Time-delay Switch For Pipe Threader

Abstract

A time-delay switch for a pipe threader which allows the length of threads to be cut by the pipe fitter to be adjusted and to automatically reverse the direction of the pipe threader after the desired length has been cut so as to remove the pipe threading die from the member being threaded. A time-delay is incorporated in the switch so that the drive motor may coast to a stop before reversal of the motor occurs.

Description

CROSS REFERENCES TO RELATED APPLICATIONS

This invention comprises an improvement on the automatic reversible electric motor tool, Ser. No. 603,838, filed Dec. 22, 1966 by Mr. John N. Cutrone, assigned to the assignee of the present application. The invention is also an improvement on that disclosed in application Ser. No. 387,929, filed Aug. 6, 1964 by Mr. John N. Cutrone, assigned to the assignee of the present invention.

This invention relates in general to time-delay switches for electric motors and in particular to a time-delay switch mechanism for a reversible electric motor-driven work-performing tool such as a pipe threader which automatically reverses and stops after completing work or a threading cycle and which also temporarily stops the motor in going from a forward to a reversing cycle so as to allow the motor to coast to a stop.

Reversing switches for reversing electric motors which drive power tools such as pipe threaders have normally instantaneously reversed the power applied to the driving motor and this gives rise to overloads on the motor since the motor must coast to a stop before it can reverse its direction. Thus, changing the power to the motor before the motor has stopped can shorten the life of the motor and result in electrical breakdown.

The present invention comprises a reversing switch for a reversible electric motor-driven work-performing tool such as a pipe threader which automatically reverses and stops after completing work or a threading cycle and which provides an electronic time-delay circuit for allowing the motor to coast to a stop before the motor is reversed to back it from the workpiece. This prevents overloads on the motor from occurring and substantially lengthens the life of the motor. Also, the time-delay switch of the present invention accurately adjusts the time delay and assures reliability in the delay time set.

Other and further objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed disclosure thereof and the drawings attached hereto and made a part hereof.

FIG. 1 is a side view partially sectioned of the time-delay switch of this invention.

FIG. 2 is an end sectional view taken along line II-II of FIG. 1;

FIG. 3 illustrates a time-delay circuit of the invention; and

FIG. 4 is an electrical schematic of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 illustrate the time-delay circuit of this invention. Since the improvement is in the time-delay switch, the complete pipe threader is not disclosed. For description of the complete pipe threader reference may be made to Ser. No. 603,838, filed Dec. 22, 1966, entitled "Automatic Reversible Electric Motor Tool," assigned to the assignee of the present invention. As shown in that application, a motor 10 has an output shaft which drives a gear train 12 that controls a shaft 13 which moves the pipe threader portion 14 of the machine toward and away from the time-delay control switch of the device. The pipe threading portion 14 travels on a pair of guides 13 and 20 which move the pipe threader relative to the switch designated generally as 55. A switch actuator 17 has a portion 16 which is attached to the pipe threader 14 and has an engaging end 18.

The time-delay switch 55 is mounted in a frame member 25 which has an upper portion 19 and a back portion 21. A length of thread adjusting knob 37 is rotatably mounted in the portion 21 of the frame member 25 and has its other end 24 rotatably supported in an extension 22 from the portion 19. The portion 23 of the adjusting knob 37 is threaded and carries a threaded lug 26 against which the end 18 of the switch actuator 17 is engageable. A washer 27 is carried on the shaft 23 and rests against a switch actuator 31 which has a portion 32 that fits about the shaft 36 of the adjusting knob 37. An indicator 38 is attached to the portion 19 of the frame and has an opening through which the position of the lug 26 may be observed to allow the distance to be threaded to be controlled by the knob 37.

The switch actuator 31 has a transversely extending portion 28 formed with an opening through which a pivot pin 29 extends. The pin 29 is attached to the wall 30 of the frame member. The member 31 also has a pawl-engaging portion 41 which engages a shoulder 42 of locking pawl 44. Locking pawl 44 is pivotally attached to the wall 21 of the frame by pivot pin 43. As shown in FIG. 2, the pawl 44 has a locking portion 45 which is engageable in a groove 46 of switch actuator 52. This switch actuator 52 is mounted in the wall 21 and is spring biased by spring 48 toward the right relative to FIG. 1. A guide 49 is attached to the wall 21 and is formed with an opening through which the switch actuator portion 52 of the member 47 passes to give it lateral stability. A pair of switches 50 and 56 are supported from the frame portion 30 and have actuator buttons 57 and 58 which engage the portion 52 of the start button 47.

An end of cycle or stop switch 61 is also mounted to the frame portion 30 and has an actuator button 62 which is engageable with a switch actuator 68. The switch actuator 68 has one end attached adjacent the switch 61 and has a portion 69 which is engageable with the actuator button 62 of the switch 61 and has a portion 71 which is engageable with the enlarged portion 18 of the actuator shaft 17.

FIGS. 3 and 4 illustrate the electrical schematic of the control circuit of the time-delay switch. With reference to FIG. 4, a power plug 83 has power lines 84 and 86 and line 84 is connected to a contact 87 of switch 50. When the push-to-start button 47 is engaged with switches 50 and 56, contact 91 of switch 50 connects contact 87 to contact 88 which is, in turn, connected to line 85 that is connected to contact 92 of a switch 90. A movable contact 93 of switch 90 is connected to line 96 which is connected to one side of the motor 10. The other side of the motor 10 is connected to line 97 which is connected to a movable contact 98 of a switch 100. A first stationary contact 99 of switch 100 is connected to lead 101 which is connected to contact 109 of switch 61 and which is connected by switch contact 95 to contact 111. Contact 111 is connected to line 104. Line 104 is also connected to contact 103 of switch 56 which is connected to contact 102 of switch 56 by switch actuator 55 when the push-to-start actuator 47 has been engaged. Contact 102 is connected to lead 101.

The switch actuators 91 and 55 engage respectively contacts 87 and 88, and 102 and 103, when the push-to-start button 47 has been depressed and the pawl 45 is in the groove 46 of the push-to-start switch. When the portion 18 of the actuator 17 has engaged the lug 26 and through the linkage 31 has moved the pawl 44 to allow the push-to-start button 47 to move to the right relative to FIG. 1, the switch actuators 91 and 55 connect respectively contacts 87 to 89 and contact 103 to open contact 105 of switch 56.

When the portion 18 of actuator 17 engages the portion 71 of switch actuator 69, the switch contact 95 will connect contact 109 to contact 111. At other times the contact 111 will be connected by the actuator 95 to contact 110 of switch 61. Contact 110 is normally open.

The contacts 93 and 98 of switches 90 and 100, respectively, are connected by mechanical linkage 94 to a time delay relay L.sub.1. The time delay relay L.sub.1 is connected to a time delay circuit 80 which has an input lead 81 connected to contact 89 of switch 50 and a second input lead 82 which is connected to lead 101.

FIG. 3 illustrates the time delay relay circuit in detail. Line 81 is connected to a series resistor R.sub.1, to a series diode D.sub.1. A transient suppression diode S.sub.p is connected from the junction between resistor R.sub.1 and diode D.sub.1 and line 82. A filter capacitor C.sub.1 is connected from line 82 to diode D.sub.1. The relay coil L.sub.1 is connected from line 82 to a biasing resistor R.sub.2 which has its other side connected to diode D.sub.1. A unijunction transistor T.sub.1 has an electrode connected to the junction between R.sub.2 and L.sub.2 and a second electrode connects to a biasing resistor R.sub.3 which is connected to diode D.sub.1. A resistor R.sub.4 is connected in series with a time constant resistor R.sub.5 between diode D.sub.1 and a gate electrode of unijunction T.sub.1. A time constant capacitor is connected between line 82 and resistor R.sub.5.

An example of operation is as follows. When the user desires to thread a shaft with a pipe threader, the start button 47 is depressed which allows the locking pawl 44 to move into the groove 46 to lock the starting button 47 in the depressed position. Simultaneously the switches 50 and 56 are actuated through the buttons 57 and 58 by the portion 52 of the start button switch 47. The switches 50 and 56 start the motor 10 such that it runs in a direction to move the pipe threading portion to the right relative to FIG. 1 and during this time the pipe threader will thread the shaft as described in greater detail in application Ser. No. 603,838. Threading will continue until the engaging end 18 of the switch actuator 17 engages the lug 26. The lug 26 rests against a washer 27 that in turn engages a switch actuator 31 that is pivotally connected to the frame 30. Switch actuator 31 will be moved by the washer 27 and lug 26 by the end 18 of switch actuator 17 so that the pawl engaging portion 41 of the switch actuator 31 engages the shoulder 42 of the locking pawl 44 to move it out of the groove 46 of the start button 47. The start button 47 will then move outwardly due to the action of the spring 48 allowing the switches 50 and 56 to be disengaged from the starting button 47. When this occurs, the switch actuator 91 will connect contact 87 to contact 89 to connect lead 81 of the time-delay circuit to lead 84 of the power supply. At the same time the power lead 86 will be connected through switch 61, contacts 111, 95 and 109 and switch 100 to the other side of the motor and thus the motor will run in the first direction, until the member 18 engages the lug 26 and releases the start switch 47 so that switches 50 and 56 change condition. When this occurs, the switches 50 and 56 will be released and contacts 87 and 89 of switch 50 will be connected together thus applying line 84 of the power supply to open contact 107 of switch 100 and simultaneously apply power from line 84 to the time-delay circuit 80 through lead 81. Power lead 86 will be connected to the switch 61 through contacts 111, 95 and 109 to the other side of the time-delay circuit through lead 82. Contact 109 is also connected to open contact 108 of switch 90 at this time.

After a time-delay determined by the time-delay circuit 80, the relay coil L.sub.1 actuates the relay to move contacts 93 and 98, respectively into engagement with contacts 108 and 107. Thus the motor 10 which has been running in a first direction has power disconnected from it until it coasts to a stop for a time dependent on the time delay circuit 80 and then has power applied in the opposite direction when the relay L.sub.1 is energized. The motor 10 will remain energized through the switches 90 and 100 until the engaging end 18 engages the portion 71 of the switch actuator 68 of switch 61. When this occurs, the button 62 of switch 61 moves so that contact 95 connects contact 111 with contact 110 to open power line 86 to the motor so that the motor coasts to a stop and the thread and reverse cycle is completed until the start button 47 is again depressed.

In operation, when voltage is initially applied to lines 81 and 82 the unijunction does not pass current and the relay L.sub.1 is not energized. The capacitor C.sub.2 charges for a time delay and fires the unijunction which then allows the relay coil L.sub.1 to actuate the relay and move switches 90 and 100. A time delay of about 5 seconds has been used in a model.

In a particular embodiment, the following component values were used:

R.sub.1 -- 1,500 ohms

R.sub.2 -- 1,300 ohms

R.sub.3 -- 330 ohms

R.sub.4 -- 5,100 ohms

R.sub.5 -- 20 k. ohms

C.sub.1 -- 40 mfd.

C.sub.2 -- 100 mfd.

D.sub.1 --Type 1 N2071

T.sub.1 --Type 2 N4870

S.sub.p --Type S- 871

It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of the present invention.

Claims

1. A control circuit for connecting a driving means for a reversible power tool to a pair of power lines comprising, (a) first switch means connected in circuit with one power line, (b) second switch means connected in circuit with the other power line, (c) means for moving said first and second switch means to a first position to provide continuity of the power lines through said switch means, (d) latching means for holding the means for moving said first and second switch means in said first position, (e) third reversing switch means in series with the first switch in a first position and connected to one side of the driving means, (f) fourth reversing switch means in series with the second switch means in a first position and connected to the second side of the driving means, (g) a time-delay means connected to the first and second switching means, (h) a switch actuator connected to the time-delay means to actuate the third and fourth reversing switch means, (i) means for engaging the latching means to unlatch it driven by said driving means, and (j) a stop switch means connected in circuit with the motor means and engaged by the means for

2. A control circuit according to claim 1 wherein the third reversing switch means is connected in series with the second switch in a second position, and the fourth reversing switch means is connected in series

3. A control circuit according to claim 1 wherein said third and fourth reversing switch means each having movable contacts and a pair of stationary contacts, with the movable contact of the third reversing switch means connected to one side of the driving means, and the movable contact of the fourth reversing switch means connected to the second side

4. A control circuit according to claim 3 wherein one of the stationary contacts of third reversing switch means is connected to a first contact of the first switch means and the second stationary contact of the third reversing switch means is connected to first contacts at the second switch

5. A control circuit according to claim 3 wherein one of the stationary contacts of the fourth reversing switch means is connected to the first contacts of the second switch means and the stop switch means, and the second stationary contact of the fourth reversing switch means is

6. A control circuit according to claim 1 wherein said switch actuator comprises a relay having a coil and armature with the armature coupled to

7. A control circuit according to claim 1 wherein said means for moving said first and second switch means in a first position comprises a push-to-start shaft, a housing in which said push-to-start shaft is movably mounted, a groove formed in said push-to-start shaft, said latching means comprising a locking pawl pivotally attached to said housing and engageable within said groove to lock said push-to-start shaft in a first position, and said means for engaging the latching means comprising a shaft for moving said locking pawl to move it out of said notch so that said push-to-start shaft will move to its initial position.

8. A control circuit according to claim 7 comprising a travel adjusting means mounted on said housing, comprising an adjusting shaft rotatably supported by said housing, a lug mounted on said adjusting shaft and movable to allow adjustment of travel, said shaft engageable with said lug to move the adjusting shaft relative to the housing, and a coupling pawl engageable with the locking pawl and movable by the adjusting shaft when

9. A control circuit according to claim 8 comprising first spring biasing means for biasing the locking pawl into said notch, and second spring biasing means for biasing the push-to-start shaft to its initial position.

10. A control circuit according to claim 9 comprising indexing means mounted on said housing and the position of the lug on the adjusting shaft relative to said indexing means indicating the length of travel of said

11. A control circuit according to claim 9 wherein said stop switch is

12. A control circuit according to claim 11 wherein said shaft has an

13. A control circuit according to claim 1 wherein said time-delay means

14. A control circuit according to claim 13 wherein said time-delay means comprises an electronic switch connected in circuit with the switch actuator, and said charging circuit connected in circuit with the electronic switch to control its time of actuation.