Information
-
Patent Grant
-
6200111
-
Patent Number
6,200,111
-
Date Filed
Thursday, January 28, 199925 years ago
-
Date Issued
Tuesday, March 13, 200123 years ago
-
Inventors
-
-
Examiners
- Thorpe; Timothy S.
- Gartenberg; Ehud
Agents
- Brinks Hofer Gilson & Lione
-
CPC
-
US Classifications
Field of Search
US
- 417 515
- 417 286
- 417 297
- 137 6275
- 137 50
- 137 628
- 251 215
- 074 25
- 074 30
- 074 DIG 7
- 074 423
- 474 69
- 123 9044
-
International Classifications
-
Abstract
A controllable positive displacement pump for liquids and gases which may contain dispersed phase particles includes a pair of pistons operating out of phase. Each of the pistons is associated with an inlet valve which includes a fixed grating defining slots which extend parallel to piston travel and a complementarily configured grating which reciprocates transversely in timed relationship with the piston to control the influx of fluid. A rotary outlet valve is also associated with each piston and includes a rotating member disposed transversely across the cylinder head and which rotates in synchronism to open a through, radial port in the member in timed relationship to the piston travel. The positive displacement pump finds particular application to transport powder paint.
Description
BACKGROUND OF THE INVENTION
The invention relates generally to positive displacement pumps for liquids and gases and more specifically to a controllable positive displacement pump having a pair of pistons operating out of phase and specially configured and controllable inlet valves.
Positive displacement pumps for liquids and gases typically include one or more piston and cylinder assemblies and associated inlet and outlet valves which control the flow of pumped fluid into and out of the cylinders. Such pumps are typically capable of relatively high pressure rise operation. A drawback of such positive displacement pumps is that both the inflow and outflow are distinctly pulsatile in character and, especially with high pressure pumps, the flow rates are generally relatively small.
Furthermore, the ability to adjust pressure and flow rates with such pump can be problematic. Typically, of course, flow rates may be adjusted simply by reducing the speed of the pump. However, such a speed reduction to reduce output flow rate is typically accompanied by a reduction in the output pressure as well.
It is apparent from the foregoing that a positive displacement pump which addresses the problems of output pulsation and controllable flow characteristics would represent an improvement over currently available devices.
SUMMARY OF THE INVENTION
The present invention is directed to a controllable, high volume positive displacement pump which provides a flow rate having temporal fluctuations which are a smaller fraction of the time mean value than those of conventional positive displacement pumps, is characterized as a higher flow rate, smaller pressure rise device in comparison to conventional positive displacement pumps and readily permits independent control of the intake and exhaust valve phasing and cycle times.
A controllable positive displacement pump for liquids and gases which may contain dispersed phase particles includes a pair of pistons operating out of phase which provide pumped fluid to a common output. Each of the pistons is associated with an inlet valve which includes a fixed grating defining slots which extend parallel to piston travel and a complementarily configured grating which reciprocates transversely in timed relationship with the piston to control the influx of fluid. A rotary outlet valve is also associated with each piston and includes a rotating member disposed transversely across the cylinder head which rotates in synchronism to open a through, radial port in the member in timed relationship to the piston travel. The phase relationship between the operation of the inlet and outlet valves and the respective pistons may be adjusted by using either independent drive mechanisms to these components or incorporating mechanical phase adjusting devices in the unitary drive mechanism. The positive displacement pump finds particular application to transport powder paint and in heating, ventilating and air conditioning (HVAC) apparatus.
Thus it is an object of the present invention to provide a controllable, positive displacement pump.
It is a further object of the present invention to provide a controllable, positive displacement pump suitable for applications such as transport of powder paint and in HVAC apparatus.
It is a still further object of the present invention to provide a controllable, positive displacement pump wherein inlet and outlet valves operate in synchronism with reciprocating pistons.
It is a still further object of the present invention to provide a controllable, positive displacement pump wherein the phase relationships of the inlet and outlet valves may be adjusted relative to the reciprocating pistons.
Further objects and advantages of the present invention will become apparent by reference to the following description of the preferred and alternate embodiments and appended drawings wherein like reference numbers refer to the same component, element or feature.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a side, elevational view in full section of a controllable positive displacement pump according to the present invention;
FIG. 2
is a full, sectional view of one of the piston and cylinder assemblies of a controllable positive displacement pump according to the present invention take along line
2
—
2
of
FIG. 1
;
FIG. 3
is an end, elevational view with portions broken away of a controllable positive displacement pump according to the present invention;
FIG. 4
is a top, plan view of a controllable positive displacement pump according to the present invention;
FIG. 5
is a fragmentary, sectional view of an inlet valve of a controllable positive displacement pump according to the present invention taken along line
5
—
5
of
FIG. 4
;
FIG. 6
is a fragmentary, sectional view of a first alternate embodiment piston and inlet valve configuration according to the present invention;
FIG. 7
is a fragmentary, sectional view of the first alternate embodiment piston and inlet valve configuration according to the present invention taken along
7
—
7
of
FIG. 6
;
FIG. 8
is an end, elevational view with portions broken away of a second alternate embodiment controllable positive displacement pump according to the present invention having independent phase adjustable drives for the pistons and valves;
FIG. 9
is a timing diagram for the upper piston and cylinder assembly of a controllable positive displacement pump according to the present invention at maximum flow rate;
FIG. 10
is a graph presenting the position of the upper inlet valve sliding plate of a controllable positive displacement pump according to the present invention as a function of the crank angle for a maximum flow rate condition;
FIG. 11
is a graph presenting the crank angle position versus time over one operating cycle of a controllable positive displacement pump according to the present invention; and
FIG. 12
is a graph presenting an asymmetric driving condition of a controllable positive displacement pump according to the present invention.
DESCRIPTION OF THE PREFERRED AND ALTERNATE EMBODIMENTS
Referring now
FIGS. 1 and 2
, a controllable, high volume, positive displacement pump according to the present invention is illustrated and generally designated by the reference number
10
. The positive displacement pump
10
includes a housing
12
which is preferably cast metal and includes various apertures, surfaces and ports which cooperate with other features of the invention. Specifically, the positive displacement pump
10
includes an upper or first piston and cylinder assembly
14
A and a lower or second piston and cylinder assembly
14
B. The upper piston and cylinder assembly
14
A and the lower piston and cylinder assembly
14
B are substantially identical and the upper piston and cylinder assembly
14
A includes a first preferably rectangular piston
16
A disposed within a complementary first rectangular cylinder
18
A defined by a first rectangular cylinder wall
20
A. The piston
16
A includes a first pair of devises
22
A which receive a respective first pair of connecting rods
24
A which are pinned to the devises by a respective first pair of retaining pins
26
A. The first pair of connecting rods
24
A are in turn pivotally received on a first pair of respective cranks
32
A of an first crankshaft
34
A. The first crankshaft
34
A is supported for a rotation in a plurality of first bearings
36
A which may define either standard journal bearings or anti-friction devices such as ball bearing assemblies (not illustrated). Secured generally centrally to the crankshaft
34
A is a first driven pinion gear
38
A which is in constant mesh with a drive pinion gear
42
. The drive pinion gear
42
is secured to a transverse drive shaft
44
and driven by a prime mover such as a variable speed electric motor
46
.
The lower or second piston and cylinder assembly
14
B is in all mechanical respects the same as the upper piston and cylinder assembly
14
A except that it operates 180° out of phase with the first or upper piston and cylinder assembly
14
A. Thus, it includes a second piston
16
B, a second cylinder
18
B, a second cylinder wall
20
B, second pairs of devises
22
B, a second pair of connecting rods
24
B, a second pair of retaining pins
26
B, a second pair of cranks
32
B, a second crankshaft
34
B, second bearings and a second driven pinion gear
38
B. It will be appreciated that the first cranks
32
A and the second cranks
32
B are arranged 180° out of phase from one another as illustrated in FIG.
1
.
Turning now to
FIGS. 1
,
3
,
4
and
5
, each of the first and second piston and cylinder assemblies
14
A and
14
B includes a respective inlet valve assembly
50
A and
50
B. The upper or first inlet valve assembly
50
A is disposed adjacent the upper cylinder wall
20
A of the first or upper piston and cylinder assembly
14
A and the second or lower inlet valve assembly
50
B is disposed adjacent the lower cylinder wall
20
B of the second or lower piston and cylinder assembly
14
B. The inlet valve assemblies
50
A and
50
B, but for their locations, are mechanically identical with the exception that once again, they operate 180° out of phase from one another. Hence, only the first or upper inlet valve assembly
50
A will be described, it being understood that the same description applies to the second or lower inlet valve assembly
50
B.
Formed in the upper portion of the cylinder wall
20
A are a plurality of longitudinally extending slots
52
defined by longitudinally extending bars
54
. Received within the slots
52
defined by the bars
54
are complementarily configured rectangular teeth or projections
56
which form and define the upper edge of the piston
16
A. Transversely, slidingly disposed immediately above and adjacent the grating defined by the bars
54
is a complementarily configured valve plate
58
having a plurality of longitudinally extending slots
62
having generally trapezoidal cross sections which are defined by a complementarily configured arrangement of trapezoidally shaped bars
64
. The adjacent, facing surfaces of the bars
54
and
64
as well as the edges of the teeth
56
of the piston
16
A are preferably uniformly polished or finished such that they slide smoothly against one another in intimate contact to provide a suitable fluid tight seal. The valve plate
58
is slidingly retained upon the top of the piston and cylinder assembly
14
A by a pair of parallel, right angle (L-shaped) guides
72
having overhanging lips
74
.
The inlet valve assembly
50
A and specifically the valve plate
58
is reciprocated in proper timed relationship with the motion of the first piston
16
A by a cam
76
and a follower
78
and is open when the first piston
16
A is on its intake stroke and is closed when the first piston
16
A is on its compression stroke.
Each of the guides
72
includes a closed end portion
82
which receives a compression spring
84
which biases the valve plate
58
A and provides restoring force to return it to the left is illustrated in
FIG. 3
to achieve proper reciprocation of the plate
58
as will readily be appreciated. The cam
76
is coupled to a drive shaft
86
to which a bevel gear
88
is secured. The bevel gear
88
, in turn, is driven by a matching bevel gear
92
. As shown in
FIGS. 2 and 3
, the bevel gear
92
is coupled to a driven pinion
94
and, through a timing belt or chain
96
, to a drive pinion
98
secured to the drive shaft
44
. The drive ratio from the drive shaft
44
, through the timing belt
96
and through the bevel gears
88
and
92
is 1:1 and thus the cams
76
and the valve plates
58
A and
58
B operate in synchronism with the motion of the pistons
16
A and
16
B.
Returning now to
FIGS. 1 and 2
, each of the piston and cylinder assemblies
14
A and
14
B also includes respective rotary outlet valve assemblies
100
A and
100
B. The upper or first rotary valve assembly
100
A and lower or second rotary valve assembly
100
B are mechanically identical and again, the only difference being operational in that they typically operate 180° out of phase from one another, in synchronism with the motion of the associated respective pistons
16
A and
16
B. Accordingly, only the first or upper outlet valve assembly
100
A will be described. In the headwall of the cylinder wall
20
A is a slot
102
A defined by the housing
12
which preferably extends substantially the full width of the piston
16
A and the cylinder
18
A. The slot
102
A opens into a passageway
104
A communicating with a rotary valve body
106
A. Disposed across the full width of the slot
102
A and between the slot
102
A and the passageway
104
A is a rotary valve body
106
A having a through radial passageway
108
A defining a height substantially equal to the height of the slot
102
A and the passageway
104
A. The remaining material in the valve body
106
A adjacent the passageway
108
A when rotated 90° is sufficiently wide to fully close off the passageway
104
A from the cylinder
18
A and the slot
102
A. The rotary valve body
106
A is coupled to a drive pinion
112
A which is driven through a timing belt
114
from a pinion
116
secured to the crankshaft
34
B. It will be noted that the driven pinion
112
A has a diameter twice as large as the drive pinion
116
and this configuration effects a 2:1 speed reduction such that the rotary valve body
106
A rotates one revolution for every two revolutions of the crankshaft
34
A. Flow through a slot
102
B and through a passageway
108
B in the rotary valve body
106
B is similarly controlled. As illustrated in
FIG. 1
, the passageway
104
A merges with a similar passageway
104
B from the second or lower piston and cylinder assembly
14
B and thus fluid flow from the cylinders
18
A and
18
B merge in a common outlet passageway
122
.
Turning now to
FIGS. 6 and 7
, a first alternate embodiment inlet valve assembly
130
which relates to the interface and seal between the pistons
16
A and
16
B and their respective inlet valve assemblies
50
A and
50
B is illustrated. The first alternate embodiment inlet valve assembly
130
includes an alternate embodiment housing
12
′ having a plurality of longitudinal slots
132
defined by a plurality of parallel, longitudinal bars
134
. The bars
134
are preferably integrally formed with the housing
12
′ when it is fabricated, for example, by casting. The slots
132
provide fluid communication between the ambient and a cylinder
136
defined by the housing
12
′. Disposed within the cylinder
136
is a reciprocating piston
138
. It will be appreciated that but for the differences about to be described, the piston
138
is the same as the first and second pistons
16
A and
16
B, respectively, described above with regard to the preferred embodiment positive displacement pump
10
. The piston
138
includes a transversely slidable plate
142
having at least a pair of elongate slots
144
through which a respective pair of shoulder bolts
146
are disposed. The shoulder bolts
146
mount into suitably configured blind apertures
148
in the piston
138
and retain and slidably position the plate
142
upon the face of the piston
138
. The plate
142
includes a plurality of rectangular teeth or projections
152
which are received within complementarily configured elongate slots
154
in a valve plate
156
.
The valve plate
156
is transversely reciprocated through the agency of a cam and follower assembly
158
which is similar in all respects to the cam
76
and follower
78
of the preferred embodiment pump
10
. As the piston
138
reciprocates within the cylinder
136
, the alternate embodiment inlet valve assembly
130
alternately allows ingress of pumped fluid and compression thereof by opening and closing in synchronism with the piston
138
by first placing the slots
132
and
154
in alignment as illustrated in FIG.
6
and then closing off the slots
132
with the bars of the valve plate
156
as it reciprocates. The plate
142
thus provides an appropriate seal while accommodating the interfacial motion of the reciprocating piston
138
along its axis and the transversely oriented reciprocating motion of the valve plate
156
.
Referring now to
FIG. 8
, a second alternate embodiment of a controllable positive displacement pump
10
′ is illustrated. The positive displacement pump
10
′ is identical to the preferred embodiment positive displacement pump
10
in all respects with regard to the mechanical configuration of the piston and cylinder assemblies
14
A and
14
B, the inlet valve assemblies
50
A and
50
B and the rotary outlet valve assemblies
100
A and
100
B. The second alternate embodiment pump assembly
10
′ differs from the preferred embodiment pump
10
in the drive mechanisms for the components and more particularly to the capability of the drive mechanisms to adjust the phasing therebetween. Accordingly, the second alternate embodiment pump
10
′ includes the drive motor
46
which directly drives the shaft
44
, the drive pinion gear
42
and the driven pinion gears
38
A and
38
B. Attached to the drive shaft
42
is a tone wheel
172
having one or more teeth
174
which are configured to permit angular or phase resolution of the position of the shaft
42
and thus of the pistons
16
A and
16
B. A sensor such as a Hall effect or variable reluctance sensor
176
is disposed in sensing relationship with the tone wheel
172
and provides a signal through a line
178
to a controller
180
.
Driving and operating completely independently of the drive motor
46
is a valve drive assembly
190
. The valve drive assembly
190
includes a variable speed electric drive motor
192
providing energy to a drive shaft
194
and a tone wheel
196
having a single or multiple set of teeth
198
from which the position or phase of the shaft
194
may be deduced. A sensor
202
such as a Hall effect variable reluctance sensor provides a signal through a line
204
to the controller
180
. Given the signals from the two phase sensor wheels
176
and
202
, the controller
180
, when provided with operating programs and criteria, is capable of providing independent electrical power through the conductors
206
to the motor
46
and through the conductors
208
to the motor
192
thereby adjusting the speed and phase of the variable speed electric drive motors
46
and
192
to adjust the relative phase relationship between the pistons
16
A and
16
B and the inlet valve assemblies
50
A and
50
B and the outlet valve assemblies
100
A and
100
B.
Affixed to the shaft
198
is a belt drive pinion
212
which drives a timing belt or chain
214
which engages drive pinions
216
A and
216
B which are coupled to the rotary valve bodies
106
A and
106
B and rotate them together.
The drive shaft
194
terminates in a first bevel gear
222
which mates with the second bevel gear
88
secured to the shaft
86
. The shaft
86
is terminated by the pair of cams
76
which cooperate with the cam followers
78
to reciprocably drive the valve plates
58
A and
58
B of the respective inlet valve assemblies
50
A and
50
B. It will thus be appreciated that the independent electric drives to, first of all, the piston and cylinder assemblies
14
A and
14
B and, second of all, the inlet valve assemblies
50
A and
50
B and the outlet valve assemblies
100
A and
100
B allow phase independent operation of these components to improve and adjust the operating characteristics of the positive displacement pump
10
′.
Such independent control may be further expanded such that the pistons
16
A and
16
B, the inlet valve assemblies
50
A and
50
B and the outlet valve assemblies
100
A and
100
B are all independently driven and thus their speed, and more importantly their phase, relative to the other components may be independently adjusted. This additional capability requires the addition of a third electric drive motor and appropriate sensor and modification to the controller
180
of the second alternate embodiment positive displacement pump
10
′ described directly above to accept a third sensor and provide a third output to the third drive motor. So configured, the drive motor
46
drives the pistons
16
A and
16
B, the drive motor
192
drives the inlet valve assemblies
50
A and
50
B and the third drive motor drives the rotary outlet valve assemblies
100
A and
100
B. As noted, the additional tone wheel and sensor is utilized to provide speed and phase information to the controller as will be readily appreciated. So configured, independent speed and phase control of the pistons
16
A and
16
B, the inlet valve assemblies
50
A and
50
B and the rotary outlet valve assemblies
100
A and
100
B may be achieved.
As shown in
FIG. 1
, a positive displacement pump
10
according to the present invention will include an pper piston and cylinder assembly
14
A and a lower piston and cylinder assembly
14
B whose pistons
16
A and
16
B operate 180° out of phase. The two passageways
104
A and
104
B deliver fluid to a common outlet
122
. This means that the outflow may be characterized as a d.c. level with a superimposed fluctuation that can be described as (for the first cycle)
where T is the reciprocal of the driving frequency (f
d
) and
ω=f
d
/2π. (2)
Turning then to the operation of the pump and
FIGS. 9
,
10
,
11
and
12
, as suggested by equation (1), the upper passageway
104
A will deliver the fluid to be pumped for the time period nT≦t≦(2n+1)T/2 and the lower passageway
104
B will deliver fluid during the period (2n+1)T/2≦t≦(n+1)T. This delivery is powered by the forward advance of the respective pistons
16
A and
16
B and it is controlled by the angular position (φ) of the rotary outlet valves
106
A and
106
B illustrated in FIG.
1
.
FIG. 9
shows the timing diagram for the rotary outlet valve
106
A for the upper piston and cylinder assembly
14
A and for the conditions of maximum flow rate. The timing diagram for the lower piston and cylinder assembly
14
B is identical to that of
FIG. 9
except it is shifted by 180°. This diagram is presented for the rotary position of φ
1
of the upper rotary outlet valve
106
A as a function of the crank angle θ
1
(t) of the crankshaft
34
A. It is assumed, for the present discussion, that θ
1
(t) is the linear function:
θ
1
(t)=ωt (3)
and that ω=constant. This restriction is modified in a subsequent section in order to gain enhanced performance of the pump
10
in HVAC heat exchanger applications.
FIG. 11
presents the crank angle position versus time of one rotation of the crankshaft showing a non-linear relationship therebetween.
The second element of the controlled flow rate condition of the pump
10
is that of the sliding plates
58
A and
58
B with respect to the fixed bars
54
.
FIGS. 4 and 5
show the top and end views of the sliding inlet valve assemblies
50
A and
50
B. The symbol ξ
B
refers to the lateral position of the sliding plate
58
A. The upper passageways are closed for ξ
B
=0; they are fully open for ξ
B
=−W
A
.
FIG. 10
shows the inlet valve plates
58
A and
58
B plate positions: [ξ
B
(t)], for the maximum flow rate condition. Once again, the independent variable is considered to be θ
1
(t) for the present discussion.
The magnitude of the volume flow rate will be linearly proportional to ω given the condition that the channel is fully filled from the surrounding plenum P on each stroke. (The filling stroke for the upper piston
16
A is π≦θ≦2π as shown in
FIGS. 9 and 10
.) Given the inertia of the elements involved, the change in flow rate that results from a change in the rotational speed (ω) of the crankshaft
34
A is considered to represent a “slow” change of the operating condition.
If the sliding inlet valve plates
58
A and
58
B (ξ
B
, ε
C
) and the outlet valves
106
A and
106
B (φ
1
, φ
2
) are used to control the flow, then the delivered mass can be adjusted on a time scale of one-half cycle. That is, for ω=constant, φ
1
can be held at φ
1
=π/2 (i.e., the rotary outlet valve
106
A is closed) and ε
B
=−W
A
(i.e., the inlet valve plate
58
A is open) for a period that is longer than that shown in
FIGS. 9 and 10
. For example,
φ
1
=π/2 for 0≦θ<30 degrees,
and
φ
1
→0 at θ=30 degrees
and
φ
1
=π/2 at θ=150 degrees
while
ε
B
=−W
A
for 0≦θ<30 degrees,
and
−ε
B
→0 at θ=30 degrees
and
ε
B
→−W
A
at θ=150 degrees
Hence, the time period for which material is delivered from the upper passageway
104
A is reduced (in terms of the crank angle) from nominally 0→180 degrees to nominally 30→150 degrees. The ingestion portion of the cycle: 180→360 degrees, is unchanged from that of the maximum flow rate condition. However, in the θ→30 degrees and the θ: 150→180 degree segments, the ingested fluid and/or material will be expelled from the channel and returned to the supply plenum P.
If a multiphase, i.e., fluid and particulate, mixture is to be pumped, and if it would be useful to stir the material in the plenum P in order to enhance the uniformity of the discharge mixture, then the fractional operation noted above will provide an added benefit to that of the pumping action. Specifically, as noted above, the ingested material in the 0→30 degree and the 150→180 degree segments participates in a stirring action within the plenum P.
By adjusting the fractional valve openings and the rotational speed (ω), an optimal combination of stirring and net flow rate can be achieved.
For a given angular speed (dθ/dt=ω) of the crankshaft
34
A, the pressure: P
face
(t) on the forward face of the piston
16
A will have a characteristic signature for an air-only operation and a given air density. (The non-dimensional representation: {[P
face
−P
atm
]/ρV
p
2
} would be expected to be relatively independent from ρ and V
p
.) The presence of a dispersed phase, i.e., the powder paint, will require the pressure at the face of the piston
16
A to be larger than the air-only case. This is shown in terms of the control volume momentum equation (for a control volume that is bounded by the interior faces of the sliding valve plate
58
A, the lower surface of the cylinder wall
20
A, the face of the piston
16
A and the centerplane of the control valve: “c”).
where the x (streamwise) component of {right arrow over (F)} is given as
and τ
W
is the wall shear stress acting on the fluid. The latter term in (5) is expected to be small with respect to the first term (RHS) and it is expected to be negligibly influenced by the presence of the particulate matter.
Since the density of the powder is nominally 10
3
times that of the continuous phase-air, a modest volume concentration (≈1 percent) will cause a readily measured increase in p
face
for a given rotational speed of the crankshaft
34
A. Also, as noted above, it can be expected that p
face
=f(C
p
) where C
p
is the concentration of the particles.
Industrial Application—Powder Paint
The suggested operating protocol for the controllable positive displacement pumps
10
and
10
′ in a powder paint application is to:
i) open the sliding plate
58
A, and
ii) open the rotary outlet valve assembly
100
A at the beginning of the stroke of the piston
16
A: θ≈0, and monitor P
face
(t) at the beginning of the delivery stroke. Given a proper calibration environment and recorded data, one can infer the volume concentration from the measured p
face
over, e.g., the first 20 degrees of motion of the crankshaft
34
A. Given this information, control circuitry can then coordinate—for θ>20 degrees—the combined: a) closing of the rotary outlet valve
100
A and b) opening the sliding plate
58
A which will cause the previously ingested “charge” to be returned to the inlet plenum P. (The stirring effect will also clearly benefit the mixture homogeneity in the plenum P as noted above.)
The above described operational protocol addresses the two principal needs of the powder paint delivery hardware: i) to identify, and ii) to control the mass of the particulate material that is to be delivered to the applicator. The use of the upper/lower piston and cylinder configuration of
FIG. 1
will result in a relatively continuous discharge of powder.
Industrial Application—HVAC Systems
Another application for the controllable positive displacement pump
10
is that of air delivery to the heating/cooling coils of an HVAC system. Of concern for such a system is the upstream propagation of flow noise. In particular, the parallel shear layers that are formed from the fixed inlet valves
50
A and
50
B are likely sources of acoustic noise.
This concern suggests that the forward (pressurizing) stroke of the pistons
16
A and
16
B be executed relatively faster than the filling (return) stroke. Various mechanical linkages which can execute such drive patterns exist.
FIG. 12
presents a representative V
p
(t) pattern than would meet the desired objectives. (V
p
=velocity magnitude of the piston).
A concomitant advantage of this V
p
(t) pattern is that the velocity of air through the heating/cooling coils will be larger than would be the velocity in a symmetric-drive pattern. Specifically, the larger the velocity, the greater will be the momentary heat transfer and the greater will be the time averaged heat transfer for a given area of heat exchanger. This benefit is in addition to the intrinsic benefit of the positive displacement pump
10
according to the present invention for such heat transfer applications. Specifically, by creating twice the cycle average velocity over one-half of the heat exchanger for one-half of the cycle time, and repeating this behavior for the other one-half of the heat exchanger for one-half of the cycle time, a greater heat transfer will be obtained as enhanced heat transfer will derive from both the larger temperature differences and the larger convection heat transfer properties of the higher speed flow.
The foregoing disclosure is the best mode devised by the inventor for practicing this invention. It is apparent, however, that methods incorporating modifications and variations will be obvious to one skilled in the art of positive displacement pumps. Inasmuch as the foregoing disclosure presents the best mode contemplated by the inventor for carrying out the invention and is intended to enable any person skilled in the pertinent art to practice this invention, it should not be construed to be limited thereby but should be construed to include such aforementioned obvious variations and be limited only by the spirit and scope of the following claims.
Claims
- 1. A controllable, positive displacement pump comprising, in combination,a drive motor, a pair of cylinders each having a sidewall and a head, a pair of pistons received in a respective one of said pair of cylinders, a crankshaft driven by said drive motor and having a respective pair of cranks for driving said pair of pistons, a pair of reciprocating inlet valves defining a pair of adjacent gratings disposed adjacent a respective one of said pair of cylinder sidewalls, and a pair of rotary outlet valves disposed adjacent a respective one of said pair of cylinder heads.
- 2. The controllable positive displacement pump of claim 1 wherein said pair of cranks are disposed in diametric opposition.
- 3. The controllable positive displacement pump of claim 1 wherein said drive motor is operably coupled to said reciprocating inlet valves and said rotary outlet valves and drives said crankshaft and said valves in synchronism.
- 4. The controllable positive displacement pump of claim 1 further including a second drive motor for driving said reciprocating inlet valves and said rotary outlet valves.
- 5. The controllable positive displacement pump of claim 4 further including tone wheels associated said crankshaft and said rotary outlet valves, sensors associated with said tone wheels and a controller for driving said drive motor and said second drive motor, said controller adapted to adjust the phase of said crankshaft and said rotary outlet valves.
- 6. The controllable positive displacement pump of claim 1 further including a second drive motor for reciprocating said inlet valves and a third drive motor for rotating said outlet valves.
- 7. The controllable positive displacement pump of claim 1 wherein said pair of adjacent gratings include elongate openings and wherein one of said gratings reciprocates transversely to said elongate openings.
- 8. The controllable positive displacement pump of claim 7 wherein at least one of said gratings define trapezoidal cross sections.
- 9. The controllable positive displacement pump of claim 1 further including a at least one drive belt pinion and at least one driven belt pinion associated with said drive motor and said rotary valves and at least one timing belt received on said belt pinions.
- 10. The controllable positive displacement pump of claim 1 further including a bevel gear drive having an input driven by said drive motor and an output driving at least one cam associated with said reciprocating inlet valves.
- 11. A controllable, positive displacement pump comprising, in combination,a drive motor, a pair of cylinders each having a sidewall and an end, a piston received in each of said pair of cylinders, a crankshaft driven by said drive motor and having a pair of cranks for driving a respective one of said pair of pistons, an inlet valve having a reciprocating grating associated with each of said pair of cylinder sidewalls, and a rotary outlet valve disposed adjacent each of said pair of cylinder heads.
- 12. The controllable positive displacement pump of claim 11 wherein said drive motor is operably coupled to said inlet valves and said rotary outlet valves and drives said crankshaft and said valves in synchronism.
- 13. The controllable positive displacement pump of claim 11 further including a second drive motor for driving said inlet valves and said rotary outlet valves.
- 14. The controllable positive displacement pump of claim 13 further including tone wheels associated said crankshaft and said rotary outlet valve, sensors associated with said tone wheels and a controller for driving said drive motor and said second drive motor, said controller adapted to adjust the phase of said crankshaft and said rotary outlet valves.
- 15. The controllable positive displacement pump of claim 11 further including a second drive motor for reciprocating said inlet valves and a third drive motor for rotating said outlet valves.
- 16. A controllable, positive displacement pump, comprising, in combination,a housing defining a pair of cylinders having sidewalls and ends, a piston received in each of said cylinders, a crankshaft defining a pair of diametrically opposed cranks, one of said cranks operably coupled to a respective one of said pistons, a reciprocating inlet valve having a pair of gratings disposed adjacent said cylinder sidewall and said cylinder and, a rotary outlet valve associated with each of said cylinders and disposed adjacent said cylinder end, and a drive assembly for providing energy to said crankshaft and said reciprocating inlet valves and said rotary outlet valves.
- 17. The controllable, positive displacement pump of claim 16 wherein said housing further defines a pair of plenums.
- 18. The controllable, positive displacement pump of claim 16 wherein said drive assembly includes a first drive motor for driving said crankshaft, a second drive motor for driving said reciprocating inlet valves and said rotary outlet valves, tone wheels associated with said first drive motor and said second drive motor, sensors associated with said tone wheels and a controller for driving said first drive motor and said second drive motor, said controller adapted to adjust the phase of said first drive motor and said second drive motor.
- 19. The controllable, positive displacement pump of claim 16 wherein said pair of adjacent gratings include elongate openings and wherein one of said gratings reciprocates transversely to said elongate openings.
- 20. The controllable, positive displacement pump of claim 16 wherein said drive assembly includes a drive motor driving said crankshaft and said valves in synchronism.
US Referenced Citations (6)