This application is a § 371 National Stage Entry of International Patent Application No. PCT/EP2018/058958 filed Apr. 9, 2018. Application No. PCT/EP2018/058958 claims priority of DE 202017102224.2 filed Apr. 12, 2017. The entire content of these applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a printer for printing marking strips having a plurality of marking elements for marking electric devices, in particular electric devices which can be arranged next to one another. Each of the marking elements has a marking plate with at least one writing field which can be printed with information such as writing. The printer has a rotatably mounted feed shaft, which can be driven by a motor, and a printing head.

If a plurality of electric devices, such as terminal blocks, are arranged next to one another on a submount, each having a latch contour such as a latch recess, the marking process is simplified by employing marking elements which are connected to one another in a strip-shaped pattern as opposed to a plurality of completely discrete marking elements. For example, for marking a terminal block assembly on a mounting rail, it is only necessary to place the marking strip above the area of the latch contours of the terminal blocks which are arranged next to one another and then to press on the individual marking elements from above such that secure latching of the marking elements to the terminal blocks is accomplished.

As an example, in order to manufacture such marking strips, injection molding methods are used in which strips of a defined length of, for example, eight marking elements are constructed, which are then joined to equip a reel with a long marking strip off of which marking strips with a desired amount of marking elements can then be cut.

From DE 10 2015 109 020 A1 it is known to produce a marking strip from at least two different plastic materials of different hardness, the latching contour of each marking element consisting of the harder material and the marking plate consisting of the softer plastic material at least in the area of the writing field. Preferably, the marking strip is initially manufactured in an extrusion process and then processed further. Extrusion allows simple production of a continuous strip for winding it, e.g., onto a reel. By using extrusion such as co-extrusion, the marking strips or their marking elements can then be used for printing by thermal transfer technology. If the latch contour of each marking element is made of a harder plastic material, it can be readily and securely latched onto the given electric device. Furthermore, it is advantageous for the marking plate to consist of the softer plastic material at least in the area of the writing field. As such it can be printed on more precisely. The softer material facilitates automatic adjustment to the printing head and is also gentler on the printing head than a harder material.

Further, it is advantageous if each connecting area between the marking elements includes at least one or more connecting web(s) and if at least one hole, in particular an elongated hole, is formed in the connecting area between adjacent marking elements. The hole penetrates the marking elements in a latching direction perpendicular to the arrangement direction. The hole allows the resilience of the connecting area to be selectively increased or adjusted. In addition, the hole is readily usable as a sensing device for a sensor of a printer to trigger or stop printing. However, it is also contemplated that the marking plate of the marking strip does not contain any holes and/or edge recesses. This makes it easy to write across devices. The marking strip is also provided with markings in the form of printings at the bottom, for example, with markings applied in a grid and having different colors compared to the material of the marking strip, which are easy to sense and are usable as a reference for the printing process. These different types of marking strips and sensing and printing methods are usable with the printer according to the invention.

Irrespective of the type of manufacture and nature of the marking strip used, it is desirable to print the marking strip in a dedicated printer in its main direction of extension as precisely as possible such that the desired print image is printed exactly within the area of the intended marking plate.

SUMMARY OF THE INVENTION

According to the invention, a printer is provided with a rotatably mounted feed shaft which has at least one protrusion section which is provided with protrusions and which rests directly against the marking strip while the feed shaft is rotated, such that the advancing speed of the marking strip is synchronized with the circumferential speed of the feed shaft.

In this manner, a defined, tolerance-free feed of the marking strip is provided resulting in a clean print image without any offset, particularly in its main direction of extension.

Further, the protrusion section rests directly against the marking strip while the feed shaft is rotated such that the protrusions of the protrusion section each introduce a deformation into the marking strip, creating a positive fit between the feed shaft and the marking strip such that the advancing speed of the marking strip is synchronized with the circumferential speed of the feed shaft.

According to one embodiment which results in a very smooth feed motion of the marking strip, the protrusion section is formed as an interlocking section. Preferably, the interlocking section creates a positive fit and also a frictional connection, thus ensuring smooth further transport of the marking strip at all times. It does not have to create any deformation during feeding of the marking strip.

Preferably, the protrusion section is formed as an axial section of the feed shaft, preferably enclosing the shaft completely or almost completely and having a surface roughness which is configured such that, when transporting a marking strip made of at least one plastic material through one or more radially extending protrusions, a positive fit is created between the section having the surface roughness and the marking strip while transporting the marking strip. A sufficiently high surface roughness may be created in several ways. For example, a section of the shaft may be provided with small, radially extending protrusions, in particular tips, all around, which penetrate the plastic material from which the marking strip is made. It may also be coated with a band of sufficiently high or increased surface roughness all around an axial section.

As such, the defined and—from a practical view—zero-tolerance feed of the marking strip may be ensured in a simple and cost-effective manner, resulting in a clean print image without offset in its main direction of extension.

According to another embodiment, the at least one interlocking section is a first interlocking section having a first diameter and a first interlock, in particular a saw-toothed interlock. The tooth shape of the interlock is preferably pointed to produce a precise feed when printing the marking strip.

According to a further embodiment, the feed shaft has one or more additional interlocking protrusion sections, which are axially offset from the first protrusion section or which each rest directly against the marking strip in at least one additional area with a defined pressure force while the feed shaft is rotated such that the advancing speed of the marking strip is synchronized with the circumferential speed of the feed shaft also in these areas.

This allows an even more precise motion of the marking strip during printing. In addition, sensing of markings such as holes or stripes or the like may be accomplished for referencing during printing.

In a further embodiment of the invention, the pressure force applied onto the marking strip by the printing head is effective to press the protrusions formed by the interlock, into the marking strip. Each tooth of the interlock creates a permanent indentation in the marking strip. This creates a positive fit between the interlock and the marking strip, enabling precise feed.

In a further embodiment of the invention, each of the additional interlocking sections also has a saw-toothed interlock on its periphery. In turn, the pointed tooth shape of this interlock creates a precise feed when printing the marking strip.

