EP1450310B1 - Module for fast weight determination - Google Patents

Description

Field of the invention

The present invention relates to the specific field of mail processing. It is particularly aimed at a dynamic weighing module of a mail processing machine interposed between a mail item supply module and a franking module of these articles.

Prior art

Dynamic weighing modules intended to be implemented with franking machines are well known. The French request N ° 2,388,352 illustrates a particular example. These devices are formed of a weighing plate and drive bands for the automatic transport of mail items from one edge to another of this tray. The weigh module can be used alone but is usually inserted into a mail processing assembly between the franking module input and the output of the feeder module from which the enclosed envelopes to be franked are ejected.

In these devices, the weighing is done on the fly, that is to say during the transfer of the envelope through the weighing module, and without interrupting the means of transport of this envelope. However, when the processing rates become important, that is to say in practice greater than 8000 envelopes per hour (more than 2 envelopes per second), it appears that the weighing can not be done without reducing the speed of transport and therefore the rate of general postage.

Object and definition of the invention

The invention proposes to overcome this disadvantage with a weighing module implementing an improved weighing method for processing envelopes on the fly with particularly high rates, in particular more than 8000 envelopes per hour. A goal of the invention is to allow this treatment without significant structural changes of the weighing module.

These objects are achieved by a weighing module comprising a weighing platform incorporating a load cell and at least one motorized drive band for transporting a mail item from one edge to the other of the weighing platform, characterized in that it comprises means for detecting the format of this mail piece and processing means for calculating the weight of this mail item in a determined weight range obtained from this format.

Thus, with this predetermination of a weight interval according to the envelope format as soon as it enters the weighing module, it is possible to very significantly accelerate the measurement of the actual weight of the envelope and therefore of obtain this weight value before it leaves the weighing module and without reducing the transport speed of this envelope.

The format detecting means comprise means for detecting the length of this article of mail, means for detecting the thickness of this article of mail and means for detecting the width of this article of mail. Preferably, said mail article length detecting means includes an occultation flag, said mailpiece thickness detecting means includes a Hall effect detector and said width detecting means. mail item includes an optical sensor.

The processing means comprise an amplification chain of a measurement signal supplied by said load cell whose gain varies selectively according to the format of the mail item.

Brief description of the drawings

• la figure 1 représente une vue de dessus d'un module de pesée selon l'invention,
• la figure 2 est une vue en coupe longitudinale du module de pesée de la figure 1, et
• la figure 3 illustre la structure matérielle du circuit de commande du module de la figure 1.

Other characteristics and advantages of the present invention will emerge more clearly from the following description, given by way of non-limiting indication, with reference to the appended drawings, in which:

• the figure 1 represents a view from above of a weighing module according to the invention,
• the figure 2 is a longitudinal sectional view of the weighing module of the figure 1 , and
• the figure 3 illustrates the hardware structure of the control circuit of the module of the figure 1 .

Detailed description of a preferred embodiment

A mail processing machine conventionally comprises at least, arranged upstream downstream with respect to the direction of advance of the mail items, a mail item supply module 10, a dynamic weighing module 12 and a module 14 postage. Each of these elements is connected to the previous by a computer link 16A, 16B.

Such a machine can free mail items of different formats, from the American format No. 5 (76.2mm * 127mm) to the European format b4 (250mm * 353mm) through the European format C6 / 5 (114mm * 229mm) and this up to a determined thickness, for example 16 mm, corresponding to the height of the slot for introducing the mail items into the feeder.

In accordance with figures 1 and 2 , the weighing module 12 comprises a weighing plate 18 with its weighing cell 20 and a single belt or drive belt 22 for transporting mail items from one edge to the other of this plate, more specifically a position upstream of this plate, at an upstream transverse face 24 of the weighing plate, to a downstream position, at a downstream transverse face 26 of this plate. These belt transport means are actuated by a drive motor 28, advantageously of electric type, actuated from processing means 30, advantageously comprising a circuit microprocessor, which also manages information passing through computer links.

A device for holding mailpieces intended to press these articles on the weighing platform during their transport comprises, for example, three support elements arranged one behind the other in the direction of transport of the mailpieces and each formed by an arm for holding 32, 34, 36 at the lower end of which is fixed a flap 38, 40, 42 or any other similar flexible pressure means (brush, roller, roller) whose length is relatively large to exert a sufficient pressure force on the mail item. These support elements are mounted perpendicularly to a longitudinal vertical wall 44 referencing the mail items.

The motorized drive belt 22 has a width at least equal to that of the flap or elastic pressure means, in order to optimize the guiding and the lateral setting of the mailpieces, advantageously favored by its inclination towards the longitudinal wall of reference of a given angle with respect to the direction of transport of mail items. The value of this angle depends in particular on the length of the weighing module. For a weigh module having a weighing platform 60 cm long on which is mounted three support elements each equipped with a flap of 8 cm wide, this angle is about 2.5 °.

The weighing module also integrates a series of transport rollers 46, 48 arranged at the input of the module at its upstream transverse face 24 and intended to ensure extraction of mail items ejected by the supply module 10. According to the configuration of the mail processing machine, these rollers can sometimes be present directly at the output of the power supply module.

According to the invention, the weighing module comprises at its input means of format detection 50 connected to the means of processing and to provide him with data relating to the thickness, the length and the width of this article of mail.

These format detecting means comprise an occultation flag 52 for measuring the length of the mailpieces advantageously arranged between the drive rollers and actuated by the front and the rear end of the mail articles, an optical sensor 54 for measuring the width of mail items and a Hall effect sensor 56 for measuring the thickness of these mail items.

It is important to note that, if in the illustrated example, these format detection means are arranged in the weighing module, it is not an obligation at all and, because of the existing computer link 16A with the power module 10, it is perfectly conceivable that the corresponding data are provided directly by this power module when it has by construction.

The figure 3 shows in more detail the material structure of the processing means 30 connected to the weighing cell 20 which delivers an analog measurement signal V1 proportional to the force exerted on its internal strain gauges. The signal V1 is amplified in a variable gain amplifier 60 which delivers an amplified signal V2 which has passed through a low-pass filter 62 in order to eliminate the high-frequency components (which also acts as an anti-aliasing filter) and at the output of which is available a filtered signal V3. This filtered signal is then sampled in an analog / digital converter 64 which delivers a series of samples Vi for a microcontroller circuit 66 which is responsible for processing these digital signals to develop a weight value P which is then transmitted to the machine through the computer link 16B to develop the postage amount. This microcontroller 66 which conventionally comprises calculation means and memory means also receives, from the different detectors 52, 54, 56, information relating to the format of the envelopes to be weighed which, if necessary (a simple counter is sufficient for the measurement of length), have previously been digitized by a second analog / digital converter 68. The sampling frequency Fi of the two converters, which may be identical or not, is developed by the circuit 66 from its internal clock . Note however that the presence of the second converter 68 is of course justified only if the signals provided by the detectors are of analog type.

The processing means 30 further comprise, at its microcontroller 66, software means for determining, before determining the weight P of a mailpiece, predetermining a probable weight interval for this article of mail according to the format of this article. mail when it is entered in the weighing module 12.

Indeed, the inventors have found that the knowledge of the format of a mail item allowed to approach its weight and therefore this finding made it possible to greatly simplify the measurement of this weight by limiting the measurement range and thus accelerating this measurement. . The table below shows the dimensions (width, length) of the different envelopes used in Europe. A similar table, of course with different values, exists for envelopes issued from the United States. Envelope type width Length C7 81 mm 114 mm C7 / 6 81 mm 162 mm C6 114 mm 162 mm B6 125 mm 176 mm E6 140 mm 200 mm DL 110 mm 200 mm C6 / 5 114 mm 229 mm C5 162 mm 229 mm Italian 110 mm 230 mm B5 176 mm 250 mm E5 200 mm 280 mm 1 / 2bc4 125 mm 324 mm C4 229 mm 324 mm B4 250 mm 353 mm E4 280 mm 400 mm C4 sleeve 324 mm 229mm

For each of these types of envelopes, the inventors have established a curve increasing the evolution of the weight of this envelope according to its thickness (up to a thickness of 16 mm) when filled with documents of standard grammage and closed. The following table shows an extract of the results of these measurements, corresponding respectively to the envelopes DL, C5 and C4 pouch for four different thicknesses, the first corresponding to a maximum permissible thickness for this envelope (beyond a closure becomes difficult without rupture) and the last being relative to a minimum thickness corresponding to the insertion of a single document per envelope. Envelope type Measured thickness Weight raised 324mm * 229mm (C4p) 16 mm 750 g 8 mm 360 g 2 mm 100 g 1 document inserted 20 g 162mm * 229mm (C5) 10 mm 240 g 6 mm 145 g 2 mm 55 g 1 document inserted 10 g 110mm * 220mm (DL) 6 mm 90 g 4 mm 50 g 2 mm 30 g 1 document inserted 10 g

Thus, knowledge of the format of the mail article to be weighed makes it possible to determine a probable weight interval for this article and to adjust accordingly the gain of the variable gain amplifier 60 so as to ensure a maximum excursion for the item. analog / digital converter 64 and thus to benefit from the totality of its resolution.

The operation of the weigh module is as follows. The measurement process begins with the passage of the front edge of the mail piece, coming out of the feed module 10, on the length detector 52. This passage indeed gives the starting point for measuring the length of this article. but also its thickness by the detector 56 and its width by the detector 54. In practice, the recording sequence of the samples from the thickness and width sensors does not start immediately when the occultation flag 52 passes but a few millimeters later (for example 20 mm) to take into account the non-linear shape of this flag. This registration process continues during the advancement of the mail article on the weighing plate 18 and its transfer to the franking module 14, but over a determined distance (for example 70 mm) less than the smallest envelope length (that of the C7 format), for the measurement of this thickness and the width. Thus, these measurements of thickness and width are completed when the rear edge of the article of mail passes over the occultation flag which resumes its initial rest position, this passage putting an end to the measurement of the length of the mail article. This passage also gives the starting signal of the actual weighing, subject as previously to a precautionary offset of 20 mm for example. It can then proceed to the reading of a series of samples from the load cell 20 through the amplification chain whose gain has previously been adapted by the microcontroller 66 according to the format of the mail item to be weighed obtained from the three aforementioned measures. The sampling frequency will determine the number of samples taken from which the weight of the mail piece will be calculated. The gain adaptation of the amplification chain always allows operation of the converter with a maximum resolution, the measurement accuracy obtained is particularly high over the entire weight range of the weighing module.

Of course, the present invention can not be limited to the format detection means described in the present application and any other similar device for the desired measurement is possible. Thus, the measurement of the length of the mail items can also be performed simply by an optical measuring device and the thickness measurement of these items by a probe for example. Similarly, if the illustrated module has only one motorized drive band, it is of course possible to consider a module having several of these bands width then reduced proportionally.

Claims (6)

1. A weighing module comprising a weighing platform (18) incorporating a weighing cell (20) and a motorized drive belt (22) for transporting a mail item from one side to the other of the weighing platform, which weighing module is characterized in that it comprises means (50) for sensing the format of said mail item located downstream the weighing platform and processing means (30) for, from said format detected before the start of the weighing, determining a probable range of weights for said mail item and thus calculating the weight of said mail item within a determined range of weights obtained from said format.
2. A device according to claim 1, characterized in that said format sensing means comprise means for sensing the length of said mail item, means for sensing the thickness of said mail item, and means for sensing the width of said mail item.
3. A device according to claim 2, characterized in that said means for sensing the length of said mail item include a flag (52).
4. A device according to claim 2, characterized in that said means for sensing the thickness of said mail item include a Hall effect sensor (56).
5. A device according to claim 2, characterized in that said means for sensing the width of said mail item include an optical sensor (54).
6. A device according to claim 1, characterized in that said processing means include a system (60) for amplifying a measurement signal supplied by said weighing cell and wherein the gain of said system (60) is varied selectively as a function of the format of the mail item.

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