Electric chainsaw blade emergency braking device

Abstract

Electric motor saw blade emergency braking device (10) for stopping the running of the saw blade (50) of an electric motor saw (1) incorporating a cutting table (2) through which the saw blade (50) of the saw (1) runs during a cutting operation, the device (10) comprising: - a first rotatably mounted saw blade brake shoe (11), - a second rotatably mounted saw blade brake shoe (12) spaced from the first saw blade brake shoe (11) for receiving the saw blade (50) in a gap (13) formed therebetween, - a drive (20) having a piston (21) arranged in a piston cylinder (22) for driving the first and second saw blade brake shoes (11, 12) from a rest position until contact with the side surfaces (51) of the saw blade (50) between the saw blade brake shoes (11, 12), - a pressure chamber (30) for maintaining a fluid (31) at a predetermined pressure, the pressure chamber (30) being arranged on the piston cylinder (22), and - a valve member (40) arranged to regulate a flow of the pressurized fluid (31) along a flow path between the valve member (40) and the piston (21) from the pressure chamber (30), with a discharge opening (41) for conducting pressurized fluid (31) from the pressure chamber (30) into the drive (20), characterized in that an actuator (14) is arranged to jointly drive the first saw blade brake shoe (11) and the second saw blade brake shoe (12) from the rest position until contact with the side surfaces (51) of the saw blade (50).

Description

[0001] The invention relates to an electric chain saw blade emergency braking device for stopping the running of the saw blade of an electric chain saw.

[0002] Such electric power saws are designed, for example, as band saws with a motor-driven band saw blade and a tensioning device for tensioning the saw blade. Furthermore, braking devices for stopping the saw blade, in particular for blocking the saw blade, are provided to protect the operator.

[0003] In these well-known band saws, for example, the saw blade, which rotates around an upper and lower roller, is tensioned by a gas spring pushing the upper roller upward relative to the usually stationary lower roller. The lower end of the gas spring rests on a fixed support in the band saw housing. The tensioning force of the saw blade is approximately equivalent to the force of the gas spring.

[0004] The braking device serves as a protective device to detect the contact of the operator with the saw blade, which is often also used as a band saw blade in the form of an endless belt, during operation and to stop the movement of the saw blade as quickly as possible in order to protect the operator from possible injuries.

[0005] From the document EP 3 194 129 B1 an emergency braking device for stopping the movement of a band saw blade of an electrically operated saw is known.

[0006] The emergency braking device comprises a drive device with a pressure chamber for supplying a gaseous or liquid medium. A magnetic drive is connected downstream of the pressure chamber. The fluid is fed into the pressure chamber through a supply line, and the pressure chamber housing is attached to a piston cylinder in which a piston is slidably arranged. The piston has a piston head and a piston rod that protrudes from the piston cylinder and acts directly on a movable shoe of the emergency brake.

[0007] The movable jaw is spaced from a stationary brake shoe and forms a gap for receiving the band saw blade. When the device is triggered by the emergency brake signal, the coil of the solenoid valve is de-energized. This releases a valve plate of the magnet and is pushed out of its closed position by the pressurized fluid in the pressure chamber. This allows the pressurized fluid to flow from the pressure chamber along a flow path defined between the solenoid valve and the piston, through an outlet opening that is in contact with the head of the piston. The piston is then driven linearly from a rest position by the pressurized fluid along the piston cylinder into a working position against the action of a tension spring.The linear movement of the piston rod along the piston cylinder drives the movable jaw from the retracted position until it makes contact with a side surface of the saw blade, clamping it between the movable and fixed jaws. With the solutions described, the time required for the braking device to clamp the saw blade is, at best, on the order of approximately 10 to 12 milliseconds.

[0008] Furthermore, WO 2007 / 009 172 A1 describes an operator protection system for an electric band saw used in the meat processing industry. The saw blade's movement is stopped by a clamping mechanism.

[0009] The clamping mechanism consists of a pair of spaced-apart cams that serve as clamping elements, each rigidly attached to corresponding rotating spindles on a mounting block. The spindles extend through the mounting block from its front to its rear. At the rear of the mounting block, the rotating spindles are operatively connected to each other via a further coupling element.

[0010] The band saw blade runs through a gap defined between the guide units of the mounting block and between the clamping elements. An actuating mechanism is arranged with a drive element to rotate the clamping element around its axis defined by the spindle after the band saw's control system detects a trigger signal for an emergency situation. The clamping function is triggered by functionally coupling the clamping elements via the actuator as a coupling element.

[0011] To close, the clamping elements first move toward each other until they come into contact with the saw blade. Upon contact, the movement of the saw blade further draws the individual cams together as clamping elements, clamping the saw blade more firmly. The control system is designed to achieve reliable clamping of the saw blade within a few milliseconds. A particularly effective and time-saving feature is that, in addition to clamping, the band saw blade is sheared off by additional blade edges on the clamping elements. However, this shearing leads to longer downtimes for the saw, since replacing the saw blade is equivalent to a repair when restarting the machine.

[0012] Crucial to the protective function is the time span and thus the distance a saw blade can travel before coming to a standstill in the event of a danger. After an emergency stop of the saw, it is also important to be able to return it to an operational state without great effort once the hazardous situation has been resolved.

[0013] The object of the present invention is to further develop an emergency braking device for stopping the rotation of a saw blade of an electric chain saw, which eliminates the disadvantages resulting from the specific solutions of the prior art.

[0014] This object is achieved by a device having the features of independent claim 1. The subclaims relate to advantageous developments and variants of the invention.

[0015] An electric motor saw blade emergency braking device according to the invention for stopping the saw blade's travel comprises an electric motor saw incorporating a cutting table through which the saw blade of the saw runs during a cutting operation. The emergency braking device comprises: - a first rotatably mounted saw blade brake shoe, - a second rotatably mounted saw blade brake shoe spaced from the first saw blade brake shoe for receiving the saw blade in a gap formed therebetween, - a drive having a piston arranged in a piston cylinder for driving the first and second saw blade brake shoes from a rest position until contact with the side surfaces of the saw blade between the saw blade brake shoes, - a pressure chamber for maintaining a fluid at a predetermined pressure, the pressure chamber being arranged on the piston cylinder, and - a valve member arranged to regulate a flow of the pressurized fluid along a flow path between the valve member and the piston from the pressure chamber, with a drain opening for directing pressurized fluid from the pressure chamber into the actuator.

[0016] According to the invention, an actuator is arranged for jointly driving the first saw blade brake shoe and the second saw blade brake shoe from the rest position until contact with the side surfaces of the saw blade.

[0017] A saw blade can, for example, be designed as an endless band saw blade suitable for meat saws or bone saws with hardened tooth tips.

[0018] A particular advantage of the invention is that the saw blade of a band saw can be stopped mechanically within a few milliseconds despite the large mass inertia of the rotary drive and the deflection pulleys, without subjecting the saw blade of a band saw, for example, to extreme stress.

[0019] To stop the saw blade after a detection unit detects a critical usage situation, the tensioning device of a band saw blade is moved from a tensioned position, in which the saw blade is tensioned, to a release position, in which the saw blade is relieved of tension. At the same time, or almost at the same time, the emergency braking device is activated. This device can be switched by an electrical control system, so that the braking device is designed as a mechanical brake acting on the saw blade. To stop the saw blade, both the tensioning device is switched from the tensioned to the release position, and the emergency braking device is activated.

[0020] To stop, the saw blade is completely released, thus decoupled from the large inertia of the rotary drive and the deflection pulleys. This means that the saw blade is no longer driven and the mass to be stopped is reduced to the mass of the saw blade. The saw blade is stopped by the emergency braking device in milliseconds. To minimize the braking time, switching the tensioning device to the release position and actuating the emergency braking device can occur simultaneously or with only a slight delay.

[0021] In particular, the fat, meat, or bone residues that accrue when cutting all types of meat products, some of which are present in the form of adhering material on the sawblade and the adjacent components and guides, must be able to be removed by cleaning. To prevent the transfer of contamination from the carcasses, the saw requires thorough cleaning. During regular operation of the saw, the emergency braking device according to the invention, with its sawblade brake shoes and other components, is openly accessible, allowing for convenient cleaning of the contaminated parts or disinfection.

[0022] In a preferred embodiment, the saw blade brake shoes can be designed as eccentrics with guide surfaces for guiding the saw blade.

[0023] During normal operation of the saw, the saw blade brake shoes, which are designed as eccentrics, remain in an initial position in which the guide surfaces and the gap they form guide the saw blade with laterally stable movement and, if possible, do not interfere with the path of movement of the saw blade teeth.

[0024] Advantageously, the saw blade brake shoes can be designed as eccentrics with clamping surfaces for clamping the saw blade.

[0025] The eccentric sawblade brake shoes can be rotated between an initial position, in which they do not engage the sawblade teeth, and a locking position, in which they engage the sawblade's side surfaces. To stop and lock the sawblade, the sawblade brake shoes are moved from the initial position to the locking position by a control system via the drive actuator.

[0026] In a particular embodiment of the invention, the actuator can be designed as a guide plate with suitable recesses for driving the saw blade brake shoes.

[0027] The guide plate can be a guide plate of a suitable material thickness, which can transfer the closing forces required in an emergency stop to the sawblade brake shoes with as little play as possible. The locking mechanism requires only short travel distances to quickly close the gap between the sawblade brake shoes.

[0028] Advantageously, the actuator can be designed as a guide plate symmetrically with regard to an evenly distributed force introduction with respect to the saw blade brake shoes.

[0029] A symmetrical force introduction shortens the force flow for closing the saw blade brake shoes until contact with the saw blade.

[0030] In a preferred embodiment, the surfaces of the clamping surfaces and / or the guide surfaces of the saw blade brake shoes can be polished.

[0031] Regarding the clamping surfaces, a polished surface should, on the one hand, clamp the saw blade more firmly through frictional forces and cause the saw blade to stop immediately. Damage to the saw blade surface or teeth should be avoided at all costs. This shortens the saw's downtime until it can be put back into operation, as no further maintenance or repair work is required.

[0032] Advantageously, the surfaces of the clamping surfaces and / or the guide surfaces of the saw blade brake shoes can be coated.

[0033] Coatings tailored to the mechanical stress can prevent damage to the sawblade. Ductile coatings, in particular, can prevent damage to the sawblade surface, and especially to the cutting teeth, when the sawblade brake shoes are subjected to force and mechanical stress when the emergency brake device is closed.

[0034] In a particular embodiment of the invention, the eccentrics with clamping surfaces and / or the guide surfaces can be designed to be mirror-symmetrical with respect to a plane of symmetry running parallel to the axis of rotation.

[0035] Mirror symmetry has the particular advantage that each eccentric has two installation positions. In other words, once the side surfaces facing the sawblade in one installation position become worn during operation of the system, they can be remounted by simply turning and swapping the mounting position with the second side surfaces created by the mirror symmetry. In this way, the originally outer side surfaces then form a gap in the new installation position and face the sawblade.

[0036] Advantageously, when clamping the saw blade, the clamping surfaces can have a contact area of less than 50 mm with the respective side surface of the saw blade. 2 have.

[0037] The contact surface with the saw blade is elongated, perpendicular to its direction of movement. For hygiene reasons, the contact surface should be as small as possible to reduce contamination of the system, especially from meat residue. On the other hand, the contact surface must be large enough to ensure that the friction between the clamping surfaces and the saw blade makes the emergency braking device effective.

[0038] In a preferred embodiment, the guide surfaces can be curved with a radius of curvature between 30 and 90 mm.

[0039] With the specified radius, the guide surfaces have a relatively slight curvature to guide a band saw blade. For curved saw blade brake shoes, the gap width is measured at the narrowest point of the opposing saw blade brake shoes.

[0040] Advantageously, the clamping surfaces can be curved with a radius of curvature between 5 and 15 mm.

[0041] The clamping surfaces have a smaller radius and a more pronounced curvature than the guide surfaces. The larger curvature correspondingly reduces the contact area with the sawblade brake shoes after the sawblade brake shoes close in an emergency situation.

[0042] In a preferred embodiment, the gap for receiving the saw blade can have a gap width of less than 3 mm.

[0043] The entire arrangement should preferably be designed with the smallest possible gap width to minimize travel and thus the closing times when the emergency braking device is activated. However, for normal sawing operation, the gap should be large enough to minimize contact between the saw blade and the guide surfaces.

[0044] Good accessibility of the eccentrics allows for easy rinsing with water and, if necessary, other cleaning agents. If necessary, cleaning with a damp cloth or brush is also possible. Regular and thorough cleaning not only ensures hygienic conditions but also a long service life of the saw and reduces wear on the saw blade.

[0045] Advantageously, the drive for driving and closing the first and second saw blade brake shoes from a rest position to contact with the side surfaces of the saw blade between the saw blade brake shoes can result in a shooting time of less than 9, in particular less than 6 milliseconds.

[0046] In order to achieve such short braking times, the processes for decoupling the rotary drive and the control of the drive of the emergency braking device must be precisely coordinated and take place simultaneously or immediately one after the other due to the high mass inertia of the rotary drive and the deflection pulleys of the saw blade when the emergency braking device is triggered.

[0047] The emergency braking device according to the invention, which brings the saw blade to a standstill within a few milliseconds, can prevent serious injuries. Factors that influence the service life of the saw and saw blade include unintentional or intentional activation of the braking process by the operator. It may therefore be advisable to perform regular, if not daily, checks to ensure the brakes are functioning properly. However, practice has shown that all parts of the emergency braking device, including the saw blade, withstand even these extreme stresses.

[0048] Another aspect of the invention includes an electric motor saw having a cutting table through which the saw blade runs during a cutting operation, with an electric motor saw blade emergency braking device according to the invention for stopping the running of the saw blade.

[0049] Advantageously, the saw can be designed as a band saw. In particular, band saw blades in the form of an endless band are used.

[0050] In particular, a detection unit for detecting a critical usage situation may be provided, with a controller connected to the detection unit. Means for decoupling the saw blade from a drive may be provided, and the controller may be suitable for controlling both the emergency braking device and the decoupling means.

[0051] In cases where the saw is designed as a band saw with a saw blade, a means for decoupling can be designed as a tensioning device for the saw blade, which can be switched from a tensioned to a relaxed position.

[0052] The control system can be designed to first control the decoupling means and then the emergency braking device.

[0053] In a particularly advantageous variant of the invention from a hygiene perspective, a cover for components of the emergency brake device is designed in such a way that it has no horizontal surfaces above. This largely prevents residues or water residues (after cleaning the saw) from accumulating on the cover.

[0054] In the following, embodiments and variants of the invention are explained in more detail with reference to the drawings. Fig. 1 schematically shows an oblique view of an emergency braking device according to the invention with two eccentrics, Fig. 2 schematically shows a side view of the emergency braking device according to the invention, Fig. 3 schematically shows an oblique view of an eccentric of an emergency braking device according to the invention, Fig. 4 schematically shows a vertical section through the emergency braking device in the plane of the actuator on the rear side, Fig. 5 schematically shows a vertical section through an electric chainsaw in the plane of the emergency braking device in a side view.

[0055] Fig. 1 shows schematically an oblique view of an emergency braking device 10 according to the invention with two saw blade brake shoes designed as eccentrics 11, 12.

[0056] The eccentrics 11, 12 are each mounted for rotation about an axis A. The first eccentric 11 is spaced from the second eccentric 12 at such a distance that a gap 13 is created between them for the passage of the band saw blade 50. The gap width is as small as possible in order to minimize the closing times when the emergency brake device 10 is triggered. However, the gap 13 must still provide sufficient space for the saw blade 50 for normal operation of the saw, even in the event of deformation during the cutting process.

[0057] Still visible in Fig. 1 is the cover 60, through which further components of the emergency braking device are encapsulated from the outside. The emergency braking device is intended to be fastened to a saw chassis by means of screws 70 in such a way that only the cover 60 and the eccentrics 11 and 12 are located in an area of the saw that can be reached, for example, by accumulating meat or bone residues or - in the case of cleaning the saw - by water. Clearly visible in the figure is the curved shape of the cover 60, in particular the absence of horizontal surfaces on which residues or water residues could accumulate after cleaning. In this way, the device according to the invention meets extended hygiene standards.

[0058] Fig. 2 shows a schematic side view of the emergency braking device 10 according to the invention.

[0059] The band saw blade 50 has a Fig. 2 Not further shown, toothing for cutting on the cutting edge 52. This cutting edge 52 is located by the toothing in front of the eccentric 11 with its clamping surfaces for clamping the saw blade 50. The toothing on the cutting edge 52 is not clamped when the emergency brake device 10 is triggered. Only the smooth surface of the side surface 51 is subject to the clamping process in this case.

[0060] Fig. 3 shows schematically an oblique view of an eccentric 11, 12 of a Fig. 1 and Fig. 2 shown emergency braking device 10 according to the invention.

[0061] The sawblade brake jaws are designed as eccentrics 11, 12 with guide surfaces 111, 121 for guiding a sawblade. The guide surfaces 111, 121 are slightly curved and merge seamlessly into the adjacent clamping surfaces 112, 122. These clamping surfaces 112, 122 for clamping the sawblade have a more pronounced curvature than the guide surfaces 111, 121.

[0062] The eccentrics 11, 12 with clamping surfaces 112, 122 and guide surfaces 111, 121 are mirror-symmetrical with respect to a plane of symmetry running parallel to the rotation axis and the recess 113 provided for this purpose. Due to this mirror symmetry, each eccentric 11, 12 has two installation positions. Once the surfaces in one installation position become worn during operation, they can be mounted by turning and swapping the installation position with the second guide surfaces 111, 121 or clamping surfaces 112, 122.

[0063] Fig. Figure 4 shows schematically a vertical section through the emergency braking device 10 in the plane of the actuator 14 on the rear side.

[0064] Shown is the drive 20, which has a piston 21 arranged in a piston cylinder 22, for driving the saw blade brake shoes on the Fig. 4 not visible front of the emergency braking device 10. Furthermore, a pressure chamber 30 is provided for holding a fluid 31 at a predetermined pressure, wherein the pressure chamber 30 is arranged below the piston cylinder 22. A valve member 40 regulates the flow of the pressurized fluid 31 along a flow path between the valve member 40 and the piston 21. A drain opening 41 directs the pressurized fluid 31 from the pressure chamber 30 into the drive 20. The return spring 24 acts on the piston 21 and holds it in an operational position.

[0065] The piston rod 23 arranged on the piston 21 is operatively connected to the actuator 14, which initiates the rotary movement of the saw blade brake shoes arranged on the front side via an eccentric drive 15.

[0066] The actuator 14 is arranged downstream of the drive 20 to rotate the clamping element about an axis defined by the eccentric drive 15 after a control system of the band saw has detected a current flow from the operator to the saw blade as a trigger signal, for example. The clamping function is triggered by the functional coupling of the clamping elements via the coupling element.

[0067] Fig. 5 shows schematically a vertical section through an electric chain saw 1 in the plane of the emergency braking device 10 in a side view.

[0068] The electric motor saw 1 comprises a cutting table 2 through which the saw blade passes during a cutting operation. To stop the saw blade, the tensioning device 3 of a band saw blade is moved from a tensioned position, in which the saw blade is tensioned, to a release position, in which the saw blade is unloaded. Simultaneously or almost simultaneously, the emergency braking device 10, which can be switched via an electrical control, is activated. To stop the saw blade, therefore, both the tensioning device 3 is moved from the tensioned to the release position and the emergency braking device 10 is actuated. List of reference symbols 1 saw, electric chainsaw 2 cutting tables 3 clamping device 10 Electric chainsaw blade emergency braking device 11 First saw blade brake shoe, eccentric 111 Guide surface 112 clamping surface 113 Recess for rotary axis 12 Second saw blade brake shoe, eccentric 121 guide surface 122 clamping surface 13 gap 14 Actuator 15 Eccentric drive, spindle 20 drive 21 pistons 22 piston cylinders 23 Piston rod 24 Return spring 30 pressure chamber 31 Fluid 40 valve element 41 Drain opening 50 saw blade, band saw blade 51 side surface 52 cutting edge 60 Cover 70 screw A axis QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 3 194 129 B1

[0005]

Claims

[1] Electric motor saw blade emergency braking device (10) for stopping the running of the saw blade (50) of an electric motor saw (1) incorporating a cutting table (2) through which the saw blade (50) of the saw (1) runs during a cutting operation, the device (10) comprising: - a first rotatably mounted saw blade brake shoe (11), - a second rotatably mounted saw blade brake shoe (12) spaced from the first saw blade brake shoe (11) for receiving the saw blade (50) in a gap (13) formed therebetween, - a drive (20) having a piston (21) arranged in a piston cylinder (22) for driving the first and second saw blade brake shoes (11, 12) from a rest position until contact with the side surfaces (51) of the saw blade (50) between the saw blade brake shoes (11, 12), - a pressure chamber (30) for maintaining a fluid (31) at a predetermined pressure, the pressure chamber (30) being arranged on the piston cylinder (22), and - a valve member (40) arranged to regulate a flow of the pressurized fluid (31) along a flow path between the valve member (40) and the piston (21) from the pressure chamber (30), with a discharge opening (41) for conducting pressurized fluid (31) from the pressure chamber (30) into the drive (20), characterized by that an actuator (14) is arranged for jointly driving the first saw blade brake shoe (11) and the second saw blade brake shoe (12) from the rest position until contact with the side surfaces (51) of the saw blade (50). [2] Electric motor saw blade emergency braking device (10) according to claim 1, characterized by that the saw blade brake shoes (11, 12) are designed as eccentrics with guide surfaces (111, 121) for guiding the saw blade (50). [3] Electric motor saw blade emergency braking device (10) according to claim 1 or 2, characterized by that the saw blade brake shoes (11, 12) are designed as eccentrics with clamping surfaces (112, 122) for clamping the saw blade (50). [4] Electric motor saw blade emergency braking device (10) according to one of claims 1 to 3, characterized by that the actuator (14) is designed as a guide plate with suitable recesses for driving the saw blade brake shoes (11, 12). [5] Electric motor saw blade emergency braking device (10) according to claim 4, characterized by that the actuator (14) is designed as a guide plate symmetrically with regard to an evenly distributed force introduction with respect to the saw blade brake shoes (11, 12). [6] Electric motor saw blade emergency braking device (10) according to one of claims 2 to 5, characterized by that the surfaces of the clamping surfaces (112, 122) and / or the guide surfaces (111, 121) of the saw blade brake shoes (11, 12) are polished. [7] Electric motor saw blade emergency braking device (10) according to one of claims 2 to 5, characterized by that the surfaces of the clamping surfaces (112, 122) and / or the guide surfaces (111, 121) of the saw blade brake shoes (11, 12) are coated. [8] Electric motor saw blade emergency braking device (10) according to one of claims 2 to 7, characterized by that the eccentrics with clamping surfaces (112, 122) and / or the guide surfaces (111, 121) are designed to be mirror-symmetrical with respect to a plane of symmetry running parallel to the axis of rotation (A). [9] Electric motor saw blade emergency braking device (10) according to one of claims 1 to 8, characterized by that when clamping the saw blade (50), the clamping surfaces (112, 122) have a contact area of less than 50 mm with the respective side surface (51) of the saw blade (50) 2 have. [10] Electric motor saw blade emergency braking device (10) according to one of claims 2 to 9, characterized bythat the guide surfaces (111, 121) are curved with a radius of curvature between 30 and 90 mm. [11] Electric motor saw blade emergency braking device (10) according to one of claims 3 to 10, characterized by that the clamping surfaces (112, 122) are curved with a radius of curvature between 5 and 15 mm. [12] Electric motor saw blade emergency braking device (10) according to one of claims 1 to 11, characterized by that the gap (13) for receiving the saw blade (50) has a gap width of less than 3 mm. [13] Electric motor saw blade emergency braking device (10) according to one of claims 1 to 12, characterized by that the drive (20) for driving and closing the first and second saw blade brake shoes (11, 12) from a rest position to contact with the side surfaces (51) of the saw blade (50) between the saw blade brake shoes (11, 12) results in a shooting time of less than 9, in particular less than 6 milliseconds. [14] Electric motor saw (1) with a cutting table (2) through which the saw blade (50) runs during a cutting operation, with an electric motor saw blade emergency braking device (10) for stopping the running of the saw blade (50) according to one of claims 1 to 13. [15] Electric motor saw (1) according to claim 14, wherein - a detection unit is available to detect a critical usage situation, - a control unit connected to the detection unit is present - means for decoupling the saw blade from a drive are provided - wherein the control is suitable for controlling both the emergency braking device (10) and the decoupling means. [16] Electric motor saw (1) according to claim 14 or 15, wherein the saw (1) is designed as a band saw with a saw blade (50) and wherein a means for decoupling is designed as a tensioning device (3) of the saw blade, which can be switched from a tensioned to a relaxed position. [17] Electric motor saw (1) according to one of claims 14 to 16, wherein the control is arranged to first control the means for decoupling and then the emergency braking device (10). [18] Electric motor saw (1) according to one of claims 14 to 17, wherein a cover (60) of components of the emergency braking device (10) is designed such that it has no horizontal surfaces on top.

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