CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Serial No. 60/657,231, filed on February 28, 2005, the teachings and disclosures of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to electromagnetic motors and their control circuitry for power tools and devices, and more particularly, to a continuously variable frequency swinging armature motor and drive for improving the performance of such power tools and devices.

2. Description of Related Art

In the design of power tools and other work devices and machines, it is a continuing design goal to improve performance parameters to enhance user operation and productivity. In such devices as airless paint sprayers, high pressure washers, electric caulk guns, speed staplers, low volume water or air pumps, portable high pressure air compressors, power chisels and scrapers, among others, such parameters may include increasing output volumes, increasing user adjustability of output, increasing operating frequency ranges, and reducing acoustic noise, heat, and weight. The ability to improve these parameters, particularly the output volume (e.g., of a paint sprayer), without increasing the size and power of the motors and pumps within such devices would be highly advantageous. hi devices using electromagnetic-based swinging armature motors, it has been found that the electromagnets that use single windings can be designed to improve performance of the devices. Such devices that use a single winding are usually powered directly from an alternating current ("AC") line. This allows the armature to close at twice the line frequency, i.e., one time for the positive one-half of the AC waveform and one time for the negative one-half of the AC waveform. For a 60Hz line, for example, the armature will move, open, and close 120 times per second with such an arrangement. Control over output volume (or other work done) is commonly accomplished by limiting

how far the armature can move. This is sometime done by an adjustable mechanical stop. In other words, in order to control the output volume, you have to limit how far the armature can move, which is commonly accomplished by providing an adjustable mechanical stop. It would be preferable to electronically adjust the output, not mechanically.

Using a sine wave voltage to power the electromagnet is generally inefficient because the waveform has to fall to near zero volts before the armature can start to move to its open position. Therefore, there is less time for the pump's piston to fully open, and thus, there is less time for paint to enter into the pump section or reservoir of a typical paint sprayer, hi addition, the armature also experiences a so-called bounce when it hits its open position stop. The bounce increases the settling time of the armature, thereby decreasing the overall output volume of the paint delivered from the typical paint sprayer. Therefore, it has been found that using other waveforms can improve electromagnetic motor performance. Also, where a DC signal is used to power an electromagnetic-based swinging armature motor, there is a need to have a current signal with a pulse width and associated circuitry that will allow the magnetic field generated by the electromagnet to collapse quickly and store the resulting energy within the circuit.

Accordingly, there is a need in the industry for a variable frequency driven swinging armature motor that can be continuously driven over a wide range of frequencies. Previous frequency adjustment solutions provided a circuit to selectively skip cycles or half cycles of the AC waveform. See e.g., U.S. Pat. Nos. 4,517,620 and 4,705,995 to Hans- Joachim Boll, the disclosures of which are hereby incorporated by reference in their entirety. Typically, this was accomplished by using a triac-type device (e.g., two thyristors wired in series, but pointing in opposite directions) that turns on and off at the zero crossings. Because the minimum period that can be skipped is one-half of a 60Hz cycle, the frequency can only be reduced in 30Hz increments while maintaining steady symmetrical output pressure and flow in the associated pump, which translates into drive frequencies of 120Hz, 90Hz, 60Hz, and 30Hz. Such frequency control limitations are commonly recognized as shortcomings in the industry. Therefore, a continuously variable frequency driven swinging armature motor would provide numerous benefits to the industry. Such a motor would provide more versatility and increase control in many applications. And for any applications where the lowest desired frequency is higher than the normal AC line frequency (i.e., 50-60 Hz), the electromagnet can be made physically

smaller and still generate the same force, or alternatively, generate more force with the same size of electromagnet. hi accordance with the foregoing, an electromagnet based motor and associated circuitry incorporating improvements not heretofore employed for use in power tools and devices would be highly desirable.

BRIEF SUMMARY OF THE INVENTION

A power device, comprising a power source; timing circuitry powered by said power source for producing a current pulse output having a pulse width; a switch for triggering said current pulse output from said timing circuitry; and an armature motor powered by said power source and in electrical communication with said timing circuitry for receiving said current pulse from said timing circuitry, said armature motor comprising an electromagnetic core; a first winding for carrying electrical current to energize a magnetic field associated with said electromagnetic core; a second winding for carrying electrical current to re-set said magnetic field associated with said electromagnetic core, said first winding and said second winding bifilar wound about said electromagnetic core; and a swinging armature for providing movement in response to energizing said magnetic field associated with said electromagnetic core, wherein when said switch triggers said current pulse from said timing circuitry, said armature operates at said current pulse output pulse width.

BRIEF DESCRIPTION OF THE SEVERAL VIEW OF THE DRAWINGS

Many aspects of the invention will be better appreciated and understood in conjunction with the following drawings and Detailed Description of the Invention, which form integral components of this Specification, in which like reference numerals generally represent like elements, and in which:

FIG. 1 is an electrical schematic of an electromagnet and associated circuitry in accordance with one aspect of the present invention; and FIG. 2 is a side-elevation, partially in cross-section, of a hand-held spray gun incorporating the control circuit of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to Fig. 1, an electrical circuit 10 of a variable frequency driver and control circuit for a swinging armature motor is shown 10. The circuit 10 includes a common power source 11 (such as 120V AC) that provides the requisite input voltage for the applications and circuitry desired.

The circuit 10 is associated with a power device (e.g., see FIG. 2) to improve the performance thereof, examples of which include, but are not limited to, airless paint sprayers, high pressure washers, electric caulk guns, speed staplers, low volume water or air pumps, portable high pressure air compressors, power chisels and scrappers, and the like. Many other types of applied technologies may also be used in the present invention, which is particularly well-suited for applications in which additional throughput (e.g., of air, paint, water, etc.) of the power device is desired. Such devices commonly have pump pistons that are driven by a coil/oscillating armature combination.

A preferred way to adjust throughput within a desired range of a given power device (e.g., in painting applications, from a fine mist to full droplets) may be accomplished with an adjustment mechanism VRl . The adjustment mechanism VRl is shown as a variable resistor or potentiometer, but other suitable adjustment mechanisms VRl may also be used. The adjustable mechanism VRl permits continuous frequency adjustment control within a given range, with the size of the adjustment mechanism VRl being selected to obtain the desired drive frequency within the desired frequency adjustment range. In a preferred embodiment, a frequency adjustment range of 25-150Hz is selected, although other ranges are also possible.

A low level signal switch SWl is in electrical communication with the adjustment mechanism VRl. When closed, the switch SWl provides a signal path to ground. In a preferred embodiment, the adjustable mechanism VRl and switch SWl are electrically connected to the circuit 10 through an external mounting 12 that is not otherwise physically mounted to the circuit 10. Alternatively, these components may also be integrated components of the electrical circuit 10.

In any event, the adjustable mechanism VRl and switch SWl are electrically connected to and associated with a timing module 14 of the circuit 10. Although many timing circuit configurations may be used as part of the timing module 14, one exemplary embodiment includes a pair of 7555 timing chips ICl (7555 Clock) and IC2 (7555 One Shot), which are used to control the timing and duration of signal pulses to be used within the circuit 10. In a preferred embodiment, both timing chips ICl and IC2 have the following pin assignments:

The various functionalities of the timing chips ICl and IC2 are well-known and will not be further described except as they are used herein to produce the necessary signal pulse.

Li any event, the timing module 14 of the circuit 10 preferably includes the following components: resistors Rl, R2, R3, and R4; timing chips ICl and IC2; and capacitors C3, C4, C5, C6, C7, and C9. As shown, resistors Rl and R2 are electrically associated with ICl, as are capacitors C4, C5, and C9. Likewise, resistors R3 and R4 are electrically associated with IC2, as are capacitors C6 and C7. Capacitor C3 is electrically associated with both timing chips ICl and IC2.

As an exemplary, representative, and non-limiting example, numerical values are set forth below for the electrical circuit 10 of FIG. 1. They are only provided to convey an understanding of the invention, and they are not intended to restrict the scope of the invention in any way. Nevertheless, preferred circuit elements of the circuit 10 can be dimensioned as follows:

As shown in FIG. 1, the switch SWl triggers a low level signal on and off by making one of its signal paths into an open circuit. As the adjustment mechanism VRl is adjusted, its variable resistance, in series with a resistor Rl, will produce a total resistance at pin 6 of ICl, thereby adjusting the clocking function thereof. The operation of ICl is also linked to IC2 since the output pin 3 of ICl is connected to the input trigger pin 2 of IC2. In operation, it is the output from output pin 3 of IC2 that has the desired square wave on branch 16 with the desired pulse width. In the configuration depicted, a pulse width of about 2.8 ms is preferred. However, the pulse width is optimized according to a given electromagnet size. For example, if the size of the electromagnet is changed, the desired pulse width would also need to change in order to be optimized to the new electromagnet size. It is further contemplated that automatic adjustment of the pulse width based on, for example, the slope of current in the electromagnet, or another suitable parameter, is possible to allow for fully automatic optimization of the pulse width to accommodate fluids having varying properties, such as different fluid viscosities. The signal on branch 16 is then transmitted to a switching network 18, which preferably includes the following: a common base/common emitter NPN-PNP transistor pair Ql, Q2; a switching device such as a MOSFET Q3; resistors R6, R7, R9; and a capacitor C2. The switching of the MOSFET Q3 is tied into, and affects the operation of, an armature motor Ml in communication therewith. The armature motor Ml is a swinging armature motor, and it includes an electromagnetic wound coil. The coil includes an electromagnetic core 22 and a first winding 24 for carrying electric current to energize a magnetic field associated with the electromagnetic core 22. The coil also includes a second winding 26 for carrying current to re-set the magnetic field associated with the electromagnetic core. Both the first winding 24 and the second winding 26 are wound about the electromagnetic core 22 The first winding 24 and the second winding 26 are bifilar wound together about the electromagnetic core 22. As will be described, the motor Ml also includes a swinging armature for providing movement in response to energizing the magnetic field about the electromagnetic core 22.

The circuit 10 also includes at least one storage capacitor Cl in electrical communication with the second winding 26. When the magnetic field collapses, the storage capacitor Cl stores residual electrical energy from the electromagnetic core. The storage capacitor Cl also filters a rectified signal from a diode rectification bridge 28 (i.e., diodes Dl - D4) that rectifies the 120V AC input signal from the power source 11. The electrical switching device Q3 is also in electrical communication with the storage

capacitor Cl such that, when it is biased on, the storage capacitor Cl releases the electrical energy stored therein from the second winding 26. In addition, when the electrical switching device Q3 is biased on, electric current flows through an electrical steering device such as a steering diode D6 electrically connected thereto. The steering diode 36 provides an electrical path for magnetic energy to be removed from the electromagnetic core through the second winding 26. On the other hand, when the electrical switching device Q3 is biased off, the storage capacitor Cl stores electrical energy obtained from the second winding 26 when the magnetic field collapses, hi a preferred embodiment, the electrical switching device Q3 is a MOSFET, and the electrical steering device is a steering diode D6.

In order to prevent undesirable or excessive heat generation, a cooling device, such as a fan Fl, can also be added to the circuit 10. To power the cooling device, a winding can be added to generate an appropriate voltage level. During normal operation, that is, within a typical frequency range of about 25HZ to about 150HZ, if the frequency is adjusted above a certain level (e.g., above 150 HZ), then when the winding temperature exceeds 125° Celsius, the frequency can be automatically reduced to a pre-determined certain level. If the temperature of coil or winding reaches a second level (e.g., 140° Celsius), the frequency can be reduced even further, for example, to 80 HZ. Should the temperature continue to climb and reach a maximum allowed temperature (e.g., 155° Celsius, the unit can be configured to automatically shut off until that temperature falls below a predetermined temperature, or until the power device is turned off. The coil can also be driven unipolar with pulsating DC power. The power winding 1-3 can be wound bifilar with reset winding 2-4.

As described, the stored magnetic energy in the electromagnet is largely conserved and returned to the storage capacitor Cl at the end of each duty cycle, whereby it can then be re-used. This increases electrical efficiency. This is possible because two bifilar windings (for optimal magnetic coupling) are used instead of only one winding. The first winding 24 is the power winding for the electromagnet. The second winding 26, which in one preferred embodiment is smaller in current-carrying capacity than the first winding, is connected electrically and in anti-parallel. It functions as a re-set winding. This second winding 26, combined with the steering diode D6, allows a path for the energy to be removed from the magnetic core, which is necessary before the next power cycle is applied. Since a square wave voltage is applied to the electromagnet, the armature can close more swiftly. Thus, this second winding 26 decreases the magnetic field more

rapidly and allows the armature to move to its open position more quickly. The net result is that this allows higher frequency operation and greater output volume for a given power device.

As further exemplary, representative, and non-limiting examples, component types are set forth below for the electrical circuit 10 of FIG. 1. They are only provided to convey an understanding of the invention, and they are not intended to restrict the scope of the invention in any way. Nevertheless, preferred components of the circuit 10 can be as follows, as available from any suitable vendor:

Referring now to FIG. 2, a power device is shown, as readily suited for the inventive arrangements as described hereinout. More specifically, the representative power device is a spray gun 100, although numerous other power devices are also hereby contemplated. In any event, the representative spray gun 100 includes a gun casing 102 and handgrip 104 depending therefrom, with a representative on/off trigger switch 106 provided therein the grip 104. A reservoir 108 for the medium to be sprayed (e.g., paint or other) is secured to the underside of the gun casing 102. This medium to be sprayed is drawn up by a representative pump 110, which is driven by a coil/oscillating armature combination and disposed within the gun casing 102. Thereafter, this medium to be sprayed is conveyed to a representative spray nozzle 112 for application. Internally, an electric swinging armature drive 114 is mounted within the gun casing 102 to drive the pump 110. An electronic control circuit 116 for the pump 110 and swinging armature drive 114 is also disposed within the gun casing 102, although relative positions thereof are only depicted for exemplary, representative, and non-limiting purposes. Other suitable arrangements thereof are also contemplated hereby. In any event, the electronic control circuit 116 for the swinging armature drive 114 preferably comprises the electrical circuit of FIG. 1, as described hereinout.

Referring again to FIG. 1, when the switch SWl triggers the current pulse from the timing circuitry 14, the armature of the motor Ml operates at the desired current pulse output pulse width. An exemplary winding structure for winding 1-3 is 380 turns of 3 X #25AWG wire and winding 2-4 is 380 turns of 1 X #25 AWG wire. In a preferred embodiment, the electrical circuit 10 is used as part of a power device. As such, the power device can also include the afore-described power source 12; timing circuitry 14 powered by the power source 12 for producing a current pulse output having a pulse width; a switch Q3 for triggering the current pulse output produced by the timing circuitry 14; and an armature motor Ml powered by the power source 12 and in electrical communication with the timing circuitry 14 for receiving the current pulse therefrom.

The power device can also comprise a frequency adjustment control mechanism in electrical communication with the timing circuitry 14 for electronically varying the pulse width by adjusting the frequency adjustment control mechanism, hi one embodiment, the frequency adjustment control mechanism can be a potentiometer, hi one embodiment, the power device of the pulse width can be about 2.8 ms. hi one embodiment, the current pulse output is a continuous symmetrical output, hi one embodiment, the frequency adjustment control mechanism permits infinite frequency adjustment within a desired operating frequency range. hi another preferred embodiment, a variable speed swinging armature motor can comprise an electromagnetic core; a first winding for carrying electric current to energize a magnetic field about the electromagnetic core; a second winding for carrying current to re-set the magnetic field associated with the electromagnetic core, the first and second windings wound about the electromagnetic core; and a swinging armature for providing movement in response to the energizing of the magnetic field associated with the electromagnetic core. The first winding and the second winding are bifilar wound together about the electro-magnetic core. The removal of energy from the electromagnetic core can occur prior to a succeeding tenderization cycle of the electro-magnetic core. The second winding can have a current-carrying capacity that is less than a current- carrying capacity of the first winding. The motor can utilize an AC line frequency. In one embodiment, a square wave voltage is applied to the first winding and the second winding. The AC line frequency can be about 50-60 Hz.

In another embodiment, disclosed herein is a variable frequency driver and swinging armature motor combination. The combination comprises: a variable speed

swinging armature motor as previously described and a control circuit for controlling the variable speed swinging armature motor. The control circuit comprises: timing circuitry for producing a current pulse output having a pulse width; a switch for triggering the current pulse output produced by the timing circuitry; a storage capacitor in electrical communication with the second winding and wherein the storage capacitor stores residual electrical energy collected from when the magnetic field associated with the electromagnetic core collapses; and an electrical switching device in electrical communication with the storage capacitor such that, when the electrical switching device is biased so as to be turned on, the storage capacitor releases the electrical energy stored therein from the second winding. hi one embodiment, the combination further comprises a frequency adjustment control mechanism in electrical communication with the timing circuitry for electronically varying the pulse width by adjustment of the frequency adjustment control mechanism.

It should be understood that this specification describes exemplary, representative, and non-limiting embodiments of the invention. Accordingly, the spirit and scope of this invention are not limited to any of these embodiments. Rather, the details and features of these embodiments were disclosed as required. Thus, many changes and modifications - as apparent to those skilled in the art — are within the scope of the invention without departing from the spirit hereof, and the inventive arrangements are inclusive thereof. Accordingly, to apprise the public of the spirit and scope of this invention, the following claims are made: