Patent CA-1043767-A (CA)
Inventor: GRIGORIEV VLADIMIR K
IPC: E21B19/08
Filed: 1975-08-29
Granted: 1978-12-05
Abstract: ABSTRACT OF THE INVENTION      The present invention provides a drilling boom assembly comprising: a telescopic boom, the boom being expandable and contractable in length and having a first end and a second end, the first end being hinged to a pivot mounted on a bearing plate, the pivot and the boom being pivotal relative to the bearing plate about a vertical axis; a first hydraulic cylinder assembly for controlling the length of the boom, the first hydraulic cylinder assembly being carried by the boom; a feed bar hinged to the second end of the boom, the feed bar being provided with a drifter and having a working end, the feed bar being axially movable forwards and backwards relative to the second end of the boom by means of a second hydraulic cylinder assembly, the second hydraulic cylinder assembly being mounted on the boom; a third hydraulic cylinder assembly for tilting the feed bar in a vertical plane, the third hydraulic cylinder assembly being connected to the boom; a fourth hydraulic cylinder assembly for turning the feed bar in a horizontal plane, the fourth hydraulic cylinder assembly being connected to the boom; a mechanism for rotating the feed bar about an axis parallel to the axis of the feed bar; a fifth hydraulic cylinder assembly for lifting the boom, one end of the fifth hydraulic cylinder assembly being hinged to the boom, the other end of the fifth hydraulic cylinder assembly being hinged to the pivot; a sixth hydraulic cylinder assembly for turning the telescopic boom in a horizontal plane, one end of the sixth hydraulic cylinder assembly being hinged to the bearing plate; a servomechanism for controlling operation of either the first or alternatively the second hydraulic cylinder assembly (hereinafter referred to as the controlled cylinder assembly), the servomechanism comprising a support rod, a seventh hydraulic cylinder assembly mounted on the rod and a servovalve, each of the aforementioned hydraulic cylinder assemblies comprising a respective cylinder accommodating a piston defining a first variable volume space and a second variable volume space in the cylinder, the first variable volume space of the seventh hydraulic cylinder being in communication with the first variable volume space of the controlled cylinder, said communicating spaces being equal in volume at any one time, the servovalve comprising a body and a plunger accommo-dated in the body and attached to the rod, the body having a first duct for supply of working fluid in to the servovalve, a second duct communicating with the second variable volume space of the controlled cylinder for supplying working fluid to that space and a third duct communicating with the second variable volume space of the seventh hydraulic cylinder for return of working fluid from that space, the plunger controlling communication between the ducts; and A connecting means coupling the rod with the boom which causes the seventh hydra-ulic cylinder assembly and the body of the servovalve to dis-place with respect to the plunger, thus bringing the first duet into communication via the second duct with the second variable volume space of the controlled hydraulic cylinder assembly, thus either extending or retracting the controlled hydraulic cylinder assembly and compensating to maintain the working end of the feed bar in a desired vertical plane, when either (1) the controlled cylinder assembly is the first hydraulic cylinder assembly and the boom turns in a vertical plane or (ii) the controlled cylinder assembly is the second hydraulic cylinder assembly and the boom turns in a horizontal plane