JPH0523928A - Thread unfastener - Google Patents

Abstract

PURPOSE:To prevent any collapse on a thread ridge and a screw head from occurring by engaging a pit with the screw head, which clamped plural number of members, pressing it and loosening the screw with rotation of this pit, while making its pressing force variable. CONSTITUTION:First of all, a lifting member 4 is lowered by a first cylinder 5, and the lower end of a pit 13 is made contact with a head part 15a of a screw 15. Next, this pit 13 is rotated at low speed and torque by a pit rotation driving part 11, and a tip of the pit 13 is set to such a state as engaging with a cross recess of the screw head part 15a. In succession, at the time of screw loosening, a pressing member 7 is pressed by an air cylinder 8 with pressing force being larger than axial tension the pit 13 receives. After starting the screw loosening, pressing force against the pressing member by the air cylinder 8 is eliminated, and the pressing member is made so as to be pressed with small pressing force by a compression coil spring 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw tightening device for loosening a screw that fastens a plurality of members.

[0002]

2. Description of the Related Art When loosening a screw fastening a plurality of members with a bit, conventionally, the screw is rotated by keeping the pressing force of the bit against the screw head constant.

[0003]

However, in order to keep the bit fully engaged with the screw head at the start of screw tightening, a large pressing force is applied to loosen the engaged threads. As the number decreases, there is a problem that the screw threads 50 are easily crushed as shown in FIG.

On the other hand, if the pressing force of the bit is reduced so that the threads are not crushed even if the number of meshed threads is small, the bit does not fully mesh with the screw head at the start of screw tightening, and There was a risk of crushing the screw head 60 as shown in FIG. 9 when rotating.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a screw tightening device capable of securely tightening a screw without crushing the screw thread and the screw head.

[0006]

A screw tightening device of the present invention comprises a pressing means for engaging and pressing a bit on the head of a screw in which a plurality of members are fastened, and a driving means for rotating the bit. In the screw tightening device, the pressing force by the pressing means is variable.

[0007]

According to the screw tightening device having the above structure, the pressing force of the pressing means for engaging and pressing the bit with the screw head is changed according to the progress of the screw tightening, and when the screw tightening starts, the bit is pressed with a large pressing force. After pressing the screw, it is pressed with a small pressing force. As a result, it is possible to reliably engage the bit with the screw head at the start of screw tightening and prevent the screw head from being crushed. Even if the number of thread engagements is small after starting screw tightening, the thread is not crushed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the screw tightening device of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of the present invention. A U-shaped frame 2 is attached to the device body 1, and a first linear guide 3 is fixed to the frame 2 in the vertical direction. The U-shaped lifting member 4 is slidably guided by the first linear guide 3 and is lifted and lowered by a first air cylinder 5 attached to the upper end of the frame 2. Further, a second linear guide 6 is vertically fixed to the elevating member 4, and a pressing member 7 is slidably guided to the second linear guide 6. The pressing member 7
Is pressed by the second air cylinder 8 attached to the upper end of the elevating member 4 with a predetermined pressure. Further lifting member 4
A compression coil spring 9 is mounted between the upper and lower surfaces of the pressure member 7 and the upper end of the pressing member 7, and presses the pressing member 7 downward with a pressure smaller than the pressing force of the second air cylinder 8.

A bit rotation driving unit 11 as a driving means is attached to the pressing member 7 via an arm 10 with its axial direction being vertical. The rotation shaft of the bit rotation driving unit 11 has a suction sleeve 12 interposed therebetween. Bit 13 is installed. An air passage (not shown) communicating with the tip of the bit 13 is formed in the suction sleeve 12, and the air passage is connected to a vacuum pump (not shown) via a tube 14. Then, the screw can be attracted to the tip of the bit 13 by applying a negative pressure to the inside of the sleeve 12 after the screwing is completed.

A fixing jig 18 for holding a pair of members 16 and 17 integrally fastened with a screw 15 is provided below the bit 13.
Is provided, and the pair of members 16 and 17 are firmly fixed to the fixing jig 18 by the press fittings 19 and 20, respectively. Reference numerals 21 and 22 in the drawing are shock absorbers with stoppers that regulate the descending ends of the elevating member 4 and the pressing member 7, respectively.

Next, the operation of this embodiment will be described. 2 and 3 show the shape of the screw 15 used in this embodiment. A cross hole 15b is formed on the upper surface of the screw head 15a,
The lower surface is a seat surface 15c. A screw thread 15e is formed on the outer periphery of the screw body 15d. The screw 15 used in this embodiment has a short length under the neck.

First, the elevating member 4 is lowered by the first air cylinder 5, and the lower end of the bit 13 is attached to the head 15 of the screw 15.
Contact a. Next, the bit 13 is rotated at low speed and low torque by the bit rotation driving unit 11 so that the tip of the bit 13 is sufficiently meshed with the cross hole 15b of the screw head 15a. At this time, if the bit 13 is rotated at high speed and high torque, a defect that the shape of the screw head 15a is crushed easily occurs.

When tightening the screw, the bit 13 receives a force F in the direction perpendicular to the surface of the cross hole 15b of the screw 15 and an axial force FA as a component force in the axial direction, as shown in FIG. The axial force FA received by the bit 13 changes as the screw tightening progresses, as shown in FIG. That is, at the start of screw tightening, as shown in (a), the seat surface 15c of the screw head 15a is
It is necessary to tighten with a high torque due to a frictional force between the member 16 and the surface of the member 16. The axial force FA1 received by the bit 13 due to this is greater than in other states. At this time, in order to maintain the state in which the bit 13 is sufficiently meshed with the cross hole 15b of the screw head portion 15a, as shown in FIG.
The air cylinder 8 presses the pressing member 7 in the direction indicated by the arrow A with a pressing force larger than the axial force FA1 received by the bit 13.

When the screw tightening starts, the number of meshes of the screw threads 15e of the screw 15 gradually decreases as shown in FIG. 5 (b), and the screw 15 is tightened with a torque corresponding to the frictional force. The axial force F received by the bit 13 at this time
A2 is smaller than FA1. Immediately before the screw tightening is completed, the number of meshes of the screw threads 15e is about 1 as shown in FIG. 5 (c). At this time, the axial force FA3 received by the bit 13 is smaller than FA2. That is, FA1 >>
FA2> FA3. In particular, when the length under the screw 15 is short and the number of meshes of the screw thread 15e is small, FA1
>>FA2≈> FA3 is established.

After the screw tightening is started, as shown in FIG. 6B, the pressing of the pressing member 7 by the second air cylinder 8 is deleted, and the pressing member 7 is pressed by the compression coil spring 9 with a smaller pressing force. As a result, when the number of meshes of the thread 15e of the screw 15 becomes small, the thread 15e
It is possible to prevent the occurrence of defects that are crushed. Further, as the screw tightening progresses, the screw 15 rises in the axial direction as is clear from FIG. With this rise, the lifting member 4 is gradually raised by the first air cylinder 5 shown in FIG.
Also, an unreasonable load is not generated on the bit 13 and an appropriate pressing force is maintained.

The vacuum pump is operated immediately before the screw tightening is finished, and the screw 15 starts to be attracted to the tip of the bit 13, and the elevating member 4 is raised in this state. This allows the screw 15 to be separated from the members 16,17. At this time, by raising the bit 13 while rotating it, the thread 13e can be smoothly separated even if burrs are generated.

According to this embodiment, at the start of screw tightening, the tip of the bit 13 is pressed against the screw head 15a by the second air cylinder 5 with a strong force, so that the bit 13 is inserted into the cross hole 15b of the screw head 15a. Fully mesh, screw head 15
Do not crush a. Further, after the screw tightening is started, the tip of the bit 13 is pressed against the screw head 15a by the weak force of the compression coil spring 9. Therefore, even if the number of the screw threads 15e of the screw 15 is small, the shape of the screw thread 15e cannot be crushed. Absent.

In the above embodiment, the elevating member 4 and the pressing member 7
Although the case where the air cylinders 5 and 8 are used as the drive sources of the above, respectively, these drive sources may be hydraulic cylinders or motors.

In the above embodiment, the screw 15 is held by air suction at the end of screw tightening. However, magnetic force or a mechanical chuck may be used as a holding means for the screw 15.

Further, in the above-mentioned embodiment, the screw tightening device suitable for tightening the screw 15 having a short length under the neck has been described. As shown in FIG. 7, a third air cylinder 30 may be used instead of the compression coil spring 9. Then, the air pressure applied to the air cylinder 30 is changed according to the number of meshes of the screw threads 15e of the screw 15 to secure the axial force required to tighten the screw 15.

[0022]

As described above, according to the screw tightening device of the present invention, the pressing force of the pressing means for pressing the bit is changed in accordance with the progress of screw tightening, so that the screw thread and the screw head are crushed. Can be tightened without screwing.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of an embodiment of a screw tightening device of the present invention.

FIG. 2 is a plan view showing the shape of a screw used in this embodiment.

FIG. 3 is a front view of FIG.

FIG. 4 is an explanatory view showing an axial force acting on a bit when tightening a screw.

FIG. 5 is an explanatory diagram showing the relationship between the progress of screw tightening and the axial force received by the bit.

FIG. 6 is an explanatory side view showing the relationship between the progress of screw tightening and the bit pressing force applying operation in the screw tightening device of the present embodiment.

FIG. 7 is a side view showing the configuration of another embodiment of the screw tightening device of the present invention.

FIG. 8 is a front view showing an example of a state in which the shape of the screw thread is collapsed.

FIG. 9 is a plan view showing an example of a state in which the shape of the screw head is collapsed.

[Explanation of symbols]

 8 Second Air Cylinder (Pressing Means) 9 Compression Coil Spring (Pressing Means) 11 Bit Rotation Drive Unit (Drive Means) 13 Bits 15 Screws 15a Screw Heads 16 and 17 Members

[Procedure amendment]

[Submission date] October 17, 1991

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title of invention Screw loosening device

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw loosening device for loosening a screw fastening a plurality of members.

[0002]

BACKGROUND ART When loosening a plurality of members fastening the screws with a bit, conventionally in the constant pressing force to the bit in the screw head, was performed the screw loosening by rotating the screw.

[0003]

However, screw loosening
In order to keep the bit fully engaged with the screw head at the beginning of the screwing, a large pressing force is applied, as shown in Figure 8 as the screw loosens and the number of engaged threads decreases. There is a problem that the screw thread 50 is easily crushed.

On the other hand, if the pressing force of the bit is reduced so that the threads are not crushed even if the number of engaged threads is small, the bit does not sufficiently engage with the screw head at the start of screw loosening , and the bit is There was a risk of crushing the screw head 60 as shown in FIG. 9 when rotating.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a screw loosening device capable of surely loosening a screw without crushing a screw thread and a screw head. To aim.

[0006]

A screw loosening device of the present invention comprises a pressing means for engaging and pressing a bit on the head of a screw having a plurality of members fastened thereto, and a driving means for rotating the bit. In the screw loosening device, the pressing force by the pressing means is variable.

[0007]

According to the screw loosening device of the working-described structure, the screw head pressing force of the pressing means for engaging presses a bit to the screw head changed according to the progress of the screw loosening, at the start screw loosening a large pressing force bit After the screw is loosened , it is pressed with a small pressing force. As a result, it is possible to reliably engage the bit with the screw head at the start of screw loosening and prevent the screw head from being crushed. Even if the number of thread engagements is small after the start of screw loosening , the thread is not crushed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the screw loosening device of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of the present invention. A U-shaped frame 2 is attached to the device body 1, and a first linear guide 3 is fixed to the frame 2 in the vertical direction. The U-shaped lifting member 4 is slidably guided by the first linear guide 3 and is lifted and lowered by a first air cylinder 5 attached to the upper end of the frame 2. Further, a second linear guide 6 is vertically fixed to the elevating member 4, and a pressing member 7 is slidably guided to the second linear guide 6. The pressing member 7
Is pressed by the second air cylinder 8 attached to the upper end of the elevating member 4 with a predetermined pressure. Further lifting member 4
A compression coil spring 9 is mounted between the upper and lower surfaces of the pressure member 7 and the upper end of the pressing member 7, and presses the pressing member 7 downward with a pressure smaller than the pressing force of the second air cylinder 8.

A bit rotation driving unit 11 as a driving means is attached to the pressing member 7 via an arm 10 with its axial direction being vertical. The rotation shaft of the bit rotation driving unit 11 has a suction sleeve 12 interposed therebetween. Bit 13 is installed. An air passage (not shown) communicating with the tip of the bit 13 is formed in the suction sleeve 12, and the air passage is connected to a vacuum pump (not shown) via a tube 14. After the screw is completely loosened , a negative pressure is applied to the inside of the sleeve 12 so that the screw can be attracted to the tip of the bit 13.

A fixing jig 18 for holding a pair of members 16 and 17 integrally fastened with a screw 15 is provided below the bit 13.
Is provided, and the pair of members 16 and 17 are firmly fixed to the fixing jig 18 by the press fittings 19 and 20, respectively. Reference numerals 21 and 22 in the drawing are shock absorbers with stoppers that regulate the descending ends of the elevating member 4 and the pressing member 7, respectively.

Next, the operation of this embodiment will be described. 2 and 3 show the shape of the screw 15 used in this embodiment. A cross hole 15b is formed on the upper surface of the screw head 15a,
The lower surface is a seat surface 15c. A screw thread 15e is formed on the outer periphery of the screw body 15d. The screw 15 used in this embodiment has a short length under the neck.

First, the elevating member 4 is lowered by the first air cylinder 5, and the lower end of the bit 13 is attached to the head 15 of the screw 15.
Contact a. Next, the bit 13 is rotated at low speed and low torque by the bit rotation driving unit 11 so that the tip of the bit 13 is sufficiently meshed with the cross hole 15b of the screw head 15a. At this time, if the bit 13 is rotated at high speed and high torque, a defect that the shape of the screw head 15a is crushed easily occurs.

When the screw is loosened , the bit 13 receives a force F in a direction perpendicular to the surface of the cross hole 15b of the screw 15 and an axial force FA as a component force in the axial direction, as shown in FIG. The axial force FA bit 13 is subjected, as shown in FIG. 5, the screw loose
It changes with the progress of the order. That is, at the start of screw loosening , as shown in (a), the seat surface 15c of the screw head 15a is
Due to friction between the surface of the member 16 and the member 16
There needs to loosen. The axial force FA1 received by the bit 13 due to this is greater than in other states. At this time, in order to maintain the state in which the bit 13 is sufficiently meshed with the cross hole 15b of the screw head portion 15a, as shown in FIG.
The air cylinder 8 presses the pressing member 7 in the direction indicated by the arrow A with a pressing force larger than the axial force FA1 received by the bit 13.

When the screw loosening is started, the number of meshes of the screw threads 15e of the screw 15 gradually decreases as shown in FIG. 5 (b), and the screw 15 is loosened with a torque corresponding to the frictional force. The axial force F received by the bit 13 at this time
A2 is smaller than FA1. Immediately before the screw loosening is completed, the number of meshes of the screw threads 15e is about 1 as shown in FIG. 5 (c). At this time, the axial force FA3 received by the bit 13 is smaller than FA2. That is, when the FA1 length is short and the number of meshes of the thread 15e is small,
The relationship FA1A3 is established.

After starting the screw loosening , as shown in FIG. 6 (b), the pressing of the pressing member 7 by the second air cylinder 8 is deleted, and the pressing member 7 is pressed by the compression coil spring 9 with a smaller pressing force. As a result, when the number of meshes of the thread 15e of the screw 15 becomes small, the thread 15e
It is possible to prevent the occurrence of defects that are crushed. Further, as the screw loosening progresses, as is clear from FIG. 5, the screw 15 moves upward in the axial direction. With this rise, the pressing member 7 shown in FIG.
The screw 15 and the bit 13 are gradually raised, and an unreasonable load is not generated on the screw 15 and the bit 13, and an appropriate pressing force is maintained.

The vacuum pump is operated immediately before the screw loosening is finished, and the screw 15 is started to be adsorbed to the tip of the bit 13, and the elevating member 4 is raised in this state. This allows the screw 15 to be separated from the members 16,17. At this time, by raising the bit 13 while rotating it, even if burrs or the like are generated on the thread 5e , they can be separated smoothly.

According to this embodiment, at the start of screw loosening , the tip of the bit 13 is pressed against the screw head 15a by the second air cylinder 8 with a strong force, so that the bit 13 is inserted into the cross hole 15b of the screw head 15a. Fully mesh, screw head 15
Do not crush a. Further, since the tip end of the bit 13 is pressed against the screw head portion 15a by the weak force of the compression coil spring 9 after the screw loosening is started, the shape of the screw thread 15e cannot be crushed even if the number of the screw threads 15e of the screw 15 is small. Absent.

In the above embodiment, the elevating member 4 and the pressing member 7
Although the case where the air cylinders 5 and 8 are used as the drive sources of the above, respectively, these drive sources may be hydraulic cylinders or motors.

Further, in the above embodiment, the case where the screw 15 is held by the air suction at the end of the screw loosening has been described, but a magnetic force, a mechanical chuck or the like may be used as the means for holding the screw 15.

[0021] More particularly in the above embodiment has been described screw loosening device suitable for the length of the lower neck that loosen the short screw 15, when the length of the lower neck that loosen the long screw 15 As shown in FIG. 7, a third air cylinder 30 may be used instead of the compression coil spring 9. Then by changing the air pressure applied to the air cylinder 30 according to the number of engagement of the threads 15e of the screw 15, so as to ensure the axial force required to that loosening the screws 15.

[0022]

As described above, according to the screw loosening device of the present invention, the pressing force of the pressing means for pressing the bit is changed according to the progress of the screw loosening. The screw can be loosened without crushing the head.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of an embodiment of a screw loosening device of the present invention.

FIG. 2 is a plan view showing the shape of a screw used in this embodiment.

FIG. 3 is a front view of FIG.

FIG. 4 is an explanatory view showing an axial force acting on the bit when the screw is loosened .

FIG. 5 is an explanatory diagram showing the relationship between the progress of screw loosening and the axial force received by the bit.

FIG. 6 is an explanatory side view showing the relationship between the progress of screw loosening and the bit pressing force applying operation in the screw loosening device of the present embodiment.

FIG. 7 is a side view showing the configuration of another embodiment of the screw loosening device of the present invention.

FIG. 8 is a front view showing an example of a state in which the shape of the screw thread is collapsed.

FIG. 9 is a plan view showing an example of a state in which the shape of the screw head is collapsed.

[Explanation of Codes] 8 Second Air Cylinder (Pressing Means) 9 Compression Coil Spring (Pressing Means) 11 Bit Rotation Drive (Drive Means) 13 Bits 15 Screws 15a Screw Heads 16 and 17 Members

Claims (1)

Claim: What is claimed is: 1. A screw tightening device comprising: a pressing unit that engages and presses a bit with the head of a screw that fastens a plurality of members; and a drive unit that rotates the bit. A screw tightening device, wherein the pressing force by the pressing means is variable.