| 摘要 |
1,062,775. Boring earth &c; pile driving. P. GROSPAS. Dec. 3, 1963 [Dec. 5, 1962], No. 47673/63. Headings E1F and E1H. A percussive device such as a pile driver, hammer, or drill for earth boring has a rammer or bit 2 attached to a cable 1 and reciprocated by means of a crank 16 rotated by a differential gearing 13. The gearing is driven by a shaft M and has driven shafts 14, 15 respectively carrying the crank 16 and a crank 17. The cable runs over guide pulleys 3, 22, 23 and a pulley 20 on the crank 16, and is fixed to a drum 5 which pays out cable as the depth of the bore increases. A line 24 fixed at 29 passes over a pulley 21 on the crank 17 and a guide pulley 25 to connect to an elastic member 26 fixed at B. The resistance of the member is such that in normal operation the crank 17 does not pass top dead centre causing the crank 16 to accelerate after passing top dead centre so that rotation of the crank 17 is reversed until bottom dead centre is reached, the arrangement permitting free fall of the bit. In the event of a stuck bit the crank 17 rotates, the resistance of the elastic member being such that the cable is not unduly loaded. A cam 27 rotating with the crank 17 actuates a machine stop or reduces the resistance of the elastic member which may be a spring, an air filled piston and cylinder, or a combination of spring and piston and cylinder. |
