EP0718859B1 - Device for the switching of an electric motor, in particular for braking an electric power tool - Google Patents

Abstract

The electric motor switching apparatus includes two alternating switches for switching the current supply to the electric motor on and off, changing the poling of a field winding of the motor and switching a braking circuit for the motor on and off. A moving contact (32') is provided for each alternating switch. The contact can move between a stationary on-contact (30') and an off-contact (28'). A device is provided for at least the moving contact by which the moving contact is guided over part of its path when switching over.

Description

The invention relates to a device for switching a Electric motor, in particular for braking an electric tool, according to the preamble of claim 1, as already known from EP-A-0 197 436.

The aim of the invention is to create a so-called Brake switch for electromotive tools, the use of a suitable contact arrangement, in particular for switches with housing dimensions according to European standards shall be.

For the electrical braking of an electric motor you need two toggle switches. The changeover switches are used to Power on or off, one To reverse the field or armature winding of the electric motor and one switch the electrical brake circuit on or off. When turning off, especially when you turn it off quickly it has so far been disadvantageous that between the two intended stationary for the production of the power supply Arcing contacts in an undesirable manner, that from the contact breakaway sparks and the switching of the inductors results. This arc closes the field winding of the engine short, and the current that is now only through the armature winding is limited increases so much that a Back-up fuse responds. Critical and therefore in need of improvement is furthermore that when switching on again during the Braking between the contacts for the power supply again an arc arises with the aforementioned consequences.

So far, there has been no electric braking Switches that have either two contact bridges with double break or have two toggle contacts. These are function-related the contact distance is too small, so that there are rollovers and in addition to contact welding. The Rollover formation is also caused by a too fast Switching promoted.

With the invention, a device for switching a electrical braking of an electric motor, in particular for Power tools, created with stable switch positions be, in which the risk of Arcing, arcing and contact welding is significantly reduced.

This is according to the invention by those mentioned in claim 1 Characteristics achieved. Preferred features of the invention Advantageous further training are the subordinate claims refer to.

The device has ON and OFF contacts with regard to "arc-safe removal" so far apart that arcing occurs and their negative effects when switching reduced is. In addition, an increased switching time due to the enlarged contact section reached. This helps to avoid contact welding in that at least one mobile Contact when switching after a contact friction movement phase from the corresponding stationary Contact against which he previously touched against the action of a pressure spring can be lifted off by means of the guide device.

According to a preferred embodiment of the invention, this is Actuator articulated to both movable contacts. According to a first alternative is the actuator connected to each movable contact via a spring, whereby the arrangement is preferably made so that the actuator is articulated on a rocker arm, which with everyone movable contact is connected via a tension spring. Here ensure the springs on the one hand in a favorable way good contact pressure and on the other hand switch the mobile Contacts when the actuator becomes effective.

Alternatively, there is a pressure spring for each moving contact intended.

According to a preferred embodiment, each guide device has a sliding guide for the movable contact, which preferably each of one Starting slope to generate a certain moment switching function can be limited. The intended sliding guide, which is preferably designed as a sliding rib, provides advantageous on the one hand for the fact that the movable contact on the can set up each stationary contact properly and a certain distance is still available for contact friction stands. On the other hand, can be favorably through the ramp when switching a pressure point will be generated that it largely enables the critical phase of the contact opening to quickly pass or close.

The movable contact is in a preferred embodiment the invention on a pivot lever, preferably laterally on this, provided that is stored with play, this Storage preferably designed rotatably and preferably is formed in that the pivot lever in an elongated hole is rotatably supported with lateral play. This leaves the switching kinematics are extremely simple and with few Train parts safely and reliably.

According to a further embodiment, the swivel lever has Invention a plastic part with a sliding rib for the Slideway, preferably at least one guide device on one side of a housing for the changeover switch is formed.

Alternatively, in the embodiment with a rocker arm, that on the rocker arm at least one sliding guide for the movable contact is formed.

The result is a spatial and functionally favorable concept especially when the two toggle switches are in one single housing symmetrically arranged in separate chambers if the fastening element consists of a slide switch, which pivots the moving contacts when the Pressure spring or the tension spring of each movable contact supports the shift lever or the rocker arm, and if the Switch slide mounted in the housing in the area of a wall which is the two housing chambers with the changeover switches separates.

Fig. 1

eine teilschematisierte Darstellung eines ersten Ausführungsbeispiels einer erfindungsgemäßen Vorrichtung in einer Stellung, in der die elektrische Stromversorgung für einen Elektromotor ausgeschaltet ist;

Fig. 2

eine Darstellung der Vorrichtung gemäß Fig. 1 in einer Mittelstellung des beweglichen Kontaktes;

Fig. 3

einen Schnitt entlang der Schnittlinie III-III in Fig. 2;

Fig. 4

eine teilschematisierte Darstellung eines zweiten Ausführungsbeispiels einer erfindungsgemäßen Vorrichtung in einer Stellung, in der die elektrische Stromversorgung für einen Elektromotor ausgeschaltet ist;

Fig. 5

eine Darstellung der Vorrichtung von Fig. 4 in einer mittleren Stellung des Kipphebels;

Fig. 6

eine Darstellung der Vorrichtung gemäß Fig. 4 in einer Stellung, in der die elektrische Stromversorgung für einen Elektromotor eingeschaltet ist; und

Fig. 7

einen Schnitt entlang der Schnittlinie VII-VII in Fig. 6, wobei der bewegliche Kontakt und der Kipphebel in ihrer Mittelstellung dargestellt sind.

Further details, features and advantages of the invention can be found in the subsequent description part, in which an embodiment of the invention is explained in more detail with reference to the accompanying drawings. Show it:

Fig. 1

a partially schematic representation of a first embodiment of a device according to the invention in a position in which the electrical power supply for an electric motor is switched off;

Fig. 2

a representation of the device of Figure 1 in a central position of the movable contact.

Fig. 3

a section along the section line III-III in Fig. 2;

Fig. 4

a partially schematic representation of a second embodiment of a device according to the invention in a position in which the electrical power supply for an electric motor is switched off;

Fig. 5

an illustration of the device of Figure 4 in a middle position of the rocker arm.

Fig. 6

an illustration of the device of Figure 4 in a position in which the electrical power supply for an electric motor is turned on. and

Fig. 7

a section along the section line VII-VII in Fig. 6, wherein the movable contact and the rocker arm are shown in their central position.

Fig. 1 shows a schematic representation of a first embodiment the invention with a housing 10, in which how 3 shows the front cover-like housing wall 11 is omitted to go into a front housing chamber 12 see. The housing 10 is, as in this context 3 can be seen from two closed housing chambers 12 and 13.

According to FIG. 1, the housing chambers 12 and 13 have a right one common side wall 14, a left common side wall 15, a common lower wall 16 and a common upper one Wall 17. The walls 14 to 17 are in one piece with a partition 18 formed and consist of an insulating plastic.

A changeover switch 19 is located in the front housing chamber 12 housed, is located in the rear housing chamber 13 a changeover switch 20 for switching off the power supply for the electric motor. The changeover switches 19 and 20 are used for and switching off the power supply to reverse the polarity of a field or armature winding of the electric motor and for switching on or off of an electrical brake circuit and are symmetrical with respect the partition 18 is constructed. You will go through together actuates a slide valve 21 which passes through the upper wall 17 and is guided in the partition wall 18. The shift lever 21 has one on both sides in the area of its lower end right-angled protruding arrangement of pins 22 and 23, the are each surrounded by a pressure spring 24 or 25, which is supported by the slide switch 21, the pressure spring 24 a pivot lever 26 of the changeover switch 20 and the Pressure spring 25 a pivot lever 27 of the changeover switch 19th acted upon.

The toggle switch 19 includes, as is best related 2 shows a stationary OFF contact 28, of a conductor 29 through the side wall 14 to the outside of the housing 10 is guided. In the area of the bottom wall 16 there is a stationary ON contact 30, which with a electrical conductor 31 is connected, which also by the side wall 14 is led out of the housing 10. To the free end of the pivot lever 27 is a side Contact 32 by moving the pivot lever 27 either with the OFF contact 28 or with the ON contact 30 to the system can be brought. The pivot lever 27 is a playful Swivel joint 42 in an elongated hole 33 of a connecting plate 34 mounted such that the movable contact 32 also perpendicular to the swivel plane of the swivel lever 27 for a contact lifting and an upward contact movement is movable. Accordingly, the bearing pin 23 with play in a larger one Bore 35 of the pivot lever 27 is arranged. The connection 34 is via an electrical line through the wall 15 to Guided outside of the housing 10.

On the pivot lever 27 is in an area between the bore 35 and the end contact 32 a plastic part 37 attached to which perpendicular to the front wall 11 facing Sliding rib 38 is formed, which is shown in FIG Position on an arcuate sliding rib 40 under effect the pressure spring 25 rests. The sliding rib 40 is arcuate educated. 1 and 2 are only dashed to the Sliding rib 40 belonging to bevels 39 and 41 shown those in slide rib 38 from the level of slide rib 40 when pivoting the pivot lever 27 to abut the movable Contact 32 with the stationary contact 28 and 30 performed becomes. The slopes 39 and 41 can be ramp-like under 45 ° or be designed as a transition curve profile.

The operation of the device for switching an electrical Braking an electric motor is easier Way from the position shown in Fig. 1 by the slide switch 21 in the direction of the arrow shown in FIG Housing 10 is inserted. This is initially done via a certain swivel range still a laterally shifting Contact friction between contacts 32 and 28 until the Slide rib 38 reaches the run-up slope 39. With a switching movement the movable contact 32 is quickly on the slide rib 40 raised and thus a safe contact separation achieved. When pivoting the pivot lever 27 further the sliding rib 38 reaches the run-up slope 41, and the movable one Contact 32 comes into sliding contact with the stationary one Contact 30 until the end position reached in Fig. 1 is dashed.

The changeover switch 20 is indeed symmetrical to the changeover switch 19 built, but has functional reasons an opposite contact assignment insofar as there the stationary contacts are swapped in terms of function.

The device according to the invention can thus be advantageous large contact openings, rubbing contacts, a simple manufacturable structure with simple parts as well as a lightweight Assembly can be realized.

4 to 7, a second embodiment is one Device according to the invention with a housing 10 'and a modified slide switch 21 'with integrated button and Compression spring. As far as this second embodiment identical or similar parts have been simplified the same reference numerals as in the first embodiment, however, used with an apostrophe. To avoid Repetitions will subsequently only differ from the second Embodiment compared to the first embodiment explained, with appropriate modifications of components bear a reference sign with an apostrophe.

The second embodiment differs from the first Embodiment essentially in that the Changeover switches 19 'and 20' always have a stable ON or OFF position take, while with the changeover switches 19 and 20 of the first embodiment also intermediate positions of movable contact 32 together with the associated pivot lever 27 are possible.

The slide switch 21 ', to achieve a reset function has an operating button 50 at its upper end, which is supported on the housing 10 'via a compression spring 51, is, as can be seen in connection with FIG. 7, performed in the region of the partition 18 'of the housing 10'. He owns a groove-shaped recess 52 for the pivotable mounting a pin 53, which is formed laterally on a rocker arm 54 or is attached. The rocker arm 54 is at 55 (see also Fig. 7) pivotable on the partition 18 'via a side Pin 56 stored and between the in Fig. 4 and the Fig. 6 shown pivotable, its position according to Fig. 4 of the OFF position and its position according to Fig. 6 the ON position of the changeover switches 19 'and 20' is assigned.

The rocker arm 54 has a front end 57 which is on the side a portion of the partition 18 'is guided. The partition 18 'is open in the pivoting range of the rocker arm 54. in the The area of the front end 57 of the rocker arm 54 is on both Side hooks 58 and 59 for tension springs 60 and 61 respectively integrally formed from there at an angle of about 15 ° towards the movable contacts 32 ' extend outside. The tension springs 60 and 61 are with their other End hung on a plastic part 62 or 63, the each on the pivot lever 27 'for the movable contact 32 'are attached. The springs 60 and 61 on the one hand a desired one due to its line of action and its preload Safe contact pressure reached in the switch positions. On the other hand, they serve the movable contacts 32 'to switch. This is done in such a way that when pressing in the slide switch 21 ', the movable contact 32' initially remains in its respective switch position until the tension springs 60, 61 due to the pivoting of the rocker arm 54 further stretched and in their direction of action over the to Swivel joint 42 'directed switching position (dead position) are pivoted. This creates a sufficiently large torque generated, which overcomes the contact friction and more leads the movable contact 32 'immediately into the second stable position jumps. In the event that by welding or sticking the contacts, the intended spring force is not is sufficient, two opposite one another on the slide valve 21 ' Contact tear ribs 66 are provided, each at the OFF or ON switch position of the pivot lever 27 ' of the movable contact 22 'are spaced apart and only as shown in Fig. 5, in the region of the center position of the rocker arm 54 to the pivot lever 27 'for tearing the contacts attack.

The trained as a spring holding and motion control part Plastic part 62 has a molded pin 67, the guided over a sliding rib 40 'during the switching process is formed on the rocker arm 54. The slide rib 40 ' as well as the sliding rib 40 of the first embodiment Sloping ceilings 41 'and 39'. How they work reference is made to the above statements.

The trained as a spring holding and motion control part Plastic part 63 has an inwardly facing pin 68, which in the second exemplary embodiment according to FIG. 7 a wall section 69 is slidably guided. The wall section 69 also serves to guide the slide switch 21 '. Alternatively, a slide rib 40 ′ can also be attached to wall 69 here. for the pin 68 to be provided for both pivot levers 27 'in addition to the movable contacts 32' to the partition 18 provide mirror-symmetrical movement when switching.

Claims (16)

1. Apparatus for switching an electric motor, particularly in particular for braking an electric power tool, including two double-throw switches (19, 19', 20, 20') for switching the power supply for the electric motor on and off, for reversing the polarity of a field or armature winding of said electric motor, and for connecting and disconnecting an electric braking circuit for said electric motor;

   an actuator (21, 21') for said double-throw switches (19, 19', 20, 20');

   a mobile contact (32, 32') provided for each double-throw switch (19, 19', 20, 20'), which is arranged for movement between a stationary ON contact (30, 30') and an OFF contact (28, 28') spaced therefrom at an arc-sae distance; and including

   means (40, 40') for at least one mobile contact (32, 32') which serves to guide this contact at least over a part of its path in change-over,

      characterised in
      that said means (40, 40') guides in a way that at least one mobile contact (32) may be lifted off the corresponding stationary contact (28, 30), against which it had been bearing before, by means of said guiding means (40) in opposition to the action of a pressure spring (24, 25) after a phase of contact friction movement.
2. Apparatus according to Claim 1, characterised in that said actuator (21, 21') is articulated on both mobile contacts (22, 42').
3. Apparatus according to Claim 1 or 2, characterised in that an actuator (21, 21') is connected to each mobile contact (32, 32') via a spring (24, 25, 60, 61).
4. Apparatus according to any of the preceding Claims, characterised in that said actuator (21') is articulated on a rocking lever (54) which is connected to each mobile contact (32') via a tension spring (60, 61).
5. Apparatus according to any of the preceding Claims, characterised in that each guiding means includes a sliding guide (40, 40') for said mobile contact (32, 32') which is limited by leading ramps (39, 39', 41, 41').
6. Apparatus according to any of the preceding Claims, characterised in that each mobile contact (32, 32') is provided laterally of a pivoting lever (27, 27').
7. Apparatus according to Claim 6, characterised in that said pivoting lever (27) includes a plastic part (37) with a sliding rib (38) for said sliding guide (40).
8. Apparatus according to Claim 6 or 7, characterised in that said pivoting lever (27) is supported for rotation in an elongate hole (33) with lateral clearance.
9. Apparatus according to Claim 4, characterised in that at least one sliding guide (40') is formed on said rocking lever (54) for said mobile contact (32').
10. Apparatus according to any of the Claims 5 to 9, characterised in that at least one pivoting lever sliding guide is provided on a wall (11, 69) of a housing for said double-throw switches (19, 19', 20, 20').
11. Apparatus according to any of the preceding Claims, characterised in that said two double-throw switches (19, 19', 20, 20') are arranged in a single housing (10, 10') in separate chambers (12, 12', 13, 13') in mutual symmetry.
12. Apparatus according to any of the preceding Claims, characterised in that said actuator consists of a sliding switch (21, 21').
13. Apparatus according to Claims 4 and 12, characterised in that two mutually facing contact-tearing ribs (65, 6) are provided on said sliding switch (21') which are each spaced from said mobile contact (32') in the OFF or ON switching position.
14. Apparatus according to any of Claims 6 to 13, characterised in that a spring retainer and motion-guiding element (62, 63) is provided on each pivoting lever (27, 27').
15. Apparatus according to Claim 1, characterised in that said pressure springs (24, 25, 60, 61) are disposed between the respective mobile contacts (32, 32') and said sliding switch (21) or said rocking lever (54, respectively.
16. Apparatus according to Claim 12, characterised in that said sliding switch (21, 21') is supported in said housing (10, 10') in the area of a wall (18, 18', 69) which separate said two housing chambers (12, 12', 13, 13') with said double-throw-switches (19, 19', 20, 20') located therein.

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