Activation switch for a power tool

A power tool includes a linear activation switch incorporating features to prevent accidental activation. More particularly, the switch includes a switch cap that must be first rotated or pivoted before it can be linearly translated to activate the switch. The power tool includes a housing defining a guide track having a first section and an second section, offset from each other by a third section. The switch includes a switch cap having guide ribs, a first slidably disposed within the first section and a second rib one initially situated within the third section. The switch cap is pivotable about the first guide rib so that the second guide rib moves within the third section into alignment with the second section of the guide track. The switch cap can then be moved linearly with the second guide rib sliding within the second section, with this movement activating the switch.

FIELD OF THE INVENTION

The present disclosure relates to power tools and more particularly to activation switches for such tools.

DESCRIPTION OF THE RELATED ART

A myriad of power tools exist that are electrically powered and activated by a manual switch. One common type of switch is a linear switch that is pushed in one direction to activate the power tool and in the opposite direction to de-activate the device. It is desirable to employ a switch that is resistant to inadvertent activation, such as when the power tool is accidentally dropped or bumped against an object. Thus, some switches are recessed within the housing of the power tool. However, this switch design can be difficult to manually access, particularly when the power tool is operating.

For pistol-grip type tools, the switch can be conveniently configured as a trigger. However, more compact tools capable of more nimble operation typically utilize a linear grip in which the tool housing itself is held by the craftsman. Power tools of this type frequently use a linear switch that is pushed in one direction to activate the power tool and in the opposite direction to de-activate the device. The switch is positioned near the cord-end of the tool for easy access when the tool is in use. One problem with this typical switch is that it can be susceptible to inadvertent activation since the linear switch cannot be as effectively shielded, like the pistol grip trigger switch. There is a need for an improved switch that avoids the problem of inadvertent activation but without sacrificing ergonomics.

SUMMARY

In one aspect of the present disclosure, a switch assembly for a power tool having a housing is provided which comprises an interior track defined in the housing, the track including first and second elongated channels offset from each other by an intermediate section and an activation switch mounted within the housing adjacent the interior track, the switch including an actuator movable from a first position to a second position. In one feature, a switch cap is supported within the housing and coupled to the actuator, the switch cap movable within the housing from an initial position corresponding to the first position of the actuator to an activation position corresponding to the second position of the actuator.

The switch cap includes a first rib disposed within the first channel when the switch cap is in the initial position and a second rib disposed within the intermediate section when the switch cap is in the initial position. The first and second ribs are configured to pivot the switch cap about the first rib to an intermediate position in which the second rib is disposed within the second channel of the interior track. The first rib is configured for sliding within the first channel and the second rib is configured for sliding within the second channel to the activation position of the switch cap. The switch cap includes a portion accessible from outside the housing that is configured to be manually engaged to pivot the switch cap from the initial position to the intermediate position and then to slide the switch cap from the intermediate position to the activation position.

DETAILED DESCRIPTION

A power tool10shown inFIG. 1includes an elongated housing12. The housing is configured to be gripped by the craftsman between the cord end13and the working end14. The tool may be configured to accept a variety of bits, such as a spiral saw bit. The housing contains an electrical motor (not shown) for driving the tool bit in which the motor may be an AC motor connected to a power supply by a power cord, or may be a DC motor powered by a battery pack (not shown) mounted within the housing12. The tool10includes an activation switch assembly15that activates and de-activates the tool, or more particularly that connects and disconnects the motor to the electrical power supply. The switch assembly15is mounted within a recessed opening17in the housing12.

Details of the switch assembly15are shown inFIGS. 2a-2c. In particular, the switch assembly includes a switch cap16that engages an activation switch in the form of a toggle switch18mounted within the housing. The toggle switch18includes an actuator in the form of a toggle19that pivots through a throw angle T (FIG. 3) from a first “off” or de-activated position, as shown inFIG. 2a, to a second “on” or activated position, as shown inFIG. 2c. The toggle19includes a post20projecting therefrom that engages the cap16as described herein. The switch cap16is mounted within the housing12for linear actuation. When the cap16is in the position shown inFIG. 2a, the cap is wholly contained within the switch opening17, as depicted inFIG. 1. When it is desired to activate the power tool10, the switch cap16is moved toward the cord end13of the housing, as illustrated inFIG. 2c. This movement of the switch cap moves the switch actuator toggle19from the “off” position to the “on” position.

As thus far described, the switch assembly is similar to other linear switches in that linear movement of the switch cap turns the power tool on and off. However, in order to prevent inadvertent activation of the switch, or accidental sliding of the switch, the switch assembly15is configured so that the switch cap16must first be rotated before it can be translated to move the toggle19, as illustrated inFIGS. 2a-2c. The switch cap16is shown in its baseline position fully contained within the opening17in the housing12. In this position the toggle switch18is in the “off” position. A biasing member24is configured to push the switch cap outward to this baseline position. In one embodiment the bias member is a spring, such as a leaf spring as depicted inFIG. 2a. The base25of the biasing member is fixed within a spring mount28defined in the housing12, while a foot26of the biasing member bears against the switch cap16. It can be appreciated that the view ofFIG. 2arepresents one half12aof the housing, with the other half being substantially identical so that when the two halves12aare joined the biasing member, as well as the toggle switch and switch cap, are captured within the housing.

The housing and switch cap are configured to prevent the switch cap16from being pushed out of the housing by the biasing member. More particularly, the housing defines an interior guide track38(FIG. 4), and the switch cap includes first and second guide ribs34,35, respectively (FIGS. 5a-5b), that are slidably disposed within the track. The guide track38may be formed between an interior wall37and an outboard wall42immediately adjacent the switch cap opening17. As depicted inFIG. 4, the track extends along the length of the tool and housing half12a(it being understood that the other housing half includes a similarly configured track). The walls37and42of the housing are configured so that the track38includes a first channel39, an intermediate section40and a second channel41. The two channels may be substantially linear and generally parallel to each other. The intermediate section40communicates between both channels and may be generally perpendicularly oriented relative to the two channels.

The switch cap is in the baseline, of “off” position (FIG. 2a) when the switch cap is aligned within the first channel39of the guide track. The first channel has a length that is slightly less than the distance between the guide ribs34,35on the switch cap so that the switch cap can pivot, as described in more detail herein. The first guide rib34is thus fully seated within the first channel39of the track while the second guide rib35is situated beyond the end of the first channel. In the illustrated embodiment the first and second channels are linear so that the switch cap can move in a linear fashion during activation and deactivation of the power tool.

Referring toFIGS. 5a-5b, the switch cap includes a body30from which the guide ribs34,35project laterally outward. The switch cap further includes a manually accessible portion32that is offset from the body at a relief33. The underside of the cap is configured to engage the biasing member24and the toggle19of the toggle switch18. Thus, the cap defines a toggle recess44between two walls45that is sized to accept the toggle post20therein. An access opening46may be provided in the side of the cap to facilitate assembly of the switch cap and toggle switch within the housing halves12a. The cap further defines an interior wall47against which the foot26of the biasing member24bears. The interior wall47of the cap slides along the foot of the biasing member24when the cap is rotated and translated, while the biasing member maintains a continuous outward pressure on the switch cap.

The switch cap16is in its initial or first position shown inFIG. 5acorresponding to the first “on” position of the switch18. As suggested above, in order to activate the tool10, the switch cap16is first depressed against the biasing member24toward the interior of the housing12. The guide track38of the housing includes an intermediate section40, or pivot section, at the end of the first channel39, with the second guide rib35residing within the intermediate section. When the manual portion32of the switch cap is depressed to an intermediate position, the second guide rib35moves inward through the intermediate/pivot section40until it is aligned with the second or activation channel41. In order to accommodate this pivoting movement, the first guide rib34that is situated within the first channel operates as a pivot fulcrum and may be accordingly configured in a teardrop shape, tapering from one end34ato the opposite end34b. This tapered shape allows the guide rib to maintain a close sliding fit within the guide track38yet still accommodate pivoting of the switch cap. In the initial position the tapered first rib34is oriented generally parallel to the length of the guide track38, while in the pivoted intermediate and activation positions shown inFIGS. 2b-2cthe tapered rib is canted at an angle relative to the guide track. With this tapered configuration of the first guide rib34, the first channel39of the guide track can have a constant width that provides a close running fit between the rib and the track. The second guide rib35may be oblong, as shown inFIGS. 2a-c. Since the second guide rib35only translates within the second channel41the width of the channel41and the orientation of the rib35may be coordinated to provide a close running fit.

It can be appreciated that until the switch cap is pivoted, as shown inFIG. 2b, the second guide rib35butts against a stop surface39a(FIG. 4) at the end of the first channel39of the guide track. With the biasing member24pushing the switch cap outward the cap is positively restrained from moving longitudinally to a position in which the toggle switch is activated. However, once the manual portion32is depressed, the second guide rib35falls into the second channel41of the guide track in which the cap is now free to slide toward the end of the tool to the activated position, as depicted inFIG. 2c. With the second guide rib35in the second channel and the first guide rib34in the first channel, the switch cap16is translated by pushing the manual portion32upward toward the end of the tool. The toggle post20moves with the switch cap since it is engaged within the toggle recess44, and this movement causes the toggle19to pivot to the “on” position shown inFIG. 2c. The switch cap opening17in the housing is configured to prevent the switch cap from sliding out of the housing when it is moved to its activation position. Thus, the opening may be provided with a stop edge17athat the relief portion33of the switch cap16may contact to prevent further movement of the cap. Alternatively, the second channel41may be provided with a stop surface against which the second rib35may contact.

When the switch cap is in the activated position, the biasing member24attempts to push the switch cap back to its initial position. However, the second rib35is constrained within the second channel41of the guide track38so the switch cap is unable to pivot back to the initial position. The pressure of the biasing member can be sufficient to prevent the switch cap from translating back toward the intermediate section40. In addition, or alternatively, the activation switch18may hold the switch cap in its activation position.

The configuration of the two channels of the guide track38and the two offset ribs34,35prevent the switch cap16from being accidentally moved to the activated position. In the initial or “off” position (FIG. 2a) the switch cap cannot be advanced within the first channel34because the second rib35will contact the stop42at the end of the first channel. Moreover, although the switch cap may be inadvertently depressed so that the cap pivots to its intermediate position (FIG. 2b), the toggle switch18coupled to the switch cap cannot be moved to its “on” position. It is only with the additional linear movement of the switch cap from the intermediate position to the activation position (in which the second rib35slides within the second channel41) that the toggle switch can be flipped to its “on” position shown inFIG. 2c.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications and further applications that come within the spirit of the invention are desired to be protected. For instance, the switch cap16is described as translating upward or toward the cord end15of the tool10. The switch cap movement may be reversed so that the switch cap is translated downward toward the bit end14, with appropriate changes to the orientation of the guide track38and toggle switch18. In addition, the guide track38, and particularly the first and second channels39,41, may be non-linear or arcuate while still preserving the linear activation aspect of the switch cap.

Moreover, in the illustrated embodiment the guide track38is defined in the housing12while the guide ribs34,35are formed on the switch cap. Alternatively the track may be defined in a side wall of the switch cap and the ribs may project inward from an interior face of each housing half12a. With this modification the guide track in the switch cap may be L-shaped, as depicted inFIGS. 6a-6c. In particular, a modified switch cap50includes an L-shaped guide track52with a first channel53and a second channel54. A modified housing includes two guide ribs55and56with the rib55initially disposed in the first channel53of the guide track, corresponding to the “off” position of the toggle switch. The rib56is slidably disposed within the second channel54. When the switch cap50is depressed or pivoted inward the guide rib55moves into the second channel54with the switch cap canted within the housing due to the offset alignment of the two guide ribs, as shown inFIG. 6b. The switch cap is then free to translate toward the end of the tool to flip the toggle switch, while the two ribs55,56are slidably disposed within the second channel54, as illustrated inFIG. 6c.

In addition, the power tool10disclosed herein utilizes a toggle switch18, although other types of activation switches are contemplated, with appropriate modifications to the switch cap16. For instance the switch may be a push button switch and the switch cap may be modified to incorporate a cam surface to depress the push button upon rotation and translation (or upward movement) of the cap. Other switch and switch cap arrangements are contemplated provided they incorporate the rotation or pivoting feature described herein.