(19) |
|
|
(11) |
EP 0 083 961 A3 |
(12) |
EUROPEAN PATENT APPLICATION |
(88) |
Date of publication A3: |
|
25.07.1984 Bulletin 1984/30 |
(43) |
Date of publication A2: |
|
20.07.1983 Bulletin 1983/29 |
(22) |
Date of filing: 05.01.1983 |
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(84) |
Designated Contracting States: |
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AT BE DE FR GB NL SE |
(30) |
Priority: |
06.01.1982 CA 393583
|
(71) |
Applicant: BRALORNE RESOURCES LIMITED |
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() |
|
(72) |
Inventors: |
|
- Ring, Curtis Phillip
()
- Tomm, Wayne R.
()
|
|
|
|
(54) |
Improved jar tool for drill strings |
(57) A jar tool for use in a drill string for use in dislodging a drill bit or well-tools
trapped in well bores. The tool comprises an outer housing adapted to move longitudinally
with respect to an inner spline mandrell. A piston assembly is acted on by a piston
actuator and hydraulic fluid restricts the movement of the piston assembly and, therefore,
the movement of the mandrell relative to the housing while the piston assembly is
within a narrower portion of a hydraulic cylinder. When the piston assembly reaches
a larger diameter portion of the cylinder, the hydraulic fluid rushes past the piston
assembly which allows a knocker connected to the spline mandrell to collide with the
outer housing. A compression spring returns the piston assembly to its rest position
abutting a shoulder on the outer housing. Provision is made for a valve to be inserted
in the piston assembly so that the system can be temperature compensated and more
desirable hydraulic fluids can be used.