EP2540461A1 - Hot knife - Google Patents

Abstract

The portable device (1) comprises a handle (2) and a heatable cutting unit (3). The cutting unit has a blade (4) and the blade has a heating wire (6). The cutting unit is arranged in the longitudinal direction of the handle and pushes out a corresponding recess (7). The cutting unit is displaceable and lockable relative to the handle. An ejected potion (8) of the heating wire is heated, where a triggering device is arranged for heating the cutting unit. A resistance element has a resistance value, which is dependent on the cutting unit corresponding to the handle.

Description

Field of the invention

The invention relates to a portable device for cutting thermoplastics, in particular polystyrene, which comprises a handle and a heatable cutting device, wherein the cutting device comprises a blade and a heating wire disposed upstream of the blade.

Background of the invention

Devices for cutting thermoplastics are already state of the art. They are often used in the implementation of facade work for cutting blocks or sheets of polystyrene as thermal insulation material. Such polystyrene blocks or plates usually have a standard format and can be cut by appropriate devices into smaller pieces of various lengths, widths and shapes. For cutting often common saws or stationary devices are used, with particular stationary devices have the disadvantage that they are difficult to transport because of their large external dimensions and their heavy weight. A conventional saw is portable, but also has some disadvantages. For example, it can happen that the edges cut easily when sawing. In general, polystyrene plates near the cut surfaces tend to crack, which, when cut with a saw, causes dust to form from small polystyrene particles which spread in the environment and can be a nuisance to the neighborhood.

There are already known cutting devices with a heatable blade, such as in the DE 197 50 247 A1 or the WO 20051023497 A1 shown. Although these bring improvements for the cutting process through cleaner cuts without significant dust, but in this case each of the entire blade is heated. Therefore, such devices have a very high energy requirement.

In a generic device for cutting thermoplastics no longer the entire blade must be heated, but it is sufficient to heat the heating wire, which is upstream of the blade. The actual cutting process is performed by the heated heating wire of the cutting device and the blade can serve as a stabilizing and guiding element. So here are the advantages of a blade - a high stability - Connected with the advantage of low energy consumption of the cutting device, since the heating wire is compared to the blade only a small mass to be heated.

The term "upstream" as a location designation of the heater wire relative to the blade also includes embodiments in which the heater wire is in direct contact with the blade, where the heater wire may run along the edge of the blade or be configured to engage the blade edge forms, for example, in that he is partially embedded in the blade.

For example, the shows CN 201357461 Y a cutting device for cutting expanded polystyrene (EPS), the cutting device having a heating wire disposed upstream of the blade. The current flow to heat the blade is done by the heating wire and the Künge. The JP 7266300 A also has a cutting device with a heated blade on the subject. Here, a heating element, which comprises a heating wire, received by the blade. A disadvantage of these cutting devices is an increased risk of injury, due to the relatively large length of protruding from the handle, heated blade.

The object of the invention is to avoid the disadvantages described above and to provide a comparison with the prior art improved, portable device for cutting thermoplastics. In particular, the device should have a relatively low energy requirement with high stability of the cutting device and reduce the risk of injury.

This object is achieved by the features of claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

According to the invention it is provided that the cutting device is displaceable relative to the handle. Thereby, the active portion of the cutting device, ie that part of the cutting device which is used to cut a thermoplastic, can be adapted to the thickness of the plate to be cut. This facilitates the work and reduces the risk of injury. Typical thicknesses of polystyrene plates range from about 1 to 20 cm. Depending on the thickness of the plate to be cut so the active portion of the cutting device can be adjusted by moving the cutting device relative to the handle. In a device with a stationary relative to the handle cutter For example, this would have to be designed for the largest thickness to be cut. However, such a cutting device would be very unwieldy, if you would cut very thin plates. In addition, one would have a high risk of injury, for example by burning at that part of the cutting device, which projects beyond this when cutting a thin plate.

Preferably, it can be provided that the cutting device in the longitudinal direction of the handle in a corresponding recess thereof is inserted and pushed out. In this case, only the active section of the cutting device protrudes from the handle and the section of the cutting device not required for cutting a specific plate is located inside the handle. This facilitates handling and reduces the risk of injury.

Particularly advantageous is that embodiment of the invention in which the cutting device is continuously displaceable relative to the handle. In this case, the cutting device can be adjusted to any thickness of the polystyrene plate to be cut. But it can also be provided that the cutting device is displaceable relative to the handle in stages lockable. This is particularly advantageous when panels are to be cut in standard sizes. To facilitate the adjustment of the active portion of the cutting device can be arranged, for example, on the handle a scale which indicates how far the cutter protrudes from the handle.

A particular embodiment of the invention provides that only a portion of the heating wire is heated. It is particularly advantageous if only the ejected from the handle portion of the heating wire is heated. Since only the active portion of the cutter is used to cut a polystyrene plate, it is useful to heat only this portion as well. This also prevents unfavorable heat build-up inside the handle, since the part of the heating wire running inside the handle is not heated.

Particularly advantageous is that embodiment of the invention in which the heating wire is tensioned. Furthermore, a retractor can be provided, through which the heating wire can be rolled up. As a result, the heating wire can be biased accordingly, which favors a clean cut and a stable cut.

In order to reduce the energy demand further, a triggering device for heating the cutting device can be provided. This allows you to heat the heating wire exactly when you make a cut through a workpiece - such as a polystyrene plate - and interrupt the flow of current when no cut is to be made.

It has proved to be particularly advantageous if at least one resistance element is provided which has a resistance value dependent on the relative position of the cutting device with respect to the handle. Thereby, in particular for those embodiments of the invention in which only a portion of the heating wire is heated, a constant temperature of the heating wire can be achieved regardless of the length of the active portion of the cutting device. Thus, the temperature of the heating wire (about 300 to 400 ° C) can be kept substantially constant, regardless of the length of the heating wire, which is heated in each case. The resistance element can generally be used to adjust the temperature of the heating wire.

In a preferred embodiment of the invention can be provided that the heating wire is spaced from the blade. The heating wire is not directly adjacent to the blade, whereby no direct dissipation of the heat of the heating wire is on the blade. As a result, less energy is needed to provide a proper cutting temperature of the heating wire.

According to a particularly preferred embodiment it can be provided that an adjusting device is provided for aligning the cutting device relative to the workpiece. As a result, for example, certain cutting angles of the cutting device with respect to the workpiece can be preset. At the same time, such adjusting device can form a stop, by which the device can be applied to the workpiece, whereby a stable cut is favored. It is particularly advantageous if the adjusting device is pivotally hinged to the handle. It can be provided that the adjusting device can be fixed in a correspondingly pivoted by the handle position, which corresponds to a certain cutting angle, which is particularly easy special cuts, such. Make cuts with certain cutting angles for mitres or door and window reveals.

Brief description of the drawings

Fig. 1

eine perspektivische Darstellung einer Ausführungsform der Erfindung mit aus dem Handgriff aufgeschobener Schneideinrichtung,

Fig. 2a

ein Ausführungsbeispiel der Erfindung in einer Seitenansicht,

Fg. 2b

die Schneideinrichtung gemäß Fig. 2a in einer Detaildarstellung,

Fig. 3

ein Ausführungsbeispiel der vorgeschlagenen Vorrichtung in einer Frontansicht,

Fig. 4

eine schematische Darstellung der elektrischen Komponenten eines Ausführungsbeispiels der Erfindung,

Fig. 5a

ein Ausführungsbeispiel der Erfindung mit Justiereinrichtung in einer Seitenansicht,

Fig. 5b

eine Vorrichtung gemäß Fig. 5a in einer Draufsicht,

Fig. 6

ein weiteres Beispiel einer Ausführungsform der Erfindung und

Fig. 7

das Schneiden eines Werkstücks mit einer Ausführungsform der Erfindung mit einer Justiereinrichtung.

Further details and advantages of the present invention will be explained in more detail below with reference to the description of the figures with reference to the exemplary embodiments illustrated in the drawings. Show:

Fig. 1

a perspective view of an embodiment of the invention with deferred from the handle cutting device,

Fig. 2a

an embodiment of the invention in a side view,

Fig. 2b

the cutting device according to Fig. 2a in a detailed view,

Fig. 3

An embodiment of the proposed device in a front view,

Fig. 4

a schematic representation of the electrical components of an embodiment of the invention,

Fig. 5a

an embodiment of the invention with adjusting device in a side view,

Fig. 5b

a device according to Fig. 5a in a plan view,

Fig. 6

another example of an embodiment of the invention and

Fig. 7

the cutting of a workpiece with an embodiment of the invention with an adjusting device.

Detailed description

Fig. 1 shows an embodiment of the proposed device 1 for cutting thermoplastics in a perspective view. The portable device 1 comprises a handle 2, in which by a corresponding recess 7, a cutting device 3, under Zuhiffenahme a knob 25, and is pushed out. The cutting device 3 comprises a blade 4 and a heating wire 6 located upstream of the blade 4. In this example, the heating wire 6 is spaced a distance from the lower edge of the blade 4 in the use position of the device 1. The heating wire 6 extends along the longitudinal extent of the lower edge of the blade 4 to its front end 19 in the region of the end face of the blade 4. This heating wire 6 may be, for example, a nichrome wire which can be heated by an electrical energy source 16, not shown here At its front end 19, the heating wire 6 is connected to an electrical conductor 15, for example a copper wire, which runs along the front side and the upper edge of the blade 4, whereby the circuit for heating the heating wire 6 is closed by the electrical conductor 15 can. In order to keep unwanted heat development in the handle 2 of the device 1 as low as possible, in this example, only that portion 8 of the cutting device 3 is heated, which protrudes from the handle 2. In other words, will heated only the length of the heating wire 6, which extends between the contact point 14 and the front end 19 of the heating wire 6. The device 1 also comprises an adjusting device 11, by means of which the cutting device 3 can be aligned relative to a workpiece 12, not shown here.

Fig. 2a shows the device 1 according to Fig. 1 in a side view, wherein further details of the internal structure of the device 1 are shown. By the adjusting knob 25, the cutter 3 has been inserted far into the handle 2, so that the active portion 8 of the cutting device 3 - this is the portion that protrudes from the handle 2 - is very small. As a result, for example, very thin polystyrene plates can be cut with little risk of injury. The electrical energy source 16 for heating the cutting device 3 is shown only schematically and can be arranged for example in the form of a rechargeable battery in the handle 2 of the device 1. The positive line 21 of the electrical circuit extends from the positive pole of the electric power source 16 to the contact point 14. This contact point 14 establishes an electrical connection between the positive line 21 and the heating wire 6. Upon pressure on the knob 25, this electrical connection can be achieved in that the mechanical connection between the heating wire 6 and the contact point 14 is released. As a result, the heating wire 6 can also be moved accordingly during the insertion and removal of the cutting device 3. Upon omission of the adjusting knob 25, the mechanical connection between the contact point 14 and the heating wire 6 is restored, which subsequently also the electrical connection between the positive wire 21 and the heating wire 6 is restored. The heating wire 6 extends at a distance from the blade 4, starting from its front end 19 along the longitudinal extent of the blade 4 via an insulator 24 to a retractor 9, which can be performed simultaneously as a tension spring for the heating wire 6. As a result, the heating wire 6 can be pushed out of the handle 2 during the pushing out of the blade 4 and at the same time kept at tension. At the front end 19 of the heating wire 6, this is connected to the electrical conductor 15. This electrical conductor 15 may for example be designed as insulated copper wire. The electrical conductor 15 extends, starting from the front end 19 of the heating wire 6, along the front side and the upper edge of the blade 4 to the current collector 23, which connects the electrical conductor 15 with the electrical resistance element 10.

The electrical resistance element 10 is designed here as a sliding potentiometer. One end of the resistance element 10 is connected to the negative line 22, which leads to the negative terminal of the electric power source 16. By a triggering device 13, the electrical circuit can be closed and thus the heating wire 6 are heated. Since the positive line 21 for Contact point 14 leads, in each case only that portion 8 of the heating wire 6 is heated, which protrudes from the handle 2. As a result, unnecessary heat development in the handle 2 can be avoided. When the cutting device 3 is pushed out of the handle 2 by the adjusting knob 25, the current collector 23 is also displaced along the resistance element 10 at the same time. That is, the further the cutter 3 protrudes from the handle 2, the lower the electrical resistance of the resistive element 10. At the same time, however, the electrically active length of the heating wire 6 from its front end 19 to the contact point 14 is longer. Overall, this results in a resistance value along the entire electric circuit such that the temperature of the heating wire 6 caused by the current flow at the respective resistance value remains essentially the same regardless of the length of the section 8 of the cutting device 3 protruding from the handle 2. This ensures that an appropriate temperature is always provided for cutting a polystyrene plate, regardless of the length of the protruding from the handle 2, active portion 8 of the cutter 3. For displaceable mounting of the blade 4 in the handle 2, a corresponding bearing rail 26th intended.

Fig. 2b shows the cutter 3 of the device according to Fig. 2a in a detailed view. Shown is the blade 4, which may for example consist of a steel plate and which has a knob 25 in the form of a protruding from the blade 4 element at the rear end. The adjusting knob 25, for example, by a slot in the handle 2 protrude through the handle 2 (see Fig. 5b ) and for displacing the blade 4 or the cutting device 3 from or into the handle 2. Starting from the current collector 23, which taps the electrical resistance element 10, not shown here, along the upper edge of the blade 4 and along the front side of the blade 4, the electrical conductor 15, which may be isolated from the blade 4, to the front end 19 of the Heating wire 6. The heating wire 6 is in this example spaced from the blade 4 and extends along the lower edge of the blade 4 via the insulator 24 to the retractor 9, which can additionally tension the heating wire 6.

Fig. 3 shows a front view of an embodiment of the proposed invention, in addition, some details are visible, which are located within the handle 2. The cutting device 3 can be pushed out of the handle 2, wherein the blade 4 of the cutting device 3 can be mounted on a bearing rail 26. To increase the stability of the cutting device 3, two rollers 20 are provided adjacent to the left and right of the blade 4, which are each rotatable about a vertical axis in this view. Furthermore, Two resistance elements 10 are shown. Two current collectors 23 arranged on the left and right of the blade are in each case displaceably attached to the resistance elements 10 so that the resistance elements 10 have correspondingly different resistance values depending on the position of the blade 4 or the cutting device 3 relative to the handle 2. The device 1 further comprises two adjusting devices 11, by means of which the cutting device 3 can be aligned relative to a workpiece 12, not shown here, for example a polystyrene plate.

Fig. 4 shows a schematic representation of the electrical components of an embodiment of the proposed invention. The circuit is powered by an electrical energy source 16 and can be closed by a triggering device 13. This closing process can be coupled, for example, to an actuation of the adjusting knob 25, so that the electric circuit can be closed by means of triggering device 13 by exerting pressure on the adjusting knob 25. The positive line 21 of the circuit runs from the positive pole of the electric power source 16 to the contact point 14, which is fixed in position with the handle 2. This contact point 14 establishes the electrical connection between positive line 21 and heating wire 6. As can be seen from the electrical diagram, only that portion 8 of the heating wire 6 is traversed by current, which extends from the contact point 14 to the front end 19 of the heating wire 6. At the front end 19 of the heating wire 6, this is connected to an electrical conductor 15, which extends to the current collector 23. The current collector 23 is arranged displaceably on the resistance element 10, the position of the current collector 23 being dependent on the relative position of the blade 4 with respect to the handle 2. As a result, the resulting resistance value of the resistance element 10 is dependent on the position of the blade 4 with respect to the handle 2. One end of the resistance element 10 is connected to the Minusteitung 22 which extends via the triggering device 13 to the negative pole of the electric power source 16.

Fig. 5a shows an embodiment of the invention in a side view and Fig. 5b shows a corresponding plan view. Here, the electric power source 16 is integrated in the rear region of the handle 2. The handle 2 has a slot-shaped recess through which the adjusting knob 25 protrudes through the handle 2. Along this slot, the cutting device 3 can now be pushed out of the handle 2 or pushed into the handle 2 by actuating the adjusting knob 25. Along the slot, a scale 18 is mounted in order to determine the length of the protruding from the handle 2, active portion 8 of Schneldeinrichtung 3 can. The device 1 also has two Justiereinrichtungen 11, which are pivotally hinged to the handle 2. By means of corresponding positioning devices 17 for the two adjusting devices 11, these can be fixed in defined active positions relative to the longitudinal direction of the handle 2. This facilitates in particular the cutting of certain angles or, for example, the cutting of grooves, depressions, mitres and soffits.

Fig. 6 shows a further embodiment of the device 1 in a perspective view. In this case, the cutting device 3 is arranged transversely to the longitudinal extension of the handle 2 and the heating wire 6 is spaced from the blade 4. This variant of the device 1 is particularly suitable for planarizing vertical polystyrene surfaces.

Fig. 7 shows the use of the adjusting means 11 for cutting defined angles in a plan view. For this purpose, the two adjusting devices 11 of the device 1 are adjusted according to the desired angle to be cut and, for example, by means of positioning devices 17 (see Fig. 5b ) fixed accordingly. The adjusting devices 11 simultaneously serve as a stop on the workpiece 12. Thus, a stable cut can be performed by the adjusting device 11 through the workpiece 12 with a desired cutting angle.

Claims (13)

Portable device (1) for cutting thermoplastics, in particular polystyrenes, comprising a handle (2) and a heatable cutting device (3), wherein the cutting device (3) comprises a blade (4) and a heating wire (6) located upstream of the blade (4) ), characterized in that the cutting device (3) relative to the handle (2) is displaceable. Apparatus according to claim 1, characterized in that the heating wire (6) from the blade (4) is spaced. Apparatus according to claim 1 or 2, characterized in that the cutting device (3) in the longitudinal direction of the handle (2) in a corresponding recess (7) of the same and can be pushed out. Device according to one of claims 1 to 3, characterized in that the cutting device (3) relative to the handle (2) is continuously displaceable. Device according to one of claims 1 to 3, characterized in that the cutting device (3) relative to the handle (2) is lockable in stages displaceable. Device according to one of claims 1 to 5, characterized in that only a portion (8) of the heating wire (6) is heated. Apparatus according to claim 6, characterized in that only the out of the handle (2) pushed out portion (8) of the heating wire (6) is heated. Device according to one of claims 1 to 7, characterized in that the heating wire (6) can be tensioned. Device according to one of claims 1 to 8, characterized in that a retractor (9) is provided, through which the heating wire (6) can be rolled up. Device according to one of claims 1 to 9, characterized in that a triggering device (13) for heating the cutting device (3) is provided. Device according to one of claims 1 to 10, characterized in that at least one resistance element (10) is provided, which has a dependent of the relative position of the cutting device (3) with respect to the handle (2) resistance value. Device according to one of claims 1 to 11, characterized in that an adjusting device (11) for aligning the cutting device (3) is provided retativ to a workpiece (12). Apparatus according to claim 12, characterized in that the adjusting device (11) is pivotally articulated on the handle (2).

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