or to prevent the dispensing of the hot melt adhesive or other thermoplastic material when the valve member is disposed at its SEATED or CLOSED position with respect to the valve seat. In addition, conventional dispensing valve assemblies also comprise a seal cartridge which includes a seal mechanism for preventing the leakage of the hot melt adhesive or other thermoplastic material out from the dispensing valve assembly. The seal cartridge is provided with a weep hole from which the hot melt adhesive or other thermoplastic material can effectively escape indicating to the operator that the seal mechanism has undergone failure and that the valve assembly needs to be replaced. Since a pressure differential is effectively defined across the seal mechanism barrier, due to the fact that one side of the seal mechanism is exposed to the pressure comprising the hot melt adhesive or other thermoplastic material while the other side of the seal mechanism is effectively at atmospheric pressure, this constant pressure differential always tends to push or force the hot melt adhesive or other thermoplastic material past the seal mechanism. However, as long as the structural integrity of the seal mechanism is maintained intact, there will effectively be no leakage of the hot melt adhesive or other thermoplastic material out from the seal cartridge and the dispensing valve assembly. To the contrary, when the structural integrity of the seal mechanism is in fact eventually compromised and effectively fails, leakage of the hot melt adhesive or other thermoplastic material out from the seal cartridge and the dispensing valve assembly will occur.
The operative service life of a hot melt adhesive or other thermoplastic material valve dispensing assembly is conventionally measured in cycles. Conventional valve dispensing assemblies employing conventional seal mechanisms can normally have an operative service life of approximately 250,000,000 cycles. During each cycle, the valve stem is moved in a reciprocal manner past the seal mechanism. As the valve stem moves past the seal mechanism in accordance with its reciprocal cyclic movements, the hot melt adhesive or other thermoplastic material tends to cling or adhere to the valve stem and therefore the hot melt adhesive or other thermoplastic material also moves past the seal mechanism in a reciprocal manner. As a result, that portion of the hot melt adhesive or other thermoplastic material which bypasses the seal mechanism, and effectively enters the interior portion of the seal cartridge, is exposed to the air or oxygen contained within the seal cartridge since the seal cartridge is fluidically connected to the ambient atmosphere as a result of the provision of the aforenoted weep hole. Accordingly, such portion of the hot melt adhesive or other thermoplastic material effectively becomes a hardened and abrasive mass. As can therefore be appreciated, each time this hardened and abrasive mass reciprocates past the seal mechanism during the aforenoted cyclic operations, the hardened and abrasive mass will begin to erode the seal mechanism eventually leading to its failure. When failure of the seal mechanism does in fact occur, substantial leakage of the hot melt adhesive or other thermoplastic material past the seal mechanism will also occur whereby the leaked hot melt adhesive or other thermoplastic material will eventually leak out from the weep hole defined within the seal cartridge thereby indicating to the operator that the seal mechanism has in fact failed and that the valve dispensing assembly needs to be replaced.
A need therefore exists in the art for a new and improved seal assembly for use within a hot melt adhesive or other thermoplastic material dispensing valve assembly, whereby the effective service life of the seal assembly, as well as that of the hot melt adhesive or other thermoplastic material dispensing assembly, will be substantially increased.
The foregoing and other objectives are achieved in accordance with the teachings and principles of the present invention through the provision of a new and improved seal assembly for use within a hot melt adhesive or other thermoplastic material dispensing valve assembly, wherein the new and improved seal assembly comprises a sealing cartridge or casing comprising a first or primary seal member, a secondary seal member, and a viscous incompressible silicone grease or similar fluid disposed internally within the sealing cartridge or casing. The viscous silicone grease or similar fluid effectively distributes the pressure forces such that internal pressure forces within the silicone grease or similar fluid are substantially equal to the external pressure forces of the hot melt adhesive or other thermoplastic material whereby a pressure differential across the primary seal member is effectively eliminated thereby effectively eliminating the tendency or propensity for leakage of the hot melt adhesive or other thermoplastic materials. In addition, the viscous silicone grease or similar fluid acts as a lubricant thereby reducing friction and wear of the primary and secondary seal members whereby the cyclic operation and service life of the hot melt adhesive valve dispensing assembly can be substantially increased, such as, for example, by a factor of two or three, such that the operative cycles can be approximately within the range of 500,000,000-750,000,000.
Various other features and attendant advantages of the present invention will be more fully appreciated from the following detailed description when considered in connection with the accompanying drawings in which like reference characters designate like or corresponding parts throughout the several views, and wherein:
Referring now to the drawings, and more particularly to
With reference now being made to
Accordingly, it can be appreciated that when the valve stem 110 is moved toward its lowered position, as illustrated within
With reference still being made to
It is to be further appreciated that the electro-pneumatic solenoid assembly 106 is also provided with fluid passageways, not shown, which fluidically interconnect the pair of control air output fittings 140,142 with the pair of control air input/output fittings 144,146, and in a similar manner, the dispensing valve actuator assembly 104 is likewise provided with fluid passageways, also not shown, which fluidically interconnect the pair of control air input/output fittings 144,146 to regions of the piston chamber 154 above and below the piston 152. Accordingly, it can therefore be appreciated that when control air 137 is conducted, for example, into the control air input fitting 136 of the electro-pneumatic solenoid assembly 106, and when the electro-pneumatic solenoid assembly 106 has been operated in a first mode, the control air 137 will be fluidically conducted from the control air input fitting 136, into the first control air input/output fitting 144 and into the upper portion of the piston chamber 154, that is, into that region of the piston chamber 154 disposed above the piston 152, so as to force the piston 152, the valve stem 110, and the valve member 112 to move downwardly toward the valve member's UNSEATED or OPENED position. At the same time, the air within the lower portion of the piston chamber 154, that is, the air beneath the piston 152, is forced outwardly and exhausted to atmosphere through the second control air input/output fitting 146 and the first one of the control air output fittings 140. Conversely, when the electro-pneumatic solenoid assembly 106 has been operated in a second mode, the control air 137 will be fluidically conducted from the control air input fitting 136, into the second control air input/output fitting 146 and into the lower portion of the piston chamber 154, that is, into that region of the piston chamber 154 disposed beneath the piston 152, so as to force the piston 152, the valve stem 110, and the valve member 112 to move upwardly toward the valve member's SEATED or CLOSED position. At the same time, the air within the upper portion of the piston chamber 154, that is, the air above the piston 152, is exhausted outwardly through the first control air input/output fitting 144 and the second one of the control air output fittings 142. It is to be lastly noted that while the piston 152 is normally spring-biased toward its upper position at which the valve member 112 will be disposed at its SEATED or CLOSED position with respect to valve seat 114, the provision of the control air, to move the piston 152 to its upper position, effectively supplements the bias of the coil spring 156 and serves to rapidly move the piston 152 and the valve stem 110, and therefore the valve member 112, to its SEATED or CLOSED position.
Continuing further, and with additional reference being made to
The uppermost portion of the seal cartridge or casing 202 is provided with a containment washer 206 and a retaining ring 208, and it is to be appreciated from
In addition, the sealing assembly 200 of the present invention comprises sealing members which operate in conjunction with the aforenoted silicone grease or similar fluid in order to effectively prevent the hot melt adhesive or other thermoplastic material from passing through the sealing assembly 200 and into the piston chamber 154 of the dispensing valve actuator assembly 104 and thereby fouling the operation of the piston 152. More particularly, the sealing assembly 200 comprises a first or primary seal member 216 which annularly surrounds a central portion of the valve stem 110 and is mounted in a vertically reciprocal manner within the lower end portion of the sealing cartridge or casing 202. First and second washers 218,220 are operatively associated with the first primary seal member 216, and a preloading or compression spring 222 is interposed between the first and second washers 218,220 as a result of being disposed within a chamber 223 defined between the first and second washers 218,220. As can best be appreciate from
Accordingly, since the chamber 223 also contains, and is fluidically connected to, the viscous silicone grease or similar fluid disposed within the annular space or chamber 214, the upwardly oriented pressure forces 224 will cause the first primary seal member 216 to move upwardly, such movement compresses the preloading or compression spring 222, and the pressure forces are further transmitted to the viscous silicone grease or similar fluid disposed within the annular space or chamber 214. The upper portion of the sealing cartridge or casing 202 is also provided with a secondary seal member 226, however, since the secondary seal member 226 cannot move upwardly because the upper portion of the sealing cartridge or casing 202 is effectively closed by means of the containment washer 206 and the retaining ring 208, and because the viscous silicone grease or fluid comprises an incompressible fluid, pressure forces 228,230 are respectively exerted by the viscous silicone grease or similar fluid upon the valve stem 110 and the underlying surface portion of the secondary seal member 226. Therefore, a static pressure condition exists within the sealing cartridge or casing 202 whereby the internal pressure forces 228,230, characteristic of the incompressible viscous silicone grease or similar fluid, are equal to the external pressure forces 224 characteristic of the hot melt adhesive or other thermoplastic material.
It can therefore be further appreciated or realized that with the sealing assembly 200 of the present invention, the pressure differential, normally existing across the first or primary seal member 216, no longer exists whereby the tendency or propensity for leakage of the hot melt adhesive or other thermoplastic material has effectively been eliminated. It is to be noted that during cyclic operations, that is, when the valve member 112 is moved between its SEATED or CLOSED position, and its UNSEATED or OPENED position, the pressure forces characteristic of the hot melt adhesive or other thermoplastic material varies. The reciprocating first or primary seal member 216 dynamically compensates for such changes in the pressure forces. It is to be noted that canted spring members 232,234 are respectively disposed internally within the primary and secondary seal members 216,226 so as to help maintain the structural integrity and configurations of the primary and secondary seal members 216,226 in order to permit the same to perform their sealing functions with respect to, for example, the valve stem 110 and the sealing cartridge or casing 202. In addition, the primary and secondary seal members 216,226 may be fabricated from a suitable material, such as, for example, polyether-ether-ketone (PEEK) or a similar material.
It is also to be noted that the use or employment of the viscous silicone grease or similar fluid, internally within the sealing cartridge or casing, is important for additional reasons. Firstly, for example, the viscous silicone grease or similar fluid is a lubricant. Accordingly, due to laminar flow characteristics, small amounts of the silicone grease or similar fluid may cling or adhere to the valve stem 110 or to the primary or secondary seal members 216,226 as extremely thin film layers. Therefore, friction developed between the valve stem 110 and the primary or secondary seal members 216,226, as the valve stem 110 undergoes its cyclic reciprocating movements, will be substantially reduced. Secondly, as a result of the lubricity of the viscous silicone grease or similar fluid, the tendency of the hot melt adhesive or other thermoplastic materials to in fact cling or adhere to the valve stem is markedly reduced. Thirdly, due to similar laminar flow characteristics of the hot melt adhesive or other thermoplastic materials, and despite the aforenoted lubricity characteristics of the silicone grease or similar fluid, small amounts of the hot melt adhesive or other thermoplastic materials may nevertheless possibly cling or adhere to the valve stem 110 as extremely thin film layers, and effectively bypass, for example, the first or primary seal member 216. However, if such in fact occurs, and if the hot melt adhesive or other thermoplastic materials becomes dislodged from the valve stem 110, the hot melt adhesive or other thermoplastic materials will effectively be encapsulated within the viscous silicone grease or similar fluid. Fourthly, as a result of the aforenoted encapsulation of the hot melt adhesive or other thermoplastic materials within the viscous silicone grease or similar fluid, the hot melt adhesive or other thermoplastic material will not in fact be exposed to the ambient air or oxygen such that the hot melt adhesive or other thermoplastic material cannot harden and become an abrasive mass conventionally acting upon the seal members.
It is lastly noted that as a result of new and improved sealing assembly 200 of the present invention, the sealing point or barrier has effectively been moved from the primary seal member 216 located at the lower end portion of the sealing assembly 200 to the secondary seal member 226 located at the upper end portion of the sealing assembly 200. This is because at the primary seal member 216, the pressure forces 224,228 across the sealing member, sealing point, or barrier 216 have effectively been equalized such that a pressure differential no longer exists, as has been explained hereinbefore, however, at the secondary seal member 226, a pressure differential does exist because the internal pressure forces 230 are relatively larger than the external pressure forces which are atmospheric pressure forces. This is important in that the secondary seal member 226 is effectively protected from any deleterious effects normally caused by the hot melt adhesive or other thermoplastic materials.
Obviously, many variations and modifications of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.
This patent application is related to, based upon, and effectively a utility/non-provisional patent application conversion from United States Provisional Patent Application Ser. No. 61/573,089, which was filed on Aug. 31, 2011, the filing date benefits of which are hereby claimed.
| Number | Date | Country | |
|---|---|---|---|
| 61573089 | Aug 2011 | US |
