Pneumatic drive motor

Abstract

A pneumatically operated drive machine (1) for an oscillating saw or file as a tool, comprising a tool housing (3) for a motor housing (17) mounted longitudinally displaceably in the tool housing (3), with a longitudinally oscillating piston (21) inserted therein, having a piston rod (23) attached thereto which can be connected to the tool, and a valve (25) inserted in the tool housing (3) for alternately supplying the two end faces of the piston in the motor housing (17) with supply air, wherein the supply air, after an actuating valve (35) connected to a compressed air source, passes through a cylinder (46) penetrating the rear end of the motor housing (17) in a sealed manner and traversing the rear displacement section (15") for the motor housing (17) in the tool housing (3), with a blind-hole supply air bore (45), directly into the interior of the motor housing. (17) is initiated,wherein both end faces of the motor housing (17) have substantially the same cross-sectional areas and the two displacement sections (15', 15") bounding the end faces of the motor housing (17) are connected to each other, such that the pressure of the exhaust air on both end faces of the motor housing (17) is substantially identical, so that regardless of the magnitude of the supply and exhaust air pressure, no displacement of the motor housing (17) occurs in the bore (13) of the tool housing (3), and the motor housing (17) is held in a central position by two springs (22, 24) when the engine is not running and there is no air supply.

Description

[0001] The invention relates to a compressed air-operated drive machine for an oscillating saw or file according to the preamble of claim 1.

[0002] Pneumatic drive machines are known in various designs from the prior art. One such drive machine is described in EP 1 028 826 B1 and comprises a tool housing with a motor housing that is longitudinally displaceable within the tool housing. A piston with a piston rod, which penetrates the motor housing, is oscillating within the motor housing. The compressed air supplied to both sides of the piston is alternately fed to the two cylinder chambers by a reed valve. A file or saw, which protrudes from the tool housing, is attached to the free end of the piston rod by a fastening device. A compression spring rests against the end of the motor housing on the tool side, pressing the motor housing backward, i.e., toward the compressed air supply side.The design aims to hold the motor housing in a central position within the cylinder chamber during operation by the compressed air pressure acting on the rear end of the motor housing. During operation, i.e., when compressed air is supplied and the piston oscillates within the motor housing, the motor housing can vibrate back and forth longitudinally within the tool housing, thus significantly reducing the transmission of the piston's oscillations and vibrations to the tool housing and the operator's hand, effectively decoupling these movements.

[0003] Due to the one-sided application of the supply pressure to the longitudinally movable motor housing, the position of the motor housing within the tool housing shifts depending on the supply pressure, which is adjustable by the user.

[0004] Further known drive machines can be found in documents DE 10 2010 015 484 A1 and JP 2007 - 203 446 A.

[0005] DE 10 2010 015 484 A1 discloses a pneumatically operated saw or file with a working chamber in which a piston with a shaft guided in a bushing can be moved up and down. To drive the piston, compressed air is alternately supplied to an upper and a lower part of the working chamber, the pneumatic motor having a control housing equipped with a reed valve through which this alternating supply of compressed air is made possible.

[0006] JP 2007-203446A discloses a pneumatically operated drive motor with a cylindrical housing in which two pistons are axially movable. A tool mounting element for holding a tool, such as a saw, is provided at a front end of the housing. The drive motor also includes a compressed air supply with a fixed shaft extending through the housing. This shaft has a supply channel or feed air through-bore for supplying compressed air between the first and second pistons. The compressed air supply is connected to the supply channel at a rear end of the shaft and is connected to the supply channel via valves.

[0007] DE 698 06 320 T2, US 2 899 934 A and DE 27 10 920 A1 further disclose drive machines in which it is fundamentally possible to introduce supply air into a motor housing of a compressed air-operated oscillating hand-held machine tool by means of a cylinder penetrating the motor housing in order to drive a piston to an oscillating movement.

[0008] One object of the present invention is to eliminate the disadvantages of the known saw and to create a compressed air-operated drive machine in which the central position of the motor housing within the tool housing can be defined independently of the pressure of the supply air and independently of the pressure of the exhaust air.

[0009] This problem is solved by a drive machine according to the features of patent claim 1. Advantageous embodiments of the drive machine are described in the dependent claims.

[0010] The inventive drive motor eliminates the disadvantages of the known machine, solves the stated tasks, and achieves optimal vibration damping. The guide length of the tool holder 9 in the guide 49 increases because the central position of the motor housing remains unchanged. The supply and exhaust pressures can be varied over a wider range, thereby increasing the frequency and stroke ranges. Furthermore, the power of the drive motor, and consequently also of the saw or file, can be increased.

[0011] The invention is explained in more detail using an illustrated embodiment. The illustrations show: Fig. 1 a longitudinal cut through a drive machine for a saw or file, Fig. 2. An enlarged section of the central part with the motor housing, the path of the supply air and the exhaust air colored grey. Fig. 3 A schematic representation of the motor housing (hatched), grey shaded are the spaces with exhaust air which act on the end faces of the motor housing.

[0012] Reference numeral 1 denotes a compressed air-operated drive machine. The drive machine 1 comprises a housing 3, at the rear end 5 of which supply air can be introduced. At the front end 7, a tool holder 9 for a file or saw (both not shown) protrudes from the housing 3. The central part of the housing 3 is tubular. The cylindrical inner wall, or cylindrical first bore 13, forms a space 15 between the rear and front sections of the housing 3. A cylindrical motor housing 17 is axially displaceably mounted in this space.

[0013] Within the motor housing 17, a concentric second bore 19 is formed in which a piston 21 is axially displaceable. A piston rod 23 is attached to the piston 21, the end of which projects out of the tool housing 3 and on which the tool holder 9 for a tool is formed.

[0014] The engine housing 17 is held axially elastically in the center of the displacement 15 by a front coil spring 22 and a rear coil spring 24.

[0015] The engine housing 17 contains a so-called reed valve 25 or another component which triggers an alternating supply of feed air to the chamber sections (27' and 27") in the second bore 19 in front of and behind the piston 21. The displacement 27 for the piston 21 is formed by the second bore 19 recessed in the engine housing 17, bounded at the rear by a plate 29 and at the front by a guide tube 31, which guides the piston rod 23 axially.

[0016] A supply air line 33 leads from the rear end 5 of the tool housing 3 to an actuating valve 35, which can be opened or closed by the operator using a lever 37. From the actuating valve 35, a cylinder 46 then extends into an axial bore 41 in the motor housing 17. Suitable sealing materials 43, for example O-rings, form a seal between the stationary cylinder 46, which is rigidly connected to the housing 3, and the motor housing 17, which is axially displaceable relative to the tool housing 3. An axially extending supply air bore 45, designed as a blind hole, is provided in the cylinder 46. At the other end of the supply air line 33, radially oriented holes 47 are formed, which open into a circumferential groove 51. The groove 51 also extends axially towards the front end of the motor housing 17 and terminates in the reed valve 25.In the reed valve 25, the feed air is directed alternately into the displacement sections 27' and 27", that is, alternately to the front and the back of the piston 21 in a known manner. The pipe routing from the reed valve 25 to the two displacement sections 27' and 27" is also known from the prior art and is therefore not explained.

[0017] In the schematic Fig. In Figure 3, spaces 15' and 15" are shown shaded gray. Exhaust air flows from the drive motor 1 in these spaces and in the axially extending connecting channels in the direction of arrow A. The hatched area (hatching running from top left to bottom right) represents the motor housing 17. The piston 21, which is axially movable within the motor housing 17, is not shown. The machine housing 3 is represented by hatching lines running from top right to bottom left. To the left and right of the machine housing 3, the end faces of the motor housing 17, upon which the exhaust air acts, are shown. The two annular or annular and circular end faces A2 and A5 and A4 are identical. Therefore, the forces acting on the motor housing 17 from the exhaust air at 1 to 4 bar are equal or cancel each other out. The left side in Fig. The end face exposed to the exhaust air pressure is composed of the cross-section of the motor housing 17 minus the cross-section A1 of the guide tube 31, shown here as a cylinder. The opposite end face exposed to the exhaust air pressure consists of two individual surfaces: the annular surface A5 and the circular surface A4 at its center. The total area on this side is therefore the difference between the cross-sectional area of ​​the motor housing 17 and the area of ​​the annular surface A6.

[0018] The following explains the operation of the drive motor 1. By opening the actuating valve 35, supply air or intake air at, for example, 6 bar enters the supply air bore 45 and from there directly into the interior of the motor housing 17. The supply air is in Fig. 2 is shown with dotted lines. Due to this direct routing of the supply air into the interior of the motor housing 17, the housing is held centrally within the first bore 13 in the tool housing 3 solely by the two springs 22 and 24 during a service interruption. The exhaust air exiting the cylinders 27' and 27" within the motor housing 17 then enters the cylinder sections 15' and 15" in the cylinder 15, so that essentially the same pressure conditions prevail both in front of and behind the motor housing 17. Consequently, the motor housing 17 is neither loaded nor displaced forwards or backwards by the exhaust air. The exhaust air areas, which are under a pressure of approximately 1 to 4 bar, are in Fig. 3 are shown shaded in grey.

[0019] The two Fig. 2 and Fig.Figure 3 shows how the supply air acts only inside the engine housing 17 and there on the piston 21, while the exhaust air acts only on the engine housing 17 from the outside and also with the same pressure on the two opposing end faces.

[0020] To ensure that the two opposing end faces are of equal size, a vented annular space with a cross-sectional area A6 was created. A6 is equal in size to A1. This allows the forces generated by the exhaust air in front of and behind the motor housing 17 to cancel each other out.

[0021] The two end faces, which are exposed to exhaust air, are joined at the following ring faces: A2 = A5 + A4. Legend of reference symbols 1 drive motor 3 cases 5 rear end 7 front end 9 tool holders 11 middle part of 3 13 first bore 15 engine displacement 17 engine housings 19 second bore 21 pistons 22 front spring 23 Piston rod 24 rear spring 25 reed valve 27 Engine Displacement Section 29 plate 31 Guide tube 33 Feed air duct 35 Actuating valve 37 levers 39 Pipe section 41 Axial bore 43 Sealants 45 Feed air bore 46 cylinders 47 holes 49 Leadership 51 Nut

Claims

A pneumatically operated drive machine (1) for an oscillating saw or file as a tool, comprising a tool housing (3) for a motor housing (17) mounted longitudinally displaceably in the tool housing (3), with a longitudinally oscillating piston (21) inserted therein, having a piston rod (23) attached thereto which can be connected to the tool, and a valve (25) inserted in the tool housing (3) for alternately supplying the two end faces of the piston in the motor housing (17) with supply air, wherein the supply air, after an actuating valve (35) connected to a compressed air source, passes through a cylinder (46) penetrating the rear end of the motor housing (17) in a sealed manner and traversing the rear displacement section (15") for the motor housing (17) in the tool housing (3), with a blind-hole supply air bore (45), directly into the interior of the motor housing. (17) is initiated,wherein both end faces of the motor housing (17) have substantially the same cross-sectional areas and the two displacement sections (15', 15") bounding the end faces of the motor housing (17) are connected to each other, such that the pressure of the exhaust air on both end faces of the motor housing (17) is substantially identical, so that regardless of the magnitude of the supply and exhaust air pressure, no displacement of the motor housing (17) occurs in the bore (13) of the tool housing (3), and the motor housing (17) is held in a central position by two springs (22, 24) when the engine is not running and there is no air supply. Drive machine according to claim 1, characterized in that the pipe section (39) is firmly connected to the housing (3) and is axially guided in a bore (41) in the motor housing (17). Drive machine according to claim 2, characterized in that at least two circumferential sealing means (43) are inserted between the pipe section (39) and the bore (41). Drive machine according to one of claims 1 to 3, characterized in that radially extending holes (47) are formed at the end of the feed air bore (45), which ends between the sealing means (43), which open into a groove (51) which leads into the motor housing (17). Drive machine according to claim 4, characterized in that the groove (51) is connected to the valve (25).

Images