| 摘要 |
1,258,173. Draughting heads. HUGHES-OWENS CO. (Ltd). Nov.4, 1969 [Dec. 5, 1968], No. 53932/69. Heading G1X. A draughting head comprises a base 10 which is secured by means of screws 17 to a mounting plate on a draughting machine linkage (not shown), the base 10 having an upstanding hollow body 13 with a cylindrical bore 20 in which is rotatable a carrier assembly 14, consisting of an upper shaft portion 25 and a lower shaft portion 26 secured together by a screw 27 and a pair of rules 15 secured to the lower shaft portion 26, the rules being mutually at right angles, and the upper shaft portion 25 having a diametral slot 31 in which is received a depending lug 32 integral with an annular cap 33, the lug being pivotally mounted on a pin 35 in the shaft portion 25, and cams 36 formed integral with the cap disposed offset from the axis of the pin 35 and arranged to contact either a shoulder 24 or a flange 23 on the body 13 on tilting of the cap one way or the other about the pin 35 so as to either force into engagement or release co-operating frusto-conical surfaces 22, 29 on the body 13 and lower shaft portion 26 to lock or release the carrier assembly 14 for rotation with respect to the base 10. A transparent protractor scale 18 is rotatably retained at the lower end of the body 13, a clamping screw (not shown) being provided to clamp the scale 18 in a desired position with respect to the body 13. A pair of spaced resilient fingers 37 extend downwardly from the lug 32 of the cap 33 towards the bottom of the slot 31 to bias the cap to the position shown in the figure wherein the carrier assembly 14 may be freely rotated within the body 13 by rotation of the cap 33. The assembly 14 may be locked in position by tilting the cap so as to cause engagement between the lower ends of the cams 36 and the shoulder 24. The body 13 and carrier assembly shaft portions 25, 26 may be moulded from nylon, and the cap 33 from an acetal resin. |
