Method for producing coil springs

Abstract

In a method for producing coil springs, an electric pulse is generated for every predetermined length of wire fed through a wire feeding mechanism; a predetermined number of these pulses, which are adapted for the production of the shape and dimensions of a coil spring, are applied at a time also adapted for the formation of the shape and dimensions of the coil spring, to at least one of a pitch controlling circuit, a wire length controlling circuit, and a coil diameter controlling circuit all included in a control device; and the output of the control device is utilized for controlling at least one of a pitch forming device, a wire feeding device, and a coil diameter regulating device, and also a wire cutting device, whereby the shape and dimensions of the coil springs are controlled numerically.

Description

BACKGROUND OF THE INVENTION

THis invention relates generally to the production of coil springs, and more particularly to a numerically controlled method for producing coil springs.

Heretofore, coil springs have been produced by machines of the type including a main shaft, the rotation of which is transmitted through cams and levers to feed rollers, a pitch-forming mechanism, a coil diameter controlling mechanism, a cutting mechanism, and the like. In such a conventional machine, each coil spring is ordinarily produced during one revolution of the main shaft, and for this reason, the number of turns of the feed roller is maintained as far as possible at a constant value during the one cyclic period of the production.

However, in this conventional coil spring production machine, a slip has been inevitably caused between the feed rollers and the wire material thereby fed, thus reducing the length of the wire material fed by the feed rollers by an amount corresponding to the slip. A reduction in the length of the wire material causes a shortening in the free length of the coil spring or in the coil pitch, and the operational characteristics thereof are also varied.

Furthermore, when a slip occurs between the feed rollers and the wire material during the formation of the coil ends, the adjacent turns in each coil end cannot be in contact with a required tightness, and the seating plane of the coil end cannot be made to be perpendicular to the longitudinal axis of the coil spring.

Furthermore, the mass of the wire material transported by the feed rollers and the tension applied to the wire material always vary during the feeding operation, and the above-mentioned slip between the feed roller and the wire thereby varies in a wide range. Such variation in the amount of the slip constitutes a principal reason for the occurrence of wasteful products whose dimensions and characteristics cannot meet the application requirements.

In addition, cam and levers of various sizes and kinds must be prepared in the machine for producing various kinds of coil springs, and the presetting and adjustment of these cams and levers have required a considerable amount of labour and an extremely high level of skill.

SUMMARY OF THE INVENTION

In view of the above described difficulties in the prior art procedure of producing coil springs, it is an object of the present invention to provide a novel method for producing coil springs whereby coil springs of extremely high precision can be easily produced regardless of the slip between the feed roller and the wire material thereby transported.

Another object of the invention is to provide a method for producing coil springs wherein troublesome adjustments of cams and levers are entirely eliminated even in cases where the type and size of the coil springs to be produced therein are to be altered.

These and other objects of the present invention can be achieved by a novel method for producing coil springs, the method comprising the steps of generating electric pulses of a number determined by the length of wire fed through a wire feeding mechanism, applying a certain number of these pulses at a certain time to at least one of a pitch control circuit, wire length control circuit, and a coil-diameter control circuit all included in a controlling device, the number of the pulses and the time of application thereof being so selected that a required shape and dimensions of the coil springs are thereby obtained, and utilizing the outputs of the control device for operating at least one of a pitch forming device, the wire feeding device, and a coil-diameter forming device, and also a cutting device, whereby the shape and dimensions of the coil springs are controlled in a numerical manner.

The nature, principle, and utility of the present invention will be made apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIGS. 1(a) and 1(b) are a combination of a plan view of a coil spring producing machine and a block diagram of an example of a circuit of a control device for practicing the method according to the present invention;

FIG. 2 is an elevational view of the coil spring producing machine shown in FIG. 1;

FIG. 3 is a side view of a cylindrical coil spring which has been produced by the machine shown in FIG. 1;

FIGS. 4(a) and 4(b) are graphical diagrams indicating a sequence of operations of various parts of the control device with the length of the wire material being taken as the abscissa;

FIG. 5 is a side view of a coil spring-like product having a non-cylindrical configuration;

FIGS. 6(a) and 6(b) are graphical diagrams indicating a sequence of operations of various parts of the control device with the length of the wire material taken as the abscissa;

FIGS. 7A through 7F are diagrams showing various outlines of coil springs and the like which can be produced by the coil spring production machine shown in FIGS. 1 and 2; and

FIG. 8 is a circuit diagram of a part of the control device wherein the pulse motor is made manually rotatable.

DETAILED DESCRIPTION

Referring now to FIGS. 1 and 2 showing a coil spring producing machine for practicing the method according to the present invention, there is indicated a wire material 1 fed by a pair of wire-feeding rollers 2. The wire material 1 (which is frequently called simply a wire) is then passed through a wire guide 3 to a coil forming position wherein the wire material is fabricated into a coiled spring by means of coiling pins 4 and 5.

An electric motor 6 is coupled through electromagnetic clutches 7 and 10 to a rotating shaft 8 and a crank shaft 11, respectively. When the clutch 7 is energized, the rotating shaft 8 is rotated by the electric motor 6, and a pair of feed rollers 2 are rotated by the shaft 8 through a pair of gear wheels 9. The feed rollers 2 feed the wire material to the coil forming position in the coil spring producing machine.

When the electromagnetic clutch 10 is energized, the torque of the electric motor 6 is transmitted to the crank shaft 11 for cutting the wire material 1 each time a coil spring is completed. More specifically, when the crank shaft 11 is rotated, a crank pin 12 provided at an end thereof moves a connecting rod 13, which in turn causes a sliding member 15 to be reciprocated along a sliding guide 14. The sliding member 15 is provided with an upper cutting blade 16 which cooperates with a lower cutting blade 17 provided in the coiling position to cut the wire 1 each time the formation of a coil spring is completed. Electromagnetic brakes 18 and 19 are energized only while the electromagnetic clutches 7 and 10 are not energized, and the rotating shaft 8 and the crank shaft 11 are thereby maintained in the immobile condition.

A proximity switch 20 is provided adjacent to the crank shaft 11 and creates an output signal when a projection 21, made of a metal, of the crank shaft 11 is brought into the sensitive range of the same switch 20. The output thus produced is used for resetting the control device as will be hereinlater described in more detail.

A pitch forming device is provided with a pulse motor 22, the rotation thereof being transmitted through gear wheels 23 and 24 to a screw-threaded shaft 25. A nut 26 engaging the shaft 25 is combined with a rod 27 and a supporting member 28 for a pitch forming tool 29 in an integral manner. Upon rotation of the pulse motor 22, the screw-threaded shaft 25 is rotated, and the pitch forming tool 29 is advanced or retracted along the longitudinal axis of the coil spring, so that a desired pitch is provided in the coil spring thus produced.

The coil spring producing machine is further provided with another pulse motor 30 which rotates another screw-threaded shaft 31. The rotation of the screw-threaded shaft 31 causes a sliding member 32 formed integrally with a nut meshing with the screw-threaded shaft 31 to be reciprocated along a guide 33, and the coiling pin 4 provided at an end of the sliding member 32 thereby advances or retracts in the radial direction of the coil spring.

A lever 35 swingable around a pivot pin 34 is provided at a position adjacent to the sliding member 32, and a roller 36 provided on the sliding member 32 urges the lever 35 to swing around the pivot pin 34. The swinging movement of the lever 35 in turn actuates another roller 37 on another sliding member 38, so that the latter reciprocates along another sliding guide 39, and the hereinbefore described coiling pin 5 provided at the tip of the sliding member 38 is also reciprocated in synchronism with the reciprocation of the coiling pin 4. The forward and backward movements of the coiling pins 4 and 5 change the coil diameter of the coil spring to be produced.

On a supporting bracket 41 secured to the structural framd 40 of the machine, a rotation converter 42 of a photoelectric type is mounted, and a roller 44 for detecting the length of the wire 1 fed by the feed rollers is provided on the shaft 43 of the rotation converter 42. A roller 47 cooperating with the detecting roller 44 is rotatably supported by a supporting member 46 slidable along a guide 45 and is urged toward the detecting roller 44 by means of a spring 48, so that a suitable friction is maintained between the wire material 1 and the wire length detecting roller 44. The resilience of the spring 48 can be adjusted to a suitable value by means of an adjusting screw 49 which can be further locked by the use of a locking nut 50.

When the wire material 1 is fed into the coil spring producing machine, the wire-length detecting roller 44 is rotated, and the rotation is converted by the rotationconverter into electric pulses, the number of which is proportional to the rotating angle of the shaft 43 of the rotation converter 42. Since the rotation converter 42 is of a non-contacting type, the shaft 43 of the converter 42 can be rotated under an extremely small torque.

On the other hand, the rotation of the feed rollers requires a considerable torque for counteracting a force exerted on the wire material by the coiling pins 4 and 5 and another force for accelerating the wire material having a considerable mass. Because of the existence of the load torque, a considerable amount of slip is caused between the wire material 1 and the wire feed rollers.

Since the load torque for the wire length detecting roller 44 is far smaller than the load torque for the feed rollers 2 as described above, the slip in the wire length detecting roller 44 is far less than that in the wire feed rollers 2, and the slip in the roller 44 can be minimized by adjusting the resilience of the spring 48 to a suitable value. In other words, the number of pulses obtained from the wire length detecting roller 44 is exactly proportional to the length of the wire fed by the wire feeding rollers 2, and these pulses are applied to a control device for controlling the formation of coil springs in the coil spring producing machine.

Another proximity switch 51 is provided below the coil spring to be produced, and the position of the proximity switch 51 may also be adjusted in a suitable manner. When the axial length of the coil spring reaches a predetermined value, the proximity switch 51 produces an output pulse which is sent back to the control device as described in more detail hereinafter.

Another photoelectric rotation converter 52 is coupled directly to the output shaft of the pulse motor 22. The rotation converter 52 detects the direction of the rotation and the rotated angle of the pulse motor 22, and the output of the converter 52 is sent to a reversible counter which will be hereinafter described with respect to the control device.

As clearly shown in FIG. 1, the control device is generally divided into a pitch block I, a wire length control block II, and a coil diameter control block III. Ganged switches SW1, SW2, and SW3 are included in the blocks I and II, and ganged selector switches SW4 and SW5 are provided in the block III.

In the example of the control device shown in FIG. 1, the rotation converter 42 and the diameter of the detecting roller 44 are so designed that the rotation converter emits one electric pulse for every 0.01 mm of the wire material 1 fed through the detecting roller 44. Preset counters 1a through 4a and 6a through 10a are included in the control device, and these are all output-holding counters of a decimal type having two decimal places. Numerical values defining the shape and dimensions of the coil spring are preset directly in these preset counters. On the other hand, preset counters 5a, 11a, and 12a are automatically reset counters also of decimal type, and these are operated as pulse frequency dividers.

The operation of the coil-spring production machine will now be described with respect to an example thereof for producing a cylindrical coil spring as shown in FIG. 3. The coil spring has a constant coil diameter of 10 mm, measured from center to center of the wire material, a total number of turns equal to 10, and a coil pitch equal to 2.5 mm. Such a coil spring is of a most ordinary type having wide applications.

It will be assumed that the switches SW1, SW2, SW3, SW4, and SW5 are all in their positions A. Since the switches SW4 and SW5 are in the position A, no input is provided for a pulse-motor driving circuit 2b, and the coil diameter of the coil spring is not changed. The coiling pins 4 and 5 are initially set to produce a coil diameter of 10 mm.

The preset counters 1a, 2a, 3a, 4a, and 5a are preset to 31.41 mm, 251.25 mm, 314.16 mm, 31.50 mm, and 63, respectively. These preset values may be finely adjusted after a required number of test production runs so that accurate dimensions of the coil spring can be obtained.

When an output signl from the proximity switch 20 is introduced into the control device as a reset signal, all the memorized values in the counters are erased, and the outputs thereof become zero. The reset signal from the proximity switch 20 is further applied to all of the flipflop circuits FF1 through FF7, and the output Q thereof is brought into the OFF state, while the output Q is brought into the ON state.

When the reset signal is introduced into the control device, the rotation of the feed rollers 2 is initiated, and the wire material is therby fed into the production machine. The rotation converter thereby starts to produce output pulses, the counters 1a, 2a, and 3a count these output pules. This step corresponds to an instant L.sub.0 indicated in FIG. 4, and also to a point a in FIG. 3.

When wire material of 31.41 mm is fed to the coil spring producing machine, and 3,141 pulses from the converter 42 are sent back to the control device, the counter 1a produces one output pulse. The leading edge of the output pulse from the counter 1a is differentiated, and the thus differentiated signal is sent through an OR element OR1 to an input terminal J of the flip-flop FF1. The Q output of the flip-flop FF1 is thereby brought into the ON state, and the input pulses are thereby passed through an AND element AND 1 to pulse counters 4a and 5a, and the pulse counters 4a and 5a start counting the input pulses. This stage corresponds to L.sub.1 in FIG. 4 and also to a point b in FIG. 3.

Since the counter 5a is set at 63, it produces one output pulse for every 63 input pulses, and this output pulse is passed through and AND element AND 3 to a tool advancing circuit CCW in a pulse-motor driving circuit 1b. The pulse motor 22 is thereby rotated in the counter-clockwise direction, as seen from the front of the machine, for a predetermined angle per each pulse applied to the pulse motor, and the screw-threaded shaft 25 is thereby rotated in the clockwise direction. The pitch forming tool 29 is thus advanced for 0.05 mm per each pulse applied to the pulse motor.

The above described distance of advancing the pitch forming tool per each input pulse is determined by the rotating angle per one step of the pulse motor 22, gear ratio of the gear wheels 23 and 24, and the pitch of the screw 25. Each time the pulse motor 22 is rotated in the counter-clockwise direction for one step, the rotation converter 52 produces four output pulses which are then applied to (+) terminal of the reversible counter RC.

Since the counter 4a is preset at 31.50 mm, the counter 4a produces one output pulse for every reception of 3,150 input pulses. The output pulse is differentiated and introduced into J terminals of the flip-flop circuits FF2 and FF3, whereby the Q and Q outputs of these flip-flop circuits are brought into ON and OFF states, respectively. When the Q output of the flip-flop FF3 assumes the ON state, the output pulse, the leading edge thereof being differentiated, is passed through an OR element OR2 to the input terminal K of the flip-flop 1. Thus, the Q output of the flip-flop 1 assumes the OFF state, and the AND element AND 1 is closed, whereby the input pulses are prevented from entering the counters 4a and 5a.

Since the Q output and the Q output of the flip-flop FF2 are brought into ON and OFF states, respectively, the AND element AND 3 is closed and AND 2 is opened. The output of the counter 4a is passed through an ON-delay circuit OND and another differentiation circuit and sent back to the counter 4a for resetting the same.

Since 3,150 input pulses are applied to the counter 5a while the AND 1 is opened, the counter 5a produces 50 output pulses, whereby the pulse motor 22 is rotated for 50 steps. The rotation of the pulse motor 22 causes the pitch forming tool 29 to advance through a distance of 0.05 mm .times. 50, that is 2.5 mm. The rotation converter 52 generates altogether 200 pulses for this period, and the pulses are applied to (+) terminal of the reversible counter RC. This stage corresponds to L.sub.2 in FIG. 4 and also to C in FIG. 3.

During the period between the instants L.sub.2 and L.sub.3 in FIG. 4, the wire material is fed continuously while the pitch forming tool 29 is held immobile at a 2.5-mm advanced position from the initial position, whereby the portion between the points c and d in FIG. 3 of the coil spring is formed into a constant pitch of 2.5 mm.

When the wire material of 251.25 mm length is fed to the coil spring producing machine, the counter 2a creates an output pulse, which is thereafter differentiated and applied through the switch SW1 and the OR element OR1 to an input terminal J of the flip-flop FF1. The Q output of the flip-flop FF1 is thus brought into the ON state, and the AND element AND1 is thereby opened. The counters 4a and 5a thus start counting the input pulses, and the output of the counter 5a is applied through the AND element AND2 to an input CW of the pulse-motor driving circuit 16. The pulse motor 22 is thus rotated in the clockwise direction.

The pitch forming tool 29 now starts to retract, and the rotation converter 52 is rotated in the clockwise direction. The output of the rotation converter 52 is applied to (- ) terminal of the reversible counter RC wherein the input pulses are counted reversely (or subtracted). This stage corresponds to L.sub.3 in FIG. 4 and also to the point d in FIG. 3.

When the wire material of 282.75 mm length is fed through the detecting roller 44, the pulse-motor 22 is rotated for altogether 50 steps in the clockwise direction, whereby the pulse-motor 22 is brought back to its original position. Until that instant, the rotation converter 52 has applied altogether 200 pulses to the (-) terminal of the reversible counter RC, and the counted result in the reversible counter RC is brought back to zero. The reversible counter RC thus creates an output pulse, which is thereafter differentiated and applied through an OR element OR2 to an input terminal K of the flip-flop FF1. The Q output of the flip-flop FF1 is thus brought into OFF state, whereby the AND1 is closed, and the output of the counter 5a becomes zero. The pulse-motor driving circuit 1b stops its operation, and the pulse-motor 22 is thereby stopped. This instant corresponds to L.sub.4 in FIG. 4 and also to e in FIG. 3.

When the wire material of 314.16 mm is sent through the detecting roller 44, the counter 3a produces an output pulse. This output is then amplified in an amplifier AM1 and used for energizing the electromagnetic clutch 10 and the electromagnetic brake 18. The output of the counter 3a is further amplified in the reversed sense in another amplifier AM2, and the output thereof is used for energizing the electromagnetic clutch 7 and the electromagnetic brake 19. The rotation of the feed rollers 2 is thus stopped, and the rotation of the crank shaft 11 is started. This instant corresponds to L.sub.5 in FIG. 4 and to the point f in FIG. 3. The rotation of the crank shaft 11 causes the upper blade 16 tp descend, whereby the coil spring just completed is cut off from the wire material.

The cutting device is so adjusted that the metal projection 21 on the crank shaft 11 enters in the sensitive range of the proximity switch 20 when the upper blade 16 is approximately at the upper dead center of the cranking movement. The output of the proximity switch 20 is thereafter differentiated and applied to all of the counters and flip-flops as their resetting signals. The control device is thus set back to its initial state. This instant corresponds to L.sub.7 in FIG. 4 which is equal to L.sub.0 in the same FIGURE. The crank shaft 11 is then stopped, and the feed rollers 2 are again rotated. By repeating all of the above described steps of operations, coil springs of a desired kind can be produced.

The position L.sub.1 indicated in FIG. 4, which corresponds to the point b in FIG. 3, can be determined by a preset value in the preset counter 1a. Likewise, the position of the instants L.sub.3 and L.sub.5 in FIG. 4 can be determined by preset values in the counters 2a and 3a. The length of the wire material fed between the instants L.sub.1 and L.sub.2 is determined by a preset value in the counter 4a. The length of the wire material fed between the instants L.sub.3 and L.sub.4 is automatically equalized to the length of the wire material fed between the instants L.sub.1 and L.sub.2 by means of the rotation converter 52 and the reversible counter RC.

The variation rate of the pitch per unit length of the wire material in the period between L.sub.1 and L.sub.2 or between L.sub.3 and L.sub.4 is determined by the preset value in the counter 5a. Thus, it is apparent that according to the present invention, the measurements in various portions of the coil spring can be determined by simply presetting numerical values in the corresponding counters.

In the case where the switches SW1, SW2, and SW3 are transferred to the positions B, coil springs having uniform free lengths can be produced even if irregularities are caused in pitches due to the variation in quality of the wire material. In this case, the instant L.sub.3 in FIG. 4 is not determined by the output of the counter 2a, but is determined by the output of the proximity switch 51. The position of the proximity switch 51 is so adjusted that it produces an output when the axial length of the coil spring is equal to a predetermined value. The output of the proximity switch is thereafter differentiated, and applied through the switch SW1 and the OR element OR1 to an input J of the flip-flop FF1. Thus, the Q output of the FF1 is brought into ON state, and the AND element AND1 conducts. The counter 5a starts producing output, and the formation of the coil end portion of the coil spring is thereby commenced.

When the pulse-motor 22 is rotated reversely to its original position, the reversible counter RC creates an output, which is thereafter differentiated and applied to the input J of the flip-flop FF4. The Q output thereof is brought into ON state, and an AND element AND4 is made conductive. Thus, the input pulses from the rotation converter 42 are passed through the switch SW2, AND element AND4, and an OR element OR3 to the counter 3a. This instant corresponds to L.sub.4 in FIG. 4.

In this case, the length of the wire material fed during the period between the instants L.sub.4 and L.sub.5 is preset in the counter 3a. When the counter 3a produces an output, the feeding operation of the wire feeding rollers 2 is stopped, and the cutting operation begins. More particularly, when the switches SW1, SW2, and SW3 are placed in their B positions, the length in the free state of the coil springs thus produced can be equalized regardless of the slightly different lengths of the wire material required for producing these coil springs and of the slight irregularities in the pitches.

As a second example, the operation of the control device, particularly the third block thereof, will now be described for the case of producing a coiled article as shown in FIG. 5 wherein the coiling diameter is varied.

This article is used for an end tool of a pipe cleaner. It is assumed that the production of the article is started from the left end. In this case also, the pitch controlling block I of the control device operates in a similar manner as in the above described case, and hence detailed description thereof will not be repeated.

The switches SW1, SW2, and SW3 are placed in their positions A, and the switches SW4 and SW5 are placed in their positions B. In the counters 3a, 6a, 7a, 8a, 9a, 10a, 11a, and 12a, values 1,020 mm, 560 mm, 120 mm, 670 mm, 850 mm, 1,030 mm, 110 and 20 are preset, respectively. In the present operation, the output of the counter 10a is not necessary, so that the above described value preset in the counter 10a is selected at an arbitrary value greater than the preset value in the counter 3a.

When the output of the proximity switch 20 resets the control device, the outputs of all of the counters are brought into OFF state, and the Q and Q outputs of the flip-flops FF1 through FF7 are all brought into OFF and ON states, respectively. Thus, the feed rollers 2 start to rotate, and the counters 3a, 6a, 7a, 8a, 9a, 10a, and 12a start counting the input pulses. This instant corresponds to L.sub.0 in FIG. 6 and also to the point a in FIG. 5.

Since the Q outputs of the flip-flops FF6 and FF7 are both in the ON state, the AND element AND6 is brought into the conductive state, and the input pulses are allowed to enter the counter 12a. Since a value 20 is preset in the counter 12a, the latter produces an output pulse upon reception of every 20 input pulses. Furthermore, the Q output of the flip-flop FF5 is in the ON state, the output of the coutner 12a is passed through OR7, AND8, and SW5 to the tool retracting terminal CCW of the pulse-motor control circuit 2b. The pulse-motor 30 is thus rotated counter-clockwisely as seen from the side of the output shaft, whereby the sliding member 32 integrally combined with the nut is retracted. The coiling pins 4 and 5 are thereby retracted, and the coil diameter thus formed is enlarged. In the present example, the coiling pin 4 is advanced or retracted by 0.01 mm with respect to the rotation of the pulse-motor 30 for one step, and the coiling pin 5 is thereby advanced or retracted by one third of the above-mentioned value.

While a wire material of 120 mm is fed through the detecting roller 44, and 12,000 pulses are sent out of the rotation converter 42, the counter 12a emits 600 pulses to the pulse-motor control circuit 2b, whereby the coiling pin 4 is retracted by 6 mm. At this instant, the counter 7a produces an output which is thereafter differentiated and passed through an OR element OR4 to the input terminal T of the flip-flop FF6. The outputs Q and Q of the flip-flop FF6 are thereby brought into the ON and OFF states, respectively. AND elements AND6 and AND5 are thus closed and opened, respectively, and the input pulses are introduced into the counter 11a. This instant corresponds to L.sub.1 in FIG. 6 and also to a point b in FIG. 5.

Each time 110 pulses of the input pulses are introduced into the counter 11a, the latter emits an output pulse which is thereafter sent through OR7, AND8, and SW5 to an input terminal CCW of the pulse-motor control circuit 2b. Since the above-mentioned preset value for the counter 11a is greater than that for the counter 12a, the variation of the coil diameter obtained when the counter 11a operates is far smaller than the variation of the coil diameter obtained when the counter 12a operates.

During the period between the instants L.sub.1 and L.sub.2 indicated in FIG. 6, wire material of 440 mm is fed through the detecting roller 44, and the counter 11a receives 44,000 input pulses. Thus the counter 11a delivers 400 output pulses and the coiling pin 4 is retracted by 4 mm.

After 560 mm of wire material has been fed, the counter 6a delivers one output pulse, and the output pulse is thereafter differentiated and sent to an input terminal J of the flip-flop FF5. The Q and Q outputs of the flip-flop are thereby brought into ON and OFF states, respectively, whereby AND8 is closed and AND7 is opened. Thus the output from the counter 11a is passed through OR6, AN7, and SW4 to an input terminal CW of the pulse-motor driving circuit 2b. The coiling pins 4 and 5 now start moving forwardly, whereby the coil diameter starts decrease. This instant corresponds to L.sub.2 in FIG. 6 and also to a point c in FIG. 5.

During the period between the instants L.sub.2 and L.sub.3, the wire material of 110 mm is further supplied, and hence the counter 11a, receives 11,000 input pulses and delivers 100 output pulses, thus advancing the coiling pin 4 through 1 mm.

When altogether 670 mm of the wire material is supplied to the machine after the initiation of the coiling operation, the counter 8a produces an output which is thereafter differentiated and passed through OR4 to the input terminal T of the flip-flop FF6. Thus, the Q and Q outputs of the flip-flop FF6 are brought into OFF and ON state, respectively, and AND5 is closed and AND6 is opened. Input pulses are again counted in the counter 12a, and the ratio of the coil-diameter variation against the supplied length of the wire material is again increased. This instant corresponds to L.sub.3 in FIG. 6 and also to a point d in FIG. 5.

During the period between L.sub.3 and L.sub.4, 180 mm of the wire material is further supplied, and the counter 12a receives 18,000 input pulses. The counter 12a thus delivers 900 output pulses, and the coiling pin 4 is further advanced by 9 mm.

When altogether 850 mm of the wire material have been supplied to the coil spring producing machine, the counter 9a produces an output which is thereafter differentiated and passed through OR5 to the input terminal T of the flip-flop FF7. Thus, the Q output of the flip-flop FF7 is brought into OFF state, and the AND5 and AND6 are both closed. Since the pulse-motor driving circuit 2b receives no input pulses, the coil diameter is not varied. This instant corresponds to L.sub.4 in FIG. 6 and also to a point e in FIG. 5.

During the period between the instants L.sub.4 and L.sub.5, the wire material is fed to the machine with the positions of the coiling pins 4 and 5 held constant, whereby the coil diameter of the coil-formed article is left unchanged.

When altogether 1,020 mm of the wire material is supplied to the machine, the counter 3a produces an output, and the electromagnetic clutch 7 is brought into the OFF state, while the electromagnetic clutch 10 is brought into the ON state. Thus, the feeding of the wire material is stopped and a cutting operation is started. This instant corresponds to L.sub.5 in FIG. 6 and also to f in FIG. 5. After the cutting operation, an article adapted to be used at the end of a pipe cleaner is obtained.

When the cutting operation terminates and the proximity switch 20 delivers an output, the output is thereafter differentiated and sent for resetting all of the counters and the flip-flops. The feed rollers now start rotating. This instant corresponds to L.sub.6 which is the same as L.sub.0 in FIG. 6. During the above described operation, the counter 10a is reset before the preset number of input pulses are counted in the counter 10a, whereby no output is delivered therefrom.

In FIG. 7, there are indicated, by envelopes, various types of coiled articles which can be produced in accordance with the present invention. Assuming that the coiling operation of each coiled body is started from the leftward end thereof, the coiled bodies A, B, and F in FIG. 7 are produced by placing the switches SW4 and SW5 in their positions C, and the coiled bodies C, D, and E are produced by placing the switches in their positions B.

In all of the above described operations, the time instant at which the rotating direction of the pulse-motor 30 is reversed is determined by the preset value of the counter 6a. Furthermore, the changing instant of the rate of the coil-diameter variation relative to the fed length of the wire material is determined by the preset values in the counters 7a and 8a, and the rate itself is determined by the preset values in the counters 11a and 12a. The starting and ending positions of the portion wherein the coil diameter is not changed are determined by the preset values in the counters 9a and 10a. Thus, it is apparent that, according to the present invention, all of the dimensions and shapes of coil springs having varying coil diameters can also be numerically determined.

In the case where a plurality of products of the same dimensions are successively produced, the pitch forming tool and the coiling pins must be returned exactly to their original positions after the formation of each product. For this purpose, the pulse-motors 22 and 30 must be returned exactly to their original positions after the completion of each product. If the returning of the pulse-motors to their original positions should fail, all of the subsequent products will have dimensions deviating from the required values and hence will be wasted. Since the pulse-motor used for the pitch forming tool is required to be rotated at a considerably high pulse frequency, there is a high possibility of pulsemiss failing to follow the high pulse frequency.

As a first countermeasure to prevent pulse-miss a position detecting device is provided on the output shaft of the pulse-motor, on an end portion of the screw-threaded shaft, or on the linear movement portion driven by the screw-threaded shaft, whereby the actual movement thereof is detected. The output signal from the position detecting device is fed back to the control device, and the difference between a preset numerical value and the position detected signal is utilized for compensating for the error of the pulse-motor.

By this procedure, it is assured that each time an article is produced, the tool is always shifted to a predetermined position and then retracted to the original position, and any possibility of waste products is thereby eliminated. For the above described position detecting device, an inductive type, magnetic type, capacitive type, or a photoelectric type position detecting device such as a synchro resolver, inductosyn, magnetoscale, capacitive scale, optical coded plate, or a diffraction grating may be used.

As a second countermeasure to prevent pule-miss, there is a procedure which has been adopted in the above described example of the coil spring production machine. According to this procedure, a signal indicative of the retraction of the pulse-motor to its original position is issued from a position detecting device described hereinbefore, and the rotation of the pulse-motor is stopped upon reception of the above-mentioned signal. In this case, if the pulse-motor is subjected to a pulse-miss, the pulse-miss cannot be corrected during the operation cycle in which the pulse-miss has occurred, and hence the product produced during the same cycle will be wasted. However, since the pulse-motor is positively set back to its original position under the action of the position indicating signal, the subsequent products obtained thereafter will be satisfactory. In the above described example, the circuit may be so composed that the signal indicative of the retraction of the pulse-motor 22 to the original position is issued from the reversible counter RC which adds or subtracts the output pulses from the rotation converter 52 to or from the already counted value. As a third countermeasure for preventing pulse-miss, a procedure for varying the rotational speed of the feed rollers 2 may be recommended. As will be apparent in FIG. 4, one pulse-motor 22, which is easily subject to pulse-miss, is operated during short periods of from L.sub.1 to L.sub.2, and from L.sub.3 to L.sub.4.

For this reason, if the mechanism is so constructed that the wire material is fed at a lower speed during these periods, with the pulse-motor 22 being driven at a lower pulse frequency, the possibility of causing pulse-miss can be substantially eliminated. In a practical example, the feed rollers have been operated at a slower speed in the periods of from L.sub.1 to L.sub.2 and from L.sub.3 to L.sub.4, and at a higher speed in the period of from L.sub.2 to L.sub.3. This can be realized, for instance, by providing the shaft 8 in FIG. 1 with one more electromagnetic clutch for the low speed operation, and this clutch and the existing clutch 7 may be operated in an alternate manner at the instants of, for instance, L.sub.2 and L.sub.3.

Otherwise, the object may be achieved by the use of a motor 6 of a d, e, type and changing the motor speed at the instants of L.sub.2 and L.sub.3. In the production of coil springs having a great number of tunrs, the production efficiency can be elevated by operating the feed rollers at a high speed as described above, during the period from L.sub.2 to L.sub.3.

In FIG. 8, there is indicated an example of a circuit which allows manual operation of the pulse-motor and facilitates the positional adjustment of the pitch forming tool or the coiling pin. When a switch SW1a in the circuit is switched to the side of the contact CWa, an electric current flows from the terminal +V through a resistor R1 and the switch SW1a to the terminal OV, whereby the voltage at the point u is brought into low state which is thereafter reversed in an inverter ia into a high state.

When a switch SW3a is closed, the output of an oscillator is sent through the switch SW3a, an OR element OR, and an AND element AND1a to an input terminal CWb of a pulse-motor driving circuit 3b, and the pulse-motor is driven in the clockwise direction as long as the switch SW3a is closed. When a switch SW2a instead of the switch SW3a is depressed, the current flowing from the terminal +V through a resistor R3 is interrupted, and the voltage at the point W becomes high. The high state of the voltage at the point W is passed through the OR element and the AND1a to the input terminal CWb of the pulse-motor driving circuit 3b, whereby the pulse-motor is rotated in the clockwise direction by one step.

When the switch SW2a is depressed several times, the pulse-motor is rotated in the clockwise direction by a corresponding number of steps. In this case, the switch SW2a operates as a stepped movement switch, and the switch SW3a operates as a jog switch to control the pulse-motor.

In the case where the switch SW1a is switched to the side of the contact CCWa, the AND element AND2b is thereby opened, and the pulse-motor is rotated in the counterclockwise direction. On the other hand, when the switch SW1a is switched to the OFF position, the AND elements AND1a and AND2a are both closed, and the pulse motor cannot be moved manually. It should be noted that when the position of the tool is to be moved through a long distance, the jog switch SW3a is operated, and when the position of the tool is to be finely adjusted, the step movement switch SW2a is operated. By the provision of the circuit allowing the manual control of the pulse-motor as described above, the adjustment of the production tool is much facilitated.

Furthermore, in the case where a tension coil spring having closely contacting coil turns is to be produced, the manual control device for the pulse-motor may be utilized advantageously for properly adjusting the initial tension thereof.

Although a pitch control block I, a wire length control block II, and a coil diameter control block III are provided in the control device as described above, it is of course possible that one or two blocks thereof be omitted when it is so desired. It the coil diameter control block III is omitted, a machine specifically adapted to produce a cylindrical coiled spring as shown in FIG. 3 can be obtained. It the pitch control block I is omitted, a machine specifically adapted to produce a constant pitch coil spring can be obtained. Furthermore, when the pitch control block I and the coil diameter control block III are both omitted, a machine specifically adapted to produce a coil spring wherein both of the pitch and the coil diameter are maintained constant can be obtained. The latter type machine is extremely advantageous for producing a tension spring having closely contacting coil turns.

In the example of the above description, although electric pulse-motors have been used for driving the pitch-forming tool and the coiling pins, electrohydraulic pulse-motors or a combination of a d, c, motor and a position detecting device may also be utilized for driving these tools.

Furthermore, instead of the above described photoelectric type rotation converter, a rotation converter of induction type, magnetic type, or a capacitive type may also be utilized for acquiring the substantially same effects. In addition, instead of the above described access switches, a contact type switch may be employed, and instead of the above described pushout type pitch-forming tool, a wedge type pitch-forming tool may also be utilized.

Claims

What I claim is:

1. An improved method for producing coil springs in which an electrical pulse is generated each time a predetermined length of wire material is fed through a wire feeding mechanism, a number of said pulses being applied to a wire length control circuit included in a control device, and the output of said wire length control circuit emitted at the time a predetermined number of said pulses are applied to said circuit is utilized for stopping the movement of the wire feeding device and for starting the movement of a cutting device, wherein said improvement comprises the steps of:

a. applying said electric pulses to a pitch control circuit also included in said control device;

b. emitting phase output pulses from said pitch control circuit for a period during which a pitch increasing portion of the coil spring is produced;

c. utilizing said phase output pulses for advancing a pitch forming tool a predetermined distance for each of said output pulses of said pitch control circuit, whereby a required pitch increase is obtained in the coil spring;

d. suspending the emission of output pulses from said pitch control circuit for a period during which a constant pitch portion of the coil spring is produced, whereby said pitch forming tool is so securely held that pitches of the constant pitch portion of the coil spring are reliably uniform;

e. emitting opposite phase output pulses from said pitch control circuit for a period during which a pitch decreasing portion of the coil spring is produced;

f. and utilizing said opposite phase output pulses for retracting said pitch forming tool a predetermined distance for each of said opposite phase output pulses of said pitch control circuit,

whereby a required pitch decrease is obtained in the coil spring, reciprocating movement of said pitch forming tool is thereby completed, and said pitch forming tool returns to its original position to be ready for a succeeding coil spring production.

2. A method as set forth in claim 1, in which said electric pulses are applied to a coil-diameter control circuit also included in said control device; wherein phase output pulses of said coil-diameter control circuit are emitted for a period during which a coil-diameter increasing portion of the coil spring is produced, said phase output pulses of said coil-diameter control circuit being utilized for retracting the coil-diameter forming pin a predetermined distance per each of said output pulses of said coil-diameter control circuit, whereby a required coil-diameter increase is obtained in the coil spring; and wherein the emission of output pulses from said coil-diameter control circuit is suspended for a period during which a constant coil-diameter portion of the coil spring is produced, whereby said coil-diameter forming pin is so securely held that coil-diameters of the constant coil-diameter portion of the coil spring are reliably uniform; and wherein opposite phase output pulses of said coil-diameter control circuit are emitted for a period during which a coil-diameter decreasing portion of said coil spring is produced, said opposite phasic output pulses of said coil-diameter control circuit being utilized for advancing the coil-diameter forming pin a predetermined distance per each of said opposite phasic output pulses of said coil-diameter control circuit, whereby a required coil-diameter decreasing is obtained in the coil spring, and said coil-diameter forming pin returns to its original position to be ready for a succeeding coil spring production.

3. A method as set forth in claim 1 in which the attainment of a predetermined axial length of the coil spring is detected by a position detector during production of the constant pitch portion without emitting output pulses of said pitch control circuit, thereby starting the emission of opposite phase output pulses of said pitch control circuit at the instant of said detection, whereby the retraction of said pitch forming tool is started, and the formation of a coil end portion having a closely adjacent turn of the coil is thereby commenced, whereby an accurate axial free length of the coil spring is obtained each and every time a coil spring is produced.

4. A method as set forth in claim 2 in which displacements of the pitch forming tool means and coil-diameter forming pin means are detected respectively by position detecting devices provided respectively on a part driven by a feeding screw of each of said devices, and the outputs of said position detecting devices are fed back to said pitch and coil-diameter control circuits and respectively compared therein with numerical signals obtained from said control circuits, the rotations of motors for driving said devices being corrected by respective differences obtained by said comparison, whereby exact reciprocating movements of said pitch forming tool means and said coil-diameter forming pin means between respective predetermined positions are secured.

5. A method as set forth in claim 2 wherein displacements of pitch forming tool means and coil-diameter forming pin means are detected respectively by position detecting devices provided respectively on a part of a feeding screw of each of said devices, and the outputs of said position detecting devices are fed back to said pitch and coil-diameter control circuits and respectively compared therein with numerical signals obtained from said control circuits, the rotations of said driving motors being corrected by respective differences obtained by said comparison, whereby exact reciprocating movements of said pitch forming tool means and said coil-diameter forming pin means between respective predetermined positions are secured.

6. A method as set forth in claim 2 wherein position detecting devices are respectively provided on a part driven by a feeding screw of each of said pitch forming device and coil-diameter forming device, an output being generated from each of said position detecting devices when the corresponding driving motor is reversely rotated to its original position, and a logic gate in the motor controlling circuit in said control device is closed by said output from said position detecting device thereby to stop the rotation of said motor, whereby returning of the pitch forming tool and the coil-diameter forming pin to the predetermined positions is assured each time the production of one coil spring is completed.

7. A method as set forth in claim 2 wherein position detecting devices are respectively provided on a part of a feeding screw of each of said pitch forming device and coil-diameter forming device, an output being generated from each of said position detecting devices when the corresponding driving motor is reversely rotated to its original position, and a logic gate in the motor controlling circuit in said control device is closed by said output from said position detecting device thereby to stop the rotation of said motor, whereby returning of the pitch forming tool and the coil-diameter forming pin to the predetermined positions is assured each time the production of one coil spring is completed.

8. A method as set forth is claim 1 in which by varying the speed of a motor for driving the wire feed mechanism, the wire material is fed at a low speed during the formation of the coil end portions, and the wire material is fed at a high speed when the middle portion of the coil spring is formed wherein the coil pitch is maintained at a constant value.

9. A method as set forth in claim 1 wherein a step-movement switch is provided in said pitch control circuit included in said control device for operating a motor in such a manner that each time the step-movement switch is depressed, the motor is rotated in a desired direction through a predetermined angle to drive the pitch forming tool in the corresponding direction through a predetermined distance, whereby the positional adjustment of said pitch forming tool is greatly facilitated.