GB2209130A - Drive transmission device for grinding wheel of cutlery grinder - Google Patents

Abstract

There is described a cutlery grinder having a grinding wheel (5, 6), a drive shaft (2) for the grinding wheel, an input shaft (12), and a drive transmission device for rotationally coupling the drive shaft (2) and the input shaft (12) together in a manner permitting relative axial displacement of the shafts. The device comprises a cam projection (14) formed on either one of the shafts (2, 12) and a cam surface (17) formed on the other one of the shafts and abutting against the cam projection. The cam surface (17) includes guide surfaces (18a, 18b) shaped oblique to the axial direction such as to allow both the shafts to relatively move in the axial direction and stopper surfaces formed contiguous to the guide surfaces such as to prevent both the shafts from relatively moving beyond a fixed extent in the axial direction. <IMAGE>

Description

Rotation Drive Transmission Device of Grinding Wheel in Cutlery Grinder FIELD OF THE INRENTION This invention relates to a rotation drive transmission device of a grinding wheel disposed between a rotation shaft of the grinding wheel and a rotation drive shaft in a cutlery grinder which grinds cutters such as a kitchen knife, a pocket knife and the like.

DESCRIPTION OF TFE RELATED ART Cutlery grinders of this kind have been disclosed in Japanese official gazettes such as Utility Model Publication No. 55-1793 and Provisional Publication No. 598752 wherein a rotation shaft of a grinding wheel is designed to move in its axial direction thereby enabling an easy grinding work. All of these cutlery grinders have their rotation shafts of grinding wheels directly coupled with rotation drive shafts. These rotation drive shafts or electric motors which drive them are pressed by springs, thereby grinding wheels are adapted to be in pressed contact with cutters. However, since the grinding wheels are invariably urged to the axial direction by the springs, the grinding wheels readily produce vibration in the axial direction when they rotate.

Additionally, as shown in the Japanese utility model publication No 59-40991 a cutlery grinder has been disclosed wherein a spring is interposed between a rotation drive shaft and a rotation shaft of a grinding wheel. This cutlery grinder has also the same defect as the one mentioned above, due to the provision of the spring urging the grinding wheel.

According to the invention there is provided a cutlery grinder comprising a grinding wheel, a drive shaft for driving the grinding wheel, an input shaft for driving the drive shaft, and a drive transmission device for rotationally coupling the input shaft and the drive shaft together in a manner permitting relatively axial displacement of the shafts, in which the transmission device comprises: a cam projection formed on one of said shafts; and a cam surface formed on the other one of said shafts and abutting against the cam projection in accordance with a rotation of both the shafts, the cam surface including a guide surface shaped oblique to the axial direction such as to allow both the shafts to move relatively in the axial direction and a stopper surface formed contiguous to the guide surface such as to prevent both the shafts from moving relatively beyond a fixed extent in the axial direction and for transmitting a rotations drive force of the rotation drive shaft to the rotation shaft through an engagement of the cam projection with the cam surface.

Therefore, as will become apparent from the detailed description of a preferred embodiment, there is provided wheels retain reliable elasticity in the axial direction of the rotation shaft without using a spring, thereby producing no vibration on the grinding wheel due to the spring.

One embodiment of cutlery grinder according to the invention will now be described in detail with reference to the accompanying drawings, in which: Fig. 1 is a partially broken plan view showing a cutlery grinder embodying the present invention; Fig. 2 is a cross-sectional view along line I-- I of Fig. 1; Fig. 3 is a fragmentally enlarged plan vlew of Fig. 1 showing a state of a rotation drive shaft rotated before grinding a cutlery blade; Fig. 4 and 5 are corresponding to Fig. 3 showing a case of grinding a blade.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of this invention will be described hereinafter with reference to the drawings.

As shown in Figs. 1 and 2, a rotation shaft 2 is supported at bearing portions 3 and 4 such as to be movable in the direction of the axis in one side of a case 1. A pair of grinding wheels 5 and 6 with different roughness of their surfaces are disposed in parallel. In correspondence with the end surfaces of both grinding wheels 5 and 6, openings 7a, 7b, 8a and 8b for insertion of the blades are formed on the upper surface of the case 1. Leaf springs 9 and 10 are attached to these openings 8a, 8b, Sa and 8b such as to pressingly contact the blades inserted into the openings 7a, 7b, 8a and 8b with the inside surfaces of the openings 7a, 7b, 8a and 8b.The blades inserted into the openings 7a, 7b, 8a and 8b are adapted to come in contact with a part of the periphery of the end surfaces of the grinding wheels 5 and 5.

In the other side of the case 1, an electric motor (not shown) driven by means of a switch 11 and a power source (not shown) are housed. A rotation drive shaft 12 of the electric motor is projected to the side of the rotation shaft 2 of the grinding wheels 5 and 6.

To the tip of the rotation drive shaft 12, a column shaped coupling member 13 is attached. On the outer peripheral surface of the coupling member 13, a pair of cam projections 14 are formed 1800 spaced apart. Also to the tip of the rotation shaft 2 of the grinding wheels 5 and 6, a cylindrical coupling member 15 is attached.

Into this coupling member 15, the coupling member 13 of the rotation drive shaft 12 is inserted. On the outer circumference of the coupling member 15, a pair of notches 16 opened toward the tip thereof are formed 1800 spaced apart.

V-shaped cam surfaces 17 are formed on the notches 16. Both the cam projections 14 of the rotation drive shaft 12 are inserted into and engaged with both the notches 16, thereby being adapted to come in contact with the cam surfaces 17 in accordance with the rotation of the rotation drive shaft 12. Each of the V-shaped cam surfaces 17, as shown in Fig. 3, comprises a pair of guide surfaces 18a and 18b which are obliaue to the axial direction of the rotation shaft 2 and extend in the direction of intersecting with each other and a pair of stopper surfaces 19a and 19b which are formed contiguous to the guide surfaces 18a and 18b at an intersecting portion thereof. Angles of inclination of the guide surfaces 18a and lab are the same relative to the axial direction of the rotation shaft 2.

And, for example, even when the cam projection 14 of the rotation drive shaft 12 comes in contact with either one of the guide surfaces 18a and 18b of the cam surface 17 due to the rotation of the rotation drive shaft 12, the rotation shaft 2 of the grinding wheels 5 and 6 moves to the axial direction due to the axial component of the force given by the cam projection 14 to the guide surface 18a, 18b. As a result, the cam projection 14 relatively moves along the guide surface 18a, 18b toward the stopper surface 19a, 19b and then comes in contact with the stopper surface 19a, 19b as shown in Fig. 3. In this state, the rotation of the rotation drive shaft 12 is transmitted to the cam projection 14 and both the stopper surfaces 19a, 19b, thereby the rotation shaft 2 of the grinding wheels 5 and 6 rotates integrally with the rotation drive shaft. At this time, the grinding wheels 5 and 6 are respectively on central positions 51 between the blade insertion openings 7a and 7b and also between the blade insertion openings 8a and 8b.

In case of the blade being inserted into the one insertion opening 7a, 8a of the blade, a force in the arrow 101 direction shown in Fig. 1 is given to the grinding wheels 5 and 6. Thereby, the rotation shaft 2 of the grinding wheels 5 and 6 moves in the arrow 101 direction. With respect thereto, the cam projection 14 moves along the one guide surface 18a as shown in Fig. 4.

When the force in the arrow 101 direction given by the blade to the grinding wheels 5 and 6 is balanced with the component of the force, in the direction opposite to the arrow 101 direction, given by the cam projection 14 of the rotation drive shaft 12 to the one guide surface 18a, the relative movement between the cam projection 14 and the one guide surface 18a is ceased. In this state, the rotation of the rotation drive shaft 12 is transmitted to the rotation shaft 2 of the grinding wheels 5 and 6 through the intermediary of the cam projection 14 and the one guide surface 18a.

On the other hand, when the blade is inserted into the other openings 7b, 8b for insertion of the blade, a force in the arrow 102 direction shown in Fig. 1 is given to the grinding wheels 5 and 6. Thereby, the rotation shaft 2 of the grinding wheels 5 and 6 moves in the arrow 102 direction. Then, the cam projection 14 moves with respect thereto along the other guide surface 18b as shown in Fig. 5. Similarly to the case mentioned above, when the force given to the grinding wheels 5 and 6 is balanced with the axial component of the force given to the other guide surface 18b, the relative movement between the cam projection 14 and the other guide surface 18b is ceased.

In this state, the rotation of the rotation drive shaft 12 is transmitted to the rotation shaft 2 of the grinding wheels 5 and 6 through the intermediary of the cam projection 14 and the other guide surface 18b.

In grinding a cutlery blade, when a force exceeding a fixed strength is given to the grinding wheel 5, 6, the grinding wheels 5 and 6 have the elasticity in the axial direction of the rotation shaft 2 and move such as to move off the above mentioned force while pressing the blade. Therefore, griding work is very easy.

Especially in this embodiment, when the force given by the blade to the grinding wheel 5, 6 is balanced with the force given by the rotation drive shaft 12 to the guide surface 18a, 18b of the cam surface 17 through the intermediary of the cam projection 14, the rotation drive shaft 12 and the rotation shaft 2 of the grinding wheel 5 and 6 rotate together. Therefore, the rotation can be transmitted to the grinding wheels 5 and 6 while the grinding wheel retaining elasticity in the axial direction of the rotation shaft 2 without using a spring as in the cutlery grinder according to the related art.

Consequently, there is no vibration due to the spring produced on the grinding wheels 5 and 6.

Further, the above mentioned embodiment may be modified as follows: (a) The cam projection 14 is formed on the rotation shaft 2 of the grinding wheel 5 and 6, while the cam surface 17 is formed on the rotation drive shaft 12.

(b) The numbers of the cam projections 14 and cam surfaces 17 are one or more than two, respectively.

(c) Only the one guide surface 18a and the one stopper surface 19b are formed or only the other guide surface 18b and the other stopper surface 19b are formed, instead of both the guide surfaces 18a and 18b, and both the stopper surfaces 19a and 19b concerning the cam surface 17.

(d) The whole of the cam surface 17 is shaped substantially like an arc.

As many apparently widely different embodiments of the invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

Claims (5)

1. A cutlery grinder comprising a grinding wheel, a drive shaft for driving the grinding wheel, an input shaft for driving the drive shaft, and a drive transmission device for rotationally coupling the input shaft and the drive shaft together in a manner permitting relatively axial- displacement of the shafts, in which the transmission device comprises: a cam projection formed on one of said shafts; and a cam surface formed on the other one of said shafts and abutting against the cam projection in accordance with a rotation of both the shafts, the cam surface including a guide surface shaped oblique to the axial direction such as to allow both the shafts to move relatively in the axial direction and a stopper surface formed contiguous to the guide surface such as to prevent both the shafts from moving relatively beyond a fixed extent in the axial direction and for transmitting a rotations drive force of the rotation drive shaft to the rotation shaft through an engagement of the cam projection with the cam surface.

2. A cutlery grinder according to Claim 1, wherein the rotation drive shaft includes a first coupling member having said cam projection on an outer peripheral surface thereof, and the rotation shaft includes a second coupling member provided with a notch having said cam surface, the first coupling member being insertable into the second coupling member and the cam projection being insertable into the notch.

3. A cutlery grinder according to Claim 2, wherein a pair of cam projections are integrally formed 1800 spaced apart on an outer peripheral surface of the first coupling member while a pair of the notches are integrally formed 1800 spaced apart on the second coupling member.

4. A cutlery grinder according to any one of Claims I to 3, wherein the cam surface is substantially V-shaped, a pair of the guide surfaces are formed such as to extend in an intersecting direction with each other, and a pair of the stopper surfaces are formed at an intersecting portion of the guide surfaces.

5. A cutlery grinder according to Claim 1 and substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.