Giovanni
Battista
Andrina, Giovanni Battista
| 1. | A tool for a demolition hammer or the like, comprising an elongate body (1) having an attachment end (3) for connection to the hammer actuator and a working tip (5) , characterised in that the elongate body (1) has at least one elongate recess (7) in its outer surface, this recess (7) extending from the working end (5) . |
| 2. | A tool according to Claim 1, characterised in that the at least one elongate recess consists of a plurality of grooves (7) . |
| 3. | A tool according to Claim 2, characterised in that the grooves (7) extend substantially axially along the elongate body (1) . |
| 4. | A tool according to Claim 2 or Claim 3, characterised in that the grooves (7) are each bounded by a pair of symmetrical side faces (9) and a bottom (11) shaped so as to fillet the bases of the side faces (9) . E 055 *& 12. |
| 5. | A tool according to any one of Claims 2 to 4 , characterised in that the grooves (7) extend through part of the axial length of the elongate body (1) from the working tip (5) . |
| 6. | A tool according to any one of Claims 2 to 4, characterised in that the grooves (7) are equiangularly spaced about the axis (A) of the elongate body (1) . |
| 7. | A tool according to Claim 6, characterised in that the bottom (11) of each groove (7) has an axial portion (15) inclined to the axis (A) of the elongate body (1) . |
| 8. | A tool according to Claim 7, characterised in that the bottom (11) of the groove (7) has a straight portion (13) which extends from the working tip (5) and terminates at the axial inclined portion (15) which connects it to the radially outer surface of the elongate body (1) . |
| 9. | A tool according to Claim 8, characterised in that the grooves (7) are separated by ribs (18) which project from a central core (20) of the elongate body (1) , this core (20) having a generally circular crosssection, the diameter of which, in correspondence with the straight portions (13) of the bottoms (11) of the grooves (7) , is between about one third and about two thirds of the diameter of the substantially circular outer section of the elongate body (1) . |
| 10. | A tool according to Claim 9, characterised in that the diameter of the generally circular crosssection of the central core (20) of the elongate body (1) is approximately half the diameter of the substantially circular outer section of the elongate body (1) . |
| 11. | A tool according to any one of the preceding claims, characterised in that the elongate body (1) has a chisel shaped working tip with a cutting edge (5a) transverse the axis (A) of the elongate body (1) , in which the elongate body (1) has two pairs of grooves (7) , each pair being disposed on one side of the cutting edge (5a) , the grooves (7) of each pair being separated from each other by an axial rib (18) having an end portion (15a) adjacent the cutting edge (5a) inclined to the axis (A) of the elongate body (1) . |
The present invention relates to tools for demolition hammers
or the like used in general in roadworks, building work, in
quarries or mines, in foundries, for demolition work, breaking
up, piercing or excavating materials of various types such as,
for example, asphalt, concrete, rock, foundry slag, tiles,
etc. Such tools may be used with small, manually operated,
pneumatic or electric drills or hammers or with heavy equipment, even of several tons' weight, controlled fluid-
dynamically and associated with earth-moving equipment or like
movable plant.
More particularly, the invention relates to a tool for a demolition hammer or the like which comprises an elongate body having an attachment end for connection to the hammer actuator
and a working tip.
Tools of the known type indicated above are subject to very
serious stress in use. In particular, the attachment end is
subject to the direct percussive action of a beater mass
reciprocated within the actuator while the working tip is
subject to impacts with the material being worked.
Such tools are generally made from heat-treated steel alloys,
possibly with parts of composite materials such as sintered ceramics.
Normally these tools have a cylindrical body with, for
example, a circular or hexagonal section, which extends to the working tip which may be shaped like a chisel, cone or pyramid, or may be flat, depending on the work the tool is
intended to carry out and the material being worked.
The elongate body and its working tip are usually made by hot
or cold pressing or by mechanical working by milling of a
metal bar.
Once the desired shape of the body has been formed it is then
hardened by heat treatment at about 850°C and subsequent
tempering at about 300°C to toughen the tool.
In use, however, such tools, exactly because of the high stress to which they are subject, tend to overheat,
particularly at the working tip, which may even reach
temperatures of the order of 600°C or more, which softens the
tool and results in the partial or total loss of the
hardening. This problem must be attributed mainly to the
cylindrical shape of the known tools, which does not enable
the heat which builds up in use to disperse effectively.
Moreover, when the working tip of the tool penetrates the
material being worked, forming a hole therethrough, detritus from the material accumulates in the bottom and at the sides of the hole in the form of dust and/or chips and forms a sort
of cushion between the material which has yet to be worked and
the working tip of the tool which damps the impacts of the tool, opposing further penetration into the material.
Because of the presence of this cushion and high overheating,
which also results from the fact that the cushion absorbs some of the energy from the impact of the tool, prior-art tools
wear rapidly whereby their working tips become blunted and not
very effective so that their penetrating characteristics fall
off and they have a short useful life.
In an attempt to avoid these problems, valued materials, such
as steel alloys containing relatively high percentages of very durable metals such as nickel, chromium, vanadium or tungsten,
are used to make these tools which are thus very expensive.
In order to avoid the problems mentioned above, the present
invention provides a tool of the type defined at the beginning
of the description, characterised in that the elongate body
has at least one elongate recess in its outer surface, the
recess extending from the working tip.
By virtue of this solution, the tool of the invention has a shape which effectively facilitates heat exchange whereby, in
use, it is less subject to the overheating which can cause
loss of hardness .
Moreover, the presence of the or each recess provides an
effective pathway for the escape of detritus formed by the breaking up of the material so that this does not accumulate
between the working tip and the material but is expelled by virtue of the movement of the tool, considerably improving the ability of the tool to penetrate the material. More
particularly, the life of the tool is lengthened considerably since the wear it incurs per unit working time is reduced.
The use of a tool according to the invention is also beneficial to the life of the hammer actuator with which it is
used since, by virtue of the fact that the tool penetrates the
material better, it transmits fewer reactive blows to the
actuator.
According to a preferred characteristic of the invention, the
at least one elongate recess comprises a plurality of grooves .
The formation of these grooves in the outer surface of the
tool gives it a shape which enhances the uniformity and
rapidity of distribution of the hardening, the entire section of the tool in the zone including the grooves being hardened whereas, in known tools the hardening occurs mainly in the outermost part of the tool section. By virtue of the fact
that the hardening is distributed more uniformly and more rapidly, a less severe hardening medium, for example oil instead of water, may be used for the hardening treatment, thus reducing the risk of the tool deforming or cracks forming
in it.
Moreover, as the effect of the hardening treatment is
improved, steels which are less rich in alloying elements may be used to form such a tool, all of which improves the economy
of production, while providing a tool which has a better
penetrating capacity than known tools .
As the working end of the tool is subject to less heat and
more uniform hardening, this end does not deform appreciably
in use but, as a result of the inevitable wear, is worn away
gradually, the original profile of the working tip remaining
substantially unchanged, the tool thus having a self-
sharpening property.
Further characteristics and advantages of the invention will
become clearer from the detailed description which follows,
provided purely by way of non-limitative example with
reference to the appended drawings, in which:
Figure 1 is a perspective view of a tool according to
the invention,
Figures 2 and 3 are side elevations of the tool of
Figure 1, staggered by 90° about the axis of the tool, and
Figure 4 is a cross-sectioned elevational view taken on
the line IV-IV of Figure 1.
With reference to the drawings, a tool for a demolition hammer
or the like is generally indicated 1. The generally
cylindrical elongate body of the tool 1, for example, with a
circular or hexagonal section, is made from steel, possibly
with parts of steel-based composite and sintered ceramics.
The tool 1 has an attachment end 3, occupying about a third of
its total length, for connection to the hammer actuator (not illustrated in the drawings) and intended to be received
within the actuator and an opposite, working end or tip 5
which may be shaped in various ways according to the type of
work to be carried out and the type of material to be worked, for example being in the form of a chisel, cone or pyramid or
being flat. A tool 1 having a chisel-shaped working tip 5 is
shown in the drawings .
At least one groove 7 extends in the outer surface of the tool
1 from the working tip 5 towards the attachment end 3. This
groove may extend axially along the body of the tool 1 or may have a slight helical curvature around the surface of the tool
Preferably the surface of the body 1 has a plurality of grooves 7 equiangularly spaced about its axis A, for example
there being four such grooves .
Each groove 7 is bounded by a pair of opposing side faces 9
and a bottom 11 which is suitably curved so as to fillet the
bases of the opposed faces 9 to avoid cracks forming at the bases of the faces 9.
Each groove 7 preferably extends through only part of the
axial length of the tool 1 and has at least one portion 15 the
bottom of which is inclined to a plane through the axis A of
the tool 1.
In the preferred embodiment shown in the drawings, each groove 7 has a straight axial portion 13 which extends from the working tip 5 and another axial portion 15 inclined to the
axis A of the body 1 so as to connect the straight portion 13 to the outer surface of the body 1.
Each groove 7 is separated from the adjacent grooves 7 by an
axial rib 18 which projects radially from a central core 20 of
the elongate body 1. This core has a cross-section which may
be likened to a generally circular area, the diameter of
which, in correspondence with the straight portions 15 of the bottoms of the grooves 7, is between about one third and about
two thirds of the diameter of the area of the outer section of
the tool 1 and is preferably about half the diameter of the
outer section of the elongate body 1.
When the elongate body 1 has a chisel-shaped working tip, it
has a cutting edge 5a transverse the axis A. In this case, the elongate body 1 conveniently has two pairs of grooves 7,
each pair located on one side of the cutting edge 5a. The rib 18 which separates those grooves 7 on the same side of the
cutting edge 5a has an end portion 18a adjacent the cutting
edge 5a which is inclined to the axis A. Thus the working tip
5 wears gradually, in use, always retaining substantially the
same shape as a result of the wear which means that the
penetrating ability of the tool 1 remains constant with time.
By virtue of the conformation of the tool of the invention, it has a shape close to the working tip 5 which means that it hardens uniformly throughout its section. This zone of the tool is thus very hard which makes it more capable of withstanding the repeated impacts with the material to be
worked without its original profile being changed appreciably.
In that zone of the tool in correspondence with the end
portions of the inclined portions 15 of the grooves and in
that zone close to the attachment end 3 where the section of
the tool is cylindrical or almost cylindrical, hardening
occurs mainly at the surface so that this portion of the tool
1 is less hard and the attachment end 3 has better toughness
characteristics, which enables it to withstand the compressive
and flexural stresses to which this portion of the tool is
subject more effectively, avoiding the tendency for cracks to
form or for this portion of the tool to distort.
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