Adjustable groove depth

Figure 7.27 Feed housing with adjustable groove depth, zero groove depth position...

There are several advantages of the adjustable groove depth ... 

C.J. Rauwendaal, U.S. Patent 5,909,958, Screw Extruder with Adjustable Groove Depth (1999)... 

The adjustable grooved feed extruder developed at Rauwendaal Extrusion Engineering [246] uses a grooved feed section in which the depth of the grooves can be continuously adjusted while the extruder is in operation. Parallel developments have taken place in Poland at the Technical University of Lublin [244, 245). Earlier concepts have been developed [247], however, due to the complexity of the adjustment mechanism, these have not been applied on a wide scale. 

There are two basic methods by which the groove depth can be adjusted ... 

Groove Depth Adjustment by Radial Movement of Keys... 

One of the drawbacks of the pivoting key mechanisms is that there is a chance of material getting between the key and the keyway. When this happens, the key cannot move radially outward and mechanical problems may occur. One way of circumventing this problem is to make the keys and keyways tapered, and adjust the groove depth by sliding the keys along the base of the keyways. This is illustrated schematically in Fig. 7.29. 

Figure 7.29 Groove depth adjustment by sliding key axially...

Since the groove depth can be adjusted to zero depth, the feed throat can be easily cleaned out upon material change-over in other words, no material can get trapped in the grooves. 

The depth of the grooves can be adjusted while the machine is running, allowing optimization of the groove depth under actual operating conditions. 

With electronic actuators the groove depth can be adjusted quickly, automatically, and precisely the groove depth can be automatically optimized to produce the smallest pressure variation at the discharge end of the extruder or to achieve other process objectives. 

The adjustable depth of the grooves allows a grooved feed to be easily used on vented extruders. The groove depth can be adjusted to make sure that vent flow does not occur. 

Being able to adjust the depth of the grooves in a feed housing will greatly expand and improve process adjustment capability of screw extruders. 

Fluoride. Fit a 4 ml (75 x 10 mm) test-tube with a cork carrying a tube about 8 cm long and of about 3 mm bore cut a V-shaped groove in the cork. Adjust the tube in the cork so that the lower end is about 2-5 cm from the bottom of the test-tube (cf. Fig. V. 1). Place 15-20 mg of the substance and 0-5 ml concentrated H2S04 in the test-tube, dip the glass tube into water so that a film of water almost seals the lower end to a depth of about 5 mm, insert into the test-tube, and place in the hot water rack. The formation of a white film in the water confirms fluoride (IV 17, 1). 

ISO 15496 uses an inverted cup method for measuring the water vapour permeability of textile fabrics. A cup filled with a desiccant (e.g. potassium acetate) is sealed with a circular piece of waterproof and vapour-permeable membrane. A circular specimen of 180 mm is fitted to the groove of the specimen holder and covered by another piece of waterproof and vapour permeable membrane. The specimen holder is then inserted into the support frame, which is fitted with four vertically adjustable screws so that the specimen holder is immersed to a depth of 5 2 mm in a water bath fiUed with distilled water at 23 °C. The measuring cup is weighed at a precision of 1 mg, inverted and inserted into the specimen holder. After 15 min, the measuring cup is removed and reweighed. The water vapour transmission of the specimen is calculated by ... 

The test apparatus was modified by the addition at the lubricant supply Inlet of a length of 10 mm diameter copper tube formed into a coll of some 150 mm diameter and Immersed In a bath of water. The water temperature could be adjusted to effect a change In lubricant viscosity. All the results reports were carried outwlth one glass pad (number 2 of reference (6)) which had a length (in the surface motion direction) of 100 mm, a width of 45 mm and a central square supply groove of 9.5 mm side. The depth of the groove was 1.5 mm. 

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