Pneumatic hammer device and a method pertaining to a pneumatic hammer device

Abstract

A pneumatic hammer including a connector for connection to an external compressed air source and a striking mechanism. The striking mechanism includes a housing and a piston arranged for reciprocating motion in the housing. The striking piston has front and rear piston portions. The piston and the housing form front and rear spaces. A compressed air conduit is arranged in airflow communication with the front space via a second passage in the housing, at which second passage a first valve is arranged. There is an intermediate space between the front and rear piston portions and the housing. The control unit is alternately subjected to air pressure of the rear space with respect to the intermediate space during reciprocating motion of the piston. The control unit controls the first valve based on air pressure to alternately supply compressed air to the front space and achieving a return movement of the piston.

Claims

1. A pneumatic hammer device, comprising: a connector configured to be connected to a compressed air conduit of an external compressed air source, and a striking mechanism comprising a striking mechanism housing and a striking piston arranged for reciprocating motion in said striking mechanism housing, the striking piston having a front piston portion and a rear piston portion, wherein the front piston portion affects an insert tool arranged at the hammer device, wherein the striking piston and the striking mechanism housing together form a front space and a rear space, wherein the front space is limited rearwards by the front piston portion and the rear space is limited forwards by the rear piston portion, wherein said compressed air conduit is arranged in air flow communication with the rear space via a first passage in the striking mechanism housing, and wherein said compressed air conduit is arranged in air flow communication with the front space via a second passage in the striking mechanism housing, at which second passage a first valve is arranged, wherein the striking piston is configured such that an intermediate space is formed between the front piston portion and the rear piston portion and the striking mechanism housing, wherein a control unit is arranged to alternately be subjected to an air pressure at said rear space and said intermediate space respectively during the reciprocating motion of the striking piston, and wherein said control unit is arranged to control said first valve on the basis of said air pressure to alternately supply compressed air to the front space and achieve a return movement of the striking piston.

2. The pneumatic hammer device according to claim 1, further comprising: a first venting passage arranged at said striking mechanism housing for maintaining atmospheric pressure at said intermediate space.

3. The pneumatic hammer device according to claim 1, wherein the control unit comprises a control passage arranged at said striking mechanism housing and a control conduit arranged between the control passage and the first valve.

4. The pneumatic hammer device according to claim 1, further comprising: a second venting passage arranged at the striking mechanism housing such that the second venting passage is in communication with the front space when the control unit is in communication with the intermediate space.

5. The pneumatic hammer device according to claim 1, further comprising a feed conduit arranged in air flow communication with the compressed air conduit and the first valve.

6. The pneumatic hammer device according to claim 1, wherein the connector comprises a second valve arranged in connection with the air conduit for controlling the supply of compressed air.

7. The pneumatic hammer device according to claim 6, further comprising: an actuator arranged in communication with the second valve, in order to manually achieve the opening/closing of the second valve.

8. The pneumatic hammer device according to claim 7, wherein the actuator comprises a servo valve.

9. The pneumatic hammer device according to claim 1, further comprising: a venting device arranged for venting of said front space.

10. The pneumatic hammer device according to claim 1 further comprising: an intermediate block arranged between the insert tool and the front portion of the striking piston.

11. The pneumatic hammer device according to claim 1, further comprising: a rotation mechanism for rotation of the insert tool.

12. A method pertaining to a pneumatic hammer device comprising a connector arranged for connection to a compressed air conduit of an external compressed air source and a striking mechanism comprising a striking mechanism housing and a striking piston arranged for reciprocating motion in said striking mechanism housing, the striking piston further comprising a front piston portion and a rear piston portion, wherein the front piston portion affects an insert tool arranged at the hammer device, wherein the striking piston and the striking mechanism housing together form a front space and a rear space, wherein the front space is limited rearwards by the front piston portion and the rear space is limited forwards by the rear piston portion, wherein said compressed air conduit is arranged in air flow communication with the rear space via a first passage in the striking mechanism housing, and wherein said compressed air conduit is arranged in air flow communication with the front space via a second passage in the striking mechanism housing, at which second passage a first valve is arranged, the method comprising: controlling the first valve with a control unit arranged to be alternately subjected to an air pressure of said rear space and an intermediate space respectively, during the reciprocating motion of the striking piston, wherein said intermediate space is formed between the striking mechanism housing, the front piston portion and the rear piston portion, wherein the control unit controls said first valve based on said air pressure to alternately supply compressed air to the front space and achieve a return movement of the striking piston.

13. The method pertaining to a pneumatic hammer device according to claim 12, further comprising: controlling said first valve such that the first valve opens and supplies compressed air to said front space when the striking piston is positioned such that the control is in communication with the rear space, in order to achieve a rearward movement of the striking piston in the striking mechanism housing.

14. The method pertaining to a pneumatic hammer device according to claim 12, further comprising: controlling said first valve such that the first valve closes when the striking piston is positioned such that the control unit is in communication with the intermediate space.

15. The method pertaining to a pneumatic hammer device according to claim 12, further comprising: venting said front space when the first valve is closed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a more complete understanding of the present invention and further objects and advantages thereof, reference is now made to the following detailed description to be read together with the accompanying drawings wherein equal reference numbers refer to equal parts in the various figures, and in which:

(2) FIG. 1 schematically shows a hammer device according to an embodiment of the invention;

(3) FIG. 2 schematically shows a cross sectional view of a striking mechanism of a hammer device according to an embodiment of the invention;

(4) FIG. 3a schematically shows a flow chart of a method according to an embodiment of the invention; and

(5) FIG. 3b in further detail schematically shows a flow chart of a method according to an embodiment of the invention;

DETAILED DESCRIPTION OF THE DRAWINGS

(6) In the description of the drawings position terms such as front, rear, forward and rearward are mentioned. Forward is here defined as a direction in the striking direction and rearward thus as a direction opposite to the striking direction.

(7) FIG. 1 schematically shows a hammer device 100 according to an embodiment of the present invention. The hammer device 100 comprises T-shaped handles 126, a striking mechanism 105 and connecting means 156 for connection to a compressed air conduit 102 of an external pressure source (not shown). The striking mechanism 105 comprises a striking mechanism housing (not shown), a striking piston (not shown) movably arranged at the striking mechanism housing and a front part 120 for connecting an insert tool 124 to the striking mechanism 105. The front part 120 is in this embodiment integrated with the striking mechanism housing and comprises a bushing/sleeve (not shown) to fit with the insert tool 124. The striking piston may be moved axially along the extension of the striking mechanism housing and strikes, in a front position, the insert the tool 124, which results in a transfer of energy to the insert tool 124. The pressure source which supplies compressed air to the hammer device 100 is suitably a compressor. The hammer device 100 also comprises a sound dampening housing 123 arranged around the striking mechanism 105.

(8) FIG. 2 schematically shows a cross sectional view of a hammer device 200 according to an embodiment of the present invention. The hammer device 200 comprises a striking mechanism 205. The striking mechanism 205 in turn comprises a striking mechanism housing 210, in which a striking piston 230 is arranged for a reciprocating motion along the extension of the striking mechanism housing 210. The striking mechanism housing 210 is configured as a cylinder and has a front portion 212 and a rear portion 214, wherein the front portion 212 has a larger inner diameter and thereby a larger exposed area than the rear portion 214. A contact surface 216 is formed at the diameter transition between the front portion 212 and the rear portion 214. Integrated with the front portion 212 of the striking mechanism housing 210 a front part 220 with a bushing 222 is arranged for connection of an insert tool 224 to the hammer device 200. At the rear portion 214 of the striking mechanism housing 210 the handles 226 of the hammer device 200 are arranged. Between the striking mechanism housing 210 and the front part 220 an intermediate block 228 is arranged. When the striking piston 230 moves forward to a front position, the striking piston 230 strikes the intermediate block 228. The intermediate block 228 then transfers the kinetic energy of the striking piston 230 to the insert tool 224. The intermediate block 228 also prevents dirt from entering the striking mechanism housing 210.

(9) The striking piston 230 is configured with a front piston portion 232 and a rear piston portion 236 and an intermediate portion 238 extending there between. The front piston portion 232 impacts, in the front position of the striking piston 230, the insert tool 224 which is connected to the hammer device 200, such that an energy transfer to the insert tool 224 is achieved. The front piston portion 232 comprises a first portion 233 and a second portion 234, wherein the first portion 233 has a larger diameter than the second portion 234. The second portion 234 of the front piston portion 232 is the portion that abuts the intermediate block 228 upon striking. The first portion 233 of the front piston portion 232 has substantially the same diameter as the inner diameter of the front portion 212 of the striking mechanism housing 210. The front piston portion 232 thus forms a front space 240 together with the striking mechanism housing 210. The front space 240 is thus limited rearwards by the first portion 233 of the front piston portion 232 and limited forwards by the intermediate block 228 and the striking mechanism housing 210. The rear piston portion 236 has a smaller diameter than the first portion 233 of the front piston portion 232. The rear piston portion 236 has substantially the same diameter as the inner diameter of the rear portion 214 of the striking mechanism housing 210. The rear piston portion 236 thereby forms a rear space 250 together with the striking mechanism housing 210. The intermediate portion 238 of the striking piston 230 has a smaller diameter than the first portion 233 of the front piston portion 232 and the rear piston portion 236 such that an intermediate space 260 is formed between the striking mechanism housing 210, the front piston portion 232 and the rear piston portion 236. The front space 240, the intermediate space 260 and the rear space 250 are separated and sealed by slot seals 270, radially between the first portion 233 of the front piston portion 232 and the striking mechanism housing 210 and between the rear piston portion 236 and the striking mechanism housing 210. The slot 270 between the striking piston 230 and the striking mechanism housing 210 is between 10-60 micrometers. By using the slot sealing 270, the friction between the striking piston 230 and the striking mechanism housing 210 is minimized. In this way, a hammer device 200 which has an optimized striking effect is achieved.

(10) The hammer device 200 further comprises connecting means 256 for connection to a compressed air conduit 202 of an external compressed air source (not shown). The compressed air conduit 202, in the form of a hose, is arranged in air flow communication with the rear space 250 of the striking mechanism housing 210 via a first passage 252 in the striking mechanism housing 210, and the front space 240 of the striking mechanism housing 210 via a second passage 242. At the second passage 242 a first valve means 246 is arranged. The first valve means 246 is arranged to regulate the supply of compressed air to the front space 240 via the second passage 242. The connecting means 256 comprises a second valve means 257 arranged to regulate the air flow between the air conduit 202 and rear space 250. Further, an actuator means 258 in the form of a servo valve is arranged in communication with the second valve means 257. The servo valve 258 is manually operated by an operator, via for example a button, a lever or the like (not shown) and a power steering of the second valve means 257 is thereby achieved. By activating the servo valve 258, the second valve means 257 opens and the hammer device 200 is started. When the servo valve 258 is deactivated the second valve means 257 is closed and the hammer device 200 is stopped. As long as the servo valve 258 is activated, the second valve means 257 is maintained open and compressed air is thereby constantly supplied to the rear space 250 during use of the hammer device 200. Between the second valve means 257 and the first valve means 246 is a feed conduit 272 arranged for feeding of compressed air from the compressed air conduit 202 to the front space 240. When the servo valve 258 is activated and the second valve means 257 is open, the feed conduit 272 is substantially constantly pressurized.

(11) The hammer device 200 further comprises control means 280 for controlling the first valve means 246 and thereby controlling the compressed air supply to the front space 240. The control means 280 comprise a control passage 282 at the striking mechanism housing 210, and a control conduit 284 connected between the control passage 282 and the first valve means 246. The control conduit 284 is constituted by a hose. The control passage 282 is arranged such that it alternately is in communication with the rear space 250 respectively the intermediate space 260, depending on the position of the striking piston 230 in the striking mechanism housing 210. In this way, the control passage 282 and thereby the control conduit 284 are alternately subjected to an air pressure of the rear space 250 and an air pressure of the intermediate space 260 during the reciprocating motion of the striking piston 230. The first valve means 246 is controlled based on the air pressure which the control means 280 are subjected to.

(12) A first venting passage 290 is arranged in the striking mechanism housing 210 such that that the intermediate space 260 is in constantly communication with the atmosphere. This way, an atmospheric pressure is maintained in the intermediate space 260, regardless of the position of the striking piston 230.

(13) A second venting passage 292 is further arranged in the striking mechanism housing 210 such that it is in communication with the front space 240 only when the control means 280 are in communication with the intermediate space 260.

(14) When an operator activates the servo valve 258, the second valve means 257 opens such that air freely can flow between the compressed air conduit 202 and the rear space 250 via the first passage 252. The compressed air in the rear space 250 affects the rear piston portion 236 such that the striking piston 230 is pressed forward in the striking direction. When the rear piston portion 236 has passed the control passage 282 (as shown in the figure) the compressed air of the rear space flows into the control conduit 284. The air in the control conduit 284 then has the same pressure as the air of the rear space 250. The first valve means 246 is a mechanically controlled 3/2 valve having a first closed idle position and a second controlled open position. In the idle position, the valve 246 is closed to the front space 240 such that no compressed air may be supplied to the front space 240. The valve 246 comprises a venting device 248 by also being connected to the atmosphere in the idle position. The idle position thus results in that the front space 240 is vented. When the pressure in the control conduit 284 increases to the same pressure as that of the rear space 250, the compressed air controls the first valve means 246 to its second position. The controlled second position causes the valve 246 to be opened to the front space 240 and the compressed air in the supply conduit 272 may be supplied to the front space 240 via the second passage 242. The positioning of the control passage 282 is adapted such that the first valve means 246 not will switch and open until the striking piston 230 has reached the insert tool 224.

(15) When the first valve means 246 is open, the front space 240 is filled with compressed air while the rear space 250 constantly is supplied with compressed air. Since the first portion 233 of the front piston portion 232 has a larger diameter, and thereby area, than the rear piston portion 236, the striking piston 230 is pressed rearward in the striking mechanism housing 210. The volume of the rear space 250 thereby decreases and the air in the rear space 250 flows due to the constantly open second valve means 257 back into the compressed air conduit 202 which thus serves as an accumulator. The accumulator in the form of the compressed air conduit 202 is so much larger than the rear space 250 that the rear space 250 obtains a substantially constant pressure and thus achieves a substantially constant acceleration of the striking piston 230 both during its forward and return movement. The substantially constant pressure results in substantially constant reaction forces and thereby minimizes the vibrations in the striking mechanism 205.

(16) The striking piston 230 is thus moved rearward in the striking mechanism housing 210 and when the rear piston portion 236 has passed the control passage 282, the control passage 282 and the control conduit 284 are in communication with the intermediate space 260 instead of the rear space 250. The intermediate space 260 is in constant communication with the atmosphere via the first venting passage 290, causing the compressed air in the control conduit 284 to flow out to the atmosphere and the pressure in the control conduit 284 is substantially reduced to atmospheric pressure. When the pressure in the control conduit 284 is reduced, the first valve means 246 returns to its closed idle position and the supply of compressed to the front space 240 is stopped. The striking piston 230 will however move rearward in the striking mechanism housing 210 as long as the energy of the air in the front space 240 and the kinetic energy in the striking piston 230 is greater than the pressure on the rear piston portion 236 in the rear space 250. Finally, the striking piston 230 has been moved rearward so far that the first portion 233 of the front piston 232 is positioned behind the second venting passage 292, such that the second venting passage 292 is in communication with the front space 240. In this way, the front space 240 is vented through the second venting passage 292. The air discharged through the second venting passage 292 thus has a relatively low pressure and therefore contains a lower energy. This reduces the sound emissions from the hammer device 200 and a high efficiency is obtained. When the compressed air in the rear space 250 affects the striking piston 230 and the striking piston 230 is moved forward, the front space 240 is compressed. Due to that the front space 240 is vented via the second venting passage 292 there is substantially no compressed air which significantly decelerates the forward movement of the striking piston 230. The front space 240 is also vented via the venting device 248 of the first valve means 246 the whole time when the first valve means 246 is in its closed idle position which further minimizes the deceleration of the forward movement of the striking piston 230. By configuring the hammer device 200 according to the present invention, an optimal timing between the position of the striking piston 230 and the control of the supply of compressed air to the front space 240 is achieved, in this way mechanical stopping of the striking piston 230 when the hammer device 200 is in use is prevented.

(17) To switch off the hammer device 200, the servo valve 258 is inactivated and the second valve means 257 is closed. By throttling all supply of compressed air to the hammer device 200 during switching off, the internal leakage is minimized when the hammer device 200 is switched off. The second valve means 257 comprises a venting function. When the second valve means 257 has been closed the rear space 250 is thus vented through the venting function to minimize the amount of compressed air in the rear space 250 at the next start of the hammer device 200. By venting the rear space 250, the feed power demand is minimized at every new start of the hammer device 200. When the hammer device 200 is switched off, the striking piston's 230 eventual rearward movement is stopped by the first portion 233 of the front piston portion 232 being received by the contact surface 216 at the diameter transition of the striking mechanism housing 210.

(18) FIG. 3a shows a flow chart of a method pertaining to a pneumatic hammer device 200 according to an embodiment of the present invention. The hammer device 200 comprises connecting means 256 arranged for connection to a compressed air conduit 202 of an external compressed air source and a striking mechanism 205. The striking mechanism 205 comprises a striking mechanism housing 210 and a striking piston 230 arranged for reciprocating motion in said striking mechanism housing 210, which striking piston 230 has a front piston portion 232 and a rear piston portion 236, wherein the front piston portion 232 affects an insert tool 224 arranged at the hammer device 200, wherein the striking piston 230 and the striking mechanism housing 210 together form a front space 240 and a rear space 250, wherein the front space 240 is limited rearwards by the front piston portion 232 and the rear space 250 is limited forwards by the rear piston portion 236, wherein said compressed air conduit 202 is arranged in air flow communication with the rear space 250 via a first passage 252 in the striking mechanism housing 210, and wherein said compressed air conduit 202 is arranged in air flow communication with the front space 240 via a second passage 242 in the striking mechanism housing 210, at which second passage 242 a first valve means 246 is arranged.

(19) The method comprises a first method step s301. The step s301 comprises controlling the first valve means 246 by means of control means 280 arranged to alternately be subjected to an air pressure of said rear space 250 respectively an intermediate space 260, formed between the striking mechanism housing 210, the front piston portion 232 and the rear piston portion 236, during the reciprocating motion of the striking piston 230, wherein the control means 280 controls said first valve means 246 on the basis of said air pressure. After the method step s301 the method ends.

(20) FIG. 3b shows a flow chart of a method pertaining to a pneumatic hammer device 200 according to an embodiment of the present invention. The hammer device 200 comprises connecting means 256 arranged for connection to a compressed air conduit 202 of an external compressed air source and a striking mechanism 205. The striking mechanism 205 comprises a striking mechanism housing 210 and a striking piston 230 arranged for reciprocating motion in said striking mechanism 210, which striking piston 230 has a front piston portion 232 and a rear piston portion 236, wherein the front piston portion 232 affects an insert tool 224 arranged at the hammer device 200, wherein the striking piston 230 and striking mechanism housing 210 together form a front space 240 and a rear space 250, wherein the front space 240 is limited rearwards by the front piston portion 232 and the rear space 250 is limited forwards by the rear piston portion 236, wherein said compressed air conduit 202 is arranged in air flow communication with the rear space 250 via a first passage 252 in the striking mechanism housing 210, and wherein said compressed air conduit 202 is arranged in air flow communication with the front space 240 via a second passage 242 in the striking mechanism housing 210, at which second passage 242 a first valve means 246 is arranged.

(21) The method comprises a first method step s310. The step s310 comprises starting the hammer device 200 by activating the supply of compressed air to the rear space 250 of the striking mechanism housing 210. After the method step s310 has been performed a subsequent method step S320 is performed.

(22) Method step s320 comprises providing a forward movement of the striking piston 230 in the striking mechanism housing 210 towards a forward position of the striking piston 230, in which the striking mechanism 230 strikes an insert tool 224 arranged at the hammer device 200. After the method step s320 a subsequent method step s330 is performed.

(23) Method step s330 comprises providing a return movement of the striking piston 230 by controlling the first valve means 246 such that it opens and compressed air is supplied to the front space 240. When the rear piston portion 236 has passed control means 280 arranged at the striking mechanism housing 210 such that the control means 280 are in communication with the rear space 250 and thereby are subjected to the pressure in rear space 250, the first valve means 246 is controlled to an open position. In this way a pressure build up is achieved in the front space 240, which pressure affects the front piston portion 232 such that the striking piston 230 is moved rearward in the striking mechanism housing 210. After the method step s330 a subsequent method step s340 is performed.

(24) Method step s340 comprises controlling the return movement of the striking piston 230 by controlling the first valve means 246 such that it is closed and the supply of compressed air to the front space 240 is stopped. When the rear piston portion 236 during its rearward movement has passed the control means 280 such that the control means 280 are in communication with an intermediate space 260 formed between the striking mechanism housing 210, the front piston portion 232 and the rear piston portion 236, and thereby are subjected to the pressure in the intermediate space 260, the first valve means 246 is controlled to a closed position. When the first valve means 246 has been closed, the striking piston 230 continues to move rearward in the striking mechanism housing 210 by its own kinetic energy until the pressure of the rear space 250 completely decelerates the rearward movement of the striking piston 230. After the method step s340 a subsequent method step s350 is performed.

(25) Method step s350 comprises venting the front space 240 when the first valve means 246 is closed, in order to minimize the decelerating effect when the striking piston 230 is pressed forward again. After the method step s350 a subsequent method step s360 is performed.

(26) Method step s360 comprises switching off the hammer device 200 by interrupting the supply of compressed air to the striking mechanism housing 210 and venting the striking mechanism housing 210. The method is ended after the method step s360.

(27) The foregoing description of the preferred embodiments of the present invention has been provided for the purpose of illustrating and describing the invention. It is not intended to be exhaustive or to limit the invention to the variants described. Obviously, many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, and thereby allowing the person skilled in the art to understand the invention for various embodiments and with the various modifications suitable for the intended use.