GB2236859A - Determination of dimensions of mail items - Google Patents

Abstract

Apparatus for determining the thickness dimension of a mail item 40 works by feeding the item between a feeding surface and a roller 42 which has an outer surface 44 of piezo-resistive material so that its resistance changes in dependence upon the deformation of the surface by passage of the item and thereby provides a signal representing its thickness. In addition means are disclosed to determine other dimensions of the item either by providing the roller with a plurality of piezo-resistive segments so that the number of deformed segments indicates width of the item or by non-contact sensors. The dimension signals together with weight signals may be input to a franking meter to set the postage charge to be franked. The necessary signal processing may be performed within hollow roller shaft 52, Fig. 11, and the result fed out by an infra-red link or slip rings 45. Fig. 11 shows a roller having a plurality of coaxial segments 48 each having a piezo-resistive surface element 47 connected via electrodes 50, 51 which are insulated by spacers 53. <IMAGE>

Description

DETERMINATION OF DIMENSIONS OF MAIL ITEMS This invention relates to the determination of the dimensions of mail items and in particular to apparatus for use in conjunction with a franking machine where the postage rate for an item is dependent upon the dimensions of that item.

According to one aspect of the invention apparatus for determining a dimension of a mail item comprises a rotatable deformable roller formed of a material having a variable electrical resistivity dependent upon the extent of deformation of the material; means to feed a mail item between a feed surface and said roller whereby the roller is deformed to an extent determined by a dimension of the item in a direction perpendicular to the feed surface.

Preferably the apparatus includes means for determining a transverse dimension of the mail item.

According to a second aspect of the invention apparatus for determining at least one dimension of an item comprises means to support an item; sensing means operative to produce an electrical signal representing the presence of the item at a plurality of spaced locations when the item is supported by said support means; and means operative in response to said electrical signal to generate a signal representing a dimension of the item.

According to a third aspect of the invention apparatus for determining at least one dimension of a mail item comprises a planar surface for supporting a mail item; means to provide illumination at said planar surface; sensing means responsive to the illumination at a plurality of positions of said surface; an item supported on the surface being effective to change the illumination in the area of the item whereby the sensing means provides a determination of at least one dimension of the item.

According to another aspect of the invention apparatus for determining a dimension of a mail item comprises a planar surface for supporting a mail item; sensing means responsive to the presence of a mail item at a position along a feed path for a mail item; and means responsive to feeding of said mail item and to said sensing means to determine a dimension of the item in the direction of feed of the item.

According to a further aspect of the invention apparatus for determining a dimension of a mail item in a direction of feed of the item comprises a roller engaged by a mail item and rotatable by feeding of the mail item and means for sensing the extent of rotation of the roller.

Embodiments of the invention will now be described by way of example with reference to the drawings in which: Figure 1 shows a plan view of a sensing platform provided with a matrix of sensing devices, Figure 2 shows a side view of the sensing platform in combination with a common light source, Figure 3 is shows an electrical selection network for the sensing devices, Figure 4 shows a side view of an alternative sensing platform in which light sources are located adjacent the sensing devices, Figure 5 shows a side view of a sensing platform using a single light source and photosensitive sensor, Figure 6 shows a side view of a dimension sensing arrangement using a television camera, Figure 7 shows a plan view of an autofeed for a franking machine provided with dimension determining means, Figure 8 illustrates a device for determining length of an item, Figure 9 illustrates a roller device for determining thickness of an item, Figure 10 illustrates a modification of the roller device shown in Figure 9, Figure 11 is a part sectional view through a part of the roller of Figure 10, Figure 12 is a block diagram of a circuit for determining resistance of elements of the roller, and Figure 13 is a flow chart of a software routine for determining thickness of a mail item.

Referring first to Figure 1 and 2, a sensing platform 10 has an upper horizontal surface 11 and a plurality of sensing devices 12 are located in apertures in the surface 11. The sensing devices are arranged in matrix formation in rows and columns. The sensing devices are photoelectric devices such as phototransistors and have one electrical state when illuminated and another electrical state when not illuminated whereby electrical signals can be generated to represent the state of illumination of the devices. A light source 13 is supported above the surface, for example by means of a support stem 14 secured to the platform, and is arranged such that light from the source is received by all the sensing devices 12. Thus usually electrical signals representing an illuminated state are generated for all the sensing devices.When an item, such as a mail item comprising an envelope, is placed on the platform some of the sensing devices will be obscured by the item and will not receive light from the source 13. The sensing devices are electrically connected in a selection network shown in Figure 3. Emitter electrodes 15 of the sensing devices are connected through column selector transistors 16 to one common line 17 while collector electrodes of the devices are connected through row selector transistors 18 to a second common line 19. The column selector transistors and the row selector transistors are switched on sequentially so as to scan each sensing device in turn, the state of illumination of the devices being determined by current therethrough as each one is scanned. A determination of the number of devices not receiving light from the source represents the area of the mail item.

Alternatively if the dimensions of the item in the directions of the rows and columns of sensing devices is required to be determined, this may be accomplished by determining the number of sensing devices not receiving light in each row and in each column. The largest number of obscured devices in all the columns and in all the rows is then utilised to represent the dimensions of the item.

It will be appreciated that the sensing devices are located below the surface 11 of the platform in order that the platform presents an even surface to receive mail items and in order to protect the device from damage.

While the light source may radiate light in the visible band and the sensing devices be sensitive to light in the visible band of the spectrum, if desired the light source may radiate in the infra red band of the spectrum and the sensing devices be sensitive to infra red radiation.

In an alternative embodiment shown in Figure 4, a plurality of light sources 20 are provided, each being associated with a different one of the sensing devices 12 respectively. Each light source 20 and sensitive device pair is located below an aperture 21 in the surface 11 of the platform 10 such that when the aperture 21 is covered, by a mail item 40 supported on the platform, light radiated from the source 20 is reflected by the item and is received by the sensitive device associated with that light source. The sensitive devices are connected in a selection network as hereinbefore described with reference to Figure 3. It will be appreciated that ambient light from the environment of the platform will be received by the sensing devices. Accordingly, sensing devices relatively insensitive to light in the visible band of the spectrum are used in this embodiment.Preferably the light sources and sensitive devices operate in the infra red band of the spectrum.

Figure 5 shows another embodiment in which the surface 22 of the platform 10 is reflective and is illuminated by a light source 23 supported above the platform. A light sensitive device 24 is located adjacent the light source and means are provided to confine the field of view of the device 24 to the reflective surface 22 only. The sensitive device 24 receives light reflected from the surface 22 and the quantity of light received is represented by the electrical state of the device. When an item having a lower reflectivity than the surface 22 is placed on the surface 22, the light received by the device 24 is less than when nothing is supported on the surface 22. The area of the item on the surface 22 may be determined by comparing an electrical signal obtained from the device when the item is on the surface with an electrical signal obtained when nothing is on the surface.

Figure 6 shows an arrangement utilising a television camera 25 to scan the surface 26 of a platform 27. The surface 26 may be either highly reflective or highly absorbent to light. The area of the table viewed by the camera 25 is stored in an electronic memory of a video analysis module 28 as an array of 512 x 512 pixels. Each pixel is stored as a digital value between 0 and 255 corresponding to the brightness thereof. Pixels corresponding to areas of an item placed on the platform have a first range of digital values while those pixels corresponding to areas of the platform which are not covered by an item have a second range of digital values.

A software routine in the module 28 causes a count of the number of pixels of first range of digital values to be determined and this count represents the area of the item.

Alternatively if desired, the software routine may be arranged to determine the number of pixels having the first range of digital values in a row and in a column, the row and column numbers representing the dimensions of the item. From this determination of the dimensions, the area may be calculated.

The embodiments described hereinbefore determine the dimensions of an item when the item is placed on a platform. An embodiment will now be described with reference to Figure 7 in which the determination of dimensions of the item is carried out while the item is being fed along a platform and may be incorporated in an autofeed for feeding items to a franking machine.

The autofeed 29 comprises a platform 30 aligned with the entry end of the feed path of a franking machine 31. Mail items are fed from a stack of items 32 one at a time along the platform 30 in the direction of arrow 33 to the franking machine. An adjustable stop 34 retains the items in the stack against a rear guide 35. The adjustable stop 34 is movable transversely to the direction of feed of the items. The stop 34 is mechanically connected to a position transducer to provide an electrical signal representing the position of the stop relative to the guide 35 and hence representing the width of the items in the stack. A photosensitive device 36 is located at a position along the platform such that it responds to the leading and trailing edge of each item.The speed of feeding of the item is maintained substantially constant and hence a determination of the time lapse between sensing of the leading and trailing edges of each item provides a representation of the length of the items. The photosensitive device is located a sufficient distance upstream of the entry to the franking machine as to allow the trailing edge of the mail item to be sensed and calculation of the postage charge for that item to be carried out prior to printing of the franking impression on the item.

Instead of determining the width of items by a transducer coupled to the stop 34, a row of photosensitive devices 41 extending across the feed path of the mail items may be provided. The state of the devices is checked to determine the width of the item in a similar manner to that described in relation to the embodiments shown in Figures 1 and 4.

As an alternative to sensing the leading and trailing edges of the mail items to determine the length of the items, the length of the items may be determined by providing a roller which is rotated by engagement with mail items as they are fed. Reference is now made to Figure 8 showing a roller 37 rotatable about an axis extending transversely to the direction of feed of mail items and parallel to the platform on which the items are fed. The roller 37 is located such that its peripheral surface is spaced by a minimum small distance, less than the expected thickness of mail items, so that as a mail item is fed along the platform it engages the surface of the roller and causes rotation of the roller.The roller is rotated only for so long as a mail item engages it and hence the extent of rotation represents the length of the tem. An encoder, for example a slotted disc 38 and an electro-optic sensor 39, is mechanically coupled to the roller to provide electrical signals as the roller is rotated. These signals are counted to provide a digital value representing the length of the item, the count being reset each time the roller ceases to be rotated. It will be appreciated that the roller is resiliently mounted to accommodate items of varying and of different thickness.

The embodiments described hereinbefore enable the measurement of two linear dimensions or of an area of a mail item in a plane. It may be desired to measure the thickness of items, that is to say to measure a dimension in a direction perpendicular to the plane of the platform surface. This may be accomplished by determining the deflection of a roller, for example the roller 37, away from the platform 10 due to feeding of an item between the roller and the platform. Alternatively as illustrated in Figure 9, a roller 42 of resilient material may be provided in which the material has an electrical resistivity which varies in dependence upon the compression of the material. A suitable material is a socalled piezo resistive elastomer.The roller 42 is supported to freely rotate on a shaft extending transversely of the direction of feed of items and parallel to the platform surface, the shaft being in fixed relation to the platform. The roller has a rigid core 43 supporting a cylinder of piezo resistive elastomer 44. A slip ring 45 is provided adjacent each end of the roller.

When a mail item passes between the platform and the roller, the elastomer 44 is deformed resulting in a change in electrical resistance measured between the slip rings 45. Accordingly the magnitude of change in the electrical resistance is used to generate an electrical signal representing the thickness of the item. It will be appreciated that if the mail item is of less width than the length of the roller, only a part of the length of the roller will be deformed and hence the change in resistance between the slip rings will be dependent upon the thickness and the width of the mail item. The width of the item may be determined by the output from a row of sensors extending transversely to the direction of feed of the mail item as described hereinbefore with reference to Figure 7. Utilising this determination of width of the item and the change in resistance between the slip rings, the thickness of the item may be calculated.

A modification illustrated in Figure 10 enables a roller 46 similar to the roller of 42 of Figure 9 to be utilised to determine both width and thickness of a mail item.

Instead of determining the. electrical resistance of the piezo resistive material along the entire length of the roller, the resistance of of each of a plurality of cylindrical segments 47 of piezo resistive material extending end to end along the shaft is determined. In one construction, as shown in Figure 11, the roller 46 comprises a plurality of co-axial elements 48 each comprising a cylindrical segment 47 of piezo resistive material mounted on an electrically insulating hub 49.

The ends of the hubs 49 are provided with electrodes 50, 51 in electrical contact with the respective ends of the cylinder 47. The hubs 49 are mounted on a hollow shaft 52 through which connections to each electrode 50, 51 are taken. Adjacent ends of the elements 48 are spaced by annuli 53 of resilient electrically insulating material so as to electrically isolate adjacent electrodes 50, 51 and adjacent ends of the piezo resistive segments 47.

Referring to Figure 12, one electrode 50 of each element 48 is connected to a common supply line 54 and the other electrode 51 of each element is connected to an analogue switch 55 which switches each segment 47 into circuit in sequence and contains a sensing circuit operative to output an analogue voltage signal proportional to the resistance of the segment 47 currently switched into circuit. The analogue voltage signal output from the switch 55 is converted by an analogue to digital converter 56 to a digital signal representing the resistance of the cylinder. This digital signal is input to a microprocessor 57.

The microprocessor 57 is operated under a "measure" software module to sequence the operation of the switch 55 to enable sensing of the resistance of each one of the segments 47 in turn. Referring to the flow chart of Figure 13, the microprocessor loads a count corresponding to the number of segments 47 into a register. The value of resistance of each segment is read and stored in consecutive locations of an area of memory. A memory stores normal resistance values of the segments in a lookup table. Each value of resistance read and stored in the consecutive locations of an area of memory is compared with the corresponding normal value in the look-up table.

For each segment of which the resistance differs from the corresponding normal value, a counter is incremented.

Thus when the resistance of all the segments 47 has been compared with the corresponding normal values, the count value in the counter is equal to the number of segments 47 which have been deformed by passage of a mail item.

Segments 47 which lie outside the transverse edges of the mail item as it is being fed will not be deformed and hence the count value in the counter represents the width of the mail item. As the resistance value of each segment is compared with the normal value, the count in the register is decremented. When the count is decremented to zero, indicating that the resistance of all the segments has been compared with the normal value, the microprocessor calculates the sum of the resistive values of all the segments and subtracts this sum from the sum of normal values. In combination with the count value in the counter, representing the width of the mail item, the total change in resistance is utilised to determine thickness of the mail item.

All or part of the electronic circuit of Figure 12 connected to the segments 47 may be housed within the hollow shaft 52. Communication with other circuits may be by means of an infra red serial data link or by means of slip rings. Alternatively the circuit could be external to the roller and electrical connections to each electrode 50, 51 be made by way of slip rings.

Instead of connecting one electrode 50 of each element to a common supply line as shown in Figure 12, the segments 47 of piezo resistive material may be connected in series with adjacent electrodes 50, 51 interconnected to provide tapping points. The analogue switch would then be arranged to determine the resistance values between each pair of adjacent tapping points. With this construction the insulating annuli 53 would not be required and the piezo resistive material may be in the form of a single segment extending along the length of the roller and making electrical contact with a plurality of spaced electrodes.

The software module illustrated by the flow chart of Figure 13 may be modified by summing the resistance values of only those elements of which the resistance has changed due to passage of a mail item and subtracting this from the sum of normal resistance values of the corresponding number of piezo resistive elements.

The sensors of the dimension determining apparatus hereinbefore described provide electrical output signals providing a representation or indication of dimensions of a mail item. The apparatus may include a look-up table stored in an electronic memory which provides a relationship between a plurality of different dimensions of a mail item and the postage charges applicable to items of those dimensions. The apparatus is provided with electronic circuits, such as a microprocessor, connected to the dimension indicating signals and operative to utilise the look-up table to derive the value of postage charge appropriate for an item being sensed. It will be understood that the charges may be based upon the linear dimensions of the item or upon volume or area of an item.

Where required the electronic circuits are arranged to utilise the dimension signals and calculate the volume or area. The dimension determining apparatus may be electrically connected to a franking machine whereby signals representing a value of postage charge derived by the electronic circuits from sensing of the dimensions of the item may be input to the franking machine to set the franking machine to print that value in a franking impression to be printed by the franking machine.When the franking machine itself incorporates electronic circuits such as a microprocessor for carrying out accounting and control functions, if desired the franking machine may receive the signals representing dimensions of the item and by means of a look-up table stored in the franking machine derive a value of postage charge appropriate to an item and set the printing device of the franking machine to print that value of postage charge. A signal representing weight of an item may be input to be utilised in deriving an appropriate value of postage charge.

Hereinbefore the dimension determining apparatus has been described as using optical sensing devices responsive to illumination by light in the visible or infra-red regions of the spectrum. However it is to be understood that such sensing devices are merely described as examples of devices suitable for this purpose and that if desired other types of sensing device may be utilised. Such sensors may comprise proximity sensors which respond to change in electrical capacitance or inductance due to the presence of a mail item. For example in the embodiments illustrated in Figures 1, 2, 4 and 7 the sensors located in the platform may be capacitative or inductive proximity devices. The source or sources of illumination would not be required and would be omitted.

Claims (25)

1. Apparatus for determining a dimension of a mail item comprising a rotatable deformable roller formed of a material having a variable electrical resistivity dependent upon the extent of deformation of the material; means to feed a mail item between a feed surface and said roller whereby the roller is deformed to an extent determined by a dimension of the item in a direction perpendicular to the feed surface.

2. Apparatus as claimed in claim 1 including means responsive to change in resistance of the roller due to deformation of the roller by a mail item, said means being operative in response to magnitude of change of resistance to generate a signal representing the dimension of said item.

3. Apparatus as claimed in claim 1 or 2 including means response to a transverse dimension of the mail item.

4. Apparatus as claimed in claim 1 wherein the roller has a plurality of segments of a material having a resistivity dependent upon deformation thereof, said segments being disposed along the length of the roller and including means responsive to change in resistance of each segment whereby the change in resistance of the segments represents the dimension of the item in a direction perpendicular to the feed surface and the number of segments of which the resistance changes represents a transverse dimension of the item in a direction parallel to an axis of rotation of the roller.

5. Apparatus as claimed in claim 4 wherein the segments are defined by electrodes making electrical connection to the material at spaced locations along the roller.

6. Apparatus as claimed in claim 5 wherein the segments are physically separate and electrodes are provided to make electrical connection with opposite ends of the segments respectively.

7. Apparatus as claimed in claim 6 wherein the segments are electrically isolated from one another.

8. Apparatus as claimed in any one of claims 4 to 7 including switch means to connect the segments sequentially to the means responsive to change in resistance.

9. Apparatus as claimed in any preceding claim wherein the roller comprises a hub rotatable about an axis and the material having an electrical resistance dependent upon deformation is in the form of a cylinder extending around the hub.

10. Apparatus as claimed in any preceding claim wherein electrodes for making electrical connection to the material are carried by the hub.

11. Apparatus for determining at least one dimension of a mail item comprising a support for an item; sensing means operative to produce an electrical signal representing the presence of the item at a plurality of spaced locations when the items supported by said support; and means operative in response to said electrical signal to generate a signal representing a dimension of the item.

12. Apparatus for determining at least one dimension of a mail item comprising a planar surface for supporting a mail item; means to provide illumination at said planar surface; sensing means responsive to the illumination at a plurality of locations of said surface; an item supported on the surface being effective to change the illumination ln the area of the item whereby the sensing means provides a determination of at least one dimension of the item.

13. Apparatus as claimed in claim 12 wherein the means providing illumination is located above the surface and an item supported on the surface obscures the surface in the area of the item.

14. Apparatus as claimed in claim 12 or 13 wherein the sensing means are located at apertures in said surface.

15. Apparatus as claimed in claim 12 or 13 wherein the means providing illumination is located below the surface and an item supported on the surface reflects light to the sensing means.

16. Apparatus as claimed in claim 12 or 13 wherein the sensing means comprises a television camera.

17. Apparatus as claimed in any one of claims 11 to 16 wherein the plurality of locations of the surface lie along a row.

18. Apparatus as claimed in any one of claims 11 to 17 wherein the plurality of locations are located in an array of rows and columns.

19. Apparatus for determining a dimension of a mail item comprising a planar surface for supporting a mail item; sensing means responsive to the presence of a mail item at a location along a feed path for a mail item; and means responsive to feeding of said mail item and to said sensing means to determine a dimension of the item in the direction of feed of the item.

20. Apparatus as claimed in claim 19 wherein said means responsive to feeding of a mail is responsive to the speed of feeding of the mail item.

21. Apparatus for determining a dimension of a mail item in a direction of feed of the item comprising a roller engaged by a mail item and rotatable by feeding of the mail item and means for sensing the extent of rotation of the roller.

22. Apparatus for determining dimensions of a mail item in two mutually perpendicular directions as claimed in claim 3 and including apparatus for determining a transverse dimension as claimed in any one of claims 11 to 21.

23. Apparatus as claimed in any one of the preceding claims including means to input a signal representing one or more dimensions of a mail item or a postage charge charge dependent upon the dimension or dimensions to a franking meter to effect franking of that postage charge.

24. Apparatus as claimed in any one of claims 1 to 22 including means to input a signal representing one or more dimensions of a mail item together with a signal representing weight of the mail item, or a postage charge dependent upon the dimension or dimensions and the weight of the item, to a franking meter to effect setting of the meter to print a franking of that postage charge.

25. Apparatus for determining a dimension of an item constructed and arranged to operate substantially as hereinbefore described with reference to Figures 1, 2 and 3; Figures 1, 3 and 4; Figure 5; Figure 6; Figure 7; Figure 8; Figure 9; Figures 10, 12 and 13; or Figures 10, 11, 12 and 13.