GB2310325A

GB2310325A - A spring biassed resisitor mounting

Info

Publication number: GB2310325A
Application number: GB9701428A
Authority: GB
Inventors: Ichio Sakabe
Original assignee: Makita Corp
Current assignee: Makita Corp
Priority date: 1996-02-02
Filing date: 1997-01-24
Publication date: 1997-08-20
Anticipated expiration: 2017-01-24
Also published as: DE19703017A1; GB9701428D0; GB2310325B; JPH09213501A

Description

1 a 2310325 MOUNTING DEVICE FOR MOUNTING ELECTRICAL COMPONENT ON

ELECTRICAL MACHINERY OR APPARATUS

Background of the Invention

1. Field of the Invention

The present invention relates to a mounting device for mounting an electrical component such as a resistor and a capacitor on an electrical machinery or apparatus such as a power driven tool.

2. Description of the Prior Art

A conventional power driven tool as an example of an electrical machinery or apparatus has a housing having two housing halves. When the housing is assembled, an electrical component such as a resistor is mounted on the tool such that the electrical component is held between two housing halves. To this end, a seat-like holder portion is formed on each of the housing halves, so that the resistor is held between the housing halves with both ends of the resistor held by the corresponding holder portions. In case that the housing is made of synthetic material, the holder portions are normally formed integrally with the housing, so that the holder portions are also made of synthetic 1 material.

Thus, with the conventional power driven tool, the electrical component such as a resistor is held within the housing with the electrical component directly contacting the holder portions of the housing halves made of synthetic material. With such a construction, if the electrical component is a resistor which may produce heat during the operation, the holder portions may be heated, so that the holder portions may be deformed in some cases.

With the conventional power driven tool, a fan is accommodated within the housing and is driven for introducing air from the outside to the interior of the housing, so that the electrical component can be prevented from being excessively heated to some extent. However, in case that the holder portions have a cylindrical configuration for receiving both ends of the electrical component, both ends of the electrical component are covered by the holder portions, so that the cooling effect by the air from the outside may be considerably degraded. For this reason, the receiving portions may be heated to a high temperature, resulting in that the holder portions and their adjoining parts of the housing may be deformed.

2 Summary ofthe Invention

It is, accordingly, an object of the present invention to provide a mounting device which is adapted for mounting an electrical component on an electrical machinery or apparatus and which can prevent the electrical machinery or apparatus from being excessively heated by heat produced in the electrical component.

According to the present invention, there is provided a mounting device for mounting an electrical component on an electrical machinery or apparatus, comprising:

a spring; and a holder for holding the electrical component by means of the spring in a state that the electrical component does not contact any portions or parts other than the spring of the electrical machinery or apparatus.

With this construction, since the electrical component such as a resistor does not contact any portions or parts other than the spring of the electrical machinery or apparatus such as a power driven tool, heat produced in the electrical component can be radiated to the atmosphere via the spring and is not conducted to any portions of parts other than the spring member of the electrical machinery or apparatus such as a power driven tool.

Thus, since cooling air in a sufficient amount may flow 3 around or through the spring for efficiently cooling the spring. As the result, the heat produced in the electrical component is reduced and is then conducted or transmitted to the part of the electrical machinery or apparatus. Therefore, if such a part of the electrical machinery or apparatus is a housing made of synthetic resin, the housing may be prevented from being deformed by heat.

In addition, since the electrical component is held by the holder by means of the spring, the electrical component may be protected from vibrations or impacts applied to the electrical component, so that any troubles such as breakage of connection of the electrical component can be reliably prevented.

Preferably, the spring includes at least one spring member which is a coil spring.

With this construction, by virtue of the wire length of the coil spring. the heat radiation effect can be further improved. In other words, the cooling effect can be improved. In addition, the vibrations and impacts applied to the electrical component in any directions can be absorbed.

The spring member may be made of stainless steel. The stainless steel has a heat conductive efficiency lower than spring steel which is generally used for a spring. Therefore, a smaller amount of heat is conducted from the 4 electrical component to any parts of the electrical machinery or apparatus other than the electrical component when the electrical component is heated.

In a practical construction, a pair of spring members are provided and are disposed on both ends of the electrical component, so that the spring members bias the electrical component in opposite directions to each other. The holder includes a pair of holder portions formed on the housing of the electrical machinery or apparatus for holding the corresponding spring members.

Preferably, each of the spring members has a substantially conical configuration having a diameter decreasing toward the corresponding holder portion. Each of the holder portions includes a guide surface so as to form a substantially conical bottom, so that each of the spring members is held by the corresponding holder portion in a state that the axis of each of the spring members is in alignment with the axis of the corresponding holder portion with the aid of the guide surface.

With the conical configurations of the spring members and the bottoms of the holder portions, the axes of the springs members are automatically brought in alignment with the axes of the holder portions, so that the electrical component can always be fixed in a predetermined position when the electrical component is mounted on the electrical machinery or apparatus. Therefore, the efficiency in assembling the electrical machinery or apparatus can be improved.

Further, preferably, each of the holder portions may include a base part and an extension part. The base part has the guide surface, and the extension part extends from the base part toward the electrical component and partly surrounds the electrical component not to contact the electrical component. Each of the holder portions comprises a plurality of holder segments equally spaced from each other in the circumferential direction of the electrical component, so that the cooling air can efficiently flow through the spring members.

Brief Description of the Drawings

FIG. 1 is a side view of a disc grinder, with its one of housing halves removed, incorporating a mounting device according to an embodiment of the present invention; FIG. 2 is a sectional view taken along line II-II in FIG. 1; FIG. 3 is an exploded perspective view, with a part broken away. of FIG. 1; and FIG. 4 is an exploded perspective view showing a modification of the mounting device of the embodiment.

6 Detailed Description of the Preferred Embodiment

An embodiment of the present invention will now be explained with reference to the drawings.

FIG. 1 shows a handle part of a disc grinder as an example of an electrical machinery or apparatus. A housing 1 of the disc grinder which forms the handle part is made of synthetic resin and are divided into housing halves la and lb. The housing halves la and lb are joined to each other and can be separated from each other in left and right directions (vertical direction as viewed in FIG. 2). A plurality of windows lc are formed in the rear portion of the housing 1, so that air can be introduced from the outside to the interior of the housing 1 through the windows lc. With such flow of air, a resistor 2 or other electrical components disposed within the housing 1 can be cooled. A fan (not shown) is provided within the housing 1 and is mounted on an output shaft of a motor (not shown), so that the cooling air is introduced into the housing 1 when the fan is rotatably driven by the motor.

The resistor 2 as an example of an electrical component is mounted within the housing 1 adjacent the windows lc. The resistor 2 is held between holder portions 3 which are formed integrally with inner surfaces of the housing halves la and lb, respectively. As will be best seen from FIG. 3, 7 each of the holder portions 3 includes four holder segments each including a base part 3e and an extension 3a. The extension 3a extends from the base part 3e in parallel to the longitudinal axis of the resistor 2. The base parts 3e are connected together In an X-like configuration. The extensions 3a are equally spaced from each other in the circumferential direction of the resistor 2 and extend along the resistor 2 to a position corresponding to substantially the central position of the resistor 2 in Its longitudinal direction. Each of the extensions 3a is spaced from the resistor 2 slightly in a diametrical direction of the resistor 2, so that a substantially cylindrical inner space 3c is defined by the extensions 3a for accommodating the resistor 2. Here, the extensions 3a are determined to have a length which is sufficient to hold the resistor 2 not to be removed from the space 3c or not to fall down when the resistor 2 is inserted into one of the housing halves la and 1b with its extensions 3a in an upstanding position during an assembling process.

Each of the base parts 3e has a guide surface 3b on the upper inner side thereof. The guide surface 3b is inclined upwardly outwardly and is connected to the inner surface of the corresponding extension 3a. Thus, the guide surfaces 3b of the base parts 3e cooperate to form a substantially conical bottom 3d of the inner space 3c within 8 which corresponding one of spring members 4 is received.

Each of the spring members 4 has one end secured to one end of the resistor 2 and has the other end adapted to be received within the bottom 3d of the inner space 3c of the corresponding holder portion 3. In this embodiment, the spring 4 is a coil spring made of stainless steel and has a substantially conical configuration having a diameter decreasing in a direction away from the resistor 2 or the direction toward the bottom 3d of the inner space 3c. Lead wires 2 are connected to both ends of the resistor 2.

In an assembled state of the housing 1 where the housing halves la and 1b are joined to each other, the holder portions 3 are opposed to and in alignment with each other, and the other end of each of the spring members 4 is pressed on the bottom 3d of the corresponding holder portion 3. Thus, the distance between the bottoms 3d of the holder portions 3 in the mounting state of the housing 1 is determined such that the spring members 4 are compressed to an appropriate degree. Otherwise, the length of the spring members 4 in a non-loaded state is determined such that the spring members 4 are compressed to the appropriate degree in the assembled state of the housing 1.

In addition, as explained previously. each of the extensions 3a is spaced from the resistor 2 slightly in the diametrical direction of the resistor 2. In other words, 9 the distance between two adjacent extensions 3a in the circumferential direction of the resistor 2 is determined such that the resistor 2 does not contact any of the extensions 3a in the mounting state. Thus, the diameter of the inner space 3c is determined to be greater than the diameter of the resistor 2.

The operation of the above embodiment will now be explained.

With this embodiment, the resistor 2 is assembled into the housing 1 with its both ends held by the holder portions 3 by means of the spring members 4 and the resistor 2 contacts only the spring members 4 and does not contact any other parts of the housing 1 including the extensions 3a of the holder portions 3. Therefore, although the heat produced in the resistor 2 may be conducted to the housing 1 via the spring members 4, the cooling air introduced from the outside through windows lc may pass through the inner spaces 3c of the receiving portions 3 and the springs 4 may not prevent the cooling air from passing therethrough. Therefore, a sufficient amount of the cooling air can flow between both ends of the resistor 2 and the housing 1.

Therefore, with this embodiment, the cooling efficiency of the resistor 2 by the air may be considerably improved in comparison with the conventional mounting device in which both ends of a resistor directly contact a housing as described in the description of the prior art. In addition, since the resistor 2 does not directly contact the holder portions 3, the holder portions 3 may not be heated to a high temperature.

Thus, the housing 1 and in particular, the holder portions 3 may not be deformed by heat even if the heat has been produced in the resistor 2.

In addition, since, In this embodiment, the spring members 4 are coil springs which have long wire length. the spring members 4 themselves have a greater heat radiation effect.

Further, since the spring members 4 are made of stainless steel which has a lower heat conductive efficiency in comparison with spring steel which is normally used as the material of a spring member, the conduction of heat produced in the resistor 2 to the holder portions 3 is reduced in this respect.

Furthermore, since the resistor 2 is held by the housing 1 by means of the spring members 4 with the spring members 4 being compressed to the appropriate degree, the resistor 2 can be reliably held in position without causing chatters. Thus, any vibrations or impacts produced in the disc grinder may be absorbed and reduced by the spring members 4, so that the resistor 2 can be protected from vibrations or impacts.

Further, in order to assemble the housing 1, the resistor 2 having the spring members 4 secured to both ends is inserted into the inner space 3c of the holder portion 3 of one of the housing halves la and 1b with the holder portion 3 in the upstanding position, so that the resistor 2 is held by the extensions 3c not to be fallen down. Then, the other of the housing halves la and 1b is overlapped with that one. Since the spring members 4 have a substantially conical configuration and since the guide surfaces 3b form the substantially conical bottom 3d of the inner space 3c of the holder portion 3, the spring members 4 are guided by their corresponding guide surfaces 3b in such a manner that the axes of the spring members 4 are automatically brought in alignment with the central axis of the inner spaces 3c. Therefore, the operation for mounting the resistor 2 on the housing 1 can be easily performed. In addition, since the resistor 2 can be mounted within the housing 1 without using screws or the like, the mounting operation can be easily performed in this respect.

The above embodiment may be modified in various manners. For example, each of the springs 4 may be replaced by a spring member 10 shown in FIG. 4. The spring member 10 includes two ring parts 10a and 10b and three leaf spring parts 10c. The leaf spring parts 10c are connected between the ring parts 10a and 10b and are spaced from each other in 12 the circumferential direction of the ring parts 10a and 10b. Each of the leaf spring parts 10c is bent to have an Sshaped configuration so that the leaf spring parts 10c can be resiliently deformed to vary the distance between the ring parts 10a and 10b. In this modification, the ring part 10a on the left side as viewed in FIG. 3 is adapted to be secured to one end of the resistor 2 and the ring part 10b on the left side is adapted to abut on the bottom 3b of the inner space 3c of the holder portion 3.

Also with this modification, the resistor 2 is supported by the housing 1 only by means of the spring members 10 and does not directly contact the housing 1. Therefore, the whole resistor 2 can be efficiently cooled by the air. so that this modification can provide the same function and effects as the above embodiment.

In addition, with the provision of the guide surfaces 3b of the holder portions 3, the axis of the resistor 2 may be automatically brought in alignment with the axis of the holder portions 3.

Further, since the spring members 10 are made of stainless steel as in the first embodiment, the conduction of heat from the resistor 2 to the holder portions 3 can be reduced.

Furthermore, although in the above embodiment, the resistor 2 is mounted within the housing 1 which can be 13 separated into the handle halves la and 1b by using the same mounting device of the above embodiment, the resistor 2 can be mounted within a housing having an integral structure and having a pair of holder portions formed on the inner surface of the housing and confronting each other. Thus, In this case, the resistor 2 can be mounted on the housing by inserting one of the spring members secured to the resistor into one of the holder portions and thereafter inserting the other of the spring members into the other of the holder portions with both spring members being compressed. With this construction, the same function and effects as the above embodiment can be obtained. Thus, the heat radiation efficiency as well as the operability for mounting the resistor 2 can be improved.

Although the above embodiment has been described in connection with a mounting device for mounting the resistor 2 within the housing of the electrical machinery or apparatus, the present invention can also be applied to a mounting device for mounting the resistor 2 or other electrical component on an outer side of the housing. Further, the present invention may also be applied to a mounting device for mounting the resistor 2 or other electrical component on an object such as a printed wiring board other than the housing. In such a case, a mounting device may include one spring member and one holder member 14 which cooperate to hold the electric component from only one side of the same.

While the invention has been described with reference to a preferred embodiment thereof, it is to be understood that modifications or variations may be easily made without departing from the spirit of this invention which is defined by the appended claims.

Claims

1. A mounting device for mounting an electrical component on an electrical machinery or apparatus, comprising:

spring means; and holder means for holding the electrical component by means of said spring means In a state that the electrical component does not contact any portions or parts of the electrical machinery or apparatus.

2. The mounting device as defined in claim 1 wherein said holder means serves to hold the electrical component relative to a housing of the electrical machinery or apparatus.

3. The mounting device as defined in claim 1 or 2 wherein said spring means comprises at least one spring member.

4. The mounting device as defined in claim 3 wherein the electrical component includes both ends positioned in opposite directions, and a pair of said spring members are provided and are disposed on both ends of the electrical component, so that said spring members bias the electrical component in opposite directions to each other.

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5. The mounting device as defined In claim 4 wherein the electrical machinery or apparatus is a power driven tool, and the electrical component is a resistor.

6. The mounting device as defined in claim 4 or 5 said holder means includes a pair of holder portions formed on the housing of the electrical machinery or apparatus for holding corresponding said spring members.

7. The mounting device as defined in claim 6 wherein each of said spring members has a substantially conical configuration having a diameter decreasing toward corresponding said holder portion, each of said holder portions includes a guide surface so as to form a substantially conical bottom, so that each of said spring members is held by corresponding said holder portion in a state that the axis of each of said spring members is in alignment with the axis of corresponding said holder portion with the aid of said guide surface.

8. The mounting device as defined in claim 7 wherein each of said holder portions Includes a base and an extension, said base having said guide surface. and said extension extending from said base toward the electrical component and partly surrounding the electrical component not to contact 17 4 the electrical component.

9. The mounting device as defined in claim 8 wherein each of said holder portions comprises a plurality of holder segments equally spaced from each other in the circumferential direction of the electrical component.

10. The mounting device as defined in any of claims 3 to 9 wherein said spring member is a coil spring.

11. The mounting device as defined in any of claims 3 to 10 wherein said spring member is made of stainless steel.

12. A mounting device for mounting an electrical component on electrical machinery or apparatus, such device being constructed and arranged substantially as hareinbefore described with reference to and an Illustrated in the accompanying drawings.

13. Electrical machinery or apparatus including an electrical component mounted thereon by a mounting device according to any preceding claim.

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