Dispensing valves

Valves. The dispensing valve and actuator serve to close the opening through which the product and frequently the propellant entered the container, to retain the pressure within the container and to dispense the product in the precise form and dosage intended by the manufacturer and expected by the consumer. An aerosol valve shown in Figure 4, consists of seven components. Many variations exist both for special purposes and to avoid existing patents. 

BIB refers to a sealed, sprouted (small too large, with or without dispensing valves) plastic film bag inside a molded rigid container, generally for packaging liquid products. Outer box may be made of disposable corrugated cardboard, disposable or reusable... 

After carbonation at ambient temperature the carbonated water passes through a cooling coil in a cooler and on to the dispense head, where the dispensing valves are housed. The cooler is a tank of water with refrigerated walls on which a layer of ice (the ice bank ) accumulates. This ice allows a reserve of cooling capacity to be built up during less busy periods. 

Syrup is pumped from a BiB container or syrup reservoir by a pressure activated pump, through another cooling coil in the cooler and on to one of the dispense valves. When the valve is opened to dispense product, pressure in the syrup line drops and the pump is activated until the valve shuts. The ratio of syrup to carbonated water is adjusted by flow restrictors in the feed pipes to the valve. 

Carbonated water is teed-off to each dispense valve and when the valve is opened it feeds annularly round a central syrup flow (Figure 13.4). Mixing occurs as the liquids leave the valve. 

Figure 13.5 shows the much simpler equipment needed for pre-mix dispensing. Top pressure is applied from a carbon dioxide cylinder to a pre-mix tank, factory filled with carbonated drink. When the dispense valve is opened the pressure delivers product from the base of the tank via die dip tube through die cooler to the valve. Product in the python feed to the valve is kept cold by the pumped circulation of chilled water from die cooler bath. 

A rigorous hygiene programme must be operated at the outlet with daily cleaning of the dispensing valves and drip trays, and of the disconnects when syrup containers are changed. Periodic sanitation of syrup lines is required. This must be done more often when fruit drinks or juices are dispensed. 

Alternatively, a purpose-built dispenser can be used. One counter-top system stores a BiB container of concentrate in a refrigerated compartment above a water chiller. Concentrate is transferred directly to the dispense valve by a peristaltic pump acting on a tube that is replaced with every BiB. This ensures that the only permanent part of the equipment contacting the juice is the valve. 

Not only concentration pulses have been used as input signals. Wojciechowski used temperature ramps with his temperature scanning reactor [99, 103] and Kobayashi and Kobayashi [104] applied concentration step functions. Typical process parameters, which can be changed, are the pressure, the temperature or the composition of the gas mixture. Fast mixture or pressure pulses can be realized by the injection of reaction gas into the system by a micro-dispense valve. An appropriate flow sensor will then record the transition into the next stationary mode. 

Header systems with manual or automatic dispensing valves have been designed to carry adhesives and sealants over long distances within the plant. Distances of as much as 300 ft are not uncommon with drops at points of application. Figure 17.7 shows a modular header system. Adhesives and sealants are nearly ideal materials for application by robots. Robotic application is commonly used in the automobile industry to increase quality and to reduce labor and material cost.7,8... 

The type of pumps used to dispense epoxy adhesives depends on whether it is a one-part or two-part adhesive. One-part epoxy adhesives are dispensed using direct metering extrusion pumps. An electric motor pushes a follower plate into a drum of adhesive, which is then extruded through a hose to the dispensing valve. This technique is used for medium-and high-volume production rates. 

This company s new 2600-093 Micro-Kiss series mix-dispense valves are designed for the low-flow mixing and dispensing of two-component adhesives and sealants such as silicones, epoxies, urethanes, and acrylics. The valves can be used to apply two-part adhesives and sealants for bonding, gasketing, potting and filling processes in aerospace, appliance, contractor, defense, electronics, filters, marine. 

Pressure is applied to bulk liquid and timer-controlled valves meter the quantity dispensed. Figure 6 shows a typical pressure-time system for adhesives where the viscosity is up to approximately 100,000 mPa. Pressurization of the prodnct tank pushes the adhesive through a feed line to a dispensing valve. A timer controls the opening time of the dispenser valve to obtain a metered quantity. Regulated pressure behind the product and the valve opening time control the quantity dispensed. The adhesive can be applied in dots or in bead form. 

Pressure time using advancing valve The advancing pinch valve is utilized in operator-paced or fully automatic lines where the component part itself cannot be moved to the valve nozzle. The advancing pinch valve, which can be between a stroke of 25 and 150 mm (1 and 6 in), advances the application nozzle to the component part. The dispenser valve then opens, allowing a metered quantity of product to flow through the valve nozzle on to the component part. The valve then closes and the advancing cylinder retracts from the nozzle. In this way dots or continuous beads of product may be applied. 

Pressure time using a rotospray unit This unit is used to apply anaerobic products to machined bores. The unit consists of an electric motor with an integral dispenser valve. At the end of the motor shaft (here is a plastic cup around the periphery of which are a number of holes. 

For those products having a low viscosity, less than 30,000 centipoise, it is possible to apply them by means of a pressure pot and some type of valve and nozzle. Pressure vessels for this purpose range from the small devices generally sold for materials such as cyanoacrylates up to paint-type pressure pots of several gallons. Dispensing valves can be manually operated or in some cases electric or air-operated automatic valves can be employed. Air spray guns, both manual and automatic, can sometimes be adapted for this use. A suitable fluid tip size is selected and the gun is used without the atomization air cap or air supply. This provides a convenient, inexpensive flow gun for use with products that do not require fluid pressures above the working pressure of the spray gun. 

Figure 85 Automatic dispensing valve Posidot from Liquid Control.

Dispensing valve The two components are fed separately to the dispensing valve. The components are fed to the relevant valve stems via the material inputs which are protected by check valves. These stems exert a snuff effect when closing, thus preventing dripping of the mixed material from the outlet. 

The adhesive is put under pressure and the dispense valve is opened for a certain time to provide the correct quantity of adhesive (see Figure 10.15). Since the cyanoacrylate contacts the pressurised air, the dryness of the air is important and an air filter on the mains air line is recommended. A pressure/time system is best suited for cyanoacrylates up to a viscosity of 5,000 mPa-s, i.e., self levelling products. 

A pressure/time system usually consists of a reservoir, a dispense valve and a controller. The type of dispense valve depends on whether it needs to be hand-held, stationary or advancing, and if there are standard or high precision requirements. 

A number of dispense valves are available for dispensing cyanoacrylates including pinch valves, diaphragm valves and seat valves. The wetted parts are typically manufactured from PTFE or acetal to prevent premature curing and often incorporate some form of stroke adjustment for fine-tuning of the dispense characteristic. 

Baby care articles Food dispensing valves Various gaskets... 

Figure 9.12 Structural bonding application for a reinforced plastic bumper assembly for a truck. The equipment dispenses a two-component structural adhesive onto the bumper assembly before it is integrated into the truck. In production, this is typically done robotically with a manual backup system (shown). The system being used is a See-Ro 488 meter/mix system the dispense gun in the picture is model 2200-250-000 dual-spool Snuf-Bak dispense valve that utilizes a No-Rush disposable static mixer nozzle. (Photo provided by Sealant Equipment and Engineering, Inc.)...

The dispensing valve and actuator serve to close the opening through which the product and frequently the propellant entered the container, to retain the pressure within the... 

Dispensing valves range from simple ball valves to pinch valves and needle valves. The suck-back or snuffer valve is invaluable for dripless dispensing. The liquid flow commences on the forward stroke of the valve spool. If the spool retracts, a vacuum is created and an adjustable, drip-less snuff-back occurs at the dispense-nozzle outlet. 

The rheology of some adhesives can be quite complex and these non-Newtonian fluids may require special attention, particularly if they have a tendency to separate in a dispense valve causing blockage and thus significantly affecting the quantity dispensed. 

Normally a dispensing system consists of a tank, a dispensing valve and a control console. They require only a pneumatic line or nitrogen bottle to provide the... 

---