Technical Field

This invention relates to a printing apparatus, and more particularly, to a printing apparatus for use in a rotary endorsement printer.

Background Art

Endorsement printers constitute an essential part of many high-speed document processing systems, such as item processors and check sorters, for exam¬ ple. Such printers can imprint various information on the backs and fronts of checks, such as endorsement statements, bank name or other identification, date, etc. Document processing systems of this type are normally designed for a long effective life, such as one hundred million cycles or more, and it is impor¬ tant that the various elements of such systems be capable of long-term reliability with minimum down¬ time for repair.

Endorsement printers are generally either of the continuously operating type, in which the endorse¬ ment printing element is continuously rotating, or of the intermittent operating type, in which the endorse¬ ment printing element operates only when a document has been transported to the printing position.

Continuous operation has certain advantages in terms of minimizing acceleration and deceleration of the printing elements, so that some wear and tear on these elements attributable to starting and stop¬ ping is avoided. However, there are also disadvantag¬ es in this type of system. One of these is a tendency for this type of system to cause undesired ink mark¬ ings on the documents being processed, since the ink supply roller is in constant motion, and ink is con¬ tinuously being applied to the printing element. Another disadvantage is that selection of the location

of printing by the stamp on the document is difficult or impossible in the case of a continuously rotating system. Furthermore, the fact that the system is continuously operating does tend to increase certain types of wear.

Intermittent operation avoids the above disadvantages, but tends to subject the apparatus to shock loadings, from frequent starts and stops. Also, the intermittent operation tends to be noisier than continuous operation. Existing intermittent operation apparatus may use a clutch to give controlled initia¬ tion of the printing sequence for controlled location on the document, but may suffer from electromechanical reliability problems, due to the high accelerations and decelerations involved. Other alternatives in¬ clude the use of a stepping motor or a D.C. servo motor to rotate and control the endorsement printing element. This requires a large, costly motor, due to the force which must be supplied during the inking and printing cycles, as well as forces required for accel¬ eration and deceleration.

Disclosure of Invention

It is an object of the present invention to provide a printing apparatus in which the above drawbacks are alleviated.

Thus, according to the invention, there is provided a printing apparatus including printing means for printing data on a record medium, characterized by first driving means for driving said printing means in acceleration and deceleration modes; second driving means for driving said printing means in a substantially constant velocity mode; and transfer means for transferring the driving of the printing means from said first driving means to said second driving means when a desired velocity has been reached for causing printing on said record medium, and for

transferring the driving of said printing means from said second driving means to said first driving means for deceleration of the printing means as printing on the record medium is completed.

Brief Description of the Drawings

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which Fig. 1 is a plan view of a printer of the present invention, also showing associated drive mechanism, inking mechanism and document transport mechanism.

Fig. 2 is an elevation view of the mechanism of Fig. 1.

Fig. 3 is an end view of the mechanism of Fig. 1.

Fig. 4 is a perspective view of the printer drive mechanism.

Fig. 5 is a perspective view similar to Fig. 4, showing details of ink transfer roller drive means.

Figs. 6, 7, 8 and 9 are diagrammatic views of certain elements of the printer drive mechanism at different points in a cycle of printing operation.

Fig. 10 is a diagrammatic rear view showing the printer drive mechanism, one of the motors for driving said mechanism, and the electronic circuitry for controlling the operation of said motor.

Best Mode for Carrying Out the Invention

Referring now to the drawings, and particularly to Figs. 1-3 inclusive, a document 20, which may for example be a check, is carried by a document transport 22 to a position in which an en¬ dorsement or other indicia may be printed thereon by an endorsement stamp head 24. The document transport 22 comprises first and second walls 26 and 28 secured to a base 30, and defining a document path 32.

Rollers such as 33, 34, 36, 38, 40, project through apertures 41, 42, 44, 46, 48, in the wall 26 and cooperate with complementary rollers 49, 50, 52, 54, 56, which extend through apertures 57, 58, 60, 62, 64, to drive the document 20 from left to right, as viewed in Fig. 1. The drive rollers 33, 50, 36, 38, 40, are driven by a motor 68, which is preferably a constant speed, constantly operating motor, such as, for example, an AC induction motor, through various belt and pulley arrangements, as shown in Figs. 1 to 4 inclusive.

Pulleys 17 and 19 are fixed to a shaft 21 of the motor 68 and are driven by said motor. A belt 23 is driven by pulley 17 and in turn drives pulleys 25, 27, 29 and 31, to which drive roller 36 is coupled. Pulleys 27 and 29 are fixed to shafts 35 and 37, respectively, journaled in the machine framework. Also fixed to the shafts 35 and 37, respectively, are additional pulleys 39 and 43. The pulley 39 acts through a belt 45 and a pulley 47 to drive the feed roller 33 and also drives an additional drive roller (not shown). The pulley 43 acts through a belt 51 and pulleys 53 and 55 to drive the drive rollers 38 and 40 respectively. The pulley 19 on the shaft 21 acts through the belt 66 and idler pulley 59 to drive pulleys 70 and 61. Back-up roller 74 is coupled to pulley 70, and a further pulley 63 is coupled to pulley 61. A belt 65 on the pulley 63 drives a pulley 67 to which is coupled the drive roller 50.

As may best be seen in Figs. 1 and 4, the motor 68, acting through the belt 66, also drives a pulley 70 secured on a shaft 72. Also secured on the shaft 72 are a back-up roller 74 which cooperates with the stamp head 24 for printing on the document 20, and a friction gear or "tire" 76 which operatively engages at times with a driven cam member 78 of generally circular peripheral configuration, having a flattened sector portion 80.

As the document 20 proceeds along a path 32, its presence is sensed by a sensor 82 (Figs. 2, 4 and 10) which may be of any suitable design, such as an optical sensor, and which is located adjacent to an aperture 84 (Fig. 1) in the wall 26, so that it can detect the leading edge of a document 20 being trans¬ ported along the path 32. Rotational printing move¬ ment of the stamp head 24 does not commence until after the document 20 has been detected by the sensor 82. An electronic delay following detection of the document 20 by the sensor 82 is provided by a control¬ ler 130 (Fig. 10). This delay can be adjusted or programmed to vary the position at which the stamp appears on the document 20 which is being processed.

When the document 20 reaches the location of the stamp head 24, said stamp head, in a rotational printing movement, and acting in cooperation with the back-up roller 74, effects printing on the document 20 of indicia which are carried on the arcuate portion 86 of the stamp head 24. The stamp head 24 and the roller 74 coact through cut-away portions 88 and 90 in the walls 26 and 28 respectively.

As may be seen most clearly in Fig. 10, the stamp head 24 is fixed to a shaft 92 journaled in the supporting structure of the printing mechanism. Also fixed to the shaft 92 are a timing disk 94, a pulley 96, a gear 98 for driving an ink transfer roll 100, and the previously-mentioned driven member 78. The pulley 96 is driven through a belt 102 (Fig. 4) by a driving pulley 104 fixed to the shaft 106 of an inter¬ mittently operable motor 108 which may, for example, be a stepping motor.

The gear 98 on the shaft 92 cooperates with a gear 110 (Fig. 5) fixed to a shaft 112 on which is also fixed the transfer roller 100 which serves the function of transferring ink from an ink roll 114 mounted to roll freely on a shaft 116 to the stamp head 24.

The ink roll 114 is housed in a protective plastic shell 115 (Fig. 1). The shaft 116, in turn, is mounted on an arm 118 pivotally mounted on the base 30 and urged in a counterclockwise direction by a toggle spring 120 to cause the ink roll 114 to be pressed against the transfer roller 100, and to thus be rotated by the roller 100, which transmits ink from the roll 114 to the stamp head 24. The toggle spring 120 causes the ink roll 114 to be held in either an engaged position in which it is rotated by the trans¬ fer roller 100 and provides ink to the stamp 24, or in a disengaged position in which it is shown in Fig. 1, for maintenance and replacement purposes. A finger

119 at the end of the arm 118 opposite from the spring

120 engages a switch 121 which provides information to a controller 130 (Fig. 10) as to whether or not the ink roll 114 is in place in position to provide ink to the stamp 24. The total printing operation is under control of the controller 130, which includes a micro¬ processor 132 and other appropriate components, as will readily be apparent to one skilled in the art. The controller 130 communicates with a document pro¬ cessing computer host (not shown) via a bus 134, in order to receive a command as to whether a document 20 is to be printed upon. The controller 130 acts through a driver circuit 136 to operate the motor 108. After the document 20, in its movement along the path 32, has been detected by the sensor 82, a command to operate is transmitted to the step motor 108, which commences rotation of the stamp head 24. The tran¬ sient position of the stamp head 24 is monitored by the two-channel disk 94 which is fixed to the shaft 92. The disk 94 contains both an inner channel of slots 140 and an outer channel of slots 142, and is sensed by a sensor 138 electrically coupled to the controller 130.

Referring now to Figs. 6-9 inclusive, these show the relative orientations of the cam member 78, the tire 76, the stamp head 24, the back-up roll 74, the transfer roll 100, the timing disk 94 and the sensor 138 at various stages during a complete revolu¬ tion of the stamp head 24.

In Fig. 6, the stamp head 24 is shown in its "home" position. This is detected by the microproces¬ sor 132 in the controller 130 by the receiving of signals from the sensor 138 indicating that it has detected both a slot 140 in the inner channel and a slot 142 in the outer channel of the disk 94, which is unique to the "home" position. In this position, it can be seen that the cam member 78 makes no contact with the constantly rotating tire 76, and that the stamp head 24 is not in contact with either the trans¬ fer roll 100 or the back-up roll 74.

After a document 20 being transported along the path 32 is sensed by the sensor 82, a signal indicating this is transmitted to the controller 130, and causes a command to be passed to the driving circuit 136 to commence operation of the stepping motor 108. The stepping motor 108 then begins to drive the stamp head 24 at an accelerating rotational velocity in a direction which moves the arcuate printing surface 86 of the head 24 toward engagement with the transfer roll 100. Only slots 140 from the inner disk track or channel of the disk 94 feed pulses to the microprocessor 132, which uses these pulses in standard closed-loop acceleration processes, to cause accelerating movement of the stamp head 24 and associ¬ ated elements until these elements reach the respec¬ tive positions shown in Fig. 7, in which the last slot 140 of the inner channel has been sensed, and the sensor senses no slots in either channel. The step¬ ping motor 108, under command of the controller 130, ceases operation and thus ceases applying torque at this point.

Also at this point, the cam element 78 has been rotated sufficiently that the circular portion of its periphery has been brought into engagement with the circumference of the "tire" 76, and the speed of the shaft 92 and the various elements associated therewith, including the cam member 78, have been brought to a rotational speed essentially the same as that at which the shaft 72 and associated elements are driven by the motor 68. Frictional driving engagement between the cam member 78 and the "tire" 76, which is driven by the motor 68, now causes rotation of the stamp head 24 in a printing operation which rotates the indicia-bearing ink surface 86 to the position shown in Fig. 8, in which said surface 86 engages the document 20, said document passing between the head 24 and the back-up roll 74. The rotational speed of the head 24 is such as to provide a linear speed of the surface 86 which is substantially the same as the track speed of the document 20.

The motor 68 continues to drive the head 24 through the printing operation and until the various elements reach the respective positions shown in Fig. 9. At this point, the cam member 78 has rotated sufficiently that the flattened portion of its periph¬ ery is about to be positioned opposite the circumfer¬ ence of the tire 76, thus interrupting the engagement of these two elements, and terminating the driving of the head 24 by the motor 68. At the same time, the disk 94 has been rotated sufficiently that the end slot 142 of the outer channel is sensed by the sensor 138, which causes the controller 130, acting through the driver circuit 136, to initiate operation of the step motor 108. Pulses generated by sensing of the slots 142 are used in standard closed-loop decelera¬ tion processes to cause deceleration of the head 24 and to stop it at the "home" position shown in Fig. 6.

It may be noted that in the illustrated embodiment, the ratio of the pulleys 96 and 104 re¬ quires the motor 108 to rotate twice for one revolu¬ tion of the stamp head 24. This is done in order to reduce the load inertia seen by the motor 108.

One benefit of the design of the present invention is that it uses the greater, relatively low cost, power of the constant-speed motor 68, present in the printing apparatus and used for other purposes as well, to provide motive power for the stamp head 24 while it is in rolling engagement with the transfer roll 100 and the document 20. Since the motor 68 is also used to drive the rollers comprising the document transport means, the movement of the document 20 is synchronized with the movement of the stamp head 24 during the imprinting operation. Movement during this interval requires substantial power, and would also present shock loads to the motor 108, if it were used during this part of the cycle. In this system, the motor 108 may be of relatively smaller size, since it is needed only to provide accelerating and decelerat¬ ing torque. System power supply costs and driver circuitry, as well as a smaller motor, thus provide opportunities for economy.