Automatic chain identification method and apparatus
United States Patent H Bovett et al.  
 [45] Apr. 29, 1975 AUTOMATIC CHAIN IDENTIFICATION METHOD AND APPARATUS [73] Assignee: Burroughs Corporation. Detroit.  
 Mich.  
  22 Filed: Dec.26. I973 21 Appl. No.: 427.417  
  OTHER PUBLICATIONS IBM Technical Disclosure Bulletin. Vol. IS. No. to,  
 March I973. Gilbreth et al.. pp. 3113-3] [4.  
 Primary Examiner-Edgar S. Burr Asxistum blruminer-Edward M. Coven Attorney. Agent. or F irmAlhin H. Gess; Nathan Cass: Kevin R. Peterson [57] ABSTRACT Chain printers presently in the art are constructed to permit replacement or changing of the type carriers to facilitate the use of a variety of character sets or fonts. In order to handle a plurality of type slug carriers of different fonts. a translator must be provided for each font set. In order to indicate that the translator being used matches the font set of the type carrier placed on the printer. several teeth on the type carrier are filed down. The filed teeth are later sensed as an identification code unique to that type carrier. This code is stored in a register in the printer controller to be compared with a code in another register that identifies the translator being used.  
 10 Claims. 3 Drawing Figures MENTEB Z E S 3. 880, 075  
 sum 1 OF 2 BCDEFGH WWI/72? $1 jay w 2 17 WNW era/m2 m/rwr 0 0 0 0 AUTOMATIC CHAIN IDENTIFICATION METHOD AND APPARATUS BACKGROUND OF THE INVENTION The present invention relates generally to improvements in chain printers and more particularly pertains to the type of chain printers that are able to interchangeably utilize a variety of different font set type carriers. Examples of such printers can be found in patents having U.S. Pat. Nos. 3.699.884 and 3.629.861.  
  When a variety of interchangeable font set type carriers are available for use on the same printer. a broblem arises in insuring that the translate table. utilized for converting the character code signals into type carrier position signals. matches the particular font set type carrier that has been placed in the printer.  
 SUMMARY OF THE INVENTION An object of this invention is to prevent a chain printer from operating with a type carrier having a character or font set that does not correspond with the translator being used.  
  Another object of this invention is to compare the identification code generated by the type carrier placed in the chain printer with the code identifying the trans- BRIEF DESCRIPTION OF THE DRAWINGS Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered inconjunction with the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof and wherein:  
  FIG. 1 shows a perspective view of drive wheels and a type carrier that is common to a chain printer.  
  FIG. 2 illustrates in block and logic diagram form an embodiment of the circuitry associated with the present invention.  
  FIG. 3 is a pulse diagram illustrating the signals present at various points of the circuitry .of FIG. 2 during its operation.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates the typical arrangement in a chain printer of a type carrier l5-and driving wheels Il.and 13. The type carrier. or belt 15, has mounted thereon a plurality of type slugs which carry the font set 17 illustrated as the blocked alphabet A, B, C, D etc. The type slugs are backed with teeth 19 that engage the driving wheels I] and 13 to be driven in a non-slipping manner.  
  The font set of a particular type carrier may be identified by filing flat a certain minimal combination of these teeth 19. For example, by filing down three teeth 21. 23 and 25. a certain six-bit identification code may be produced. This provides for 2&#34; unique identification codes. The first flattened tooth 2!. assuming the type carrier is moving in a counter-clockwise direction. represents a synchronizing pulse. The six teeth that follow that synchronizing pulse represent the six digit type carrier identification code. This code is generated by a reluctance-type sensing device 27 every time that a flattened tooth. like 23 for example. passes the reluctance sensor 27. Reluctance sensors are considered well known in the art and will not be further discussed herein. Every time a flattened tooth passes the sensor. a pulse is generated on line 29 which delivers that pulse to the printer control 31. The printer control interfaces with a computer system over a communication link 33. Any well known printer control utilized for chain printers may be utilized for printer control 3!. For example. the US. Pat. Nos. 3.699.884 and 3.629.861 illustrate one type of printer control that may be used.  
  FIG. 2 illustrates an example of structure to practice the present invention. This logic circuitry 35 is made up ofa pair of AND gates 37.. 39; a D-type flip-flop 41 that receives the output of AND gate 39; a one-shot multivibrator 43 that receives the output of the flip-flop 41; a clock source triggered by the multivibrator 43 for clocking data from AND gate 37 into a serial-input parallel-output register 47 and a parallel input. paralleloutput register 49; and a comparator 51 for receiving the outputs of the two registers 47 and 49 and generating a signal to indicate a match. or mismatch.  
  The operation of the circuitry of FIG. 2 will now be explained in connection with the pulse trains of FIG. 3. The parallel-input. parallel-output register 49 which. for example. may be a buffer register manufactured by the Signetics Corporation. and listed in their I972 catalogue on page 3-16 as Buffer Register No. 8202. receives the binary code identifying the translate table being used. This buffer register may be loaded with. for example. a six-bit binary code from the computer system. which contains the translate table in memory. over a communication link 33, or it may be manually inserted. either method being well known in the art and not comprising any part of this invention. Prior to the initiation of a print cycle, and during the initializing stage. then. the buffer register 49 is loaded with a particular binary code. For purposes of example. it shall be assumed that the binary code loaded into the buffer register 49 is OIOOIO, as shown in FIG. 3.  
  Upon a particular type carrier 15 (FIG. I being placed on the chain printer. prior to a print cycle. the type carrier is rotated several full revolutions so that the reluctance pickup 27 can sense the flattened teeth on the carrier. The reluctance pickup 27 senses the flattened teeth and generates a pulse on line 29 which is connected to the appropriate circuitry in the printer control. The appropriate circuitry 35 in the printer control receives these pulses at point A which are illustrated in FIG. 3 as pulses 73, and 77. These are the pulses generated for the specific example of flattened teeth in F 1G. 1. Obviously. many other combinations of flat teeth might be used. The example chosen represents a six-bit identifying code.  
  Prior to the reception of any pulses by the logic circuit 35 in the printer control 31, the signal output of the one-shot multivibrator 43 in the logic circuit 35, which is illustrated at B of FIG. 3, is low. causing an enabling input to supplied to AND gate 39. This same signal level is also supplied to AND gate 37 as an inhibiting signal. At the time of occurrence. of the first pulse 73 sensed by the pickup 27. AND gate 39 generates a pulse output on line 67 that is supplied to the clock input of D-typc flip-flop 4l causing the 0 output of the flip-flop to send a signal on line 69 to the one-shot multivibrator 43, thereby initiating it. It may be assumed. for purposes of example. that the multivibrator is of the type manufactured by the Signetics Corporation and described in their 1972 parts catalogue on page Z-l l2 as Monostablc Multivibrator No. N74l2l.  
  Upon being initiated. the output of the multivibrator 43 goes high thereby inhibiting AND gate 39 and enabling AND gate 37. in addition. this high signal level is supplied over line (ii to a clock source 45 causing the clock source to provide clocking signals. over line 63. to a modulo counter 46 and a register 47 and. over line 65. to another register 49.  
  The clock source 45 may be the printer control system clock which is tapped by the signal on line 6i or a timer. such as produced by the Signetics Corporation and described in their I972 catalogue on page 6-4) as Timer No. 555. that is synchronized to the printer control clock.  
  These clock signals. illustrated at D in FIG. 3. cause the data pulses. appearing at the output of AND gate 37. on line 71 to be clocked into the type carrier identification register 47. Register 47 may be of the type manufactured by the Signetics Corporation and described in their 1972 catalogue on page 3-78 Serial input. Parallel-output Shift Register No. 78273. Thus for example of flattened teeth illustrated in FIG. 1. the pulses 75 and 77, as well as the lack of pulses therebetween. occuring after the initial synchronizing pulse 73.  
 within the window generated by the multivibrator 43 causes the contents of register 47 to be 010010. Any pulses appearing on line 71 after the time-out of the one-shot multivibrator 43 at 8| will not be clocked into the type carrier identification register 47.  
  Upon the last bit of the six bit code being clocked into the register 47. the modulo counter 46, which may. for example. be a divide by six modulo counter such as manufactured by the Signetics Corporation and described in their 1971 TTL family catalogue on page lOl as Divide by Six Counter No. S5492. would. upon the occurrence of the sixth clock pulse 83 on line 63 cause a pulse to be generated and supplied to a comparator 51 by way of line 64.  
  At this time the six-bit binary code identifying the type carrier is completely loaded in the type carrier identification register 47. Buffer register 49. and type carrier identification register 47 have their contents clocked out to comparator Si by the last clock pulse 83.  
  The comparator 51 may be a pre-packaged computer circuit manufactured by the Fairchild Corporation and listed in their June 1972 catalogue on page 8-l24 as Comparator No. 9324. The output of the modulo counter 47 on line 64 would be connected to the enable input of the comparator. Only the output of the comparator would be utilized. Thus, in case of a mismatch between any of the like bits being compared. out of the contents of registers 47 and 49, it would be indicated as a signed level on line 53 of the comparator 51.  
  This signal may be supplied to the computer system (not shown) to inhibit the print cycle or may simply be supplied to a display device (not shown) to warn an operator that a type carrier having an incorrect font set has been loaded onto the chain printer.  
  What has been described is a method and particular apparatus for preventing a type carrier to be utilized in a chain printer whenever its particular translate table is not loaded in the computer system. Obviously many modifications and variations of the invention are possible in light of the above teachings. It is therefor to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.  
 What is claimed is:  
  l. in a chain printer wherein the type carrier has a font set thereon and utilizes a plurality of teeth for engaging driving mens. apparatus for generating a unique binary code identifying the font set on the carrier comprising:  
 a predetermined plurality of flattened teeth located on said type carrier so as to be representative of said unique binary code;  
 sensing means adjacent said type carrier for sensing the flattened teeth when said type carrier is being driven; and  
 means responsive to said sensing means for generating a binary code representative of the sensed flattened teeth.  
 2. The apparatus of claim I further comprising:  
 means for storing the binary code representative of the sensed flattened teeth;  
 means for storing a standard binary code; and  
 means for comparing the binary codes stored in said storing means.  
  3. The apparatus of claim 2 wherein said storing means for storing a binary code representative of the sensed flattened teeth comprise a serial-input. paralleloutput shift register.  
  4. In a chain printer wherein the type carrier has a font set thereon and utilizes a plurality of teeth for engaging driving means. a method for generating a unique binary code identifying the font set on the type carrier comprising:  
 flattening a plurality of teeth on said carrier in a preselected order representative of said unique binary code;  
 sensing the flattened teeth when said type carrier is driven; and  
 generating a binary code representative of the sensed flattened teeth.  
 5. The method of claim 4 further comprising:  
 storing the binary code representative of the sensed flattened teeth;  
 storing a standard binary code; and  
 comparing the stored binary codes.  
  6. In a chain printer wherein the type carrier has a font set thereon and utilizes a plurality of teeth for engaging driving means, one of said teeth being physically modified and sensed by a detection means for generating a synchronizing pulse, apparatus for generating a unique binary code identifying the font set on the carrier. comprising:  
 an additional plurality of physically modified teeth located on said type carrier displaced from the physically modified tooth for representing said binary code. said additional plurality of physically modified teeth being sensed by said detection means; and  
 means responsive to said detection means for generating the binary code represented by said representing means.  
 7. The apparatus of claim 6 further comprising:  
 means for storing the generated binary code:  
 means for storing a standard binary code: and  
 means for comparing the binary code stored in said storing means.  
  8. The apparatus of claim 7 wherein said physically modified teeth are flattened. and wherein said storing means for storing the binary code generated by said detection responsive means comprises a seriaLinput. parallel-output shift register.  
  9. In a chain printer wherein the type carrier has a font set thereon and utilizes a plurality of teeth for engaging dri ing means. a method for generating a unique binary code identifying the font set on the type carrier.