GB2157509A - Wiring system for mini tools - Google Patents

Abstract

An electric device, particularly a small power tool, is wired with preformed, dimensionally stable conductors (14, 15, 16) formed from metal strips and having bent ends (25, 29; 24, 26; 27, 28) for forming plug connections. These conductors are inserted into one part (1) of the device's housing (1, 2) and engaged in slots to positively position them therein. Thereafter, electric components (3, 12) are inserted into the housing part (1) or the assembled housing (1, 2) with plug connections between these components (3, 12) and the ends of pairs of the conductors (14, 15, 16) being simultaneously effected upon insertion. For example, a switch (12) can be inserted through an opening (13) with male terminals (22, 23) of the switch automatically plugging into female connector ends (26, 27) of a pair of conductors (14, 16). <IMAGE>

Description

SPECIFICATION Wiring system for mini tools Field of the Invention This invention relates to a method of wiring electric devices, particularly portable power tools such as, for example, so called mini tools. The invention also relates to electric devices having a wiring system.

Background of the Invention It has been proposed in German Utility Model 82 27 275 and Germany Patent 749,405 to employ metal conductor strips in place of conventional wiring.

In German Utility Model 82 27 275 a strip conducting line is disclosed with plug connectors spaced apart along the length thereof and formed by bending portions of the bared strip upon itself.

The series of male plug connectors so formed are inserted in female plug connectors of the electric components to be connected.

Such a procedure necessitates the insertion into an electric device of the electric components prior to the insertion of the preformed conductor strip. The electric components have to be precisely positioned and secured in place to enable the strip conducting line to be plugged thereinto; this is similar to conventionally wiring components after they are in position. Thus, it is necessary when inserting the strip conducting line, to carefully position both the male plug connectors and the strip conductor sections located between these male plug connectors in a precise and predetermined manner; otherwise either difficulties would occur during the positioning of the conductor sections in the electric device or the plug connections into the electric components could not be made.

In German Patent 749,405 no plug connections with the metal conductor strips are formed. Either soldered or conventional spring contact connections are suggested.

Summary of the Invention The object of the present invention is to provide an improved system of wiring an electric device using dimensionally stable strip conductors.

A feature by which this is achieved is by employing preformed conductor strips with bent over ends formed as male or female plug connectors, and then securing these conductor strips in a housing part before the electric components to be connected therewith are inserted.

In this way the plug connections can be made as the various electric components are inserted in place.

Thus, these components are plugged into position and held in position in the housing not only by engaging the latter but also by engagement with the dimensionally stable conductors.

This has the advantage that the assembly of the electric device is simplified, particularly in the case of small portable power tools which have a housing formed from two half-shells in clam shell fashion.

Accordingiy, therefore, there is provided by the present invention a method of wiring an electric device comprising selecting preformed, dimensionally stable conductors formed from striplike electrically conductive material and having bent ends for forming plug connections, inserting the conductors into one part of a housing of the electric device and engaging the conductors with positioning means in the housing part to positively position the conductors therein, and then inserting an electric component into the housing part and simultaneously effecting plug connections between the electric component and ends of two of the conductors.

Preferably the positioning means comprises slots in which the conductors are inserted, for example slots in internal partitions in the housing part. The conductors may also be engaged with support surfaces which may, for example, be associated with the internal partitions. Advantageously, the strip conductor may be preformed with a sharp bend intermediate its length, so that a portion of the conductor may engage against the side of a partition after engaging through a slot therein.

With electric appliances, the assembly of the onl off switch often represents a labor-intensive step.

However, according to a preferred aspect of the present invention, the switch may be plugged into an opening in the housing wall and, during this plugging-in, also engage its own plug parts with plug-receiving parts of two strip conductors positioned in the housing. In this way the assembly of the switch is extremely simplified.

According to another aspect of the invention, there is provided an electric device comprising a wiring arrangement of preformed, self-supporting conductors of strip-like conductor material, the ends of the conductors being folded over to form male and female plug connectors, electric components connected by plugging to ends of the connectors, and positioning means in a housing part of the electric device for positively supporting and locating the conductors.

Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiment, the appended claims and the accompanying drawings.

Brief Description ofthe Drawings In the accompanying drawings: FIGURE 1 shows somewhat diagrammatically a perspective exploded view of a mini power drill according to the invention, the strip conductors being shown rather enlarged and some details being omitted for clarity; FIGURE 2 is a longitudinal section through the assembled mini power tool of Fig. the section being taken through the centers of the two housing half-shells in an upward direction in Fig. 1; FIGURE 3 is a part section on the staggered line Ill-Ill of Fig.2; FIGURE 4 is a plan view of one of the strip connectors, similar to as shown in Fig. 3 but on a larger scale; FIGURE 5 is a side view of the connector of Fig. 4 taken in the direction V in Fig. 4;; and FIGURE 6 is an end view of the connector taken in the direction VI in Fig. 5.

Detailed Description of the Preferred Embodiment Figs. 1, 2 and 3 show a mini power drill, such as used for delicate work and for hobby activities, and which is operated from a source of low voltage direct current, for example at 12 volt or 15 volt. It has a direct-current motor 3, on the armature shaft 4 of which a fan rotor 6 and a conventional drill chuck 5 are mounted. The motor 3 is held in clam-shell fashion in the tool's housing consisting of two ha Ifshells 1 and 2, a cap 7 helping to hold the two housing shells 1,2 together at the front end (see Fig.

2). As also can be seen in Fig. 2, conventional bearings are provided for the armature shaft, and the casing of the motor 3 is positioned in the two housing halves 1, 2 in such a way that it cannot be displaced.

A receptacle 8 is inserted into the rear end of the tool's housing and secured by engagement studs 8'.

A female plug 10, connected on one end of a voltage supply cable 9, can be plugged into the receptacle 8.

At the other end of the supply cable 9 is a male plug 11 for connection to a suitable direct-current voltage source.

As will be described further below, the terminals of the electric motor 3, which consist of flat pins 20 and 21 are connected to ends of preformed strip conductors 14 and 15. The other end of the conductor 15 extends into the aperture region of the receptacle 8. The other end of the conductor 14 is connected to a flat pin terminal 22 of a switch 12 inserted into an opening 13 in the housing half 2.

The switch 12 is retained in this opening by spring clips 39 extending along the sides of the switch housing as shown in Figs. 1 and 2. The other male terminal 23 of the switch 12 is connected to one end of a third strip conductor 16, the other end of which extends into the orifice of the receptacle 8.

The conductors 14,15, 16 consist of metal strips, preferably of CuSn 6 HV 180 chromium-plated or CuNi 18 Zn 20 HV 170 K. They are brought into the forms illustrated solely as a result of bending, the conductors 15 and 16 having two identically formed male plug connectors 29 and 28 produced bytwo ends being bent over, whereas the other ends of conductors 15, 16 form female plug connectors 25 and 27. Conductor 14 has female plug connectors and will be described further later with reference to Figs. 4,5 and 6.

The conductors 14, 15,16 are bent in such a way that they can be inserted into slots formed in the housing part 1. Forthis purpose, there are formed on the inside of the housing part 1, partitions in the form of ribs or projections 30, 31,32,33, 35, 36 and 37 which each have one or more slots for receiving the conductors therein (see particularly Figs. 2 and 3). Thus, as shown in Fig. 3, the conductor 14, with a narrow flat edge directed towards the slot bottom, is inserted into each of the slots in the ribs 36 and 30 and in the projections 35 and 33. In this way, the conductor 14 is retained in the housing part 1 in accordance with its shape, and its ends are located in a supported position.The conductor 15 is located correspondingly in slots in the ribs 36 and 30 and in the projections 31 and 37, and the portion of the conductor 15 extending between the projections 31, 37 abuts support surfaces on these projections. The inner end 21 of the conductor is thus supported, and the male plug connector 29 is secured against displacement in the direction of its longitudinal extension because of the engagement of the conductor 15 with the slot in the projection 37 and because it rests up against the projection wall. The conductor 16 is inserted into slots in the projection 32, and a portion of it likewise rests against a projection wall, so that appropriate positioning of its ends is guaranteed. Some of the partitions and slots for supporting and holding the conductor strips can be seen near the rear of the half-shell 1 in Fig. 1.

As shown in Figs. 4,5 and 6 the conductor 15 has at one end a male plug connector 29 which is produced when one leg 29' is bent back on itself so that the free end of the leg 29' is art a small distance from the adjacent portion of the conductor 15. The bent back leg 29' deforms elastically when inserted in a receiving orifice in the plug 10.

Afemale plug connector 25 is formed at the opposite end of the conductor 15. This female connector has two legs 25' and 25" which are connected to one another via a curved, essentially circular loop region, so that they rest against one another in the entrance mouth region, but are at a greater distance from one another in the circular region loop. From the region of contact of the legs 25' and 25" in the entrance mouth region, the two legs diverge outwards to form a guide for the introduction of a male plug part. The leg 25' is bent back towards the conductor 15, so that the legs 25' and 25" alone form a plug receptacle, the remaining part of the conductor 15 merely serving as a mounting for this plug receptacle.It has been shown that a female plug receptacle designed in this way exhibit a high clamping force and permanent elasticity, thus resuiting in a long service life.

The part of the conductor 15 located between the male plug connector 29 and the female plug connector 25 is sharply bent at several locations.

This serves two functions, on the one hand, to comply with the internal configuration of the housing part 1 receiving it and, on the other hand, to form supporting surfaces for positioning and support in the housing part 1.

The male and female connectors of the conductors 14 and 16 are similarly formed to those of conductor 15. All three conductors can be produced as a result of simply bending metallic strip material, and this can be achieved with low production cost.

To assemble the small drilling machine illustrated, the conductors 14, 15, 16 are first inserted into the above mentioned slots provided in the housing part 1. The motor 3, including the armature shaft 4 with bearings, is then inserted into the housing part 1, but without the drill chuck 5. The motor's plug pins 20, 21 automatically and simultaneously engage with the female plug connectors 24,25 of the conductors 14, 15 previously positioned in the housing part 1. The housing part 2 is now attached to the housing part 1, and the two housing parts are screwed to one another via the mating studs 40,41 (see particularly Fig. 2) and the spaced apart studs 42,43 (see Fig. 1), the cap 7 being pushed over the armature shaft 4 and engaging with the front ends of the housing parts 1 and 2. The drill chuck 5 can then be mounted on the armature shaft 4.The switch 12 is next pressed into the opening 13, so that its spring clips 39 engage with corresponding engagement recesses in the housing part 2, and the flat connecting pins 22,23 extending from the switch engage in the female plug connectors 26 and 27 of the conductors 14 and 16, respectively. When pressed in, the switch 12 is guided into the correct position by guide ribs 34 formed on the housing part 2. The receptacle 8 is lastly inserted into the orifice at the rear end of the housing until the locking studs 8' have been pressed through appropriate holes in the rear end wall of the housing, the male plug connectors 28, 29 being caused to protrude into the receptacle 8 ready for connection to the supply cable 9.

The above described embodiments, of course, are not to be construed as limiting the breadth of the present invention. Modifications, and other alternative constructions, will be apparent which are within the spirit and scope of the invention as defined in the appended claims.

Claims (17)

1.A A method of wiring an electric device comprising selecting preformed, dimensionally stable conductors formed from strip-like electrically conductive material and having bent ends for forming plug connections, inserting the conductors into one part of a housing of the electric device and engaging the conductors with positioning means in the housing part to positively position the conductors therein, and then inserting an electric component into the housing part and substantially simultaneously effecting plug connections between the electric component and ends of two of said conductors.

2. The method of Claim 1,wherein said positioning means comprises slots into which the conductors are inserted.

3. The method of Claim 2, wherein said positioning means further comprises support surfaces with which said conductors are engaged.

4. The method of Claim 1,2 or 3, wherein said electric component is an electric motor.

5. The method of any preceding claim, further comprising subsequently securing another housing part to said one housing part to enclose said electric component and said conductors in the housing.

6. The method of Claim 5, further comprising inserting a second electric component into an opening in said housing and simultaneously effecting plug connections between the second elastic component and ends of two of said conductors.

7. The method of Claim 6, wherein said second electric component is a switch having two male terminals which are plugged into two female plug connectors formed at ends of two conductors.

8. The method of any preceding claim, comprising inserting a receptacle into an orifice in the housing and causing two plug connectors formed at ends of two conductors to protrude into said receptacle.

9. The method of any preceding claim, wherein all electric components to be connected with said conductors are inserted into said one housing part or into said housing after insertion of said conductors into said one housing part to effect electrical connection of said electric components with the ends of said conductors.

10. An electric device, comprising: a wiring arrangement of preformed, self-supporting conductors of strip-like conductor material; the ends of said conductors being folded over to form male and female plug connectors; electric components connected by plugging to ends of said connectors; and positioning means in a housing part of the electric device for positively supporting and locating said conductors.

11. The electric device of Claim 10, wherein said positioning means comprises slots formed in said housing part, said conductors being inserted in said slots.

12. The electric device of Claim 11, wherein said support means further comprises support surfaces in said housing part, said slots and said support surfaces holding said conductors and positioning the ends thereof.

13. The electric device of Claim 10, 11 or 12, wherein each female plug connector comprises a portion of a strip folded over back on itself with the formation of a fold, a free end portion of the strip extending back from the folded over portion to the vicinity of the fold, the free end portion connecting to the folded over portion in a loop, and the extreme end of the free end and the fold being bent away from each other to form a flared entrance opening into the female plug connector.

14. The electric device of any one of Claims 10 to 13, wherein an electric component comprising a switch is inserted through an opening in a wall of the housing of the electric device, the switch having two male terminals engaged in female plug connectors of two said conductors.

15. The electric device of any one of Claims 10 to 14, wherein two of said conductors are provided with male plug connectors at one end for connection with a power supply cable, and female plug connectors at their other ends, and a third conductor is provided with female plug connectors at both ends.

16. A method of wiring an electric mini tool substantially as hereinbefore described.

17. An electric mini tool substantially as hereinbefore described with reference to the accompanying drawings.