EP2581175B1

EP2581175B1 - Cord protector for power tools

Info

Publication number: EP2581175B1
Application number: EP12187073.7A
Authority: EP
Inventors: Carl F. Merhar Iii; Jr. Franklin B. Ports
Original assignee: Black and Decker Inc
Current assignee: Black and Decker Inc
Priority date: 2011-10-11
Filing date: 2012-10-03
Publication date: 2015-05-27
Anticipated expiration: 2032-10-03
Also published as: EP2581175A1

Description

The present disclosure relates to various improvements for power tools, and particularly to a cord set load protector.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
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.
According to an aspect of the present invention, there is provided a power tool, comprising: a tool body having a housing; a motor disposed in said housing; a power cord connected to said motor, the power cord having a cord jacket as an outer layer; and a cord protector operably engaging said power cord and surrounding the cord jacket, said housing including an internal labyrinth, the cord protector passing through the internal labyrinth such that a frictional force occurs between the cord protector and the cord jacket in response to a load being applied to the power cord, characterised in that said labyrinth includes a first boss on a first side of the cord protector, extending radially inward from an interior surface of the housing and engaging the cord protector and a second boss on a second, opposed side of the cord protector, extending radially inward from the interior surface of the housing and engaging the cord protector, the first boss extending farther radially inward than the second boss.
DE20000230 (U1) relates to an electric hand-operated machine tool comprising a device for accommodating a power cable on an assembly shell of a housing of an electric appliance. The assembly shell has a first opening through which the power cable is guided and has a labyrinth-shaped fixing device which is provided for the power cable and which is arranged in the vicinity of the first opening.
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.
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.

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.
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.
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.
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.
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.
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.
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.
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.
With reference to Figure 15, spring lever 402 can comprise a slotted end 422 for receiving power cord 112 therethrough.
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.
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.
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.
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.
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 protector110. 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.
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.
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.

Claims

A power tool (10), comprising:
a tool body having a housing (118);

a motor disposed in said housing;

a power cord (112) connected to said motor, the power cord (112) having a cord jacket (452) as an outer layer; and

a cord protector (114) operably engaging said power cord (112) and surrounding the cord jacket (452), said housing (118) including an internal labyrinth, the cord protector passing through the internal labyrinth such that a frictional force occurs between the cord protector (114) and the cord jacket (452) in response to a load being applied to the power cord (112),

characterised in that said labyrinth includes a first boss (456) on a first side of the cord protector (114), extending radially inward from an interior surface of the housing (118) and engaging the cord protector (114) and a second boss (458) on a second, opposed side of the cord protector (114), extending radially inward from the interior surface of the housing (118) and engaging the cord protector (114), the first boss (456) extending farther radially inward than the second boss (458).