With the advent of the computer there has been a need for storing
vast amounts of data. Several devices have been used to accomplish this task. One
of these devices is a hard disk drive. A hard disk drive includes one or more
disks mounted on a spindle for rotation. Data is typically stored in concentric
tracks which are like rings on a tree. A transducer is passed over the surface
of the disk or disks and data is read from the surface of the disk or written
to the surface of the disks. Hard disk drives are used in all types of computers
ranging from the largest supercomputer to many of the personal computers used in
homes and offices throughout the world.
The disks within a hard disk drive are permanently mounted to the
spindle. In addition, the environment within the housing of a disk drive is carefully
controlled to prevent contaminants since particles the size of smoke from a cigarette
can "trip" the transducer and cause it to contact the disk which results in a disk
crash or undesirable loss of data. As a result, the individual disks from a disk
drive are not replaced by the user of the computer. Since physical access to the
hard disk drive is typically not needed most computers are physically configured
so that the hard disk drive is placed within the computer where it is not seen
by the user. In most computers the hard disk drive is attached to the data bus
within the computer and is not removed until the hard disk drive is replaced.
Of course, there are always exceptions to such common configurations.
In some instances, where particularly sensitive information is being stored on
a hard disk drive, computer user's prefer to have an entire hard disk drive they
can remove from the computer and lock within a safe when not being used. This prevents
computer hackers from breaking codes and accessing the information on the hard
disk drive since there is no way for a hacker to electronically access the information
on the hard disk drive.
In the past, there have been removable hard disk drives and removable
cartridges of hard disks. Disk cartridges, in which only the disks are removable,
have shortcomings. U.S. Patent 4,717,981 issued to Nigam et al. shows such a disk
cartridge which has an automatically activated door. U.S. Patent 4,870,518 shows
the bay into which the cartridge from U.S. Patent 4,717,981 is inserted. The disk
cartridges are more susceptible to contamination since the cartridge is inserted
into a port in the computer. The contaminated air must be cleaned by filtration
or otherwise before the access door to the disk drive can be opened and the actuator
arm which carries the read and write transducer heads can be inserted for reading
and writing. Another shortcoming is that cartridge must be precisely aligned mechanically
each time the cartridge is inserted into the bay to prevent misreads and so that
the disk spins on a level plane. Mechanical alignment using clutching mechanisms
and centering mechanisms is not as precise as a fixed hard disk drive in which
mechanical alignment is permanently set at manufacture. Such alignment is becoming
more critical as the track density on the disk drives increases. Currently, track
densities of over 1000 tracks per inch (2540 tracks per cm) are being used. At
some point, the track densities in a cartridge will be unable to keep up with the
track densities in a hard disk drive.
The removable hard disk drives of the past have also had shortcomings.
Most of the removable hard disk drives have made electrical contact with the computer
system using the pins or connectors on the disk drive. U.S. Patent 5,010,426 issued
to Krenz is an example of such a drive. The pins associated with connector 30 are
engaged with the openings in connector 28. In U.S. Patent 4,633,350 issued to Hanson,
the pins 37 are moved into a mating connector by the camming motion after the
disk drive is rotated into position. U.S. Patent 4,833,554 issued to Dalziel et
al. shows yet another example of pins aligned and slid into engagement with a
mating connector. In the Dalziel et al. patent a pair of alignment pins are used.
Among the shortcomings associated with each of these methods is the fact that
the means for making the connection has a very limited life. For example, the number
of cycles that such connections have would at best be approximately 500 cycles.
In other words, in an environment where a user would be removing the drive on
a daily basis, these drives would last around two years and then would "fail".
The "failure" would actually be a failure of the connectors rather than a failing
of the hard disk drive itself. Another shortcoming is that these removable disk
drives are not easy to remove. The disk drive must be gripped and pulled to break
the electrical contacts unlike a floppy disk which is ejected a short distance
so that the operator can easily grip the floppy.
U.S. Patent 4,893,210 issued to Mintzlaff is a hard disk drive assembly
which can be attached and removed from a power supply to form a stand alone unit
external to a computer. The Mintzlaff patent uses a zero insertion force type
connector that acts or impinges directly onto the pins of the hard disk drive which
carry the inputs to and outputs from the disk drive. The pins would be very susceptible
to damage with this arrangement since the elements 42a and 42b which contact the
pins of the hard disk drive must be nearly perfect aligned to prevent side loading.
Even if the elements 42a and 42b are perfectly aligned, some bending of the pins
of the hard disk drive is likely to occur since the pins in the hard disk drives
generally stand unsupported. Elements 42a and 42b act outwardly and there is no
support behind the pins. Thus, the Mintzlaff patent suffers from the same shortcomings
with respect to the number of times the disk drive could be removed and attached
as do the patents mentioned above. In addition, the Mintzlaff reference is a stand
alone unit which does not have to fit within an opening in a computer. A computer
case would have to be modified in order to accommodate a crank such as 15 in the
The arrangements for making electrical connections in the above references
appear to be for making the insertion of the disk drives easier and more reliable
rather on the first or subsequent times when a hard disk drive required field
service. The above arrangements do not appear to be adapted for removal and insertion
on a frequent basis, such as one or more times daily.
Yet another problem associated with current removable disk drives
is the repeated forces placed on the hard disk drive unit. The hard disk drive
units are able to absorb some shocks however they are still somewhat sensitive.
If too much force or a force is repeatedly placed on a hard disk drive distortion
may result in the housing and result in tracking errors and possible errors in
Therefore, a hard disk drive capable of being removed daily or even
a number of times per day is needed. Furthermore, a hard disk drive that can be
removed easily would be advantageous. This requires an electrical connector which
can be used over and over and which has a high duty cycle and an ejection mechanism.
In addition, a removable hard disk drive which does not have alignment problems
and reads and writes reliably is also needed. Further, a removable hard disk drive
that can be inserted and removed from the computer with little or no force placed
thereon is also desirable.
US patent number US-A-5041924 discloses a removable hard disk drive
system according to the preamble of claim 1 of the present application. In particular,
it describes a removable hard disk drive which can be inserted into a docking bay
to be fitted into a computer. However, there is no described support for 'hot-plugging'
of the hard disk drives, and no disclosed means for preventing writing data to
a second hard disk drive which has replaced a first hard disk drive.
One object of the invention is to allow 'hot-plugging' of the hard
disk drives. Another object is to prevent writing of data to the hard disk drive
after a hard disk drive has been replaced by another one.
A removable hard disk drive system according to the invention is defined
in claim 1.
Advantages of the invention are that it allows "hot plugging" of
the hard disk drive to the bus of the computer and it also acts as a lockout to
prevent writing to the removable hard disk drive until after the computer system
has been rebooted. This prevents data loss resulting from write operations to the
hard disk drive at areas which were previously unfilled on the previous disk drive.
For a better understanding of the present invention, reference is
made to the accompanying drawings in which:
- Fig. 1 is a perspective view of a personal computer.
- Fig. 2 is a perspective view showing where an interprocessor board fits within
a system unit of a personal computer.
- Fig. 3 is a perspective view of the cartridge, docking bay and the interposer
- Fig. 4a is a front view of the docking bay.
- Fig. 4b is a side view of the docking bay.
- Fig. 5a is a front elevation view of the cartridge in the docking bay.
- Fig. 5b is a side view of the cartridge in the docking bay.
- Fig. 6a is a frontal view of the cartridge in the docking bay with a broken
away portion detailing the finger latch.
- Fig. 6b is a side view of the cartridge in the docking bay with a broken away
portion detailing the finger latch.
- Fig. 6c is a view detailing the finger latch.
- Fig. 7 shows the timing diagram for the circuitry which allows "hot plugging"
of the hard disk drive.
- Fig. 8 is a state diagram which relates to the timing diagram shown in Fig
These drawings are not intended as a definition of the invention
but are provided solely for the purpose of illustrating the preferred embodiment
of the invention described below.
Detailed Description of the Preferred Embodiment
Fig. 1 shows a typical personal computer system 10. The typical personal
computer system 10 includes a system unit 12, a monitor 14, and a keyboard 16.
The system unit 12 is the heart of the computer system 10 and includes a motherboard
which has the main processor thereon. The main processor is the brain of the computer
system 10. The system unit 12 also includes a bus which is connected to the various
components within the computer system 10. The bus can be analogized to the spinal
cord of the computer system. Signals, which include various commands, pass from
the main processor along the bus to the various items attached to the bus. Also
connected to the bus are various disk drives such as a floppy disk drive 20 and
a hard disk drive (not shown in Fig. 1) which is typically housed within the system
unit 12. The disk drives act as file cabinets at a human's desk. The main processing
unit, like the brain, has only so much room for vital information. Sometimes other
information or data is needed to make a decision at which time the file cabinet
or disk drive is tapped for the information stored within.
Referring now to Figs. 2 and 3, the removable hard disk drive system
is comprised of an interposer board 24 which has been modified, a docking bay 40
which fits within the system unit 12, and a cartridge 60 which fits within the
docking bay 40. Each one of these components of the removable hard disk drive
system will now be discussed in more detail.
Fig. 2 details the interposer board 24 and shows how the disk drives
are connected to the mother board of a system unit 12. The interposer board 24
has an end 26 which connects to the motherboard located in the system unit 12.
The interposer board 24 also includes a connector 28 which connects the floppy
disk drive 20 to the motherboard. The interposer board also includes a connector
30 for connecting the hard disk drive 22 to the motherboard. It should be noted
that all computer systems 10 may not have an interposer board but may have a substitute
such as a cable attached to the bus. The interposer board 24 shown in Figure 2
has been modified so that the connector 30 for the hard disk drive 22 is located
toward the front of the system unit 12. In many instances the connector 30 for
the hard disk drive 22 is positioned so that the hard disk drive 22 is positioned
near the back of the system unit 12 since there is no need for the gaining access
to the hard disk drive 22, however, since the invention is a removable hard disk
drive the connector 30 is positioned so that the docking bay will face forward.
Figs. 4a, 4b, 6a, 6b and 6c detail the docking bay 40. The docking
bay 40 includes a base 42. Attached to one side of the base is a top 44. The top
44 and the base 42 form a housing 46. The housing 46 of docking bay 40 has an open
end 48 which receives the cartridge 60. Opposite the open end 46 is a spring loaded
end 41. The spring loaded end 41 includes an upturned portion 43 of the base 42
having two openings which receive a pair of elongated fasteners 45. The fasteners
45 are attached to a spring plate 47 at one end. The other end of the fasteners
45 have a nut attached thereto to keep the fasteners 45 within the two openings
in the upturned portion 43. The two fasteners 45 can ride through the two openings
in the upturned portion 43. A spring 49 is placed around each of the fasteners
45 and between the upturned end 43 and the plate 47. The springs bias the plate
47 toward the open end 48.
The docking bay 40 also includes a finger lever 51, having an actuator
end 53 and a hook end 55. The actuator end 53 is accessible and can be actuated
from the front of the system unit 12. Moving the actuator end 53 causes the hook
end 55 to move from slightly below the floor of the docking bay 40 to above the
floor of the docking bay 40. The finger lever 51 has a pivot axis between the actuator
end 53 and the hook end 55.
The dimensions of the open end 48 are selected so that it fits within the opening
in the front of the system unit 12 which was for a disk drive having a particular
form factor. The docking bay 40 is dimensioned so that it fits within the bay
in the system unit 12. Attached to the opposite side of the base 42 is a first
printed circuit card 50. The first printed circuit card 50 includes a printed circuit
card connector 52 located so that it attaches to the hard disk drive connector
30 on the interposer board 24 (shown in Fig. 3). The first printed circuit card
50 also includes the male portion 54 of a zero insertion force connector. The
male portion 54 is elongated and terminates in a long string of connectors located
within the housing 46 of the docking bay 40. The first printed circuit card 50
also includes circuit paths which electrically attach each pin of the connector
52 to an individual "pin" or conductor associated with the male portion 54 of the
zero insertion force connector situated within the housing 46.
The first printed circuit card 50 also includes circuitry which allows
a hard disk drive within the cartridge 60 to be "hot plugged" and circuitry which
prevents any write operations to a hard disk drive within the cartridge before
the computer system 10 has been rebooted. This last bit of circuitry prevents
data loss from mistakenly writing to sectors on the hard disk drive which were
free on the hard disk previously in the docking bay but which are not free on
the hard disk drive currently in the docking bay. Each of these circuits is implemented
using devices known as programmable logic arrays (not shown). The programmable
logic arrays are an array of logic elements whose interconnections are programmed
either by use of a mask or by using a special instrument in the field for making
the interconnections. The programmable logic arrays are used to produce a set
of logical outputs given certain inputs which can be represented by the timing
diagram shown in Fig. 7 and the state diagram shown in Fig. 8. These will be discussed
in further detail after the cartridge has been described in detail.
Now turning to Figs. 3, 5a, 5b, 6a, 6b and 6c, the cartridge will
be discussed. The cartridge 60 is a container which fits within the docking bay
40. The cartridge 60 contains a hard disk drive 62 which has a smaller form factor
than the form factor of the drive that is provided for in the system unit 12. For
example, the bay in the system unit 12 will accommodate a disk drive with a 3
1/2" form factor. The docking bay 40 fits within the 3 1/2" form factor bay in
the system unit 12. The hard disk drive within the cartridge is a 2 1/2" form factor
drive which is a drive having length approximately equal to the width of a 3 1/2"
form factor drive and having a width approximately equal to one half the length
of the 3 1/2" form factor drive. The height of the 2 1/2" form factor drive is
approximately one half the height of a 3 1/2" form factor drive. The 2 1/2" form
factor drive has a volume which is one fourth the volume of the 3 1/2" form factor
The cartridge 60 has an small opening 61 dimensioned to receive the
hook end 55 of the finger lever 51. The cartridge 60 also includes a second printed
circuit card 64. The second printed circuit card 64 includes a connector 66 which
connects the pins of the hard disk drive 62 to circuit paths on the second circuit
card 64. Also attached to the circuit card 64 is a female portion 68 of a zero
insertion force connector. The female portion 68 of the zero insertion force connector
is attached to the second circuit card 64 and to the circuit paths on the circuit
card 64. There is one electrical contact on the female portion 68 of the zero
insertion force connector for each of the pins of the hard disk drive 62. The female
portion 68 of the zero insertion force connector is positioned along one edge
of the cartridge 60. The female portion 68 of the zero insertion force connector
used acts like a clamp and pinches the male portion 54 of the zero insertion force
connector so that electrical contact is made. A small handle 70 accessible from
the outside of the cartridge 60 is turned to connect or clamp the female portion
of the zero insertion force connector onto the male portion 54 of the zero insertion
force connector. The female portion 70 can also be unclamped by turning the handle
Advantageously, the zero insertion force connector selected is rated for a high
number of cycles, such as 5000 cycles, to allow the cartridge 60 to be placed in
and out of the docking bay 40 many times. The zero insertion force connector used
here is available as Part Number 531414-4 from A M P INC of Harrisburg, Pennsylvania.
The zero insertion force connector has both a female portion 68 and a male portion
54. The high cycle life allows a cartridge and docking bay to be connected repeatedly
over a number of years.
The hard disk drive 62 is mounted within the cartridge 60 in the
space left after accommodating the female portion 68 of the zero insertion force
connector. The second circuit card is mounted on the top surface inside the cartridge
60. The cartridge is sized to fit within the opening in the front of the system
unit 12 and within the docking bay 40. The only other electronics on the second
circuit board 64 are termination resistors and power indicator LEDs which are
well known in the electronics art and will not be discussed further.
In operation, the cartridge 60 is inserted within the docking bay
40. The female portion 68 of the zero insertion force connector in the cartridge
is placed over the end of the male portion 54 in the docking bay 40 and guides
the cartridge 60 into the docking bay 40. The cartridge 60 is pushed into the
docking bay 40 until it abuts the spring plate 47. The cartridge 60 is pushed against
the spring plate 47 until the hook end 55 of the finger lever 51 engages the opening
61 in the cartridge 60. The cartridge 60 is then "let go" whereupon the spring
plate 47 biases the cartridge 60 to a position where the end of the opening 61
abuts the end of the hook end 55 of finger lever 51. At this position, the pins
of the male portion 54 and the female portion 68 of the zero insertion force connectors
are aligned. Advantageously, the cartridge is held in place by the finger lever
51 and the spring plate 47 which prevents any side loading on the zero insertion
force connector. The next step is to turn handle 70 and engage the female portion
68 with the male portion 54 of the zero insertion force connector. To remove the
cartridge 60 the handle 70 is turned to disengage the female portion 68 from the
male portion 54 of the zero insertion force connecter. The finger lever 51 is then
actuated by lifting it slightly upward. This removes the hook end 55 from the opening
61 in the cartridge 60. The spring plate 47 urges the cartridge 60 outward. The
springs 49 are selected to eject the cartridge 60 slightly.
A power sequencing circuit included in the first printed circuit
card 50 attached to the docking bay 40 allows "hot plugging" and a lockout feature
for preventing unintentional overwriting of data.
Now turning to Figs. 7 and 8, the circuit on the first circuit card
50 which allows "hot plugging" will be discussed. Fig. 7 is a timing diagram and
Fig. 8 is a state diagram which relates to the timing diagram of Fig. 7. As mentioned
previously, the circuit is made using programmable logic arrays whose use are well
known in the art. The sequence shown by the timing diagrams is the critical component
of the circuits rather than the specific times between the various states. The
overall sequence must be accomplished within a selected time. In the present invention
it was noted that the female portion 68 of the zero insertion force connector is
controlled by a bar (not shown) which distorts slightly within the elastic range
of the material when the handle 70 is turned to engage or disengage the female
portion 68 and the male portion 54. It was found that due to this distortion the
electrical contact nearest the handle was made or broken slightly before all the
other contacts were made or broken along the zero insertion force connector. The
sequence to allow "hot plugging" occurs within this amount of time.
The timing diagram in Fig. 7 which reflects the power sequencing
circuit, will now be generally described. The signal -SENX 80 is controlled by
the pin of the female portion 68 of the zero insertion force connector which breaks
first or makes contact first due to the distortion of the bar within the elastic
range as mentioned in the previous paragraph. When the -SENX 80 signal changes
it indicates a change in the connection between the female portion 68 and the
male portion 54 and also indicates that power to the hard disk drive 62 will be
turned off or turned on. To prevent damage to the hard disk drive 62 certain events
must occur to assure that the hard disk drive 62 will not be damaged.
To prevent damage to the disk drive 62 when power is removed from
the disk drive 62, +/- 5 volts must be maintained to the disk drive until after
all the other electrical contacts are broken. The power sequencing circuit basically
produces an accelerated the shutdown of the all the electrical contacts of the
zero insertion force connector which correspond to the pins on the disk drive 62
before all the electrical contacts are physically broken as a result of turning
the handle 70 to assure that the +/- 5 volts is the last to leave. In other words,
the power sequencing circuit turns off all the connections to the hard disk drive
before the last contact in the zero insertion force connector is broken. This occurs
in less than 500 milliseconds which is approximately the time between when the
first contact is broken and the last contact is broken along the zero insertion
To prevent damage to the disk drive 62 within a cartridge 60 during
power up, each of the electrical contacts of the disk drive 62 must be brought
up in a certain sequence. The +/- 5 volts must be connected and stabilized to the
disk drive 62 before the sequence is started. The power sequence circuit senses
when the first electrical contact is made, sequences all the pins in the disk drive
62 and assures that the +/- 5 volts has been connected to the disk drive 62 before
the sequence is started. The power sequence circuit basically prevents electrical
signals from passing to the disk drive 62 even though electrical contact may have
been made along the contacts of the zero insertion force connector. A delay is
used to accomplish this in the present invention.
Fig. 7 details how the power sequencing in this invention works.
Fig. 7 is a timing diagram that can be implemented with programmable logic arrays
which are well known in the art. Now looking at Fig. 7, when -SENX is low, electrical
contact is made and when -SENX 80 goes high this indicates that electrical contact
has been broken. When -SENX 80 goes high, the power down sequence starts. A signal
+HFP 82, which is a signal indicating hard file presence is basically a slightly
delayed reflection of the signal -SENX 80, goes from a high state to a low state
in response to the signal -SENX 80 goes high. In response to +HFP going low, a
signal + RESET 84 goes high for several clock cycles to acquiesce the hard disk
drive 62 so that it does not send signals to the bus during a power shutdown or
during a power startup. When the hard disk drive 62 is disengaged, a signal -PWRON
86, goes high. Also when the hard disk drive is disengaged a signal -BUSEN 88 goes
high indicating the bus has been disengaged or disabled. In response to the -PWRON
86 going high, a signal VCC 90, which is the dc voltage to the hard disk drive
62, begins to go low. In response to the VCC 90 signal beginning to go low, a signal
-POR 92, which is the power on reset which is the sequencing procedure that the
drive 62 must go through at a power down or at power up to prevent CMOS latchup,
goes low. Upon removal of the cartridge 60, the power reset goes through its power
down sequence. A signal +PORQ 94 is a slightly delayed reflection of the -POR 92
signal so that when -POR goes low, +PORQ goes high.
After a cartridge 60 is replaced or inserted into the docking bay
40 and the female portion 68 of the zero insertion force connector makes electrical
contact with the male portion 54, the power up sequence begins. When the first
female portion contacts the male portion, the signal -SENX 80 drops from high to
low which causes the signal +HFP to go from low to high. The high state of +HFP
causes the signal -PWRON 86 to go low indicating that power is available to the
disk drive 62. The signal -PWRON 90 going low triggers the signal VCC 90 to begin
rising which indicates that all the pins to the disk drive 62 are being placed
at the proper power levels at the proper sequence. Once this proper power level
at the proper sequence has been achieved, VCC is in its high state. VCC high causes
signal -POR 92 to go high which in turn causes -PORQ 94 to go low. -PORQ 94 going
low triggers the +RESET signal 84 to go high for a number of clock signals. Finally
a delay line 96 goes low after a certain amount of time which indicates that the
last pin on the zero insertion force connector already made electrical contact.
In response to the delay line 96 going low, the -BUSEN signal 88 goes low which
indicates the bus can now engage.
The state diagram shown in Fig. 8 merely shows the various states
which the power sequencer circuit, does through. The states are also shown at the
top of Fig. 7. Fig. 8 merely details the various states.
The power sequence circuit also provides a data integrity service
for the user who has more than one removable cartridge 60 for use on a single personal
computer system 10. The data integrity service is basically a lockout device which
prevents a user from inserting a new cartridge 60 into the docking bay 40 and having
critical portions written over with new information because the operating system
does not realize a new cartridge has been inserted and writes to the new disk drive
62 as if it were the disk drive 62 previously in the docking bay 40.
This lock out circuitry is rather straight forward and it is felt
a separate timing diagram and state diagram is not necessary to aid in the understanding
of this portion of the invention. Therefore the feature will be described in writing.
The power sequence circuit also monitors the presence or absence of a cartridge
60 through two signals -SENS1 and -SENS2 which could also be the two states of
the signal -SENX in Fig. 7 Whenever the cartridge 60 is absent, a signal +FCHG,
indicating a file change, is activated and remains active even after a new cartridge
60 has been inserted since it is latched by the power sequence circuit. The +FCHG
signal remains active until a channel reset signal is activated which indicates
that the computer system 10 has been rebooted either by turning off the on/off
switch or by pressing the proper keys on the keyboard 16 to cause it to reboot.
An LED can be activated when the +FCHG signal is active to indicate that the system
must be rebooted before normal operations can resume.
The present invention and the best mode for practicing it has been
described. It is to be understood that the foregoing description is illustrative
only and that other means and techniques can be employed without departing from
the full scope of the invention defined by the appended claims.