Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25D—PERCUSSIVE TOOLS
  • B25D11/00—Portable percussive tools with electromotor or other motor drive
  • B25D11/005—Arrangements for adjusting the stroke of the impulse member or for stopping the impact action when the tool is lifted from the working surface
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25D—PERCUSSIVE TOOLS
  • B25D11/00—Portable percussive tools with electromotor or other motor drive
  • B25D11/06—Means for driving the impulse member
  • B25D11/12—Means for driving the impulse member comprising a crank mechanism
  • B25D11/125—Means for driving the impulse member comprising a crank mechanism with a fluid cushion between the crank drive and the striking body
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H21/00—Gearings comprising primarily only links or levers, with or without slides
  • F16H21/10—Gearings comprising primarily only links or levers, with or without slides all movement being in, or parallel to, a single plane
  • F16H21/16—Gearings comprising primarily only links or levers, with or without slides all movement being in, or parallel to, a single plane for interconverting rotary motion and reciprocating motion
  • F16H21/18—Crank gearings; Eccentric gearings
  • F16H21/20—Crank gearings; Eccentric gearings with adjustment of throw
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25D—PERCUSSIVE TOOLS
  • B25D2250/00—General details of portable percussive tools; Components used in portable percussive tools
  • B25D2250/005—Adjustable tool components; Adjustable parameters
  • B25D2250/021—Stroke length

Definitions

• EP-A 63 725 already includes a
• the percussion piston is driven by a crank mechanism.
• the stroke of the crank mechanism can be changed by turning a ring gear belonging to the crank mechanism.
• the stroke is shortened evenly on both sides, that is, the front dead center and the rear dead center of the percussion piston approach each other by the same amounts.
• pneumatic striking mechanisms for hammers this has the disadvantage that the air cushion between the striker and the piston increases with the stroke becoming smaller.
• a small stroke with a relatively long air cushion only causes a very small change in pressure in the air cushion. As a result, the
• the hand tool according to the invention with the characterizing feature of claim 1 has the advantage that the impact force of the striking mechanism can also be set to low values without misfires.
• the invention ensures that the front dead center of the piston does not move away from the racket when the stroke of the eccentric gear is reduced.
• the front dead center remains the same when the stroke is adjusted or even approaches the racket. This means that the length of the air cushion remains the same or decreases as the stroke becomes smaller.
• the transmission member connecting the crank disk and the connecting rod is mounted so as to be longitudinally displaceable on a rotatably mounted bridge.
• the direction of action of the constant stroke of the transmission member can thus be changed, so that the stroke acting in the striking axis and transmitted to the piston can be adjusted.
• the formation of two parallel guide rods on the bridge ensures tilt-free operation of the eccentric gear.
• the bridge advantageously has a rotary head penetrating the housing, with which the stroke can be adjusted. Latching means on the rotary knob ensure that the bridge is clearly defined in different rotational positions.
• the transmission element can be driven by the crank disk either via an eccentric bolt which is guided in a slot transversely to the guide rods of the bridge or via a ball finger which has at least one ball joint on the crank disk or on the bridge.
• the transmission link can also be guided as a sliding block on simple longitudinal guides.
• the longitudinal guides are advantageously incorporated into an adjustment ring which can be rotated from the outside. drawing
• FIG. 1 shows a partial cross section through a handheld power tool and FIG. 1 shows a plan view of the eccentric gear in a first exemplary embodiment.
• Figure 3 shows a schematic representation of the piston position at different lifting heights.
• Figures 4 to 6 show a second and Figure 7 shows a third embodiment.
• a handheld power tool has a housing 2, in the interior of which a hammer mechanism 3 and an eccentric gear 4 driven by a motor, not shown, are accommodated.
• This gear has a rotatably driven crank disk 6 on which a bolt 7 is arranged eccentrically as an eccentric member.
• the bolt 7 engages in a slot 8 of a transmission element 9 which can be seen better in FIG.
• the transmission member has on its side opposite the crank disk 6 a crank pin 10, the axis of which is designated 11.
• To the side of the slot 8, the transmission member 9 has two guide tubes 12 which are oriented toward the slot. These each enclose a guide rod 13 and are slowly displaceable thereon.
• the guide rods 13 are connected at their ends and, together with a bracket 14, form a bridge 15.
• a bracket 16 is attached in the center of the bracket 14 and runs coaxially with the axis of rotation 17 of the crank disk 6.
• the bridge 15 can be rotated about the axis 17 by means of a rotary knob 18.
• the rotary knob 18 is arranged outside the housing and can be latched in different rotational positions with latching means 19 relative to the housing 2.
• the rotary knob 18 can be fixed in relation to the housing 2 in the selected rotational position by means of a locking device 21. From the locking device 21 is. schematically shown a pawl 23, when actuated, the locking device is released.
• the axis 11 of the crank pin 10 serves as a point of attack for the rear or crank-side end 24 of a connecting rod 25.
• the connecting rod 25 extends beyond the transmission member 9 to the striking mechanism 3.
• the bridge 14 is recessed at least on one side for the passage of the connecting rod 25.
• the piston-side end 26 of the connecting rod is, as usual, connected to a piston 28 by means of a hinge.
• This is designed as a hollow piston in which a racket 29 is guided.
• An air cushion is formed in the space 30 between the piston 28 and the striker 29, which is compressed periodically during operation of the hammer and thereby accelerates the striker 29 in the direction of the tool, not shown.
• Piston 28 has an opening 31 through which the air loss occurring in the air cushion is periodically compensated during operation.
• the rear edge 32 of the racket 29 passes over the opening 31 for a short period of time so that air can be sucked into the space 30.
• the eccentric 4 is shown without the bridge 15 in plan view.
• the bridge 15 is in a rotational position in which a relatively small piston stroke H is generated.
• the piston 28 is shown in its front dead center.
• the position of the transmission element 9 and of the crank-end connecting rod end 24 is shown in dashed lines in the position in which the piston reaches its rear dead center.
• crank disk 6 causes a reciprocating stroke H of the transmission member 9 along the guide rods 13.
• the movement of the bolt 7 directed transversely to the guide rods 13 is not transmitted from the slot 8 to the transmission member.
• the stroke H U oriented in FIG. 2 at an angle ⁇ to the striking mechanism axis is only partially implemented in the stroke H of the piston 28 in the rotational position of the bridge 15 shown.
• the arrow indicates the direction of rotation of the transmission member 9 about its axis of rotation 17, in which the piston stroke increases.
• the maximum stroke H max indicated by dashed lines is reached, which then the
• FIG. 3 schematically shows the point of application of the connecting rod end 24 on the crank side with different stroke settings.
• the piston 28 is shown in its front dead center, namely in solid lines with a minimum stroke.
• the connecting rod end 24 attacks at point 35.
• the crank pin 10 of the eccentric gear At this moment there is the crank pin 10 of the eccentric gear.
• the rear connecting rod end 24 is located at point 36, which lies on a circular path around the piston end of the connecting rod 26 through point 35. This means that the rear dead center of the piston 28 exactly coincides with the front dead center.
• the rear connecting rod end 24 moves along the line 37, which approximately coincides with the circular arc through the points 35 and 36.
• the piston 28 is practically stationary with this stroke setting.
• the dashed illustration of the piston 28 shows it in its front dead center when the transmission member 9 is in the rotational position for maximum stroke.
• the rear connecting rod end 24 engages at point 38.
• the connecting rod end 24 moves along the line 39 to the point 40.
• the line 39 lies exactly in the extension of the striking axis 41 and its length corresponds exactly to the maximum stroke.
• a line 42 is drawn, along which the rear connecting rod end 24 moves at the stroke H ′ which is reduced compared to the maximum stroke.
• the front dead center of the piston 28 is somewhat closer to the striker 29 than at maximum stroke setting.
• a front dead center of the piston 28 which cannot be changed at different stroke settings can be achieved if the distance A between the axis of rotation 17 and the point of engagement 35 or 38 of the rear connecting rod end 24 measured at the position of the piston 28 in the front dead center is set to zero.
• the size of the distance A can be selected individually for each hammer mechanism so that an optimal air cushion length is achieved for all stroke sizes.
• the second exemplary embodiment according to FIGS. 4 to 6 differs from the first only in another coupling of the transmission member 9 'to the crank disk 6'.
• a rotary bearing 45 is arranged eccentrically in the crank disk 6 ', in which a ball 46 of a ball finger 47 engages.
• the finger 47 is fixedly attached to a tube piece 48 which is rotatable about one of the guide rods 13.
• the pipe section 48 belongs to the transmission member 9 '. It passes through a tapered section 49 through a guide tube 12 'and is connected to it by means of a locking ring 50 so as to be rotatable but axially non-displaceable.
• the transmission member 9 'further has a second guide rod 12'', which is designed as in the first embodiment.
• the transmission member 9 ' is guided on guide rods 13 and are provided with a bracket 14 as in the first embodiment.
• the third exemplary embodiment according to FIG. 7 differs from the first exemplary embodiment only in the construction of the transmission element 9 ′′ and its twisting expression.
• An eccentric 7 of a crank disk 6 engages in a slot 8 'of the transmission member 9''.
• This in turn carries a crank pin 10 and is designed as a sliding block.
• the sliding block 9 ′′ is guided in two longitudinal guides 53, which are arranged on an adjusting ring 54 rotatably mounted about an axis 17. In FIG. 7, axis 17 is perpendicular to the plane of the drawing.
• the adjusting ring 54 has on its outside a toothing 55, in which a gear 56, in particular
• Worm gear engages, which is connected to a handle, not shown, on the outside of the housing.
• the stroke H can be increased in the exemplary embodiment in FIG. 7 by rotating the adjusting ring 54 in the direction indicated by the arrow.
• the dashed representation of the connecting rod 25 shows this in its rear extreme position, in which the piston, not shown, reaches a rear dead center.
• the function of this embodiment corresponds exactly to that of the first.

Applications Claiming Priority (2)

Publications (1)

Family

ID=6419531

Family Applications (1)

Country Status (4)

Cited By (2)

Families Citing this family (4)

Citations (5)

• 1990
  • 1990-12-04 DE DE19904038586 patent/DE4038586A1/de not_active Withdrawn
• 1991
  • 1991-11-19 EP EP19910919889 patent/EP0513269A1/de not_active Withdrawn
  • 1991-11-19 JP JP51797691A patent/JPH05503044A/ja active Pending
  • 1991-11-19 WO PCT/DE1991/000907 patent/WO1992010338A1/de not_active Application Discontinuation

Patent Citations (5)

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