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EP-4117860-B1 - IMPACT TOOL

EP4117860B1EP 4117860 B1EP4117860 B1EP 4117860B1EP-4117860-B1

Inventors

  • TEH, Cheu, Chyong
  • WAHLE, QUIRIN
  • CHEN, JIM

Dates

Publication Date
20260513
Application Date
20210301

Claims (8)

  1. Impact tool (10), comprising a casing (1), a driving force means disposed in the casing, a main shaft (3) and a gear assembly (2) connected to the driving force means, a hammer assembly (4) connected to the gear assembly (2) and main shaft (3), and an anvil (5), the main shaft (3) defining a rotation axis around which the hammer assembly (4) and anvil (5) can rotate, the anvil (5) having a head (6) and a stem part (7), the stem part (7) being substantially cylindrical, and at least one lug (8) extending radially from that end of the stem part (7) which is remote from the head (6), forming a bottom face (12) substantially perpendicular to the rotation axis R, wherein the anvil (5) further comprises a guide part (9) extending axially from that end of the stem part (7) which is remote from the head (6), wherein in the direction of the rotation axis R, the guide part (9) extends axially beyond the bottom face (12) of the lug (8), wherein the guide part (9) is tubular, characterised in that a front end (13) of the main shaft (3) is accommodated in the guide part (9)
  2. Impact tool (10) according to Claim 1, characterized in that the outer diameter of the tube shape is substantially equal to or slightly smaller than the outer diameter of the stem part (7), and the inner diameter of the tube shape is substantially equal to the outer diameter of the main shaft front end (13).
  3. Impact tool (10) according to Claim 2, characterized in that a peripheral wall of the tube shape is continuous and of uniform thickness.
  4. Impact tool (10) according to Claim 2, characterized in that an inner hole (14) of the tube shape extends into the stem part (7).
  5. Impact tool (10) according to any one of Claims 1 - 4, characterized in that the anvil (5) comprises two lugs (8) arranged opposite one another radially with respect to the rotation axis R.
  6. Impact tool (10) according to Claim 5, characterized in that the anvil (5) further comprises a reinforcing rib (15), which extends radially outwards from the stem part (7) in a position adjoining the lug (8); the radial extension gradually increases from a region near the stem part towards a region remote from the stem part, and a position of maximum radial extension of the reinforcing rib (15) coincides with an outer edge of the lug (8).
  7. Impact tool (10) according to Claim 1, characterized in that the anvil (5) is a single piece.
  8. Impact tool (10) according to any one of Claims 1- 7, characterized in that the impact tool (10) is an impact wrench.

Description

FIELD OF THE INVENTION The present invention relates to a power tool, in particular to an impact tool capable of rotating a striking force to perform jobs such as screw-thread fastening, as known from US2009014193A and described in the preamble of claim 1. BACKGROUND OF THE INVENTION Impact power tools are already widely known. An impact wrench is an illustrative example of an impact tool, which can be used to install and remove threaded fasteners. Specifically, an impact tool, in particular an impact wrench, generally comprises a motor as a drive source, a gear speed reduction mechanism and main shaft which rotate as the motor performs a driving action, and a striking mechanism having a hammer body that engages with a main shaft cam; the striking mechanism is accommodated in a hammer body housing, such that the hammer body engages with an anvil shaft-supported at a front end of the hammer body housing. The main shaft and hammer are driven by the motor, and can convert rotation of the main shaft to an intermittent rotational striking force (impact) of the hammer body to act on the anvil, in order to provide rotation and striking to the anvil, thereby intermittently transmitting a rotational striking driving force to a top end tool, e.g., a socket or screwdriver head mounted on the anvil to perform tightening/removal of bolts and screws. An anvil assembly of an existing impact tool is generally used to transmit torque from the motor to a tool element in order to perform work on a workpiece. In general, due to the striking rotational force, the anvil used in the anvil assembly is subjected to high stress levels. High stress levels might cause fatigue failure, with possible breakage, of the head of the anvil. For example, the patent document CN 101163571B has disclosed an anvil; the anvil comprises an annular or tubular stem part, and at least one adjoining part extending radially therefrom, the adjoining part forming at least one adjoining surface. The hammer comprises at least one impact face, and is adapted to strike the adjoining surface by means of the impact face to provide a rotational pulse to the anvil. In the patent just described, the adjoining part and tubular stem part of the anvil are flush with each other, i.e. a shoulder of a main shaft is aligned with the bottom of the impact face of the hammer once the main shaft has extended into the tubular stem part. Thus, the height of the impact face and the height of the adjoining surface restrict the length of extension of the main shaft into a hole of the tubular stem part. If the hole of the tubular stem part is too deep, the strength of the anvil will be affected; in particular, stress concentration is highly likely to occur at the boundary between the adjoining part and stem part, causing cracks and leading to failure of the anvil as a whole. Document US 2009/223690 A1 shows an impact tool according to the preamble of claim 1. Thus, we desire an impact tool that is more compact while having higher durability. SUMMARY OF THE INVENTION The present invention provides an impact tool, comprising a casing, a driving force means disposed in the casing, a main shaft and a gear assembly connected to the driving force means, a hammer assembly connected to the gear assembly and main shaft, and an anvil, the main shaft defining a rotation axis around which the hammer assembly and anvil can rotate, the anvil having a head and a stem part, the stem part being substantially cylindrical, and at least one lug extending radially from that end of the stem part which is remote from the head, forming a bottom face substantially perpendicular to the rotation axis R; the anvil further comprises a guide part extending axially from that end of the stem part which is remote from the head, and a front end of the main shaft is accommodated in the guide part, in the direction of the rotation axis R, the guide part extends axially beyond the bottom face of the lug. According to the present invention, the guide part is tubular in other embodiments the outer diameter of the tube shape is substantially equal to or slightly smaller than the outer diameter of the stem part, and the inner diameter of the tube shape is substantially equal to the outer diameter of the main shaft front end. More preferably, a peripheral wall of the tube shape is continuous and of uniform thickness. Preferably, an inner hole of the tube shape extends into the stem part. According to another preferred embodiment of the present invention, the anvil comprises two lugs arranged opposite one another radially with respect to the rotation axis R. According to another preferred embodiment of the present invention, the anvil further comprises a reinforcing rib, which extends radially outwards from the stem part in a position adjoining that side of the lug which is close to the head; the radial extension gradually increases from a region near the stem part towards a region remote from the stem part, and a position