Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23D—PLANING; SLOTTING; SHEARING; BROACHING; SAWING; FILING; SCRAPING; LIKE OPERATIONS FOR WORKING METAL BY REMOVING MATERIAL, NOT OTHERWISE PROVIDED FOR
  • B23D51/00—Sawing machines or sawing devices working with straight blades, characterised only by constructional features of particular parts; Carrying or attaching means for tools, covered by this subclass, which are connected to a carrier at both ends
  • B23D51/16—Sawing machines or sawing devices working with straight blades, characterised only by constructional features of particular parts; Carrying or attaching means for tools, covered by this subclass, which are connected to a carrier at both ends of drives or feed mechanisms for straight tools, e.g. saw blades, or bows
  • B23D51/18—Sawing machines or sawing devices working with straight blades, characterised only by constructional features of particular parts; Carrying or attaching means for tools, covered by this subclass, which are connected to a carrier at both ends of drives or feed mechanisms for straight tools, e.g. saw blades, or bows actuated by fluid or gas pressure
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25D—PERCUSSIVE TOOLS
  • B25D9/00—Portable percussive tools with fluid-pressure drive, i.e. driven directly by fluids, e.g. having several percussive tool bits operated simultaneously
  • B25D9/14—Control devices for the reciprocating piston
  • B25D9/26—Control devices for adjusting the stroke of the piston or the force or frequency of impact thereof

Definitions

• the present invention relates to a pressure medium operated reciprocating impact mechanism according to the preamble of the appended claim 1.
• Impact mechanisms of this type may be used for pressure medium operated devices working by a reciprocating movement of most various types and sizes and widely different ranges of the size and frequency of the impact movement or stroke.
• Devices for driving down and in objects, such as poles and tongues, for drilling, chiselling, engraving, hammering, vibrating screens, feed shoes and similar devices as well as compacting ballast masses etc. may be mentioned as examples.
• Another common field of use is as slag hacker.
• SHEET definable it is also, despite that it may be increased by choosing a weaker spring between the working member and the housing of the tool in question, to ⁇ - short for certain ap ⁇ plications, since the pressure medium leaves the working chamber as soon as the sealing member leaves the contact with either the bottom of the working chamber or said second of said members.
• a shorter length of the stroke has the conse ⁇ quence that the frequency tends to get to high for certain applications, whereby local points with very high tempera ⁇ tures in the working tool in question may be created, and the the working life of said tool may by that be considerably shortened by premature material fatigue. This is for example valid especially when using the impact mechanism for carry ⁇ ing out sawing movements and the like, since only a very re ⁇ stricted part of for instance a saw blade is then utilized and exerted to a high frequency.
• the object of the present invention is to provide an impact mechanism of the kind mentioned in the introduction, which enables to exactly define the length of the stroke of the mechanism substantially independently of the pressure of the pressure medium driving the tool as well as obtain large lengths of the stroke with respect to the dimensions of the sealing member if so is desired.
• This object is according to the invention obtained by an im ⁇ pact mechanism of the kind mentioned in the introduction, in which the sealing member is adapted to, on movement of the working member and the stop member apart caused by action of the pressure medium entering into the working chamber, move axially with respect to one of these members while bearing sealingly against the circumferential wall of the working chamber and axially sealing the working chamber to the other of these members, and that one of the working and stop mem ⁇ bers has means adapted to allow the pressure medium to es- cape out of the working chamber when the other of said members has reached a position located at a predetermined distance from the position thereof in which said members are brought most together.
• the distance between the working and the stop members, at which the pressure medium is allowed to leave the working chamber, is in the impact mechanisms previously known depend ⁇ ent on the pressure of the pressure medium, since the axial extension and by that the sealing action of the sealing mem ⁇ ber is dependent on the pressure prevailing, whereas the sealing member in the device according to the invention has moved axially with respect to the working and stop members while bearing sealingly against the circumferential wall of the working chamber and axially sealing the working chamber to the other of the said members and got a shape considerably less dependent on the medium pressure when this other member reaches the position in which the pressure medium is allowed to escape out of the working chamber.
• the sealing member is arranged to, on movement of the working member and the stop member apart caused by action of the pressure medium entering into the working chamber starting from said position in which the members are brought most together, follow said other of these members while moving axially along the circumferential wall of the working chamber, and the circumferential wall of the working chamber has means adapted to allow the pressure medium to escape out of the working chamber when the sealing member has reached a position located at a predetermined distance from the position thereof in which said members are brought most together.
• said pressure medium escape means comprise at least one open ⁇ ing arranged radially in the circumferential wall of the working chamber, and this opening is preferably supplemented by an increase of the cross-section of the working chamber, so that the radial as well as the axial sealing of the work ⁇ ing chamber by the sealing member are simultaneously inter ⁇ rupted and the ceasing of the stroke gets more distinct and well defined.
• Tools provided with the impact mechanism according to the in ⁇ vention get by that a more smooth function and they are ac ⁇ cordingly obtaining a result of a higher quality than tools provided with the impact mechanisms previously known on proc ⁇ essing surfaces and the like.
• Tools provided with this type of impact mechanisms get thanks to the achievable increased length of the stroke new possible fields of use, where a greater length of the stroke is almost a condition, such as sawing and the like.
• Fig. 1 is a side view of a tool provided with a pressure me ⁇ dium operated impact mechanism according to the invention.
• Fig. 2 is a longitudinally sectioned view of the tool shown in fig. 1, which is enlarged compared with fig 1 and illus ⁇ trates the construction of an impact mechanism according to a preferred embodiment of the invention.
• Fig. 3 is a partially sectioned partial view, which is en ⁇ larged with respect to fig. 1 and 2 and illustrates the con ⁇ struction of the working chamber and the sealing member in the impact mechanism shown in fig. 2 with the working member and the stop member in the position in which they are brought most together, and
• Fig. 4 is a view substantially corresponding to fig 3, but with the working member and the stop member moved apart into substantially the opposite extreme position.
• a tool 1 is shown in fig 1, which in an exemplifying but not limiting way is provided with a saw 2 , arranged to carry out a reciprocating movement thanks to the impact mechanism ac ⁇ cording to the invention arranged inside the casing 3 of the tool.
• the tool has at one end thereof a means 4 for connec ⁇ tion of pressure medium, in this case air through a hose 5 cut off in figure for space reason, and a conduit 6, preferably a flexible plastic hose, for leading consumed pressure medium away.
• the working member 7 comprises at its opposite end a plate 12 secured by a screw to the elongated part 11 of the working member with a circular bottom 13 turned in the axial direction away from said end 8 and circumferential walls 14 with a cylinder casing shape projecting substantially perpendicularly therefrom in the same direction.
• a stop member or balance body 15 is arranged guidingly displaceable in the axial direction along an elongated body 32 received at the end 16 of the tool for supply of compressed air and extends into the room inside the circumferential wall 14 of the plate while being axially guided also through guide means in the form of O-rings 17, 17' , which bear against the interior wall of the casing as well as the circumferential wall 14 (a ring 17').
• the elongated body 32 is also guided with respect to the casing 3 through an O-ring 17.
• the working member 7 and the stop member 15 are influenced in the direction towards each other by a compression spring 18 and 19, respectively, each which are adapted to act between axially directed surfaces of the casing and the respective member and in a rest position in absence of compressed air in the connection means 4 hold the stop member 15 with the axi ⁇ ally directed front surface 20 thereof preloadedly bearing against a sealing member 21, here in the form of a conven ⁇ tional elastic O-ring, bearing against said bottom 13.
• the impact mechanism described so far is except for the very construction of the plate 12 already known, and the new and characteristic features of the impact mechanism according to the invention, namely the way to determine the length of the stroke of the working member, will now be described with ref ⁇ erence to fig 3 and 4.
• a position in which the working member 7 and the stop member 15 are maximally brought together and which substantially corresponds to said rest position is illustrated in fig 3.
• a working chamber 22 sealed with respect to the exterior is in this position formed between said bottom 13 and the axial surfaces of the stop member turned towards said bottom.
• the sealing member 21 bears radially tight against the circumfer ⁇ ential wall 14 and axially seals the working chamber 22 be ⁇ tween the stop member and the circumferential wall.
• the seal ⁇ ing member 21 is in this position somewhat deformed by the forces trying to press the working member and the stop member towards each other.
• the body 32 has an inner channel 23, which at one end thereof opens towards the means 4 for connection of compressed air and in the opposite direction continues in the stop member 15 and at its other end 24 emerges into the working chamber 22 (see also fig. 2).
• this compressed air will press the working member 7 and the stop member 15 apart, so that the working member 7 moves forwardly against the ac ⁇ tion of the spring 18, at the same time as the stop member 15 moves in the opposite direction against the action of the spring 19.
• the sealing member 21 is arranged freely movable in the work ⁇ ing chamber and will during this movement apart be pressed by the compressed air radially against the circumferential wall and at the same time axially against axial surfaces 20 of the stop member and by that follow the stop member in the move- ment thereof while maintaining the sealing of the working chamber 22 with respect to the exterior.
• the bottom 13 of the working chamber is preferably formed by a lubricated Teflon- washer, so that the sealing member may easily be released from the bottom on the movement of the working and stop mem ⁇ bers apart.
• the circumferential wall 14 of the working cham ⁇ ber 22 is provided with circuraferentially evenly distributed through bores 25 at a distance from the bottom .13 of the working chamber.
• the circumferential wall 14 of the working chamber 22 has at the level of said limitations 26 of the bores 25 closest to said bottom 13 a diameter increase concentrically made, so that the circumferential wall has a wall portion 29 extending from the limitations 26 away from the bottom 13 and having a greater interior diameter than the wall portion 30 located closer to the bottom 13.
• the diameter increase of the circumferential wall will cause an interruption of the axial sealing between the circumferen ⁇ tial wall and the stop member, so that compressed air present in the working chamber may axially flow past the sealing member 21 and here out of the bores 25.
• this length of the stroke may also be given every length desired by suit ⁇ ably dimensioning the working chamber and locating the compressed air escape means.
• a tool equipped therewith may be used in working situations in which a comparatively great length of the stroke and a lower frequency are desired.
• the compression springs 18 and 19 are made weaker or softer for the obtainment of this lower frequency as in the impact mechanism already known, but the increased length of the stroke ensures this.
• An example of such a use is sawing of small contures, since a greater part of the saw blade may be utilized in this way and a generation of high temperature for the saw blade material is avoided.
• the well defined length of the stroke results in a clearly improved function and an increased efficiency of the tool • when using it for example as slag hacker so as to for example hack welding slag or the like away, but this well defined length of the stroke has of course advantages in all kinds of conceivable applications of a tool provided with an impact mechanism of this type.
• a tool of the kind shown in the figure the following may be mentioned: the interior di ⁇ ameter of the circumferential wall 20 ram's, the cross-section of the O-ring 2 mm's, the distance between the bottom 13 and the limitation 26 3 mm's, the diameter of the bores 25 2 mm's, the interval between the bores 25 2 mm's, the increase of the diameter of the working chamber at the limitation 26 0,3 mm.
• Such a tool gets a length of the stroke of 4 mm's.
• the frequency of the tool will be about 221 strokes per second.
• the working chamber has another cross-section shape than circular, and the sealing member has then to be designed in the corresponding way.
• the bottom and the circumferential walls of the working chamber could also be arranged on the stop member and the end of the working member directed thereto could be designed in adaption thereto.
• the sealing member could be fixedly arranged on the member movable with respect to the circumferential walls of the working chamber, the stop member in the case shown, and it would then also be conceivable to arrange a separate spacer secured to the bottom of the working chamber so as to define the position in which the members are brought most together and a sealing member surrounding the. member movable with respect to the circumferential wall while radially bearing against the circumferential wall and axially sealing the working chamber.
• a practically complete balancing of the mechanism is achieved thanks to the arrangement of the compression springs and it is also resiliently arranged in the tool casing, so that firstly no or insignificant vibrations are transferred to the casing, when the tool is in no-load operation, and secondly no harmful vibrations are either transferred to the casing when the tool is applied against a working surface for chis ⁇ elling or the like.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Automation & Control Theory (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Percussive Tools And Related Accessories (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20385552

Family Applications (1)

Country Status (3)

Citations (1)

• 1992
  • 1992-03-09 SE SE9200710A patent/SE469971B/sv not_active Application Discontinuation
  • 1992-12-10 TW TW81109896A patent/TW241216B/zh active
• 1993
  • 1993-03-08 WO PCT/SE1993/000197 patent/WO1993017835A1/en active Application Filing

Patent Citations (1)

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