Patent Publication Number: US-8113458-B2

Title: Device for printing on a strip of paper in the form of a roll about a spool

Description:
The present invention relates to a device for printing a strip of paper in the form of a roll about a spool. By way of example, the device can be used in a system for issuing receipts or slips in respect of transactions or bets, or indeed in a cash register or any other apparatus or system of the same type. 
     BACKGROUND OF THE INVENTION 
     Such a printer device generally includes a housing for receiving the roll, a travel path for the strip of paper from the housing to a printer member, and a control member associated with a drive member for driving the strip of paper along the travel path. The housing is fitted with support means for supporting the roll from beneath inside the housing and for horizontally centering the roll on a vertical reference axis. Those means commonly comprise two parallel cylinders that are spaced apart from each other and that are mounted to rotate in the bottom of the housing so as to support the roll, while automatically centering it between them so as to encourage regular delivery of the strip of paper into the travel path without jolting. The control member controls the drive member to operate at a speed that is substantially constant and compatible with the speed of the printer member, with the power consumed by the drive member, and with the power consumed by the printer member. In practice, this speed is set to the maximum drive speed that the drive member can achieve when the roll is full, where this speed is always slower than the speed of the printer member during ordinary printing operations. Nevertheless, when printing dense zones that put a heavy demand on the printer member, it can happen that the control member causes the drive member to operate at a slower speed in order to limit the electricity consumption of the drive member for the benefit of the printer member. 
     It has been envisaged to increase the drive speed during ordinary printing operations by using a more powerful drive member. Unfortunately, such a drive member significantly increases the electricity consumption of the printer device and runs the risk of being under used because of the way electrical power is shared between the drive member and the printer member, with power being fed to the printer member on a priority basis. 
     OBJECT OF THE INVENTION 
     An object of the invention is to provide simple means enabling the printing speed of a printer device to be increased. 
     BRIEF DESCRIPTION OF THE INVENTION 
     To this end, the invention provides a device for printing on a strip of paper in the form of a roll about a spool, the device comprising a housing for receiving the roll, means for supporting the roll from beneath in the housing and for horizontally centering the roll substantially on a vertical reference axis, a travel path for the strip of paper from the housing to a printer member, and a control member associated with a drive member for driving the strip of paper along the travel path, the device including at least one sensor for sensing the position of the spool along the vertical reference axis, the sensor being secured to at least one side face of the housing, and being connected to the control member for controlling the drive member. 
     Thus, the sensor for sensing the position of the spool serves to detect the position of the spool along the vertical reference axis, i.e. the height of the spool relative to the support means, which corresponds to the radius of the roll. The radius of the roll is directly representative of the weight of the roll, and thus of the force that the drive member needs to deliver in order to drive the strip of paper when taking paper from the roll. This force determines the maximum drive speed. Since the weight of the roll decreases as the strip of paper is used up, it is possible to increase the drive speed. In the device of the invention, the control member thus causes the drive member to operate at a speed that is a function of the signal that is delivered thereto by the position sensor and that is representative of the radius of the roll. The sensor is positioned on a side face of the housing which constitutes a stationary portion of the printer device, thereby making it easier to install the sensor. In addition, the positioning of the sensor on the side face of the housing can limit the interference caused by the sensor when changing roll, which generally takes place through the top of the housing. In addition, if the housing is closed by a transparent cover, the lateral position of the sensor makes it completely or almost invisible from the outside when looking through the cover of the housing. The lateral positioning of the sensor, when the sensor is an optical sensor, also makes it possible to limit the quantity of interfering light that might reach the sensor. 
     In a particular embodiment, the device includes a plurality of sensors for sensing the position of the spool, the sensors being secured to at least one of said side walls of the housing, substantially along the reference axis. 
     It is then possible, by means of sensors that are simple, to detect a plurality of values for the radius of the roll, and to control the drive member as a function of said values. 
     Advantageously, the sensors are spaced apart by a distance that is shorter than a diameter of the spool. 
     Thus, there is always one sensor detecting the spool. As a result there is no need to have recourse to a memory for recording the position of the spool. 
     Also advantageously, each sensor is arranged to emit and receive an electromagnetic ray in a direction parallel to a central axis of the spool of the roll and, preferably, the spool is tubular, and each sensor comprises an emitter element secured to said side face and a receiver element secured facing it on an opposite side face of the housing. 
     The structure of the device is then particularly simple, and the use of optical sensors ensures that the device presents good reliability. 
     In a variant, the sensor is a passive sensor for sensing the presence of the spool and the spool includes a portion making it detectable by the sensor. 
     Other characteristics and advantages of the invention appear on reading the following description of a particular, non-limiting embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Reference is made to the accompanying drawing, in which: 
         FIG. 1  is a diagrammatic longitudinal section view of a device in accordance with the invention; and 
         FIG. 2  is a diagrammatic cross-section view of the device on plane II of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the figures, the printer device in accordance with the invention is for printing on a strip of paper  100  in the form of a roll  101  about a spool  102  of tubular shape and having a central axis  103 . The spool  102  in this example does not have cheek plates. 
     The printer device, given overall reference  1 , comprises a case  2  defining a housing  3  for receiving the roll  101 . The housing  3  has two side walls  4  between which means are located for supporting and horizontally centering the roll  101  substantially on a vertical reference axis. The support and centering means comprise two cylinders  6  spaced apart from each other, each having a central axis perpendicular to the side walls  4 , and both mounted in the housing  3  so as to rotate freely about their respective central axes (the vertical chain-dotted line referenced  5  is the perpendicular bisector of a line intersecting the axes of the two cylinders  6  perpendicularly). The housing has a top opening that is closed by a cover  12 , in this case a transparent cover, that is mounted to tilt on the side walls  4 . 
     The case  2  defines a travel path  7  for the strip of paper  100  from the housing  3  to a printer member  8  of known type. A driver member  9  for driving the strip of paper  100  projects into the travel path  7 . The driver member  9  is conventional and comprises a wheel rotated by an electric motor. 
     The printer member  8  and the electric motor of the drive member  9  are connected to a conventional control member  10 . Nevertheless, in this device, the control member includes a memory containing a table associating values of a parameter for controlling the speed of the drive member with signals delivered by sensors  11 , to which the control member  10  is also connected. The sensors  11  serve to sense the vertical position of the spool  102  along the reference axis  105 . In this example, the sensors  11  are active sensors arranged to emit and receive light rays in directions parallel to the central axis  103  of the spool  102  of the roll  101 . In this example, the sensors  11  operate in the visible range, but they could equally operate in the near infrared (preferably in the sensitivity range of silicon). Each sensor  11  comprises an emitter element  11 .A secured on one of the side faces  4 , and a receiver element  11 .B secured facing it on the opposite side wall  4  of the housing  3 . The emitter and receiver elements  11 .A and  11 .B are secured on the side faces  4  of the housing substantially along the reference axis  5 . The sensors  11  are spaced apart in pairs by a distance that is shorter than the diameter of the spool  102 . 
     The operation of the printer device  1  is described below. 
     When a new roll  101  is placed in the housing  3 , none of the sensors  11  is facing the spool  103 . During subsequent printing operations, the control member  10  acts by default and causes the drive member to operate at its slowest nominal speed corresponding to a full roll. 
     After a predetermined length of the strip of paper  100  has been delivered, the spool  102  comes into the vicinity of the highest sensor  11 . The light ray emitted by the corresponding emitter element  11 .A passes through the spool  102  and is detected by the facing receiver element  11 .B. The receiver element  11 .B then delivers an electrical signal that is received by the control member  10 , which causes the drive member  9  to operate at a higher speed determined on the basis of the received signal. 
     After another predetermined length of the strip of paper  100  has been delivered, the highest sensor  11  is no longer in register with the spool  102 , which has moved to become level with the sensor  11  situated immediately below it. As before, the light ray emitted by the corresponding emitter element  11 .A then passes through the spool  102  and is detected by the facing receiver element  11 .B. The receiver element  11 .B then sends an electrical signal that is received by the control member  10 , which causes the drive member to run at an even faster speed determined on the basis of the received signal. 
     When the lowest sensor  11  detects the spool  102 , the control member  10  causes the drive member  9  to run at its highest speed and also issues a warning signal, e.g. by means of an indicator lamp or an audible signal, warning that the roll  101  is coming to its end and will need to be changed. 
     Although the drive speed is determined by the control member  10  in nominal manner as a function of the signals from the sensors  11 , the control member  10  can nevertheless reduce this speed whenever the printer member  8  needs to print dense zones. 
     It should be observed that in the event of one or more of the sensors  11  failing, the control member  10  that has not received a signal causes the drive member  9  to run at its slowest speed, thus avoiding any risk of the strip of paper  100  becoming torn or jammed. 
     In addition, when the printer device is designed to receive rolls of different radii, the sensors  11  can detect the radius of the roll  101  placed in the housing  3  and cause the drive member  9  to be run at a speed that is appropriate for the radius. 
     The lowest sensor  11  can also serve to detect whether or not a roll is present. 
     Naturally, the invention is not restricted to the embodiment described but covers any variant coming within the ambit of the invention as defined by the claims. 
     In particular, the printer device may be of a structure that is different from that described and, by way of example, it may include a plurality of drive members, a scanner head, a travel path of some other shape, . . . . 
     The number of sensors may be different, and the printer device need have only one sensor. The sensors may also be spaced apart by a distance that is greater than the diameter of the spool. The sensors may also be disposed in alternation on the two side faces of the housing so as to make them easier to install. The sensors may also be slightly offset from the reference axis  105  and they may be embedded to a greater or lesser extent in the side face, or on the contrary they may project to a greater or lesser extent therefrom. 
     The sensor may be of a structure that is different from that described: for example, the sensor may comprise a single transceiver element, with detection operating as a result of the contrast that exists between the side face of the roll  101  (generally white) and of the spool (in which case there is no need for the spool to be hollow). The sensor may be active or passive and may operate on a variety of principles: optical, magnetic, thermal, . . . . The sensor may be a passive magnetic sensor if the spool includes a magnet. 
     The spool may have side cheek plates of small diameter.