1. A pig for movement within a pipeline comprising:
a cylindrical housing;
at least first and second annular elements circumferentially mounted to the housing and extending outwards for engagement with a pipeline;
an internal flow cavity passing longitudinally through the housing;
a gate capable of being opened, positioned within the internal flow cavity, obstructing flow through the internal flow cavity; and
a locking device connected to the gate, preventing it from being opened, the locking device being releasable to open the gate in the event the pig becomes stuck.
2. The pig of claim 1 further comprising:
an unlocking device mounted adjacent the locking device for releasing the locking device; and
a sensing device capable of receiving a signal indicating the pig is stuck, wherein the signal will activate the unlocking device thereby releasing the locking device, permitting the gate to open.
3. The pig of claim 1 wherein the gate is capable of rotation about an axis perpendicular to the internal flow cavity.
4. The pig of claim 1 wherein the locking device comprises a rod that engages the gate.
5. The pig of claim 2 wherein the unlocking device comprises at least one cutter that severs the locking device.
6. The pig of claim 5 further comprising a hydraulic accumulator for storing hydraulic fluid connected to power the cutter.
7. The pig of claim 1 further comprising a pinger mounted to the pig for tracking and locating the pig within the pipeline.
8. The pig of claim 2 wherein the sensing device comprises a pressure switch that senses pressure on an upstream end of the pig.
9. The pig of claim 1 wherein the sensing device is capable of receiving an electromagnetic signal from an operator to release the locking device.
10. A pig for movement within a pipeline comprising:
a cylindrical housing;
at least first and second annular elements circumferentially mounted to the housing and extending outwards for engagement with the pipeline;
an internal flow cavity passing longitudinally through the housing;
a gate positioned within the internal flow cavity and mounted to a shaft that is perpendicular to the internal flow cavity, the gate and shaft being capable of rotation;
a locking device that engages the gate to prevent the gate from rotating and opening;
an unlocking device adjacent the locking device; and
a sensing device that senses when the pig is stuck in the pipeline and causes the unlocking device to release the locking device.
11. The pig of claim 10 wherein the locking device comprises a rod that passes through a hole in the gate, thereby preventing the gate from rotating and opening.
12. The pig of claim 11 wherein the unlocking device comprises a cutter that severs the rod in response to receiving a signal from the sensing device.
13. The pig of claim 12 wherein the cutter is hydraulically powered.
14. The pig of claim 13 further comprising a hydraulic accumulator for storing hydraulic fluid and supplying hydraulic fluid to the cutter.
15. The pig of claim 10 further comprising a pinger mounted to the pig for tracking and locating the pig within the pipeline.
16. The pig of claim 10 wherein the sensing device comprises a pressure switch.
17. The pig of claim 10 wherein the sensing device is capable of receiving an electromagnetic signal from an operator to release the locking device.
18. A method for deploying a pig within a pipeline comprising:
(a) providing an internal cavity extending through the pig and placing a gate in the cavity;
(b) placing the pig in the pipeline with the gate closed, allowing the flow of the fluid to drive the pig through the pipeline; and
(c) if the pig becomes stuck in the pipeline, opening the gate to allow fluid to flow through the internal cavity.
19. The method according to claim 18, wherein step (c) further comprises:
sending a signal to the pig if it becomes stuck, opening the gate.
20. The method according to claim 18, wherein step (b) further comprises locking the gate in a closed position with a locking device; and
wherein step (c) further comprises sending a signal to the pig, releasing the locking device.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An imaging lens comprising:
a first lens group;
a second lens group having positive refractive power; and
a third lens group having negative refractive power, which are arranged in order from an object side,
wherein the first lens group includes a former lens group having a negative lens in a most object side, a diaphragm, and a rear lens group,
wherein, when focusing is performed, the second lens group is moved in the optical axis direction,
wherein the imaging lens satisfies the following Conditional Equation:
\u22122.0<f3f<\u22120.8\u2003\u2003(1),
wherein
f3: a focal length of the third lens group, and
f: a focal length of a whole lens system.
2. The imaging lens according to claim 1, satisfying following Conditional Equation:
0.1<\u03b22<0.5\u2003\u2003(2)
1.0<\u03b23<2.5\u2003\u2003(3)
wherein
\u03b22: lateral magnification of the second lens group, and
\u03b23: lateral magnification of the third lens group.
3. The imaging lens according to claim 1,
wherein the rear lens group includes a negative lens and a positive lens, and satisfies following Conditional Equation:
\u03bd1Rp\u2212\u03bd1Rn>25\u2003\u2003(4)
wherein
\u03bd1Rp: Abbe number for \u201cd\u201d line of the positive lens of the rear lens group, and
\u03bd1Rn: Abbe number for \u201cd\u201d line of the negative lens of the rear lens group.
4. The imaging lens according to claim 1,
wherein the third lens group includes a negative lens in which an absolute value of a curvature radius of an image surface side is smaller than that of the object side.
5. The imaging lens according to claim 1,
wherein the third lens group includes a negative lens, and satisfies following Conditional Equation:
1<t3iR3b<4\u2003\u2003(5)
wherein
t3i: a length to an image surface from a surface apex of an image surface side of the negative lens of the third lens group, and
R3b: the curvature radius of the image surface side of the negative lens of the third lens group.
6. The imaging lens according to claim 1,
wherein the rear lens group is a cemented lens having a negative lens and a positive lens.
7. The imaging lens according to claim 1,
wherein the second lens group includes one positive lens.
8. The imaging lens according to claim 1,
wherein the diaphragm is arranged between the former lens group and the rear lens group of the first lens group.
9. An imaging apparatus comprising:
an imaging lens; and
an imaging device which outputs a photographing signal based on an optical image formed by the imaging lens,
wherein the imaging lens includes a first lens group, a second lens group having positive refractive power, a third lens group having negative refractive power, which are arranged in order from an object side,
wherein the first lens group includes a former lens group having a negative lens in a most object side, a diaphragm, and a rear lens group,
wherein, when focusing is performed, the second lens group is moved in an optical axis direction,
wherein the imaging lens satisfies the following Conditional Equation:
\u22122.0<f3f<\u22120.8\u2003\u2003(1),
wherein
f3: a focal length of the third lens group, and
f: a focal length of a whole lens system.
10. The imaging lens according to claim 9, satisfying following Conditional Equation:
0.1<\u03b22<0.5\u2003\u2003(2)
1.0<\u03b23<2.5\u2003\u2003(3)
wherein
\u03b22: lateral magnification of the second lens group, and
\u03b23: lateral magnification of the third lens group.