Patent GB-814157-A (GB)
Title: Improvement in or relating to disc mills
Inventor: EIRICH WILHELM
Filed: 1957-07-09
Abstract: 814,157. Disc mills. EIRICH, W., and EIRICH, G. July 9, 1957 [July 11, 1956], No. 21730/57. Class 59 [Also in Group XXX] In a disc mill having two discs rotatable with respect to one another to form a grinding zone at least over part of their adjacent surfaces, said surfaces are at least partially covered in the grinding zone with a coating comprising a layer of resistant metal having embedded splinters of hard metal, i.e. sintered metal carbide having a melting point above 2000‹C. and preferably above 2500'C. The disc mill shown in Fig. 1 is disposed in a cylindrical housing 1 and comprises a rotatable grinding disc 10 having a grinding coating carrier 11, a counterweight ring 12 provided with clearing blades 13, a reinforcing ring 14 and an intake cone 15. The carrier 11 and ring 12 may consist of sectors secured to th disc 10 by bolts 16. Disposed opposite the carrier 11 is a counter-grinding coating carrier 17 which is secured to the housing 1 by bolts 18. The carriers 11, 17 are shaped so as to provide a tapering pre-grinding zone and a main grinding zone of uniform thickness. Grinding ribs may be mounted, e.g. by welding, on the carriers 11, 17 in both the pregrinding and main grinding zones and these ribs are disposed obliquely to the radial direction and opposed to the direction of rotation of the disc 10. The carriers 11, 17 are provided over their entire co-operating surfaces with a grinding coating consisting of steel having embedded splinters of hard metal e.g. tungsten carbide bonded with cobalt. The steel may be admixed with powder-fine splinters of the same material to prevent the steel from being washed out between the larger splinters. The ribs may be applied to the carriers 11, 17 by first being pressed into the form of ribs in a hot process and then being applied to a previously-applied hard surface. Material to be treated is supplied through a double inlet cone 2. The ring 14 has an annular flange 20 to cause material sliding radially over the ring by centrifugal force to be thrown against the plate 17 then to rebound against the plate 11 and so on. The housing 1 is lined with plates 27 which may also have a coating of resistant metal with embedded hard metal splinters. Cooling air is drawn through a duct 21 by means of fan blades 26 mounted on the ring 12. In a modification, Fig. 2 (not shown), air intake apertures are provided in the cover plate of the mill housing. In another modification, Fig. 3, clearing members 13<SP>1</SP> are formed as grinding jaws and provided with a coating of resistant metal with embedded hard metal splinters. The plates 27 have a similar coating which may be of trough-shaped profile (Fig. 4, not shown). Air required to convey the material is sucked through an inlet 101 into an annular duct 102 and then through apertures 22. The finelycrushed material is discharged through the duct 21 by the aid of a blower. Blades 103 are attached to the ring 12. In a further modification, Fig. 7, for treating plastic material, the mill has a feed duct 29 for the plastic material and a feed duct 30 for liquid to be admixed with the plastic material. Intake blades 36 are mounted on the intakecone 15. The feed duct 29 has a lining 37, preferably of hard metal, surrounded by an electric heating device 38. To prevent plastic material adhering to the lower part of the lining 37, fingers 23 provided with a coating 24 of resistant metal with embedded hard metal splinters are mounted on the ring 14. To facilitate the clearing of treated material, the base plate 39 of the mill housing 28 is slowly rotated by a motor 40 and has strippers 41, 42 which keep the cover and side walls of the housing 28 free from treated material. The treated material thereby enters an annular space 43 defined by the base plate 39, an annular wall 44 secured to the base plate and the housing walls. A fixed stripped 45 at the delivery point or points engages in the space 43 and takes up the material lying on the base plate and continuously discharges it. Means (Figs. 8 to 10, not shown) are provided for adjusting the distance between the grinding discs and for momentarily separating them in the event of overload.