JP2009101478A - Wire elongation detecting device in counterbalance mechanism of spindle head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wire elongation detecting device which can surely and simply detect whether or not elongation of a wire or a chain exceeds an elongation limit allowable value L, and does not require adjustment of a position of a sensor or the like after replacing the wire. <P>SOLUTION: Signal generating means 20, 21, which generate a signal for detecting the wire elongation when the balance weight is located on a predetermined reference position, are provided in the middle of an elevating/lowering path for a balance weight 15. A position of a spindle head 12 where the signal is generated in an initial setting at installment of the wire is defined as an initial position Z1, a position set in the middle of an elevating/lowering path for the spindle head 12 below the initial position Z1 with a distance of the predetermined elongation limit allowable value L is defined as a movement start position Z2, and a section between the movement start position Z2 and the initial position Z1 is defined as a detection section. It is determined whether or not the elongation of the wire exceeds the elongation limit allowable value L based on whether the signal is generated or not during movement of the spindle head 12 from the movement start position Z2 to the initial position Z1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wire elongation detection device in a spindle head counterbalance mechanism, and in particular, in an NC machine tool, detects the elongation of a wire connecting the spindle head and a balance weight and accurately grasps whether or not the usage limit has been reached. The present invention relates to a wire elongation detecting device in a spindle head counterbalance mechanism.

  In a machine tool in which the spindle head moves in the vertical direction, the load on the spindle head feed mechanism is reduced by suspending a balance weight that balances the weight of the spindle head. In this type of counter balance mechanism, a pulley or sprocket is installed at the upper end of a column, one end of a wire or chain wound around the pulley or sprocket is connected to the spindle head, and the other end is connected to a balance weight.

  In such a counterbalance mechanism, since a large load is always applied to the wire or chain, elongation occurs gradually. If this elongation is left to the limit, it may break.

As a prior art for detecting the elongation of a wire or a chain, for example, there is one described in Patent Document 1.
This Patent Document 1 describes that a spindle head is positioned at a specific position determined in advance, and a detector is arranged so that a detection signal is generated at the balance weight position at this time. If the chain length increases, a detection signal is not given from the detector when the spindle head moves to a specific position, so that it can be determined that the chain length exceeds a specified amount.
Japanese Utility Model Publication No. 61-9235

  However, as in the prior art cited in Patent Document 1, detecting the elongation of the chain based on the position of the balance weight when the spindle head is positioned at a predetermined specific position substantially measures the chain length. It is nothing but what you do.

  For this reason, when the chain is replaced, it is indispensable to precisely measure the length of the chain and adjust the position of the detector according to the length.

  In addition, the conventional counter balance mechanism only checks periodically whether there is any abnormality in the amount of elongation, and the problem is that the elongation of the wire or chain cannot be grasped in relation to the use limit. there were.

  Furthermore, the work of exchanging wires and chains is a large-scale work. Therefore, after preparing the wire or chain to be replaced in advance, the replacement work is planned while observing the operation status of the machine.

  However, in the past, there was no way of knowing that the elongation was approaching the limit of the allowable range during normal processing, so the operating rate was not lowered in anticipation of the preparation period for replacement work. An appropriate management plan could not be established.

  Therefore, the object of the present invention is to solve the problems of the prior art and to detect the elongation of the wire or chain reliably and simply in relation to the allowable limit, such as a sensor after replacing the wire. An object of the present invention is to provide a wire elongation detecting device in a spindle head counterbalance mechanism that does not require position adjustment.

  In addition, another object of the present invention is to make it possible to grasp the elongation of wires and chains so that an appropriate management plan can be made without deteriorating the operation rate in anticipation of the preparation period for replacement work. An object of the present invention is to provide a wire stretch detection device in a counterbalance mechanism.

  In order to achieve the above object, the present invention provides a spindle head counterbalance mechanism of an NC machine tool in which a balance weight that balances the weight of the spindle head is connected to a spindle head provided in a column so as to be movable up and down via a wire. The signal generating means for generating a signal for detecting the wire elongation when the balance weight is at a preset reference position in the middle of the lifting / lowering path of the balance weight, and the signal at the initial setting when the wire is installed The position of the spindle head at the time of occurrence is set as an initial position (Z1), and is set to a position below the initial position (Z1) by a predetermined extension limit allowable amount (L) in the middle of the spindle head lifting path. The storage means for storing the determined position as the movement start position (Z2), and a detection interval between the movement start position (Z2) and the initial position (Z1), Based on the presence or absence of the signal during the movement of the spindle head from the moving position start position (Z2) to the initial position (Z1), the wire exceeded the allowable elongation limit (L). And a judging means for judging whether or not.

  In the present invention, the signal generating means includes a position sensor disposed at a position along the lifting / lowering path of the balance weight of the column, and an operating member attached to the spindle head side and generating a signal to the position sensor. It is characterized by comprising.

  According to the present invention, it is possible to reliably detect that the elongation of the wire or chain of the counter balance mechanism exceeds the elongation limit (L), and it is necessary to adjust the position sensor after the replacement. Disappears. Furthermore, it is possible to grasp the growth of wires and chains so that an appropriate management plan can be made without deteriorating the operating rate in anticipation of the replacement work preparation period.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a wire elongation detecting device for a spindle head counterbalance mechanism according to the present invention will be described with reference to the accompanying drawings.
First embodiment
FIG. 1 shows a counter balance mechanism of an NC horizontal lathe to which the present invention is applied. In FIG. 1, reference numeral 10 indicates a column of a horizontal center lathe. Reference numeral 12 indicates the spindle head. In this horizontal center lathe, the spindle head 12 moves up and down along the guide surface of the column 10 (Z axis), and the spindle 14 of the spindle head 12 is fed out in the front-rear direction (direction perpendicular to the paper surface). (W axis).

The horizontal center lathe is provided with the following spindle head counterbalance mechanism. Reference numeral 15 indicates a balance weight that is a weight that balances the weight of the spindle head 12.
A set of pulleys 16 a and 16 b is installed at the top of the column 10. Wires 17 for connecting the spindle head 12 and the balance weight 15 are wound around the pulleys 16a and 16b. When the spindle head 12 moves up and down by the Z-axis feed mechanism, the balance weight 15 moves in the opposite direction as the spindle head 12 moves. Although not shown in this horizontal lathe, the table moves in the front-rear direction (X-axis) and the saddle on which the table is placed moves in the left-right direction (Y-axis).

  In the column 10, a position sensor 20 is disposed at an appropriate height position along the lifting / lowering path of the balance weight 15. A proximity switch is used for the position sensor 20. An operation member 21 for operating the position sensor 20 is attached to the side surface of the balance weight 15. As shown in FIG. 1, the operating member 21 is attached at a position lower than the position of the operating member 21 when the balance weight 15 is at the upper limit position.

  The position sensor 20 and the actuating member 21 are for detecting the extension of the wire 17 and for setting the reference position of the balance weight 15. In this embodiment, when the balance weight 15 is located at the reference position, the actuating member 21 activates the position sensor 20, so that the balance weight 15 is at the reference position by taking in a signal output from the position sensor 20. I understand that.

In FIG. 1, the balance weight 15 is not in the reference position. In FIG. 2, the wire 17 is shown as not being stretched and the balance weight 15 is located at the reference position.
Here, in FIGS. 1 and 2, the position of the spindle head 12 will be described in relation to the position of the balance weight 15, and a mechanism for detecting the extension of the wire 17 will also be mentioned.

  In FIG. 1, the spindle head 12 is located at the origin Z0 on the Z axis. This origin Z0 is a position close to the lower limit position for lowering the spindle head 12. The balance weight 15 at this time is in a position close to the upper limit of the rise. The origin Z0 is a position not directly related to the detection of the extension of the wire 17. When the spindle head 12 is located at the origin Z 0, the actuating member 21 of the balance weight 15 is located away from the position sensor 20.

  Next, in FIG. 2, the initial position Z1 is defined as the position of the spindle head 12 when the wire 17 is not stretched and the balance weight 15 is at the reference position. This initial position Z1 is set when the machine is installed or when the wire 17 is replaced with a new one. That is, it is the position of the spindle head 12 when the spindle head 12 rises and the actuating member 21 of the balance weight 15 actuates the position sensor 20 assuming that the wire 17 is not newly extended. When the wire 17 does not stretch, the position of the spindle head 12 where the position sensor 20 is turned on does not always change. On the other hand, if the wire 17 is stretched, the position of the spindle head 15 when the position sensor 20 is turned on is located below the initial position Z1.

  Next, in FIG. 2, the movement start position Z <b> 2 is defined as the position where the spindle head 12 starts moving and the elongation detection process starts in the elongation detection operation of the wire 17. In this embodiment, the movement start position Z2 is set at a position separated from the initial position Z1 by an elongation limit allowable amount (L).

  In the process of detecting the elongation of the wire 17, the spindle head 12 moves upward from the movement start position Z2 toward the initial position Z1. Suppose that the movement start position Z2 is determined as an appropriate position below the initial position Z1. If the wire 17 is stretched, the position sensor 20 is turned on at a position where the spindle head 12 is below the initial position Z1, so that it can be detected that the wire 17 is stretched. However, it cannot be determined whether the elongation of the wire 17 at this time is within an allowable range or whether it is out of the allowable range, i.e., an extension that requires replacement.

  Therefore, in this embodiment, the movement start position Z2 is set to a position that is lower by a preset elongation limit allowable amount L. If the elongation of the wire 17 exceeds the elongation limit allowable amount L, the position sensor 20 is not turned on even if the spindle head 12 is moved from the movement start position Z2 to the initial position Z1. Thus, by setting the movement start position Z2 in association with the initial position Z1 and the extension limit allowable amount L, when the position sensor 20 is not turned on, that is, the extension of the wire 17 exceeds the allowable range. It will be nothing else.

  On the other hand, if the wire 17 is stretched but does not exceed the allowable elongation limit L, the position sensor 20 is turned on while the spindle head 12 moves from the movement start position Z2 to the initial position Z1. It will be.

  In this way, based on the presence or absence of a signal output when the position sensor 20 is turned on, it is determined whether or not the wire is stretched and whether or not it exceeds the stretch limit allowable amount L. Will be able to.

  Next, FIG. 3 is a block diagram of the wire stretch detection device according to the present embodiment. The control unit 30 is configured as a part of the NC device by controlling the arithmetic device of the NC device with software. The position coordinate of the spindle head 12 is input to the control unit 30 from the position control system of the NC device. Further, a signal when the position sensor 20 is turned on is input. These signals are stored in the storage means 32 via the signal processing means 31. The storage means 32 is provided with registers 1 to 5. Among these, the register 1 stores a signal when the position sensor 20 is turned on in the initial initial setting. Similarly, the register 2 stores the position of the spindle head 12 when a signal is generated in the initial setting, that is, the position coordinate Z01 of the initial position Z1. The register 3 is initially set to 0 in the process of detecting the actual wire elongation, and stores the position coordinate Z03 of the spindle head 12 when the position sensor 20 is turned on. The register 4 stores the elongation limit allowable amount L described above. The data on the allowable elongation limit L is set by the data input means 33 such as a keyboard or a touch panel of the operation panel. The register 5 stores the position coordinate Z02 of the movement start position Z2 of the spindle head 12.

  The comparison calculation means 34 operates according to the flowchart of FIG. 4 and starts the elongation detection process after moving the spindle head 12 to the movement start position Z2. Then, a means for determining whether or not the wire 17 has been stretched beyond the stretch limit allowable amount L depending on whether or not a signal is generated in the course of movement, with the detection section from the movement start position Z2 to the initial position Z1 is configured. is doing. When the elongation is determined, a signal is output to the alarm device 36.

  Next, the wire elongation detection operation according to the present embodiment will be specifically described with reference to the flowchart of FIG.

This elongation detection program is automatically executed by a user macro incorporated in the NC apparatus.
First, it is selected from the operation panel or touch panel of the input means 33 whether to perform wire extension detection (step S10). When execution is selected (yes in step S10), in step S11, it is confirmed whether or not the initial position Z1 of the spindle head 12 when the position sensor 20 is turned on is already set. This can be confirmed by referring to whether or not the initial setting signal is stored in the register 1.

When the initial position Z1 of the spindle head 12 is not set (no in step S11), the process of setting the initial position Z1 of the spindle head 12 is performed according to the procedure of steps S21 to S24.
First, in step S21, the spindle head 12 is moved to the origin Z0 in FIG. Next, the spindle head 12 starts to rise (step S22). When the spindle head 12 starts to rise, the balance weight 15 descends. When the balance weight 15 is lowered to the position shown in FIG. 2, the position sensor 20 is turned on by the actuating member 21 (yes in step S23). At this time, the spindle head 12 is stopped. The position sensor 20 outputs a signal to the control unit 30. This signal is stored in the register 1. The position of the spindle head 12 at this time is stored in the register 2 as the position coordinate Z01 of the initial position Z1 (step S24).
On the other hand, if the initial position Z1 of the spindle head 12 is already set, the process proceeds from step S11 to step S12, and the spindle head 12 is moved to the movement start position Z2 shown in FIG. Next, 0 is set in the register 3 in which the position coordinate Z03 indicating the position Z3 of the spindle head 12 when the signal is generated is stored (step S13).

  Next, the movement of the spindle head 12 to the initial position Z1 is started (step S14). When the spindle head 12 starts to rise, the balance weight 15 descends. The subsequent operation differs depending on the degree of elongation of the wire 17 and is roughly divided into three ways.

The first case, that is, the case where the elongation of the wire 17 exceeding the elongation limit allowable amount L is detected will be described.
As described above, since the initial position Z1 is separated from the movement start position Z2 by an equivalent distance corresponding to the elongation limit allowable amount L, if the elongation of the wire 17 exceeds the elongation limit allowable amount L, the movement starts from the movement start position Z2. Even if it moves to the initial position Z1, the position sensor 20 is not turned on.

  Therefore, the process advances from step S15 to step S17. In this step S17, the position of the spindle head 12 is monitored, and when it arrives at the initial position Z1, the process proceeds to step S18 to determine whether or not an alarm is required to notify that the elongation of the wire 17 has exceeded the allowable elongation limit L. Do. In this first case, the position sensor 20 is not turned on, and it is determined that the elongation exceeds the limit allowable amount L based on the fact that the Z03 value stored in the register 3 remains zero. Based on the determination result, the alarm device 36 issues an alarm (step S19).

Next, the detection operation in the second case, that is, when the elongation of the wire 17 is smaller than the allowable elongation limit L will be described.
In this second case, the position sensor 20 is turned on while the spindle head 12 is moving. Accordingly, when the spindle head 12 starts moving in step S14 and the position sensor 20 is turned on in step S15 and a signal is generated, the process proceeds to step S16, and the value of the position coordinate Z03 of the spindle head 12 at this time is stored in the register 3. Store. If the wire 17 is elongated, the position Z3 of the spindle head 12 at this time is a position as shown in FIG. Thereafter, the spindle head 12 reaches the initial position Z1 and stops (step S17).

  In step S18, since the position coordinate Z03 is stored in the register 3 and the value is not 0, it is determined that the elongation of the wire 17 does not exceed the allowable elongation limit L and that no alarm is required. As a result, the alarm device 36 does not generate an alarm. However, in this embodiment, instead of issuing an alarm, the wire elongation occurring at this time is caused by the difference between the position coordinate Z03 of the spindle head 12 and the position coordinate Z01 of the initial position Z1 when the position sensor 20 is turned on. The amount is calculated and the value is displayed on the monitor (step S20). Thereby, the present condition of the amount of extension of wire 17 can be grasped.

Finally, the detection process in the third case, that is, when the elongation of the wire 17 is substantially equal to the allowable elongation limit L will be described.
In the third case, if the elongation of the wire 17 is equal to the elongation limit allowable amount L, if there is no detection position error due to the accuracy of the position sensor 20, the spindle head 12 is moved to the movement start position Z2 in step S14. Thus, the position sensor 20 should be turned on simultaneously with the start of the detection operation (yes in step S15). The coordinate value Z03 of the position Z3 of the spindle head 12 at this time is stored in the register 3 (step S16). Then, after the spindle head 12 reaches the initial position Z1 (yes in step S17), it is determined that there is no alarm based on Z03 stored in the register 3 (no in step S18).

In this case, the difference in the position coordinate between the initial position Z1 and the position Z3 of the spindle head 12 when the signal is generated is equal to the allowable elongation limit L as shown in the equation (1), and the elongation of the wire 17 is L. .
| Z01−Z03 | = L (1)

  In this third case, if there is no detection position error due to the accuracy of the position sensor 20 or the like according to the expression (1), the determination that the alarm performed in step S18 is not issued is correct, and the above-mentioned There is no problem with such processing.

  On the other hand, if the position sensor 20 has a detected position error that cannot be ignored, the position detection error is actually caused by the presence of the position detection error in spite of the wire 17 having an extension exceeding the allowable elongation limit L. There is a possibility that the sensor 20 is turned on and no alarm is issued.

Therefore, it is preferable to perform the following processing in step S18 in consideration of the detection position error.
That is, in determining whether or not an alarm is required in step S18, it is determined that an alarm is issued when the Z03 value of the register 3 is zero or the following equation (2) obtained by correcting the above equation (1).
| Z01-Z03-L | ≦ A (2)
However, A is a constant determined in advance as 1 (mm), for example, corresponding to the detected position error.

  By determining whether or not an alarm is necessary based on the equation (2), it is detected that the elongation of the wire 17 has reached the allowable elongation limit L without depending on the accuracy of the position sensor 20, An alarm can be issued.

  If the position sensor 20 itself fails and cannot be operated, the value of the register 3 set in step S13 remains zero, so that an alarm is issued through the determination in step S18. It will be different. Therefore, not depending on the error of the position sensor 20, not only an alarm is issued, but also a failure of the position sensor 20 can be dealt with.

  As described above, when the elongation of the wire 17 exceeds or substantially equals the elongation limit allowable amount L, an alarm can be surely issued, so that attention is drawn to the necessity of wire replacement. .

  Further, according to the present embodiment, it is not necessary to adjust the positions of the position sensor 20 and the actuating member 21 according to the length of the wire 17 after replacing the wire. That is, after the wire is replaced with a new one, the length of the new wire is not strictly measured, and the processing of steps S21 to 24 is performed again without changing the position sensor 20 and the operating member 21. Immediately after replacement, the register data such as the value of the initial position Z1 of the spindle head 12 may be updated.

  In addition, although the detection operation of the wire 17 may be performed once a day during the operation of the machine, it may be performed once a week, ten days, or once a month.

Second embodiment
Next, the operation of the counterbalance apparatus according to the second embodiment of the present invention will be described with reference to the flowchart of FIG.

  In the process of the flowchart of FIG. 6, the difference from the first embodiment is the process from step S <b> 30 to step S <b> 35. The other steps are the same as those in the flowchart of FIG. 4, and thus the same step numbers are assigned and detailed description is omitted.

  This second embodiment is characterized by the method of setting the movement start position Z'2. As shown in FIG. 7, the movement start position Z′2 is a provisional elongation allowance temporarily set to a predetermined ratio, for example, 90% with respect to the elongation limit allowance L from the initial position Z1. It is set at a position separated by LL (L> LL). Hereinafter, a position corresponding to the allowable elongation limit L is referred to as a first movement start position Z2, and a position corresponding to the allowable elongation amount LL is referred to as a second movement start position Z'2.

  In the control unit 30 shown in FIG. 8, a register 11, a register 41, and a register 51 are added as compared with the control unit in FIG. Among these, the register 11 stores an alarm signal for prompting preparation for wire replacement described later. Further, when an elongation limit allowable amount L and a provisional elongation allowable amount LL are input from the data input means 33 such as a keyboard or a touch panel of the operation panel, the elongation limit allowable amount L is stored in the register 4 and the provisional elongation allowable amount LL is Stored in the register 41. At this time, the position coordinate Z02 of the movement start position Z2 is calculated and stored in the register 5, and the position coordinate Z'02 of the second movement start position Z'2 corresponding to the temporary extension allowance LL is stored in the register 51. .

  In FIG. 6, in step 11, it is confirmed whether or not the initial position Z1 has been set. If not set, the process proceeds from step S21 to step S24, and then proceeds to the process from step S30. This process is the same as in the first embodiment.

  In step S <b> 30, it is determined whether an alarm that prompts for wire replacement preparation has been issued even once. This can be confirmed by referring to the alarm signal stored in the register 11.

  If no alarm has been issued, the process proceeds to step 31 to move the spindle head 12 to the second movement start position Z'2 shown in FIG. Next, 0 is set in the register 3 in which the position coordinate Z03 indicating the position Z3 of the spindle head 12 is to be stored (step S32). Thereafter, the movement of the spindle head 12 to the initial position Z1 is started (steps S14 to S17).

  Thereafter, as in the first embodiment, if the position sensor 20 is not turned on before moving from the second movement start initial position Z′2 to the initial position Z1, the elongation of the wire 17 becomes the provisional allowable elongation LL. If it has exceeded, it is determined to issue an exchange preparation warning (yes in step S33). A signal for instructing an alarm for prompting replacement is stored in the register 11 (step S34), and is given to the alarm device 36 to issue an alarm for prompting for replacement (step S35).

  As described above, the elongation of the wire 17 at the time when the alarm for prompting the replacement of the wire is issued exceeds the provisional elongation allowable amount LL set to 90% of the allowable elongation limit L, for example. It is in. This means that there is a margin up to the elongation limit allowable amount L that can be used safely in relation to the elongation limit allowable amount L. Will be encouraged. Therefore, there is an advantage that a wire replacement plan can be made while observing the operation status of the machine.

  On the other hand, after the warning for prompting replacement is generated once in the above procedure, if the elongation detection is executed in step S10, the process proceeds from step S30 yes to step S12 and subsequent steps, and the process corresponding to the elongation limit allowable amount L is reached. The spindle head 12 is moved from the first movement start position Z1, and elongation detection is performed in the same manner as in the first embodiment of FIG.

  As described above, according to the second embodiment, with respect to the elongation of the wire 17, the wire 17 is set by combining the two stages of allowable elongation, such as the allowable elongation limit L and the temporary allowable elongation LL. Elongation detection is performed. If the alarm has never been issued, the elongation is first detected based on the provisional elongation allowable amount LL. After the alarm is issued, the elongation limit allowable amount L becomes the elongation reference. In this way, since the reference elongation allowance changes step by step, finer wire management becomes possible. Even if it is decided that the detection is to be executed once a month, it is possible to reliably grasp the wire elongation state.

  As described above, the present invention has been described with respect to the counter balance mechanism in which the spindle head and the balance weight are connected by the wire. However, the present invention also applies to the counter balance mechanism that uses a chain instead of the wire. Can be applied to.

The front view which shows the spindle head counterbalance mechanism of the machine tool to which this invention is applied. FIG. 2 is a front view of the spindle head counterbalance mechanism of FIG. 1 when a balance weight is positioned at a position where a sensor used for detecting elongation is turned on. The block block diagram of the wire elongation detection apparatus of the spindle head counterbalance mechanism by the 1st Embodiment of this invention. The flowchart which shows the operation | movement of the wire elongation detection by 1st Embodiment of this invention. The figure explaining the position of the spindle head in the wire elongation detection by 1st Embodiment of this invention. The flowchart which shows the operation | movement of the wire elongation detection by 2nd Embodiment of this invention. The figure explaining the position of the spindle head in the wire extension detection by 2nd Embodiment of this invention. The block block diagram of the wire elongation detection apparatus of the spindle head counterbalance mechanism by the 2nd Embodiment of this invention.

Explanation of symbols

10 Column 12 Spindle head
14 Spindle
15 Balance weight
16a, 16b pulley
17 wire
20 Position sensor 21 Actuating member Z0 Origin Z1 Initial position Z2 Movement start position L Elongation limit allowable amount

Claims (11)

In a spindle head counterbalance mechanism of an NC machine tool in which a balance weight that balances the weight of the spindle head is connected via a wire to a spindle head that is freely movable up and down in a column.
A signal generating means for generating a signal for wire extension detection when the balance weight is at a preset reference position in the middle of the lifting and lowering path of the balance weight;
The initial position (Z1) is the position of the spindle head when the signal is generated in the initial setting at the time of wire installation, and the initial value is set to a predetermined elongation limit allowable amount (L) in the middle of the spindle head lifting path. Storage means for storing a position set as a position below the position (Z1) as a movement start position (Z2);
Generation of the signal during the movement of the spindle head from the movement position start position (Z2) to the initial position (Z1), with a detection interval between the movement start position (Z2) and the initial position (Z1). Determining means for determining that an elongation exceeding the allowable elongation limit (L) has occurred in the wire based on the presence or absence of
An apparatus for detecting wire elongation in a spindle head counterbalance mechanism. The signal generating means includes a position sensor disposed at a position along the lifting / lowering path of the balance weight of the column;
The wire elongation detecting device for a spindle head counterbalance mechanism according to claim 1, further comprising an actuating member attached to the spindle head side and generating a signal to the position sensor.   The determination means determines that the wire extends beyond the allowable elongation limit (L) when the signal is not generated before the spindle head moves from the movement start position (Z2) to the initial position (Z1). The wire elongation detection device for a spindle head counterbalance mechanism according to claim 1, wherein the wire elongation detection device is determined to have occurred.   The movement start position (Z2) includes a first movement start position that is separated from the initial position (Z1) by the elongation limit allowable amount (L), and the elongation limit allowable amount (Z1) from the initial position (Z1). L) and a second movement start position separated by a provisional elongation allowance (LL: L> LL) provisionally set at a predetermined ratio with respect to L). The wire elongation detection apparatus in the spindle head counterbalance mechanism according to claim 1.   In order to set the allowable elongation limit (L) and the temporary allowable elongation (LL) of the wire, the storage means has an allowable elongation setting means for storing the allowable elongation limit (L) in the storage means. The wire elongation detection device in the spindle head counterbalance mechanism according to claim 4.   The storage means has a register in which the position coordinate (Z03) of the spindle head is stored, and when it moves to the movement start position (Z2), 0 is set in the register, and when the signal is generated 2. The wire elongation detecting device in a spindle head counterbalance mechanism according to claim 1, wherein the position coordinate (Z03) of the spindle head is stored in the register.   The determination means determines whether the signal is not generated and the value of the register in which the position coordinate (Z03) of the spindle head is stored is 0, or the position coordinate (Z01) of the initial position (Z1) when the signal is generated When the absolute value obtained by subtracting the spindle head position coordinate (Z03) and the elongation limit allowable amount (L) is smaller than a preset allowable error A, the wire exceeds the elongation limit allowable amount (L). The wire elongation detection device for a spindle head counterbalance mechanism according to claim 6, wherein the wire elongation detection device determines that the occurrence of the failure has occurred.   The spindle head counter according to claim 7, further comprising a calculation means for calculating an elongation amount generated in the wire from a difference between the position coordinates (Z03) and the position coordinates (Z01) of the initial position. Wire elongation detection device in balance mechanism.   8. The wire elongation detecting device in a spindle head counterbalance mechanism according to claim 7, further comprising alarm means for issuing an alarm based on a determination result that the wire is elongated beyond the allowable elongation limit (L). .   If the position of the spindle head when the signal is generated in the initial setting is not stored as an initial position, the determination unit does not start execution of a series of wire elongation detection operation processes, and the initial position The wire elongation detecting device in the spindle head counterbalance mechanism according to claim 1, wherein the device has a function of proceeding to a setting operation.   The spindle head counterbalance mechanism according to any one of claims 1 to 10, wherein the spindle head counterbalance mechanism is a counterbalance mechanism that connects the spindle head and a balance weight with a chain instead of the wire. Wire elongation detection device.

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