MXPA99005893A - Portable electric tool for desol - Google Patents

Abstract

The present invention is directed to a self-contained desoldering gun having a built-in vacuum pump. The vacuum pump is operated by a low voltage electric motor electrically connected, at least partially in series, with a heating tip. In accordance with the exemplary embodiment of the invention, a full-wave bridge rectifier is used to supply power to the vacuum pump motor and the built-in vacuum pump, while using a half-wave rectifier to supply power to the heater. In the exemplary embodiments, the vacuum pump is provided to suck the molten solder and, when the trigger is activated, the motor is subsequently energized and the heated tip outlet increases.

Description

PORTABLE ELECTRIC TOOL FOR WELDING BACKGROUND OF THE INVENTION This invention relates in general to tools for desoldering and in particular to a desoldering tool with improved power control. Currently, most of the desoldering operations in the field of electronics are carried out by desoldering systems consisting of an electric power base and a hand piece for desoldering. Typically, the base includes a pump and a transformer and is connected to the handpiece for desoldering by an electric cable and a vacuum tube. The base rests on a work table and the operator holds the hand piece to desolder while working. A power tool to desolder can execute a number of functions. For example, the tool can be used to generate the heat at the tip that is applied to the components of a circuit board to melt the solder joint that holds the different components on the board. The tool can also supply a vacuum for sucking molten solder into a reservoir, for example, in the handpiece. Current desoldering devices are cumbersome. For example, they require an electrical cable to be coupled with the gun to provide power to the heating element. Also, a vacuum hose must be attached to the gun to remove the molten solder from the circuit board. Both accessories must be dragged around the operator, which makes the operation difficult. This arrangement also requires that the vacuum pump and transformer be mounted on a table near the desoldering operation. The main disadvantage of the arrangement described above is the lack of mobility and portability as a result of the hand piece being coupled to the base by an electric cable and a pneumatic tube. Therefore, according to this arrangement, the operator can only move about 4 or 5 feet from the base. In addition, the nature of the cable and the tube makes the device operation unmanageable. One method that has been used in an attempt to overcome some of the problems associated with these prior systems was to make a self-contained desoldering gun that places a vacuum pump on the handle of the desoldering gun. In accordance with this arrangement, the need for a pneumatic tube connected to the base is eliminated. However, typically the motors used to power the vacuum pump were operated with voltage line motors that are heavier and larger. In addition, these AC electric motors operate at 100 or 120 volts and require significant insulation in addition to the considerable weight of these devices. Consequently, the portable tool itself became larger, heavier and more difficult to handle by the operator, especially over extended periods of time. Another method for making a self-contained desoldering gun provided an improvement over previous desoldering guns when operating a built-in vacuum pump with a low voltage DC electric motor that is electrically connected at least partially in series with a heating tip. According to this arrangement, the heating tip reduces the voltage in the circuit. Subsequently, the required size of the motor to operate the pump was reduced and the total weight of the desoldering gun was also reduced. The reduced weight allows operators to handle the gun more easily. An example of the desoldering gun incorporating this arrangement is shown in Figure 1. With reference to Figure 1, the number 10 indicates the desoldering gun and contains the main components of the tip 20, vacuum pump 40 and a motor 50 DC of low voltage. The low-voltage DC 50 motor located on the handle of the desoldering gun operates a vacuum pump 40 mounted on the gun. An AC line voltage is received through cable 42. Figure 2 shows an exemplary circuit diagram corresponding to the desoldering gun of Figure 1. According to this arrangement, the line 32 AC voltage is converted into DC current by the rectifier 36 and is reduced in voltage by placing a heating element 34 of the gun to desolder, partially in series with the motor pump 50. A portion of the heating element 34 that is not in series with the motor 50 of the pump is in parallel with the motor pump 50, when the pump motor is energized. The switch 38 is a trigger switch (See Figure 1) used to energize the motor 50 through the serial array of the switch 38 and the motor 50 as shown in Figure 2. While this mode provides an improvement over the guns for In the previous desoldering, the desoldering gun may be susceptible to electromagnetic interference (EMI) and radio frequency interference (RFI). This arrangement can also result in a decreased power associated with the use of the engine during the operation of a vacuum pump.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved desoldering device with improved power control, which results in increased power from the engine. Another object of the invention is to provide a desoldering device that is less susceptible to EMI and RFI during use in the work environment. Another object of the present invention is to provide a desoldering device with a more efficient total power consumption than the previous desoldering devices. These and other objectives are provided in a desoldering gun that includes a DC low voltage vacuum pump motor, heater, and power source. In accordance with the exemplary embodiment of the invention, a bridge wave rectifier is used to supply power to the vacuum pump motor and a built-in vacuum pump while using a half-wave bridge rectifier to supply power to the heater.

BRIEF DESCRIPTION OF DRAWINGS Other objects and advantages of the invention will be apparent to those skilled in the art upon reading the following detailed description together with the accompanying drawings, wherein: Figure 1 is a perspective view, partially in section of a Desoldering gun; Figure 2 is a schematic view of a circuit of a desoldering gun with a vacuum pump motor embedded therein; Figure 3 is a schematic view of a gun circuit for desoldering in accordance with an exemplary embodiment of the present invention; and Figure 4 is a schematic view of the wiring of a desoldering gun in accordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION The present invention will also be better understood with reference to the following detailed description and the accompanying drawings, wherein like elements are provided with the same reference number. With reference to Figure 3, a desoldering gun according to an exemplary embodiment of the present invention will generally refer to the number 10. The main components of the desoldering gun 10 are heater 34, pump motor 50 vacuum and a power source 33. In accordance with the exemplary embodiment, the motor can be a low voltage DC 50 motor, operates in a gun mounted on a vacuum pump (not shown). A line voltage AC is received via a cable 42. A terminal block 70 is used to convert an AC voltage to a DC voltage for the DC motor 50 and to connect the heater 34 to the power source 33. In addition, two switches, a power switch 35 and a trigger switch 38 are connected to the terminal block to provide the user with control over the operation of the gun 10. According to an exemplary embodiment, the heater 34, the motor 50 of FIG. The vacuum pump and a power switch 35 may be located in the upper or "barrel" portion of the gun, while the block 20 and the trigger switch 38 may be placed in the handle.

Figure 4 illustrates an exemplary circuit diagram of the desoldering gun according to the embodiment shown in Figure 3. According to this exemplary embodiment, the desoldering gun is provided with a heating element 34. The heater 34 may be formed by a multiple layer winding located at the tip of the desoldering gun. The multi-layer winding and the tip can be used with the present invention as described in detail in copending application No. 08 / 926,801 filed September 26, 1997, entitled "Portable Electronic Desoldering Tool" (or electronic portable desoldering tool). "), expressly incorporated herein by reference, an AC line voltage 33 (namely, 110/240).

VAC) is supplied to the power switch 35. The AC current is converted to DC current by a bridge half-wave rectifier consisting of a diode 36. The half-wave bridge rectifier is connected in series with a heater 34 whenever the desoldering gun is turned on to allow the heater 34 operate at half the line voltage level. This arrangement has some advantages over previous devices for desoldering, among which are: reduce the number of windings required in the heater, reduce the heater resistances and reduce the physical size of the heater. When the power switch 35 is activated by the operator, the heater is energized and heated. The diode 36 is used to run the heater at all times in low heat (namely, 60 volts). By using a half-wave bridge rectifier to supply power to the heater, the diode 36 decreases the heater voltage 34 during its idle mode, when only the "standby" heat is required from the heater 34, providing an output, for 23 watts example. In this mode, the heater temperature is high enough to melt the weld (ie, 700 degrees Fahrenheit). Also provided in parallel with the heater is an indicator lamp 37 which allows the operator to know when the heating tip has been energized. According to one embodiment, the power indicator lamp 37 can be integrated into the power switch itself. Also shown in Figure 4, there is the low voltage vacuum pump motor 50. An AC line voltage 33 is converted to DC current by the full wave bridge rectifier 71.

The DC pump motor 50 is also partially connected in series with the heater element 34 of the desoldering gun. A portion of the heater element 34 that is not in series with the pump motor 50 is in parallel with the pump motor 50 when the pump motor has no power. The switch 38 is a trigger switch used to energize the motor 50 through the serial array of the switch 38 and the motor 50, as shown in Figure 4. The present invention solves the problems associated with the operation of a heavy manual tool and results in essential savings in its cost. The invention uses a low voltage motor 50, for example, a 24 volt DC motor in a preferred embodiment. According to this embodiment, the motor can include a varistor and disk capacitor 3. The low-voltage motor is used without a transformer, which reduces the weight of the desoldering gun. This is achieved by using a full wave bridge rectifier 71 to convert the current to DC and the heating element 34 as part of the voltage drop (IR drop) which reduces the line voltage 32 to the amount required by the motor 50 DC. The voltage drop creates the heat that is used in the desoldering process.

While an AC motor without a rectifier can be used, there are some advantages to using a low voltage motor. Low-voltage DC motors are practically cheaper than AC line voltage motors. DC line voltage motors are also smaller in size than AC line voltage motors and, therefore, result in a tool that is easier to operate and smaller. The DC low voltage motors are also lighter in weight than the AC line voltage motors, which produces a much lighter desoldering tool and reduces the fatigue of the operation. In addition, DC permanent magnet motors operate with more power and are more efficient than their AC counterparts. According to an exemplary embodiment of the invention shown in Figure 4, the engine 50 is arranged with a "central" outlet of the heater 34. This arrangement operates to prevent cooling of the tip 20 for desoldering. When the desoldering device is used to melt the weld, only the half wave bridge rectifier is used to energize the heater 34 at a 34 watt output, as described above, for example. However, when the trigger 38 is activated with the reflow of the weld and the subsequent energization of the motor 50 of the vacuum pump, the motor decreases its resistance since fewer coils are used; as a result the heater coils become hotter and the output of the coil increases (namely, to 45-50 watts). Therefore, the present invention is much more efficient than previous devices for desoldering, wherein the heater operates with a wattage of approximately 150 watts or more when the engine is running. When the tip to desolder touches a component or the circuit board, the temperature of the tip will drop as a result of the capabilities of the heat drop of the component on the printed circuit board. The drop in temperature can prevent backflow of the weld and the success of the desoldering operation. Another complication arises when the vacuum pump is energized and drags cold air over the molten solder. This also causes the temperature to drop. However, the use of the central current tap arrangement of the present invention provides a thermal increase at the same time as the activation of the vacuum pump. This helps to maintain the reflow of the molten solder and prevents further temperature drops of the hot tip. Other advantages of the design of the present invention arise with the use of a full wave bridge rectifier to operate the motor and the half wave rectifier to operate the hot heater. This arrangement results in an increased power output from the motor due to the elimination of motor pulses. Another advantage of using the half-wave rectifier to supply power to the heater is the resulting decrease in the required voltage, which allows the heater to work with a low output when the vacuum pump motor does not work and reduces the number of windings in the heater. In addition, the use of two separate rectifiers also decreases the susceptibility of the desoldering device to RFI and EMI interference. Of course, persons skilled in the art will appreciate that the above exemplary embodiments are only by way of illustration and that there are numerous varieties. For example, exemplary embodiments may be energized at 120 or 220 volts supply by changing the resistance of the heater to match higher voltages, however, the voltage motor may remain the same. It can be appreciated by those skilled in the art that the present invention can be incorporated into other specific forms without departing from the spirit and essential characteristics thereof. The modalities currently exposed are, therefore, considered in all their aspects as illustrative and not restrictive. The scope of the invention is indicated by the appended claims more than in the foregoing description and all changes that fall within the meaning or range and equivalence thereof are intended to be encompassed by the invention.

Claims (20)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property; 1. An electronic desoldering gun that consists of: a power switch; a heating tip; a first rectifier arranged in series with the heating tip; an electric motor connected to a vacuum pump; at least a portion of the heating tip is electrically connected in series with the motor; and a second rectifier arranged in series with the electric motor; wherein, when the power switch is turned on, electricity is supplied to the heating tip through the first rectifier, regardless of whether the power is supplied to the electric motor or not.
2. 2. A desoldering gun according to claim 1, wherein the motor is a DC motor.
3. 3. A desoldering gun according to claim 1, wherein the power switch includes an integrated power indicator lamp.
4. 4. A desoldering gun according to claim 1, further comprising a trigger switch and when the trigger switch is activated, power is supplied to the engine.
5. 5. A desoldering gun according to claim 1, wherein the vacuum pump is provided for sucking the molten solder during the operation of the heating tip.
6. 6. A desoldering gun according to claim 4, wherein the vacuum pump is provided for sucking the molten solder and when the trigger is activated with the reflow of the solder and the subsequent energization of the motor, the output of the heating tip increases .
7. 7. A desoldering gun according to Claim 4, wherein the outlet of the heating tip is approximately 24 watts.
8. 8. A desoldering gun according to the Claim 7, wherein the heating tip increases to approximately 40-50 watts with the activation of the motor.
9. 9. A desoldering gun according to Claim 1, wherein the first rectifier is a half wave rectifier and the second rectifier is a full wave bridge rectifier.
10. 10. A desoldering gun according to claim 7, wherein the first rectifier is a half wave rectifier and the second rectifier is a full wave rectifier.
11. 11. A desoldering gun according to claim 7, wherein the heating tip consists of a multilayer winding.
12. 12. An electronic desoldering gun that consists of: a heating tip; a first rectifier arranged in series with the heating tip. a first switch for controlling the electricity towards the heating tip through the first rectifier; an electric motor connected to the vacuum pump; at least a portion of the heating tip is electrically connected in series with the motor; a second rectifier arranged in series with the electric motor, and a second switch to control the electricity for the electric motor.
13. 13. A desoldering gun according to Claim 12, wherein the motor is a DC motor.
14. 14. A desoldering gun according to Claim 12, wherein the first switch includes an integrated power indicator lamp.
15. 15. A desoldering gun according to claim 12, wherein the vacuum pump is provided for sucking the molten solder during the operation of the heating tip.
16. 16. A desoldering gun according to Claim 12, wherein the vacuum pump is provided for sucking the molten solder and when the second switch is activated with the reflow of the solder and the subsequent energization of the motor, the tip output increases heater
17. 17. A desoldering gun according to Claim 12, wherein the outlet of the heating tip is approximately 24 watts.
18. 18. A desoldering gun according to the Claim 12, wherein the heating tip increases approximately 40-50 watts with the activation of the motor.
19. 19. A desoldering gun according to Claim 12, wherein the first rectifier is a half wave rectifier and the second rectifier is a full wave bridge rectifier.
20. 20. A desoldering gun according to Claim 12, wherein the heating tip consists of a multilayer winding.