Patent Application
20060006911
1. Field of the Invention
The present invention relates generally to an electrical nailing gun, and more specifically to a driving circuit for an electrical nailing gun, which uses a capacitor to accumulate electrical energy for increasing the power of the electrical nailing gun.
2. Description of the Related Art
Conventionally, high power nailing guns are air nailing guns to be used with an air compressor to fire nails. However, an air nailing gun produces much noise during operation. Further, the air compressor requires much work space. In order to eliminate these drawbacks, electrical nailing guns are developed. An electrical nailing gun uses electricity to energize a coil, thereby producing a magnetic force to attract the piston, and therefore the piston drives the nail into the workpiece. This design of electrical nailing gun produces low noise during operation. Because this design of electrical nailing gun does not use with an air compressor, it requires less work space. However, conventional electrical nailing guns still have drawbacks. A conventional electrical nailing gun requires a heavy transient current when firing the nail, and such a heavy transient current is a heavy burden to the AC power cord. Different AC power cord conditions, such as wire diameter, power cord extension length, or power cord material, cause different transient current to further result in different firing power. Due to the limitation of firing power, there is a limitation to the application of conventional electrical nailing guns, thereby resulting in a barrier to market promotion.
The driving circuit of a conventional electrical nailing gun simply uses one half-cycle or one full-cycle. However, the frequency of city power supply is 60 Hz, and the period of a half-cycle is as short as 8.3 ms. This short period results in a limitation to the action of the magnetic force upon the piston. Because magnetic force varies with the variation of AC power supply waveform, the magnetic force converted from the electrical energy for attracting the piston cannot be optimized, i.e., the piston firing power is limited. Further, in order to increase magnetic force, electrical current must be relatively increased. However, increasing electrical current may cause an overload at the AC power cord, thereby resulting in flashing of fluorescent lamps in the house. Furthermore, if the resistance is increased due to the use of an electrical extension cable, the energizing current will drop, thereby reducing nail firing power. Therefore, the use of an electrical extension cable is limited. Further, if three or more coils are used to increase nail firing power, the length of the electrical nailing gun must be relatively increased, and the weight of the electrical nailing gun will be relatively increased. Further, because every coil works at a saturated status, the temperature of the electrical nailing gun will be greatly increased, not able to meet safety code (for example, UL) requirements.
The present invention has been accomplished under the circumstances in view. It is therefore the main object of the present invention to provide a driving circuit for electrical nailing gun, which greatly increases nail firing power without increasing the electrical current.
To achieve this and other objects of the present invention, the driving circuit for electrical nailing gun comprises a capacitive charging/discharging unit, the capacitive charging/discharging unit comprising a first resistor, a first diode, and a capacitor connected in series, the capacitive charging/discharging unit having two opposite ends respectively connected to the positive and negative poles of AC power source; an excited field unit, the excited field unit comprising a first coil and a first electrically-controlled switch connected in series, the first coil having two opposite ends connected in parallel to the capacitor; and a control unit electrically connected to the first electrically-controlled switch for activating the first electrically-controlled switch.
Referring to
The capacitive charging/discharging unit 11 comprises a first resistor R1, a first diode D1, and a capacitor C1 connected in series. The capacitive charging/discharging unit 11 has two ends respectively connected to two ends of AC power source.
The excited field unit 15 comprises a first coil 16 and a first electrically-controlled switch 17 connected in series. The excited field unit 15 has two ends connected in parallel to the capacitor C1. The first electrically-controlled switch 17 according to this embodiment is a SCR (silicon-controlled rectifier).
The control unit 19 is electrically connected to the first electrically-controlled switch 17 for activating the first electrically-controlled switch 17.
Upon connection of the electrical nailing gun (not shown) to AC power source, the control unit 19 deactivated the first electrically-controlled switch 17. At this time, AC positive half-cycle passes through the first resistor R1 and the first diode D1 to charge the capacitor C1 to the saturated standby status. Thus, the control unit 19 sends a signal to activate the first electrically-controlled switch 17 when received a triggering signal (firing signal), i.e., at the proper time corresponding to AC power source, wherein the first electrically-controlled switch 17 is activated during positive half-cycle of AC power source, and closed during negative half-cycle of AC power source. The capacitor C1 discharges when the first electrically-controlled switch 17 is activated, thereby increasing current to the first coil 16 to enhance the nail firing force.
During operation, the second diode D2 and the third diode D3 are used to guide the direction of current. Same as the aforesaid first embodiment of the present invention, the discharging operation of the capacitor C1 is used to increase the current of the first coil 16, thereby enhancing the nail firing force.
When in use, the first coil 16 and the second coil 36 are connected in series. During AC power source positive half-cycle, the control unit 19 activates the second electrically-controlled switch 37, enabling AC power source positive half-cycle to energize the second coil 36. During AC power source negative half-cycle, the control unit 19 activates the first electrically-controlled switch 17, enabling the discharging action of the capacitor C1 to increase the current of the first coil 16 and to further accelerate the nail firing action of the electrical nailing gun. The accelerating effect of these two coils 16 and 36 is much better than the accelerating effect of one single coil. The other operation of this third embodiment is same as the aforesaid first embodiment of the present invention; therefore no further detailed description is necessary.
When in use, the control unit 19 activates the second electrically-controlled switch 37, the first electrically-controlled switch 17, and the third electrically-controlled switch 47 at proper time, enabling AC power source positive half-cycle to energize the second coil 36 and the first coil 16 and AC power source negative half-cycle to energize the third coil 46. The accelerating effect of this fourth embodiment is much better than the accelerating effect of the aforesaid third embodiment. The other operation of this fourth embodiment is same as the aforesaid first embodiment of the present invention; therefore no further detailed description is necessary.
According to the aforesaid fourth embodiment as shown in
As indicated above, the invention uses a capacitive charging/discharging unit to provide an added coil accelerating effect that fully utilizes every full cycle of AC power source. Therefore, the invention greatly enhances the nail firing power without increasing AC power source. Further, the invention uses a capacitor providing electricity, thereby increasing the current of a coil. Due to coils is energized during unsaturated status, the invention achieves a high performance without increasing much temperature. Therefore, the invention can greatly increase nail firing power without changing the total weight and length of the electrical nailing gun and producing much heat.
A prototype of driving circuit for electrical nailing gun has been constructed with the features of
Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.
