Field of the invention
This invention finds application in the machining of stones
and the like, and particularly relates to a method for forming a pattern of surface
markings on flat or curved surfaces, particularly for surface machining of slabs
of hard material or the like, and to an apparatus for carrying out such method.
Background of the invention
As is known, machining processes such as bush hammering,
grooving, chiseling or others, on the surface of products of relatively hard material,
such as marble, concrete or stone in general, generally having a plate-like shape,
are carried out to add a particular aesthetic or functional effect to the product,
which could not be obtained by other processes. These processes may add several
degrees of roughness to the product surface, thereby possibly forming a particular
pattern or texture thereon.
In prior art solutions, for instance, bush hammering is
usually performed using a particular piston-operated tool, known as bush hammer,
which may be formed of several different steel alloys. The tool is composed of a
shank connected to a particular striking member which has a predetermined number
of point- or wedge-shaped elements on its striking face. The points are generally
arranged evenly on the tool face and they may be provided in various numbers depending
on their size and on the tool size. The aesthetic effect is thus obtained by repeatedly
striking the surface of the product with the bush hammer.
Bush hammering as well as slab displacement may be carried
out either manually or automatically by means of special bush hammering machines.
An apparent drawback of the manual solution is the difficulty
and slowness of the machining process. Furthermore, the tool striking pressure imparted
by the operator is not always adequate to achieve the desired effect.
Automatic machining is conversely carried out in particular
lines on which the slab is fed by means of rollers or bands and struck with one
or more usually air-operated hammers, which strike against it at high pressure.
The hammers are mounted to an arm that can be stationary or displaced transversely
to the feed direction of the product being machined.
An apparent drawback of these solutions is that the machining
tools strike the product on the line in repetitive patterns of one type. Therefore,
although the machining process is faster than in manual solutions, it is still rather
slow, as the tool is likely to operate on one point several times. Furthermore,
this operation actually prevents the formation of particular patterns on the machined
surface, which affects the aesthetic quality of the final product.
In order to obviate one or more of these drawbacks, a number
of controlled machining solutions have been proposed.
discloses a bush hammering device for use with hard materials, particularly
marbles, which comprises a support arm driven by a control apparatus, and with a
single tool fitted thereon. While this solution partly overcomes the problem associated
to the lack of control, it still has the apparent drawback that machining is carried
out by a single tool. As a result, the process is still too slow and provides a
non optimized yield.
Summary of the Invention
The object of this invention is to overcome the above drawbacks,
by providing a method for forming a predetermined pattern of markings on flat or
curved surfaces, particularly in surface machining of slabs of hard material or
the like, that is highly efficient and cost-effective.
A particular object is to provide a method that allows
to form evenly arranged markings over the surface of the product being machined.
A further object of the invention is to provide a method
that optimizes individual product machining times, thereby speeding up the overall
Another object is to provide a method that allows machining
to be carried out in a controlled manner.
Yet another object is to provide a method that allows to
obtain an aesthetically pleasing finished product.
Another important object is to provide an apparatus for
carrying out such method.
These and other objects, to be further detailed hereafter,
are achieved thanks to a method for forming markings in a predetermined arrangement
on a flat or curved surface of a semifinished product, as claimed in claim 1, which
comprises the steps of: providing a plurality of tools, translating the plurality
of tools parallel to the lying plane with movements of predetermined wideness in
the transverse direction to form a first succession of markings, feeding the product
being machined relative to the plurality of tools and parallel to the lying plane
with a feed pitch of predetermined wideness in the longitudinal direction to subject
the surface to be machined to another succession of markings, repeating the previous
steps so that the whole longitudinal extension is covered. According to the invention,
the center-to-center distances of the tools are dimensioned and related to the feed
pitch so that the successive markings are arranged over the surface either in offset
positions, or in at least partly overlapping positions in a predetermined pattern.
Thanks to this particular configuration, the method of the invention allows to form
markings in a predetermined pattern over the surface of the product being machined.
Advantageously, the center-to-centre distances may have
values substantially, but not necessarily, constant for all tools.
Conveniently, the value of center-to-center distance may
be directly proportional of the feed pitch and inversely proportional to the number
Also, the values of center-to-center distance may be directly
proportional to the maximum diameter of each tool and may be dimensioned according
to the following algorithm:
with an experimental coefficient k of a predetermined value, preferably of 0 to
Thanks to this configuration, the method of the invention
allows machining time optimization, thereby speeding up the overall process. Furthermore,
the tools may be totally controlled in a simple and effective manner, thereby affording
highly accurate and even machining.
According to a further aspect of the invention, there is
provided an apparatus for carrying out the method, as defined in claim 8, which
comprises a supporting structure for the products being machined, means for feeding
the products to be machined along a lying plane in a longitudinal direction and
with a predetermined feed pitch, a plurality of product machining tools, means for
controlling the plurality of tools. According to the invention, the tools have predetermined
center-to-center distances therebetween, which are related to the feed pitch, to
prevent any random repetition of strokes on one point of the product.
This particular configuration provides a particularly pleasing
Brief description of the drawings
Further features and advantages of the invention will be
more apparent from the detailed description of a preferred, non-exclusive embodiment
of a method and related apparatus according to the invention, which are described
as a non-limiting example with the help of the annexed drawings, in which:
Detailed description of a preferred embodiment
- FIG. 1 is a side view of an apparatus according to the invention;
- FIG. 2 is a top view of the apparatus of FIG. 1;
- FIG. 3 is a perspective view of a first detail of the apparatus of FIG. 1;
- FIG. 4 is a top view of the detail of FIG. 3;
- FIG. 5 is a bottom view of the detail of FIG. 3;
- FIG. 6 is a perspective view of a further detail of the apparatus of FIG. 1;
- FIG. 7 is a view of a pattern of impression of evenly arranged markings according
to the invention;
- FIG. 8 shows a flowchart of a method for forming the evenly arranged markings
according to the invention.
Referring to the above figures, the apparatus of the invention,
generally designated by numeral 1, allows to form evenly arranged markings over
a substantially flat surface of a product P, and particularly to bush-hammer a slab
of hard material, such as marble or the like. The surface S to be machined extends
over a lying plane
which defines a longitudinal direction X and a transverse direction Y.
As shown in FIG. 1, the apparatus 1 is composed of a substantially
flat support structure 2 having an in-feed section 3 for the product P and a longitudinally
opposite out-feed section 4. Means 5 are further provided for feeding the product
P being machined, and convey it from the in-feed section 3 to the out-feed section
4. along the essentially horizontal lying plane
p, in the longitudinal direction X. The means 5 preferably include a
movable surface 6 between the sections 3 and 4, which is mounted, for instance,
on a succession of idle rolls, driven by a common electrical motor, both not shown
for their being widely used. The movable surface 6 is of common use, and made of
a resilient material, having the property of withstanding machining stresses provided
by the operation.
The means 5 allow the product P to be displaced over such
with a predetermined feed pitch
for each machining operation. A plurality of tools 8 specially designed for
such machining operate over the movable surface 6, and are driven by suitable control
means 9. Such tools 8 are suitably connected to suitable translating means 10 to
be displaced in the transverse direction Y, essentially perpendicular to the longitudinal
feed direction X, with movements s of predetermined wideness in such direction
Y. The feed pitch p and the transverse movement s may nevertheless
vary from a machining operation to another and may be preset before each operation.
Finally, each tool 8 operates along a machining axis W
incident on the lying plane
p, which is preferably, according to a preferred, non limiting embodiment
of the invention, perpendicular to the work surface. According to the peculiar feature
of the invention, the tools 8 are mounted with predetermined center-to-center distances
i, which are related to the predetermined feed pitch p for the
current machining process. This prevents multiple random striking on the same point
during machining of the product P on the line, optimizing the overall surface machining
Preferably, the tools 8 are remotely controlled through
a special logical unit 11, such as a processor controlled by specially designed
As shown in FIGS. 3-5, the translating means 10 include
a carrier block 12 operating over the movable surface 6, with the tools 8 fitted
thereon. The annexed figures show a block 12 with five similar tools 8 fitted thereon.
This does not exclude the provision of a larger or smaller number n of tools 8.
The block 12 is connected to the supporting structure 2 by means of a portal 13,
which allows translation thereof in a direction Y1 essentially parallel
to the transverse direction Y of the lying plane
of the slab. Fitting of each tool 8 to the tool carrier block 12 is carried
out by means of a plurality of supporting slides 14 which are slideably engageable
on a pair of guides 15, 15' formed on the block 12. This allows displacement of
each tool 8 to adjust the respective values of center-to-center distances
i. By this arrangement, different values of center-to-center distances
may also provided, although being substantially equal for proper machining.
FIG. 6 shows one tool 8, consisting of a support member
16, extending in the work direction W, and an underlying striking member 17. This
has a bottom surface 18 designed to interface with the product P being machined
to operate thereon, and having a dimension D parallel to the longitudinal feed direction
X of the product P along the support structure 2. On the bottom face 18, each tool
8 has a plurality of specially shaped e.g. blade-shaped, elements 19, evenly arranged
on such face 18. These elements 19 are the real striking member operating on the
product P being machined and have a predetermined radius of curvature in their end
portion 20, which depends on the particular effect to be obtained in the specific
machining process. Similarly, they may be also provided in various numbers. Each
tool 8 is made of steel or other similar alloys and may be formed in casting molds.
The material of each tool 8 shall have such hardness properties as to be able to
form a marking on the surface S of the product P, by surface deformation of the
material being machined.
Conveniently, the control means include a plurality of
actuators 21, each associated to one respective tool 8, for transmitting thereto
the requested operating motion along the work direction W to perform the striking
operation on the product P. The actuators 21 are preferably of the pneumatic type
and may interact with their respective tools 8 by means of a suitable spring mechanism
FIG. 7 shows a particular exemplary pattern that can be
obtained with the apparatus and the method as claimed.
A method for forming evenly arranged markings on the flat
surface S of the product P comprises the following sequence of steps.
In a first step a), a plurality of tools 8 is provided,
which are designed to form one or more aligned markings on the surface S, with predetermined
i, by reciprocating movements in a work direction W incident on the lying
In the next step b), the tools 8 are translated parallel
to the lying plane
with movements s of predetermined wideness along the transverse direction
Y to form a first succession A of aligned markings, equally spaced and arranged
all along the transverse extension of the product P.
The machining steps are such that, as the carrier block
12 first passes over the surface S to be machined, a first succession of markings,
aligned in the transverse direction Y, is formed, as shown in FIG. 7a. Markings
are formed by deformation of the surface S of the product P being machined.
Each partial succession of markings formed by each tool
8 is spaced from the next one, at the respective median points, by a value corresponding
to the preset center-to-center distance i. This value is directly proportional
to the feed pitch p and inversely proportional to the number n of
tools 8 fitted on the carrier block 12, and cannot be smaller than the dimension
D of the bottom face 18 of each striking member 17. Particularly, the value of center-to-center
is dimensioned according to the algorithm:
where k is an experimental coefficient of a predetermined value, preferably of 0
to 50. If the value of center-to-center distance
obtained from the above algorithm satisfies the following condition:
then the actually set value of center-to-center distance
for each tool 8 will be
In the next step c), the product P being machined is fed
relative to the plurality of tools 8 and parallel to the lying plane
p, with a feed pitch p of predetermined wideness in the longitudinal
direction X. Such relative feed may occur either by moving the movable surface 6
or by feeding the carrier block 12 parallel to the lying plane
p. Thus, the surface to be machined S will be ready for another succession
of aligned and equally spaced markings B, different from the former A. According
to the invention, as shown in FIG. 7b, this second succession of markings B is arranged
on the working surface S in offset and non overlapping positions, or in at least
partly overlapped positions according to a predetermined pattern. Finally, in step
d), the previous steps are repeated in such a manner as to cover the whole longitudinal
extension of the surface S of the product P.
The above disclosure clearly shows that the method and
apparatus of the invention fulfill the intended objects and particularly optimize
individual product machining times, thereby speeding up the whole process.
The combination of the means that form the apparatus and
the sequence of steps that form the method allows to form successive markings on
the product being machined, which are arranged on the surface either in offset,
non-overlapping positions or in at least partly overlapped positions according to
a predetermined pattern, thereby preventing any undesired repeated strokes on one
or more points of the product surface.
The method and apparatus of this invention are susceptible
to a number of changes or variants, within the inventive concept disclosed in the
appended claims. All the details thereof may be replaced by other technically equivalent
parts, and the materials may vary depending on different needs, without departure
from the scope of the invention.
While the method and apparatus has been described with
particular reference to the accompanying figures, the numerals referred to in the
disclosure and claims are only used for the sake of a better intelligibility of
the invention and shall not be intended to limit the claimed scope in any manner.