Rectifier assembly for a lawn mower

An electric lawn mower having a permanent magnet motor and a dynamic braking feature includes a rectifier which is assembled in a switch-box. The novel arrangement of the rectifier in the switch-box assembly is attached to an upper portion of the handle of the mower to permit use of standard three wire cord for connection between the switch-box and the motor.

This invention relates to a switch-box assembly for use with a lawn mower 
having a permanent magnet motor and a dynamic braking feature. 
In the construction of a lawn mower it is common practice to provide a 
switch to control the operation of the electric motor of the mower. The 
switch is usually enclosed within a switch-box assembly located on a 
handle portion of the mower having easy access thereto by a human 
operator. A permanent magnet motor is one type of motor presently being 
used in a lawn mower. When a permanent magnet motor is employed it 
requires a rectifier to convert electrical energy from alternating current 
to direct current. The rectifier is usually located on the motor casing or 
in the motor itself resulting in rather complex wiring between the switch 
and motor to provide a dynamic braking function. To date, the manner in 
which to accomplish the complex switching function is to use a 
non-standard heavy duty six wire electrical cord between the switch-box 
and rectifier of the motor. The six wire electrical cord is relatively 
less available and more expensive than the standard three wire electrical 
cord. The extra expense and poor availability of six wire cord can be 
better appreciated when one considers that each lawn mower requires three 
to four feet of six wire cord and that tens of thousands of mowers are 
manufactured annually. Also, the six wire cord results in an increased 
number of electrical connections on the deck of the mower which 
connections may become dangerous. 
It is therefore an object of the present invention to provide a novel 
switch-box assembly that eliminates the need to employ a six wire 
electrical cord to accomplish the dynamic braking function. 
The present invention relates to a switch-box assembly for a lawn mower 
where the rectifier of the mower is located in the housing of the 
switch-box assembly. 
By locating the rectifier in the housing of the switch-box assembly, 
electrical energy may be supplied to and carried from the assembly by 
three wire electrical cord. The present invention, by permitting the use 
of standard three wire electrical cord, takes advantage of the relatively 
lower cost of the three wire cord. 
In accordance with a broad aspect of the present invention there is 
provided a switch-box assembly operable for use with a lawn mower having a 
permanent magnet motor, comprising a housing operably to be mounted to the 
mower remote from the motor, a switch supported in the housing for 
controlling the operation of the motor, and a rectifier supported in the 
housing for converting electrical energy passing through the switch to the 
motor from an alternating current to a direct current.

Referring to the figure the preferred embodiment of the switch-box assembly 
10 is now described. 
Switch-box assembly 10 comprises a housing 12 shown split into two 
identical sub-sections. Housing 12 is provided with insulating bushings 14 
which insulate screws 16 passing therethrough from electrical components 
located within housing 12. Screws 16 are secured in place by nuts 18 which 
mount housing 12 about tubular handle 20. Handle 20 consists of a handle 
portion of the lawn mower (not shown) which is remote from the permanent 
magnet motor of the mower. Housing 12 is provided with a first pair of 
aligned cut-outs 22 through which handle 20 passes. 
A support means comprising a U-shaped metal bracket 24 is mounted to handle 
20 by means of one or more spot welds in the area of its base portion 26 
such that base portion 26 lies flush against handle 20. Bracket 24 has two 
arms 28 extending outwardly from the base portion 26. Arms 28 locate and 
carry ribs 30 which extend into the interior of the housing 12 from walls 
32 of the housing 12. Rectifier 34 is secured to bracket 24 by screw 61, 
as shown, and is in heat transfer relation with handle 20. In other words, 
handle 20 acts as a heat sink for rectifier 34. Switch 36 is shown 
supported to upper arm 28 of bracket 24. Upper arm 28 is provided with an 
aperture through which threaded hollow stud 38 passes. Nut 40 shown 
tightened about stud 38 secures switch 36 in position as shown. Switch 36 
is provided with a movable lever 42 which passes through upper cut-out 44 
of the housing 12 so as to be accessible to a human operator. Wires 
generally designated 46 are connected as shown to carry electrical energy 
from three wire power supply cord 48 through rectifier 34 and switch 36 
and out through three wire motor cord 52, which is connected to the motor 
of the lawn mower. Screw 54 fastened to base portion 26 of bracket 24 
grounds wires 46A to handle 20. 
The lower arm 28 of bracket 24 is provided with an aperture through which 
motor cord 52 passes. A strain relief member 55 counters any forces acting 
against cord 52. Cord 52 passes through lower cut-outs 53 of housing 12. 
Supply cord 48 passing through cut-out 49 of housing 12 is also provided 
with a strain relief member 56 which is housed in sub-housing 58 of 
housing 12. Sub-housing 58 has clamping arms 60 which surround handle 20 
to help mount housing 12 to handle 20. 
In operation, switch-box assembly 10 controls electrical energy passing 
therethrough to the motor of the mower. Electrical energy is supplied by 
power cord 48 when plug 50 is inserted into an electrical supply. Energy 
from cord 48 is carried first by wires 46B to rectifier 34 where the 
energy is converted from alternating current to direct current. The energy 
is then carried from rectifier 34 to switch 36 by wires 46C shown 
interconnected therebetween. Assuming switch 36 to be in its closed 
position, energy passes through switch 36 along wires 46D and out 
switch-box assembly 10 to the motor by motor cord 52. By manually moving 
lever 42, switch 36 is movable from its closed position into its open 
position, precluding passage of electrical energy therethrough to the 
motor. 
It will be appreciated that alternate embodiments for the present invention 
will be readily apparent to a man skilled in the art in light of this 
disclosure. For example, should the motor be grounded to the deck of the 
lawn mower, then a two wire electrical cord from the switch-box to the 
motor will suffice. Accordingly the present invention should be limited 
only to that which is claimed in the accompanying claims.