Note: Descriptions are shown in the official language in which they were submitted.
Backqround_of t ~
This invention relates to a fluid compressing apparatus
and particularly such an apparatus which is especially adapted
to form a small pneumatic compressor unit fo~ incorporation
in commercial and institutional air conditioning and process
control systems.
Conditioning and process con-trol systems may be of
an all pneumatic, all electric or a combination pneumatic
and electric variety; depending upon the particular design
requirements~ Purely electrical systems have certain distinct
advantages from the design of suitable sensors for detecting
variables such as temperature, pressure, humidity and the
like. Further, electrical signals can be conveniently trans-
mitted to operating and actuating control devices. However,
pneumatic systems have been widely employed because of the
high power characteristic of pneumatic operators at relatively
low cost and because the overall control systems are generally
somewhat simpler, more reliable and less costly than a comparable
electrical design. This is particularly true because in elec-
trical systems, it is difficult to modulate accu~ately the
significant electrical power levels required to produce the
necessary mechanical output. Thus, the electrical output
.
will normally drive a motor device which, in turn, is converted
into a mechanical output through a motor driven gear train
or a motor driven hydraulic pump operator.
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.
~ 5
Althou~h pneumatic systems have generally predominated
in the commercial control field particularly for institutional and
commercial air conditioning systems and the l;ke, all electric
systems have more recently found increasing applicability9 partic-
ularly in relatively smaller systems where the additional expense
associated with the electrical operators is only slightly greater
than the cost associated with the necessity of a relatively large
single air compressor. Thus3 the compressors must be capable of
producing pressures of the order of twenty pounds per square inch
~psi). The same advantage does not apply in larger overall systems
where a generally similar compressor cost is relatively a much
smaller percentage of the total cost.
As pointed ou-t in Applicant's issued patent 3,411,704~
; very substantial need exists for a small, compact and efficient
electromagnetic fluid compressing apparatus which can be constructed
at a minimum cost such as to permit application in relatively small
environmental conditioning and process control systems. The above
patent discloses a small~ electromagnetically driven compressor.
Thus in the environmental control field, new installation often
employs a plurality o~ individual roof top units in which local
pneumatic supplies are required, which can advantageously be
; such a compressor.
`~ Although such devices operate satisfactorily, the effic-
iency and construction requirements are not particularly adapted
to low cost, mass production processes such as often required for
commercial manufacutre and sale of products.
SUMMARY OF THE PRESENT INVENTION
The present invention is particularly directed to a highly
efficient compressing apparatus which can drive pneumatic operators
and particularly for environmental and process control systems in
response to an electrical drive.
453~S
Generally in accordance with the present invention~
the compressor includes a diaph~gmmember coupled to and forming
a part of a mova~le piston means. The piston means includes
an intake valve structure preferably in the form of a resilient
disc overlying a suitable axial inlet opening in-the face of the
piston which automatically opens during the return stroke of
the piston and closes during the compression stroke. A similarly
constructed exhaust valve is mounted in the wall opposite the
piston and thus is opened during compression stroke at a
selected position and is automaticly closed during the return
stroke as the pressure drops to a selected level. The location
of the intake valve within the piston employes the inertial
effect of the piston movement to open the intake valve at the
start of the suction stroke. Further in accordance with a
particular novel aspect of the present invention, the diaphragm
is formed with a convolution and the opposed compression chamber
wall i5 ~ormed with an aligned and preferably corresponding
projection which permits a longer operating stroke and results
in a higher volumetric efficiency. The construction of the
intake and exhaust valve members is essentially the same and
significantly contributes to the practical construction of a
low cost unit.
~ More particularly, in accordance with a further novel
feature and construction of the present invention, an annular
diaphr~gmmember has a central opening with the periphery
secured within an annular recess in the face of a piston.
The outer peripheral edge of the diaphragm is affixed between
a clamp member and a valve plate which has a central recess
to form a pumping or compression chamber. The diaphragm
has a convolution which opens toward the compression chamber
~ 4C1 ~65
generally aligned with the outer peripherial portion of the
compression chamber wall. The latter peripheral portion
includes a projection complementing the convolution and mating
therewith in the center position of the piston. The piston
includes suitable axial annular spaced intake openings suitably
located inwardly of the diaphragm and centrally of the piston
unit. A mushroom shaped valve member formed of a suitable
flexible material includes a stem locked within the pis+on
concentrically of the intake opening and with a planar seal
lid or disc abu~ting the inner face of the piston and with the
peripheral edge located outwardly of the intake opening. The
stem may pass through a central opening with an outer stem
enlargement creating a resilient clamping of the valve member
to a holding portion of the piston, The outer peripheral edge
of the disc is formed with a slight raised portion facing and
abutting the piston to resiliently preload the disc to es-tablish
a closed position. The valve plate is formed of a thickness
corresponding to the holding portion of the piston unit such
that an identical valve member is secured within the exhaust or
output plate. A plurality of circumferentially dis-tributed
openings are formed in the valve plate inwardly of the periphery
of the output valve dic. Thus, the inward movement of the
piston and associated diaphragm, compresses the fluid within
the compression chamber and at a selected position, the fluid
- is compressed to establish a sufficient force to overcome
the force of the output valve disc. The compressed fluid
flows from chamber through the output passageways to a suitable
load, preferably through an output chamber formed in an outer
mounting plate.
In a particularly practical structure, the several
body portions are formed as platelike members including a
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mounting plate, a valve plate and a clamping ring
mounted in a stacked formation, with the outer periphery of
a diaphra~m located between the valve plate and the clamping
ring, Suitable U-shaped spring members or the like snap over
the outer peripherial edge to lock the several body portions
in superimposed relationship. The inner edge of the diaphragm
is secured to the pis~on which couples to a suitable drive such
as a vibrating electromagnetic drive means. The piston and
body members are formed of a suitable plastic medium to--permit
convenient molding of the parts. The similar valve members
and other parts are readily and conveniently assembled with
a minimum amount of skill required.
Applicant has found that the present invention thus
provides a relatively compact, compressing means having a
relatively high degree of efficiency,
Brief Description of the Drawinqs
The drawings furnished herewith illustrate preferred
.
constructions of the present invention in which the above
advantages and features are clearly disclosed as well as others'
that will readily be understood from the following description,
In the drawings:
Fig, 1 is a front elevational view of the electro-
magnetically driven fluid compressing apparatus constructed in
accordance with the present invention;
Fig, 2 is a side elevational view of Figs~ 1 and 2;
Fig. 3 is an enlarged front view with parts broken
away and sectioned to show details of the contruction;
Fig. 4, is an axial sectional view of an alternate con-
struction of the invention;
Fig, 5 is a fragmentary view of Fig, 4 showing the piston
position at an intermediate position in full line and at the end
of a compression stroke in phantom;
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;:
Fig. 6 is a sectional view taken generaly on line
6~6 of FigO 4, and illustrating the inlet port arrangement
of the compressing apparatus;
Fig, 7 is a view taken generally on line 7-7 of Fig,
: 54 and illustrating the output part of the exhaust valve con~
struction; and
Fig, 8 is an exploded illustration of the components
shown in Figs, 4-7,
10Description of the Illustrated Embodiment
Referring to the drawing and particularly to Fig. 1, a
fluid compressing apparatus is illustrated including a pair
of corresponding air compressors 1 and 1', each of which is
constructed in accordance with the present invention. The
compressors are interconnected to actuate a suitable pneumatic
actuator 2 and are similarly coupled to a driven element 3
forming a coupling element between the compressors and an
electromagnetic drive means 4. A pair of synchronized alter-
nating current supplies 5 and 6 are connected to actuate the
drive means 4 as more fully developed hereinafter to produce
oscillation of the element 3 with a corresponding continuous
opposite actuation of the compressors 1 and 1' to maintain
: a predetermined and related output to the pneumatic actuator
:~2. A common support 7 is provided upon which the compressors
1 and 1' are mounted immediately below the electromagnetically
driven means 4.
In the illustrated embodiment of the invention, the
compresso.rs 1 and 1' are correspondingly constructed and
consequently the air co~mpressor 1 will be described in detail with
the corres~onding elements of the compressor 1l identified by
corresponding primed numbers.
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The air compressor 1 includes a base body portion 8
which is secured to the right lower ed~e or side of the support
7 by a suitable clamping bracket 9. The bracket 9 is bolted or
otherwise secured to the support plate 7 and allows lateral
positioning of the compressor 1 with respect to the normal
standby position of the driven element 3, The compressor 1'
is similarly mounted by a bracket 9' to allow corresponding
positioning of the two compressors with respect to element 3.
The base portion 8 is provided with an output chamber
10 centrally formed thereof and with an outlet passageway 11
connected in common with the outlet passageway 11' of compressor
1' to the pneumatic actuator 2. The chamber 10 is closed by an
intermediate body member or portion 12. An outer clamping ring
13 clamps a diaphragm 14 against the outer face of the body 12.
The three body portions 8, 12 and 13 are clamped together in any
suitable means; shown as a simple plurality of U-shaped clamping
springs 15 which project over the outer periphery of the body
portions.
The central body portion 12 is provided with a recess
16 which is closed by the diaphragm 14 and defines a compression
chamber, The diaphragm 14 is a suitable flexible member such as
: a conventional rubber on fabric diaphragm, with the central
portion thereof bonded or otherwise affixed to an adjacent end
of a piston 17. The movement of the piston 17 results in the
expansion and contraction of the compression chamber. The pistcn
17 includes a plurality of L-shaped inlet passageways 18 which
extend from the periphery inwardly and then axially toward the
diaphragm. A cup valve 19 is disposed within a valve chamber 20
from in the face of the piston 17 immediately adjacent the
diaphragm 14 and is biased to close the inlet passageway 18.
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~ 5
The valve member 19 is -formed of a suitable soft rubber such
as silastic or "Buna N", Thus the reciprocation of the piston
17 results in the alternate establishment of suction and
compression strokes to produce timed spaced output pulses at
line 11.
The diaphragm 14, in turn, is provided with openings
establishing communication betwee~n the compression chamber
16 and the piston chamber 20. Thus when the piston 17 is
moved outwardly or to the right, as shown in Fig. 1, the valve
member 19 is free to open thereby admitting air into the chamber
20 and the compression chamber 16. When the piston moves during
a compression stroke in the opposite direction, however, the
reduction of chamber 16 compresses the air within the chamber
16 resulting in a build-up of pressure which is fed back
through the chamber 20 to the exterior of the valve 19 and
causes it to close. The air within the chamber 16 will,
consequently, be compressed during the compression stroke.
A plurality of coaxially arranged outlet passageways 21
are provided in the base of the wall 12 and provide communication
; 20 between the compression chamber 16 and the outlet chamber 10.
An outer valve cap 22 overlies the passageways 21 with chamber
10. During the compression stroke, the air within the chamber
16 will be compressed to a level sufficient to overcome the
holding force on the valve member 22, causing it to move out-
wardly and allowing discharge of the compressed air outwardlythrough the chamber 10 and passageway 11 to the actuator 2,
The air compressor 1' is similarly located to the
opposite side of the element 3 and thus operates in alternate
synchronism with the compressor 1, such that its output pulse
occurs during the suction stroke of the piston 1. In this
--8--
.
manner a continuous output pressure signal is supplied to the
- pneumatic actuator 2,
The pistons 17 and 17' are coupled to each other and
to the driven element 3 in the illustrated embodiment as
follows. A pin 23 extends through an opening 24 in the element
3 in coaxial alignment with the pistons 17 and 171, Suitable
recesses or central openings are provided within the ends of
the pistons 17 and 17' with the pin 23 secured therein to produce
a rigid interconnection between the pistons 17 and 17 f ~ The
opposed ends of the pistons 17 and 17' are spaced slightly from
the driven element 3 with an 0-ring members 25 and 26 iocated betwee-
the piston 17' and the element3. The 0-ring members 25 and 26
are formed of a suitable relatively soft rubber and establish
a resilient contact or engagement of the corresponding piston
with the driven element 3 to establish a significantly quiet
operation as the lever 3 moves to drive the pistons 17 and 17',
~ The driven element 3 is formed as a flat lever extending
downwardly from the pin 23 to the outer portion of the support
plate 7. A leaf spring 27 is riveted or otherwise secured to the
end of the adjacent lever 3 and extends outwardly in a corres-
: ponding plane therefrom. The spring 27 is located between a pair
of clamping blocks 29, one of which is secured to the support
plate~7 and the other of which is releasably forced against
the opposite face of the spring 27 by a suitably clamping screw
30,
The opposite end of the lever 3 projects outwardlyin the opposite direction to the drive means 4. A magnet 31,
shown as a permanent magnet, is integrally formed with, or may
be separately formed and suitably secured to, the outer end of
the lever 3. Magnet 31 extends outwardly from lever 3 with the
_g _
, .
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po3es to the opposite side of the plane through the lever 39
as the result of the polarization thereof.
The magnet 31 is a generally rectangular block-type
permanent magnet 9 with the north pole formed to the right side
of the magnet and the sourth pole to the left side thereof, as
viewed in Figs 1 and 3. The magnet 31 is located within a
generally rectangular magnetic frame 32, the one branch of
which is formed with an opening through which the lever 3
extends. The opposite side legs or portions of ~he frame 32
are provided with coils 33 and 34, respectively, which coils
are connected to the alternating current power supplies 5
and 6.
The frame 32 is secured to the support 7 by suitable
clamping bolts 35 and 36 with the frame encircling the magnet 31
and furthermore with the magnet 31 located generally centrally
of the frame 32. The magnet 31 is provided with pole shoes 37
and 38 along the opposite pole edges adjacent the poles of the
magnet 31. The upper end of the magnet and the poles 37 and
38 are spaced inwardly from the base portion of the frame 32,
~hich, in turn, is provided with an inwardly projecting extensicn
39 terminating in slightly spaced relation to the magnet 31.
The width of the pole 39 generally corresponds to the width of
the magnet 31 such that the pole shoes 37 and 38 project out-
wardly or laterally of the pole 39 The opposite side of the
magnetic frame is provided with the opening through which element
j 3 passes and thus defines a pair of pole arms or ends 40 and 41.
The pole arms 40 and 41 are spaced from each other generally in
accordance with the total width of the magnet 31 and in parti-
cular to loca-te the ends generally in alignment with the outer
face of the pole shoes 37 and 38, as shown in Fig. 1. Further-
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., .
,..... , .
more, the ends are curved as at 42 to extend outwardly and
laterally away from the corresponding pole shoe. The sources
5 and 6 are operated in sychronism, or a single supply is usedg
and in a predeterminèd phase relationship in accordance with the
5 orientation of the coils 33 and 34 to establish oppositely directed
fluxes in the magnetic frame 32. The coils 33 and 34, therefore,
provide a corresponding directional flux within the frame 32 at
the position of the magnet 31.
During one half cycle, the pole 39 will be at a
relative north polarity with respect to the arms 40 and 41,
with a flux as diagrammatically shown by the flux lines 43.
' A repelling force is established between the pole 39 and the
right edge or north pole of the magnet 31. Simultaneiously 9
there is an attractive magnetic force between the pole 39
and the shoe 37 connected to the sourth pole of the magnet 31.
This tends to move the upper or outermost end of the element 31
and lever 3 to the right as viewed in Fig. 1. Simultaneously
the end of arm 40 defines a south magnetic pole which interacts
with the south magnet shoe 37 with a repulsive force thereby
tending to also move the magnet 31 to the right. The shoe 41,
which is also a south pole, attracts the north pole shoe 38
of the magnet 31, thereby establishing a further force moving
the magnet 31 to the right. As a result, the lever 3 will
pivot to the right about the leaf spring 27. When the o~tputs
of the alternating current power supplies 5 and 6 are reversed,
the magnetic field 43 reverses thereby generating an effective
north pole at the end of arms 40 and 41 and a south pole at the
element 39. This will reverse the force interaction with the
magnet 31 causing the magnet 31 to move in the opposite direction
A highly practical alternate construction of the
compressing apparatus is illustrated in Figs, 4-8 which
- 1 1 -
generally employs a multiple body arrangement similar to that
shown in the embodiment of Fig. 3.
Re~erringto Fig~ 4, the illustrated pneumatic compressor
or pump apparatus generally includes a piston unit 44 having a
diaphragm 45 secured to its working face. The outer peripheral
edge of the diaphram 45 is clamped between a valve plate 46 and
an outer clamping ring 47. A mounting plate 48 is clamped in
abutting relationship to the opposite side of valve plate 46.
A plurality of generally U-shaped springs 49 are snapped over
the periphery of the assembled plates 46 and 48 and clamping
ring 47 as in the previous embodiment, A working or compression
chamber 50 is formed between the base of a recess within the
valve plate 46 and the opposed face of the piston 44 and
diaphragm 45. A plurality of circumferentially distributed
valved inlet passageways or openings 51 are formed in the piston
44 for the introducing of air into the chamber 50, where it is
compressed and transferred through valve outlet openings 52
in plate 46 to an output chamber 53 provided with a suitable
output connecting conduit or tap 54, as in the first embodiment.
More particularly in the preferred construction of
Figs. 4-89 the piston 44 is a cylindrical member having a central
~ opening passing therethrough and with the outer end stepped to
; accommodate an incoming coupling shaft 55 which is lbcked thereto as
by a suitable set screw 56. Shaft 55 is connected to any
driving source such as that previously illustrated. The inlet
openings 51 are generally L-shaped and project radially in-
wardly in axially spaced relation to shaft 54 to an annular common
axial opening 57 which is concentric of the shaft axis and
terminates in the working face of the piston 44. A generally
mushroom-shaped valve member 58 is secured within central
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~14~5
opening of piston 44 to selectively open and close the opening
57 and thereby control introduction of air into the chamber 50.
In accordance with present invention, the valve member 58
includes a stem 59 projecting into the central piston opening 60
and terminating in spaced relation to shaft 55, The opening
for stem 59 is formed with a stepped portion defining a stem
opening 60 of a preselected axial length and defining an
inner locking ledge 61. The end of the stem is enlarged to
form a locking head ~a which abutts the ledge 61, The valve
member 58 further includes an integrally formed sealing lid
or disc 62 which is located within the chamber 50 in abutting
relation to the face of the piston 44. Thus, the disc 62 is
a plate like member which extends radially outwardly beyond the
location of the axial annular passageway 57, The outer
periphery of the disc 62 is further provided with a small beaded
surface or projection 63 facing the piston 44 and defining valve
seat, The length of the stem 59 between the clamping enlargement
61 and the inner planar face oE the disc 52 is selected to be
slightly less than the length of the stem opaning 60 such that
the stem 59 is placed under slight tension with head61a engaging
ledge 61 to firmly clamp the flexible disc 62 abutting the face
of the piston 44, The beaded surface 63 is especially formed
to be essentially completely free of imperfections such that,
with a smooth~ planar valve face provided on the piston 44,
a fluid tight engagement can be created ~here between. The bead
63 deflects the outer peripheral edge of the valve disc 62
with respect to the stem 59 and thus provides a resilient
preloading or bias urging the valve to the closed position.
The valve member 58 can be formed of any suitable material and
is advantageously formed of a suitable silicone rubber for
application in pneumatic system.
-13-
~t~ 5
The inner face of the piston 44 is further provided
with an annual clamping recess 64 spaced outwardly of the
periphery of the valve disc 62 to accomodate a corresponding
cylindrical portion or flange 65 of the diaphragm 45~ The
radial wid~h of the recess 64 is significantly larger than the
thickness of the diaphram flange 65 and a wedging or clamping
grommet 66 is forced into the recess to rigidly clamp the
corresponding portion of diaphram 45 to piston 44, The grommet
66 has as a radial flange also abutting and clamping the
adjacent surface of the diaphragm against the face of the
piston 44 to provide a firm and reliable interconnection such
that mo~ement of the piston 44 is imparted to the corresponding
inner periphery of the diaphragm 45.
The diaphragm 45 of the illustrated embodiment of the
invention is a preformed member formed of a suitable resilient
flexible materia~ such as a Buna "N" rubber on a nylon fabric
base. The diaphragm 45 includes an intermedia-tely located
convolution 67 and an outer planar clamping portion. The
convolution 67 is located between the outer edge of the piston
44 and the inner periphery or edge of the mounting ring 47, and
with the convolution opening inwardly of the chamber 50, The
oute-r periphery of the diaphram 45 is clamped between plate
46 and ring 47 which are formed with a small complementing
recess and projection as at 68 to provide a firm fluid tight
connection to the diaphragm. The ring 47 may be formed with an
outer circling lip 68a to properly locate the clamping ring 47
in over lying relationship to the valve plate 46 and insure
a firm clamping of diaphragm 45, The diaphragm 45 and
particularly convolution 67 thereof forms a part of the working
surface of the chamber 50, the opposite wall of which is formed
~ -14-
by a recess in the valve plate 46. The valve plate 46 is
pro~ided with a generally cylindrical chamber forming recess
with the radially oute~ wall spaced outwardly of and con-
centrically of the piston 44 in general alignment with the
inner circumferential edge of the convolution 67, The outer
face of the valve plate 46 is formed with an outwardly projecting
bead 69 essentially aligned with the convolution 67 in the
diaphragm 45. In the assembled relation, the diaphram 45 is
thus clamped in position with the convolution 67 in the
diaphragm 45 and bead 69 in mati~g relationship, with the piston
in an intermediate position of Fig. 5. - .
The portion of the valve plate 46 outwardly of the bead
69 is generally a planar wall to define, with the opposed surface
of the ring 47, a clamping means for the diaphragm, as previously
described.
The valve plate 46 is a generally planar member having
the base portion with the plurality of outlet openings 52
extending axially therethrough and on a diameter generally in
accordance with the diameter of the annular inlet ~assageway
57. The discharge openings 52 terminate in the exterior face,
which forms a part of the output chamber S2, in slight enlarged
recesses 70 located beneath the lid or disc il of a valve
member 72 which is essentially identical to valve member 58
and similarly secured within the valve plate 46. The valve member
72 in paxticular includes a valve stem 73 which passes through a
central opening in the valve plate 46 with a head 74 abutting
the adJacent portion of the valve plate 46 within the compression
chamber 50. The valve member lid 71 also includes the sealing
valve bead 75 abutting the face of valve plate 46, The depth
of the valve plate at the stem corresponds to that of the
opening 60 of the piston 44 within which stem 59 is located and
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is thus slightly longer than the unstressed state of the
stem 73. It thus holds the beaded va lve lid 71 in ov~r-
lying sealing relationship to the discharge openings 52.
Both of the valve members 58 and 7~ are essentially
interchangeable and the lid portions 62 and 75 similarly
function to selectively open and close the respective
passageways for developing a pressure in chamber 53.
The chamber 53 is formed by a recess wit'nin the
outlet or mounting plate 48, the outer portion abutting
the outer face of the valve plate 46 which is provided with
a recess 76 in the abutting portion. The plate 48 further
includes an encircling lip 77 with a slight undercut portion
78 immediately adjacent to the lip to permit firm clamping
interengagment of the plate adjacent to face of plate 46.
The recess forming chamber 53 includes a step
portion immediately adiacent plate 46 within which an 0-ring
seal 79 is compressed to establish a fluid tight joint
readily containing the output pressures.
The mounting plate 48 further includes an outward
extension 82 which may be employed for mounting of the
valve, similar to the illustration of the previous
embodiment.
The operation of the embodiment of Figs. 4-7
essentially corresponds to that of the previous embodiment.
Thus, the reciprocation of the piston 44 results in the
selective expansion and con-traction of the chamber 50,
as a result of the movement of piston 44 and attached
diaphragm 45. The convolution 57 permits significant
increase in the stroke of the piston 44 (Fig..4) without
adversely affecting the diaphragm characteristic and
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~ 6~1 ~ 5
and there~y promotes higher volumetric efficiency while
maintaining proper pressure output. As the piston 44 moves
to the right, the valve disc 62 is closed as a result of
the compressing forces established in the chamber 50. At
a selected position and particularly as the pressure in
chamber 50 rises, the fluid pressure is sufficient to overcome
the resilient ~orce of the diaphragm disc 75 of the outlet
valve member 72. The disc 75 deflects outwardly and ~he com-
pressed fluid then moves through the passages 70 and chamber
52 to output 53. At the end of the stroke, the inle~ valve
disc 62, shown in phantom in Fig. 5, is closely spaced from
or may even slightly engage the head 74 of the ~alve member 72.
Chamber 50 is at a minimum volume and essentially at the output
pressure. The location of the intake valve 5& within the
reciprocating piston 44 further contributes to the efficiency
of the pumping system because, the inertia effects tend to
contribute to a rapid opening of the intake valve disc 62 at
the start of a return stroke. As the piston 44 reverses
direction, the resilient disc 62 as a result of its inertial
20 Jeffect will tend to delay following of the piston and thereby
contribute to the opening of the valve and the introduction
of fresh charge into the chamber 50. This also rapidly
reduces the pressure in chamber 50, with the output pressure
of chamber 55 rapidly moving the exhaust valve disc 72 into
sealing engagement wi.th the valve plate.
The several rigid elements, 44, 46, 47, 48 and 66 of
the apparatus can be readily constructed of a suitable plastic
such as polyphenylene oxide plastics, with all but the piston
unit 44 preferably being fl.berglass fileed to increase the
strength of the unit. The spring member is formed of a
suitably steel strap formed to a generally U-shaped member as
-17-
s
more clearly illustrated in Fig. 8, Such a structure can
be mass produced and as previously noted provide a very small
compact and efficient fluid compressing apparatus. For example 9
the compressor can be constructed as a generally cylindrical
member having an outer diameter of less than 1 inch and of
the order of 3/4 inch, with a total over all length of
approximately 1 1/2 inches.
The present invention thus provides a small, compact
pumping apparatus having a relatively high operating efficiency
-and which is particularly adapted to use as a local compressor
for operating a pneumatic control in a local operating unit,
'
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