Battery-powered chainsaws equipped with one or more handle heating elements

Abstract

The present disclosure relates to a battery-powered chain saw (1) comprising a cutting tool in the form of a saw chain (4) running on a guide bar, a front handle (7) extending at least partially transverse to the length of the guide bar, and a rear handle (5) extending at least partially approximately in the longitudinal direction of the guide bar. A battery-operated heating unit comprises a first heating element (15) in the rear handle, a second heating element (13) in the front handle, and a temperature sensor (17) located in the rear handle or the front handle. The heating unit (19) is configured to provide power to the first and second heating elements based on a reading from the temperature sensor (17). Upon start-up, a temporary power boost is provided to the first and second heating elements, followed by a steady state power lower than the power of the power boost.

Description

[Technical Field]

[0001] The present disclosure relates to a battery-powered chainsaw comprising a cutting tool in the form of a saw chain traveling on a guide bar, a front handle extending at least partially transverse to the length of said guide bar, and a rear handle extending at least partially generally longitudinally of said guide bar. [Background technology]

[0002] Such battery-powered chainsaws have become increasingly popular due to improvements in battery technology, and in many cases have replaced internal combustion engine-powered chainsaws, especially when the saw is only used occasionally (such as for hobby use) or when light weight is particularly important (such as for tree-climbing arborists).

[0003] To achieve a more comfortable use of the chainsaw, it has been desired to provide a heated handle even in battery-powered chainsaws, but this can be difficult in view of the power limitations caused by the use of batteries. Summary of the Invention [Problem to be solved by the invention]

[0004] Accordingly, it is an object of the present disclosure to provide a battery-powered chainsaw that has handle heating capabilities in an efficient manner. [Means for solving the problem]

[0005] This object is achieved by a battery-powered chainsaw as set forth in claim 1. More specifically, in a battery-powered chainsaw of the first-mentioned type, a battery-powered heating unit is provided that includes one or more heating elements in one of the rear handle and the front handle, and a temperature sensor. The heating unit is configured to supply power to one or more of the handles based on an indication from the temperature sensor. The heating unit is also configured to provide a temporary power boost upon startup. The heating unit then provides a steady-state power that is lower than the power of the power boost. This allows the chainsaw to relatively quickly achieve a suitably heated handle without draining the battery too rapidly during extended use.

[0006] The battery-operated heating unit may include a first heating element in the rear handle and a second heating element in the front handle. The temperature sensor may be located, for example, in the rear handle.

[0007] If two heating elements (the first heating element and the second heating element) are provided, they may be connected in series. The duration and level of the power boost may be determined based on a temperature reading taken at start-up or startup of the chainsaw. Alternatively, the power boost may be continuously controlled, for example based on a PI controller.

[0008] The chainsaw may include a compartment for a battery and, optionally, a short-range communication interface. [Brief explanation of the drawings]

[0009] [Figure 1] A diagram showing the body of a battery-operated chainsaw. [Figure 2] FIG. 2 shows the chainsaw of FIG. 1 with the heated area highlighted. [Figure 3]FIG. 10 is a diagram showing wiring related to steering wheel heating. [Figure 4] A diagram showing the heating of the rear handle. [Figure 5] 10 is a flow chart showing the supply of power to the handle. DETAILED DESCRIPTION OF THE INVENTION

[0010] Chainsaws with heated handles are highly valued by professional forestry workers, especially in cold climates. Because chainsaws are operated by firmly gripping the chainsaw handle, heat is transferred very efficiently from the user's hands, even when wearing gloves, resulting in uncomfortably cold hands unless the chainsaw handle is heated.

[0011] In the early days, chainsaws were provided with handles in which a portion of the exhaust from the chainsaw's internal combustion engine was directed through the handle, thereby heating the handle. In more recent developments, a small generator is connected to the internal combustion engine, and the electrical energy generated thereby is used to heat the chainsaw handle. However, in battery-powered chainsaws, available energy is scarcer. Despite significant improvements in battery technology in recent decades, its energy density is very low compared to gasoline, and batteries, by definition, require access to an electrical grid or the like to be charged. Using a large portion of the available energy for handle heating is not a viable option. Therefore, a more careful approach is required to achieve handle heating in battery-powered chainsaws, as explained below.

[0012] FIG. 1 shows a chainsaw 1 powered by a battery 3. The battery 3 is replaceably housed in a battery compartment 6. The chainsaw 1 has a general configuration similar to that of a conventional chainsaw powered by an internal combustion engine, including a guide bar 2 on which a saw chain 4, driven by an electric motor, runs. The chainsaw 1 also includes a rear handle 5 and a front handle 7. The rear handle 5 is intended to be held by a user's right hand and includes a lock button 9. The lock button 9 must be depressed to enable activation of a throttle button 10. The throttle button 10 is operated by the user's index and middle fingers or by the user's thumb, depending on the orientation of the chainsaw 1. The front handle 7 is intended for left-handed use, and the left hand can be positioned in various locations along the front handle 7 depending on the operation being performed.

[0013] Handle heating may be controlled by a user interface 11, including, for example, buttons. Figure 2 highlights the areas of the rear handle 5 and the front handle 7 that can be heated as a result. However, if lower power consumption is desired, it is possible to heat only a smaller portion of the front handle 7. Alternatively, it is also possible to heat only one handle (such as the rear handle 5).

[0014] Instead of or in combination with setting the heating using the illustrated user interface 11, for example, the chainsaw 1 may be provided with a short-range communication interface (such as Bluetooth®) to control the heating using a nearby smartphone. It is also possible to store user-specific settings that are activated based on identifying the current user, and to set the desired temperature based on that. As yet another option, the current usage situation (e.g., felling or cutting firewood) may be identified and the temperature setting based on that usage. Figure 3 shows the wiring of the handle heating unit 19, which is connected to the chainsaw's normal electrical system 18. This wiring is used to control the chainsaw motor and is therefore also considered to include the heating unit 19. Accordingly, the front and rear handles 7, 5 are provided with resistive heating elements 13, 15, respectively. These resistive heating elements are sized according to the specific heat of the respective handles and the expected radiation from the handles 5, 7. Accordingly, the resistive heating wire 13 in the front handle 7 is configured to generate more heat for a given setting in larger front handles and is made of a metal that radiates heat to a greater extent. However, it is possible to drive a single current by connecting both heating wires 13, 15 in series.

[0015] Heating may be provided by means of resistive heating wires or by a conductive resistor on a printed circuit board. Typically, in the rear handle, about 1.2 m of copper conductor may be provided, printed in a serpentine pattern on a circuit board.

[0016] Figure 4 shows in more detail the heating of the rear handle 5 through which the heating conductor 15 passes. A temperature sensor 17 is located in the rear handle to provide an instantaneous temperature reading. Alternatively, the sensor 17 could be located in the front handle 7, or a temperature sensor could be located in each handle.

[0017] The sensor may typically be an NTC resistor, although other components such as PTC or RTD resistors are also contemplated. In principle, it is also possible to measure the voltage drop across one of the heating elements to provide a temperature reading.

[0018] However, locating the temperature sensor 17 in the rear handle is more convenient for manufacturing, as the rear handle is typically made of plastic and may have a removable shell portion (removed in FIG. 4) to facilitate installation in the handle 5. In contrast, the front handle 7 is typically made from bent metal tubing. Also, using only one temperature sensor for both handles as shown naturally reduces costs compared to using two or more sensors while still being able to implement the control scheme described below. Note that in some versions of the control scheme described below, it may be useful to locate the sensor elsewhere than in the handle.

[0019] Thus, very generally and with reference to Figure 1, the present disclosure provides a battery powered chainsaw 1 comprising a cutting tool, typically in the form of a saw chain 4 running on a guide bar 2. A front handle 7 extends at least partially transverse to the length of the guide bar 2 and a rear handle 5 extends at least partially approximately longitudinally of the guide bar 2. With reference to Figure 3, the battery operated heating unit comprises a first heating element 15 in the rear handle 5, a second heating element 13 in the front handle 7 and a temperature sensor 17.

[0020] The following control mechanism is configured to provide comfortable handle heating without excessively wasting battery power. When a user first begins operating a chainsaw, the handle is likely to be near the same temperature as the ambient air, which may be several degrees below zero in winter conditions. This can be very uncomfortable, especially if the user is wearing thin gloves or no gloves at all. Therefore, it is desirable to rapidly increase the temperature at the handle 5,7 by supplying a high-energy flow to the handle 5,7.

[0021] However, as the handle approaches a comfortable temperature, it may be preferable to conserve battery power instead, and after some time of physical activity, the user may find a somewhat cooler handle more comfortable.

[0022] Thus, in the present disclosure, the heating unit 19 is configured to provide power to the first heating element 15 and the second heating element 13 based on readings from the temperature sensor 17. More specifically, upon start-up, the heating unit 19 provides a temporary power boost to the first and second heating elements 15, 13. Subsequently, a steady-state power lower than the power of the power boost can be provided to the first heating element 15 and the second heating element 13. In a very basic manner, this can be visualized by the flowchart of FIG. 5, which shows step 41 of providing a power boost, followed by step 43 of providing steady-state power.

[0023] There are different, more specific ways to achieve this. In a first example, the temperature can be measured by sensor 17 upon start-up or startup of chainsaw 1 and a duration and / or level of power boost (e.g., providing about 60 W for a few minutes, then delivering a steady state level of, say, 15-20 W) can be determined for as long as the chainsaw is running or until the battery is depleted to a predetermined level. As a comparison, a chainsaw motor may function in the range closer to 1.5 kW.

[0024] This power supplied to the handles 5, 7 may be supplied using a stored look-up table based on temperature readings or using a very basic algorithm, where the ambient temperature at start-up or startup of the chainsaw is a critical parameter, and temperature measurements can be made elsewhere on the saw other than at one of the handles, if desired.

[0025] In another example, temperature sensor 17 is located on one of handles 5, 7, as shown in FIG. 4, and the power boost can vary depending on the instantaneous temperature. For example, a desired target temperature for sensor 7 can be set, and the applied power can be controlled based on the difference between the desired temperature and the actual temperature, using, for example, a PI or PID controller. The power boost then continues until the target temperature is reached, with the applied power decreasing as the measured temperature approaches the target temperature at which steady-state power is supplied. Of course, such a control scheme can be modified in various ways, such as disabling the handle heating function entirely when the ambient temperature is above a predetermined threshold.

[0026] The invention is not limited to the described embodiments but may be varied and modified in various ways within the scope of the appended claims.

Claims

1. A battery-powered chainsaw (1) comprising: a cutting tool in the form of a saw chain (4) running on a guide bar (2); a front handle (7) extending at least partially transverse to the length of said guide bar (2); a rear handle (5) extending at least partially generally in the longitudinal direction of said guide bar (2); and a battery (3); a battery-operated heating unit (19) comprising one or more heating elements (13, 15) in one of the rear handle (5) and the front handle (7) and a temperature sensor (17); The battery (3) is configured to drive the saw chain (4) and is connected to the heating unit (19); the heating unit (19) is configured to supply power to a first heating element (15), a second heating element (13), or both of the one or more heating elements based on a reading from the temperature sensor (17); The battery-powered chainsaw (1), wherein the heating unit (19) is configured to supply a temporary power boost to the first heating element (15), the second heating element (13), or both at startup, and subsequently supply a steady-state power to the first heating element (15), the second heating element (13), or both that is lower than the power of the power boost.

2. 2. The battery-powered chainsaw (1) of claim 1, wherein the battery-operated heating unit (19) comprises a first heating element (15) on the rear handle (5) and a second heating element (13) on the front handle (7).

3. 2. The battery-powered chainsaw (1) according to claim 1, wherein the temperature sensor (17) is arranged in the rear handle (5).

4. 3. The battery-powered chainsaw (1) according to claim 2, wherein the first heating element and the second heating element are connected in series.

5. 2. The battery-powered chainsaw (1) of claim 1, wherein the duration and level of the power boost is determined based on the temperature obtained at start-up or startup of the chainsaw.

6. 2. The battery-powered chainsaw (1) according to claim 1, wherein the power boost is continuously controlled.

7. 7. The battery powered chainsaw (1) according to claim 6, wherein the power is continuously controlled based on a temperature reading and a PI regulator.

8. 2. A battery-powered chainsaw (1) according to claim 1, comprising a compartment for a battery.

9. A battery-powered chainsaw (1) according to any one of claims 1 to 8, comprising a short-range communication interface.

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