Title:
アースドリル
Document Type and Number:
Japanese Patent JP6758764
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To provide an earth drill capable of protecting a coil spring which mitigates an impact transmitted to a kelly-bar with a simple structure and preventing a breakage of the coil spring.SOLUTION: An earth drill includes a fixed spring receiver 37 at a lower end part outer periphery of a first kelly-bar member 28 of an innermost layer, a floating spring receiver 38 loosely fitted in an outer periphery of a first kelly-bar member above a fixed spring receiver, a coil spring 40 arranged between the fixed spring receiver and the floating spring receiver and supporting a second kelly-bar which lies adjacent to the first kelly-bar via the floating spring receiver, and a protection cover 39 which is arranged around the coil spring and limits the coil spring from contracting more than a predetermined amount by abutting to the fixed spring receiver when the coil spring contracts upon receiving a compression load.SELECTED DRAWING: Figure 3
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| WO/2011/094429 | SHOCK REDUCTION TOOL FOR A DOWNHOLE ELECTRONICS PACKAGE |
| WO/2017/004399 | ISOLATOR |
Inventors:
Tokuo Murate
Okumura Takayoshi
Okumura Takayoshi
Application Number:
JP2016243219A
Publication Date:
September 23, 2020
Filing Date:
December 15, 2016
Export Citation:
Assignee:
Nippon Vehicle Manufacturing Co., Ltd.
International Classes:
E21B17/07
Domestic Patent References:
| JP2119982U | ||||
| JP3115193U | ||||
| JP2000034879A | ||||
| JP2001115763A |
Foreign References:
| US4997037 | ||||
| US5263899 | ||||
| CN101975033A |
Attorney, Agent or Firm:
Yoshihiko Kido
Kazuhiko Kido
Kazuhiko Kido