U.S. patent number 3,626,118 [Application Number 04/849,821] was granted by the patent office on 1971-12-07 for radial arm saw with a depressible key for unlocking a switch-actuating trigger.
Invention is credited to Harold R. Botefuhr.
United States Patent |
3,626,118 |
Botefuhr |
December 7, 1971 |
RADIAL ARM SAW WITH A DEPRESSIBLE KEY FOR UNLOCKING A
SWITCH-ACTUATING TRIGGER
Abstract
A handtool is provided with a manipulating handle and includes a
key-operated structure such that the tool cannot be operated
without the key being in position in the tool. In addition, in one
form of the invention the tool will not operate unless the key is
depressed to a predetermined position against a force tending to
return the key to the inoperative position.
Inventors: |
Botefuhr; Harold R. (Geneva,
IL) |
Family
ID: |
27081871 |
Appl.
No.: |
04/849,821 |
Filed: |
August 13, 1969 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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594084 |
Nov 14, 1966 |
3482610 |
Dec 2, 1969 |
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Current U.S.
Class: |
200/43.01;
200/43.17 |
Current CPC
Class: |
B27B
5/201 (20130101); H01H 21/10 (20130101) |
Current International
Class: |
B27B
5/00 (20060101); B27B 5/20 (20060101); H01H
21/10 (20060101); H01H 21/00 (20060101); H01h
027/06 (); H01h 009/06 () |
Field of
Search: |
;200/42R,44,157,61.85
;74/61,224,387 ;310/68.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
"Latch Operated Switch"; IBM Technical Disclosure Bulletin; Vol. 8,
No. 5; 10/1965; by Greenfield..
|
Primary Examiner: Schaefer; Robert K.
Assistant Examiner: Vanderhye; Robert A.
Parent Case Text
This application is a divisional application of my copending
application entitled RADIAL ARM SAW filed Nov. 14, 1966, Ser. No.
594,084, now U.S. Pat. No. 3,482,610, issued Dec. 2, 1969 and
assigned to the common assignee G. W. Murphy Industries, Inc.
Claims
I claim:
1. For use in an electric tool having a hand grip member and a
switch for actuating the electric tool, a trigger mechanism,
comprising: a trigger member mounted on the handle for movement
between an extended switch-deactuated position and a depressed
switch-actuating position; means linking the trigger member to the
switch so that movement of the trigger member to the depressed
switch-actuating position actuates said switch; means biasing said
trigger member into said extended, switch-deactuated position; a
trigger-locking member pivotally mounted in the handle for movement
between a first and a second position, said first position being a
trigger-blocking position for preventing movement of the trigger
member to the depressed switch-actuating position, and a second
position being a trigger release position permitting movement of
said trigger member to the depressed switch-actuating position; a
removable key adapted to be inserted through a slot in said handle,
said first position being an inactive position and said second
position being a depressed active position, said key being linearly
movable from said inactive position to said active position for
engaging a portion of said key with said locking member for
pivoting said locking member out of trigger-blocking position
whereby said trigger member may be depressed for actuation of said
switch.
2. The apparatus of claim 1 wherein the key has a yieldable shank,
the shank being slightly wider than the slot afforded in the handle
so that insertion and extraction of the key is afforded by means of
the yieldable nature of the shank.
3. The apparatus of claim 2 wherein the key has an enlargement
formed on one portion of the yieldable shank, the enlargement
holding the key against the accidental dislodgement relative to the
shank but permitting manual insertion and withdrawal of the key
from the slot.
4. The apparatus of claim 3 wherein the shank of the key is split
to provide the yieldable characteristic thereof.
5. The apparatus of claim 1 wherein the locking member is pivoted
to the interior of the handle and normally spring urged to a
blocking position.
Description
The invention relates to handtools and more particularly to the key
locking of handtools.
Radial arm saws have been known in one form or another for many
years. The principal advantage generally to radial arm saws lies in
the fact that the workpiece is held on a worktable while the saw is
moved over and through the workpiece. Known radial arm saws have
provision for performing many different types of cuts and are
adaptable for conversion for use as a drill press, sander, grinder
and the like.
The prior and current radial arm saws can be unsafe for children or
people who are unfamiliar with power tools in general or with
radial arm saws in particular. Also, current radial arm saws have
awkwardly placed or inconveniently operative adjusting means for
setting the angular position of the arm relative to the worktable,
for setting the angle of the saw blade relative to the workpiece,
for guiding the vertical column relative to the workpiece and for
guiding the horizontal position of the saw along the arm, all of
which limits the efficiency, acceptability and usefulness of the
saw as a convenient home and commercial workshop tool.
It is therefore a principal object of this invention to overcome
the above-noted disadvantages of the prior art and to produce an
improved radial arm saw thereby.
It is another important object of my invention to provide an
improved key-actuated pistol grip actuator member which prevents
accidental operation of a power tool.
Another object of my invention is to provide an improved power tool
having a pistol grip actuator mechanism with a key which completely
deactivates the trigger mechanism when removed.
Another object of my invention is to provide an improved power tool
having a key means associated with a pistol grip mechanism wherein
the key means in one position in the mechanism prevents actuation
of the trigger mechanism and in a second position in the mechanism
permits the trigger mechanism to be operative.
The foregoing objects and advantages of the invention will be made
clear in the following specification taken in conjunction with the
accompanying drawings, in which:
FIG. 1 is a perspective view showing my new radial arm saw with the
improved actuator key in position and with the improved adjusting
means illustrated;
FIG. 2 is an exploded perspective view of the improved radial
arm-positioning and locking means;
FIG. 3 is a cross-sectional view taken on the line 3--3 of FIG.
1;
FIG. 4 is a front view, partially broken away, of the motor housing
and saw blade arbor showing the hand grip and key arrangement;
FIG. 5 is a cross-sectional view taken on the line 5--5 of FIG.
4;
FIG. 6 is a partial cross-sectional view of the mechanism of FIG. 5
only with the key depressed so that the trigger switch can
operate;
FIG. 7 is a bottom view of the forward portion of the hand actuator
showing the work illuminating means;
FIG. 8 is a cross-sectional view through the vertical column and
radial arm with the front portion of the arm taken on a plane
spaced in front of the plane of the centerline of the arm;
FIG. 9 is a partial cross-sectional view taken on the line 9--9 of
FIG. 1;
FIG. 10 is an enlarged cross-sectional view of the forward portion
of the radial arm similar to FIG. 3;
FIG. 11 is a cross-sectional view through part of the motor-housing
bracket with the motor housing and hand actuator shown in full
lines; and
FIG. 12 is an enlarged cross-sectional view taken on the line
12--12 of FIG. 11.
As illustrated generally in FIG. 1, a radial arm saw mechanism 20
is comprised of a base 21 which is adapted to rest on a solid,
preferably level surface, such as a concrete floor. The top portion
of the base has a laterally and transversely extending worktable
support 22 upon which is adjustably positioned a guide fence 25. A
column support 27 is bolted to a rearwardly extending portion 28 of
the base 21 and has a vertical column 30 upwardly projecting
therefrom. A radial arm member 32 is pivotally mounted on the top
portion of the column 30. A plate 33 is secured to the bottom of
arm 32, the opposite longitudinally extending edges of the plate
affording a pair of horizontally disposed tracks 33a and 33b along
which is movably positioned a motor-housing bracket 35 supporting a
motor housing 36. Motor housing 36 includes motor assembly 37 which
drives a shaft from which projects the arbor member 38. A saw blade
40 is locked to the arbor 38 and has a saw blade guard 42
positioned over the major portion of the blade. A handle 45 and
pistol grip mechanism 46 are connected rigidly together and with
the motor housing and are pivotally mounted about an axis
transverse to the axis of the arbor shaft 38 in the lower portion
of the motor housing 36 as will be described later herein.
As shown in FIGS. 1, 3 and 8, the vertical column 30 is slidably
positioned in the column support 27 and is adapted to be
telescopically extended into and out of said support 27 by means of
the interaction between the screw 48 and nut 49 arrangement in the
lower portion of said support 27. The screw 48 is rotatably mounted
in a bracket 50 in the rear portion of the base 21 and has a
beveled gear 51 keyed to the lower end portion of said screw 48.
For rotating the screw 48, a horizontally disposed rod 53 is
mounted for rotation about its axis in a pair of bearings 55
carried in brackets in said base. One portion of said rod 53 has a
beveled gear 56 which meshes with the beveled gear 51 on the screw
48. The forward portion of the rod 53 extends through the front of
the base 21 and is keyed to a crank arm 58 projecting forwardly of
said base whereby rotation of the crank 58 in one direction will
raise the column 30 and its attached radial arm 32 and rotation in
the opposite direction will lower same.
The vertical column 30 has a keyway 60 formed in the rear surface
thereof. A threaded opening 61 is formed in the column member 27 in
alignment with said keyway 60 in the column. A guide pin 62 having
a wedge-shaped forward portion 63 is slidably disposed in the
opening 61 in the column 27 with the wedge 63 nesting in the keyway
60 in the column. A locator pin 64 projects rearwardly from the
guide pin 62 and passes through the center of a Belleville spring
65. A threaded plug 66 is screwed into the opening 61 of the column
with the locator pin 64 on the guide pin 62 sliding freely in a
mating aperture formed in the plug. A hexagonal head is formed on
the plug 66 so that the plug 66 and guide pin 62 can be adjusted
together toward the column. The wedge-shaped portion 63 of the
guide pin 62 is urged into the keyway 60 of the column by means of
the compression of the Belleville spring 65 and the tightening of
the plug 66 toward said column. The spring 65 provides a small
amount of resilience to the guide pin 62 so as to keep the guide
pin 62 nested in the keyway 60 without a positive bind
therebetween. The coaction between the guide pin 62 and the keyway
60 will limit, if not eliminate, the sidewise or lateral play of
the arm about its pivotal axis.
A stop 67 in the lower end of the keyway 60 is adapted to engage
with the guide pin 62 so that the column 30 cannot advance beyond a
predetermined point relative to the table 22. Upon turning the
crank 58 on the front of the base 21, the column 30 and the radial
arm 32 will raise and lower with the guide pin 62 sliding in the
keyway 60 so as to prevent rotation of the column 30 about its
axis. The fit is sufficient to permit the column 30 to slide
axially relative to the column support but substantially eliminates
lateral play between the column and the support.
The radial arm 32, as shown in FIGS. 1, 2, 3, 8 and 10, has a
die-cast body portion 69 which is hollow and ribbed from below. The
arm has an enlarged rear portion 70 in which is formed a
cylindrical opening 71. The internal diameter of the opening 71 is
such as to slidably fit about the outer diameter of the column 30.
The upper cylindrical portion of the column 30 has a segment 73
bolted thereto in a centrally located position facing toward the
worktable 22. The segment 73 has at least three vertically disposed
wedge-shaped grooves 74 formed in the outer surface thereof. The
middle groove 74 has its centerline extending in the vertical plane
cutting the table 21 in half while the centerlines of the two
additional grooves 74 lie in planes which are angled 45.degree.
away from the plane of the middle groove with all three planes
intersecting at the centerline of the column 30. The rear enlarged
portion 70 of the radial arm 32 also has a die-cast lower half or
mounting member 75 which is assembled by bolts to the portion 70 of
the radial arm so as to encase the arm 32 about the segment 73 on
the column 30.
As shown in FIGS. 2, 3 and 8, a pair of mating brake members 77, 78
are bolted at 79 to the inside of the mounting member 75 so as to
substantially encircle the column 30. Brake members 77, 78 are
movable relative to each other and relative to column 30 which they
encircle. When the brake members are moved toward the column, they
engage the same in clamping relation to lock the arm against
swinging movement. Each brake member 77, 78 has a generally
radially outwardly extending free end 77a, 78a, respectively, which
may be engaged to pinch or draw the two brake members together.
A radial arm-adjusting arrangement is provided in the arm for
releasing or locking the arm relative to the axis of the column
either in predetermined steps or in infinite adjustments.
Specifically, an elongate actuator rod 80 extends from a position
just forward of the front of the radial arm through the inner
cavity of the arm to a right angular bend 81 therein located near
the rear end portion of said arm. The leg 81' of the rod that
extends upwardly therefrom fits into a slot 82 formed in a
positioning pin 83 axially guided along the length of the arm. A
forward end 84 of said pin is wedge-shaped and is adapted to fit in
any one of the grooves 74 formed in the positioning segment on the
column. A compression spring 85 is positioned by the one web of the
arm and an undercut projection 86 on the rear of the pin for urging
the pin into the grooves in the positioning segment.
An actuating handle 87 is mounted forward of the front of the arm
in position to be gripped and pulled toward the operator. Handle 87
is connected to rod 80 so that outward movement of handle 87 will
move the rod 80 to compress the spring 85 to permit the arm to be
swung about the column to any desired position. Release of the
handle will permit the spring to drive the pin 83 toward the
segment 73 so that the forward part 84 of the pin will drag along
the surface of the segment until it drops into an aligned groove 74
therein.
The means for infinitely adjusting the arm relative to the column
is provided by an elongate tubular sleeve 90 slidably positioned
about the outer surface of the rod 80 within the confines of the
die-cast arm. Sleeve 90 has a cap member 91 having a flared
cam-surfaced flange 91' fastened thereto threaded on the forward or
one end of said sleeve. The other or rear end of said sleeve is
connected to a split brake actuator 92 such that the split ends 92a
and 92b thereof are movable toward and away from column 30
responsive to movement of sleeve 90. Split ends 92a and 92b are
generally of a size to nestably engage ends 77a, 78a of the brake
members to draw brake members 77 and 78 together when sleeve 90
moves actuator 92 toward column 30 and brake members 77 and 78. The
upper surface of the sleeve has an elongate axially extending slot
93 formed therein through which the upwardly extending leg 81' of
the rod 80 projects such that the rod 80 can be moved relative to
the sleeve 90 without interference therewith.
A U-shaped handle 94 is pivotally mounted on the side walls of the
front portion of the arm and has cam-shaped projections 95 formed
on the bifurcated legs 96a and 96b thereof such that pivoting the
handle about its mountings will cause the cam surfaces on the
projections 95 to engage the flange member 91' on the cap member 91
of the sleeve for moving the sleeve 90 along the axis of the arm
for actuating the brake members 77 and 78 relative to the column
30. Downward movement of the handle 94 will release the friction
brake members 77 and 78 from the column. The flange member 91' is
fastened to the member 91 which is threaded on the forward end of
rod 80 and as can be seen in FIG. 2, has notches 98 formed around
the outer circumference thereof. These notches can be used to grip
the flange 91' to rotate the flange and member 91 relative to the
sleeve 90 for adjusting the operative distance between the contact
surface of the flange 91' relative to the brake members 77, 78 on
the column. In this way, wear or slack can be taken up without
affecting the operativeness of the angular adjusting means of the
arm relative to the column. A cover 99 is adapted to be fastened to
the front end of the radial arm through which the handles 94 and 87
project.
Means are provided for rotating the motor housing 36 relative to
the motor-housing bracket 25 about an axis transverse to the length
of arm 32 to thereby adjust the saw blade 40 for mitering at
different selected angles. To this end, motor-housing bracket 35
includes a base plate 100 which is pivoted to the motor housing 36
in a manner to be described later. Opposite side cover plates or
frames 102a and 102b extend upwardly from either side of base plate
100 and embrace arm 32 to generally complete the bracket assembly.
Each side cover plate 102a and 102b has an opening exposing the
appropriate indicia along the length of the arm 32. An indicator is
carried on each side frame to indicate the distance the center of
the blade is from the center of the column. A plurality of track
bearings 104 are secured to base plate 100 on either side of the
bottom plate 33 of arm 32 in rolling contact with the opposite
tracks 33a and 33b formed along the longitudinal edges of plate 33.
Preferably, these track bearings take the form of pulley-like
wheels.
As best seen in FIG. 9, a lock handle 107 projects through side
cover frame 102b and is threaded through the lug 106 carried by the
base plate 100 with the threaded shank 108 of handle 107 carrying a
pin 109 which is in a position to abut track surface 33b of plate
33. By loosening and tightening handle 107, the motor housing
bracket 35 and motor housing 36 may be moved and locked at selected
positions along the length of arm 32.
With particular reference to FIGS. 9 and 11, a pivot bolt 110
extends through an opening 111 in plate 100 and an opening 112 in
bridge portion 113 of housing 36. An index plate 114 is positioned
in a recess 115 in the underside of bridge 113 and secured therein
by means of machine screw 116 (FIG. 11) which extends through one
of a plurality of positioning openings 117 formed in index plate
114 and into threaded opening 117' in bridge 113. Index plate 114
is also provided with a D-shaped opening 118 of a size and shape to
conform to the flat portion 119 formed on the threaded shank 120 of
bolt 110.
A turning handle 121 has an end portion 122 which is threaded on
bolt shank 120 below index plate 114. Loosening movement of handle
121 relative to bolt 110 permits a rotational movement of housing
36 relative to the base plate 100 of the motor housing bracket 35,
and tightening movement of handle 121 locks housing 36 against
rotational movement relative to plate 100 of the motor-housing
bracket 36. Since handle 121 extends through a slot in the side of
the motor housing 36, its swinging movement is limited so that over
a period of time the wear and set of the parts becomes such that
the handle movement is not enough to lock the motor housing 36
relative to the motor-housing bracket 35. At that time, by removing
the screw 116 and rotating plate 114 and screw 110 sufficient to
align the next hole 117 with the opening 117' and reinserting screw
116 will provide sufficient adjustment that the movement of the
handle 121 will again lock the housing 36 relative to the base
plate 100 of the motor-housing bracket 35. This adjustment does not
require disassembly of part of the arm as was necessary
heretofore.
The rotational adjustment means further includes a lock handle 124
which is pivoted at 125 to a portion of plate 100 of the bracket
35. A downwardly projecting finger 126 of handle 125 occupies one
of a plurality of spaced notches 127 formed in bridge 113 of
housing 36. Before housing 36 can be rotated relative to plate 100,
even after handle 121 is loosened, it is necessary for handle 124
to be raised so that the finger 126 is extracted from occupation in
one of the notches 127. When this is done, the housing 36 may be
rotated to an infinite number of positions of angular adjustment
with respect to plate 100 of bracket 35 and, therefore, likewise
relative to the arm 32. In the preferred embodiment, four such
notches 127 are formed so that rapid coarse adjustment to four
positions spaced 90.degree. apart may be accomplished simply by
swinging the housing to one of the remaining three notches 127 and
returning the handle 124 to the locking position.
Means are further provided for adjusting the planar disposition of
the saw blade 40 relative to the worktable 22 for bevel cutting or
the like. With particular reference to FIGS. 4, 5, 11 and 12, index
handle 45 to which pistol grip 46 is secured includes an upper or
support half 130a and a bottom cover half 130b. The support half
130a has an uprightly disposed rounded flange portion 132 which
abuts the side of housing 36 adjacent opening 134 formed in the
lower end of housing 36. A pivot bushing 136 is positioned in
opening 134 and secured by means of cap screws 138 to the motor
assembly 37 which is positioned between the legs of motor housing
36. The bushing 136 has an undercut portion 138' in which extends
the continuous flange portion 36' of the wall of the housing for
retaining the motor assembly 37 for rotation relative to the
housing 36 about an axis perpendicular to the axis of the arbor 38.
At the opposite end a bushing 141 with an overhanging portion 141a
is secured by screws 141b to motor assembly 37 to rotatably mount
the motor with respect to an opening 141c formed in the opposite
side of the motor housing 36. In this manner, the motor assembly 37
is pivotally mounted with respect to the motor housing 36.
A brake ring 142 is positioned in the peripheral groove 144 of
pivot bushing 136 by means of a pin 145 extending through the ring
142 and into the bushing 136. The ring is split at 146 with a
ball-like opening 147 for receiving a wedging member such as a
free-floating ball 148. The wedging member or ball 148 is forced
into the opening by movement of a handle 150 which is threaded into
the threaded opening 152 formed in the flange portion 132 on the
handle 45 so that turning of the handle 150 urges the wedging
member or ball inwardly to spread the ring for locking the motor
relative to the housing 36. Reverse turning of the handle permits
the resiliency of the ring and the taper of the opening 147 to
force the wedging member or ball outwardly from the beveled
ball-like split opening 147 in brake ring 142 to release the brake
and permit turning of the motor relative to the housing. Depending
upon whether the wedging member or ball is pushed inwardly or
permitted to move outwardly from opening 146 in split 147, the
brake ring 142 will expand or retract thereby tightening or
loosening, respectively, the pivot bushing 136, brake ring 142 and
its associated motor assembly 37 and handle 45 with respect to the
opening 134 and housing 36.
The outer periphery of bushing 136 is provided with a plurality of
index openings 154 which are adapted to mate with the reduced
beveled end 156 of plunger 158. An indexing member such as a
plunger 158 is urged laterally inwardly into the openings 154 by
means of spring 160 which is positioned behind the indexing member
or plunger 158 within the sidewall of the housing 36 by means of a
threaded plug 157. When handle 150 is turned to permit the wedging
member or ball 148 to retract from the opening 147 and thereby
loosen the bushing 136 and brake ring 142 relative to the wall of
the opening 134, the bushing 136, brake ring 142 and the motor
assembly 37 will be permitted to rotate with respect to the bracket
36, thereby tilting blade 40. As the handle 46 is grasped to turn
the motor assembly structure, the indexing member or plunger 158 is
cammed outwardly from the notches 154. A plurality of such notches
are formed in the periphery of the bushing 136 at predetermined
locations such that the saw blade can be indexed to positions of
standard angular displacement for instance along a plane at
45.degree. and 90.degree. with respect to the vertical position
thereof. For adjustment of the blade to an infinite number of
angular positions between the range afforded by the spaced notches
154, the handle 150 is merely tightened at the desired position of
angular displacement. To assist in determining the proper angular
orientation, a pointer 162 is mounted on housing 36 for cooperation
with a scale 164 provided on the outer face of flange portion 132
from which the reading of angular displacement of the motor
assembly may be obtained.
The pistol grip portion 46 of the handle is provided with a novel
locking means for preventing actuation of the saw structure. This
means is best illustrated in FIGS. 5, 6 and 11. As shown therein,
handle 46 includes two half pieces 168a and 168b which are secured
together to form the unit. A switch unit 170 is mounted interiorly
of the handle means, secured to the handle half 168b. Lead wires
172 extend from the switch to a connection with the motor means
(not shown) in the usual manner so that appropriate actuation of
the switch will activate the motor accordingly. A trigger member
174 is pivoted to 168b and is linked by means (not shown) to switch
170 so that retraction of trigger 174 actuates switch 170 to the
"on" position in a fashion which is typical for power tools in
other similar electrically operated devices.
A dog 176 is pivoted at 177 to 168b and urged by leaf spring 178 to
normally occupy a position blocking retraction of trigger 174 so
that it is impossible to retract the trigger and therefore
impossible to activate switch 170 when the dog 176 is in the
position as shown in FIG. 5. The dog 176 has a finger 176a which
protrudes upwardly adjacent a key 180 occupying a slot 182 formed
in the top of the handle 46. The key has an enlarged transversely
disposed head or button 184 and a split shank 185, one side 185a of
the shank having an enlargement 186 so that the key shank 185 has a
portion which is wider than slot 182.
Preferably, the key is made of a suitable yieldable material such
as plastic or the like so that the key may be withdrawn from the
slot by the camming of the enlargement 186 past the relatively
smaller confines of the slot 182, this camming facilitated by the
split nature of the shank of a key. In the same manner, the key may
be reinserted in the slot by the reverse movement of that required
to withdraw the same. When so inserted, the enlargement 186
prevents accidental dislodgement or withdrawal of the key from the
slot but, as previously described, it does permit manual extraction
of the key from the slot.
When the key is depressed by pushing on the head or the button
portion 184, the enlarged side 185a of the shank 185 on the key
strikes the finger portion 176a of the dog and rotates the dog
about the pivot 177 in opposition to the influence of spring 178 to
a position where the dog is out of the path of movement of the
trigger 174. Then the trigger 174 may be squeezed to actuate the
switch, the relative positioning of the trigger and the dog for
actuation of the trigger 174 being shown in FIG. 6. The handle
structure is provided with the usual lock button 188 for locking
the trigger in the "on" position as is conventional with powersaws
and the like.
Thus, in operation, to actuate the saw, the key 180 is depressed by
applying pressure to the head or button end 184, thereby swinging
the dog 176 out of its position blocking retraction of trigger 174.
Trigger 174 is then squeezed to retract the same and actuate switch
170, which sends an appropriate signal to the motor in the motor
housing, thereby activating the saw. Once pressure on trigger 174
is released, it returns to the position shown in FIG. 5; and if
pressure is released from the key 180, it also returns to the
position shown in FIG. 5, with the dog 176 blocking retraction of
the trigger 174 and therefore preventing actuation of the device.
During periods of nonuse, the key 180 may be simply withdrawn from
the slot 182 and without the key it is impossible for others to
activate the saw.
It is believed to be obvious that the key-operating system just
described is not exclusively confined to a radial arm saw
application. Any electrically operated hand device using a pressure
switch can be equipped with my key system whereby the device cannot
be operated either without the key or even with the key in place
unless the key is depressed to a point to deactivate the blocking
means so that the device can be switched on and off.
The handle 45 is further provided with light means for lighting the
area of the work station. To this end, the handle is provided with
a switch 190 which is operatively associated with a source of power
(not shown) and with light bulbs 191 which are mounted in sockets
192, see FIG. 7. The usual wiring 193 extends from the sockets to a
suitable connection with the switch structure (not shown). The
portion of the bottom cover half 130b of the handle 45 which
underlies light bulbs 191 may be provided with a translucent or
lightly shaded, slightly opaque panel 194 to thereby cast a
diffused light ray on the area of the worktable 22 immediately
below the handle 45.
The angular position of the arm relative to a central vertical
plane containing the centerline of the column 30 and a line
perpendicular to said centerline and also perpendicular to the
fence 25 on the horizontal worktable 22 is indicated in a novel
manner by means of a scale 195 and an indicator 196. The scale 195
is calibrated on the front surface of a dome-shaped cap 197 snapped
or screwed onto the top end portion of the column 30. The 0
position of the scale 195 lies in the plane defined above. A cover
198 encircles the rear end portion of the radial arm 32 and has a
window 199 facing along the length of the arm. The indicator or
pointer 196 is screwed to the arm along its centerline so that
alignment of the pointer 196 with any number on the scale 195 will
record the angular position of the arm 32 to the left or right of
the vertical plane. The pointer 196 will sweep with the arm past
the fixed scale carried by the column 30.
The radial arm saw of this invention is both safe and convenient to
use. The several controls for positioning the arm of the blade are
all located forwardly on the structure at a point of convenient
access. The indicators for recording the angular positions of the
arm, saw blade and housing are clearly visible. In addition, the
unique key which is associated with the trigger switch for
actuating the saw insures that the saw may not be set in motion
either when the key is withdrawn from the opening in the hand grip
or when the key is withdrawn from the opening in the hand grip or
when the key is not completely depressed and held in the depressed
position. Even with the key in the slot in the handle 45, the motor
cannot be started until the key is depressed.
The foregoing detailed description has been given for clearness of
understanding only, and no unnecessary limitations should be
understood therefrom, as some modifications may be obvious to those
skilled in the art.
* * * * *