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Having thus set forth the nature of the invention what is claimed herein
is:
1. A releaseable lock mechanism for a trigger-switch mounted in the handle
of a drill housing for activating a motor of a drill, said mechanism
selectively to lock the trigger-switch in the activated condition
comprising:
(a) a trigger of the trigger-switch slidably connected in the handle and
normally biased with the switch off and extending outwardly of the handle,
and being depressed to activate the switch,
(b) a camming member affixed in the handle in spaced relation to the
trigger,
(c) a locking member shiftably disposed in the handle, and having a lever
extending outwardly of the handle and a cam shoe engaging the camming
member,
(d) the lever being moved relative the handle to cam the cam shoe against
the camming member causing it to shift into a wedge lock against the
trigger, and
(e) a resilient means in the housing normally to urge the locking member
out of engagement with the trigger and to cause release of the wedge-lock
upon slight depression of the trigger resulting in release of the trigger
and deactivation of the switch.
2. The combination claimed in claim 1 wherein:
(a) the camming member defines a tapered bracket disposed in spaced
relation to the trigger, and
(b) the cam shoe has a tapered surface with a slope corresponding to that
of the tapered bracket adjacent thereto to permit relative sliding motion
between the bracket and the shoe upon shifting of the lever.
3. The combination claimed in claim 2 wherein:
(a) the trigger partakes of straight line motion into and out of the handle
to activate or deactivate the switch,
(b) the locking member disposed in super position to and independently of
the trigger,
(c) the tapered bracket being tapered downwardly in the direction of the
normal outward bias of the trigger, and
(d) the tapered surface of the cam shoe having a slope corresponding to
that of the tapered bracket.
4. The combination claimed in claim 3 wherein:
(a) the trigger has a flat locking contact surface, and
(b) the locking member has a flat locking contact surface parallel to the
contact surface of the trigger and normally out of engagement therewith,
and adapted to be wedge-locked thereto upon straight line motion of the
locking member.
5. The combination claimed in claim 4 wherein:
(a) each of the contact surfaces of the respective trigger and locking
member defining a high friction surface.
6. The combination claimed in claim 5 wherein:
(a) each of the high friction surfaces formed of a material of
substantially equal hardness.
7. The combination claimed in claim 5 wherein:
(a) one of the high friction surfaces formed of a relatively hard material,
and
(b) the other of the high friction surfaces formed of a material having a
lesser hardness and more resiliency.
8. The combination claimed in claim 7 wherein:
(a) the locking member having a contact surface of less hardness and more
resiliency then that of the trigger contact surface.
9. The combination claimed in claim 4 having a trigger switch controlling
the speed of the motor responsive to the extent of the trigger depression
wherein:
(a) the contact surface of the trigger of greater length then the contact
surface of the locking member.
10. The combination claimed in claim 9 wherein:
(a) the contact surface of the trigger at least twice as long as the
contact surface of the locking member.
11. The combination claimed in claim 3 wherein:
(a) a circuit board carrying a printed circuit and interconnected
electrical components thereon is disposed in the handle,
(b) the tapered bracket affixed to the circuit board,
(c) the trigger slidably disposed in the tapered bracket,
(d) the locking member slidably disposed in the tapered bracket whereby
motion of the locking member will force it downwardly into contact with
the trigger.
12. The combination claimed in claim 11 wherein:
(a) the lever of the locking member exits from the forward portion of the
handle the resilient means defines a spring,
(b) the spring is connected between the tapered bracket and the locking
member to urge the locking member rearwardly into the handle in unlocked
position out of contact with the trigger.
13. The combination claimed in claim 11 wherein:
(a) the lever of the locking member exits the rear portion of the handle,
(b) the resilient means defines a spring,
(c) the spring is disposed between the locking member and the housing to
bias the locking member out of contact with the trigger toward the
rearward portion of the handle.
14. A speed control switch mounted in the handle of a drill housing for
controlling the speed of a motor of a drill comprising:
(a) a circuit board carrying a printed circuit in circuit with a series
connected armature and field windings of the motor,
(b) a control circuit operatively connected on the circuit board in circuit
with the printed circuit, and including a silicon controlled rectifier,
variable resistor and a capacitor to control the motor speed below line
current,
(c) a shunt line included in the printed circuits for selectively bypassing
the control circuit,
(d) a pair of mounting brackets affixed to the circuit board,
(e) a plurality of terminals formed on the mounting bracket side of the
circuit board to be connected in selective pairs to successively operate
the control circuit and the shunt line,
(f) a trigger slidably disposed in the mounting brackets to be normally
biased outwardly of the handle,
(g) a recess formed in the trigger on the side thereof facing the
terminals,
(h) a switch plate disposed in the trigger recess yieldably biased toward
the circuit board and out of contact with the terminals when the switch is
in the extended outward position, and on depression of the trigger to
successively place the pairs of terminals in circuit to operate the motor
at increasing speeds,
(i) a locking member slidably connected to one of the mounting brackets and
shiftable into contact with the trigger to lock the trigger in depressed
position,
(j) a resilient means connected to the locking member to normally urge the
locking member away from the trigger and in the locked position to release
the locking member from trigger engagement upon depressed motion of the
trigger subsequent to locking.
15. The combination claimed in claim 14 wherein:
(a) a tapered section formed on one of the mounting brackets in spaced
relation to the trigger,
(b) the trigger having a contact surface adjacent the tapered section,
(c) a tapered surface formed on the locking member in contact with the
tapered section,
(d) the resilient means defining a spring member engaging the locking
member to urge the same away from contact with the trigger,
(e) a high friction surface formed on the locking member in superposition
to the contact surface of the trigger whereby on shifting of the locking
lever the tapered surface of the lever to ride downwardly toward the
trigger causing a wedge-lock between the friction surface and contact
surface, which wedge-lock is releaseable upon depression of the trigger
causing the tapered surface to rise away from engagement with the contact
surface of the trigger via urging from the spring.
16. The combination claimed in claim 15 wherein:
(a) a reversing switch affixed to the circuit board and connected in series
with the printed circuit,
(b) an actuator for the reversing switch interlocked with the trigger in
one of two positions switchable when the trigger is fully extended, and
prevented from motion upon depression of the trigger.
17. The combination claimed in claim 14 wherein:
(a) the handle of the drill housing has a support portion and a cover
portion.
(b) the circuit board is connected to the support portion of the handle
whereby it will be entrapped therein upon the cover portion being joined
to the support portion. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
Trigger switches for power tools, such as drills, are available in plastic
cases, which switches may be simply the on-off type or the speed control
type with speed variably responsive to the amount of trigger depression. A
side lock button is usually provided for locking the switch in either the
"on" position or at a predetermined speed. Reversing the motor direction
also is possible through the use of a reversal switch which may be
included as part of the trigger switch package. The trigger switches
housed in small plastic cases are susceptible to overheating, and because
visual inspection of the case is not possible improper assembly is never
detectable by simple visual inspection. Even when a switch malfunctions,
disassembly is impractical. The use of a side mounted lock button presents
particular difficulty for left handed operators in that it is possible in
grasping the handle with the left hand to inadvertently engage the lock
button. Also, the flexibility in locking the switch at a predetermined
speed is very limited and resort has been made to the use of some form of
settable dial mechanism which has the added disadvantages of complex
structure and difficulty of repeatability at a desired speed. Attempts at
switches constructed in the handle without separate cases have met with
only limited success, while still presenting the disadvantages present in
the lock button mechanism, and assembly is slower.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved
trigger switch and lock therefore which overcomes the prior art
disadvantages; which is simple and economical to assemble, and reliable;
which is capable of visual inspection; which is releasably lockable in the
"on" position; which for a speed control switch is selectively lockable in
any one of an infinite number of variable speed control settings; which
includes an interlocked reversing switch; which uses a front actuated
locking member; which locking member includes a cam shoe capable of being
wedge locked between a bracket and the trigger; which locking member is
releasable on slight trigger depression; which locking member is spring
biased in the unlocked position; which uses a coacting tapered bracket and
tapered cam shoe; which uses a speed control circuit carried on a printed
circuit (PC) board having the electrical components connected thereto;
which PC board includes the camming bracket; which PC board is uncased and
defines a subassembly of the trigger switch; and, which locking member and
trigger have complimentary high friction contact surfaces; and, which
trigger switch and lock therefore are assembled on the PC board to be
mounted as a subassembly in a clam shell handle.
Other objects and advantages will be apparent from the following
description of several embodiments of the invention and the novel features
will be particularly pointed out hereinafter in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
This invention is illustrated in the accompanying drawings in which:
FIG. 1 is a side elevational view of a power tool, preferably a drill,
embodying the present invention.
FIG. 2 is a side elevational view, partly in section, of the trigger switch
mounted in the handle with only the rear portion thereof shown, with the
switch in the "off" position, the locking member disengaged and the
reversing switch interlocked in the forward position.
FIG. 3 is a side elevational view, partly in section, showing the trigger
switch of FIG. 2 in the "on" position, the locking member engaged and the
reversing switch interlocked in the reverse position.
FIG. 4 is a top plan view taken along lines 4--4 of FIG. 2.
FIG. 5 is a top plan view taken along lines 5--5 of FIG. 2.
FIG. 6 is an elevational view taken along lines 6--6 of FIG. 2.
FIG. 7 is a side elevational view, partly in section, showing another
embodiment of the improved trigger switch wherein the locking lever and
the reversing switch are activated from the rear of the handle, only a
portion of which is shown.
FIG. 8 is a partial side elevational view of the camming member of the
locking member of FIG. 7 disengaged from the contact surface of the
trigger wherein dissimilar high friction materials are used.
FIG. 9 is a schematic circuit diagram of the improved trigger switch.
DESCRIPTION OF THE INVENTION
A power tool, such as a portable power drill 10 is shown in FIG. 1
embodying the present invention. The drill 10 includes an electric motor
12 having an armature shaft 14 which carries a commutator 16 engaged by a
brush assembly 18. The armature shaft 14 is journaled in a pair of spaced
bearings 20, and has a drive pinion 22 formed at its forward end. The
pinion drives a gear train 24 and a driven spindle 26 the front of which
exits the drill housing 28 to be threadedly connected to a chuck 30 which
is adapted to drive a suitable bit or implement (not shown) that comes
into engagement with the work. The motor 12 is journaled in the housing 28
as shown in FIG. 1 which is preferably of a clam shell construction as
indicated in FIGS. 4 and 5 wherein a support portion 32 and a cover
portion 34 are suitably connected to each other as by screw means 36
illustrated in FIG. 1 extending through the cover portion 34 of the
housing 28 to be threadedly connected to the support portion or separate
nut means (not shown) to form what is commonly termed a clam shell
housing. The housing 28 has an integrally formed pistol grip handle 38
which receives an electric cord 40 depicted in FIGS. 1 and 9 that in turn
is connected through a trigger switch 42 which is in circuit with the
motor 12 as will be described more fully hereinafter under the schematic
circuit diagram of FIG. 9.
In assembling the drill 10, the cover portion 34 will be removed from the
support portion 32 of the housing 28 to permit easy access and visibility
of all the drill components particularly those included in the trigger
switch 42.
In the preferred embodiment of the invention illustrated in FIG. 2 the
improved trigger switch 42 has a printed circuit (PC) board 44 the face
side 46 of which carries the discrete devices which are suitably
electrically connected through the PC board 44 to the opposite side of the
PC board 44, and in circuit with various PC conductor paths 48 some of
which are shown by the dotted line representation. The PC board 44 is
disposed to be connected in the handle 38 either by being entrapped
between the handle halves 32 and 34 or by means of suitable bent tabs or
screw fasteners or the like.
A trigger 50 is slidably affixed to the PC board 44 by a rear mounting
strap or bracket 52 and a front mounting strap or camming bracket 54, the
top 56 of which is tapered to extend forwardly and downwardly for purposes
which will be explained more fully hereinafter. Each of the brackets 52
and 54 are connected to the PC board 44 by staking as illustrated in FIGS.
4 and 6 at stake points 58, 58.
The trigger 50 has a front portion 60 which projects from an opening in the
handle as shown in FIG. 1 and is gently curved for comfortable engagement
by the operator's finger. The trigger 50 will be longitudinally depressed
into the handle 38 by the operator. A recess 62, shown in FIGS. 2, 3 and
4, is formed in the top of the forward portion 60, the base of which
extends into the mid-portion 64 and serves as the top surface 65 thereof.
The top 65 is serrated substantially along its entire length to form a
high friction contact surface. A cavity 66 is formed in the mid-portion 64
on the side adjacent the PC board 44 to receive a substantially "U" shaped
switch contact wiper 68 shown in FIGS. 2, 5 and 6 as having a
substantially flat base 70 which is loaded to the PC board 44 by two
springs 72 and 74 disposed on round bosses 76, 76 formed in the side wall
of cavity 66. The down turned legs of the wiper 68 serve to entrap the
wiper 68 within the cavity 66. A resistance wiper 78 is disposed on the
left most boss 76 and held in position by the spring 72 as illustrated in
FIGS. 5 and 6. A contact finger 80 is formed integrally with the wiper 78
and extends downwardly from the open bottom of the cavity 66 to slidably
engage a resistance strip 82 of the resistance-capacitance module 83 as
shown in FIGS. 2, 3 and 6. Contact rivets 84, 86 and 88 are connected to
the PC board 44 in the path of travel of the contact wiper 68 and
positioned so that upon trigger 50 depression into the handle 38, the
wiper 68 will first engage the contacts 84 and 86 and after predetermined
further depression of the trigger contact will be made with the rivet
contact 88 for purposes more fully explained hereinafter. A rear portion
90 extends from the mid portion 64, with the rear face having a setback 92
formed on the PC board 44 side to receive a trigger load spring 94 the
other end of which seats within a handle recess 96. The side face of the
rear portion 90 facing the PC board 44 has a shallow recess 98, best seen
in FIG. 5, which communicates with the cavity 66 and is sized to permit
that portion of the trigger 50 to travel past, without interfering with,
the contact rivets 84, 86 and 88. This is so because a boss 100 is formed
at the rearward end of the recess 98 to slidingly engage the face 46 of
the PC board 44 to the left of the contact rivet 88. A side 105 provides
continuity for portions 60, 64 and 90 of the trigger 50, extends adjacent
to the PC board 44 and contains the cavity 66 and recess 98 therein. The
trigger 50 has a different width for each portion, with the front portion
60 having the largest dimension and the mid-portion 64 having the smallest
dimension. The brackets 52 and 54 are sized corresponding to the adjacent
portion of the trigger 50 to be accommodated so that once assembled to the
PC board 44 the trigger 50 will not be accidently dislodged. The rear
portion 90 of the trigger 50 has a vertically extending projection 106
formed at its rear face side as shown in FIGS. 2 and 3 which acts as a
forward stop to engage the top rear edge 108 of the rear bracket 52 as
shown best in FIG. 2 to prevent excessive forward motion of the trigger
50. An opening 110 shown in FIGS. 2, 3 and 5 is formed at the rear of the
face side of the rear trigger portion 90 and leads into parallel
horizontal slots, separated by a horizontal rib 112, with the upper slot
114 being designated for forward motor rotation, and the lower slot 116
being designated for reverse motor rotation, which slots are depicted in
FIGS. 2 and 3.
A reversing switch 118 is affixed to the PC board 44 in circuit therein.
The reversing switch 118 is a double pole-double throw (DPDT) type and it
has a slide button 119 used to position it in either forward or reverse.
An actuator 120 having a body portion 122 with a central aperture 124
which is disposed about and in engagement with the slide button 119 of the
reversing switch 118 so that movement of the actuator 120 will place the
reversing switch in an upward position for forward motion of the motor 12
or in a downward position for reverse motion of the motor 12. An interlock
arm 126 extends upwardly from the body 122 to terminate in an inwardly
facing flange 128 shown in FIGS. 2, 3, 4 and 5, which is sized to be
slidingly disposed in the opening 110 to be shifted between slots 114 or
116 of the trigger 50. An actuator arm 130 extends rearwardly, as shown in
FIGS. 2 and 3, from the interlock arm 126 to reside within an elongated
slot 132 formed in the rear end of the handle 38 for sliding movement
therein. The operator will position the actuator arm 130 in one of two
positions, with the upper position shown in FIG. 2 for forward motion of
the motor 12 whereby the flange 128 will be received in the forward slot
114 of trigger 50, and the lower position shown in FIG. 3 for reverse
motion of the motor 12 whereby the flange 128 was moved downwardly to be
received in the reverse slot 116. The rib 112 acts to prevent operation of
the reversing switch 118 during operation of the motor upon depression of
the trigger 50. Therefore, once the trigger 50 has been depressed the
flange 128 will engage the rib 112 to prevent the reversible operation of
switch 118. Thus the actuator 120 can only change the position of switch
118 when the flange 128 resides in the opening 110, corresponding to the
trigger switch off position shown in FIG. 2.
A locking or lock-release member 134 is illustrated in FIGS. 2, 3, 4 and 6,
and has a forwardly extending external lever 136 which terminates in a "T"
shaped handle 138 which extends on either side of the trigger 50 as shown
in FIG. 4. The lever 136 extends externally of the housing 38 immediately
above and forwardly of the trigger 50 for convenient operator manipulation
as more fully described hereinafter. The lever 136 is stepped down at its
inner end for an offset connection to a midsection 140 shown in FIGS. 2
and 4 which extends rearwardly to terminate in a cam shoe 142 the upper
surface 144 of which is tapered corresponding to the tapered top 56 of the
camming bracket 54. The lower surface 146 of the shoe 142 lies
horizontally below the lower surface of the midsection 140 and is serrated
to define a high friction contact surface. A spring retainer 148 projects
upwardly from the rear of the cam shoe 142 at the rearward end of the
tapered surface 144. A bracket extension 150 in the form of an upwardly
turned flange extends from the lower portion of the tapered top 56 to face
the retainer 148. A spring 152 is disposed between the retainer 148 and
the extension 150 to normally urge the locking member 134 in its rearmost
position within the handle 38 as shown in FIG. 2. The spring 152 is held
in position by pegs 153a and 153b formed on the retainer 148 and extension
150, respectively. The cam shoe 142 of the locking member 134 is entrapped
within the bracket 54 and the tapered surface 144 is in continual contact
with the tapered top 56 of the bracket. With the cam shoe 142 in the
rearmost position the lower surface 146 will remain out of contact with
the upper serrated surface 65 of the trigger 50. The midsection 140 of the
locking member 134 being disposed in the recess 62 of the trigger 50
wherein the inner side 154 slidingly engages the side 156 of the recess 62
to guide the motion of the locking member 134 and limit it to the linear
direction. The spring 152 will load the locking member 134 toward an
unlocked position because the bracket extension 150 has a fixed position
while the spring retainer 148 is movable along with the locking member
134. When the trigger 50 is in the unlocked position shown in FIG. 2, it
can be moved freely through its entire depressed movement wherein it will
compress the trigger load spring 94 so that upon release the spring 94
will force the trigger to return to its normally "off" position. Though
the present invention is useable with a simple "on-off" switch, it has
been embodied in the trigger switch 42 which includes speed control
capabilities so as to more completely describe the advantageous results of
the present invention. The extent of trigger 50 depression will determine
the speed at which the drill motor 12 operates with the speed increasing
as the trigger depression increases with the maximum depression of the
trigger 50 being shown in FIG. 3.
To lock the trigger 50 at any desired speed setting of the trigger switch
42, the trigger 50 will be retracted to obtain the desired speed, which in
the present instance is assumed to be the maximum speed corresponding to
the setting illustrated in FIG. 3, and held in that position while the
locking member 134 is pushed forwardly. Forward movement of the locking
member 134 causes the tapered surface 144 of the cam shoe 142 to slide
forwardly and downwardly under the urging of the tapered top 56 of the
camming bracket 54 until the cam shoe 142 becomes wedged-locked under the
angled tapered top 56 of the camming bracket 54, thus forcing the lower
surface 146 to seat its serrations into those formed on the top surface 65
of the trigger 50. The trigger load spring 94 exerts a forward pressure on
the trigger 50 to maintain a sufficient force on the locking member 134 to
keep the contact surfaces 65 and 146, respectively, engaged with each
other, and the cam shoe 142 wedged under the camming bracket 54 prevents
any further forward movement of the trigger 50, and therefore, any change
of speed from the maximum illustrated in FIG. 3.
To release the locking member 134, the trigger 50 is pulled rearwardly to
physically shift the cam shoe 142 rearwardly out from under the angled
face or tapered surface 56 of the camming bracket 54 so as to initiate a
disengagement of the serrated surfaces 65 and 146 whereby the spring 152
will continue to push the locking member 134 rearwardly to cause the
tapered surface 144 to ride upwardly along the tapered top 56 and away
from the serrated top surface 65, thus freeing the trigger 50 and
permitting its release. Once the wedge-lock of the locking member 134 has
been broken and the serrated surfaces 65 and 146 separated the spring 94
has no influence on the locking member 134. The length of the serrated top
surface 65 of the trigger 50 is substantially twice the length of the
lower serrated surface 146 of the cam shoe 142. This permits the trigger
50 to be locked in any desired speed setting from "off" to the maximum
speed in the "on" setting.
The switch contact wiper 68 illustrated in FIGS. 2, 5 and 6 is loaded to
the PC board 44 by the contact springs 72 and 74. The wiper 68 is
entrapped in the trigger cavity 66 and will slide with the trigger 50. As
the trigger 50 is pulled rearwardly, the wiper 68 first bridges the rivet
contacts 84 and 86 shown in FIGS. 2 and 6, and in the schematic circuit
diagram of FIG. 9. The various printed circuit conductor paths are
designated generally 48, and are formed on the underside of the PC board
44 as illustrated in FIG. 2, and these conductor paths are shown in
circuit in the schematic of FIG. 9, in which the lines or conductor paths
will still be referred to by the general designation 48, but the
electrical devices or components interconnected by the lines 48 will be
specifically identified. Also, for a better understanding of the
explanation of the electrical operation of the improved trigger switch 42
reference may be had to FIGS. 2 and 9.
Contact 86 is connected to the anode 158 of the silicon control rectifier
(SCR) 160 via one of the PC conductor paths 48. Likewise contact 84 is
connected to the reversing switch 118, the motor 12 to be controlled as
indicated by the armature 162 and the field 164 disposed within the dotted
lines for the motor 12 of FIG. 9, and one side of the line voltage cord 40
via a PC conductor path 48 and a jumper wire or path also formed on PC
board 44, and quick disconnect terminals 166, 168, 170, 172, 174 and 176.
Terminals 166, 168, 170 and 172 serve as output terminals, while terminals
174 and 176 serve as line cord terminals. Contact 84 connects to the line
voltage terminals 174, while the cathode 178 of the SCR 160 is connected
to the other line voltage terminal 176, and therefore, bridging the
contacts 84 and 86 will start the motor 12.
With the SCR 160 in series with the motor 12, the speed can be varied by
the point into every other half cycle of line voltage (when the SCR 160
anode to cathode voltage is positive) at which SCR 160 is triggered into
conduction via the gate 180 of the SCR 160. The gate 180 trigger point is
determined by the position of the resistance wiper 78 on the primary
resistance strip 82 of the RC module 83. The wiper 78 is carried on the
boss 76 of trigger 50 and is connected to line voltage through the spring
72 and wiper 68 to the contact 84. As the trigger 50 moves rearwardly the
wiper 78 decreases the effective resistance on the module 83 and causes
the capacitor 182 of the module 83 to charge faster. A trigger diode
(diac) 184 breaks down sooner dumping the capacitor 182 charge into the
gate 180 of the SCR 160 and therefore turns the SCR 160 on sooner. When
the SCR 160 turns on sooner in each half cycle, the effective voltage of
the motor 12 is higher and, therefore the motor 12 speed is
correspondingly higher. Diode 183 is connected in parallel with capacitor
182 so as to prevent 182 from charging when the anode to cathode voltage
of SCR 160 is negative. This starts the voltage on capacitor 182 near zero
at the start of each positive half cycle of line voltage and helps
stabilize the trigger point. Further, since capacitor 182 cannot charge
negative causing trigger diode 184 to break down and dumping the negative
capacitor charge into gate 180 of SCR 160, no false triggering or
gate-cathode junction damage of SCR 160 can occur during a negative half
cycle of line voltage. As the trigger 50 moves rearwardly toward the end
of its stroke, wiper 68 connects rivet contact 88 via a PC path 48 to the
terminal 176 which shunts, or bypasses, the anode 158 and cathode 178 of
the SCR 160. This connects the motor 12 to full A.C. line voltage and
places the motor 12 into high speed operation. Of course, as the trigger
50 is released from the full "on" position, the above described operations
are reversed in order of occurrence and the motor 12 speed decreases to
zero at the full "off" position.
The reversing switch 118 is a DPDT PC switch which, when actuated, reverses
the armature 162 terminals of the motor 12 relative to the field 164 which
always remains connected in the same direction relative to the line
voltage terminals 174 and 176. The armature 162 is connected to the common
center terminals 166 and 170 and suitable PC conductor paths 48. A
crossing pattern consisting of a PC conductor path 48 and a jumper wire or
path 48 located on the underside of the body of the switch 118 connects
the outside switching terminals of the switch and allows reversing to take
place. It should be noted that the connected positions of the armature 162
and the field 164 can be interchanged, reversing the field relative to the
armature with no change in performance and achieving proper motor
reversal.
The RC module 83 contains a secondary resistor 186 in series with the main
variable resistor 82. By trimming the secondary resistance 186 the initial
speed of the motor, when it is first turned on, can be adjusted for the
desired slow or "creep speed". Trimming can be accomplished with a laser
or other suitable means of increasing the resistance by removing material
from the secondary resistor 186.
In the embodiment of the invention illustrated in FIG. 7 like reference
characters have been used for like components shown and described
hereinbefore under the embodiment of the invention illustrated in FIG. 2.
In some instances a component will function in a similar manner but may
have been structurally modified and therefore will carry a suffix "a" at
the end of the reference character. The electrical circuit associated with
the trigger switch 42a depicted in FIG. 7 will be substantially the same
as that illustrated in the schematic circuit diagram of FIG. 9.
A PC board 44a is suitably mounted in a handle 38a of a power tool such as
a drill similar to that shown in FIG. 1. The PC board 44a has the discrete
devices such as the RC module 83, reversing switch 118, SCR 160 and diac
184 mounted on the face side thereof to extend through and be connected in
circuit with suitable PC conductor paths (not shown).
The trigger 50a is slidably mounted to the PC board 44a and held in
assembled position by a rear mounting bracket 52a and a front camming
bracket 54a, through which brackets 52a and 54a the trigger 50a slides in
its movement.
A trigger load spring 94a is held captive within a recess 96a of the handle
38a and the rear of the trigger 50a to urge the trigger to remain in the
"off" switch position. Rearward pressure by the operator on the trigger
50a will compress the spring 94a during operation so that the spring 94a
will restore the trigger 50a in the extended "off" position when released.
When the trigger 50a is retracted sufficiently to place the wiper 68 in
contact with contact rivets 84 and 86, the trigger switch 42a will be in
the "on" position causing the motor of the power tool to operate.
A reversing switch actuator 120a has an integrally formed inwardly facing
flange 128a which will be placed in alignment for sliding engagement in a
forward slot 114a or a reverse slot 116a so as to prevent reversing the
output direction of the motor while the tool is on. The actuator has a
body 122a which fits securely over the reversing switch to change its
position from forward to reverse or back again, with the forward position
corresponding to the raised position shown in FIG. 7 and the reverse
position corresponding to the lower position. Once the interlock flange
128a has entered either of the slots 114a or 116a a rib 112a will prevent
actuation of switch 118 during the period of time the switch 50a remains
depressed. The actuator 120a has a control button 130a which exits the
handle 38a at slot 132a for convenient operator actuation.
The locking member 134a has a rearwardly exiting lever 136a which is spring
loaded by a lock release spring 152a entrapped in a counterbore handle
boss 188, which spring 152a urges the locking member 134a to remain in the
released position. A lever stop 190 is affixed to the locking member 134a
to limit the retracted position. With the locking member 134a in the
retracted position the trigger 50a is free to move through its entire
range of on-off movement. To lock the trigger switch 42a at any desired
speed the trigger 50a will be retracted to obtain the desired speed, held
in that position while the lever 136a is depressed or pushed forward to
also cause the locking member 134a to be shifted forwardly. Forward
movement of the locking member 134a will cause the tapered top surface
144a to slide forwardly and downwardly along the top tapered surface 56a
of the camming bracket 54a to produce a wedge-lock action between its
lower serrated surface 146a and the serrated top surface 65a of the
trigger 50a. The angle face of the camming bracket 54a forces the
respective serrations of the surfaces 146a and 65a to be securely
interlocked so long as the cam shoe 142a remains wedged between the
trigger 50a and the bracket 54a. Since the force of the spring 94a which
urges the trigger in the forward direction so as to retain the wedge-lock
is substantially larger than the force of the release spring 152a, also
the wedge shaped components and the high friction engagement all aid in
keeping the trigger 50a in locked position.
To release the locking member 134a the trigger 50a is pulled rearwardly
forcing the camming shoe 142a rearwardly and away from under the angle
face of the camming bracket 54a a sufficient distance to separate the
serration and permit the locking member 134a to be solely under the
influence of the release spring 152a. This pushes the cam shoe 142a
rearwardly along the tapered surface 56a so that the trigger 50a once
released from the locking member 134a will be pushed forwardly under the
influence of the trigger load spring 94a to its normally "off" position.
In each of the embodiments of the present invention serrated contact
surfaces have been used to produce a high friction engagement between the
respective locking member and the trigger. The high friction contact
surface may take any one of a number of forms with serrations being only
one of the many possibilities. An alternate form is illustrated in FIG. 8
wherein the locking member 134b has a cam shoe 142b in sliding engagement
with a camming member 54b and disposed in superposition to the serrated
top surface 65b of a trigger 50b. In this instance the lower surface 146b
is formed of a resilient plastic or rubber material which yieldably
engages the serrated surface 65b to produce the necessary wedge-lock
engagement therewith and is also a high friction contact surface so as not
to slip loose from the locked position. Release of the trigger 50b will be
as described hereinbefore wherein slight depression of the trigger 50b
will loosen the wedge-lock action of the locking member 134b which being
shifted rearwardly will cause the disengagement between the contact
surfaces.
It will be understood that various changes in the details, materials,
arrangements of parts and operating conditions which have been herein
described and illustrated in order to explain the nat | | |
