Patent Description:
The lawn mower is a common garden tool. When a working area is large it will take a lawn mower with a single and small-size blade a lot of time to mow a lawn. However, if a large-sized lawn mower is used, there will be two problems. Firstly, as the blade is heavy, the current is high and the energy consumption will increase, but the working time will be reduced. Secondly, when the large blade is rotated, the mower will more easily vibrate, which affects the life of the machine.

In prior art, in order to solve the above-mentioned problems, two small size blades are provided on the lawn mower, and the two blades can be rotated simultaneously by a gear box or belt. In addition, in order to cut the grass between the two blades, when the mower working, the cutting range of the two blades is configured to partially overlap. The two blades must be kept at a certain angle during operation.

<CIT> discloses a supporting and driving assembly for a blade carrier disc of a rotary multiple disc mowing machine. Following an impact of the blades of the disc with an external body the blade carrier disc and a hub fixed to the blade carrier disc are rotationally disengaged from a plate that transfers rotary movement for a shaft.

<CIT> discloses a power transmission for a mower, which when a load acts on the cutting blades of the mower disengages the driving source.

<CIT> discloses a resilient spacer element inserted between the drive shaft mounting bolt and the central aperture of a horizontal cutting blade, such that when one end of the rotating cutting blade contacts an object the shear stress will cause the axis of the cutting blade to shift relative to the axis of the shaft rather than break or bend the shaft and mounting bolt.

<CIT> discloses a blade mounting structure of a lawn mower, including a drive hub mounted on an output shaft. A friction member for transmitting driving force from the drive hub to a blade holder is provided and a energy absorbing member is disposed in the space defined by the blade holder and peripheral members. The energy absorbing member maintains its shape during normal operation but is deformable when a load acts on the energy absorbing member.

In addition, in order to reduce noise, plastic gears are used. However, there may be obstacles like stone on the lawn. When the cutting blade rotates at high speed and hits a hard obstacle, the reaction force of the obstacle will cause the blade to stop rapidly and the blade, the gear box or the motor will be damaged.

Therefore, it is necessary to provide a lawn mower to solve the problems mentioned.

An object of the present disclosure is to provide a lawn mower with an impact protection function.

In order to achieve the above object, the present disclosure adopts the following technical solution: A lawn mower, which comprises a driving assembly, an impact protection assembly, a transmission assembly comprising a first gear connected to a motor shaft and a second gear meshed with the first gear and a cutting assembly comprising a first blade connected to the second gear. The driving assembly comprises a motor. The impact protection assembly comprises a pressing member and an elastic piece. The pressing member is arranged to press the elastic piece against the transmission assembly and drive the transmission assembly and the cutting assembly to rotate synchronously with a motor shaft. When the resistance received by the cutting assembly is greater than a predetermined value, a relative rotation occurs between the transmission assembly and the motor shaft. The impact protection assembly further comprises a pressing block and a friction plate, and the elastic piece, the pressing block and the friction plate are sequentially clampable by the pressing member and the first gear. The first gear comprises a gear connection member and a gear ring fixed on the gear connection member, and the friction plate is in contact with the gear connection member.

In one embodiment, the transmission assembly further comprises a third gear and a fourth gear, and the third gear meshes with the first gear and the fourth gear respectively, and the cutting assembly further comprising a second blade connected to the fourth gear.

In one embodiment, the second gear and the third gear are located on opposite sides of the first gear respectively, and the fourth gear is arranged away from the first gear.

In one embodiment, the first gear, the second gear, the third gear and the fourth gear all rotate in the same plane, and the first blade and the second blade rotate perpendicular to each other and rotate in the same plane.

In one embodiment the friction plate is a copper plate.

In one embodiment, the motor further comprises a shaft sleeve fixed on the motor shaft, one end of the shaft sleeve is provided with a groove for mounting the pressing member, and the other end is provided with a protrusion in the radial direction, the elastic piece, the pressing block, the friction plate and the gear connection member are sequentially sleeved on the shaft sleeve and pressed between the pressing member and the protrusion, the pressing member is an opening retaining ring.

In one embodiment, the transmission assembly further comprises a gear box for receiving the four gears, and the gear box is provided with an opening for installing the driving assembly, and the driving assembly included a bracket that mates with the opening to mount the driving assembly on the gear box.

In one embodiment, the lawn mower further comprises a control unit configured to stop the driving assembly in response to that the current of the lawn mower is higher than a predetermined threshold, when a relative rotation occurs between the transmission assembly and the motor shaft.

It can be known from the above technical solutions that the lawn mower of the present disclosure provides an impact protection assembly between the driving assembly and the transmission assembly, so that when the reaction force of the cutting assembly by an external obstacle is greater than the frictional force of the impact protection assembly, the relative rotation between the transmission assembly and the motor shaft is generated, thereby achieving the purpose of protecting the transmission assembly.

In order to make the objectives, technical solutions, and advantages of the present disclosure clear, the following describes the present disclosure in detail with reference to the accompanying drawings and specific embodiments.

With reference to <FIG> and <FIG>, the invention provides a lawn mower, which comprises a main body <NUM>, a rear walking wheel <NUM>, a front walking wheel <NUM>, and a push rod <NUM>.

Please further refer to <FIG>, the main body <NUM> comprises a housing <NUM>, a driving assembly <NUM> disposed in the housing <NUM>, a transmission assembly <NUM>, an impact protection assembly <NUM> which is located between the driving assembly <NUM> and the transmission assembly <NUM>, a cutting assembly <NUM> which is located under the housing <NUM> and is connected to the transmission assembly <NUM>, and a control unit (not shown). The rear walking wheel <NUM> and the two front walking wheels <NUM> are disposed below the housing <NUM>. The push rod <NUM> is provided at the rear of the housing <NUM>. The push rod <NUM> is preferably a U-shaped structure, which comprises a left handle and a right handle extending rearward and upward along the rear portion of the housing <NUM>. The left and right handles are connected by a cross bar. The handles and the cross bar may be integrally formed or assembled together. A driving switch and a self-propelled switch are fixed on the push rod <NUM>. The driving switch is used to control the driving assembly <NUM>. The self-propelled switch is used to control the movement of the lawn mower.

Referring to <FIG> and <FIG>, the driving assembly <NUM> is a motor, the motor comprises a motor shaft <NUM>, a shaft sleeve <NUM> fixed to the motor shaft <NUM> and a bracket <NUM>. The bracket <NUM> is mounted on the motor shaft <NUM> through a bearing <NUM>. The shaft sleeve <NUM> is specifically fixed at the lower end of the motor shaft <NUM> by screws <NUM>. In the radial direction, the motor shaft <NUM> and the shaft sleeve <NUM> are fixed together by a flat key <NUM>.

The transmission assembly <NUM> is used to transmit the power of the motor to the cutting assembly <NUM>. Please refer to <FIG> and <FIG>. Specifically, the transmission assembly <NUM> comprises a first gear <NUM> connected to the motor shaft <NUM> and a second gear <NUM> meshed with the first gear <NUM>. Preferably, the transmission assembly <NUM> further comprises a third gear <NUM> and a fourth gear <NUM>. The third gear <NUM> meshes with the first gear <NUM> and the fourth gear <NUM>, and the second gear <NUM> and the third gear <NUM> are respectively located on the opposite sides of the first gear <NUM>. The fourth gear <NUM> is arranged away from the first gear <NUM>. The first gear <NUM>, the second gear <NUM>, the third gear <NUM> and the fourth gear <NUM> all rotate in the same plane.

The cutting assembly <NUM> comprises a first blade <NUM> connected to the second gear <NUM> and a second blade <NUM> connected to the fourth gear <NUM>. The first blade <NUM> is connected to the second gear <NUM> through a first connection shaft <NUM>, and the second blade <NUM> is connected to the fourth gear <NUM> through a second connection shaft <NUM>. The first blade <NUM> and the second blade <NUM> rotate in the same plane. In this way, the distance between the first blade <NUM> and the second blade <NUM> is increased, so that no collision occurs between the two blades during operation. During installation, the first blade <NUM> and the second blade <NUM> are at a certain angle, preferably <NUM> degree. As the first blade and second blade are rotated with the same speed, collision between the first blade <NUM> and the second blade <NUM> is avoided while mowing the lawn. In other embodiment, the number and layout of gears and blades can be set according to actual needs, which is not limited herein.

With reference to <FIG>, the transmission assembly <NUM> preferably further comprises a gear box for receiving the above four gears, and the motor is at least partly located above the gear box. Specifically, the gear box comprises an upper box <NUM> and a lower box <NUM>. The upper box <NUM> is provided with an opening <NUM>, and the bracket <NUM> is mounted on the opening <NUM>. In this way, the lower end of the motor shaft <NUM> extends into the gear box through the opening <NUM> and is fixed to the first gear <NUM>. The lower box <NUM> is provided with through holes through which the first connecting shaft <NUM>, corresponding to the second gear <NUM>, and the second connecting shaft <NUM>, corresponding to the fourth gear <NUM>, are connected to the cutting blades.

With reference to <FIG>, <FIG> and <FIG>, the impact protection assembly <NUM> comprises a pressing member <NUM> and an elastic piece <NUM>. The pressing member <NUM> presses the elastic piece <NUM> against the first gear <NUM>, and the first gear <NUM> is connected to the motor shaft through the elastic piece <NUM>. There is friction between the motor shaft <NUM> and the first gear <NUM>. The first gear <NUM> is driven through friction between the motor shaft and the first gear <NUM>. When the resistance received by the cutting assembly <NUM> is greater than a predetermined value, the first gear <NUM> and the motor shaft <NUM> will rotate relative each other. The impact protection assembly <NUM> further comprises a pressing block <NUM> and a friction plate <NUM> mounted between the elastic piece <NUM> and a gear connection member <NUM>. The friction plate <NUM> is preferably a copper plate, which increases the frictional force between the elastic member <NUM> and the first gear <NUM>.

With reference to <FIG> and <FIG>, the first gear <NUM> comprises a gear connection member <NUM> and a gear ring <NUM>. The gear ring <NUM> is specifically fixed on the gear connection member <NUM> by five screws <NUM>. The pressing member <NUM>, the elastic piece <NUM>, the pressing block <NUM>, the friction plate <NUM> and the gear connection member <NUM> are sleeved on the shaft sleeve <NUM> in that order. The elastic piece <NUM>, the pressing block <NUM>, the friction plate <NUM> and the gear connection member <NUM> are clamped by the pressing member <NUM> and the shaft sleeve <NUM>. The friction plate <NUM> is in contact with the gear connection member <NUM>. Specifically, as shown in <FIG>, the pressing member <NUM> is an opening retaining ring. The upper end of the shaft sleeve <NUM> is provided with a groove <NUM> for mounting the pressing member <NUM>. The pressing member <NUM> is fixed on the upper end of the shaft sleeve <NUM> through the groove <NUM>. The lower end of the shaft sleeve <NUM> is provided with a protrusion <NUM> for blocking the gear connection member <NUM>. The elastic piece <NUM>, the pressing block <NUM>, the friction plate <NUM> and the gear connection member <NUM> are clamped by the pressing member <NUM> and the protrusion <NUM>. In addition, the frictional force of the elastic piece <NUM> can be set by setting the position of the groove <NUM> on the sleeve <NUM>.

When the resistance received by the cutting assembly <NUM> is bigger than the frictional force of the elastic piece <NUM>, a relative rotation is caused between the first gear <NUM> and the motor shaft <NUM>. That is, the resistance of obstacles passes through the second gear <NUM> or the third gear <NUM> to the first gear <NUM>, and is then transmitted to the elastic piece <NUM> through the gear connection member <NUM>. Since the frictional force between the elastic piece <NUM> and the gear connection member <NUM> is smaller than the resistance, the rotation of the gear connection member <NUM> and the first gear <NUM> is stopped. The motor shaft <NUM> is still in a rotating state at this time, which causes slippage, so the teeth of each gear will not be damaged.

In the present disclosure, the control unit is used to control the driving assembly <NUM>, specifically being a PCB board. When the transmission assembly <NUM> and the motor shaft <NUM> rotate relative each other (i.e., slip), the output power of the motor is larger than during normal operation, and the current increases. When the current of the lawn mower is higher than a set threshold, the control unit controls the driving assembly <NUM> to stop. In one embodiment, the threshold value is set to 30A. This can effectively protect the motor and the gears.

The motor drives the gears to rotate, thereby driving the first blade <NUM> and the second blade <NUM> to rotate for cutting. When the first blade <NUM> or the second blade <NUM> are stopped by an obstacle, the reaction force of the obstacle will be transmitted to the second gear <NUM> or the third gear <NUM> and the fourth gear <NUM> through the first connecting shaft <NUM> or the second connecting shaft <NUM>, respectively, and further transmitted to the first gear <NUM>. Since the first gear <NUM> and the shaft sleeve <NUM> are pressed and fixed together by the elastic piece <NUM> and the gear connection member <NUM>, there will be no relative rotation between the first gear <NUM> and the motor shaft <NUM> when the reaction force transmitted to the first gear <NUM> is greater than the frictional force of the elastic piece <NUM>, which will prevent damaging the gear. At this moment, the current increases and when the current of the lawn mower is higher than a predetermined threshold, the control unit controls the driving assembly <NUM> to stop.

In summary, the lawn mower of the present disclosure provides an impact protection assembly between the driving assembly and the transmission assembly, so that when the reaction force of the cutting assembly caused by an external obstacle is greater than the frictional force of the impact protection assembly, the relative rotation between the transmission assembly and the motor shaft occurs, and then the purpose of protecting the transmission assembly is achieved. In addition, the number of blades is set to two, which improves the working efficiency of the lawn mower.

Claim 1:
A lawn mower, comprising:
a driving assembly (<NUM>), comprising a motor;
an impact protection assembly (<NUM>), comprising a pressing member (<NUM>) and an elastic piece (<NUM>);
a transmission assembly (<NUM>), comprising a first gear (<NUM>) connected to a motor shaft (<NUM>) and a second gear (<NUM>) meshed with the first gear (<NUM>),
a cutting assembly (<NUM>) comprising a first blade connected to the second gear (<NUM>);
wherein the pressing member (<NUM>) is arranged to press the elastic piece (<NUM>) against the transmission assembly (<NUM>) and drive the transmission assembly (<NUM>) and the cutting assembly (<NUM>) to rotate synchronously with the motor shaft (<NUM>), such that the transmission assembly (<NUM>) and the motor shaft (<NUM>) rotate relative each other, when the resistance received by the cutting assembly (<NUM>) is greater than a predetermined value;
characterized in that the impact protection assembly (<NUM>) further comprises a pressing block (<NUM>) and a friction plate (<NUM>), and the elastic piece (<NUM>), the pressing block (<NUM>) and the friction plate (<NUM>) are sequentially clampable by the pressing member (<NUM>) and the first gear (<NUM>) and in that the first gear (<NUM>) comprises a gear connection member (<NUM>) and a gear ring (<NUM>) fixed on the gear connection member (<NUM>), and the friction plate (<NUM>) is in contact with the gear connection member (<NUM>).