FI120864B - Mechanical safety coupling for a machine-driven tool - Google Patents

Description

Mechanical safety switch for power tool

The invention relates to a mechanical safety switch for a power tool to prevent simultaneous operation of two independent functions.

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The invention has been especially developed for an application where the tool is a pipe cutting device and the functions that can be selected with the safety switch are rotary actuation of the cutting head and use of displacement of the clamping jaws of the pipe to be cut.

It is an object of the invention to provide a simple and reliable mechanical safety switch which ensures that only one of the two independent functions can be actuated even though they are operated by the same power unit.

This object is achieved by the invention on the basis of the features set forth in claim 1 below.

Claims 2 and 3 describe a preferred embodiment of the safety switch according to the invention and claims 4 and 5 describe one practical embodiment of the safety switch.

In the following, the invention will be illustrated by means of an exemplary embodiment with reference to the accompanying drawings, in which: Figure 1 is a block diagram of a pipe cutter having a safety switch 3 according to the invention;

Fig. 2 illustrates in more detail the structural implementation of the safety switch 3, and Figs. 3-5 illustrate an essential part of the safety switch in its various connections.

Fig. 1 is a block diagram showing a tube cutting device in which the tube held by the clamping jaws 4 is cut by a rotary cut-off top 5. In Fig. 1, the motor 1 drives a drive shaft 6 Although the drive jaws 4 drive actuation 7 and the cutting head 5 rotary drive 8 have a common drive motor 1 and a common drive shaft 6, it must be possible to ensure that the simultaneous operation of the fastening jaws 4 transfer function and the cutting head 5 rotation function is prevented.

This prevention of simultaneous operation is implemented by a mechanical safety switch 3 according to the invention, the structure and operation of which are described in more detail with reference to Figures 2-5. The rotary drive shaft 6 has a drive wheel 7, e.g. a screw 10 gear which rotates the transfer screw moving the mounting jaws 4 back and forth, whereby the jaws 4 also move towards each other or away from each other to secure or detach the tube. Reversing direction of rotation can be done by either the engine 1 or the gear associated with the reduction gear 2. The drive shaft 6 also has a second drive wheel 8, e.g. a gear wheel, which in the illustrated embodiment rotates the cut-off head 15, the cut-off bar having two support rollers and a cutting blade to be rotated around the tube during cutting.

As shown in Fig. 3, a rocking lever 17 is embedded in the drive shaft 6, in which at different swing positions only one drive wheel 7 or 8 at a time can be engaged to rotate the drive shaft 6 20.

The drive shaft 6 has a recess 16 receiving the rocker lever 17 having a spring 18 between the bottom and the rocker lever 17 which tends to partially push the rocker lever 17 out of the notch 16. The drive shaft 6 and rocker lever 17 are surrounded by an axially movable slide 9,25. and having a peripheral groove 10. When the slide is in its center position (Fig. 4), it holds the rocking lever 17 at each end of the drive shaft 6 inside the cylinder casing, which prevents operation of both functions. 3, prevents the end of the rocker lever 17 from engaging in the locking groove 8a of the sprocket 8, but allows the other end of the rocker lever 30 to be pushed outside the cylinder housing 7a by pressing the spring 18. When the slide 9 is in its second end position as shown in Fig. 5, the opposite is true, i.e. the rocker lever 17 is prevented from engaging in the locking notch 8a, but again the spring presses the second end of the rocker lever into the locking slot 8a. In this way, the gears 7 and 8 are rotated, but only one at a time, 35 to rotate the drive shaft 6.

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Fig. 2 shows how the drive slider 11, 12 engages the circumferential groove 10 of the slider 9, which in turn engages the threaded groove 14 of the pin 15 with a rotatable shaft 13. The gear 13 '(Fig. 1) at the shaft 13 can be rotated e.g. 5 with a protective cover 19. The opening movement of the protective cover 19 of the blade head 5 is arranged 5 to engage the safety switch 3 in the displacement position of the pipe clamps 4. In other words, when the protective cover 19 is open, the tube may be brought in with a cut-off 5 and secured in a cut-off position between the clamping jaws 4 or after the cut-off In this case, the use of the clamping jaws 4 must be prevented so that the pipe does not come loose during cutting.

The drive actuator 11, 12 shown in Fig. 2 comprises a sleeve 11 surrounding the shaft 13, from which a U-shaped flange 12 protrudes, the U-arms (not shown) of which engage the peripheral groove 10 on opposite sides of the shaft 6.

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The invention is not limited to the embodiment of Fig. 1 or the structural embodiment of Figures 2-5, but many other applications or details of the structural implementation may be contemplated within the scope of the following claims.

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Claims (5)

A mechanical safety switch (3) for a power tool to prevent simultaneous operation of two independent functions (4, 5), characterized in that the sa-5 stick rotatable drive shaft (6) has a first drive wheel (7) for the first operation (4) and a second drive wheel. (8) for the second function (5) and that a rocking lever (17) is embedded in the drive shaft (6), in which at different rocking positions only one drive wheel (7, 8) can be engaged to rotate the drive shaft (6). Safety switch according to Claim 1, characterized in that the drive shaft (6) has a recess (16) for receiving the rocking lever (17), the bottom of which and the rocking lever (17) having a spring (18) which tends to push the rocker lever (17) (16) that the rocker arm (17) has a first end which engages in a locking groove (7a) of the first drive wheel (7) when it comes out of the cylinder sheath of the shaft (6) and a second end 15 which engages the second drive. the locking groove (8a) of the wheel (8), that the drive shaft (6) and the rocker lever (17) are surrounded by an axially movable slide (9) having a central position and two end positions, and that the slide (9) holds the rocking lever (17) inside the cylinder housing of the end drive shaft (6) and at each end position, the slide (9) allows one end of the rocker lever (17) to fall outside the cylinder shell of the shaft (6). Safety switch according to Claim 1 or 2, characterized in that the slide (9) is a ring or sleeve with a peripheral groove (10), the peripheral groove (10) of which is actuated by an actuator (11, 12) which in turn engages with a rotatable shaft 25 (13). ) in the threaded groove (14). The application of a safety switch according to any one of claims 1 to 3, characterized in that the tool is a pipe cutting device, the first function being the rotation drive (8) of the cutting head (5) and the second function being the movement (7) of the clamping jaws (4) 30. Application according to Claim 4, characterized in that the opening movement of the protective cover (19) of the cutting head (5) is arranged to engage the safety switch (3) in the displacement position of the pipe clamps (4) and the closing movement of the protective cover (19) (5) rotation position.