Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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~ Back~round of the Invention
In the British patent No. 1,40~,167 a device is
described for grinding or polishing workpieces made of
various materials, the grinding or polishing being done with
th~ help of a oonventlonal solid, pasty or llquld abrasive
containing, for example, alumina, carborundum or diamond
powder. The abrasive substance is injected between the sur-
~ace of the workpiece and the working surface of the device,
which is not itself the abra~ive agent. ~he device can be a
plate with a flat surface or a body having a oylindrical,
spherical or conical working suri?aoe, depending on the nature
of the workpiece. In the known device the working surface
~arles ln nature from region to region, portlon~ of the de-
vlce consi~ting of oomparatively hard m~tal, such as ca~t
iron or ca~t steel, other portlons consieting of a less hard
materlal euoh ac oopper, lead, tin, graphite or aluminium.
~he devioe is arranged ln suoh a way that the different por-
tiona of its working ~urface, Or different hardnesses, make
contact periodically and regularly with all the regions of
the workpiece surface.
In this known device the softer portions, which are
usually made of copper, are f~r~ed by conglomerating a metal
powder with a synthetic resinO ~he mixture Or powder and
resin is poured directly into recesses in a
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cast iron plate, Thus the different regions of the working sur-
face of the device are alternately cast iron and copper conglom-
erate,
The Present Invention
Starting out from a grinding and polishing device of
this known kind as above described, the device according to the
present inventlon is characterized in that the harder and softer
portions of the working face are both conglomerates of metal
powders of different hardnesses bonded with synthetic resins,
the bodies being assembled together by a moulding or adhesive
bonding operation to form a composite grinding or polishing plateO
The device includes a plate having cylindrical studs
of a conglomerated powder containing a relatively soft metal,
the studs being imbedded in a matrix of a conglomerated powder
containing a relatively hard metal,
The present invention is also directed toward a process
~or making a polishing tool whlch comprises the steps of forming
the cylindrical studs by moulding copper powder bonded with a
synthetic resin, introducing the studs into a circular mould,
in positions required to occupy in the polishing plate, filling
the mould with iron foundry powder mixed with a synthetic resin,
conglomerating the mixture, so as to form a polishing plate, and
finally grinding and polishing the working face of the plate.
The above construction of the grinding or polishing
device considerably facilitates manufacture and the results ob-
tained, in regard to the rapidity of removal of material from
the workpiece surface, is at least as good as what can be obtained
using the prior device consisting of a massive casting containing
imbedded inserts made of a conglomerated copper powder, The
device according to the invention has the advantage that it
operates more economically in regard to consumption of abrasive
substances, in particular diamond paste~ Furthermore, the com-
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posite plate of the device according to the invention wears downevenly, the grinding or polishing surface remaining flatO
A further and special advantage of the device
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according to the invention derives from the fact
that the known cast iron grinding or polishing plates,
even those containing copper inserts or inserts made
of conglomerated copper powder, cannot be used in
preparing metallurgical polished specimens because
they modify the crystalline structure near the surface
of the specimen. The device according to the present
invention does not suffer from this disadvantage.
Several examples of the invention will now be
described with the help of the drawing, in which :
Figure 1 is a plan view of the grinding or
polishing device according to the invention;
Figure 2 is a section taken in the plane II-II
of Figure 1;
Figure 3 shows another example of the invention;
FiSure 4 shows a variant of the devioe shown in
F~gur~ 3;
Figure 5 is a side view of a grinding or polishing
: device according to the inve~tion in the form of a disc
whose-working surface is its peripheral cylindrical
: surface;
Figure 6 is a front view of the device of Figure 5;
Figure 7 is an axial section through a hand-tool
- according to the invention, for manual grinding operations.
The grinding or polishing device according to the
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invention comprises a composite plate 1 made by
- conglomcrating iron foundry powder ¦or a mixture
of this with another hard subst~nce such as a
-carbide or an oxide). Imbeclded in the pl~te 1
there are several cylindrical studs 2, 3, 4 made,
from example of conslomèrated copper powder. Both
the powders (iron and coppcr) are preferably
conglomerated by using the same synthetic resin
binder~
The composite plate 1 is mounted, preferably
by sticking by means of an adhesive, on a rigid base
plate 5 made, for example, of cast iron or cast
steel and precision ground.
The composite plate 1 is made by the following
method :
The cylindrical studs 2, 3, 4 ... are made by
introducing a mixture of coppcr powder and synthetic
re~in into a mould, where the mixture is hardened
either in the cold or with the application of heat and
pressure. The moulded studs are initially longer than
what will finally be required. The ends of the studs
are then cut off with a saw and at least one face of
each stud is ground true. The studs are then inserted
into a circular mould, with the ground face of the stud
in contact with the bottom of the mould. The studs
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are positioned in the mould on concentric. circles,
for example as represented in Figure 1. The studs
on the different concentric circles can have the
same or different diameters~ There is then
introduced into the circular mould containing the
6tuds a mixture of iron foundry powder and synthetic
re~in~ so that tho powder fills the space bctween the
stude. The upper surface of the material is then
equalized and the powder is hardened, either in the
cold or with the application of heat. If desired
pressure can be applied by using a cover for the moul.d.
The composite plate thus formed is ground true
' on both faces and preferably stuck to the rigid
supporting plate 5.
In the example shown in l~igure 3 the composite
. pIate 1 con-~ists of sectors 6, 7, ~, 9 ... . Neighbouring
sector~ are made o' powdered metal~ of dif'erent hardnesses,
Por exàmple alternating between iron foundry powder and
,. , copper powder. The sectors are made by a moulding
operation, as described above for the studs. The sectors
are then stuck together to form the composite plate, which
is then ground true on both faces and finally stuck to a
,rigid supporting plate 5, as described for the example
of Figures 1 and 2. This example of the invention has
the advantage that. a worn or damaged sector can easily be
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replaced by unsticking it from the supporting plato 5,
without disturbing the other sectors. A new sector
can then be stuck in place.
If desired, more than two different powder
mixtures can be used for making the sectors, the sectors '
bcing nevertheless arranged in a regular and repeated
, ' pattern.
In the example in ~igure 4 all the sectors 10, 11,
12, 13 ... are the same as each other. Each sector
consists of a matrix of iron foundry powder with a resin
binder, each sector containing imbedded copper studs 1~,
15, 16 ... . The method of manufacture is essentially
as described for the example of Fi$ures 1,a,nd 2, the only
difference being that the body of the composite plate
~15 'is in this case made up of individually moulded sectors
rather than being simply a circular moulded disc. This
example also has the advantage of the example of Figure 3
! that worn or damaged sectors can casily be replaced.
In another example of the invention, which is not
,
shown in the drawing, each sector 6, 7, 8, 9 ... (compare
Figure 3) is itself subdivided into annular segments. The
, segments are made of métal powders of different hardnesses,
bonded with resin binders; the powders, for example iron
'foundry'powder and copper powder, alternating both radially
and circumferentially.
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The different portions of the composite platc,
some harder and some softer, can if desired be made
- using mixtures of different powders.
The example of the invention shown in Figures 5
and 6 is a composite circular plate 17 which functions
after the manner of an ed~e grinding wheel. The main
body of thc composite plate can, for example, be mado
' of iron powder bonded with a synthetic resin and ha~ing
regularly distributed peripheral teeth 18, 18', 18" ... .
Betwoen the teeth there are moulded inserts 19, 19', 19''
made of copper powder bonded with a resin, the inserts being
stuck to the circular plate 17. Composite plates of this
kind can be made by startin$ out from a comparatively long
cylinder of conglomerated iron dust with imbedded bars of
conglomerated copper powder. ~he comparati~ely long
cylinder is then cut with a saw into discs of the desired
- thicknQss. Finally each composite disc is mounted on a
~hAft 20.
~igure 7 shows a manual tool for grinding or polishing,
in particular the kind o~ tool used for grinding and
polishing the apertures in wire-drawing dies. The tool has
a core 21 made, for example, of conglomerat0d copper, and an
outer plate 22 which can consi~t of conslomerated iron or
steel powder. The tool can be made in the lcnown way by
extrusion through a double extrusion die.
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