US 3731027 A
An electrical press key with a locking device and thermic excess current release wherein the actuating member of the locking device for the switch slide constitutes at the same time the rotary axle of a potentiometer of an electronic switching device for power regulation.
Description (OCR text may contain errors)
O C v United States Patent 91 [111 3,731,2'7 Arnhold 1 May 1, 1973  ELECTRICAL PRESS KEY DEVICE  References Cited WITH THERMIC EXCESS CURRENT UNITED STATES FATE TS RELEASE N 75 Inventor; Hans h l Kamerau, Germany 3,590,194 6/1971 Frenzel ..200/l57 4 4 3,603,757 9/197] Sahrbacker ..20O/l57 Asslgneel Heinrich PP Kahl, Mam, 3,439,248 4/1969 Winchester et al ..200 1s7 many 22 Filed; Jam 12 1971 Primary Examiner-Herman J. Hohauser Attorney-Richards & Geier  Appl. No.: 105,895
I  ABSTRACT  Foreign Apphcahon Pnomy Data An electrical press key with a locking device and ther- Mar. 18, 1970 Germany ..P 20 12 748.4 mic excess current release wherein the actuating member of the locking device for the switch slide con- U-S- CL titutes at the ame time the rotary axle of a poten-  Int. Cl. ..H0lh 21/10 tiometer f an electronic Switching device for power  Field of Search ..200/157, 153 R;
4 Claims, 4 Drawing Figures Patented May 1', 1973 q A .v H. ii
Figgis ELECTRICAL PRESS KEY DEVICE WITH TIIERMIC EXCESS CURRENT RELEASE This invention relates to an electrical press key device with thermic excess current release.
Switching devices of this type consisted initially of separate switching elements fixed at different locations of the apparatus. At the present time this has been changed by combining the multi-pole press key and the electrothermic releasing device into a single structural unit. This combination was attained by providing a special, construction of the switching and actuating mechanisms cooperating with the release member, wherein one of the switch members was constructed as an equal-armed lever rotatably mounted under spring pressure in a guide slit of the spring-engaged switch slide, the slit being inclined to the actuating direction, the construction being used for a contact-providing bridge connection of the fixed contact with the swingable coupling point of the bimetallic releasing member. By this construction a protective switch construction was provided which does not differ in structure and size or in the contact arrangement from the usual press key switches without excess current release, but is superior to them in its operation due to the additional protection from overload.
Press key devices of this type may combine a springengaged switch slide with a locking device so that the electrical apparatus can remain if desired in a switched on condition without it being necessary to actuate the press key for that purpose.
Furthermore it has been also suggested that the switch slide may be coupled with an electronic device which due to the continuous actuation of the press key provides additionally in the end position parallel to the available overload protection a regulation without steps of the revolutions of an electrical driving motor. A device of this type is particularly useful for small electrical tools for boring, polishing, cutting operations and the like, wherein in'view of the mutual reaction between the tool and the treated material it is important to adapt as precisely as possible the running condition of an electrical driving motor mostly of small power to the operational procedure being used and to the different materials. I
An object of the present invention is to improve the described constructions.
Other objects will become apparent in the course of the following specification. The construction of the present invention starts with the well known electrical press key used for switching on and off electrical tools, such as, for example, electrical hand boring machines. These press keys are connected as a rule with a mechanical actuating device for continuous working and also often with an electrothermic excess current release in the form of a bimetallic switch. The main object of the present invention is to additionally combine such a press key for an actuating device and excess current release with a device for output steering (speed regulation).
The construction of the present invention improves the described apparatus to a very substantial extent-in that the present invention separates the output actuation produced by operating. the press key from the movement of the spring-engaged switch slide and combines the adjusting procedure with its locking: device. To attain this the actuating handle of the locking device of the switch slide is so constructed that it constitutes at the same time the rotary axis of the potentiometer of an electronic switching device for output actuation, although the pressure actuation of the handle produces as before the fixing of the switch slide which can be released by actuating once again the press key.
According to a preferred embodiment of the present invention the electronic device for regulating the rotation consists of a thyristor switch which is actuated by a RC (potentiometer-condenser) member and produces without steps a change in output and thus in the rpm. of the corresponding electric motor. In that case the electronic switch member operates in phase channel and thus substantially without loss. This device can be brought together into a very narrow space and can be fixed sidewise upon the pressure key of the present invention with the thermic excess current release,
whereby the rotary axle of the actuating potentiometer extends through the actual press key and its switch slide so as to provide in described manner the locking function at the same time with and completely independently from the speed actuation.
According to a further development of the present invention the electronic switching device for speed regulation constitutes a bridge-over of the length of contact formed by the normally actuated switch contact of the multi-polar press key. Furthermore, this switch contact is mechanically short-circuited in the corresponding stop position of the setting potentiometer by a cam provided upon its rotary axle, so as to enable the electromotor to attain its full nominal output.
The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawing showin by way of example only, a preferred embodiment of the inventive idea while leaving out details of an existing press key structure with thermic excess current release.
In the drawing: 7
FIG. 1 is a plan view of an open press key device looking from the sides of the switch mechanics and excess current release. 1
FIG. 2 is a side view of the press key device, partly in section illustrating the locking device for the switch slide.
FIG. 3 shows the closed press key device from the side of the switch slide.
FIG.'4 is an electrical circuit diagram of the entire construction. v
As shown in FIGS. 1 and 2 the switch slide 1 which is subjected to spring pressure and which is a part of the press key, actuates mechanically from the outside a switch contact device 3 secured by a bimetallic release member 2. A special locking device is used to stop at will the switch slide in the switched-on condition. This device consists of a press button 4 having an axle 5 extending through a recess of the switch slide 1. When the press button is actuated it engages and holds the switch slide from the rear by a locking shoulder 7 against the action of a pressure spring 6. This locking is released in a simple manner by once again actuating the switch slide 1 which results in a release of the shoulder and spring actuated return movement of the press button 4 intoth'e initial position.
In accordance with the present invention the press button 4 is also constructed as a rotary pin and in that capacity it is used, independently of the locking function, for regulating the motor speed of the electrical apparatus which is provided with the press key device. For this purpose the axle 5 of the press button 4 is provided with a rearwardly extending piece having, for example, the shape of a rectangular pin 8 and extending into the adjusting member of the potentiometer of the electronic switching device for regulating the motor speed. The switching device consists of a narrow part 10 extending along the inner side of the press key device and located opposite the side used for actuating the press button 4. Furthermore, the axle 5 carries a cam 9 used when the potentiometer is turned completely to the right for mechanically short circuiting the switch contact 3 which otherwise is electrically bridged by the electronic switching device for speed regulation; then the electromotor of the apparatus receives the full network voltage.
FIG. 4 illustrates a possible electronic circuit arrangement for regulating the speed of an electromotor of an apparatus provided with the press key of the present invention. The circuit includes an ac. motor 11. A thyristor 12 is used to vary its output in accordance with the phase channel procedure; it is triggered during the positive half wave by a R-C member 13, 14 over a triac 15 and a normal diode 16. The potentiometer 13 which can be actuated by the press button 4 of the above described locking device, is used to regulate the ignition angle and thus the speed of rotation of the electromotor-11. When the resistance of the potentiometer 13 is fully effective the resistance 17 will limit the network voltage at the charge condenser 14. In order to be able to operate the electromotor 11 with full output as well, the switch contact 3 of the press key can be short-circuited by actuating the potentiometer 13 operated by the press button 4 with the use of the shoulder 7 carried by the axle 5; then the motor 1 l is connected directly to the network.
The construction of the present invention utilizes existing structural parts to provide a press key device for apparatus driven by electric motors, whereby the device in addition to thermic overload protection also has means for operating the rpm. of the apparatus,
without differing from the existing press key device in construction, size and connection arrangement and without having any additional structure. This is achieved by using the press button 4 of the mechanical locking device for the switch slide 1 of the press key as a rotary axle 5 of the potentiometer 13 of the electronic switch device 10 for output steering. Thus the device of the present invention can be built in most effectively in various domestic devices, hand operated boring machines, fast saws, floor polishers, mixing devices for kitchens, hair driers and the like.
I claim: 1 I
1. In an electrical actuating device, in combination, a movable switch slide, means resiliently supporting said switch slide, a switch contact device actuated by said switch slide, a rotary press button having an axle extending through a recess in said switch slide substantially perpendicularly to the direction of movement of said switch slide, said press button having a locking shoulder adapted to engage and hold said switch slide, a pressure spring engaging said press button, a pin carried by said press button, a potentiometer, said in being operatively connected with said potentiome er,
and an electronic switching device connected with said potentiometer.
2. The combination in accordance with claim 1, further comprising a casing, said press button extending from one side of said casing, said electronic switching device constituting a narrow structural unit located upon the opposite side of said casing.
3. The combination in accordance with claim 1, wherein said electrical actuating device comprises a switch contact device consisting of a plurality of switch contacts and actuated by said switch slide, said electronic switching device bridging said switch contacts.
4. An electrical press key device in accordance with claim 3, comprising a cam carried by said rotary. axle and actuating said switch contacts in one of the two limit positions of the potentiometer.