Mail piece feeder for vertically orientated mail pieces and having reversible retard rollers

Abstract

A postal meter mail piece feeder comprising a hopper section, a singulating section and a mail piece turner. The hopper section comprises a bottom mail piece support deck for supporting mail pieces thereon, a rear wall having a mail piece drive for contacting and moving the mail pieces along the support deck, and a front stop for biasing the mail pieces towards the rear wall. The singulating section is downstream from the hopper section and comprises a retard drive and a sensor connected to the retard drive. The mail piece turner is downstream from the singulating section and comprises a turning surface for turning the mail pieces about 90° from the singulating section for entry into a postage applying section of a postage meter.

Description

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to postage meters and, more particularly, to a mail piece feeder.

[0004] 2. Prior Art

[0005] Many different types of mail piece feeders for postage meters are well known in the art. Typically, these mail piece feeders can include a hopper in which mail pieces are stacked in a column; each mail piece being generally horizontally orientated, or at least feed away from the hopper in a horizontal orientation by a singulating or separating section. A problem with such feeders is that the vertical size of the stack of mail pieces in the hopper is usually limited. Too high a stack can cause feeding problems because of too much weight on the bottom mail piece. There is a desire to allow larger quantities of mail pieces to be located in a postage meter mail piece feeder hopper at any given time.

SUMMARY OF THE INVENTION

[0006] In accordance with one embodiment of the present invention, a postal meter mail piece feeder is provided comprising a hopper section, a singulating section and a mail piece turner. The hopper section comprises a bottom mail piece support deck for supporting mail pieces thereon, a rear wall having a mail piece drive for contacting and moving the mail pieces along the support deck, and a front stop for biasing the mail pieces towards the rear wall. The singulating section is downstream from the hopper section and comprises a retard drive and a sensor connected to the retard drive. The mail piece turner is downstream from the singulating section and comprises a turning surface for turning the mail pieces about 90° from the singulating section for entry into a postage applying section of a postage meter.

[0007] In accordance with one method of the present invention, a method of feeding mail pieces from a hopper comprising steps of feeding the mail pieces between a feed drive and a retard drive in a substantially vertical orientation; sensing presence of more than one mail piece between the feed drive and the retard drive at a same time; and when more than one mail piece is sensed between the feed drive and the retard drive at the same time, reversing direction of movement of the retard drive relative to the feed drive from a forward direction to a reverse direction.

[0008] In accordance with another method of the present invention, a method of determining a presence of mail pieces in a mail piece singulator section of a mail piece feeder is provided comprising steps of determining a first value of a first characteristic of a retard drive for a first condition; determining a second value of the first characteristic of the retard drive for a second condition, the second condition comprising a single mail piece being located directly between the retard drive and a feeder drive; and comparing the first and second values to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The foregoing aspects and other features of the present invention are explained in the following description, taken in connection with the accompanying drawings, wherein:

[0010] FIG. 1 is a schematic view of a postage meter apparatus incorporating features of the present invention;

[0011] FIG. 2 is a schematic perspective view with a cut away section of the feeder section shown in FIG. 1;

[0012] FIG. 2A is a partial perspective view of an alternate embodiment of the hopper section;

[0013] FIG. 2B is a partial perspective view of an alternate embodiment of the turner of the feeder section shown in FIG. 2;

[0014] FIG. 3 is a schematic view of the controller, feeder drive and retard drive of the feeder section shown in FIG. 2;

[0015] FIGS. 4A-4E are schematic views of the feed rollers and retard rollers with various different conditions of mail pieces between them;

[0016] FIG. 5 is a chart of loads on the retard rollers at different times/conditions;

[0017] FIG. 6 is a flow chart of one method of the present invention; and

[0018] FIG. 7 is a flow chart of another method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] Referring to FIG. 1, there is shown a schematic view of a postage meter apparatus 10 incorporating features of the present invention. Although the present invention will be described with reference to the embodiments shown in the drawings, it should be understood that the present invention can be embodied in many alternate forms of embodiments. In addition, any suitable size, shape or type of elements or materials could be used.

[0020] The apparatus 10 generally comprises a feeder section 12, a scale and postage meter section 14 and an output section 16. The three sections 12, 14, 16 could be provided as a single unit or could be modular units connected in series to each other. The output section 16 could be any suitable type of output section, such as a stacking bin for example. Many different types of output sections are known in the art. Many different types of scale and postage meter sections are also well known in the art. Any suitable type of scale and postage meter section 14 could be provided. The section 14 could also merely be a postage meter without a scale, or the scale could be provided as part of the feeder section 12 or between the two sections 12 and 14.

[0021] Referring also to FIG. 2, one embodiment of the feeder section 12 is shown. In the this embodiment the feeder 12 generally comprises a hopper section 18, a singulating section 20, and a mail piece turner section 22. In alternate embodiments the turner section 22 might not be provided or could be provided with the section 14. The hopper section 18 generally comprises a portion of the mail piece support deck 24, a portion of the rear wall 26, a portion of the feeder drive 28 and a front stop 30. The support deck 24 extends the length of the feeder 12, at least up until the turner section 22. The rear wall 26 has a front facing mail piece contacting surface 32 which is preferably vertical, but may be inclined slightly forward or backward. The feeder drive 28 includes at least one drive motor 34 (see FIG. 3) connected between a controller 36 and high friction feed rollers 38. The vertical series of feed rollers 38 are orientated in a substantially vertical plane and extend outward past the surface 32 through holes in the surface 32. In an alternate embodiment the feed rollers 38 might not be connected to the controller. In another alternate embodiment the feed rollers 38 could be replaced by any suitable type of mechanical transport, such as belts for example. The front stop 30 is preferably spring biased towards the rear wall 26 to bias the mail pieces M towards the rear wall. However, any suitable type of system could be provided to move the mail pieces towards the feeder drive 28. The feeder section 12 is adapted to have the mail pieces M loaded into the hopper section 18 in a substantially vertical orientation with the flap edge preferably located down against the deck 24 and the mail piece flap preferably facing forward. The motor 34 preferably rotates the feed rollers 38 at a constant velocity. However, in an alternate embodiment the velocity of the feed rollers 38 could be varied, such as by the controller 36 for example. The feed deck 24 could be flat or, as shown in FIG. 2A, an alternate embodiment could comprise light, low friction idler rollers 40 extending through holes 42 in a top surface of the deck 24′ on which the flap edges of the mail pieces move. The rollers 40 could project into the rear wall surface 32′ if desired. In alternate embodiments any suitable type of hopper section could be used including those well known in the art, such as a horizontally stacked or substantially horizontally reorientating feeding hopper for example.

[0022] The singulating section 20 generally comprises a portion of the feeder drive 28, a portion of the rear wall 26 and surface 32, and a retard drive 44. Referring also to FIG. 3, the retard drive 44 generally comprises a motor 46, retard rollers 48 and at least one sensor 50. The feed rollers and retard rollers might share the same motor with the retard rollers merely having a different variable and reversible transmission. The motor 46 could be a common motor with the motor 34, the controller 36 controlling a reversible transmission between the common motor and the retard rollers 48. In an alternate embodiment the retard rollers 48 could be replaced by drive belts or any other suitable mechanical drive. The sensor 50 is preferably a load or force sensor. However, in alternate embodiments any suitably type sensor(s) could be used, such as a speed sensor. The motor 46 is preferably a reversible motor and is connected to the controller 36. The motor 46 drives the retard rollers 48. The series of retard rollers 48 are orientated in a general vertical plane substantially parallel to the vertical plane of the series of feed rollers 38. The retard rollers 48 are located opposite some of the feed rollers 38 and are preferably spring loaded in a direction towards the feed rollers 38 and contact the feed rollers 38 when no mail piece is located in the feed path between the two sets of rollers.

[0023] In a preferred embodiment, the retard drive 44 is adapted to configure movement of the retard rollers in at least two movement configurations; both at least partially independent of movement of the opposing feed rollers 38. In a first movement configuration the retard rollers 48 are rotated in a forward direction to move a mail piece between the sets of rollers 38, 48 in a forward lateral direction from the hopper section 18 towards the takeaway rollers 52. The retard rollers 48 could be actively moved by the motor 46 at a speed slower than the feed rollers 38, and/or be passively moved by direct contact with the feed rollers 38 or mail piece(s) driven by the feed rollers 38. The sensor 50 can sense a predetermined characteristic of the retard rollers 48, such as speed of the retard rollers or, preferably, a force different or load on the retard rollers 48 between the motor 46 and the feed rollers 38 or mail piece pushing against the retard roller. The sensor 50 sends this information to the controller 36. In a second movement configuration, the retard rollers 48 are rotated in a reverse direction to move a mail piece located against the retard rollers 48 in a reverse lateral direction back towards the hopper section 18. In a preferred method, during both the first and second movement configurations of the retard drive, the feeder drive 28 continues to move the feed rollers 38 in a forward direction. However, in alternate methods the feeder drive 28 could vary the speed of the feed rollers 38 or even stop rotation of the feed rollers 38 while the retard rollers experience the second movement configuration. In another alternate method, the second movement configuration could comprise the retard rollers being positively or actively stopped from rotation, such as by motor 46 or a brake, while the feed rollers 38 continue to rotate in the forward direction. As seen in FIG. 2, the retard rollers 48 are arranged in laterally offset sets along the mail piece feed path. The controller 36 and motor(s) 46 could be configured to rotate the offset sets of retard rollers at different speeds and/or directions relative to each other, or even allow the rollers to function as brakeable idler rollers. This could also be done for the horizontally spaced sets of feed rollers 38 in the singulating section 20.

[0024] Referring now also to FIGS. 4A-4E, 5 and 6, one method of operation of the singulating section 20 will be described. FIG. 6 corresponds to the embodiment wherein the sensor 50 is a load sensor and a signal of load 54 is sent to the controller 36. At an initial time 4A corresponding to FIG. 4A, the feed rollers 38 and retard rollers 48 are located against each other and are driven in a same feed direction; block 56 in FIG. 6. No mail pieces are located between the rollers 38, 48. As indicated by block 58 in FIG. 6, the sensor 50 senses the load on the retard rollers 48. This produces a signal corresponding to load 54a from the sensor 50. At about time 4B a mail piece M1 is fed by the feed rollers 38 between the sets of rollers 38, 48 as seen in FIG. 4B. The load on the retard roller 48 will reduce because of slippage between the mail piece M1 and the retard roller 48; the feed roller 38 having a higher coefficient of friction than the mail piece M1. This produces a signal corresponding to lower load 54b from the sensor 50.

[0025] In the event that more than one mail piece M1, M2 are feed between the rollers 38, 48 at the same time, as shown in FIG. 4C, and time 4C in FIG. 5, the output signal corresponding to load 54c from the sensor 50 will indicate a much lower load, such as 50% or less than the signals for loads 54a and 54b. This is because the two mail pieces M1, M2 can slide relative to each other; even though they are moving in the same forward direction. As indicated by block 60 in FIG. 6, the controller 36 is programmed or otherwise configured to determine if the load on the retard roller 48 has reduced past a first predetermined load sensor setting LS1. The setting LS1 could be fixed, or manually adjustable and/or automatically adjustable. One example of an automatically adjustable system will be discussed further below with regard to FIG. 7, but any suitable adjustment system could be provided. If the information sent by the sensor to the controller matches or is reduced past setting LS1 then, as indicated by block 62, the controller 36 can change operation of the retard drive from the first movement configuration to the second movement configuration; in this case reversing direction of movement of the retard rollers as indicated by arrow B in FIG. 4C. Thus, at time 4C′, when the roller 48 reverses direction, the load increases and then subsequently decreases to load 54c″ at time 4C″ when the two mail pieces M1, M2 slide in reverse directions relative to each other. The system can have suitable filters or otherwise be configured such that the load spike 54c′ does not cause the retard rollers 48 to return back to the forward direction of rotation A.

[0026] The system continues to monitor the output from the sensor 50. At time 4D, when the second mail piece M2 is no longer between the rollers 38, 48 but the first mail piece M1 is between the rollers 38, 48 as shown in FIG. 4D, the load on the retard roller 38 increases to the load 54d. However, this load 54d is below a second predetermined load sensor setting LS2. The second setting LS2i similar to the setting LS1, could be fixed or manually and/or automatically adjustable. At time 4E, corresponding to FIG. 4E, the first mail piece M1 exits from between the rollers 38, 48. The two rollers 38, 48 then directly contact each other again. This causes the load on the retard roller 48 to spike to its highest level 54e. Load level 54e is above the second setting LS2. As indicated by block 64 in FIG. 6, when the controller determines that the load on the retard roller has increased past the second predetermined load sensor setting, the controller can reverse the motor and reverse the direction of rotation of the retard roller back from direction B to a forward feed direction as indicated by block 66 in FIG. 6 and arrow A in FIG. 4E. Thus, the two mail pieces M1 , M2 have been separated and the second mail piece M2 can now be feed forward. The load at the sensor, thus, returns to level 54a as indicated at time 4E′ in FIG. 5. Of course, this is only an example of how features of the present invention can function. Variations will occur in timing, conditions (such as more than two mail pieces between the rollers 38, 48), and loads (due to such factors as coefficients of friction of the mail pieces, thickness of the mail pieces and rigidity of the mail pieces).

[0027] The first setting LS1 can be automatically adjustable based upon the mail pieces being fed. One example of automatically adjusting the system will now be described with reference to FIG. 7. This system adjusts the first setting LS1 based upon frictional properties of the mail pieces being fed. As indicated by block 70 the system first determines the force or load on the retard roller during static feeding; time 4A and force 54a. As indicated by block 72, then the system determines the force or load on the retard roller during dynamic sliding feeding of a single mail piece; time 4B and force 54b . The controller 36 can then determine a ratio of the two forces/loads 54a and 54b as indicated by block 74. Based upon information in the controller 36, such as an algorithm or a chart or table of precollected imperical data for example, the controller 36 can vary the first setting LS1 based upon this ratio as indicated by block 76. This can prevent unnecessary triggering of reversal of the retard rollers for mail pieces having relatively low coefficients of friction, or prevent non-triggering of reversal of the retard rollers for mail pieces having relatively high coefficients of friction. Of course, this is only one example of adjustability. Other variations and alternate embodiments could be evident to those skilled in the art after reading the present description.

[0028] Referring back to FIG. 2, once the mail pieces as separated by the singulating section 20, the faster speed take away rollers 52 can move the mail pieces away from the singulating section and down the feed path. In this embodiment the feeder section 12 further comprises an angled flap roller 80, a deflector 82 and a moistening brush 84. The angled flap roller 80 can open the flap of the mail piece and drive the mail piece against the deck 24. The deflector 82 can open the flap to allow the brush 84 to moisten the glue on the inside of the flap. In alternate embodiments the members 80, 82 and/or 84 might not be provided. The feeder section 12 can also comprise a sensor 51 which can be a mail piece sensor or sensing the leading edge or the trailing edge or presence of a mail piece. This could be used to determine when no mail pieces are in between the feeding wheels and for recording the static forces or loads on the wheels in this condition. The system could also be configured to turn the driving motion of the wheels ON and OFF based upon time and the input from the sensor 51, or any other suitable input. In other words, the time chart shown in FIG. 5 does not need to be continuous, but may be intermittent or comprise periodic sampling of the loads (i.e.: by use of periodic clock signals). In alternate embodiments variations in timing of operations, and specific control operations (perhaps based upon inputs) could be varied.

[0029] The turner section 22 generally comprises opposing belts 86 rotatably mounted on pulleys 88, 90. The first pulleys 88 have rotation axes 92a, 92b parallel to each other in a substantially vertical orientation. The second pulleys 94, 96 have rotation axes 98a, 98b parallel to each other in a substantially horizontal orientation. The mail pieces M enter between the first pulleys 88 in a substantially vertical orientation and are moved by the belts 86 towards the opposite end at the pulleys 90. As the belts 86 move the individual mail pieces, the orientation of the mail piece rotates about 90° to a substantially horizontal orientation. As the mail pieces exit the turner section 22 from between the pulleys 90, they are propelled into the scale and postage meter section 14. In alternate embodiments the turner section 22 might not be provided, such as when the postage meter applies postage to vertically orientated mail pieces.

[0030] Referring also to FIG. 2B, an alternate embodiment of the turner section is shown. In this embodiment the surface 32′ of the rear wall 26′ has a deflector or pusher 33. As the vertically orientated mail piece moves along the deck 24 and surface 32′, it contacts the projecting deflector 33. This causes the top of the mail piece to tilt forward. Gravity then causes the top of the mail piece to rotate towards the deck 24. Thus, a gravity system can be provided to reorientated the mail pieces to a substantially horizontal orientation.

[0031] The present invention can provide a mixed mail feeder (which can feed different thickness mail pieces as well as different size mail and also handles sealed or unsealed mail) as well as nested and unnested mail. This invention utilizes a combination of paper handling technologies and a unique architecture to achieve desired features. The user preferably loads the mail into the hopper in the prescribed manner. In this case, an important aspect of this design is that the system will use gravity to advantage. The mail can be loaded into the system with the flap edge down and the flap facing the operator. In order to make loading more convenient, the loading deck is displaced up stream of the feed separation station, which allows additional mail to be loaded while the machine is running and not effect the machine operation. Since letters are on edge, the feeding forces are not effected by the size of the stack. The stack can be retained by a spring-loaded front stop, which can be opened with one hand while the mail is loaded with the other hand. The stack can lean approximately 10 degrees to the rear so that the stack will remain in place when the stop is pulled back for loading.

[0032] Important features of the feeder are multiple (minimum two) separate high friction feed wheels along the rear wall and a similar number of separate retard feed rollers (independently spring loaded on a tapered input guide or throat leading to the takeaway rollers). The feed rollers and the retard rollers are located opposed to each other and are controlled/driven independently. The feeder deck can be provided with light, low friction idler rollers on which the incoming mail moves. An important feature of the invention is that the feed and retard opposing rollers can be driven by motors which can sense the force on the retard drive and determine whether the mail piece is being retarded; that is sliding on the adjacent mail piece closer to the feed deck, or whether it is being driven by the feeder with the high friction rollers.

[0033] The detection system could also monitor and filter the instantaneous peaks in load caused by the breaking apart of two mail pieces caused by the force of static friction. Further capability of the system is selectable control for differences in friction between different mail; by monitoring the ratios of the static and sliding forces on the rollers. Typically the different between static and dynamic is between 20% and 50%. The difference between rubber to paper and paper to paper can be at least a factor of two, and can be easily detected to determine when one mail piece is in the roller nips. Since the mail pieces are moving slowly (during the period of static friction and sliding friction) the effect of their size and weight are minimized.

[0034] If sliding (paper to paper) retard forces are detected, the retard system should continue to drive back the mail piece. If high feeding forces are detected than it can be assumed that the mail piece has been singulated and the retard system should reverse back to a forward direction and assist the feeding of the piece into the takeaway rollers. Once the mail piece is in the nip of the takeaway; the retard rollers could revert to the reverse action required for separation.

[0035] The architecture and feeding logic provide very important features for the operator/customer. The input stack can be much larger than normally provided in a machine of this type (limited only by the size of the feed deck assembly), since the feeding forces are unaffected by a stack. The prior art stack height is normally limited to several inches (typically 5 inches). The feeding forces are primarily determined by the backstop pushing on the stack. The retard system is extremely robust, with three stages of retard or sets of retard rollers before the mail piece is taken away, providing additional capability to separate and feed mixed mail reliability. The lead edge alignment is optimally provided by gravity, which is more reliable than existing systems which attempt to drive a mail piece into alignment from the bottom of a stack. The feeder system can separate both sealed and unsealed mail over a range of sizes compatible with the size of the system.

[0036] Once into the takeaway system, an angled driven friction roller can open the flap if it is not already sealed, and pass the flap through a moistening system while the mail piece is still vertical. After the piece has passed the sealing section, it could be passed through a set of turning belts which would turn the piece 90 degrees to present it to the horizontal dynamic scale transport deck. Optionally, a simpler less costly turning system could be provided by simply dropping the mail piece onto the dyna scale deck with appropriate guiding so that it would fall onto the deck aligned with the rear wall.

[0037] It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.

Claims

1. A postal meter mail piece feeder comprising: a hopper section comprising a bottom mail piece support deck for supporting mail pieces thereon, a rear wall having a mail piece drive for contacting and moving the mail pieces along the support deck, and a front stop for biasing the mail pieces towards the rear wall; a singulating section downstream from the hopper section comprising a retard drive and a sensor connected to the retard drive; and a mail piece turner downstream from the singulating section comprising a turning surface for turning the mail pieces about 90° from the singulating section for entry into a postage applying section of a postage meter.

2. A mail piece feeder as in claim 1 wherein the support deck comprises idler rollers for supporting the mail pieces thereon.

3. A mail piece feeder as in claim 1 wherein the mail piece drive comprises friction feed rollers connected to a first drive motor, wherein the feed rollers are all orientated along a substantially vertical plane.

4. A mail piece feeder as in claim 3 wherein the singulating section comprises some of the feed rollers being located opposite retard rollers of the retard drive.

5. A mail piece feeder as in claim 4 wherein the retard drive comprises a second drive motor connected to the retard rollers.

6. A mail piece feeder as in claim 5 wherein the first and second drive motors are connected to a controller, and wherein the controller is adapted to vary the direction of rotation of the retard rollers relative to the feed rollers.

7. A mail piece feeder as in claim 1 wherein the sensor is adapted to sense a load on retard rollers of the retard drive.

8. A mail piece feeder as in claim 1 wherein the sensor is adapted to sense speed of rotation of retard rollers of the retard drive.

9. A mail piece feeder as in claim 1 wherein the sensor is connected to a controller adapted to control direction of rotation of retard rollers of the retard drive.

10. A mail piece feeder as in claim 1 wherein the retard drive comprises retard rollers all orientated in a substantially vertical plane substantially parallel to a plane of the rear wall.

11. A mail piece feeder as in claim 1 wherein the mail piece turner comprises opposing turning belts which turn about 90° along their length.

12. A mail piece feeder as in claim 1 wherein the mail piece turner comprises a gravity drop system to allow generally vertically orientated mail pieces to rotatably fall about 90°.

13. A mail piece feeder as in claim 12 wherein the gravity drop system comprises a deflector system to push against one side of the mail pieces to insure that they start their rotating fall.

14. A method of feeding mail pieces from a hopper comprising steps of: feeding the mail pieces between a feed drive and a retard drive in a substantially vertical orientation; sensing presence of more than one mail piece between the feed drive and the retard drive at a same time; and when more than one mail piece is sensed between the feed drive and the retard drive at the same time, reversing direction of movement of the retard drive relative to the feed drive from a forward direction to a reverse direction.

15. A method as in claim 14 wherein the step of sensing the presence of more than one mail piece comprises sensing a load on a retard roller of the retard drive.

16. A method as in claim 14 wherein the step of sensing the presence of more than one mail piece comprises sensing a speed of a retard roller of the retard drive.

17. A method as in claim 14 wherein the step of sensing comprises a sensor connected to a retard roller of the retard drive, and wherein the sensor senses a predetermined characteristic of the retard roller.

18. A method as in claim 17 wherein the sensor is connected to a controller and wherein the controller is adapted to at least partially control rotation of the retard roller based upon information sent to the controller from the sensor.

19. A method as in claim 18 wherein the controller reverses direction of the retard drive back to a forward direction when the sensor senses a predetermined condition.

20. A method as in claim 18 further comprising comparing the information sent to the controller from the sensor to a first predetermined sensor setting, wherein when the sent information reaches the first sensor setting, the step of reversing direction occurs.

21. A method as in claim 20 further comprising varying the first predetermined sensor setting.

22. A method as in claim 21 wherein the step of varying comprising comparing information sent by the sensor to the controller for at least two different conditions, one of the conditions comprising no mail pieces between the feed drive and the retard drive.

23. A method as in claim 20 further comprising comparing the information sent to the controller from the sensor to a second predetermined sensor setting and reversing direction of the retard drive back to the forward direction when the information sent reaches the second predetermined sensor setting.

24. A method as in claim 14 further comprising turning the mail pieces from the substantially vertical orientation to a substantially horizontal orientation and delivering the reoriented mail pieces to a scale and postage meter section of a postage meter apparatus.

25. A method of determining a presence of mail pieces in a mail piece singulator section of a mail piece feeder comprising steps of: determining a first value of a first characteristic of a retard drive for a first condition; determining a second value of the first characteristic of the retard drive for a second condition, the second condition comprising a single mail piece being located directly between the retard drive and a feeder drive; and comparing the first and second values to each other.

26. A method as in claim 25 wherein the first condition comprises no mail pieces being located between the feeder drive and the retard drive.

27. A method as in claim 25 wherein the first characteristic comprises a load on a retard roller of the retard drive.

28. A method as in claim 25 wherein the first characteristic comprises a speed of rotation of a retard roller of the retard drive.

29. A method as in claim 25 wherein the step of comparing comprises determining a ratio of the first and second values.

30. A method as in claim 25 wherein the first condition comprises more than one mail piece between the retard drive and the feeder drive.