Tool driving or impacting – Impacting devices – Selective axial direction of impact
Patent
1996-08-19
1999-03-30
Smith, Scott A.
Tool driving or impacting
Impacting devices
Selective axial direction of impact
173 17, 173135, 173210, 173206, B25D 1706
Patent
active
058876650
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates generally to striking elements for producing mechanical shocks transmitted to a tool.
Striking elements are well known as parts of an impact tool. They produce shocks and transmit them to the tool belonging to the impact tool. Mention may be made here, for example, of percussion drills, wherein an unbalanced mass connected to the drill drive acts as the striking element which, when the drill is operated as a tool, additionally allows it to execute axial shocks.
A striking element used chiefly in surgery is described in EP 0,452,543 A1. There a single piston, displaceable in a cylinder by compressed air, does the work. On a forward stroke--directed against a tool connected to the striking element--this piston acts on a first impact surface, and this shock is transmitted to the tool. On its subsequent return stroke the piston acts on a second impact surface. The tool--a rasp, for example, is mentioned there --is successively exposed to a forward-thrust working shock and an opposing loosening shock. At least one high-pressure channel between the first and the second impact surfaces is present in the striking element, by which the pressure necessary for motion of the piston is built up during the motion cycle. In addition, at least one inlet and one outlet are provided for compressed air.
For the construction of this striking element, a total volume consisting of a first partial volume, which lies between the first impact surface and the piston area belonging to it, and the volume of the high-pressure channel is determined at particular positions of the piston. The necessary pressure may be built up and the striking element functions only when the ratio of the value of this total volume to the area of the active first impact surface and of the second impact surface exceeds predetermined values. Embodiments are indicated by which the loosening shock may in each instance be suppressed either permanently or at times.
The striking element according to EP 0,452,543 has a relatively complicated mechanical structure. For example, it has two different diameters for the cylindrical bore and the piston diameter, a column running within the piston and a total of six impact surfaces requiring machining. Compared to the overall arrangement of the striking element, the piston itself has only a small mass. Since the pressure in the volume between the respective impact plate and the associated piston area is built up or let down only during its motion, the piston motions proceed relatively slowly, so that the energy transmitted to the tool by the piston motions per unit of time is relatively small.
Therefore an object of the invention is to procure a striking element which, with external dimensions comparable to those of the striking element described above, achieves a higher striking rate and transmits a greater amount of energy to the tool per shock.
SUMMARY OF THE INVENTION
This object is accomplished in the striking element according to the invention by the features of the characterizing portion of claim 1. The other claims characterize advantageous embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained with the aid of the drawing, wherein
FIG. 1 shows a first example of a striking element having two pistons in a longitudinal section,
FIG. 2, the striking element of FIG. 1 in a cross section A--A,
FIG. 3, the striking element of FIG. 1 in a cross section B--B,
FIG. 4 shows the striking element of FIG. 1 in a side view,
FIG. 5 shows a simplified diagram of the method of operation of the striking element of FIG. 1,
FIG. 6 shows the location of openings of the pressure lines and pressure supply lines within the bores in an impact element of FIG. 1,
FIG. 7 shows part of a striking element wherein the loosening shock proceeds with little energy
FIG. 8 shows a striking element similar to that of FIG. 1 wherein shocks are transmitted through the intermediacy of impact pins; and
FIG. 9 shows a second example of a striking element.
Where different parts of
REFERENCES:
patent: 891472 (1908-06-01), Fowler
patent: 2210020 (1940-08-01), Anderson
patent: 2787123 (1957-04-01), Delvaux
patent: 3425499 (1969-02-01), Fisher
patent: 3583499 (1971-06-01), Cordes
patent: 4825960 (1989-05-01), Krone
patent: 5152352 (1992-10-01), Mandanis
patent: 5485887 (1996-01-01), Mandanis
Delfosse Peter
Seifert Hans-Carsten
Smith Scott A.
Synthes (U.S.A.)
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