Pneumatic impact tool

Abstract: The pneumatic impact tool comprises a body of a pneumatic motor which body is separated from a body-casing (4) of the impact tool by means of a vibro-isolating system, an air feeder system, a noise suppressor having a double-­ chamber, and a working tool (1) slidably connected with a tool sleeve (3). According to the invention the working tool (1) has a flange protecting it from falling down during operation and resting, when said impact tool is being pressed down, on a thrust ring (2) which is mounted on a barrel seat. One of the chambers of the noise suppressor consists of a conic sleeve (34) pushed on the body-casing (4) such that it can rotate around its axis, and is connected with the other chamber defined by a space between the body-casing (4) and the body of the pneumatic motor, by means of orifices (35) forming an acute angle with the main symmetry axis of the impact tool and extending tangentially to the plane of the ca­ sing of the pneumatic motor. The body of the pneumatic motor is connected with a vibro-isolator having a con­ stant interaction force by means of vibro-isolating spa­ cers (14) and releasable fasteners (16). Between the body-­ casing (4) and a grip (23) an additional vibro-isolation is provided consisting of a sleeve (25) mounted between a pipe (24) of the feeder and a barrel head (31) and of an elastic layer (38). A space in front of the pipe (24) of the feeder in the sleeve (25) is connected with the first chamber (33) of an air decompressor by means of air passages (32).

Description: The invention relates to a pneumatic impact tool comprising a pneumatic motor which is separated from a casing by means of a vibro-isolating system, an air feeder system, and a working tool slidably supported in a tool sleeve, the working tool having a flange which prevents the working tool from falling down during operation, and a sleeve is mounted in the barrel head of the pneumatic motor, a feeding pipe being slidably disposed in the sleeve and mounted to the grip means. Such a tool is known from the PL-B-122 477. The vibro-isolating system of this tool comprises an elastic ring which is provided between the casing and a barrel of the pneumatic motor. A barrel holder is slidably mounted on a ring protrusion of the barrel. At the end where the working tool is provided the barrel is slidably mounted in a sleeve having a flange. The barrel holder and the sleeve are connected by bolts which pass through the elastic ring. Springs are provided between the end of the bolts and the flange of the sleeve. The pneumatic motor is driven by compressed air supplied from an air compressor via the air feeder system to a timing unit. When the impact element of the pneumatic motor is moved towards the working tool, the air between the working tool and the impact element is compressed and the timing unit is activated. Thus, compressed air from the air compressor is passed between the impact element and the working tool, the air acting as a cushion therebetween. However the kinetic energy of the impact tool is high enough for overcoming the air pressure. The air is additonally compressed and simultaneously a stroke is exerted on the working tool. A part of the kinetic energy of the impact tool is transferred to the sleeve by the air cushion. This energy is absorbed by the springs between the bolts and the sleeve. The uplift pressure exerted by the air cushion leads to strong vibrations of the tool. These vibrations and other vibrations which are generated during the operation of the tool are not sufficiently absorbed by the vibro-isolating system. Therefore working with this pneumatic impact tool can result in the so-called "vibration white finger" of an operator. Further, due to the vibrations the tool is very noisy. The problem underlying the invention is to provide by simple means a pneumatic impact tool generating low vibrations and noise during operation. Starting out from the pneumatic impact tool of the generic kind this problem is solved in that a first chamber of a noise suppressor is defined by a space between the casing end the pneumatic motor, a second chamber of the noise suppressor is defined by a space between a conical sleeve and the casing, the conical sleeve being pushed onto the casing such that it con rotate around its axis, air outlet holes being provided in the conical sleeve, the first and the second chamber are connected by means of orifices in the casing forming an acute angle to the central axis of the impact tool and extending tangentially to the plane of the pneumatic motor, vibro-isolator means having a constant interaction force being connected with a barrel head of the pneumatic motor and with grip means by means of vibro-isolating spacers and releasable fasteners, the sleeve is mounted in said barrel head by means of an elastic layer, a space in the sleeve in front of the feeding pipe is connected with the first chamber via air passages and the working tool rests on a thrust ring which is mounted at a barrel seat of the pneumatic motor, when said impact tool is being pressed down. Advantageously a groove is provided in the body casing and in that the vibro-isolator comprises cams which are mounted in the groove and fixed by means of washers consisting of elastic material. Preferably a rubber-spring sleeve is screwed onto the casing, the rubber-spricg sleeve serving as a vibro-isolated grip for the left hand of an operator. The design of the pneumatic impact tool according to the invention prevents the operator from being overstrained by holding-down forces, so it provides safe and hygenic working with higher productivity. Moreover, the tool has an entire vibration protection of the operator's both hands in all directions of vibration. The left-hand grip of the tool prevents the operator from directly touching the working tool strongly activated by vibrations and protects him against noxious effects of vibrations. The compressed air supply systems suppresses any uplift Pressure that would change under the effect of air pressure fluctuations and would cause vibrations of the pipe. The diameter of the air supply orifices in the sleeve and that of the supply pipe are matched such that the tool can sag in a pre-set range when the feeder is entirely switched on. The hammer operation is stable in the full range of amplitudes of the body of the pneumatic motor and of the casing where both hand-grips for the operator are mounted. The tool is further provided with an automatic lock-out of the air supply system in order to protect the casing of the pneumatic motor against strokes and the operator's both hands against additional vibrations. Moreover, the double-chamber noise suppressor applied in the tool is designed such that the operator is capable of setting the direction of the air out-flow. An embodiment of the invention is further explained with the aid of a drawing showing a pneumatic impact tool in a section along the tool's symmetry axis. The pneumatic impact tool shown in the drawing comprises a pneumatic motor separated from a casing 4 by means of a vibro-isolating system, a supply or air feeder system, a double-chamber noise suppressor and a working tool 1 which is slidably connected with a tool sleeve 3. The pneumatic motor includes a ram reciprocating in a barrel provided one end thereof with a distributor slider body in which an air distribution slider moves. The distribution slider body is pressed against a barrel face by a barrel head that is screwed on the barrel and fastened by a pin and a ring. The other end of the barrel comprises a tool sleeve 3 pushed in the barrel seat. In the bottom of the barrel seat a thrust ring 2 is mounted. The working tool 1 moves in the tool sleeve 3 and rests on a thrust ring 2 the impact or hammer tool is being pressed down against the material to be worked on. The tool sleeve 3, the barrel, the distributor slider body, the air distribution slider and the barrel head define the body of the pneumatic motor. The body of the pneumatic motor is separated from the casing 4 by means of a vibrator-isolating system that consists of a constant interaction force vibro-isolator and silent block guides. A constant interaction force vibro-isolator is connected in series with a washer 5 made of an elastic material of vibro-isolator characteristic and with sleeves 6. These sleeves 6 together with bolts 7 and washers 8 fasten a guide 9 of the vibro-isolator to a barrel head 31. While working guide rollers 10 of a carriage 11 of the vibro-isolator roll on the guide 9. The carriage 11 acts at the same time as a guide for the spring system of the vibro-isolator. The central rollers of the carriage 11 roll on cambers of cams 12 which are mounted in grooves 13 in the casing 4. The cams 12 are protected from falling out of the grooves 13 by a vibro-isolationg spacer 14 that is pressed against the cams 12 by vibro-isolating sleeves 15 and releasable fasteners 16 having washers 17. The body of the pneumatic motor is guided in the casing 4 by an upper and a lower guide which also define the first stage of vibro-isolation between the body of the pneumatic motor and the hand grips for the operator. The upper guide consists of a slide bearing in form of a sleeve 18 which is made of a material characterized by a low friction factor and which is mounted in the vibro-isolating sleeve 19 firmly connected to the casing 4. The lower guide consists of a sleeve 20 with a multi-slot shaped orifice. The sleeve 20 is connected with an oval sleeve 22 through a layer 21 of vibro-isolating material. The sleeve 22 is pushed in the casing 4. The sleeve 20 matches with the tool sleeve 3. The supply or air feeder system is provided with a cut-off valve which is connected to a lever being located in the operators left hand grip 23. The lever directly affects the valve head mounted in the operator's right hand grip. A spring pressing the head against the seat causes the valve to close. A sealing consists of one additional gasket made of an elastic material. In the grip 23 there is also mounted a pipe 24 of the feeder which is connected with the sleeve of the feeder and matches with an "indirect" sleeve 25 which is pushed in the barrel head 31. The sleeve 25 is made of a material characterized by a low friction factor and by high vibro-isolation properties. The pipe 24, the one end of which is blanked off has two small holes 26 extending perpendicularly to the symmetry axis of the impact tool. The holes 26 aligne with two openings 29 in the sleeve 25. An indirect supplying is possible right after pressing the grip 23 which results in increasing the diameter of a hole 27 being provided in the pipe 24 perpendiculary to the holes 26 and overlapping two subsequent holes 29 which are perpendicular to the holes 26. Holes 28 of the pipe 24 are open parallel to the holes 26. After the vibro-isolator with constant reaction force deflects so as the holes 28 come in line with the holes 29, the feed passage is entirely opened. Continued pressing of the vibro-isolator causes the air to be chocked as the holes 28 and 29 become gradually blanked off till entirely being closed. Stopping of the impact tool operation is a signal for the operator to reduce pressing of the grip to avoid the supply air from freely flowing through. The supply air, after having passed through the holes 28 and 29, flows through a chamber 30 between the sleeve 25 and a seat of the barrel head 31, parallel to the symmetry axis of the tool and then through air passages 32 in the barrel head 31 to the air distributor slider body. The air distribution slider controls the air flow and guides it alternately above or below the ram causing the ram to reciprocale. The position of the air distribution slider depends on the position of the ram causing the hammer tool to start to work automatically after switching the air supply on. The air flows out of the pneumatic motor and comes into the space between the body of the pneumatic motor and the casing 4, i.e. the first air decompression chamber 33. Then the air flows through the outflow suppressor on the casing 4 through wall holes 35. The outer wall of the outflow supressor consists of the conic sleeve 34 made of an elastic light material in which several outlet holes 36 are provided. The air is led down from the operator. As the conic sleeve 34 is able to be turned around the axis of the hammer tool, the operator may adjust it as he wants. The chamber of the sleeve 25 in the supply system is additionally decompressed in front of the supply face of the sleeve. The purpose is to decompress the casing 4 with the body of the pneumatic motor that would take place in case of closing of that chamber. The additional vibro-isolation of both grips ensures complete vibro-isolation of the hammer tool. The second stage of the vibro-isolation of the operator's left hand consists of a sleeve 37 that is made of a material characterized by a high vibration damping coefficient and that is screwed on the body-casing 4 by means of a spring emersed in this sleeve 37. The second stage of the vibro-isolation of the operator's right hand consists of an elestic washer and an elastic sleeve. Furthermore, the supply system is also double-isolated. The first stage consists of the sleeve 25 made of a material characterized by a high vibration damping coefficient and mounted in the body of the pneumatic motor. The second stage consists of an elastic layer 38 by means of which the pipe 24 is installed in the operator's right hand grip 23. The hammer tool is designed in a streamline shape, so its form is esthetic and makes operation more easy.

Claims: A pneumatic impact tool comprising a pneumatic motor which is separated from a casing (4) by means of a vibro-isolating system, an air feeder system, and a working tool (1) slidably supported in a tool sleeve (3), the working tool (1) having a flange (39) which prevents the working tool (1) from falling down during operation, a sleeve (25) being mounted in the barrel head (31) of the pneumatic motor, a feeding pipe (24) being slidably disposed in the sleeve (25) and mounted to the grip means (23), characterized in that a first chamber (33) of a noise suppressor is defined by a space between the casing (4) and the pneumatic motor, a second chamber of the noise suppressor is defined by a space between a conical sleeve (34) and the casing (4), the conical sleeve (34) being pushed onto the casing (4) such that it can rotate around its axis, air outlet holes (36) being provided in the conical sleeve (34), the first and the second chamber are connected by means of orifices (35) in the casing (4) forming an acute angle to the central axis of the impact tool and extending tangentially to the plane of the pneumatic motor, vibro-isolator means having a constant interaction force being connected with a barrel head (31) of the pneumatic motor and with grip means by means of vibro-isolating spacers (5,6;14,15) and releasable fasteners (7, 16), the sleeve (85) is mounted in said barrel head (31) by means of an elastic layer (38), a space in the sleeve (25) in front of the feeding pipe (24) is connected with the first chamber (33) via air passages and the working tool rests on a thrust ring (2) which is mounted at a barrel seat of the pneumatic motor, when said impact tool is being pressed down. Tool according to claim 1, characterized in that a groove (13) is provided in the body casing (4) and in that the vibro-isolator comprises cams (12) which are mounted in the groove (13) and fixed by means of washers (14,15) consisting of elastic material. Tool according to claim 1 or 2, characterized in that a rubber-spring sleeve (37) is screwed onto the casing (4), the rubber-spricg sleeve (37) serving as a vibro-isolated grip for the left hand of an operator.

Inventors: CEMPEL CZESLAW, DOBRY MARIAN WITALIS, GARBATOWSKI WIESLAW, CEMPEL, CZESLAW, DOBRY, MARIAN WITALIS, GARBATOWSKI, WIESLAW
Applicants: POLITECHNIKA POZNANSKA
Application year: 1989
Main classification: B25D9
IPC codes: B25D9, B25D17