[0002] The present disclosure relates to various improvements for power tools, and particularly
to a cord set load protector.
[0003] The statements in this section merely provide background information related to the
present disclosure and may not constitute prior art.
[0004] A common field failure with heavier portable power tools, such as portable saws,
is a separation of the power cord from the tool due to an impulse load, or jerk, applied
to the cord. This can occur when the tool is dropped while the plug end of the power
cord is secured, or when a user carries the tool or lowers it from floor to floor
or down a ladder by holding the power cord.
[0005] To isolate the power cord conductors or connections from the high forces imposed
by jerking the power cord, the power cord according to the present disclosure is installed
in the tool housing with a small service loop, or extra length of cable, between the
cord clamp and the portion of the tool housing that secures the cord protector. A
crimp-on device is installed on the power cord cable next to the cord protector. When
the cord is subjected to jerking, the cable moves axially relative to the cord protector.
As the cable moves, the crimp-on device compresses the extended end of the cord protector
absorbing energy and reducing the forces transmitted to the cord set conductors or
connections that are disposed within the housing.
[0006] 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.
[0007] The drawings described herein are for illustration purposes only and are not intended
to limit the scope of the present disclosure in any way.
Figure 1 is a perspective view of an exemplary worm drive saw with a tool hanger according
to the principles of the present disclosure;
Figure 2 is a cross-sectional view showing the cord set load protector according to
the principles of the present disclosure, in an unloaded condition;
Figure 3 is a view similar to Figure 2 with a load applied to the cord;
Figure 4 is a perspective view of an exemplary cord clamp utilized with the cord set
load protector according to the principles of the present disclosure;
Figure 5 is a perspective view of a first clamp half;
Figure 6 is a perspective view of a second clamp half;
Figure 7 is a perspective view of an alternative cord set load protector design with
the handle partially removed for illustrative purposes;
Figure 8 is a front view of the cord set load protector design in an initial position
according to some embodiments having a spring lever;
Figure 9 is a front view of the cord set load protector design according to Figure
8 in a deflected position;
Figure 10 is a front view of the cord set load protector design in an initial position
according to some embodiments having a spring lever and supplemental spring;
Figure 11 is a front view of the cord set load protector design according to Figure
10 in a deflected position;
Figure 12 is a front view of the cord set load protector design in an initial position
according to some embodiments having a spring lever and torsion spring;
Figure 13 is a front view of the cord set load protector design according to Figure
12 in a deflected position;
Figure 14 is a perspective view of a cord set load protector design according to some
embodiments having a spring lever and cord clamp;
Figure 15 is a perspective view of the spring lever;
Figure 16 is a perspective view of cord clamp;
Figure 17 is a front view of the cord set load protector design in an initial position
according to some embodiments having a spring member; and
Figure 18 is a front view of the cord set load protector design according to Figure
17 in a deflected position.
Figure 19 is a side, partial sectional view of an alternate embodiment of a cord set
load protector of the present invention.
Figure 20 is a side, sectional view of the cord set load protector of Figure 19.
Figure 21 is a top, sectional view of the cord set load protector of Figure 19.
[0008] 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.
[0009] With reference to Figures 1 and 2, an exemplary power tool 10 is shown having a cord
set load protector device 114 for preventing high forces imposed on a power cord 112
from impacting the connections of the cord 112 to the electrical power tool 10. As
illustrated in Figure 1, the power tool 10 includes a cord 112 and a cord protector
114 extending from the rear end of the tool. The cord protector 114 is mounted within
a recess 116 provided in the power tool housing 118. The recess 116 can be square
or round in cross-section and defines a cavity therein for receiving a radially extending
flange portion 120 of the elastomeric cord protector 114. The radial extending flange
portion 120 is disposed against a shoulder portion 122. A crimp-on device 124 is clamped
or crimped onto the power cord 112 and includes a radially extending flange portion
126 which is disposed against an end portion of the cord protector 114 inside of the
chamber 116 of housing 118. The flange portion 126 is disposed against a radially
inwardly extending shoulder 128 of the cavity 116 provided in the housing 118.
[0010] The crimp-on device 124 engages the power cord so as to be axially and rotatably
fixed to the power cord 112 in a manner that will be described in greater detail herein.
The power cord 112 is also clamped to the tool housing by a cord clamp 130 provided
within the power tool 10 in such a way that an extra cable length 112a is provided
within the housing between the crimp-on device 124 and cord clamp 130. The cord clamp
130 can be mounted to the housing by fasteners 132 or by other known securing methods,
such as rivets, welds, grommets, etc. The cord clamp 130 can be spaced from the recess
116 by up to several inches. Locating the cord clamp 130 further inward from the recess
116 improves cord flex durability by placing the cord stresses from the cord being
flexed and the stresses on the cord due to the clamp at two different locations instead
of both being generally at the same location. This improves the flex life of the conductors.
[0011] When a large force F is applied to the power cord 112, as illustrated in Figure 3,
the power cord 112 is pulled in the axial direction of the force F. The movement of
the power cord 112 relative to the housing 118 causes the crimp-on device 124 to move
axially relative to the shoulder portion 128 so that the flange portion 126 of crimp-on
device 124 compresses the flange portion 120 of cord protector 114, thereby absorbing
the force exerted on the cord 112. The axial movement of the crimp-on device relative
to the cord clamp 130 takes up some of the extra cable length 112a provided therebetween
without exerting forces upon the cord clamp 130.
[0012] The crimp-on device 124 can take-on many forms. By way of example, as illustrated
in Figures 4 and 6, the crimp-on device 124 can include a first clamp half 136 and
a second clamp half 138. Each clamp half 136, 138 is provided with semicylindrical
body portions 140 each provided with a plurality of radially inwardly extending ribs
142 designed to engage and clamp against the outer surface of the power cord 112.
The first clamp half 136 is provided with a plurality of apertures 144 each adapted
to receive a plurality of corresponding locking fingers 146 provided on the second
clamp half 138. Each of the first and second clamp halves 136, 138 include radial
flange portions 126a, 126b, respectively, which define the radially extending flange
portion 126 of the crimp-on device 124. The locking fingers 146 secure the second
clamp half 138 to the first clamp half 136 in a clamping engagement on the power cord
112 so as to prevent axial or rotational movement of the power cord 112 relative to
the clamp device 124. It should be understood that other clamp or crimp-on arrangements
can be utilized with the cord-set load protector 110, according to the principles
of the present disclosure.
[0013] With reference to Figure 7, an alternative cord set load protector 110' is shown
including a split clamp device 124' received in a recess 302 within the handle section
300 to prevent the assembly from twisting or being pushed into the handle set. The
split clamp 124' is independent of the handle set 300 and traps the complete cord
set 112 and secondary wrap of filler strands. The cord protector 114' includes added
material at the mounting end that prevents twist and creates a spring to absorb shock.
[0014] In some embodiments, as illustrated in Figures 8-16, cord set load protector 110
can comprise a spring lever assembly 400. In some embodiments, spring lever assembly
400 can comprise a spring lever 402 and a cord clamp 130 fixedly coupled to spring
lever 402 and power cord 112. As illustrated in Figures 8-14, spring lever 402 can
be fixedly coupled to housing 118 via one or more retaining members 404 extending
from housing 118. More particularly, spring lever 402 can comprise a plurality of
corresponding mounting apertures 406 (see Figure 15) sized to receive retaining members
404 therethrough. In some embodiments, retaining members 404 can be deformable, such
as through heat staking or welding, to permanently retain spring lever 402 in a predetermined
operable position (see Figure 14). Retaining members 404 can be spaced apart to define
a plane extending between the centers thereof, wherein the plane is generally orthogonal
to a longitudinal axis of power cord 112. Additionally, retaining member 404 can be
a sleeve or slot formed in housing 118 for receiving and retaining an end of spring
lever 402.
[0015] In some embodiments, cord set load protector 110 can comprise a cord clamp 408 fixedly
coupled to spring lever 402. In some embodiments, as illustrated in Figures 8-16,
cord clamp 408 can comprise a pair of clamping members 410 adapted to be coupled together
via fasteners 412 (Figure 14). Specifically, each clamping member 410 can comprise
an enlarged aperture 414 for permitting a shank portion of fastener 412 to pass through
and a threaded aperture 416 for threadedly engaging fastener 412. Each clamping member
410 can comprise a slot 418 formed therein to capture a side of spring lever 402 and
a generally circular portion 420 to capture power cord 112. In this manner, cord clamp
408 can be mounted on an end of spring lever 402 such that the slot 418 of each clamping
member 410 engages a side of spring lever 402. Similarly, power cord 112 can extend
between clamping member 410. Upon tightening of fasteners 412, clamping members 410
are drawn together to exert a clamping and retaining force on both spring lever 402
and power cord 112. In this manner, cord clamp 408 is fixedly coupled to power cord
112 for movement therewith. It should be appreciated that clamping members 410 are
configured such that a single manufacturing piece can be used on opposing sides of
spring lever 402.
[0016] With reference to Figure 15, spring lever 402 can comprise a slotted end 422 for
receiving power cord 112 therethrough.
[0017] During use, if sufficient force is applied to power cord 112, the associated force
is transmitted through cord clamp 408 and against spring lever 402 to deflect spring
lever 402 between a relaxed position (Figures 8, 10, 12, and 14) and a deflected position
(Figures 9, 11, and 13). This deflection provides force absorption along axis PC.
The biasing force of spring lever 402 can be determined based upon, in part, the size
and length of spring lever 402 and the material thereof. It should be understood,
however, that in some embodiments additional biasing force may be desired. In such
cases, a supplemental spring member 430 (Figures 10 and 11) may be used disposed between
cord clamp 408 and housing 118. Supplemental spring 430 can be a compression spring
having either linear or progressive spring rates. Additionally, supplemental spring
member 430 could include a coil spring, torsion spring, elastomeric member, or the
like. Spring member 430 can be disposed coaxial with power cord 112 to maintain alignment
of spring member 430 with power cord 112. It should be appreciated that spring member
430 can be used separate from spring lever 402, such as illustrated in FIGS. 17 and
18.
[0018] In some embodiments, as illustrated in Figures 12 and 13, spring lever 402 can be
pivotally coupled about an axis 450 for pivotal movement between a relaxed position
(Figure 12) and a deflected position (Figure 13). In this embodiment, a torsion spring
452 can be used for applying an opposing biasing force to power cord 112 when under
load.
[0019] In some embodiments, a bellmouth 434 can be used to limit the deflection of power
cord 112 exiting housing 118. Bellmouth 434 can comprise a generally linear body portion
436 and a curved exit 438 having an curved profile. Bellmouth 434 can be fixedly coupled
to cord clamp 408 for movement therewith such that it moves together with cord clamp
408 when power cord 112 is under load.
[0020] It should be appreciated that spring lever 402 can include features, materials, or
employ other manufacturing techniques directed to tailoring a compliant response when
under load (i.e. a biasing profile). For instance, in some embodiments, spring lever
402 can comprise a molded or formed member having a cross-sectional shape that is
non-planar and/or non-uniform. This cross-sectional shape can provide a nonlinear
compliant response when under load to permit initial deflection under light loads
and progressively less deflection under heavier loads.
[0021] In an alternate embodiment illustrated in Figures 19 - 20, the housing 118 includes
an internal labyrinth 450 that engages the cord set load protector 110. In this embodiment,
the cord 112 includes a cord jacket 452. The cord set load protector 110 engages and
surrounds the cord jacket 452. The cord set load protector 110 extends from an interior
space of the housing 118 through an opening 454 in the housing 118. In this exemplary
embodiment, at an interior end of the cord set load protector 110 the cord set load
protector includes the supplemental spring member 430. In this embodiment, the supplemental
spring member 430 is adjacent to and abuts the cord clamp 408. In this embodiment,
the labyrinth 450 is positioned between the cord clamp 408 and the opening 454. The
labyrinth 450 includes a first boss 456 that extends radially inward from a first
portion of an interior surface of the housing 118 and a second boss 458 that extends
radially inward from a second portion of the interior surface of the housing 118,
the second portion being opposed to the first portion of the interior surface. The
first boss 456 extends farther radially inward than the second boss 458. The cord
set load protector 110 passes through the labyrinth 450. As the cord set load protector
110 passes through the labyrinth 450 a curve or bend 460 is created in the cord 112/cord
jacket 452/cord load set protector 110. As a result of the curve or bend 460 of the
cord set load protector 110, cord 112 and cord jacket 452, when a load is applied
to the cord 112 in a direction away from the housing118, a frictional force is developed
between the cord jacket 452 and the cord set load protector 10. The frictional force
prevents the cord jacket 452 from shearing at a point in which the cord jacket 452
enters the cord clamp 408. This results in improved protection for the cord 112.
[0022] Figure 21 illustrates an additional cord protection feature. This embodiment may
include an additional bend in the cord 112. Specifically, as the cord 112 extends
past the cord clamp 408 towards the motor, a supplementary bend 462 is created in
the cord 112 as the cord 112 is curved about the cord clamp 408. This additional bend
creates a friction force between conductors of the cord 112 and the cord jacket 452.
This frictional force prevents the conductors from being pulled through the cord jacket
452 when the load is applied to the cord 112, as noted above.
[0023] It should be appreciated from the foregoing that one or more of the disclosed embodiments
can be used concurrently to provide improved tailoring of the biasing profile and
increased cord protection.