Abstract:
There is disclosed a hand-held portable tool which is driven by an electric motor from a source of electricity. The tool has a housing for the motor which has a commutator which extends into a hollow handle. The hollow handle has mounted therein a printed-circuit board having electrically conductive pathways. An electric switch is mounted on the board and incorporates a bridging element which engages contact terminals on the printed-circuit board when the switch is manually actuated thereby closing the electric circuit of the tool motor. In this way, separate electrical connections to the switch assembly per se are avoided and substantial time in assembly of the tool is saved.

Description:
BACKGROUND OF THE INVENTION 
     The principles embodied in hand-held portable electric tools are well known. Essentially they include a housing for the electric motor and the appurtenant elements for supplying and controlling the electrical energy needed to supply the electric motor. Usually such control means are located in the hollow handle which is usually of the pistol grip type, the main body being occupied by the electric motor. Such electric control means usually encompasses a separate switch with which there is operatively associated an actuating trigger and frequently a lateral locking pushbutton to retain the tool in its energized state when desirable. Suitable and necessary linkages are supplied to make it possible to operate the tool. 
     The trigger switch arrangement just mentioned is usually a separate component of the tool which is usually mounted on means located internally of the handle. Likewise electric terminal blocks as receivers of electricity from an outside source of electricity are necessary. But these too must also be suitably mounted internally of the hollow handle. Additionally, the assemblies for supplying electricity to the commutator of the electric motor must also be suitably mounted. Any additional speed control electronics such as a thyristor must be accounted for within internal mounting means of the hollow handle. Finally, all of these stated electrical components require suitable wiring one from the other. In the conventional arrangement, the trigger switch too must be wired into the tool and somehow mounted into the tool body often with screws or other fastening means. The assembly of the switch into the tool body requires additional assembly time and effort. 
     BRIEF SUMMARY OF THE INVENTION 
     In order to reduce assembly time in the manufacture of the tool, the present invention contemplates the utilization of suitably printed circuit boards. The printed-circuit boards are designed to not only provide the electrical pathways for distribution of the energy to components requiring electrical energy but also to provide support to the various components. 
     More specifically, the invention contemplates an arrangement for a portable tool including a trigger switch which is conveniently mounted proximate the printed-circuit board and to which no electrical wires have to be connected. 
     Therefore, and according to a preferred embodiment of the invention, the switch assembly is inserted into a slot provided in the board. The switch assembly includes a leaf-spring bridging element which can be actuated upon pressing the trigger of the switch. The switch assembly is mounted in such a way that the movable leaf-spring bridging element contacts a set of contact buttons provided as terminals on the printed-circuit board. To this end, the body of the switch assembly disclosed and utilized is provided with a crosswise slot for insertion into the slot of the board. 
     In this way, the switch assembly is conveniently mounted in the tool and separate electrical connections to the switch assembly per se are avoided and substantial time in assembly of the unit is saved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described with reference to the drawing wherein: 
     FIG. 1 is a side elevation of a portable electric drill with a portion of the housing broken away to show the trigger switch and printed-circuit board arrangement for a portable tool; 
     FIG. 2 is an end view of the mounting printed-circuit board showing the slot for receiving the trigger switch; 
     FIG. 3 is a side elevation of the mounting printed-circuit board; 
     FIG. 4 is a side elevation of the trigger switch assembly of one embodiment wherein the switch assembly has one leaf-spring electrical bridging element; 
     FIG. 5 is an exploded view showing the structure and inter-relationship of the components; 
     FIG. 6 is a similar view as in FIG. 1 to illustrate another embodiment wherein the trigger switch assembly is provided with two leaf-spring electrical bridging elements; and 
     FIG. 7 is a schematic wiring diagram employed in carrying out the principles of the second embodiment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Now, turning to FIG. 1, it will be noted that the inventive principles hereinafter to be discussed are applicable to a conventional drill 10 shown in a general manner. The drill 10 has a conventional chuck 11 at the left side of the drawing. A pistol type handle 12 is located at the right side. Intermediate therebetween is an electric motor 13. The electric motor 13 and the parts in the handle are mounted in a housing 14, usually constructed of clam shell molded parts of approximately equal volume. An electric cord 15 depends from the handle which goes to a suitable source of electricity. 
     From FIG. 1, it will be seen that all of the electrical components including the wiring, the trigger switch assembly 18 and the commutator contact assemblies 16 for the commutator 17 are mounted on a printed-circuit board 20. 
     In FIG. 1 an elongated printed circuit board 20 is positioned axially with respect to the pistol grip handle 12. The board 20 can be constructed of conventional materials such as fiberglass polyester laminate. The board 20 has been printed on one or both surfaces with a metal, or other conductive material, a series of electrical pathways which supply electric current from a point of ingress to points of use. 
     For instance, at the bottom portion of the board 20 is a conventional two terminal block 21 to which two electric wires 22 are connected. The conductive pathways on the board 20 (not shown) interconnect the terminals with the motor 13 and the contact buttons 24 and 25. It will be noted that the respective contact buttons are positioned on the other side of the board to that of the terminal block 21. The contact buttons 24, 25 can be viewed as constituting terminal means. 
     The board 20 in the vicinity of the contact buttons 24, 25 is supplied with the trigger switch assembly 18 which fits into a horizontal slot 27 in the board 20 which slot is located inbetween the aforementioned contact buttons. 
     The switch assembly 18 incorporates manually actuable means including a trigger 28 connected to a plunger 26. The plunger 26 is slideably mounted in a housing 31 of the assembly and is spring-loaded by spring (not shown) so that it is urged to left in the normally open position of the trigger switch. 
     The plunger 26 moves perpendicularly with respect to the board 20 when manually actuated by the operator. The plunger 26 terminates in the outwardly facing trigger 28 that extends through a forwardly facing opening 29 in the handle 12 and essentially fits sufficiently tightly to inhibit the entrance of dirt and grime into the housing 14. The plunger 26 is adapted to carry contact means in the form of an arcuate leaf-spring bridging element 30 that completes the electric pathway when the trigger 28 is depressed against the pressure of the spring. The electric pathway is completed between buttons 24 and 25 when the leaf-spring bridging element 30 contacts said contact buttons. When the trigger 28 is released, the spring in the housing returns the plunger 26 to the position shown in FIG. 1 whereby the circuit between contacts 24 and 25 is once again open. 
     The aforementioned housing 31 has a forwardly extending portion 42 (seen in FIG. 5) that is dimensioned to fit into the slot 27. The forwardly extending portion has perpendicular thereto a small housing 32 having a spring-loaded button 33 with a short secondary plunger 34 that may be depressed when the plunger 26 has been moved so that to make electric contact whereby the main plunger 26 can be retained in that position without further need to hold the trigger 28. The plunger 26 has a recess 19 into which the secondary plunger 34 moves when the button 33 is depressed, which secondary plunger 34 is suitably held in position by a detent arrangement not shown) thereby acting as a stop for the main plunger 26. The secondary plunger 34 as a stop is defeated by depressing the trigger 28 slightly more to thereby release the secondary plunger 34 from its position as a stop. The trigger 28 may then be released and, as the way is now clear, the plunger, trigger and the electric contacts will move to its normal open, i.e., off position. 
     It will be seen that there are additional components located on the board 20 above the electric switching elements. It is necessary to view these additional components in the light of other figures as well, especially, for instance, FIGS. 2, 3, 4 and 5. The view of the rear of the board as shown in FIG. 2 depicts the board having a relatively large circular opening 35 through which the commutator 17 of the electric motor projects. 
     At points 180° apart are two carbon brush holders 36 in which carbon brushes 39 are held in position against the commutator 17. The holders are constructed of conducting metal and have metal projections 37 to which spiral clock springs 38 are attached having an active end which impinge resiliently on the surface of the carbon brushes 38 opposite to the surfaces presented to the commutator 17. The manner in which this set up finds utilization can be seen from FIG. 1. The carbon brushes 39 are thereby retained in the carbon brush holders 36. Suitable electric conductive pathways are provided on the printed-circuit board to supply electricity to the carbon brush holders when the aforementioned switch 18 is in a closed circuit position. 
     Opposite to the side of the board 20 are a plurality of perpendicularly extending electric connector members 40 designed to supply electricity to the stator (not shown) of the electric motor 13. Suitable electrically conducting pathways are provided on the board to supply electricity to the connector members when the switch 18 is in a closed or on position. 
     Turning to FIG. 5, it will be noted that the aforementioned forwardly extending portion 42 of the housing 31 has an upper and lower horizontal slots 43 which mate with the downwardly facing edge portion 44 and the upwardly facing edge portion 45 of the slot 27. 
     Thus, in this way, a most simple and convenient arrangement of mounting the switch assembly 18 on the printed-circuit board 20 is achieved which requires no separate wiring of leads to the switch assembly. 
     The trigger 28 is affixed to the plunger 26 by means of a forwardly extending knob 49 which fits into a rearwardly facing recess (not shown) rearward of the trigger 28. 
     It has been discovered to the efficacious to also provide a variable speed control for the drill. To accomplish this, a two button contact arrangement is provided as in the embodiment disclosed in FIGS. 1 to 5; however, a second set of two button contacts is provided for a second leaf-spring electrical bridging element. Accordingly, attention is now directed to FIGS. 6 and 7 wherein the additional embodiment is illustrated. 
     In regard thereto, the switch is essentially as hereinbefore depicted. However, it will be noted that the spring-loaded plunger operable by depressing the trigger moves a first leaf-spring bridging element 47 into contact with a first set of contact buttons 48. The contact buttons 48 are in an electric pathway to supply electricity to the electric motor 13 of the drill through a conventional thyristor speed controller 50. The board 20 is also supplied with a second set of contact buttons 52 and the switch assembly 18 with a second leaf-spring bridging element 51 as shown in FIG. 6. The two leaf-spring bridging elements are connected together centrally at 56 as shown in FIG. 7. Suitable electrically conductive pathways are provided on the board. 
     Attention is directed to the circuit diagram shown in FIG. 7. Note that when the first leaf-spring bridging element 47 completes its contact with contact buttons 48 electricity flows through a thyristor speed controller 50 which controls the speed of the motor 13. Further, when the trigger 28 is depressed further, the second leaf-spring bridging element 51 completes contact with the second set of contact buttons thereby shorting out the thyristor so that full live voltage is supplied to the motor. It will be seen that when the trigger-plunger moves distance D 1  the thyristor speed controller 50 is in circuit and that when the trigger-plunger moves a total of D 2  the thyristor speed controller 50 is shorted out of circuit. 
     It will be appreciated that numerous means may be employed to suitably mount the printed-circuit board 20 in the housing. A suitable construction is to provide ridge portions (not shown) with appropriate longitudinal grooves internally each of the clam shell moldings so that when the moldings are secured together, the board is transversely located between the clam shell moldings. Additionally, these ridges 53 may be constructed to have portions perpendicular to the internal walls of the housing wherein a groove 54 may be located to accept and retain the bottom portion of the board 20. A similar construction may be accomplished in association with the top of the board.