JP2000304024A - Slack preventive mechanism for lock nut for power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent slackness of a power tool. SOLUTION: Pins 24, 25, the central sides of which are tip end parts 26, are stored in storage holes 22, 22 drilled in the radial direction in a lock nut 20 free to slide. A ring plate spring 28 is wound in a recessed groove 27 formed on an outer periphery of the lock nut 20, the pin 24 is energized to the central side on an inner peripheral surface of the plate spring 28, the pin 25 is energized to the central side on a key type bent end part 29, and each of the tip end parts 26 projected from an opening 23 of the storage hole 22 is pressurized in a wedge shape between screw threads of a male screw part 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power tool such as a disk grinder in which a lock nut is screwed to fix a disc-shaped tool or the like to a spindle. About.

[0002]

2. Description of the Related Art For example, a lock nut in a disk grinder is screwed into a male screw portion of a spindle while a tool is sandwiched between a spindle and an inner flange integrated with the spindle, so that the tool can be tightened and fixed. The direction in which the lock nut is screwed is usually so-called tightening, in which a force in the tightening direction is applied at the moment when the spindle starts rotating. On the other hand, some motors for driving the spindle are provided with an electric brake that applies a reverse torque to the spindle so that the tool does not rotate long due to inertia when the power switch is turned off. When the brake is actuated, a force in the loosening direction is applied to the lock nut due to friction with a tool that continues to rotate due to inertia, so that the lock nut may be loosened.
Therefore, according to German Patent Specification No. 4305317, a ring spring is press-fitted into a ring-shaped groove provided in a lock nut,
A configuration is disclosed in which both ends of the ring spring are bent in the axial direction of the spindle and abut on the outer periphery of the male screw portion of the spindle to thereby prevent the lock nut from being loosened by the frictional force between the ring spring and the male screw portion. .

[0003]

However, according to the invention of the above-mentioned German Patent Specification, since the end of the ring spring abuts on the apex of the thread of the male thread portion, the thread is worn out when using continuously, and the thread is worn. In such a case, there is a possibility that a malfunction such as rattling of the lock nut may occur. In addition, since the outer periphery of the end of the ring spring is in contact with the top of the thread, it is difficult to obtain a sufficient frictional force, and the frictional force also varies due to dimensional tolerances of the ring spring and the groove.

Therefore, the invention according to claim 1 can maintain the proper screwing of the lock nut without causing abrasion of the screw thread, even if the friction with the male screw portion is similarly used. It is an object of the present invention to provide a lock nut loosening prevention mechanism capable of realizing stable loosening prevention with a high frictional force.

[0005]

In order to achieve the above object, according to the present invention, a lock nut having a female screw portion screwed into a male screw portion of a spindle is provided with a screw of the female screw portion. A storage hole opening in the crest portion is formed in a direction crossing the circumferential direction of the lock nut, and the storage hole can be inserted between the threads of the male screw portion, and the angle of the screw thread of the male screw portion A pin having a sharp end having the above angle is housed by a biasing means so that the sharp end protrudes from the opening on the female screw portion side by a biasing means, and is screwed into the male screw portion of the spindle. The pointed end of the pin can press the flank between the threads of the male screw portion. According to the second aspect of the present invention, in addition to the object of the first aspect, in order to easily and rationally configure the urging means, the urging means is wound around a lock nut and the rear end of the pin. Is formed into a ring-shaped leaf spring that presses against the female screw portion.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partial cross-sectional view of the grinder 1. A motor shaft 5 of a motor 4 (with an electric brake) housed in a motor housing 2 is inside a gear housing 3 connected to the front of the motor housing 2 (left side in FIG. 1). And a pinion gear 7 is fixed to a tip end thereof. On the other hand, in the gear housing 3, a spindle 8 is supported at right angles to the motor shaft 5 by a needle bearing 9 at an upper end and a ball bearing 10 at an intermediate portion in front of the motor shaft 5. The bevel gear 11 that rotates integrally with the pinion gear 7
Is engaged. A lock member 12 parallel to the spindle 8 is slidably accommodated above the bevel gear 11 in the gear housing 3. The lock member 12
1 separated from the bevel gear 11 by a coil spring 14 which is provided under a peripheral flange 13.
Of the spindle 8 together with the bevel gear 11 by pushing the lock member 12 into the recesses 15, 15,...
The rotation of can be locked.

The lower end of the spindle 8 projects downward from the gear housing 3 to form a large-diameter portion 16 having a two-sided width and a male screw portion 17. The male screw portion 17 has a disk-shaped lock nut 20. By screwing a female screw portion 21 at the center of the spindle 8, a tool 19 such as a disc-shaped grindstone is held between the spindle 8 and the inner flange 18 which is integrated with the spindle 8 by fitting with the large diameter portion 16. It can be fixed. The lock nut 20 is screwed into the male screw portion 17 with a right-hand screw. The lock nut 20 is provided with a loosening prevention mechanism for preventing the male screw portion 17 from loosening from a tightened state. Hereinafter, details of the loosening prevention mechanism will be described.

[0008] As shown in FIGS.
Inside, a pair of storage holes 22, 22 are drilled in the radial direction so as to open at the threaded portions of the female screw portion 21, respectively. Pins 24 and 25 having different lengths are slidably stored. Here, since the diameter of the opening 23 on the center side of each storage hole 22 is formed slightly smaller than the diameter of the pins 24 and 25, the pins 24 and 25 Side pin 24
The storage hole 22 is in a state where the sharp end 26 is in contact with the opening 23.
It is long enough to fit in a cup. Further, pins 24 and 25
Is larger than the pitch of the threads 30 of the male thread portion 17 of the spindle 8, and the angle of the pointed end 26 is set to be larger than the angle of the threads 30. On the other hand, lock nut 2
A groove 27 is continuously formed on the outer circumference of the groove 0. The groove 27 has a bent end portion 29 bent in a key shape and a short pin 25.
A ring-shaped leaf spring 28 inserted into the storage hole 22 on the side is wound around the lock nut 20 substantially one round. The leaf spring 28 has an inner diameter that is slightly smaller than the outer diameter of the groove 27 in a normal state.
Is elastically tightened. Therefore, the short pin 25 is urged toward the center by contact with the bent end portion 29 of the leaf spring 28, and the long pin 24 is urged toward the center by contact with the inner peripheral surface of the leaf spring 28. And each point 2
6 is projected from the opening 23.

In the grinder 1 configured as described above, when the tool 19 is mounted on the spindle 8, the lock nut 20 is inserted into the male screw portion 17 while the tool 19 is sandwiched between the inner flange 18 as described above. When screwed together, as shown in FIG. 5, the tips 26, 26 of the pins 24, 25 are
7 between the threads 30, 30. Here, pin 2
Since the diameter of the threads 4 and 25 is greater than the pitch of the threads 30 and the angle of the pointed section 26 is greater than the angle of the threads 30, the pointed section 26 enters the wedge shape between the threads 30 and 30. Opposing flanks (surfaces connecting the crests and valleys) 31, 31 between the threads 30, 30 are pressed. Here, when the motor 4 is started by turning on a power switch (not shown) and the motor shaft 5 starts rotating (here, rightward rotation forward), the spindle 8 rotates rightward downward via the bevel gear 11. To start,
Since the lock nut 20 is screwed into the male screw portion 17 with a right-hand screw, a force in the tightening direction is applied to the lock nut 20. When the electric brake is applied to the motor 4 by turning off the power switch, the bevel gear 11 and the spindle 8
Is transmitted to the lock nut 20, but a force in a loosening direction is applied to the lock nut 20 due to friction between the lock nut 20 and the tool 19, which keeps rotating due to inertia. However, since the pins 24 and 25 urged toward the center press the flanks 31 and 31 of the threads 30 and 30 of the male screw portion 17, the friction between the two causes the lock nut 20 to move in the loosening direction. The effect of preventing rotation is obtained.

The function of preventing the looseness of the pins 24 and 25 and the screw thread 30 is such that there is no electric brake, and the lock member 12 is pushed into the tool 19 which rotates by inertia after the power switch is turned off, and the brake is replaced. Also obtained when used for That is, even in these cases, the rotation speed of the spindle 8 is reduced with respect to the tool 19 which continues to rotate, so that a force is applied to the lock nut 20 in the loosening direction due to friction with the tool 19. 24,2
The friction between the flank 5 and the flank 31 of the thread 30, 30 can prevent the lock nut 20 from rotating in the loosening direction.

As described above, according to the loosening prevention mechanism, the lock nut 20 can be prevented from being loosened during braking by the pins 24 and 25 provided in the lock nut 20 being pressed against the thread 30 of the male screw portion 17. Becomes In particular, pin 2
Since the directions of the nuts 4 and 25 are set in the radial direction of the lock nut 20, the urging force of the leaf spring 28 can be effectively applied to the male screw 17 and the angle of the pointed end 26 can be set. Flank 31, 31 of screw thread 30, 30
Is pressed in a wedge shape, a high frictional force is obtained with the pointed end portion 26, and effective prevention of loosening can be realized. Further, since it does not abut against the apexes of the threads 30, 30, the abrasion of the threads 30 can be prevented, and the screwing itself between the male thread portion 17 and the lock nut 20 is not affected. Further, here, the pins 24,
Since the urging of the pin 25 is realized by the leaf spring 28, the winding around the lock nut 20 provides a simple and rational configuration in which the pins 24 and 25 can be simultaneously prevented from coming off and urged.

Incidentally, the number of pins is not limited to the above-described embodiment, and three or more pins can be arranged evenly, or conversely, only one pin can be used. Further, the urging means of the pin is not limited to the leaf spring, and a design change such as installing a coil spring behind the pin in the storage hole and closing the storage hole with a C ring wound around the concave groove is also possible. It is. Furthermore, the shape of the pin tip is
In addition to the conical shape as in the above embodiment, the lock nut may have a tapered shape or the like which tapers in the circumferential direction, but the diameter of the pin is equal to or larger than the pitch of the male screw portion as in the above embodiment. It is preferable to set the value to because a high frictional force due to the wedge action can be effectively obtained. Of course, the direction of the storage hole is not limited to the radial direction, but may be inclined or provided in a tangential direction as long as the storage hole is linearly urged to face the male screw portion of the spindle.

[0013]

According to the first aspect of the present invention, it is possible to prevent the lock nut from being loosened by the pressing of the male screw portion by the pin provided inside the lock nut. In particular, since the direction of the pin is set in the direction intersecting the circumferential direction of the lock nut, the urging force of the urging means can be effectively applied to the male screw portion, and the pin tip of the pin can be formed. By setting the angle, the flank of the thread is pressed in a wedge shape, so that a high frictional force is obtained between the flank and the pointed end, and effective prevention of loosening can be realized. Further, since the thread does not come into contact with the apex of the thread, abrasion of the thread can be prevented, and the screwing of the male thread portion and the lock nut itself is not affected. According to the second aspect of the present invention, in addition to the effect of the first aspect, the biasing means is a leaf spring wound around the lock nut and pressing the rear end of the pin toward the female screw portion. This provides a simple and rational configuration in which the pin can be simultaneously prevented from coming off and urged by being wound around the lock nut.

[Brief description of the drawings]

FIG. 1 is a partially sectional explanatory view of a grinder.

FIG. 2 is an explanatory cross-sectional view of a lock nut.

FIG. 3 is a sectional view taken along line AA.

FIG. 4 is an explanatory longitudinal sectional view of a pin portion of a lock nut.

FIG. 5 is an explanatory diagram showing a contact state between a pin and a screw thread.

[Explanation of symbols]

1. Grinder, 3. Gear housing, 4. Motor, 5. Motor shaft, 8. Spindle, 11. Bevel gear, 12. Lock member, 17. Male screw part, 18
..Inner flange, 19 tool, 20 lock nut, 21 female screw part, 22 storage hole, 23
Opening, 24, 25 pins, 28 leaf springs, 30
Thread, 31 ... Frank.

Claims (2)

[Claims] 1. A lock nut having a female screw portion to be screwed into a male screw portion of a spindle is provided with a storage hole opened in a thread portion of the female screw portion in a direction intersecting a circumferential direction of the lock nut. Then, the pin having a pointed end which can be inserted between the threads of the male screw portion and has an angle equal to or greater than the angle of the screw thread of the male screw portion is slidable and biased by the urging means. The tip is stored so that the tip protrudes from the opening on the female screw side, and in a screwed state with the male thread of the spindle, the tip of the pin can press the flank between the threads of the male thread. Lock nut loosening prevention mechanism in a power tool. 2. The lock nut according to claim 1, wherein the biasing means is a ring-shaped leaf spring wound around the lock nut and pressing the rear end of the pin toward the female screw portion. Loose prevention mechanism.