Follower plate

Individual graphic elements in the following plates are based on the following sources, used with the kind permission of the authors and publishers concerned. 

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. 

A simple periodic table, with 41 elements designated, is given on the adjacent page, and a complete periodic table following plate 57. These tables show the elements in the sequence of their atomic numbers, which is nearly the same as the atomic-weight sequence. Atomic numbers were reliably assigned to the elements in 1914. 

In the crystal and in the liquid, the hydrogen molecules may be described as in contact with one another. The observed distance between the centers of two nonbonded atoms in contact is given reasonably well by the sum of the packing radii of the two atoms. Distances between the centers (the nuclei) of two atoms connected to one another by a chemical bond are given reasonably well by the sum of their covalent-bond radii. (See the tables following plate 57.)... 

The increase in size of related atoms with increase in atomic number is shown by the bond lengths for these four molecules. The values found by experiment, shown in the adjacent drawing, are very nearly equal to the corresponding sums of covalent radii given in the table following plate 57. 

Preparation of Hg film electrode. The Hg film electrode, although possessing superior sensitivity characteristics, is more subject to irreproducible behavior than is the hanging Hg drop electrode. The following plating procedure is satisfactory. 

Traditionally, either plate and frame filters or pressure leaf filters have been used for bleach-clay removal. The sequence of change in usage was approximately as follows plate and frame filters, pressure leaf filters, self-cleaning closed filters, and automated filters. Pressure leaf filters began to replace plate and frame presses for several... 

Where the corrosion resistance of a coating depends upon its passivity, it is common to follow plating with a conversion coating process to strengthen the passive film. Zinc, cadmium and tin in particular are treated with chromate solutions which thicken their protective oxides and also incorporate in it complex chromates (see Section 1S.3). There are many proprietary processes, especially for zinc and cadmium. Simple immersion processes are used for all three coatings, while electrolytic passivation is us on tinplate lines. Chromate immersion processes are known to benefit copper, brass and silver electrodeposits, and electrolytic chromate treatments improve the performance of nickel and chromium coatings, but they are not used to the extent common for the three first named. 

On these fast lines, the adhesive or sealant is delivered in 200 1 drums, the follower plate is powered by hydraulic jacks in order to increase the pressure on the product in the drum. The pump ratio may vary from 20/1 upto 60/1 or even more, and the hose should resist upto 200-300 bars pressure. 

Follower plate with elastomer wiper seal or rings... 

The choice of the adhesive determines the type of application equipment required. For most industrial applications, pump-operated applicator systems are used which are designed to pump the adhesive directly from bulk drums at relatively high working pressures. Systems for using hot-applied adhesives need to be equipped with heated follower plates, hoses and guns. For automated application, additional dispensing units are necessary to meter the exact quantity of adhesive required for each application. 

Just as in many modern automotive engines, it was decided to employ follower plates, which can be changed much easier than a complete follower. Because of their compact size and simple shape they are easy to manufacture and fit in most evaporation jars. 

Fig.5 shows a detail of the test rig. The camshaft is removed to allow a view on the follower plate with transducers. 

Full film conditions in the cam-follower contact can easily be checked by a measurement of the Ohmic resistance or the capacitance of the film. For this, the follower plate is insulated by a 5 mm. perspex layer. In addition, the follower is insulated from the test rig mass by the hydrostatic bearing, and at the load cell and the guide blocks of the follower body. 

Indeed a sudden rise in the global film thickness could be detected. If a worn sliding area of the follower plate is used, resulting in a low A value (relative film thickness), surface films will form even at 5 s shaft speed within 1800 s. When a fresh part of the plate surface is used, reac on films can develop at speeds over 13 s after 2500 till 5000 s. See Fig.8b. In this Figure surface layers are formed after about 700 s, probably initiated by a short period of slightly increased speed. If these layers are formed on the follower surface, an even number of capacitance jumps is needed, see Section 3. In addition, when employing an eccentric cam, they have to be located symmetrically around 0= 0. This is not the case. Consequently, the surface layers are on the cam and not on the follower. 

A possible explanation is the high content of Cr in the follower plate material (41). 

There are many experiments supporting the diagnosis of misalignment. Fig.18 is the result of another experiment, where a new follower plate has been used. Here the left side transducer indicates a minimum film thickness of about 0.4 pm at maximum follower lift. What happens when the load is increased, can be seen in Fig.19. The minimum film thickness drops to a value of about 0.3 pm at 15(X) N. 

The minimum film thickness at the right is about 0.7 pm, at the left 0.8 pm for the first extrema, and about 0.9 pm (right) and 0.8 pm (left) for the second extrema in Fig. 21 A, and 1.1 pm (right) and 1.0 pm (left) in Fig.21 B. Obviously, the second conductor wire is located at the point of maximum contact sweep on the follower plate. The conclusion is near that the alignment in the contact is much better now at 5 10 rad. This should be supported by temperature measurements. 

Fig.22 was obtained under exactly the same conditions as Fig.18, except that the elastic hinge support is mounted between follower plate and follower body. The minimum film thickness is about 0.5 pm. 

Figures 24, 25, and 26 show some comparisons between left and right side temperatures on the follower plate. In Fig.24 and 25 the long transducer type was used, in Fig.26 the short type (Fig.15). The cam cycle temperature is scanned in Fig.27.

This may not seem large, but it should be viewed on the very thin film thickness scale. The Figures presented in this paper could lead to the conclusion that the left side of the follower plate is always on the heavy load side. Many other experiments falsify this. The misalignment problem can only be alleviated by a self aligning support. 

Without the elastic follower plate support, maximum temperature variations were found to be 16.4 C at maximum lift on the left (heavy load) side, measured with a long type transducer. A short type, having its sensor more outwards, would definitely have detected a higher temperature. 

Under isothermal conditions the minimum film thickness can be estimated by employing empirical formulae, like the Dowson and Higginson expression (4). At 40 C follower plate temperature it can be found that the steady state minimum film thickness amounts about 1.8 pm at maximum lift, and about 1.6 pm at minimum lift. This is in contrast with the experimental findings. The measurements show that (1) the film thickness is much smaller, and (2) the film thickness at maximum lift is always smaller than the film thickness at minimum lift. It is known from steady state EHD lubrication that the oil inlet temperature plays a decisive role in film thickness calculations. First, the inlet position needs to be known as a function of time, and next temperature measurements must be carried out at that location. From Fig.27 it can be concluded that the contact temperature at maximum lift rises about 12 C, and at minimum lift about 1C. At 55 C and maximum lift the steady state minimum film thickness will drop to 0.8 pm. Hence temperature effects cannot remain out of it, but also they cannot explain the difference comprehensively. A 60 c temperature rise at maximum lift is needed to obtain film thicknesses as low as 0.2 pm, which can develop... 

Most follower plates did show some wear after some time. Occasionally no wear was observed, after 15 hrs. of running, which is sufficient for laboratory applications. 

When bulk unloader A reaches empty drum, another limit switch sends a signal to the system controller indicating that bulk unloader A is out of material. The system controller automatically then switches bulk unloader B to on-line status and signals manufacturing personnel that a changeover has occurred and that a new drum of material is required. Bulk unloader A will remain at application temperature to facilitate easy removal of the drum follower plate. After the follower plate has been raised and the empty drum removed and replaced by a new drum, the follower plate is then reinserted followed by purging of air from beneath the fol-... 

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