AU2015101847A4 - Insulation devices for motors and double commutators motors as well as lawn mowers containing the same - Google Patents

Abstract

INSULATION DEVICES FOR MOTORS AND DOUBLE COMMUTATORS MOTORS AS WELL AS LAWN MOWERS CONTAINING THE SAME Abstract The invention discloses a motor insulating apparatus suitable to be installed onto a motor. The motor includes a stator, a rotor and a motor casing circumferentially surrounding the stator and the rotor. The motor insulating apparatus contains a first insulating member disposed between the motor casing and a first commutator assembly member to insulate the motor casing and the first commutator assembly member from each other; and a second insulating member disposed between the motor casing and a second commutator assembly and insulating the motor casing and the second commutator assembly from each other. Also disclosed are a dual-commutator motor and a lawn mower including the aforesaid motor insulating apparatus. The motor insulating apparatus according to the present invention is capable of completely insulating two commutator assemblies of the AC/DC motor from the motor casing, in order to avoid damages to the motor components caused due to accidental electrical connection between the two commutator assemblies.

Description

- 1 INSULATION DEVICES FOR MOTORS AND DOUBLE COMMUTATORS MOTORS AS WELL AS LAWN MOWERS CONTAINING THE SAME TECHNICAL FIELD 5 The present invention relates to a power tool for outdoor use and, more particularly, relates to a lawn mower for trimming grasses on the lawn or greensward utilizing a cutting device. . 10 BACKGROUND ART Lawn mower is a power tool commonly used for trimming grasses on large tracts of land such as outdoor garden lawns or the like. In general, such lawn mower comprises a chassis onto which four wheels are installed so that it can 15 independently stand on the ground. In addition, a handle extending upwards is provided on the housing of the lawn mower, in order to facilitate the user to push the mower forward on the lawn. An electrical motor and control circuits, etc. are installed in the interior of the lawn mower, and the grass-cutting impellor is driven by the motor via mechanical transmission. During rotating of the grass-cutting 20 impellor, grass of excessive height is cut by the blades. A certain type of lawn mower utilizes AC/DC power supply, meaning that it can operate with a DC power supply such as batteries, as well as an AC power supply. The flexibility of such lawn mower is greatly enhanced since it can adapt to different power supply conditions. 25 Unfortunately, the existing AC/DC lawn mowers have drawbacks that the -2 motor is coupled to an AC circuit and a DC circuit simultaneously which may have mutual interference since they are characterized by different electrical parameters and circuit constructions. More particularly, if electric leakage or poor contact occurs, the power supplied by the AC power supply may be accidentally 5 introduced to the DC circuit and vice versa, in which case the respective components may be damaged and the circuits may malfunction. SUMMARY 10 Therefore, an embodiment of the present invention provides an alternative lawn mower which adopts an effective motor insulating apparatus capable of completely insulating two commutator assemblies of the AC/DC motor from the motor casing, in order to avoid damages to the motor components caused due to accidental electrical connection between the two commutator assemblies. 15 In another aspect, the present invention provides a motor insulating apparatus suitable to be installed onto a motor. The motor includes a stator, a rotor and a motor casing circumferentially surrounding the stator and rotor. The motor insulating apparatus contains a first insulating member disposed between the motor casing and a first commutator assembly member, and insulating the motor 20 casing and a first commutator assembly member from each other; and a second insulating member disposed between the motor casing and a second commutator assembly, and insulating the motor casing and a second commutator assembly from each other. Preferably, the motor insulating apparatus further contains a fixing assembly 25 by which the first and second insulating members are fixedly connected to each -3 other. More preferably, the fixing assembly has an equal or greater length than the motor casing in the axial direction of the motor. According to one implementation, the fixing assembly is a connection rod is a 5 connection rod connected to the first and second insulating members on its two ends respectively by threads. According to another implementation, the connection rod also fixedly connects the second insulating member to a flange used for fixing the motor. According to a variation, the connection rod also fixedly connects the first 10 insulating member to an end cap of the motor. According to one implementation, the first insulating member is an insulating ring having an inner diameter and an outer diameter configured such that an outer diameter of the motor casing is between the inner and outer diameters of the insulating ring. 15 According to another implementation, the second insulating member is an insulating ring having an inner diameter and an outer diameter configured such that an outer diameter of the motor casing is between the inner and outer diameters of the insulating ring. In another aspect, the present invention discloses a dual-commutator motor 20 including a stator, a rotor, a motor casing circumferentially surrounding the stator and rotor, and a first commutator assembly and a second commutator assembly disposed at both ends of the rotor. The dual-commutator motor further contains the motor insulating apparatus as described above. In another aspect, the present invention discloses a lawn mower comprising a 25 chassis, wheels installed on the chassis, a housing disposed on the chassis, a -4 motor disposed within the housing, a drive transmission connected to drive shaft of the motor, a cutting device connected to the drive transmission, and a handle mounted on the housing. The motor of the lawn mower is the dual-commutator motor as described above. 5 Therefore, the lawn mower provided by the present invention possesses many advantages as compared to the prior art. Due to the fact that an insulating ring is interposed between the motor casing and either of the two commutator assemblies disposed at both ends of the AC/DC motor in the lawn mower, any potential inductance or electric leakage between the motor casing and the two 10 commutator assemblies can be completely eliminated, preventing any mutual interference produced between the AC and DC circuits due to the motor casing. This guarantees circuit integrity of the motor, prevents damages to the internal components due to mismatched type power supply, and reduces the maintenance service while prolonging the service life. Moreover, the dual-insulation structure is detailed above is simple and can be easily implemented, and satisfies various industrial standards and laws and regulations in different countries and regions. BRIEF DESCRIPTION OF THE DRAWINGS 20 The function and advantages of the present invention can be further understood with reference to the remaining part of the specification and drawings in which the same component is indicated by the same reference number. In some situations, sub-markings are placed after a certain reference number to indicate one of multiple similar components. Every of the similar components are referred 25 to when a certain reference number is referred to without indicating any existing -5 sub-markings. Fig.1 is a perspective view showing appearance of a lawn mower according to a first embodiment of the present invention; Fig.2 is a bottom view of the lawn mower shown in Fig.1; 5 Fig.3 illustrates arrangement of the motor assembly included in the lawn mower shown in Fig.1 on the chassis; Fig.4 is a perspective view showing appearance of the motor assembly shown in Fig.3; Fig.5 is an exploded view of the motor assembly shown in Fig.4; 10 Fig.6a is an illustration showing the motor assembly shown in Fig.5, in which the insulating rings are separated from the motor casing after the end cap is removed; and Fig.6b is a perspective view taken from another angle of view of the motor assembly shown in Fig.6a. 15 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention describe a dual-commutator motor provided with an insulating apparatus and a lawn mower completely 20 eliminating the problems such as accidental electric leakage between the AC and DC circuits of the motor. Other benefits and advantages provided by respective embodiments of the present invention will be easily appreciated from the following description. Referring to Fig.1, the first embodiment of the present invention discloses a 25 four-wheel lawn mower containing a chassis 28, four wheels 24 arranged at both -6 sides of the chassis 28, a housing 22 installed on the chassis, a lower handle 26 and an upper handle 25 connected to a rear end of the chassis 28. The upper handle 25 has a substantially U shape, and lower ends of the upper handle 25 are connected to two lower handles 26 respectively, while the lower ends of the lower 5 handle are fixedly connected to both sides of the chassis 28. A motor cover 23 is disposed at front portion of the housing 22 and a controller 30 is mounted at top end of the upper handle 25. It shall be noted that the four wheels 24 are not completely the same in dimension. In fact, the two front wheels 25 have a smaller radius than the two rear wheels 24. In addition, a grass collection box 20 is 10 connected to rear of the housing 22. More particularly, the grass collection box 20 is disposed behind the rear wheels 24 of the lawn mower. As shown in Fig.2 which illustrates the bottom of the lawn mower shown in Fig.1, each pair of wheels 24 symmetrically opposing to each other at both sides of the lawn mower are connected via an axle. In addition, a strip-shaped blade 36 15 is disposed at a central position of the chassis 28 and fixed to the bottom of the lawn mower via a rotation shaft 38 at a central position of the blade 36. The blade 36 serves as a grass cutting device of the lawn mower. A vortex structure 32 is formed at center of the bottom 28 and an air intake 34 is formed in the vortex structure 32 at a position proximal to front end of the lawn mower. The air intake 20 34 serves to suck the grass clippings cut by the blade 36. Now referring to Fig.3, a motor assembly 40 is disposed at a position close to center of the bottom 28. It can be seen that the motor assembly 40 is disposed vertically with respect to the bottom 28. As shown in Fig.4, the appearance of the motor assembly 40 is separately illustrated. It shall be noted that for sake of clarity 25 and conciseness no internal cables connected to the motor assembly are shown.

-7 In the motor assembly 40 shown in Fig.4, the motor comprises a motor casing 48, an armature assembly mounted with the motor casing including a rotor, a stator, a rotation shaft or the like (not shown). In addition, at one end of the motor there is arranged a top cap 50 completely covering said end. Moreover, the top cap 50 is 5 connected via four connection rods 46 to a flange 42 installed on an end of the motor opposite to the top cap 50. These connection rods are also called fixing assembly in this embodiment. The flange 42 is provided with four connection bulges 43. The connection rods 46 are fixed to the flange 42 by threaded connections such as nuts and bolts (not shown). A plurality of screws 44 is 10 disposed on surface of the flange 42 along the circumference thereof at more peripheral positions with respect to the connection bulges 43, in order to fix the flange 42 to the bottom 28 of the lawn mower (as shown in Fig.3). Fig.5 is an exploded view illustrating certain components of the motor assembly shown in Fig.4. An end cap 60 is disposed at an end of the motor is proximal to the top cap 50. As well known to those skilled in the art, the end cap 60 serves to enclose rotation structure of the motor and provide bearings etc. to enable the stator to rotate within the stator. What makes the end cap 60 according to an embodiment of the present invention different is that the end cap 60 is formed with a plurality of through holes 61 along the circumferential direction. 20 These through holes 61 exactly corresponds to the ends of the connection rods 46 outside the motor casing 48 after the end cap 60 is mounted onto the motor. The connection rods 46 are fixed to the through holes 61 of the end cap 60 via several screws 59. Moreover, because the top cap 50 covers the end cap 60, the top cover 50 is also formed to have several bulges 63 according to height of the 25 screws 59, such that these bulges 63 can accommodate the height of the screws -8 59 after the motor assembly 40 is completely assembled. Also, Fig.5 shows two insulating rings 52 and 54 disposed at both ends of the motor assembly. In this embodiment, the insulating ring 52 is also called the first insulating member and the insulating ring 54 is also called the second 5 insulating member. The insulating ring 52 is interposed between the first commutator assembly 58 and the motor casing 48. The insulating ring 54 is interposed between the second commutator assembly 56 and the motor casing 48. Accordingly, in this embodiment the motor is called a dual-commutator motor. Each one of the insulating rings 52 and 54 has a larger outer diameter than the 10 motor casing 48. As shown in the figures, the connection rods 46 have a length substantively equal to the distance between the insulating rings 52 and 54. Since the insulating rings 52 and 54 are disposed outside to both ends of the motor casing 48, the connection rods 46 have an equal or greater length than the motor casing 48 in axial direction of the motor. In addition, the four connection rods 46 15 are outside the insulating rings 52 and 54, i.e., these four connection rods 46 delimitate the insulating rings 52 and 54 within the enclosure of the connection rods 46, such that the insulating rings 52 and 54 are fixed to both ends of the motor. In the above embodiment, the insulating rings 52 and 54 are made of 20 materials providing electrical insulation, as well known to those skilled in the art. The first commutator assembly 58 and the second commutator assembly 56 each contains an commutator fixedly connected to the motor shaft and rotate therewith, a brush connected to the motor casing etc., as well known to those skilled in the art and therefore are not detailed here. However, in the embodiment of the present 25 invention the first commutator assembly 58 and the second commutator assembly -9 56 correspond to two types of DC current, one of which is provided by batteries directly, and the other of which is provided through rectification of the AC current. These two types of DC current are of different magnitudes. Now referring to Figs.6a and 6b, in which the insulating rings 52 and 54 are 5 separated from both ends of the motor so as to better illustrate the connections therebetween. A rim of the motor casing 48 proximal to the first commutator assembly 58 is perfectly received in a recessed annular portion 61 formed in a corresponding surface of the insulating ring 52. Similarly, at the other end of the motor casing 48, i.e., the end proximal to the second commutator assembly 56, a 10 rim is perfectly received in a recessed annular portion 57 formed in a corresponding surface of the insulating ring 54. Note that each of the recessed annular portion 61 formed in the insulating ring 52 and the recessed annular portion 57 formed in the insulating ring 54, is defined by relatively higher sidewalls at both sides of the recessed annular portion. Such design enables the insulating 15 rings 52 and 54 to be exactly jacketed onto the end rims of the motor casing 48. It can be seen that each of the insulating rings 52 and 54 has an inner diameter and an outer diameter configured such that an outer diameter of the motor casing 48 is in a range between the inner and outer diameters of the insulating ring 52 or 54. Due to the presence of said two insulating rings 52 and 54, electric leakage 20 or interference will not occur between the motor casing 48 and the motor driving circuit presented by either one of the commutator assemblies during use of the lawn mower. Therefore, the possibility of the motor casing 48 acting as a common medium to put the two commutator assemblies at both ends of the motor into electrical connection is eliminated.

-10 In view the above describe embodiments, those skilled in the art will appreciate that other modifications, structures and equivalents may be used without departing the nature of the present invention. Accordingly, the above description shall not be construed as limiting the scope of the present invention as 5 defined in the appended claims. For example, although the above embodiments describe a motor insulating apparatus which utilizes dual insulating rings that are fixed to each other by screws with the aid of long connection rods outside the motor casing, the gist of the present utility mode lies in providing insulation to the two commutator 10 assemblies at both ends of the motor simultaneously. The shape and material of the insulating members, whether they are fixedly connected to each other and in which way they are connected may vary. The description of above embodiments would not hinder those skilled in the art utilizing other dual-insulation structures under the teachings of the present invention. 15 In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in 20 various embodiments of the invention. It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

Claims (10)

1. A motor insulating apparatus adapted to be installed onto a motor, the motor comprising a stator, a rotor, and a motor casing circumferentially surrounding the stator and the rotor, characterized in that the motor insulating apparatus comprises: a first insulating member disposed between the motor casing and a first commutator assembly member, and insulating the motor casing and a first commutator assembly member from each other; and a second insulating member disposed between the motor casing and a second commutator assembly, and insulating the motor casing and a second commutator assembly from each other.

2. The motor insulating apparatus according to claim 1, further comprises a fixing assembly by which the first and second insulating members are fixedly connected to each other.

3. The motor insulating apparatus according to claim 2, wherein the fixing assembly has an equal or greater length than the motor casing in an axial direction of the motor.

4. The motor insulating apparatus according to claim 3, wherein the fixing assembly is a connection rod connected to the first and second insulating members on its two ends respectively by threads.

5. The motor insulating apparatus according to claim 4, wherein the connection rod further fixedly connects the second insulating member to a flange configured for fixing the motor.

6. The motor insulating apparatus according to claim 4, wherein the connection rod further fixedly connects the first insulating member to an end cap of the motor. -12

7. The motor insulating apparatus according to claim 1, wherein the first insulating member is an insulating ring having an inner diameter and an outer diameter configured such that an outer diameter of the motor casing is between the inner and outer diameters of the insulating ring.

8. The motor insulating apparatus according to claim 1, wherein the second insulating member is an insulating ring having an inner diameter and an outer diameter configured such that an outer diameter of the motor casing is between the inner and outer diameters of the insulating ring.

9. A dual-commutator motor, comprising a stator, a rotor, a motor casing circumferentially surrounding the stator and the rotor, and a first commutator assembly and a second commutator assembly disposed at both ends of the rotor, characterized in that the dual-commutator motor further comprises the motor insulating apparatus according to any of claims 1 to 8.

10.A lawn mower comprising a chassis, wheels installed on the chassis, a housing disposed on the chassis, a motor disposed within the housing, a drive transmission connected to drive shaft of the motor, a cutting device connected to the drive transmission, and a handle mounted on the housing, characterized in that the motor is the dual-commutator motor according to claim 9.