Hand-held cutting saw for cutting concrete and stone and comprising a drive for driving a circular cutting tool

Abstract

A handheld cutting saw (300) for cutting concrete and stone, the handheld cutting saw comprising a drive device (100, 200, 600, 800) for driving a circular cutting tool (110), the drive device comprising: a belt drive portion (120) comprising a first pulley (121) and a second pulley (122), wherein the first pulley is arranged to be powered by a power source (130) and drives the second pulley via a belt (123), wherein the second pulley (122) has a larger pitch diameter than the first pulley (121); and a gear transmission portion (140) comprising a first gear (141) and a second gear (142), wherein the first gear (141) is coaxially connected to the second pulley (122) and radially connected to the second gear (142), and wherein the second gear (142) is arranged to be coaxially connected to the circular cutting tool (110).

Description

Technical Field

[0001] A drive device for powering a rotatable work tool is disclosed. The present disclosure relates generally to power tools such as cutting saws. Background Art

[0002] When using power tools to cut concrete, stone and other hard materials, a lot of dust is usually generated. This airborne dust is harmful to the operator and usually requires a thorough cleaning of the workplace after cutting. Therefore, it is desirable to minimize the amount of airborne dust.

[0003] During the cutting operation, water or other liquids may be added to the cutting tool to bind the airborne dust. This makes the cutting environment less hazardous to the operator and also prevents the airborne dust from spreading to a larger area.

[0004] It is known to arrange a liquid dispensing system on a power tool in order to reduce the amount of dust generated. US 9,604,297 B2 discloses a liquid dispensing system for adding a controlled amount of liquid to a rotatable working tool.

[0005] However, it is not always desirable or even possible to add liquid during the cutting operation. Dry cutting is then an option. When dry cutting material with a power tool, it is advantageous to reduce the rotational speed of the tool because the reduced blade speed does not propel dust particles as much, thus making it easier to collect the generated dust using, for example, a vacuum system.

[0006] Unfortunately, power sources such as electric motors and internal combustion engines that run at reduced engine speeds are more expensive and are also typically heavier than standard electric motors that run at approximately 9,000-10,000 revolutions per minute (rpm). Therefore, various forms of transmission systems having a gear ratio for reducing the speed of the motor drive shaft are often used in dry cutting power tools.

[0007] It is known to use a drive belt having a smaller pulley connected to the motor drive shaft and a larger pulley connected to the work tool to reduce blade speed. However, having the larger pulley close to the work tool may adversely affect the achievable cutting depth of the tool. Moreover, the belt will be subjected to greater torsional forces, which increases the requirements for belt size.

[0008] There is a need for a power tool drive that provides reduced blade speed while maintaining cutting depth and without requiring the engine drive shaft to be slowed down. Summary of the invention

[0009] It is an object of the present disclosure to provide an improved drive device, power tool and method that allow for a reduction in blade speed.It is another object of the present invention to optimize the depth of cut.

[0010] These objects are achieved at least in part by a drive device for driving a rotatable working tool. The drive device includes a belt drive portion having a first pulley and a second pulley. The first pulley is arranged to be powered by a power source and drive the second pulley via a belt. The second pulley has a larger pitch diameter than the first pulley. The drive device also includes a gear transmission portion, which includes a first gear and a second gear. The first gear is coaxially connected to the second pulley and radially connected to the second gear. The second gear is arranged to be coaxially connected to the rotatable working tool.

[0011] Therefore, when the first pulley rotates, force is transmitted to the working tool via the belt and the gear, causing the working tool to rotate in the opposite direction to the first pulley.

[0012] This drive arrangement provides an efficient way to reduce the cutter speed to a speed suitable for dry cutting operations. The generated dust is propelled at a reduced speed, resulting in slower moving dust particles that are easier to handle, which is an advantage.

[0013] The combination of belt drive and gear transmission allows design freedom, as will be exemplified in the detailed description below. For example, due to the gear transmission part, the requirements on the size of the belt drive can be relaxed. Moreover, the working tool can be stopped suddenly without exerting excessive forces on, for example, the belt drive part.

[0014] The disclosed drive arrangement allows for relaxed requirements on the engine power output, which is an advantage.

[0015] According to various aspects, the second gear has a pitch diameter that is smaller than the pitch diameter of the second pulley. The smaller second gear diameter provides an increased cutting depth, which is an advantage.

[0016] According to some aspects, a distance D1 from a center axis of the first pulley to a center axis of the second pulley is less than a distance D2 from a center axis of the first pulley to a center axis of the second gear.

[0017] In other words, the second pulley has moved away from the cutting edge of the tool. Therefore, the larger second pulley no longer limits the cutting depth of the work tool, which is an advantage.

[0018] According to some aspects, the second gear has a larger pitch diameter than the first gear.

[0019] In this way, the gear transmission provides a further speed reduction. The gear ratio also reduces the mechanical stress exerted on the belt in the belt drive section, which is an advantage. For example, in an emergency, it is possible to stop the tool quickly without increasing the size of the belt.

[0020] According to some other aspects, the second gear has an equal or smaller pitch diameter than the first gear.

[0021] Like this, gear transmission part eliminates some speed reduction that can be achieved by belt drive part, but it is disadvantageous.However, advantageously, second gear is now smaller, and this can further increase the reachable cutting depth of tool.

[0022] The disclosed drive device is particularly suitable for use with an electric motor, which can be designed to operate in both clockwise and counterclockwise directions. However, the drive device can also be used with a conventional internal combustion engine, or with a hybrid electric internal combustion engine.

[0023] According to one example, the transmission ratio of the entire drive arrangement is between 1:3 and 1:4, preferably between 1:3.0 and 1:3.5, more preferably 1:3.2. This means that the power source can be arranged to operate between 9000 and 10000 rpm, giving a rotatable working tool speed of between 2500 and 5000 rpm, preferably about 3000 rpm, which is a suitable speed for dry cutting.

[0024] Also disclosed herein are power tools, blade guards, and methods associated with the above-mentioned advantages.

[0025] Generally, unless otherwise explicitly defined herein, all terms used in the claims will be interpreted according to their ordinary meaning in the technical field. Unless explicitly stated otherwise, all references to "one / an / the element, device, part, device, step, etc." will be openly interpreted as referring to at least one instance of the element, device, part, device, step, etc. Unless explicitly stated otherwise, the steps of any method disclosed herein do not have to be performed in the exact order disclosed. When studying the attached claims and the following description, other features and advantages of the present invention will become apparent. Those skilled in the art recognize that, without departing from the scope of the present invention, the different features of the present invention can be combined to create embodiments other than those described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present disclosure will now be described in more detail with reference to the accompanying drawings, in which:

[0027] Figure 1 to Figure 2 A drive device for a power tool is schematically shown;

[0028] Figure 3 An example power tool is shown;

[0029] Figure 4 An example blade guard for a power tool is schematically illustrated;

[0030] Figures 5 and 6 A drive device for a power tool is schematically shown;

[0031] Figure 7 is a flow chart illustrating a method; and

[0032] Figures 8 to 11 An example drive arrangement for a power tool is schematically shown. DETAILED DESCRIPTION

[0033] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain aspects of the invention are shown. However, the present invention may be implemented in many different forms and should not be construed as limited to the embodiments and aspects set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. Throughout the specification, the same numerals represent the same elements.

[0034] The belt drive may be configured to provide a gear ratio that reduces the rotational speed of the engine drive shaft to a speed suitable for dry cutting. Such a gear ratio requires the use of a smaller pulley at the drive shaft to drive a larger pulley connected to the work tool. However, if the larger pulley is directly coaxially attached to the rotatable work tool, the achievable cutting depth may be reduced due to the large pulley.

[0035] The drive device discussed here is based on a combination of a belt drive section and a gear drive section; in order to avoid reduced cutting depth, a large pulley is used instead to drive a first gear in the gear drive section of the drive device. The first gear then drives a second gear coaxially attached to a rotatable working tool. The large pulley can then be moved away from the cutting edge of the working tool to a distance determined by the gear size, thereby avoiding the limitation of the cutting depth by the large pulley.

[0036] In the drive device discussed here, only two pulleys and two gears are required. The power source for powering the rotatable working tool is arranged to rotate in a direction opposite to the direction of the working tool. This is not a problem when an electric motor is used as the power source, which can be configured to rotate in any direction. Therefore, the disclosed drive device is particularly suitable for use with an electric motor.

[0037] It should be understood that the drive arrangements discussed herein may also be used with internal combustion engines.

[0038] JP3002414U discloses a driving device including a combination of a belt driving part and a gear transmission part.

[0039] DE 416 354 A also describes a drive device comprising a combination of a belt drive part and a gear transmission part.

[0040] Yet, JP3002414U and DE416354A all do not disclose the drive device similar to the drive device discussed here, and it only needs two pulleys and two gears.In addition, the purpose of maximizing the cutting depth is not mentioned in the prior art document.

[0041] It should be understood that the specification of the sizes of gears and pulleys is not simple and direct. Therefore, the present disclosure adopts a simplified definition of gear and pulley diameters, which determine the transmission ratio;

[0042] The standard reference pitch diameter is the diameter of the standard pitch circle. In spur and helical gears, the standard pitch diameter is related to the number of teeth and the standard transverse pitch diameter. The diameter can be roughly estimated by averaging the diameter of the tip of the measuring gear tooth and the base of the gear tooth.

[0043] The pitch diameter of a pulley is not the outside diameter, nor is it the inside diameter. If you cut the belt and look at the end, you will usually see a row of fibers near the outside surface. This is the tension-carrying portion of the belt; the rest of the belt is there only to carry the forces from the pulley to and from these fibers. The pitch diameter of the pulley is measured at these fibers. Therefore, the pitch diameter of a pulley depends not only on the pulley itself, but also on the width of the belt.

[0044] The ratio of the pitch diameters is called the transmission ratio or gear ratio, i.e. the ratio at which torque increases and speed decreases, or vice versa. Power is the product of speed and force, or in the case of rotation, speed and torque. Pulleys and gear drives do not affect power (not taking friction, etc. into account); when they increase torque, they do so at the expense of speed, and vice versa.

[0045] Here, for simplicity, the sizes of pulleys and gears are expressed in terms of "pitch diameter". It will be understood that a small pitch diameter wheel driving a larger pitch diameter wheel results in a reduction in speed and an increase in torque. Methods for determining the exact pitch diameter that provides the required gear ratio are known and will not be discussed in more detail here. Methods for determining the necessary specifications of, for example, a drive belt to be able to withstand a specific range of torque are also known and will not be discussed in more detail here.

[0046] Figure 1 A driving device 100 for driving a rotatable working tool 110 is shown. Figure 3An example power tool is discussed that includes a rotatable work tool driven by a drive device.

[0047] The present disclosure relates primarily to power tools, such as cut-off saws, although aspects of the drive described are potentially applicable to abrasive chain saws, circular saws, hole saws, drills, and other rotatable work tools.

[0048] The drive device 100 includes a belt drive portion 120. The belt drive portion includes a first pulley 121 and a second pulley 122. The first pulley is arranged to be driven by a power source 130 (only in Figure 1 ) provides power.

[0049] To reduce the blade speed relative to the rotational speed of the first pulley, the second pulley has a larger pitch diameter than the first pulley. This transmission ratio increases torque and reduces speed, making the rotatable working tool suitable for dry cutting operations.

[0050] The drive device 100 further includes a gear transmission portion 140. The gear transmission portion includes a first gear 141 and a second gear 142. The first gear 141 is coaxially connected to the second pulley 122, and the second gear 142 is arranged to be coaxially connected to the rotatable working tool 110. Therefore, when the first pulley rotates, the belt ( Figure 1 121 and the working tool 110 are connected to the first gear (not shown) and the second pulley is driven in the same rotation direction. Then, the second pulley coaxially connected to the first gear drives the first gear in the same rotation direction as the first pulley. The first gear is radially connected to the second gear and thus drives the second gear in the opposite rotation direction. Therefore, the rotation direction R1 of the first pulley 121 and the rotation direction R2 of the working tool 110 are opposite to each other.

[0051] In other words, according to some aspects, the rotation direction R1 of the drive shaft of power source 130 is opposite to the rotation direction R2 of rotatable work tool 110 .

[0052] According to some aspects, the power source 130 is arranged to operate at a speed between 9000 rpm and 10000 rpm, and the rotatable working tool is driven at a speed of about 4000 rpm to 5000 rpm. Therefore, the rotatable working tool is suitable for dry cutting operations and a standard size motor can be used. This is an advantage due to cost and weight reasons.

[0053] According to some aspects, the distance D1 from the center axis of the first pulley 121 to the center axis of the second pulley 122 is less than the distance D2 from the center axis of the first pulley 121 to the center axis 143 of the second gear 142. This means that the second pulley has been positioned away from the cutting area of ​​the work tool in the direction C. Therefore, the larger second pulley 122 no longer directly limits the cutting depth of the work tool 110.

[0054] It should be understood that, generally, the rotation axes of the first pulley 121, the second pulley 122, the first gear 141, and the second gear 142 are arranged parallel to each other.

[0055] According to some aspects, the rotation axes of the first pulley 121, the second pulley 122, the first gear 141 and the second gear 142 are arranged as follows: Figure 1 On the straight line L shown. This arrangement provides a relatively narrow support structure for holding the tool, which can be an advantage.

[0056] However, it should be understood that it may be advantageous to offset the position of the second pulley away from this straight line L. For example, the axis of rotation of the second pulley 122 may be offset from the straight line L in a direction O away from the cutting portion of the rotatable working tool 110. This type of configuration is Figure 6 Shown in.

[0057] This can also be seen as the rotational axis of the second pulley 122 being offset from a plane P3 extending through and parallel to the central axis of the first pulley 121 and the central axis of the second gear 142 in a direction O away from the cutting portion of the rotatable work tool 110 .

[0058] The cutting portion of the working tool may include the lower front quadrant Q1 of the working tool, which means that the second pulley may be offset in direction O to further remove from the object to be cut. The first pulley 121, the second pulley 122 and the second gear 142 thus form the corners of a triangle, such as Figure 6 As shown. The working tool 110 is Figure 6 It is only shown schematically.

[0059] The transmission ratio of the entire drive device 100, including the belt drive portion and the gear transmission portion, can be modified by changing the pitch diameter of the gear transmission portion 140. For example, by using a smaller first gear 141 compared to the second gear 142, a further reduction in speed can be obtained. This is an advantage because it reduces the mechanical stress on the belt, so the belt drive portion 120 does not need to be the same size to achieve the overall transmission ratio.

[0060] In other words, according to various aspects, the second gear 142 has a larger pitch diameter than the first gear 141. Such a gear transmission portion is, for example, Figure 1 and Figure 6 The drive device can be configured to have a transmission ratio including a belt drive part and a gear transmission part, for example, the transmission ratio is between 1:3 and 1:4, preferably between 1:3.0 and 1:3.5, and more preferably 1:3.2.

[0061] Figure 6 An example drive device 600 is shown in which a fifth plane P5 extends through and is parallel to the center axis of the first gear 141 and through and is parallel to the center axis of the second gear 142. The fifth plane P5 forms an angle A relative to a third plane P3, which extends through and is parallel to the center axis of the first pulley 121 and through and is parallel to the center axis of the second gear 142. Figure 6 As schematically shown in the example in FIG. 1 , the angle A is between 20 and 180 degrees, preferably between 100 and 150 degrees, and more preferably about 135 degrees. This particular feature can be combined with the above Figures 1 to 5 Other example drive devices discussed herein are combined and applicable to Figures 8 to 11 . It is noteworthy that in the example drive 600, and also in many of the example drives discussed herein, the second gear 142 has a pitch diameter that is smaller than the pitch diameter of the second pulley 122. This means that the depth of cut (when engaging an object in the general direction C) is increased compared to the case where a larger diameter second gear is used.

[0062] According to some aspects, the gear drive portion 140 is sized to support the braking action of the power source to stop the rotatable working tool from a rotational speed of about 50 m / sec in 5 ms for a given belt size. In practice, this means that, due to the gear drive portion 140, the power source can be more aggressively parameterized for braking operations without placing excessive demands on the belt drive portion (particularly the belt). Therefore, the belt size can be reduced depending on the gear ratio of the gear drive portion 140.

[0063] According to some aspects, the ratio of the pitch diameter of the first gear 141 to the pitch diameter of the second gear 142 is between 0.4 and 0.6, and preferably 0.56.

[0064] According to an example, the first gear 141 has a pitch diameter between 20 and 35 mm, preferably 28 mm, and the second gear 142 has a pitch diameter between 40 and 60 mm, preferably 50 mm.

[0065] With regard to the belt drive portion 120, the first pulley 121 may be associated with a pitch diameter between 30 and 40 mm, preferably 35.4 mm, and the second pulley 122 may be associated with a pitch diameter between 60 and 70 mm, preferably 64.85 mm.

[0066] According to various aspects, the ratio between the pitch diameter of the first pulley 121 and the pitch diameter of the second pulley 122 is between 0.4 and 0.6, and preferably is about 0.55.

[0067] Various types of drive belts, such as a V-belt, may be used in the belt drive portion 120 .

[0068] The belt drive portion 120 may also include a toothed belt, a timing belt, a toothed belt, a toothed belt or a synchronous belt. This is an advantage because the first pulley 121 can then be made very small, i.e., sized to have a very small pitch diameter of the order of 20 mm. By sizing the first pulley within this range, a further reduction in rotational speed is increased, and / or a second pulley of a smaller pitch diameter can be used. The toothed belt also provides increased friction, which may be an advantage in some cases.

[0069] Figure 2 An example drive arrangement is shown where the gearing section instead increases the rotational speed of the work tool compared to the rotational speed of the second pulley 122. In other words, the second gear 142 has a smaller pitch diameter than the first gear 141, or where the first and second gears have equal pitch diameters. This configuration is advantageous where extreme cutting depths are important because the second gear now has a small pitch diameter.

[0070] Figure 2 Also shown is an optional washer 150 disposed between the rotatable working tool 110 and the second gear 142. This washer 150 provides increased mechanical integrity of the entire drive assembly, which is an advantage. The washer also protects the drive transmission during very deep cuts because the object to be cut hits the washer 150 before it hits the second gear 142.

[0071] Figure 3 An example power tool 300 is shown, which includes a rotatable working tool 110, a power source 130, and a drive arrangement according to the above discussion. Figure 3 The power tool is associated with a base line B defined by the first ground support element 310A and the second ground support element 310B. Figure 3 In the view of FIG. 1 , quadrant Q1 , where cutting is typically performed, is shown as being located in the lower right sector of tool 110. Note that first gear 141 has been offset from quadrant Q1 .

[0072] The rotatable working tool 110 is arranged to move in a downward cutting direction (eg Figure 3 The device rotates on the surface (as shown in R2 in FIG), that is, rotates into the material to be cut.

[0073] The drive arrangement comprises a cover 320 arranged to protect the belt drive arrangement, i.e. the first pulley 121, the second pulley 122 and the belt 123. The cover 320 is also arranged to protect the first gear 141 and the second gear 142. It is worth noting that this cover 320 is positioned away from the cutting area of ​​the work tool in the direction C, i.e. away from the quadrant Q1, in order to further optimize the cutting depth.

[0074] According to some aspects, the power tool 300 includes a blade guard 310 arranged to cover a portion of the rotatable work tool 110. This blade guard protects the user from debris during cutting operations and may also be configured to collect dust generated.

[0075] The blade guard 310 is shown in detail 400. Figure 4 4. The blade guard is pivotally arranged about a pivot point 410. Notably, the distance D3 from the center axis of the first pulley 121 to the pivot point is less than the distance D2 from the center axis of the first pulley 121 to the center axis 143 of the second gear 142. Therefore, the blade guard can be supported at the pivot point by a relatively large bushing without adversely affecting the cutting depth, which is an advantage. The first ground support element 310A support arm 170 holds the working tool, drive device and blade guard.

[0076] According to some aspects, the difference between distances D2 and D3 corresponds to approximately half of the pitch diameter of second gear 142 .

[0077] According to some aspects, the first gear 141 and the second gear 142 are arranged on a straight line L. The rotation axis of the blade guard 310 is parallel to the central axis 143 of the second gear 142 and is located along the straight line L between the rotation axes of the first gear and the second gear.

[0078] According to some other aspects, the rotation axis of the blade guard 310 is parallel to the central axis 143 of the second gear 142 and is located between the rotation axes of the first gear and the second gear, but offset from the straight line L.

[0079] Figure 5Another view of some power tool details 500 is shown. An example drive arrangement disposed on a support arm 510 is shown along with a blade guard 310. It will be appreciated that because the larger second pulley 122 and the blade guard pivot point have been offset in direction C, the power tool provides a greater depth of cut in direction C. It will be appreciated that increased depth of cut in other directions, such as direction C', may be obtained by offsetting the second pulley 122 and the blade guard pivot point in direction O.

[0080] Figure 6 discussed above. It is worth noting that Figure 6 The drive arrangement 600 shown includes a second pulley and a first gear that have been offset from quadrant Q1 to further optimize the depth of cut. By moving the first pulley away from quadrant Q1, the belt and other moving parts are also better protected from mechanical shock and debris during the cutting operation.

[0081] According to some aspects, the first plane P1 extends through the center axis of the first gear 141 and is parallel to the center axis of the first gear, and the second plane P2 extends through the center axis of the second gear 142 and is parallel to the center axis of the second gear. The first plane P1 and the second plane P2 are parallel. When the two planes are at a maximum distance from each other, the blade guard is arranged to be pivotable about a pivot point 410 arranged between the first plane P1 and the second plane P2. This means that the pivot point of the blade guard is slightly retracted from the center axis of the second gear in the general direction of the first pulley 121. The first plane P1 and the second plane P2 are at Figure 1 It will be appreciated that the orientation of the first plane and the second plane depends on the geometry of the gear.

[0082] According to some other aspects, the pivot point 410 of the blade guard is offset from a third plane P3 extending through and parallel to the center axis of the first pulley 121 and through and parallel to the center axis of the second gear 142 in a direction O away from the cutting portion of the rotatable working tool 110. In this way, the blade guard will not get in the way even when making deep cuts. The third plane P3 is parallel to the center axis of the second gear 142. Figure 1 and Figure 6 The line L in coincides.

[0083] According to some further aspects, the fourth plane P4 extends through and is parallel to the central axis of the first gear 141. The fourth plane P4 is parallel to the third plane P3. The pivot point 410 of the blade guard is arranged between the third plane P3 and the fourth plane P4. The fourth plane P4 is Figure 6 Example in.

[0084] Figure 7is a flow chart showing a method of driving a rotatable working tool 110 using a driving device 100, 200, 600. The method comprises:

[0085] In step S1, a belt drive portion 120 including a first pulley 121 and a second pulley 122 is configured, wherein the first pulley is arranged to be powered by a power source 130, and wherein the second pulley has a larger pitch diameter than the first pulley;

[0086] In step S2, a gear transmission portion 140 including a first gear 141 and a second gear 142 is configured, wherein the first gear 141 is coaxially connected to the second pulley 122 and radially connected to the second gear 142, and wherein the second gear 142 is coaxially connected to the rotatable working tool 110; and

[0087] In step S3 , the rotatable working tool 110 is driven by operating the power source 130 .

[0088] According to various aspects, a distance D1 from the center axis of the first pulley 121 to the center axis of the second pulley 122 is shorter than a distance D2 from the center axis of the first pulley 121 to the center axis of the second gear 142 .

[0089] Figures 8 to 11 Details of example drive devices 800 , 900 , 1000 , 1100 for power tools according to the above discussion are schematically shown. Figures 8 to 11 The features shown may be combined with any of the drive devices and power tools described above.

[0090] Figure 8 A drive device 800 is shown having a vent hole 810 for passing air into the at least partially combined Figure 3 The cover 320 in question encloses a volume 820. The vent provides cooling for the drive means and optionally also creates an overpressure inside the volume 820 which prevents dust and moisture from entering the volume 820 during operation.

[0091] Figures 8 to 10 Also shown is a fastening member 830, here exemplified by a bolt, for holding the drive device in position relative to other components of the power tool. Figure 8 Only a subset of the fastening members are shown.

[0092] Fig. 9 A detail 900 of the first and second pulleys 121 , 122 and the drive belt 123 is shown.

[0093] Fig.10The details of the first gear 141 and the second gear 142 relative to the drive belt 123 are shown. The second pulley 122 is not Fig.10 An example gear ratio between the first gear and the second gear is shown in Fig.10 It is schematically shown in FIG.

[0094] Fig.11 Shows Figure 8 Cross section DD shown. Fig.11 An example drive device 1100 is provided, showing a device 1110 for holding a blade and a motor 1120 arranged to provide power to a first pulley 121. The motor 1120 is an example power source 130. The motor 1120 is connected on one end to the first pulley 121 and on the other end to a fan 1130. The fan generates an airflow that cools the motor and also enters the volume 820 via the vents 810. Fig.11 An efficient way of fitting the various components of the drive device into a small volume is shown.

[0095] The motor 1120 drives the first pulley 121. When the first pulley rotates, the force is transmitted to the working tool via the belt 123 and the gear. The working tool is caused to rotate in the opposite direction compared to the first pulley. This drive device provides an effective way to reduce the tool speed to a speed suitable for dry cutting operations. The dust generated is propelled at a reduced speed, thereby producing slower moving dust particles that are easier to handle, which is an advantage. The combination of belt drive and gear drive allows design freedom. For example, due to the gear drive part, the requirements on the size of the belt drive can be relaxed. Moreover, the working tool can be stopped suddenly without applying excessive force on, for example, the belt drive part. With the disclosed drive device, the requirements on the power output from the motor 1120 can be relaxed, which is an advantage.

[0096] The following list of numbered embodiments summarizes some aspects disclosed herein.

[0097] 1. A driving device (100, 200, 600, 800, 900, 1000, 1100) for driving a rotatable working tool (110), the driving device comprising:

[0098] a belt drive portion (120) comprising a first pulley (121) and a second pulley (122), wherein the first pulley is arranged to be powered by a power source (130) and to drive the second pulley via a belt (123), wherein the second pulley (122) has a larger pitch diameter than the first pulley (121); and

[0099] A gear transmission portion (140) includes a first gear (141) and a second gear (142), wherein the first gear (141) is coaxially connected to the second pulley (122) and radially connected to the second gear (142), and wherein the second gear (142) is arranged to be coaxially connected to a rotatable working tool (110).

[0100] 2. A drive device (100, 200, 600, 800, 900, 1000, 1100) according to embodiment 1, wherein the distance (D1) from the center axis of the first pulley (121) to the center axis of the second pulley (122) is smaller than the distance (D2) from the center axis of the first pulley (121) to the center axis (143) of the second gear (142).

[0101] 3. The drive device (100, 600, 800, 900, 1000, 1100) according to any one of the preceding embodiments, wherein the second gear (142) has a larger pitch diameter than the first gear (141).

[0102] 4. The drive device (100, 600, 800, 900, 1000, 1100) according to embodiment 3, wherein the ratio of the pitch diameter of the first gear (141) to the pitch diameter of the second gear (142) is between 0.4 and 0.6, preferably 0.56.

[0103] 5. A drive device (100, 600, 800, 900, 1000, 1100) according to any of the preceding embodiments, wherein the first gear (141) has a pitch diameter between 20 and 35 mm, preferably 28 mm, and wherein the second gear (142) has a pitch diameter between 40 and 60 mm, preferably 50 mm.

[0104] 6. The drive device (200) according to embodiment 1 or 2, wherein the second gear (142) has a pitch diameter that is equal to or smaller than that of the first gear (141).

[0105] 7. A drive device (100, 200, 600, 800, 900, 1000, 1100) according to any of the preceding embodiments, wherein the ratio between the pitch diameter of the first pulley (121) and the pitch diameter of the second pulley (122) is between 0.4 and 0.6, preferably about 0.55.

[0106] 8. A drive device (100, 200, 600, 800, 900, 1000, 1100) according to embodiment 7, wherein the first pulley (121) has a pitch diameter between 30 and 40 mm, preferably 35.4 mm, and wherein the second pulley (122) has a pitch diameter between 60 and 70 mm, preferably 64.85 mm.

[0107] 9. A drive device (100, 200, 600, 800, 900, 1000, 1100) according to any of the preceding embodiments, wherein a transmission ratio of the drive device is between 1:3 and 1:4, preferably between 1:3.0 and 1:3.5, and more preferably 1:3.2.

[0108] 10. The drive device (100, 200, 600, 800, 900, 1000, 1100) according to any one of the preceding embodiments, wherein the belt (123) of the belt drive portion (120) is a toothed belt.

[0109] 11. The drive device (100, 200, 600, 800, 900, 1000, 1100) according to any one of embodiments 1 to 9, wherein the belt (123) of the belt drive portion (120) is a V-belt.

[0110] 12. The drive device (100, 200, 600, 800, 900, 1000, 1100) according to any one of the preceding embodiments, wherein the power source (130) is an electric motor.

[0111] 13. The drive device (100, 200, 600, 800, 900, 1000, 1100) according to any one of embodiments 1 to 11, wherein the power source (130) is an internal combustion engine or a hybrid electric internal combustion engine.

[0112] 14. A drive device (100, 200, 600, 800, 900, 1000, 1100) according to any of the preceding embodiments, wherein the power source (130) is arranged to operate at a rotational speed between 9000 and 10000 revolutions per minute (rpm), and wherein the rotatable working tool (110) operates at a rotational speed between 2500 and 5000 rpm, preferably approximately 3000 rpm.

[0113] 15. A drive device (100, 200, 600, 800, 900, 1000, 1100) according to any one of the preceding embodiments, wherein a rotation direction (R1) of a drive shaft of the power source (130) is opposite to a rotation direction (R2) of the rotatable working tool (110).

[0114] 16. A drive device (100, 200, 600, 800, 900, 1000, 1100) according to any of the preceding embodiments, wherein the rotatable working tool (110) is arranged to rotate in a downcutting direction into the material to be cut.

[0115] 17. A drive device (100, 200, 600, 800, 900, 1000, 1100) according to any of the preceding embodiments, wherein the gear transmission portion (140) is sized to support the braking action of the power source to stop the rotation of the rotatable working tool from a rotation speed of approximately 50 m / sec within approximately 5 ms.

[0116] 18. A drive device (100, 200) according to any one of the aforementioned embodiments, wherein the rotation axes of the first pulley (121), the second pulley (122), the first gear (141), and the second gear (142) are arranged on a straight line (L) between the center axis of the first pulley (121) and the center axis of the second gear (142).

[0117] 19. A drive device (600, 800, 900, 1000, 1100) according to any one of embodiments 1 to 17, wherein the rotation axis of the second pulley (122) deviates from the straight line (L) between the center axis of the first pulley (121) and the center axis of the second gear (142) in a direction (O) away from the cutting portion of the rotatable working tool (110).

[0118] 20. A drive device (600, 800, 900, 1000, 1100) according to any one of embodiments 1 to 17 and 19, wherein the rotation axis of the second pulley (122) deviates from a plane P3 in a direction (O) away from the cutting portion of the rotatable working tool (110), the plane extending through the center axis of the first pulley (121) and the center axis of the second gear (142) and parallel to these center axes.

[0119] 21. A power tool (300, 400, 500) comprising a rotatable working tool (110), a power source (130), and a drive device (100, 200, 600) according to any one of the preceding embodiments.

[0120] 22. The power tool (300, 400, 500) according to embodiment 21 comprises a blade guard (310) arranged to cover a portion of a rotatable working tool (110), the blade guard being arranged to be pivotable about a pivot point (410), wherein a distance (D3) from a center axis of the first pulley (121) to the pivot point is smaller than a distance (D2) from a center axis of the first pulley (121) to a center axis (143) of the second gear (142).

[0121] 23. The power tool (300, 400, 500) according to any one of embodiments 21 to 22, wherein the difference between the distance D2 and the distance D3 corresponds to approximately half of the pitch diameter of the second gear (142).

[0122] 24. A power tool (300, 400, 500) according to any one of embodiments 21 to 23, wherein the first gear (141) and the second gear (142) are arranged on a straight line (L), wherein the rotation axis of the blade guard (310) is parallel to the center axis (143) of the second gear (142) and is located between the rotation axis of the first gear and the rotation axis of the second gear along the straight line (L).

[0123] 25. A power tool (300, 400, 500) according to any one of embodiments 21 to 24, wherein the first plane P1 extends through the central axis of the first gear (141) and is parallel to the central axis of the first gear, wherein the second plane P2 extends through the central axis of the second gear (142) and is parallel to the central axis of the second gear, wherein the first plane P1 and the second plane P2 are parallel, and wherein the blade guard is arranged to be pivotable about a pivot point (410) arranged between the first plane P1 and the second plane P2 when the two planes are at a maximum distance from each other.

[0124] 26. A power tool (300, 400, 500) according to any one of embodiments 21 to 25, wherein the pivot point (410) of the blade guard device deviates from a third plane P3 in a direction (O) away from the cutting portion of the rotatable working tool (110), the third plane extending through and parallel to the center axis of the first pulley (121), and extending through and parallel to the center axis of the second gear (142).

[0125] 27. A power tool (300, 400, 500) according to any one of embodiments 21 to 26, wherein the fourth plane P4 extends through the central axis of the first gear (141) and is parallel to it, wherein the fourth plane P4 is parallel to the third plane P3, and wherein the pivot point (410) of the blade guard device is arranged between the third plane P3 and the fourth plane P4.

[0126] 28. A method of driving a rotatable working tool (110) using a driving device (100, 200, 600), comprising:

[0127] Step (S1), configuring a belt drive portion (120) including a first pulley (121) and a second pulley (122), wherein the first pulley is arranged to be powered by a power source (130) and drives the second pulley via a belt (123), and wherein the second pulley has a larger pitch diameter than the first pulley;

[0128] Step (S2), configuring a gear transmission portion (140) including a first gear (141) and a second gear (142), wherein the first gear (141) is coaxially connected to the second pulley (122) and radially connected to the second gear (142), and wherein the second gear (142) is coaxially connected to the rotatable working tool (110); and

[0129] In step (S3), the rotatable working tool (110) is driven by operating the power source (130).

Claims

1. A handheld cutting saw (300) for cutting concrete and stone, the handheld cutting saw comprising a drive device (100, 200, 600, 800) for driving a circular cutting tool (110) having a single blade, the drive device include: a belt drive portion (120) comprising a first pulley (121) and a second pulley (122), wherein the first pulley is arranged to be powered by a power source (130) and to drive the second pulley via a belt (123), wherein the second pulley (122) has a larger pitch diameter than the first pulley (121); and a gear transmission part (140) comprising a first gear (141) and a second gear (142), characterized in that the first gear (141) is coaxially connected to the second pulley (122) and radially connected to the second gear (142) in a directly meshing manner, and wherein the second gear (142) is arranged to be coaxially connected to the circular cutting tool (110) of a single blade; The second gear (142) has a pitch diameter that is smaller than the pitch diameter of the second pulley (122).

2. The handheld cutting saw (300) according to claim 1, in, A distance D1 from a center axis of the first pulley (121) to a center axis of the second pulley (122) is smaller than a distance D2 from a center axis of the first pulley (121) to a center axis (143) of the second gear (142).

3. The handheld cutting saw (300) according to claim 1 or 2, in, The second gear (142) has a larger pitch diameter than the first gear (141).

4. The handheld cutting saw (300) according to claim 3, in, A ratio of a pitch diameter of the first gear (141) to a pitch diameter of the second gear (142) is between 0.4 and 0.

6.

5. The handheld cutting saw (300) according to claim 1 or 2, in, The first gear (141) has a pitch diameter between 20 and 35 mm, and wherein the second gear (142) has a pitch diameter between 40 and 60 mm.

6. The handheld cutting saw (300) according to claim 1 or 2, in, The second gear (142) has a pitch diameter equal to or smaller than that of the first gear (141).

7. The handheld cutting saw (300) according to claim 1 or 2, in, The ratio between the pitch diameter of the first pulley (121) and the pitch diameter of the second pulley (122) is between 0.4 and 0.

6.

8. The handheld cutting saw (300) according to claim 7, in, The first pulley (121) has a pitch diameter between 30 and 40 mm, and wherein the second pulley (122) has a pitch diameter between 60 and 70 mm.

9. The handheld cutting saw (300) according to claim 1 or 2, in, The transmission ratio of the drive device is between 1:3 and 1:

4.

10. The handheld cutting saw (300) according to claim 1 or 2, in, The belt (123) of the belt driving part (120) is a toothed belt.

11. The handheld cutting saw (300) according to claim 1 or 2, in, The belt (123) of the belt driving part (120) is a V-belt.

12. The handheld cutting saw (300) according to claim 1 or 2, in, The power source (130) is an electric motor.

13. The handheld cutting saw (300) according to claim 1 or 2, in, The power source (130) is an internal combustion engine or a hybrid electric internal combustion engine.

14. The handheld cutting saw (300) according to claim 1 or 2, in, The power source (130) is arranged to operate at a rotation speed between 9,000 and 10,000 revolutions per minute, ie, 9,000 to 10,000 rpm, and wherein the circular cutting tool (110) operates at a rotation speed between 2,500 and 5,000 rpm.

15. The handheld cutting saw (300) according to claim 1 or 2, in, The rotation direction (R1) of the driving shaft of the power source (130) is opposite to the rotation direction (R2) of the circular cutting tool (110).

16. The handheld cutting saw (300) according to claim 1 or 2, in, The circular cutting tool (110) is arranged to rotate in a downcutting direction into the material to be cut.

17. The handheld cutting saw (300) according to claim 1 or 2, in, The gear drive portion (140) is sized to support the braking action of the power source to stop the rotation of the circular cutting tool from a rotation speed of about 50 m / sec in about 5 ms.

18. The handheld cutting saw (300) according to claim 1 or 2, in, The rotation axes of the first pulley (121), the second pulley (122), the first gear (141), and the second gear (142) are arranged on a straight line (L) between a central axis of the first pulley (121) and a central axis of the second gear (142).

19. The handheld cutting saw (300) according to claim 1 or 2, in, The rotation axis of the second pulley (122) is offset from a straight line (L) between a center axis of the first pulley (121) and a center axis of the second gear (142) in a direction (O) away from a cutting portion of the circular cutting tool (110).

20. The handheld cutting saw (300) according to claim 19, in, The third plane P3 extends through the central axis of the first pulley (121) and is parallel thereto, and extends through the central axis of the second gear (142), and the rotation axis of the second pulley (122) deviates from the third plane P3 in a direction (O) away from the cutting portion of the circular cutting tool (110).

21. The handheld cutting saw (300) according to claim 1 or 2, comprising a blade guard (310) arranged to cover a portion of the circular cutting tool (110), the blade guard being arranged to be pivotable about a pivot point (410), in, A distance D3 from the center axis of the first pulley (121) to the pivot point is smaller than a distance D2 from the center axis of the first pulley (121) to the center axis (143) of the second gear (142).

22. The handheld cutting saw (300) according to claim 21, in, The difference between the distance D2 and the distance D3 corresponds to approximately half of the pitch diameter of the second gear (142).

23. The handheld cutting saw (300) according to claim 21, in, The first gear (141) and the second gear (142) are arranged on a straight line (L), wherein the rotation axis of the blade guard (310) is parallel to the central axis (143) of the second gear (142) and is located between the rotation axis of the first gear and the rotation axis of the second gear along the straight line (L).

24. The handheld cutting saw (300) according to claim 21, in, A first plane P1 extends through a center axis of the first gear (141) and is parallel to the center axis of the first gear, wherein a second plane P2 extends through a center axis of the second gear (142) and is parallel to the center axis of the second gear, wherein the first plane P1 and the second plane P2 are parallel, and wherein the blade guard is arranged to be pivotable about a pivot point (410) arranged between the first plane P1 and the second plane P2 when the first plane P1 and the second plane P2 are at a maximum distance from each other.

25. The handheld cutting saw (300) according to claim 21, in, The pivot point (410) of the blade guard device deviates from a third plane P3 in a direction (O) away from the cutting portion of the circular cutting tool (110), and the third plane P3 extends through the central axis of the first pulley (121) and is parallel thereto, and extends through the central axis of the second gear (142) and is parallel thereto.

26. The handheld cutting saw (300) according to claim 25, in, A fourth plane P4 extends through a central axis of the first gear (141) and is parallel thereto, wherein the fourth plane P4 is parallel to the third plane P3, wherein the pivot point (410) of the blade guard is arranged between the third plane P3 and the fourth plane P4.

27. The handheld cutting saw (300) according to claim 26, comprising a drive device (600, 800), in, The fifth plane P5 extends through the center axis of the first gear (141) and is parallel to it, and also extends through the center axis of the second gear (142) and is parallel to it, wherein the fifth plane P5 forms an angle (A) relative to the third plane P3, and the third plane P3 extends through the center axis of the first pulley (121) and is parallel to it, and extends through the center axis of the second gear (142) and is parallel to it, wherein the angle (A) is between 20 and 80 degrees.

28. The handheld cutting saw (300) according to claim 4, in, The ratio of the pitch diameter of the first gear (141) to the pitch diameter of the second gear (142) is 0.

56.

29. The handheld cutting saw (300) according to claim 5, in, The first gear (141) has a pitch diameter of 28 mm.

30. The handheld cutting saw (300) according to claim 5, in, The second gear (142) has a pitch diameter of 50 mm.

31. The handheld cutting saw (300) according to claim 7, in, A ratio between a pitch diameter of the first pulley (121) and a pitch diameter of the second pulley (122) is approximately 0.

55.

32. The handheld cutting saw (300) according to claim 8, in, The first pulley (121) has a pitch diameter of 35.4 mm.

33. The handheld cutting saw (300) according to claim 8, in, The second pulley (122) has a pitch diameter of 64.85 mm.

34. The handheld cutting saw (300) according to claim 9, in, The transmission ratio of the drive device is between 1:3.0 and 1:3.

5.

35. The handheld cutting saw (300) according to claim 34, in, The transmission ratio of the drive device is 1:3.

2.

36. The handheld cutting saw (300) according to claim 14, in, The circular cutting tool (110) is operated at a rotation speed of approximately 3000 rpm.

37. The handheld cutting saw (300) according to claim 27, in, The angle (A) is between 100 and 150 degrees.

38. The handheld cutting saw (300) according to claim 37, in, The angle (A) is approximately 135 degrees.

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