into the threaded hole 614 and pushes against the first side 412 an elastic element 62 u2032 in the present embodiment is disposed between the first side 412 and the sliding block 61 and can also offer the above function as shown in fig8 the adjusting apparatus 60 can also be configured such that the sliding block 61 having an engaging portion 615 with continuous teeth is mounted on the pivot shaft 21 and the pivotal portion 41 is formed on an inner surface of the top end 43 with an engaging portion 413 to be engaged with the engaging portion 615 of the sliding block 61 the sliding block 61 is formed with a bigger disc shaped head portion on an end thereof exposed out of the sliding groove 410 so that the user can pull the head portion 616 in the adjustment to make the sliding block 61 move away from the sliding groove 410 along the axial direction of the pivot shaft 21 after the pivotal portion 41 is moved to a proper position the sliding block 61 will be re installed on the pivot shaft 21 in the sliding groove 410 and the engaging portion 615 will be re engaged with the engaging portion 413 of the sliding groove 410 as shown in fig9 the sliding block 61 can also be in the form of a column and includes a sector engaging portion 617 to be engaged with the engaging portion 413 of the sliding groove 410 in the above embodiment the pivotal portion 41 can be horizontally moved for adjustment by rotating the.