A chainsaw with an automatic chain tensioning mechanism

Abstract

This invention discloses an automatically tensioning chainsaw, comprising a guide plate, an engine, a cylinder, a piston, a channel, and a one-way valve A. The engine is a crankcase-scavenging two-stroke engine. The cylinder is fixedly mounted on the outside of the engine. The piston is slidably mounted on one end of the cylinder, and has an extension on its outward-facing side. The free end of the extension abuts against the guide plate. The two ends of the channel lead to the inside of the crankcase of the engine and the inside of the cylinder, respectively. The one-way valve A is installed in the channel to open or close the channel. This invention has a simple structure, reliable operation, and can utilize the engine's air pressure to drive the guide plate, thus meeting the requirement of automatically adjusting the chain tension.

Description

Technical Field

[0001] This invention relates to the field of garden tool technology, specifically to a chainsaw with an automatic chain tensioning mechanism. Background Technology

[0002] Gardeners often need to prune shrubs or trim or fell trees, which requires the use of chainsaws. When working outdoors, gasoline-powered chainsaws are often used due to the inconvenience of power connections.

[0003] After a period of use, chainsaws often become loose, requiring adjustment of the chain tension. When the chain wears down to a certain extent, it needs to be replaced. Even after replacing the chain, the tension needs to be adjusted to ensure proper operation. Conventional chainsaws use bolts to secure the guide plate. When the chain is too loose or needs replacement, tools are used to loosen the bolts, the guide plate position is manually adjusted, and the position is determined by feel before tightening the bolts again. This process is relatively cumbersome and requires a certain level of skill and experience from the operator. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects and shortcomings of the existing technology and provide a chainsaw with a simple structure and reliable operation that automatically tensions the chain. It can use the air pressure of the engine to drive the guide plate to meet the requirements of automatically adjusting the chain tension.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] An automatic chain tensioning chainsaw, characterized in that it comprises a guide plate, a drive wheel, a chain, an engine, a cylinder, a piston, a channel, and a one-way valve A. The engine is a crankcase scavenging two-stroke engine, which drives the drive wheel to rotate. The chain is mounted on the guide plate and is driven to rotate by the drive wheel. The cylinder is fixedly mounted on the outside of the engine. The piston is slidably mounted on one end of the cylinder, specifically located inside the cylinder. The piston has a protrusion on its outward-facing side. The right end of the cylinder has an opening for the protrusion to extend outwards, and the free end of the protrusion abuts against the guide plate. The two ends of the channel lead to the inside of the crankcase of the engine and the inside of the cylinder, respectively. The one-way valve A is installed in the channel to open or close the channel.

[0007] The cylinder or piston is provided with a pressure relief hole, and a one-way valve B is installed inside the cylinder or on the inner side of the piston to open or close the pressure relief hole.

[0008] Furthermore, the outer wall of the engine is provided with screw holes, and a fixing bolt passes through the inside of the cylinder and is screwed into the screw holes to fix the cylinder to the outside of the engine.

[0009] Furthermore, the piston is provided with a seal at the junction with the cylinder.

[0010] Furthermore, the free end of the protrusion is provided with a groove, and the guide plate is provided with a slot at the position corresponding to the cylinder. The side edge of the slot facing the protrusion is inserted into the groove and abuts against the groove wall.

[0011] Furthermore, the cylinder is provided with guide grooves on both the upper and lower sides, and the upper and lower edges of the grooves are respectively slidably engaged with the guide grooves on the upper and lower sides.

[0012] Furthermore, the chainsaw with automatic chain tensioning also includes a drive wheel and a chain. The engine drives the drive wheel to rotate, and the chain is mounted on the guide plate and is driven to rotate by the drive wheel.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] 1. This invention introduces the pressure inside the engine crankcase into an external drive cylinder to drive the piston. This driving force automatically adjusts the position of the guide plate, thereby achieving automatic chain tensioning. There is no need to adjust the chain tension constantly during use. Only when the chain needs to be replaced, the pressure inside the cylinder is released, the guide plate is moved, and the chain is replaced. After replacement, the new chain tension can also be automatically adjusted.

[0015] 2. The piston and cylinder of the present invention have relatively free design in terms of shape and size. Different structures and sizes can be adopted for different power and other performance characteristics of engines and chainsaws to achieve different tension forces and meet the requirements of a series of products.

[0016] 3. The piston and cylinder of the present invention are provided with guide grooves on the outside, which contact and cooperate with the guide plate of the chainsaw, so as to provide good support, fixation, protection and guidance for the guide plate. Attached Figure Description

[0017] Figure 1 This is a front view of the structure of a first embodiment of an automatically tensioning chain chainsaw according to the present invention.

[0018] Figure 2 This is a cross-sectional view along line A-A of a first embodiment of an automatically tensioning chain chainsaw according to the present invention.

[0019] Figure 3 This is a schematic diagram of the cylinder, piston, and guide plate assembly structure of an embodiment of an automatically tensioning chain chainsaw according to the present invention.

[0020] Figure 4 This is a schematic diagram of a second embodiment of an automatically tensioning chain chainsaw according to the present invention.

[0021] Figure 5 This is a front view of the structure of a third embodiment of the chainsaw with an automatic chain tensioning according to the present invention.

[0022] Figure 6 This is a cross-sectional view along line A-A of a third embodiment of an automatically tensioning chain chainsaw according to the present invention.

[0023] Figure 7 This is a schematic diagram of a fourth embodiment of an automatically tensioning chain chainsaw according to the present invention.

[0024] Explanation of reference numerals in the attached diagram: 1-guide plate, 2-drive wheel, 3-cylinder, 4-piston, 5-fixing bolt, 6-channel, 7-chain, 8-engine, 9-one-way valve A, 10-one-way valve B, 11-pressure relief hole, 12-slot, 13-hollow bolt, 14-one-way valve, 15-slot, 16-guide groove. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] See Figure 1-3 In this embodiment, an automatically tensioning chainsaw includes a guide plate 1, a drive wheel 2, a chain 7, an engine 8, a cylinder 3, a piston 4, a channel 6, and a one-way valve A9. The engine 8 is a crankcase scavenging two-stroke engine. The engine 8 drives the drive wheel 2 to rotate. The chain 7 is mounted on the guide plate 1 and is driven to rotate by the drive wheel 2. The cylinder 3 is fixedly mounted on the outside of the engine 8. The piston 4 is slidably mounted on one end of the cylinder 3, specifically inside the cylinder 3. The piston 4 has an extension 41 on the outward side (right side). The right end of the cylinder 3 has an opening for the extension 41 to extend out. The free end of the extension 41 abuts against the guide plate 1. The two ends of the channel 6 correspond to the inside of the crankcase of the engine 8 and the inside of the cylinder 3, respectively. The one-way valve A9 is installed in the channel 6 to open or close the channel 6.

[0028] In this embodiment, the outer wall of the engine 8 is provided with a screw hole, and a fixing bolt 5 passes through the inside of the cylinder 3 and is screwed into the screw hole to fix the cylinder 3 to the outside of the engine 8.

[0029] In this embodiment, the piston 4 is provided with a seal (i.e., a sealing ring, not shown in the figure) at the joint with the cylinder 3 to improve the sealing effect and prevent gas leakage.

[0030] In this embodiment, the cylinder 3 is provided with a pressure relief hole 11, and a one-way valve B10 is installed inside the cylinder 3 to open or close the pressure relief hole 11. Thus, when the chain 7 is worn to a certain extent and needs to be replaced, the one-way valve B10 is opened with a tool to release the high-pressure gas in the cylinder 3, thereby relieving the tension on the chain 7 and allowing the chain 7 to be removed from the guide plate 1.

[0031] In this embodiment, the free end of the protrusion 41 is provided with a groove 12, and the guide plate 1 is provided with a slot 15 at the position corresponding to the cylinder 3 (the left side of the guide plate 1). The slot 15 is inserted into the groove 12 at one side edge of the protrusion (the right side edge of the slot 15) and abuts against the groove wall of the groove 12. Thus, the free end of the protrusion 41 abuts against the guide plate 1.

[0032] In this embodiment, guide grooves 16 are provided on both the upper and lower sides of the cylinder 3, and the upper and lower edges of the slot 15 are respectively slidably engaged with the guide grooves 16 on the upper and lower sides. Thus, the guide plate 1 can slide along the guide grooves 16.

[0033] When the engine (crankcase scavenging two-stroke engine) 8 is running, the piston of the engine 8 moves downwards using the scavenging function of its crankcase. After the intake port on the cylinder liner of the engine 8 is closed, the gas in the crankcase is compressed and the gas pressure increases. When the pressure in the crankcase is higher than the pressure in the cylinder 3, the one-way valve A9 opens, and the gas with a certain pressure enters the cylinder 3 through the one-way valve A9 and the passage 6, pushing the piston 4 to move to the right, pushing the guide plate 1 to move to the right in sync, and tensioning the chain 7.

[0034] This process occurs continuously during the operation of engine 8, especially before the clutch at drive wheel 2 engages, i.e., when engine 8 is running and the chainsaw is in the ready-to-work state. At this time, chain 7 is in a free, stationary state, thus allowing for natural chain tension. After the clutch at drive wheel 2 engages, i.e., when the chainsaw enters the working state, chain 7 is driven by drive wheel 2 to rotate. The rotation of chain 7 exerts a certain pressure on guide plate 1, which is transmitted through guide plate 1 to piston 4. Piston 4 compresses the gas in cylinder 3, causing one-way valve A9 to close, maintaining the tension of chain 7 during operation and preventing instability or even malfunctions caused by factors such as chain 7 loosening.

[0035] During the operation of the chainsaw, since the engine 8 is always running, when the chain 7 stretches due to factors such as loosening of its own mechanism, the pressure inside the cylinder 3 naturally drives the piston 4 to move to the right, pushing the guide plate 1 to move to the right as well. This ensures that the chain 7 always maintains a corresponding tension. That is, due to the action of the one-way valve A9, the pressure inside the cylinder 3 always maintains the maximum pressure inside the crankcase of the engine 8, thus maintaining a certain tension force to push the guide plate 1 to the right, ensuring that the chain 7 always maintains the corresponding tension. During this process, the one-way valve B10 remains closed.

[0036] When chain 7 wears to a certain extent and needs replacement, use a tool to open the one-way valve B10 to release the high-pressure gas in cylinder 3. At this point, push guide plate 1 to the left, and piston 4 will move to the left along with guide plate 1. Then release one-way valve B10, remove chain 7 from guide plate 1, and replace it with a new chain. No further operation is required. Then start engine 8. Utilizing the scavenging function of engine 8's crankcase, high pressure will be re-established in cylinder 3, pushing piston 4 and guide plate 1 to the right, thus tensioning the new chain. This process can be completed before the drive pulley 2 rotates. Therefore, when replacing chain 7 and re-tensioning the new chain, the chain is stationary; only guide plate 1 moves. The tensioning process is completed before chain 7 rotates, so no other abnormalities will occur. Replacing chain 7 requires virtually no experience or skill from the operator; the required tension can still be reliably achieved.

[0037] Example 2

[0038] See Figure 4 In this embodiment, the right end of the cylinder 3 is open, and the piston 4 is no longer located inside the cylinder 3, but outside the cylinder 3, that is, it is installed outside the open end of the cylinder 3 by sliding fit. The right side of the piston 4 has an extension 41 that closes the open end of the cylinder 3. The outer wall of the free end of the extension 41 abuts against the guide plate 1. The pressure relief hole 11 is located on the piston 4. The one-way valve B10 is no longer located inside the cylinder 3, but is located on the piston 4. The channel 6 is located inside the fixing bolt 5. At this time, the fixing bolt 5 passes through the inside of the cylinder 3 and is screwed into the screw hole, fixing the cylinder 3 to the outside of the engine 8. The channel 6 connects the inside of the engine 8 and the inside of the cylinder 3. When it is necessary to release the pressure inside the cylinder 3, it can be released through the one-way valve B10, or by loosening the fixing bolt 5 containing the channel 6, so that the channel 6 is connected to the outside, the pressure inside the cylinder 3 can be released.

[0039] The other parts are basically the same as in Example 1, and will not be described again here.

[0040] It should be noted that the fixing bolt 5 is equipped with a sealing element (i.e., a sealing ring, not shown in the figure) at the joint with the cylinder 3 to improve the sealing effect and prevent gas leakage.

[0041] Example 3

[0042] See Figure 5 , 6 In this embodiment, an automatically tensioning chainsaw includes a hollow bolt 13 mounted on an engine 8. The hollow bolt 13 has a channel 6 inside, and a one-way valve 14 is installed in the channel 6. One end of the channel 6 is open at the tail of the hollow bolt 13 and communicates with the inside of the crankcase of the engine 8. The other end of the channel 6 is open near the head of the hollow bolt 13 and communicates with the inside of a cylinder 3. The cylinder 3 is fixedly mounted on the outside of the engine 8 by the hollow bolt 13. The left end of the cylinder 3 is supported on a fixing bolt 5, and the right end of the cylinder 3 is open. A piston 4 is slidably mounted inside the open end of the cylinder 3. The right side of the piston 4 has a protrusion 41, and the free end of the protrusion 41 abuts against a guide plate 1. A chain 7 is mounted on the guide plate 1 and is driven to rotate by a drive wheel 2.

[0043] It should be noted that the hollow bolt 13 is provided with a sealing element (i.e., a sealing ring, not shown in the figure) at the joint with the cylinder 3 to improve the sealing effect and prevent gas leakage.

[0044] When the engine (crankcase scavenging two-stroke engine) 8 is running, the piston of the engine 8 moves downwards by utilizing the scavenging function of its crankcase. After the intake port on the cylinder liner of the engine 8 is closed, the gas in the crankcase is compressed and the gas pressure increases. When the pressure in the crankcase is higher than the pressure in the cylinder 3, the one-way valve 14 opens. Gas with a certain pressure enters the cylinder 3 through the one-way valve 14 and the channel 6 in the hollow bolt 13, pushing the piston 4 to move to the right, pushing the guide plate 1 to move to the right in sync, and tensioning the chain 7.

[0045] This process occurs continuously during engine operation, especially before the clutch at the drive pulley 2 engages, i.e., when the engine 8 is running and the chainsaw is in the ready-to-work state. At this time, the chain 7 is in a free, stationary state, thus allowing for natural chain tension. After the clutch at the drive pulley 2 engages, i.e., when the chainsaw enters the working state, the chain 7 is driven by the drive pulley 2 to rotate. The rotation of the chain 7 exerts a certain pressure on the guide plate 1, which is transmitted through the guide plate 1 to the piston 4. The piston 4 compresses the gas in the cylinder 3, at which point the one-way valve 14 closes, maintaining the tension of the chain 7 during operation and preventing instability or even malfunctions caused by factors such as a loose chain 7.

[0046] During the operation of the chainsaw, since the engine is always running, when the chain 7 stretches due to factors such as loosening of its own mechanism, the pressure inside the cylinder 3 naturally drives the piston 4 to move to the right, pushing the guide plate 1 to move to the right as well, so that the chain 7 always maintains the corresponding tension. That is, due to the action of the one-way valve 14, the pressure inside the cylinder 3 always maintains the maximum value of the pressure inside the engine crankcase, so it always maintains the effect of pushing the guide plate 1 to the right with a certain tension force, so that the chain 7 always maintains the corresponding tension.

[0047] When chain 7 wears down to a certain extent and needs replacement, loosen the hollow bolt 13 to open its internal channel 6 to the outside, releasing the high-pressure gas in cylinder 3. Then, push guide plate 1 to the left, and piston 4 will move to the left along with guide plate 1, removing chain 7 from guide plate 1. Replace with a new chain, and then tighten the hollow bolt 13. No other operations are required; simply ensure the seal between the hollow bolt 13 and cylinder 3 at the head of the hollow bolt 13, and the seal between cylinder 3, the hollow bolt 13, and engine 8 inside cylinder 3. Then start engine 8. Utilizing the scavenging function of engine 8's crankcase, high pressure will be re-established in cylinder 3, pushing piston 4 and guide plate 1 to the right, thus tensioning the new chain 7. Therefore, for operators, there are virtually no experience or skill requirements; the chain 7 can still be reliably tensioned to the desired level.

[0048] Example 4

[0049] See Figure 7 In this embodiment, the right end of the cylinder 3 is open, and the piston 4 is no longer located inside the cylinder 3, but outside the cylinder 3. That is, it is installed outside the open end of the cylinder 3 by sliding fit. The right side of the piston 4 has a protrusion 41 that closes the open end of the cylinder 3. The outer wall of the free end of the protrusion 41 abuts against the guide plate 1. Other parts are basically the same as in embodiment 3, and will not be described again here.

[0050] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0051] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A chainsaw with an automatic chain tensioning mechanism, characterized in that: The system includes a guide plate, a drive wheel, a chain, an engine, a cylinder, a piston, a channel, and a one-way valve A. The engine is a crankcase-scavenging two-stroke engine that drives the drive wheel to rotate. The chain is mounted on the guide plate and is driven to rotate by the drive wheel. The cylinder is fixedly mounted on the outside of the engine. The piston is slidably mounted on one end of the cylinder, specifically located inside the cylinder. The piston has a protrusion on its outward-facing side. The right end of the cylinder has an opening for the protrusion to extend outwards, and the free end of the protrusion abuts against the guide plate. The two ends of the channel lead to the inside of the crankcase of the engine and the inside of the cylinder, respectively. The one-way valve A is installed in the channel to open or close the channel. The cylinder or piston is provided with a pressure relief hole, and a one-way valve B is installed inside the cylinder or on the inner side of the piston to open or close the pressure relief hole.

2. The chainsaw with an automatic chain tensioning mechanism according to claim 1, characterized in that: The outer wall of the engine is provided with screw holes, and a fixing bolt passes through the inside of the cylinder and is screwed into the screw holes to fix the cylinder to the outside of the engine.

3. A chainsaw with an automatically tensioned chain according to claim 1, characterized in that: The piston is provided with a seal at the joint with the cylinder.

4. A chainsaw with an automatically tensioned chain according to claim 1, characterized in that: The free end of the protrusion is provided with a groove, and the guide plate is provided with a slot at the position corresponding to the cylinder. The side edge of the slot facing the protrusion is inserted into the groove and abuts against the groove wall.

5. A chainsaw with an automatically tensioned chain according to claim 4, characterized in that: The cylinder is provided with guide grooves on both the upper and lower sides, and the upper and lower edges of the grooves are respectively slidably engaged with the guide grooves on the upper and lower sides.

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