초록 ▼

An eddy current brake includes a diamagnetic member, a first support wall and a second support wall with the first and second linear arrays of permanent magnets disposed on the walls facing one another. Apparatus is provided for moving at least one of the walls in order to control eddy current induc

An eddy current brake includes a diamagnetic member, a first support wall and a second support wall with the first and second linear arrays of permanent magnets disposed on the walls facing one another. Apparatus is provided for moving at least one of the walls in order to control eddy current induced in the member in the passage of the member therepast to adjust the braking force between the magnets and the member. Apparatus is also provided for causing the velocity of the member to change the braking force between the magnets and the member.

대표청구항 ▼

An eddy current brake includes a diamagnetic member, a first support wall and a second support wall with the first and second linear arrays of permanent magnets disposed on the walls facing one another. Apparatus is provided for moving at least one of the walls in order to control eddy current induc

An eddy current brake includes a diamagnetic member, a first support wall and a second support wall with the first and second linear arrays of permanent magnets disposed on the walls facing one another. Apparatus is provided for moving at least one of the walls in order to control eddy current induced in the member in the passage of the member therepast to adjust the braking force between the magnets and the member. Apparatus is also provided for causing the velocity of the member to change the braking force between the magnets and the member. lades proximate a line between a longitudinal axis of the bit and a pass through axis of the bit, the at least one cutting element oriented to cut earth formation when the at least one cutting element moves opposite a direction of rotation of the bit. 6. The bi-center drill bit as defined in claim 1 wherein positions for the cutting elements are selected so that lateral forces exerted by said cutting elements disposed on the pilot blades and the reaming blades are balanced as a single structure. 7. The bi-center drill bit as defined in claim 6 wherein the lateral forces are balanced to less than about 10 percent of a total axial force exerted on the bit. 8. The bi-center drill bit as defined in claim 6 wherein the lateral forces are balanced to less than about 5 percent of a total axial force exerted on the bit. 9. The bi-center drill bit as defined in claim 1 wherein a radially outermost surface of each of the reaming blades extends at most to a radially least extensive one, with respect to a longitudinal axis of the bit, of a pass-through circle and a drill circle, the drill circle substantially coaxial with the longitudinal axis, the pass-through circle axially offset from the drill circle and defining an arcuate section wherein the pass-through circle extends laterally from the longitudinal axis past a radius of the drill circle, so that radially outermost cutting elements disposed on the reaming blades drill a hole having a drill diameter substantially twice a maximum lateral extension of the reaming blades from the longitudinal axis while substantially avoiding wall contact along an opening having a diameter of the pass through circle. 10. The bi-center drill bit as defined in claim 1 wherein at least one jet is disposed proximate to the reaming blades, the at least one jet oriented so that its axis is within approximately 30 degrees of a line normal to a longitudinal axis of the bit. 11. The bi-center drill bit as defined in claim 1 wherein at least one jet is disposed proximate to the reaming blades, the at least one jet oriented so that its axis is within approximately 20 degrees of a line normal to a longitudinal axis of the bit. 12. The bi-center drill bit as defined in claim 1 wherein a center of mass of the bit is located within about 2.5 percent of a diameter of the bit from a longitudinal axis of the bit. 13. The bi-center drill bit as defined in claim 1 wherein a center of mass of the bit is located within about 1.5 percent of a diameter of the bit from a longitudinal axis of the bit. 14. A bi-center drill bit, comprising: a bit body having pilot blades and reaming blades thereon distributed azimuthally around the body, selected ones of the blades having cuffing elements thereon at selected locations, the body and blades defining a longitudinal axis of the bit and a pass-through axis of the bit; and at least one bidirectional cutting element attached proximate a line extending between the pass-through axis and the longitudinal axis, the bidirectional cutting element comprising a primary cutting surface oriented to cut earth formation when the bidirectional cutting element moves along the direction of rotation of the bit, the bidirectional cuffing element comprising a secondary cutting surface oriented to cut earth formation when the bidirectional cutting element moves opposite the direction of rotation of the bit. 15. The bi-center drill bit as defined in claim 14 wherein selected azimuthally corresponding ones of the pilot blades and the reaming blades are formed into unitized spiral structures. 16. The bi-center drill bit as defined in claim 14 wherein positions for the cutting elements are selected so that lateral forces exerted by said cutting elements disposed on the pilot blades and the reaming blades are balanced as a single structure. 17. The bi-center drill bit as defined in claim 16 wherein the lateral forces are balanced to less than about 10 percent of a total axial force exerted on the bit. 1