The Model 826 is a dual piston, pneumatically operated, normally closed pinch valve with suck back. The 826 features precise, lockable controls to facilitate the adjustment of three critical parameters:
1) the flow rate through the valve (i.e., the amount the tube opens)
2) the amount of tube closure (which insures the accuracy and repeatability of operation and greatly extends tube life
3) suck back (which allows 3 things: a) clean shutoff of stringy materials, b) prevention of the formation of a droplet at the end of the nozzle and c) minimization of the "skinning" over of materials that tend to dry out at the end of the nozzle).

The Model 828 valve is a higher flow rate version of the 826 valve which still maintains precise and individual control over flow rates and suck back.

The valve can be controlled by our Digital Controller or a 4 way solenoid valve.  

Applications: Used in our Model 1200 syringe filler machine. It is recommended for stringy and tacky materials as well as low to medium viscosity materials.

Pinch Tubing: We supply 3 ft. of 3/16 O.D., 1/8 I.D. Urethane Tubing and the appropriate nozzle adapter with the valve as standard. We stock a variety of other materials: Teflon®, Silicone, Vinyl, etc. for special orders. Most materials have a life in the 2 to 20 million cycle range. Materials such as Natural Rubber or Silicone may have a life of billions of cycles.

Features:
Dual Piston Pinch Valve
High flow rate, 3/8" OD x 1/4" ID tubing
Broad tubing & material choices (see options below)
Precise Flow Rate control adjustments
Precise Suck-Back control adjustments
Pinch stop adjustments greatly extend tube life
Operated: Electrically (PLC), Pneumatically, or Manually

Specifications:
Size:  2 7/8” x 3 1/2 “ 1 1/2”
Weight:  1/2 Lb
Body Material: Anodized Aluminum
Air Inlet: Accepts 1/4” OD, others available
Mounting:  1/4” Clearance Hole
Supply Air Pressure: 75 to 100 Psi

Optional Equipment:
Digital Valve Controller
Supply Reservoirs
Tubing Materials: Teflon, Silicone , Urethane
Tube Size, 3/16” to 1/2” OD.
Nozzle Adapters

OPERATION

826 Valve Startup: When the supplied 3-way, spring returned, normally closed valve (which can be operated electrically, pneumatically or manually) is off (un-actuated), the pinching surface of the upper, spring-closed piston prevents flow by collapsing the tube. The pinch-stop, adjustable screw limits the amount of pinch which limits the stress on the tube (this greatly extends tubing life and insures shot to shot repeatability). The blunt lower piston is held in its open position by a spring. The adjusting screw, which determines the amount that this piston will close the tubing when it is actuated, is set to a position that will allow approximately a 50% tube closure.

826 Valve Dispensing: When the supplied valve is activated, the adjustable stop controls the amount the tube opens which, in turn, controls the rate of flow through the tube. These actions, combined with nozzle size (if a nozzle is used), fluid pressure and the amount of time the 826 is open, govern the amount of fluid dispensed. Simultaneously to the action of the upper piston, the lower, blunt piston moves forward until it stops against the adjusting screw. This causes the piston to partially occlude the tubing.

826 Valve Shutoff: When the valve is deactivated at the end of the dispense cycle, the actuating air exhausts. This allows the upper piston spring to move the piston forward where it once again pinches the tubing. At precisely the same moment the lower blunt piston is also released so that its spring can also return it to its original position. This action allows this portion of the tube to return to its normal (open) shape. It is this return to shape from its partially closed position (the extent of which is adjustable) that creates a precise suck back. The valve is now ready to repeat the cycle. Fine adjustments can be made to both flow rate and suck back to obtain the required results.

© Drawbridge Leaders, Inc. 2006-8