DE102019128328B3 - Method for joining tape ends - Google Patents

Abstract

The invention relates to a method for the endless connection of at least two belt ends of a belt designed as a transport or drive belt, which belt is preferably equipped with a tension member and at least on one side with a toothed profile. For this purpose, the band ends of the band to be connected are briefly heated in their respective end faces to a temperature above their softening temperature and the band ends are connected at their end faces by a joining movement. The joining movement of the softened strip ends takes place as a function of the path up to a predetermined target position in which no pretension is transmitted between the mutually abutting end faces of the strip ends. In this target position, a heat sink with a negative contour tailored to the profile is placed against the surface of the strip so that the heat is quickly dissipated and the strip is cooled to a temperature below the solidification temperature.

Description

The invention relates to a method for the particularly endless connection of at least two belt ends of at least one belt designed as a transport or drive belt, which is equipped, for example, with a tension member and preferably on one side with a profile, in particular a toothed profile, the belt ends to be connected Bands are briefly heated in their respective end faces to a temperature above their softening temperature and the band ends are connected at their end faces by a joining movement.

Such methods are already used in practice to connect the belt ends of a conveyor belt to form an endless belt. Conveyor belts without textile reinforcements consist of a homogeneous, relatively thick thermoplastic material. This plastic material must achieve the required surface properties as well as transfer the tensile forces acting in the belt.

Conveyor belts without textile reinforcements have the advantage that they are easy to clean thanks to the all-round pore-free surface. Also, no particles or unbound fibers can lead to contamination.

Due to the undesirable creep of the thermoplastic plastic material under constant tensile stress, tensile carriers are often inserted into the interior of the conveyor belt.

Conveyor belts with textile reinforcements have the advantage that they are only very slightly elongated despite the constant tensile stress to which they are exposed. They are characterized by a good flat position, also in the area of the endless connection. Thin and correspondingly flexible conveyor belts with high tear resistance can be implemented.

In contrast, reinforcements of the fabric on the transport side or the running side have a disadvantageous effect on the cleaning properties: the pores that arise in the fabric after a certain period of operation fill up with impurities that are difficult to remove. In the area of food transport, a breeding ground for undesirable microorganisms and fungi often forms. If the tape is damaged by mechanical influences on the edge or on the back, the reinforcing fabric layers begin to fray or fluff easily. Fibers or fiber residues loosened from the composite can contaminate the transported goods and impair the function of the belt.

In order to create the end connection, both ends of the belt are cut perpendicular to the running direction or at an angle slightly different from the perpendicular, for example 75 °. The ends of the tape are then butt-joined and fused together with heat and pressure or welded with a welding cord made of thermoplastic material.

It is known from the prior art to first heat the end of the strip ends by means of a heating mirror and then to press them butt against each other. This often results in bulge-shaped bulges, a so-called compression bulge, as a result of which the optionally enclosed tension member is also deflected in the direction of the upper or lower side and can optionally emerge from the upper or lower side. Such protrusions are then removed over a large area by a cutting tool, which, however, leads to reworking and also to changed tape properties in the connection area. This cutting process often first exposes the fiber.

Furthermore, a method is already known from the prior art in which a heating bar is placed on the end sections of the two strip ends to be connected, and thus heat and pressure force are transmitted at the same time. This creates a smooth surface, with the material thickness in the connecting area being adapted to the remaining belt areas. The acting pressure force results in recognizable changes in the surface properties, so that this type of connection is only suitable to a limited extent for many applications of such tapes.

The U.S. 4,071,388 A already discloses a device for winding plastic tapes lengthways or spirally around cable cores. The device has a heating element for heating the belts and adjusting means for feeding the belts. The device also has heat sinks on the sides and under the bands.

Further relevant state of the art can be found in DE 195 19 184 A1 .

In all known methods, in the production of endless connections, it turns out to be disadvantageous that the surface properties of the tape differ visually and functionally from the surface of the tape in the adjacent areas. As a result, in practice, these connection areas often require increased maintenance and also lead to material weakening.

Furthermore, any tension member that may be present, for example cord tension member, can emerge due to the compression through the belt surface, so that it is no longer completely enclosed. Such exposed tension members can permanently change the properties of the conveyor or drive belt due to environmental influences.

As a result, in the case of applications in the food or pharmaceutical sector, the respective requirements for the hygiene regulations to be complied with can no longer be reliably met.

The invention is based on the object of creating an endless connection, the properties of which are at least almost identical to the remaining belt sections.

This object is achieved according to the invention with a method according to the features of claim 1. The further embodiment of the invention can be found in the subclaims.

According to the invention, a method is provided in which the joining movement of the softened strip ends is carried out in a controlled manner as a function of the path up to a predetermined target position in which no or only a very low bias or force is transmitted between the opposing end faces of the strip ends, and in which in the target position reached in this way, at least one heat sink is brought into contact with a negative contour matched to the profiling in an end section adjoining the end face of at least one band surface by an infeed movement, in particular transversely to the band surface, the infeed being adjusted to the band thickness of the band up to a profile not changing target position is limited, so that a heat transfer takes place from the strip ends to the heat sink and this is thereby cooled to a temperature below its softening temperature and thus the connection between the strip ends by fusing and first arrest is generated. According to the invention, for this purpose, only the end faces or end faces of the strip ends are heated, for example by means of a heating mirror. As soon as the softening temperature is reached, these are then joined together in a defined relative position according to the profile of the strip, the infeed not leading to uncontrolled deformation. Rather, a path control ensures that the approach of the end faces takes place according to a predetermined distance or grid dimension of the profiling of the band. In this target position, the heat sink is applied to the connection area, which is precisely fed in the direction of the strip surface according to the respective strip thickness, so that there is flat contact, but not strong compression or deformation of the strip material.

So there is essentially no force-dependent pressure, but a path-controlled fixation. The heat sink has a contact surface so that the strip material is cooled to a temperature below the softening temperature while it is being moved into the end position. As a result, the heat sink makes contact with the strip surfaces, but in contrast to the prior art, no or only a very low compressive force is transferred to the strip, so that upsetting and the resulting bulging is avoided. At the same time, the belt ends resting against one another in a predetermined relative position also prevent the tension member ends from escaping. The cooling effect not only ensures rapid heat dissipation and thus solidification of the strip material in the connection area, but at the same time also prevents plastic deformation or changes to the surface.

The heat sink is preferably brought into contact with both ends of the strip from at least one side in the connection area. According to a particularly advantageous embodiment of the invention, the heat sink has two cooling elements that are applied by a synchronized feed movement against opposing outer surfaces of at least one end of the strip in order to achieve uniform heat dissipation of the strip ends from both outer sides. This makes it possible to counteract an undesirable distortion or a deformation from the aligned setpoint position of the two tape ends in the connecting area of the tape ends.

The heating could take place according to the principle known per se by means of a heating mirror. In contrast, it is particularly advantageous if the end face of the strip ends is heated without contact, for example by means of radiant heat, in order to avoid direct contact of the heat source with the strip material. In addition, the temperature in the end face can be measured continuously in order to ensure, on the one hand, a desired course of the temperature increase and, on the other hand, reliable maintenance of a maximum temperature. So-called hybrid devices can also be used, which can also perform a heating or cooling function in a quick change.

To carry out the method, a device is provided for the particularly endless connection of at least two belt ends of at least one belt designed as a transport or drive belt, which is preferably equipped with a tension member and at least on one side with a profile, in particular a tooth profile, with a heating element for heating the strip ends of the strip, with an adjusting means for transmitting a relative feed movement to the strip ends and with a heat sink that can be placed against the surface of at least one strip end.

It has already proven to be particularly expedient if the cooling body has a support surface with a surface quality that is adapted to the structure of the two tape ends and bridges the mutually adjacent tape surfaces. This ensures that the ends of the tape are correctly positioned while maintaining the regular profiling of the tape through the form fit.

According to an advantageous embodiment, the heat sink consists of two heat sink elements which can be placed on either side of the band and, when in use, enclose the band between them. At least one heat sink element can have a shape, in particular a recess, for the profiling of the strip, in particular a tooth profile. Since at least one heat sink element forms a negative shape for the profiling of the strip and receives the end sections of both strip ends in a form-fitting manner, the setpoint distance between the strip ends is already determined geometrically.

The desired cooling effect can be achieved by selecting a passive heat sink with suitable thermophysical properties. For example, the cooling body can be equipped with cooling ribs on a surface facing away from the strip. In contrast, it is particularly advantageous if the heat sink has a feed for a coolant or an active cooling element, for example a Peltier element, in order to be able to control the cooling effect and in particular to be able to optimally adapt it to the respective operating conditions.

Particularly preferably, the heat sink has a particularly exchangeable heat dissipation surface that is adapted to the profile of the band in order to be able to connect the band ends of bands with different band profiles or without a profile to the same device. For this purpose, the heat dissipation surface is connected to the heat sink, for example by means of a quick-release fastener.

It can be advantageous if the heat dissipation surface is movable relative to the heat sink in the direction of the belt surface, so that the heat dissipation surface, for example, initially rests against the belt surface, ahead of the infeed movement of the heat sink, only under the influence of gravity or with a predetermined force. As a result, heat is dissipated even before the target position of the heat sink is reached, thus accelerating the connection process.

The device is particularly preferably equipped with a temperature sensor for detecting the strip temperature in the contact zone of the strip ends. The temperature sensor can be provided to control the strip temperature. In connection with the control, it is thus ensured, for example, that the end-face joining only takes place above a minimum temperature, in particular the softening temperature, or that the resetting of the heat sink from its working position against the strip surface only takes place when the temperature falls below a lower temperature threshold, for example the solidification temperature.

Claims (4)

Method for connecting at least two belt ends of at least one belt designed as a conveyor or drive belt, the belt ends of the belt to be connected being heated in their respective end faces to a temperature above their softening temperature and connected at their end faces by a joining movement, characterized in that the joining movement of the softened strip ends is carried out in a controlled manner up to a predetermined target position, in which no or only a very little force is transmitted between the opposing end faces of the strip ends, and that in the target position thus reached at least one heat sink is attached to the end face subsequent end section of at least one strip end is brought into contact with the latter by an infeed movement, so that heat is transferred from the strip ends to the heat sink and this thereby cools to a temperature below its softening temperature lt and so the connection between the belt ends is created. Procedure according to Claim 1 , characterized in that the heat sink is brought into contact with both ends of the tape from at least one side in the connection area. Procedure according to Claim 1 or 2 , characterized in that the cooling body has two cooling elements which are applied by a synchronized feed movement against mutually opposite outer surfaces of at least one end of the tape. Method according to at least one of the preceding claims, characterized in that the end face of the band ends is heated without contact.