The invention relates generally to machines for dispensing high viscosity materials and more particularly, to improved valve designs to help those machines operate more efficiently.
A variety of valve systems have been employed in automated processing equipment to dispense metered quantities of materials, among which are included solid, liquid and even gaseous materials. One of the more difficult problems facing the dispensing industry has been the metered dispensing of viscous materials. These materials, while flowable, are difficult to handle. A particular problem resides in their relatively high viscosity and surface tension. The materials tend to cling together and to the dispensing equipment with which they are associated.
Examples of viscous materials for which accurate dispensing remains an issue may be found in the food industry and include such viscous products as butter, peanut butter, jams, and cheeses. In the cosmetic industry, these viscous materials can include thick lotions, gels, creams and the like. Household chemicals include such diverse products as caulk, silicone adhesive, sealant, shoe polish, greases, and hand cleaners. Industrial chemicals include greases and other petroleum products, sealants, adhesives, and a host of others. All of these industries experience difficulties with automated packaging equipment due to the difficulties encountered while dispensing high viscosity materials.
One example of a metering valve apparatus used in the food industry is described in U.S. Pat. No. 2,649,996, incorporated herein by reference. A dual dispensing valve system employs specially constructed piston heads as part of the valve structure to produce a section at the end of respective dispensing nozzles, so that material clinging to the end of a nozzle is drawn back into the valve or discharge conduit. Other examples of valve systems which utilize this “snuff-back” feature to reduce spillage or dripping are shown in U.S. Pat. No. 3,731,716 and U.S. Pat. No. 3,717,284, also incorporated herein by reference.
A dispensing valve assembly and system is also disclosed in U.S. Pat. No. 4,974,755, the contents of which are incorporated herein by reference. The valve assembly includes a dispensing valve including a valve casing having an interior chamber. An inlet intersects the valve passageway and connects to a source of material to be dispensed. The system includes a valve element that is received in the passageway. Seals are provided and the valve element reciprocates over a cycle, with the seal elements constraining the flow of material, so that it is directed in the desired direction, without undue leakage.
Valve assemblies and systems for dispensing high viscosity materials have drawbacks. For example, many machines including these assemblies have proved to be insufficiently reliable and can be overly prone to breakdown or to require excessive maintenance.
Accordingly, in improved valve assembly and dispensing system is desired, which overcomes drawbacks of the prior art.
Generally speaking, in accordance with the invention, an improved valve assembly is provided, having a material inlet, a metering chamber and a port to a discharge chamber. A valve element reciprocates within a valve passageway, such that in a retracted condition, a flow path is created for material to flow from the inlet to the metering chamber, but the valve element seals the flow path to the discharge port. The valve element then extends, to unseal the passageway to the discharge port, but seals the flow path to the inlet. A piston forces the material out of the metering chamber, and because the flow path to the discharge port is unsealed and the flow path to the inlet is sealed, the material is directed from the metering chamber, to the discharge port, where it can be dispensed as desired.
The seal between the metering chamber and the discharge port is a metal-to-metal seal, having appropriate smoothness, length and/or angle to the longitudinal axis of the flow passageway and valve element, to prevent leakage. A metal-to-metal seal is also present to seal the flow path from the metering chamber to the material inlet. The metal-to-metal seal has been determined to provide advantages in terms of maintenance and reliability. Sensors should be present to monitor the position of the valve element and a piston that retracts to draw material into the metering chamber and then forces that material out of the metering chamber and into the discharge chamber.
Accordingly, it is an object of the invention to provide an improved valve assembly, dispensing unit and method of operating the valve assembly and dispensing unit.
Still other objects of the invention will in part be obvious and will, in part be apparent from the specification and drawings. The invention accordingly comprises the apparatus and method of operation which will be exemplified in the structures and methods hereinafter described, and the scope of the invention will be indicating the claims.
For a fuller understanding of the invention, reference is had to the following description, taken in connection with the accompanying drawing, in which:
A dispensing apparatus, in accordance with one preferred embodiment of the invention, is shown generally in
An inlet supply conduit 18 can be in communication with an upstream source of the material to be dispensed (not shown). Dispensing valve 12 is preferably located downstream of conduit 18 and receives the material from conduit 18, as described more thoroughly below. Nozzle 14 has an interior 15, defining a discharge flow path through which the material is to be dispensed.
Metering cylinder 16 is mounted in fluid communication to dispensing valve 12. A metering piston 56 retracts in metering cylinder 16 to draw the material into cylinder 16. A drive mechanism 24, such as an air cylinder, is mounted to metering cylinder 16 to provide force to metering piston 56. Other sources of force, such as a servo motor or a hydraulic drive can be used to reciprocate piston 56 in cylinder 16.
Dispensing valve 12 includes a valve element 100, described more thoroughly below. Valve element 100 is preferably a one piece element, but can be formed in two or more pieces, joined as one or separated. Valve element 100 includes a base drive shaft 102, which is connected to an air cylinder 26, having an air supply 22 and a piston 27, which is connected to and applies force to a proximal end 101 of valve element 100. Other sources of force, such as a servo motor or hydraulic drive can also be used to reciprocate valve element 100 within dispensing valve 12. Metering cylinder 16 can include position sensors (not shown), to insure proper positioning of piston 56. The sensors can send signals to a microprocessor to control function and displacement of piston 56 to electronically adjust the volume of the product to be dispensed. Likewise, air cylinder 26 can have position sensors (not shown) to help properly position piston 27 and valve element 100. Signals from these sensors can also be sent to a microprocessor.
As shown in
A valve passageway 76 is formed longitudinally from rear seal section 68 to nozzle section 64, through meter section 62 and inlet section 66 of valve casing 60 along the axis of valve element 100. Valve passageway 76 has a first opening 78 at its distal end, defined by a stop insert 178, described below. When not sealed, first opening 78 permits material to flow between dispensing chamber 70 and meter section 62. Valve passageway 76 has a second opening 80 at the proximal end of inlet section 62 and at the distal end of rear seal section 68. Drive shaft 102 passes through second opening 80, into and out of rear seal section 68 as it reciprocates during use.
A material inlet port 82 is formed in inlet section 66 and can extend transversely with respect to valve passageway 76, at an exterior inlet opening 84. Inlet conduit 18 has an interior 19, which is in fluid communication with inlet port 82 when conduit 18 is mounted to dispensing valve 12. Similarly, a metering port 88 is formed through meter section 62, transversely to valve passageway 76 and is in communication with valve passageway 76. Metering port 88 extends from an exterior metering opening 90 to an interior metering opening 92. Metering port 88 is also in communication with interior 17 of metering cylinder 16, so that the material can flow through meter section 62, into and out of metering cylinder 16.
Metering cylinder 16 includes metering piston 56, which is slidably mounted in interior 17 and connected to a piston rod 58 for mechanical movement thereof under air power or another power source. Inlet port 82, valve passageway 76, dispensing chamber 70 and dispensing port 72 define a flow path for material to be dispensed from an upstream location at exterior opening 84 to a downstream location at dispensing port 72 in the directions of an arrow F.
To dispense the material, as described more fully below, valve element 100 retracts in passageway 76. This seals first opening 78 and opens a passageway from material inlet conduit 18 to metering cylinder 16. Then, piston 56 retracts and the material flows through inlet port 82 to fill interior 17 of metering cylinder 16. Valve element 100 then extends to seal inlet port 82 from dispensing chamber 92. Valve element 100 continues to extend and unseals first opening 78. Valve element 100 and valve casing 60 are preferably configured and arranged such that first opening 78 and inlet port 82 are not both open at the same time. Thus, flow will not occur through both openings at the same time. Then, piston 56 extends and the material exits metering cylinder 16, into dispensing chamber 70 and nozzle 14.
Valve element 100 and its operation are shown in
Referring to
Referring to
A third seal 120 (see, e.g.,
Inner surface 79 is preferably formed on a hardened, replaceable insert 77. The material and hardness of insert 77 can be the same as valve element 100. Preferably, insert 77 and/or valve element 100 are formed from stainless steel with a Rockwell hardness over about 20 Rc, preferably at least about 42. Insert 77 can seat to a housing shoulder in passageway 76 and can be retained by setscrews or a locking pin. The seating and sealing surfaces on valve element 100 and/or insert 77 are preferably machined and polished to at least about a 24 RMS finish, preferably at least about a 16 RMS finish.
Metal-to-metal seal 112 is formed with similar materials. For example, replaceable insert 178 is preferably formed from stainless steel with a Rockwell hardness of at least 20, preferably at least about 42. Insert 178 can seat to a housing shoulder and can be retained by setscrews or a locking pin. The seating and sealing surfaces on insert 178 are preferably machined and polished to at least about a 24 RMS finish, preferably at least 16 RMS.
The operation of valve assembly 10, including dispensing valve 12, can be shown with references to
As is shown in
After metering cylinder 16 is filled with selected quantity 142, valve element 100 extends to the position shown in
Next, valve element 100 continues to advance to the fully open position shown in
After metered quantity of material 142 is dispensed, valve element 100 is caused to return in the retracted path, as is shown in
As is shown in
Similarly, control unit 150 controls a pair of three-way air valves 152 and 153 so that pressurized air from a pressurized air supply 154 is selectively provided through appropriate conduits to meter air cylinder 24 and valve air cylinder 26. To this end, control unit 150 monitors the condition of air cylinders 24 and 26, respectively, through a pair of position sensors 36, 38 and a pair of sensors 46, 48. Control unit 150 then operates valves 152 and 153 so that pressurized air to valve air cylinder 26 reciprocates valve element 100 and so that pressurized air to air cylinder 24 reciprocates meter piston 56.
In order to lubricate and clean drive shaft 102 during use with a viscous material, a wick, preferably constructed of a felt material, can be mounted in a circumferential groove around shaft 102 and can be in fluid communication through a port with a reservoir of cleaner/lubricant selected to be compatible with the material to be dispensed. An O-ring seal can retain the cleaner/lubricant to prevent ingress of unwanted containments. Finally, a rod wiper can be used to clean drive shaft 102.
It has been determined that considerable improvements in reliability and reduction in maintenance cost can be obtained by employing a metal-to-metal seal at the first and second seals 112 and 120. Thus, seating face 115 meets circumferential stop 114 in an inclined relationship. Preferably, circumferential stop 114 and seating face 115 are inclined at an angle M, shown in
It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and, since certain changes may be made in carrying out the above method and in the compositions set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.