Industrial reversing speed control trigger switch with snap-in modules

An industrial grade trigger switch having an on-off switch and a resistor controlled speed control circuit both controlled by trigger depression and a reversing switch provided with an operating lever overlying the trigger, and characterized by a large heat sink for the solid state current control elements for continuous service, a large substrate area for the speed control circuit, higher current rating double-pole wiping contacts, relatively simple metal parts, and the capability of being mounted also in consumer grade tools. The switch has modular construction with snap-in coupling of reversing switch and base to the frame.

BACKGROUND OF THE INVENTION 
Speed control trigger switches with an attached reversing switch have been 
known heretofore. For example, C. J. Frenzel Pat. No. 3,260,827, dated 
July 12, 1966, shows such switch including a reversing operating lever 
overlying the trigger. While these prior switches have been useful for 
their intended purpose, this invention relates to improvements thereover. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide an improved speed control trigger 
switch especially adapted for industrial applications. 
Another object of the invention is to provide a speed control trigger 
switch with an improved snap-in reversing switch. 
A more specific object of the invention is to provide a trigger switch with 
improved snap-together modular construction. 
Another specific object of the invention is to provide a trigger switch 
with improved double-pole wiping contacts. 
Another specific object of the invention is to provide an improved speed 
control trigger switch having relatively simple metal parts. 
Another object of the invention is to provide an improved speed control 
trigger switch having a relatively large substrate area for its speed 
control circuit. 
Another specific object of the invention is to provide an improved speed 
control trigger switch having a relatively large heat sink for the solid 
state power element. 
Another specific object of the invention is to provide an improved speed 
control trigger switch for industrial applications but affording use also 
in consumer tools. 
Other objects and advantages of the invention will hereinafter appear.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1 and 2, there is shown an industrial speed control 
trigger switch with snap-in reversing switch according to the invention. 
This switch comprises an insulating housing including a frame 2 and a 
snap-in base 4, a trigger 6 slidably mounted in the frame above the base, 
and a snap-in reversing switch including an insulating switch enclosure 8, 
a reverse lever 10 and a pivotal link 12 coupling and translating the 
angular motion of the reverse lever to linear motion for reversing switch 
actuation. 
Snap-in means are provided for attaching the lower part of the housing or 
base 4 to the upper part of the housing or frame 2. This snap-in means 
comprises lateral flanges 2a and 2b at the lower left and right sides, 
respectively, of frame 2 as shown in FIGS. 2 and 11. These flanges are 
provided at their center with elongated narrow slots 2c and 2d, 
respectively, extending up through these flanges, there being a shoulder 
inwardly of each such slot as shown in FIG. 11. The base is provided with 
corresponding flat hooks 4a and 4b that are pushed up through these slots 
and snap over such shoulders to lock the base to the frame as shown in 
FIG. 11. 
Snap-in means are also provided for attaching the reversing switch to the 
top of frame 2. This snap-in means comprises three wide hooks 8a-c at the 
lower edges of the reversing switch enclosure that snap into respective 
undercut slots 2e-g in the upper edges of the frame. As shown in FIGS. 1 
and 2, two of these hooks 8a and 8b are on opposite sides near the forward 
part of the reversing switch enclosure and the third such hook 8c is 
centrally at the rear end of this enclosure. Also, two of these slots 2e 
and 2f are on opposite sides near the forward part of the frame and the 
third such slot 2g is centrally at the rear end of this frame for matching 
locations with the three hooks. 
The reversing switch is provided with operating means comprising the 
aforementioned reverse lever 10 and pivotal link 12 shown in FIG. 2. A 
snap-in, integral stud 8d extends up from the forward part of reversing 
switch enclosure 8 and is provided with a pair of tapered, arcuate teeth 
that snap through a stepped hole 10a in the reverse lever and spread out 
above the shoulder in this hole to journal the lever on top of the 
enclosure for limited rotary movement. A pair of integral, spaced apart 
stops 8e and 8f in the form of ridges rearwardly of stud 8d limit the 
pivotal movement of the reverse lever therebetween. Another snap-in, 
integral, upstanding stud 8g at the rear portion of the enclosure is 
provided with a pair of tapered, arcuate teeth that snap through a stepped 
hole 12a in link 12 and spread out above the shoulder in this hole to 
journal the link on top of the enclosure. This link is provided with an 
overcut portion having an integrally molded upstanding cylindrical stud 
12b that extends into an oblong hole 10b in the undercut rear end portion 
of the reverse lever to allow mounting of the reverse lever and link 
substantially in the same plane as shown in FIG. 1. Thus, as the forward 
end 10c of the reverse lever is swung to the left or right, link 12 is 
rotated in opposite directions on its pivot stud and a lateral slot 12c 
therein engages a projection 14a of a printed circuit (PC) board 14 and 
slides it forward or back to the rear to actuate the reversing switch as 
hereinafter described in connection with FIG. 9. 
Frame 2 is provided with a spring-biased lock button 16 as shown in FIGS. 1 
and 2. This button is retained in a sleeve 2h integrally molded on the 
frame so as to extend left from the forward part thereof. A spring (not 
shown) biases this lock button outwardly and the inner end of a shaft 
attached to the lock button engages in a slot 18a of an adjustable stop 
block 18 mounted in the trigger. An adjusting screw 20 extends from the 
forward end through the trigger for setting this stop block in a desired 
forward-rearward position to set the desired speed as hereinafter 
described. The trigger is provided with a pair of forwardly-extending 
slots 6a and 6b shown in FIG. 2, one of which embraces a downward 
projection 10d on the reverse lever shown in FIG. 3 in each position of 
the reverse lever when the trigger is depressed. This constitutes an 
interlock to prevent actuation of the reversing switch when the trigger is 
depressed. 
Insulating, molded frame 2 is provided with a longitudinal rib 2j extending 
throughout the length of its internal upper surface as shown in FIGS. 3 
and 6 that fits into a groove 6j (FIG. 2) on the trigger and into groove 
18c (FIGS. 2, 4, and 6) of the stop block to guide both the trigger and 
the stop block in forward-rearward movement. This trigger is also confined 
for guidance in the frame by its lateral flanges 6k and 6m that slide in 
the complementary spaces under flanges 2a and 2b of the frame as shown in 
FIG. 6, forward movement of the trigger being limited by flanges 6k and 6m 
thereof abutting the forward inner wall of the base as shown in FIG. 4. 
Base 4 houses a double-pole on-off switch. As shown in FIGS. 3-6, the 
interior of the base is divided left and right by a subassembly including 
a PC substrate 22 and a heat sink 24, and is divided forward-rearward by 
integrally-molded dividing walls 4c and 4d within the base, as shown most 
clearly in FIGS. 4 and 5, to provide four compartments. 
The left pole of this on-off switch is shown in FIG. 4 and the right pole 
thereof is shown in dotted lines in FIG. 3. As shown in FIG. 3, the right 
pole includes a stationary contact 26 in the forward right compartment, 
stationary contacts 28 and 30 spaced apart in the rear right compartment, 
and a slidable bridging contactor 32 arranged for bridging these 
stationary contacts when the trigger is depressed. The bottom of the 
trigger is provided with a pair of recesses 6c and 6d for retaining the 
upturned ends of contactor 32 and a center recess 6e therebetween for 
retaining a helical compression spring 34 that biases the contactor down 
onto the stationary contacts as shown in FIGS. 3, 7 and 11. The left pole 
includes a stationary contact 36 in the forward left compartment, a 
stationary contact 38 in the rear left compartment, and a slidable 
contactor 40 for bridging these stationary contacts when the trigger is 
depressed as shown in FIG. 4. The bottom of the trigger, shown in FIG. 7, 
is provided with a pair of recesses 6f and 6g for retaining the upturned 
ends of contactor 40 and a center recess 6h therebetween for retaining a 
helical compression spring 42 that biases the contactor down onto the 
stationary contacts as shown in FIGS. 4 and 11. These two poles of the 
on-off switch are also shown diagrammatically in the circuit diagram in 
FIG. 10. 
These two poles of the on-off switch are also provided with suitable 
press-in lead connectors for making the connections, shown in FIG. 10. For 
this purpose, stationary contact 26 is provided with a spring clip 44 held 
in a slot in the forward right compartment of the base and having a 
deflectible end pressing against the shank of stationary contact 26 so 
that the bare, soldered end of a stranded wire can be inserted through a 
hole in the bottom of the base and pressed-in and gripped therebetween for 
electrical connection and retention therein thereby to connect power line 
L1 to the right pole of the on-off switch as shown in FIG. 10. In a 
similar manner, stationary contact 36 is provided with a similar spring 
clip 46 shown in FIG. 4 for connecting power line L2 to the left pole of 
the on-off switch. And likewise, stationary contact 38 is provided with a 
spring clip 48 as shown in FIG. 4 for connecting a wire from side F2 of 
the motor field winding thereto as shown in FIG. 10. 
As shown in FIGS. 3 and 4, stationary contacts 26 and 36 are mounted in 
suitable recesses in the base. 
Means are provided on substrate 22 for mounting and electrically connecting 
stationary contacts 28, 30 and 38 in the circuit. For this purpose, 
tubular terminal-supports 28a, 30a and 38a, FIG. 8, are rigidly secured to 
the substrate as by slightly reduced sections frictionally fitting into 
holes therein. Lateral projections extend from stationary contacts 28 and 
30 into terminals 28a and 30a to frictionally and rigidly support the 
same, respectively, therein. The heat sink is provided with a suitable 
slot 24a adjacent terminals 28a, 30a and 38a to avoid short circuit 
thereby as shown in FIG. 6. A lateral projection also extends from 
stationary contact 38 into terminal 38a as shown in FIG. 6 to support the 
same therein. Heat sink 24 is provided with a suitable insulating film 24b 
on its right surface to prevent shorting the stationary contacts thereto 
as shown in FIG. 6 and 8. 
The speed control circuit is formed as a printed circuit on substrate 22 as 
shown in FIG. 8. This substrate is made of a good heat conducting and 
electrically insulating material such as alumina so to conduct heat from 
Triac T to copper heat sink 24. This printed circuit strip connects one 
side of capacitors C1 and C2 to terminal 28a and thus to contact 28 as 
shown in FIG. 8 and 10. A wire connects this printed circuit strip to 
terminal T1 of the Triac. The other side of capacitor C1 is connected by a 
PC strip to one side of resistor R1 and to wiper 50 of variable resistor 
R2, this wiper being shown in FIG. 7. As shown therein, this wiper is 
provided with a pair of spaced lateral projections 50a that extend into a 
slot in the trigger to mount the wiper in the trigger so that its other 
wiping end portion is biased to the right against the substrate to bridge 
PC conductor strip 52 and resistor R2. This wiping end portion is 
preferably bifurcated to provide a pair of fingers for good electrical 
contact with PC conductor strip 50 and resistor R2. 
On the aforesaid PC substrate, the other side of capacitor C2 is connected 
to the other side of resistor R1 and also to bidirectional thyristor diode 
D. A wire connects diode D to the gate terminal of the Triac. Terminal T2 
of the Triac is connected by a PC strip to shunting contact 30 through 
terminal 30a and also to resistor R2 and internal connector IC, the latter 
being connected to the second contact-terminal 62 of contact-terminals 
61-64 of the reversing switch as hereinafter described with reference to 
FIGS. 6 and 8-10. 
This reversing switch as shown in FIGS. 6 and 9 is provided with four 
contact-terminals 61-64 mounted on an insulating mounting board 66 made of 
phenolic or the like that is mounted within the bottom of enclosure 8. 
Each contact terminal may be rigidly attached to the mounting board by a 
pair of tabs extending through a corresponding pair of narrow slots in the 
board and the tabs bite into the edges of the slots or are bent over on 
the other side. The contacting portions 61a-64a of these contact-terminals 
are bifurcated to insure good electrical contact with PC bridging members 
14b and 14c on PC board 14 slidable between them and the left wall of 
enclosure 8. The terminal portions 61b-64b of these contacts terminals are 
angular portions that spring back and bite into the bare soldered ends of 
press-in conductors inserted between them and the adjacent wall 8h of the 
enclosure shown in FIG. 6. A lug 14d, FIG. 9, on the lower edge of PC 
board 14 traverses a slot 66a, FIG. 4, in the left edge of mounting board 
66 to limit the forward and rearward movements of the reversing switch PC 
board. As shown in FIGS. 2 and 6, there are four holes 8j in the right 
wall of this reversing switch enclosure through which press-in leads may 
be inserted to contact with the terminal portions 61b-64b. As shown in 
FIGS. 6 and 8-10, internal connector IC of brass or the like connects 
contact-terminal 62 to the PC substrate. For this purpose, one end of this 
connector IC is clamped between the mounting tabs of contact-terminal 62 
and the top of frame 2 as shown in FIG. 6 and it extends down through a 
slot 2k in the top of the frame, shown in FIGS. 2 and 6, and then down 
along the right side of the trigger. Its lower end is bent to the left and 
hooked into a slot 22a, shown in FIG. 8, and electrically connected to the 
printed circuit strip of the substrate at this slot. This affords the IC 
connection shown in FIG. 10. 
The reversing switch operates in the following manner. When forward end 10c 
of the reverse lever is moved to its leftward position, link 12 rotates 
clockwise (FIG. 2) and slides PC board 14 forward, in the direction of the 
arrow in FIG. 9, thus causing contactor 14b to bridge contacts 62 and 63 
and causing contactor 14c to bridge contacts 61 and 64. In FIGS. 9 and 10, 
the motor armature winding of a universal motor or the like is connected 
across terminals A1 (63) and A2 (61) whereas the motor field winding is 
connected across terminals F1 (64) and F2 (38), the latter contact being 
shown also in FIG. 4. Thus, with the aforesaid operation, the reversing 
switch will be in the solid line position shown in FIG. 10. This presets 
the motor for running in the forward direction with current flowing to the 
left in FIG. 10 through both the armature and field. 
On the other hand, when the reverse lever is moved to the right, link 12 
rotates counter-clockwise and slides PC board 14 rearward, thus causing 
contactor 14b to bridge contacts 61 and 62 and causing contactor 14c to 
bridge contacts 63 and 64. The reversing switch will now be in the dotted 
line position shown in FIG. 10. This presets the motor for running in the 
reverse direction with current flowing to the right in the armature and to 
the left in the field as viewed in FIG. 10. This reversal of the current 
in the armature only reverses the motor direction of rotation when the 
trigger is depressed to close the on-off contacts. 
This trigger switch is of the momentary type in that the trigger is 
normally biased into its forward, off position by a helical compression 
spring 68 as shown in FIG. 3. The rear end of this spring bears against 
the rear wall of frame 2 whereas the forward end thereof bears against the 
rear end of threaded shaft 20a which is an integral part of speed 
adjusting screw 20. As shown in FIG. 3, this speed adjusting screw has 
means preventing longitudinal movement in the trigger while permitting 
rotary movement thereof. This means comprises an annular groove 20b 
directly behind the external knob and a suitable resilient constriction 6c 
within the hole in the trigger which will snap into the annualar groove 
when the adjusting screw is pressed into its hole. The rear end of this 
screw is provided with a boss projecting within the end of the spring to 
retain the latter thereon. Thus, whenever the trigger is released after 
being depressed, this spring will restore it to its off position. 
Stop block 18 shown in FIGS. 2-4 may be preset for a desired motor speed. 
Thus, rotation of screw 20 causes the stop block to move. For this 
purpose, the stop block is provided with a channel 18b along its bottom 
having half-circle threads that rest in mesh with the threads of shaft 20a 
to allow the shaft when rotated by its forward knob to drive the stop 
block rearwardly or forwardly to position locking slot 18a with respect to 
the lock pin of button 16. Once the lock pin is engaged in the slot, 
rotation of the screw affords vernier adjustment of the trigger position 
and thus the motor speed. A slight depression of the trigger allows the 
spring-biased lock pin to disengage whereafter the return spring restores 
the trigger to off position when released. 
When the trigger is depressed, the circuit in FIG. 10 first turns the motor 
on and then increases the speed. For this purpose, initial depression of 
the trigger causes movable contactors 32 and 40 to bridge contacts 26-28 
and 36-38 of the doublepole on-off switch thereby to apply power through 
lines L1 and L2 to the motor. Thus, current flows from line L1 through 
contact 26, contactor 32, contact 28, capacitor C1 and in parallel 
therewith through capacitor C2 and resistor R1, and then through variable 
resistor R2, reversing switch contactor 14b, the armature winding of the 
motor, reversing switch contactor 14c, the field winding of the motor, 
contact 38, contactor 40 and contact 36 to line L2. This causes capacitor 
C1 and C2 to charge and when they have charged to the triggering level of 
diode D, this diode suddenly passes a pulse of current through the gate 
and terminal T1 junction to fire the Triac into conduction for the 
remainder of the A.C. half-cycle. On each alternate half-cycle the current 
flows in the opposite direction to fire the Triac into conduction for 
full-wave control of the motor. 
As the trigger is depressed further, the speed of the motor is increased. 
This depression of the trigger moves wiper 50 of variable resistor R2 to 
reduce the resistance in the circuit. This causes increase in the charging 
current to the capacitors so that they charged to the breakover level of 
the Diac sooner, thus increasing the energy applied to the motor causing 
an increase in motor speed. The speed adjusting screw may be adjusted to 
any desired motor speed and left there so that the operator can depress 
the trigger to this same speed thereafter and lock the trigger thereat. 
Full depression of the trigger shunts the Triac for maximum motor speed by 
putting the motor across the power line. Thus, full trigger depression 
causes contactor 32 to bridge contacts 26 and 30 to shunt the speed 
control circuit. Then full line A.C. is applied to the motor for full 
speed operation. 
To reverse motor operation, the trigger is released and the reversing 
switch lever is shifted. This moves bridging contactors 14b and 14c to the 
dotted line position shown in FIG. 10. When the trigger is now depressed, 
the current will be reversed in the armature with respect to the field to 
reverse motor rotation. Speed control functions as before by further 
depression of the trigger. 
While the apparatus hereinbefore described is effectively adapted to 
fulfill the objects stated, it is to be understood that the invention is 
not intended to be limited to the particular preferred embodiment of 
industrial reversing speed control trigger switch with snap-in modules 
disclosed, inasmuch as it is susceptible of various modifications without 
departing from the scope of the appended claims.