US 3552168 A
Description (OCR text may contain errors)
Jan. 5, 1971 L. E. SVENSSON EIAL 3,552,168
APPARATUS FOR TEMPERING SPRINGS IN A SPRING SPINNING MACHINE Filed May 17, 1968 United States Patent 3,552,168 APPARATUS FOR TEMPERING SPRINGS IN A SPRING SPINNING MACHINE Lars Erik Svensson, Tullinge, and Nils Lennart Wahlstriim, Monsteras, Sweden, assignors to AB Industrifjadrar, Monsteras, Sweden Filed May 17, 1968, Ser. No. 730,165 Claims priority, application Sweden, May 17, 1967,
Int. Cl. B21k 21/00 US. Cl. 72-128 4 Claims ABSTRACT OF THE DISCLOSURE In an apparatus for tempering springs in a spring spinning machine the heating of the spring wire to temper it is realized with the aid by means of electric current which is brought to flow through the spring wire. The heating current is controlled in such a way in relation to the speed of advancing the spring wire that the heating current in regard of output is increased or decreased linearly with respect to the increase or decrease of the speed of advance of the spring wire. This is attained in that the speed of the spring Wire is caused to influence a tachometer generator which produces a control current directly proportional to said speed.
This invention relates to an apparatus in machines for bending or spinning springs, in which the tools for bending or spinning the springs have associated with them means which in connection with the shaping of the spring provide a heating thereof with the aid of electric current so that the spring is tempered, and the current causing the heating of the spring is caused to flow through the spring, whereby the spring serves as a resistance wire.
The features characteristic of this apparatus reside in that the intensity of the current causing the heating of the spring is regulated in relation to the speed of advancing the spring wire and that means are provided for respectively increasing and decreasing the current output linear ly with respect to the increase and decrease, respectively, of the speed of advance of the spring wire.
For greater clarity, an embodiment of the apparatus according to the invention will be more fully described in the following with reference to the acocmpanying diagrammatic drawing which illustrates the electric circuit diagram of the apparatus and also indicates the mechanical details of the spring spinning device.
'In the drawing, I designates the wire to be spun or bent. The wire is moved between the feed rolls II through the wire guide designated III towards the tools IV, V and VI which perform spinning or bending of the wire about the mandrel designated VII.
The feed rolls II which are insulated from the support are connected over carbon brushes 1 to one pole 2 of the controllable source of current generally designated 3. In the example illustrated in the source of current is a rectifier. The second pole 4 of the source of current 3, which pole is connected to the support, is thus connected to the tool V so that the circuit is closed when the spring wire engages said tool, whereby current will flow through the wire and heat it. The wire 1 is thus heated from room temperature to the desired tempering temperature when it reaches the tool V and is bent about the mandrel.
To provide an efficient control of the current in relation to the speed at which the wire is moved past the tools the source of current or the rectifier 3 includes control means actuated by a control current.
The control current is produced by a so-called tachometer generator 5 the shaft of which is driven from the rolls II and is thus given a speed proportional to that of the rolls. The current produced by the tachometer generator and increasing linearly with the increase of the speed of the rolls, is passed over a voltage divider 6 through a system of resistors 7, 8 producing control of the current curve, and through a number of diodes 9 optionally connectible by shunt. The tachometer voltage is converted by said diodes into a control voltage which operates the control means of the source of current 3 so that the output voltage thereof, instead of being linear in relation to the rpm. of the rolls or the speed of wire like the voltage from the tachometer generator 5, becomes a logarithmic function of the r.p.m. of the rolls or the speed of the wire.
The current to output ratio is squared so that I XR N. By conversion of the linear function from the tachometer generator into a logarithmic function one obtains a linear output change in relation to the speed variations of the feed rolls II.
The means realizing this conversion of the curve of the control current are the diodes 9 at which the current curve squaredly rises with respect to the voltage applied to the diodes within certain given limit values. The current curve can be controlled stepwise to a certain extent by parallel connection of one, two or three diodes.
The control current obtained in the above manner is caused to actuate the control means of the source of current 3 so that the output current of said source is varied in relation to the incoming control voltage.
The source of current has also associated with it a device 10 for adjusting the zero current, i.e., the current which during short standstill periods must be allowed to pass through the spring wire I in order that the temperature of the wire shall not sink appreciably for example during the short standstill that occurs when a spun or coiled spring is severed.
A further device (not shown) is connected in such a way that at temporary shutdown of the apparatus the so-called zero current is further reduced and is allowed to act as a heating current which prevents too large a temperature reduction of the wire guide III. Use is made of this device also before the start of the apparatus for heating the wire guide which is provided for this purpose with a heating coil 11 at one end. In operation there is the risk that the wire guide III shall be heated too much, resulting in an uncontrollable heating of the Wire 1 before the current is allowed to pass therethrough. To prevent this, a cooling device is arranged at the end of the wire guide adjacent the rolls II. As in the example illustrated, the cooling device preferably is a cold air nozzle VIII.
For controlling the speed and the tempering current in the tempering apparatus during operation, an oscilloscope terminal 12 is provided in the line leading from the tachometer generator 5, in which also a voltage meter 13 is arranged. An oscilloscope terminal 14 is connected by shunt for measuring the low voltage in the line between the support and one pole 4 of the current source 3. With the use of Oscilloscopes the operation of the tempering apparatus can be precisely checked although the speed is high and the time for each tempering cycle is very short. Conventional measuring instruments will not be useful because the individual operations in each cycle are of very short duration.
An operating cycle in the spring spinning or bending and tempering apparatus according to the invention begins with the standstill of the wire I after a prior severing operation. The wire is then accelerated to the maximum speed and is braked to standstill for an extremely short period, whereupon fine adjustment of the wire length is effected at lower speed. The wire which in the meantime has been bent about the mandrel VII by means of the tools IV-VI and has been tempered when engaging the tool V, is finally stopped altogether and severed.
While the invention has been described in the preferred embodiment outlined above andillustrated in the drawing, those skilled in the art will readily understand that the invention can be modified within the scope of the appended claims.
What we claim and desire to secure by Letters Patent 1. Apparatus for bending or coiling of springs from spring wire comprising:
tools for coiling or bending the springs mounted for operation in cooperation with a mandrel,
feed rolls to advance the spring wire to said mandrel and said tools,
control voltage means to control the intensity of the current causing the heating of the spring wire being bent or coiled in relation to the speed of advancement of the spring wire including a tachometer generator driven by said feed rolls,
a voltage divider connected to the output of said tachometer generator,
resistance means connected to said voltage divider,
a means to convert the linear control voltage pro duced by said tachometer generator from being linear from its production by the rotary speed of said feed rolls and said tachometer generator to a logarithmic function of said speed to thereby vary the heating of the spring wire relative to the speed of advance of the wire including diodes connectible by shunting means,
said diodes connected to said resistance means,
a controllable source of current connected to said resistance means,
electrical connecting means to the spring wire from said controllable source of current,
and means to provide a supply of heating current of given intensity to the spring wire at standstill operation of said feed rolls and said tachometer generator connected to said controllable source of current.
2. The apparatus of claim 1, further characterized by said means to supply heating current at standstill including inductive heating means with the spring constituting one spring in an induction apparatus.
3. The apparatus of claim 1, further characterized by cooling means to prevent overheating of the wire at standstill operatively located in conjunction with said means to provide heating current at standstill.
4. The apparatus of claim 1, further characterized by said electrical connecting means to the spring wire being made through at least one feed roll and at least one tool.
References Cited UNITED STATES PATENTS 2,163,565 6/1939 Thomas 72-128X 2,432,801 12/1947 Rendel 219-455 2,995,648 8/1961 Heal 72-128 3,290,481 12/1966 Hinkel 219- MILTON S. MEI-IR, Primary Examiner US. Cl. X.R. 219-155