U.S. patent number 3,859,484 [Application Number 05/395,520] was granted by the patent office on 1975-01-07 for cyclic pressure switch with plural diaphrams.
Invention is credited to Robert E. Nelson.
United States Patent |
3,859,484 |
Nelson |
January 7, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
CYCLIC PRESSURE SWITCH WITH PLURAL DIAPHRAMS
Abstract
A liquid level sensing system comprises a pumping section with a
housing across which there is stretched a flexible diaphragm
dividing the housing into a pair of chambers one of which is in
communication by a probe with a container such as a crank case
containing oil above which there is a pulsating air pressure due to
the operation of an engine or compressor. When the termination of
the probe is immersed in the oil there are substantially no
pressure undulations transmitted to the diaphragm, but when the oil
level drops sufficiently to expose the probe termination the
undulating air pressure above the oil is transferred to the
diaphragm which thereby reciprocates so that the chamber at the
side of the diaphragm opposite that of the probe draws in air
through a valve and pumps it into an accumulator-actuator section
which also comprises a housing containing a flexible diaphragm
dividing it into two chambers. The pumping pulsations applied to
the first chamber of this accumulator-actuator section push this
diaphragm in increments of movement until it activates a switch
which is connected with the ignition system of the engine to shut
down the engine. In case the pumping actuations are not sustained
and strong as when the duct termination is exposed to the air in
the oil container, the diaphragm in the accumulator-actuator
section does not move far enough to operate the switch because of a
bleed which bleeds off pumped air if only a few pumping actuations
occur or if the actuations are weak. In another embodiment the
output of the pumping section is connected to an
accumulator-actuator device comprising a diaphragm mounted to a
rigid element enclosing a cavity between them in such a manner that
the action of the pumping section draws air from the
accumulator-actuator section so that its diaphragm is pulled
inwardly to decrease the volume of its cavity. The diaphragm is
connected to an arm which operates an engine shut-down mechanism. A
bleed at the pumping section serves to prevent actuation of the
accumulator-actuator section except in the presence of sustained,
strong pumping pulses.
Inventors: |
Nelson; Robert E. (Rosamond,
CA) |
Family
ID: |
23563393 |
Appl.
No.: |
05/395,520 |
Filed: |
September 10, 1973 |
Current U.S.
Class: |
200/83Y; 200/34;
200/83Q; 73/716 |
Current CPC
Class: |
H01H
35/242 (20130101); G01F 23/164 (20130101) |
Current International
Class: |
G01F
23/14 (20060101); H01H 35/24 (20060101); G01F
23/16 (20060101); H01h 035/34 () |
Field of
Search: |
;91/52 ;73/389
;200/81R,83Q,83R,83J,83T,83V,83U,83W,34,153V,61.25 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schaefer; Robert K.
Assistant Examiner: Tolin; Gerald P.
Attorney, Agent or Firm: Mon; Donald D. Angus; D. Gordon
Claims
I claim:
1. An undulating fluid pressure responsive device comprising:
a reciprocable element having two sides maintained out of
communication with each other;
means adapted to provide fluid communication between a first of
said sides and a body of fluid subject to undulating pressure which
can reciprocate said reciprocable element in opposite directions,
the other of said sides forming part of the wall of a fluid pulse
generating chamber whose volume is changed by the
reciprocation:
means for developing an output pulse of fluid pressure each time
the reciprocable element moves in a first of said directions;
means for permitting fluid flow from a source of fluid into said
pulse generating chamber each time the reciprocable element moves
in a second of said directions;
a fluid pulse accumulating chamber in communication with said pulse
generating chamber to accumulate the generated pulses;
valve means between the fluid source and the accumulating chamber
preventing the return of fluid from the accumulating chamber to the
fluid source;
a fluid displaceable element forming part of the wall of the
accumulating chamber and
bleed passageway means providing communication between said
accumulating chamber and said fluid source thereby permitting flow
of fluid from said accumulating chamber at a rate sufficient to
prevent a substantial displacement of said displaceable element
when the fluid pulse output of said pulse generating chamber is not
both strong and sustained.
2. A device according to claim 1 in which:
the fluid displaceable element undergoes incremental displacements
in a path of movement by the fluid pulses applied to it.
3. A device according to claim 2 in which a movable actuating
member is connected to said fluid displaceable element such that a
substantial degree of movement of said fluid displaceable element
must take place before movement is imparted to said member.
4. A device according to claim 1 in which the means adapted to
provide fluid communication comprises a duct in communication with
said first side of said reciprocable element and having a
termination adapted to be placed within a container holding a body
of liquid and containing a gaseous fluid above the liquid subject
to pressure undulations, so that the termination may or may not be
submerged in the liquid.
5. A device according to claim 1 including means providing a
pressure bias on at least one side of said reciprocable
element.
6. A device according to claim 1 including means providing a
pressure bias against both sides of said reciprocable element.
7. A device according to claim 4 in which said reciprocable element
comprises a flexible diaphragm.
8. A device according to claim 7 in which said fluid displaceable
element comprises a second flexible diaphragm.
9. A device according to claim 8 in which said means for permitting
fluid flow from a source of fluid into said pulse generating
chamber comprises a valve means which admits pulses of fluid to
said pulse generating chamber when said first diaphragm
reciprocates.
10. A device according to claim 9 in which a second valve means
admits pulses of fluid from said pulse generating chamber into said
pulse accumulating chamber.
11. A device according to claim 9 in which said bleed means
comprises an opening through said second diaphragm.
12. A device according to claim 11 in which a poppet is placed at
said opening, said poppet having a head which closes said opening
when the second diaphragm moves some distance in its path of
incremental movement.
13. A device according to claim 11 including an element moved by
said second diaphragm when its incremental movement has been
sustained for a time.
14. A device according to claim 4 in combination with a container
comprising a crankcase containing oil and gas above the oil subject
to undulating pressure and the means responding to the sustained
incremental movement comprises means for terminating operation of
equipment creating the undulating pressure.
15. A liquid level responsive device comprising:
a first housing;
a first flexible reciprocatable diaphragm crossing the interior of
said first housing and creating a first chamber and a second
chamber within the housing on opposite sides of the diaphragm;
means for introducing pulsating fluid pressures into the second
chamber;
a first valve through which gas from a source of gas is introduced
into the first chamber;
a second housing;
a second flexible diaphragm crossing the interior of the second
housing and creating a first cavity and a second cavity on opposite
sides of the second diaphragm within the second housing;
a second valve between said first chamber and the first cavity
through which pulses of gas pass from the first chamber to the
first cavity, said second valve preventing the return of gas from
the second cavity to the first chamber thereby causing the second
diaphragm to move in one direction in a path of movement when the
first diaphragm reciprocates;
an actuator movable by substantial uni-directional movement of the
second diaphragm in said path of movement; and
bleed means at said first cavity for bleeding off gas therefrom,
thereby preventing substantial movement of said second diaphragm
when said pulsating fluid pressures are weak or unsustained.
16. A device according to claim 15 in which a fluid pressure
sensing duct is in communication with said means for introducing
pulsating fluid pressures.
17. A device according to claim 16 including a switch having a
member operated by said actuator.
18. An undulating fluid pressure responsive device comprising:
a reciprocable element having two sides maintained out of
communication with each other;
means adapted to provide fluid communication between a first of
said sides and a body of fluid subject to undulating pressure which
can reciprocate said reciprocable element in opposite directions,
the other of said sides forming part of the wall of a fluid pulse
generating chamber whose volume is changed by the
reciprocation;
means for developing an output pulse of fluid pressure each time
the reciprocable element moves in a first of said directions;
means for permitting fluid flow to a delivery region from said
pulse generating chamber each time the reciprocable element moves
in a second of said directions;
a fluid pulse accumulating chamber in communication with said pulse
generating chamber to accumulate the generated pulses;
valve means between the delivery region and the accumulating
chamber preventing the return of fluid from the delivery region to
the accumulating chamber;
a fluid displaceable element forming part of the wall of the
accumulating chamber and
bleed passageway means providing communication between said
accumulating chamber and said delivery region thereby permitting
flow of fluid into said chamber at a rate sufficient to prevent a
substantial displacement of said displaceable element when the
pulse output of said pulse generating chamber is not both strong
and sustained.
19. A device according to claim 18 in which:
the fluid displaceable element undergoes incremental displacements
in a path of movement by the fluid pulses applied to it.
20. A device according to claim 19 in which a movable actuating
member is connected to said fluid displaceable element such that a
substantial degree of movement of said fluid displaceable element
must take place before movement is imparted to said member.
21. A device according to claim 18 in which the means adapted to
provide fluid communication comprises a duct in communication with
said first side of said reciprocable element and having a
termination adapted to be placed within a container holding a body
of liquid and containing a gaseous fluid above the liquid subject
to pressure undulations, so that the termination may or may not be
submerged in the liquid.
22. A device according to claim 18 including means providing a
pressure bias on at least one side of said reciprocable
element.
23. A device according to claim 18 including means providing a
pressure bias against both sides of said reciprocable element.
24. A device according to claim 21 in which said reciprocable
element comprises a flexible diaphragm.
25. A device according to claim 24 in which said fluid displaceable
element comprises a second flexible diaphragm.
26. A device according to claim 25 in which said means for
permitting fluid flow from a source of fluid into said pulse
generating chamber comprises a valve means which admits pulses of
fluid to said pulse generating chamber when said first diaphragm
reciprocates.
27. A device according to claim 26 in which a second valve means
admits pulses of fluid from said pulse generating chamber into said
pulse accumulating chamber.
28. A device according to claim 26 in which said bleed means
comprises an opening through said second diaphragm.
29. A device according to claim 28 in which a poppet is placed at
said opening, said poppet having a head which closes said opening
when the second diaphragm moves some distance in its path of
incremental movement.
30. A device according to claim 28 including an element moved by
said second diaphragm when its incremental movement has been
sustained for a time.
31. A device according to claim 21 in combination with a container
comprising a crankcase containing oil and gas above the oil subject
to undulating pressure and the means responding to the sustained
incremental movement comprises means for terminating operation of
equipment creating the undulating pressure.
Description
This invention relates to cyclic pressure responsive devices.
In my U.S. Pat. No. 3,134,332, granted May 26, 1964, there is
described and claimed a liquid level regulating system in which a
container partially filled with a liquid is in fluid communication
with a fluid displaceable element, usually a diaphragm, by means of
a ducted probe having a termination which may, or may not be below
the level of the liquid. A pressure cycle present within the
container activates the fluid displaceable element whenever the
probe termination is above the level of the liquid and activates
this element only slightly, if at all, when the probe termination
is submerged. Pumping means is coupled with the fluid displaceable
element to transfer liquid to the container from a reserve source
of liquid whenever the probe termination is above the level of the
liquid.
It is often desirable to perform other functions than merely
replenishing liquid in response to the liquid level, for example,
signaling the liquid level condition or the shutting down of
associated equipment, such as an engine or compressor, requiring a
lubricating oil system wherein the oil must be maintained at a
sufficient level, whenever the liquid level drops below a specified
level.
An object of the present invention is to produce a response to a
cyclic pressure which may be translated to any of a variety of
functions which may include an electrical, mechanical or fluid
output function.
Another object is to replenish a liquid to bring the liquid to a
desired level or to signal low liquid level or to shut down related
equipment when the liquid level is low.
A related object is to provide for the occurrence of the response
when the liquid level is at a sustained low value but not when the
low level is momentary or when mere transient impulses like those
due to low level may be experienced.
A sensing system according to this invention responds to
undulations of gaseous pressure such as may occur in a contianer of
liquid above the liquid therein. Thus it can respond to the level
of a body of liquid partially filling a container which has a
pressure cycle within it. A duct normally terminating below the
level of liquid in the container communicates with a fluid
displacement element. When the liquid level falls below the
termination of the duct the pressure cycle is transmitted strongly
to the fluid displacement element and causes it to reciprocate.
When the termination is submerged the response of the fluid
displacement element is slight. The fluid displacement element,
when driven by the pressure cycle, pumps air or other gas in a
series of impulses. Bleed means is provided to discriminate against
weak activation. The output function of the system may be means for
restoring the liquid level, signaling means, or means for shutting
down operation of associated equipment.
The present invention is carried out by provision of a pumping
section which performs a substantial pumping function only when
receiving pressure pulses corresponding to low liquid level in the
container. The output of the pumping section may be connected to an
accumulator-actuator section which accumulates pulses of pressure
transmitted by the pumping system such that when sufficient pulses
are accumulated it functions to actuate an output device which may
comprise an indicator, a shut-down device or a liquid replenishing
device.
A feature of the invention resides in provision for discriminating
against casual or spurious pressure impulses from the liquid
container which could cause false output signals or functions. A
related optional feature resides in provision for the accumulation
of sensed impulses before activation of an output. A further
related feature resides in provision of means for bleeding away
accumulated impulses to such degree as may be required to permit
output response only to strong, steady impulses such as are present
under normal conditions of activation.
An alternative feature resides in provision of an output function
in the form of fluid impulses which may be delivered to a
responsive device together with bleed means for the desired
discrimination.
The accumulator means when used may be responsive to pressure
impulses which are either positive or negative as compared with
atmospheric pressure and may either be closely coupled to the
primary fluid displacement from the liquid container or
alternatively may be remotely coupled to the primary fluid
displacement.
The bleed means may be associated directly with the primary fluid
displacement means or with its output.
The output function may be self-restoring or may require
re-setting, as by manual means. It may be one of a variety of
possible output functions, which may include not only fluid
displacement means but also mechanical or electrical signaling or
actuating means.
The foregoing and other features of the invention will be better
understood from the following detailed description and the
accompanying drawings of which:
FIG. 1 is a cross-section view of a cyclic pressure sensing device
according to this invention;
FIG. 2 is an elevation view, partially in cross-section, showing
the device of FIG. 1 in operative relationship with an internal
combustion engine to shut down the engine under a condition of low
oil level in the crankcase;
FIG. 3 is a view, mostly in cross-section, showing another form of
device according to this invention in operative relationship with
an engine or compressor, arranged to create a shut-down under a
condition of low oil level in the crankcase; and
FIG. 4 shows a detail of a device, partially in cross-section,
which may be substituted for the shut-down mechanism of FIG. 3 for
the purpose of providing oil replenishment under a condition of low
level of crankcase oil.
The liquid level responsive device 10 shown in FIG. 1 of the
drawings comprises a pressure sensing group of elements 11 and an
accumulator-actuator group 12 and a group of elements joining them
represented generally by numeral 13. In assembling the device 10
the joining or intermediate group 13 will generally be assembled
first. This comprises a dish or a cup 14 having a circular outer
periphery at 15 flaring inwardly to form a flat base portion 16
with a central circular opening 17 centered at the longitudinal
axis 18 of the cup, which is the longitudinal axis of the entire
device 10. The flat annular portion 16 is placed against the
similar flat annular portion 18 of a cup 19 similar in
configuration and dimensions to cup 14 so that its outer periphery
20 is spaced apart in the longitudinal direction from outer
periphery 15. The surfaces 16 and 18 of the cups are held in
contact with each other by sandwiching them between a flange 21 of
a thimble 22 and a retaining ring 23 placed around the stem 24 of
the thimble and secured in place by swaging the end of the thimble
25 to over lie a shoulder 26 of the retainer ring. If desired,
adhesive may be placed between portions 16 and 18, which will
inhibit possible rotation between these parts. A porous air filter
ring, or annulus 27, is fitted between the cups 14 and 19 at a
position outside the members 16 and 18 and may consist of a
conventional open structured filtering medium such as open urethane
foam. A cylindrical screen 28 is fitted between the peripheries 15
and 20 of the respective cups to protect against introduction of
coarse objects or dirt and to afford mechanical protection for
filter ring 27.
Retainer ring 23 is grooved at 29 to receive the inner edge of an
annular flexible valve element 30. This is normally a flat sheet of
resilient material such as nitrile rubber so that when its inner
edge is snapped into groove 29 it is forced to assume a gently
conical shape because its outer portion makes contact with a flat
portion 31 of cup 14 which is substantially perpendicular to the
longitudinal axis 18 but offset from groove 29 to force the
resilient ring 30 to its conical shape. Another resilient valve
element 32 similar in material and dimensions to element 30 is
snapped into a groove 33 of the thimble and dimensioned similarly
to groove 29 such that element 33 is forced to take a gently
conical form by contact with valve seat 34 similar to valve seat 31
and displaced longitudinally from groove 33 in the same manner.
The space 35 between valve element 32 and portion 36 of cup 19
communicates with passages 37 and 37a passing through the wall of
thimble 22 to communicate with a longitudinal bore 38 opening into
region 39 at the opposite side of cup 14 from cup 19. When valve
element 30 is forced away from its normal position of contact with
seat 31 it also opens up into region 39.
Region 39 is further abounded by a diaphragm 40.
Diaphragm 40 is circular in form and typically made of a flexible,
impermeable material such as nylon fabric coated with nitrile
rubber, although it will be understood that some other flexible
material may be used instead. At its peripheral edge diaphragm 40
is secured by clamping between a peripheral face 41 of cup 14 and a
juxtaposed face 42 of a cup 43 constructed and dimensioned
similarly to cup 14 and positioned relative to cup 14 so that it
provides a space 44 between the diaphragm 40 and the inside surface
of cup 43 somewhat similar to space 39. The clamping of the
periphery of the diaphragm is secured by crimping the peripheral
edge of cup 43 around the peripheral edge of cup 14. Thus,
diaphragm 40 separates for the purpose of fluid displacement the
space 39 generally within cup 14 from space 44 generally within cup
43.
The unit 10 will be normally supported by a nipple 45 which
contains a central passage 46 providing communication between space
44 and the exterior of the unit. Threads 47 at the exterior of the
nipple provide means for attaching an external supporting
means.
Before clamping the diaphragm between cups 14 and 43, diaphragm
plates 47 and 48 are placed on opposite sides of the diaphragm and
centered at the longitudinal axis 18, and loading springs 49 and 50
are set against the respective plates. Spring 49 is supported in a
recess 51 formed in ring 23 and snaps into lugs 52 formed in a
circular group out of plate 47. Similar lugs 53 in plate 48 receive
spring 50 which bears at its opposite end against portion 54 of cup
43 and is centered by a projection 55 of nipple 45. The plates 47
and 48, although bearing against the diaphragm, need not be secured
to it as they are held approximately on center of the diaphragm by
their respective loading springs.
It will usually be desirable to use both of the pair of springs and
diaphragm plates with the diaphragm portion 40 when the unit is
used with an engine or compressor having crankcase pressure cycles
of approximately atmospheric average pressure. It is possible
however to omit either one, or the other, of plates 47 and 48 and
its respective spring where it may be desired to compensate for
crankcase average pressures substantially greater than or less than
atmospheric. Thus, whether to use both plates and springs or only
one plate and spring is subject to choice and will usually be
dependent on the application for which unit 10 is to be used.
The group 12 elements can be assembled in a manner similar to the
assembly of the group 11 elements. Group 12 contains a diaphragm 56
of a resilient material similar to that of diaphragm 40 and is
secured at its outer peripheral edge by forming or crimping the
peripheral edge 57 of a cap 58 around the edge 20 of cup 19.
Diaphragm 56, with cup 19, valve 32 and thimble 22 bounds a space
59. Assembled with diaphragm 56 are plates 60 and 61 held against
opposite sides of the diaphragm, provided with openings at their
centers which fit over a stud 62 and held against a shoulder 63 by
a washer 64 secured by swaging a rim of the stud at 65 over the
washer. The stud 62 contains a central longitudinal passageway 66
which provides communication between the space 59 at one side of
the diaphragm and space 67 at the opposite side of the diaphragm,
the space 67 being bounded by the diaphragm 56 and the cap 58. A
poppet 68 has its stem inserted through a passageway 66 with its
head 69 outside the passageway. The diameter of stem 68 is somewhat
smaller than that of passage 66 so that fluid flow is permissible
through passage 66 around the stem. The end of stem 68 opposite
head 69 normally makes contact with the adjacent face 70 of thimble
22 such that the poppet head 69 is normally located some distance
from face 71 of the stud 62. The poppet cannot move out of the stud
62 however, because its movement in the outward direction is
restricted by the presence of an operating button or arm 72 of a
switch 73. A spring 74 bears at one end against face 75 of cap 58,
and at the other end against the exposed face of plate 60 and is
centered around the longitudinal axis 18 by having its spiral
around stud 62. The spiral spring is under a degree of compression
which biases the diaphragm 56 towards space 59, thereby providing a
type of discrimination in the operation of the unit 10, depending
upon its degree of activation as is described in more detail
hereinafter.
The output of the unit may be sensed in any of a variety of ways,
usually involving the movement or alteration of some element. In
FIG. 1 the output is sensed by switch 73 whose arm or moving
element 72 is assumed to be operable by relatively low force
applied to it. The switch may, for example be a single-pole
double-throw snap switch, which is a well-known type of switch
needing no detailed description here. The switch may be an
automatically resetting-type or it may be a manual resetting-type
which is the type illustrated in FIG. 1, the operator extension arm
76 being adapted to snap the switch manually to the opposite
position from that to which it is snapped when the button 72 is
engaged by poppethead 69.
The unit 10 is operable to produce an output in response to
pressure undulations of sufficient amplitude and duration, but not
to produce an output when there are no pressure undulations, or
when the undulations are of relatively small amplitude or duration.
When undulating pressure is applied at nipple 45 and hence into
space 44 diaphragm 40 is acted upon to undulate accordingly, which
thereby produces corresponding pressure variations in space 39.
During intervals when diaphragm 40 moves toward the inlet nipple 45
pressure in space 39 becomes reduced, which opens valve 30 to draw
in atmospheric air through filter 27 and ports 77 to region 78 and
past open valve 30 into space 39. Upon movement of the diaphragm in
the opposite direction towards space 39, the air in space 39 is
compressed and the valve 30 closed, thereby forcing air from space
39 through bores 38 and through passages 37 and 37a to region 35,
the pressure of which opens valve 32 to admit air into space 59
from whence the air flows through the restricted passageway between
poppet stem 68 and opening 66 into region 67 from whence it readily
passes to atmosphere through ports 79. If the amplitude of movement
of diaphragm 40 is relatively small due to small amplitude of input
undulation, the restricted bleed between poppet stem 68 and hole 66
is sufficient to bleed-off the resulting air sent into regions 59
and 67. If, however, the undulations are strong, the air is pumped
into region 59 faster than it can be bled out with the result that
at each pumping pulse the diaphragm 56 makes a net movement into
space 67.
With a long-enough train of such pulses the continued movement of
the diaphragm carries face 71 of stud 62 toward switch button 72
until head 69 of poppet 68 becomes entrapped between switch button
72 and face 71 of stud 62. At this point the bleeding of air
through passage 66 ends, making further pumped increments of air
into space 59 completely available to drive forward diaphragm 56
and thus face 71. Movement then proceeds rapidly and forcefully to
set switch 73 through button 72.
From the foregoing, it will now be seen that even one or two
relatively strong impulses from the primary or pumping section 11
will be insufficient to set switch 73 unless immediately followed
by further pulses; if not, the bleeding of air through passage 66
will promptly allow spring 74 to restore diaphragm 56 to its normal
position and no output function will result.
FIG. 2 illustrates a specific example of the use of a unit
according to FIG. 1 in a system for providing low oil level
protection for an engine or compressor. In FIG. 2 there is shown a
single-cylinder internal combustion engine 80 having a cylinder 81
containing a piston 82 with a connecting rod 83 operating a crank
84 on a crankshaft with a spark plug 85 mounted on cylinder head
86. A magneto 87 is used to fire the spark plug over an electrical
line 88 at times related to the position of piston 82 in its cycle
as determined by a timer which properly energizes the magneto, such
timing means being common equipment. It is not illustrated. The
engine is assumed to be cooled by a cooling means 89 ordinarily
comprising a storage facility for a cooling fluid and a radiator
for cooling it which circulates the cooling fluid through a cooling
fluid channel 90 related to the cylinder wall. The engine is shown
with the usual crankcase 91 resting on a sump 92 constructed as a
lower extension of the crankcase. According to common practice, the
sump contains a supply of lubricating oil 93 which for good and
safe operation of the engine should be maintained between a full
level indicated by broken line 94 and a low or cut-off level
indicated by broken line 95.
A probe 96 in the form of a hollow tube extends into the crankcase
and sump from a position outside the crankcase where it is secured
in a suitable manner as by brazing to a plate 97 attached to the
exterior of the crankcase. Outside the crankcase th probe 96 is
connected to a hose 98 by a clamp 99, the other end of the hose
being clamped to a nipple 100 attached to a coupling 101 threaded
to the nipple 45 of unit 10. The coupling 101 is fastened to a
bracket 102 secured to the wall of the crankcase 91. The inner end
103 of the probe 96 may be left open if desired, or alternatively
it may be closed by a plug 104 in which case a port 105 must be
provided behind the plug to provide communication between the
interior of the probe and the interior of the crankcase sump.
According to conventional practice the magneto 87 is provided with
a grounding terminal 106 which in effect short circuits the magneto
to terminate ignition of the spark plug whenever the grounding
terminal is grounded to the engine. To provide for thus grounding
the magneto at desirable times a conductor 107 is connected between
terminal 106 and a terminal 108 of switch 73. Another terminal 109
of switch 73 is grounded to the motor by conductor 110 which is
connected at 111 to the bracket 102 fastened to the crankcase. When
switch contact points 112 and 113 are out of contact with each
other as shown in FIG. 2 the magneto is ungrounded. But, when
contacts 112 and 113 are brought together by actuation of switch 73
the magneto becomes grounded and ignition is terminated.
During the running of the engine, piston 82 sequentially moves into
and out of crankcase 91 to compress and decompress the gases
therein alternately, resulting in pressure undulations within the
crankcase of sufficient intensity to activate unit 10 by sustained
reciprocation of its diaphragm 40 over a sufficient time period as
has been explained heretofore. A breather 114 comprising a hollow
nipple 115 provided with a seat 116 on which a ball 117 loaded by a
spring 118, seats, providing for venting crankcase gases to
tmosphere through passages 119 formed in cap 120 of the breather.
This provides an average pressure reference to atmosphere for the
gases within the crankcase. In the form of breather illustrated,
peaks of pressure within the crankcase which slightly exceed
atmospheric pressure cause ball 117 to lift from seat 116 against
light pressure from the spring 118, thereby permitting gas passage
through passage 119. With this form of breather, average pressure
of the crankcase is usually negative with respect to
atmosphere.
There are many engines and compressors which do not use a breather
valve as illustrated and described in FIG. 2 but, instead, simply
breathe limited amounts of gases on each cycle to atmosphere, which
can be achieved by a breather such as 114 if the ball and spring be
omitted. In such case, the breather simply serves as a restricted
means of venting the crankcase to atmosphere and creates within the
crankcase an average pressure either substantially atmospheric, or
if engine blow-by passed by piston 82 be strong, may be somewhat
positive. Regardless of which form of breather is used, the amount
of gases passing between the crankcase and atmosphere during a
single-engine cycle will not be great enough to affect materially
the amplitude of the crankcase cycle within the range of speeds in
normal operation of the engine.
When the port 105 of the probe (or the end 103 of the probe in case
there is no plug 104 or port 105) is immersed, as is the case
whenever the oil level in the sump is above the cut-off level 95,
some oil will ultimately move into the probe through the port
during the more positive parts of the pressure cycle and move out
of it during the more negative parts. The air displacement within
the probe resulting from this in-and-out movment of oil is
communicated from the probe through the hose 98 to diaphragm 40
within unit 10. The relatively small amount of displacement due to
this in-and-out movement of oil to and from probe 96 will be
incapable, during normal engine operation, of being in sufficient
volume during a pressure cycle to produce more than a moderate
disylacement of volume within the probe and therefore will be
incapable of producing a substantial displacement of diaphragm
40.
When however, the port 105 is no longer immersed in oil, as will
occur when the level of the oil within the crankcase or sump has
been depleted to become below that of port 105 the port 105 is no
longer greatly restricted in its capacity to pass substantial
volumes of fluid into it, which in this case, is the gas within the
crankcase above the oil. Thus, there is a substantial volume of gas
into-and-out-of the probe in this case, which produces a
corresponding substantial displacement of diaphragm 40. This
ability to discriminate between oil, providing little volume of
flow through port 105 during a cycle, and the gases of the
crankcase, producing relatively high volume of flow during a cycle,
occurs because of the very great difference between the density of
oil and that of crankcase gases. Thus, typically, the ratio of
potential flow of gases to potential flow of oil, assuming the
probe to be open to one or the other, is in the general order of
about 30 to 1, providing an ample basis for discrimination by unit
10.
Any substantial movement of diaphragm 40 results in pumping of air
from the atmosphere into space 39 and delivery of air through
passages 38, 37, 37a into space 59 as described heretofore. From
space 59 the air may either displace diaphragm 56 into space 67
against the force of spring 74 or else pass through passage 66 into
space 67 and out through ports 79 as described heretofore.
From the foregoing, it is observed that when the movement of
diaphragm 40 is slight or even non-existent, as will be the case
when port 105 of the probe is immersed in the oil, little or no air
will be pumped into space 59. When the delivery of air into space
59 is low, passage 66 is sufficiently large to pass this air
without development of sufficient pressure in space 59 over that
prevailing in space 67 to cause the assembly of diaphragm 56 to
move in opposition to spring 74. Thus, immersion of port 105 in the
oil prevents development of any movement of the diaphragm assembly
56.
When however, port 105 ceases to be immersed in oil and becomes
open to gases of the crank case, the pumping action of diaphragm 40
becomes strong, causing relatively large volumes of air to be
pumped into space 59. In this case, the rate of delivery of the air
through passage 66 must increase until the pressure difference
across diaphragm 56 becomes great enough to overcome spring 74. The
assembly of diaphragm 59 now moves towards space 67 closing the
distances between face 71 of stud 62, head 69 of the poppet and
switch button 72, at which time the poppethead closes passage 66
except for the very small bleed channel 26a formed in face 71 to
permit later return of diaphragm 56 to its original position after
cessation of air pumping, but insufficient to affect appreciably
the degree of closure of passage 66 afforded by poppet 29.
With the by-passed delivery of passage 66 now virtually eliminated
by contact of the poppethead 69 with face 71, most of the air
pumped into space 69 becomes available to drive the diaphragm
assembly 56 forward so that the poppethead moves against switch
operator 72 under the increased pressure which follows the
elimination of venting through passage 66, and thus driving switch
41 into operation to snap switch contact 113 against switch contact
112, which of course will immediately stop the engine by
terminating ignition.
It will be recognized that operation of the system is not dependent
upon use of the particular switch illustrated in FIG. 2, as there
are many other types of switches which could be used instead. The
switch, for example, may be a manual resetting type which will
remain in its thrown position until later reset by an extension 76
or it may be automatically reset. In either case, resetting of the
switch requires some passage of air from space 59 to permit the
diaphragm 56 to return to its initial position and this air passage
is afforded by the bleed channel 26a. Under most conditions of
service, the automatically resetting type switch can be made to
continue in its thrown position until engine shut-down is
accomplished unless bleed channel 26a be made too large, because of
the lock-out action of poppet 29.
The unit 10 may be used to control the oil level by replenishment
of the oil instead of shutting down the engine. For example, the
closing of the switch contacts of switch 41 may be used to operate
a valve which permits flow from an oil supply to replenish the oil
in the crankcase until it is brought up to the level required to
immerse end 103 of the probe. In such case, an automatically
resetting switch will ordinarily be used.
As explained heretofore, the action of unit 10 normally requires a
series of cycles in which the primary or pumping section 11 must
continue its action before the secondary or accumulator-actuator
section 12 may be activated, in conjunction with the bleed means,
and this serves to discriminate against casual single-stroke or
short-burst action of the primary section. This is useful when the
unit 10 is used with an engine crankcase as illustrated in FIG. 2.
It is occasionally possible during starting and at other times
that, usually because of casual entrapment of air adjacent to port
105, momentarily vigorous probe action can occur even though the
port 105 be immersed in oil. With the requirement of a substantial
number of closely-occurring strong pumping cycles to activate the
accumulator-actuator section, the unit becomes relatively
invulnerable to false action which might result in unwanted
shutdown.
In FIG. 3 there is shown a liquid level responsive system which
differs somewhat from the device of FIG. 1 and its installation in
FIG. 2. The system 125 of FIG. 3 is shown applied to a crankcase
126 which may be that of an engine or a compressor. A sump 127 is
attached to the crankcase and the lubricating oil may be carried at
various possible levels above the bottom 128, a full level being
indicated by broken line 129 and a cut-off level indicated by
broken line 130 being that below which the oil should not be
allowed to go. A pressure cycle is assumed to be present during
operation similar to that described in connection with FIG. 2. A
hollow probe 131 is fastened and passed through a plate 132
covering a port 133 through the side of the crankcase. The end of
the probe within the crankcase is plugged at 134 and a port 135
just inside the plug provides communication from the inside of the
probe to its exterior. The probe is positioned so that its port 135
is located at the cut-off level 130 of the oil in the sump.
The system 125 comprises a pumping unit 136 which bears some
similarity to the pumping unit 11 of FIG. 1, in that it comprises a
cup member 137 and a second cup member 138 having respective
peripheral portions 139 and 140 juxtaposed to each other and
binding between them the peripheries of a circular flexible
diaphragm 141, such that the bases of the two cup members are
remote from each other leaving respective spaces 142 and 143 on
opposite sides of the diaphragm. The base portion 144 of cup member
137 is fastened to plate 132 of the crankcase and base 145 of cup
member 138 has attached to it a valve assembly 146. Aligned holes
147 and 148 through plate 132 and base portion 144 respectively
communicate with probe 131 providing communication from within the
probe to cavity 142 of the pump unit 136. Diaphragm plates 149 and
150 are provided on opposite sides of the diaphragm and their
curved peripheral rims contain helical springs 151 and 152, the
opposite ends of which are held in place by enveloping bosses 153
and 154 on respective cup members 137 and 138. These springs
perform a function similar to the springs in the pumping section of
FIG. 1 in that they load the diaphragm against average crankcase
pressure or vacuum. Depending upon the application with which the
system is to be used either one or the other of these two sets of
diaphragm plates and springs may be omitted.
The valve assembly 146 is incorporated in an extension 155 of base
portion 145 of cup member 138. A bore 156 is provided along the
longitudinal axis of pumping unit 136 and extends a substantial
distance into the extension 155. Bore 156 communicates with
passageways 157 and 158 extending from opposide sides and
perpendicular to the longitudinal axis of bore 156 and these
passageways 157 and 158 communicate with respective larger
passageways 159 and 160. A plug 161 provided with a central
passageway 162 is threaded into bore 159 and another smaller plug
163 having a central passageway 164 is threaded into plug 161.
A conduit 165 is attached to plug 163 by a coupling at 166. The
face of plug 161 at opening 159 io provided with a raised annular
boss 167 which serves as a valve seat for a flat valve plate 168
normally held against it by a compression spring 169.
The face of extension member 155 which faces space 160 is provided
with an annular protuberance 170 serving as a valve seat for a flat
valve 171 normally held against the seat by a compression spring
172. There is threaded to opening 160 a coupling 173 against which
the spring 172 bears, and this coupling is provided with an
internal passageway 174 aligned with passageway 158. A length of
tubing 175 communicates with passageway 174 by means of a coupling
at 176 and terminates to outside atmosphere.
The end of conduit 165 opposite that which is attached to coupling
163 is coupled to an accumulator-actuator assembly 177. This
assembly comprises a cup-like member 178 to the circular peripheral
rim 179 of which there is secured and may be sealed by a suitable
adhesive or other means a resilient diaphragm member 180. The
diaphragm also has a cup-like shape maintained by attachment of a
circular plate 181 at its central position and a spiral compression
spring 182 which engages plate 181 at one end and engages the base
portion 183 of the cup member 178. Thus, the flexible diaphragm is
normally positioned in its distended condition as illustrated in
FIG. 3.
For the purpose of providing communication between conduit 165 and
the interior space 184 bounded by the cup 178 and the diaphragm 180
there is provided a coupling 185 which passes through the base
portion 183 of the cup 178. The exterior part of the coupling has a
shoulder 186 which abuts a structural member 187 mounted on a
suitable support 188 and fastened to the base of the cup. The inner
end of the coupling is swaged around a washer 189 at the inner
surface of base portion 183. A coupling nut 190 serves to couple
conduit 165 to coupling 185.
The forward face 191 of diaphragm 180 has attached to it a bracket
192 at the forward end of which there is placed a link 193 which
extends forwardly to a bearing 194 which pivotally engages within
it a pin 195 fastened to a crank arm 196 fastened and keyed to a
shaft 197. Link 193 is slidable through a hole 198 at the forward
end of the yoke 192 so that it is free to move inwardly relative to
the yoke. The inner end of the link is provided with a head 199
which prevents the link from being pulled out of the yoke and by
which the link is pulled to the right when the yoke moves to the
right with reference to FIG. 3, head 199 being initially separated
from yoke 192 to permit initial lost motion before being
engaged.
There is fitted into the wall of cap 178 a bleeder 200 comprising a
plug 201 staked to the wall of cup 178 and having a passageway 202
comprising communication from the interior space 184 to a
passageway 203 leading to atmosphere. A cap 204 protects the
bleeder from entry of dirt.
Considering the pumping unit 136, diaphragm 141 is activated by
gaseous fluid displacement through probe 131 whenever port 135 is
unsubmerged by the liquid. The diaphragm reciprocates, displacing
air in space 143 and causing pumping of air through the valves 168
and 171 and to atmosphere through tube 175. This pumping is caused
by alternate movement of diaphragm 141 to increase the volume of
space 143, causing air to be drawn from conduit 165 past valve
element 168 and to space 143, and reverse movement of diaphragm 141
to deliver air from space 143 through valve element 171 to
atmosphere. Whenever port 135 is submerged in the liquid, action of
diaphragm 141 becomes negligible as any residual cyclical
displacement is vented to atmosphere through a by-pass channel 205
which leads from space 143 to space 160, thus preventing opening of
either valve 166 or 171 and hence, creating no pulse in conduit
165.
It is assumed that the crankcase 126 is that of an engine or a
compressor and is subjected to cyclical pressure as described in
connection with FIG. 2, and that the system is operating with the
level of the body of oil within the crankcase at some point above
that of the cut-off level 130. Because port 135 is then immersed in
oil, very little cyclical displacement of fluid can occur into and
from probe 131 for reasons explained heretofore in connection with
the system of FIG. 2. Correspondingly, even though the primary
diaphragm 141 may make some cyclical movement, such movement will
be slight, and any resulting small displacement of space 143 can
readily vent to atmosphere through by-pass 205. Hence, no positive
or negative pressures, relative to atmosphere, will be generated in
space 143 sufficient to open valve elements 166 and 171, and no
pulse signal will then be transmitted to conduit 165.
Now assuming that the oil level has dropped to or below the cut-off
level 130, the gases of the crankcase can now reach port 135 which
now can deliver their positive or negative cyclical pulses through
probe 131 to diaphragm 141. Pumping displacement of space 143 now
becomes substantial, resulting in actuation of valve elements 168
and 171 as the by-pass passage 205 is too small to transmit the
relatively great cyclical displacements without generation of
valve-opening pressures. Air is then drawn in a series of pulses
from conduit 165 which, transmitting these to diaphragm 180, will
cause the forward part 191 of that diaphragm to move inwardly
toward cup 178 against the force of spring 182 and begin to move
yoke 192 toward engagement with end 199 of linkage 193. After such
motion has progressed enough to engage head 199 with yoke 192,
further motion causes shaft 197 to turn and to operate to shut down
the engine or compressor in a well-known manner.
Had the pulsing at conduit 165 been casual or momentary as can
sometimes occur in the operation of engines or compressors, action
of diaphragm 191 would have commenced but would then have
terminated upon the cessation of pulsing before the initial lost
motion between end 199 and yoke 192 had been satisfied, which would
thereby permit diaphragm 191 to be returned to its initial position
shown in FIG. 3 by the action of compression spring 182 and the
admission of air from the atmosphere into space 184 through the
bleeder 200. However, with the oil level below the cut-off level,
the strong pulsing action will continue until actuation of the
cut-off or shut-down means is complete.
It should be recognized that the structure comprising the probe
131, the pump assembly 136 and the valve assembly attached at its
output side constitute a complete system which can accomplish
shut-down or control in response to fluid level. Thus, the series
of pulses developed as negative pressure or partial vacuum at
conduit 165 can, for example, be used to activate shut-down of the
Diesel engine of a locomotive in response to low oil in an air
compressor driven by that Diesel engine.
Alternatively, linkage 193 in FIG. 3 may be attached to actuate any
movement translating or otherwise movable shut-down means, and of
course, shaft 197 in FIG. 3 may be any conventional means for
accomplishing shut-down such as a throttle shaft. In the case of an
electrically driven compressor, shaft 197 may be an actuator of a
circuit interrupting means.
Diaphragm 180 in FIG. 2 serves not only the function of an
actuating motor to move a linkage, but also acts as an accumulator
of pulses in conduit 165 as the actuating linkage 193 is adapted to
permit a degree of early motion of diaphragm 180 before linkage 193
is actuated. In that respect, the arrangement of diaphragm 180 and
linkage 193 is somewhat analogous to diaphragm 56 and poppet 68 in
FIG. 1.
FIG. 4 illustrates a linkage system which may be used in place of
the linkage assembly involving link 193 and arm 196 in FIG. 3. In
FIG. 4 there is shown the forward end of yoke 192 of FIG. 3 to
which there is engaged a rod 210 instead of linkage 193 of FIG. 3.
The rod is held within the yoke by a nut 211 and washer 212,
adjustable to permit a desired degree of lost motion, so that the
rod is free to slide through hole 198 of the yoke but cannot be
withdrawn from the yoke, this arrangement being similar to that of
link 193 in FIG. 3. The opposite end of rod 210 enters a bore 213
of a valve housing 214 containing a cavity 215 into which the rod
protrudes. A valve head 216 is attached to the end of the rod and
provided with a conical forward surface 217 adapted to seat on an
annular valve seat 218 formed around an opening 219 through a cap
220 of the valve housing. The cap has a threaded outwardly
extending protrusion 221 on which there is threaded a coupling nut
222 which couples a conduit 223 to passageway 219 into the valve
housing. The valve housing is provided with a protruding boss 224
through which there is a passageway 225 from the interior cavity
215 to which there is coupled by coupling nut 226 a conduit 227. A
small compression spring 230 serves to maintain the valve 216
seated on its seat 218 to shut off communication between conduits
223 and 227. O-rings 228 in grooves 229 of the housing prevent
leakage from cavity 215 to the exterior.
When there are no vacuum pulses produced in conduit 165 of FIG. 3
by actuation of the pumping section 136, the diaphragm 180 is
distended to the fullest extent as shown in FIG. 3 so that the
valve 216 of FIG. 4 is seated in its normal position as shown in
FIG. 4. When, however, pulsing occurs in conduit 165 the diaphragm
180 is retracted inwardly against the force of its spring 182
thereby pulling rod 210 to the right with reference to FIG. 4 and
opening the valve so that fluid can flow from conduit 223 to
conduit 227. In practice, conduit 223 will lead from a source of
replenishment oil and conduit 227 will lead into the crankcase of
the engine or compressor. Thus, this operation of the valve by
pulsing in conduit 165 will permit oil to flow from conduit 223
through conduit 227 into the crankcase to raise its level to a
position above the cut-off level, whereupon the pulsing in conduit
165 will cease and diaphragm 180 will return to its original
distended position causing the spring 230 to seat the valve
again.
As stated in connection with link 193 of FIG. 3, when rod 210 and
the diaphragm 180 are in their normal position, there will be a
space between the end of yoke 192 and the washer 212 so that the
diaphragm 180 will undergo a traction for some distance before it
commences to pull rod 210 to the rear to unseat the valve. FIG. 4
illustrates the condition of the diaphragm already having moved to
the point where yoke 192 engages the washer ready to pull the valve
off its seat. This corresponds to the condition of the diaphragm
180 in FIG. 3 which has already retracted sufficiently, so that the
yoke engages the head 199 of link 193 to commence pulling the crank
arm 196.
It will be recognized that by the present invention there is
provided a sensor-operated pumping unit which functions to pump
impulses as its output in which the impulses are relatively strong
when the oil level is low. On the other hand, when the oil level is
relatively high at most only weak pulses are generated and these
are suppressed by the bleed means which is provided. Such an
assembly is illustrated both in FIGS. 1 and 3. It should then be
recognized that the sensor pumping section 136 of FIG. 3
constitutes for this purpose a complete device having an output
line 125 to which the pulses are transmitted and with which any of
the conventional means for sensing pressure differences may be
employed. In FIG. 3 the output line 125 is described as a vacuum
line, but it will be understood that either positive or negative
pressures may be provided as the output. For example, although the
unit 136 of FIG. 3 as shown produces a vacuum output in conduit
125, it will be obvious that it could equally be constituted to
produce a pressure output as described in the disclosure of FIG.
1.
It will be recognized that the assembly 136 in FIG. 3 corresponds
in this respect with the unit 11 in FIG. 1 with the exception that
in FIG. 1 the bleed means is associated with the output from the
pumping chamber of section 11, whereas in FIG. 3 it is connected
directly into the pumping chamber of assembly 136.
It will also be recognized that in both FIGS. 1 and 3 there is
provided an accumulator-actuator in addition to the sensor-operated
pumping unit, this being the assembly 12 in FIG. 1 and being the
assembly 177 in FIG. 3.
It will be understood that the embodiments of the invention
illustrated and described herein are given by way of illustration
and not of limitation, and that modifications or equivalents or
alternatives within the scope of the invention may suggest
themselves to those skilled in the art.
The term "output pulse" or "output pulse of gas" as used herein
means a flow in either direction and the pulse may be of a pressure
which is either negative or positive relative to atmospheric
pressure. The term "permitting fluid flow in relation to a chamber"
covers a flow of fluid either into or out of the chamber, and
likewise the term "flow" means a flow in either direction unless
otherwise stated. The terms "pressure pulse" and "pulse of
pressure" and the like as used in the specification and claims
cover either positive or negative increments of pressure.
* * * * *