Note: Descriptions are shown in the official language in which they were submitted.
CA 02135285 2000-03-23
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VIBRATORY SCREENING APPARATUS
This invention relates to vibratory screening
apparatus suitable for use in screening drilling muds
returned from a bore hole.
Hitherto, in connection with the screening of drilling
muds, vibratory screening apparatus generally was
constructed to operate in a single vibratory mode with
orbital (circular/elliptical) movement.
The expression "drilling mud" embraces a variety of
substances; and the need for screening in this context
relates to th= saparation, from returned mud, of various
particles of differing sizes and compositions. This
variety has led to the realisation that efficiency of
screening drilling muds is related to, inter alia,
choosing between orbital and linear vibratory movements.
Therefore, there has emerged a demand foY vibr_ator~J
screening apparatus constructed to operate with linear
movement.
Generally, it is accepted that out-of-balance vibrator
motors provide the best practical and cost-effective means
for producing vibratory motion. A single vibrator motor
produces orbital movement which is circular or ellint~.cal
depending upon the relative positions of the motor and the
centre of mass of the apparatus. Two vibrator motors
appropriately arranged and rotating in mutually opposite
directions produce linear movement. However, whereas two
such vibrator motors will self-sychronise to produce ,
CA 02135285 2000-03-23
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linear movement when rotating oppositely, they will not do
when rotating uni-directionally.
There is now a need for vibratory screening apparatus
operable selectively to perform orbital and linear vibratory
movements. One solution for such a selectively-operable or
"dual motion" apparatus might be to isolate (switch off)
either one of the vibrator motors in a two-motor
arrangement, thus converting from linear movement to orbital
movement. De-isolating (switching on) the said one vibrator
motor would accomplish reversion to linear motion. However,
this solution would have the disadvantage that one vibrator
motor would be idle during orbital movement and this
undesirably would introduce a significant power-rating
differential between the respective modes of operation.
According to the present invention, in one aspect there
is provided vibratory screening apparatus comprising: a
substantially horizontal screen; two vibrator motors adapted
to vibrate the screen in a feeding direction for material
maintained on the screen; and electrical control means
connected to the motors; the motors having respective
rotatable shafts, each of which forms an angle with the
feeding direction and is disposed in non-alignment with the
other rotatable shafts, so that the two shafts may be
rotated in mutually opposite directions; out-of-balance
weights being mounted on the shafts and adapted to provide
substantially equal out-of-balance forces from the two
motors when the shafts are rotated in the mutually opposite
directions; wherein the electrical control means is
selectively operable between two running modes for the
motors, in one of which modes the shafts of the motors
rotate in the mutually opposite directions, producing a
linear vibratory movement of the screen in the feeding
direction, and in the other one of which modes the shaft of
one of the motors is rotationally reversed, so that the two
motor shafts rotate uni-directionally, causing orbital
vibratory movement of the screen in the feeding direction.
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The two vibrator motors may be mounted on a horizontal
cross-beam of the vibratory apparatus with their shafts
normal to the feeding direction, the cross-beam having a
rectangular or square hollow cross-section, and further the
vibrator motors may be arranged respectively on mutually
adjacent faces of the cross-beam. As viewed in cross-
sectional elevation, the rotational axis of each vibrator
motor may lie substantially on one or other of the principal
axes of inertia of the cross-beam.
The vibrator motors may be arranged with their shafts
normal to the feeding direction, or with their shafts
mutually parallel. Also, the vibrator motors may be arranged
with their shafts substantially horizontal.
In a further aspect, the invention provides vibratory
screening apparatus, comprising: a substantially horizontal
screen; two vibrator motors adapted to vibrate the screen in
a feeding direction for material maintained on the screen;
and electrical control means connected to the motors; the
motors having respective rotatable shafts, each of which
forms an angle with the feeding direction and is disposed in
non-alignment with the other rotatable shaft, so that the
two shafts may be rotatable in mutually opposite directions,
out-of-balance weights being mounted on the shafts and
adapted to provide substantially equal out-of-balance forces
from the two motors when the shafts are rotated in the
mutually opposite directions; wherein the electrical control
means is selectively operable between two running modes for
the motors, in one of which modes the shafts of the motors
rotate in the mutually opposite directions, producing a
linear vibratory movement of the screen in the feeding
direction, and in the other one of which modes the shafts of
both the motors are rotationally reversed to cause orbital
vibratory movement of the screen in the feeding direction,
the shaft of one of the motors carrying a first weight fixed
rotationally with respect to the shaft and a second weight
free on the shaft and engageable by angularly spaced stops
disposed for driving the second weight with a first angular
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relationship with the first weight in one direction of
rotation and with a different angular relationship with the
first weight in the opposite direction of rotation.
Coupling means may be provided for imposing
synchronization of the vibratory motors in the other running
mode, the coupling means being removable or releasable to
permit self-synchronization of the vibratory motors in the
one running mode. The coupling means may comprise a
removable or disengageable mechanical drive connected to the
shafts.
CA 02135285 2000-03-23
Embodiments of the present invention will now be
described, by way of example, with reference to the
accompanying drawings in which:-
Fig. 1 is a side elevation of vibratory screening
apparatus in accordance with the present invention;
Fig. 2 is an end elevation in the direction of arrow
A in Fig. 1;
Figs. 3 and 4 are respectively cross-sectional and
elevational views of part of a cross-beam in Figs. 1 and 2
- Fig. 3 being a section on the line III-III in Fig. 4;
Fig. 5 is a cross-sectional view detailing the
construction of one end of the cross-beam in Figs. 1 and
2, and to a larger scale;
Figs. 6 and 7 are partly diagrammatic elevations of
part of Fig. 2 concerning vibrator motors;
Figs. 8, 9 and 10 are views showing the construction
and operation of a self-adjustable out-of-balance weight
incorporated in one of the vibrator motors of Figs. 6 and
7 and to a larger scale;
Figs. 11 and 12 are partly diagrammatic elevations of
. part of Fig. 2 concerning vibrator motors, and showing a
different embodiment of the invention; and
Figs. 13 and 14 are partly diagrammatic elevations of
part of Fig. 2 concerning vibrator motors, and showing a
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further embodiment of the present invention;
In Figs. 1 and 2 of the drawings, vibratory screening
apparatus, simply known as a "shaker", consists of a base
on which is mounted a shaker basket 11 by means of
flexible suspension elements 12. The basket 11 carries
upper and lower screen assemblies 13, 14 which are
supplied with material to be screened from a tank 15 which
is mounted firmly on the base 10 and which communicates
with the screen assemblies 13, 14 by way of a flexible
connecting duct 16. The basket 11 carries a vibrator head
assembly 17 which consists principally of a rigid
cross-beam 18 which carries two vibrator motors 19, 20 and
which is secured at each end to respective side cheeks 21,
22 of the vibratory head assembly 17. The side cheeks 21,
22 are firmly fixed to the basket 11. The cross-beam 18
is a hollow rolled steel section of square cross-sectional
configuration and the principal axes of inertia of the
cross-beam 18 are indicated by the reference numerals 23
and 24. The rotational axes of the motors 19, 20 are
indicated by reference numerals 25, 26 respectively.
The motors 19, 20 are arranged respectively on
mutually adjacent faces of the cross-beam 18 centrally of
the cross-beam as shown in Fig. 2 and with the rotational
axis of each motor lying substantially on one or other of
the principal axes of inertia 23, 24. As is shown more
clearly in Figs. 3 and 4, the motors 19, 20 are secured to
respective bridge plates 27 which themselves are welded to
~13~~28~
WO 93/23179 PGT/SE93l00437
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support flanges 28 each of which is welded to the
cross-beam 18. These arrangements for mounting of the
vibrator motors 19, 20 have been found to be capable of
transmitting satisfactorily each of the different
vibrational modes described herebelow.
The cross-beam 18 is mounted to the side cheeks 21,
22 by means of flanges 29 which are welded to the ends of
the cross-beam 18. The flanges 29 are bolted to the side
cheeks 21, 22 as can be seen in Fig. 2 and the bolted
connections effectively transmit at least some of the
.vibratory movements generated by the vibe°-or motors 19,
20. However, the flanges 29 are additio:v~: iy coupled with
the side cheeks 21,~ 22 by way of stub shafts 30 each of
which is welded to a flange 29 and each of which extends
into a tapered comp:~ssion coupling assembly 31 as shown
in Fi 5. The st:. shafts 3~7 are arranged on th.= central
longitudinal axis of the cross-beam 18. Each coupling 31
has an outer member 32 securely fitted to one of the side
cheeks 21, 22 and an inner member 33 in the form of a
collet which can be urged into tight locking engagement
with its stub shaft 30 by means of screws 3~. In addition
to the transmission of vibratory movements into the side
cheeks 21, 22, the stub shafts 30 conveniently support the
cross-beam 18 in the event of making angular position
adjustments thereof about the longitudinal axis of the
cross-beam. Such adjustments may be required in order to
"fine-tune" the vibratory performance of the screening
21~ i~8~
WO 93/23179 PCf/SE93/00437
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apparatus.
Each of the vibrator motors 19, 20 consists of an
electric motor within a motor housing 35 and
out-of-balance weights within weight housings 36 located
at opposite ends of the motor housing 35. In Figs. 6 and
7, the electric motors within the motor housings 35 are
rotatable in either direction of rotation under the
control of electrical control means in the form of
reversing switchgear 37 in which respectively opposite
directional conditions are represented by blank and shaded
portions. In each switchgear 37, the active condition is
represented by the shaded portion; and the direcaions of
rotation of the vibrator motors 19, 20 are indicated by
arrows 19A and 20A. The switchgear 37 is capable of
stopping the motors 19, 20 as is indicated
diagrammatically by the full-line switch position at 38.
In the embodiment of Figs. 6 and 7, the vibrator
motor 20 is different from the vibrator motor 19 in that
the out-of-balance weights incorporated in the vibrator
motor 20 are self-adjustable according to the construction
illustrated in Figs. 8, 9 and 10. In these ffigures, the
out-of-balance weight at each end of the vibrator motor
r
shaft consists of a first weight 39 which is driven by the
motor shaft 40 by means of a key 41, and a second weight
42 which is free on the shaft 40 and retained by a circlip
43. The driven weight 39 is associated with two angularly
spaced stops 44, 45 for driving the weight~42. The stop
sa,,, " . ; ~'S ~ ~,~i;' ", ,.,,1y. .. . ,~i~~'. . ~ ~.::, . , ~ ... '.
. . . .. ...... . . . ~,d.,. .
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WO 93/23179 PCT/SE93100437
44 i :jttached ;~.... ~~ctly to the driven weight 39, and the
stop 45 is carried by an arcuate member 46 which is
attached to the weight 39. T!~us, when the shaft 40 (as
seen in Fig. 8) rotates counter-clockwise, the stop 44
drives the weight 42 with the latter in registration with
the weight 39 providing a relatively high out-of-balance
weight value. With the shaft 40 rotating clockwise (as
seen in Fig. 10), the alternative stop 45 drives the
weight 42 with the latter displaced from registration with
the weight 39 providing a relatively lower out-of-balance
weight value. Referring now to Figs. 6 and 7, in a first
running mode (Fig. 6) to produce linear vibratory motion,
the switchgear 37 runs the vibrator motors 19, 20 in
opposite directions and with the effective out-of-balance
weight value for the motor 20 equal to that of the motor
19. In a second running mode (Fig. 7) to produce orbital
vibratory motion, the switchgear 37 reverses the
directions of rotation of both vibrator motors 19, 20 so
that these motors again run in opposite directions, but
this time with the automatic adjustment of the
out-of-balance weights in motor 20. xn this condition,
the vibrator motors 19, 20 are no longer equal in terms of
out-of-balance masses with the result that orbital
vibratory motion is produced.
In Figs. 11 and 12, parts corresponding with those in
Figs. 6 and 7 are given the reference numerals used in
these figures; and the same diagrammatic representations
21~~~8
WO 93/23179 ~ PCT/SE93100437
_g _
are used. In Figs. 11 and 12, vibrator motors 19', 20'
are mounted on the cross-beam 18 in the same manner as
shown in Figs. 1 to 4. The vibrator motors 19', 20' are
mutually identical. The shafts of the vibrator motors
19', 20' are extended to project beyond one of the weight
housings 36 and these shafts are mechanically coupled with
respective rotary encoders 47 which provide data in the
form of electrical signals as to the angular positions of
the shafts of the vibrator motors 19', 20'. The encoders
47 have outputs connected to an extension of the
switchgear 37 in the form of data processing means 48
which can be set to run the vibrator motors 19', 20'
angularly synchronised within close limits. Thus, the
encoders 4? together with the data processing means 48
constitute a form of coupling means which can be activated
to impose rotational synchronisation of the vibrator
motors. In a first running mode (Fig. 11) to produce
linear vibratory motion, the switchgear 37 runs the
vibrator motors 19', 20' in opposite directions of
rotation and the data processing means 48 is inactive. In
this condition, the operation corresponds with that of
Fig. 6. In a second running mode (Fig. 12) for producing
orbital vibratory motion, the switchgear 37 runs the
vibrator motors 19', 20' uni-directionally; and the data
processing means 48 is now activated to use data from the
encoders 47 to impose angular synchronisation of the
motors 19', 20'. In a modification of the embodiment of
CA 02135285 2000-03-23
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Figs. 11 and 12, the switchgear 37 and the data processing
means 48 are used to impose angular synchronisation of the
motors 19', 20' in both running modes.
In Figs. 13 and 14, parts corresponding with those in
Figs. 11 and 12 are given the same reference numerals as
are used in in Figs. 11 and 12; and the vibrator motors
19', 20' are mounted on the cross-beam 18 in the same
manner as is described for Figs. 1 to 4. In Figs. 13 and
14, the shafts of the vibrator motors 19', 20' are '
provided with removable or releasable coupling means in
the forn of a positive or non-slip drive 49. In Fig. 13,
the drive 49 is illustrated diagrammatically as a belt
drive. However, it will be understood that the drive 49
may be chosen from a variety of known drives including the
use of gears and/or clutches. In a first running mode
(Fig. 13) to produce orbital vibratory motion, the control
means 37 runs the motors 19', 20' uni-directionally and
these motors are constrained to remain angularly
sychronised by means of the drive 49. In a second running
mode (Fig. 14) to produce linear vibratory motion, the
control means 37 runs the motors 19', 20' in opposite
directions or rotation with the drive 49 removed or
disabled. In this condition, the motors 19', 20'
self-sychronise in known manner.
