LABEL PRINTERS

Description

[0001] The invention relates to a label printer for printing on a paper tape wound on a roll, comprising a printer housing in which a receiving space is provided for the roll of paper tape or for a cassette containing the roll of paper tape, wherein the paper tape can be inserted into a paper path and transported along the paper path, a housing element attached to the printer housing and foldable between an open position and a closed position, in particular a housing door, which allows access to the receiving space for inserting and removing the roll or cassette in the open position and prevents access in the closed position, and a control unit which is designed to detect the state of the label printer, namely whether the housing element is closed or the cassette is inserted and whether the paper tape is inserted into the paper path.

[0002] The control unit requires various sensors to determine the status of the label printer. Firstly, it must check whether the printer door is closed and whether the cassette is inserted into the printer. Only in this case can the printer be used. If the printer door is open or if the cassette is not inserted or not fully inserted, the printer is not functional. A door sensor is provided for this purpose. Secondly, it must check whether a paper ribbon is inserted into the paper path. Only then can printing take place. If there is no paper ribbon in the paper path, the paper ribbon must be inserted correctly into the paper path. A paper sensor is provided for this purpose.

[0003] A label printer with a door sensor and a paper sensor is known, for example, from document EP 2 103 531 A1. The door sensor comprises a light barrier with a transmitter and a receiver, which is provided on the printer housing and which can be interrupted in the closed position by a projection provided on the printer door. The paper sensor is usually designed as a forked light barrier in which the transmitter and the receiver are U-shaped, with the edge of the paper strip being guided between the transmitter and the receiver. However, such a sensor system with two transmitters and two receivers is expensive, i.e., associated with correspondingly high manufacturing costs. A label printer with the features of the preamble of claim 1 is known from document JP 2007 106556 A. Document US 2014 / 0227017 A1 discloses a label printer with a housing and a foldable housing element.A reflective light barrier with a light transmitter and a light receiver is provided in the housing, and a reflective plate is provided in the hinged housing element.

[0004] The invention is based on the object of providing a label printer of the type mentioned above which offers a more cost-effective way of recording the status of the label printer.

[0005] This object is achieved by a label printer having the features of claim 1, and in particular in that a reflection light barrier with a light transmitter for emitting a transmitted light beam and a light receiver for receiving a reflected portion of the transmitted light beam as well as a further light receiver for receiving a transmitted portion of the transmitted light beam are provided, wherein the reflection light barrier is provided on the printer housing and the further light receiver is provided on the housing element or the cassette, or vice versa, iethe reflective light barrier is provided on the housing element or the cassette and the further light receiver is provided on the printer housing, and wherein, in the closed state of the housing element, the reflective light barrier and the further light receiver are arranged on two opposite sides of the paper path, and that the control unit is designed to detect the state of the label printer based on a joint evaluation of the reception intensity of the light receiver of the reflective light barrier and the reception intensity of the further light receiver.

[0006] According to the invention, only one transmitter and two receivers are required. Compared to label printers known from the prior art, one transmitter can be omitted. The special placement and arrangement of the reflective light barrier and the additional receiver makes a second transmitter unnecessary. In other words, the transmitter of the paper sensor can also be used to detect whether the housing element is closed and / or the cassette is inserted, or the transmitter of the door sensor can also be used to detect whether the paper ribbon is inserted into the paper path. Ultimately, according to the invention, the door sensor or the label sensor are combined.

[0007] The joint evaluation of both reception intensities means that both the reception intensity of the light receiver of the reflective light barrier and the reception intensity of the additional light receiver must be evaluated to determine the status of the label printer. Evaluating only the reception intensity of the light receiver of the reflective light barrier or only the reception intensity of the additional light receiver is not sufficient for this purpose.

[0008] As already mentioned, the roll of paper tape can also be contained in a cassette, also called a tape cassette, with the cassette being accommodated in the receiving space. The receiving space is then a cassette compartment. When using a cassette, instead of checking whether the printer door is closed, it can be checked whether the cassette is inserted. Checking whether the cassette is inserted does not preclude checking whether the printer door is open, and vice versa.

[0009] Detecting the condition that the paper tape is not inserted into the paper path may mean that after inserting the roll or cassette into the receiving space, in particular after changing the roll or cassette, the paper tape has not yet been inserted into the paper path by the operator, or that the end of the paper has been reached.

[0010] The light transmitter can be, for example, a laser diode, which in particular has a wavelength in the visible red or infrared light range. The two receivers can be, for example, a photodiode or a phototransistor. The transmitted light beam can be modulated to reduce the sensitivity of the two light receivers to external light, especially ambient light. For this reason, a filter can be arranged in front of each of the two light receivers, which can be used to filter out external light in the visible range, for example.

[0011] In principle, it is also possible for the additional light receiver to be part of an additional reflective light barrier with an additional light transmitter, whereby the additional light transmitter is inactive or not used. Compared to the state of the art, this also offers the advantage of lower costs, since the additional light transmitter does not need to be wired, operated, or maintained.

[0012] The label printer comprises a print head and a counter element thereto, in particular a printing roller, wherein the paper path is predetermined such that the paper web can be guided between the print head and the counter element. The reflective light barrier and the further light receiver are arranged upstream of the print head and the counter element, in particular at a distance of no more than 10 cm, in particular no more than 5 cm, as seen in the transport direction of the paper web.

[0013] In particular, the control unit is designed to detect, when a transmitted light beam is emitted by the light transmitter, that the housing element is open or the cassette is not inserted if the reception intensity of the light receiver of the reflective light barrier is less than a predetermined reflection reference value and the reception intensity of the further light receiver is less than a predetermined transmission reference value, and that otherwise the housing element is closed or the cassette is inserted. When the housing element is open, the two light receivers receive at least substantially only ambient light.

[0014] If the additional light receiver is provided on the cassette and the cassette is not inserted and the additional light receiver cannot deliver a reception signal to the control unit, in particular due to a lack of electrical contact, this corresponds to an additional light receiver connected to the control unit that sees no light, i.e. has a reception intensity that is lower than the specified transmission reference value, so that in this case too, it can be correctly detected that the cassette is not inserted. This applies accordingly to the light receiver of the retro-reflective light barrier if the retro-reflective light barrier is provided on the cassette, and in particular also if the light transmitter of the retro-reflective light barrier does not emit a transmitted light beam due to a lack of electrical contact.

[0015] The control unit can be configured to detect, with the light transmitter deactivated (i.e., when no transmitted light beam is being emitted from the light transmitter), that the housing element is open or the cassette is not inserted if the reception intensity of the light receiver of the reflective light barrier is greater than a predetermined reflection threshold and / or the reception intensity of the additional light receiver is greater than a predetermined transmission threshold. If light is received with the light transmitter deactivated, this can only be external or ambient light.

[0016] Preferably, the predetermined reflection threshold value is smaller than the predetermined reflection reference value and / or the predetermined transmission threshold value is smaller than the predetermined transmission reference value. These values allow the status of the label printer to be detected with particularly high reliability.

[0017] Furthermore, it can be provided that—if it has been detected that the housing element is closed or the cassette is inserted—the control unit is configured to subsequently detect whether the paper tape is inserted into the paper path. The check as to whether the paper tape is inserted into the paper path can thus be performed after the check as to whether the housing element is closed or the cassette is inserted, and is performed, in particular, only if it has previously been detected that the housing element is closed or the cassette is inserted.

[0018] Preferably, the control unit is configured to detect, when the light beam is emitted by the light transmitter, that the paper ribbon is not inserted into the paper path if the reception intensity of the light receiver of the reflective light barrier is less than a predetermined reflection threshold or the reception intensity of the additional light receiver is greater than a predetermined transmission threshold, and that otherwise the paper ribbon is inserted into the paper path. If no paper ribbon is inserted, only a small amount of light is reflected, namely by the additional light receiver, which receives a large amount of light from the light transmitter.

[0019] Preferably, the predetermined reflection threshold value is smaller than the aforementioned predetermined reflection reference value and / or the predetermined transmission threshold value is greater than the aforementioned predetermined transmission reference value. Using these values, the status of the label printer can be detected with particularly high reliability.

[0020] In particular, it is provided that the control unit is configured to block the printing operation of the label printer if, based on the joint evaluation of the reception intensity of the light receiver of the reflective light barrier and the reception intensity of the additional light receiver, it is detected that the housing element is open, the cassette is not inserted, or the paper ribbon is not inserted into the paper path. The label printer is then not ready to print.

[0021] According to a preferred embodiment, the control unit is designed to differentiate between paper tape types that differ from one another in terms of their reflectivity and / or light transmittance, in particular in terms of the location dependence of their reflectivity and / or light transmittance in the tape direction, based on at least one of the two received intensities when the light beam is emitted by the light transmitter. The operation of the label printing can then be adapted to the respective paper tape type detected. A paper tape type can in particular be a label tape or an endless tape. A label tape is understood to mean, for example, a carrier tape with self-adhesive labels applied thereto, a self-adhesive linerless tape with black marks, and a carrier tape with self-adhesive labels and black marks applied thereto.An endless tape includes, for example, a self-adhesive linerless tape without black marks and a non-self-adhesive receipt paper.

[0022] Specifically, the control unit can be configured to detect, based on a temporal profile of the reception intensity of the further light receiver, whether the paper tape is a paper tape of a first type whose light transmittance varies in the tape direction according to a repeating pattern, in particular a label tape as explained above, or a paper tape of a second type whose light transmittance is constant in the tape direction, in particular an endless tape as explained above, when a transmitted light beam is emitted by the light transmitter and when the paper tape is inserted into the paper path and transported along the paper path. The predetermined time period can result, in particular, from a predetermined time value or from offsetting a predetermined path by which the paper tape is transported with the transport speed of the paper tape.

[0023] It is preferred if the control unit is designed to detect that the paper tape is a paper tape of the first type if the temporal profile of the reception intensity of the further light receiver changes from a first value to a second value that differs from the first value by at least a predetermined reference difference, and that otherwise the paper tape is a paper tape of the second type. By the change in the reception intensity of the further light receiver from the first value to the second value, a label gap can be detected. However, if the value of the reception intensity of the further light receiver remains constant within a fluctuation range, there is no label gap.

[0024] The retroreflective light barrier and the additional light receiver can be arranged centrally with respect to the paper path. This allows the label printer to be operated in such a way that the paper ribbon used is always aligned centrally with respect to the paper path and does not have to touch the edge of the paper path, as is necessary with conventional forked light barriers. This can be particularly advantageous when using narrow paper ribbons.

[0025] Furthermore, a cable connection can be provided, via which the additional light receiver provided on the housing element or the reflective light barrier provided on the housing element is electrically connected to the printer housing. Alternatively or additionally, electrical contacting elements, e.g., spring contact pins, can be provided that establish electrical contact between the printer housing and the additional light receiver provided on the cassette or the reflective light barrier provided on the cassette when the cassette is inserted into the receiving space.

[0026] The invention further relates to a scale, in particular a shop scale, with a label printer as described above.

[0027] The invention further relates to a method for operating a label printer for printing on a paper tape wound on a roll, the label printer comprising a printer housing in which a receiving space is provided for the roll of paper tape or for a cassette containing the roll of paper tape, wherein the paper tape can be inserted into a paper path and transported along the paper path, and a housing element attached to the printer housing and foldable between an open position and a closed position, which allows access to the receiving space for inserting and removing the roll or cassette in the open position and prevents access in the closed position, wherein in the method the state of the label printer is detected by means of a control unit,namely, whether the housing element is closed or the cassette is inserted, and whether the paper ribbon is inserted into the paper path. The method is characterized in that a reflective light barrier with a light transmitter and a light receiver, as well as a further light receiver, are provided, wherein the reflective light barrier is provided on the printer housing and the further light receiver is provided on the housing element or the cassette, or vice versa, and wherein, in the closed state of the housing element, the reflective light barrier and the further light receiver are arranged on two opposite sides of the paper path, wherein a transmitted light beam is emitted by the light transmitter, a reflected portion of the transmitted light beam is received by the light receiver of the reflective light barrier, and a transmitted portion of the transmitted light beam is received by the further light receiver.and wherein the reception intensity of the light receiver of the reflective light barrier and the reception intensity of the further light receiver are jointly evaluated by means of the control unit and the status of the label printer is recorded based on the joint evaluation.

[0028] Advantageous embodiments of the method according to the invention result analogously to the advantageous embodiments of the label printer according to the invention described above.

[0029] Further advantageous embodiments of the invention are described in the subclaims, the description of the figures and the drawing.

[0030] Non-limiting embodiments of the invention are illustrated in the drawings and are described below.

[0031] They show, in schematic representation, Fig. 1a scale, in particular a shop scale, with a label printer according to a first embodiment of the invention, Fig. 2A, B the label printer from Fig. 1 in a single view from the front with a printer door and in a view in which the printer door is omitted, Fig. 3 the printer door from Fig. 2A in the unfolded state, Fig. 4 a flowchart for detecting the state of the label printer from Fig. 1 , Fig. 5 a flow chart for detecting the inserted paper tape type, Fig. 6 a scale, in particular a shop scale, with a label printer according to a second embodiment of the invention, Fig. 7 the label printer from Fig. 6 with a cassette compartment, a partially inserted tape cassette and partially opened printer door in a top view, Fig. 8 the label printer from Fig. 6 in side view, with the printer door omitted, and Fig. 9 the bank cassette from Fig. 7 in individual representation.

[0032] The Fig. 1 The exemplary retail scale 11 shown comprises a load plate 13 which determines the weight of an article lying on it, which is displayed both on a display 15 for the customer and on a display 17 for the salesperson. The display 17 is designed as a touchscreen so that the retail scale 11 can also be operated via this. An identification number (PLU) assigned to the respective article can be entered via the touchscreen 17 so that, taking the weight into account, a price for the article can be calculated, which price is then also displayed on the two displays 15, 17. In addition, the retail scale comprises a label printer 19 for printing a label with the weight, the name of the article and the calculated price.

[0033] The label printer 19 comprises a printer housing 23 and a housing element in the form of a printer door 25 which is hinged thereto and which can be moved between a closed position, which is in the Fig. 1 and 2A shown, and an open position, which consists of Fig. 3 visible, is movable. In Fig. 2B The printer door 25 is omitted so that the interior of the label printer 19 is visible. A receiving space 27 is visible inside the label printer 19. With the printer door 25 open, a roll of paper tape on which printing is to take place can be inserted into the receiving space 27 or a used paper tape roll can be removed from the receiving space 27. After inserting the roll, the beginning of the paper tape is unwound and inserted into the paper path of the label printer 19. The paper tape can then be fed via a driven pressure roller 33, which is attached to the inside of the printer door 25, as shown in Fig. 3 can be seen, are transported along the paper path. Furthermore, a deflection roller 29 for the paper ribbon and a print head 45 are visible.

[0034] The label printer 19 can be operated with a self-adhesive linerless ribbon or with a non-self-adhesive receipt paper. Therefore, the label printer 19 has a basically known cutter, which Fig. 2B However, it is concealed by a front cover element 31 and can be used to separate individual labels from the linerless tape or receipt paper. However, the label printer 19 can also be operated with a carrier tape with self-adhesive labels applied to it.

[0035] The control unit, which is not visible and is arranged on the printer housing side, is designed to detect the state of the label printer 19, namely whether the printer door 25 is closed and whether the paper ribbon is inserted into the paper path. For this purpose, the label printer 19 comprises a reflective light barrier 35 provided on the printer housing side (see FIG. Fig. 2B ) with a light transmitter and a light receiver as well as a further light receiver 37 provided on the printer door side (cf. Fig. 3 ), which is connected to the control unit via a cable connection. However, the arrangement can also be reversed. In both cases, the arrangement is such that, when the printer door 25 is closed, the reflective light barrier 35 and the further light receiver 37 are arranged on two opposite sides of the paper path. During operation, the light transmitter of the reflective light barrier 35 emits a transmitted light beam, with a reflected portion of the transmitted light beam being received by the light receiver of the reflective light barrier 35 and a transmitted portion of the transmitted light beam being received by the further light receiver 37. The control unit is then designed to detect the aforementioned state of the label printer 19 based on a joint evaluation of the two received intensities of the light receiver of the reflective light barrier 35 and the further light receiver 37.

[0036] The process steps that are carried out to detect the status of the label printer 19 are shown in Fig. 4 shown. The method starts in step S41. In step S42, the light transmitter of the reflective light barrier 35 emits a transmitted light beam. In step S43, a reflected portion of the transmitted light beam is detected by the light receiver of the reflective light barrier 35, and a transmitted portion of the transmitted light beam is detected by the further light receiver 37. In step S44, a check is made to determine whether the printer door 25 is open. For this purpose, a check is made to determine whether the received signal intensity of the light receiver of the reflective light barrier 35 is less than a predetermined reflection reference value, for example, 1,000, and whether the received intensity of the further light receiver 37 is less than a predetermined transmission reference value, for example, 250. If this is the case, it is determined according to step S45 that the printer door 25 is open. The label printer 19 is not ready to print.The method for detecting the state of the label printer 19 is terminated according to step S50. If this is not the case, it is determined according to step S46 that the printer door 25 is closed. In step S47, it is checked whether the paper ribbon is not inserted into the paper path. For this purpose, it is checked whether the reception intensity of the light receiver of the reflective light barrier 35 is less than a predetermined reflection threshold, for example 900, or the reception intensity of the further light receiver 37 is greater than a predetermined transmission threshold, for example 3000. If this is the case, it is determined according to step S48 that the paper ribbon is not inserted into the paper path. The label printer 19 is not ready to print. The method for detecting the state of the label printer 19 is terminated according to step S50. If this is not the case, it is determined according to step S49 that the paper ribbon is inserted into the paper path.The label printer 19 is ready to print. The process for detecting the status of the label printer 19 is terminated according to step S50.

[0037] The above-explained evaluation of the two reception intensities of the light receiver of the reflective light barrier 35 and the further light receiver 37 takes place when a transmitted light beam is emitted by the light transmitter, i.e. when a transmitted light beam is emitted by the light transmitter. In addition, it can be provided that the two reception intensities of the light receiver of the reflective light barrier 35 and the further light receiver 37 are evaluated before step S42 when the light transmitter is still deactivated, i.e. when no transmitted light beam has yet been emitted by the light transmitter. It can be detected that the printer door 25 is open if the reception intensity of the light receiver of the reflective light barrier 35 is greater than a predetermined reflection limit value, for example 10, and / or the reception intensity of the further light receiver 37 is greater than a predetermined transmission limit value, for example 10, as is the case due to external orAmbient light may be the case. If it is detected that the printer door 25 is open when the light transmitter is deactivated, the label printer 19 is not ready to print. The method is terminated according to step S50. If it is not detected that the printer door 25 is open when the light transmitter is deactivated, the method continues with step S42.

[0038] As can be seen from the method for detecting the state of the label printer 19 explained above, the printing operation of the label printer 19 is blocked if, based on the joint evaluation of the reception intensity of the light receiver of the reflective light barrier 35 and the reception intensity of the further light receiver 37, it has been detected that the printer door 25 is open or the paper ribbon is not inserted in the paper path.

[0039] In addition, it can be detected which paper tape type is used in the label printer 19, ie whether a label tape (where the label length of the separated labels is predetermined) or an endless tape (where the label length of the separated labels is not predetermined) is used. The process steps carried out to detect the paper tape type used are described in Fig. 5 shown. The method starts in step S51. In step S52, a maximum label length stored in the label printer 19, for example 20 cm, is read in. In step S53, the light transmitter of the reflective light barrier 35 emits a transmitted light beam, and the paper strip is transported along the paper path. In step S54, over the time period until the paper strip has been transported by the stored label length, a reflected portion of the transmitted light beam is detected by the light receiver of the reflective light barrier 35, and a transmitted portion of the transmitted light beam is detected by the further light receiver 37. In step S55, a check is carried out to determine whether the reception intensity of the further light receiver 37 has changed from a first value, for example 1,400 (e.g., backing paper and label), to a second value, for example 2,500 (e.g.,only backing paper) which differs from the first value by at least a predetermined reference difference. If this is not the case, no label gap is detected according to step S56. According to step S57, it is determined that an endless tape is being used. The method for detecting the type of paper tape used is ended according to step S60. If this is the case, a label gap is detected according to step S58. According to step S59, it is determined that a label tape is being used. The method for detecting the type of paper tape used is ended according to step S60.

[0040] The information related to the Figuren 4 and 5 With the exception of the label length mentioned, the values mentioned are given as dimensionless quantities, since only the ratio of these values is important for the process steps S41 to S60.

[0041] In Fig. 6 Another retail scale 11' with another label printer 19' is shown. In contrast to the retail scale according to Fig. 1 the label printer 19' is not arranged on a stand, but is located below the load plate 13. In addition, the customer display 15 and the operator touchscreen 17 are arranged in the area of the load plate 13.

[0042] The label printer 19' comprises according to Fig. 7 also a printer housing 23', in which a receiving space 27' is formed in the form of a cassette compartment, into which a tape cassette 39 with a roll of paper tape can be inserted. In addition, a housing element in the form of a printer door 25' is attached to the printer housing 23' so as to be foldable about a pivot axis and which can be adjusted between an open position and a closed position. In the open position of the printer door 25', access to the receiving space 27' is free, i.e. the tape cassette 39 can be inserted into the receiving space 27' or removed from the receiving space 27'. In the closed position of the printer door 25', however, this is not the case, since the access is then closed.

[0043] In addition, a control unit 21 is provided which, analogous to the control unit of the label printer 19, can detect the status of the label printer 19'. However, in the case of the label printer 19', the control is not based on whether the printer door 25' is closed, but rather on whether the tape cassette 39 is inserted into the receiving space 27'. For this purpose, the label printer 19' also includes a reflective light barrier 35' provided on the printer housing side (see Fig. 8 ) with a light transmitter and a light receiver as well as a further light receiver 37' provided on the printer door side (cf. Fig. 9 ), which is connected to the control unit 21 via electrical contacting elements 41, e.g., spring contact pins, and corresponding contact surfaces 43. The arrangement can also be reversed here, and in both cases the arrangement is such that, when the tape cassette 39 is inserted, the reflective light barrier 35' and the further light receiver 37' are arranged on two opposite sides of a paper path of the label printer 19'. Bezugszeichenliste

[0044] 11, 11'Shop scale 13Load plate 15Customer display 17Operator touchscreen 19, 19'Label printer 21Control unit 23, 23'Printer housing 25, 25'Printer door 27, 27'Accommodation space 29Deflection roller 31Cover element 33Print roller 35, 35'Reflection light barrier 37, 37'Additional light receiver 39Tape cassette 41Electrical contact elements 43Contact surfaces 45Print head S41-S60Process step

Claims

1. A label printer for printing on a paper tape wound onto a roll, said label printer comprising a printer housing (23, 23') in which a reception space (27, 27') for the roll with the paper tape or for a cartridge (39) comprising the roll with the paper tape is provided, wherein the paper tape can be placed into a paper path and transported along the paper path; a housing element (25, 25') which is attached to the printer housing (23, 23'), which is foldable between an open position and a closed position, and which enables access to the reception space (27, 27') for the insertion and removal of the roll or the cartridge (39) in the open position and prevents access in the closed position; and a control unit (21) which is configured to detect the state of the label printer (19, 19'), namely whether the housing element (25, 25') is closed or the cartridge (39) is inserted and whether the paper tape is placed into the paper path, wherein a reflection light barrier (35, 35'), comprising a light transmitter for transmitting a transmission light beam and a light receiver for receiving a reflected portion of the transmission light beam, and a further light receiver (37, 37') for receiving a transmitted portion of the transmission light beam are provided, wherein the reflection light barrier (35, 35') is provided at the printer housing (23, 23') and the further light receiver (37, 37') is provided at the housing element (25, 25') or the cartridge (39), or vice versa, and wherein, in a closed state of the housing element (25, 25'), the reflection light barrier (35, 35') and the further light receiver (37, 37') are arranged at two mutually oppositely disposed sides of the paper path, characterized in that the control unit (21) is configured to detect the state of the label printer (19, 19') based on a joint evaluation of the reception intensity of the light receiver of the reflection light barrier (35, 35') and the reception intensity of the further light receiver (37, 37').

2. A label printer according to claim 1, characterized in that the control unit (21) is configured to detect, in the case of a transmission light beam transmitted by the light transmitter, that the housing element (25, 25') is open or the cartridge (39) is not inserted when the reception intensity of the light receiver of the reflection light barrier (35, 35') is smaller than a predefined reflection reference value and the reception intensity of the further light receiver (37, 37') is smaller than a predefined transmission reference value, and that otherwise the housing element (25, 25') is closed or the cartridge (39) is inserted.

3. A label printer according to claim 2, characterized in that the control unit (21) is configured to detect beforehand, when the light transmitter is deactivated, i.e. when no transmission light beam is transmitted by the light transmitter, that the housing element (25, 25') is open or the cartridge (39) is not inserted when the reception intensity of the light receiver of the reflection light barrier (35, 35') is larger than a predefined reflection limit value and / or the reception intensity of the further light receiver (37, 37') is larger than a predefined transmission limit value, in particular wherein the predefined reflection limit value is smaller than the predefined reflection reference value, and / or in that the predefined transmission limit value is smaller than the predefined transmission reference value.

4. A label printer according to one of the claims 2 to 3, characterized in that, if it has been detected that the housing element (25, 25') is closed or the cartridge (39) is inserted, the control unit (21) is configured to subsequently detect whether the paper tape is placed into the paper path.

5. A label printer according to any one of the preceding claims, characterized in that the control unit (21) is configured to detect, in the case of a transmission light beam transmitted by the light transmitter, that the paper tape is not placed into the paper path when the reception intensity of the light receiver of the reflection light barrier (35, 35') is smaller than a predefined reflection threshold value or the reception intensity of the further light receiver (37, 37') is larger than a predefined transmission threshold value, and that otherwise the paper tape is placed into the paper path.

6. A label printer according to any one of the claims 2 to 4 and claim 5, characterized in that the predefined reflection threshold value is smaller than the predefined reflection reference value, and / or in that the predefined transmission threshold value is larger than the predefined transmission reference value.

7. A label printer according to any one of the preceding claims, characterized in that the control unit (21) is configured to block the printing operation of the label printer (19, 19') if it has been detected based on the joint evaluation of the reception intensity of the light receiver of the reflection light barrier (35, 35') and the reception intensity of the further light receiver (37, 37') that the housing element (25, 25') is open or the cartridge (39) is not inserted or the paper tape is not placed into the paper path.

8. A label printer according to any one of the preceding claims, characterized in that the control unit (21) is configured, in the case of a transmission light beam transmitted by the light transmitter, to distinguish paper tape types from one another, based on at least one of the two reception intensities, that differ from one another in their reflection capability and / or their light transmission, in particular in the location dependence of their reflection capability and / or their light transmission in the tape direction.

9. A label printer according to any one of the preceding claims, characterized in that the control unit (21) is configured, in the case of a transmission light beam transmitted by the light transmitter and in the case of a paper tape placed into the paper path and transported along the paper path, to detect, based on a time development of the reception intensity of the further light receiver (37, 37'), in particular over a predefined time period, whether the paper tape is a paper tape of a first type whose light transmission varies in the tape direction according to a repeating pattern, in particular a label tape, or a paper tape of a second type whose light transmission is constant in the tape direction, in particular an endless tape, in particular wherein the control unit (21) is configured to detect that the paper tape is a paper tape of the first type when the time development of the reception intensity of the further light receiver (37, 37') changes from a first value to a second value, which differs from the first value by at least a predefined reference difference, and that otherwise the paper tape is a paper tape of the second type.

10. A label printer according to any one of the preceding claims, characterized in that the reflection light barrier (35, 35') and the further light receiver (37, 37') are arranged centrally with respect to the paper path.

11. A label printer according to any one of the preceding claims, characterized in that a cable connection is provided via which the further light receiver (37, 37') provided at the housing element (25, 25') or the reflection light barrier (35, 35') provided at the housing element (25, 25') are electrically connected to the printer housing (23, 23'), and / or in that electrical contacting elements (41), e.g. spring contact pins, are provided that establish an electrical contact between the printer housing (23, 23') and the further light receiver (37, 37') provided at the cartridge (39) or the reflection light barrier (35, 35') provided at the cartridge (39) when the cartridge (39) is inserted into the reception space (27, 27').

12. A scale, in particular a store scale, comprising a label printer (19, 19') according to any one of the preceding claims.

13. A method for operating a label printer (19, 19') for printing on a paper tape wound onto a roll, the label printer (19, 19') comprising a printer housing (23, 23') in which a reception space (27, 27') for the roll with the paper tape or for a cartridge (39) comprising the roll with the paper tape is provided, wherein the paper tape can be placed into a paper path and transported along the paper path; and a housing element (25, 25') which is attached to the printer housing (23, 23'), which is foldable between an open position and a closed position, and which enables access to the reception space (27, 27') for the insertion and removal of the roll or the cartridge (39) in the open position and prevents access in the closed position, wherein, in the method, the state of the label printer (19, 19') is detected by means of a control unit (21), namely whether the housing element (25, 25') is closed or the cartridge (39) is inserted and whether the paper tape is placed into the paper path, wherein a reflection light barrier (35, 35'), comprising a light transmitter and a light receiver, and a further light receiver (37, 37') are provided, wherein the reflection light barrier (35, 35') is provided at the printer housing (23, 23') and the further light receiver (37, 37') is provided at the housing element (25, 25') or the cartridge (39), or vice versa, and wherein, in a closed state of the housing element (25, 25'), the reflection light barrier (35, 35') and the further light receiver (37, 37') are arranged at two mutually oppositely disposed sides of the paper path, wherein a transmission light beam is transmitted by the light transmitter, a reflected portion of the transmission light beam is received by the light receiver of the reflection light barrier (35, 35'), and a transmitted portion of the transmission light beam is received by the further light receiver (37, 37'), characterized in that the reception intensity of the light receiver of the reflection light barrier (35, 35') and the reception intensity of the further light receiver (37, 37') are jointly evaluated by means of the control unit (21) and the state of the label printer (19, 19') is detected based on the joint evaluation.

14. A method according to claim 13, characterized in that it is detected by means of the control unit (21), in the case of a transmission light beam transmitted by the light transmitter, that the housing element (25, 25') is open or the cartridge (39) is not inserted when the reception intensity of the light receiver of the reflection light barrier (35, 35') is smaller than a predefined reflection reference value and the reception intensity of the further light receiver (37, 37') is smaller than a predefined transmission reference value, and that otherwise the housing element (25, 25') is closed or the cartridge (39) is inserted.

15. A method according to claim 14, characterized in that it is detected beforehand by means of the control unit (21) when the light transmitter is deactivated, i.e. when no transmission light beam is transmitted by the light transmitter, that the housing element (25, 25') is open or the cartridge (39) is not inserted when the reception intensity of the light receiver of the reflection light barrier (35, 35') is larger than a predefined reflection limit value and / or the reception intensity of the further light receiver (37, 37') is larger than a predefined transmission limit value, in particular wherein the predefined reflection limit value is smaller than the predefined reflection reference value, and / or in that the predefined transmission limit value is smaller than the predefined transmission reference value.

16. A method according to any one of the claims 14 to 15, characterized in that, if it has been detected that the housing element (25, 25') is closed or the cartridge (39) is inserted, it is subsequently detected by means of the control unit (21) whether the paper tape is placed into the paper path.

17. A method according to any one of the claims 13 to 16, characterized in that it is detected by means of the control unit (21), in the case of a transmission light beam transmitted by the light transmitter, that the paper tape is not placed into the paper path when the reception intensity of the light receiver of the reflection light barrier (35, 35') is smaller than a predefined reflection threshold value or the reception intensity of the further light receiver (37, 37') is larger than a predefined transmission threshold value, and that otherwise the paper tape is placed into the paper path.

18. A method according to any one of the claims 14 to 16 and claim 17, characterized in that the predefined reflection threshold value is smaller than the predefined reflection reference value, and / or in that the predefined transmission threshold value is larger than the predefined transmission reference value.

19. A method according to any one of the claims 13 to 18, characterized in that the printing operation of the label printer (19, 19') is blocked by means of the control unit (12) if it has been detected based on the joint evaluation of the reception intensity of the light receiver of the reflection light barrier (35, 35') and the reception intensity of the further light receiver (37, 37') that the housing element (25, 25') is open or the cartridge (39) is not inserted or the paper tape is not placed into the paper path.

20. A method according to any one of the claims 13 to 19, characterized in that, by means of the control unit (21), in the case of a transmission light beam transmitted by the light transmitter, paper tape types are distinguished from one another, based on at least one of the two reception intensities, that differ from one another in their reflection capability and / or their light transmission, in particular in the location dependence of their reflection capability and / or their light transmission in the tape direction.

21. A method according to any one of the claims 13 to 20, characterized in that, in the case of a transmission light beam transmitted by the light transmitter and in the case of a paper tape placed into the paper path and transported along the paper path, it is detected by means of the control unit (21), based on a time development of the reception intensity of the further light receiver (37, 37'), in particular over a predefined time period, whether the paper tape is a paper tape of a first type whose light transmission varies in the tape direction according to a repeating pattern, in particular a label tape, or a paper tape of a second type whose light transmission is constant in the tape direction, in particular an endless tape, in particular wherein it is detected by means of the control unit (21) that the paper tape is a paper tape of the first type when the time development of the reception intensity of the further light receiver (37, 37') changes from a first value to a second value which differs from the first value by at least a predefined reference difference, and that otherwise the paper tape is a paper tape of the second type.