JP6753391B2 - Top - Google Patents

Description

The present invention relates to a top, and more particularly to a top in which a string is wound around a top body and rotated by winding the string while throwing, and the shaft and the top body can rotate relative to each other.

In a well-known top, since the top body and the rotating shaft (shaft) rotate together, the friction between the rotating shaft and the ground or the ground is large, and the load torque associated with this is large. As a result, the kinetic energy of the top decreases quickly. For this reason, it has been difficult for conventional tops to maintain stable rotation for a long period of time. Also, when you grab the shaft and move the top, or when you hook it on the string and make it move like an acrobat, the loss of rotational energy is large because you grab the shaft, or the string and the shaft you hook on There is a problem that it is difficult to maintain a stable rotation of the top for a long time due to a large load torque between them and a large fluctuation.

Patent Document 1 discloses a top in which a top shaft and a top body are rotatably held by ball bearings. Since the shaft of this top is supported by ball bearings, the rotational torque between the top and the shaft can be reduced, and long-term rotation can be obtained. In addition, inertia can be increased by providing inertia ring in the internal space of the top body, which enables longer rotation. Furthermore, by providing a restricting member whose upper surface is fixed to the shaft at the same axial position (height) as the upper surface of the top body, it is ensured that the top body and the finger come into contact with each other when grasping the shaft with a finger. It is said that operability can be improved because it can be prevented.

Patent Document 2 discloses a top that can be disassembled and assembled into parts of a top body (body), a shaft (mandrel), and a balance ring (inertia), and the bearing is a plain bearing. This will give children the pleasure of disassembling and assembling, and will be an opportunity to understand the functions of each part. Further, since the tip of the shaft has a spherical shape, it is disclosed that even if the top accidentally hits a person, it will not be injured and the tatami mat, carpet, and floor material will not be damaged.

Patent Document 3 discloses that a cover is provided on the upper part of the top, and it is said that the cover can also serve as an edge of the top by covering a parallel member as a mechanism inside the main body for balancing. Further, a configuration in which the cover is transparent and the inside can be seen through is disclosed.

Utility Model Registration No. 3208091 Japanese Unexamined Patent Publication No. 2004-154473 Utility Model Registration No. 3058365

However, in the frame according to Patent Document 1, since the empty space inside the frame body is open, dust may easily invade from the outside. Further, since the air flow generated when the top rotates at high speed is disturbed by the unevenness inside the top, the loss due to the air flow (hereinafter referred to as wind loss) is large, so that the rotation speed drops quickly and the top rotates. There was a problem that the time was shortened. In addition, ball bearings used for this type of top are often unshielded for easy maintenance. In that case, there is a possibility that small dust or the like that invades from the outside invades the inside of the ball bearing and causes a rumbling noise or scratches.

In the top of Patent Document 2, since the components of the top can be disassembled and assembled, the balance ring may come off if the top falls down when thrown strongly, so sufficient care must be taken in handling the game. It was a burden on the person. Also, since the shaft does not protrude above the top body, if the balance ring comes off, it will rotate in the surface of revolution according to the law of inertia, but because there is little overlap with the shaft, the balance ring will move out from the top body. There is a possibility of popping out. When the rotation is small, the inertia is also small, so that it may pop out more easily.

In the top of Patent Document 3, since it is realized by combining a weight and a balancing part that are balanced inside so that even a person who has never turned the top can easily balance it, practice how to turn the top. Tends to stop trying to master. In addition, a balancing structure is added, which makes disassembly and assembly complicated. Furthermore, fine dust generated by the movement of the weight and the equilibrium parts inside cannot be removed from the inside of the top without removing the cover, so let's apply it to the top where the shaft and the top body can be rotated by ball bearings. Then, it is necessary to remove the cover to remove the dust, which causes a problem that maintenance becomes complicated.

The present invention solves such a conventional problem, and an object of the present invention is to provide a frame that is highly safe and can rotate stably for a long period of time to enable more advanced performance by improving by practice. The purpose is to provide a piece that can be used as an educational playground equipment that promotes the growth of children and fosters a rich sensibility by intensifying the aspirations of the players in addition to the fun of the piece. .. Further, it is an object of the present invention to provide a top capable of obtaining stable rotation for a long time by reducing wind damage by reducing the inflow of air into the top.

The object of the present invention is achieved by the following configuration.
(1) A shaft, a top body rotatably attached to the shaft via a plurality of ball bearings, and a cover fixed to the top body at substantially the same axial position as the upper surface of the top body are provided. A top characterized in that an outer peripheral portion of the cover is fixed to the top body, and an insertion hole through which the shaft is inserted is formed in the cover with a radial gap between the top and the shaft.
(2) The top according to (1), wherein an inertia ring is fixed to an internal space formed by the top body and the cover.
(3) The top according to (2), wherein the inertia ring is made of a material having a higher density than the top body.
(4) The top according to any one of (1) to (3), wherein a plurality of penetrating portions are provided on the outer edge portion of the cover.
(5) The top according to any one of (1) to (4), wherein the ball bearing is an open type.

According to the top of the present invention, the shaft, the top body rotatably attached to the shaft via a plurality of ball bearings, and the cover fixed to the top body at substantially the same axial position as the upper surface of the top body. The outer peripheral portion of the cover is fixed to the top body, and an insertion hole for inserting the shaft is formed in the cover with a radial gap between the top surface of the top and the top surface of the top. Can be. As a result, wind damage can be reduced and the rotation time of the top can be lengthened.

It is a perspective view of the 1st Embodiment of the top which concerns on this invention. It is a vertical sectional view of the frame of FIG. It is an enlarged view of the part A of the frame of FIG. It is the B part enlarged view of the frame of FIG. It is a top view of the cover of FIG. It is a vertical sectional view of the 2nd Embodiment of the top which concerns on this invention. It is a top view of the cover of FIG. It is a top view of the cover of the 3rd Embodiment of the top which concerns on this invention.

Hereinafter, each embodiment of the frame according to the present invention will be described in detail with reference to the drawings.

(First Embodiment)
The first embodiment of the frame according to the present invention will be described with reference to the drawings.

As shown in FIGS. 1 to 5, the top 1 of the present embodiment is mainly composed of a top body 2, a shaft 3, and a pair of ball bearings 4 that rotatably support both of them.

The top body 2 is made into a required shape by, for example, turning a material such as polyacetal (POM) as a thermoplastic resin. The shape of the top body 2 is a substantially straight conical trapezoid, the outer diameter is about 80 mm, and the height is about 30 mm. The inside of the top body 2 is hollowed out by thinning a substantially straight cone trapezoid. Therefore, the weight is reduced, and the total weight of the top body 2 is about 110 g.

The shaft 3, which is the center of rotation of the top 1, is made of stainless steel such as SUS303B or SUS420J2 into a required shape by turning or the like. Further, the shaft 3 is subjected to heat treatment, polishing of the outer diameter, or the like, if necessary. Further, the shaft 3 is fitted and held in the inner ring 42 of the pair of ball bearings 4 provided at the lower part of the top body 2 with a slight gap, and is fixed by the retaining ring 72.

The ball bearing 4 is a deep groove ball bearing, and two ball bearings having the same specifications are arranged side by side along the axial direction of the shaft 3. The outer ring 41 of the ball bearing 4 is fitted and held in a sleeve 7 made of high-tensile aluminum or the like with a slight gap. The sleeve 7 is fitted to the top body 2 and fixed by a retaining ring 71. The thrust directions of the ball bearings 4 and the sleeve 7 are positioned and fixed by retaining rings 71, 72, spacers 73, and the like. As a result, the top body 2 is rotatably attached to the shaft 3 via a pair of ball bearings 4, and the top body 2 and the shaft 3 are configured to be relatively rotatable. Further, the ball bearing 4 and the shaft 3 are disassembled with respect to the sleeve 7, and the sleeve 7 is disassembled with respect to the top body 2. As a result, the rotating main parts can be replaced, so that repair and maintenance can be easily performed.

A small diameter portion 31 for winding a string (not shown) for rotating the top body 2 is provided on the lower side of the shaft 3. The outer diameter of the small diameter portion 31 is as thin as 4 mm. Further, the tip end face of the tip portion 32 of the shaft 3 is formed in a flat shape, and the outer diameter of the tip end face is as small as 4 mm. The outer diameter of the collar portion of the tip portion 32 is 8 mm so that the string does not come out in the axial direction. This shape can be appropriately selected in consideration of the size and material of the string to be used and the strength of the stiffness. In many cases, the ball bearing 4 rotates without rotating the shaft 3 due to the relationship between the floor surface to be rotated and the shaft 3. Therefore, by forming the tip end surface of the shaft 3 in a flat shape, more stable contact with the floor surface can be obtained, and stable rotation can be obtained as the top 1.

A substantially disk-shaped cover 6 is provided above the ball bearing 4 on the shaft 3. The cover 6 is fixed to the top body 2 so that the upper surface thereof is substantially the same height (axial position) as the top surface of the top body 2. Further, the outer peripheral portion of the cover 6 is fixed to the inner wall surface (inner diameter portion) of the upper part of the vacant space of the frame main body 2 by press fitting or the like. Further, an insertion hole 61 slightly larger than the outer diameter of the shaft 3 is provided at the center position of the cover 6, and the shaft 3 is inserted through the insertion hole 61. A radial gap is provided between the insertion hole 61 and the shaft 3, and the shaft 3 and the cover 6 are in a non-contact state. Further, the cover 6 is made by punching a transparent sheet of PET (polyethylene terephthalate) having a thickness of 0.8 mm by a Thomson type or the like. PET is usually manufactured by biaxial stretching and has anisotropy with respect to the stretched shaft. In addition, since it shrinks irreversibly at about 80 ° C., it is desirable to stabilize the physical properties by annealing in advance.

A ring (inertia ring) 8 for increasing the inertia of the top body 2 is fixed by press fitting below the cover 6 and above the inner diameter surface of the top body 2. That is, the ring 8 is fixed to an internal space formed by the top body 2 and the cover 6. In the present embodiment, the ring 8 has an outer diameter of about 62 mm and an inner diameter of about 48 mm. As the material, free-cutting steel (SUM) having a density of about 7.8, which is higher than that of the top body 2, is used, and the surface is plated. This is because the rotation of the top 1 is stabilized by increasing the inertia and the rotation is held for a long time. By using a material having a higher density than the top body 2, a large inertia can be obtained while the shape is small. Given. In the present embodiment, an inertia of about 230 g · cm ² is obtained, and the inertia of the entire frame 1 is about 680 g · cm ² . Further, as the material of the ring 8, it is possible to use a copper alloy (brass) or tungsten (W) having a higher density than that of the top body 2. Since the ring 8 is arranged inside the top body 2, even if the ring 8 comes off when the top 1 is rotated, it is considered that there is almost no possibility of the ring 8 jumping out of the top 1. .. Further, it is less likely that the ring 8 protrudes from the top body 2 due to the presence of the cover 6 and the shaft upper portion 33 of the shaft 3 extending above the top body 2.

The ball bearing 4 is a deep groove ball bearing, which has an inner diameter of 6.35 mm (1/4 inch), an outer diameter of 12.7 mm (1/2 inch), and a width of 4.76 mm (3/16 inch), and has an internal radial gap. Is an open type with a diameter of 3 to 8 μm.
As the material of the inner ring 42, the outer ring 41, and the ball 43, a martensitic stainless steel equivalent to SUS440C is used. The inside of the ball bearing 4 is in a non-lubricated dry state in order to reduce the rotational torque as much as possible, but if necessary, a small amount of low-viscosity oil may be applied. This also makes it possible to lubricate the oil with a low torque due to a low shear resistance.
Further, since the material of the ball bearing 4 is martensitic stainless steel, it has higher corrosion resistance than the bearing steel (SUJ2 or equivalent) used for ordinary bearings, so that it has special rust prevention. Does not need. By plating the surface of the ball 43 with gold, lubrication using thin adsorbed water can also be used. Generally, the surface-adsorbed water of gold is thinner than other elements, so lower torque can be realized and long-term rotation can be expected.

Next, the operation of the frame 1 in the present invention will be described. First, in order to turn the top 1, how to wind the string will be described. A string (not shown) is placed on the upper surface of the frame body 2 and wound around the upper portion 33 of the shaft 3. At this time, the upper surface of the cover 6 is substantially the same height as the upper surface of the top body 2, and the string is wound so as to rest on the upper surface of the cover 6, so that the string does not hang down below the top body 2 and the string It is possible to wind the product stably and with little variation. Since the string does not hang down, the string can be easily and surely unwound even when the string is pulled back, so that a high rotation can be stably given to the top 1.

It is also possible to form a loop at the tip of the string, insert it from the upper portion 33 of the shaft 3, and hang it through the upper surface of the cover 6. The string is wound around the small diameter portion 31 of the shaft 3 on the upper surface of the top body 2 via the side surface opposite to the winding start. After that, it is wound around the shaft 3 and further wound around the side surface of the top body 2, and the string is wound upward along the outer peripheral surface of the top body 2. In this way, the small diameter portion 31 of the cover 6 and the shaft 3 makes it possible to wind the string stably with little variation.

The outer peripheral surface of the top body 2 of the present embodiment is provided on a smooth surface. This is the peripheral speed of the outer circumference of the top body 2, which depends on the skill of the person who operates the top, but assuming that it can be rotated at about 5000 min ^-1 (rpm), the peripheral speed of the top body L (km / h). ) Is calculated as follows,
L (km / h) = π ・ 80 ・ 5000 ・ 60 / (1000 ・ 1000)
≒ 74 (km / h)
Therefore, the speed will be faster than when driving on a general road by car.

On the other hand, when the disk-shaped disk is rotated, the surface flow becomes turbulent due to the viscosity of the air from the time when the Reynolds number is exceeded, so it is estimated using the following equation (1). Since the diameter of the main body 2 is 80 mm, it is expected that laminar flow will occur when the rotation speed is about 14000 min ^-1 (rpm) or less. As a result, the air flow on the surface of the top body 2 can be treated as a laminar flow, so that the surface is smooth. In addition, in order to prevent the isolation of the air flow due to the generation of a large vortex if necessary, a slight dimple is appropriately provided on the outer peripheral surface and the surface of the upper surface of the top body 2 to positively separate the air flow due to the generation of a large vortex. It is also possible to prevent it.

ただし、Ｄ：ディスク直径
ρ：空気密度
ω：ディスク角速度
μ：空気の粘性係数

However, D: disk diameter
ρ: Air density
ω: Disk angular velocity
μ: Viscosity coefficient of air

Next, when the top 1 and the end of the string are sandwiched between fingers and the top body 2 is thrown forward and the string is pulled back rapidly, the top 1 tries to move forward due to inertia. Since the string wound around the main body 2 is pulled rapidly, the top 1 is given a strong rotational movement to rotate, falls due to gravity, reaches the floor surface (not shown), and continues the rotational movement.

By practicing many times, such as the speed and angle of throwing the top 1 forward, the timing and force of pulling the string, it becomes possible to give stronger and more stable rotation, which is a good teaching material for children to develop aspirations. It can also be used as. It goes without saying that adults can enjoy themselves enough.

The top body 2 is mechanically coupled to the shaft 3 by a ball bearing 4 with a low rotational torque. That is, assuming that the rotational torque of the ball bearing 4 is Tb and the frictional rotational torque generated between the shaft 3 and the floor surface is Tf, the coma main body 2 rotates together with the shaft 3 when Tb ≧ Tf. When Tb <Tf, the shaft 3 is stationary, only the top body 2 rotates, and a relative rotational movement occurs between the shaft 3 and the top body 2 via the ball bearing 4. In the present embodiment, since the rotational torque of the ball bearing 4 is about 0.1 g · cm or less, when the friction with the floor surface is very small, the top 1 operates as if the shaft 3 and the top body 2 are integrated. However, when the friction with the floor surface is not so small, the shaft 3 does not rotate, so that the precession movement is not taken and the conical movement is maintained.

In the present embodiment, the weight of the top 1 is about 110 g, and the outer diameter of the tip end face of the shaft 3 is 4 mm. Therefore, when the friction coefficient μ between the shaft 3 and the floor is about 0.005 or less [μ = 0. 1 / (110.0.2) ≈0.0045], the top body 2 rotates with the shaft 3. Generally, the sliding friction coefficient of the shaft 3 with stainless steel is about 0.05 to 0.10 even with a low friction material such as Teflon, so when turning on a floor surface such as wood or tile, Since the shaft 3 does not rotate, the coma 1 can be stably supported on the floor surface by forming the tip end surface of the tip portion 32 in a flat shape. It is also possible to support the top 1 more stably by making the periphery of the lower surface of the tip portion 32 a flat surface and recessing an inner surface having a diameter of 4 mm to form a concave surface. In this case, it is not necessary to process the parting residue (so-called protrusion) that occurs due to the misalignment with the parting tool in the turning process of the shaft 3, so that the process can be easily managed.

Further, it is known that the top body 2 is made of POM (polyacetal), and POM cannot generally be adhered. Therefore, in the present embodiment, the ring 8 is press-fitted and fixed to the top body 2. When the top body 2 is rotated and the string is pulled strongly, the ring 8 also rotates, but it hits the floor surface strongly, so even if the press-fitting is loosened, the ring 8 will be the top body 2 according to the law of inertia. Try to stay in the same plane of revolution. Further, the density of the ring 8 is higher than that of the top body 2, but since the ring 8 is provided on the inner diameter of the top body 2, chipping is unlikely to occur even if it hits a hard floor surface such as concrete, and the top body 2 is the ring 8. You can play safely because you can surely prevent the concrete from jumping out.

Further, since the cover 6 is press-fitted and fixed to the top body 2 above the ring 8, even if the ring 8 is press-fitted off, the ring 8 does not jump out from the top body 2 and is safe. Is secured. Since the upper shaft 33 of the shaft 3 extends above the top body 2, even if the ring 8 comes off and the cover 6 comes off, the ring 8 moves to the point where it gets over the upper shaft 33 and goes out. The possibility of popping out is low, and it is safer than a frame in which the shaft 3 does not protrude from the frame body 2.

When the top 1 can be rotated stably, friends can play to compete for the rotation time, but further, a string can be looped and hooked on the small diameter portion 31 of the shaft 3 to walk a tightrope. .. As described above, the top 1 is rotated to grasp the upper portion 33 of the shaft 3 with a finger. The number of fingers may be two or three, but when the upper portion 33 of the shaft is gripped, the shaft 3 does not rotate, so that Tb <Tf, and only the top body 2 rotates. The shaft 3 can be easily picked and moved, the handleability can be improved, and the operation can be facilitated. As a result, it is possible to reduce failures in unexpected places, so that it is possible to concentrate on the main part of the competition, and it is expected that the operation technique of the top will be improved.

Further, when the top 1 is rotated, if it is repeatedly applied to the floor surface more than necessary, Brinell indentations may occur on the ball bearing 4. Elastic deformation due to Hertz's stress circle occurs between the raceway grooves (not shown) provided in the inner ring 42 and outer ring 41 of the ball bearing 4 and the ball 43, but when the elastic limit of the material is exceeded, elastic deformation occurs. Brinel indentations are generated in the track groove as permanent deformation. When Brinell indentation occurs, loud noise and unnecessary vibration are generated during rotation. Since these noise and vibration energies are converted from rotational energy, the rotational time of the top 1 is reduced as a result. Since the hardness of the ball 43 is higher than that of the inner ring 42 and the outer ring 41 of the ball bearing 4, the Brinell indentation is made to be generated on the raceway groove side of the inner and outer rings.

For such a case, in the present embodiment, the ball bearing 4 is configured to be easily replaceable. Specifically, by removing the cover 6 from the top body 2 and removing the retaining ring 71, the shaft 3 and the ball bearing 4 can be removed from the top body 2 in a unit state in the sleeve 7. After that, the shaft 3 can be pulled out from the ball bearing 4 by removing the retaining ring 72 and the spacer 73. Further, the ball bearing 4 can be replaced by removing the ball bearing 4 from the sleeve 7. As for the assembly, the replacement of the ball bearing 4 is completed by assembling in the reverse procedure of the disassembly. The shaft 3 can also be replaced and maintained during this work.

Next, the cover 6 will be described with reference to FIG. As described above, the cover 6 is made transparent by PET, and an insertion hole 61 having a diameter slightly larger than that of the shaft 3 is formed at the center position thereof. The insertion hole 61 is formed so that the shaft 3 can be inserted into the insertion hole 61, and is not in contact with the shaft 3. Further, the cover 6 is press-fitted and fixed to the inner diameter portion of the top body 2 at the outer peripheral portion thereof. Further, in the present embodiment, the cover 6 is flat, but it can also have a convex shape (dome shape) that approaches the direction of the upper portion 33 of the shaft 3 toward the insertion hole 61. In this case, it is considered that the air flow described later can be made smoother.

Further, as the ball bearing 4, an open type (so-called open type) ball bearing having no shield is used so that maintenance such as cleaning and oil application can be facilitated. As a result, the state of the ball bearing 4 can be observed from above the top body 2, which is suitable for prior confirmation and maintenance of the top competition. It is also possible to add a highly designed design or the like to the cover 6, and it is also possible to enhance the design and increase the familiarity.

It is considered that the provision of the cover 6 limits the air flow to the vacant space of the top body 2 and reduces the wind damage. When the top body 2 rotates, the air on the surface of the cover 6 is pulled by the rotation of the cover 6 due to its viscosity. As a result, the pressure on the outer peripheral side where the flow velocity is high is lower than that on the inner peripheral side where the peripheral speed is slow according to Bernoulli's principle, so that the air flow flows from the inner peripheral side of the cover 6 to the outer peripheral side. If the cover 6 is not provided, air will flow into the empty space of the top body 2, hit the end face of the ring 8 and be pushed back in the inner peripheral direction (direction of the axis 3), and will move to the outer peripheral side of the top. , It is thought that the wind damage will increase because the air flow travels in a complicated manner while hitting the wall.

According to the top 1 of the present embodiment, the shaft 3 and the top body 2 are configured to be relatively rotatable via the ball bearing 4, and the cover 6 is fixed to the top body 2 at substantially the same height as the upper surface of the top body 2. Since the insertion hole 61 through which the shaft 3 is inserted is formed in the cover 6 with a radial gap between the cover 6 and the shaft 3, the air flow on the upper surface of the top 1 can be smoothed. As a result, wind damage can be reduced, and the rotation time of the top 1 can be lengthened. Since the ring 8 for increasing the inertia is also provided inside the top body 2 as described above, it is considered to be useful for reducing the wind damage.

(Second Embodiment)
Next, a second embodiment of the top according to the present invention will be described with reference to FIGS. 6 and 7A. The same or equivalent parts as those in the first embodiment are designated by the same reference numerals in the drawings, and the description thereof will be omitted or simplified.

In the present embodiment, as shown in FIGS. 6 and 7A, a plurality of through holes (through portions) 62 are formed at substantially equal intervals in the circumferential direction at the outer edge portion of the cover 6. Further, the number of through holes 62 in this embodiment is 30, but the number is not limited. Further, the inner diameter of the through hole 62 of the present embodiment is 1 mm, but the size is not limited. Other configurations are the same as those in the first embodiment.

Next, the air flow generated by the rotation of the top body 2 of the second embodiment will be described. As shown in FIG. 6, due to the rotation of the top body 2, the viscosity of air on the surface of the cover 6 lowers the pressure on the outer peripheral side where the flow velocity is high as compared with the inner peripheral side where the peripheral speed is slow due to Bernoulli's principle. The air flow flows on the upper surface of the cover 6 from the inner peripheral side to the outer peripheral side. That is, the rotation of the top body 2 generates an air flow as shown by arrow A. Further, since the internal vacant space of the top body 2 becomes a negative pressure due to the air flow of the arrow A through the through hole 62 at the outer edge portion of the cover 6, air is drawn out from the internal vacant space. Further, since there is a gap between the shaft 3 and the insertion hole 61 of the cover 6, air flows into the empty space of the top body 2 through this gap due to negative pressure, and the air flow inside the top body 2 is indicated by arrow B. It flows like.

The fine dust generated or invaded inside the frame body 2 is discharged from the inside of the frame body 2 to the outside by the air flow indicated by the arrow B. Therefore, since fine dust can be discharged from the empty space of the top body 2 by rotating the top, the possibility of dust entering the inside of the open ball bearing 4 can be reduced, and the life of the top can be extended. Is possible. Although it is possible to observe the specific air flow using dry ice or incense sticks, it is possible to analyze and visualize it more accurately using CFD (Computational Fluid Dynamics). it can. Further, it is generally known that the size of floating dust is about 50 μm or less in diameter, and it is said that when the diameter is smaller than 20 μm, the dust hardly falls and continues to float. On the other hand, since the internal gap of the ball bearing 4 is about several μm (3 to 8 μm in this embodiment), if floating dust enters the internal gap of the ball bearing 4, it may cause a failure of the ball bearing 4.

According to the frame 1 of the present embodiment, since a plurality of through holes 62 are formed in the outer edge portion of the cover 6, the frame 1 can be inserted even when dust enters the vacant space of the frame body 2 from the outside. By rotating and playing, fine dust can be discharged from the empty space of the top body 2 without using any special means by using the air flow generated on the surface of the cover 6. As a result, the possibility of dust entering the inside of the ball bearing 4 can be reduced, and the life of the top 1 can be extended.

(Third Embodiment)
Next, a third embodiment of the top according to the present invention will be described with reference to FIG. 7B. The same or equivalent parts as those in the first embodiment are designated by the same reference numerals in the drawings, and the description thereof will be omitted or simplified.

In the present embodiment, as shown in FIG. 7B, a plurality of notches (penetrating portions) 63 are formed at substantially equal intervals in the circumferential direction on the outer edge portion of the cover 6. The notch 63 is formed in a fan shape (arc shape). The number of notches 63 in the present embodiment is 32, but the number is not limited. The 32 notches 63 are formed continuously in the circumferential direction. The notch 63 operates in the same manner as the through hole 62 of the second embodiment. Other configurations are the same as those in the second embodiment.

The major difference between the notch 63 of the present embodiment and the through hole 62 of the second embodiment is that the contact area between the outer peripheral edge of the cover 6 of the present embodiment and the inner peripheral surface of the top body 2 is smaller. It is a point. As a result, the outer edge portion of the cover 6 can be easily deformed, so that the range of the shimeshiro in press fitting can be increased, the degree of freedom in design can be improved, and the dimensional control becomes easier as compared with the second embodiment. Further, as shown in FIG. 7B, the notches 63 do not have to be continuous, and may be provided discontinuously in the circumferential direction. Furthermore, the notch is not limited to a fan-shaped notch, and may be a U-shaped notch, a rectangular notch, or a thin notch. Needless to say, the notch 63 of the present embodiment and the through hole 62 of the second embodiment can coexist.

(Fourth Embodiment)
Next, a fourth embodiment of the top according to the present invention will be described. In this embodiment, high-strength aluminum A5052, which is an aluminum alloy, is used as the material of the top body 2. The surface can be made black, red, or various colors by anodizing, etc., and it can be modified to the owner's favorite color, and by forming an oxide film, it is less likely to be scratched, and the appearance is kept in good condition for a long time. It becomes possible. As a result, you can feel more attached to your own piece, and it is thought that it will be useful for the formation of a rich human being who values things.

Furthermore, if weight reduction is aimed at, the material of each part of the top is an alloy or magnesium alloy whose main material is titanium (Ti), which has a high specific strength, and super duralumin / super duralumin. It is also possible to do. For further weight reduction, it is possible to use a metal whose density is sufficiently low enough to float on water by using a foamed metal. It is also possible to appropriately use a resin using nanofiber cellulose as a strengthening agent, CFRP (carbon filler reinforced resin), or the like. At the same time, it is possible to appropriately improve the material and shape of the top body 2 and the ring 8.

The present invention is not limited to those exemplified in the above embodiments, and can be appropriately modified without departing from the gist of the present invention.

1 piece 2 piece body 3 shaft 31 small diameter part 32 tip part 33 shaft upper part 4 ball bearing 41 outer ring 42 inner ring 43 ball 6 cover 61 insertion hole 62 through hole (through part)
63 Notch (penetration part)
7 Sleeve 71, 72 Retaining ring 73 Spacer 8 Ring (inertia ring)

Claims (4)

Axis and
Rotatably mounted via a plurality of ball bearings in the shaft, inner substantially frustoconical internal space is provided, having a substantially frustoconical outline, and co Ma body,
Top so is substantially the same or slightly lower axial position as the upper surface of the front Symbol frame body, the outer peripheral portion is fixed to the vicinity inside the outermost periphery of the upper surface of the frame body, and a cover,
With
Inertia ring is fixed to the internal space formed by the top body and the cover.
An insertion hole through which the shaft is inserted is formed in the cover with a radial gap between the cover and the shaft, and the air flow flowing into the inside of the top body is reduced. The frame to be. The top according to claim 1, wherein the inertia ring is made of a material having a higher density than the top body. The top according to claim 1 or 2, wherein a plurality of penetrating portions are provided on the outer edge portion of the cover. The top according to any one of claims 1 to 3, wherein the ball bearing is an open type.

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