Non-contact sensing system
A non-contact sensing system for detecting a double feed condition of mail. The non-contact sensing system generally includes a mail sorting machine that routes and moves the mail, a non-contact sensor, and a controller. The non-contact sensor is positioned proximate to the conveyor and generates a signal that is indicative of the thickness of the mail. The controller receives the signal from the non-contact sensor and generates an output signal that indicates a double feed condition.
The present invention relates to a non-contact sensor. More specifically, the present invention relates to a non-contact sensor that is applied in a mail sorting facility.
Mail is sorted and delivered to locations all over the world every day. Often, mail is automatically processed by mail sorting equipment to expedite delivery. For example, a large stack of letters can be separated by a pick off feeder, which then feeds the separated letters into mail sorting equipment at a predetermined rate (e.g., 10-12 pieces per second) and with a predetermined pitch or letter separation (e.g., approximately two to three inches). In some instances, a “double feed” condition may occur, in which two pieces of mail are fed into the mail sorting equipment by the pick off feeder simultaneously and without the proper separation between each piece. The double feed can result in a mis-sorting of the mail pieces, because the mail sorting equipment downstream of the pick off feeder cannot properly recognize or track the double-fed mail.
SUMMARYIn one embodiment, a non-contact sensing system for detecting a double feed condition of mail includes a mail sorting machine having a conveyor, a non-contact sensor, and a controller. The mail sorting machine moves the mail, while the non-contact sensor is positioned proximate to the conveyor and generates a signal indicative of a thickness of the mail. The controller receives the signal from the non-contact sensor and generates an output signal indicative of a double feed condition.
In another embodiment, a method of calculating the likelihood of a double feed condition of mail includes generating a thickness profile for the piece of mail. The thickness profile is then compared to a historical thickness profile. The historical thickness profile is based on a previously generated thickness profile. Finally, a confidence value associated with the likelihood of a double feed condition is calculated. The confidence value is at least partially based on a comparison of the thickness profile to the historical thickness profile.
In another embodiment, a method of calculating the likelihood of a double feed condition of mail includes generating a thickness profile of the mail piece. A first distinct thickness and a second distinct thickness are then identified within the generated thickness profile of the mail. A transition between the first distinct thickness and the second distinct thickness is assigned a position value, and the thickness profile includes at least two position values. Finally, a double feed condition is identified based on the at least two position values.
In another embodiment, a method of generating a double feed thickness profile for detecting a double feed condition includes measuring the thickness and length of potentially overlapping pieces of mail with a non-contact sensor; generating a historical length that is based at least partially on previously measured lengths of mail; calculating an offset value between the potentially overlapping pieces of mail; and generating a thickness profile of the potentially overlapping pieces of mail that is based at least partially on the offset value.
Other aspects will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
The mail sorting machine 14 can be configured a variety of ways to route and move the mail 30 through a mail sorting facility. In the embodiment shown in
As shown in
In operation, the sensing unit 38 transmits a signal 50 toward the outer belt 26. The signal 50 is then reflected off of the outer belt 26 and returned to the sensing unit 38. Consequently, the sensing unit 38 can accurately measure and calculate the distance between the outer belt 26 and the sensing unit 38, as well as generate a corresponding output signal. The output signal can then be transmitted to a controller (as described in greater detail with respect to
As described above, the controller 64 is electronically linked to both the displacement sensing unit 38 and the IPD 60. In some embodiments, the controller 64 is a conventional personal computer (“PC”) that includes a data acquisition card 68 (e.g., a DAQ NI DAQ6013 PCI card). In other embodiments a different type of controller 64 may be implemented. For example, a programmable logic controller (“PLC”) or other controller unit capable of receiving input signals and generating output signals may be employed. As described in greater detail below, the controller 64 communicates with both the IPD 60 and the displacement sensing unit 38 to generate an appropriate output 72, if the output 72 is required. The output 72 can include, for example, an audible and/or visual alert (e.g., a beeping sound, a flashing light, etc.). Alternatively or additionally, the output 72 may affect the mail sorting equipment downstream of the displacement sensor 34, for example, by removing or culling out double-fed mail.
Referring now to
The process 100 begins by inputting a thickness profile for a new piece of mail (“TP”) (step 104). As previously described, a thickness profile is related to the thickness of the mail 30 along its length. Accordingly, the thickness profile is input after the displacement sensing unit 38 measures the thickness of the mail 30 along the length of the mail 30 (see
If there are at least three unique thickness points along the length of the TP, the next step in the process 100 is to build an array of difference values or “deltas” along the length of the TP (step 124). As shown in
If there is at least one valid delta pair, the process 100 continues by relating the delta values and the physical dimensions of the overlapping mail pieces (step 136). As shown in
The process 200 begins by inputting a thickness profile for a new piece of mail (step 204). As previously described, the thickness profile for a new piece of mail can be created from the data provided by the displacement sensing unit 38. After a thickness profile has been created and input, the process 200 continues by checking if there is a “historical” thickness profile (step 208). A historical thickness profile is a thickness profile that has already been created and stored in the controller 64 (see
If a historical thickness profile has not yet been created, the thickness profile of the new mail type is temporarily stored so that a new historical profile can be created (step 212). After a certain number of matching thickness profiles is temporarily stored, a new historical profile is created (also step 212). For example, a new historical profile may be created after five new and matching thickness profiles are consecutively stored. The number of matching thickness profiles that are needed to create a new historical thickness profile is a configurable value, and is generally large enough to provide confidence that the historical thickness profile represents the thickness profile of the current mail stream. After the new historical profile is created, or is in the process of being created (step 212), the process 200 returns a double feed confidence factor of zero (step 216). If a double feed condition interrupts the creation of a new historical thickness profile (e.g., overlapping mail passes by the displacement sensing unit 38 after only three matching thickness profiles), the mail pieces with the non-matching thickness profile may be culled out, and the process 200 may start over.
If a historical thickness profile has already been created (and confirmed in step 208), the process 200 continues by comparing the new thickness profile to the historical profile (step 220). If the new thickness profile matches the dimensions of the historical thickness profile, the process 200 assumes that a double feed condition has not occurred and returns a double feed confidence factor of zero (step 224). However, if the new thickness profile does not match the historical thickness profile, the next step in the process 200 is to generate an expected double feed thickness profile (step 228). As described in greater detail with respect to
However, if the generated double feed thickness profile does not match the new thickness profile, the historical thickness profile used to create the double feed thickness profile in step 228 is invalidated (step 240). The process 200 continues by temporarily storing the new thickness profile so that a new historical thickness profile can be created as described above with respect to step 212. In other embodiments, the process 200 may have more or fewer steps than those shown in
The process 300 continues by verifying that the length (L) is a viable value (step 308). For example, the length (L) of the double feed profile must be greater than or equal to the historical profile length (“HPL”) (i.e., the double feed cannot be shorter than a single piece of mail). Additionally, the length (L) of the double feed must also be smaller than two times the HPL (i.e., the double feed cannot be longer than two pieces of mail). If either of the conditions set forth in step 308 is not true, the process 300 ends (step 312) and returns an empty or null double thickness profile (i.e., the length (L) is invalid and a double feed thickness profile cannot be generated). However, if the length (L) is greater than or equal to the HPL, and the length (L) is less than two times the HPL, the process 300 continues by calculating the offset between the pieces of mail 30 (step 316). The offset is approximately equivalent to the amount or length of one piece of mail that extends beyond the other piece of mail (e.g., offset=length (L)−HPL), if the overlapping mail pieces are not stacked directly on top of one another. For example, as shown in
The process 300 continues by generating an “add-on” thickness profile (step 320). The add-on thickness profile is of length (L), and has a value of zero between the zero mark and the offset value, as shown in
In some embodiments, the controller 64 can switch from one process to another and/or complete multiple processes, such as those described with respect to
Various embodiments of the invention are set forth in the following claims.
Claims
1. A non-contact sensing system for detecting a double feed condition of mail pieces, the non-contact sensing system comprising:
- a mail sorting machine having at least one conveyor configured to move the mail;
- a non-contact sensor positioned near the conveyor and configured to generate a signal indicative of a thickness of the mail being moved by the at least one conveyor; and
- a controller configured to receive the signal from the non-contact sensor and generate an output signal indicative of a double feed condition.
2. The non-contact sensing system of claim 1, wherein the non-contact sensor is an optical sensor.
3. The non-contact sensing system of claim 1, wherein the non-contact sensor is a laser sensor.
4. The non-contact sensing system of claim 1, wherein the non-contact sensor is a reflective sensor.
5. The non-contact sensing system of claim 1, further comprising a second sensor configured to generate a second signal indicative of a leading edge of a mail piece.
6. The non-contact sensing system of claim 5, wherein the controller is configured to receive the second signal from the second sensor and initialize the non-contact sensor in response to the receipt of the second signal.
7. The non-contact sensing system of claim 1, wherein the controller is configured to generate a thickness profile, and the output signal is at least partially based on the thickness profile.
8. The non-contact sensing system of claim 7, wherein the thickness profile includes at least one thickness delta value, the thickness delta value corresponding to a change in thickness.
9. The non-contact sensing system of claim 7, wherein the thickness profile includes an add-on value, the add-on value based at least partially on an expected mail overlapping amount.
10. A method of calculating the likelihood of a double feed condition of mail, the method comprising:
- generating a thickness profile for the mail;
- comparing the thickness profile of the mail to a historical thickness profile, the historical thickness profile at least partially based on a previously generated thickness profile; and
- calculating a confidence value associated with the likelihood of a double feed condition, the confidence value at least partially based on the comparison of the thickness profile to the historical thickness profile.
11. The method of claim 10, further comprising temporarily recording the thickness profile.
12. The method of claim 11, further comprising creating the historical thickness profile after comparing and matching a number of recorded thickness profiles.
13. The method of claim 10, further comprising generating an expected double feed profile, the expected double feed profile based at least partially on a comparison between the length of the thickness profile and the length of the historical thickness profile.
14. The method of claim 13, wherein generating the expected double feed profile comprises
- measuring the thickness and length of potentially overlapping pieces of mail with a non-contact sensor;
- generating a historical length based at least partially on a previously measured lengths of mail;
- calculating an offset value between the potentially overlapping pieces of mail, the offset value based at least partially on the historical length; and
- generating a thickness profile of the potentially overlapping pieces of mail based at least partially on the offset value.
15. The method of claim 13, further comprising generating the confidence value based at least partially on the comparison of the thickness profile and the expected double feed thickness profile.
16. A method of calculating the likelihood of a double feed condition of mail, the method comprising:
- generating a thickness profile of the mail;
- identifying a first distinct thickness and a second distinct thickness in the generated thickness profile of the mail, wherein a first transition between the first distinct thickness and the second distinct thickness is assigned a first position value; and
- identifying a double feed condition based at lest partially in response to the detection of a second position value at a second transition between the first thickness and the second thickness.
17. The method of claim 16, further comprising relating the first position value and the second position value to a first piece of mail and a second piece of mail.
18. The method of claim 17, further comprising calculating the length of the first piece of mail and the length of the second piece of mail based at least partially on the first position value and the second position value.
19. The method of claim 18, further comprising verifying the length of the first piece of mail and the length of the second piece of mail are greater than a minimum length.
20. The method of claim 18, further comprising identifying a double feed condition based on the calculated length of the first piece of mail and the calculated length of the second piece of mail.
Type: Application
Filed: Aug 14, 2006
Publication Date: Feb 14, 2008
Inventors: Gregory Reyner (Apalachin, NY), Daniel P. McHugh (Binghamton, NY)
Application Number: 11/503,748
International Classification: B65H 5/00 (20060101); B65H 7/12 (20060101);