U.S. patent application number 12/816614 was filed with the patent office on 2010-10-07 for mid-handle drill construction and assembly process.
This patent application is currently assigned to Black & Decker Inc.. Invention is credited to Edward J. Grasso, Craig A. Oktavec, James D. Schroeder, Paul K. Trautner, Paul S. White, Paul J. Wisniewski.
Application Number | 20100252295 12/816614 |
Document ID | / |
Family ID | 40436251 |
Filed Date | 2010-10-07 |
United States Patent
Application |
20100252295 |
Kind Code |
A1 |
Schroeder; James D. ; et
al. |
October 7, 2010 |
MID-HANDLE DRILL CONSTRUCTION AND ASSEMBLY PROCESS
Abstract
A power tool can include a gear case, a motor having first and
second sets of lead wires, a housing assembly, and a field case.
The field case may include a front portion configured for engaging
the gear case and a rear portion. The housing assembly may include
first and second generally symmetrical housing segments configured
for engaging the field case and forming a mid-handle grip. The
first set of lead wires may be routed through the front portion of
the field case directly to a trigger switch assembly. A method for
assembling a mid-handle power tool is also provided and may include
routing lead wires through a ventilation path between the field
case and trigger assembly.
Inventors: |
Schroeder; James D.;
(Dallastown, PA) ; White; Paul S.; (Ellicott City,
MD) ; Oktavec; Craig A.; (Forest Hill, MD) ;
Wisniewski; Paul J.; (Baltimore, MD) ; Grasso; Edward
J.; (Baltimore, MD) ; Trautner; Paul K.;
(York, PA) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
Black & Decker Inc.
Newark
DE
|
Family ID: |
40436251 |
Appl. No.: |
12/816614 |
Filed: |
June 16, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11986668 |
Nov 21, 2007 |
7770660 |
|
|
12816614 |
|
|
|
|
Current U.S.
Class: |
173/217 ;
173/171; 29/428 |
Current CPC
Class: |
H02K 11/28 20160101;
H02K 11/33 20160101; Y10T 29/49826 20150115; H02K 5/20 20130101;
H02K 23/66 20130101; B25F 5/02 20130101; B25F 5/008 20130101; H02K
5/08 20130101; H02K 9/06 20130101 |
Class at
Publication: |
173/217 ;
173/171; 29/428 |
International
Class: |
B25F 5/02 20060101
B25F005/02; B23P 11/00 20060101 B23P011/00 |
Claims
1. A power tool housing assembly comprising: a base housing segment
and a cover housing segment generally symmetrical to the base
housing segment, each housing segment comprising a plurality of
assembly bosses defining a respective plurality of apertures
accessible from an exterior of the housing assembly, the base
housing segment further comprising at least one intermediate
fastening boss defining an aperture accessible from an interior of
the housing assembly; and a field case having at least one
cooperating assembly fastening boss configured for attaching the
field case to an interior of the base housing segment, wherein the
field case, base housing segment, and cover housing segment
cooperate to form a housing assembly that includes an end cap and a
mid-handle grip integrally connected via a bridge section and
having a longitudinal parting line.
2. A power tool housing assembly according to claim 1, further
wherein the field case comprises at least one wire retention member
configured to secure at least one lead wire within the bridge
section.
3. A power tool housing assembly according to claim 1, wherein the
field case defines an aperture forming a ventilation path that
provides fluid communication between the field case and an interior
of the mid-handle grip.
4. A power tool housing assembly according to claim 1, wherein the
field case further comprises at least one assembly boss defining an
aperture configured to align with one of the base and cover housing
segment assembly boss apertures such that a threaded fastening
device can engage each of the base housing segment, cover housing
segment, and field case.
5. A power tool housing assembly according to claim 1, wherein at
least a portion of the field case defines an exterior surface of
the housing assembly.
6. A power tool housing assembly according to claim 1, wherein at
least one of the base housing segment and the cover housing segment
further comprises an attachment member located a distance past the
mid-handle grip and configured to attach with a gear case.
7. A power tool housing assembly comprising: a motor field case;
first and second clamshell segments coupled to the motor field
case, the first and second clamshell segments being shaped
generally symmetrical to each other and joined to each other along
a part line extending longitudinally along the tool, the first and
second clamshell segments forming a mid-handle grip for the power
tool and an end cap for the motor field case that are connected via
a bridge section; wherein the motor field case, the first and
second clamshell segments each form an exposed part of an overall
tool housing.
8. A power tool housing assembly according to claim 7, wherein the
motor field case defines an aperture forming a ventilation path
that provides fluid communication between the field case and an
interior of the mid-handle grip and wherein the mid-handle grip
comprises a vent to provide fluid communication between the
interior of the mid-handle grip and the exterior of the tool.
9. A power tool housing assembly according to claim 7, further
comprising a metal gear case forming an exposed part of the overall
tool housing located adjacent the mid-handle and an attachment
member configured for securing a ground screw operable to ground a
metal gear case.
10. A power tool housing assembly according to claim 7, further
comprising at least one wire retention member configured to secure
at least one lead wire within the bridge section.
11. A method of assembling a mid-handle power tool, comprising:
coupling a gear case cover to a gear case housing cooperating
attachment features located inside an outer radial periphery of the
gear case housing, thereby creating a combined gear case housing
assembly; coupling a field case assembly to the combined gear case
housing assembly using cooperating attachment features located
outside an outer radial periphery of the gear case housing;
coupling each of a pair of clamshell housing elements, which
together comprise a mid-handle grip, to the field case assembly;
and coupling the pair of clamshell housing elements to each other;
wherein each of the gear case housing, the field case assembly, and
the pair of clamshell elements forms a part of a final exterior
housing the mid-handle power tool.
12. A method according to claim 11, wherein coupling each of the
pair of clamshell housing elements to the field case assembly
comprises coupling one of the pair of clamshell housing elements to
the field case assembly and thereafter coupling the other one of
the pair of clamshell housing elements to the field case
assembly.
13. A method according to claim 12, further comprising retaining
wires in the one of the pair of clamshell housing elements prior to
coupling the other one of the pair of clamshell elements.
14. A method according to claim 11, further comprising coupling
each of the pair of clamshell housing elements to the gear case
housing.
15. A method according to claim 14, wherein the step of coupling
each of the pair of clamshell housing elements to the gear case
housing and the step of coupling the coupling the pair of clamshell
housing elements to each other occurs simultaneously.
16. A method according to claim 11, wherein the step of coupling
each of a pair of clamshell housing elements to the field case
assembly comprises providing an end cap for the field case
assembly.
17. A method according to claim 11, wherein the step of coupling a
gear case cover to a gear case housing comprises screwing screws
into cooperating threads located in an interior of the gear case
housing, the screws and cooperating threads being the cooperating
attachment features.
18. A method according to claim 17, wherein screwing screws into
cooperating threads comprises locating a head of each of the screws
below an outer surface of the gear case cover.
19. A method according to claim 17, wherein the step of coupling
the field case assembly to the combined gear case housing assembly
comprises screwing screws into cooperating threads located in
protruding bosses of the gear case housing, the screws and
cooperating threads being the cooperating attachment features.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional application of U.S. patent
application Ser. No. 11/986,668 filed on Nov. 21, 2007. This
disclosure of the above application is incorporated herein by
reference
[0002] The present disclosure relates generally to power tools such
as drills, screwdrivers, and hammer mechanisms, and more
particularly to a power tool having a mid-handle grip housing and
an assembly process for the same.
BACKGROUND
[0003] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0004] A common problem with power tools, particularly portable
power tools of the mid-handle configuration having a "jam-pot"
construction, concerns the ability with which a power tool so
constructed may be assembled. Typically, power tools having a
jam-pot construction may be assembled in a process wherein the
subcomponents which form the wiring are initially installed into a
first jam-pot opening and thereafter, the subcomponents may be fed
out through a second jam-pot opening.
[0005] An often and time-consuming operation in this process
concerns the connection of the wires from a power source such as a
cord or a battery pack to the trigger switch and motor assembly. In
a mid-handle tool, the connection of these wires can require that
the tool be reoriented multiple times. The assembly operation may
be such that the wires are routed through narrow openings in the
housing to later be connected to the field and brushes. The tool
may need to be reoriented to make these connections. Additionally,
lead wires may be prone to being trapped or pinched between the
housing components during the assembly process.
[0006] In addition, portable power tools of the mid-handle
configuration having a "jam-pot" construction are generally complex
to mold. For example, the jam-pot is typically molded with at least
a portion of the handle attached thereto. This typically requires
the use of multiple additional components such as a housing end cap
and a separate handle housing portion.
SUMMARY
[0007] A power tool is provided including a gear case, a motor
having at least one set of lead wires, a housing assembly, and a
field case. The field case may include a front portion configured
for engaging the gear case and a rear portion. The housing assembly
may include first and second generally symmetrical housing segments
configured for engaging the field case and forming a mid-handle
grip. At least one set of lead wires may be routed through the
front portion of the field case to a trigger switch assembly.
[0008] In another aspect, the present teachings provides a power
tool housing assembly comprising a base housing segment and a cover
housing segment generally symmetrical to the base housing segment.
Each housing segment may include a plurality of assembly bosses
defining a respective plurality of apertures accessible from an
exterior of the housing assembly. A field case may be provided
having at least one fastening boss defining an aperture accessible
from an interior of the housing assembly and configured for
attaching the field case to an interior of the base housing
segment. The field case, base housing segment, and cover housing
segment cooperate to form a housing assembly. In various
embodiments, the housing assembly may include an end cap and a
mid-handle grip integrally connected via a bridge section having a
longitudinal parting line.
[0009] In yet another aspect, the present teachings provide a power
tool comprising a motor, a field case, a self contained gear case
assembly, and a housing assembly. The field case has a front
portion for engaging the gear case assembly and a rear portion. The
field case may define a generally cylindrical chamber for receiving
the motor. The gear case assembly may include a metal gear case and
a cover plate, wherein the cover plate is secured to the gear case
and is not removably accessible from an exterior of the power tool.
The housing assembly may be partially defined by the field case and
include first and second generally symmetrical housing segments
forming a mid-handle grip and configured for engaging the field
case and gear case.
[0010] The present teachings further provide a method of assembling
a mid-handle power tool. The method includes providing a housing
assembly having first and second generally symmetrical housing
segments. In various embodiments, the housing assembly forms an end
cap and a mid-handle grip connected by a bridge section. At least
one set of lead wires may be connected to a motor. The wires can be
routed to the front portion of a field case while the motor is
pressed into the field case from the front portion. The field case
defines a generally cylindrical chamber for receiving the motor and
is attached to a gear case and the first housing segment. The
second housing segment can be attached to the field case and the
first housing segment.
[0011] According to one example, a combined gear case housing
assembly is created by coupling a gear case cover to a gear case
housing cooperating attachment features located inside an outer
radial periphery of the gear case housing. A field case assembly is
coupled to the combined gear case housing assembly using
cooperating attachment features located outside an outer radial
periphery of the gear case housing. A pair of clamshell housing
elements is coupled to the field case assembly to each other
forming a mid-handle grip. Each of the gear case housing, the field
case assembly, and the pair of clamshell elements forms a part of a
final exterior housing the mid-handle power tool.
[0012] Further areas of applicability will become apparent from the
description provided herein. It should be understood that the
description and specific examples are intended for purposes of
illustration only and are not intended to limit the scope of the
present disclosure.
DRAWINGS
[0013] The drawings described herein are for illustration purposes
only and are not intended to limit the scope of the present
disclosure in any way.
[0014] FIG. 1 is side perspective view of an assembled exemplary
power tool constructed in accordance with the teachings of the
present;
[0015] FIG. 2 is a partial perspective view of the power tool as
illustrated in FIG. 1;
[0016] FIGS. 3a and 3b is are exploded views of the power tool as
illustrated in FIG. 2;
[0017] FIG. 4 is a side plan view of the power tool of FIG. 1 with
the cover housing segment removed;
[0018] FIG. 5 is a perspective view of a field case according to
the present disclosure;
[0019] FIG. 6 is an alternate perspective view of a field case
according to the present disclosure; and
[0020] FIGS. 7A and 7B are partial magnified views of FIG. 6;
and
[0021] FIG. 8 is a partial perspective view of a gear case
according to the present disclosure.
DETAILED DESCRIPTION
[0022] The following description is merely exemplary in nature and
is not intended to limit the present disclosure, application, or
uses. It should be understood that throughout the drawings,
corresponding reference numerals indicate like or corresponding
parts and features.
[0023] With reference to FIGS. 1 through 8 of the drawings, a power
tool constructed in accordance with the present teachings is
generally indicated by reference numeral 10. As those skilled in
the art will appreciate, various embodiments of the power tool of
the present disclosure may be either a corded or cordless (battery
operated) device, such as a portable screwdriver, drill, impact
wrench-type power tool, hammer drill, and other mid-handle type
power tools.
[0024] In the particular embodiments illustrated herein, the power
tool 10 is a corded drill having a two component clam shell housing
assembly 12 having a longitudinal part line 23. The power tool 10
is provided with a motor assembly 14, a field case 16 configured to
house the motor assembly 14, a gear case 18 having a gear assembly,
a trigger switch assembly 20, and a power cord (not shown).
[0025] Those skilled in the art will understand that several of the
components of power tool 10, such as the motor assembly 14, gear
assembly, chuck, and trigger details, may be conventional in nature
and need not be described in significant detail in this
application. Reference may be made to a variety of publications for
a more complete understanding of the operation of the conventional
features of power tool 10. One example of such publications is
commonly assigned U.S. Pat. No. 5,897,454 issued Apr. 27, 1999, the
disclosure of which is hereby incorporated by reference as if fully
set forth herein.
[0026] The power tool housing assembly 12 of the present disclosure
can be formed from first and second housing segments 22, 24, such
as claim shell-type halves, and a plurality of fasteners, such as
screws. Each of the first and second segments 22, 24 can be
generally symmetrical and include cooperating halves of an end cap
26 and a mid-handle grip 28 separated by an integral bridge section
30 extending there between. The first and second segments 22, 24
are joined together along a longitudinal parting line 23. In
various embodiments, the field case 16 can form at least a portion
of the exterior surface of the power tool 10. The housing segments
22, 24 can be formed from injection molded plastic or a similarly
suitable material and may be referred to individually herein as a
base housing segment 22 and a cover housing segment 24. It should
be understood that while the present disclosure may refer to
certain features, elements, or parts in a dimensional respect, such
reference is not meant to be limiting, and it is envisioned that
elements such as the base housing segment and cover housing segment
may, in certain instances, be interchangeable with one another.
[0027] The fastening devices, or screws, that typically secure clam
shell-type housing halves together can go through both housing
segments, and in some cases can go additionally through a boss on
the field case. According to the present disclosure, each housing
segment 22, 24 can have an interior surface 22a, 24a and exterior
surface 22b, 24b and may include a plurality of assembly screw
bosses 32 laterally disposed throughout the end cap 26 region, the
mid-handle grip 28, and the bridge section 30. Each assembly boss
32 can have an aperture 34 for receiving a suitable threaded
fastener configured to secure the power tool housing assembly 12
together. The apertures 34 can be accessible from the exterior of
either of the housing segments 22, 24.
[0028] At least one of the housing segments, such as the base
housing segment 22, can include at least one intermediate fastening
boss 36. The intermediate fastening boss 36 may define an aperture
38 accessible from an interior of the base housing segment 22 and
is configured for attaching the field case 16 to an interior
surface 22a of the base housing segment 22. In certain embodiments,
the intermediate fastening boss 36 may not be accessible from an
exterior of the power tool 10. As described in more detail below,
by using the intermediate fastening boss 36 and separately
fastening the field case 16 to the base housing segment 22 first,
various wire leads may be routed within the housing assembly 12 and
secured to certain areas such that when the cover housing segment
24 is attached to the base housing segment 22. In this respect,
there is less opportunity for such wire leads to be pinched or
compromised between various portions of the housing assembly
12.
[0029] In one example, the motor assembly 14 can include a motor
that is coupled to a typical output spindle and chuck by way of a
gear assembly (details not shown). The gear assembly can be housed
in a typical gear case assembly 18 and may simply be a shaft or
transmission providing drive from the motor assembly 14 through a
gear train. In certain embodiments, the power tool includes a
self-contained gear case assembly that may include a gear case and
a cover plate 80 secured thereto with internal fasteners 82 as best
shown in FIG. 8. With such a design, the cover plate 80 is not
removably accessible from an exterior of the power tool 10. For
example, the gear case 18 would need to be detached from the field
case 16 prior to removing the cover plate 80 since the cover plate
fasteners would otherwise be concealed.
[0030] The gear case 18 includes a housing 76 that defines an outer
surface 78. It is understood that the outer surface 78 of the gear
case housing 76 partially defines the overall outer surface of the
power tool 10. In other words, the outer surface 78 is exposed to
allow a user to hold and grip the outer surface 78 during use of
the power tool 10.
[0031] The cover plate 80 is coupled to the gear case housing 76
via a plurality of first fasteners 82. As shown in FIG. 8, the
first fasteners 82 are arranged in a first pattern 84 (represented
by a bolt circle in FIG. 8). The first fasteners 82 can be located
within the periphery of the gear case housing 76 and can hold the
cover plate 80 against a lip (not shown) within the gear case
housing 76. In one embodiment, the gear case 18 includes a seal
(not shown) between the gear case housing 76 and the cover plate
80, which reduces leakage of any lubricant (not shown) out of the
gear case 18.
[0032] The gear case 18 and the field case are coupled via a
plurality of second fasteners 88 (FIG. 1). In the embodiment
represented in FIG. 8, the second fasteners 88 are arranged in a
second pattern 90 (represented by a bolt circle in FIG. 8). As
shown, the second pattern 90 of the second fasteners 88 has a
larger periphery than the first pattern 84 of the first fasteners
82. In other words, the second fasteners 88 are further outboard
than the first fasteners 82. Thus, when the gear case 18 and the
field case 16 are coupled, they cooperate to enclose the first
fasteners 82.
[0033] Also, in the embodiment shown, the cover plate 80 can
include a plurality of pockets 92. The pockets 92 can be provided
such that the heads of the first fasteners 82 are disposed beneath
an outer surface 94 of the cover plate 80. As such, the first
fasteners 82 are unlikely to interfere with the coupling of the
gear case 18 and field case 16.
[0034] The cover plate 80 may also include a plurality of
projections 96 that extend from the outer surface 94. The
projections 96 extend into the field case 16 to ensure proper
orientation of the gear case 18. The cover plate 80 may further
include a first aperture 98 for an output member (not shown) of the
motor assembly 14 that may extend there through.
[0035] In various embodiments, the motor assembly 14 can be housed
in a field case 16. A typical power cord can supply current from an
AC source to the motor assembly 14 and can be controlled by the
trigger switch assembly 20. The motor assembly 14 may include a
first set of lead wires 40 routed from the motor field to the
trigger switch assembly 20 and a second set of wire leads 42 routed
from the commutator brushes (not shown) to the trigger switch
assembly 20.
[0036] The field case 16 may be made of a non-metallic material,
such as injection molded plastic, and may define a generally
cylindrical interior chamber 44 for receiving the motor 14. The
field case 16 may have a front portion 46 for engaging the gear
case 18 and a rear portion 48, at least a portion of which may be
covered by the end cap 26. The front portion 46 may include one or
more laterally extending bosses 50 configured for securing the
field case 16 to the gear case 18 via fastening devices. The
fastening devices can be screws extending through the apertures of
bosses 50 and mating with cooperating threads provided in a metal
gear case 18. In various embodiments, the field case 16 may form a
part of the exterior housing of the power tool 10.
[0037] As best shown in FIG. 5, the field case 16 may define one or
more venting apertures 52 formed within the front portion 46. In
the assembled power tool 10, the apertures 52 partially define a
venting path to provide fluid communication between the exterior of
the housing assembly 12 and the interior of the power tool 10,
including an interior area of the mid-handle grip 28. The venting
path is configured to allow the passage of intake or exhaust air
flow there through. In various embodiments, the housing assembly 12
may further be provided with one or more apertures, or slots, to
additionally allow for air to either be taken in or exhausted,
depending on the location of the slots and placement of an armature
fan unit, through the mid-handle 28 via vents 29 therein. In this
way cooling airflow can be provided over the switch 20 located in
the midhandle 28. Additional venting apertures, or slots, can be
located in the parts of the clam shell halves 22, 24 that form the
end cap 26.
[0038] As shown in FIGS. 2 and 5, the field case 16 may be provided
with a suitable recessed area 53 configured to house an armature
fan unit 54. The fan unit 54 can include a fan member 54a and a
baffle 54b and may serve to vent the motor 14, the gear case 18, or
both. Additionally, the fan unit 54 may be used to aid in cooling
of the trigger switch assembly 20 and its electronics that may be
located within an interior 56 of the mid-handle grip 28. For
example, such an intake or exhaust configuration may create an air
flow that can be directed via vents 29 to pass through the interior
56 of the mid-handle grip 28 and over the internal portion of the
trigger switch assembly 20, which may often be a heat sink. This
would allow the trigger switch assembly 20 to be adequately cooled
or maintained at a suitable operating temperature.
[0039] In various embodiments, the present disclosure provides a
simplified method for wiring a trigger switch assembly 20 in a
mid-handle power tool 10. Once a first set of lead wires 40, or
field wires, is connected to the motor 14, the field wires 40 can
be folded or routed to a front portion 46 of the field case 16
while the motor 14 is being press fitted therein. In this manner,
the wires would not have to be fished out from the back of the
assembly. The field wires 40 may be routed out of a front end of
the field case 16 and through the lowermost venting aperture 52,
and past the fan unit 54 area. In certain embodiments as best shown
in FIG. 5, the field case 16 may comprise one or more retaining
slots 58 adjacent a venting aperture 52. In particular, once past
the fan recessed area 52, the field wires 40 exit out the bottom of
the field case 16 through the retaining slots 58 and connect to the
trigger switch assembly 20. In certain embodiments, the fan 54, and
in particular the fan baffle 54B, can be juxtaposed to the
retaining slots 58 and positioned to secure the field wires 40
within the retaining slots 58. This type of wire routing enables
the use of shorter wires, leading to cost savings and ease of
manufacturing.
[0040] As one skilled in the art can appreciate, routing the field
wires 40 through a ventilation path may allow for a more compact
power tool housing design, for example, by minimizing additional
separate space necessary in the housing assembly used for wiring
purposes. This design is also less prone for pinching or
compromising a wire during the assembly process. In certain
aspects, the field wires may be attached to the trigger switch
assembly 20 prior to pressing the motor 14 into the field case
16.
[0041] The present disclosure also provides a method of securing
lead wires within the housing assembly 12. As shown in FIGS. 4-8, a
second set of lead wires 42, or brush leads, may be attached to the
motor and are routed through a rear portion 48 of the field case 16
to commutator brushes (not shown). Such lead wires 42 may be
attached prior to assembly of the motor 14 into the field case 16
or after the insertion of the motor 14. The brush leads 42 may
continue through the bridge section 30 of the housing assembly 12
and are routed to the trigger switch assembly 20. In certain
aspects, as best shown in FIGS. 7A and 7B, the field case may
include one or more wire retention members 62 configured for
securing the brush wires 42 in the bridge section 30. For example,
the wire retention members 62 may extend from, and be integrally
formed with, a lower region of the field case 16. As shown in FIG.
4, in various embodiments, this second set of lead wires is routed
during an intermediate assembly stage, in particular, after the
base housing segment 22 is attached to the field case 16 and prior
to the cover housing segment 24 being attached.
[0042] In other embodiments, the bridge section 30 of at least one
of the base housing segment 22 and the cover housing segment 24 may
be provided with similar wire retention members 62. It is
envisioned that if two or more wire retention members are used,
they may be orientated in alternating directions so as to better
retain the brush wires 42. The bridge section 30 of at least one of
the base housing segment 22 and the cover housing segment 24 may be
provided with wire retention members 62 in the form of extending
webs or rib sections (not shown) that provide structural support to
the bridge section 30 and may improve the integrity of the housing
assembly 12 when high torque is applied to the power tool 10.
Alternatively, such extending webs or rib sections (not shown) may
be provided independent of the wire retention members 62.
[0043] In various embodiments of the present disclosure, the field
case 16 may include at least one assembly boss 64 defining an
aperture 66 configured for cooperating with the base housing
segment 22 intermediate fastening boss 36 for attaching the field
case 16 to an interior 22a of the base housing segment 22. A
fastening member can be used to engage each of the base housing
segment 22, cover housing segment 24, and field case 16 to secure
the housing assembly 12. The field case 16 may be mounted to the
base housing segment 22 as a separate step. Once secure, other
parts may be attached in place, such as the trigger switch assembly
20, and the lead wires 40, 42 can be routed accordingly. The lead
wires 40, 42 can be held in place through the bridge section 30 by
the wire retention members 62. This can help prevent or eliminate
the possibility of getting wires pinched between the housing
segments 22, 24 and the field case 16.
[0044] As one skilled in the art can appreciate, a strong
connection between the field case 16 and gear case 18 may minimize
potential damage to the power tool 10 in the event of a sudden drop
or other impact. Since the gear case 18 is typically aluminum or
other metal, in certain embodiments the fastening devices, such as
screws, are tapped into the gear case bosses 70 as opposed to the
field case bosses 50, so that they may be held by stronger metallic
threads. This may also increase the torque holding capability and
the creep resistance of aluminum threads may result in a more
consistent joining of the parts.
[0045] In various embodiments, a rear portion of the gear case 18
may include one or more protruding or longitudinally extending
attachment member 72, such as a screw boss, that will cooperate
with a fastening device to attach the gear case 18 to at least one
of the first and second housing segments 22, 24. In this instance,
at least one of the first and second housing segments 22, 24 may be
provided with a cooperating attachment member 74 as shown in FIG.
4. As shown, the cooperating attachment member is disposed a
sufficient distance away from the mid-handle grip in order to
couple the housing assembly 12 to the gear case 18. As shown in
FIG. 4, the attachment member is located at a distal end, in front
of the mid-handle grip. Further mounting examples are also shown
commonly assigned U.S. Pat. No. 6,446,734 issued Sep. 10, 2002, the
disclosure of which is hereby incorporated by reference as if fully
set forth herein.
[0046] According to one method of assembly, a combined gear case
housing assembly 18 is created by coupling a gear case cover 80 to
a gear case housing 76 using cooperating attachment features
located inside an outer radial periphery of the gear case housing
76, as best illustrated in FIG. 8. In one example, this may include
locating fasteners 82, such as screws, into cooperating threads
located in an interior of the gear case housing 18 (as shown by a
bolt circle 84 in FIG. 8). A field case assembly 16 may then be
coupled to the combined gear case housing assembly 18 using
cooperating attachment features, such as fasteners 88 and
cooperating threads, located outside an outer radial periphery of
the gear case housing 76 (as shown by a bolt circle 90 in FIG.
8).
[0047] The pair of clamshell housing elements 22, 24 is then
coupled to the field case assembly 16 and then to each other,
forming an integral mid-handle grip 28 and end cap 26. As shown in
FIG. 1, each of the gear case housing 76, the field case assembly
16, and the pair of clamshell elements 22, 24 forms a part of a
final exterior housing of the mid-handle power tool 10.
[0048] In certain embodiments, one of the pair of clamshell housing
elements (the base housing segment 22) is coupled to the field case
assembly 16 as an intermediate step. Thereafter, the other one of
the pair of clamshell housing elements (the cover housing segment
24) is coupled to the field case assembly 16 and the base housing
segment 22. According to the present disclosure, at least one set
of lead wires 42 is retained adjacent to the field case 16 in the
one of the pair of clamshell housing elements, in particular, the
base housing segment 22, prior to coupling the other one of the
pair of clamshell elements, or the cover housing segment 24. Each
of the pair of clamshell housing elements 22, 24 may then be
coupled to the gear case housing 76. In various embodiments, the
steps of coupling each of the pair of clamshell housing elements
22, 24 to the gear case housing 76 and the step of coupling the
coupling the pair of clamshell housing elements 22, 24 to each
other occurs simultaneously.
[0049] Those skilled in the art will understand that in the normal
operation and process of using such a power tool 10 according to
the present disclosure, there is a risk of contact and damage that
can accidentally be made with existing electrical conduit and the
wires inside, or plumbing pipes. Midhandle power tools, in
particular, generally have their handle disposed close to the
metallic gear cases. In certain instances, a barrier may be
provided to prevent or minimize a user's fingers from contacting
the gear case when a user's hands are in the normal operating
position. However, if the integrity of such a barrier were to be
compromised, the user may accidentally be subject to live
electrical current if the power tool were to unexpectedly contact
an electrical source. To reduce these risks, in various
embodiments, the present disclosure provides a mid-handle power
tool that is grounded. For example, a ground path may be provided
such that a risk of the gear case becoming live if a drill bit
touches a live wire is minimized. In one embodiment, as best shown
in FIG. 5, the gear case 18 may include a ground lead extending
there from for connection to a ground screw 73 (i.e., via a
separate ground wire) that may be fastened to a boss disposed in
one of the pair of clamshell housing elements 22, 24, wherein the
ground screw 73 is, in turn, grounded to a power supply. In another
embodiment, a connector may be provided (not shown) that has a
ground terminal for a more direct electrical connection between the
motor and a ground line. In these instances, the motor power device
can be grounded when using a common corded power supply.
[0050] With the power tool housing design and assembly method of
the present disclosure, the front routing of the field wires 40 and
the securing of the brush wires 42 in the bridge section 30
simplifies the wire-up of the power tool 10. The assembly is
simplified primarily because the field wires 40 are routed a
shorter distance, and the brush wires 42 are able to be secured in
place, minimizing assembly concerns that the wires may be pinched
or compromised. In addition, the routing of the wires through
ventilation paths eliminates the need for extra space within the
housing. The specific clam shell-type housing including a base
housing segment 22 and a cover housing segment 24 provides
additional rigidity and integrity of the power tool 10.
[0051] While the invention has been described in the specification
and illustrated in the drawings with reference to various
embodiments, it will be understood by those skilled in the art that
various changes may be made and equivalents may be substituted for
elements thereof without departing from the scope of the invention
as defined in the claims. Furthermore, the mixing and matching of
features, elements and/or functions between various embodiments is
expressly contemplated herein so that one of ordinary skill in the
art would appreciate from this disclosure that features, elements
and/or functions of one embodiment may be incorporated into another
embodiment as appropriate, unless otherwise limited above.
Moreover, many modifications may be made to adapt a particular
situation or material to the teachings of the invention without
departing from the essential scope thereof. Therefore, it is
intended that the invention not be limited to the particular
embodiment illustrated by the drawings and described in the
specification as the best mode presently contemplated for carrying
out this invention, but that the invention will include any
embodiments falling within the foregoing description and the
appended claims.
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