Lawn-Edge Trimmer With Detachable Handle

My present invention relates to a lawn-edge trimmer of the type described in my prior U.S. Pat. No. 3,693,255 dated Sept. 26, 1972.

The lawn trimmer described in my prior patent comprises a motor housing which is rigid at the top with a laterally extending grip and at the bottom with a generally horizontal shield plate overlying a rotary cutter driven by a motor in the housing. The user may hold the apparatus by the grip, bending close to the ground in that instance, but may also employ a long-stemmed handle allowing the operation of the trimmer in an erect position. The handle is received in a socket forming part of a mounting member which is detachably secured to the housing between the grip and the shield plate. The patent, in fact, shows two such sockets with different angles of inclination, the handle being insertable into either socket for the convenience of persons of different height.

In order to start and stop the motor, the grip of the trimmer disclosed in my prior patent is provided on its underside with a manually operable switch which opens and closes upon alternate depressions of its trigger. This indexing of the switch in either an open or a closed position is necessary since the user, when employing the long handle, cannot keep the trigger continually depressed in order to maintain the motor in operation. It could, however, lead to an accident if the user, holding the apparatus by its grip, happens to drop it with the switch closed. It is, of course, possible to provide both the handle and the grip with individual spring-biased switches connected in parallel so that depression of either trigger closes the motor circuit; in that case, however, special connectors must be provided for completing the circuit to the second switch when the handle is being emplaced.

The object of my present invention, therefore, is to provide means in such a lawn trimmer for automatically coupling an actuator on the handle with the existing switch on the grip when the handle and its mounting member are secured to the motor housing.

In accordance with my present invention, the handle has a tubular stem accommodating a movable force-transmitting element which forms part of a linkage between the switch trigger on the grip and an ancillary actuator therefor on the handle.

More particularly, the linkage may comprise a cam on the mounting member positively connected with the force-transmitting element -- which is preferably a thrust rod -- and a cam follower on the mounting member displaceable by the cam to depress the trigger.

The above and other features of my invention will now be described in detail with reference to the accompanying drawing in which:

FIG. 1 is a side view, partly broken away, of a trimmer embodying my present invention; and

FIGS. 2, 3, 4 and 5 are cross-sectional views respectively taken on the lines II--II, III--III, IV--IV and V--V of FIG. 1.

In the drawing, as far as practical, I have employed the same references as in my prior U.S. Pat. No. 3,693,255 to designate corresponding parts. Thus, the trimmer shown in FIGS. 1-5 comprises a housing 1 for a motor M with a vertical axis having a shaft 4 which carries a hub 3 supporting a cutting element 2 in the form of a wire of synthetic resin. The cutter assembly 2-4 is overlain by a shield plate 6 rigid with the lower end of motor housing 1, the plate 6 being tray-shaped and provided with an upstanding rim 6a. The housing 1 can be supported above the ground by skids 6b secured to plate 6.

A mounting member 7 for a handle 9a, attached to the top of a tubular stem 9, is detachably secured to a lateral grip 5, rigid with the top of housing 1, and to the shield plate 6. Member 7, which is a vertical web in an axial plane of stem 9, is reinforced by a peripheral flange 7a carrying an upper lug 10' and a lower lug 10" snap-fitted into respective holes 11 and 12 of grip 5 and plate 6. Web 7 has a cutout 19 accommodating a trigger 18 for a switch, not further illustrated, lying in the energizing circuit of motor M to which power is supplied via a cable C. Trigger 18, unlike its counterpart in my prior patent, is biased by a spring 34 so as to close the motor circuit only when being pressed upwardly against the spring force. Stem 9 is received in an inclined socket 8 integral with member 7. Two bifurcate claws 13 and 14 on that member embrace respective fins 15 and 16 rigid with housing 1, fin 15 being located in an air-intake slot 17 for the motor M.

In accordance with my present invention, a thrust rod 20 extends axially within stem 9 where it is guided by a bearing 35 and from which it projects downwardly through the lower end of socket 8, terminating in a cross-bar 20a. The bar 20a bears down upon a cam 23 slidably received in an aperture 30 of web 7, the cam 23 having a pair of wings 31 bracketing a sloping upper edge of aperture 30. An inclined lower edge 32 of this aperture forms a guide path for the cam 23 which can thus shift, against the force of a compression spring 32 also lodged in aperture 30, in the axial direction of stem 9 when the rod 20 is displaced downwardly by means of an actuating knob 21 located just below handle 9a; knob 21 has an extension passing through a longitudinal slot 22 of stem 9 and embracing the rod 20. Upon such downward sliding of cam 23, as indicated by an arrow 26 in FIG. 1, a ramp 24 thereof acts upon a lower extremity of a thrust member 25 designed as a lever which is fulcrumed on web 7 by a pivot pin 29 passing through a bifurcate extension 33 of that lever and straddling an edge of cutout 19. An upper extremity of lever 25 contacts the trigger 18 so as to press it upwardly against the force of its restoring spring 34, as indicated by an arrow 27, when the lever is displaced by the cam 23 upon a downward shifting of knob 21; cross-bar 20a slides in an extension 30a of aperture 30 parallel to edge 32 and aligned with a pair of side slots 8a of socket 8. Fulcrum 29 is laterally offset from the two extremities of lever 25 coacting with cam 23 and with trigger 18.

It will thus be seen that the emplacement of supporting web 7 with socket 8 properly positions the cam follower 25 in engagement with trigger 18 so that the switch controlled by the trigger can be closed with the aid of knob 21 as soon as the stem 9 with its handle 9a and thrust rod 20 is inserted into the socket 8. The two springs 28 and 34 prevent any accidental closure of the switch during that insertion.