EP1907134A1 - A method of sorting objects, such as letter, a system for the sorting of letters and uses of the method and the system - Google Patents

A method of sorting objects, such as letter, a system for the sorting of letters and uses of the method and the system

Info

Publication number
EP1907134A1
EP1907134A1 EP06742423A EP06742423A EP1907134A1 EP 1907134 A1 EP1907134 A1 EP 1907134A1 EP 06742423 A EP06742423 A EP 06742423A EP 06742423 A EP06742423 A EP 06742423A EP 1907134 A1 EP1907134 A1 EP 1907134A1
Authority
EP
European Patent Office
Prior art keywords
rollers
letters
speed
letter
sorting
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP06742423A
Other languages
German (de)
French (fr)
Inventor
Find Jakob Madsen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ihpostal AS
Original Assignee
Ihpostal AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ihpostal AS filed Critical Ihpostal AS
Publication of EP1907134A1 publication Critical patent/EP1907134A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
    • B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
    • B07C5/16—Sorting according to weight
    • B07C5/165—Sorting according to weight of letters

Definitions

  • a method of sorting objects such as letters
  • a system for the sorting of letters uses of the method and the system
  • the invention relates to a method of sorting objects, such as letters which are advanced on a conveyor belt.
  • the invention moreover relates to a system for the sorting of objects, such as letters, which are advanced on a conveyor belt, in which the letters are sorted after having been weighed.
  • the invention relates to uses of the method and the system.
  • the letters are advanced at a great speed on conveyor belts.
  • the weighing takes place by means of mechanical scales, which puts an upper limit on how fast the letters can be advanced on the conveyor belt, since a certain amount of time elapses from a letter is placed on a scale until the result of the weighing is provided.
  • US Patent No. 5 689 092 discloses a scale for the weighing of parcels, which is based on the transfer of parcels, which are transported on a belt, to a scale which is formed by a weighing area in the form of a weighing conveyor belt, which is in contact with a rail on its lower side.
  • a scale which is formed by a weighing area in the form of a weighing conveyor belt, which is in contact with a rail on its lower side.
  • the weight may be determined by measuring the friction between the weighing conveyor belt and the rail.
  • This known measuring method cannot be applied to the weighing of very light objects, such as letters, which typically have a weight of 50 g or less.
  • an object of the invention is to provide a method, wherein let- ters, which are advanced at a great speed on a conveyor belt, may be weighed within a period of time which is short enough to avoid accumulation of the letters near the weighing area.
  • the weight of the letters is determined on the basis of the change of speed of the letters and on the basis of the change of speed of the rollers.
  • the weight of letters may be determined at a speed which is high enough to avoid accumulation of the letters in the weighing area.
  • an expedient computation-technical way of weighing the letters is that the weight of the letters is determined on the basis of the relation:
  • I is the moment of inertia of the system
  • w is the weight of the letter
  • CO 1 is the angular speed of the rollers wherein the letters and the roll- ers engage
  • ⁇ 10 is the angular speed of the rollers before the letters engage the rollers
  • v is the speed of the letters when they engage the rollers
  • v lB is the speed of the letters before they engage the rollers.
  • the relation stated in claim 2 may be implemented in terms of measurement as stated in claim 3 in that ⁇ t and ⁇ l0 are measured by an encoder arranged on the axis of the rollers, while v l0 is measured by a photosensor, and v, is determined from ⁇ t , as the speed of the letters is the same as the peripheral speed of the rollers.
  • the invention also relates to a system.
  • this system is characterized in that the weighing is performed by a scale formed by two rollers which are mounted on their respective shafts, and that the rollers with their surfaces are disposed close to each other and are adapted to move the letters between the rollers, said rollers being driven by a drive unit at a peripheral speed which is different from the speed of the letters on the conveyor belt, and that speed sensors are provided for measuring the speeds of the letters and of the conveyor rollers before the letters reach the rollers and for measuring at the moment when the letters reach the rollers, and that the drive unit is provided with a switch which disconnects the drive unit each time a letter reaches the rollers.
  • the speed sensors and the drive unit are, as stated in claim 5, that the speed sensors are formed by an encoder arranged on one of the shafts of the rollers and by a photosensor arranged above the conveyor belt, and, as stated in claim 6, that the drive unit is formed by a motor arranged on the shaft of the one roller, while the other roller is driven by the first roller by friction.
  • the invention also relates to uses. These uses are defined in claim 7 and claim 8.
  • fig. 1 shows a letter which is moved toward two rollers according to the invention
  • fig. 2 shows the letter of fig. 1 , but now introduced between the rollers,
  • fig. 3 shows the structure of a system according to the invention, seen from the front, while
  • fig. 4 shows the system of fig. 1 , seen from the left.
  • the numeral 1 designates a letter which is moved in the direction of the arrow 2 toward two rollers 3 and 4, which are driven in their respective directions, as shown by the arrows 6 and 7, so that the one roller, e.g. the roller 3, is driven by a motor (not shown), while the other roller 4 follows the first roller by friction.
  • the motor is disconnected, and the mass of the letter may be determined, as will be explained below.
  • the letter 1 which is moved toward the two rollers 3 and 4 have a constant speed.
  • the energy of the letter is:
  • the rollers 3, 4 rotate at a constant peripheral speed which is different from the speed of the letter 1.
  • the energy of the rollers is:
  • the total energy of the system is:
  • the motor is disconnected, which means that the speed of the letter is accelerated or decelerated, while the speed of the rollers decreases or increases, until the peripheral speed of the rollers and the speed of the letter are the same.
  • the constituent quantities, ⁇ t , o>to, v to may be measured, while v, is determined from co t , since the speed of the letter is equal to the peripheral speed of the rollers when the letter passes the rollers. Thus, it is possible to determine m which is the mass of the letter.
  • Figures 3 and 4 also show the letter 1 and the rollers 3, 4.
  • the roller 3 is driven by a motor 8 which is provided with a shaft 11 on which the roller 3 is arranged.
  • an encoder 9 is connected with the shaft 11 , said encoder being intended to determine the angular speeds ⁇ t , ⁇ t o of the rollers 3, 4.
  • the second roller 4 is also connected with a shaft 12 and is driven by friction from the first roller 3.
  • the numeral 10 designates a photosensor which is intended to determine the speed v r0 of the letter.
  • the set-up in fig. 3 and fig. 4 it is possible to determine the mass m of the letter.
  • a particular expedient use is the determination of the weight of letters which are around 50 g, the number of which is generally quite high in a sorting course at a postal service.
  • the system may then be adjusted such that letters weighing more than 50 g within a specified tolerance are sorted out for extra stamping, while letters weighing less than 50 g are passed on for delivery.
  • a very obvious use of the system according to the invention may be weighing of food products, such as sliced meat.

Landscapes

  • Rollers For Roller Conveyors For Transfer (AREA)
  • Sorting Of Articles (AREA)
  • Delivering By Means Of Belts And Rollers (AREA)
  • Structure Of Belt Conveyors (AREA)

Abstract

In a method and a system for the sorting of flat objects, such as letters, by weight, the letters are advanced on a conveyor belt toward two rollers which rotate in their respective directions, and which are driven by a motor, where the angular speed of the rollers is different from the speed of the letters. At the moment when a letter engages the rollers, the drive unit is disconnected, and by measurement of the speeds of the letter and of the rollers before the letter engages the rollers and measurement of the speed of the rollers when the letter engages the rollers, the weight of the letter is determined on the basis of the relation: (I) where I is the moment of inertia of the system, m is the weight of the letter, ωt is the angular speed of the rollers when the letters and the rollers engage, ωto is the angular speed of the rollers before the letters each the rollers, vt is the speed of the letters when they engage the rollers, and vto is the speed of the letters before they reach the rollers. Hereby, a sorting system is provided, where the weight of letters may be determined more rapidly than before. The invention may also be used for determining the weight of food products.

Description

A method of sorting objects, such as letters, a system for the sorting of letters and uses of the method and the system
The invention relates to a method of sorting objects, such as letters which are advanced on a conveyor belt.
The invention moreover relates to a system for the sorting of objects, such as letters, which are advanced on a conveyor belt, in which the letters are sorted after having been weighed.
Finally, the invention relates to uses of the method and the system.
In connection with machine sorting and weighing of letters, the letters are advanced at a great speed on conveyor belts. The weighing takes place by means of mechanical scales, which puts an upper limit on how fast the letters can be advanced on the conveyor belt, since a certain amount of time elapses from a letter is placed on a scale until the result of the weighing is provided.
US Patent No. 5 689 092 discloses a scale for the weighing of parcels, which is based on the transfer of parcels, which are transported on a belt, to a scale which is formed by a weighing area in the form of a weighing conveyor belt, which is in contact with a rail on its lower side. When a parcel is advanced on the weighing conveyor belt, friction occurs between the rail and the weighing conveyor belt. The weight may be determined by measuring the friction between the weighing conveyor belt and the rail.
This known measuring method cannot be applied to the weighing of very light objects, such as letters, which typically have a weight of 50 g or less.
Accordingly, an object of the invention is to provide a method, wherein let- ters, which are advanced at a great speed on a conveyor belt, may be weighed within a period of time which is short enough to avoid accumulation of the letters near the weighing area.
The object of the invention is achieved by a method of the type defined in the introductory portion of claim 1, which is characterized by comprising the following steps:
a) The letters are advanced on the conveyor belt at a speed V toward two rollers which are driven by a drive source, said rollers rotating opposite each other and each at a peripheral speed P, where P -V ≠ 0.
b) Each letter is introduced between the rollers which are disconnected from the drive unit at the moment when the letter touches the rollers.
c) The weight of the letters is determined on the basis of the change of speed of the letters and on the basis of the change of speed of the rollers.
Hereby, the weight of letters may be determined at a speed which is high enough to avoid accumulation of the letters in the weighing area.
As stated in claim 2, an expedient computation-technical way of weighing the letters is that the weight of the letters is determined on the basis of the relation:
m = — - — iϋ LL
2 2 V f — V Wo where
I is the moment of inertia of the system, w is the weight of the letter,
CO1 is the angular speed of the rollers wherein the letters and the roll- ers engage, ω10 is the angular speed of the rollers before the letters engage the rollers, v, is the speed of the letters when they engage the rollers, and vlB is the speed of the letters before they engage the rollers.
The relation stated in claim 2 may be implemented in terms of measurement as stated in claim 3 in that ωt and ωl0 are measured by an encoder arranged on the axis of the rollers, while vl0 is measured by a photosensor, and v, is determined from ωt , as the speed of the letters is the same as the peripheral speed of the rollers.
As mentioned, the invention also relates to a system.
As stated in claim 4, this system is characterized in that the weighing is performed by a scale formed by two rollers which are mounted on their respective shafts, and that the rollers with their surfaces are disposed close to each other and are adapted to move the letters between the rollers, said rollers being driven by a drive unit at a peripheral speed which is different from the speed of the letters on the conveyor belt, and that speed sensors are provided for measuring the speeds of the letters and of the conveyor rollers before the letters reach the rollers and for measuring at the moment when the letters reach the rollers, and that the drive unit is provided with a switch which disconnects the drive unit each time a letter reaches the rollers. Expedient embodiments of the speed sensors and the drive unit are, as stated in claim 5, that the speed sensors are formed by an encoder arranged on one of the shafts of the rollers and by a photosensor arranged above the conveyor belt, and, as stated in claim 6, that the drive unit is formed by a motor arranged on the shaft of the one roller, while the other roller is driven by the first roller by friction.
As mentioned, the invention also relates to uses. These uses are defined in claim 7 and claim 8.
The invention will now be explained more fully with reference to the drawing, in which
fig. 1 shows a letter which is moved toward two rollers according to the invention,
fig. 2 shows the letter of fig. 1 , but now introduced between the rollers,
fig. 3 shows the structure of a system according to the invention, seen from the front, while
fig. 4 shows the system of fig. 1 , seen from the left.
In figs. 1 and 2, the numeral 1 designates a letter which is moved in the direction of the arrow 2 toward two rollers 3 and 4, which are driven in their respective directions, as shown by the arrows 6 and 7, so that the one roller, e.g. the roller 3, is driven by a motor (not shown), while the other roller 4 follows the first roller by friction.
At the moment when the letter 1 reaches the rollers 3 and 4, the motor is disconnected, and the mass of the letter may be determined, as will be explained below.
The letter 1 which is moved toward the two rollers 3 and 4 have a constant speed. The energy of the letter is:
Letter 1
(I) E = -mv2
Kin 2
where m is the mass of the letter, and v is the speed of the letter.
The rollers 3, 4 rotate at a constant peripheral speed which is different from the speed of the letter 1. The energy of the rollers is:
where / is the moment of inertia of the rollers, and ω is the angular speed of the rollers.
The total energy of the system is:
(\ \ \\ j7 _ πRoller , τrLettεr
U") Etotal = £Km + EKin
At the moment when the rollers grip the letters, the motor is disconnected, which means that the speed of the letter is accelerated or decelerated, while the speed of the rollers decreases or increases, until the peripheral speed of the rollers and the speed of the letter are the same.
Since there is no change of the total energy, i.e. (IV) AEToul = 0 , it must apply that
(V) Δ£*.fer = -AE*?er , and thus
(Vl) ΔEr Rollerr _=÷ 1 M r „2 -^ 1 M τ^2o . and
(VII) AE -%ierrter _ = - 1 m „„y.]2 -→ „t.v.]2, hence
(IX) « = 7^ -^
The constituent quantities, ωt, o>to, vto, may be measured, while v, is determined from cot, since the speed of the letter is equal to the peripheral speed of the rollers when the letter passes the rollers. Thus, it is possible to determine m which is the mass of the letter.
Figures 3 and 4 also show the letter 1 and the rollers 3, 4. The roller 3 is driven by a motor 8 which is provided with a shaft 11 on which the roller 3 is arranged.
Further, an encoder 9 is connected with the shaft 11 , said encoder being intended to determine the angular speeds ωt, ωto of the rollers 3, 4.
The second roller 4 is also connected with a shaft 12 and is driven by friction from the first roller 3.
In addition, the numeral 10 designates a photosensor which is intended to determine the speed vr0 of the letter. Thus, with the set-up in fig. 3 and fig. 4 it is possible to determine the mass m of the letter.
A particular expedient use is the determination of the weight of letters which are around 50 g, the number of which is generally quite high in a sorting course at a postal service. The system may then be adjusted such that letters weighing more than 50 g within a specified tolerance are sorted out for extra stamping, while letters weighing less than 50 g are passed on for delivery.
Although the invention has been explained in particular in connection with the weighing of letters, the established principles apply to all types of objects where it is possible to introduce these between two rollers without the occurrence of friction between the rollers and the objects, since the equa- tions set forth above will also apply to other objects than letters, of course.
Nor do the objects have to entirely flat. They just have to be capable of being introduced between the rollers, as explained above.
A very obvious use of the system according to the invention may be weighing of food products, such as sliced meat.
Also other objects, e.g. electronic, flat semiconductor wafers may be weighed, if it is desirable to know the weight of these.

Claims

PATENT CLAIMS
1. A method of sorting objects, such as letters, which are advanced on a conveyor belt, characterized by comprising the following steps:
a) The letters are advanced on the conveyor belt at a speed V toward two rollers driven by a drive source, said rollers rotating opposite each other and each at a peripheral speed P, where P-V ≠ 0. b) Each letter is introduced between the rollers which are disconnected from the drive unit at the moment when the letter touches the rollers. c) The weight of the letters is determined on the basis of the change of speed of the letters and on the basis of the change of speed of the rollers.
2. A method according to claim 1, characterized in that the weight of the letters is determined on the basis of the relation:
where
/ is the moment of inertia of the system, m is the weight of the letter, a), is the angular speed of the rollers when the letters and the rollers engage, ωta is the angular speed of the rollers before the letters engage the rollers, v, is the speed of the letters when they engage the rollers, and vl0 is the speed of the letters before they engage the rollers.
3. A method according to claim 2, characterized in that ωt and ωl0 are measured by an encoder arranged on the axis of the rollers, while vt0 is measured by a photosensor, and v, is determined from ωt , as the speed of the letters is the same as the peripheral speed of the rollers.
4. A system for the sorting of objects, such as letters which are advanced on a conveyor belt, in which the letters are sorted after having been weighed, characterized in that the weighing is performed by a scale formed by two rollers which are mounted on their respective shafts, and that the rollers with their surfaces are disposed close to each other and are adapted to move the letters between the rollers, said rollers being driven by a drive unit at a peripheral speed which is different from the speed of the letters on the conveyor belt, and that speed sensors are provided for measuring the speeds of the letters and of the conveyor rollers before the letters reach the rollers and for measuring at the moment when the letters reach the rollers, and that the drive unit is provided with a switch which disconnects the drive unit each time a letter reaches the rollers.
5. A system according to claim 4, characterized in that the speed sensors are formed by an encoder arranged on one of the shafts of the rollers and by a photosensor arranged above the conveyor belt.
6. A system according to claim 5, characterized in that the drive unit is formed by a motor arranged on the shaft of the one roller, while the other roller is driven by the first roller by friction.
7. Use of the method according to claims 1 -3 and the system according to claims 4 - 6 for the sorting of mail.
8. Use of the method according to claims 1 - 3 and the system according to claims 4 - 6 for the weighing of food products.
EP06742423A 2005-05-17 2006-05-17 A method of sorting objects, such as letter, a system for the sorting of letters and uses of the method and the system Withdrawn EP1907134A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DK200500717A DK176214B1 (en) 2005-05-17 2005-05-17 Method for sorting objects, such as letters, letter sorting systems, and the method and system used
PCT/DK2006/000268 WO2006122557A1 (en) 2005-05-17 2006-05-17 A method of sorting objects, such as letter, a system for the sorting of letters and uses of the method and the system

Publications (1)

Publication Number Publication Date
EP1907134A1 true EP1907134A1 (en) 2008-04-09

Family

ID=36694169

Family Applications (1)

Application Number Title Priority Date Filing Date
EP06742423A Withdrawn EP1907134A1 (en) 2005-05-17 2006-05-17 A method of sorting objects, such as letter, a system for the sorting of letters and uses of the method and the system

Country Status (5)

Country Link
EP (1) EP1907134A1 (en)
JP (1) JP2008541105A (en)
CA (1) CA2609858A1 (en)
DK (1) DK176214B1 (en)
WO (1) WO2006122557A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008058543A1 (en) * 2006-11-16 2008-05-22 Ihpostal A/S Procedure for the weighing of letters; letter balance; and use of procedure and letter balance
US8126387B2 (en) * 2007-06-08 2012-02-28 Ricoh Company, Ltd. Sheet conveying device and image forming apparatus

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3648839A (en) * 1970-11-06 1972-03-14 Burroughs Corp Method and apparatus for detecting and separating out overweight letters

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2006122557A1 *

Also Published As

Publication number Publication date
DK176214B1 (en) 2007-02-12
DK200500717A (en) 2006-11-18
JP2008541105A (en) 2008-11-20
CA2609858A1 (en) 2006-11-23
WO2006122557A1 (en) 2006-11-23

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