Note: Descriptions are shown in the official language in which they were submitted.
EPS/bt
01MP32017
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MOLDED SCROLLER SAW
LOCK BUTTON SPRING
DESCRIPTION
BACKGROUND OF THE INVENTION
This invention relates to a detent mechanism for a hand
held powered tool; more particularly, to a detent spring
molded as part of a plastic housing to provide detents and
an audible indication when traversed in either direction by
a slide button having a projection with tapered sides en-
gaging the spring.
The prior art in detent mechanisms ~or hand held
powered tools has provided for a separate spring and screw
for retaining the same to a molded housing. Such a device
is disclosed and described in U.S. Patent No. 3,729,822,
which relates to a sabre saw having a saw bar which is
manually rotatable and selectively lockable about its own
axis to set the cutting edge of the saw blade in different
angularly oblique positions relative to the line of movement
of the tool. A control knob is coupled to the saw bar by
means which allow the saw bar to reciprocate within the con-
trol knob. Turning of the control knob will cause a like
turning of the saw bar. A lock pin is transversely slidable
with respect to the control knob and is carried by a slide
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button mounted in the handle oE the housing. When the lock
pin is in an unlocked position, the control knob can be
manually manipulated. However, when the lock pin is in a
locked position, a tapered tip thereof will lock the con-
trol knob by engagement with angled slots in an externalflange of the bushing for the saw bar, so as to prevent
turning of the control knob. In the prior art U.S. Patent
No. 3,729,822, the slide button is retained in the locked or
unlocked position by a keeper implemented by a light leaf
spring which cooperates with tapered sides on the slide
button to define a particular position. This light leaf
spring is retained to the tool housing by a screw. The dif-
ficulties with this arrangement are the cost of the screw
and of the leaf spring, plus the cost of assembling the
spring to the housing. Further, variability in manufac--
turing of the leaf spring frequently causes the detent to be
excessive or insufficient at times, necessitating dis-
assembly of the housing and reforming or replacing of the
leaf spring until a proper detent is attained.
SUMMARY OF THE INVENTION
The above noted disadvantages are avoided in the ar
rangement in which a scroller lock button spring is molded
as part of the housing for the sabre saw. The sabre saw
housing is a clam shell design having a support half for
the components of the sabre saw and a cover half substantial-
ly a mirror image of the support half. The plastic spring
is molded, for example, with the cover half and extends with
an arched upper and lower sur~ace for increased regidity,
from a web thereof con~iguous the slide button which is
slidably trapped between the support half and the cover half
of the sabre saw. When the operator slides the slide button
back and forth between the locked and unlocked position for
the control knob, tapered sides and flat base portion on a
projection thereof engage with the p}astic spring, and the
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operator feels a noticeable detent when in the locked or
unlocked position and is provided with an audible indication
when traversing from one position to the other by the de-
~lection and snap back of the plastic spring. The arrange-
ment thus provided avoids the variability in manufacture ofthe prior art leaf spring and in location of the same with--
in the housing so as to provide for a uniformity of effort
required to actuate the slide switch due to the uniformity
of location and stiffness of spring.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated in the accompanying draw-
ings in which:
FIG. 1 is a longitudinal elevational view, partly in
section, of a sabre saw illustrating a preferred embodiment
of the present invention;
FIG. 2 is an enlarged perspective view of the scroller
slide lock arrangement; and
FIG. 3 is a view of the lock button in the opposite
extreme position from that shown in Figures 1 and 2.
DETAILED DESCRIPTION OF THE INVENq'ION
. .
~ ith reference now to the drawings, particularly to
FIG. 1 thereof, there is shown and illustrat~d therein a
sabre saw designated generally by the ref~rence character
10. While a sabre saw 10 is illustrated, it is to be under-
stood that the invention to be explained below might be
included in any power hand tool having a switch in which
discrete positions and audible indication of traverse from
one position to another is required.
The sabre saw 10 comprises a motor housing portion 12,
a front or drive housing portion 14, and a handle portion 16
of clam shell construction in which, as is known in the art,
the components of the sabre saw are mounted in a support
half which is closed off by a cover half that is substan-
A 35 tially a mirror image of the support half. A portion of the
sabre saw 10 has been broken away to expose the cover half
18 of the handle portion 16 construction to which the
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invention has been added. A trigger switch 20 is shown ex-
tending from the handle portion 16, depression of which
serves to initiate endwise reciprocation of a saw bar 22 and
saw blade 23 attached thereto, in a manner well known in the
art. An electric cord 26 extends from the handle portion 16
to a source of power to enable operation of the sabre saw
10. The saw blade 23 extends through a work contacting shoe
28 to operate upon the work positioned therebeneath.
The saw bar 22 extends up~ardly through the drive
housing portion 14, in a manner which allow~ it to be
selectively endwise reciprocated by action of the trigger
switch 20, while it is free to turn about it's axis within
the drive housing portion 14. Such a teaching is ~ontained
in the U.S. Patent No. 3,729,822 issued on May 1, 1973, to
Batson, and assigned to the assignee of this invention.
A saw bar 22
reciprocates within a bearing ~not shown) in the bottom of
the drive housing portion 14, and a journal bushing 30
captured in the top of the drive housing portion and fully
explained in the above referenced patent to which the
reader is referred. It is sufficient to note that the saw
bar is formed with a pin 32 extending therethrough at the
top thereof, the ends of the pin extending into diametral
slots in the internal diameter of ~ournal bushing 30. Thus,
rotation of the journal bushing 30 will implement rotation
of the saw bar while allowing endwise reciprocation thereof.
A control knob 34 is attached to the journal bushing 30 by
set screw 35. The journal bushing 30 is further formed with
a flange 38 having four tapered slots 40 extending radially
inwardly from the periphery thereof, only two of which are
shown. The tapered slots 40 of the flange 38 of the journal
bushing 30 are used to locate the saw bar 22 in the four
discretP angular positions. In order to effectively utilize
the sabre saw 10 with the saw bar 22 and saw blad~ 23 at
tached thereto in an angular position provided for, a means
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must be provided for locking the control knob 34 and the saw
bar 22 in the selected angular position. As disclosed in
the above referenced U.S. Patent No. 3,729,822, this is ac-
complished by providing a slide lock button ~4 having a lock
pin 45 extending therefrom, the lock pin having a tapered
front surface 46 to be received in the tapered apertures 40
of the flange 38 of the journal bushing 30. The slide :Lock
button 44 is slidably mounted within the handle portion 16
adjacent the upper surface thereof, so -that a button portion
47 having a stepped upper surface which inclines downwardly
in either direction from the high point in the center there-
of, projects through an aperture 48 formed in the upper sur-
face of the handle for ease and convenience of operator
actuation thereof. The slide lock button 44 further in-
cludes a central fin 49 on which the button portion 47 sits,which fin projects sidewardly into slots 50 formed in the
handle portion 16 to support the slide lock button 44.
Below the central ~in 49, the slide lock button 44 is
fashioned with a protuberance 52 which supports the lock
pin 4~ and a downwardly extending projection 53 with tapered
sides 55 which extend towards each other to terminate in a
flat base portion 54. Preferably, the slide lock button 44
is molded with the lock pin 45 as an insert thereto.
Referring to FIGS. 1 and 2, there is molded as part of
the handle portion 16, a plastic spring 60 formed as part of
and extending cantilevered from the cover half 18, although
it might have also been formed as part of the support half
19. The plastic spring 60 is formed with an arched upper
and lower surface to increase rigidity and spring constant,
and to provide a surface to coact with the tapered sides 55
and flat base portion 54 on the slide lock button 44
beneath which it extends. The plastic spring derives ad-
ditional support from support rib 62 connected to support
rib 63 extending between posts 64. The plastic spring 60
is arranged to have the arched upper surface thereof coact
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with the flat base portion 54 and tapered sides 55 of slide
lock button 44 during withdrawal or engagement of the
tapered front portion 46 of the lock pin 45 with the tapered
aperture 40 in the journal bushing 30. As the flat base por
tion 54 of the slide lock button 44 is drawn over the canti-
levered portion of the arched surface 60, a detent action is
felt indicating the transition from a first to a second posi-
tion, or vice versa, of the button. An audible indication
of the transition is provided by the cantilevered arched
surface cooperating with the slide lock button 44. In order
to obtain an appropriate detent, that is, one that is
tactile or evident to the touch, and also an appropriate
audible indication, the spring constant of the plastic
spring 60 may be adjusted by changing the thickness between
the arched upper and lower surface, as well as by modifying
where possible the length of the plastic spring between the
point of contact of the slide lock button 44 and the point
where the spring merges into the housing. By merging the
plastic spring 60 with the rib 62 of the cover half 18, ad-
ditional rigidity for the plastic spring is provided without
requiring a buildup of material on the cover half to obtain
a shorter plastic spring. Thus, a selected length for the
plastic spring is established by the depth of the support
rib.
25As shown in Figure 3, the slide lock button ~4 is
indicated in the opposite extreme position from that shownin Figures 1 and 2, the opposing abutment surfaces 42 and
51 being clearly indicated.
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As indicated by the above description, a new and
improved detent mechanism has been provided which also pro-
vides an audible indication of actuation. This invention
has allowed the elimination of parts and obviated the oc-
casional necessity for disassembly and realigning of a metallock button spring.
The invention was described with respect to a preferred
embodiment. Various changes may be made without departing
from the spirit and scope of the invention.
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