Chemistry: electrical current producing apparatus – product – and – Cell support for removable cell – Having switch or interlock means
Utility Patent
1998-08-14
2001-01-02
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Cell support for removable cell
Having switch or interlock means
C429S100000, C429S123000, C292S219000
Utility Patent
active
06168881
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to battery operated power tools and, in particular, relates to a latch mechanism to attach the battery pack to a power tool.
2. Scope of the Prior Art
Powers tools, such as drills, screwdrivers, saws, etc., have long been used by professional builders, amateur fix-it people, and others. Electric power tools can be powered by an AC power source using an electrical cord and connector that is a part of the power tool. As battery technology has improved, power tools are now commonly powered by battery packs. The battery pack improves the mobility of the power tool by avoiding the need to use cumbersome extension cords. As the use of battery operated tools have increased, the demand to supply ever-increasing power to the battery operated power tools has also increased. This demand in increased power has increased the weight of the battery pack and therefore the weight of the power tool. Thus, power tool manufacturers have redesigned the shape and weight distribution of power tools to accommodate the size and weight of the battery packs.
For the power tool to continue operating, the batteries must be recharged. Accordingly, the battery pack must be removable from the power tool. A battery latch mechanism is therefore provided on the power tool or the battery pack. The latch mechanism secures the battery pack in a mechanically and electrically coupled position to the power tool so that the power tool has the necessary power to operate for its intended use. The battery latch mechanism must be appropriately strong to hold the battery pack in mechanical and electrical coupling during the rigors of use. In addition, the latch mechanism must be easy to maneuver so that the battery pack can be removed from the power tool for recharging.
Moreover, the battery latch mechanism should be designed so that the power tool operator can easily remove the battery pack while holding the power tool. Traditionally, the battery pack is positioned at the base of the power tool. In one example of the prior art, the battery pack is provided with a latch mechanism. The latch mechanism is positioned along the top edge of the battery pack where the pack mates with the power tool. The mechanism includes a pushing surface at its lower end and a latching flange at the top end. Below the pushing surface and in the battery pack housing, a spring is positioned to bias the mechanism into a position that secures the battery pack to the power tool. That latching surface of the power tool is oriented on the inside of the power tool housing. When the pushing surface is pressed, the latch mechanism moves about the lower end and the latch flange disengages with the latching surface.
When the battery pack needs to be removed from the power tool, the operator holds the hand grip portion of the power tool with one hand. In the other hand, the operator holds the bottom of the battery pack and cradles the battery pack in the throat of the hand between the index finger and thumb. The tip of the index finger and thumb are placed on the battery latch mechanism and maneuvered to disengage the latch mechanism from the power tool thereby removing the battery pack from the power tool. Latch mechanisms of this sort are difficult to use because they move about a point below the pushing surface within the housing of the battery pack. In other words, as the latch mechanism is pushed into the housing of the battery pack the latch flange of the latch mechanism is also pushed in away from the latching surface of the power tool housing. The spring force for this type of latch mechanism is below the pushing surface. As the battery packs get larger and heavier, the spring force must be increased and the latch mechanism of this design becomes harder to use. Of course, the battery pack must have sufficient space to accommodate the size of the spring. Moreover, the pushing surface must remain at the top of the battery pack housing because the location of the spring presents design constraints. When the operator places the hand in the hand throat underneath the battery pack the leverage available at the fingertips is not always sufficient to bias the spring to therefore remove the battery pack.
In another prior art battery pack latch mechanism, a clip is connected to the housing of the power tool. The clip pivots about a point on the power tool between an engaged position and a release position. In the engaged position the clip is connected to the battery pack housing to secure the battery pack into its electrically coupled position. In the release position, the clip is disengaged and pivoted from the battery pack so that the battery pack can be removed from the power tool. As the battery packs have become heavier from increasing battery size, the clip has become stiffer and therefore harder to use.
Although battery packs are becoming larger, smaller and less powerful battery packs are still used. Different types of power tools also require different designs of battery packs. Power tool manufacturers therefore have many different battery pack sizes and designs which may require different types of battery latch mechanisms. These different designs increase the cost for battery packs.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a latch mechanism for a battery operated power tool that avoids the disadvantages of the prior art. Therefore, the present invention relates to a battery latch mechanism that is easy to use regardless of the battery size and that allows the battery pack to fit in the throat of a hand. In addition, the present invention provides a latch mechanism that is not stiff to use regardless of the size of the battery pack.
In accordance with the objects of the invention, a power tool is provided that has a power tool housing. The power tool housing has an upper portion where a motor is provided, a grip portion to be gripped by an operator, and a base. A recess is provided into the outer surface of the power tool housing. The bottom of the recess can serve as a latch surface.
In order to power the power tool, a battery pack is provided that electrically and mechanically couples with the power tool. The battery pack has an upper and lower housing to define a container into which battery cells are placed.
The battery pack includes a battery latch mechanism to electrically and mechanically secure the battery pack to the power tool. The battery latch mechanism comprises a latch member and a spring. The spring fits into the lower housing and is positioned to bias the latch mechanism in an engaged position. The latch member fits into a space provided in the lower housing and is positioned on top of the spring. The latch member includes an outer side and an inner side wherein the inner side faces the inside of the housing and the outer side is approximately flush with the outer surface of the housing. A latch flange is provided on the inner side of the latch member at the upper end of the latch member. A pushing surface is provided toward the opposing lower end on the outer side of the latch mechanism. A pivot axis is oriented width-wise across the latch member between the latch flange and the pushing surface.
As stated, the latch mechanism is biased by the spring into an engaged position so that the latch flange is positioned within the recess and connected to the latch surface on the power tool housing. In order to remove the battery pack from the power tool, the latch mechanism is pivoted from an engaged position to a release position. To pivot the latch mechanism, the pushing surface is pushed into the battery pack housing against the spring. By pushing the pushing surface, the latch mechanism rotates around the pivot axis so that the latch flange disengages from the latch surface provided on the power tool. The battery pack can therefore be mechanically and electrically decoupled from the power tool.
To reconnect the battery pack to the power tool, the latch mechanism can be snap engaged into the latch surface. Alternatively, the p
Fischer Ernest
Williams Alston
Gardner Carton & Douglas
Kalafut Stephen
S-B Power Tool Company
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