Note: Descriptions are shown in the official language in which they were submitted.
ELECTRICAL CONNECTlûN SYâTEM FOR MOTORS
CROSS-REFERENCE TO RELATED APPLICAT101~,'
The subject matter of this patent application is
related to that disclosed in corresponding Canadian
5 . application Slrial No. 447,398 _ , filed
on. May 8, ?~_ , for Electrical Connection System
for Switches, and assigned to ~he same assignee as the
present application.
This is a divisional of application 447,400, filed
February 14, 19 84.
FIELD OF THE INVE~TIO~'
The present invention relates to an improved system
for the electrical connection of electric motors, and more
particularly, to the electrical connection Or universal
motors used in power tools and other devices.
BACKGROUND OF THE INVENTION
lS In power tools and related devices, the motor housing
comprises a field case, which may be made from a
dielectric or insulating material (such as a suitable
plastic which may be injection molded for economy of
manufacture). The field case may include an integral weh
portion having a rear bearing boss and further having a
plurality of circumferentially-spaced bridge members
joining the rear bearing boss to the generally-cylindrical
main portion of the field caseO The universal motor
-2-
includes an armature and a field. The field is inserted
within the field case and is secured therein. The
armature is inserted within the field and has a shaft
journaled in a bearing in the rear bearing boss. A
commutator is carried on the armature shaft, and
spring~loaded brushes are slidably received in respective
brush holders mounted on the field case for engagement
with the commutator. With this arrangement the motor
wire-up must often be conducted by hand.
Also the prior art has resorted to various forms of
manually-manipulatable reversing members. For example,
the reversing member may be adapted to ro~ate a hrush
carrier pivotally mounted in the tool housing. Access ~o
the reversing member is through an aperture in the tool
housing.
While generally practical for the purposes intende~,
these structures (with or without the separate reversing
mechanisms) are not readily adaptable to a wide range of
power tools, appliances and other motor-driven devices for
standardization of manufacture and assembly. Moreover,
the electrical connection of the motors within the final
product inYolves various wires and connections which
further delay the overall assembly time, and inhibits
reali~a~ion of many beneits associated with automation of
the assembly processes. This is especially important
during the assembly of a compact power tool having
relatively high motor performance and further having an
overall "double insulated" design.
SUMMARY OF THE INVEN~ION
Accordingly the present divisional case in one aspect
provides a reversing switch for an electrical device having
a housing, comprising: a support member, means for rotatably
--3~
mounting the support member on the housing, means formed on
the housing and the support member for restric-ting the movement
of the support member to thereby accommodate a limited pivotal
movement of the support member relative to the device, a pair of
spaced-apart reversing contacts wherein the major flat surfaces
of the contacts are formed in a prescribed arc to provide a
natural resiliency in the contacts, the contacts carried by the
support member, each of the reversing contacts having bifurcated
end sections formed in a continuation of the prescri.bed arc in
end portions of the reversing contacts, two pairs of contact means,
and means for mounting the two pairs of contacts on the device and
in position for selective engagement, alternately, with the
bifurcated sections of the respective end portions of the reversing
contacts.
lS In a further aspect the present divisional provides a reversing
switch for an electrical device having a housing, comprising: a
support member, means for rotatably mounting the support member on
the housing, means formed on the housing and the support member
for restricting the movement of the support member to thereby
accommodate a limited pivotal movement of the support member
relative to the device, spaced-apart reversing contacts mounted
within the support member and formed to provide a natural
resiliency in the contacts, the housing for the device including
a portion having an external annular surface, two pairs of contact
elements fixedly mounted on the housing, each of the contact
elements having respective end portions supported on the external
annular surface of the housing portion, and the contact elements
being mounted on the housing in position for alternately engaging
the respective reversing contacts, the respective contact elements
being wedged in a radial direction between the housing portion and
the support member of the reversing switch.
In a still further aspect there is provided the method of
assembling a reversing switch, comprising the steps of providing
an inner annular member made from an insulating material, the
inner annular member having first keying means therein, providing
--4--
a pair of arcuately-formed reversing contacts, mounting the
pair of reversing contacts wlthin the inner annular member,
whereby the reversing contacts are spaced-apart, circumerentia.~1y
with respect to each other and whereby the reversing contacts
S project radially within the inner annular member, providing an
outer a.nnular member made from an insulating material, the
outer annular member having second keying means therein, circum-
ferentlally aligning the outer and inner annular members, and
moving the members axially towards one anotller, whereby the inner
member is nested within the outer member, and whereby the first
and second keying means are brought together thereby assuring
conjoint rotation of the members.
The motor housing comprises a ~olded field case having
an integral web portion including a plurali~y of
circumferentially-spaced bridge members joining the rear
bearing boss to the generally-cylindrical main portion of
the field case. Openings (or channels) are formed in the
brid8e members for ~ounting the respective contact
elements therein. These contact elements are formed as
bent contact strips, at least some of which are can~ilever
mounted on the respective bridge membersO
These and other objects of the presen~ invention will
become apparent from a reading of the following
description, taken in conjunction with the enclosed
d rawi ng s .
BRIEF DESCRIPTIO~' OF THE DRAh'lNGS
~ IGURE l is a side elevation of a typical power ~ool
which is illus~rative of one type o~ products to which ~he
2~
teachings of the present inven~ion may be applied;
- FIGURE 2 is the circled portion of Figure 1, drawn to
an enlarged scale, and wi~h parts broken away and
sectioned to illustrate one e~bodi~ent of the present
invention,
FIGURE 3 is a rear elevation of the tool shown in
Pigure 2, but with ~he rear handle cover removed, and
showing an annular wire harness mounted on the rear
bearing boss of the integral web portion of the field case;
FIGURE 4 is a section view, taken slong the lines 4-4
of Figure 3 and drawn to an enlarged scale, showing the
armature shaft journaled in a bearing in the rear bearing
boss, and further showing the brushes mounted in
respective brush hvlders and engaging the co~mutator on
15 the armature shaft;
FIGURE 5 is a section view, taken along the lines 5-5
of Figure 3 and drawn to an enlarged scale, showing one of
the first pair of contact elemen~s carried by the
respective bridge members 9 and further showing one of the
rearwardly-projecting terminals on the field assembly
which automatically engage the forwardly-projecting end
portion of the respective contact element when the field
subassembly is inserted within the field case and is
secured therein;
FIGURE 6 is a section viewg taken along the lines 6-6
o$ Figure 3 and drawn ~o an enlarged scale, showing one of
the second pair of contact elements carried by the
respective bridge members, and further showing a portion
of the annular wire harness mounted on the rear bearing
30 boss, the respective contact on the wire harness engaging
the rearwardly-projec~ing end portion of the respective
contact elemen~;
FIGURE 7 is a section view, taken along the lines 7-7
of Figure 6 and drawn to an enlarged scale, and showing
the respective channel-shaped bridge member for supporting
one of ~he second pair of contact elements;
~ ~IGURE 8 is an exploded perspective, showing ~he
integral web por~ion on the rear of the field case, the
firs~ and second pairs of co~act elements~ and the wire
harness to be mounted on the rear bearing boss on ~he
field case;
FIGURE 9a, 9b, and gc are schematic views, some in
exploded for~, showing the method of assembly of the
conventional motor components in relation to a preferred
em~odiment of the electrical connection sys~em of the-
present invention;
FIGURE 10 is an alterna~e embodiment of the wire
harness of Figure 8;
FIGURE 11 corresponds substantially to Figure 2, but
shows a second embodiment of the present invention,
including a reversing subassembly;
FIGUR~ 12 is a rear eleYation, ~aken along ~he lines
12-12 of Figure 11, but with the rear handle cover removed;
FIGURE 13 is a partial top perspective of the rear
handle coYer assembled to the field case, showing the
accessible portion of the reversing subassembly nested
within a dwell în the rear handle cover;
FIGURE 14 is an exploded perspective, similar to
Figure 8, but showing the three pairs of contact elements
mounted on the integral web portion of the field case, and
further showing the components of the reversing
subassembly including the pair of spaced arcuate contacts;
FIGURE 15 is a section view, taken along the lines
15-lS of Figure 14 and drawn to an enlarged scale, and
showing one of the third pair of contact elements oarried
by the respective bridge member on the web portion of the
field case;
FIGURE 16 is a front elevation of the reversing
member, ~lookiJIg from field rearwardly towards the handle)
35 in its assembled form and drawn to an enlarged scale~ the
- ~L2~
broken lines showing the respective rearwardly-projecting
- end portions of the second a~d ~hird pair o contact
elements for reversibly eng~ging ~he respective pair of
spaced arcuate contac~s on ~he reversing subassembly~
FIGURE 17 is a section Yiew, taken along the lines
17-17 o Figure 16;
F15URE 18 is a plan layout of one of the arcuate
contacts on the reversing memberD showing its
longitudinally-split bifurca~ed contact portions; and
. FIGURE l9a, l9b and l9c are electrical schematic
diagrams, respec~ively showing one ~non-reversing)
e~bodiment, an alterna~e ~reversing) em30diment in its
"forward" position, and the al~ernate (reversing)
embodiment in its "reverse'l position.
FIGURES 20a and 20b are electromechanical schematic
dia~rams showing the operation of a double reduction drive
system of the present invention in forward and reverse,
re spec~ i vely .
FIGURES 21a and 21b are electromechanical schematic
20 diagrams illustrating the compensating means of the
present invention in a triple-reduction transmission, in
forward and reverse, respectively.
DESCRIPTION OF THE PREFERRE~ EMBODIMENT
With reference to Figure 1, there i5 illustrated a
portable electric drill 10. It will be appreciated by
those skilled in the art, however, that the scope of the
presen~ invention is not restric~ed thereto, but that the
teachings of the present invention are equally applicable
to a wide variety of power tools, appliances and other
electric motor driven devices~ and indeed~ to a wide
variety of electric motors, per seO With this in mind,
the drill 10 generally comprises a motor housing ll, a
gear case 12 secured forwardly of the motor housing, a
chuck 13 forwardly of ~he gear case, a trigger switch 14
-for controlling the energization of ~he tool, a rear
handle cover 15 secured rearwardly of the motor housing, a
pistol-grip handle 1~ depending from the motor housing,
and a strain relief means 17 depending fro~ the handle,
the strain relief means being assoeiated with a li~e cord
(not shown) or connection to a suitable power source.
With referçnce to Figures 2-89 the motor housing
comprises a field case 18 formed from a suitable
insulating or dielectric ~aterial. Preferably, the field
case is injection molded from a suitable plastic material
having relatively high impac~ s~rength and structural
rigidity, as well as good electrical insulating
qualities. The field case includes a generally-
15 cylindrical main portion 19 and further includes a rearweb portion ~or spider) 20 formed integrally therewith.
The web portion 20 includes an annular rear bearing boss
21, and a plurality of circumferentially-spaced inclined
bridge members 22 joining ehe bearing boss to the main
portion of ~he field case, as shown in Figure 8. The
field case further has a rearwardly-projecting boss 23, as
shown in Figure 2, and the rear handle cover is secured
thereon by means of a ~astener 24.
An electric motor 25 is housed within the ield case.
~s The motor is of the universal type and încludes a stator
or field subassembly 26 and a rotor or armature
subassembly 27 nested therein. The field subasse~bly
includes a field core or stack of laminations 28 having
longitudinal passageways 29 for respective screws 30. The
screws extend beyond the field st~ck, and a molded carrier
31 ~for the brushes) is piloted ~hereon. The field stack,
together with the screws and brus}l carrier9 is inserted
within the open forward portion 32 of ~he field c~se and
is seated therein; and the screws are received in
L2~
respective holes 33 in the rearward portion of the field
case. As a resul~, the field subassembly i5 secured
within the field case, and the brush carrier is retained
between the ield subassembly and the field case~ The
carrier includes rearwardly-extending brush holders 34,
diametrically opposite to one another as shown in Figure
4, for receiving respective brushes 35. The brushes are
resilien~ly biased by respec~ivç springs 36 re~ained
within the holders Each of the brushes has a shunt wire
37; the end of each shunt is provided with a terminal 38.
The armature has a shaft 39 journaled in a bearing 40 in
the rear bearing boss. The armature shaft carries a
commutator 41 shown in Figures 2 and 4~ for engagement
with ~he brushes. The field subassembly also includes a
15 terminal block 42 with terminal means thereon.
Preferably, the terminal means includes four terminals,
one of which is shown at 43 in Figure 5. The motor field
is of the two-coil type, each of the coils having two
leads (not shown) which are connected to the our
terminals 43 in a suitable manner.
In accordance with the teachings of the present
invention, a plurality of contact elements 4S, 46 are
carried on the integral rearward portion of the inslulated
~ield case. As shown in Figures 5 and 6, the respecti ve
bridge members have slots or openings 44 formed therein.
Each of the openings 44 is formed in the upper portion of
its respective bridge member, substantially adjacent ~o
the main portion of the field case. As shown in Figure 8,
first and second contact elements, 45 and 46,
respectively, are received in the respective openings in
the bridge members. (These eontact elements may be
mounted on the housing in first and second pairs,
respectively.) Each of the contact elements includes a
sui~ably formed or bent contact strip. Each of ~he bridge
members has a rearward ledge (or face) 47 and a forward
--10--
ledge (or face) 48, adjacen~ to the respective openings
and transverse theretoO Each of $he contact strips has a
~ain body portion formed with a downwardly-plojecting
lanced-out tab 49 ~nd a downwardly-ben~ ledge 50. With
~his arrangemen~, and as shown more clearly in Figures 5
and 6, each contact strip may be inserted forwardly
through i~s respective openings, such ~hat i~s ledge 50
engages the rearward ace 47, and such that its lanced-out
tab springs down and engages ~he forward face 48, thereby
axially retaining each contact strip in its respec~ive
opening with respect to the respective bridge member. The
contact strips are thus cantilever mounted and have
forwardly-projecting ends or end portions 51. The
terminals on the field are each provided with leaf-spring
emale sockets 57 (or other sui~able socket ~eans) for
enBagement with the respective forward ends of the contact
strips, as shown m~re clearly in Figures 5 and 6, thereby
making electrical contact be~ween ~he firs~ and second
pairs of contact strips 45) 46 and the coils on the field
subassembly. This engagement and electrical connection
between the contact strips and the field terminals occurs
automatically upon the insertion of the field within the
field case and the securing of the field ~herein. The
first pair of contact strips have respective cantilevered
25 rearwardly-projecting ends or end portions 531 as shown in
Figure S, The second pair of contact strips 46 have
respective downwardly-inclined rearward portions ~4
supported in complementary channels 55 formed on the
respective bridge members, as shown in Figures 6 and 7.
These inclined rearward portions have respective rear ends
56~ ben~ thereto, and disposed adjacent to the external
annular surface of the rear bearing boss.
A wire harness 57 is provided in accordance with the
further teachin~s of the present invention. The wire
harness 57 is made from an insulating material (such as a
~uitable molded plastic~ and is annular in form, although
it ~ay take other forms as well, depending upon ~he shape
of the motor housing. Spaced contacts 58 are mounted on
~he wire harness and are connected to respective
5 conductors 59 carried thereon. The annular wire harness
is receivçd on the rear bearing boss and ~ay be
press-fitted thereon. As a result, ~he contacts on ~he
wire harness enga~e the rearward ends of the second pair
of contact strips, making electrical connection thereto,
as the rearward ends of the contact s~rips are wedged
between the bearing boss and the contacts on the wire
harne$s tas shown in Figures 6, 9b and 9c). The wires on
the wire harness are then connected to the switch ~in a
conventional manner), which is ultimately connected to a
source of elec~rical energy.
Thus, it will be appreciated that the first and second
pairs of contact strips 45 and 46, respec~ively, in
co~bination with the wire harness 57, ~reatly facilitate
the connection of the field to the brushes and ~o ~he
switch leading to the power source. The formed contact
strips are easily inserted into the integral web portion
of the field case; the terminals on the field
automatically engage the respective con~act strips when
the field is inserted into the field case and is secured
~5 therein; the terminals on ~he brush shunts are readily
slipped over two of the contact strips and connec~ed
thereto; the wire harness is ~ounted on the rear bearin~
boss for automatic engagement with the remaining two
contact strips on the web, and finally, the wires on the
wire harness are connected to the switch in the usual
manner. With this arrangement, a plethora of loose wires
is eliminated; assembly and electrical connection ti~e are
subs~antially reduced; and the motor connections are
standardized for a wide variety o power tools, appliances
or other motor-driven devices. Thus opportunities for
~ 2 ~
automated asse~bly are enhanced~ since ~ost of the
~assembly ~otions described above are in directions
parallel to the axis of ~he motor. Thus each brush shunt
is a first means for connec~ing the rearward end portions
of one of the first or second cont~ct elements (or pairs
of contac~ elements) to at least one of ~he ~rushes; and
the wire harness is a second means for connecting the
rearward end portion of the o~her of the contact elements
(or pairs of elements) to a source of elec~rical energy.
- With reference to Figures 9a9 9b, and 9c, the
advantages and benefits of the impro~ed apparatus and
method of the present invention will be readily
appreciated. As shown in Figure 9a, the contac~ strips 45
and 46 are mounted on the rearward portion of ~he field
case 18, being slipped into their respec~ive openings 44
in the bridge members 22. The mounting scre~s 30 are
slipped into the field subassembly 26, extending
therethrough, and the brush carrier 31.The field
subassembly ~with the brush carrier) is inserted through
the open forward portion 32 of ~he field case, is sea~ed
therein, and the screws are driven into the field case.
In this manner ~he four terminals 43 on the field
automatically engage (and hence make electrical
connection) to the cantilevered forward ends 51 of the
~our contact strips 45, 46, as shown in Figures 6, 9b, and
9c. The armature 27 is inserted within the field, such
that its commutator-end bearing 40 is recei~ed within the
rear bearing boss 21, and when the armature i5 in placeg
the brushes 35 are released to engage the commu~tor 410
The brush shunt terminals 38 are connec~ed to the
cantilevered rearward ends 53 of the first pair of contact
strips 45. The wire harness 57 is mounted on the rear
bearing boss 21, such that its contacts 58 are wedged
against (and hence ~ake electrical connection with) the
3~ resr ends 56 of the remaining (second) pair of contact
strips 4~. The wires 59 on the wire harness 57 are t~en
~connected ~o the switch.
With reference to Figure 10, a modified wire harness
57' includes means for retaining the annular harness or
member on the housing, including a pair of subs~antially
diametrically opposed resilient latch members 60 formed
integrally therewith. These latch ~embers define ~atch
apertures 61 and project forwardly of the wire harness.
The latch members 61 are sufficien~ly flexible, such that
~he latch member may be flexed slightly (outwardly) as the
wire harness 57' is slipped over the rear bearing boss
210 The respectiYe latch apertures 61 engage latch bosses
61a on the bearing boss (as shown in Figure 8) and the
wire harness 57t is retained on the bearing boss with a
"snap ac~ion". Moreover, if desired, the wire harness 57'
may be provided with a suitable key (not shown) for
cooperation with a corresponding keyway on the bearing
boss (again, not shown) to 2ssure the proper
circumferential position of the wire harness on the
bearing boss for proper engagement between the contacts 58
and the ends 56 on the second pair of contact strips 46.
Moreover, and again if desired, the shape of the wire
harness could be other than annular, and could be f ixedly
mounted elsewhere within the housing.
With reference to Figures 11-1~, a second embodiment
of the present inYention is provided. In this second
embodiment, a reversing subassembly 62 is used in lieu of
a wire harness, and a ~hird bent contact strip 63 is
mounted on the bridge as shown in Figures 14 and 15.
~Again, the third cont~ct strip may be ~ounted on the
housing in third pairs of contact elements.) The
reversing subassembly 62 includes an ou~er (or first)
reversing member 64 which is a support member preferably
made from an insulating material 9 such as a suitable
molded pl~stic. This first reversing member 64 has means
~2~
-14-
for rotatably retaining the reversing subassembly on the
rear portion ~f ~he housing, including a resilient plug 66
shown in Figure 17, and which is engaged by a portion of
the handle 15~ as shown in Figurç 11. The resilient plug
66 therefore ac~s as a vibration isolation ~eans between
the handle and the res~ of the tool. In this manner, the
outer reversing member is mounted on the bearing boss for
a limited rotary or pivoted movement thereon, but is
precluded from axial dislodgement therefrom.
An inner (or second) reversing member 68 is nested
within the outer reversing memberp as shown in Figures 16
and 17, and is keyed thereto (as at 69) for conjoint
limited rotary movement therewith. This inner reversing
member is also made from an insulating material, such as a
15 suitable molded plastic. A pair of curved contact means,
or spaced-apart arcuately formed reversing contaets 70 are
carried by the inner reversing member, and are ~ounted
transverse to the plane of the reversing member. These
reversing contacts 70, as shown in Fi~ure 18, each have a
cen~ral portion 71 and longitudinally-split bifurca~ed
contact-engaging ends 72 and 73, respectiYely. Each of
these ends are in turn provided with respective dimples 74
for engagement with the respective rearwardly-projecting
ends of the second and third pair of cont~ct s~rips, 46
and 63~ respectively, as shown in Figure 16. Also as
shown in Figure 16, this bifurcated configuration is part
of a ~eans for compensating for tolerance buildup
associated with the po~ential differenees in radial
distances Rl, R2 to the respective ends 56, 76 of the
cantilever-mounted contacts 46, 73. ~here Rl does not
equal R2, a single cantilever-mounted curved contact
strip could enBage strip 46, and be levered out of
engagement with strip 63. Therefore by splitting contact
strip 70 into two strips of different lengths, the strips
are self~biased, more or less independently) against
contact elements 46, 63, thereby taking up variations in
their respectiYe radial distances from the axis "A" of the
subassem~ly, &nd accommodating stress due to the amount of
deflection in the free ends of the strips. Further, and
5 as shown in Figure 14~ the rearwardly-projecting ends 53
of the iEirst pair of contact strips 45 are connected to
the switch ( in a suitable manner); the forward ends 75 of
the third pair of contact strips 63 (shown in Figures 14
and 15) are connected to the brush shunt terminals 38; and
the forwardly~projecting ends of ~he first and second
pairs of contact strips 45 and 469 respectively,
automatically engage the four ~erminals 43 on the field
(as in the first embodiment of Figures 2-8)~ The
rearwardly-projec~in~ respective ends 56 and 76 of the
second and third pairs of contact strips, 46 and 63, are
alternately connec~ed to the arcuate reversing contacts 70
for reversing the electrical connections be~ween the field
and the armature for reversing the motor rotation in the
conventional manner. Thus the reversing subassembly
includes reversing means for selectively interconnecting
the respective rearward end portions of the second and
third pairs of contact elements ~o change the direction of
rotation of the armature. However it should be noted that
reversing subassembly 62 need not include discrete
reversing members 64, 68. Instead, members 64, 68 may be
integrally ~olded as one unit. Thus the reversing
subasse0bly is yet another for~ of the first means for
connecting the rearward end portions of one of the first
or second contact ele~ents (or pairs of contact elements)
to ~t leas~ one of ~he brushes.
With reference again to Figures 12-149 the reversing
subassembly 62 has a radially-extending integral por~ion
or switch operator 77 which is formed with a generally
oval aperture 78 wi~hin which the rearwardly;projectin~
boss 23 on the field case is received. The integral
~2~
portion 77 is further proYided with a ~anually-~anipulate~
-portion or serrated reYersing bu~ton 79 which passes
through an opening 80 in the rear switch cover and is
nested within a dwell 81 therein tas shown in Figure 13).
The reversing subassembly also has a downwardly-projecting
integral tab 82 for interlocking engagemen$ with the
switch, thereby precluding movement of the reversing
subassembly in the "on" position of the switch. As shown
in Figure 17,`if desired9 a-fel~ washer 83 may be tr~pped
between the reversing subassembly and the field case t.o
minimize the flow of dirt or dus~ particles to the
reversing contacts and the rearwardly-projecting ends of
the respective contact s~rips.
With reference eo the schematic diagrams of Figures
l9a, l9b, and l9c, the electrical interconnection of the
present invention will be further appreciated. In the
non-reversing embodiment of Figure 19A~ the firs~ contact
elements 45 connect the field coils 84, 85 to the brushes
35 on the armature 27, and the second contact elements 46
connect the field coils to the switch 14 (Yi8 the wire
harness 57) to the power source 8~. In the reversing
embodiment shown in Figures l9b and 19c, the first contact
elements 45 now connect the field coils 84, 85 to the
switch 14~ and the second contact elements 46 and third
contact elements 6~ reversibly cGnnect the field coils ~4,
85 to the brushes 35 via the reversing subassembly 62.
The reversing subassembly has two alternate positions; the
first or "forward" postion is shown in Figure l9b, and the
second or "reverse" position is shown in Figure l9c.
Another advantage of the electrical interconnection
and reversing systems of the present invention is the
creation of a drive system having compensating means for
csusing the output shaft to rotate in a predetermined
direction responsive to movement of the reversing switch
from a first (forward) position to a second (reverse)
~.2;2~
17-
position, for any given number of trans~isslon drive
elements. This ea~ure is illus~rated in Figures 20a and
20b, showing a double-reduction tr~nsmission 100, and in
Figures 21a and 21b, which illustrate a ~riple-reduction
transmission 102~
The drive system schematically shown in ~igure 20a
includes armature shaft 39, which rotates in one directio
indicated by arrow 104 ~correspondin~ to the current
direction indicated by arrow 106), when the reversin~
swi~ch is in its "forward" or first position. The drive
system further includes "N" number of drive elements 108
which form a ~ransmission connecting the armature shaft 39
to the output shaft 110, which rotates in a predetermined
direction indicated by arrow 112. Referring now to Figure
20b, when the reversing switch is moved to îts second or
"reverse" position, the current flow 106 is reversed,
thereby reYersing the armature shaft direction of ro~ation
104 and the ou~put shaft direction of rotation 112.
HoweYer~ i~ is now necessary to address the problem posed
when the drive system for a particular application
includes "N ~ 1", "N ~ 2" or another number of drive
elements 108, since changing the number of drive elements
from one application to another will result in changing
the direction of rotation 112 of the output shaft 110 for
a given direction of current flow, Also it is desirable
to maintain the orientation of the "forwardl' and "reverse"
positions of switch reversing button 79 with respec~ to
the housing configurations, ~5 shown in Figure 13, whether
the particular power tool or other applicstion contains a
3~ double- or triple-reduction transmission. The solution to
the problem is the compensating means shown in Pigures 21a
and 21b, and in Figure 16. Referring now to Figure 169 an
alterna~e keyway 69a is formed at diametrically opposi~e
points on the inner (reversing) member 68, and i5 spaced
cireumferentially approximately 25 from keyway 69.
~2~
-18
Recalling that Figure 16 is taken looking rearwardly from
the field, and that Figures 20a, 20b, 21a and 21b are
taken looking forwardly ~oward the field~ it can be
apprecia~ed that if the subassembly of curved contact
strips 70 and (inner) reversing member 68 is first rota~ed
25, and then assembled so that alternate keyway 69a is
now located at the position formerly occupied by keyway
69, the curved contact strips 70 will therefore be
selectively oriented or locatable wi~h respect to the
respective contact elements 56, 76, (and to the first ~nd
second switch positions) as shown in Fi~ures 21a and 21b.
The result is a change in direction of current flow, as
seen when comparing Figure 21a with Figure 20a, and Figure
21b with Figure 20b. Therefore when it is desired to use
the subject invention in conjunction with a
triple-reduction reversing power tool instead o a
double-reduction reversing power tool, the tool is
assemblet with ~ reversing subassembly utilizing keyway
69a as just described7 thereby yielding the same
predetermined direction of ro~ation for output shaft 110
as was generated in the double-reduction system. This can
be seen by again comparing ~igure 21a with Figure 20a ~ and
Fi~ure 21b with Figure 20b. It can be appreciated that
this feature of the present invention is ~pplicable not
only to drive systems u~ilizing gear trains, but to belt
drives, chain drives, rollers, ~hreads, and others.
However it should be noted then if the reversing
subassembly 62 does not include ~wo discrete members 649
68, but rather is composed of a single integrally-molded
~ember, compensation for variations in the number of
transmission elements can be effected by molding two types
of reversing members, such that one type orients the
reversing contacts 25 with respect to ~he other type.
Thus it will be ~ppreci~ted that the first and second
pairs of contact elements (s~rips 45 and 46, ~espectively)
~9~
--19--
are used in both embodiments, that is, the non-re~ersing
embodiment of Figures 2-B, and reversin~ smbodiment of
Figures 11-18. In ~he non-reversing emebodiment, ~he wire
harness 57 ~or 57' ) is used; and in the reversing
5 embodimen~, ~he reversing subassembly 62 is used in
addition to the third pair of contact elements (strips
63). Preferably9 both the wire harness 57b and the
reYersing subassembly 62 are mounted on the re~r bearing
boss. In each case~ the pairs of respectiYe contac~s 58
10 and 70 carried by the wire harness and reversing
subassembly9 respectively automatically engage (and make
electrical contact with~ the respectiYe rearward ends of
the appropriate contact elements. The contact elements
are mounted on the integral web portion of the field case;
and in each case, the forward ends of two pairs of contact
elements automatically engage (and make electrical contact
with) the four terminals on the field, when the fleld is
seated within the field case and is secured therein. As a
result, the electrical connections for the motor are
greatly simplified; standardiza~ion is assured for a wide
variety of motors, both reversing and non-reYersing;
production economies are re~lized; and the quality,
relisbility and serviceability of the end product are
substan~ially improYed.
Obviously, many modifications ~ay be made without
departing from the basic spirit of the presen~ invention.
Accordingly, it will be appreciated by those skilled in
the art that within the scope of the appended claims 9 the
inYention may be practiced other ~han has been
specifically described herein.
