Disk/shaft attachment

Fig. 6.28 Schematic view of the normal stress extruder. Polymer melt is placed between the disks. The upper disk is attached to a rotating shaft at frequency of rotation fi. A pressure profile of increasing pressure toward the center develops, and the melt is extruded through the die.

Fig. 6.31 Schematic view of a co-rotating-disk pump, (a) The disks are attached to a rotating shaft and placed within a harrel having an inlet and an outlet port, separated by a channel block attached to the stationary barrel. The space between inlet and outlet ports, the disks, and the channel block form the processing chamber, (b) parallel arrangements of the disks (c) wedge-shaped disks.

In screw extruders, as we have seen, the processing takes place in the helical channel formed between the screw and the barrel. In a co-rotating disk processor (CDP), on the other hand, processing takes place in flat doughnut-shaped processing chambers formed by two neighboring disk surfaces, the inner surface of the barrel, the shaft to which the disks are attached, and the channel block attached to the barrel, with very small clearance to the disk surfaces. It thus blocks the channel and separates inlet from outlet, as shown in Fig. 9.44. Processing chambers can be connected in series, parallel, or any other... 

In contrast to gas circulation in the stirrer plane, the gas stream which escapes above the stirrer from the liquid vortex, can be easily determined, if it can be ensured that it is not entrained by the stirrer again and mixed back into the liquid. In [609] a vertically displaceable tube, concentrically positioned round the stirrer shaft, was air-tight mounted on the vessel lid and dipped into the liquid vortex (see sketch in Fig. 1.22). A thin, smooth disk was attached to the lower end of the tube, which dipped into the liquid vortex, without disturbing the flow pattern, thereby separating the vortex into two zones. The lower zone is connected via the tube with the atmosphere, and the gas stream escaping into the upper zone can now be determined with a gas-meter. 

Disk Filters A disk filter is a vacuum filter consisting of a number of vertical disks attached at intervals on a continuously rotating horizontal hollow central shaft (Fig. 18-127). Rotation is by a gear drive. Each disk consists of 10 to 30 sectors of metal, plastic, or wood, ribbed on both sides to support a filter cloth and provide drainage via an outlet nipple into the central shaft. Each sector may be replaced individually. The filter medium is usually a cloth bag slipped over the sectors and sealed to the discharge nipple. For some heavy-duty applications on ores, stainless-steel screens may be used. 

Expander-compressor shafts are preferably designed to operate below the first lateral critical speed and torsional resonance. A flame-plated band of aluminum alloy or similarly suitable material is generally applied to the shaft in the area sensed by the vibration probes to preclude erroneous electrical runout readings. This technique has been used on hundreds of expanders, steam turbines, and other turbomachines with complete success. Unless integral with the shaft, expander wheels (disks) are often attached to the shaft on a special tapered profile, with dowel-type keys and keyways. The latter design attempts to avoid the stress concentrations occasionally associated with splines and conventional keyways. It also reduces the cost of manufacture. When used, wheels are sometimes secured to the tapered ends of the shaft by a common center stretch rod which is pre-stressed during assembly. This results in a constant preload on each wheel to ensure proper contact between wheels and shaft at the anticipated extremes of temperature and speed. 

Fig ure 5-20. The disk containing the rotating blades is attached to the end of the shaft by means of eight studs with nuts. Disk-to-shaft juncture is an axial-face (curvic) spline, allowing transmission of torque and concentricity of the disk under high temperature conditions. 

The calculation for torque is a primary example of a single degree of freedom in a mechanical system. Figure 43.15 represents a disk with a moment of inertia, /, that is attached to a shaft of torsional stiffness, k. 

This type of flow meter is normally used for water service, such as raw water supply and evaporator feed. The movable element is a circular disk which is attached to a central ball. A shaft is fastened to the ball and held in an inclined position by a cam or roller. The disk is mounted in a chamber which has spherical side walls and conical top and bottom surfaces. The fluid enters an opening in the spherical wall on one side of the partition and leaves through the other side. As the fluid flows through the chamber, the disk wobbles, or executes a nutating motion. Since the volume of fluid required to make the disc complete one revolution is known, the total flow through a nutating disc can be calculated by multiplying the number of disc rotations by the known volume of fluid. 

Fig. 9.45 Multiple disks attached to the shaft with (a) processing chambers connected in parallel, (b) processing chambers connected in series, and (c) combined parallel and series connection.

The Robatel extractor is a series of mixer-settlers stacked on their sides, with mixing in each stage being carried out by a stationary disk attached to the shaft while... 

HK between them. The rubber sheet is clamped between two metal disks on to a steel rod R which goes out of the box through a stuffing box S. The lower end of the rod rests on a cam V which can be rotated by turning the handle N attached to the shaft U. The box above the rubber sheet contains water on which a wooden disk LM floats. The... 

All stage divider openings must be designed so that the column can be free draining. For this reason, draft tubes are often extended below the opening, or, if they extend above the stage divider, then small weep holes are drilled into the draft tube just above the stage divider. If a disk attached to the shaft is used to minimize back-... 

Another type of gravity-flow, vertical contactor with a rotating axial shaft is the rotating disk contactor developed by the Shell Development Company [R1, R2], shown schematically in Fig. 4.28. It consists of alternate annular stator disks attached to the outer shell and circular rotor disks attached to the rotating shaft. Rotation of the central shaft, at peripheral speeds up to 6 m/s, provides controlled dispersion of the two phases and sets up a toroidal flow pattern within each stator compartment. There are no settling chambers, and the two phases drift past each other in countercurrent flow. 

---