Labelling machine and method of operation

Abstract

There is provided a labelling machine comprising a supply spool support (10) for supporting a supply spool (16) comprising label stock (18), the label stock comprising a web and a plurality of labels attached to the web, a take-up spool support (12) configured to take up a portion of the web, a motor (14) configured to advance the web along a web path from the supply spool support towards the take up spool support, a labelling peel beak (30) located along the web path and configured to peel the labels from the web as the web passes the labelling peel beak, a movable member (28), the movable member configured to contact a portion of the web and define a portion of the web path between the supply spool support and the labelling peel beak, wherein movement of the movable member changes a length of the web path, a biasing mechanism (501; 502) coupled to the movable member and configured to apply a force to the movable member, the force acting against the web to provide tension in the web, and a controller (60) configured to control the biasing mechanism to vary the force applied to the movable member so as to control tension in the web.

Description

[0001] Labelling machine and method of operation

[0002] Technical Field

[0003] The present disclosure relates to a labelling machine, and in particular to a controller configured to vary a force applied to a movable member in contact with a web so as to control tension in the web.

[0004] Background

[0005] Labelling machines typically use label stock comprising a web and a plurality of labels attached to the web and which are separable from the web. Such machines are sometimes referred to as “roll-fed self-adhesive labelling machines”.

[0006] A label stock comprising a web carrying labels is usually manufactured and supplied as a wound roll (hereinafter referred to as a spool). For a given spool, all the labels are typically the same size, within manufacturing tolerances. However, in some instances, this is not the case.

[0007] Labels are commonly used to display information relating to an article and are commonly disposed on the article such that the information is easily readable either manually or automatically. Such labels may, for example, display product information, barcodes, stock information or the like. Labels may be adhered to a product or to a container in which the product is packaged.

[0008] In the manufacturing industry, where such labels are read automatically, it is important for the information to be printed such that it is clear and positioned accurately so that an automated reader can consistently and correctly read the information.

[0009] Some known labelling machines apply pre-printed labels to an article. Other known labelling machines print information onto labels immediately before printed labels are applied to an article. Such labelling machines may be referred to as print and apply labelling machines. It is desirable to be able to advance a web of labels to be applied to an article accurately, so as to ensure that print is accurately positioned on the label and / or to ensure that the label is accurately positioned on the article.

[0010] Given that labels are often removed from the moving web by passing the label stock under tension around a labelling peel beak (sometimes referred to as a peel beak, a peel blade or a label separating beak), it is sometimes desirable to ensure that a predetermined optimum tension in the web of the label stock is maintained. In some applications, it is also desirable that the label stock can be moved at a predetermined speed of travel along a defined web path, so as to ensure that the speed at which labels are dispensed is compatible with the speed at which products or containers move along a path adjacent the device.

[0011] A known labelling machine comprises a tape drive which advances the label stock from a supply spool support to a take up spool support. The tape drive has a capstan roller of known diameter which is accurately driven to achieve desired linear movement of the label stock along the web path. This capstan roller is also often referred to as a drive roller. The label stock is often pressed against the capstan roller by a nip roller, in order to mitigate risk of slip between the capstan roller and the label stock. For the reliable running of such machines the nip / capstan mechanical arrangement is designed so as to ensure respective axes of the two rollers are substantially parallel to one another and that the pressure exerted by the nip roller (which is typically sprung loaded) is generally even across the width of the label carrying web. This often results in relatively expensive and complex mechanical arrangements, and it is often a time consuming process to load the machine with a supply spool of label stock and feed the label stock from the supply spool support to the take-up spool support, through the nip / capstan rollers, before the labelling machine is operated. This is because the nip roller has to be temporarily disengaged or removed to allow the web of the label stock to be positioned along the web path between the supply spool support and the take up spool support. The nip roller is then repositioned such that the label stock is pressed against the capstan roller by the nip roller and the web of the label stock can be moved between the spool supports by rotation of the capstan roller.

[0012] Furthermore, in such labelling machines, the take-up spool (and hence the take up spool support) itself typically needs to be driven in order to maintain adequate tension in the web, between the nip / capstan roller and the take-up spool support. If the tension is too low, the web can become wrapped around the capstan roller, causing the machine to fail, and if the tension is too high, the capstan roller can be “over-driven” by the take-up spool support, resulting in the web being fed at the wrong speed, or indeed the web snapping. The drive for the take-up spool support must also deal with the changing diameter of the take-up spool which carries the web from which labels have been removed. This is because the diameter of the take-up spool increases from an initial value where the take-up spool is empty, to a value greater than the initial value, when the supply spool is exhausted.

[0013] Known tape drives of labelling machines have mechanisms for achieving appropriate drive of the take-up spool including so-called slipping clutch arrangements. The take-up spool support may either driven by an independent drive means, such as a variable torque motor, or driven via a pulley belt and gears from a motor driving the capstan roller.

[0014] Tape drive mechanisms which rely upon capstan rollers add cost and complexity to the labelling machine, and have the disadvantages referred to above.

[0015] Another known problem associated with nip / capstan roller arrangements of the type described above is that the pressure exerted by the nip roller onto the web and against the capstan roller can cause label adhesive to “bleed” out, over time, from the edges of the label. This adhesive can eventually build up on the capstan or nip rollers. This adhesive can then cause the label stock to stick to the rollers such that it is not transported properly along the desired web path. Furthermore, it is common for labels to be accidentally removed from the web and become attached to the capstan roller or nip roller, impeding proper operation of the labelling machine.

[0016] Known labelling machines typically use a dancing arm in the web path, where movement of the dancing arm changes the web path length. Dancing arms are sprung so as to provide compliance in the web path. As such, dancing arms are able to react to changes in the web tension, changing the length of the web path to counteract changes in the web tension. A dancing arm therefore helps maintain tension in the web. However, the compliance provided by known dancing arms is not dynamically controlled. There remains a need to provide an improved labelling machine.

[0017] Summary

[0018] In a first aspect, there is provided a labelling machine comprising a supply spool support for supporting a supply spool comprising label stock, the label stock comprising a web and a plurality of labels attached to the web, a take-up spool support configured to take up a portion of the web, a first motor configured to advance the web along a web path from the supply spool support towards the take up spool support, a labelling peel beak located along the web path and configured to peel the labels from the web as the web passes the labelling peel beak, a movable member, the movable member configured to contact a portion of the web and define a portion of the web path between the supply spool support and the labelling peel beak, wherein movement of the movable member changes a length of the web path, a biasing mechanism coupled to the movable member and configured to apply a force to the movable member, the force acting against the web to provide tension in the web, and a controller configured to control the biasing mechanism to vary the force applied to the movable member so as to control tension in the web.

[0019] Advantageously, controlling the biasing mechanism to vary the force applied to the movable member so as to control tension in the web leads to better control over the web. The movable member may be configured to move between a first position and second position, the first position having an associated first web path length and the second position having an associated second web path length, the first web path length being longer than the second web path length. The movable member may be mechanically restricted such that it moves only in two directions. The movable member may pivot about a pivot point when moving between the first and second positions. That is, the movement of the movable member that changes the length of the web path may be a rotation. Alternatively, the movable member may move linearly (e.g. along a straight path). The first and second positions may be at each end of a range of motion of the movable member.

[0020] The biasing mechanism may comprise a motor and a spring. Alternatively, the biasing mechanism may comprise a motor without a spring. The force acting on the movable member by the biasing mechanism may act against the web to provide tension in the web. That is, under the force of the biasing mechanism, the movable member may push against the web to generate tension in the web. The force provided by the biasing mechanism may be reduced or increased, reducing or increasing the tension in the web. That is, the controller being configured to control the biasing mechanism to vary the force applied to the movable member so as to control tension in the web, may be so as to achieve a desired tension in the web.

[0021] The controller being configured to control the biasing mechanism to vary the force applied to the movable member so as to control tension in the web may comprise the controller being configured to determine an operational condition associated with the labelling machine and control, based on the operational condition, the biasing mechanism to vary the force applied to the movable member so as to control tension in the web.

[0022] The operational condition associated with the labelling machine may comprises any one or more of: an operating phase of the labelling machine, an acceleration condition associated with the advancement of the web, a position of the movable member, and a physical property of the web.

[0023] The operating phase may comprise a stationary phase in which the web is stationary, constant speed phase in which the web is advanced at a constant speed, and an acceleration phase in which the web is accelerated / decel erated. When in the stationary phase, or constant speed phase, the force applied by the biasing mechanism to the movable member may be a predetermined force to maintain a predetermined tension in the web. Of course, the predetermined force applied may differ when in the stationary phase to the constant speed phase, with the predetermine force for the constant speed phase being higher than the predetermined force for the stationary phase. When in the acceleration phase, the force may be varied from the predetermined force to increase or decrease web tension. For example, when the web is accelerating, the force may be decreased relative to the predetermined force and when decelerating the force may be increased relative to the predetermined force.

[0024] The controller being configured to control the biasing mechanism to vary the force applied to the movable member so as to control tension in the web may comprise the controller being configured to control the biasing mechanism to apply one or both of i) a force that varies with the position of the movable member and ii) a force that is independent of the position of the movable member.

[0025] For example, the controller may provide damping, where the force applied is independent of the position of the movable member. Additionally, the controller may provide compliance, where the force varies with position of the movable member. The controller may apply damping based on a first operational condition and compliance based on a second operational condition. The controller may apply damping based on a first position of the movable member and compliance based on a second position of the movable member.

[0026] The controller being configured to control the biasing mechanism to vary the force applied to the movable member so as to control tension in the web may comprise the controller being configured to determine an acceleration condition associated with the advancement of the web, and control the biasing mechanism so as to vary the force applied to the movable member so as to control tension in the web based on the acceleration condition associated with the advancement of the web.

[0027] The acceleration condition may be the acceleration phase of the operational condition associated with the labelling machine described above. The acceleration condition associated with the advancement of the web may relate to the acceleration / deceleration state of the web.

[0028] The acceleration condition associated with the advancement of the web may be determined in a number of ways. For example, the controller may obtain timing information from the labelling machine, the timing information relating to the operation of the labelling machine. For example, the timing information may be based on the period or speed at which items to be labelled are advanced along on a conveyor of a production line. Timing information is typically used to control the labelling machine during normal operation. For example, the operation of a labelling machine may be periodic, and so knowing the associated timing information of the periodic nature would allow the controller to determine when the web is going to be accelerated and decelerated. The controller may receive an encoder signal from an encoder coupled to the web, and may determine the acceleration condition associated with the advancement of the web based on the encoder signal. The controller may receive data indicating the state of the motor. For example, if the controller receives data that indicates that the motor is being commanded to accelerate / decelerate, or is about to be accelerated / decelerated, or has been accelerating / decelerating for a period of time, the controller can determine the acceleration condition of the web. A combination of these examples may be used by the controller to determine the acceleration condition associated with the advancement of the web.

[0029] The controller being configured to determine the acceleration condition associated with the advancement of the web and control the biasing mechanism so as to vary the force applied to the movable member so as to control tension in the web based on the acceleration condition associated with the advancement of the web may comprises, the controller being configured to determine that the web is i) going to be accelerated along the web path in a first predetermined time, ii) is presently being accelerated along the web path, or iii) has been undergoing acceleration along the web path for a second predetermined time, and in response reduce the force applied to the movable member by the biasing mechanism.

[0030] A reduction in the force applied to the movable member by the biasing mechanism may reduce the resistance to the path length decreasing. That is, the movable member experiences less resistance to move in a direction so as to decrease the web path length. This results in lower web tension which then leads to reduced friction around the labelling peel beak, thus assisting acceleration of the web by reducing the load on the motor. The reduction in force may be a reduction from a predetermined force. For example, the predetermined force may be a force that is applied when the web is stationary, or is travelling at a constant speed.

[0031] Determining an acceleration condition associated with the advancement of the web may comprise determining that the web is i) about to undergo acceleration in a first predetermined time, ii) is starting to accelerate, or iii) has been accelerating for a second predetermined time. That is, the force may be reduced as soon as the controller determines that the web is accelerating, or may instead be reduced prior to, or after, acceleration starting. For example, the controller may determine that the web will undergo acceleration in the first predetermined time, and may reduce the force in response. As such, when the web does undergo acceleration, the force will already have been reduced. The first and second predetermined times may depend on the specific arrangement of the labeller and of the particular web being used. A typical predetermined time may be in the region of 5 ms - 50 ms. Of course, other predetermined times are possible. The predetermined time may change as the supply spool diameter changes in order to account for reduction in inertia of the spool as the diameter is reduced. The predetermined time may also depend on the width of the web being used.

[0032] The first and second predetermined times may be the same or may be different.

[0033] The controller being configured to determine the acceleration condition associated with the advancement of the web and control the biasing mechanism so as to vary the force applied to the movable member based on the condition associated with the advancement of the web may comprise the controller being configured to determine that the web is i) going to be decelerated along the web path in a third predetermined time, ii) is presently being decelerated along the web path, or iii) has been undergoing deceleration along the web path for a fourth predetermined time, and in response increase the force applied to the movable member by the biasing mechanism.

[0034] An increase in force applied to the movable member by the biasing mechanism may increase the resistance to the path length decreasing. That is, the movable member may experience more resistance to move in a direction so as to decrease the web path length. This results in higher web tension which then leads to increased friction around the labelling peel beak, thus assisting deceleration of the label web. The increase in force may be an increase from the predetermined force applied when the web is stationary, or is travelling at a constant speed.

[0035] As noted above, determining an acceleration condition associated with the advancement of the web may comprise determining that the web is i) about to undergo deceleration in the third predetermined time, ii) is starting to decelerate, or iii) has been decelerating for the fourth predetermined time. That is, the force may be increased as soon as the controller determines that the web is decelerating, or may instead be increased prior to, or after, deceleration starting. For example, the controller may determine that the web will undergo deceleration in the third predetermined time and may increase the force in response. As such, when the web does undergo deceleration, the force will already have been increased.

[0036] As with the first and second predetermined times, the third and fourth predetermined times may depend on the specific arrangement of the labeller and of the particular web being used and a typical predetermined time may be in the region of 5 ms - 50 ms. Of course, other predetermined times are possible. The predetermined time may change as the supply spool diameter changes in order to account for reduction in inertia of the spool as the diameter is reduced. The predetermined time may also depend on the width of the web being used.

[0037] The third and fourth predetermined times may be the same or may be different. Furthermore, the third and fourth times may be the same as the first and second predetermined times or may be different.

[0038] The biasing mechanism comprises a second motor. The biasing mechanism may only comprise a second motor.

[0039] The force may comprise a first force component and a second force component. The biasing mechanism may comprise a first biasing member configured to apply the first force component to the movable member, a second biasing member configured to apply the second force component to the movable member and the controller being configured to control the biasing mechanism to vary the force applied to the movable member so as to control tension in the web may comprise the controller being configured to control the second biasing member so as to vary the second force component.

[0040] That is, the force acting on the movable member by the biasing mechanism may be provided by a combination of the first force component and second force component, where the second force component is controllable. That is, the controller can directly control the second force component so as to vary the force acting on the movable member.

[0041] The first biasing member may comprise a spring. The second biasing member may comprise a second motor. The term “second” is used here merely to differentiate this motor from the first mentioned motor that advances the web along the web path.

[0042] For example, the second motor may be a torque control motor. The second motor may be an electric motor such as a DC motor, or a stepper motor operating in a closed-loop field controlled manner.

[0043] The motor may be a stepper motor, wherein the labelling machine may further comprise a sensor configured to generate a signal indicative of an angular position of an output shaft of the stepper motor; and the controller may further be configured to generate control signals for the stepper motor so as to cause a predetermined torque to be generated by the stepper motor, the control signals being at least partially based upon an output of the sensor.

[0044] The control signals for the stepper motor may be arranged to cause a magnetic field to be generated by windings of the stepper motor, a field angle being defined between an angular position of the output shaft of the stepper motor, and an orientation of the generated magnetic field, and the control signals may be arranged to cause the field angle to have a predetermined value, and to cause the magnetic field to have a predetermined magnitude.

[0045] The controller may be further configured to vary the control signals based at least partially upon a torque demand signal.

[0046] By use of an encoder associated with the output shaft of the stepper motor, it is possible to provide accurate positional information regarding the actual rotor position, thereby allowing a motor field angle to be accurately controlled. Control of the field angle in this way allows a maximum output torque to be generated by the motor for a given current level, while also reducing the risk that a stepper motor will stall. In this way, it is possible to provide a smaller stepper motor (i.e. one having a smaller maximum torque capacity), and a correspondingly smaller power supply for a given torque requirement. That is, rather than having to provide an excess torque capacity, so as to prevent against stall conditions (and the associated loss of motor control), the motor can be controlled in a closed-loop field controlled manner to generate a maximum torque at all times, without any risk that the motor will stall. The signal indicative of the angular position of the motor output shaft can thus be used to update the control signals supplied to the motor, so as to cause the magnetic field to rotate, thereby maintaining the predetermined (and optimal) field angle.

[0047] The control of a stepper motor using positional feedback allows the commutation of currents supplied to the motor to be controlled so as to cause the magnetic field generated by the energised windings of the motor to have an orientation which causes a predetermined torque to be generated. Current feedback may also be used so as to allow the controller to cause that a desired current to flow in the motor windings. Thus, there are two parameters which can be controlled (field orientation and current magnitude) in order to achieve a directed motor output characteristic (e.g. generated torque).

[0048] By controlling (and varying) both of the orientation and magnitude of the magnitude of the magnetic field generated by a stepper motor, it is possible achieve precise and adaptable control of the motor. This enables the motor output torque to be controlled both accurately and efficiently so as to be a required value. For example, where high precision is needed, the field angle may be the primary controlled variable, whereas where high torque is needed, the field magnitude may be the primary controlled variable.

[0049] The control signals for the stepper motor may comprise control signals supplied to windings of the stepper motor.

[0050] The control signals may be generated based upon the signal indicative of an angular position of the output shaft of the stepper motor so as to cause the field angle to have the predetermined value.

[0051] That is, the magnetic field may be controlled as to maintain a predetermined angle between the field orientation and the actual rotor position. Thus, the actual rotor position may be used to orient the field so as to cause the determined torque to be generated. For example, a stepper motor may generate a maximum torque for a given magnitude of winding current when the field angle has a predetermined value (e.g. 90 electrical degrees). The generated magnetic field may have a predetermined angular orientation with respect to a housing of the stepper motor. The predetermined angular orientation with respect to the housing of the stepper motor may be varied in order to maintain the value of the field angle at the predetermined value. That is, the motor housing may be physically stationary (with respect to the body of the apparatus), with the generated magnetic field at any point in time having a predetermined angular orientation with respect to the housing. However, the predetermined angular orientation may be controlled as required (for example based upon rotation of the rotor) so as to maintain the value of the field angle at the predetermined value.

[0052] The control signals for the stepper motor may be generated so as to cause a predetermined torque to be generated by the stepper motor. Generating the control signals for the stepper motor so as to cause a predetermined torque to be generated by the stepper motor may comprise generating control signals for the stepper motor so as to cause a predetermined magnitude of current to flow in windings of the stepper motor. By causing the predetermined magnitude of current to flow in windings of the stepper motor the magnetic field is caused to have the predetermined magnitude.

[0053] The controller being configured to control the second biasing member so as to vary the second force component may comprise the controller being configured to apply the second force component so as to act in an opposite direction to the first force component to reduce the force applied to the movable member by the biasing mechanism. That is, the net force provided by the biasing mechanism is reduced, where the net force is equal to the sum of the magnitudes of the first and second force components.

[0054] That is, the force provided by the second motor may act to oppose the force provided by the spring. Applying the second force component so as to act in an opposite direction to the first force component may increase the compliance in the web path.

[0055] The controller being configured to control the second biasing member so as to vary the second force component may comprise the controller being configured to apply the second force component so as to act in a same direction as the first force component to increase the force applied to the movable member by the biasing mechanism. That is, the net force provided by the biasing mechanism is increased. That is, the force provided by the second motor may act with the force provided by the spring. Applying the second force component so as to act in the same direction to the first force component may decrease the compliance in the web path.

[0056] The controller being configured to control the biasing mechanism so as to vary the force applied to the movable member so as to control tension in the web may further comprise the controller being configured to, determine a position of the movable member, and control the biasing mechanism so as to vary the force applied to the movable member based on the acceleration condition associated with the advancement of the web and the position of the movable member.

[0057] For example, the controller being configured to control the second biasing member so as to vary the second force component may comprise the controller being configured to determine a position of the movable member and control the second biasing member so as to vary the second force component based on the position of the movable member.

[0058] That is, the second force component may be a function of the position of the movable member, as well as a function of the acceleration condition of the web. Varying the second force component as a function of position of the movable member enables the controller to effectively change a spring constant of the biasing mechanism. The position of the movable member may be a position of the movable member relative to a predetermined position, such as a home position of the movable member. The home position may be a position in which the web path length is at its shortest.

[0059] The motor may be coupled to the take up spool, and configured to rotate the take up spool to advance the web along the web path.

[0060] That is, the labelling machine does not rely on a capstan roller driven system. Accelerating the label web using the take up spool means that complex capstan roller driven systems are not required. However, improved control over the acceleration / deceleration of the web may be required when driving the web using the take up spool due to, for example, the variability in the mass of the take-up spool during use. The controller configured to control the biasing mechanism to vary the force applied to the movable member so as to control tension in the web provides such improved control.

[0061] In a second aspect, there is provided a method of operating a labelling machine, the labelling machine comprising: a supply spool support for supporting a supply spool comprising label stock, the label stock comprising a web and a plurality of labels attached to the web; a take-up spool support configured to take up a portion of the web; a motor; a labelling peel beak located along the web path; a movable member; a biasing mechanism coupled to the movable member; a controller; and wherein the method comprises: the motor advancing the web along a web path from the supply spool support towards the take up spool support; the labelling peel beak peeling the labels from the web as the web passes the labelling peel beak; the movable member contacting a portion of the web and defining a portion of the web path between the supply spool support and the labelling peel beak; the biasing mechanism applying a force to the movable member, the force acting against the web to provide tension in the web; and the controller controlling the biasing mechanism to vary the force applied to the movable member so as to control tension in the web.

[0062] The controller controlling the biasing mechanism to vary the force applied to the movable member so as to control tension in the web may comprise the controller determining an acceleration condition associated with the advancement of the web and controlling the biasing mechanism so as to vary the force applied to the movable member so as to control tension in the web based on the acceleration condition associated with the advancement of the web.

[0063] The controller controlling the biasing mechanism to vary the force applied to the movable member so as to control tension in the web may comprise the controller determining an operational condition associated with the labelling machine and controlling, based on the operational condition, the biasing mechanism to vary the force applied to the movable member so as to control tension in the web.

[0064] The controller controlling the biasing mechanism to vary the force applied to the movable member so as to control tension in the web may comprise the controller controlling the biasing mechanism to apply one or both of i) a force that varies with the position of the movable member and ii) a force that is independent of the position of the movable member.

[0065] The controller determining the acceleration condition associated with the advancement of the web and controlling the biasing mechanism to vary the force applied to the movable member so as to control tension in the web based on the acceleration condition associated with the advancement of the web may comprise, the controller: determining that the web is i) going to be accelerated along the web path in a first predetermined time, ii) is presently being accelerated along the web path, or iii) has been undergoing acceleration along the web path for a second predetermined time, and in response reducing the force applied to the movable member by the biasing mechanism.

[0066] The controller determining the acceleration condition associated with the advancement of the web and controlling the biasing mechanism so as to vary the force applied to the movable member based on the acceleration condition associated with the advancement of the web may comprise, the controller: determining that the web is i) going to be decelerated along the web path in a third predetermined time, ii) is presently being decelerated along the web path, or iii) has been undergoing deceleration along the web path for a fourth predetermined time, and in response increasing the force applied to the movable member by the biasing mechanism.

[0067] The biasing mechanism comprises a second motor.

[0068] The biasing mechanism may comprise a first biasing member configured to apply a first force to the movable member, a second biasing member configured to apply a second force to the movable member, wherein the controller controlling the biasing mechanism so as to vary the force applied to the movable member so as to control tension in the web may comprise the controller controlling the second biasing member so as to vary the second force component.

[0069] The first biasing member may comprise a spring.

[0070] The second biasing member may comprise a second motor. The second motor may be a stepper motor and the labelling machine may further comprise a sensor, the method further comprising: generating, by the sensor, a signal indicative of an angular position of an output shaft of the stepper motor; and generating, by the controller, control signals for the stepper motor so as to cause a predetermined torque to be generated by the stepper motor; the control signals being at least partially based upon an output of the sensor.

[0071] The control signals for the stepper motor may be arranged to cause a magnetic field to be generated by windings of the stepper motor, a field angle being defined between an angular position of the output shaft of the stepper motor, and an orientation of the generated magnetic field, and the control signals may be arranged to cause the field angle to have a predetermined value, and to cause the magnetic field to have a predetermined magnitude. The controller may be further configured to vary the control signals based at least partially upon a torque demand signal.

[0072] The controller controlling the second biasing member so as to vary the second force component may comprise the controller applying the second force component so as to act in an opposite direction to the first force component to reduce the force applied to the movable member.

[0073] The controller controlling the second biasing member so as to vary the second force component may comprise the controller applying the second force component so as to act in a same direction as the first force component to increase the force applied to the movable member.

[0074] The controller controlling the biasing mechanism to force applied to the movable member so as to control tension in the web may further comprise the controller determining a position of the movable member, and controlling the biasing mechanism so as to vary the force applied to the movable member so as to control tension in the web based on the acceleration condition associated with the advancement of the web and the position of the movable member.

[0075] The motor may be coupled to the take up spool, and wherein the motor advancing the web along the web path from the supply spool support towards the take up spool support comprises the motor rotating the take up spool to advance the web along the web path from the supply spool support towards the take up spool support.

[0076] In a third aspect there is provided a computer readable medium comprising computer readable instructions which when executed by a processor, caused the processor to carry out the method of the second aspect.

[0077] For example, the instructions can be executed by the controller to cause the controller to control the biasing mechanism to vary the force applied to the movable member so as to control tension in the web.

[0078] Any features of the labelling machine of the first aspect may be combined with the method of the second aspect.

[0079] Brief description of drawings

[0080] Figure 1 shows a schematic side elevation of a labelling machine;

[0081] Figure 2 shows a schematic side elevation of a labelling machine;

[0082] Figure 3 shows an enlarged view of a portion of a labelling machine without a supply spool installed;

[0083] Figure 4 shows an enlarged view of a portion of the labelling machine of Figure 3 with a supply spool installed;

[0084] Figure 5 shows an enlarged rear view of a portion of the labelling machine of Figure 3;

[0085] Figure 6 shows an enlarged perspective view of the labelling machine of Figure 3;

[0086] Figure 7 shows a schematic of a controller suitable for use with a stepper motor;

[0087] Figure 8 shows a plot of web velocity against time without a controllable biasing mechanism;

[0088] Figure 9 shows a plot of web velocity against time with a controllable biasing mechanism;

[0089] Figure 10 shows a flow chart of a method; Figure 11 shows an enlarged view of a portion of an alternative labelling machine without a supply spool installed; and

[0090] Figure 12 shows a schematic of a controller suitable for use with a labelling machine.

[0091] Detailed description

[0092] Figures 1 and 2 show schematic side views of portions of two different types of labelling machine, such as that described in WO2014 / 072728 A1, which is hereby incorporated by reference. Figure 1 shows a labelling machine with no integrated printer and Figure 2 shows a labelling machine with an integrated printer.

[0093] The labelling machines shown in Figures 1 and 2 both include a supply spool support 10 and a take up spool support 12. The supply spool support 10 and take up spool support 12 are both mounted for rotation about respective axes A and B. In the labelling machines shown in Figures 1 and 2 the axes A and B are substantially parallel to one another; however, in some examples this may not be the case. The take up spool is connected to a motor 14 such that the motor 14 can be powered in order to rotate the take up spool 12 about the axis B. In the labelling machines shown in Figures 1 and 2, the motor 14 is connected to the take up spool support 12 via a belt (not shown).

[0094] However, it will be appreciated that any appropriate linkage may be used to connect the motor 14 to the take up spool support 12. For example, while in the described example the belt will provide a fixed transmission ratio between rotation of the motor shaft and rotation of the take up spool support, in other examples a linkage providing a variable transmission ratio (such as a gearbox) may be provided. Indeed, the take up spool support 12 may be directly driven by the motor 14. By directly driven it is meant that the spool support may be mounted co-axially with the shaft of the motor 14, that is the shaft of the motor 14 may extend along the axis B. In the case where the take up spool support 12 is directly driven by the motor 14, the take up spool support may be mounted to a motor spindle of the motor 14. This arrangement is quite different from other arrangements which may use capstan rollers to contact the outside circumference of a spool or a spool support in order to rotate the spool and / or spool support.

[0095] In the labelling machine shown in Figures 1 and 2 the motor 14 is a stepper motor. An example of a suitable stepper motor is a 34H318E50B stepper motor produced by Portescap, USA. An example of a suitable belt which connects the motor 14 to the take up spool support 12 is a synchroflex timing belt. The gearing ratio for the belt drive may be 4:1 whereby the motor revolves four times for every revolution of the take up spool support. It will be appreciated that in other examples any appropriate gearing ratio for the belt drive may be used.

[0096] In this case the stepper motor is capable of being controlled such that it can execute substantially equal angular movements per complete rotation of the stepper motor. These substantially equal angular movements may be referred to as micro-steps. Each micro-step is equivalent to a rotation of about 0.225° or about 0.00392 radians. In this case, the stepper motor has 200 steps per revolution, but the stepper motor is controlled to produce 8 micro-steps per step, such that the number of micro-steps per revolution is 1600. Because the belt drive gearing ratio is 4 to 1 , the number of micro steps of the motor per revolution of the take up spool support is 6400. Stepper motors are generally driven by a stepper motor driver. In the case of the motor and control arrangement described above, if the stepper motor driver is commanded to advance one step, the stepper motor driver will provide a signal to the stepper motor which causes the stepper motor to rotate by one micro-step (i.e. about 0.225°). It will be appreciated that the stepper motor may undertake any appropriate number of steps per complete rotation of the stepper motor, and the stepper motor may be controlled to produce any appropriate number of micro-steps per step of the stepper motor. Furthermore, the belt drive gearing ratio may be chosen such that the number of micro steps of the motor per revolution of the take up spool support is any appropriate desired number.

[0097] While the term ‘step’ is sometimes used to denote a physical property of a stepper motor, in the present description, the term ‘step’ is used to denote any desired angular movement of the stepper motor, for example a micro-step.

[0098] Stepper motors are an example of a class of motors referred to as position-controlled motors. A position-controlled motor is a motor controlled by a demanded output rotary position. That is, the output position may be varied on demand, or the output rotational velocity may be varied by control of the speed at which the demanded output rotary position changes. A stepper motor is an open loop position-controlled motor. That is, a stepper motor is supplied with an input signal relating to a demanded rotation position or rotational velocity and the stepper motor is driven to achieve the demanded position or velocity. Some position-controlled motors are provided with an encoder providing a feedback signal indicative of the actual position or velocity of the motor. The feedback signal may be used to generate an error signal by comparison with the demanded output rotary position (or velocity), the error signal being used to drive the motor to minimise the error. A stepper motor provided with an encoder in this manner may form part of a closed loop position-controlled motor.

[0099] An alternative form of closed loop position-controlled motor comprises a DC motor provided with an encoder. The output from the encoder provides a feedback signal from which an error signal can be generated when the feedback signal is compared to a demanded output rotary position (or velocity), the error signal being used to drive the motor to minimise the error. A DC motor which is not provided with an encoder is not a position-controlled motor.

[0100] It will be appreciated that in a labelling machine other than those shown in Figures 1 and 2, the motor may take any convenient form. For example, the motor may be any appropriate open or closed loop position-controlled motor.

[0101] When the labelling machines shown in Figures 1 and 2 are in use, a supply spool of label stock may be mounted to the supply spool support such that the supply spool support 10 supports the supply spool. The label machine shown in Figure 1 does not have a supply spool mounted to the supply spool support 10. However, the labelling machine shown in Figure 2 does have a supply spool 16 mounted to the supply spool support 10. The supply spool 16 is mounted to the supply spool support 10 such that the supply spool 16 co-rotates with the supply spool support 10. The supply spool comprise label stock 18, where the label stock 18 comprises a web and a plurality of labels attached to the web.

[0102] As can be seen best in Figure 2, in use, web of the label stock 18 extends between the supply spool support 10 (and in particular the supply spool 16 mounted to the supply spool support 10) and the take up spool support 12. A web path 20 is defined between the supply spool support 10 and take up spool support 12 by various components and, in use, the web of the label stock is transported along the web path 20. In the labelling machines shown in Figures 1 and 2, first, second and third rollers (22, 24 and 26) define the web path 20 between the supply spool support 10 and take up spool support 12. It will be appreciated that components other than rollers may be used to define the web path 20. Suitable components may be those which impart only a small friction force to the web of the label stock when the web stock contacts it.

[0103] The web path 20 is also defined by a dancing arm 28 and a labelling peel beak 30. The dancing arm 28 includes a dancing arm roller 32 mounted at one end of the dancing arm 28.

[0104] In use, the web of the label stock 18 extends along the web path 20 from the supply spool support 10 (and in particular from the supply spool 16) around the first roller 22, around the dancing arm roller 32, around the second roller 24, around the labelling peel beak 30, around the third roller 26 and is wound onto the take up spool support 12 to form a take up spool 34. It will be appreciated that any appropriate number of rollers (or any other appropriate components) may be used to define a desired shape / length of web path 20.

[0105] The dancing arm 28 is a movable member which is rotatable about axis A. That is to say, in the labelling machines shown in Figures 1 and 2, the axis of rotation of the dancing arm 38 is coaxial with the axis of rotation of the supply spool support 10 (and the supply spool 16). In other examples this need not be the case. For example, the dancing arm 28 may rotate about an axis which is spaced from the axis A of rotation of the supply spool support 10 (and supply spool 16 if attached).

[0106] It will also be appreciated that in the labelling machine shown in Figures 1 and 2, the dancing arm 28 is a movable member which defines the web path 20 and movement of the dancing arm 28 changes the length of the web path between the supply spool support 10 and take up spool support 12. It will be appreciated that any other appropriate movable member may be used, providing that movement of the movable member changes the length of the web path between the supply spool support and take up spool support.

[0107] The labelling machine shown in Figure 2 includes a printer 36 (however, as previously discussed, other examples need not include a printer, such as the example shown in Figure 1). The printer in this case is a thermal transfer printer. However, it will be appreciated that the printer may include any appropriate type of printer, for example, an inkjet printer, a thermal printer or a laser marking system. The printer 36 includes a ribbon supply spool support 38, a ribbon take up spool support 40, a print head 42 and a ribbon guide member 44. In use, a spool of printer ribbon is mounted to the ribbon supply spool support 38, such that said spool of printer ribbon constitutes a supply spool 46 of printer ribbon which is supported by the ribbon supply spool support 38.

[0108] In use, print ribbon from the supply spool 46 passes along a print ribbon path past the print head 42 and is wound on to the ribbon take up spool support 40 so as to form a take up spool 48. In order for print ribbon to be transported from the ribbon supply spool support 38 to the ribbon take up spool support 40, at least the ribbon take up spool support 40 is connected to a motor such that the motor can rotate the ribbon take up spool support 40.

[0109] Because the printer 36 shown in Figure 2 is a thermal transfer printer, the print ribbon is thermally sensitive such that, as the print ribbon passes the print head 42, at least a portion of the print head 42 can be selectively energised to heat a desired portion of the print ribbon and transfer ink from that portion of the print ribbon to an adjacent substrate. In this case the adjacent substrate is a label that forms part of the label stock 18. During operation of the printer 36, the guide block 44 comprises guide rollers which help to guide the print ribbon as it is transported from the ribbon supply spool support 38 to the ribbon take up spool support 40.

[0110] The labelling machine may comprise one or more encoders which are capable of outputting a sensor signal which is indicative of an amount of movement of the label web along the label web path. For example, an encoder which measures the rotation of a roller which contacts the label web may be used. Alternatively, a periodic property of the label stock may be used to determine an amount of movement of the label web along the label web path. In such examples, the encoder may measure a property of the label stock which is periodic in order to provide a sensor signal which is indicative of an amount of movement of a label web along the label web path. For example, the encoder may use a gap sensor. As the label web advances along the label web path, the gap sensor will measure a periodic property of the label web (i.e. periodic electromagnetic transmission coefficient of the label web). If a pitch length of the labels (i.e. the distance between equivalent portions of adjacent labels) is known by a controller of the labelling machine, then the controller can use this information to calculate an amount of movement of the label web along the label web path based upon the periodic encoder signal.

[0111] The label stock which is used by either of the labelling machines shown in Figures 1 and 2 comprises a web and a plurality of labels attached to the web. The labels attached to the web are separable from the web. The labelling peel beak 30 is configured such that, during operation of either of the labelling machines shown in Figures 1 and 2, as the label stock 18 is transported along the web path 20 past the labelling peel beak 30, the labelling peel beak 30 separates a passing label from the web.

[0112] The separated label may then be attached to a desired article. An example of such a desired article is an item passing on a conveyor (not shown) of a production line. However, it will be appreciated that the desired article may be any appropriate article. In the case of the labelling machine shown in Figure 2, it will be appreciated that, prior to the label being attached to a desired article, the printer 36 may print a desired image on the label. The printing may occur prior to the labelling peel beak 30 separating the label from the web of the label stock, or the printing of the image may occur after the labelling peel beak 30 separates the label from the web of the label stock.

[0113] During operation of the labelling machines shown in Figures 1 and 2 the motor 14 is energised to rotate the take up spool support 12 about its axis B. As this is done, the take up spool support 12 winds label stock 18 onto the take up spool support 12 to form a take up spool 34. The take up spool 34 will include the web of the label stock. Any labels separated from the web of the label stock as they pass the labelling peel beak 30 will not form part of the take up spool 34. The labelling peel beak 30 may be configured to selectively separate labels from the web. In this case, any labels which are not separated from the web of the label stock by the labelling peel beak 30 will be wound onto the take up spool support 12 and therefore form part of the take up spool 34.

[0114] The winding of the label stock 18 (and in particular the web of the label stock) onto the take up spool support 12 will cause the label stock 18 to move along the web path 20 in the direction indicated by arrows C (Figure 2). The winding of the web of the label stock onto the take up spool support 12 causes label stock to be paid out from the supply spool 16 which is supported by the supply spool support 10.

[0115] This arrangement, whereby the take up spool support 12 is driven so as to transport the label stock in the direction C of label stock transport, and where the supply spool support 10 is not driven may be referred to as a pull-drag system. This is because, in use, the supply spool support 10 provides some resistance (or drag) to the movement of label web so as to provide tension in the label web. In this case friction within the system provides the drag. For example, the friction may include the friction between the supply spool support and the means which supports the supply spool support for rotation. Drag may also be provided by the inertia of the supply spool. In other examples the drag in a pull-drag system may be actively controlled. For example, a DC motor may be attached to the to the supply spool support and may be energised in a direction which is opposite to the direction in which the supply spool support rotates due to label stock being wound off the supply spool support and on to the take up spool support. In this case, the amount of drag that the DC motor provides to the system can be controlled by controlling the current supplied to the motor and therefore the torque applied by the motor.

[0116] In other examples, the supply spool support 10 may be driven so that, in use, it rotates the supported supply spool 16. The supply spool support 10 may be driven for rotation in a direction which opposes movement of the label stock in the direction C of label stock transport (which is effected by the rotation of the take up spool support 12). This kind of arrangement is also referred to as a pull-drag system.

[0117] In other examples the supply spool support 10 may be driven such that it is rotated by a motor in a direction which is complementary to movement of the label stock in the direction C of label stock transport (which is effected by rotation of the take up spool support 12). This type of arrangement may be referred to as a push-pull system. It will be appreciated that in examples of the labelling machine which include a driven supply spool support 10, the supply spool support 10 may be driven by any appropriate motor. Examples of such motors include a DC motor or a position-controlled motor such as, for example, a stepper motor.

[0118] A drawback of the labelling machines described with respect to Figures 1 and 2, which rely on a spring to help maintain tension in the web, is that tension in the web cannot be dynamically controlled. A manufacture of such a labelling machine will choose a specific spring to act on the movable member 28, where the specific spring chosen has to work with different types of web and different operating phases of the labelling machine. In some applications a relatively stiff spring may be desirable, but in others a relatively weak spring may be desired. As such, selecting a single spring leads to a compromise in the performance of the labelling machine. There is now described, with reference to figures 3 to 12, an improved labelling machine that is able to control tension in the web through use of a motor. The motor is coupled to the movable member 28, and may be augmented with a spring or may operate independent of a spring. Coupling a motor to the movable member 28 allows a desired force to be applied to the web, at any given time, providing greater control over the tension in the web. As such, as user is no longer bound by the constraints and compromises associated with using a spring alone.

[0119] Figures 3 shows an enlarged view of a portion of a labelling machine 300. The labelling machine 300 may be the same type of any of the labelling machines described with respect to Figures 1 and 2. For clarity, not all of the labelling machine is depicted in Figure 3, and no supply spool is shown as being installed. Figure 4 shows the portion of the labelling machine 300 of Figure 3 with a supply spool 401 installed, but not wound about the rollers 22, 32. The labelling machine 300 comprises a housing 301 , which supports the movable member 28, supply spool support 10, roller 22, a motor mounting plate 305, and a stop 309.

[0120] The movable member 28 (sometimes referred to as a dancing arm) is configured to rotate about axis A. As described above, rotation of the movable member changes the length of the web path. The movable member 28 is biased towards a first direction C by spring 502 (shown in Figure 5). The spring 502 may be any suitable spring, but in this example is an extension spring, with a first end 502a (which may be a hook) attached to the housing 301 via connector 503 and a second end 502b (which may be a hook) attached to a hub 505 of the movable member 28 via connector 504.

[0121] When a web is installed on the labelling machine 300, such as shown in Figure 2, the web is held in tension due to the movable member 28 being urged in direction C by the spring 502. Conversely, tension in the web will cause the web to impart a force on the movable member 28, urging the movable member in direction D. When the net force acting on the movable member 28 from the spring 502 and the web is zero, and in the absence of any other net force, the movable member 28 will be stationary. Depending on a desired tension for the web, the position of the movable member 28 may differ from that shown in Figure 3. For example, Figure 3 shows the movable member 28 at an extreme end of its travel in direction C, abutting elements 310, 311 of the stop 309. The elements 310, 311 may be cushioning elements, and may comprise rubber or plastic material in order to protect the movable member 28. While not shown, a stop could also be used to define an extreme end of travel in direction D. Alternatively, the arrangement of the spring 502 may dictate the extreme end of travel in direction D. Typically, when web is wound around the roller 32, and a desired tension set, the movable member 28 will occupy a position between the extreme ends of the movable member’s travel.

[0122] The sprung arrangement of the movable member 28 provides compliance in the web path in that changes in the tension of the web away from an optimal, or desired, tension will cause the movable member 28 to move in direction C or D. Such movement will reduce or increase the web path length, bringing the tension in the web back to the optimal tension. For example, as tension increases in the web, such as when the web is accelerated, the web will impart a force on the movable member 28, overcoming the force provided by the spring 502 and thus urging the movable member in direction D. As the movable member moves in direction D, the web path length is reduced and the spring 502 is deformed to store a corresponding quantity of potential energy. While the spring obeys Hooke’s law, the force provided by the spring 502 to oppose the force provided by the web (e.g. to urge the movable member 28 in direction C) will increase proportional to the displacement of the movable member 28. As tension decreases in the web, such as when the web is decelerated, the force imparted by the web on the movable member 28 will be reduced. The force provided by the spring 502 will overcome the force imparted by the web, thus urging the movable member towards direction C as the spring 502 releases its stored potential energy. The web path length will thus be increased. As can be seen, the web, movable member 28 and spring 502 provide a balanced system which maintains web tension. The arrangement of the spring 502 is such so as to act to resist a reduction in the length web path (e.g. to move the movable member 28 towards direction C). While an extension spring is described, any suitable spring may be used, such as a compression spring.

[0123] While the arrangement discussed so far provides compliance in the web path, it can be beneficial in some cases to vary the compliance provided. For example, it has been found by the inventors that when the web is being accelerated it is beneficial to increase the compliance provided by the movable member 28 (e.g. reduce the resistance to movement of the movable member in the direction D). That is, it can be advantageous to assist the movable member 28 in reducing the length of the web path during acceleration. For example, increasing compliance during acceleration has been found to reduce friction generated between the web and the labelling peel beak 30, which assists with the acceleration of the web.

[0124] It has further been found by the inventors that when the web is being decelerated it is beneficial to decrease the compliance provided by the movable member (e.g. reduce the resistance to movement of the movable member in the direction C). That is, it can be advantageous to assist the movable member 28 in increasing the length of the web path during deceleration. For example, decreasing compliance during deceleration has been found to increase friction generated between the web and the labelling peel beak 30, which assists with the deceleration of the web.

[0125] In order to provide changes in compliance, the labelling machine 300 comprises an actuator, which in the present example is a motor 501. The motor 501 is visible in Figures 5 and 6. The motor may be a torque controlled motor. For example, the torque controlled motor may be DC motor or may be a stepper motor and encoder arrangement which operates as a torque controlled motor, an example of which is described below with respect to Figure 7. In the example shown, the motor 501 is fixed to the housing 301 using the motor mounting plate 305, where the motor 501 is mounted on the motor mounting plate 305, and the motor mounting plate 305 is mounted on the housing 301. The mounting may be achieved using screws, bolts and the like, for example. Of course, the motor 501 could be integrally formed with the hosing 301. In other examples, no motor mounting plate 305 is required when the motor 501 is mounted directly on the housing 301 , or integrally formed with the housing 301.

[0126] The motor 501 is configured to apply a force to the movable member 28. In the present example, the motor 501 applies a torque to the movable member 28. The torque is transferred using a drive belt 307, which couples to a cylindrical cam 306 of the motor 501 and a cylindrical cam 601 of the movable member 28. Torque applied to the cylindrical cam 306 by the motor 501 is transferred through the drive belt 307 to the cylindrical cam 601. The cylindrical cam 601 transfers the torque to the movable member 28. For example, the cylindrical cam 601 is integrally formed with the movable member, or is attached to the movable member 28 in such a way so as to be rotationally fixed relative the movable member 28. The drive belt 307 may be formed from any suitable material, such as rubber or synthetic polymers. In alternative examples, the drive belt may be a drive chain, and the cams 306, 601 may be sprockets. In yet further examples, a drive shaft of the motor 501 may be directly coupled to movable member 28 without using a drive belt or chain.

[0127] The force provided by the motor 501 can act with, or against, the force provided by the spring 502. In a sprung system as described, controlling the motor 501 to vary the force applied to the movable member has the effect of varying the compliance in the web path. For example, in cases where an increase in compliance is required the motor 501 acts against the force provided by the spring 502 to reduce the net force applied to the movable member 28 by the combination of the spring 502 and motor 501. That is, the total force acting to resist a reduction in the length of the web path is reduced. In other words, the force provided by the motor 501 acts on the movable member 28 in an opposite direction to the force provided by the spring 502, lowering the total force acting to resist a reduction in the length of the web path. This is analogous to reducing the spring constant of the spring 502, providing increased compliance in the web path.

[0128] With an increased compliance, the movable member 28 provides less resistance to being accelerated in direction D under the force applied by the web. This reduces friction generated between the web and the labelling beak 30 and thus assists with accelerating the web.

[0129] In cases where a decrease in compliance is required the motor 501 acts with the force provided by the spring 502 to increase the net force applied to the movable member 28 by the combination of the spring 502 and motor 501. That is, the total force acting to resist a reduction in the length of the web path is increased. In other words, the force provided by the motor 501 acts on the movable member 28 in the same direction as the force provided by the spring 502, increasing the total force acting to resist a reduction in the length of the web path. This is analogous to increasing the spring constant of the spring 502. With a decrease in compliance, the force urging the movable member 28 in direction C is greater. The increase in force over using the spring 502 alone means that the movable member 28 accelerates in direction C quicker than would otherwise be achieved with the spring 502 alone. This increased force in direction C during deceleration of the web leads to an increase in friction generated between the web and the labelling beak 30 and thus assists with decelerating the web. Furthermore, the increased force provided by the motor 501 also aids in reducing the likelihood of web overshooting the labelling beak 30. The spring 502 and the motor 501 may therefore work together as a biasing mechanism acting to bias the movable member 28 in a particular direction to provide a desired tension in the web.

[0130] A controller (not shown in Figure 3) is configured to control the motor 501 to apply a rotational force (i.e. torque) to the movable member 28. The controller controls the motor 501 based on an acceleration condition of the web. If the acceleration condition of the web is that the web is accelerating, the controller controls the motor 501 to apply a rotational force to the movable member 28 to act against the force provided by the spring 502 so as to reduce the force acting to resist a reduction in the length of the web path. That is, the force provided by the motor 501 acts in an opposite direction to the force provided by the spring 502. If the acceleration condition of the web is that the web is decelerating, the controller controls the motor 501 to apply a rotational force to the movable member 28 to act with the force provided by the spring 502 so as to increase the force acting to resist a reduction in the length of the web path. That is, the force provided by the motor 501 acts in the same direction to the force provided by the spring 502. The controller may determine the acceleration condition of the web using any suitable means. For example, the controller may obtain timing information from the labelling machine 300, the timing information relating to the operation of the labelling machine 300. For example, the timing information may be based on the speed at which items to be labelled are advanced along on a conveyor (not shown) of a production line. The controller may receive an encoder signal from an encoder coupled to the web, and may determine the acceleration condition based on the encoder signal. The controller may receive data indicating the state of the take up motor (or a rewind motor, if present, coupled to the supply spool), and determine the acceleration condition based on the received data.

[0131] As well as an acceleration condition, the controller may also control the motor 501 based on additional factors, such as time. For example, the controller may increase the compliance at the start of acceleration for a predefined duration of time, or may decrease the compliance at the start of deceleration for a separate predefined duration of time. That is, it is not necessary that the compliance is increased the entire time that the web is accelerating, or that the compliance is decreased the entire time that the web is decelerating. The predefined duration of time and separate predefined duration of time may be the same or different. Furthermore, the predefined duration of time and separate predefined duration of time may be less than, greater than, or equal to the acceleration period and deceleration period respectively, where the acceleration period is the period of time over which the web is accelerating, and the deceleration period is the period of time over which the web is decelerating.

[0132] The controller may increase the compliance a predefined duration of time before or after the web begins to accelerate, or may decrease the compliance predefined duration of time before or after the web begins to decelerate. Additionally or alternatively, the altered compliance may be maintained for predefined duration of time after acceleration / deceleration ends. For example, maintaining a relatively low compliance during a predefined duration of time after deceleration has ended may help dampen oscillations in the movable member 28.

[0133] The force applied by the motor 501 (and hence the variation in compliance) may be changed gradually or may represent a step change. The force applied by the motor 501 may be position independent. For example, while the force applied by the spring will obey Hooke’s law, increasing as the movable member 28 is displaced, the force applied by the motor may not change as the movable member 28 is displaced. Alternatively, the force applied by the motor may be position dependent. That is, the controller may determine a position of the movable member 28, using an appropriate sensor, and calculate a corresponding force to apply. The controller may determine the position of the movable member 28 using any suitable technique, such as by using an output of one or more sensors monitoring the movable member 28. In examples where the force applied by the motor is position dependent, the force applied by the motor may be proportional to a distance between a position of the movable member 28 and a predefined position, such as the position shown in Figure 3 where the movable member 28 abuts the stop 309.

[0134] The force applied by the spring Fspring on the movable member is -kspringd where kspring is the spring constant and d is the distance through which the movable member 28 has travelled. The force applied by the motor Fmotor on the movable member may be expressed as -kmotord, where kmotor is an effective motor spring constant (having the same units as the spring constant, e.g. N / m). The total force acting on the movable member 28 by the spring 502 and the motor 501 may be expressed as F-rot = Fspring + Fmotor—("kspringd) + ("kmotord) —_d(kmotor + kspring), where (kmotor + kspring) is an effective total spring constant. kmotor may be positive or negative, depending on whether compliance is to be decreased or increased. That is, when it is desired to increase compliance, the controller may set kmotor to be a positive value so as to increase the effective total spring constant. When it is desired to decrease compliance, the controller may set kmotor to be a negative value so as to decrease the total effective spring constant. The force required from the motor at a given time t can be calculated as a function the value of kmotor at time t and the distance, d, at time t.The absolute value of kmotor may always be less than the absolute value of kspring, such that regardless of whether kmotor is positive or negative, the effective total spring constant is positive.

[0135] As noted above, the motor 501 may be a DC motor or may be a stepper motor with encoder (e.g. sensor) arranged to operate as a torque controlled motor. Figure 7 illustrates an example implementation where the motor is a stepper motor with sensor arranged to operate as a torque controlled motor. Figure 7 shows a motor controller 60, which may be the controller described above, or may be a separate controller which works with the controller described above. The motor controller 60 comprises a torque controller 69.

[0136] The motor controller 60 generates control signals which are provided to a stepper motor driver 71. The stepper motor driver 71 in turn generates control signals which are provided to transistors (not shown) which control the current flowing in the windings of the motor 501. An encoder 72 is configured to generate a signal indicative of the angular position of the output shaft of the motor 501. The stepper motor drive 71 may be a TMC262 controller provided by Trinamic Motion Control GmbH, Germany, and may be controlled via an SPI interface to directly control winding currents.

[0137] The motor controller receives as an input a torque demand signal 61. The torque demand signal 61 is indicative of the torque required to be applied to the movable member 28 to either increase or decrease the compliance in the web path (e.g. increase or decrease the effective compliance of the spring). The torque demand signal 61 is passed directly to the torque controller 69. The torque controller 69 generates a current scaling signal 101, which is passed to the stepper motor driver 71, and a field angle control signal 100. The field angle control signal 100 is passed to the phase angle adder 70, where it is summed with a motor position signal received from the encoder 72. An output 102 of the phase angle adder 70 is passed to the stepper motor driver 71.

[0138] In this way, the motor controller 60 generates control signals 101 , 102 that are passed to the stepper motor drive 71 to control the currents supplied to the windings of the motor 501 so as to cause the motor to move to generate a desired torque. Rather than being an open loop position control system, or a simple closed loop position control system, a closed loop torque control system, or field angle control system, is provided. Such an arrangement allows a greater degree of control to be provided over the torque generated by the motor, with reduced risk of motor stall, and lower power consumption than would be exhibited for an open loop stepper motor.

[0139] The motor drive 71 generates electrical signals which are provided to the stepper motor 501 which in turn cause the windings of the stepper motor to be energised so as to cause the stator field to rotate to a position which will cause the motor’s rotor to move in the desired way. In this way, the torque generated by the stepper motor 501 can be controlled and optimised.

[0140] The controller may be generally similar to that described in WO2017 / 216573 or in W02020 / 200823 when configured as a printhead motor controller. For example, the stepper motor driver 71 may be configured substantially as illustrated in Figure 6 of W02020 / 200823.

[0141] The torque generated by a stepper motor depends upon an angle formed between the magnetic field of the rotor and the magnetic field generated by the energised motor windings. By controlling the torque (or field) angle (that is, an angular offset between a stator field position and a rotor position) the torque generated by the motor can be maximised for a particular magnitude of current supplied to the motor windings. For example, it is known that a stepper motor produces maximum torque when a field angle of 90 (electrical) degrees is used. Thus, the use of such a field angle allows the stepper motor to generate a maximum torque for a given winding current. Either or both of the current magnitude and field angle can be varied by the torque controller so as to achieve a desired torque output. By providing accurate information relating to the angular position of the output shaft (and thus the rotor) of the stepper motor 501 , it is possible to achieve many of the benefits conventionally associated with stepper motors (e.g. high torque output, low- cost, and high-speed operation) while also providing advantageous characteristics usually associated with DC motors (e.g. a well-known relationship between the current supplied to the motor and the torque output by the motor). Moreover, by providing accurate positional information, and controlling the stator field based upon this information, there is no risk that a stepper motor will stall if the load is greater than the maximum torque capacity. Rather than the motor stalling, the stator field will simply be controlled so as to rotate to an angle which allows the required torque to be provided.

[0142] Moreover, the use of positional feedback based upon the output of the encoder 72 allows the motor winding currents to be modulated so as to produce a desired torque level at all times. That is, a controlled torque can be generated by the motor by setting the magnetic field angle to lead the rotor position by a predetermined angle. Then, as the rotor rotates in response to the application of the field, the applied field can be immediately updated using a feedback loop so as to ensure that the field is continually applied at an angle which leads the actual rotor position by the predetermined amount. This form of closed-loop control may be referred to a closed-loop field control, or field- oriented control. More generally, a desired motor output characteristic can be achieved by controlling the magnetic field to have a predetermined relationship with the rotor position.

[0143] Of course, it will be appreciated that the use of a stepper motor also allows the use of conventional open-loop stepper motor control (which may be referred to as stepping mode) when beneficial. Further, at some times a stepper motor may be operated in a closed loop position controlled manner (as opposed to a closed-loop torque controlled manner, or an open-loop position controlled manner). Such control may be effected by use of a position controller (not shown). Further, the description above relates to one possible implementation of a torque controller as applied to a stepper motor. Other forms of motor control may be used to cause a stepper motor to output a desired torque. Similarly, other motors may also be used to output a desired torque.

[0144] Figures 8 and 9 show experimental plots highlighting the effect of changing the compliance provided by the movable member 28. Both plots plot velocity of the web against time. In the plot of Figure 8, a spring is used to bias the movable member, whereas in the plot of Figure 9 both a spring and motor are used to bias the movable member as described with respect to Figures 3 to 6. As can be seen, addition of the motor to vary the compliance has increased the rate of acceleration when accelerating the web and has increased the rate of deceleration when decelerating the web. Additionally, as can be seen in the Figures, better control over the velocity of the web is obtained, with less overshoot of a target velocity during acceleration and deceleration.

[0145] While a movable member has been described which moves rotationally, it will be appreciated that the movable member may move linearly. In such a case, the spring and motor will apply a linear force to the movable member, rather than a rotational force (i.e. torque).

[0146] The motor 501 and spring 502 shown in Figures 3 to 6 are in a parallel arrangement, where each of the motor and the spring independently apply a force to the movable member 28. It will be appreciated that in other implementations, the motor 501 and the spring 502 may be in series. That is, the output of the motor 501 may directly couple to one end of the spring 502, with the other end of the spring directly coupled to the movable member 28.

[0147] While the biasing mechanism has been described as comprising a spring 502 and motor 501 , in some implementations a spring may not be required. In such implementations, the motor 501 may act alone to provide a force that acts on the movable member 28 to provide tension in the web. For example, a desired tension in the web may be achieved by applying a corresponding force to the movable member 28 using the motor 502. Advantageously, this implementation negates the need for a spring. An example illustration of such an implementation is shown in Figure 11 , which shows an enlarged view of a portion of an alternative implementation of a labelling machine 1101 to that shown in Figures 3 to 6. The labelling machine 1101 may be the same type of any of the labelling machines described with respect to Figures 1 and 2. For clarity, not all of the labelling machine 1101 is depicted in Figure 11 , and no supply spool is shown as being installed. Elements of the labelling machine 1101 that correspond to elements of the labelling machine 300 shown in Figures 3 to 6 share the same reference numerals. The alternative implementation shown in Figure 11 differs from that shown in Figures 3 to 6 in that there is no spring coupled to the movable member 28 (e.g. spring 502 is not required). In the example of Figure 11 , the movable member’s axis of rotation, E, is spaced apart from the axis of rotation A of the supply spool support 10. However, it will be appreciated that the movable member’s axis of rotation E may instead be aligned with the axis of rotation A of the supply spool support 10 as shown in Figures 3 - 6. Similarly, the labelling machine 300 of Figures 3 - 6 may have its movable member’s axis of rotation spaced apart from the axis A of rotation of the supply spool support 10.

[0148] Additionally, the location and orientation of the motor 501 shown in Figure 11 differs from that of Figures 3 to 6. The motor 501 is shown in Figure 11 as being located within the housing 301, mounted directly to an internal wall of the housing 301. Of course, any suitable way of securing the motor 501 inside the housing 301 may be used. The motor 501 is also orientated such that the torque output by the motor 501 is perpendicular to the axis of rotation E of the moveable member 28. As such, additional guide rollers 1150, 1151, 1152, 1153 are used to guide the drive belt 307 coupled between the output cylindrical cam 306 of the motor 501 and the cylindrical cam 601 of the movable member 28. The specific orientation and location of the motor 501 shown is for example only, and the motor 501 can be orientated or located in any suitable way, or arranged as shown in the examples of Figure 3 to 6.

[0149] The controller (not shown in Figure 11) is configured to control the motor 501 to apply a desired force (e.g. torque) to the movable member 28 in a particular direction. For example, the controller can control the motor 501 to provide a force such that the movable member 28 is urged towards direction C. In doing so, the controller is able to provide a desired tension in the web at any given time. The controller may operate the motor 501 to mimic a compliance (i.e. generate a force that varies with position of the movable member 28), such as would be provided by a spring. Alternatively, or additionally, the controller may operate the motor to apply a fixed force (e.g. provide damping). Alternatively, the controller may operate to both provide compliance and damping. For example, in some situations it may be beneficial to apply a fixed force, and in others it may be beneficial to mimic the effect that a spring would provide. For example, in some implementations, most of the movable range of the movable member 28 may be subject to a constant force provided by the motor 501. As the movable member approaches the stop 309 (not shown in Figure 11, but visible in Figure 3) the movable member 28 may then be subject to a force by the motor 501 that varies with position of the movable member 28. For example, as the movable member 28 approaches the stop 309, the force applied to the movable member 28 by the motor 501 may vary so as to avoid the movable member 28 contacting the stop 309 at relatively high speed. In this way, components of the labelling machine are protected, and the noise associated with operating the labelling machine is reduced.

[0150] The desired force to be applied to the movable member by the motor 501 may depend on the operating phase in which the labelling machine 1101 is in at any given time (e.g. advancing web at a constant speed, accelerating web, decelerating web, holding the web stationary, etc.). The force applied by the motor 501 may be varied based on the operating conditions of the labelling machine, such as acceleration conditions of the web as described above. For example, the force applied to the movable member in direction C may be reduced during acceleration of the web and may be increased during deceleration of the web.

[0151] In order to illustrate how the labelling machine 1101 may operate, there is now described the following illustrative example. Consider a situation in which the labelling machine 1101 is operating on a production line and is applying labels to objects, such as boxes, travelling along a conveyor.

[0152] The labelling machine 1101 operates in a cyclic manner, which can be broadly described as having three distinct phases. In a first phase, the web is accelerated from a first speed (which could be 0 m / s) to a second speed so as to match a speed of an object travelling along the conveyor. In a second phase, the web is advanced at the second speed while the label is applied to the object. In a third phase, the web is decelerated to the first speed (which could be 0 m / s) so as to wait for the next object along the conveyor. This process repeats for each object travelling along the conveyor that is to be labelled.

[0153] When the web is held stationary, or being advanced at a constant speed, it is desirable to hold the web at a predetermined tension. The predetermined tension may be based on, for example, the physical properties of the web such as web thickness, web width, web material, etc. The controller applies a corresponding force to the movable member 28 so as to hold the web at the predetermined tension. Just prior to the start of the first phase, the web is held at the predetermined tension. During the first phase, the web is accelerated from the first speed to the second speed and the controller controls the force acting on the movable member 28 so as to reduce the force acting against the web by the movable member 28 (e.g. the force applied in direction C is reduced). That is, resistance to reducing the length of the web path is decreased. As discussed above, decreasing the resistance to reducing the length of the web path during acceleration of the web assists with acceleration as the friction between the web and peel beak 30 is reduced.

[0154] During the second phase, when the web is held at the second speed to match the speed of the object travelling along the conveyor, the web is again held at the predetermined tension. The controller controls the motor 501 to apply the appropriate force to the movable member 28 in order to hold the web at the predetermined tension.

[0155] Just prior to the start of the third phase, the web is held at the predetermined tension. During the third phase, the web is decelerated from the second speed to the first speed and the controller controls the force acting on the movable member 28 so as to increase the force acting against the web by the movable member 28 (e.g. the force applied in direction C is increased). As discussed above, increasing the force acting against the web by the movable member 28 assists with deceleration as the friction between the web and peel beak 30 is increased.

[0156] The controller may use any suitable way of determining the required force to be applied to the movable member 28. For example, the controller may access a look up table to determine the required force to be applied to the movable member 28. The look up table may link specific operational conditions associated with the operation of the labelling machine to specific motor drive data. The specific operational conditions may be one or more of an operating phase in which the labelling machine is in, an acceleration condition associated with the web, a position of the movable member 28, a physical property of the web, or a user set correction value. The controller may determine the specific operational conditions at any given time using any suitable means. For example, the controller may receive periodic signals from one or more sensors or encoders monitoring the labelling machine and / or production line which can be used to determine operational conditions. The periodic signals may indicate where in the cycle the labelling machine is operating (e.g. first, second or third phase as described above). An encoder or sensor may be used to determine the position of the movable member 28 at any given time. The controller may receive data directly from users. For example, a user may input into a user interface physical characteristics of the web, which can be used by the controller. The controller may receive data from external machines used in a production line, such as a production line controller configured to operate a production line. For example, a production line controller may send a periodic signal based on the detection of an object to be labelled travelling along a conveyor.

[0157] The specific motor drive data provides the necessary information for the controller to control the motor 501 to apply the appropriate force to the movable member 28 for the given specific condition associated with the operation of the labelling machine. For example, the motor drive data may be a value of current when using a DC motor, or may be a current scaling (also referred to herein as magnitude), and / or field angle when using a stepper motor as described above. The values of the look up table may be determined empirically.

[0158] An interpolation algorithm may be used with the lookup table. For example, a look up table may link discrete values associated with the operation of the labelling machine (such as discrete positions of the movable member 28) with discrete values of motor drive data (such as discrete values of current). Interpolation can be used to determine values that fall between the discrete values contained within the lookup table.

[0159] In other examples, no look up table is required. For example, the controller may execute an algorithm that takes as input one or more specific conditions associated with the operation of the labelling machine and outputs the specific motor drive data suitable for the one or more specific conditions. The algorithm may be determined empirically. The algorithm may be a trained machine learning model, such as a neural network or support vector machine. Alternatively, the algorithm may be a rules based algorithm.

[0160] As described above, when using a stepper motor, torque can be controlled by setting the field angle and / or the current scaling. The controller may vary the field angle or current scaling based on the specific condition associated with the operation of the labelling machine. For example, the efficiency of the motor may be optimised by maintaining a difference between the rotor and the field at 90 (electrical) degrees as described above, and varying the current scaling to change the torque. This would give a maximum torque for any current scaling setting, and therefore corresponds to the most efficient use of the motor. Alternatively, the field angle may be varied to provide finer granularity in the torque output. In other cases, a combination of varying the field angle and current scaling may be used. For example, at low torque demands (and therefore low current) the field angle may be varied to provide fine control, and at high torque demands, the field angle may be fixed at 90 degrees and the current scaling varied. The specific values to be used at any given time may be determined from the lookup table or by executing an algorithm as described above.

[0161] A further advantage of providing control over the force applied to the movable member 28 by the motor 501 is that a user or service engineer is able to fine tune the force applied, and thus fine tune the tension in the web. For example, if a user is suffering from poor results during labelling, such as experiencing web snapping or poor positional control of the web, the user may increase or decrease the tension in the web by a percentage, such as by 15%, 10%, or 5%. That is, the user may input into the controller via a user interface a user set correction value, which can be used by the controller to update the force applied to the movable member 28. For example, if the user requests an increase in tension by 5%, the controller may modify values obtained from the look up table, or output from an algorithm, to take into account the user’s correction.

[0162] A further advantage of providing control over the force applied to the movable member 28 by the motor 501 is that a shorter movable member 28 can used. When using only a spring to apply a force to the movable member 28 as in examples shown in Figures 1 and 2, the web tension drops as the movable member moves towards its home position (e.g. towards stop 309). This can mean that for a portion of its travel the movable member 28 fails to maintain sufficient web tension, and this part of its movable range must be avoided during labelling operations. As such, a relatively large movable range is required, since some of the range is not usable. By controlling the force acting on the movable member 28, the range of movement of the movable member 28 can be reduced since all of the range can be used. While the implementation shown in Figure 11 does not use a spring, it will be appreciated that the implementation shown in Figure 11 could be augmented with a spring 502, as with the implementations shown in Figures 3 to 6. For example, augmenting with a spring 502 may allow the power requirement and size of the motor 501 to be reduced, but may decrease the level of control over tension in the web. The motor 501 may work with a spring 502 to provide constant tension in the web. For example, the motor 501 may cancel out the compliance effect of the spring to provide constant tension regardless of the position of the movable member 28.

[0163] In some cases, such as when the labelling machine is not in use, it may be beneficial to hold the movable member 28 stationary. In the labelling machine 300, when not in use, the movable member 28 is held stationary by the spring 502 biasing the movable member 28 against the stop 309. When there is no spring 502 coupled to the movable member 28, an alternative way of holding the movable member 28 stationary may be required. The movable member 28 can be held in place using any suitable method, either manually or automatically. For automatic cases, a solenoid may be used. The solenoid may be mounted to the housing 301 and selectively couple to the movable member 28 to prevent / allow movement of the movable member 28 relative the housing 301. When there is no electrical power being supplied to the solenoid, such as when the labelling machine is turned off, the solenoid couples to the movable member 28, preventing the movable member 28 from moving. When electrical power is applied to the solenoid, the solenoid decouples from the movable member 28 so as to no longer prevent the movable member 28 from moving.

[0164] The coupling may be any suitable coupling. For example, the movable member 28 may comprise a number of holes, the holes configured to receive a pin. In this example, the solenoid is coupled to the pin such that when electrical power is removed from the solenoid, the solenoid moves the pin into one of the holes, preventing the movable member 28 from moving. When electrical power is applied to the solenoid, the solenoid extracts the pin from the hole, allowing the movable member 28 to move. The holes may be arranged circumferentially in a disc, the disc coupled to, and rotatably fixed relative to, the movable member 28. The pin may engage any hole aligned along the pin’s axis of movement. Rather than a pin and hole arrangement, the coupling may be via a brake pad and brake disc. For example, the movable member 28 may comprise a brake disc, and the solenoid may engage a brake pad. The solenoid pushes the brake pad into the brake disc when power is removed from the solenoid, and removes the brake pad from the brake disc when power is applied to the solenoid. In other examples of automatically holding the movable member 28, a detent torque provided by the motor 501 may be used to hold the movable member 28 stationary. For example, the phases of the motor 502 may be shorted to increase the detent torque.

[0165] With reference to Figure 10 there is now described a method of controlling a biasing mechanism in a labelling machine, such as those shown in Figures 3-6 and 11 , to vary the force applied to the movable member so as to control tension in the web. The biasing mechanism may be the spring 502 and motor 501 described above, or may be the motor 501 acting independent of a spring.

[0166] In a first step S1, the controller determines an acceleration condition associated with the advancement of the web. For example, as described above, the controller may determine that the web is being accelerated or decelerated, is about to be accelerated / decelerated within a predetermined time, or has been accelerating / decelerating for a predetermined time.

[0167] In a second step S2, the controller controls the biasing mechanism so as to vary the force applied to the movable member based on the acceleration condition associated with the advancement of the web. For example, when it is determined that the web is i) going to be accelerated along the web path in a predetermined time, ii) is presently being accelerated along the web path, or iii) has been undergoing acceleration along the web path for a predetermined time, the force applied by the biasing mechanism is reduced. In examples where the biasing mechanism comprises both a spring and motor, such as shown in Figures 3-6, reducing the force leads to an increase in the compliance in the web path. When it is determined that the web is i) going to be decelerated along the web path in a predetermined time, ii) is presently being decelerated along the web path, or iii) has been undergoing deceleration along the web path for a predetermined time, the force applied by the biasing mechanism is increased. In examples where the biasing mechanism comprises both a spring and motor, such as shown in Figures 3-6, increasing the force leads to a decrease in the compliance in the web path. The compliance may be varied as described above, by varying a force provided by the motor 501. Of course, as described with reference to Figure 11 , in some implementations only a motor is used (e.g. no spring is required). In such cases, compliance may not be varied if the motor does not mimic a compliance.

[0168] An example controller 1100 which could be used to control the labelling machine 300 or labelling machine 1101 is shown in more detail in Figure 12. The controller 1100 comprises a processor 1100a which is configured to read and execute instructions stored in a volatile memory 1100b which could be a random access memory. The volatile memory 1100b stores instructions for execution by the processor 1100a and data used by those instructions.

[0169] The controller 1100 further comprises non-volatile 1100c, which could be a ROM or hard disk drive. The controller 1100 further comprises an I / O interface 1100d. A network interface 1100f allows the controller 1100 to be connected to an appropriate computer network so as to receive and transmit data from and to other computing devices. The network interface 1100f may comprise the transceiver. The processor 1100a, volatile memory 1100b, hard disc drive 1100c, I / O interface 110Od, and network interface 1100f, are connected together by a bus 1100g. It will be appreciated that the controller 1100 may have fewer components than described. For example, it may not be necessary for the controller 1100 to have a network interface 1100f and / or I / O interface 1100d.

[0170] It will be appreciated that embodiments disclosed herein can be implemented in any convenient form. For example, embodiments disclosed herein may be implemented by appropriate computer programs which may be carried on appropriate carrier media which may be tangible carrier media (e.g. disks) or intangible carrier media (e.g. communications signals). Embodiments disclosed herein may also be implemented using suitable apparatus which may take the form of programmable computers running computer programs arranged to implement the embodiments disclosed herein.

[0171] Embodiments of the subject matter and the operations described in this specification can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware. Embodiments of the subject matter described in this specification can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on computer storage medium for execution by, or to control the operation of, data processing apparatus. Alternatively or in addition, the program instructions can be encoded on an artificially-generated propagated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to suitable receiver apparatus for execution by a data processing apparatus. A computer storage medium can be, or be included in, a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or device, or a combination of one or more of them. Moreover, while a computer storage medium is not a propagated signal, a computer storage medium can be a source or destination of computer program instructions encoded in an artificially-generated propagated signal. The computer storage medium can also be, or be included in, one or more separate physical components or media (e.g., multiple CDs, disks, or other storage devices).

[0172] The operations described in this specification can be implemented as operations performed by a processor on data stored on one or more computer-readable storage devices or received from other sources.

[0173] The term “processor” encompasses all kinds of apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, a system on a chip, or multiple ones, or combinations, of the foregoing. The apparatus can include special purpose reprogrammable logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit). The apparatus can also include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, a cross-platform runtime environment, a virtual machine, or a combination of one or more of them. The apparatus and execution environment can realize various different computing model infrastructures, such as web services, distributed computing and grid computing infrastructures.

[0174] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. Devices suitable for storing computer program instructions and data include all forms of computer-readable media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry and fiber-optic platform for faster data transfer remotely.

[0175] To provide for interaction with a user, embodiments of the subject matter described in this specification can be implemented on a computer having a display device, e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor including audio, for displaying information (e.g. an indication and / or alert) to the user. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback.

[0176] Although the disclosure has been described in terms of preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only and that the claims are not limited to those embodiments. The skilled person will be able to make modifications and alternatives in view of the disclosure which are contemplated as falling within the scope of the appended claims. Each feature disclosed or illustrated in the present specification may be incorporated in the disclosure, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein.

Claims

CLAIMS:

1. A labelling machine comprising: a supply spool support for supporting a supply spool comprising label stock, the label stock comprising a web and a plurality of labels attached to the web; a take-up spool support configured to take up a portion of the web; a motor configured to advance the web along a web path from the supply spool support towards the take up spool support; a labelling peel beak located along the web path and configured to peel the labels from the web as the web passes the labelling peel beak; a movable member, the movable member configured to contact a portion of the web and define a portion of the web path between the supply spool support and the labelling peel beak, wherein movement of the movable member changes a length of the web path; a biasing mechanism coupled to the movable member and configured to apply a force to the movable member, the force acting against the web to provide tension in the web; and a controller configured to control the biasing mechanism to vary the force applied to the movable member so as to control tension in the web.

2. The labelling machine according to claim 1, wherein the controller being configured to control the biasing mechanism to vary the force applied to the movable member so as to control tension in the web comprises the controller being configured to: determine an operational condition associated with the labelling machine; control, based on the operational condition, the biasing mechanism to vary the force applied to the movable member so as to control tension in the web.

3. The labelling machine according to claim 1 or 2, wherein the controller being configured to control the biasing mechanism to vary the force applied to the movable member so as to control tension in the web comprises the controller being configured to: control the biasing mechanism to apply one or both of i) a force that varies with the position of the movable member and ii) a force that is independent of the position of the movable member.

4. The labelling machine according to any preceding claim, wherein the controller being configured to control the biasing mechanism to vary the force applied to the movable member so as to control tension in the web comprises the controller being configured to: determine an acceleration condition associated with the advancement of the web; and control the biasing mechanism so as to vary the force applied to the movable member so as to control tension in the web based on the acceleration condition associated with the advancement of the web.

5. The labelling machine according to claim 4, wherein the controller being configured to determine the acceleration condition associated with the advancement of the web and control the biasing mechanism so as to vary the force applied to the movable member so as to control tension in the web based on the acceleration condition associated with the advancement of the web comprises, the controller being configured to: determine that the web is i) going to be accelerated along the web path in a first predetermined time, ii) is presently being accelerated along the web path, or iii) has been undergoing acceleration along the web path for a second predetermined time, and in response reduce the force applied to the movable member by the biasing mechanism.

6. The labelling machine according to claim 4 or 5, wherein the controller being configured to determine the acceleration condition associated with the advancement of the web and control the biasing mechanism so as vary the force applied to the movable member based on the condition associated with the advancement of the web comprises, the controller being configured to: determine that the web is i) going to be decelerated along the web path in a third predetermined time, ii) is presently being decelerated along the web path, or iii) has been undergoing deceleration along the web path for a fourth predetermined time, and in response increase the force applied to the movable member by the biasing mechanism.

7. The labelling machine according to claim, wherein the biasing mechanism comprises a second motor.

8. The labelling machine according to any preceding claim, wherein the force comprises a first force component and a second force component, and wherein the biasing mechanism comprises: a first biasing member configured to apply the first force component to the movable member; a second biasing member configured to apply the second force component to the movable member; wherein the controller being configured to control the biasing mechanism to vary the force applied to the movable member so as to control tension in the web comprises the controller being configured to control the second biasing member so as to vary the second force component.

9. The labelling machine according to claim 8, wherein the first biasing member comprises a spring.

10. The labelling machine according to claim 8 or 9, wherein the second biasing member comprises the second motor.

11. The labelling machine according to claim 10, wherein the second motor is a stepper motor; the labelling machine further comprising a sensor configured to generate a signal indicative of an angular position of an output shaft of the stepper motor; and the controller is further configured to generate control signals for the stepper motor so as to cause a predetermined torque to be generated by the stepper motor; the control signals being at least partially based upon an output of the sensor.

12. The labelling machine according to claim 11 , wherein the control signals for the stepper motor are arranged to cause a magnetic field to be generated by windings of the stepper motor, a field angle being defined between an angular position of the output shaft of the stepper motor, and an orientation of the generated magnetic field; andthe control signals are arranged to cause the field angle to have a predetermined value, and to cause the magnetic field to have a predetermined magnitude.

13. The labelling machine according to claim 11 or 12, wherein the controller is further configured to vary the control signals based at least partially upon a torque demand signal.

14. The labelling machine according to any one of claims 8 to 13, wherein the controller being configured to control the second biasing member so as to vary the second force component comprises the controller being configured to: apply the second force component so as to act in an opposite direction to the first force component to reduce the force applied to the movable member by the biasing mechanism.

15. The labelling machine according to any one of claims 8 to 14, wherein the controller being configured to control the second biasing member so as to vary the second force component comprises the controller being configured to: apply the second force component so as to act in a same direction as the first force component to increase the force applied to the movable member by the biasing mechanism.

16. The labelling machine according to any preceding claim, when dependent on claim 4, wherein the controller being configured to control the biasing mechanism so as to vary the force applied to the movable member so as to control tension in the web further comprises the controller being configured to: determine a position of the movable member; and control the biasing mechanism so as to vary the force applied to the movable member based on the acceleration condition associated with the advancement of the web and the position of the movable member.

17. The labelling machine according to any preceding claim, wherein the motor is coupled to the take up spool, and configured to rotate the take up spool to advance the web along the web path.

18. A method of operating a labelling machine, the labelling machine comprising: a supply spool support for supporting a supply spool comprising label stock, the label stock comprising a web and a plurality of labels attached to the web; a take-up spool support configured to take up a portion of the web; a motor; a labelling peel beak located along the web path; a movable member; a biasing mechanism coupled to the movable member; a controller; and wherein the method comprises: the motor advancing the web along a web path from the supply spool support towards the take up spool support; the labelling peel beak peeling the labels from the web as the web passes the labelling peel beak; the movable member contacting a portion of the web and defining a portion of the web path between the supply spool support and the labelling peel beak; the biasing mechanism applying a force to the movable member, the force acting against the web to provide tension in the web; and the controller controlling the biasing mechanism to vary the force applied to the movable member so as to control tension in the web.

19. The method according to claim 18, wherein the controller controlling the biasing mechanism to vary the force applied to the movable member so as to control tension in the web comprises the controller: determining an operational condition associated with the labelling machine; controlling, based on the operational condition, the biasing mechanism to vary the force applied to the movable member so as to control tension in the web.

20. The method according to claim 18 or 19, wherein the controller controlling the biasing mechanism to vary the force applied to the movable member so as to control tension in the web comprises the controller: controlling the biasing mechanism to apply one or both of i) a force that varies with the position of the movable member and ii) a force that is independent of the position of the movable member.

21. The method according to claim 18, 19 or 20, wherein the controller controlling the biasing mechanism to vary the force applied to the movable member so as to control tension in the web comprises the controller: determining an acceleration condition associated with the advancement of the web; and controlling the biasing mechanism to vary the force applied to the movable member so as to control tension in the web based on the acceleration condition associated with the advancement of the web.

22. The method according to claim 21, wherein the controller determining the acceleration condition associated with the advancement of the web and controlling the biasing mechanism to vary the force applied to the movable member so as to control tension in the web based on the acceleration condition associated with the advancement of the web comprises, the controller: determining that the web is i) going to be accelerated along the web path in a first predetermined time, ii) is presently being accelerated along the web path, or iii) has been undergoing acceleration along the web path for a second predetermined time, and in response reducing the force applied to the movable member by the biasing mechanism.

23. The method according to claim 21 or 22, wherein the controller determining the acceleration condition associated with the advancement of the web and controlling the biasing mechanism so as to vary the force applied to the movable member based on the acceleration condition associated with the advancement of the web comprises, the controller: determining that the web is i) going to be decelerated along the web path in a third predetermined time, ii) is presently being decelerated along the web path, or iii) has been undergoing deceleration along the web path for a fourth predetermined time, and in response increasing the force applied to the movable member by the biasing mechanism.

24. The method according to claims 18 to 23, wherein the biasing mechanism comprises a second motor.

25. The method according to any of claims 18 to 24, wherein the biasing mechanism comprises: a first biasing member configured to apply a first force component to the movable member; a second biasing member configured to apply a second force component to the movable member; wherein the controller controlling the biasing mechanism so as to vary the force applied to the movable member so as to control tension in the web comprises the controller controlling the second biasing member so as to vary the second force component.

26. The method according to claim 25, wherein the first biasing member comprises a spring.

27. The method according to claim 25 or 26, wherein the second biasing member comprises the second motor.

28. The method according to claim 27, wherein the second motor is a stepper motor and the labelling machine further comprising a sensor, the method further comprising: generating, by the sensor, a signal indicative of an angular position of an output shaft of the stepper motor; and generating, by the controller, control signals for the stepper motor so as to cause a predetermined torque to be generated by the stepper motor; the control signals being at least partially based upon an output of the sensor.

29. The method according to any of claims 25 to 28, wherein the controller controlling the second biasing member so as to vary the second force component comprises the controller: applying the second force component so as to act in an opposite direction to the first force component to reduce the force applied to the movable member by the biasing mechanism.

30. The method according to any of claims 25 to 29, wherein the controller controlling the second biasing member so as to vary the second force component comprises the controller: applying the second force component so as to act in a same direction as the first force component to increase the force applied to the movable member by the biasing mechanism.

31. The method according to any of claims 18 to 30, when dependent on claim 21 , wherein the controller controlling the biasing mechanism to vary the force applied to the movable member so as to control tension in the web further comprises the controller: determining a position of the movable member; and controlling the biasing mechanism to vary the force applied to the movable member so as to control tension in the web based on the acceleration condition associated with the advancement of the web and the position of the movable member.

32. The method of any one of claims 18 to 31 , wherein the motor is coupled to the take up spool, and wherein the motor advancing the web along the web path from the supply spool support towards the take up spool support comprises the motor rotating the take up spool to advance the web along the web path from the supply spool support towards the take up spool support.

33. A computer readable medium comprising computer readable instructions which when executed by a processor, caused the processor to carry out the method of claims 18 to 32.

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