Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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APPARATUS FOR RESURFACING CYLINDRICAL ROLLS
AND A SELF-SERVICING ROLLER MILL ASSEMBLED THEREWITH
Technical Field
The present invention relates to mills for comminuting materials, and in
particular to an apparatus for resurfacing the rolls of roller mills designed tocomminllte materials.
Ba-~kpround of the Invention
Roller mills are widely used for comminuting materials in a broad range of
industrial processes. They are also widely used in the food industry to prepare
ingredients for food products and to prepare animal rations. Roller mills comminute
material by crushing or cutting the material between a pair of opposed rotating rolls
supported in an axially parallel relationship to define a small space between the rolls
called the "nip". Materials passing through the nip are subjected to the crushing
cutting force of the rotating, juxtaposed rolls. In order to facilitate comminlltion, the
rolls of a roller mill may be corrugated in a variety of patterns dependent on the
desired product.
The rolls of roller mills are commonly made from cast iron which is tempered
to a hardness of 48 to 54 Rockwell C. In spite of their hardness, the rolls in a roller
mill must be resurfaced periodically, typically every six to eighteen months depending
on a variety of factors including the product processed by the mill, the number of
hours of operation, and the amount of cont~min~tion such as stones and other foreign
matter in the product stream.
Roller mill rolls have been traditionally resurfaced by one of two methods.
Those m:~n~ging small operations commonly remove the rolls from the mill and return
them to the manufacturer where they are resurfaced on a lathe or some other precision
surfacing instrument using specially constructed grinders for removing surface material.
Those m~n~ging large production operations who cannot afford to shut down while
rolls are shipped out for resurfacing either invest in a set of spare rolls which are
rotated between production and resurfacing, or hire special service providers who set
up grinding equipment to grind the rolls without removing them from the mill.
Grinding rolls in a mill presents two problems. First, expensive equipment and skilled
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operators must be brought in to effect the resurfacing operation. Second, the grinding
operation produces copious sparks. Most roller mills are operated in dusty and/or oily
environments where sparks are a hazard. It is therefore generally necessary to isolate
the mill from the surrounding environment during a resurfacing operation. This is time
5 consuming, disruptive and expensive.
United States Patent 4,707,946 which issued November 24, 1987 to Hirohata
teaches a grinding machine that can continuously grind a cylindrical object rotating
around its axis supported by a head and tailstock. Grinding tools are attached to a
rotating circular plate which is provided on a carriage that moves along a bed adjacent
10 to the axis of the cylindrical object at a constant rate to grind the outer surface of the
object. The circular plate includes a front side on which a plurality of first and second
grinding tools are mounted. The grinding tools include tools for roughing and tools
for fini~hing and are mounted in circular patterns of different radii according to their
use in grinding. The plate is moved up and down so that the cylindrical object can be
15 ground with tools relevant to the phase of finishing in progress. The tool holder is
reciprocated along the bed by a threaded rod which is rotated by a motor. A nut on
the rod urges the tool to slide along the bed. While this apparatus may be suitable for
resurfacing smooth rolls removed from a mill, it is not adapted to resurfacing rolls in a
mill. Furthermore, it performs a grinding action and therefore produces copious sparks
20 which present a hazard in most environments where roller mills must operate.
C~n~ n Patent Application 2,092,995 was laid-open to public inspection on
February 1, 1993 in the name of Farros Blatter AG. This patent application describes
a grinder for grinding a cylindrical surface of a roll, especially a paper machine roll.
The grinder is attached to a carriage that is designed to roll along a top of a scraper
25 blade for the roll. The grinder uses a continuous belt abrasive for resurfacing the roll.
Apparently, the roll is rotated at its operating rotation speed while it is ground by the
grinder that rides along the top edge of the scraper blade. This ~palaLus could not be
used satisfactorily on most roller mills for several reasons. First, the scraper for a
roller mill roll is commonly improperly positioned to accommodate a grinder with a
30 large carriage. Second, the configuration of the grinder and carriage would prevent
dressing an entire roll in a roller mill because the side panels of the mill would prevent
the belt from reaching at least one end of the roll. Finally, the abrasive belt produces
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copious sparks which are a hazard in most environments where roller mills must
operate.
There therefore exists a need for an apparatus which can be used to safely and
economically resurface the rolls of roller mills without removing the rolls from the
mill.
Summary of the Invention
It is an object of the present invention to provide a resurfacer for the rolls of
roller mills which minimi7~s the hazards of explosion or fire due to sparks by
resurfacing rolls using a metal cutting rather than a metal abrading process.
It is a further object of the invention to provide an apparatus which may be
built in to a roller mill as a part of the original equipment that is supplied with the
mill.
It is a further object of the invention to provide an apparatus which may be
retrofit to a compatible existing roller mill.
It is yet a further object of the invention to provide an apparatus which may beadapted to the resurfacing of smooth rolls and corrugated rolls of a roller mill.
In accordance with the invention, there is therefore provided an apparatus for
resurfacing a roll of a roller mill without removing the roll from the mill, comprising
in combination:
a rail for supporting a cutting head, the rail being mounted to the roller mill in
an axial relationship with respect to the roll of the mill so that a cutting bit mounted to
the cutting head is adjustably movable to and from cutting relationship with a surface
of the roll;
means for driving the cutting head in a controlled reciprocal movement along
the rail to effect the removal of a surface layer of the roll; and
means for conkolling rotation of the roll so that a controlled removal of the
surface layer is accomplished, whereby the mill may be operated in a normal
production mode without removing the apparatus from the mill.
The present invention therefore provides two significant advantages over the
prior art. First, it provides a method of minimi7.ing the hazards of resurfacing roller
mills in their operating environment by using a metal cutting rather than a metal
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abrading technique. Cutting bit material is available in diamond, ceramics and
~i~aniu~ll nitrate coated carbides that is capable of cutting 54-56 Rockwell C. tempered
ron.
Second, the apparatus in accordance with the invention provides a kit which
5 may be installed in a roller mill as original equipment or retrofitted to existing mills in
order to completely elimin~te any requirement for removing the rolls from the mills for
resurfacing. This facilitates production, cuts operating costs, and enhances product
quality and conserves energy because mill operators are more inclined to keep the rolls
of their mills in optimum operating condition.
The apparatus in accordance with the invention comprises a rail for supporting
a cutter head. The rail is preferably a square tube which houses a threaded drive rod
for the cutting head. The threaded drive rod engages a threaded drive block which
reciprocates inside the tube and is in turn attached to the cutter head. The drive rod is
rotated by a motor and the rotational movement of the drive rod is translated into
15 reciprocal movement of the cutter head along the rail. The cutter head adjustably
supports a cutting bit which is appropliately shaped to resurface a roll of the mill.
The apparatus also includes means for controlling the roll so that the controlled
removal of the surface layer is accomplished. The means for controlling the rotation
of the roll is dependent on the type of roll which is being resurfaced. In the instance
20 of a flaking mill, the rolls are smooth and the means for controlling the rotation of the
roll is preferably a dual speed gear box attached to the main drive motor of the mill,
the gear box providing a normal operating speed and a resurfacing speed for the rolls.
The resurfacing speed for the rolls is preferably about 60-80 r.p.m. Alternatively, a
hydraulic or an electric gear motor may be attached to the idler shaft for the idler
25 sheave on the roll's drive belts. The motor is adapted to turn the rolls at the optimum
speed for resurfacing. The motor idles on the idler shaft at all times when the mill is
operating in normal production mode.
If the mill has corrugated rolls, the means for controlling rotation of the roll so
that a controlled removal of the surface layer is accomplished is different than30 described above. Corrugated roll mills are resurfaced by reciprocating the cutting head
longitudinally of the roll and removing a surface layer of one corrugation with each
pass. In order to effectively resurface a corrugated roll, it is essential that the cutting
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tool be properly indexed with the corrugations in the roll's surface. Indexation is
preferably accomplished using al)plo~liately constructed dogs and a ratchet gear affixed
to the journal of the roll. The dogs mesh with the ratchet gear to lock the roll in a
position appropriate for cutting each corrugation on the roll. Between cuts, a stepper
motor or a hydraulic motor advances the roll one notch on the ratchet gear. Each time
the cutting head reaches an end of its cutting stroke, it trips a sensor that alerts a
controller to release the dogs to permit the roller to advance to the next corrugation to
be resurfaced.
Thus, an ~pal~lus for resurfacing the rolls of any roller mill is provided. The
apparatus permits the assembly of an improved roller mill that is substantially self-
servicing.
Furthermore, the uses of the apparatus is not limited to the resurfacing of roller
mill rolls. The a~palalus may be adapted to resurface a cylindrical roll in practically
any equipment, including dryer drums, paper machines and the like.
Brief Dcse~ ;I,lion of the Drawin~s
The invention will now be further explained by way of example only and with
reference to the following drawings wherein:
FIG. 1 is a side elevational schematic view of a typical prior art roller mill
construction;
FIG. 2 is a schematic top plan view of the rail and cutter head in accordance
with the invention mounted to a bearing housing of a roll of the roller mill shown in
FIG. 1;
FIG. 3 is a side elevational view of the apparatus shown in FIG. 2;
FIG. 4 is a cross-sectional view of the rail and the cutter head taken along lines
IV-IV of FIG. 2;
FIG. 5 is a partial longitudinal cross-sectional view of the rail taken along lines
V-V of FIG. 2;
FIG. 6 is an end elevational view of the cutter head shown in FIG. 4;
FIG. 7 is a cross-sectional view taken along lines VII-VII of FIG. 6;
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FIG. 8 is a schematic view of an alternate position for mounting the rail and
cutter head to a roller mill in order to effect the resurfacing of the drive roll and the
driven roll simultaneously;
FIG. 9 is a plan view showing the apparatus for controlling rotation of the rolls
of flaking mills to permit a controlled removal of a surface layer to resurface the rolls;
FIG. 10 shows an alternate embodiment of the ~pa dlus shown in FIG. 9,
FIG. 11 shows an appaldlus for controlling rotation of a corrugated roll of a
rolling mill so that a controlled removal of a surface layer of the roll is accomplished
to resurface the corrugated roll.
Detailed DCSL ;~Iion of the Preferred Embodiments
FIG. 1 is a schematic side elevational view of a typical prior art construction
for a roller mill, generally indicated by the reference 20. Rollers mills invariably
include at least two rolls supported in a side-by-side parallel relationship. One of the
rolls is known as a drive roll 22 and the other is known as the driven roll 30. The
drive roll is rotated by a main drive sheave 24 which is driven by a motor 26,
generally an electric motor. A plurality of V-belts 28 encircle the main drive sheave
24 and a motor sheeve 27 (see FIGs. 9-11) in a manner well known in the art. Thedrive roll 22 is provided on each end with a concentric drive roll journal 50. The
main drive sheave 24 is affixed to one journal 50 (see FIGs. 9-11) and a drive sheave
32 is affixed to the opposite journal 50. Typically, a plurality of V-belts 38 encircle
the drive sheave 32, engage the lower half of a driven sheave 34 which is attached to
the driven roll journal 56 and encircles an idler sheave 36. The arrangement of the V-
belts 38 turns the driven sheave 34 and the driven roll 30 in an opposite direction to
the drive sheave 32 and the drive roll 22. In this illustration, the roller mill is a
flaking mill having smooth rollers. Such mills are generally used for processing food
and feed products such as flaked grains, etc. Other mills designed for grinding,crumbling or cracking usually have corrugated rolls. The rolls of the flaking mill
shown in FIG. 1 are normally driven at the same rate of rotation, so the drive sheave
32 and the driven sheave 34 have the same diameter. Corrugated rolls are normally
driven at different rates of rotation in order to accentuate the comminutive action of
the rolls. The relative rate of rotation depends on the product being processed. The
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drive sheave and the driven sheave of a mill with corrugated rolls (not illustrated)
therefore generally have different diameters. These principles are well understood in
the art.
During the operation of the flaking mill shown in FIG. 1, a product such as
5 whole grain oats is introduced into a feed hopper 40. A feed roller 42 feeds the
material to be comminuted 46 into the nip between the drive roll 22 and the driven roll
30. When the material passes between the closely spaced rolls, it is pinched in the nip
and flattened. Unless the material 46 is very dry, it generally sticks to the rolls.
Scrapers 48 positioned under each roll scrape the treated material from the rolls where
10 it discharges into a storage bin or a collection trough that feeds an auger (not
illustrated) or the like. Roller mills may include up to three or more stacks of the rolls
shown in FIG. 1. The construction and operation of roller mills is well known and
therefore not explained here in detail.
FIG. 2 shows a schematic top plan view of a rail 58 for supporting a cutter
head 60 in accordance with the invention. The rail 58 and cutter head 60 are
supported by mounting brackets 62 which are bolted to the drive roller bearing housing
54 that houses the drive roller bearing 52 (see FIG. 3) which supports the drive roll
journal 50. The mounting brackets 62 support the rail 58 in a parallel relationship to
the axis of the drive roll 22. The cutter head 60 is driven along the rail by a cutter
drive motor 92 which turns a bevel gear 91 that meshes with a complementary bevel
gear 90 affixed to a drive rod (see FIG. 5). The cutter head 60 is driven reciprocally
on the rail 58 while the drive roll 22 is rotated at a speed to permit resurfacing of the
roll by a metal cutting operation, as will be explained in more detail with reference to
FIG. 5.
FIG. 3 shows a side elevational view of the apparatus shown in FIG. 2. As
explained above, the mounting brackets 62 are bolted to the roll bearing housings 54.
The mounting brackets 62 include a plurality of slots 64 which receive drive roll
bearing housing bolts 66. The slots 64 permit the mounting brackets 62 to be
adjustably positioned relative to the outer circumference of the drive roll 22. Thus, as
the drive roll 22 is repeatedly resurfaced, the bracket 62 may be repositioned to permit
the cutter head 60 the remove a surface layer from the circumference of the roll.
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FIG. 4 shows a cross-sectional view of the drive rail and the drive head taken
along lines IV-IV of FIG. 2. The rail 58 is preferably a square tube made of stainless
steel, though other materials may also be used. Captured within the rail 58 is a drive
block 68 which is threadedly received on a drive rod 70. Each of the drive block 68
5 and the drive rod 70 are threaded in an ACME thread pattern in a manner well known
in the art. The rail 58 includes a pair of longitudinal slots 72 and 74 (see also FIG. 5).
The slots accommodate bolts 76 which pass through the slots and connect the cutter
head 60 to the drive block 68. The cutter head 60 is secured with set screws 78 to
bronze wear plates 80 which slide back and forth along the rail 58 as the cutter head
60 is reciprocated. The bronze wear plates 80 are connected to retainer plates 82 by
retainer bolts 84. As can be appreciated, when the drive rod 70 is rotated, the drive
block 68 is urged along inside the rail 58. This in turn urges the retainer plates 82 to
move along the rail due to the connection of the retainer plates 82 to the drive block
68 by bolts 76. Likewise, the bronze wear plates 80 are urged along the rail due to the
connection of the retainer plates 82 to the bronze wear plates 80 by the retainer bolts
84. Thus, as the drive block 68 is reciprocated inside the rail 58, the cutter head 60 is
reciprocated along the drive roll 22. This apparatus is equally adapted to be attached
in the same manner to the driven roll 30. That attachment is not illustrated but is
readily understood because the same principles apply.
FIG. 5 shows a partial longitudinal cross-section of the rail 58 taken along lines
V-V of FIG. 3. The drive rod 70 extends completely through the rail 58 and is
rotatably supported on each end by roller bearings 86 which are mounted in an end cap
88 that bolts to the mounting bracket 62 (see FIGs. 2 and 3). Affixed to an outer end
of the drive rod 70 is a bevelled drive gear 90. A complementary bevelled gear 91 is
affixed to the shaft of a cutter drive motor 92 (see FIG. 2). The cutter drive motor 92
may be any suitable reversible motor capable of driving the cutter head 60 along the
rail 58 during a resurfacing operation. The cutter drive motor 92 may be a hydraulic
motor, an electric gear motor or the like. The direction of rotation of the motor cutter
drive 92 is controlled by sensors such as limit switches 102 (see FIGs. 9-11) that sense
an end of travel of the cutter head 60, in a manner well known in the art.
FIG. 6 shows an end elevational view of the cutter head 60 removed from the
bronze wear plates 80. The cutter head 60 supports a cutting bit 94. The cutting bit
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94 is a triangular bit suitable for fini~hing smooth rolls. The bit is shown in solid lines
in a position suitable for resurfacing a single roll. The bit is shown in dotted lines in a
position suitable for resurfacing two rolls simultaneously, as will be explained in more
detail in relation to FIG. 8. Cutting bits for resurfacing corrugated rolls are shaped to
match the corrugation pattern of the roll as will be explained in more detail with
reference to FIG. 11.
FIG. 7 shows a longitudinal cross-section taken along lines VII-VII of FIG. 6.
The cutter head 60 includes a base 96 which is connected to the bronze wear plates 80
using set screws 78 (see FIG. 4), a height adjustment section generally indicated by the
reference 98 and a bit retainer 100. The height adjustment section 98 includes astationary wedge 102 and an adjustment wedge 104. The adjustment wedge 104
includes an elongated slot 105 which permits the position of the wedge to be changed.
The position of the adjustment wedge 104 is changed within limits by an adjustment
screw 106. Moving the adjustment wedge 104 raises or lowers the fixed wedge 102 to
raise or lower the cutting bit 94 with respect to the rail 58 (see FIG. 4). A retainer
bolt 108 passes through a bore in the base 96, the elongated slot 105 in the adjustment
wedge 104, a bore in the fixed wedge 102 and threadingly engages the bit retainer 100
of the cutter head 60. The cutting bit 94 is attached to the bit retainer 100 of the
cutter head 60 by a cutting bit retainer screw 110.
FIG. 8 shows an alternate position for mounting the rail 58 and the cutter head
60 to a roller mill. In this position, each of the drive roll 22 and the driven roll 30 can
be resurfaced simultaneously. The mounting brackets 62, shown in dotted lines for
clarity, are mounted to bores drilled in the side plates (not illustrated for clarity) of the
roller mill 20 (see FIG. 1) which support the bearing housings 54 for the drive roll 22
and the driven roll 30. When installed in this position, the cutting bit 94 is inverted so
that two cutting edges are simultaneously positioned for resurfacing the rolls
simultaneously.
FIG. 9 shows a top plan view of the roller mill 20 shown in FIG. 1 and
illustrates one embodiment of the invention for driving the rolls 22, 30 during a
resurfacing operation of the rolls. In this embodiment, an idler shaft drive motor 112
is mounted to a free end of the idler shaft 114 that supports the idler sheave 36, the
idler shaft drive motor 112 is preferably an electric gear motor although a hydraulic
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motor may also be used. The idler shaft drive motor 112 should rotate the driven roll
30 and the drive roll 22 at about 60-80 r.p.m. for optimum resurfacing using the cutter
head 60 in accordance with the invention. When the idler shaft drive motor 112 is
energized, it turns the idler sheave 36 which turns the driven sheave 34 and the drive
5 sheave 32 to rotate the respective rolls. When the mill is in production mode and
driven by the drive motor 26, the idler shaft drive motor 112 is de-energized and idles
with the shaft.
FIG. 10 shows an alternate embodiment of the invention shown in FIG. 9. In
this embodiment, the idler shaft drive motor 112 is replaced with a dual speed gear
box 118. The dual speed gear box 118 is adapted to drive the mill in a first gear at
the preferred resurfacing speed of 60-80 r.p.m. and in a second gear at the normal
operating speed for the mill. The rollers of a flaking mill cannot be resurfaced at the
normal operating speed using a metal cutting technique with the cutting bit materials
currently available.
A plurality of roll corrugation profiles are commonly used for comminuting
material in various industrial processes. A few of the well known roll corrugation
profiles f~mili~r to those skilled in the art have been named Lepage, Lepage Ring, Flat
Bottom V, Round Bottom V, Sawtooth, Oat Crimper, Dawson, Modified Dawson,
Stevens and Ross Flaking Cut. As will be appreciated by one skilled in the art, each
20 profile requires a cutting bit specifically shaped for the profile to be resurfaced.
Cutting bits suitable for resurfacing corrugated profiles may be made by those skilled
in the art. The present invention can be used to resurface rolls of any useful profile
and is not limited in utility to those profiles listed above.
FIG. 11 shows one embodiment of the invention adapted to resurface the rolls
25 of a roller mill equipped with corrugated rolls. In order to resurface a corrugated roll,
it is necessary to index the corrugations of the roll with a cutting bit 94 having a
profile that is compatible with the corrugation profile of the roll. The cutting bit is
driven longitudinally of the roll along each corrugation in the roll while the roll is held
in a stationary position to remove a surface layer of the corrugation and thus renew the
30 corrugation profile. The cutting resistance pressure encountered during resurfacing
corrugated rolls will depend on the depth of cut and the coarseness of the corrugation.
Pressures of 75-250 psi are common. The rail 58, the drive rod 70 and the drive block
~l~23 l5~
ll
68 must be constructed to withstand those pressures without deflection or distortion
and the cutter drive motor 92 must be sized to provide the required torque.
To control rotation of a roll 22, 30, a dog 124 and ratchet gear arrangement
120 are preferably used in conjunction with a stepper motor installed as the idler shaft
5 drive motor 112. When the cutter head 60 reaches an end of its travel, it activates a
sensor 122 such as a limit switch or the like. The sensor triggers a controller (not
illustrated) to release the dogs 124 on the ratchet gear 120 and to advance the idle
shaft drive motor 112 the proper number of steps to advance the roll to the nextcorrugation. When the dogs re-engage the ratchet gear 120, the controller reverses the
direction of the cutter drive motor 92 (see FIG. 3) to drive the cutter head 60 in an
opposite direction and resurface the next corrugation on the corrugated roll surface.
The control of the dogs 124 and ratchet gear 120 are well known in the art. The dogs
124 may be controlled by an electromechanical, hydraulic or pneumatic linkage.
Although the apparatus in accordance with the invention has been described
15 with specific reference to roller mills, it will be appreciated by those skilled in the art
that it may be adapted to use with practically any machine which includes at least one
right circular cylindrical roll, such as a drum dryer, a paper machine and the like.
The preferred embodiments described above are intended to be exemplary only.
Variations of the construction of the described embodiments may be apparent to those
20 skilled in the art. The scope of the invention is therefore intended to be limited solely
by the scope of the appended claims.
