Patent GB-272417-A (GB)
Title: Apparatus for grading abrasive and applying the same to continuous grinding systems
IPC: B24B57/00
Filed: 1927-02-02
Abstract: 272,417. Hitchcock, H. K. Feb. 2, 1927. Disc, wheel, and roller apparatus.-Apparatus for surfacing sheets of material such as glass, marble, and the like by a series of continuous grinding operations comprises a series of grinding machines which act in succession on the sheet to be surfaced and are supplied with abrasive in liquid suspension which is delivered from grading apparatus arranged to deliver progressively finergrades of abrasive to successive machines, means being also provided to supply fresh abrasive to the system and to remove mud and spent abrasive. The supply system is duplicated so that one part of the system may be shut down while the full supply of abrasive is obtained from the other part. Two parallel series of machines of the suspended type A' - - A<8> and B<1> - - B<8> are supplied from main graders C<a> and Cb which normally supply the A and B series, respectively. Adjacent each pair of machines and arranged in staggered relation as shown in Fig. 1 are distributing vessels D<1> - - D<4> and E<1> - - E<4>. These vessels preferably serving also as secondary graders. The main graders are of the upward flow type as described in Specification 1210/13 the abrasive and water being admitted at the bottom of the conical portions and coming into equilibrium in horizontal strata of different fineness. The mixture is drawn off from the graders by pipes F<1>- - F<1> and G<1> - - G<1> extending into the mixture to 'different depths and delivering into the distributing vessels. The glass or other material is laid on tables 2<a>, 2<b>, which travel on parallel tracks 3<a> and 3<b> located beneath the grinding heads and which are moved forward continuously. The distributing vessel are of the. form shown in Fig. 5, mixture from the main grader entering at 5 and settling into layers of different fineness. Mixture is withdrawn through two pairs of pipes 7<a>, 7<b> and 6<a>, 6<b> which extend to different depths, the short pipes from the vessel D<1> leading c the grinders A<2>, B<2> respectively and the long pipes with the coarser abrasive to the grinder A<1>, B<1>. This arrangement is repeated for all the secondary grading vessels, so that each grinding machine is, as shown, supplied from two secondary graders, the fine grade from one vessel and the coarse grade from another vessel, these mixtures being of approximately the same fineness. This arrangement allows one series of secondary graders to be shut down without stopping the grinding machines. Troughs 8<a>, 8<b> are arranged beneath each series of machines to catch abrasive and these communicate with troughs 10<a>, 10<b>. Each secondary grader has an outlet 13 which is closed by a valve carried by a vertical pipe 15 supplying water from the upward flow in the grader. This water supply is drawn from tank 19, through pipes 18, 17. The return troughs 10<a>, 10<b> discharge respectively into sumps 11<a> which have cross connections so that either sump may be used alone if required. Return water enters the sumps through revolving screens 26<a>, 26<b> which are rotated from motors 27<a>, 27<b> and which serve to catch dirt glass &c. Withdrawal pipes 31a, 32a and 31<b>, 32<b> extend into the respective sumps and are connected through pumps 34 - - 37 to the primary graders, but in case of necessity either or both graders can be supplied from either sump. In a modification, the sumps are connected to the pumps through rotary valves 33a, 33<b>, as shown in Fig. 7. Each sump is provided with an overflow 41 and a lower overflow 42 both leading to a sewer. Overflows are also provided on the primary graders. Pipes 45 extend downwards into the sumps for washing out the corners where heavy sand tends to accumulate. Fresh abrasive such as green sand is supplied automatically to the two systems from a storage bin 50, which through troughs 51a, 51<b> discharges into the return troughs from the grinding machines. If the system becomes overcharged, the coarsest abrasive may be withdrawn from the bottom of the main graders through valves connected to a pipe leading to a storage bin. A fresh water pipe-line 20 supplying the tank 19 is provided with flexible branches having nozzles which may be snapped over the ends of the pipes 5 coming from the main graders to blow out any obstructions. The surplus water and mud is eliminated in part by the overflow pipes 41 from the sumps and in part by overflow from the main graders.