The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 20, 1990
Filed:
Dec. 21, 1988
Pekka Salmi, Tampere, FI;
Oy Tampella AB, Tampere, FI;
Abstract
In a rotary drilling apparatus, a rotary head is advanced against an object to be drilled and a neck element included in the rotary head and connected with drilling member is rotated around its longitudinal axis relative to a rotary head body. The neck element is subjected, in a normal drilling situation to the action of two oppositely-directed forces produced by means of a pressure medium, the first force acting in the drilling direction and the second force acting in the direction opposite to the drilling direction, the first force being greater and the difference between the forces producing a feeding force. The neck element is movable in the direction of the feeding force. In a drilling situation, when the force acting in the direction opposite to the feeding force is greater than the feeding force, the neck element moves in the direction opposite to the drilling direction relative to the rotary head body. During this movement, the first force is maintained at least equal to that which is required in a normal situation and the action of the second force is eliminated. As the force exerted on the neck element opposite to the feeding force is diminished, the action of the first and second forces, and thus the feeding force is restored with the neck element moving in the drilling direction.