1. A system for charging a capacitor used to power measurement-while-drilling equipment, the system comprising:
(a) a power bus, wherein the capacitor is electrically connected to the power bus;
(b) a first pair of battery terminals for connecting to a first battery;
(c) switching circuitry operable to electrically connect the power bus to and to disconnect the power bus from the first pair of battery terminals; and
(d) a controller, operable to control the switching circuitry, and configured to charge the capacitor by intermittently connecting the power bus to and disconnecting the power bus from the first pair of battery terminals, wherein durations for which the power bus is connected to the first pair of battery terminals are selected such that battery voltage remains above a first minimum operating voltage while the capacitor is being charged.
2. The system of claim 1 wherein the controller is configured to charge the capacitor by applying a first pulse width modulated control signal to control the switching circuitry, wherein the first pulse width modulated control signal has a duty cycle selected such that the voltage of the first battery remains above the first minimum operating voltage while the capacitor is being charged.
3. The system of claim 2 wherein the minimum operating voltage is a reset voltage, and wherein the controller is further configured to reset the system if the voltage of the first battery drops below the reset voltage.
4. The system of claim 3, wherein the controller is further configured to disconnect the first pair of battery terminals from the power bus when the voltage of the first battery drops below a voltage floor, wherein the voltage floor is above the reset voltage.
5. The system of claim 4 wherein the voltage floor is approximately 50% of the maximum voltage of the first battery.
6. The system of claim 2 wherein the first pulse width modulated control signal is configured to cause the first battery to be connected to the power bus for approximately 1.5 ms and disconnected from the power bus for approximately 2 ms for each charging cycle.
7. The system of claim 2 wherein the controller is configured to charge the capacitor for a charging period.
8. The system of claim 7 wherein the controller is further configured to electrically connect the first pair of battery terminals to the capacitor following the charging period and to subsequently indefinitely keep the first pair of battery terminals and the capacitor electrically connected.
9. The system of claim 2 further comprising a first voltmeter, communicative with the controller, and electrically connected in parallel to the first pair of battery terminals such that the voltage of the first battery can be determined.
10. The system of claim 2 further comprising a first ammeter electrically connected in series to the first pair of battery terminals such that current flowing out of the first battery can be determined.
11. The system of claim 2 further comprising a second pair of battery terminals for connecting to a second battery and electrically connected in parallel to the first pair of battery terminals, wherein the switching circuitry is operable to electrically connect the power bus to and to disconnect the power bus from the second pair of battery terminals independently from the first pair of battery terminals and wherein the controller is further configured to apply a second pulse width modulated control signal to the switching circuitry such that the system alternates between:
(a) only charging the capacitor using the first battery by electrically connecting the first pair of battery terminals to the power bus and electrically disconnecting the second pair of battery terminals from the power bus; and
(b) only charging the capacitor using the second battery by electrically connecting the second pair of battery terminals to the power bus and electrically disconnecting the first pair of battery terminals from the power bus,
wherein the second pulse width modulated control signal has a duty cycle selected such that the voltage of the second battery remains above a second minimum operating voltage while the capacitor is being charged.
12. The system of claim 11 wherein the first and second minimum operating voltages are identical.
13. The system of claim 12 wherein the minimum operating voltages are a reset voltage, and wherein the controller is further configured to reset the system if the voltage of the first or second batteries drops below the reset voltage.
14. The system of claim 13, wherein the controller is further configured to disconnect the first pair of battery terminals from the power bus when the voltage of the first battery drops below a first voltage floor and to disconnect the second pair of battery terminals from the power bus when the voltage of the second battery drops below a second voltage floor, wherein the voltage floors are above the reset voltage.
15. The system of claim 14 wherein the first and second voltage floors are identical.
16. The system of claim 15 wherein the voltage floors are approximately 50% of the maximum voltage of the first battery.
17. The system of claim 11 wherein the pulse width modulated control signals are configured to cause the capacitor to always be charged by at least one of the batteries if the voltage of the capacitor is lower than the voltage of at least one of the batteries.
18. The system of claim 11 wherein the pulse width modulated control signals are configured to cause each of the batteries to be connected to the power bus for approximately 1.5 ms for each charging cycle and disconnected from the power bus for approximately 2.0 ms for each charging cycle.
19. The system of claim 11 wherein the controller is configured to charge the capacitor for a charging period.
20. The system of claim 19 wherein the controller is further configured to electrically connect at least one of the pairs of battery terminals to the capacitor following the charging period and to subsequently indefinitely keep the at least one of the pairs of battery terminals and the capacitor electrically connected.
21. The system of claim 11 further comprising first and second voltmeters, communicative with the controller, and electrically connected in parallel to the first and second pairs of battery terminals, respectively, such that the voltages of the first and second batteries can be determined.
22. The system of claim 11 further comprising first and second ammeters electrically connected in series to the first and second pairs of battery terminals, respectively, such that current flowing out of the first and second batteries can be determined.
23. A method for charging a capacitor used to power measurement-while-drilling equipment, the method comprising intermittently electrically connecting the capacitor to and disconnecting the capacitor from a first battery, wherein durations for which the capacitor and the first battery are electrically connected are selected such that first battery voltage remains above a first minimum operating voltage while the capacitor is being charged.
24. The method of claim 23 wherein a first pulse width modulated control signal is used to intermittently electrically connect the capacitor to and disconnect the capacitor from a first battery, wherein the first pulse width modulated control signal has a duty cycle selected such that the voltage of the first battery remains above the first minimum operating voltage while the capacitor is being charged.
25. The method of claim 24 wherein the minimum operating voltage is a reset voltage, and further comprising:
(a) monitoring the voltage of the first battery; and
(b) resetting circuitry used to charge the capacitor if the voltage of the first battery drops below the reset voltage.
26. The method of claim 25 further comprising disconnecting the first pair of battery terminals from the capacitor when the voltage of the first battery drops below a voltage floor, wherein the voltage floor is above the reset voltage.
27. The method of claim 26 wherein the voltage floor is approximately 50% of the maximum voltage of the first battery.
28. The method of claim 23 wherein the first pulse width modulated control signal is configured to cause the first battery to be connected to the power bus for approximately 1.5 ms and to be disconnected from the power bus for approximately 2 ms for each charging cycle.
29. The method of claim 23 wherein the first battery charges the capacitor for a charging period.
30. The method of claim 29 further comprising, following the charging period, electrically connecting the first pair of battery terminals to the capacitor and subsequently indefinitely keeping the first pair of battery terminals and the capacitor electrically connected.
31. The method of claim 24 further comprising applying a second pulse width modulated control signal to intermittently electrically connect the capacitor to and disconnect the capacitor from a second battery, wherein the pulse width modulated control signals are configured to alternate between:
(a) only charging the capacitor using the first battery by electrically connecting the first pair of battery terminals to the power bus and electrically disconnecting the second pair of battery terminals from the power bus; and
(b) only charging the capacitor using the second battery by electrically connecting the second pair of battery terminals to the power bus and electrically disconnecting the first pair of battery terminals from the power bus,
wherein the second pulse width modulated control signal has a duty cycle selected such that the voltage of the second battery remains above a second minimum operating voltage while the capacitor is being charged.
32. The method of claim 31 wherein the first and second minimum operating voltages are identical.
33. The method of claim 32 wherein the minimum operating voltages are a reset voltage and further comprising:
(a) monitoring the voltages of the first and second batteries; and
(b) resetting circuitry used to charge the capacitor if the voltage of the first battery drops below the reset voltage.
34. The method of claim 33 further comprising disconnecting the first pair of battery terminals from the power bus when the voltage of the first battery drops below a first voltage floor and disconnecting the second pair of battery terminals from the power bus when the voltage of the second battery drops below a second voltage floor, wherein the voltage floors are above the reset voltage.
35. The method of claim 34 wherein the first and second voltage floors are identical.
36. The method of claim 35 wherein the voltages of the first and second batteries are identical and the voltage floors are approximately 50% of the maximum voltage of the first battery.
37. The method of claim 31 wherein the pulse width modulated control signals are configured to cause the capacitor to always be charged by at least one of the batteries if the voltage of the capacitor is lower than the voltage of at least one of the batteries.
38. The method of claim 31 wherein the pulse width modulated control signals are configured to cause each of the batteries to alternately be connected to the power bus for approximately 1.5 ms for each charging cycle.
39. The method of claim 31 wherein the capacitor is charged for a charging period.
40. The method of claim 39 further comprising electrically connecting at least one of the pairs of battery terminals to the capacitor following the charging period and subsequently indefinitely keeping the at least one of the pairs of battery terminals and the capacitor electrically connected.
41. A non-transitory computer readable medium having encoded thereon statements and instructions configured to cause a controller to perform the method of claim 23.
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. A magnetic disk drive comprising:
a disk assembly including at least one magnetic disk medium;
a head assembly including at least one magnetic head for writing magnetic signals onto and reading out magnetic signals from said at least one magnetic disk medium, and at least one arm that supports said at least one magnetic head;
a ramp assembly including at least one ramp which guides said magnetic head to a retreat position when said magnetic head is moved away from said magnetic disk medium; and
shroud fins as many in number as there actually are said magnetic disk media, each shroud fin being disposed integrally with said ramp assembly and in association with and next to one of said magnetic disk media in order to guide an air stream produced by rotation of said disk assembly,
wherein each of said shroud fins includes a tapered region reduced in thickness as said shroud fin extends in a direction away from and without covering any part of said magnetic medium associated with said shroud fin.
2. The magnetic disk drive according to claim 1, wherein each of said shroud fins is disposed such that when said magnetic head is guided to the retreat position by said ramp, said at least one arm can be moved along the surface of said shroud fin.
3. The magnetic disk drive according to claim 1, wherein each of said shroud fins extends from said ramp assembly and has a curved surface opposed to, with a spacing from, and next to a lateral face of said magnetic disk medium associated with said shroud fin.
4. The magnetic disk drive according to claim 3, wherein said curved surface has a radius of curvature approximately equal to a radius of curvature of said lateral face of said magnetic disc medium associated with said shroud fin.
5. The magnetic disk drive according to claim 3, wherein each of said shroud fins has a thickness approximately equal to a height of said lateral surface of said magnetic disk medium associated with said shroud fin.
6. The magnetic disk drive according to claim 5, wherein an upper surface of each said shroud fin is positioned on approximately the same plane as an upper surface of said magnetic disk medium associated with said shroud fin, and a lower surface of each said shroud fin is positioned on approximately the same plane as a lower surface of said magnetic disk medium associated with said shroud fin.
7. The magnetic disk drive according to claim 3, wherein each of said shroud fins includes a tapered region reduced in thickness as said shroud fin extends in a direction opposite from a neighboring portion of said lateral face of said magnetic disk medium associated with said shroud fin.
8. The magnetic disk drive according to claim 1, wherein said ramp assembly includes an upper ramp to guide one said magnetic head associated with an upper face of one said magnetic disk medium, and a lower ramp to guide another said magnetic head associated with a lower face of said associated magnetic disk medium.
9. The magnetic disk drive according to claim 8, wherein one of said shroud fins extends from an interstice between said upper ramp and said lower ramp, and is disposed at a position facing, and next to, said associated magnetic disk medium.
10. The magnetic disk drive according to claim 1, wherein said ramp assembly includes proximal portions as many in number as said magnetic heads in the head assembly, and wherein each of said shroud fins extends from one of said proximal portions.