118,170. Watts, F. C., Watts, G. W., and Fearnley, J. L., (trading as Watts & Son, E. R.). Sept. 12, 1917. Levelling-heads.- In ball-and-socket adjusting-heads for gun directors, surveying, and other scientific instruments, &c., adjustment is permitted on two axes at right-angles but not on a third axis at right-angles to the other two. A rod 8 screwing into the base G of the . instrument carries a butterfly head 9 pressing a cup 11 into engagement with a spherical socket 1 carrying the tripod-legs. A ball 4 with a flat head 5 with V- shaped projections engaging recesses in the base 6 can oscillate about horizontal axes at rightangles, but is prevented from oscillating about the axis of the rod 8 by a collar 14 rotatable on a pin 13 screwed in the socket 1 and sliding in a slot 12 in the plane of the axis of the rod 8. A spring 10 is arranged between the head 9 and cup 11. Leather rings 15, 16 exclude dust. A separate cap may be provided to screw on the end of the rod 8 when the adjusting-head is removed from the base 6.
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