GB2290258A - A postage meter - Google Patents

Abstract

The meter comprises a rotatable print drum (10), an imprinting die (20) (see Fig. 2 not shown) being rotatable secured within the drum (10), a controlled drive for selectively displacing the die (20) by a discrete angular rotation, and means, e.g. an encoder disc (16) and optosensor (18) for detecting the operational position of the drive or the die (20). <IMAGE>

Description

A Postage Neter This invention relates to a postage meter. In particular, the invention relates to a postage meter having a print drum capable of printing inter alia a slogan or a like imprint on a mailpiece. Such slogans, etc. generally bear information that is of use to the postal authorities such as information identifying whether the mailpiece is being sent by first or second class mail. In some countries the printing of such information is a mandatory requirement made by the postal authorities.

The invention is also potentially of benefit in relation to the printing of optional slogans carrying e.g., advertising messages, company logos and similar matter of a promotional nature. Nonetheless, the primary use of the invention is concerned with the printing of mandatory slogans.

It is desirable for users of postage meters to change the slogans printed on their mailpieces from time to time. For instance, it may be required to mark mail sent by one class with a first slogan and mail sent by another class with a second slogan. In some territories, it is required that certain kinds of mail are identified by the absence of an officially approved slogan. There may also be a requirement for a further slogan type, such as one identifying that the mailpiece is an air mail item.

Hitherto, one method of printing of slogans and like imprints on mailpieces has been by means of a reversible, removable imprinting die known as a slogan block. An example of a slogan block is shown in EP A-0217576. In this document, there is disclosed a postage meter print drum having a longitudinal recess formed in the outer surface thereof.

The recess is open-ended at one end of the print drum, and is shaped to dovetail with a removable slogan block that may be slid laterally into the recess. A spring loaded detent retains the slogan block in position in the recess. The slogan block is generally symmetrical about a horizontal, transverse plane, so that it may be inserted with one of two facets presented on the exterior of the print drum for printing onto mailpieces. A user of the postage meter may alter the slogan, message or logo printed by the slogan block by removing the slogan block, inverting it and re-inserting it into the recess.

While this arrangement has proved to be of considerable utility, the slogan changing procedure is entirely manual and therefore too slow for some postage meter users. Moreover, since the recess and the slogan block have to engage one another to ensure that the slogan block is correctly located, the number of facets of the slogan block is generally limited to two since there is a need for projections and/or recesses to be formed extending longitudinally along edges of the slogan block that could otherwise usefully be occupied by printing facets.

Accordingly, effort has been directed at improving the changing of the slogan to be printed by the slogan block. To this end, it is known to use a four-faceted slogan block that is mounted within a postage meter print drum on a rotatable shaft.

The shaft protrudes beyond the end wall of the drum and terminates in an actuating member shaped like a Maltese Cross. The actuating member is selectively engageable by hand to index the slogan block and present a selected facet for printing on the mailpiece. The Maltese Cross is connected via a short gear train to the mounting shaft of the slogan block, so that a user of the meter may change the slogan to be printed.

This arrangement has simplified the operations necessary to change the slogan to be printed, but suffers from the disadvantage that it is necessary to open the postage meter cover before the slogan can be changed. Moreover, there is a disadvantage in that the choice of slogan to be printed is made by the user of the postage meter. If the user fails to select the correct slogan for the class of mailpiece being franked, there is a risk that the franking of the mailpiece would be deemed invalid by the postal authorities. At best, this situation causes waste in the user's office. It may alternatively lead to nondelivery of mailpieces that the user believed had been correctly franked.

Thus, there is a need for an improved apparatus whereby the selection and printing of mailpiece slogans may be made more reliable.

According to the invention, there is provided a postage meter comprising a rotatable print drum; an imprinting die rotatably secured in the print drum such that a portion of the imprinting die is presentable for printing on a mailpiece on operation of the print drum; a drive means for selectively causing displacement of the imprinting die by a discrete angular rotation, the imprinting die having a plurality of facets spaced one from another by an angular amount corresponding to said discrete angular rotation; control means for controlling operation of the drive means; and position detecting means for detecting the operational position of the drive means or the imprinting die, the position detecting means being operatively connected to the control means, whereby the imprinting die may selectively be indexed to present different facets for printing on mailpieces.

Thus, there is provided an automated mechanism whereby the operative facet of, e.g., a slogan block may readily be changed. The drive means comprises in preferred embodiments a drive train including a drive gear adapted to transmit drive from, e.g., a motor output shaft of the postage meter and disposed substantially externally of the print drum; and a transfer gear in driving relation with the imprinting die and rotatable with the print drum. The drive gear and the transfer gear are preferably meshingly engageable when the print drum occupies its home position and the teeth of one of the gears are spaced from one another in at least part of the circumference of said gear to permit disengagement of the drive and transfer gears on operation of the print drum.The apparatus of the invention may advantageously be operatively connected to the postage meter control means (if present) so that a correct facet of the imprinting die is presented for printing, in dependence on the postage meter settings.

In particularly preferred embodiments of the invention, the drive gear and/or the transfer gear is constituted as a star wheel. This provides a reliable mechanism without the need to eliminate backlash from the drive train.

Conveniently, the position detecting means includes an encoder means mounted on a shaft drivingly engaged with or carrying the drive gear; and sensor means, e.g. an optosensor, for detecting the setting of the encoder means.

The encoder means may optionally include an encoder disc mounted for rotation with the drive shaft, the drive means being such that the encoder disc completes 180 of rotation for each 360" rotation of the imprinting die. The encoder disc preferably includes encoding indicia, e.g. apertures, in a pattern repeated every 1800 about the encoder disc; and the indicia advantageously include datum indicia for providing absolute position sensing of the encoder disc.

Preferably, the postage meter includes lock means operative during operation of the print drum. The lock means is adapted to prevent inadvertent rotation of the imprinting die while the drive gear and the transfer gear are disengaged.

In preferred embodiments, the imprinting die is mounted on a shaft rotatably secured in the print drum. In such embodiments the lock means may comprise a biassed cam and follower arrangement operative between the shaft and the print drum to permit relative rotation therebetween when the shaft is driven by the drive means and prevent such relative rotation when the drive means is inoperative.

Preferably the cam and follower are biassed into mutual engagement and are of complementary profile to permit relative rotation between the two shaft parts in one direction only; and the cam and follower may be annular and each include a series of saw teeth disposed on a circumference thereof, the number of teeth corresponding to the number of indexable positions of the imprinting die.

These features provide an advantageously reliable, unidirectional drive. The lock means may alternatively be configured as a plate engageable in a slot formed in e.g. the transfer gear such that the plate and slot are mutually engaged during that part of the rotation of the print drum when the transfer and drive gears are incapable of meshing together.

A practical embodiment of the invention includes an imprinting die having four facets. Optionally, one of the facets is adapted to make no imprint when presented for printing on a mailpiece.

There now follows a description of a preferred embodiment of the invention, by way of example, with reference being made to the accompanying drawings in which: Figure 1 is schematic view of the main components of a postage meter according to the invention, in the vicinity of the print drum thereof; Figure 2 is a perspective view of the mounting shaft assembly for the imprinting die of Figure 1; Figure 3 shows an arrangement of optosensors for reading the encoder disc shown in Figure 2; and Figure 4 shows part of the mounting shaft of Figure 2 in greater detail.

Referring to the drawings, there is shown a postage meter print drum 10 that is rotatable in the direction of arrow A to print postage indicia and other matter such as slogans and logos on mailpieces. The print drum 10 is driven by e.g. an AC motor (not shown), and operation of print drum 10 is controlled e.g. by a microprocessor incorporated into the postage meter. The microprocessor may in a typical application be arranged selectively to operate a clutch between the output shaft of the AC motor and the mounting shaft 12 of the print drum 10.

Alternatively, operation of drum 10 may be initiated by the insertion of a mailpiece into the machine, as is the case in postage meters constructed without microprocessor control.

Print drum 10 includes an imprinting die in the form of e.g. a multi-faceted slogan block 20. The imprinting die is mounted on a rotatable shaft 11 (Figure 2) disposed within the print drum 10 and extending parallel to but spaced from the mounting shaft 12 of the print drum 10. Shaft 11 is located adjacent the outer periphery of the print drum 10 to permit the presentation for printing of the respective facets of the imprinting die in the region 10a at the outermost periphery of the print drum 10, depending on the rotational position of the imprinting die. An advertising die, a so-called "town die" and a stamp (postage value) die are secured on the print drum periphery in the respective regions 10b, 10c and 10d.

The print drum 10 includes a suitable aperture whereby a selected facet of the imprinting die is presented for imprinting on a mailpiece on operation of the postage meter to cause rotation of the print drum 10.

A transfer gear in the form of star wheel 13 is mounted on a shaft 22, spaced radially from the mounting shaft 12. The star wheel 13 is arranged for simultaneous rotation with a gear 23 with which gear wheel 13 forms a cluster. Gear 23 is in meshing engagement with a further gear 24 rigidly secured on the free end of shaft 11 (e.g. by means of a key and keyway arrangement) so that rotation of star wheel 13 causes rotation of the imprinting die 20.

The star wheel 13 is disposed externally of the end wall of print drum 10. A drive gear in the form of star wheel 14 is disposed adjacent star wheel 13 so that the teeth 14a of star wheel 14 may mesh with the teeth 13a formed on the star wheel 13.

Star wheel 14 is rotatably mounted on drive shaft 14d that is rotatably captive in the postage meter and drivingly connected (directly or indirectly) to a suitable motor, eg a dc motor. Star wheel 14 includes an essentially circular disc 14c having a plurality (four in the embodiment shown) of spike-like teeth protruding normal to the circumference thereof. In the embodiment shown, the teeth 14a are equi-spaced at 900 intervals about the periphery of star wheel 14.

In normal use of the apparatus, star wheel 14 is arranged to rotate in the direction of arrow B. The teeth 13a of star wheel 13 each optionally incorporate an inclined or chamfered leading portion 13b (Figure 1), so that the teeth of the star wheels 13 and 14 mesh for a predetermined time, according to the timing requirements in the postage meter.

Star wheel 14 is constituted as cluster of two gears, with a smaller gear 14b secured on the shaft 14d adjacent the circular disc 14c.

The drive shaft 14d is controllable by e.g. a solenoid actuated clutch under the command of the postage meter microprocessor, whereby gear 14b is only rotated when it is desired to index the imprinting die to present a new facet for printing. The same effect may be achieved by dispensing with the solenoid operated clutch and employing a d.c.

motor or a stepper motor.

Rotation of star wheel 14 causes rotational indexing of the imprinting die 20 by virtue of the periodic engagement of the teeth 14a of star wheel 14 with the teeth 13a of star wheel 13.

Indexing of the imprinting die in this manner is typically carried out under the control of the microprocessor of the postage meter. Thus it is possible to provide for automatic indexing of the imprinting die, according to the settings of the postage meter, and the need for operator intervention is eliminated.

Gear 14b is of conventional design, and is arranged in permanent, meshing engagement with a further, conventional gear 15 that is driven thereby. Shaft 15a carrying gear 15 also carries an encoder disc 16 mounted for rotation therewith. The encoder disc 16 includes a plurality of apertures 17, arranged on a common pitch circle, that are readable by a pair of through-beam optosensors 18 and 18a. A pair of datum apertures 17' are provided spaced 1800 apart on a separate pitch circle of different diameter from the common pitch circle referred to.

The postage meter control apparatus, e.g. a microprocessor, enables the position of the encoder disc (and hence the star wheel 14) to be accurately determined relative to the half circumference of the encoder disc being sensed, once one of the datum apertures constituted by apertures 17' passes the optosensor 18.

Since the ratio of the number of teeth on gear 15 to those on gear 14b is 2:1, it will be appreciated that in a 360" rotation of gear 14b the encoder disc 16 is caused to rotate by 1800. The presence of two datum points 17' on the encoder disc 16 allows for accurate positional control of the star wheel 14 whilst obviating the need for a 1:1 gear ratio, which could result in slow operation of the star wheel 14.

The ratio of the number of teeth 14a on the star wheel 14 to the number of teeth 13a on the star wheel 13 is 1:2. Thus, a 90" rotation of star wheel 14 (i.e. the engagement of one tooth 14a with a tooth 13a) is necessary to cause a 450 rotation of star wheel 13 and hence of the gear 23. Since the ratio of the number of teeth on gear 23 to those on gear 24 is 2:1, this causes a 90" rotation of gear 24 and hence of imprinting die 20. Of course, other tooth ratios may be used throughout the gear train shown in Figure 1, especially in embodiments using imprinting dies having more or fewer than four facets.

The microprocessor control of the gear train is such that, when the print drum normally occupies its home position (as shown in Figure 1) the star wheel 14 adopts the position shown, i.e. with none of its teeth 14a engaged with teeth 13a of star wheel 13. With star wheel 14 in this position, the print drum 10 may be rotated without the teeth 13a contacting the teeth 14a. The teeth 14a only engage the teeth 13a when the drum is stationary and gear 15 is driven under the control of the microprocessor and as determined by the signals from the optosensors 18, 18a to index a fresh facet of the imprinting die to the printing position. Thus, damage to the respective sets of teeth is avoided. The microprocessor control prevents movement of star wheel 14 while the print drum 10 is rotating.

An advantage of using star wheels such as those shown in the An advantage of using star wheels such as those shown in the drawing figures is that the print drum and the drive train do not have to be positioned with great accuracy, since the spacings of the various gear teeth and to a certain extent the profiles of the teeth 13a mean that the star wheels 14 and 13 will always mesh satisfactorily when it is required to index the imprinting die, regardless of slight errors in the positioning of the print drum, etc. However, alternative arrangements could be provided.For example, the star wheel 13 could be replaced by a conventional ring gear and the star wheel 14 by a gear having conventional teeth formed on portions of its periphery with toothless spaces between such portions to allow rotation of the print drum without fouling between the drive gear and driven gear when the drive gear occupies specific positions.

It is desirable to lock the rotational position of the imprinting die 20 during rotation of the print drum against the so-called "printing pressure" that tends to tilt the die 20 in one direction on shaft 11 during imprinting operations.

In preferred embodiments, this locking is achieved by means of a two part cam acting to make shaft 11 rotatable in only one direction, as shown in Figures 2 and 4.

Shaft 11 passes from gear wheel 24 through a collar 25 nonrotatably secured to the end face of the print drum 10. Collar 25 acts as a journal bearing for shaft 11. Collar 25 includes an integral cam extension ring portion 26a and shaft 11 includes slideably mounted thereon a corresponding follower ring portion 26b. Follower portion 26b is arranged to rotate with shaft 11 by virtue of pin 28 (described below) and the portions 26a and 26b have mutually engaging annular surfaces at their respective free ends.

The two portions 26a and 26b are urged into mutual engagement by means of a spring 27 acting between the imprinting die 20, which is secured at the free end of shaft 11, and the shoulder formed by the terminus of portion 26b.

Follower portion 26b is secured relative to shaft 11 by means of a cross pin 28 secured transversely thereon. Pin 28 is captive in a slot 31 formed in follower portion 26b so that portion 26b is axially slideable against the influence of spring 27 on the shaft 11.

Imprinting die 20 is rigidly secured to shaft 11 by means of a further cross pin 29 received in a suitable recess formed in the end face of the die 20. As a result any rotation of shaft 11 is transmitted directly to die 20.

The distal end of die 20 includes a shaft extension lla that is journalled in a bearing (not shown) disposed within the print drum 10.

The engaging surfaces of shaft portions 26a and 26b are constituted as a cam (26a) and follower (26b) arrangement. In the embodiment shown the engaging surfaces have complementary saw tooth profiles including axially aligned surfaces 126 and inclined surfaces 226. When shaft 11 is rotated in the direction of arrow C (Figure 2), drive is transmitted to die 20 by virtue of the pairs of inclined surfaces 226 riding up on one another against the action of spring 27 in biassing the cam 26a and follower 26b together. Attempted rotation of shaft 11 in the opposite direction causes the axially aligned surfaces 126 to abut one another. Since the cam 126 is not rotatable relative to the drum 10, there is solid resistance to rotation in the direction opposite to arrow C.

The rotational direction in which shaft 11 transmits drive (which in turn is determined by the "handedness" of the saw teeth) is chosen so that there is solid resistance to the tendency of the imprinting die 20 to rotate relative to drum 10 on operation thereof. Locking in this way is achieved using the unidirectional drive shaft 11 described, since the drum 10 only ever rotates in the direction of arrow A so the tendency is for die 20 always to slip in the same direction.

For added safety, the number of saw teeth formed on the free ends of the portions 26a and 26b is equal in the embodiment shown to the number of facets on the die 20. This minimises the risk of misalignment of the die. As an alternative, the number of saw teeth could be am integer multiple of the number of facets, but this would necessitate different gearing in the drive train for the imprinting die shaft 11 to ensure that the facets are always correctly presented for printing.

The locking effect may alternatively be achieved e.g. by means of a spring loaded locking member that is engageable with a slot formed in the hub of star wheel 13 or in the imprinting die itself. Such a locking member would be mounted within the print drum 10 and could be provided with a cam follower surface that would be acted upon by a cam surface formed on star wheel 14 to cam the locking member to an unlocked position when it is required to index the imprinting die. Of course, the camming of such a locking member would have to be timed to take place slightly in advance of the engagement between the teeth 14a and 13a, otherwise the indexing mechanism would jam as a result of failure of the locking member to disengage.

Claims (12)

1. A postage meter comprising a rotatable print drum; an imprinting die rotatably secured in the print drum such that a portion of the imprinting die is presentable for printing on a mailpiece on operation of the print drum; a drive means for selectively causing displacement of the imprinting die by a discrete angular rotation, the imprinting die having a plurality of facets spaced one from another by an angular amount corresponding to said discrete angular rotation; control means for controlling operation of the drive means; and position detecting means for detecting the operational position of the drive means or the imprinting die, the position detecting means being operatively connected to the control means, whereby the imprinting die may selectively be indexed to present different facets for printing on mailpieces.

2. A postage meter according to claim 1, wherein the drive means includes a drive gear rotatably secured in the postage meter substantially externally of the print drum and adapted to transmit rotational drive from a drive shaft of the postage meter; and a transfer gear in driving relation with the imprinting die and rotatable with the print drum, the drive gear and the transfer gear being meshingly engageable when the print drum occupies its home position and the teeth of one of the gears being spaced from one another in at least part of the circumference of said gear to permit disengagement of the drive and transfer gears on operation of the print drum.

3. A postage meter according to claim 2, wherein the drive gear and/or the transfer gear is constituted as a star wheel, whereby discrete angular rotation of the imprinting die can be caused when desired.

4. A postage meter according to claim 2 or claim 3, wherein the position detecting means includes an encoder means on a shaft drivingly engaged with or carrying the drive gear; and sensor means, e.g. an optosensor, for detecting the setting of the encoder means and hence the position of the imprinting die.

5. A postage meter according to Claim 4, wherein the encoder means includes an encoder disc mounted for rotation with the drive shaft, the drive means being such that the encoder disc completes 180C of rotation for each 360C rotation of the imprinting die; the encoder disc including encoding indicia, e.g. apertures, in a pattern repeated every 180C about the encoder disc; and the indicia including datum indicia for providing absolute sensing of the position of the encoder disc relative to a 180C rotation thereof.

6. A postage meter according to any preceding claim, including lock means operative during operation of the print drum to limit or prevent inadvertent rotation of the imprinting die while the drive gear and the transfer gear are disengaged.

7. A postage meter according to Claim 6 wherein the imprinting die is mounted on a shaft rotatably secured in the print drum and driveable by the drive means, the lock means comprising a biassed cam and follower arrangement operative between the shaft and the print drum to permit relative rotation therebetween when the shaft is driven by the drive means and limit such relative rotation when the drive means is inoperative.

8. A postage meter according to Claim 7 wherein the cam and follower are biassed into mutual engagement and are of complementary profile to permit relative rotation between the two shaft parts in one direction only.

9. A postage meter according to Claim 8 wherein the cam and follower are annular and each include a series of saw teeth disposed on a circumference thereof, the number of teeth being proportional to the number of indexable positions of the imprinting die.

10. A postage meter according to any preceding claim, wherein the imprinting die has four facets.

11. A postage meter according to any preceding claim wherein one facet of the imprinting die is adapted to make no imprint when presented for printing on a mailpiece.

12. A postage meter generally as herein described, with reference to or as illustrated in the accompanying drawings.