Patent Abstract:
A switch assembly for use with a power tool that includes an enclosure with an open top, a switch body with multiple switch contacts, with the switch body being located in the enclosure and having connectors for connecting to electrical conductors that selectively extend to the motor and the power source. The switch assembly further includes a slide switch mechanism for selectively engaging certain ones of the switch contacts for determining the operating characteristics of the motor, an actuating switch cover operatively connected to the slide switch mechanism, wherein the cover is slideable between at least two operating positions, with the switch cover being operatively accessible by a user, and a compressible seal positioned between the actuating switch cover and the switch body, with the seal extending around substantially the entire circumference of the top of the switch body.

Full Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention generally relates to power hand tools and more particularly to a switch assembly of the type used with power hand tools to prevent contamination of power hand tool switch assembly components.  
           [0002]    There has been continued innovation and improvement in the design of power hand tools of the type that are used in cutting drywall. Examples of such products are those sold under the Bosch brand produced by the Robert Bosch Tool Corporation. These power hand tools have a generally cylindrically shaped housing to which a removable handle can be attached, with the housing containing a drive motor having a rotary output shaft to which a side cutting bit can be attached. When cutting drywall, there is usually a significant amount of dust that is produced and tends to coat the unit. To selectively control the motor, such power hand tools are further provided with an electrical switch assembly that typically has multiple operating positions for operating the tool at different speeds.  
           [0003]    While such switch assemblies in the form of slide-type switch operation have been available for many years, a recurring and persistent problem has been dust contamination of the switch assembly components, which can eventually result in switch assembly failure. While it is possible to purchase elaborately constructed switch assemblies that are tightly sealed so that dust cannot enter the switch components of the assembly, such sophisticated switch assemblies are significantly more expensive than the slide-type switches that are currently in commercial use.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention is related to a power hand tool having a slide switch assembly that is particularly effective in preventing contamination of switch assembly components during operation of the power hand tool. A preferred embodiment of the present invention comprises a switch assembly of generally conventional construction, but which is modified to include a seal configured and arranged to prevent entry of dust and other ambient debris into the slide switch assembly components during operation of the power hand tool. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 is a perspective view of the rotary hand tool having a slide switch assembly embodying the present invention;  
         [0006]    [0006]FIG. 2 is a perspective view of the seal that is used in the embodiment shown in FIG. 1;  
         [0007]    [0007]FIG. 3 is side cross-sectional view of a portion of the embodiment shown in FIG. 1; and  
         [0008]    [0008]FIG. 4 is a top view of the switch cover that is used in the embodiment shown in FIG. 1.  
         [0009]    [0009]FIG. 5 is a front elevational view of the switch cover that is used in the embodiment shown in FIG. 1.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0010]    Typically, a switch assembly of the type used in a drywall cutting power hand tool includes a switch cover having a slide switch mechanism that reciprocates within a stationary slide switch body to effectuate multiple operating positions. For example, a first position may de-energize the tool, while second and third positions may cause tool operation at different speeds. To actuate a drywall cutout rotary tool, a user exerts force upon the switch cover in a direction parallel to a longitudinal axis of the tool. The slide switch mechanism is disposed on an underside of the switch cover, and therefore reciprocates as the switch cover is moved. The switch body includes multiple switch contacts, and is located within an enclosure of the slide switch assembly, as are connectors for connecting to electrical conductors that selectively extend to the motor and the power source.  
         [0011]    In the absence of the seal disclosed by the instant application, the slide switch mechanism directly contacts and operatively engages the slide switch body of the switch assembly, thereby lacking an effective seal to prevent entry of drywall dust and other contaminants. Because the switch cover and the enclosure are not sufficiently sealed to one another in the absence of a seal, contaminants may enter the switch assembly at the unsealed interface of the two components.  
         [0012]    The preferred embodiment of the power hand tool, designated generally at  10 , operates in association with a slide switch assembly  12 . In addition to the slide switch assembly  12 , the power hand tool  10  includes a housing  14 , while the slide switch assembly typically includes an enclosure  16 , a slide switch body  18  having multiple switch contacts (not shown), a slide switch mechanism  20 , an actuating switch cover  22 , and a seal  24 . Optionally, the slide switch assembly  12  may be specifically modified to accommodate the seal  24 . More specifically, the instant seal  10  is configured and arranged to have a top surface  26  and a bottom surface  28  that respectively engage the switch cover  22  and the slide switch body  18 , and includes a seal body  30  having a generally rectangular circumference and a generally rectangular opening  32  extending through a central portion thereof, wherein both the generally rectangular circumference and the generally rectangular opening preferably include radiused corners.  
         [0013]    The slide switch mechanism  20  (best shown in FIG. 5) is disposed on an underside  34  of the switch cover  22 , and the generally rectangular opening  32  is configured and arranged to accommodate the slide switch mechanism, allowing reciprocation of the switch cover along a longitudinal axis of the generally rectangular opening. The slide switch mechanism  20  depends from the switch cover  22  and extends into the generally rectangular opening  32  to engage a switch lever (not shown) that extends into the generally rectangular opening. Thus, the top surface  26  of the seal  24  is configured to engage the switch cover  22 , while the bottom surface  28  of the seal is configured to engage the slide switch body  18 , thereby promoting engagement of the seal with both the switch cover and the switch body. The switch lever is actuated when the switch cover  22 , which is operably connected to the switch lever via the slide switch mechanism  20 , is reciprocated.  
         [0014]    While the instant seal  24  is suitable for use with a variety of switch assemblies of the type used with power hand tools, for purposes of illustration, the seal operating in connection with a slide switch assembly  12  of a drywall cutout rotary tool  14  will be shown and described. Such slide switch assemblies  12  typically operate using linear reciprocation of the slide switch mechanism  20  along a predetermined track having multiple operating positions along a length thereof.  
         [0015]    Accordingly, the seal of the instant invention is configured and arranged to engage both the switch cover  22  and the slide switch body  18 , enhancing a seal between the switch cover and the slide switch body while also providing an additional mechanical barrier to ambient debris.  
         [0016]    As disclosed, the preferred seal  10  has a generally rectangular body, preferably with radiused corners. Similarly, the central opening  32  disposed therethrough is generally rectangular, and preferably includes radiused corners. While the instant invention contemplates incorporation of corners having a shape other than radiused, such as square corners, radiused corners impart a flexibility to the seal  24  that prevents tearing of the seal during operation. Thus, the seal body  30  is configured to have a generally hollow, rectangular, ring shape, with a predetermined lateral wall thickness defined at its interior by an inner circumference of the opening  32  and at its exterior by an outer circumferential wall. Preferably, end walls  35  are slightly thicker than side walls  36 . The predetermined wall thickness may vary to suit individual applications, but is preferably between 4.4 mm and 5.0 mm for the end walls  35 , and between 3.5 and 4.1 for the side walls  36 . Additionally, the seal body  30  has a predetermined height, preferably between 4.3 mm and 5.2 mm.  
         [0017]    Correspondingly, the enclosure  16  of the slide switch assembly  12  has outer walls  38  of a predetermined thickness, a bottom wall  40  of a predetermined thickness, and a generally rectangular open top portion  42 . The seal  24  is generally configured so that the dimensions of the predetermined wall thickness of the seal body  30  are coextensive with the outer walls  38  of the enclosure  16  so that the seal may be disposed on a top surface of the enclosure. Moreover, the bottom surface  28  of the seal  24  is preferably provided with adhesive properties so that the seal firmly adheres to the enclosure  16 , and remains stationary with the enclosure while the switch cover  22  reciprocates with respect to both the stationary seal and the enclosure to which it adheres. The instant invention contemplates use of any suitable adhesive sufficient to maintain engagement between the stationary seal  24  and the enclosure  16 , preferably a material such as a film-supported tape. For example, one preferable film-supported tape is manufactured by Adchem Corporation of Riverhead, N.Y. under the brand name Adchem® 256-M.  
         [0018]    While the dimensions of the seal  10  may vary to suit individual slide switch assembly  12  dimensions, the preferred embodiment includes a seal having a longitudinal length of between approximately 30.05 mm and 30.85 mm and a width of between approximately 13.6 mm and 14.4 mm. More specifically, the instant seal  24  includes the seal body  30  having wall thicknesses as previously described, while the length and width of the central opening  32  preferably measure 21.05 mm and 6.4 mm, respectively.  
         [0019]    To enhance its sealing properties, the preferred seal  10  includes a compressible, elastic material, such as a cellular urethane having an open celled structure, such as Poron®, manufactured by the Rogers Corporation of Rogers, Conn. Ideally, the composite material of the seal  24  has a hardness sufficient to withstand cycling but that is soft enough so that actuation of the slide switch assembly  12  is not inhibited. When compressed, the slide switch assembly  12 , which includes the compressible seal  24 , compresses from between 20% to 40%, preferably about 20%. Because the seal  10  preferably includes a compressible material, the underside  30  of the switch cover  22  is preferably smooth to reduce friction between the switch cover and the seal as the switch cover reciprocates and to promote slideability of the switch cover atop the seal.  
         [0020]    In a typical slide switch, a slide cover reciprocates within a predetermined track. To promote adequate compression of the compressible seal  24 , which imparts sealing properties to the slide switch assembly  12 , a predetermined pair of tracks  44  is configured and arranged so that when the slide switch cover  22  is matingly engaged therewith, the preferred compression percentages will be achieved. To this end, the housing  14  preferably includes the pair of elongated tracks  44 , into which side flanges  46  (best shown in FIG. 4) of the switch cover  22  matingly engage. The side flanges  46  reciprocate within the respective on of the pair of elongated tracks  44 , which are situated at a predetermined height above the seal  24  so that when engaged with the elongated tracks, the side flanges  46  compress the seal  24  at a predetermined percentage, such as 20%.  
         [0021]    To further promote the sealing properties of the instant seal  24 , the slide switch assembly  12  in which the seal operates may be modified to specifically accommodate the dimensions of the seal. For example, in a conventional slide switch assembly, the underside  32  of the switch cover  22  directly contacts the enclosure  16 . Thus, to accommodate the seal  24  without altering the overall dimensions of the slide switch assembly  12 , the switch cover  22  may optionally be modified to accommodate the height of the seal  24 . For example, the height of the switch cover  22  may be reduced by an amount corresponding to the height of the seal  24 .  
         [0022]    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.  
         [0023]    Various features of the invention are set forth in the following claims.

Technology Classification (CPC): 7