FIELD OF THE INVENTION
- BACKGROUND OF THE INVENTION
The present invention relates to power tools and more particularly to a variable speed drill.
In many workplaces or construction site environments, it is necessary to use various substances to perform a given task. Many of these substances, for example paints, coatings, mortars, cements, powders, etc., may require a certain amount of mixing before use. As the quantity of these substances can be relatively high in any given application, a need arose for an easy and efficient way to mix these substances.
To meet this need, various mixing implements or “paddles” have been introduced into the market. These paddles are designed to be coupled to traditional drills commonly found in many workplaces and construction sites. In this regard, operation of the drill in turn rotates the paddle which may then mix a given substance.
- SUMMARY OF THE INVENTION
However, there are limitations in the art. For example, to successfully mix a thick substance such as cement or mortar, a power drill having a high torque must be employed. These drills do not have variable speed switches to regulate the rotational speed of the paddle, and therefore the drills must be turned on and off in order to reduce the rotational speed and hence splashing or over-mixing. This can be tiring to the user and is inefficient. Accordingly, the present invention seeks to improve the art with a variable speed drill for use in mixing applications.
A variable speed drill includes a housing and a motor within the housing. The motor has a lamination length of at least 30 millimeters and a lamination diameter of at least 73 millimeters. A mixing implement is rotationally coupled to the motor. A variable speed switch is mounted to the housing and is operable to vary a rotational speed of the motor and therefore of the mixing implement.
BRIEF DESCRIPTION OF THE DRAWINGS
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
FIG. 1 is a front perspective view of a variable speed drill constructed according to the principles of the present invention having an exemplary mixing implement attached thereto;
FIG. 1A is a front perspective view of an alternate mixing implement used with the variable speed drill of the present invention;
FIG. 2A is a perspective view of a motor used with the variable speed drill of the present invention;
FIG. 2B is a side view of a motor used with the variable speed drill of the present invention;
FIG. 2C is a front view of a motor used with the variable speed drill of the present invention;
FIG. 3 is a schematic connection diagram of the variable speed drill of the present invention; and
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 4 is a graph illustrating the function of the variable speed switch according to the principles of the present invention.
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
With reference to FIG. 1, a variable speed drill constructed according to the principles of the present invention is generally indicated by reference numeral 10. The variable speed drill 10 generally includes a housing 12 that partially defines a handle 14. The housing 12 encases a motor 16 including an armature 16A and field winding 16B (FIGS. 2A-2C) that are operable to rotate a chuck 18. In the particular example provided, the motor 16 receives power from a power source (not shown) through a cord 19 coupled to the handle 14 of the variable speed drill 10.
The chuck 18 is adapted to receive an implement (e.g., a tool such as a drill bit, screwdriver head, etc.) therein. In the particular example provided, the chuck 18 receives a mixing implement or “paddle” 20. Rotation of the chuck 18 upon activation of the motor (FIG. 2) in turn rotates the paddle 20. The paddle 20 is adapted to be used in mixing a particular substance via rotation of the paddle 20. For example, paint, mortar, cement, or plasters may be mixed by the paddle 20. Moreover, various other paddle designs may be used to mix these substances. With brief reference to FIG. 1A, an alternate paddle 20′ is illustrated. The paddle 20′ is adapted to be coupled to the chuck 18 of the variable speed drill 10. The paddle 20′ is best used with powder materials and paints.
Returning to FIG. 1, the variable speed drill 10 is operated by activating a trigger 22. The trigger 22 is mounted within the handle portion 14 of the housing 12. The trigger 22 is coupled to the motor 16, shown in FIGS. 2A-2C, and when depressed activates the motor. The trigger 22 engages a variable speed switch 24 which is mounted within the handle portion 14 of the housing 12. The variable speed switch 24 is operable to variably control the power output of the motor 16 and accordingly operable to variably control the rotational speed of the chuck 18 and in turn the paddle 20.
With reference to FIGS. 2A-2C, the motor is an electric motor having an output shaft 26 extending from the armature 16A. The output shaft 26 is coupled to the chuck 18 (FIG. 1) through a gear reduction system, which will increase the torque at chuck 18. The motor 16 is preferably a “heavy-duty,” electric motor. In other words, the motor 16 has a high current rating, greater than 8 amps, preferably 9 amps, a high power level, greater than 600 Watts, preferably 640 Watts, and the motor has a large size with a field lamination diameter (D) (FIG. 2C) of at least 65 mm, preferably 73 mm, and a field and armature lamination stack length (L) (FIG. 2B) of at least 30 mm. A motor of the above size provides 10-12 in-lbs of torque, which is typically necessary for heavy-duty mixing, and with a gear reduction mechanism 30 having a gear reduction of approximately 1 to 40 is capable of providing a maximum torque at the chuck which is greater than 580 in-lbs, preferably 595 in-lbs. It should be appreciated, however, that various other sized motors may be employed with the present invention. The drill 10 has a larger, heavier construction than previous variable speed drills, including a weight greater than 5.5 pounds, preferably 7.5 pounds or greater 9
Turning now to FIG. 3, an electronic diagram of the variable speed switch 24 and the motor 16 is generally indicated by reference numeral 100. The electronic diagram 100 illustrates how the power from the cord 19 is transferred to the field windings 16B of the motor. In the example provided, the variable speed switch 24 includes a variable power module 102 located therein. The variable power module 102 is connected between a power source via the cord 19 and the motor 16.
During operation of the variable speed drill 10, power received from the cord 19 is communicated through the variable power module 102. By moving the switch 24 into various positions, the switch 24 in turn sets the variable power module 102 to provide variable power flow into the motor 16 to achieve variable speeds. Accordingly, the rotational output of the motor 16 and hence the rotational speed of the paddle 20 may then be governed by simply setting the position of the variable speed switch 24. The graph of FIG. 4 shows plot of trigger travel vs. output voltage and shows that the output voltage ranges between a low power position A and a “full power” position B with the trigger travel. The drill 10 preferably has a maximum speed less than 550 RPM. In the “low power” position, only a fraction of the power supplied from the cord 19 is transferred to the motor 16. In the “full power” position, full power is supplied from the cord 19 to the motor 16. It should be appreciated that any number of switch positions may be employed with the present invention to provide a range of rotational speeds to the paddle 20. Variable output power modules of this type are known.
By allowing a user to set the rotational speed of the paddle 20 via the variable speed switch 24, the variable speed drill 10 is ideal for mixing various substances. By providing various rotational speeds for the paddle 20, the mixing can be tailored to the substance to be mixed, thereby reducing the chance of splatter, over-mixing, or under-mixing. Variable speed drills having a smaller motor than the present invention have been known. However, these known variable speed drills have insufficient power to use for typical heavy-duty mixing applications. Previous heavy-duty drills that are used for heavy-duty mixing applications have to be repeatedly started and stopped until the material being mixed reaches a consistency that allows constant running of the motor. Thus, the use of a heavy-duty motor on a variable speed drill for heavy-duty mixing applications is believed to be a novel and non-obvious improvement in the art. Heretofore, variable speed drills having: (a) a motor field lamination diameter greater than 65 mm, (b) a motor current rating greater than 8 amps, (c) a motor power level greater than 600 Watts, (d) a maximum torque level at the chuck greater than 580 in-lbs, (e) a weight greater than 5.5 pounds or (f) a maximum speed less than 550 rpm, have not existed.
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.