Patent Grant
7175456
Electronic devices such as power tools often include an electrical plug module for coupling with an electrical extension cord, thereby permitting an operator to use the power tool at locations remote from the nearest available electrical outlet. One common configuration for such a system is to include the electrical plug module within a recess of the housing such that prongs of the electrical plug module are accessible to engage the female receptacle disposed on the electrical extension cord. Thus, the electrical extension cord may be coupled to the recessed electrical plug module, with the coupling being at least partially hidden from view and at least partially protected within the power tool housing from becoming dislodged.
However, nearly all power tools produce some jarring and/or vibration of the power tool during operation, which in turn jars and vibrates the coupling between the electrical plug module and the electrical extension cord. The jarring/vibration causes the electrical plug module to vibrate at a different frequency than the extension cord. Due to the different relative vibration, the electrical plug module and electrical extension cord may become at least partially if not totally disengaged from one another, resulting in a loss of power to the power tool and possibly damaging the connection due to electrical arcing, interrupting its operation and usually aggravating the operator.
A retaining clip may be added, which is attached to the same handle/body in which the electric plug module is mounted. When provided, the retaining clip is also configured and arranged to make contact with the extension cord. The retaining clip will thereby transfer to the extension cord the vibration frequency of the handle/body that contains the plug module. The connection will reduce the effect of relative vibration and help prevent the cord from backing out. However, due to the wide range of extension cord female plug shapes, the retainer clip may make the female plug insertion difficult and may aggravate the operator. In addition, some plug shapes may not be as effective as others. The elimination of the retainer clip is desirable from an operator prospective.
In addition, where the power tools are portable, and are releasably coupled to an extension cord, inadvertent pulling or catching of the extension cord may cause the extension cord to become disengaged. For example, operators will frequently though inadvisably handle the power tool by the extension cord, and often times the weight of the power tool itself is greater than the amount of force required to disengage the extension cord from the tool. Other times the extension cord will become caught or snagged on a portion of the work surface or other part of the environment, and as the operator moves the power tool during operation, the operator inadvertently pulls the power tool away and disengages from the extension cord.
Embodiments of the invention provide an anti-disengagement assembly that minimizes vibration and disengagement of an electrical extension cord from a recessed electrical plug module disposed within a housing of a power tool. In a first preferred embodiment, axial vibration is reduced by a pair of biasing elements, which are disposed at opposing ends of the plug module, permitting a range of free movement of the plug module, where the plug module “floats” between the biasing elements. In a second preferred embodiment, axial vibration is absorbed by a plug module having a shape that is configured to permit at least limited rotation within the housing of the power tool. Additionally, a single biasing member is preferably provided in the second preferred embodiment to maintain the position and orientation of the plug module, as well as isolating the plug module from vibration. Still other embodiments of the invention include an anti-disengagement assembly.
Embodiments of the present invention include an anti-disengagement assembly for minimizing vibration induced disengagement of an electrical extension cord from an electrical plug module of a power tool. Other embodiments of the invention include an anti-disengagement assembly for minimizing disengagement of an electrical extension cord from an electrical plug module resulting from both vibration induced disengagement as well as inadvertent pulling or catching of the extension cord from the electrical plug module.
By providing one or more biasing members in close proximity to the plug module, the biasing members absorb tool vibration, thereby permitting movement of the plug module that is independent of the movement of the tool. In combination with one or more biasing members, other embodiments may include a cord retaining system that releasably retains a portion of the cord in close proximity to a tool housing to reduce the possibility that the extension cord will be inadvertently pulled or snagged. While it is contemplated that the invention may be used in connection with any electrical device, the preferred embodiments are used in connection with power tools, either hand held portable such as a circular saw or stationary such as a table saw, for example.
In the first preferred embodiment, opposing biasing members are provided at each end of a plug module, permitting the plug module to “float” between the biasing members. Vibration of the power tool during operation is absorbed by the biasing members, providing for the free movement of the plug module independent of any movement of tool or tool components. Thus, an extension cord will move with the plug module, thereby limiting the impact of tool vibration on the coupling of the plug module and the extension cord.
Turning therefore to
The housing 12 is typically composed of plastic, such as Acrylonitrile Butadiene Styrene (ABS) or glass-filled nylon, and is assembled from two halves that engage one another in a clam-shell configuration. As illustrated in
More particularly, the first preferred embodiment anti-disengagement assembly 10 includes the electrical plug module 16, inner and outer biasing members 28, 30, and inner and outer retaining members 32, 34. Generally, the inner biasing member 28 is configured and arranged to bias the plug module 16 in a first outward direction 36 toward the opening 24 in the chamber portion 20, while the outer biasing member 30 is configured and arranged to bias the plug module in a second direction 38 opposite that of the first direction. The inner and outer biasing member 28, 30 and the plug module 16 that is disposed therebetween are retained within the inner and outer retaining members 32, 34.
The plug module 16, as illustrated in
The inner biasing members 28 and 30 are preferably helical compression springs that have a relatively low spring force and small displacement which will enable the plug module to float between the springs, and to slightly move responsive to normal forces that are applied when an extension cord is connected to the plug module 16. This enables the springs to absorb vibration produced by the tool and thereby tend to isolate the plug module 16 from the effects of the vibration. The diameter of the outer biasing member 30 is larger than that of the inner biasing member 28, so it is preferred that the wire size or other force varying parameter be changed to produce generally equal spring forces of the biasing members 28 and 30.
The inside diameter of the outer biasing member 30 is slightly larger than the outside diameter of the body 40 of the plug module 16 so that it can be positioned on it. An inner end 52 of the outer biasing member 28 then abuts an annular shoulder 53 defined by the end plate 42. The inner diameter of the inner biasing member 28 is configured to permit passage of the electrical wires 26, with an outer end 54 of the inner biasing member 28 abutting the end face of the end plate 42.
The plug module 16 of the first preferred assembly 10 “floats” between the inner and outer biasing members 28, 30, with the inner and outer biasing members absorbing vibration to at least partially isolate the plug module from being jarred by the vibration. While it is contemplated that mechanical features of the housing 12 may be provided to retain the inner and outer biasing member 28 and 30, the assembly 10 includes the inner and outer retaining members 32, 34, which when assembled to one another, at least partially enclose the inner and outer biasing members and the floating plug module 16.
Specifically, as illustrated in
The outer retaining member 34 is preferably configured to include an outer ring 68 from which curved side members 70 extend rearwardly. As with the inner retaining member 32, one of the side members 70 may optionally include a window 72 to reduce the overall size of the outer retaining member 34. An inner circumference of the outer ring 68 is configured to permit passage of the prongs 22, and an inner surface of the outer ring preferably includes an annular shoulder 74 configured to engage and retain the outer end 76 of the outer biasing member 30. A pair of diametrically opposed, shelves 78 are preferably disposed on the outer ring 68 to engage a correspondingly configured shoulder 80 that extends inward from the housing 12 and prevents rotation of the retaining member 34 relative to the housing.
To promote “floating” of the plug module 16 between the inner and outer biasing members 28, 30, the inner and outer retaining members 32, 34 are configured to engage one another. While the assembly 10 contemplates numerous engagement mechanisms, one exemplary engagement is a snap-fit engagement, and is illustrated in
Thus, when assembled, the anti-disengagement assembly 10 includes the inner and outer retaining members 32, 34 connected to one another, with the plug module 16 and inner and outer biasing members 28, 30 disposed between them. The assembly 10 is retained within the chamber portion 20 of the housing 12 with the outside surface of the end portion 56 of the inner retaining member 32 abutting the ribs 66 of the housing, while the shelves 78 of the outer ring 68 engage the annular ring 80. In this manner, the assembly 10 is disposed within the housing 12, with the plug module disposed so as to “float” between the first and second biasing members 28, 30.
The assembly 10 may be modified in a variety of ways. For example, the respective structures of the inner and outer retaining members 32, 34 may be modified to provide alternative means of engaging the retaining members to one another, as well as within the housing 12. As illustrated in
Additionally, the side portions 60 may be extended in length, and instead of recesses, may instead include generally rectangular extensions 92 at the ends thereof, where each of the rectangular extensions includes a wedge-shaped locking member 94 at its underside. Similarly, the side members 70 of the outer retaining member 34 may be shortened, and instead of including extensions, may include generally rectangular depressions 96 configured to frictionally receive the rectangular extensions. Disposed within each of the rectangular depressions 96 is a rectangular window 98 configured to lockingly receive a respective one of the locking members 94 therein. Thus, the inner and outer retaining members 32, 34 may be altered and still be configured to engage one another, as well as to promote retention of the assembly 10 within the housing 12.
A second preferred embodiment, designated generally at 100 in
To this end, the plug module 102 of the second preferred assembly 100 is configured to be at least partially rounded to promote rotation within a chamber portion 20′ of the housing 12. As illustrated in
Preferably, a single biasing member 116 is provided to bias the plug module 102 in an outward direction. The inclusion of the biasing member 116 is advantageous in that compression and expansion of the biasing member promotes absorption of vibration by the plug module 102. The biasing member 116 may also promote maintenance of the position and orientation of the plug module 102 within the chamber 20. The preferred biasing member 116 is a helical coil.
The chamber portion 20 of the housing 12 is correspondingly configured to both retain the second preferred assembly 100, as well as to bias the plug module 102 in an outward direction. More particularly, an annular ring 118 extends radially inwardly from an inner circumference of the chamber portion 20. In this manner, the inner circumference is reduced at a predetermined location and is sized to permit passage of the annular collar 106, but prevents passage of a majority of the spherical body 104. Thus, a portion of the spherical body 104 is in abutment with the annular ring 118 of the housing 12.
A generally circular plate 120 is disposed at an inner end of the chamber portion 20, and an inner end 124 of the biasing member 116 abuts an outer surface 123 of the circular plate. An outer end 124 of the biasing member 116 abuts the second end 112 of the plug module 102. In addition, guide ribs 126 extend from the chamber portion 20 to promote maintenance of the orientation of the biasing member 116 within the chamber portion 20, and to help reduce distortion of the biasing member 116 as it is compressed.
Thus, when assembled, the second preferred assembly 100 includes the biasing member 116 biasing the plug module 102 outwardly. The assembly 100 is retained at an outer end by the annular ring 118, and at an inner end by the circular plate 120. The biasing member 116 absorbs the axial vibration of the spherical body 104, while permitting compression sufficient to allow the spherical body to rotate in both clockwise and counterclockwise directions 128, 130 relative to the axial lengthwise direction of the biasing member 116, thereby maintaining a position of the plug module 102 and its engagement with the extension cord.
A third preferred embodiment of the invention is especially advantageous in applications involving portable power tools, and includes both an anti-vibration assembly as well as a cord retaining system. While the anti-vibration assembly of either the first or second preferred embodiment minimize vibration induced disengagement of an extension cord from a plug module, a portion of the extension cord external to the chamber 20 of the housing 12 is susceptible to being pulled or snagged during movement of the tool during operation. Accordingly, the third preferred embodiment includes a cord retaining system for releasably retaining a portion of the cord in close proximity to the tool housing 12 to reduce the possibility that the extension cord will be inadvertently pulled or snagged and subsequently result in disengagement of the extension cord from the plug module.
While the invention contemplates that a variety of configurations will suffice to provide retention of the extension cord, an exemplary cord retaining system is illustrated in
The exemplary cord retaining system, generally designated 136, is secured to a handle portion of the housing 12 by being integrally molded thereto, or alternatively adhered by chemical adhesives or threaded fasteners. Two main components make up the cord retaining system 136, which are a cord capture formation 138 and a cord channel 140. The cord capture formation 138 is configured to retain the extension cord 134 disposed on the housing 12, and the cord channel 140 is disposed on an outside surface of the housing and is configured for supporting a loop of the cord substantially along an arc defined by the loop. The cord capture formation 138 is configured for retaining the extension cord 134 at two or more points of contact 142, 144 (
More specifically, the cord capture formation 138 is configured to define an enclosed space 150 when attached to the housing 12. Thus, the cord capture formation 138 may define a circular, oval, free form or other preferably non-cornered shape on its own or using a portion 152 of the housing 12. A non-cornered shape is preferred to avoid sharp edges which may cause wear or stress on the extension cord 134. Further, the cord capture formation 138 is configured for maintaining an orientation of the cord 134 that prevents bends and kinks in the cord when the cord is retained in the system 136.
While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims.
Various features of the invention are set forth in the following claims.
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| Number | Date | Country | |
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