Patent Application
20080053967
The present invention is illustrated by way of example and not limited in the accompanying figures in which like reference numerals indicate similar elements and in which:
a is an isometric view of an embodiment of a recess in a housing that may be used in accordance with at least one aspect of the present invention.
a-7b are schematic views of two states of an weld stud lifting module that may be used in accordance with at least one aspect of the present invention.
While certain portable welding devices which use capacitor discharge welding exist, such systems are generally unsuitable for welding studs to thicker work surfaces such as ΒΌ inch plates of steel. Instead they are at most suited for surface welds that can be used to quickly attach a stud to the surface but the resultant weld is unsuitable for supporting any significant load and typically such a device only tacks the weld stud to the surface.
Therefore, the ability to securely weld a weld stud to a work surface has instead required a connection to an alternating current (AC) source. For example, drawn arc welding is suitable for securely welding studs to thicker plates of steel.
To provide a portable weld stud system that can provide a drawn arc weld that allows the stud to support a reasonable load would, therefore, be beneficial. However, one issue that exists is providing a sufficiently portable power source that is also suitable powerful.
One technology that has provided a useful trade-off between power and weight is lead-acid battery technology. It should be noted that battery technology has progressed somewhat in recent years and a host of newer technologies have been proposed to replace lead-acid batteries. However, for industrial type operations that involve high current applications, lead-acid battery technology still has certain advantages. In addition to the ability to output high levels of current (therefore providing a high power to weight ratio), lead-acid batteries are relatively robust and do not tend to cause thermal incidents like other battery technologies such as lithium-ion battery technology. Therefore, lead-acid batteries provide advantages for harsh commercial environments. However, other energy storage technologies may also be used as a power source. For example, batteries with higher power-density then lead-acid batteries could used in combination with a capacitor so as to provide the energy storage along with the desired levels of current delivery during a welding operation.
Looking at
Also depicted is a weld stud gun 50 that is coupled to a power lead 52 and a control lead 54. The power lead 52 includes an end 52a that is configured to couple to the power terminal 22. The control lead 54 includes an end 54a that is configured to couple to the control terminal 24. The weld stud gun 50 further includes a weld trigger 51 that, when actuated, sends a signal along the control lead 54 and causes a voltage to be applied to the power terminal 22. A second power lead 53 includes an end 53a that is coupled to the power terminal 23 and includes a working end 53b that in operation is connected to a work surface 5. When the weld trigger 51 is actuated, the signal is sent to the housing that causes an arc to be created between a weld stud 60 on the weld stud gun 50 and the work surface 50 by applying a voltage, which may be 48 volts DC, to the two power terminals 22, 24 (and along the respective leads to the work surface 5 and the weld stud 60). Once the arc is created between the weld stud 60 and the work surface 5 (closing the circuit), the weld stud gun 50 draws the weld stud 60 back and increases the current flowing through the circuit so that a portion of the work surface 5 and the weld stud 60 becomes molten. The partially molten weld stud 60 is then plunged into the partially molten work surface 5 and the circuit is opened so that the metal can cool and hardened to provide a robust weld. In an embodiment, to adjust the length of the current pulse, a potentiometer (not shown) associated with a knob 19 can be adjusted by rotating the knob 19 so that the pulse length can be varied between 100 and 1100 milliseconds, depending on the thickness of the work surface 5. The knob 19, which is an example of a pulse adjustor, can be marked with positions for successive lengths of pulses ranging, for example, between 100 and 1100 milliseconds in 100 millisecond intervals.
The housing 10 may also include a door 26 and a door 27 that may be sealed with a gasket such as an o-ring to the housing 10 and held in place with one or more door fasteners 28 (as seen in
The housing 10 may further include an air inlet 49a and an air outlet 49b that are in communication with an interior 10c of the housing 10, wherein the air inlet 49a and air outlet 49b help provide ventilation for the interior 10c of the housing 10 so as to help keep the interior of the housing 10 cooler. To improve the effectiveness of the air inlet 49a and the air outlet 49b, a fan (not shown) that is part of a fan module 48 (
It should be noted that heretofore, solid state components, while recognized as being compact, were generally unsuitable for use in high current applications such as drawn-arc welding. However, with the configuration of the control module, as described below, along with various other features of embodiments of the invention, such as the described batteries, a portable weld stud system that provides acceptable performance has become possible. For example, in an embodiment a system can be configured to weighs less than forty kilograms and in an embodiment the system may weigh less than thirty-two kilograms.
To form a weld between the work surface 5 and the weld stud 60, current is allowed to flow from the power source 30, through a primary control circuit 105, through the weld stud gun 50, through the work surface 5 and back to the power source 30, the direction of current travel not being critical. In an embodiment, the primary circuit 105 may use three high current mosfet circuits in parallel (a suitable mosfet circuit includes INTERNATIONAL RECTIFIER Part No. FB180SA10) so that the required current can be routed through the control module 100 without the need for additional circuitry or damage being caused. In an embodiment, the selected mosfet circuit can provide a power dissipation of less than 500 watts during operation so as to minimize thermal load on the system. The power source 30 may be four 12-volt lead-acid batteries each with a thirteen amp-hour capacity so that the power source can provide 52 amp-hours of power and provides 48 volts of direct current (VDC). It should be noted that while twelve amp-hour batteries theoretically have only a slightly reduced capacity (about 8 percent less capacity), it is has been discovered that a battery with a thirteen amp-hr capacity provides an unexpected increase in welding performance, therefore making the weld stud system more desirable. An example of a suitable battery with a thirteen amp-hour capacity is a GENSIS XE13 12-volt sealed battery, which weighs about 5.5 kilograms and has a closed loop current of about 1300 amps, and can be used in a set of four batteries in series so as to provide 48 volts. It should be noted that a fully charged set of batteries may provide more than the rated amount for some predetermined number of discharge cycles (but after sufficient cycles may provide less than the rate amount). Therefore, depending on the power source design, eventually it may be desirable to replace it. If the XE13 is selected, the batteries may be supported in the housing 10 as depicted in
To control the provision of the current, the control module 100 includes a main power supply circuit 110, which may be a 15 volt regulated power supply coupled to the power source 30. The main power supply circuit 110 is coupled to a switch 12 that turns the weld stud system 8 on and off (the state of which may be indicated by the light 18, which may be a light emitting diode (LED)). If the charging circuit 40 is incorporated within the housing 10, a power source status light 16 (which may be one or more LEDs) may be coupled to it so as to show the status of the power source 30 as well as the status of the charging circuit 40. It should be noted that while an alternating current power source is suitable for recharging the power source 30, an external direct current power source may also be used.
As is known, drawn arc stud welding typically first applies a voltage across a gap so as to generate an arc (known as a pilot arc) that creates an ionized path for the main weld current. Then, the system shapes and controls the arc by increasing the current flowing through the arc while moving (or drawing) the stud away from the work surface so that a desired amount of material is brought into a molten state. When the main power supply 110 is turned on and the weld stud gun 50 is activated, the primary control circuit 105 provides the power for the welding pulse. However, in an embodiment, a pilot arc circuit 125 (in conjunction with a support arc circuit 120 and a shut down circuit 115) can provide the initial current used to generate the arc. This can be controlled with a process trigger control 135 and a timer circuit 130, as illustrated. To move (or draw back) the stud 60, as illustrated in the schematic
The present invention has been described in terms of preferred and exemplary embodiments thereof. Numerous other embodiments, modifications and variations within the scope and spirit of the appended claims will occur to persons of ordinary skill in the art from a review of this disclosure.
