US3215864A

US3215864A - Switch controlled circuit for energizing an electric load for no more than a single cycle

Info

Publication number: US3215864A
Application number: US416670A
Authority: US
Inventors: Richard H Doyle; Le Roy N Hermann; Joseph S Naber
Original assignee: Duo Fast Corp
Current assignee: Black and Decker Inc
Priority date: 1961-12-22
Filing date: 1964-11-10
Publication date: 1965-11-02
Anticipated expiration: 1982-11-02
Also published as: GB1008414A; FR1343241A; GB1008412A; NL287218A; BE626414A; DE1175352B; NL137795C; SE305849B

Description

SWITCH CONTROLLED CIRCUIT FOR ENERGIZING AN ELECTRIC LOAD FOR NO MORE THAN A SINGLE CYCLE Original Filed Dec. 22, 1961 NOV. 1965 R. H. DOYLE ETAL 3,

I ii W KO C) 1 INVENTORS f Eva/4A2!) H. DOYLE, w 0O 8 1.529% M HERMAN/J ATTOZNEMS United States Patent 3,215,864 SWITCH CONTRULLED CIRCUIT FOR ENERGIZ- ING AN ELECTRIC LOAD FOR NO MORE THAN A SINGLE CYCLE Richard H. Doyle, Mount Prospect, Le Roy N. Hermann,

St. Charles, and Joseph S. Naber, Wheeling, Ill., assignors to Fastener Corporation, Franklin Park, 111., a corporation of Illinois Original application Dec. 22, 1961, Ser. No. 161,727. Divided and this application Nov. 10, 1964, Ser. No. 416,670

13 Claims. (Cl. 307-885) This invention relates to a portable tool and, more particularly, to a self-contained tool in which all of the components for controlling the electrical operation of the tool are carried on the tool. This application is a division of the copending application of Richard H. Doyle et al., Serial No. 161,727, filed December 22, 1961.

The need for portable tools capable of performing the many different types of material working operations has long been recognized, and many different approaches have been tried in an attempt to provide tools that are capable of easy manual manipulation while supplying the power or energy necessary to perform the desired operation. These approaches have been used in such varied devices as staplers, nailers, staking tools, riveters, punches, chisels, scarfing tools, stud drivers and hog ring tools. The primary difficulty is to be able to supply sufiicient driving power without increasing the weight and size of the tool to the point at which it becomes so unwieldly and cumbersome that it cannot be easily handled by one hand of an operator.

One common expedient used in designing portable tools is to provide a device in which the work is performed in a series of power strokes so that the power required in any given one of the operations is greatly reduced. This approach is embodied in the use of rotating or reciprocating pneumatic and electric motors to apply increments of energy over an extended period of time. However, in addition to the obvious deficiency of the greater length of time required to complete the operation, some of the types of operations performed by the tools described above are such that they should be completed in a single power stroke. As an example, it is much more desirable to drive a staple or nail and to punch an opening in a single operation rather than to apply repeated blows to the crown or head of the staple, nail or punch element. In addition, the use of electrically operated tools over the extended periods of time required by repetitive power stroke operation presents the substantial problem of dissipating the heat due to the losses in the tool so as to keep the temperature of the tool low enough for manual use.

To overcome some of the deficiencies in this type of equipment, a number of single power stroke tools, both pneumatic and electric, have been devised. The pneumatically operated tools have been satisfactory in many applications because of the large amount of power that can be supplied to the point of impact with the work by using increased fiuid pressure and larger piston diameters. These tools also do not encounter the heating problems of electrically operated tools. However, the necessity of providing a relatively high pressure source of compressed air or other pressurized fluid severely limits the range of use of pneumatic tools to those applications in which the expected use is large enough to economically justify the expense of providing compressing facilities. These compressing facilities also are somewhat costly to maintain.

An electrically operated tool of the single power stroke type would have the advantage that electric power is almost universally available and can be used as an energy Patented Nov. 2, 1965 ice source at a nominal cost. One approach to providing an electrically operated tool having a single power stroke is to use a rotating electric motor to compress a spring that is subsequently released to drive the work engaging portion of the tool. However, the springs are subject to fatigue and the weight of the motor and linkage for stressing and releasing the spring often makes the tool unwieldly for manual operation. In other types of devices the driving force for actuating the tool is derived from an electromagnetically induced field acting on a magnetic member forming a part of the drive mechanism. However, it has been diflicult to generate sufliciently large magnetic fields with windings energized directly from the -120 volt lines commercially available without using energy storing devices, such as capacitors. The size and weight of these components as well as the related control components is generally such that they cannot be mounted directly on a portable tool and require a separate housing, such as the ones shown in the contemporaneously filed applications of Richard H. Doyle et -al., Serial Nos. 161,653 and 161,706, which applications are assigned to the same assignee as the present application.

Accordingly, one object of the present invention is to provide a new and improved electrically operated portable tool.

Another object is to provide a portable tool including new and improved means for supplying electrical energy thereto.

A further object is to provide an electrically operated tool that is self-contained so as to be capable of easymanual operation.

Another object is to provide a selfcontained and electrically operated portable tool which does not require energy storing means and which is capable of delivering a large amount of output power.

Another object is to provide a portable tool of the single power stroke type including control means: for supplying all the necessary operating energy during no more than a single cycle of an alternating current potential.

Another object is to provide a tool including a control circuit actuated by manually operable switch means for supplying operating energy to the tool for no more than a single cycle of an alternating current potential.

Another object is to provide a control or operating circuit for a tool in which a manually actuated switch selects a single cycle or less of alternating current energy for operating the tool.

In accordance with these and many other objects, one embodiment of the invention comprises an electrically operated stapler or tacker comprising a portable, lightweight housing having a chamber in which an operating winding is disposed. A work engaging element, such as a driver blade, is provided with a magnetic portion disposed adjacent the operating winding. The portable tool is connected to a source of commercially available alternating current potential by a flexible cable and includes a control circuit carried completely on or within the housing and connected between the cable and the winding. This control circuit includes a manually actuated switch means carried on the housing that is eifective, when actuated, to select the first complete half cycle of the alternating current potential following the time at which the switch is actuated for energizing the winding to operate the tacker or stapler.

The control circuit includes a controlled conduction device, such as a gated silicon rectifier, connected in series with the operating winding and an alternating current potential source. The gate or control electrode of the controlled conduction device is selectively connected to a source of gating current under the control of the manually actuated switch through a second controlled conduction means. This second controlled conduction means is placed in a conductive state to place the gated rectifier in a conductive condition at the beginning of and for only the first positive-going half cycle of the alternating current potential that occurs following the manual actuation of the switch means. Thus, the operating winding is energized from the power source for only a part of a cycle of the input alternating current potential and is provided with an operating current of relatively large amplitude to deliver a large amount of power to the workpiece. By directly energizing the operating winding from the alternating current potential source, the need for energy storing components, such as capacitors, is obviated with the result that all of the control components can be carried on the tool to provide a self-contained portable tool. Because of the extremely short duration that the operating winding is energized, the problem of excessive heating of the tool is obviated.

Many other objects and advantages of the present invention will become apparent from considering the following detailed description in conjunction with the drawing, in which:

PEG. 1 is an elevational view in partial section of a portable tool embodying the present invention; and

FIG. 2 is a circuit diagram of the controlled energy supply circuit included in the tool.

Referring now more specifically to FIG. 1 of the drawing, therein is shown a portable and electrically operated stapler or nailer, indicated generally as 10, which embodies the present invention. The tacker includes a non-magnetic housing 12 having a vertically extending forward head portion 12a defining a chamber 14 and a rearwardly extending hollow handle portion 12b defining a cavity or chamber 16. An operating winding 18 having a low resistance is disposed in the lower end of the chamber 14 and includes an axially extending opening 20 in which is received the lower end of a magnetic plunger or core 22. A fastener driving blade 24 is secured to the lower end of the magnetic plunger 22 and is adapted to engage and drive a fastener, such as a staple or nail, supplied by a magazine assembly indicated generally as 26. A tension spring 28 connected between the core 22 and the housing 12 resiliently returns the core 22 and the connected driver blade 24 to a normal position at the end of a cycle of operation.

To provide means for energizing or operating the tool 10, a flexible cable 30 is connected between a conventional source of 60 cycle alternating current potential and a control circuit, indicated generally as 32, that is carried on the tool 10 and disposed within the chamber 16 in the hollow handle 12b. The control circuit 32 is connected to the winding 18 and to a manually actuated switch 34 which is also disposed within the chamber 16 and which is actuated by a pivotally mounted trigger 36. When the switch means 34 is actuated, the control circuit 32 selects the first complete and properly polarized half cycle of the alternating current potential supplied over the cable 30 following the actuation of the switch means 34 and connects the winding 18 to the alternating current potential during this half cycle so that a relatively heavy current flows through the winding 18 for the duration of this half cycle. The duration of the current flow through the winding 18 will be extended beyond a half cycle in some applications because of the inductance of the winding 18. The energization of the winding 18 by this pulse of high energy and short duration produces a flux field that acts on the magnetic core 22 to drive the blade 24 downwardly to engage and set a fastener. After the termination of the half cycle and when the induced field collapses, the core 22 and the blade 24 are restored to their normal positions by the tension spring 28.

Although the physical construction of the electrically operated tacker or stapler 10 can be of any suitable design, the construction shown in FIG. 1 is similar to that of the electrically operated tacker shown and described in detail in the contemporaneously filed application of Richard H. Doyle et al., Serial No. 161,651, now United States Patent No. 3,141,171, which application is assigned to the same assignee as the present application. This construction, however, has been modified to permit the control circuit 32 to be mounted directly on the housing 12 of the tacker 10 so as to provide a completely self-contained tool 10 that is both portable and capable of supplying adequate power to perform a fastener driving operation. The control circuit 32 can be formed in any desired physical form, but preferably is formed on a suitable supporting means and then potted in one of the many well known compositions therefor. In order to facilitate repair of the tool 10, it is desirable to removably mount the control circuit 32 on the housing 12 or within the chamber 16 in the hollow handle 12b. Accordingly, the upper wall of the handle portion 12b is provided with a removable closure element or plate 38 that is normally secured in position by removable fasteners (not shown) to close an opening 40. When the plate 38 is removed, the control circuit 32 can be removed through the opening 40 and a replacement circuit inserted therein. This replacement of the control circuit 32 is facilitated by using detachable electrical connectors to interconnect the circuit 32 with the other components of the portable tool 10.

More specifically, the control circuit 32 is provided with a plurality of connectors or terminals 42 connected to the components in the circuit. The housing 12 for the tool 10 and the housing for the switch means 34 are provided with a plurality of electrical connectors 44 that are insulated from electric contact with the housing 12. The two terminals 42 at the right end (FIG. 1) of the control circuit 32 engage two connectors 44 connected to the cable 30 to provide means for energizing the circuit 32. The two connectors 44 on the switch 34 engage two terminals 42 at the left end of the circuit 32 to connect the switch means 34 with the control circuit 32, and the remaining two terminals 42 on the circuit 32 engage a pair of connectors 44 connected to a cable 46 to connect the control circuit 32 with the winding 18. By the provision of the detachable terminals 42 and connectors 44, the control circuit 32 can easily be replaced merely by removing the previous control circuit 32 and inserting an additional one of these circuits.

FIG. 2 of the drawing illustrates the details of one control circuit 32 that can be used to control the operation of the tool 10 or the energization of the winding 18. In general, the circuit 32 controls the conductivity of a controlled conduction device, such as a gated silicon rectifier 60, to connect the winding 18 in series with the alternating current supplied over the conductors of the cable 30 for only the first positive-going half cycle of the input voltage occurring following the manual actuation of the switch means 34. A rheostat 62 connected in series with one of the conductors of the cable 30 limits the current that can flow through the winding 18, and, thus, controls the energy supplied to the tool 10 during the half cycle in which the gated rectifier is in a conduction condition. The rheostat 62 can be mounted on the handle portion 12b of the housing 12 (FIG. 1) and includes a manually actuated dial or knob 64 for adjusting the setting of the rheostat 62. This rheostat is connected in series between one of the electrical connectors 44 and one of the conductors of the cable 30.

In the normal condition of the control circuit 32, current flows through a voltage dividing network including a resistance element 66, a diode or rectifier 68, and another resistance element during the positive half cycles. The potential appearing across the resistor 70 is applied through another diode or rectifier 72 to charge a capacitor 74 shunted by a resistor 76. This potential is also forwarded through the diode 72 and a pair of normally closed contacts 34a in the switch means 34 to charge a capacitor 77. In this manner, the capacitors 74 and 77 are normally charged to a potential determined by the value of the resistance elements 66 and 70. During the negative-going half cycles of the input alternating current potential, the charge on the capacitors 74 and 77 discharges slightly through the shunting resistor 76 and the collector-emitter circuit of a transistor 78 that is biased just above its cutoif point. However, whenever the charge on the capacitors 74 and 77 drops below the desired value, these capacitors are recharged through the diode 72 during the next following positive-going half cycle of the input voltage.

To provide means for controlling the periods of conductivity of the gated rectifier 60, a differentiating network including a capacitor 80 and a resistance element 82 are connected across the resistance element 70. The leading and trailing edges of the positive-going and basically square wave generated across the resistance element 70 during the positive-going cycles of input potential are differentiated to provide positive-going and negative-going pulses, respectively, which are coupled directly to the base electrode of the transistor 78. The positive-going pulses corresponding to the leading edges of the square wave occurring at the beginning of each positive-going halt cycle of the input alternating current signal increase conduction through the transistor 78. This transistor operates as an emitter follower with current amplification so that each positive-going input pulse applied to its base provides a corresponding positive-going output pulse across an emitter resistor 84-. This positive-going output pulse tends to drive a gate current through the gate electrode of a controlled conduction device, such as a gated silicon rectifier 86, the anode of which is connected to the capacitors 74 and 77. However, the cathode of the rectifier 86 is connected to an open circuit at a pair of normally open contacts 345 included in the switch means 34. Thus, the rectifier 86 normally cannot be placed in a conductive state. The control circuit 32 remains in this condition until the swtich means 34 is operated.

When the tacker it is to be operated, the trigger 36 is actuated to operate the switching means 34. The operation of the switching means 34 closes the normally open contacts 34b and opens the normally closed contacts 34a. The opening of the contacts 34a interrupts the charging path for the capacitor 77 and disconnects the collector electrode of the transistor 78 and the anode of the controlled rectifier 36 from all potential sources except that provided by the charged capacitor 77. The closure of the contacts 34b connects the cathode of the controlled rectifier 86 to the control electrode of the gated rectifier 60. However, the gated rectifier 86 is not placed in a conductive condition at this time unless the alternating current potential supplied by the cable 30 is at the beginning of a positive-going halt cycle. This is true because an input signal is not provided at the base electrode of the transistor 78 at any other time.

When the beginning of the next positive-going half cycle of the alternating current potential is reacted, the differentiating network including the capacitor 80 and the resistance element 32 supplies a positive-going pulse to the base of the transistor '78 so that this transistor is placed in a heavily conducting condition producing a positivegoing potential drop across the emitter resistance element 84. The drop across the resistance element 84 places the gate electrode of the controlled rectifier 86 at a positive potential relative to its cathode and places the gated rectifier 86 in a conductive condition so that the capacitor 77 now discharges through the conductive transistor 78 and the gated rectifier 36 into the gate or control electrode of the gated rectifier 60 through the closed contacts 3412. This places the gated rectifier 64) in a conductive condition so that the winding 18 is connected directly across the alternating current potential supplied by the cable 30 in series with the rheostat 62. This energizes the winding 18 to actuate the stapler or tacker 10.

At the end of the positive half cycle, the rectifier 60 lacks a proper potential across its cathode-anode circuit, and the rectifier 60 is restored to a nonconductive condition. If the switch means 34 remains in an operating condition at the beginning of the next positive-going half cycle of the applied alternating current potential, a positive-going pulse is again applied to the base of the transister 78. This positive-going pulse is not effective to initiate another period of conduction through the gated rectifier 60 because the charge on the capacitor 77 has been depleted and the components 78 and 86 lack collector and anode potential. When the switch means 34 is re leased to close the contacts 34a and to open the contacts 34b, any further conduction through the gated rectifier 86 is prevented by opening the circuit to its cathode at the contacts 34b, and the charging circuit for the capacitor 77 is established at the closed contacts 34a so that this capacitor is charged from the capacitor 74- and the alternating current potential supply. The control circuit 32 is conditioned for another cycle of operation.

Accordingly, the provision of the control circuit 32 makes possible the portable tool 10 which is electrically operated and which is completely self-contained in requiring a connection to only a conventional source of alternating current potential. In view of the fact that the gated rectifier 60 can be placed in a conductive condition for only one positive-going half cycle of the input signal following each manual actuation of the switch means 34, excessive heating of the winding 18 and the tool 10 is avoided while providing adequate power to drive the blade 24.

Although the control circuit 32 can be fabricated with components of many different values and types in ac cordance with the desired circuit application, one control circuit 32 using the following listed components supplied the Winding 18 with an operating current of between 40 and 120 peak amperes persisting for a duration of around 8% milliseconds.

Gated Rectifier 6d 2N1770 or 2N177OA. Rheostat 62 0-2 ohms.

Resistor 66 10K.

Diode 68 Sarkes-Tarzian 2P4. Resistor 7t 10K.

Diode 72 Sarkes-Tarzian 2P4. Capacitor 74 100 ,ufd.

Resistor 76 2.2K.

Capacitor 77 .47 afd.

Transistor 78 2N1304 or 2N2l3. Capacitor 80 0.1 ,ufd.

Resistor 82 22K.

Resistor 84 2.2K.

Gated Rectifier 86 2N1774.

Although the present invention has been described with reference to a single illustrative embodiment thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of this invention.

What is claimed and desired to be secured by Letters Patent of the United States is:

l. In a control circuit for a portable tool, winding means for operating said tool, an alternating current potential source, a unidirectional controlled conduction means having a control electrode, circuit means connecting said winding means and said controlled conduction means in series with said potential source, switch means operable at random times relative to the cycles of said alternating current potential, and control means controlled by said switch means for applying a signal to said control electrode to place said controlled conduction means in a conductive state during the first properly poled half cycle of said alternating current potential occurring after the operation of said switch means, said control means including means for preventing the application of a signal to the control electrode after said first 7 cycle and until the switch means is released and reoperated.

2. In a control circuit for a portable tool, an alternating current potential source, load means, a controlled conduction device connected in series with said potential source and said load means, said device having a control electrode, control means for applying a control signal to said control electrode to place said controlled conduction device in a conductive condition to connect said load means to said potential source, manually operable switching means operable at random times relative to the cycles of the alternating current potential, and a control circuit connected to said control means and said switching means and operable in response to the actuation of said switching means to control said control means to place said controlled conduction device in a conductive state for a portion of only the cycle of the alternating current potential following the operation of said switching means.

3. In a control circuit for a portable tool, an alternating current potential source, a winding, a first controlled conduction device connected in series with said winding and said potential source, said first controlled conduction device having a control electrode, a second controlled conduction device connected to said control electrode for controlling the conduction of said first controlled conduction device, energy storing means connected to said second controlled conduction device for storing a quantity of electrical energy sufficient to maintain said second device in conductive condition for less than one cycle of said alternating current potential, means for supplying an operating signal to said second device at the beginning of each cycle of said alternating current potential, charging means energized by the potential source, and manual switch means operable at random times relative to the cycles of the alternating current potential for connecting and disconnecting the energy storing means and the charging means.

4. In a control circuit for a portable tool, an alternating current potential source, a winding, a first unidirectional controlled conduction device connected in series With said winding and said potential source, said first controlled conduction device having a control electrode, a second unidirectional controlled conduction device operable to supply a signal at the beginning of each cycle of the alternating current potential capable of placing said first device in a conductive state, switching means operable at random times relative to the alternating current potential, and circuit means including said switching means and responsive to operation of the switching means for rendering said second controlled conduction device effective to supply said signal to the control electrode of said first controlled conduction device, said circuit means being operable following the operation of said switching means to prevent the application of additional signals to said control electrode until the switching means has been released and reoperated.

5. A controlled energy supplying circuit comprising load means, an alternating current potential source, a controlled conduction means having a control electrode, circuit means connecting said load means and said controlled conduction means in series with said potential source, capacitive means operative between substantially discharged and charged energy states to provide a current flow for controlling the development of a conduction initiating signal for the control electrode, and switching means for preparing circuit means for changing the energy state of the capacitive means to control the development of the conduction initiating signal for said control electrode to place said controlled conduction means in a conductive state for no more than one cycle of the alternating current potential, said switching means including first switch means manually operable at random times relative to the alternating current when the controlled conduction means is to be rendered conductive and second signal responsive switch means supplied with a signal for each cycle of said alternating current potential.

6. The circuit set forth in claim 5 in which said capacitive means is manually connected to said potential source and in which said first switch means includes means for disconnecting said potential source and said capacitive means.

7. The circuit set forth in claim 5 in which said second switch means includes a controlled conduction means having a control element, and which includes a network for coupling the alternating current potential source to said control element.

8. The circuit set forth in claim 5 in which the first switch means is operable to diiferent first and second settings, said first switch means in the first setting completing at least a portion of a charging circuit for the capacitive means and in the second setting completing at least a portion of a discharging circuit for the capacitive means.

9. A circuit for supplying a single energizing signal to a load from an alternating current potential source comprising a gated rectifier having a cathode, an anode, and a gate electrode; circuit means connecting the potential source in series with the winding and the cathode-anode circuit of the gated rectifier; and a control network for supplying a single firing signal to the gate electrode, said control network including a controlled conduction device including a control electrode, means energized by the alternating current potential source for supplying the control electrode with a firing signal once during each cycle of the alternating current potential, a capacitor operable between discharged and charged states under the control of the controlled conduction device, and manually operable switch means operable to an actuated condition at random times relative to the cycles of the alternating current potential and operable to control the controlled conduction device and the capacitor to supply a single firing signal to the gate electrode at the first full cycle of the alternating current potential occurring after the operation of the manually operable switch means, the change in the state of the capacitor preventing the application of subsequent firing signals to the gate electrode until the manually operable switch has been released and reoperated to its actuated state.

10. The combination set forth in claim 9 in which the manually operable switch means includes a first pair of normally closed contacts and a second pair of normally open contacts, the second contact being closed when the switch means is operated to an actuated state to render the controlled conduction device and the capacitor eflFective to deliver the firing signal to the gate electrode and to change the state of the capacitor, the first pair of contacts being closed when the switch means is released to restore the capacitor to its normal state.

11. A control circuit for supplying a single pulse of energy from an alternating current potential source to a winding comprising a rectifier unit having a gate electrode, circuit means connecting the winding in series with the potential source through the rectifier unit, a capacitor adapted to be placed at two different energy levels by charging and discharging currents, a manually actuated switch means operable to an actuated state at random times relative to the cycles of the alternating current potential and normally in a released state, a first circuit completed by the switch means in its released state placing the capacitor in a normal one of its two energy states, a controlled conduction device having a control electrode, means energized by the potential source for supplying a firing signal to the control electrode during each cycle of the alternating current potential source, and second circuit means completed by the switch means in its actuated state for placing the controlled conduction device and the capacitor in a circuit for placing the capacitor in the other one of its energy states when a firing signal is next applied to the control electrode of the controlled conduction device, the transition of the capacitor between its normal and other energy state providing a single firing signal to the gate electrode to place the gated rectifier in conduction during the corresponding properly poled half cycle of the alternating current potential, the operation of the switch means to its actuated state interrupting the first circuit to prevent the return of the capacitor to its normal energy level until the switch means is returned to its released state to again complete the first circuit and open the second circuit.

12. A control circuit for supplying a single pulse of energy from an alternating current potential source to a winding comprising a gated rectifier unit having gate, cathode, and anode electrodes; circuit means connecting the winding in series with the potential source through cathode-anode path of the rectifier unit; a capacitor adapted to be placed at two different energy levels by charging and discharging currents; a manually actuated switch means operable to an actuated state at random times relative to the cycles of the alternating current potential and normally in a released state; a first circuit completed by the switch means in its released state placing the capacitor in a normal one of its two energy states; and a second circuit controlled by the switch means in its actuated state for coupling the capacitor in the gate-cathode path of the gated rectifier unit for placing the capacitor in the other one of its energy states, the transition of the capacitor between its normal and other energy state providing a single firing signal to the gate electrode to place the gated rectifier unit in conduction during the properly poled half cycle of the alternating current potential, the operation of the switch means to its actuated state interrupting the first circuit to prevent the return of the capacitor to its normal energy level until the switch means is returned to its released state to again complete the first circuit and open the second circuit.

13. A manually controlled circuit for supplying a single pulse of energy to a load from an alternating current potential source comprising a controlled unidirectional conduction means having a control electrode, circuit means connecting the load and said controlled conduction means in series with the potential source, a signal generating circuit coupled to the control electrode for supplying a single conduction initiating signal to the control electrode during only a single cycle of the alternating current potential, signal responsive switch means in the signal generating circuit for controlling the application of the conduction initiating signal to the control electrode and supplied with an enabling signal from the alternating current potential source during the portion of each cycle of the alternating current potential in which the potential is of a polarity to permit conduction through the unidirectional conduction means, capacitive means in the signal generating circuit operable between substantially charged and discharged energy states, manual switch means in the signal generating circuit operable from a normal. position to an actuated position when the load is to be energized, circuit means in the signal generating circuit controlled by the manual switch means in its actuated position for changing tht normal energy state of the capacitive means and for rendering the signal responsive switch means effective to deliver a single conduction initiating signal to the control electrode when the cyclically recurring enabling signal is received, said circuit means maintaining the capacitive means in its changed energy state as long as the manual switch means is held in its actuated position to prevent the generation of further conduction initiating signals, and means in the signal generating circuit rendered efiective by placing the manual switch means in the normal position for returning the capacitive means to its normal energy state.

No references cited.

ARTHUR GAUSS, Primary Examiner.

Claims

1. IN A CONTROL CIRCUIT FOR A PORTABLE TOOL, WINDING MEANS FOR OPERATING SAID TOOL, AN ALTERNATING CURRENT POTENTIAL SOURCE, A UNIDIRECTIONAL CONTROLLED CONDUCTION MEANS HAVING A CONTROL ELECTRODE, CIRCUIT MEANS CONNECTING SAID WINDING MEANS AND SAID CONTROLLED CONDUCTION MEANS IN SERIES WITH SAID POTENTIAL SOURCE, SWITCH MEANS OPERABLE AT RANDOM TIMES RELATIVE TO THE CYCLES OF SAID ALTERNATING CURRENT POTENTIAL,AND CONTROL MEANS CONTROLLED BY SAID SWITCH MEANS FOR APPLYING A SIGNAL TO SAID CONTROL ELECTRODE TO PLACE SAID CONTROLLED CONDUCTION MEANS IN A CONDUCTIVE STATE DURING THE FIRST PROPERLY POLED HALF CYCLE OF SAID ALTERNATING CURRENT POTENTIAL OC-