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 running 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 chainsaws powered by internal combustion engines, especially when the saw is only used occasionally (such as for hobbyist use) or where light weight is particularly important (such as for arborists who climb trees).

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

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

[0005] This object is achieved by a battery-powered chainsaw as claimed in claim 1. More specifically, in a battery-powered chainsaw of the first mentioned kind, a battery-powered heating unit is provided comprising one or more heating elements in one of the rear and front handles and a temperature sensor. The heating unit is configured to provide 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 at start-up. A steady state power lower than the power of the power boost is then provided by the heating unit. This allows the chainsaw to relatively quickly obtain a suitably heated handle without draining the battery too rapidly during extended use.

[0006] The battery operated heating unit may comprise a first heating element in the rear handle and a second heating element in the front handle. The temperature sensor may, for example, be located 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 controlled continuously, for example based on a PI controller.

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

[0009] [Figure 1] A diagram showing the body of a battery-operated chainsaw. [Diagram 2] FIG. 2 shows the chainsaw of FIG. 1 with the heating area highlighted. [Diagram 3]FIG. 4 is a diagram showing wiring for steering wheel heating. [Figure 4] FIG. 13 shows rear handle heating. [Diagram 5] 4 is a flow chart showing the supply of power to the handle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Chainsaws with heated handles are highly valued by professional forestry workers, especially in cold climates: because a chainsaw is operated by gripping the chainsaw handle firmly, 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 a handle through which part of the exhaust from the internal combustion engine of the chainsaw was directed, thereby heating the handle. In more recent developments, a small generator is connected to the internal combustion engine, and the electric energy generated thereby is used to heat the handle of the chainsaw. However, in battery-powered chainsaws, the available energy is scarcer. Despite significant improvements in battery technology in recent decades, its energy density is very low compared to gasoline, and the battery naturally requires access to an electric 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 needed 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, and comprises a guide bar 2 on which a saw chain 4 driven by an electric motor runs. The chainsaw 1 then comprises a rear handle 5 and a front handle 7. The rear handle 5 is intended to be held by the right hand of a user and comprises a lock button 9. The lock button 9 must be pressed to allow activation of the throttle button 10. The throttle button 10 is operated by the index and middle fingers of the user or by the thumb of the user, depending on the orientation of the chainsaw 1. The front handle 7 is intended for the left hand, which can be positioned in various places along the front handle 7, depending on which operation is to be performed.

[0013] Handle heating may be controlled by a user interface 11, including, for example, buttons. In Figure 2 the resulting areas that can be heated in the rear handle 5 and the front handle 7 are highlighted. However, if lower power consumption is desired, it is possible to heat only a smaller part 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, it may be possible, for example, to provide the chainsaw 1 with a short-range communication interface (such as BLUETOOTH®) and 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, on which the set desired temperature is based. As yet another option, the current usage situation (e.g. felling or cutting firewood) can be identified and the set temperature based on the usage. Figure 3 shows the wiring of the handle heating unit 19 connected to the normal electrical system 18 of the chainsaw. This wiring is used to control the chainsaw motor and therefore can also be considered to include the heating unit 19. Thus, the front and rear handles 7, 5 are provided with resistive heating elements 13, 15, respectively. These resistive heating elements are dimensioned according to the specific heat of the respective handles and the expected radiation from the handles 5, 7. Thus, the resistive heating wire 13 of the front handle 7 is made of a metal that is configured to generate more heat for a given setting for larger front handles and radiates heat to a greater extent to the surroundings. 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 resistive conductor on a printed circuit board. Typically, in the rear handle, about 1.2 m of copper conductor may be provided which is printed in a serpentine fashion 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, it is possible to place the sensor 17 in the front handle 7, or to place a temperature sensor in each handle.

[0017] The sensor may typically be an NTC resistor, although other components such as PTC or RTD resistors are also possible. 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 part (removed in FIG. 4) to facilitate mounting 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 allowing the control scheme described below to be implemented. 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, 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 in the longitudinal direction 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 mechanisms are configured to provide comfortable handle heating without wasting too much battery power. When a user first begins to operate the chainsaw, the handle is likely to be near the same temperature as the ambient air, which may be a few degrees below zero Celsius in winter conditions. This can be very uncomfortable, especially if the user is wearing thin gloves or no gloves at all. It is therefore desirable to rapidly increase the temperature at the handle 5,7 by providing 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 the readings from the temperature sensor 17. More specifically, the heating unit 19 provides a temporary power boost to the first and second heating elements 15, 13 upon start-up. A steady state power lower than the power of the power boost can then 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 flow chart of FIG. 5 showing a step 41 of providing a power boost followed by a step 43 of providing steady state power.

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

[0024] This power provided to the handles 5, 7 may be provided 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 than in one of the handles if desired.

[0025] In another example, the temperature sensor 17 is located in one of the 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 the sensor 7 can be set and the applied power controlled based on the difference between the desired temperature and the actual temperature, for example using a PI or PID controller. The power boost then continues until the target temperature is reached, but the applied power is reduced as the measured temperature approaches the target temperature at which steady state power is delivered. Of course, such a control scheme may be modified in various ways, such as disabling the handle heating function altogether when the ambient temperature is above a certain threshold.

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

Claims

1. A battery-powered chain saw (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), and a rear handle (5) extending at least partially generally in the longitudinal direction of said guide bar (2), 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 heating unit (19) is configured to provide power to the first heating element (15), the second heating element (13), or both based on a reading from the temperature sensor (17); The battery-powered chain saw (1), wherein the heating unit (19) is configured to, upon start-up, supply a temporary power boost to the first handle (15), the second handle (13), or both, and subsequently supply a steady-state power to the first handle (15), the second handle (13), or both, that is lower than the power of the power boost.

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

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

5. A battery powered chainsaw (1) according to any one of claims 1 to 4, 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. The battery powered chain saw (1) according to any one of the preceding claims, wherein the power boost is continuously controlled.

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

8. A battery-powered chainsaw (1) according to any one of the preceding claims, comprising a compartment for a battery.

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

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