Patent Publication Number: US-5290022-A

Title: Device for feeding pieces of mail, especially unsealed pieces, from a stack and a method of operating the device

Description:
The present invention concerns a device for feeding flat objects from a stack, in particular pieces of mail, especially unsealed pieces of the nature of publicity or other brochures, the device comprising a feed device for a stack of mail pieces in edgewise abutment with a registration wall, means for feeding off the stack located in front of the free face of the first mail piece on the stack and formed by a device effecting translation at a speed V 1  perpendicular to the stack, transfer means for transferring the mail piece fed off the stack at a speed V 2  and an anti double feed device disposed between these two means. 
     BACKGROUND OF THE INVENTION 
     Such known devices comprise as the means for feeding off the stack a device for translating the mail pieces, formed for example by a rotary perforated drum in which a partial vacuum is created and which entrains the first mail piece with a speed V 1 . A transfer device is located downstream from the means for feeding off the stack, this transfer device acting at a speed V 2  identical with V 1 . A device for avoiding double feeds is usually located between these two devices, being formed by a brush means or by a hinged flap. 
     As a general rule, anti double feed devices do not work efficiently. 
     This is mainly the case when the mail pieces being handled are unsealed objects, of the nature of publicity or other brochures. These brochures may be composed for example of a sheet folded into several panels or of several leaves connected together like a small booklet. Any conventional device for feeding from a stack and based on braking the mail piece coming off in a double feed, then works badly and causes buckling or tearing of the mail pieces fed off the stack. 
     The invention enables these problems in feeding off a stack and of double feeds of unsealed mail pieces to be overcome. 
     SUMMARY OF THE INVENTION 
     To this end, the anti double feed device is a retention device acting on the face of the mail piece as soon as a mail piece is taken hold of by the transfer means and whose retentive force is lower than the translation force of the transfer means, and the speed V 1  of the device effecting translation is lower than the speed V 2  of the transfer means. 
     It can be said that, in practice, the number of double feeds in which the front edges of the two mail pieces coincide is very small. 
     Such cases occur with a frequency lower than the currently-tolerated frequency of double feeds. In general, there is a gap between the front edges of the two mail pieces involved in a double feed. 
     Because of its retention device, the device retains the second mail piece in the case of a double feed and allows normal passage of the mail piece fed off the stack in the case of no double feed. The positioning, the control and the effectiveness of the devices for feeding off the stack and for retention ensure that unsealed mail pieces are not damaged. 
     This freedom from damage is based on two principles: 
     the mail piece fed off the stack is speeded up progressively, in two stages, making it possible to reduce the suddenness with which it is fed off the stack, which makes it possible to handle unsealed mail pieces. 
     the retention device is rendered operative at the instant when the front edge of the mail piece is taken hold of by the transfer device. 
     The way the system is controlled ensures that the retention device is not rendered operative so long as the front edge is not entrained by the transfer device, thereby avoiding opening a mail piece under the opposing actions of the device for feeding off the stack acting on the rear edge of the mail piece and of the retention device retaining the front part of this mail piece. 
     The double-fed mail piece, if it exists, is stopped by the retention device. There is no risk that it will be damaged because it is not in contact with the device for feeding off the stack. 
     When the separation of the two mail pieces is confirmed by a detector, said stopped mail piece is engaged in its turn by the transfer device. In a preferred embodiment, in order to control the flow of the mail pieces fed off the stack three detectors are located in the path of the mail piece fed off the stack, comprising: 
     a first detector located between the jogging edge and the retention device; 
     a second detector located near to the retention device; and 
     a third detector located in line with the point at which the transfer means effect active entrainment. 
     The device can further have at least one of the following characteristics: 
     the means for feeding off the stack is located on one side of the plane of the registration wall and the retention device is located on the other side; 
     the retention device is formed by a vacuum head; 
     the means for feeding off the stack is formed by a perforated belt guided and driven by pulleys and associated with a vacuum head located behind the belt; 
     the transfer means is formed by two endless belts associated to provide a nipping action; and 
     a low pressure chamber is located near to and upstream of the means for feeding off the stack. 
     The invention also concerns a method of operating the device for feeding off a stack, according to which: 
     1) the means for feeding off the stack is activated and a mail piece is translated, the retention device being out of action; 
     2) when the second detector detects a mail piece, the retention device is activated after a delay ensuring that the first mail piece is taken hold of by the transfer means; and 
     a) if the first detector does not detect a second mail piece, the means for feeding off the stack is reactivated after a delay and when the second detector no longer detects the mail piece, the retention device is deactivated and the cycle recommences at the point 2). 
     b) if the first detector detects a second mail piece, when the second detector no longer detects a mail piece, the retention device is deactivated and the means for feeding off the stack is reactivated after a delay and the cycle recommences at the point 2). 
     c) if the first and second detectors detect a second mail piece, when the third detector no longer detects the mail piece, the retention device is deactivated and the means for feeding off the stack is reactivated; when the third detector then detects the second mail piece, the retention device is reactivated and the means for feeding off the stack is deactivated and the cycle is recommenced at the point a), b) or c). 
     When vacuum heads are employed, the activation or deactivation of the means for feeding off the stack and of the retention device is effected by starting up or stopping their respective vacuum heads. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic, side elevational view of a feeding device forming a preferred embodiment of the invention. 
     FIG. 2 is a flow diagram of a control mode of the feeding device of FIG. 1 under conditions wherein the second mail piece has not advanced beyond the first detector. 
     FIG. 3 is a flow diagram of a control mode for the feeding device of FIG. 1 wherein a delay is initiated, prior to reactivating the feeding of a following mail piece. 
     FIG. 4 is a flow diagram of a control mode for the feeding device of FIG. 1 involving a second double-fed mail piece with a delay initiated to separate the second fed mail piece from the first fed mail piece. 
    
    
     DETAILED DESCRIPTION 
     The latter represents a device for feeding from a stack in accordance with the invention in a view from above. 
     The device comprises in essence: 
     a substantially horizontal feed device for a pile of mail pieces 1 in edgewise abutment with a substantially vertical registration wall 2; 
     means 3 for feeding the first mail piece off the stack located in front of the face of the first mail piece of the stack 1 and formed by a device effecting translation at a speed V 1  perpendicular to the stack 1; this device is constituted by a perforated endless belt 8 guided and driven by pulleys and is associated with a vacuum head 9 located on the rear side of the belt 8, over the path of the mail pieces; 
     a retention device 4 formed by a vacuum head acting on the rear face of the mail piece fed off the stack; and 
     transfer means 5 operating at a speed V 2  greater than V 1  and formed by two belts 10, 12 guided and driven by pulleys and acting by nipping the mail pieces. 
     The partial vacuum of the device 4 is such that its retentive force is lower than the translating force by the nipping of the transfer means 5. 
     The means 3 for feeding off the stack is located on one side of the plane of the jogging edge 2 and the retention device 4 and the transfer means 5 are located on the other side. 
     Detectors 6, 7, 13 formed by photoelectric sensors are located in the path of the mail piece fed off the stack and sense passage of the same. 
     The first detector 13 is situated downstream of and close to the registration wall 2. 
     The second detector 7 is situated further downstream of the registration wall 2 but preferably upstream of the vacuum head 4. 
     The third detector 6 is still further downstream, close to the nip of the belts 10, 12 of the transfer means 5. 
     The means 3 for feeding off the stack entrains the mail piece at the speed V 1  as far as the nip of the transfer means 5, where the mail piece is given the speed V 2 . By way of example, V 1  may be 2 m/s and V 2  3.2 m/s. 
     The operation of the device is controlled by means of signals of the detectors 6, 7, 13 fed to a control device such as a central processing unit CPU from which control signals are sent selectively to vacuum heads 4 and 9 as follows: 
     the first mail piece is entrained by the means 3 for feeding off the stack, the vacuum head 9 being actuated; 
     when the front edge of this mail piece is detected by the sensor 7, the vacuum head 4 is activated, after a delay, ensuring that the piece of mail fed off the stack is taken hold of by the transfer means 5; and 
     when the front edge of this mail piece is detected by the sensor 6, the vacuum head 9 is deactivated. 
     There are then three possibilities: 
     1) There is no second double-fed mail piece and no second mail piece has been advanced in front of the sensor 13 by friction or impact. 
     In this case as illustrated in FIG. 2, the rear edge of the mail piece fed off the stack ceases to obscure the sensor 13, starting a delay at the end of which the head 9 is reactivated to feed the following mail piece off the stack. 
     Moreover, the rear edge of the mail piece fed off the stack ceases to obscure the sensor 7, deactivating the head 4. 
     2) There is no second double fed mail piece but a second mail piece has advanced in front of the sensor 13 by friction or impact. 
     In this case in accordance with FIG. 3, the rear edge of the mail piece fed off the stack ceases to obscure the sensor 7, deactivating the head 4 and starting a delay, at the end of which the head 9 is reactivated for feeding the following mail piece off the stack. 
     3) A second mail piece retained by the head 4 is a double feed, obscuring the sensors 13 and 7. 
     In this case, FIG. 4, the rear edge of the mail piece fed off the stack ceases to obscure the sensor 6, starting a delay, at the end of which, the head 4 is deactivated and the head 9 is reactivated. 
     The second mail piece is then brought up to speed V 2 . Its front edge obscures the sensor 6, which has the effect of reactivating the head 4 and of deactivating the vacuum head 9. 
     The rear edge of the second mail piece enables the reactivation of the head 9 and the deactivation of the head 4, depending on the states of the sensors 13 and 7, according to the possibilities described above and applying to the third mail piece. 
     The delays referred to above, V 1  and V 2 , and the positions of the sensors 13, 7, 6 and of the devices 9, 4, 5, are all chosen to maximize the flow of the objects fed off the stack and to allow feeding off the stack with a constant space between mail pieces, regardless of their lengths. 
     A chamber 11 at a vacuum pressure is fitted beside the means 3 for feeding off the stack, upstream thereof, to pre-condition the mail pieces to be fed off the stack.