Note: Descriptions are shown in the official language in which they were submitted.
11~7tj91S
The present invention relates to incinerators and other types of
furnaces in general, and more particularly to improvements in fluid-
operated motors (single-acting or double-acting cylinder and piston units)
which can be utilized to transmit motion to reciprocatory fuel feeding means
in such installations. Still more particularly, the invention relates to
improvements in means for shielding or protecting the piston rods of fluid-
operated motors against jamming, premature wear, extensive wear, con-
taminants, excessive heat, corrosive substances and/or a combination of such
undesirable influences.
United States Patent No. 3,559,823 granted February 2, 1971 to
Ostrin discloses a ram feed for incinerators wherein a hydraulically operated
ram advances batches of scrap material supplied by an upright hopper and
tamped by a vertically reciprocable packing piston. The admission of scrap
material into the path of the ram takes place when the latter is held in the
retracted positlon, and the front end portion of the ram carries a shearing
head which cooperates with a shearing edge on the outlet of the supply hopper
to comminute coarser or larger pieces of scrap material prior to admission
into the lncinerator. In order to protect the cylinder, the ram constitutes
an elongated tube (i.e., it has a skirt) which slides within a rearward
extension of the supply conduit that delivers scrap material to the
incinerator proper when the ram performs a forward stroke. The tubular or
cylindrical portion or skirt of the ram is very long so as to practically
or completely confine the cylinder in the retracted position of the ram.
Such ram further offers a pronounced resistance to tilting and other
stresses. The piston rod of the cylinder is attached to the inner side of
the front end wall of the reciprocable ram, and the length of the ram
suffices to reduce the likelihood of penetration of scrap material there-
behind, i.e., scrap material which descends from the hopper (either by
gravity or under the action of the aforementioned packing piston) is unlikely
to reach the cylinder. A body of liquid is maintained in the lower part of
the upwardly sloping supply conduit to establish a seal between the
incinerator and the cylinder. In order to prevent the body of liquid
.,
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11~76915
(normally water) from penetrating into the incinerator when the ram performs
a forward stroke, the upper side of the ram has a longitudinally extending
external groove which allows the displaced liquid to flow rearwardly by
gravity, and such liquid is allowed to penetrate behind the ram, i.e., it
can contact the cylinder of the hydraulic motor. Furthermore, the liquid
(which contains numerous contaminants and often also contains highly
corrosive substances) can reach and contact the piston rod so that the
latter undergoes pronounced and rapid wear, especially if the nature of
ingredients of the sealing liquid is such that they can readily attack the
external layer (normally chromium) of the piston rod. The skirt of the ram
surrounds the cylinder (and hence the piston rod) with substantial clearance
80 that the piston rod is likely to be contacted by large quantities of
liquid which contains dirt, scraps of foodstuffs, particles of metal, glass
or the like as well as other corrosive or otherwise aggressive substances
which reduce the useful life of the piston rod.
German Offenlegungsschrift No. 28 21 767 published on November
22, 1979 discloses a modified incinerator wherein the liquid seal is omitted
so that the piston rod of the hydraulic cylinder is less likely to be con-
tinuously exposed to the corrosive and/or other deleterious influences of
a contaminated liquid. The apparatus of this German publication is designed
to feed straw into the furnace and uses a ram with a relatively long skirt
which is dimensioned to surround the cylinder with a pronounced clearance so
that it cannot prevent aggressive gases from penetrating into contact with
and from attacking the external surface of the piston rod.
Each of the aforediscussed conventional incinerators exhibits the
drawback that the piston rod of the (normally hydraulically operated) cylin-
der is subject to pronounced corrosive and other influences so that its
useful life is rather short. The likelihood of rapid corrosion is even more
pronounced if the strokes of the piston rod are not constant, i.e., if the
piston rod is held in partially retracted or partially extended position for
relatively long intervals of time. Such situation can arise at the end of
a shift. The exposed portion of the piston rod is then subject to unint~r-
llt7tj9ls
rupted attack by solid, gaseous and/or liquid contaminants so that its
external surface (which, as a rule, is the external surface of a layer of
chromium or a like metal) is destroyed, either entirely or in part, and the
chromium layer begins to peel off the core or central portion of the piston
rod. In many instances, the defects appear in the form of spots where the
chromium layer begins to become separated from the layer therebelow, and --
such spots rapidly merge into larger zones of defective external surface on
the piston rod. The resulting and in part very sharp irregularities at
the exterior of the piston rod cause rapid destruction of the seal through
which the piston rod extends into the interior of its cylinder.
Another drawback of prolonged exposure of a portion of the piston
rod to external influences is that the film of oil on the exposed external
surface of the piston rod accumulates fragments of dust and/or other foreign
matter which tend to cake, especially at elevated temperatures to which the
piston rod is or may be subjected when the fluid-operated moto~ is used in a
furnace or the like. The caked foreign matter at the exterior of the piston
rod also contributes to or initiates and completes rapid destruction of the
seal through which the piston rod extends into the interior of the cylinder.
When the fuel feeding unit of a furnace is actuated by a
hydraulically or pneumatically operated motor in the form of a cylinder and
piston unit, the length of the piston rod often exceeds the length of working
or return strokes of the piston in the interior of the cylinder. This means
that a portion of the piston rod is always exposed. If the piston rod is
not retracted to the maximum permissible or possible extent, i.e., if the
piston is not held in the rearmost position within the confines of its
cylinder while the motor is idle for an extended period of time (such as
over a weekend or even during a longer interval of time when the furnace is
idle for any one of a number of reasons including a strike, the absence of
combustible material, vacation period, extensive repair work and/or others),
the seal surrounding the piston rod is highly likely to be destroyed in
response to initial or repeated retraction of the piston rod when the motor
is put to renewed use. Moreover, the provision of relatively large clear-
i17~91S
ances between the skirt of the ram on the one hand and the piston rod and
cylinder on the other hand renders it possible and quite likely that a
combustible gaseous, solid and/or liquid substance in such clearance catches
fire while the motor is idle so that the resulting heat causes total or
practically total destruction of the piston rod, of the cylinder or both.
SUMMARY OF THE INVENTION
An object of the invention is to provide a novel and improved
fluid-operated motor which can be used in or in connection with furnaces or
the like and which is constructed and assembled in such a way that it is
less likely to be rapidly and extensively affected by gaseous, liquid and/or
solid contaminants, corrosive substances or the like, even after extensive
periods of non-use.
The invention provides a fluid-operated motor, particularly for
reclprocating the fuel feeding means of a furnace, comprising an elongated
cylinder; a piston rod axially movable in said cylinder to perform working
and return stroke6 and having a foremost end located externally of said
cylinder in each axial position of said piston rod; and a hollow tubular
protective shroud having an end portion sealingly secured to the foremost
end of said piston rod and a second portion surrounding said cylinder and
defining therewith a narrow clearance in each axial position of said piston
rod.
The shroud should effectively shield the piston rod from dirt, dust,
fuel and/or other undesirable influences, as well as effectively shield the
piston rod and/or other parts of the motor from excessive heat. The useful
life of the sealing means between the piston rod and the cylinder is a
multiple of useful life of seals in heretofore known motors.
The motor can be used in existing incinerators and/or other types
of furnaces as a superior substitute for heretofore known motors.
The narrow clearance between the second portion of the shroud and
the cylinder admits air into the interior of the shroud while the piston rod
performs a working stroke and permits air to escape from the interior of the
shroud (together with dust and/or other foreign matter) in response to
il~7691S
retraction of the piston rod into the cylinder. The latter may be of the
single-acting or double-acting type.
If the rate of admission of air into the interior of the shroud
by way of the aforementioned clearance does not suffice, or if such
clearance is likely to be clogged from time to time, the motor can further
comprise a conduit or other suitable means for admitting a gaseous fluid
into the interior of the shroud intermediate the end portion and the second
portion thereof. The fluid admitting means may comprise a nozzle which is
disposed in the interior of the shroud and serves to spray or otherwise
discharge gaseous fluid into the intermediate portion of the shroud, i.e.,
into the portion between the end portion and the second portion.
In order to prevent tilting or other undesirable changes in
orientation of the shroud in response to reciprocation of the piston rod,
the motor can be provided with means for guiding the shroud while the latter
shares the axial movements of the piston rod. Such guiding means may com-
prise one or more supporting rollers which contact the underside of the
exterior of the intermediate portion of the shroud if the shroud and the
picton rod are mounted for reciprocatory movement along a substantially
horizontal path.
The motor can further comprise a transversely extending protective
wall or partition which is disposed in the region of the foremost end of the
cylinder (i.e., at that end of the cylinder beyond which the piston rod
extends), and such partition is provided with an opening through which the
intermediate portion of the shroud extends, either sealingly or with a
minimal or small clearance.
If the foremost end of the piston rod is connected with a sub-
stantially horizontal ram which has a top wall, the top section of the shroud
is preferably located at the level of (i.e., exactly flush with) or slightly
below the top wall of the ram.
As mentioned above, the second portion of the shroud can constitute
the rear end portion of such part, and this second or rear end portion may
constitute or comprise an end wall extending substantially radially of the
915
cylinder and defining an opening which receives the cylinder with the
aforementioned clearance. The motor can comprise one or more components
(e.g., pipes which supply or evacuate gaseous or hydraulic fluid from the
interior of the cylinder) which are adjacent to the external surface of the
cylinder; the opening of the end wall of the shroud is then configurated in
such a way that the aforementioned clearance can constitute a circumferential-
ly complete clearance also extending around the pipe or pipes or analogous
components at the exterior of the cylinder.
The intermediate portion of the shroud may have a polygonal cross-
sectional outline, and the length of the shroud (namely, the length of the
shroud between the end portion and the second portion thereof) preferably
exceeds the maximum length of forward or return strokes of the piston rod.
The novel features which are considered as characteristic of the
invention are set forth in particular in the appended claims. The improved
motor itself, however, both as to its construction and its mode of operation,
together with additional features and advantages thereof, will be best
understood upon perusal of the following detailed description of certain
specific embodiments with reference to the accompanying drawing.
FIGURE 1 is a schematic fragmentary vertical sectional view of a
furnace which can utilize the fluid-operated motor of the present invention;
FIGURE 2 is an enlarged fragmentary view of a detail of the
furnace shown in FIGURE 1 and a longitudinal vertical sectional view of the
improved motor whose piston rod is coupled to the fuel feeding ram of the
furnace; and
FIGURE 3 is a transverse vertical sectional view as seen in the
direction of arrows from the line III-III of FIGURE 2.
FIGURE 1 shows a portion of a furnace having a chute or hopper 1
which feeds fuel in front of a reciprocable ram 3. When the ram 3 performs
a forward stroke (in a direction to the right, as viewed in FIGURE 1), it
pushes a supply of fuel (i.e., scrap material, coke, coal or a combination
of two or more types of fuel) over a ledge 2 and onto the grate (not shown)
of the combustion chamber 101.
` 117~915
The motor which reciprocates the ram 3 in the directions indicated
by the double-headed arrow 3A of FIGURE 1 is illustrated in detail in
FIGURES 2 and 3. This motor is assumed to be a double-acting hydraulic
cylinder and piston unit having a substantially horizontal cylinder 4
secured to the frame F of the furnace by a horizontal pin 4a extending
through a lug 4b at the rear end of the cylinder. The front end portion or
foremost end 4c of the cylinder 4 has (but need not necessarily have) a
somewhat larger diameter than the remainder or central portion of the
cylinder and is spacedly surrounded by a radially extending wall or
partition 14 forming part of the frame F and located behind the chute 1 of
the furnace, i.e., to the left of the chute, as viewed in FIGURE 1 or 2.
The partition 14 has a polygonal opening 14a which is adjacent to a suitable
seal 14b engaging the external surface of the intermediate portion 9a of a
novel hollow tubular shroud 9 for the piston rod 5 and the cylinder 4 of the
motor. The piston rod 5 extends forwardly beyond the foremost end 4c of
the cyllnder 4 and its front end portion or foremost end 5a is sealingly
connected to the front end portion 9b of the shroud 9. To this end, the
front end portion 5a can be surrounded by a collar or sleeve 5b which is
shrunk onto its external surface and is connected to the radially inwardly
extending wall of the front end portion 9b by suitable fasteners 9c in the
form of screws, bolts or the like. The connection between the foremost end
5a of the piston rod 5 and the front end portion 9b of the shroud 9 is
such that the external surface of the piston rod within the confines of the
shroud 9 is not likely to be contacted by particles of fuel or even by
gaseous substances descending in the hopper 1 and intended for admission into
the combustion chamber 101. The frort or foremost portion 5a of the piston
rod 5 is further articulately connected with the ram 3 by a transverse shaft
or stud 6 so that the ram 3 can turn, within limits, relative to the motor
about an axis extending at right angles to the plane of FIGURE 2.
The lower end portion of the hopper 1 extends close to the top wall
3a of the ram 3, and such top wall is flush with or is located at a level
only slightly above the top portion or section 9d of the intermediate portion
il76915
9a of the shroud 9. As a matter of fact, and as shown in FIGU~E 2, the
foremost part of the top section 9d can have a shallow recess 9e for the
rear end of the top wall 3a of the ram 3. A stripping device 7 which is
articulately connected to the frame F, as at 7a, slides along the top wall
3a of the ram 3 and/or top section 9d of the intermediate portion 9 to pre-
vent penetration of solid fuel or the like into the interior of the frame F
(see the gap 8) when the piston rod 5 performs a return stroke (in a direc-
tion to the left as viewed in FIGURE 2). Since the top wall 3a is flush or
nearly flush with the top section 9d, these parts do not interfere with the
operation of the stripping device 7 behind the gap 8, i.e., the device 7 can
readily slide over such parts when the motor is in use.
The length of the forward or return stroke of the piston rod 5 is
less than the length of the shroud 9, namely, less than the distance between
the front end portion 9b and a second portion 9f which, in the illustrated
embodiment, constitutes the rear end portion of the shroud 9. In accordance
wlth a feature of the invention, the rear end portion 9f has a radially
lnwardly extendlng end wall 17 formed with an opening 18 which is slightly
larger than the maximum diameter of the cylinder 4 so that the parts 17 and
4 define a relatively narrow clearance 10 in the form of a substantially
circular orifice (see also FIGURE 3). The end wall 17 permanently surrounds
the cylinder 4, i.e., in each axial position of the piston rod 5, so that
the piston rod is invariably shielded and protected by the shroud 9
irrespective of whether it is fully or partly retracted into the cylinder 4.
FIGURE 3 shows that the intermediate portion 9a of the shroud 9
haa a polygonal (substantially square) cross-sectional outline. However, it
is equally possible to employ a shroud having a cylindrical or oval cross
section.
When the piston rod 5 performs a forward stroke (in a direction to
the right, as viewed in FIGURE 2), the clearance or orifice 10 performs the
function of a suction port and allows air to penetrate into the space 11
within the intermediate portion 9a of the shroud 9. When the piston rod S
thereupon performs a return stroke, the clearance or orifice 10 allows for
il~76915
escape of air from the interior of the portion 9a and such air entrains any
solid impurities which might have found their way into the shroud during the
preceding forward stroke. The cross-sectional area of the clearance 10 is
sufficiently small and the speed of the piston rod 5 is sufficiently high to
produce a pronounced pumping action in response to reciprocation of the
piston rod between its end positions. In other words, the rate of air flow
into and from the space 11 in the intermediate portion 9a of the shroud 9
is quite pronounced which is desirable on the aforediscussed ground (to expel
any solid impurities which might have penetrated into the shroud 9 during a
forward stroke of the piston rod S) as well as on the additional ground that
the circulating (entering and exiting) streams of air cool the shroud 9, the
piston rod 5 and the foremost end 4c of the cylinder 4. It has been found
that the ~ust discussed dimensioning of the clearance 10 and selection of the
speed of the piston rod 5 invariably prevent the deposition of substantial
quantities of or any dust or other foreign matter on the exposed surface of
the piston rod 5 when the motor is in use. The volume of the internal space
11 in the shroud 9 changes continuously when the piston rod 5 is in motion,
and this entails the aforediscussed flow of air into and from the shroud.
However, if the rate of air flow into and from the space 11 via clearance 10
does not suffice, the apparatus can be equipped with means for admitting into
the space air or another suitable gaseous fluid independently of air flow
via clearance 10. In the embodiment of FIG~RE 2, the motor comprises a
source 12a of compressed air which is connected with a conduit 12 via valve
means 12b, and the conduit 12 extends into the space 11 by way of a cutout
18a which is provided in the end wall 17 and can be said to form part of the
opening 18. The discharge end of the conduit 12 carries one or more nozzles
13 which inject compressed air into the space 11 when the valve means 12b is
actuated to permit the flow of compressed gaseous fluid from the source 12a.
The source 12a may constitute the so-called underblast which serves to admit
compressed oxygen-containing gas into the combustion chamber 101 below the
grate or grates and whose pressure is often sufficiently high to ensure a
highly satisfactory rate of admission of pressurized fluid into the space 11
769~5
of the shroud 9.
As explained above, the intermediate portion 9a of the shroud 9
is engaged by the seal 14b in the region of the opening 14a in the partition
14 so that the lower portion of the hopper 1 cannot receive air from the
region surrounding the major part of the cylinder 4. This ensures that the
burning of fuel in the chamber 101 can be controlled and regulated with a
high degree of reliability. As shown in FIGURE 2, the rear end portion or
second portion 9f including the wall 17 of the shroud 9 is located behind
the partition 14, even when the piston rod 5 assumes its fully extended
position. This prevents penetration of corrosive, extremely hot or otherwise
deleterious gaseous fluids into the space around the cylinder 4 and/or into
the clearance 10 because the seal 14b between the intermediate portion 9a
of the shroud 9 and the partition 14 is active at all times. As a rule,
gaseous fluids will tend to penetrate toward the area around the cylinder 4
and into the clearance 10 only in response to deflagration in the combustion
chamber 101 of the furnace, i.e., when the pressure in the combustion chamber
101 temporarily rises and causes hot gaseous products of combustion to
travel along the ledge 2 and into the gap 8 to find their way into the
region of the clearance 10 only if the frame F exhibits unforeseen leaks.
The motor preferably further comprises means for guiding the
shroud 9 during movement of the piston rod 5 between its two end positions.
Such guiding means comprises one or more idler rollers 15 or analogous
rotary elements which are installed in the frame F and preferably support
the intermediate portion 9a from below. FIGURE 3 shows that the motor can
comprise two rows of guiding and supporting rollers 15 which engage the
underside of the flat horizontal bottom panel or wall of the intermediate
portion 9a. The purpose of the rollers 15 is to reduce the likelihood of
jamming of the piston rod 5, e.g., when the piston rod tends to leave its
position of axial alignment with the cylinder 4 because the ram 3 encounters
a pronounced obstruction and great resistance to its forward or return move-
ment and such obstruction tends to move the front end portion 5a of the
piston rod up, down or sideways, as viewed in FIGURE 2.
--10--
il~7~915
FIG~RE 3 further shows that the motor comprises certain additional
components, namely, two pipes 16, which supply fluid (e.g., oil) to or
permit evacuation of such fluid from the chambers of the cylinder 4. The
opening 18 in the end wall 17 of the shroud 9 is configurated in such a way
that it has recesses or cutouts 18b for the pipes 16 in addition to the
aforementioned cutout 18a for the conduit 12. That portion of the opening
18 which remains unoccupied constitutes the clearance 10; as shown in FIGURE
3, this clearance is a circumferentially complete orifice which surrounds
the cylinder 4 as well as portions of the pipes 16 and of the conduit 12.
An important advantage of the improved motor is that the shroud 9
constitutes a highly satisfactory but simple and inexpensive means for
shielding the external surface of the piston rod 5 against external influ-
ences, such as solid, liquid and/or gaseous substances which can readily
penetrate into the skirts of the aforediscussed rams in conventional
furnaces. Thus, the second portion 9f surrounds the cylinder 4 with
relatively small clearance 10 which is just sufficient to allow for entry
of relatively clean air into the space 11 when the piston rod 5 performs a
forward stroke but can adequately shield the piston rod from contaminants,
i.e., from substances which are likely to leave the combustion chamber 101
or the hopper 1. The piston rod 5 is invariably shielded from sparks, hot
ashes or the like. Moreover, the end portion 9f of the shroud 9 is located
in a region (in the frame F) which is designed to prevent penetration of
ashes, sparks, hot gases or the like into its interior so that the likelihood
of penetration of such substances into the space 11 by way of the clearance
10 is very remote. However, even if the apparatus which is shown in FIGURES
2 and 3 would permit penetration of undesirable corrosive, too hot or con-
taminating substances into the region of the clearance 10 (e.g., as a result
of unforeseen malfunctioning of the furnace~ the clearance 10 is or can be
sufficiently narrow to effectively prevent penetration of large or
appreciable quantities of deleterious substances into contact with the
external surface of the piston rod 5. The aforementioned design of the
clearance 10 in the form of a substantially annular orifice also contributes
11~7~915
to prevention of contact between deleterious substances and the exterior
of the piston rod 5, i.e., the orifice or clearance 10 causes a pronounced
flow of fluid from the space 11 whenever the piston rod performs a return
stroke so that any deleterious substances which happen to penetrate into the
space 11 are expelled after a relatively short period of dwell in the
interior of the shroud 9. Pronounced circulation in the space 11 prevents
or reduces the likelihood of deposition of foreign matter on the external
surface of the piston rod 5 and effects a highly pronounced conditioning
(cooling) of the piston rod, of the shroud 9 and other parts in the region
of the space 11. It is to be borne in mind that the clearance 10 admits air
which fills the rear portion of the frame F, i.e., a space which is rather
remote from the combustion chamber 101, so that air which flows into the
space 11 when the piston rod 5 performs a forward stroke is invariably cooler
than the air in the region of the ram 3. The conduit 12 and its nozzle 13
can further enhance the cooling and solid-expelling effect of air or another
gas which is circulated in the space 11. The utilization of a nozzle 13 at
the discharge end of the conduit 12 contributes to acceleration of compressed
air whlch is supplied by the conduit 12. The source 12a need not necessarily
supply air, i.e., this source can also supply another gaseous fluid such as
an inert gas. This is especially desirable if the motor of the present inven-
tion is operated in a highly aggressive atmosphere so that the admission of
at least some inert gas into the space 11 can greatly reduce the likelihood
of premature reduction of quality of the external surface of the piston
rod 5.
The partition 14 constitutes a simple but effective barrier which
prevents excessive heating of the region around the cylinder 4 and thus
enables the clearance 10 to admit relatively cool air when the piston rod 5
performs a forward stroke. The provision of a seal 14b between the inter-
mediate portion 9a of the shroud 9 and the partition 14 is not critical but
desirable and advantageous.
The presence or absence, the distribution, the number and the
dimensions of combined supporting and guiding means 15 for the shroud 9 will
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1~7~9~5
depend on a variety of factors, namely, the overall dimensions of the
improved motor, the length of strokes of the piston rod 5, the nature of
fuel which is being conveyed by the ram 3, the likelihood of pronounced
resistance to retention of the piston rod 5 in accurate axial alignment with
the cylinder 4 and/or others. If the shroud 9 is relatively large and heavy,
the combined guiding and supporting means 15 will preferably camprise several
rows of rollers; however, a single raw of rollers will suffice in many
instances, especially if the rollers are relatively long.
The placing of the top section 9d of the shroud 9 at the level of
or slightly below the top wall 3a of the ram 3 is desirable for the afore-
discussed reasons, i.e., these parts do not interfere with the function of
the stripping device 7 because the latter can slide along the top section of
the shroud if the piston rod 5 is moved or must move beyond the extended
position of FIGURE 2. Were the top section of the shroud 9 located at a
level above the top wall 3a of the ram 3, the device 7 could interfere with
further rightward movement of the piston rod 5.
The improved motor can be used in incinerators, other types of
furnaces and/or in any such installations where the piston rod is likely to
be subjected to pronounced heating action, corrosive fluids or solids and/or
other undesirable influences which are likely to entail rapid destruction
or deterioration of quality of the external surface of the piston rod.
Without further analysis, the foregoing will so fully reveal the
gist of the present invention that others can, by applying current knowledge,
readily adapt it for various applications without omitting features that,
from the standpoint of prior art, fairly constitute essential characteristics
of the generic and specific aspects of our contribution to the art and,
therefore, such adaptations should and are intended to be comprehended within
the meaning and range of equivalence of the appended claims.
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