JPH0886306A - Locking screw - Google Patents

Abstract

PURPOSE: To provide a locking screw which can prevent rotation in a loosening direction of a shaft, and prevent loosening of a fastening member under a severe usage environment. CONSTITUTION: A locking screw has a first screw thread formed on an outer periphery of a shaft 2 with a first lead angle, and second screw threads 4, 4' each formed on the outer periphery of the shaft 2 in the same spiral direction as the first screw thread 3, with a second lead angle different from the first lead angle, and height lower than that of the first screw thread 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lock screw such as a wood screw or a drill screw capable of preventing loosening after fastening.

[0002]

2. Description of the Related Art As a screw for fastening both members by screwing them into a superposed member, there is a wood screw used for fastening timber, for example. As shown in FIG. 3, this wood screw has a dish-shaped head 31 having a cross hole (not shown) for screwdriver on the end face.
And a conical shaft portion 32 that is tapered from the head portion 31.
And a thread 33 formed in one line in the right-hand screw direction on the outer periphery of the shaft portion 32. And the shank 32 of this wood screw
Piercing the tip of, for example, the surface of the stacked wood pieces, and rotating the shaft portion 32 in the right-hand screw direction through the cross hole of the head portion 31 with a screwdriver, while the tapered screw thread 33 cuts the spiral groove, When the shaft portion 32 enters the wood piece and the whole shaft portion 32 is screwed into the stacked wood piece and tightened, both wood pieces are fastened.

[0003]

However, in the above-mentioned conventional wood screw, the shaft portion 32 is the same as the ordinary wood screw.
There is only one taper thread 33 provided on the outer periphery of the. Therefore, if a large amount of vibration is constantly applied to the fastened timber, etc., or if there is a large difference in the coefficient of thermal expansion between the fastened timber, etc. There is a problem that the screw thread loosens the close contact with the thread groove cut in the wood or the like at the time of fastening, and the wooden screw turns in the left-hand screw direction due to the accumulation of vibration and temperature change, and the fastening becomes loose.

Therefore, an object of the present invention is to prevent rotation of the shaft portion in the loosening direction by devising a screw thread provided on the outer periphery of the shaft portion such as a wood screw or a drill screw for fastening members by screwing. An object of the present invention is to provide a lock screw that can prevent the fastening member from loosening even in a severe use environment.

[0005]

In order to achieve the above object, the lock screw of the present invention has a first thread formed on the outer circumference of a shaft with a first lead angle and the outer circumference of the shaft described above. A second lead angle different from the first lead angle in the same turning direction as the first screw thread and having a height lower than that of the first screw thread, and intersecting the first screw thread; Two
It is characterized by having a screw thread.

[0006]

In the outer periphery of the shaft of the lock screw, a first thread having a first lead angle and a second thread different from the first lead angle are provided.
The second screw thread having the lead angle of 1 and lower than the first screw thread is formed in the same turning direction. Therefore, tracing the first thread along the spiral from the head to the tip results in this first
The second screw thread intersects the screw thread of the first screw thread at a predetermined interval, and the crossing angle of both the screw threads is the head of the spiral of the first screw thread even when the second lead angle is smaller than the first lead angle. It becomes an acute angle when measured from the department side. When the lock screw is rotated in the screwing direction, the high first screw thread cuts a deep spiral groove at the first lead angle, and the second low screw thread cuts a shallow spiral groove at the second lead angle, and is fastened Each bite into the material and penetrates into the material to be fastened while the screw shaft rotates, so the second lead angle is
Even if the crossing angle of both threads measured from the tip side of the spiral of the first thread is smaller than the lead angle of
When the screw shaft smoothly penetrates into the material to be fastened and the entire screw shaft is screwed in and tightened, the fastening is completed. On the other hand, when the lock screw after fastening tries to rotate in the loosening direction due to the vibration of the material to be fastened, the first and second screw threads come into close contact with the spiral groove cut by each lead angle. The resistance against rotation in the loosening direction is greater than that of a conventional tap screw having only one thread. Further, since a part of the material to be fastened is pushed into the tapered intersection of the first and second threads forming an acute angle, the lock screw is effectively prevented from rotating in the loosening direction. Therefore, even if the material to be fastened is subjected to repeated stress due to large vibration or temperature change, it is possible to prevent loosening of the material to be fastened by the lock screw.

[0007]

The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 (A) shows a wood screw which is an example of the lock screw of the present invention. This wood screw has a dish-shaped head 1 having a cross hole (not shown) for screwdriver on the end surface, A shaft 2 that extends from the head 1 in a cylindrical shape and has a conical tip,
Around the outer circumference of the shaft portion 2 at the first lead angle, 1
The first screw thread 3 formed by the thread and the second lead angle on the outer circumference of the shaft portion 2 which is twice the first lead angle, and at a height lower than the first screw thread 3 on the right side. It is formed by two threads in the screw direction and is composed of second threads 4, 4'that intersect the first thread 3 every half turn. The second threads 4, 4'which are two-threaded screws, when the shaft portion 2 is cut in a plane orthogonal to the axis,
It appears at the positions opposed to each other in the diametrical direction of the circular cross section, and alternately appears as shown in the plan view of FIG.

FIG. 1 (B) is a schematic enlarged plan view of the intersection of the first screw thread 3 and the second screw thread 4 shown in FIG. 1 (A). As shown in FIG. 1 (B), a high first thread 3 inclined at a gentle slope corresponding to the first lead angle and a second low thread thread inclined at a steep slope corresponding to the second lead angle are provided. 4 intersect each other, and the crossing angle α of both threads 3, 4 measured from the tip side A of the spiral of the first thread 3 is an obtuse angle, but from the head side B of the first thread 3 The measured crossing angle β of both threads 3 and 4 is an acute angle, and α and β are in a complementary angle relationship.

The wood screw having the above construction operates as follows. Fit the tip of a screwdriver into a cross hole (not shown) on the end face of the wood screw head 1, press the tip of the wood screw against the surface of the objects to be fastened such as stacked wood, and move the shaft portion 2 to the right screw direction. Rotate to. Then, the first; second threads 3; 4, 4'on the outer periphery of the shaft portion 2 are respectively deep spiral grooves at the first lead angle;
With a second lead angle that is twice the lead angle of biting into the wood while cutting the shallow spiral groove, the shaft 2 enters the wood while rotating, and the head 1 reaches the wood surface and tightens with a predetermined torque. At the end, both timbers are fully fastened.

When both timbers thus fastened are used, for example, when a large vibration is constantly applied, or when there is a large difference between the coefficients of thermal expansion of both timbers and there is a frequent change in ambient temperature, the wood screw will Attempt to rotate in the loosening direction indicated by arrow B of 1 (A) and B of FIG. 1 (B). At this time, since the first and second screw threads 3; 4, 4'are in close contact with the spiral groove cut in the wood at their respective lead angles, only the first screw thread 33 described in FIG. Compared to the conventional wood screw, the wood exerts a greater resistance to the rotation of the wood screw in the loosening direction. In this embodiment, the second threads 4, 4'are provided with a lead angle double that of the first threads 3 and facing each other in the diametrical direction of the circular cross section of the shank. So
There is an advantage that the resistance force becomes large and the circumferential distribution becomes more uniform. Further, as shown in FIG. 1B, when the wood screw tries to rotate in the head side B of the spiral of the first screw thread 3, that is, in the loosening direction, the first and second screw threads 3, 4 are The piece of wood fitted in the intersection C forming the acute angle β is pushed into the tapered closed intersection C, so that the rotation of the wood screw in the loosening direction is effectively prevented. Therefore, even if both woods are repeatedly stressed by a large vibration or temperature change, it is possible to prevent the both woods fastened with the wood screws from loosening.

FIG. 2A is a plan view of a drill screw according to another embodiment of the present invention. This drill screw has the same configuration as the wood screw described in FIG. 1 except that a drill blade 15 for punching an object to be fastened such as a steel plate is provided at the tip of the cylindrical shaft portion 12, and a corresponding member Are numbered with the same first digit, and description thereof will be omitted. Like the wood screw shown in FIG. 1, the drill screw intersects the first screw thread 13 with a first thread 13 on the outer periphery of the shaft portion 12 and two threads with a height lower than this thread and a double lead angle. It has the second screw threads 14 and 14 'and the drill blade 15 at the tip of the shaft portion. Therefore, a tip of an electric screwdriver or the like is fitted into a cross hole (not shown) on the end surface of the head 11 of the drill screw, and the drill blade 15 is pressed against the surface of the stacked steel plates to move the shaft portion 12 in the right screw direction. Rotate to. Then, the drill blade 15 first makes a hole in the steel plate, and then the first; second screw threads 13; 14, 14 '
The spiral groove is cut at each depth and lead angle to easily bite into the steel plate, and the shaft portion 12 is screwed in until the head 11 reaches the surface of the steel plate, whereby fastening of both steel plates is completed.

When the steel plates thus fastened are constantly subjected to repeated stress due to large vibration or temperature change, the drill screw tries to rotate in the loosening direction.
In addition to the third screw thread 14 and 14 ', the second screw thread 14 and 14' also come into close contact with the self-cut spiral groove, and, as described with reference to FIG. 1 (B), an acute angle intersection between the first and second screw threads. Since the steel piece is pushed into C, the rotation of the drill screw in the loosening direction is effectively prevented, and the loosening of both steel plates can be prevented.

FIG. 2B is a plan view showing a wood screw for hard wood which is another embodiment of the present invention. This wood screw is
It has the same configuration as the wood screw described in FIG. 1 except that the tip of the cylindrical shaft portion 22 is provided with a claw-shaped projection 26 for cutting a hard tree or a knot, and the corresponding member is the first digit. Are assigned the same numbers and explanations are omitted. Therefore, the first screw thread 23; 24, 24 'on the outer periphery of the shaft portion 22 is
For example, when it is screwed into the stacked wood in the right-hand screw direction and when it is tried to loosen in the left-hand screw direction due to vibration etc. after fastening, it acts in the same way as described in FIG. 1 (B). Can be prevented. The claw-shaped protrusion 26
When a wood screw is screwed in, it first cuts hard wood or knots and discharges the chips to the outside along the first screw thread 23, so that the first; second screw thread 23; 24, 24 ' Makes it easier to cut into wood.

With respect to the lock screws of the above-mentioned three examples, the resistance force to the twist in the loosening direction after fastening was measured by turning these screws in the left-hand screw direction with a screwdriver equipped with a torque meter. As a result of the measurement, it was confirmed that the torque value at which each screw starts to move in the loosening direction is about 1.5 times the similar torque value for the screw having the same size and shape with only the first thread. It was clarified that the lock screw of 1 has a remarkable effect on preventing loosening of the fastened object.

In the above embodiment, in order to obtain a large slack resistance, the low second screw threads 4 and 4'have two threads, and the lead angle thereof is twice the lead angle of the first screw thread 3. The second screw thread of the present invention may be a single-thread screw or a triple-thread screw or more, and it is sufficient if the lead angle thereof is different from the lead angle of the first screw thread. The same action and effect as above can be obtained. For example, when the first lead angle is larger than the second lead angle and the arrangement of the high first screw thread 3 and the low second screw thread 4 is opposite to that shown in FIG. 1 (B), The cross angle of both threads measured from the tip side of the spiral of the screw thread of 1 is an acute angle, but when screwing in,
Since the two screw threads bite into the wood at their respective lead angles to cut the spiral groove, the screwing can be smoothly carried out as in the embodiment of FIG. Further, since the crossing angle of both threads measured from the head side of the spiral of the first thread is an acute angle as in FIG. 1 (B), the resistance against rotation in the loosening direction is also different from that of the embodiment of FIG. I won't.

[0016]

As is apparent from the above description, the lock screw of the present invention has the first screw thread formed with the first lead angle on the outer periphery of the shaft and the first screw thread on the outer periphery of the shaft. A second lead angle different from the first lead angle in the same swivel direction as the first screw thread and lower than the first screw thread, and intersecting the first screw thread. Since the lock screw is provided with a screw thread, when the lock screw tries to rotate in the loosening direction, not only the first screw thread but also the second screw thread adheres to the spiral groove of the material to be fastened by itself. Since a part of the material to be fastened is pushed into the intersection of an acute angle surrounded by the second screw thread to prevent rotation in the loosening direction, even if large vibration or repeated stress is applied to the material to be fastened, It is possible to prevent loosening of the fastening material.

[Brief description of drawings]

FIG. 1 is a plan view showing an entire detail of a wood screw which is an example of a lock screw of the present invention and enlarged details of a screw thread intersection portion.

FIG. 2 is a plan view showing a drill screw and a wood screw for hard wood, which are examples of the lock screw of the present invention.

FIG. 3 is a plan view of a conventional wood screw.

[Explanation of symbols]

1,14,24 ... Head part, 2,12,22 ... Shaft part, 3,13,2
3 ... 1st screw thread, 4, 4 '; 14, 14'; 24, 24 '...
2nd screw thread, 15 ... Drill blade, 26 ... Protrusion.

Claims (1)

[Claims] 1. A first thread formed on the outer circumference of the shaft with a first lead angle, and a first thread angle different from the first lead angle on the outer circumference of the shaft in the same turning direction as the first thread. A lock screw having a second thread angle formed with a second lead angle lower than the first thread and intersecting the first thread.