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Патент USA US3093588

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June 11, 1963
w. F. HOFMEISTER
3,093,573
CHAIN ADJUSTMENT FOR TRAVELING WATER SCREENS
Filed March 25, 1960
2 Sheets-Sheet 1
June 11, 1963
w. F. HOFMEISTER
3,093,578
CHAIN ADJUSTMENT FOR TRAVELING WATER SCREENS
Filed March 23, 1960
2 Sheets-Sheet 2
540
FIG. 5.
570
430
530
400
420
520
5k:
420
42b
43a
L56
53b
43b
52b
5“,
42b
3,093,578
United States Patent 0 ” 'ice
Patented June 11, 1963
1
2
3,093,578
with the upper housing or hood in‘ place and ‘with parts
broken away and sectioned;
William F. Hofmeister, Mushego, Wis, assignor to Chain
Belt Company, Milwaukee, Wis., a corporation of
FIG. 1 showing the front and rear columns of screens ‘and
the frame as set in guides in the sides of the channel which
is also in section;
CHAIN ADJUSTMENT FOR TRAVELING
WATER SCREENS‘
Wisconsin
_
Filed Mar. 23, 1960, Ser. No‘. 17,051
1 Claim. (Cl. 210-91)
FIG. 3 is a horizontal section taken on lines 3——3 of
FIG. 4 is an enlarged elevation of one take-up means
with parts broken awayvand sectioned and showing’ the
indlicating instrument with part of the other take-up means,
This invention relates to traveling water screens and’ 10
particularly to the adjustment of the tension of the paral
lel chains which carry the individual screens or screen
baskets in an endless series and which operate over upper
and lower sprockets.
The sprockets and front guide
an
FIG. 5 is a schematic diagram of the electrical circuits
employed for indicating the adjustment of the upper
sprockets.
‘
The spaced vertical ‘frame members 1 are joined by
means {for the chain are carried by spaced frame members 15 cross~braces, not shown, and may comprise a series of
and the adjustment of chain tension by movement of the
separable sections. 'The frame is assembled as it is low
upper sprockets is periodically‘ required to compensate for
ered into the channel 2 with the out-turned ?anges 3 of
members (1 ?tting in the slots of the guides 5 set in the side
wearing of the chain and for the proper operation of the
screen unit.
'
walls 6 of the channel.
The foot plates 7 at the bottom of the frame are se->
The screen units are installed in channels used by elec 20
tric generating stations and other plants for withdrawing
cured to members 1 and support the ends of the lower
large quantities of water from natural watercourses or
shaft 8 in the blocks 9. The boot plate 10 extends across
supplies. The screens prevent debris or large objects
the bottom of the channel and frame and is curved about
from passing through such channels which may be 50
the axis of shaft 8 which rotatably carries the sprockets
to 100 feet deep ‘because of titles or variations in the‘ 25 11a and 11b above the plate.
The parallel vertical guides 12 at each side of the
water level of the ocean or river. When the front screens
frame are ?xed to the upper ends 13 of frame members
facing the ?ow become clogged, the upper sprockets are
‘1 and are spaced for movement of the bearing blocks 14
turned to drive the chains which lift the clogged screens
therebetween. The take-up screws 15a and 1517 ‘are con
from the channel for cleaning and the lowermost back
screens move under the lower sprockets and to the front 30 nected to corresponding blocks 14 and extend upwardly
between guides 12 and through the bearing plate 16'
of the screen unit. The screens pass between the lower
extending across the upper ends of guides 12.
sprockets and a boot-plate with a nominal clearance so
The upper sprockets 117a and 17b are ?xed to‘ the shaft
that nothing can pass therebetween which would be larger
18 journally supported by bearing blocks ‘14 and carry
than whatever is allowed to pass through the screens.
However, as the chains wear in service, they become
longer and allow the screens to contact the boot-plate
unless the upper sprockets are periodically raised to take
up the increased chain length.
, the parallel chains 20a and 20b.
Sprockets 17 are driven by the motor 21 through the
gear reduction unit 22 driven by the motor and ?tted with
the drive sprocket 23 carried by the frame platform 24
According to the present invention, a certain number 40 at the upper end of the screen unit. The large driven
sprocket ‘25 ?xed on one end of shaft 18 is connected to
of turnslof the nuts is always required to raise the screens
the drive sprocket 23 by the chain 26 so that operation
by the amount of the nominal clearance referred to and
of motor 21 drives the chains and the screens, generally
by reason‘ thereof, load-sensitive means supporting the
and hereinafter referred to as “baskets,” attached to the
nuts threaded on‘ the take-up screws will serve to indicate
the disposition of the chains ?rst with respect to the frame
corresponding links of each chain.
The construction of the basket may be similar to that
and then with respect to the lower sprockets. That is,
if the chains are in proper working order and free of ob
shown, for example, in Patent Nos. 2,286,332 or 2,428,
757 wherein each basket comprises an open frame ‘and
structions, no indication of a change of loadon the upper
the screening 27 which is. securely attached thereto and
sprockets should appear for at least the number of turns
referred to. By having, or setting the indicating means
across the opening.
Each basket 28 shown in ‘the drawings comprises a
at “zero-load” in effecting said number of turns, the dead
frame including transverse and end members. The ad
weight load of the screens and upper head-shaft and
joining transverse members of the adjacent baskets over
sprockets'is then positively established and the load which
lap while allowing. relative movement about a horizontal‘
thereafter appears is the load which is due to the engage
ment of the lowermost baskets with the lower sprockets. 55 axis which corresponds with the axis of articulation of
the corresponding links of the two chains. Each end‘
No signi?cant amount of chain tension is desired and
member of each basket is provided with a bolt for secure
when indicated no further tightening is effected but may
ment to the corresponding link of the respective chains
be followed by turning the nuts down a given fraction of
2i) and includes a ?ange 31 having a curved outer edge.
a turn so that any indicated tension is relieved“
The principal object of the present invention is to
provide readily operable and reliable sensing means for
the usual periodical adjustment of the ‘screen chains to
the desired minimum tension and without requiring in
spection of the screens or chains.
Flanges 32 ‘and the guides 33 parallel‘ thereto and ?xed
to the inside of members 1, provide tracks for the rollers
34 of chains 24)‘ and support the front screens against the
pressure of the water ?owing through the channel. Bas
kets 28 including ?anges 31 are dimensioned to pass boot
Other objects and advantages of the invention will ap 65 plate 10 with a minimum of clearance and to move up
wardly from the lower sprockets 11 between the forward,
in-turned ?anges 32 of members 1 at the front side of
in the accompanying drawings.
the screen.
In the drawings:
_As the front screens become clogged by debris, the
FIGURE -1 is a side elevation of‘ the traveling water
pear‘ in the following description of the same as illustrated
screen with the upper housing removed and with the 70 motor 21 is operated to lift the clogged screens up into
the upper housing not shown, where the screens are
channel and parts of the screen in section;
cleaned by high-pressure streams of water. The oper
FIG. 2 is a front view of the traveling water screen
3,093,578
3
4
ation of motor 21 and the cleaning may be done at
regular, predetermined intervals or whenever ‘the diff
of % of an inch or necessarily less than the screen mesh
and such a unit might have take-up screws of a 1%: inch
erence in water-level ‘ahead of and behind the screens
indicate a given condition of clogging of the screens.
The adverse conditions under which chains 20 oper
ate results in wearing ‘of the chain bearings and conse
pitch. Therefore capstans 37a and 37b would be turned
11/: turns and engagement of the ?anges 31 with plate 10
would be conclusive. Of course, if wearing of ?anges 31
quent elongation of the chains until they do not positively
would be no need to turn down the take-up screws. How
shows that they have been rubbing the boot-plate, there
engage the lower sprockets 11. Unless the slack is taken
ever, the object of the present invention is to provide
up, the chains eventually allow ?anges 31 of the baskets
means for adjustment of the chains before this happens.
to rub the boot plate 10. This is generally to be avoided 10 It should also be noted here, that having lowered the
because of the likelihood of damage to the baskets or
chains by the amount of the clearance, the chains may
wear ‘on the buckets and boot plate, or the misengage
then be supported in part by the boot-plate and therefore
ment of the chains with the sprockets.
the ?rst step is to determine the same before setting the
As previously mentioned, the upper sprockets are best
meters to eliminate the dead-weight load of the chains.
adjusted so that the chains positively engage the lower 15 This is done by ?rst setting meters 51a and 51b to zero
sprockets but without unnecessary tension. Such adjust
by adjustment of the corresponding potentiometers 54a
ment is provided for by capstans 37a and 37b which are
and 54b.
threaded on take-up screws 15a and 15b and are sup
alternately or simultaneously a fraction of a turn to
Thereafter, capstans 37a and 37b are turned
ported by the thrust bearing units 38a and 38b to lift
raise the screws and chains so that in lifting part of the
shaft 18 and the corresponding upper sprockets.
20 weight of the chains from the boot-plate, an increased
However, to the present time no reliable means for
such adjustment has been provided. In the embodiment
of the invention shown, the load-sensitive means referred
to, comprise the load-cells 40a and 49b assembled on
load will be indicated by meters 51a and 51b. When
a given number of turns of the capstans does not indi
cate any additional load, the chains are hanging free of
or between the boot plate 10 and the lower sprockets.
each take-up screw 15a and 15b respectively, to rest on
Meters 51a and 5112 may now be reset to zero so that the
plate 16 and support the thrust bearing units 38a and 381).
Each load cell 40a and 46b is of the construction
meters do not show the dead weight load of the chains
shown in FIG. 4 wherein the load~cell 4tla includes a
sleeve member 41a to which the several strain gauges
42a and 430 are attached and arranged so that ‘a load
applied to member 41a increases the electrical conduc
tivity of gauges 42a and increases the electrical resistance
of gauges 43a. The gauges are connected to the termi
nal 44 carried by the protective collar 45 and the leads
46 connect the instrument 47 with both load-cells as
shown in FIG. 4.
As shown in FIG. 5, the gauges 42a, 42b, 43a, and 43b
of the two load cells are connected to form two separate
Wheatstone bridges and each such bridge, as is well
known, comprises two input junctions connected to a
source of electric current and two output junctions con
nected to a galvanometer. The gauges are electrically
balanced so that the potential between the output junc
tions is zero and the gauges are differentially arranged
so that a load applied to member 41a or 4112 increases the
conductivity or resistance of the respective gauges and so
that the potential referred to is changed and is indicated
by the galvanometer or meters as will be described.
As shown in FIG. 5, the source 55 of direct current and
the switch 56 in series therewith are connected to the
input junctions 'of the respective bridges.
The meters
51a and 51b are provided with the resistors 52a and 52b
in series therewith for protection during balancing and
and screens. The
simultaneously to
responding chains
The load referred
capstans are then turned alternately or
raise each take-up screw and the cor
until a load is indicated by the meters.
to indicates the tension due to the en
gagement of the chains with the lower sprockets. The
chains may be considered adjusted to the desired tension
or the capstans may be turned back a fraction of a revo
lution such as a one-third turn to positively eliminate any
tension due to sprocket engagement.
A separate load-cell and meter is employed for each
chain so that each chain may be adjusted properly de
spite unequal lengths due to unequal wearing. The in
vention eliminates unnecessary tension of the chains
which reduces the service life of the chains and requires
their more frequent replacement.
The indication of the dead-weight load of the chains
permits the meters to be set accordingly without regard
to the actual magnitude of the loads so that simple and
45 reliable adjustment means may be employed as described.
In the screen shown in the drawings, only the forward
column of baskets and chains which operate between
?anges 32 and guides 33 are supported ‘on boot-plate 10
when the upper sprockets are lowered, as described. In
other screens, not shown, vertical tracks may also be pro
vided for the rollers of the chains of the rear column of
baskets and in such screens, both columns of baskets
would be supported on the boot-plate in the same manner.
are connected to the output junctions of the bridges. The
Various modes of carrying out the invention are con
switches 53a and 53b selectively shunt the resistors for 55 templated as being Within the scope of the following
regular use ‘of the meters. The ends of the balancing po
claim particularly pointing out and distinctly claiming the
tentiometers ‘54a and 541) are connected to the input junc
subject matter which is regarded as the invention.
tions of the respective bridges and the limiting resistors
I claim:
57a and 57b connect an output junction of each of the
In a traveling Water screen having a frame, a series of
bridges with the movable taps of potentiometers 54a
baskets, upper and lower sprockets carried by said frame,
and ‘54b, respectively whereby the bridges may be ?rst 60 a lower boot plate below said lower sprockets and ?xed
balanced by moving the taps referred to until the meters
to said frame and cooperating therewith to close the chan~
show no output current. After balancing, the capstans
nel in which the screen is installed, chains operating over
37a and 37b are then alternately turned a fraction of a
turn and, accordingly to the said invention, the response
said sprockets and carrying said baskets, each upper
sprocket having and being supported by a take-up screw
of the meters can be interpreted to show whether the 65 provided with a capstan supported by the frame and
chains are free or are being supported in part by the
threaded on the screw to raise and lower the sprocket,
boot plate.
To adjust the chains 20 before wearing of the ?anges
said chain and baskets having a predetermined clear
:ance between said boot plate and lower sprockets and said
31 on the boot plate 10 occurs, the capstans 37a and 37b 70 frame including guide means for said chains which hold
‘are turned a predetermined number of degrees or turns to
the chains in a column and cooperate with the lower boot
lower take-up screws 15a and 15b a distance that is
plate in the support of the chains on said lower boot
known to be greater than the clearance provided between
plate when the upper sprockets are lowered a distance
?anges 31 and the boot plate 10. For example, a screen
greater than said clearance, load-sensitive electrical-resist
unit having a given screen mesh might have a clearance 75 ance means mounted over each take-up screw and on the
3,093,578
5
6
frame and beneath the corresponding capstan to support
the latter, and an electrically operative indicator con
plate, and having means to indicate the lifting of the
chains from said boot plate to said lower sprockets as
when the upper sprockets have been raised the amount
of said clearance with no indicated change in load, where
nected to each of said load-sensitive means and responsive
to changes in the load carried by the respective load-sen
sitive means within a given range, said indicator having
means adjustable to selectively raise or lower said range
so that the dead weight of the chains and baskets on the
upper sprockets when the chains are hanging between the
lower sprockets and said boot plate is within said range,
each indicator in combination with the respective take 10
by the upper sprockets are thereupon properly adjusted
to provide a minimum positive tensioning of the chains
between the sprockets.
References Cited in the ?le of this patent
UNITED STATES PATENTS
up screw ‘and turnable capstan having means to indicate
a reduced load when the chains have been lowered and are
1,555,791
2,675,701
partially supported within said guide means by said boot
2,867,707
Roddy ______________ __ Sept. 29, 1925
Bidwell _____________ _... Apr. 20, 1954
MacDonald ____________ .._ Jan. 6, 1959
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