COUPLER STRUCTURE OF HAND GRINDER

Abstract

Proposed is a coupler structure of a hand grinder. The coupler structure is fastened to a rotating shaft of a grinder body to enable a machining disc to be more simply and rapidly attached to or detached from the grinder body. Fabrication costs are significantly reduced by simplifying the components associated with the coupler mounted on the rotating shaft of the grinder body. Since the consumable disc is easily attached to and detached from the coupler with one touch, a replacement operation is performed rapidly, thereby significantly improving the efficiency of work.

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a U.S. national phase application of PCT International Application PCT/KR2021/006541, which claims priority to Korean Patent Application No. 20-2020-0001783, filed on May 27, 2020, the entire contents of which are herein incorporated by reference.

TECHNICAL FIELD

The present invention relates to a coupler structure of a hand grinder, the coupler structure being configured to be fastened to a rotating shaft of a grinder body and to enable a machining disc to be more simply and rapidly attached to or detached from the grinder body.

BACKGROUND ART

In general, a hand grinder is used to, for example, smoothly trim a rough surface portion or a portion to be painted of a machined component or cut a portion of a raw material, such as a pipe, an angle iron, or a steel plate. That is, the hand grinder can perform an operation of, for example, grinding or cutting an insufficiently-machined portion, such as a corner, of a workpiece using a consumable disc by running a rotating shaft of a grinder body at high speed by driving an electric motor or using air pressure generated by driving a compressor. The disc may be easily consumed, since a grindstone or sandpaper wears together with a surface to be ground. Thus, a number of discs must be provided and a used disc must be replaced with a new disc frequently. Accordingly, there has been improvement in a structure for facilitating attachment/detachment of discs.

Some structures for mounting a disc on such a hand grinder are disclosed in Korean Utility Model Application Publication No. 20-1989-0010365 and Korean Utility Model Application Publication No. 20-1996-0026826. As disclosed in these documents, after a disc is fitted around and fixed to a rotating shaft mounted on a grinder body, the disc is fixed using a nut or by fastening a bolt to the rotating shaft. Thus, according to this structure, the disc is fastened to the grinder body simply using the bolt or the nut. In this situation, however, fastening force may be reduced by, for example, friction of the disc rotating at high speed or by minute vibrations, thereby causing a worker to be anxious. In fact, a separate cover is disposed around the disc to prepare for a situation in which the disc is loosened and causes an accident.

In addition, Korean Patent Application Publication No. 10-2009-0074461 discloses a technology in which a disc holder integrated with a disc may be fastened by screw engagement by providing a fixing holder on a rotating shaft of a grinder body. Thus, the disc may be prevented from being loosened from the fixing holder. In addition, the disc may be more easily and rapidly attached and detached using a brake unit provided on the grinder body. According to this structure, the disc holder must be fastened to the fixing holder on the rotating shaft by screw engagement. Accordingly, the disc holder must be inconveniently loosened or fastened again during work and the separate brake unit must be operated, thereby causing significant difficulty to a worker.

DISCLOSURE

Technical Problem

Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an objective of the present invention is to provide a coupler structure of a hand grinder, wherein the coupler structure mounted on a rotating shaft of a grinder body is fabricated in a simplified structure enabling a disc to be attached and detached with one touch, thereby improving the efficiency of work at low cost.

Technical Solution

In order to accomplish the above objective, the present invention may provide a coupler structure of a hand grinder. The coupler structure may include: a housing 70 configured to be attached to and detached from a rotating shaft 11 of a hand grinder; a top fastening block 80A and a bottom fastening block 80B fitted around and fixed to outer circumferential portions of the housing, respectively; and a spring 90 situated between the top fastening block and the bottom fastening block to provide elasticity. The housing 70 may include a cylindrical body through which an inner diameter portion 71 configured to be fitted around and fixed to the rotating shaft extends, four protrusions 73 extending from a top outer circumferential portion of the cylindrical body at right angles to face each other, and a male thread 74 provided on a bottom outer circumferential portion located below the protrusions. The top fastening block 80A may include four recesses 82 extending outward from a central through-hole 81a such that protrusions 73 are fitted into the recesses 82, respectively, and an outer circumferential rim 83a protruding from an outer peripheral portion of the top fastening block. A flange 85b having a female thread 85a configured to be fastened with the male thread 74 may be provided on a disc-shaped body 84 of the bottom fastening block 80B. The spring 90 may be accommodated between the outer circumferential rim 83a provided on the outer peripheral portion of the top fastening block 80A and an outer circumferential portion of the flange 85b provided on the disc-shaped body 84 of the bottom fastening block 80B.

Advantageous Effects

According to characteristics of the present disclosure, it is possible to significantly reduce fabrication costs by simplifying the components associated with the coupler mounted on the rotating shaft of the grinder body. Since the consumable disc can be easily attached to and detached from the coupler with one touch, a replacement operation can be performed rapidly, thereby significantly improving the efficiency of work.

DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded perspective view illustrating components of a hand grinder disclosed in Korean Patent No. 10-0973157;

FIG. 2 is a side view illustrating the hand grinder in which the components are fitted together;

FIGS. 3 and 4 are a cross-sectional view of the disc holder and a bottom view of part “A”;

FIG. 5 is an exploded perspective view of components of the power transmission unit;

FIGS. 6 and 7 are assembled cross-sectional views of the components illustrated in FIG. 5;

FIGS. 8 and 9 are plan and views illustrating the operational relationship between the stopper and the safety pin of the power transmission unit;

FIGS. 10 and 11 are plan and bottom views of the housing of the power transmission unit;

FIG. 12 is an exploded perspective view illustrating a coupler structure of a hand grinder according to the present disclosure;

FIG. 13 is an exploded perspective view illustrating components of the coupler;

FIGS. 14 and 15 are plan and cross-sectional views of the housing;

FIGS. 16 and 17 are plan and cross-sectional views of the upper fastening pin;

FIGS. 18 and 19 are plan and cross-sectional views of the lower fastening pin; and

FIG. 20 is a cross-sectional view of the coupler structure mounted on the grinder body.

BEST MODE

Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be understood, however, that specific structures and functions of these embodiments are merely specific examples and the present disclosure is not limited thereto.

First, a technology disclosed in Korean Patent No. 10-0973157 will be described in detail as an example to which the present invention is applied and problems thereof will be discussed, before the configuration, as well as functions and effects, of the present disclosure are described.

As illustrated in FIGS. 1 to 11, a hand grinder includes a typical grinder body 10, a power transmission unit 20, and a disc holder 30 having a disc D mounted integrally therewith.

A rotating shaft 11 having a screw hole 11a is provided on one front end of the grinder body 10. The rotating shaft 11 is configured to be rotated at high speed by driven by an electric motor or by air pressure of a compressor. The power transmission unit 20 and the disc holder 30 are mounted on the rotating shaft 11.

A plurality of recesses 32 is formed on the bottom of a through-hole 31 of the disc holder 30, the recesses 32 being spaced apart from each other at predetermined distances. Three protrusions 33 are provided between the recesses 32, thereby allowing the disc holder 30 to be mounted on or detached from the power transmission unit 20.

The power transmission unit 20 includes a stopper 40 and a housing 50 rotatable forward and backward on the stopper 40. A cylindrical binding member 60 is mounted on the central portion of the housing 50, and is fastened to the rotating shaft 11 of the grinder body 10 using a fixing bolt 12.

A through-hole 41 is provided in the central portion of the stopper 40, and spiral receiving recesses 42a and 42b are provided on both sides of the through-hole 41 so as to be gradually more spaced away from the center of the through-hole 41. Concave recesses 43a and 43b are provided between the receiving recesses 42a and 42b. A textured portion 44 is provided on the outer circumferential surface of the stopper 40 to prevent slipping, and a positioning line 44a is provided on the textured portion 44. Safety keys 46 each including a cylindrical roll 45a and a quadrangular pawl 45b are provided in the receiving recesses 42a and 42b, respectively.

The housing 50 is configured to perform a function of locking or unlocking the disc holder 30 by operating the safety keys 46 in the horizontal direction on the stopper 40. The housing 50 includes a flange 51 and a body 52 configured to be fitted into the through-hole 41 of the stopper 40.

A positioning line 51a is provided on a circumferential surface portion of the flange 51, and quadrangular guide recesses 53 facing each other are provided on the bottom of the flange 51 such that the quadrangular pawls 45b on the top portions of the safety keys 46 are fitted into the guide recesses 53, respectively. An insertion recess 54 is provided on the body 52 below the flange 51 such that the housing 50 fitted into the through-hole 41 of the stopper 40 may be bound using a fixing ring 55. Ball plungers 56 are provided on both sides of the top surface of the flange 51, thereby allowing the housing 50 to be more tightly rotated on the stopper 40.

Each of the ball plungers 56 includes a steel ball 57 and a spring 58 inserted into a corresponding one of insertion recesses 51b provided on both sides of the top surface of the flange 51, with a fixing screw 59 being fastened into the corresponding insertion recess 51b. In forward and backward rotation of the housing 50, the ball plungers 56 may be elastically inserted into or removed from the concave recesses 43a and 43b.

The binding member 60 is fitted into a seating hole 51c provided in the central portion of the housing 50 and fastened to the rotating shaft 11 of the grinder body 10. The binding member 60 has a stepped portion 61. Three catching protrusions 62 are provided above the stepped portion 61. (Each of the catching protrusions 62 includes a horizontal portion and a vertical portion extending downward from one end of the horizontal portion.) Due to this configuration, the protrusions 33 of the disc holder 30 can be fastened and fixed to or detached from the catching protrusions 62.

In the hand grinder described above, the disc holder 30 may be attached to or detached from the rotating shaft of the grinder body 10 in a simple manner. However, the stopper 40 and the housing 50 of the power transmission unit 20 are provided separately, or the safety keys 46, the steel balls 57, springs 58, the fixing screws 59 of the ball plungers 56, and the like are disposed in a complicated structure. Due to these features, fabrication costs are increased, thereby causing a significant burden in working sites using a large amount of consumables. In addition, impurities, such as fine particles, produced during, for example, grinding or cutting performed using the hand grinder may cause the operation of the safety keys to be defective and may also cause the grinder to malfunction.

FIGS. 12 to 20 are views illustrating a coupler structure of a hand grinder according to an embodiment of the present disclosure. As illustrated in FIGS. 12 to 20, a coupler K detachably attached to the rotating shaft 11 of the hand grinder includes a housing 70, top and bottom fastening blocks 80A and 80B, and a spring 90 situated between the top and bottom fastening blocks 80A and 80B to provide elasticity.

The housing 70 has an inner diameter portion 71 extending therethrough, the inner diameter portion 71 having a thread configured to be screw-engaged with the rotating shaft 11 of the grinder body 10. Four protrusions 73 are provided on the top end portion of the cylindrical body of the housing 70, each of the protrusions 73 having a catching stepped portion 72a. A male thread 74 is provided on the outer portion of the bottom end portion of the housing 70.

In addition, in the top fastening block 80A, four recesses 82 extend outward from a through-hole 81a such that the protrusions 73 of the housing 70 are fitted into the recesses 82, respectively. An outer circumferential rim 83a protrudes from the outer periphery of the top fastening block 80A. In the bottom fastening block 80B, a flange 85b having a female thread 85a protrudes from the central portion of a disc-shaped body 84, the female thread 85a being configured to be fastened with the male thread 74 of the housing 70.

Thus, the spring 90 may be accommodated between the top and bottom fastening blocks 80A and 80B. In a position in which the top and bottom fastening blocks 80A and 80B are mounted on the housing 70, individual components may be maintained. In this manner, a disc 100 can be attached to and detached from the grinder with one touch.

That is, the disc 100 is a consumable intended to be discarded after the lifespan due to use for an extensive period of time. The disc 100 typically includes a disc-shaped machining portion 101 configured to grind or cut a workpiece and a holder 102 configured to hold the machining portion 101. Protrusions 103 are provided on the inner portion of the holder 102 such that the disc 100 can be detachably attached to the housing 70.

According to this configuration, the inner diameter portion 71 of the housing 70 of the coupler K may be fixed to the rotating shaft 11 of the grinder body 10 by screw engagement. In this position, when the protrusions 73 of the housing 70 may be fitted into recesses formed by the protrusions 103 of the disc 100 and then the disc 100 is rotated slightly, the protrusions 103 of the disc 100 are fixed by the catching stepped portion 72a of the protrusions 73.

Here, the top fastening block 80A may be pressed downward while being elastically repulsed by the spring 90 situated between the top fastening block 80A and the bottom fastening block 80B and return to the original position, thereby firmly maintain the disc 100.

Thus, it is possible to operate the rotating shaft 11 of the grinder body 10 at high speed by driving an electric motor or using air pressure generated by driving a compressor. At the same time, it is possible to perform an operation of, for example, grinding or cutting an insufficiently-machined portion, such as a corner, of a workpiece by high-speed rotation of the disc 100. In addition, when intended to replace the disc 100, the disc 100 can be unfastened from the catching stepped portions 72a of the protrusions 73 of the housing 70 by slightly rotating the disc 100 in the opposite direction while pressing the disc 100. In this manner, the disc 100 can be easily detached from the housing 70.

The spring 90 may be made from silicone or any other elastic material as an alternative. For example, a cylindrical elastic member made from an elastic material, such as rubber, may be used in place of the spring 90.

As set forth above, according to the coupler structure of the hand grinder according to the present disclosure, it is possible to significantly reduce fabrication costs by simplifying the components associated with the coupler mounted on the rotating shaft of the grinder body. Since the consumable disc can be easily attached to and detached from the coupler with one touch, a replacement operation can be performed rapidly, thereby significantly improving the efficiency of work.

The objective of the present disclosure is realized by the technical configuration described above. Although the present disclosure has been described with respect to the specific embodiments and drawings, the present disclosure is not limited thereto. It will be apparent to those skilled in the art to which the present disclosure pertains that the present disclosure may be variously modified and altered in forms without departing from the spirit of the present disclosure and the scope of the appended claims and equivalents thereof.

Claims

1. A coupler structure of a hand grinder, the coupler structure comprising:

a housing (70) configured to be attached to and detached from a rotating shaft (11) of a hand grinder;

a top fastening block (80A) and a bottom fastening block (80B) fitted around and fixed to outer circumferential portions of the housing, respectively; and

a spring (90) situated between the top fastening block and the bottom fastening block to provide elasticity,

wherein the housing (70) comprises a cylindrical body through which an inner diameter portion (71) configured to be fitted around and fixed to the rotating shaft extends, four protrusions (73) extending from a top outer circumferential portion of the cylindrical body at right angles to face each other, and a male thread (74) provided on a bottom outer circumferential portion located below the protrusions,

the top fastening block (80A) comprises four recesses (82) extending outward from a central through-hole (81a) such that protrusions (73) are fitted into the recesses (82), respectively, and an outer circumferential rim (83a) protruding from an outer peripheral portion of the top fastening block,

a flange (85b) having a female thread (85a) configured to be fastened with the male thread (74) is provided on a disc-shaped body (84) of the bottom fastening block (80B), and the spring (90) is accommodated between the outer circumferential rim (83a) provided on the outer peripheral portion of the top fastening block (80A) and an outer circumferential portion of the flange (85b) provided on the disc-shaped body (84) of the bottom fastening block (80B).