Printhead compatible with various printers and ink-jet printer using the printhead

A printhead compatible with various printers, e.g. a printer having low print density or a printer having high print density, enables printing in the best capability of the printer. The printhead comprises: a determination circuit 24 which determines a type of a printer incorporating the printhead, and switches SW1 and SW2 which select a method of driving the printhead according to in the printer, on the basis of the determination result by the determination circuit 24. When the printhead is installed in the printer capable of printing at 360 dpi, four print dots printed at 720 dpi substantially express one dot printed at 360 dpi. Meanwhile, when the printhead is installed in the printer capable of printing at 720 dpi, one print dot expresses one dot printed at 720 dpi.

BACKGROUND OF THE INVENTION
 The present invention relates to a printhead and an ink-jet printer
 (recording apparatus) using the printhead, and more particularly to a
 printhead (recording head) compatible with various printers and an ink-jet
 printer utilizing the removable printhead.
 Printheads have conventionally been exchangeable in an ink-jet printer. The
 ink-jet printer where a plurality of printheads are exchangeable,
 comprises a determining terminal or a determining unit in the printhead to
 enable the apparatus to determine the type of the printhead, so that the
 apparatus can determine the type of the printhead which has just been
 installed.
 Currently, great interests have been brought to the ink-jet printing method
 since it provides various advantages, for instance, noise generated at the
 time of printing is so little that it can be disregarded; high-speed
 printing is possible; a regular sheet of paper can be utilized; particular
 processing such as fixing of printing material is unnecessary; and so on.
 More specifically, the ink-jet printing method disclosed in Japanese Patent
 Application Laid-Open No. 54-51837 and German Publication (DOLS:
 Deutschland Offenlegungsschrift) No. 2843064, has a different feature from
 those of other ink-jet printing methods in the way that it provides heat
 energy to ink liquid to generate driving force for ink discharge.
 Furthermore, according to the printing method disclosed in the
 above-mentioned patent publications, the liquid activated by heat energy
 changes its state due to rapid increase in volume. Driving force generated
 by the change in the state causes discharging of the liquid from an
 orifice provided at the end of a printhead, forming a discharging droplet,
 and the droplet adheres to a print medium to form a pixel, thereby
 executing printing.
 The printing method disclosed in DOLS No. 2843064 is not only effectively
 applied to so-called drop-on-demand printing, but also readily realizes
 printing performed by a full-line type printhead having multiple orifices
 integrated in high density, where the print width of the printhead is as
 large as the width of the print medium. Therefore, the printing method
 provides advantages in that an image having high resolution and high
 quality can be obtained at high speed.
 The printhead adopting aforementioned printing method is configured with:
 an orifice provided to discharge liquid, a nozzle connected to the orifice
 and including a liquid channel having a heating unit as a part of its
 structure to generate heat energy to act on the liquid and discharge a
 droplet, and a substrate integrating an electrothermal transducer (heater)
 serving as means for generating heat energy.
 Lately, such substrate of a printhead not only integrates a plurality of
 heaters, but also integrates drivers which drive each of the heaters,
 shift registers which can store image signals having the number of bits
 equal to the number of heaters to parallelly transfer these
 serially-inputted image signals to respective drivers, and a logical
 circuit such as a latch circuit or the like which temporarily stores data
 outputted by the shift registers.
 FIG. 14 is a block diagram showing configuration of a logical circuit of a
 printhead having 32 heaters (printing elements), which is capable of
 printing at the conventional density, 360 dpi.
 Referring to FIG. 14, reference numeral 400 denotes a substrate; 401,
 heaters (H1-H32); 402, power transistors; 403, a 32-bit latch circuit; and
 404, a 32-bit shift register. Reference numeral 415 denotes a sensor which
 monitors resistance values of the heaters 401 and temperature of the
 substrate 400, and also denotes a heater for keeping the substrate 400
 warm. A plurality of such sensors and heaters may be provided. Reference
 numerals 405 to 414-n respectively denote input/output pads. Reference
 numeral 405 denotes a clock input pad for inputting a clock signal (CLK)
 to drive the shift register 404; 406, an image data input pad for serially
 inputting image data (DATA); 407, a latch input pad for inputting a latch
 clock signal (LTCLK) in order to latch image data in the latch circuit
 403; 408, a driving signal input pad for inputting a heat pulse (HEAT) in
 order to externally control driving timing by turning on the power
 transistor 402 and sending an electric current to the heaters 401; 409, a
 driving power input pad for supplying driving power (3V-8V, generally 5V)
 for the logical circuit; 410, a GND terminal; 411, a heater's power input
 pad for supplying power to the heaters 401; and 412, a reset input pad for
 inputting a reset signal (RST) to initialize the latch 403 and shift
 register 404.
 In addition, reference numerals 413-1 to 413-8 denote
 block-selecting-signal input pads for inputting block-selecting signals
 (BLK1-BLK8) which select a block at the time of the time-divisional drive
 control where the 32 heaters 401 are divided into eight blocks to be
 driven. Reference numerals 414-1 to 414-n denote output pads of monitor
 signals and input pads of control signals for controlling driving of
 sensors and driving of heaters provided to maintain internal temperature
 of a printhead.
 Next, description will be provided on a driving sequence of a printhead
 having the above-described configuration. Herein, image data (DATA) is
 assumed to be binary data where one pixel is expressed by one bit.
 When the main unit of a printer, incorporating the printhead, serially
 outputs image data (DATA) in synchronization with a clock signal (CLK),
 the data is inputted by the shift register 404. The inputted image data
 (DATA) is temporarily stored in the latch circuit 403, which then outputs
 ON/OFF signal in correspondence with a value ("0" or "1") of the image
 data.
 Herein, when a block is selected by a block-selecting signal (BLK1-BLK8),
 if a heat pulse (HEAT) is inputted while an output of the latch circuit
 403 is "ON," the corresponding power transistor 402 is driven for the
 length of time the heat pulse (HEAT) is "ON." Accordingly, current is
 supplied to the corresponding heaters 401 to heat ink whereby discharging
 ink droplets.
 FIG. 15 is a timing chart showing the driving timing in a case where 32
 heaters (H1, H2, . . . H32) are provided, and are divided into eight
 blocks (each block having four heaters H1-H4, H5-H8, . . . , H29-H32) to
 be driven by time-divisional drive control by the block-selecting signals
 (BLK1-BLK8). The waveform illustrated in FIG. 15 only shows, among the
 signals transmitted from the printer' main unit, the block-selecting
 signals for time-divisional drive control and the heat pulse (HEAT) for
 deciding a length of time to drive the heater 401.
 When the output of the latch circuit 403 is "ON," all the heaters, being
 divided into blocks, are driven once in one print cycle at slightly
 different timings by the control signals. On account of such
 time-divisional drive control, the number of heaters to be driven
 simultaneously is reduced, the capacity of the power source is reduced,
 and noise generated at the time of driving is reduced.
 As the printer and printhead are further diversified and developed in the
 future to meet various needs, such as low price, capability to express a
 complicated image having high quality and high resolution and so on, it is
 necessary that various printers can use various types of printheads,
 instead of utilizing a dedicated printhead for each printer. To cope with
 the diversification of printheads, efforts have been made to standardize
 connecting portions among the printers and printheads. Nevertheless, the
 printer was merely able to distinguish the type of printhead that is being
 installed.
 Moreover, reflecting upon the recent tendency to prefer high-quality image
 printing, the main subject of development and manufacturing of the
 printhead is now turning into print density of 600/720 dpi from the
 conventional density 300/360 dpi. Therefore, the latest printhead requires
 new configuration for a substrate which is different from that of the
 aforementioned conventional printhead, in terms of arraying pitch of
 heaters (printing elements), drivers, logical circuits or the like.
 On the other hand, as long as printheads are used as consumables, a
 manufacturer must keep producing printheads having conventional print
 density which was produced and sold in the past, even if a printer
 incorporating the conventional printhead is no longer manufactured.
 Therefore, the types of printheads manufacturers must produce rapidly
 increase.
 The above-described tendency is quite inefficient in terms of production
 efficiency of printheads, resulting in increase in manufacturing cost. In
 addition, when a user purchases a printhead to replace an old printhead,
 the user tends to have difficulties determining which type of printhead to
 purchase.
 SUMMARY OF THE INVENTION
 The present invention has been made in consideration of the above
 situation, and has as its object to provide a printhead which can be used
 in various printers.
 According to this aspect of the present invention, the foregoing object is
 attained by providing a printhead for performing printing by discharging
 ink, comprising: determine means for determining a type of a printer
 incorporating the printhead; and select means for selecting a driving
 method according to the printer, on the basis of the determination result
 of the determine means.
 In accordance with the aspect of the present invention as described above,
 a type of a printer in which the printhead is installed is determined, and
 in accordance with the determination, a driving method according to the
 printer is selected.
 It is another object of the present invention to provide a printer which
 outputs signals to determination means of the above-described printhead.
 It is still another object of the present invention to provide a printhead
 cartridge comprising the above-described printhead and an ink tank which
 contains ink to be supplied to the printhead.
 It is still another object of the present invention to provide a method of
 printing performed by utilizing the above-described printhead.
 It is still another object of the present invention to provide a printhead
 which is compatible with the conventional-type printer having low print
 density, or with a new-type printer having a high print density, and which
 can perform printing in a print density conformable to a printer in which
 the printhead is installed; and a printer using the aforementioned
 printhead.
 According to this aspect of the present invention, the foregoing object is
 attained by providing a printhead compatible with plural types of printers
 whose print resolution are different, comprising: determine means for
 determining which type of the printers is used; and drive control means
 for controlling drivers, on the basis of the determination result of the
 determine means, such that printing is performed in accordance with a
 print resolution of the printer incorporating the printhead.
 More specifically, the printhead may contain N (positive integer) printing
 elements; N driving circuits for supplying power and driving the N
 printing elements; M (positive integer) latch circuits for latching N/M
 bits of image data; a shift register for storing the N/M bits of image
 data; L (positive integer) block-selecting-signal input terminals for
 inputting L block-selecting signals so as to divide the N printing
 elements into L blocks and drive the L blocks respectively; a
 print-density-selecting signal terminal for inputting a print-density
 selecting signal which selectively instructs printing in a first print
 density or in a second print density, which is M times as the first print
 density; and a control circuit for controlling latch operation for the M
 latch circuits in accordance with the print-density selecting signal,
 wherein each of the N driving circuits is driven for M times in one cycle
 of the L block-selecting signals.
 Further, according to the present invention, the foregoing object is
 attained by providing a printer using the aforementioned printhead,
 comprising: transmit means for transmitting the print-density selecting
 signal to the print-density-selecting signal terminal; transfer means for
 transferring image data in a unit of N/M bits to the shift register for M
 times; and latch control means for controlling the latch operation such
 that a latch signal is transferred each time the transfer means transfers
 the N/M bits of image data, and that transfer operation for M times
 realizes latching of the N bits of image data in the M latch circuits.
 In accordance with the aspect of the present invention as described above,
 for instance, in a case where a printhead is incorporated in a printer
 capable of printing in the first print density which is a low density, the
 same data is latched in M latch circuits. When L block-selecting signals
 are sequentially inputted, N driving circuits are driven for M times in
 the input cycle of the block-selecting signals to perform printing.
 In accordance with the foregoing printing, a plurality of print dots having
 the second print density, which is higher than the first print density,
 substantially express a single print dot having the first print density.
 Meanwhile, in a case where the printhead is incorporated in a printer
 capable of printing in the L second print density which is a high density,
 image data is transferred and inputted to the shift registers in the unit
 of N/M bits. A latch signal is inputted each time N/M-bit image data is
 inputted. Upon M times of transferring, the total of N bits of image data
 is latched in the M latch circuits.
 The invention is particularly advantageous since one printhead can be used
 in various printers e.g., from an inexpensive type having a simple
 function to an expensive high-performance type, or from an economical type
 to a high-quality and high-resolution type.
 Furthermore, an internal unit of the printhead distinguishes even the
 economical type of a printer and automatically selects a driving method of
 the apparatus. Therefore, the printhead can be used without providing the
 printer with any special interface.
 According to another aspect of the present invention, image data is
 transferred and inputted to the shift registers in the unit of N/M bits. A
 latch signal is inputted each time N/M bits of image data is inputted.
 Upon M times of transferring, N bits of image data in total is latched in
 M latch circuits. Therefore, a single printhead can be used for any one of
 a printer having low print density and a printer having high density.
 By virtue of the above, there is an advantage from a manufacturer's
 standpoint in that manufacturers does not need to increase types of
 printheads to be manufactured in order to conform with each print density.
 Accordingly, this contributes to manufacturing a large quantity of
 printheads of the same kind, resulting in reduction of manufacturing cost.
 In addition, there is an advantage from a user's point of view in that a
 user no longer has difficulties in selecting a type of printhead from many
 types of printheads.
 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
 Preferred embodiments of the present invention will be described in detail
 in accordance with the accompanying drawings.
 Brief Description of Apparatus Main Unit
 FIG. 1 is a perspective view showing the outer appearance of an ink-jet
 printer (ink-jet recording apparatus) IJRA as a typical embodiment of the
 present invention. It is assumed-herein that the printer IJRA is capable
 of printing at print density of 720 dpi. Referring to FIG. 1, a carriage
 HC engages with a spiral groove 5004 of a lead screw 5005, which rotates
 via driving force transmission gears 5009 to 5011 upon forward/reverse
 rotation of a driving motor 5013. The carriage HC has a pin (not shown),
 and is reciprocally scanned in the directions of arrows a and b while
 being supported by a guide rail 5003. An integrated ink-jet cartridge IJC,
 incorporating a printing head (ink-jet recording head) IJH and an ink tank
 IT, is mounted on the carriage HC. Reference numeral 5002 denotes a sheet
 pressing plate, which presses a paper sheet P against a platen 5000,
 ranging from one end to the other end of the scanning path of the carriage
 HC. Reference numerals 5007 and 5008 denote photocouplers which serve as a
 home position detector for recognizing the presence of a lever 5006 of the
 carriage in a corresponding region, and are used for switching, e.g., the
 rotating direction of the motor 5013. Reference numeral 5016 denotes a
 member for supporting a cap member 5022, which caps the front surface of
 the printing head IJH; and 5015, a suction device for sucking ink residue
 through the interior of the cap member. The suction device 5015 performs
 suction recovery of the printing head via an opening 5023 of the cap
 member 5015. Reference numeral 5017 denotes a cleaning blade; 5019, a
 member which allows the blade to be movable in the back-and-forth
 direction of the blade. These members are supported on a main unit support
 plate 5018. The shape of the blade is not limited to this, but a known
 cleaning blade can be used in this embodiment. Reference numeral 5021
 denotes a lever for initiating a suction operation in the suction recovery
 operation. The lever 5021 moves upon movement of a cam 5020, which engages
 with the carriage, and receives a driving force from the driving motor via
 a known transmission mechanism such as clutch switching.
 The capping, cleaning, and suction recovery operations are performed at
 their corresponding positions upon operation of the lead screw 5005 when
 the carriage reaches the home-position side region. However, the present
 invention is not limited to this arrangement as long as desired operations
 are performed at known timings.
 An ink-jet printer IJRA having the above-described configuration includes a
 print sheet automatic feeder (not shown) for automatically feeding a print
 sheet P.
 Note that the ink-jet cartridge IJC does not need to be the type that
 integrally incorporates the printhead IJH and ink tank IT, but may be a
 separable type.
 FIG. 2 is a perspective view showing the outer appearance of the ink-jet
 cartridge IJC where the printhead IJH and ink tank IT are separable.
 In the ink-jet cartridge IJC shown in FIG. 2, the printhead IJH having a
 plurality of discharge orifices 600 can be separated at the boundary line
 K from the ink tank IT containing ink to be supplied to the printhead IJH.
 The ink-jet cartridge IJC includes an electrical contact portion so that
 the ink-jet cartridge IJC receives electrical signals from the carriage HC
 when mounted on the carriage HC. The printhead IJH is driven by the
 received electrical signals. The ink tank IT includes a fibrous or porous
 ink absorbing member for maintaining ink.
 Description of Control Circuit
 Hereinafter, description will be provided on the control circuit for
 executing print control of the above-described printer. FIG. 3 is a block
 diagram showing the arrangement of a control circuit of the ink-jet
 printer IJRA. Referring to FIG. 3 showing the control circuit, reference
 numeral 1700 denotes an interface for inputting an image signal; 1701, an
 MPU; 1702, a ROM for storing a control program executed by the MPU 1701;
 and 1703, a DRAM for storing various data (aforementioned image signals,
 or image data supplied to the printing head IJH, and the like). Reference
 numeral 1704 denotes a gate array (G.A.) for performing supply control of
 image data to the printing head IJH. The gate array 1704 also performs
 data transfer control among the interface 1700, the MPU 1701, and the DRAM
 1703. Reference numeral 1710 denotes a carrier motor for conveying the
 printing head IJH; and 1709, a conveyance motor for conveying a printing
 sheet. Reference numeral 1705 denotes a head driver for driving the
 printhead IJH; and 1706 and 1707, motor drivers for driving the conveyance
 motor 1709 and the carrier motor 1710.
 The operation of the aforementioned control structure is now described.
 When an image signal is inputted to the interface 1700, the image signal
 is converted to print data by the gate array 1704 and MPU 1701
 intercommunicating with each other. As the motor drivers 1706 and 1707 are
 driven, the printhead IJH is driven in accordance with the print data
 transferred to the head driver 1705, thereby performing printing.
 Next, description will be provided on several embodiments commonly
 utilizing the printer having the above-described configuration.
 First Embodiment
 Detailed Description of Printhead (FIGS. 4 and 5)
 The arrangement of the printhead will now be described in detail. FIG. 4 is
 a partial view of a substrate for a driving circuit of a printhead
 incorporating a heater. The circuit's substrate is a multilayer substrate
 where a device in one layer is wired to a device in another layer via
 through hole provided at each layer. FIG. 5 is an enlarged view of a
 nozzle portion of the printhead.
 Although the configuration of a printhead may vary, in the following
 description, the printhead includes two types of heaters in one ink
 channel used for discharging ink, and includes 64 ink channels and 64
 ink-discharge nozzles.
 Among the two types of heaters shown in FIG. 4, the one that discharges a
 large ink droplet is a main heater R and the one that discharges a small
 ink droplet is a sub heater r. One end of a lead line 3 of the main heater
 R is connected to a heating power supply line 1 at the lower layer via a
 through hole 2. The other end of the lead line 3 is connected to a driver
 6. Meanwhile, one end of a lead line 4 of the sub heater r is also
 connected to the heating power supply line 1 at the lower layer via the
 same through hole 2, and the other end of the lead line 4 is connected to
 the driver 6.
 As shown in FIG. 5, the main heater R and sub heater r are arranged inside
 a nozzle 5. When the nozzle 5 is filled with ink and a predetermined
 voltage is applied to the main heater R and/or sub heater r, bubbles are
 generated. Because the size of the main heater R and that of the sub
 heater r are different, the sizes of the generated bubbles vary, thus the
 amount of ink discharged from the nozzle 5 can be changed. In other words,
 by utilizing three different driving ways: driving only the main heater R,
 or driving only the sub heater r, or driving both the main heater R and
 sub heater r, it is possible to discharge different sizes of ink droplets,
 a large ink droplet, a medium ink droplet and a small ink droplet. In
 addition, since the driver 6 includes two heat enable terminals, the main
 heater R and sub heater r can be independently driven. Therefore, the
 amount of discharging ink droplet and discharging speed can be set at a
 desired value. Similarly, even in a case where the main heater R and sub
 heater r are simultaneously driven to discharge a larger ink droplet,
 these heaters can be driven independently. Therefore, the degree of bubble
 formation can be controlled subtly, enabling to set the amount of
 discharging ink droplet and discharging speed at a desired value.
 Note that according to the printhead IJH of the present embodiment, the
 heating level or the contact area of the heater to ink are adjusted such
 that the amount of ink discharged by driving both the main heater R and
 the sub heater r is almost equal to the amount of ink discharged by a
 conventional printhead where each nozzle has one heater.
 Driving Circuit of Printhead (FIGS. 6-8)
 The arrangement of the driving circuit for the printhead will now be
 described in detail. FIG. 6 is a circuit diagram for driving the
 printhead; and FIG. 7, a timing chart of the operation executed in the
 circuit in FIG. 6.
 As shown in FIG. 6, a power supply unit VH is connected to the heating
 power supply line 1 which supplies power and applies voltage to a heater
 group 7 consisting of the main heaters R1 to R64 and sub heaters r1 to
 r64. The heater group 7 is connected to an output terminal of the driver 6
 which drives the total of 128 heaters, R and r, i.e., 64 main heaters R
 and 64 sub heaters r. The 128 gate circuits 8, each connected to an input
 terminal of the driver 6, respectively output a pulse to turn on the
 driver 6, thereby turning on the heater group 7.
 The printhead IJH according to the present embodiment operates differently
 depending on the following two cases:
 (1) the printhead is installed in a printer which performs printing by
 driving both or one of the 64 main heaters and/or 64 sub heaters; and
 (2) the printhead is installed in a printer which is designed to perform
 printing by driving only the 64 main heaters. The operation in each of the
 cases (1) and (2) will be described below.
 (1) The case where the IJH is installed in a printer which can control
 driving of both or one of the 64 main heaters and/or 64 sub heaters
 It is assumed herein that the printer incorporating the printhead IJH has a
 signal supply terminal in the carriage HC so that signals are supplied to
 a determination circuit to be described below. In this case, the printer
 operates to make the sufficient use of the function of the printhead IJH.
 The printer first resets serial data latched in the first 64-bit latch 11
 and second 64-bit latch 12, by transferring a reset signal (RESET) to a
 reset terminal 20. Then serial data (DATA) for the main heaters R1-R64,
 which is generated on the basis of image data and which corresponds to
 each nozzle, is inputted to a data input terminal 21 of the 64-bit shift
 register 10 in synchronization with a clock pulse (CLK) inputted to a
 clock terminal 22. As a result, data D1 is captured by the 64-bit shift
 register 10. The data D1 is then latched in the first latch 11 by a latch
 signal (LATCHL) inputted to a latch terminal 18. Similarly, serial data
 (DATA), for the sub heaters r1-r64, which corresponds to each nozzle is
 inputted to the data input terminal 21 of the 64-bit shift register 10 in
 synchronization with a clock pulse (CLK) inputted to the clock terminal
 22. As a result, data D2 is captured by the 64-bit shift register 10. The
 data D2 is then latched in the second latch 12 by a latch signal (LATCH2)
 inputted to a latch terminal 19.
 If all the heaters R and r are to be driven simultaneously, a large amount
 of electricity is required and it is not practical. Therefore, a block
 selecting circuit 9 divides the heater group 7 into a predetermined blocks
 B1-B8 to drive the heaters R and r by the time-divisional drive control.
 For this, the block selecting circuit 9 has block enable terminals 15, 16
 and 17 to select one of the blocks. As shown in FIG. 7, one of the
 block-selecting signals (B1-B8) is set at HIGH level in accordance with a
 combination of levels (HIGH/LOW) of the block enable signals (BLOCK ENB1,
 BLOCK ENB2, BLOCK ENB3), thereby selecting a block of the heaters R and r
 to be driven.
 A determination circuit 24 (FIG. 6) is provided to determine the type of
 the printer. For instance, in the case of the printer (1), a predetermined
 signal is sent from the printer via a determination terminal 23. An output
 of the determination circuit 24 is inputted to control-signal input
 terminals of switches SW1 and SW2. The switch SW1 connects a terminal c
 with either a terminal a or terminal b, in accordance with the output
 signal, from the determination circuit 24, which is inputted to the
 control-signal input terminal. As a result, if the terminal c is connected
 to the terminal b, a heat enable signal (HEAT ENB1), inputted to a heat
 enable terminal 13, drives the main heater R and sub heater r
 simultaneously. If the terminal c is connected to the terminal a, heat
 enable signals (HEAT ENB1 and HEAT ENB2), respectively inputted to heat
 enable terminals 13 and 14, drive the main heater R and sub heater r
 independently. The switch SW2 connects a terminal c' with either a
 terminal a' or a terminal b' in accordance with an output signal of the
 determination circuit 24, which is inputted to the control-signal input
 terminal. As a result, if the terminal c' is connected to the terminal b',
 a latch signal (LATCH1) is inputted to the latch terminal 18,
 simultaneously latching the data corresponding to the main heater R and
 sub heater r in the first 64-bit latch 11 and the second 64-bit latch 12.
 If the terminal c' is connected to the terminal a', latch signals (LATCH1
 AND LATCH2) are respectively inputted to the latch terminals 18 and 19,
 separately latching the data in the first 64-bit latch 11 and the second
 64-bit latch 12 from the 64-bit shift register 10.
 According to the present embodiment, when a determination signal (Det) at
 high level is inputted to the determination terminal 23, the determination
 circuit 24 outputs a signal respectively to the switches SW1 and SW2 to
 connect the terminal c to the terminal a, and the terminal c' to the
 terminal a'. As a result, the main heater R and sub heater r are driven
 independently by respective heat enable signals (HEAT ENB1 and HEAT ENB2)
 and respective latch signals (LATCH1 and LATCH2). Meanwhile, when a
 determination signal (Det) at low level is inputted, the determination
 circuit 24 outputs a signal respectively to the switches SW1 and SW2 to
 connect the terminal c to the terminal b, and the terminal c' to the
 terminal b'. As a result, the main heater R and sub heater r are driven
 simultaneously by the single heat enable signal (HEAT ENB1) and the single
 latch signal (LATCH1).
 Note that the printer incorporating the printhead IJH includes, in the
 carriage HC, the terminal which can provide the determination signal (Det)
 to the determination terminal 23. If the printhead IJH is mounted on a
 carriage which does not have such terminal, the determination terminal 23
 becomes electrically non-connected. In this case, the switches SW1 and SW2
 unconditionally connect the terminal c to terminal b and the terminal c'
 to terminal b'.
 Accordingly, in the above described driving circuit, the block selecting
 circuit 9 selects a block of heaters to be driven, and a predetermined
 driving waveform is inputted to the selected heat enable terminal 13
 and/or heat enable terminal 14 by the switch SW1, thereby making it
 possible to discharge a desired amount of ink droplet at a desired
 discharging speed from a desired nozzle.
 (2) The case where the IJH is installed in a printer which is designed to
 perform printing by driving only the 64 (main) heaters
 Herein, description is provided on a printer, such as those available
 conventionally, in which the printer incorporating the printhead IJH does
 not have the function to supply a determination signal (Det) to the
 determination circuit 24. In the case of such apparatus, even if the
 printhead IJH is mounted on the carriage HC, the determination terminal 23
 is electrically non-connected. Thus, the switches SW1 and SW2
 unconditionally connect the terminal c to terminal b and the terminal c'
 to terminal b'.
 Therefore, in this case, the control for the driving circuit of the
 printhead IJH substantially becomes equivalent to that for the driving
 circuit shown in FIG. 8. Referring to FIG. 8, the power supply unit VH is
 connected to the heating power supply line 1 which supplies power and
 applies voltage to a heater group 7' consisting of heaters R1 to R64. The
 heater group 7' is connected to an output terminal of a 64-bit driver 6'
 which drives 64 heaters R. The 64 gate circuits 8', each connected to an
 input terminal of the 64-bit driver 6', respectively output a pulse to
 turn on the driver 6', thereby turning on the heater group 7'. With
 relation to FIG. 8, those components that are identical to those of the
 circuit in FIG. 6 will be referred by the same reference numerals and
 description thereof will be omitted.
 The operation of the printhead IJH is now described by comparing FIG. 6 and
 FIG. 8. Depending on the connection of switches SW1 and SW2, the heat
 enable terminal 14 and the latch terminal 19 do not function; thus, only
 the heat enable signal (HEAT ENB1) inputted from the heat enable terminal
 13 and the latch signal (LATCH1) inputted from the latch input terminal 18
 drive the main heater R and sub heater r simultaneously to generate heat.
 In other words, by utilizing the driving circuit shown in FIG. 6, an ink
 droplet can be discharged in the condition identical to the condition
 where the driving circuit shown in FIG. 8 is used.
 According to the above-described embodiment, in a case where the printhead
 IJH is installed in a printer having the function to provide two types of
 heat enable signals, two types of latch signals, and a determination
 signal (Det) which is to be sent to the determination terminal 23, it is
 possible to adjust the amount of ink discharge by controlling the main
 heater and sub heater provided in each nozzle such that they are driven
 simultaneously or independently As a result, it is possible to perform
 printing in high tonality. Meanwhile, in a case where the printhead IJH is
 installed in a printer not having the function to provide a determination
 signal (Det), it is still possible to perform printing because a single
 heat enable signal can automatically set the main heater and sub heater to
 be driven simultaneously.
 As set forth above, when the printhead IJH is installed in a
 high-performance printer, the printhead utilizes the capability and
 function of the apparatus to its full capacity, and when the printhead IJH
 is installed in the conventional printer, the printhead operates to
 conform with the capability of the apparatus. In other words, the
 printhead IJH is compatible with both the conventional-type and new-type
 printers. Particularly, in the case the printhead is utilized in the
 conventional apparatus, the interior of the printhead is automatically set
 so that the signal interface is comformable to the apparatus, without any
 particular interfaces included in the apparatus.
 Second Embodiment
 It is assumed in the second embodiment that the ink-jet printer IJRA shown
 in FIG. 1 is able to perform printing at print density of 720 dpi with the
 printhead IJH whose arrangement is to be described later. To perform
 printing at the density of 720 dpi by driving the printhead IJH, the
 printer is arranged to supply an STA signal (to be described later) and
 two latch clock signals (LTCLK1 and LTCLK2) via the head driver 1705 (FIG.
 3). Furthermore, data transfer operation to the printhead IJH is
 controlled such that image data (odd-number dots) is first transferred to
 heaters of the odd-number nozzles, then the image data (even-number dots)
 is next transferred to heaters of the even-number nozzles.
 Internal Arrangement of Printhead IJH
 FIG. 9 is a perspective partially cut-out view showing the internal
 configuration of the printhead IJH.
 Referring to FIG. 9, reference numeral 100 denotes a substrate integrating
 the logical circuit to be described later; 600, a discharge orifice for
 discharging ink; 601, an ink liquid channel; 602, a common ink chamber
 connected to a plurality of the ink liquid channels for temporarily
 reserving ink; 603, an ink supply port for supplying ink from an ink tank
 (not shown); 604, a top board; 605, a wall member forming the ink liquid
 channel 601 coupled with the top board 604; 606, a heater; and 607, wiring
 for connecting the logical circuit with the heater 606.
 The logical circuit, heater 606 and wiring 607 are formed on the substrate
 100 by utilizing a semiconductor manufacturing process. The top board 604,
 to which the ink supply port 603 is attached, and the wall member 605 are
 mounted on the substrate, and the printhead IJH is constructed. Ink is
 provided from the ink supply port 603, reserved in the common ink chamber
 602 and supplied to each ink liquid channel 601. As the heater 606 is
 driven in this condition, the ink is discharged from the discharge orifice
 600.
 Arrangement of Logical Circuit of Printhead IJH
 FIG. 10 is a block diagram showing configuration of the logical circuit of
 the printhead IJH according to the present embodiment. In FIG. 10,
 components and signals identical to those in the conventional printhead
 described with reference to FIG. 14 will be referred by the same reference
 numerals and reference letters, and description thereof will be omitted.
 The printhead IJH described herein is installed in a printer capable of
 printing at 360 dpi and a printer capable of printing at 720 dpi, and the
 printhead IJH is capable of printing at either print density (360 dpi/720
 dpi). The amount of ink discharged by the printhead IJH for a single dot
 is about 20 ng. The printhead IJH has 64 heaters (H1 to H64), and print
 width thereof is equal to that of the conventional printhead having 32
 heaters, which has been described with reference to FIGS. 14 and 15.
 Meanwhile, in the case of the printhead described in FIGS. 14 and 15 which
 is capable of printing at 360 dpi, the amount of ink discharged for a
 single dot is about 80 ng.
 Referring to FIG. 10, reference numeral 101 denotes an OR circuit; 102,
 32-bit shift register (same as the conventional shift register 404 shown
 in FIG. 14); 103 and 104, 32-bit latch circuits; 105, a printer
 recognizing unit; 106, an STA-signal input pad; and 107 and 108,
 latch-clock input pads for respectively supplying latch clock signals
 (LTCLK1 and LTCLK2) to the latch circuits 103 and 104. Reference numerals
 109-1, 109-2, 109-3, . . . , 109-8 denote block-selecting-signal input
 pads which respectively input eight block-selecting signals (BLK1, BLK2, .
 . . , BLK8).
 Comparing the configuration shown in FIG. 10 with the configuration of the
 conventional printhead shown in FIG. 14, in the conventional printhead, a
 single block-selecting signal (BLK1-BLK8) selects heaters corresponding to
 one block in one print cycle, but in the present embodiment, the same
 block-selecting signal selects heaters corresponding to two blocks in one
 print cycle.
 More specifically, the block-selecting signal (BLK1) inputted from the
 block-selecting-signal input pad 109-1 selects heaters H1 to H8 and
 heaters H33 to H40. The block-selecting signal (BLK2) inputted from the
 block-selecting-signal input pad 109-2 selects heaters H9 to H16 and
 heaters H41 to H48. The block-selecting signal (BLK3) inputted from the
 block-selecting-signal input pad 109-3 selects heaters H17 to H24 and
 heaters H49 to H56. The block-selecting signal (BLK4) inputted from the
 block-selecting-signal input pad 109-4 selects heaters H25 to H32 and
 heaters H57 to H64. The block-selecting signal (BLK5) inputted from the
 block-selecting-signal input pad 109-5 selects heaters H33 to H40 and
 heaters Hi to H8. The block-selecting signal (BLK6) inputted from the
 block-selecting-signal input pad 109-6 selects heaters H41 to H48 and
 heaters H9 to H16. The block-selecting signal (BLK7) inputted from the
 block-selecting-signal input pad 109-7 selects heaters H49 to H56 and
 heaters H17 to H24. The block-selecting signal (BLK8) inputted from the
 block-selecting-signal input pad 109-8 selects heaters H57 to H64 and
 heaters H25 to H32.
 In other words, in a case where heaters are divided into blocks and driven
 by the time-divisional drive control, if a block-selecting signal is
 supplied sequentially from BLK1 to BLK8, each heater is driven twice in
 one print cycle of the printhead. By virtue of the above-described
 configuration of the logical circuit of the printhead, the number of times
 where the heaters are selected in one print cycle is increased; thus, one
 nozzle discharges ink twice in one print cycle.
 In addition, while output of each bit of the shift register 404 is
 connected to the latch circuit 403 of the conventional printhead in
 one-to-one basis (see FIG. 14), in the present embodiment, output of each
 bit of the shift register 102 is connected respectively to the latch
 circuits 103 and 104 (See FIG. 10). In other words, output-of each bit of
 the shift register 102 is connected to the latch circuits 103 and 104 in
 one-to-two basis. This is due to the fact that the number of heaters (64
 heaters) is twice as many as the number of the heaters of the conventional
 printhead described in FIGS. 14 and 15; therefore, in order to perform
 printing at density of 720 dpi, the capacity of a data memory for holding
 image data must be twice as large. As described above, even if the data
 capacity of the shift register has not been changed, the shift register is
 used plural times and latch operation is performed each time, thereby
 holding data twice as large as the conventional data in correspondence to
 the double number of heaters.
 Furthermore, as shown in FIG. 10, outputs of the latch circuit 103 are used
 to drive the heaters H1, H3, H5, . . . , H63, while outputs of the latch
 circuit 104 are used to drive the heaters H2, H4, H6, . . . , H64.
 The printer recognizing unit 105 will now be described in detail.
 FIG. 11 is a circuit diagram showing details of the printer recognizing
 unit 105.
 The printer recognizing unit 105 recognizes whether the printer, into which
 the printhead IJH is installed, operates with the printhead capable of
 printing at 360 dpi or with a printhead capable of printing at 720 dpi.
 It is assumed herein that the printer (hereinafter referred to as a
 "new-type printer"), which operates with the printhead capable of printing
 at 720 dpi, can output a "Low True" STA signal to the STA-signal input pad
 106 of the printer recognizing unit 105 and output a latch clock (LTCLK2)
 to the latch-clock input pad 108. On the other hand, the printer
 (hereinafter referred to as a "conventional-type printer"), which operates
 with the printhead capable of printing at 360 dpi, does not have the
 function to output the STA signal or latch clock (LTCLK2), nor does it
 include an interface for the STA-signal input pad or the latch-clock input
 pad 108. Thus, electrical connection to these pads are open. The other
 latch clock (LTCLK1) is inputted to the latch-clock input pad 107. Note
 that herein the latch clock (LTCLK1) is assumed to be the same signal as
 the conventional latch clock (LTCLK).
 Accordingly, in the case where the printhead IJH is installed in the
 conventional-type printer, an interface is established between the
 latch-clock input pad 107 and the printer, whereby supplying a latch clock
 (LTCLK). When the latch clock (LTCLK or LTCLK1) is supplied from the
 latch-clock input pad 107, image data is held by the latch circuit 103.
 Further, as apparent from the configuration shown in FIG. 11, the STA
 signal in this case is "HIGH". Therefore, the latch clock (LTCLK or
 LTCLK1) is also supplied to the latch circuit 104. As a result, the same
 data is latched in the latch circuits 103 and 104 by the one latch clock.
 Accordingly, as the same data is latched in the latch circuits 103 and
 104, pairs of adjacent heaters H1 and H2, H3 and H4, H5 and H6, . . . ,
 H63 and H64 are driven by the same data.
 Meanwhile, in the case where the printhead IJH is installed in the new-type
 printer, an interface is also established between the latch-clock input
 pad 108 and the printer. When the latch clock (LTCLK2) is supplied, the
 image data is held by the latch circuit 104.
 With the aforementioned assumption, according to the present embodiment, in
 a case where the printhead IJH is installed in the conventional-type
 printer, the STA-signal input pad 106 becomes open and is pulled up to
 automatically produce a "HIGH" STA signal so that the printhead IJH can
 recognize that the printer is the conventional type. Meanwhile, the
 latch-clock input pad 108 is connected to GND via a resistance.
 Accordingly, malfunction which might occur in the circuit utilizing a CMOS
 semiconductor at the time the connection of the latch-clock input pad 108
 is open, can be prevented.
 As a matter of course, the STA-signal input pad 106 may have a structure to
 be pulled down instead of pulled up, and the subsequent logic may be
 reversed.
 Next, printing operation will be described with reference to FIGS. 12 and
 13, in a case where the printhead IJH is installed in (1) the
 conventional-type printer, and a case where it is installed in (2) the
 new-type printer.
 (1) Printing operation performed in a case where the printhead is installed
 in the conventional-type printer
 In this case, the STA signal becomes "HIGH." Thus, as described above, the
 same data is held by the latch circuits 103 and 104 by a single latch
 clock (LTCLK or LTCLK1). As the block-selecting signals BLK1 to BLK8 are
 sequentially supplied in this condition, the 64 heaters of the printhead
 IJH are driven twice in one print cycle.
 In other words, all the 64 heaters have a chance to be driven at least once
 during the period of supplying the block-selecting signals BLK1 to BLK4
 (i.e. half of the one print cycle). Since a pair of adjacent heaters is
 driven by the same data, a pair of print dots are printed next to each
 other in the direction of a print width of the printhead, at the print
 density of 720 dpi.
 As the remaining block-selecting signals BLK5 to BLK8 are supplied
 successively, the 64 heaters are given another chance to be driven. At
 this stage, the same data as that used in the previous printing is still
 held in the latch circuits 103 and 104, thus printing operation is
 performed based on the same data. Since the carriage loading the printhead
 is moved in the scanning direction of the carriage in the printer to
 perform printing at density of 360 dpi, dots which are printed by ink
 discharge caused by the block-selecting signals BLK5 to BLK8 are formed
 next to those dots formed by the pervious block-selecting signals BLK1 to
 BLK4, in the carriage scanning direction.
 The printed dots formed in the above-described manner have the arrangement
 shown in FIG. 12B.
 The printed dots in FIG. 12B are compared with the printed dots in FIG. 12A
 formed by the conventional-type printer (print density 360 dpi)
 incorporating the conventional printhead which can print at 360 dpi (see
 FIGS. 14 and 15). In a print area where one dot is printed in FIG. 12A,
 four dots are printed in FIG. 12B by the same data. As a result,
 substantially the same printing is performed in FIGS. 12A and 12B.
 (2) Printing operation performed in a case where the printhead is installed
 in the new-type printer
 In this case, the STA signal is "LOW." Thus, as has been described above,
 32-bit data and the subsequent 32-bit data are respectively held by the
 latch circuits 103 and 104 in accordance with the two latch clocks (LTCLK1
 or LTCLK2).
 As shown in FIG. 13, among 64 bits of image data corresponding to the print
 width of the printhead IJH, the printer first transmits image data having
 odd-number bits (b1, b3, . . . , b63) to the 32-bit shift register 102 of
 the printhead IJH, and transmits the latch clock (LTCLK1) to latch the
 odd-number data in the latch circuit 103. The printer then transmits the
 image data having even-number bits (b2, b4, . . . , b64) to the 32-bit
 shift register 103 of the printhead IJH, and supplies the latch clock
 (LTCLK2) to latch the even-number data in the latch circuit 104. As a
 result, 64-bit data is stored in the latch circuits 103 and 104.
 Next, as the printer sequentially transmits the block-selecting signals
 (BLK1 to BLK4), heaters corresponding to the odd-number bit data which has
 been latched are driven and printing is performed. As described above, the
 block-selecting signals (BLK1 to BLK4) provide each heater with the chance
 to be driven once, and heaters corresponding to "ON" image data are
 driven. The printer then transmits a reset signal (RST) to the printhead
 IJH, resetting the 32-bit shift is register 102, and latch circuits 103
 and 104, then the same operation is repeated.
 The dots printed in the foregoing manner are shown in FIG. 12C.
 As set forth above, when printing is performed at print density of 720 dpi,
 the 32-bit shift register 102 is utilized twice, so that the image data is
 held in the unit of 32 bits respectively by the latches 103 and 104.
 Accordingly, printing in high density is realized.
 According to the above-described embodiment, in the case where the
 printhead IJH capable of printing at print density of 720 dpi is installed
 in the conventional-type printer (360 dpi), print data transmitted from
 the printer is used twice in the print-width direction of the printhead,
 and twice in the moving direction of the printhead, so that four print
 dots having print density of 720 dpi substantially forms one print dot
 having print density of 360 dpi. Meanwhile, in the case where the
 printhead IJH is installed in the new-type printer (720 dpi), the shift
 register is used twice to latch image data having the capacity twice as
 large as that of the shift register, thereby realizing printing in high
 density.
 Although the present embodiment describes the printhead having print
 density of 720 dpi and the printer capable of printing at 720 dpi as a new
 type, and the printhead having print density of 360 dpi and a printer
 capable of printing at 360 dpi as the conventional type, the present
 invention is not limited to this. Print density other than those described
 above, e.g. 300 dpi, may be the case for the conventional type, and e.g.
 600 dpi, may be the case for the new type. In addition, the number of
 heaters incorporated in the printhead is not limited to the
 above-described embodiment. In other words, the printer may have any
 configuration so long as heaters in a printhead is driven plural times in
 one print cycle of the printhead, and printing operation is executed by
 utilizing the same data for plural times.
 In the above description, the ratio of ink discharge amount per one nozzle,
 between the printhead IJH and the printhead shown in FIGS. 14 and 15 which
 is used as a typical conventional example, is 1:4. However, the ratio may
 vary. Taking image quality and high-density printing into consideration,
 it is empirically known that the ink discharge amount per one nozzle needs
 to be less than half the amount of ink discharge per dot of the
 conventional printhead; otherwise, the capability of printing in high
 density would be worthless because of the sizes of dots and the like.
 Furthermore, the above description has been made, utilizing the logical
 circuit incorporated along with the heaters in the substrate of the
 printhead. However, an IC may be provided in the printhead separately from
 the substrate integrating the heaters. However, since this must be
 manufactured as separate parts, the type integrated with the heaters is
 preferable for the purpose of cost reduction.
 Moreover, the above embodiments describe the case where the substrate of
 the printhead is employed in the printhead adopting ink-jet printing
 method. However the present invention is not limited to this, and may be
 applied to other printing methods, e.g. a substrate for a thermal head
 which performs printing by thermal printing method.
 Each of the embodiments described above has exemplified a printer, which
 comprises means (e.g., an electrothermal transducer, laser beam generator,
 and the like) for generating heat energy as energy utilized upon execution
 of ink discharge, and causes a change in state of an ink by the heat
 energy, among the ink-jet printers. According to this ink-jet printer and
 printing method, a high-density, high-precision printing operation can be
 attained.
 As the typical arrangement and principle of the ink-jet printing system,
 one practiced by use of the basic principle disclosed in, for example,
 U.S. Pat. Nos. 4,723,129 and 4,740,796 is preferable. The above system is
 applicable to either one of so-called an on-demand type and a continuous
 type. Particularly, in the case of the on-demand type, the system is
 effective because, by applying at least one driving signal, which
 corresponds to printing information and gives a rapid temperature rise
 exceeding film boiling, to each of electrothermal transducers arranged in
 correspondence with a sheet or liquid channels holding a liquid (ink),
 heat energy is generated by the electrothermal transducer to effect film
 boiling on the heat acting surface of the printhead, and consequently, a
 bubble can be formed in the liquid (ink) in one-to-one correspondence with
 the driving signal. By discharging the liquid (ink) through a discharge
 opening by growth and shrinkage of the bubble, at least one droplet is
 formed. If the driving signal is applied as a pulse signal, the growth and
 shrinkage of the bubble can be attained instantly-and adequately to
 achieve discharge of the liquid (ink) with the particularly high response
 characteristics.
 As the pulse driving signal, signals disclosed in U.S. Pat. Nos. 4,463,359
 and 4,345,262 are suitable. Note that further excellent printing can be
 performed by using the conditions described in U.S. Pat. No. 4,313,124 of
 the invention which relates to the temperature rise rate of the heat
 acting surface.
 As an arrangement of the printhead, in addition to the arrangement as a
 combination of discharge nozzles, liquid channels, and electrothermal
 transducers (linear liquid channels or right angle liquid channels) as
 disclosed in the above specifications, the arrangement using U.S. Pat.
 Nos. 4,558,333 and 4,459,600, which disclose the arrangement having a heat
 acting portion arranged in a flexed region is also included in the present
 invention.
 Furthermore, as a full line type printhead having a length corresponding to
 the width of a maximum printing medium which can be printed by the
 printer, either the arrangement which satisfies the full-line length by
 combining a plurality of printheads as disclosed in the above
 specification or the arrangement as a single printhead obtained by forming
 printheads integrally can be used.
 In addition, not only an exchangeable chip type printhead, as described in
 the above embodiment, which can be electrically connected to the apparatus
 main unit and can receive an ink from the apparatus main unit upon being
 mounted on the apparatus main unit but also a cartridge type printhead in
 which an ink tank is integrally arranged on the printhead itself can be
 applicable to the present invention.
 It is preferable to add recovery means for the printhead, preliminary
 auxiliary means, and the like provided as an arrangement of the printer of
 the present invention since the printing operation can be further
 stabilized. Examples of such means include, for the printhead, capping
 means, cleaning means, pressurization or suction means, and preliminary
 heating means using electrothermal transducers, another heating element,
 or a combination thereof. It is also effective for stable printing to
 provide a preliminary discharge mode which performs discharge
 independently of printing.
 Furthermore, as a printing mode of the printer, not only a printing mode
 using only a primary color such as black or the like, but also at least
 one of a multi-color mode using a plurality of different colors or a
 full-color mode achieved by color mixing can be implemented in the printer
 either by using an integrated printhead or by combining a plurality of
 printheads.
 Moreover, in each of the above-mentioned embodiments of the present
 invention, it is assumed that the ink is a liquid. Alternatively, the
 present invention may employ an ink which is solid at room temperature or
 less and softens or liquefies at room temperature, or an ink which
 liquefies upon application of a use printing signal, since it is a general
 practice to perform temperature control of the ink itself within a range
 from 30.degree. C. to 70.degree. C. in the ink-jet system, so that the ink
 viscosity can fall within a stable discharge range.
 In addition, in order to prevent a temperature rise caused by heat energy
 by positively utilizing it as energy for causing a change in state of the
 ink from a solid state to a liquid state, or to prevent evaporation of the
 ink, an ink which is solid in a non-use state and liquefies upon heating
 may be used. In any case, an ink which liquefies upon application of heat
 energy according to a printing signal and is discharged in a liquid state,
 an ink which begins to solidify when it reaches a printing medium, or the
 like, is applicable to the present invention. In the present invention,
 the above-mentioned film boiling system is most effective for the
 above-mentioned inks.
 In addition, the ink-jet printer of the present invention may be used in
 the form of a copying machine combined with a reader, and the like, or a
 facsimile apparatus having a transmission/reception function in addition
 to an image output terminal of an information processing equipment such as
 a computer.
 The present invention can be applied to a system constituted by a plurality
 of devices (e.g., host computer, interface, reader, printer) or to an
 apparatus comprising a single device (e.g., copy machine, facsimile).
 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.