Labeling method and device

In a method for labeling, a label strip (20) is moved by means of an electric motor (80). Arranged on this label strip are labels (26) of predetermined length (EL) with uniform interstices (SB). The motor has associated with it a position controller (218), also a sensor (44) for sensing a predetermined position of a label (26) when the latter is moved on the label strip (20) relative to the sensor (44). The method has the following steps: in accordance with a stored profile, the label strip (20) is set in motion beginning from a start position (A), a first target position (Z) of the label strip being specified to the position controller (218); during the motion of the label strip (20), a predetermined position (M) of the label strip (20) is sensed; and subsequently thereto, a revised target position (Z) is specified to the position controller (218). This makes possible fast and precise labeling, since the target position can be reached very accurately. A corresponding device has a compact design.

This application is a section 371 of PCT/EP2004/009826, filed 3 Sep. 2004 and published 28 Apr. 2005 as WO 2005-037654-A2.

FIELD OF THE INVENTION

The present invention relates to a method and an apparatus for labeling.

BACKGROUND

When labels are to be dispensed from a carrier strip at a dispensing edge, also called a detaching edge, the following factors, among others, play an important role:a) The speed of the dispensing operation. This determines the labeling speed, i.e. how many boxes, cans, bottles, etc. can be labeled per minute.b) The accuracy of the dispensing operation. What is important here is to place the label accurately at a desired location, for example on a suction device that transfers the label onto an object that is to be labeled, or also to apply the label accurately and without folds at a desired point, directly onto an object to be labeled that is passing by.

Known methods for moving a label strip work in the manner of an open-loop control system, i.e. a label sensor is used that is mounted at a specific location on a labeling device, preferably very close to the location where the labels are dispensed. This location is ascertained empirically by the person setting up the machine. When a label arrives at this sensor, the latter generates a pulse that is then used to shut off the drive system.

Such methods yield entirely acceptable results, but problems occur at higher speeds, principally for the following reasons:

Forces act on the label strip/carrier strip from outside, for example from moving, resilient pendulums on the supply spool and on the spool that takes up the carrier strip. These forces, whose occurrence is governed by chance, can accelerate or decelerate the label strip, which can lead to corresponding labeling errors.

During the motion of the label strip/carrier strip, the latter can expand or contract similarly to a rubber band, particularly at the beginning of a transport motion; this “rubber band effect” can likewise negatively affect labeling accuracy and limits the labeling speed, since such effects increase with increasing speed. This is because higher speeds result in correspondingly higher accelerations, and thus in greater forces on the label strip/carrier strip.

SUMMARY OF THE INVENTION

It is an object of the invention to make available a new method and a new apparatus for labeling.

According to a first aspect of the invention, this object is achieved by controlling motion of a label strip, using a position controller in conjunction with a label position sensor. In the context of the invention, therefore, after a part of the motion sequence has elapsed, the target position at which the motion is intended to be complete is redefined at a predetermined location on the label strip (e.g. at a label edge) while the motor is running. This is achieved, for example, by the fact that at the predetermined location, a defined residual distance, also called a follow-on distance, is inputted into the controller as the target position. This residual distance is usually defined by the user, e.g. 13 mm from a specific physical feature of a label or carrier strip, for example from an edge, a hole, a marking, etc. After passing the predetermined location the label strip then moves another 13 mm and remains stationary after those 13 mm, and that 13-mm spacing is maintained without modification for one label after another.

According to a second aspect of the invention, the stated object is achieved by first specifying a target position for the label and, during the label's motion, specifying a revised target position. By accurate specification of the residual distance, such an arrangement makes possible very precise labeling even if the label pitch varies slightly due to fluctuations in production, changes in relative humidity, etc.

Accurate maintenance of a residual distance during labeling has the following principal advantages:

a) The accuracy of the motion sequence is decisively enhanced.

b) The reproducibility of the motion sequence becomes very good.

c) So-called pitch errors in the label strip now play only a subordinate role, since they can be largely suppressed by appropriate selection of the predetermined measurement location.

d) By modifying the residual distance it is very easy to adjust the position occupied by a label at the end of a motion operation.

e) A labeling apparatus, a label printer, or the like can in many cases be set to a different label format with no need to modify the position of the label sensor that is used.

f) Labels missing from the label strip can be “skipped,” i.e. the machine continues to run despite the missing information, and is not shut off by the error. If a label is missing from the label strip, an object to be labeled will pass through the machine without being labeled, but this does not change the precision of subsequent labeling operations.

g) It is possible to stipulate that an alarm is generated when, for example, three labels in succession are missing from the label strip, but not when only one or two are missing.

h) The capability of automatically detecting a tear in the label strip is created, since no signal is then generated at the predetermined measurement location.

According to a third aspect of the invention, this object is achieved by imparting a predetermined motion profile, having multiple phases, to the label's motion. A method of this kind makes possible very fast and precise labeling, changes in the labeling speed being possible without any changes in labeling precision.

A corresponding arrangement is a motor/controller combination which causes a first accelerating motion phase, a second uniform-speed motion phase, and a third braking-to-zero phase. In this arrangement, the shape of the motion profile is automatically adapted when the labeling speed is modified, and precise labeling is consequently always obtained regardless of whether it occurs slowly or quickly.

According to a further aspect of the invention, this object is achieved by using a four-quadrant controller to drive the electric motor.

A very compact and also high-performance labeling device is obtained, according to a further aspect of the invention, by putting the motor and its power electronics in a metal housing which serves as a heat sink or cooling element. The need for additional electrical cabinets, etc. is in many cases thereby eliminated, and costs for the installation of and, if applicable, modifications to a labeling apparatus are consequently low. Cleaning is moreover facilitated, and it is possible to conform to higher electrical protection classes without increased outlay, making it possible to use such labeling devices in refineries and other explosion-hazard facilities.

A drive system of this kind, and a method according to the present invention, can of course also be used for other purposes, e.g. for rapid and precise driving of turntables for beverage filling, or for the labeling of bottles.

Further details and advantageous refinements of the invention are evident from the exemplifying embodiments, in no way to beunderstood as a limitation of the invention, that are described below and depicted in the drawings.

DETAILED DESCRIPTION

FIG. 1is a plan view of a label strip20, andFIG. 2shows that strip in a side view. In the side view, the dimensions in the vertical direction are depicted in extremely exaggerated fashion to allow better comprehension of the invention.

Label strip20has, at the bottom inFIG. 2, a carrier strip22, usually made of paper, that is provided on its upper side inFIG. 2with a release layer24, usually made of silicone. Self-adhesive labels26are adhesively bonded onto layer24by means of a contact adhesive layer25. These labels have a label length EL that can be between a few millimeters and hundreds of millimeters. It is obvious that the labeling performance can be higher with short labels than with long labels. The direction of motion of label strip20is labeled29, and the label edges that are toward the front in the direction of motion are labeled27. Because label strip20and carrier strip22are identical except for the presence or absence of labels26, the expression “strip20/22” will also be used hereinafter.

Located between two adjacent labels26is a gap28that is created during manufacture by the removal of a so-called “spacer” of label material; the width of gap28is therefore also referred to as spacer width SB. SB usually has a value of between 1 and 10 mm. Label length EL and spacer width SB together equal transport distance TW over which label web20must be moved forward upon dispensing of a single label26. The relationship is
TW=EL+SB.(1)

When label web20is pulled around a dispensing edge30, also called a detaching edge, as shown inFIG. 2, a label26detaches there from carrier web22and can be, for example, picked up by a suction plate and transferred onto a box that is to be labeled. Alternatively, the detached label can also be applied directly onto an object P (FIG. 3) that is to be labeled, as is common knowledge to one skilled in the art.

FIG. 3shows a preferred embodiment of a labeling apparatus40according to the invention. This apparatus has a table42having dispensing edge30. Dispensing edge30can also, if applicable, be movable (cf. European Patent 0 248 375 of HERMA GmbH). Label strip20is pulled over this table42as far as labeling edge30, in the manner depicted, and deflected there. At each working cycle, the frontmost label26is detached there from carrier strip22and, for example, picked up by a suction plate (not depicted) or also dispensed directly, “on the fly,” onto an object P that is to be labeled as it passes by. (The suction plate serves to transfer the picked-up label onto a stationary object, e.g. onto a can, carton, or the like.)

Located on table42is a label sensor44whose function is to generate a signal when, for example, a front edge27(FIG. 2) of a label26passes sensor44during the motion of label strip20; that signal triggers an interrupt whose function will be described below with reference toFIG. 12. The sensor can be of any suitable kind, e.g. an optical sensor or an electrically or mechanically operating sensor, as is known to one skilled in the art.

A labeling unit46is mounted on table42. Located in that unit is a computer116(FIG. 4), described below, for controlling the labeling operation, as well as an electronically commutated internal-rotor motor80(FIG. 4) having a very low axial moment of inertia, the entire power supply, EMC filters, and the commutation electronics, as described in detail below. Labeling unit46can be connected directly to the power grid via a power cable48, and requires no further electrical cabinets or the like, thereby greatly simplifying installation and use.

A supply spool52having a label strip20is rotatably articulated on device46via a support arm50indicated with dashed lines. The strip is guided from supply spool52over a deflection roller54and a swing arm56. The latter has a guide surface58with a slight curvature, and has the function of absorbing shocks in label strip20, which are unavoidable because of the high strip speeds (more than 100 m/min) that can be reached. These shocks, and the elastic properties of carrier strip22, make control operations difficult because they are transient phenomena.

In particular with fast-running labeling devices or large, wide label spools, unwinding spool52can also be driven by an electric motor (not shown) whose rotation speed is controlled by the position of swing arm56. This facilitates the control process.

For even faster labeling devices or greater demands in terms of labeling accuracy, a loop can also be provided between supply spool52and a strip brake60; at that loop the label strip is held to a predetermined length, for example by a vacuum and by means of an optical loop scan, so that it is conveyed to strip brake60with a constant tensile stress. This solution is suitable in particular for strip speeds greater than 80 m/min. Corresponding “loop pre-rollers” are offered by HERMA GmbH.

From swing arm56,58, label strip20runs to a strip brake60whose function is to keep strip20constantly in a tensioned state between that brake60and detaching edge30, and as far as transport roller62. Strip brake60acts in general as a damping system for the control system that is used. From brake60, label strip20runs over table42to detaching edge30where labels26are successively individually detached during operation, and carrier strip22(without labels26) runs under table42to a transport roller62that is driven by motor80via gears83(FIG. 17). Carrier strip22is pressed by a pressure roller64against transport roller62in order to transfer all the motions of transport roller62to carrier strip22.

From transport roller62, carrier strip22runs to a swing lever66that serves to compensate for shocks in carrier strip22; and from swing lever66it runs on to a carrier strip take-up spool68that in turn is mounted via a carrier arm70on device46, and forms one compact unit with the latter. Take-up spool68can be driven by a separate motor that is not depicted.

A product detection sensor72, which is connected via a line74to device46and supplies a start pulse when a product P moves past that sensor72, serves to sense a product that is to be labeled. That start pulse then triggers a labeling operation, as is known to one skilled in the art.

FIG. 4shows a preferred exemplifying embodiment of the construction principle of the electrical portion of labeling device46. This uses a three-phase electronically commutated internal-rotor motor80that is coupled to an encoder82for the generation of position signals. From these position signals, for example, 10,000 pulses per revolution can be derived. Motor80drives roller62ofFIG. 3via gears83that are depicted inFIGS. 17 and 18. In the exemplifying embodiment, one revolution of motor80corresponds to the transport of strip22over a distance of approximately 50 mm.

Motor80has a commutation controller84, here having an IGBT* output stage86that is also depicted inFIG. 19, and also having driver stages88and an activation system via optocouplers90in order to achieve galvanic separation from the low-voltage section. This is necessary because motor80preferably operates with a relatively high operating voltage (rectified voltage from the local alternating-current or three-phase power grid). Commutation at startup is controlled in the usual way via Hall sensors (not depicted) that are built into encoder82. A PWM signal is delivered in known fashion, via a line91, to commutation controller84, in particular for current limiting.

Motor80is supplied with energy from an alternating-current or three-phase power grid92. To eliminate EMC interference, this takes place via a power grid filtering and distribution circuit board94. The latter has, as usual, fuses96, chokes (inductances)98, and capacitors100. Connected to output102of board94via a rectifier arrangement104is a DC link circuit106that has smoothing capacitors108and a short-circuit detector110associated with it. DC link circuit106energizes motor80via output stage86[Translator's Note: *Insulated Gate Bipolar Transistor] (in the form of a three-phase full bridge that is often also referred to as a “PWM inverter”). The voltage at the motor depends on the voltage in grid92, which can be, for example, between 85 and 265 V as alternating current, or from 120 to 375 V in a DC range. The voltage at motor80is further dependent on a PWM signal that is generated by a DSP116and delivered via a line91.

The current in two of the three phases of motor80is sensed via current transformers112,114, amplified to a desired level via two operational amplifiers113,115, and delivered to arrangement116for digital signal processing, preferably to a 16-bit digital signal processor (DSP), for example of the 2407 type, in which a motor regulation system and a single-axis positioning system are integrated. Because of its high processing speed of, for example, 40 MIPS, this DSP116enables a particularly high labeling accuracy at a high labeling speed in the context of the invention, but other processors are of course also usable in the context of the invention.

The output pulses of encoder82are also delivered to DSP116via an RS 485 module118and a CPLD element120, thereby making possible regulation of position and rotation speed. The CPLD (Complex Programmable Logic Device) element120serves here to decode the serial signals from encoder82. The two current transformers112,114also make possible current regulation and current limiting, enabling a startup of motor80with a starting ramp of predetermined slope Δ1, as well as a braking operation with a predetermined ramp slope Δ2, i.e. a predetermined braking torque. Via a symbolically depicted busbar connection (bus)93, DSP116supplies the signals for commutation controller84, as well as PWM signals to line91.

DSP116is located on its own circuit board124, on which are also located an I/O interface126, a sensor128for temperature sensing on circuit board124, an EEPROM130for storing a (modifiable, if applicable) program, a RAM132as buffer memory for calculation operations, and a reset IC134. The latter serves to deliver a defined signal level to the reset input of DSP116when the voltage supply is switched on and off, thereby ensuring reliable booting and shutdown of DSP116.

Also provided is a communication module136that serves to connect DSP116to the outside world. This module is connected to DSP116via I/O interface126. It has a QEP interface138for connection to an external master encoder140that, for example when bottles are being labeled, simultaneously controls both the motion of the bottles and the operation of labeling device46synchronously therewith.

When a master encoder140is used to synchronize the speed of products P with the speed of labels26, a fixed value from the potentiometer is not used, but instead the speed is specified by this encoder.

Start sensor72has a dead time that results in different positionings of labels26in the context of a modified speed of product P. To prevent this, a startup compensation for this dead time, in the form of a distance, is calculated on the basis of an inputted dead time and the present speed of products P. This functions even when multiple start signals are present and must be processed successively because of a long start delay. A corresponding compensation is then calculated for each of these start signals, so that labels26are always applied onto products P at the same location.

Master encoder140preferably uses two traces A and B that are delivered to profile generator220as input variables. From the sequence of these pulses, a signal for the rotation direction of motor80can be calculated in known fashion. A “gear ratio” parameter, which can be positive or negative, is also generated. From the frequency of the pulses, the information as to the rotation direction, and the “gear ratio” parameter, a reference variable for positional regulation is generated; that variable usually is not constant but changes during operation.

The reference variable can be positive or negative, for the following reason: there are labeling devices in which table42projects to the left as depicted inFIG. 3, so that label strip20must be transported to the left. There are also, however, labeling devices in which table42projects to the right, and label strip20must consequently be transported to the right. This is indicated by the sign (+ or −) of the reference variable.

If the sign of the reference variable is “wrong” for the selected version, i.e. does not correspond to it, the pulses coming in from product detection sensor72are blocked in order to prevent label strip20from being driven in the wrong direction.

Because encoder140uses two traces A and B, a speed of V=0 m/min during a labeling cycle is also possible, i.e. when a label26has already been partly stuck on. In this case, the true position remains practically unchanged by the decrementing or incrementing of a position counter, and a “drift” in the backward direction is prevented. Such drift could cause carrier strip22to lose its tension.

Module136furthermore has an analog interface142to which can be connected potentiometers144,145,147with which the user can set or fine-tune the labeling speed, the residual distance (follow-on distance) S2(FIGS. 5 to 7), and a start delay. These potentiometers are shown inFIGS. 3 and 16.

Module136furthermore has a serial RS 232 interface146for connection to a PC148, an output interface150for connecting to actuation elements (in particular pneumatic cylinders)152, and an input interface154for connecting to sensor elements156, e.g. in order to specify the direction, sense the temperature, or the like. Lastly, a serial digital connection (not shown) to other devices of identical or similar construction can also be provided, if desired.

A module160serves to supply power to the electronics.

The components enclosed within a dot-dash line164constitute the connection from motor80to the outside. The components enclosed within a dot-dash line168represent the actual drive system plus control system. Further peripheral units, e.g. a keyboard or a display, can be connected to component136if applicable, so that desired functions can be adjusted manually.

Motor80is operated using a four-quadrant controller, since it must be actively braked during a labeling operation, although the capability for running backward, which is inherent in a four-quadrant controller, is suppressed because backward running must not occur in a labeling drive system (since it would eliminate the tension in the label strip and considerably disrupt control operations).

FIGS. 3,17, and19show that motor80is arranged in a tubular component300that is mounted on a housing wall302by means of screws304that also serve to mount motor80. Component300is preferably an extruded aluminum profile, and is closed off on its left side (inFIG. 19) by a solid cover306made of metal, e.g. aluminum, that is mounted on part300by means of screws305(FIG. 19). Cover306is a cast part, and serves as a heat sink and cooling element for a power module81that contains output stage86and link circuit rectifier104.FIG. 19shows further details. Component300dissipates its heat in part to housing wall302, which likewise represents part of the (passive) cooling system. Motor80, in which a great deal of heat is generated because of the high peak currents, also dissipates that heat to part300and to housing wall302. The use of an active cooling system is, of course, not excluded.

Part300and its cover306together form a kind of cover cap307, also referred to as a “scoop,” that receives motor80and a substantial portion of its electronics. Scoop307acts not only as a dust-tight sealed container for these parts, but also as a cooling element; this makes possible an extremely compact design, since external electrical cabinets can in most cases be omitted. This also simplifies installation, since it is necessary only to set up device46and connect it to grid92. It also simplifies explosion protection and protection against moisture, e.g. washing fluid from high-pressure washers.

This design is advantageous because it is thereby possible to encapsulate the entire labeling device46in liquid-tight fashion, for example so that it can be cleaned with a high-pressure washer. For industries in which an explosion hazard exists, e.g. in refineries in hot countries, such devices are preferably implemented in dust-tight fashion in order to reduce the explosion hazard, and the invention makes this very simple.

FIGS. 5 to 7show, in a highly schematic depiction, operations during the dispensing of a label26vonto a suction device170that, in this variant, serves to transfer the dispensed label, after dispensing, onto a stationary product P, e.g. onto a box, a package, or the like.

FIGS. 5,6, and7schematically show the same dispensing edge30and the same label sensor44. During dispensing of a label26, label strip20is pulled in the direction of arrow29by drive roller62driven by motor80. Because one complete revolution of drive roller62transports carrier strip22, for example, 50 mm forward, and because transport distance TW for one dispensing operation is often on the order of from 10 to 200 mm, the operations described usually occur in a range from one to two revolutions of drive roller62, which is connected via gears83to the shaft of motor80, i.e. roller62is first accelerated in accordance with a predetermined speed profile, then proceeds for a while, e.g. for half a revolution, at an approximately constant speed, and is then braked to zero in accordance with a predetermined profile. These operations can repeat, for example, thirty times within one second, if thirty labels are dispensed within that second. These operations must proceed extremely precisely, since the dispensed labels26must be placed precisely at the desired locations with tolerances that are often on the order of 0.1 mm.

InFIG. 5, label strip20is at rest on table42. Located on the latter is a front label26vand a rear label26h. Label sensor44is located on label26vat a location A that is at a spacing S2from front edge27of label26v. After the dispensing of label26v, label26hmust be located under label sensor44(cf.FIG. 7), the latter resting on label26hat a location A′ that is likewise at a spacing S2from front edge27of label26h. Location A′ should therefore correspond as exactly as possible to location A, as one skilled in the art will immediately understand. The spacing between A and A′ corresponds inFIG. 5to transport distance TW, and the latter corresponds (assuming correct transport) to one label length EL+one label spacing SB, as indicated in equation (1); it also corresponds to the sum of two distances S1and S2as depicted inFIG. 5, S1being the spacing from location A to front edge27of rear label26h, and S2the spacing from front edge27to location A′.

As shown inFIG. 6, after a start instruction, label strip20is transported in the direction of arrow29, front label26vbeing advanced with its upper and (in most cases) non-adhesive side26uonto suction device170and being picked up by it.

Front edge27of rear label26hthereby arrives (cf.FIG. 6) at label sensor44, and by it triggers an interrupt in DSP116. In this example, that interrupt therefore exactly defines a specific position of front edge27; and if the intention is to control the motion sequence so that motor80is brought to a stop exactly when label26hhas reached label sensor44at its location A1(cf.FIG. 7), the same spacing S2must then exist between front edge27and that location A′ after each labeling operation, as indicated inFIG. 7.

A new target datum S2is therefore loaded into computer116when the position inFIG. 6is passed through. This new target datum is more accurate than the target datum TW inputted at the position shown inFIG. 5, since TW is continuously subject to small fluctuations that would cause locations A, A′, etc. to “wander” to different locations on labels26over time, i.e. the label would be offset.

It should be noted in particular that although measurement at label edge27offers specific advantages, other types of measurement are nevertheless possible in many cases. For imprinted labels, for example, an optical mark can be provided at a specific location on the label, which mark is scanned during operation and then results in the above-described interrupt whereupon the value S2is loaded; or a hole can be punched in label strip20and an interrupt can be triggered at that hole, etc.

Another advantage is that distance S2can be varied by the user. This value very accurately stipulates the position of points A, A′ on labels26, i.e. that position can be modified as desired by modifying S2, thereby automatically modifying the position of the dispensed labels.

After the installation of a new label strip20, the procedure in practice is as follows:

Labels26are manually pulled off carrier strip22over a length of about 1 m, and the strip is inserted into the labeling device. The label type is usually inputted beforehand into the labeling device; data for that type are stored (or can be stored) in a format memory of the labeling device in order to enable easy switchover to different labels. The following are stored, sorted according to product groups: speed Vsoll, follow-on distance (residual distance) S2soll, and start delay, as well as the gear ratio (electronic gearbox) when master encoder140is used for speed sensing.

Once the strip is inserted, an instruction is given manually for motor80to run; it continues to run until the first label26arrives at sensor44, and is braked to zero after having traveled distance S2.

Because in this case there is still no label26at dispensing edge30, this operation is repeated by corresponding manual instructions until a label26is present at dispensing edge30. Label length EL and label spacing SB are accurately ascertained in this context, i.e. the new label strip is “surveyed” by DSP116.

From now on labeling can occur, since the data regarding label length, etc. are stored. Label length EL and label spacing SB are preferably also continuously ascertained during operation, and automatically corrected as necessary.

A button99(FIGS. 3 and 16), referred to as the “predispensing” button, is provided on the labeling device for manual control of these operations.

If a different label size, for example a longer label, is used, a new distance S2is then also automatically specified, and that distance can additionally be varied somewhat by the user. This makes it possible to install label sensor44at a specific location on table42and, when a label strip having different labels is inserted, to readjust the machine by merely setting the length S2, i.e. an electrical variable. It is therefore often unnecessary to adjust label sensor44mechanically when different types of labels need to be used.

Because the value TW is inputted accurately based on the values stored in the device, the labeling device can continue to operate even if one label26happens to be missing from label strip20, since although no interrupt is then generated by sensor44, the computer is nevertheless working in this case with the variable TW, so that label strip20is brought to a stop at least in the vicinity of positions A, A′. This is important because individual labels may occasionally be missing from a label strip because of production errors. Splices in the label strip can also result in measurement errors. At a splice, a second strip is adhesively bonded onto a first strip by means of a self-adhesive tape, and the presence of that self-adhesive tape increases the thickness of the label assemblage and can therefore lead to incorrect measurements.

If, for example, the spacing between the front edges of two labels is 42 mm, it must be ensured that even at an attachment point where two strips are joined to one another, the label strip is halted every 42 mm, so that all the labels are correctly imprinted in a printer, and none of the objects to be labeled leaves the labeling facility without an imprinted label.

If it were possible for the label strip simply to keep running at a splice, and to come to a halt again, for example, only after 84 mm, a label would then not be imprinted, but it would not be possible to prevent that unimprinted label from then being used for labeling. The invention is therefore highly advantageous especially when a printer is used, since it prevents objects from being labeled with unimprinted labels.

FIG. 8explains the invention with reference to a diagram in which, for simplification and as an aid to comprehension, label strip is depicted notionally20as stationary and label sensor44as moving in the direction of an arrow29′ from the left (i.e. a start position A) to the right, to a measurement position M and then to a target position A′. In this exemplifying embodiment the measurement position M preferably corresponds to front edge27of label26h; other variants are also possible, as already explained.

The depiction inFIG. 8is a specific depiction for motion sequences, and deviates greatly from the ordinary.

As depicted in the upper part ofFIG. 8, the horizontal axis therein shows time t, and the vertical axis shows the speed V of label strip20, i.e. V=dS/dt.

The lower part ofFIG. 8shows motion, but not on a linear scale. At locations A and A′, for example, the speed V is equal to 0.

A calculation of
S=∫V dt(2),
i.e. the integral of the speed over time, yields the distance S that has been traveled. InFIG. 8, for example, the area under curve180,184between locations M and A′ is graphically highlighted, and this area corresponds to the distance S2traveled between times M and A′. This area must not change when the labeler is operated at different speeds, provided the same label is being processed.

Locations A, M, and A′ thus on the one hand represent specific points that sensor44reaches during its (imaginary) motion from left to right; and on the other hand they represent, on the time axis, the points in time at which sensor44reaches these locations A, M, and A′ during its “motion.”

The graphically highlighted area between points M and A′ is made up of a variety of sub-areas, as follows:

An area179is the component of the distance S2soll that is adjustable by the operator of the device. The operator can modify only this portion.

An adjacent area181represents a reserve in case the labeling speed is increased (cf.FIG. 10).

Adjacent to area181on the right is an area185. To the right of area185, area F184lies under ramp184. The area under ramp176is labeled F176.

According to equation (2), the distance S2soll corresponds to the area graphically highlighted inFIG. 8, i.e. the sum of areas179,181,185, and F184; and in the event of a change in the speed Vsoll, the boundaries of these areas must be redefined by DSP116in such a way that their sum remains constant.

A distinction must be made in general betweenA) the profile S=f(t), i.e. the profile of the position setpoint plotted against the time axis; andB) the profile V=f(t), i.e. the profile of the speed of label strip20plotted against the time axis.

The profile S=f(t) is specified to position controller273in the form of small steps, e.g. every 100 μs. One instruction might be, for example: “At the end of the next 100 μs, the label strip must have reached the 13.2-mm position.” In the context of the interrupt at measurement location M, target position Z (which represents a variable) is corrected in profile generator220, so that position controller273then correspondingly receives corrected values, as already described in detail.

The profile V=f(t) is used to generate a labeling cycle as shown inFIG. 8. Ramps176,184are preferably embodied in principle with an acceleration
b=V/t[m/s2]  (3),
i.e. their slope preferably remains substantially independent of the labeling speed. The way in which this is preferably done is described below with reference toFIG. 20.

In start position A, as shown by curve portion176(first motion phase), the increase in speed V begins with a predetermined slope Δ1, i.e. in accordance with how the travel curve is stored in profile generator PG220(FIG. 13). In one exemplifying embodiment, for example, an increase in the motor rotation speed to 3000 rpm required a rotation angle of approx. 66°, corresponding to a motion of approx. 8 mm of strip20/22.

In curve segment176, the speed V increases until a speed Vsoll is reached that can be specified by the user via an adjusting element, as symbolized by an arrow178. The speed Vsoll determines the working speed of the labeler. It can be, for example, between80and 160 m/min. A value of 120 m/min corresponds to 2 m/s, and approximately 10 to 30 labeling operations can then take place every second.

When the speed Vsoll has been reached, the labeling apparatus transitions into an operating mode at a substantially constant speed (curve180=second phase of the motion profile), running through travel distance S1beginning at start position A. Before startup, profile generator220was set to a target position Z=EL+SB, i.e. to a profile in which an overall travel distance TW is traversed, that distance TW corresponding to the total area under curve176,180,184.

After passing through distance S1(measured by means of the output signals of encoder82), label sensor44arrives at measurement position M, i.e. at front edge27of label26h; and passage over this front edge27causes a measurement interrupt at location/time M. At this location, processor DSP116has reached a counter status S1ISTcorresponding to the actual distance S1that has been traveled.

The value S2soll predetermined by the user, which can also be referred to as the residual distance or follow-on distance, is then added to that counter status S1IST. The value
Z=S1ist+S2soll   (4)
is then used as a new target value Z (setpoint for the distance to location A′).

In accordance with variable S2soll and in accordance with the magnitude of speed Vsoll, DSP116now calculates a point in time182at which, according to the slope Δ2of ramp184, active braking of motor80must begin so that by time182, motor80is running at speed Vsoll and transitions there into the decreasing ramp184(third phase of the speed profile), in which motor80is braked by position controller218in such a way that at location A′ it reaches the value V=0, i.e. label strip20is at a standstill.

The predictive calculation of times182,182′ for the transition between phases2and3of the speed profile is performed in DSP116and is explained below, using examples, with reference toFIGS. 9 to 11.

The values to which the user can set the variable S2soll are limited by the program by the fact that the change in area179is limited in the manner described above. It should be noted that as speed V increases, the time interval between times A and A′ decreases, the integral defined by equation (2) (from A to A′) being kept constant by DSP116.

With the method according toFIG. 8, target position Z is therefore redefined, while the motor is running, during the interrupt at measurement location M (front edge27of label26h). This method decisively enhances labeling accuracy in practical use. This is because the result of this method is that spacing S2between point A and front edge27of front label26vvery largely corresponds to spacing S2soll between point A′ and front edge27of rear label26h, i.e. points A, A′ do not “wander,” but retain the spacing S2, set by the user, from front edge27of the respective label26. This “correction” allows the interference factors that occur during operation of the labeling device to be largely compensated for. These factors are principally:

a) The variable forces that act from outside on the strip, i.e. label strip20and carrier strip22, principally as a result of the resilient swing arms56and66(FIG. 3).

b) The effects resulting from the fact that strip20/22elongates as it is accelerated during the rising phase176, also referred to as the “rubber band effect” in such label strips.

c) Small fluctuations in label length EL and label spacing SB—so-called “pitch errors”—also have no influence, provided the measurement is made as close as possible to dispensing edge30, for which reason an effort is made to arrange sensor44as close as possible to dispensing edge30.

FIGS. 9 to 11serve to explain the automatic adaptation of the profile, by means of profile generator220, when setpoint speed Vsoll needs to be modified.

FIG. 9is a depiction analogous toFIG. 8. If angles Al and A2have the same absolute value, i.e. if rising flank176has a slope of the same absolute value as falling flank184, area F184(under flank184) is added to area F146(under flank146) to yield a rectangle as symbolically depicted by an arrow183; what is obtained overall in this simplified example, together with rectangular area F180(under portion180), is a rectangle having a height Vsoll and a length T, length T being the time between leaving point A and reaching point182, the value of which is labeled182′ on the time axis.

This area corresponds to the dimension TW ofFIG. 2, i.e. the spacing between front edges27of two successive labels26.

When speed Vsoll is modified, this area TW must not change. In this simplified example, therefore:
TW=Vsoll*T(5).
The consequence is that if label spacing TW and speed Vsoll are known, the variable T can be directly calculated as
T=TW/Vsoll(6).

What is known in this example is therefore the following: After startup at location A, speed V increases with a slope Δ1until speed Vsoll has been reached.

Once Vsoll has been reached, label strip20is driven at a constant speed Vsoll until, at time A, the time interval T=TW/Vsoll has elapsed, i.e. time182′ has been reached.

At time182′, the drive system is switched over to braking with a slope Δ2, and at time A′, position A′ on rear label26his reached in position-controlled fashion (FIG. 8) independently of the speed Vsoll that is set, i.e. labeling always occurs correctly regardless of whether the machine is running fast or slowly.

InFIG. 10, the drive system is set to a maximum speed Vmax, i.e. rising flank176and falling flank184are longer than inFIG. 9. The gray-shaded area TW must correspond to area TW shown inFIG. 9, and consequently time T here is correspondingly shorter, i.e. T=TW/Vmax.

Here as well, time T since startup at location A is measured, and if that time has elapsed upon reaching location182′, the system switches over to braking, e.g. with a slope Δ2.

FIG. 11shows the analogous case in which the drive system is set to the minimum speed Vmin. Here as well, the gray-shaded area TW must correspond to the size of the corresponding areas TW inFIGS. 9 and 10, and the result is a correspondingly long time
T=TW/Vmin
between leaving location A and reaching time182′; at this point the system switches over to the falling flank182, so that here again, labeling is performed correctly.

On the basis of these variables, profile generator220calculates the profile that corresponds to speed Vsoll that has been set, variable T being calculated predictively in the manner described.

T is particularly easy to calculate if slopes Δ1and Δ2are made equal in terms of absolute value, but these slopes can, of course, also be different. In that case areas F146, F180, and F184must be calculated or estimated separately, and the applicable equation is then
TW=F146+F180+F184   (7).

The rotation speed profile that must be generated by motor80is therefore calculated from the data delivered to DSP116; for a specific label type, spacing TW defines the size of the area under the profile176,180,184, and that area, regardless of the speed Vsoll that is instantaneously set, is kept substantially constant by automatic recalculation of the speed profile V=f(t).

It should be noted that variable T is usually equal to only a fraction of a second, since, for example, thirty labeling operations occur every second. This depends on the speed Vsoll that is set, since of course fewer labels are processed per second at a lower speed.

The fact that target variable Z is corrected at location M results automatically in an adaptation if spacing TW changes in a label strip, as has already been described in detail. This then also results in a correction of time T, as is clearly apparent to one skilled in the art from the description above, i.e. if target variable Z changes, time182′ is preferably also recalculated.

It is very important, especially for the labeling of objects P as they pass by (cf.FIG. 3), that within a predetermined period of time, a label26that is to be dispensed reach the same speed as that object P, so that the label is “stuck” onto that object at the correct location; the label must also be dispensed at exactly the speed of the product passing by, i.e. good synchronization between product P and label26must be ensured. This requires that the motion of label strip20obey corresponding instructions very exactly, i.e. that position controller273be able to control the motions of label strip20very effectively.

FIG. 12is a flow chart for execution of the CORR.Z (target correction) routine S200that controls the rotation speed profile of motor80.

S202checks whether a start signal from sensor72(FIG. 3) is present. If No (N), the routine enters a loop back to the beginning. If Yes (Y), the routine goes to step S204. There profile generator220(FIG. 10) is loaded in accordance with the predetermined parameters, e.g. the value Z:=TW and the desired speed Vsoll. The values generated by profile generator220are based on stored value tables, and the profile generator calculates the motion profile therefrom. The profile is a rotation speed profile and begins at V=0 and ends at V=0, as depicted inFIG. 8. The value Z in S204corresponds to the sum (EL +SB) for label strip20being used. (It is also possible, if applicable, to work with multiples of (EL+SB) if no printer is provided on labeler46.)

S206then checks whether measurement position M has been reached, i.e. whether label sensor44has generated, at front edge27of label26h, a signal that triggers an interrupt in the manner already described, in order to enable an immediate reaction to this event caused by rear label26h.

If measurement position M has been reached (response =Y), profile generator220is corrected in S208in the manner already described, and the measured distance S1ist, measured up to where measurement position M was reached, has the desired residual distance S2soll added to it in accordance with equation (4); the result Z=S1ist +S2soll is used as a new target variable Z, i.e. replaces target variable Z from S204, so that profile generator220regulates the operation of motor80according to the new target variable Z, i.e. the profile generator is correspondingly corrected, if applicable, as indicated in S208. (Ideally, the target variables Z from steps S204and S208are entirely identical, but small differences are unavoidable in practice. If the values are identical, profile generator S220of course need not be corrected.)

The program then goes to S210, where it checks whether target position Z has been reached. InFIG. 8, this target position corresponds to location A′ on label26h, i.e. label sensor44is then located exactly opposite this previously calculated location A′ and motor80stands still, i.e. V=0. If this is the case (Y), routine S200goes back to the beginning and waits for the next start signal.

If the response in S210is No (N), the routine goes back to step S206.

If the response in S206is continuously No, for example because a label26is missing from carrier strip22and label sensor44consequently cannot find a measurement location M and cannot trigger an interrupt, the correction of value Z in step S208does not take place and the routine goes from S206directly to S210, i.e. it continues to work with target variable Z from S204and, here as well, checks in S210whether Z has been reached. If No, the routine once again goes back to S206. If Yes, it goes back to S202and waits there for a new start signal.

If a label26is missing from carrier strip22, label strip20is therefore nevertheless halted approximately at location A′, provided target value Z has been defined in S204as the sum (EL+SB) according to equation (1). This is important especially when the individual labels26are being printed in the labeling device, as depicted inFIG. 16, since in many cases carrier strip22must be stationary for printing. If a label is missing, in that case the stationary carrier strip22is imprinted.

Depending on the application, routine S200can contain plausibility checks, for example as described for the value S2soll.

FIG. 13shows the associated control arrangement218. The number220designates profile generator PG that, after the input of data222(start instruction, slopes Δ1, Δ2, TW, Vsoll, etc.) generates a speed profile as depicted and explained, for example, inFIG. 8. PG220thus has delivered to it a target position Z which can correspond at startup to value TW according to equation (1) or also, if applicable, to a multiple of TW if no printer280(FIG. 16) is provided.

PG220generates at its output221a setpoint distance Ssoll that is delivered via a setpoint/true value comparator224to a PI position controller S-CTL226. What is delivered to comparator224as the present variable is the distance Sist actually traveled by label strip20, which distance is obtained by counting, in a counter228, pulses83supplied by encoder82. (Counter228can be located in DSP116.) The value Sist is also delivered to a calculation element230.

FIG. 13shows that in this example, encoder82has a total of six outputs, labeled A, A/, B, B/, X and X/. These are connected to a logical switching element227, where their signals are evaluated and processed into logic signals A1, B1, and X1that in turn are delivered to a converter229which generates therefrom, at an output231, a rotational position signal Ωist that indicates the rotational position of motor80. This signal is required for the generation of a space vector.

The information from three Hall sensors is transferred on the X channel as a serial signal that indicates the instantaneous position of the permanent-magnet rotor in motor80even when it is stationary.

In the exemplifying embodiment, motor80runs during operation as a so-called sine-wave motor, i.e. as a three-phase motor having sinusoidal stator currents. These sinusoidal currents cannot yet be generated immediately after switching on, however, since they require a very exact sensing of the rotor position, which is not possible at a standstill.

Approximate information as to rotor position is available via the X channel, however, so that motor80can start in an operating mode as a brushless motor80, for which approximate rotor-position information is sufficient.

As soon as motor80is rotating sufficiently fast, it is switched over to operation as a sine-wave motor, since the rotor position can then be measured with very fine resolution.

Signals A1and B1are delivered to a QEP unit233that is integrated into DSP116. This unit increases the resolution of encoder82by a factor of four, i.e. if encoder82supplies, for example, 2,500 pulses per revolution, 10,000 pulses per revolution are then obtained at the output of QEP unit233. Higher resolution, and therefore higher system accuracy, is thus obtained. In many cases, of course, a lower accuracy will also be sufficient. A rotation speed signal nist, in the form of pulses83whose frequency is proportional to the instantaneous rotation speed of motor80, is therefore obtained at the output of QEP unit233.

Pulses83are integrated in an integrating element (counter)228, yielding at its output237a distance signal Sist that corresponds to the distance traveled by label strip20.

FIG. 14shows the various signals. Signals A and A/ are generated by a first signal trace, and signals B and B/ by a signal trace offset therefrom by 90° el.

As depicted inFIG. 14, rotation speed signal nist is generated by differentiating the flanks of signals A/, B/. Signal A1corresponds to signal A, and signal B1corresponds to signal B. The phase shift between signals A and B yields the rotation direction of motor80, as is known to one skilled in the art.

Because a large difference can exist, particularly at the beginning, between Sist (=0) and Ssoll, a corresponding control variable is produced at the output of PI controller226, and this variable is then limited, if applicable, to a predetermined value in a limiting element232. (Because the PI controller is preferably digital, this limiting operation is part of the control program. The value to which limiting occurs can here, as also in limiter250, be variable and adjustable. The limitation becomes effective only if the control variable exceeds the value that is set.)

A setpoint Nsoll for the rotation speed of motor80is obtained at the output of limiter232. This setpoint is compared, in a comparator234, with the true rotation speed value Nist delivered from output235of QEP unit233.

The output signal of comparator234is delivered to a digital PI rotation speed controller238at whose output is obtained a control value to which is added, in an adding element240, the output signals of a feed forward (FF) element242for acceleration, and of an FF element244for speed Vsoll.

Element244(FF Vsoll) receives its input signal from a differentiating element270, which serves to differentiate over time the setpoint positions furnished by profile generator220at its output223, i.e. to create a speed setpoint dSsoll/dt, and this value is multiplied in element244by an empirically ascertained predetermined factor and delivered to adding element240as an input variable.

Element242(FF acceleration) receives its input signal from a differentiating element271, which serves to differentiate the speed setpoint calculated in element270over time once again, i.e. to calculate a setpoint for the acceleration; and this acceleration setpoint is multiplied in element242by an empirically ascertained predetermined factor and then likewise delivered to adding element240as an input variable. Element242thus multiplies the variable received from elements270,271and delivers it to element240.

These differentiation operations thus constitute a predictive intervention in the control loop, enhancing both the dynamics of controller218and its accuracy when positioning labels26. This is explained in detail below with reference toFIG. 20.

This is particularly important at location A inFIG. 8, i.e. at the transition from V=0 to rising ramp176, also at location177(transition from rising ramp176to region180of constant speed), also at location182(transition from region180to braking ramp184), and lastly at location A′, i.e. at the transition from the active braking portion184to a standstill, i.e. to V=0. overshooting or undershooting at locations A,177,182, and A′ is thereby very largely eliminated, and the transitions proceed substantially asymptotically. The multiplication factors in elements242,244are ascertained empirically and depend, among other factors, on the type of motor80. The principal result of correct adjustment is that backward rotation of motor80at points A and A′ becomes almost impossible. Any such backward rotation would lead to a loss of tension in carrier strip22and is therefore undesirable.

The end of horizontal region180(FIG. 8), i.e. time182′, is calculated predictively in the manner described. The predictive calculations that are preferably used in the present invention result in an increase in the system's dynamics, i.e. they make possible very good positioning accuracy and repeatability at high labeling speeds.

The output signal of element240is delivered to a limiter250, and the control value at the output of limiter250serves as the current setpoint isoll for the q axis.

Motor80, which is also referred to as a synchronous machine with permanent-magnet excitation (PMSM), operates in this exemplifying embodiment with a field-oriented control system (vector control), the field-forming current (“exciting current”) and the torque-forming current being regulated separately. The basis of a field-oriented control system of this kind is that the current components that are to be decoupled are impressed into motor80by separate current-control loops.

With a control system of this kind, a distinction is made between the so-called d component, also called the direct-axis component or field-forming component, and the q component, also called the quadrature-axis component, of the motor current.

q Component

A linear correlation exists between the torque generated by motor80and the quadrature-axis component. Because motor80has a permanent-magnet rotor whose rotor flux is constant, the output variable isoll at the output of limiter250can be used as a setpoint for the quadrature-axis component. It is compared in a comparator266with a variable Iq, and the result of the comparison is delivered to a PI current controller268.

d Component

Because motor80has a permanent-magnet rotor whose magnetic flux is constant, a value of 0 is specified by a sensor246for the d component and is delivered to a comparator258, to whose negative input a value for the current Id is delivered. Motor80is therefore regulated here so that the d component has a value of 0.

Motor80has three phases u, v, w in its stator winding, and has a permanent-magnet internal rotor (not shown). As described, motor80is controlled upon startup as a brushless motor by means of Hall sensors (or, alternatively, according to the sensorless principle), and after starting it operates as a three-phase synchronous motor with approximately sinusoidal currents.

It has for this purpose inverter86, already described, in the form of a three-phase full bridge, e.g. having IGBT transistors or other controllable semiconductors. Bridge86is controlled via optocouplers90and gate drivers88(cf.FIG. 4).

Currents Iu and Iv in two of the three supply leads u, v, w of motor80are sensed via the two current transformers112,114and converted in DSP116, in an A/D converter provided therein, to digital signals. They are then delivered to a uvw-dq coordinate converter256, along with the signal Ωist from converter229. Converter256generates therefrom, by transformation, the previously mentioned d-axis current component Id and q-axis current component Iq for the d and q axes, which serve as feedback variables for the two current controllers260and268, respectively.

As already explained, the d-axis current component Id is delivered with a negative sign to summing element258, to whose positive input a value of 0 is delivered. The output signal of element258is delivered to digital PI current controller260, at whose output a signal Ud is obtained, namely a setpoint for the d-axis voltage Ud, which signal is delivered to a dq-uvw coordinate converter262that is also referred to as a space vector modulator or space vector generator.

The output signal iSOLL of limiter250is delivered to the positive input of summing element266, to whose negative input the output signal Iq of converter256is delivered. The output signal of comparison element266is delivered to a PI current controller268, at whose output a setpoint for the q-axis voltage Uq is obtained. This value Uq is likewise delivered to dq-uvw coordinate converter262, to which the rotor position signal Ωist is also delivered; the converter generates from these input signals three signals Uu, Uv, Uw to control the module86that energizes motor80, so that a circulating rotating field is generated in motor80.

Modules86,256,260,262,268are hardware or software modules that are familiar to one skilled in electrical drive systems. These modules are used, for example, in servocontrollers for motor vehicle steering systems, and in frequency converters. In the exemplifying embodiment, they are in part constituents of DSP116.

Located in link circuit line106(FIG. 4) that leads to module86is a measurement resistor (not shown), which makes possible short-circuit sensing and ground-fault sensing in element110in order to protect module86. If a short-circuit pulse exceeds a predetermined length, component110shuts off driver88and sends a corresponding signal to DSP116.

FIG. 15shows the functions of the individual constituents of controller281. The number269designates the current controller that directly influences the sinusoidal currents Iu, Iv, Iw in motor80.

Current controller269is a constituent of a rotation speed controller271upon which, as depicted, the setpoint acceleration from element242and the setpoint rotation speed nsoll from element244act directly.

Lastly,273designates a position controller to which a setpoint Ssoll for the position of label strip20is delivered directly from profile generator220, and which causes motor80to come to a standstill exactly at the desired location A′.

Element230is triggered by label sensor44. When the latter generates a signal at a label edge27(location M inFIG. 8), that signal causes a measurement interrupt, and at that point, in accordance with equation (2), the value S2soll is added to the value S1ist that has been reached and is used as a new target variable Z, as has already been described in detail; the result is that points A, A′ do not “wander,” i.e. labels26are not “offset,” and a high level of labeling accuracy is obtained.

FIG. 16shows a labeler46analogous to the one depicted inFIG. 3, except that a printer280of known design is installed on table42. The (adjustable) table42is therefore more elongated, and printer280is located (as an example) between label sensor44and dispensing edge30. Parts identical, or having functions identical, to those inFIG. 3are labeled with the same reference characters as therein, and will not be described again.

Because printer280is usually controlled by labeling device46, i.e. in most cases by DSP116, when printer280is connected the program can be modified in such a way that variable Z can be set by the user only to [EL+SB]. This can be accomplished by a corresponding input form on which the type of labeling, label length, and label spacing must be inputted by the user, and target variable Z is set in accordance with those inputs once their plausibility has been checked. If a label26is missing from carrier strip22at any point, label strip20nevertheless comes to a halt, carrier strip22is imprinted by printer280, and transport and, if applicable, imprinting of the carrier strip then occurs again if a second label also happens to be missing.

The advantage achieved with the arrangement depicted inFIG. 16is that labels26can be imprinted in very precisely fitting fashion, because the “correction” or “synchronization” occurs at measurement location M close to printer280. Waste is thus avoided, and the invention is suitable in the same fashion, for example, for applications in which the only requirement is that labels26arranged on a carrier strip20be sequentially imprinted inline with very precise fit and at high speed.

FIG. 18shows housing part302of device46ofFIG. 3from the back side (with the back wall removed), i.e. looking in the direction of arrow XVIII ofFIG. 17. Housing part302has two openings320,322that can be used to install it on a machine.FIG. 17also shows the location of processor116in part300.

Visible inFIG. 18are motor80and its shaft324, on which a belt pulley326(e.g.14teeth) for a toothed belt328is mounted. The latter passes over a tension pulley330to a belt pulley332(e.g. 32 teeth) that drives roller62(FIGS. 3 and 16). In this example, therefore, one revolution of roller62corresponds to 32/14 revolutions of motor shaft324.

A variety of circuit boards are arranged in housing part302, e.g. circuit board94for the EMC filter, and three further circuit boards336,338,340having electronic components.

A lateral adjusting wheel344allows the position of label sensor44to be modified.

FIG. 19is an enlarged cross-sectional depiction of the unattached end of scoop307. A portion of motor80, encoder82, and board84having power module81(inverter86and rectifier104for energizing link circuit106, cf.FIG. 4) are visible. Inverter86and rectifier104are manufactured as a complete module81, for example, by the EUPEC company. Inverter86has, for example, six IGBT transistors. This module81rests at an end surface87, on which thermoconductive paste89is provided, with a preload against an inner wall85of cover306, so that heat is transferred out of module81into cover306and from there into tubular part300, as indicated symbolically by arrows18.

At the transition from cover306to tubular part300, an0-ring303is provided in a continuous groove301in order to join parts300,306to one another in liquid-tight fashion; this is important principally in terms of cleaning with a high-pressure washer, which is used in many facilities. Cover306is mounted on tubular part300by means of screws305. Part300is also mounted in liquid-tight fashion on housing302.

A panel307is provided in the interior of tubular part300, extending approximately perpendicular to its longitudinal axis. This panel is equipped with pegs309that engage, in the manner depicted, into recesses311of module86,104.

Panel307with its pegs309is pressed by springs311toward cover306with a force of, for example,150N, and by its pegs309presses module81against inner wall85of cover306so that a low heat transfer resistance is obtained there.

Because cover306is particularly thick in the region of module86,104, its thermal capacity at that point is sufficient that local overheating can reliably be avoided even when the labeling device is under heavy load.

As is evident fromFIG. 19, lower screw305is embodied in two parts. Its inner part305i serves, as depicted, to guide panel307and circuit board84, both of which are provided with corresponding cutouts for the purpose.

FIG. 20explains the working principle of position controller273that is used. The vertical axis shows distance S traveled by label strip20. The horizontal axis shows time t; one labeling cycle can last, for example, 12 ms. Within that time, label strip20must be transported from a location A to a location A′, e.g. a distance of 20 mm, corresponding to variable TW. The average speed of label strip20that results is then
0.02m/0.012s=1.7m/s=100m/min.

Within this time span of, for example, 12 ms, label strip20must stringently comply with a prescribed motion protocol, since correct labeling, “on the fly,” of products passing by would otherwise be impossible; in other words, the position controller must be a very “stiff” one that reaches the setpoint speed Vsoll exactly within a prescribed time period and also maintains that setpoint speed for a prescribed time span exactly, i.e. at a very consistent speed.

This compliance with a predetermined motion protocol is achieved by the fact that during labeling, controller218is preferably operated continuously in the position control mode, the values for the setpoint acceleration and setpoint rotation speed becoming even more strongly effective at vertices177,182(FIG. 8) of the profile, because those values abruptly change there.

For this purpose, a speed profile V=f(t) and a position profile S=g(t) are calculated from the data that are delivered, i.e. Δ1, Δ2, TW, and Vsoll.FIG. 20shows, by example, one such position profile S=g(t). Because the profile V=f(t) is easier to define and to recalculate (for example if parameters change), the position profile is preferably derived from the speed profile; this can be done with simple calculation operations, as one skilled in the art will immediately recognize.

For example, it is known from the position profile ofFIG. 20that a distance of 4 mm must be covered after a time t1, and a distance of 16 mm after a time T=TW/Vsoll; and that label strip20must have come to a standstill after moving 20 mm.

These distance data are resolved into small increments Δt and ΔS, e.g. of Δt=500 μs; and profile generator220specifies to controller273, for example at a location300(FIG. 20), that in the next 500 μs, strip20must have proceeded over a distance increment ΔS of 1.4 mm and must have reached location302(5.4 mm) (corresponding to a setpoint speed of 2.8 m/s). At location302, since speed Vsoll is constant there, profile generator220accordingly once again specifies to controller273that strip20must have covered another ΔS=1.4 mm within the next Δt of 500 μs, and reached a location304(6.8 mm), and so forth.

The working principle of a digital position controller of this kind, as indicated by the description above, is therefore that of “traversing” to a closely-packed succession of predetermined positions in accordance with a precisely defined time sequence.

The predetermined profile is thus “traversed” in a rapid succession of instructions, the result of the selected controller configuration, with a subordinate speed controller and current controller, being that the motion follows the predetermined pattern very exactly.

No overshoots therefore occur at the transition points, e.g. at locations177and182inFIG. 8, since a controller of this kind, so to speak, automatically “irons out” or “evens out” the sharp edges there. This is achieved principally by the fact that inFIG. 13, summing element240at the output of PI controller238has delivered to it, as correction values, the setpoint acceleration from element242and the setpoint rotation speed from element244.

When, for example, at location177in the profile inFIG. 8, the setpoint acceleration decreases from a positive value to zero (since as of point177the strip speed Vsoll is constant), the input signal of PI current controller268then drops correspondingly, and the motor current is immediately reduced so that an overshoot does not occur.

Similarly, at location177the setpoint Vsoll for the strip speed becomes constant, while prior to point177it was continuously rising.

The result of both facts is that at point177the strip motion transitions without overshooting into portion180having a constant speed Vsoll; this is very important, for example, for correct labeling of objects (P inFIG. 3) that are passing by.

Analogously, at location182(FIG. 8) the setpoint acceleration, which previously had a value of zero, becomes negative, with the result that the controller transitions almost immediately, and without overshooting, into braking mode; also contributing to this is the fact that as of location182, the setpoint Vsoll for the strip speed continuously decreases.

The signals from PI controller226bring about continuous position control, so that a strip speed of zero is reached at location A′. A digital position controller of this kind is thus a very effective way of achieving a predetermined distance profile, and indirectly a predetermined speed profile, with no overshooting.

The size of the steps At used by the controller, i.e. the so-called cycle time, is normally shortest in current controller269, since the motor current can change most quickly.

FIG. 20indicates by example that the time span T (cf.FIGS. 9 to 11) can have a value TW/Vsoll. This corresponds to the example ofFIGS. 9 to 11. In a different profile, of course, the time span T can have a different value, as explained in detail with reference toFIGS. 9 to 11.

At measurement location M (FIG. 8) a new value Z is used instead of TW, and in this case a new value for T
T′=Z/Vsoll(8)
can result if TW is not identical to Z, and provided the example according toFIGS. 9 to 11is taken as the basis. In this case, a new time182′ is also calculated.

Reference characters176,180, and184inFIG. 20refer to the corresponding portions of the depiction inFIG. 8, and are intended to facilitate comparison between the depictions ofFIGS. 8 and 20.

Many variants and modifications are of course possible within the scope of the present invention without departing from the basic concept of the invention. For example, a portion of the motion profile could be generated by a speed controller.