Memory cassette holding apparatus

An apparatus for holding a memory cassette in a cassette adapter wherein the memory cassette cannot be ejected from the adapter, even by pressing an eject button, while data is being written into or read from the memory cassette. Provided are means for generating a signal indicating that a read or write operation is in progress, a locking mechanism for locking a cassette ejecting mechanism to render the latter inoperable, and a drive circuit responsive to the generated signal for actuating the locking mechanism to prevent ejection of the memory cassette until the read or write operation is completed.

BACKGROUND OF THE INVENTION 
This invention relates to a memory cassette holding apparatus and, more 
particularly, to a memory cassette holding apparatus which assures that an 
ejecting mechanism will not operate while data is being written into or 
read from a memory cassette. 
To preserve numerical control (NC) data created for numerically controlling 
a machine, robot or the like, use is made of a memory cassette such as a 
magnetic tape cassette, bubble memory cassette or semiconductor memory 
cassette. This is accomplished by loading the memory cassette in a 
numerical control device or NC data creation device, writing the NC data 
stored in the internal memory of the numerical control device, or created 
by the NC data creation device, into the memory cassette, and then 
subsequently reading the NC data out of the memory cassette to execute 
numerical control based on the NC data. 
When using a memory cassette, there is always the danger that the operator 
may inadvertently press an eject button and cause ejection of the memory 
cassette while the NC data is being written into or read from the memory 
cassette. An accident of this kind will prevent the NC data from being 
correctly written into or read from the cassette, or may mutilate 
machining NC data already stored in the memory cassette at a different 
location. Thus there is need of an apparatus capable of cancelling the 
operation that would otherwise be initiated by pressing the eject button 
while data is being written into or read from the memory cassette. 
SUMMARY OF THE INVENTION 
Accordingly, it is a primary object of the present invention to provide a 
memory cassette holding apparatus so adapted that the memory cassette will 
not be ejected during the writing or reading of data. 
According to the present invention, the foregoing and other objects are 
attained by providing an apparatus for holding a memory cassette so that 
data may be written into and read from the memory cassette. The apparatus 
includes a holder for holding the memory cassette, an ejecting mechanism 
for ejecting the memory cassette from the holder, a locking mechanism for 
locking the ejecting mechanism to prevent ejection of the memory cassette 
from the holder, and a drive circuit for actuating the locking mechanism 
in response to a signal generated while data is being written into the 
memory cassette and read from the memory cassette. The locking mechanism 
renders the ejecting mechanism inoperable to prevent ejection of the 
memory cassette while data is being written into or read from the memory 
cassette. Such an arrangement assures that the data can be written and 
read correctly, and that already stored data will not be mutilated, even 
if an eject button is accidentally pressed when a read or write operation 
is in progress. 
Other features and advantages of the present invention will be apparent 
from the following description taken in conjunction with the accompanying 
drawings, in which like reference characters designate the same or similar 
parts throughout the figures thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1 illustrating the principle of the invention, a 
cassette holder 12 is adapted to hold an end portion 11a of a memory 
cassette 11. A substantially L-shaped eject lever 13 constituting part of 
an ejecting mechanism and supported for rotation about a pivot shaft 14, 
has the ejector end thereof disposed in a gap formed between the memory 
cassette 11 and the cassette holder 12. An eject button 15 is so disposed 
as to abut against the other or right end of the eject lever 13 from the 
side thereof. The arrangement is such that when the eject lever 13 is 
rotated clockwise in FIG. 1 about the pivot shaft 14 by pressing the eject 
button 15, the memory cassette 11 is ejected in the direction of the arrow 
A. A data read/write controller 16 is provided for producing a signal WR 
when NC data stored in a memory 17 is being written into the memory 
cassette 11, and a signal RD when the NC data is being read out of the 
memory cassette. Hereinafter the signals WR, RD will be referred to as 
write mode and read mode signals, respectively. When either of these 
signals is generated, a drive circuit 18 responds by causing a locking 
mechanism 19 to lock the eject lever 13 against rotation even if the eject 
button 15 is pressed. The eject lever 13 will remain locked until the 
signal WR or WD vanishes. The locking mechanism 19 may comprise an 
ordinary electromagnet and an armature (neither of which are shown in FIG. 
1), wherein the electromagnet is excited, responsive to generation of the 
write mode signal WR or read mode signal RD, to thrust the armature into 
the position indicated by the solid lines in FIG. 1, thereby preventing 
rotation of the eject lever 13. When either of these signals vanishes, the 
electromagnet is deenergized and the armature is retracted to the position 
indicated by the broken lines, allowing clockwise rotation of the eject 
lever 13 when pressed by the button 15. 
Reference will now be made to FIGS. 2 and 3 to describe a preferred 
embodiment of the invention in detail. FIG. 2 shows an adapter 21 which 
uses the memory cassette holding apparatus of the invention. The adapter 
21 has a cassette inlet 23 in which a memory cassette, such as a bubble 
memory cassette 22, is inserted so that NC data or an NC program stored in 
the cassette may be read from the cassette and transferred to a numerical 
control device (not shown) via a connecting cable 24, or so that NC data 
or an NC program transferred from the numerical control device via the 
cable 24 may be written into the bubble memory cassette 22. Projecting 
from a slot in the adapter 21 is the distal end 27a of a lever 27 
described below. A button or cap, not shown, is adapted to fit on the 
lever end 27a to facilitate the operation of the lever. 
FIG. 3 is a front view illustrating the details of a memory cassette 
holding apparatus embodying the present invention. A holding plate 26 made 
of metal is provided for supporting the holding apparatus in its entirety. 
The lever 27 mentioned above in connection with FIG. 2 is pivotally 
supported on the holding plate 26 by means of a pin 28 affixed to the 
holding plate. Fit onto the distal end 27a of the lever 27 is an eject 
button, not shown. Part of the lever 27 adjacent pin 28 is formed into a 
bifurcated locking portion 27b. The lever 27 also has a short extension 
27c having a pin 27d implanted near the root portion thereof. A link 29 is 
provided having one end attached for rotation to the distal end of the 
extension 27c of lever 27. The other end of the link 29 is attached for 
rotation to a rack 30 which, by operation of the lever 27 acting through 
the link 29, is adapted to pull up the bubble memory cassette 22 to enable 
its extraction. Although the details are not illustrated, the rack 30 is 
adapted for vertical movement along the line A--A in FIG. 3. The lever 27, 
link 29 and rack 30 comprise an ejecting mechanism. 
Numeral 31 designates a guide member penetrated by a locking rod 32 movable 
horizontally through the guide member so that one end of the rod 32 is 
engagable with the bifurcated locking portion 27b of the lever 27. A 
locking rod drive lever 33 is pivotally mounted on the holding plate 26. 
The locking rod drive lever 33 has a substantially L-shaped configuration, 
the end of one leg thereof being coupled to the other end of the locking 
rod 32, the end of the other leg thereof being coupled to an armature 35. 
The latter is so adapted as to be freely movable through the interior of a 
magnet coil 34 affixed to the holding plate 26. Energizing the magnet coil 
34 draws the armature 35 inwardly thereof to the position shown in FIG. 3. 
The magnet coil 34 is connected to the drive circuit 18 (FIG. 1) by a 
cable 34a. Numeral 38 designates a pin implanted in the holding plate 26. 
A tension spring 36 is stretched between the pin 38 and the pin 27d 
implanted in the extension 27c of the lever 27, and serves to hold the 
lever 27 in either a cassette load position, indicated by the solid lines 
in FIG. 3, or cassette eject position, which is indicated by the broken 
lines. A second tension spring 37 is stretched between the pin 38 and the 
end of the locking rod drive lever 33 coupled to the armature 35, and 
serves to constantly bias the drive lever 33 in the counter-clockwise 
direction. The locking rod 32, locking rod drive lever 33, magnet coil 34 
and armature 35 comprise a locking mechanism. Note that the cassette 
holder, shown at 12 in FIG. 1, is deleted from FIG. 3 for the sake of 
simplicity, 
In the operation of the memory cassette holding apparatus of FIG. 3, the 
bubble memory cassette 22, indicated by the dashed line, is shown already 
loaded in the cassette inlet 23 of the adapter 21 (FIG. 2), and the 
associated mechanisms are shown in the attitudes assumed during the 
writing or reading of information with respect to the bubble memory 
cassette. Specifically, the magnet coil 34 is in the energized state so 
that the armature 35 is retracted into the coil. The locking rod drive 
lever 33 therefore is rotated in the clockwise direction against the 
pulling force of the tension spring 37, thereby pushing the locking rod 32 
to the left in FIG. 3 to engage the end of the rod 32 with the bifurcated 
locking portion 27b of the lever 27. This locks the lever 27 against 
rotation, so that the bubble memory cassette 22 cannot be ejected. When 
the write or read operation is completed, the magnet coil 34 is 
deenergized to release the armature 35 from the attractive force applied 
by the coil, so that the locking rod drive lever 33 is rotated in the 
counter-clockwise direction under the pulling force applied by the tension 
spring 37, thereby pulling the locking rod 32 to the right in FIG. 3 to 
disengage the end thereof from the locking portion 27b of the lever 27. 
The lever 27 now is capable of rotation about the pin 28. The operator may 
now rotate the lever 27 from the cassette load position to the eject 
position, whereby the link 29 interconnecting the lever 27 and the rack 30 
is displaced from the position indicated by the solid lines to that 
indicated by the broken lines. The rack 30 will therefore be pulled upward 
in FIG. 3 along the line A--A, bringing the bubble memory cassette 22 to a 
position where it can be extracted from the adapter 21, shown in FIG. 2. 
Note that no problems are encountered even if the bubble memory cassette 22 
should be inserted into the cassette inlet with the lever 27 in the eject 
position and the rack 30 in the raised attitude as a result. The reason is 
that a read or write operation will not be in effect at such time so that 
the locking rod 32 will be at its rightmost position where it is 
disengaged from the locking portion 27b, allowing the lever 27 to be 
rotated freely about the pin 28. When the bubble memory cassette 22 is 
inserted, therefore, the bottom of the cassette depresses the rack 30 
which, owing to its connection to the lever 27 via link 29, rotates the 
lever 27 forcibly in the counter-clockwise direction to restore the lever 
to the cassette load position. 
FIG. 4 is a circuit diagram illustrating the data read/write controller 16 
and drive circuit 18. The read/write controller 16 comprises address 
decoders 39, 42, 43 which receive input signals from a numerical control 
device NC, described below, a gate circuit 40 receiving the outputs of the 
address decoders 39, 42, 43, the gate circuit 40 having gates G1, G2, and 
a flip-flop circuit 41 whose set and reset terminals are connected to the 
outputs of the respective gates G1, G2 of the gate circuit 40. The drive 
circuit 18 comprises diodes D1, D2, D3, resistors R1, R2, a transistor TR 
and the magnetic coil 34 of FIG. 3. MPU, ROM, RAM represent a 
microprocessor, read-only memory and random access memory, respectively, 
these comprising the numerical control device NC mentioned above. ABUS is 
an address bus, and DBUS a data bus. The numerical control device NC is 
adapted to apply a signal to the address decoder 39 at the beginning and 
end of a read or write operation. The numerical control device also 
applies a lock start signal LOS to the address decoder 42 at the onset of 
a read or write operation, and a lock end signal LOE to the address 
decoder 43 at the end of the read or write operation. 
When information is neither being written into nor read from the bubble 
memory cassette 22, the flip-flop circuit 41 is in the reset state so that 
its Q output is low and Q output high. Since the base of the transistor TR 
will be at a low potential as a result, the transistor will be 
non-conductive and no current will flow into the magnet coil 34. Now 
assume that the operator initiates a read or write operation with respect 
to the loaded bubble memory cassette 22. The numerical control device NC 
responds by simultaneously selecting the address decoder 39 by an address 
signal delivered from the address bus ABUS, whereby the address decoder 39 
produces an output signal which opens both gates G1, G2 of the gate 
circuit 40. Then, when the lock start signal LOS is applied to the input 
of the decoder 42 from the data bus DBUS of the numerical control device 
NC, the decoder 42 produces an output signal which is passed by the open 
gate G1 to place the flip-flop 41 in the set state. This sends the Q 
output of the flip-flop 41 to the high level so that transistor TR is 
driven into conduction, thereby energizing the magnet coil 34. This 
prevents the bubble memory cassette 22 from being ejected from the adapter 
21, as described above in conjunction with FIG. 3. With the bubble memory 
cassette 22 in the locked state, either a numerical control program stored 
therein is read from the cassette and transferred to the random access 
memory RAM, or a numerical control program stored in the RAM is 
transferred from the RAM to the cassette 22 for storage. 
When the above-described read or write operation is completed, the address 
decoder 39 is again selected by a signal from the address bus ABUS of the 
numerical control device and again responds by opening the gates G1, G2 of 
the gate circuit 40. The numerical control device now delivers a lock end 
signal LOE from the data bus DBUS to the input of the decoder 43, the 
latter responding by producing an output signal which the open gate G2 
aplies to the flip-flop circuit 41 to place the flip-flop in the reset 
state. This sends the Q output of the flip-flop to the low level, cutting 
of the transistor TR and de-energizing the magnet coil 34. The bubble 
memory cassette 22 is thereby released from the locked state so that the 
cassette can be ejected at will. 
As many apparently widely different embodiments of the present invention 
can be made without departing from the spirit and scope thereof, it is to 
be understood that the invention is not limited to the specific 
embodiments thereof except as defined in the appended claims.