U.S. patent number 3,831,845 [Application Number 05/389,244] was granted by the patent office on 1974-08-27 for fluid delivery system.
This patent grant is currently assigned to Partek Corporation of Houston. Invention is credited to Amos Pacht.
United States Patent |
3,831,845 |
Pacht |
August 27, 1974 |
FLUID DELIVERY SYSTEM
Abstract
A high pressure fluid delivery system is disclosed in which two
or more guns, each having a high pressure nozzle outlet and a low
pressure dump outlet, may be connected to and operated from the
same pump. Pressure responsive control apparatus is provided in the
flow line between each gun and the pump and each such apparatus
includes a valve responsive to the fluid pressure at its respective
gun for directing fluid either directly to such gun when flow is
through the gun nozzle, or through an opening through the valve
substantially the same size as the nozzle orifice of such gun when
the gun is dumping.
Inventors: |
Pacht; Amos (Houston, TX) |
Assignee: |
Partek Corporation of Houston
(Houston, TX)
|
Family
ID: |
23537441 |
Appl.
No.: |
05/389,244 |
Filed: |
August 17, 1973 |
Current U.S.
Class: |
239/76; 137/110;
137/513.3; 137/877; 239/444 |
Current CPC
Class: |
B60S
3/00 (20130101); B08B 3/026 (20130101); B05B
9/0423 (20130101); B08B 2203/0217 (20130101); Y10T
137/87829 (20150401); Y10T 137/2562 (20150401); Y10T
137/7847 (20150401) |
Current International
Class: |
B60S
3/00 (20060101); B05B 9/04 (20060101); B08B
3/02 (20060101); F16k 021/00 () |
Field of
Search: |
;239/76,443-447,411
;137/110,513.3,612.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: King; Lloyd L.
Assistant Examiner: Kashnikow; Andres
Attorney, Agent or Firm: Hubbard, Thurman, Turner &
Tucker
Claims
The invention having been described, what is claimed is:
1. In a fluid system for supplying a high pressure stream of fluid,
including a pump having a low pressure inlet adapted to be
connected to a source of fluid and a high pressure outlet, and at
least one nozzle gun having an inlet, a high pressure discharge
nozzle, a relatively low pressure dump outlet, and actuating means
for diverting flow between said nozzle and said dump outlet, the
improvement in said system comprising at least one fluid pressure
control apparatus having an inlet adapted to be connected to the
outlet of said pump, an outlet adapted to be connected to the inlet
of one of said guns, a flow passageway connected between its inlet
and outlet, a valve means in said flow passageway responsive to the
fluid pressure at said outlet to move between a first position
permitting flow through said passageway when the gun connected
thereto is actuated to discharge fluid through its nozzle, and to a
second position wherein a restriction to flow through said
passageway is provided when said gun is dumping, said restriction
to flow having substantially the same effect on flow as the
restriction to flow provided by the nozzle opening of the gun
connected to the outlet of said control means.
2. The system of claim 1 wherein said valve means includes a valve
seat member and a valve stem member for seating a said valve seat
member to close said flow passageway in said second position, and
said valve stem member includes an orifice therein for providing
said restriction to flow and to by pass said valve means when the
valve stem member is seated on said valve stem.
3. The system of claim 1 wherein said valve means includes a valve
seat member and a valve stem member, and further including
resilient means for urging said valve stem member to be seated on
said seat member, and stop means for stopping said valve stem
member in the direction of movement towards said valve seat member
before seating thereon to provide said flow restriction with said
valve stem member in said second position.
4. The system of claim 3 further including adjusting means for
adjusting the opening between said value stem member and said seat
member when said value stem member is in said second position.
5. The system of claim 1 wherein a plurality of nozzle guns are
connected to said pump and wherein one of said fluid pressure
control apparatus is connected between each such gun and said
pump.
6. The system of claim 1 wherein said valve means includes a valve
seat member mounted in said flow passageway and an elongated valve
stem mounted in said apparatus to extend into said flow passageway
for movement between said first position wherein said valve means
is open to said second position wherein said valve stem is seated
on said valve seat; an orifice in said valve stem adapted to by
pass said valve means for fluid flow to provide said restriction to
flow when said valve stem is in said second position, and resilient
means urging said valve stem into said second position except when
the fluid pressure at said outlet exceeds a preselected value.
7. The system of claim 1 wherein said valve means includes a valve
seat member and a valve stem member, and further including
resilient means for urging said valve stem member towards being
seated on said seat member, and means for providing a change in the
resilient force urging said valve stem member.
8. The system of claim 1 further including means for breaking up
the flow of fluid from said pressure control apparatus.
9. The system of claim 8 wherein said last mentioned means is a
disk inserted in to the outlet of said control apparatus said disk
having a plurality of flow ports therein.
10. Pressure control apparatus for connection in a high pressure
fluid delivery system between a pump and a gun assembly having a
high pressure nozzle outlet and a dump outlet, for maintaining a
substantially constant load on the pump, said apparatus comprising,
in combination: a housing having an inlet adapted to be connected
to the outlet of such a pump, an outlet adapted to be connected to
such a gun, and a flow passageway connected between said inlet and
said outlet; valve means in said passageway for permitting or
interrupting flow of fluid from said inlet through said passageway
to said outlet, said valve means including means for providing a
restriction to fluid flow substantially the same size as the nozzle
on said gun, said valve means being responsive to fluid pressure at
the outlet of said apparatus to be open to flow when the fluid
pressure at said outlet is relatively high; and means for causing
said valve means to interrupt flow through said main passageway
when the fluid pressure at said outlet is relatively low and divert
such flow through said means for providing a restriction to fluid
flow.
11. The apparatus of claim 10 wherein said means for providing said
restriction to fluid flow is an orifice in said valve means through
which fluid can by pass said valve means when closed.
12. The apparatus of claim 10 wherein said valve means further
includes stop means for preventing full closure of said valve means
to provide said means for providing said restriction to fluid
flow.
13. The apparatus of claim 12 further including adjusting means for
adjusting the minimum opening through said valve means.
Description
This invention relates to a high pressure fluid delivery system and
in one of its aspects to pressure control apparatus for providing
substantially constant pressures from a pump delivery fluid to the
system.
In the prior art, fluid systems are provided in which a high
pressure stream of water, i.e., at pressures of 6,000 - 10,000
pounds or more, are used for many cleaning applications. In these
systems one or more hand-held valve assemblies or guns are
provided, and are connected by a hose to a common outlet of a pump.
The guns generally include a housing having a valve therein, a
barrel extension for directing the high pressure stream of water
through a nozzle to the object to be cleaned, a handle or trigger
mechanism for operating the valve, and a relatively unrestricted
pressure relief or "dump" outlet for relieving pressure in the
assembly when flow through the high pressure nozzle outlet is
interrupted by operation of the valve. When the gun is dumping
water, pressures are generally no more than a few hundred pounds,
and a sudden reduction on the load or the pump occurs.
Because of the wide differential between water pressures when water
is dumped and when it is being discharged through the gun nozzle,
apparatus have been suggested for automatically decreasing the pump
engine speed during dumping, such as shown in U.S. Pat. No.
3,335,962. However, where two or more nozzle guns are employed in
random operation, such apparatus is generally not practical. When
two or more guns are used from a single source, it is highly
desirable that a constant inlet pressure to the guns be provided
independent of the operation of the guns. In U.S. Pat. No.
3,375,980, a system is provided where when a nozzle gun is not
discharging high pressure fluid, the fluid is passed through an
orifice that was substantially the same size as the gun's nozzle
orifice. Thus, whether a gun is discharging through its nozzle or
not, a substantially constant pressure is provided by the pump.
However, this system requires the use of a separate source of
compressed air, a diaphragm valve assembly for each gun for
switching between the gun and the added orifice, pneumatic control
means on each gun for operating the diaphragm valve, and a
considerable amount of additional piping. The addition of the
additional pneumatic system thus represents a substantial added
expense, a source of frequent maintenance and leakage problems, and
generally unduly complicates the fluid delivery system. Also, the
guns employed are of special design and are not "dump" guns which
are readily available and generally preferred since the operator is
always assured that the high pressure is being relieved.
In co-pending U.S. Pat. application Ser. No. 297,216, filed Oct.
13, 1972, now U.S. Pat. No. 3,765,607 and assigned to the assignee
of this application, a fluid delivery system is disclosed which
solves substantially all of the problems enumerated with respect to
the prior art by providing a control apparatus connected between
each nozzle gun of the fluid delivery system and the pump. Fluid
flow through the central apparatus is either through a main
passageway, which includes a pressure responsive valve, or a
by-pass passageway, which includes an orifice substantially the
same size of the nozzle orifice of the gun connected to the
respective control apparatus. When the pressure at the inlet of the
gun is high, such as when the gun is actuated to provide a high
pressure discharge, the valve in the main passageway is open to
permit relative unrestricted flow through the passageway. However,
when the gun is dumping so that the fluid pressure at the inlet of
the gun is relatively low, the valve in the main passageway is
closed and flow will be through the relatively restricted by-pass
passageway to simulate the effect of the gun on the pumping system.
In this manner, a substantially constant pressure is maintained on
the pump even though two or more nozzle guns are connected to it
and used at different times.
While the system just described is highly satisfactory, it requires
the machining of two separate passageways in a housing, and is not
as satisfactory for higher fluid flow rates as it is for lower
rates of flow. It is thus the primary object of this invention to
provide control apparatus of the kind described for use in a high
pressure fluid delivery system in which two or more "dump" guns of
standard design may be supplied fluid by a single pump and in which
a substantially constant pressure is provided by the pump during
dumping operation of any of the guns.
Another object of this invention is to provide such control
apparatus which may be machined with a single flow passageway.
Another object of this invention is to provide such a control
apparatus which is suitable for use with higher rates of fluid flow
than similar such control apparatus previously provided.
Another object of this invention is to provide such a control
apparatus in which a simple adjustment can be made to accommodate
different flow conditions, or to accommodate guns of different
orifice size.
Another object of this invention is to provide such a control
apparatus in which the above objects can be accomplished without
the need for the addition of relatively expensive, complicated or
large components.
These and other objects of this invention, which will be apparent
upon consideration of the appended drawings and claims, and the
following detailed description, are accomplished by providing a
fluid pressure control apparatus between each gun of a fluid
discharge system and the pump of the system for maintaining a
substantially constant load on the pump. Each such control
apparatus includes a flow passageway having a valve therein, and in
one embodiment an orifice in the valve sized to provide
substantially the same pressure drop across the control apparatus,
which is generally the same size orifice as the discharge orifice
of the gun connected to the control apparatus. The valve is
responsive to the pressure of fluid flowing to the gun connected to
the control apparatus and when the gun is discharging fluid at a
high pressure through its nozzle, the valve is open. However, when
the gun is dumping, the valve in the respective control apparatus
responds to the changes in pressure at the outlet of said control
apparatus to close the flow passageway and direct fluid through the
orifice in the valve. In the preferred embodiments illustrated the
valve is biased closed by a spring and means is provided for
adjusting the compression of the spring to permit the valve to
operate with pumps of different flow rates.
In another embodiment of this invention, the valve means includes a
stop to prevent it from being fully closed, so that the opening
through it when it is against the stop is of a size to provide the
required pressure drop. If desired, means can be provided for
adjusting the size of the minimum opening to accommodate different
flow conditions on different sizes of gun orifices.
One or more of the described control apparatus for controlling one
or more nozzle guns can be provided in line with a single hose
coming from a pump, so that when the pump is located at the same
distance from the guns, only one main hose need be provided for a
substantial part of this distance.
In the drawings, wherein like reference numerals are used
throughout to designate like parts, and wherein preferred
embodiments of this invention are illustrated,
FIG. 1 is a view in elevation of a fluid delivery system of this
invention;
FIG. 2 is a sectional view taken at 2--2 in FIG. 1 illustrating one
form of the control apparatus of this invention;
FIG. 3 is a view similar to FIG. 2 but with the valve means
open;
FIG. 4 is a view similar to FIG. 2 but with an alternate
arrangement of the valve means;
FIG. 5 is a view similar to FIG. 4 but with the valve means
open;
FIG. 6 is an end view taken at 6--6 in FIG. 1;
FIG. 7 is a sectional view taken at 7--7 in FIG. 2;
FIG. 8 is a sectional view taken at 8--8 in FIG. 2;
FIG. 9 is a sectional view similar to FIG. 2 of another embodiment
of the control apparatus of this invention illustrating the means
for adjusting the minimum valve opening;
FIG. 10 is a partial view similar to FIG. 9 showing a different
adjustment of the adjusting means; and
FIG. 11 is a sectional view taken at 11--11 in FIG. 9.
Referring now to the drawings, in FIG. 1 the fluid delivery system
of this invention is illustrated as including a pump P of
conventional design having a plunger assembly M driven by a prime
mover (not shown) and a high pressure fluid end F. Fluid end F has
an inlet hose 10 connected to a source of fluid (not shown) and an
outlet hose 11. A plurality of nozzle or "dump" guns, such as two
guns G.sub.1 and G.sub.2 illustrated, are generally connected to
outlet hose 11, however, according to the present invention two
fluid pressure control apparatus 12A and 12B for maintaining a
substantially constant load on pump P are connected through hoses
13 and 14 respectively to a Y junction 15 and each of guns G.sub.1
and G.sub.2 are each connected to the outlets of apparatus 12A and
12B by hoses 16 and 17 respectively through coupling 18. Guns
G.sub.1 and G.sub.2 may be any of many designs of dump guns,
however, for illustrative purposes they are shown as similar to the
gun disclosed in U.S. Pat. application of Amos Pacht, Ser. No.
278,113, filed Aug. 4, 1972, entitled "High Pressure Fluid System
and Nozzle and Valve Assembly Therefor," and assigned to the
assignee of the present application. Guns G.sub.1 and G.sub.2 each
include a valve housing 15' having a valve therein, a high pressure
nozzle outlet 16' having an orifice 16A (see FIG. 6), a low
pressure dump outlet 17', and a handle and trigger mechanism 18'
for actuating the valve and directing fluid between either nozzle
16' or dump outlet 17'. Guns G.sub.1 and G.sub.2 typically may be
used in high pressure water blasting for cleaning applications, in
which case the water pressure at the guns may reach 10,000 psi and
over when flow is through nozzle 16', and only several hundred
pounds or less when water is dumped. The water pressure at guns
G.sub.1 and G.sub.2 are determined by the size of the orifices 16A
in nozzles 16', and the flow rate of pump P.
The details of a preferred form of control apparatus 12A are shown
in FIGS. 2 and 3, wherein for purposes of this description only
reference will be made to the parts as being up or down (or lower
or upper) because of the orientation of FIG. 2. Since apparatus 12A
and 12B are identical, only apparatus 12A is shown in FIGS. 2 and 3
and its description will equally apply to apparatus 12B.
As illustrated in FIG. 2, apparatus 12A includes an elongated
housing 20 of any suitable cross-section and having a central bore
21 of varying width and circular cross-section through its entire
length. Bore 21 includes a relatively large diameter upper portion
22 which terminates at a radially outwardly extending shoulder 23
near the center of housing 20, a relatively narrow intermediate
portion 24 between shoulder 23 and a radially outwardly extending
shoulder 25 below shoulder 23, and a portion 26 of relatively small
diameter extending from shoulder 25 to the lower end of housing 20.
Both bore portions 22 and 26 are threaded at their opposite ends as
illustrated in FIG. 2, and the threaded part of bore portion 26
extends from the lower end thereof to a shoulder 27 intermediate
the ends of portion 26. Also, a threaded inlet passageway 28 is
connected for fluid communication to the upper end of bore portion
26.
Central bore portion 26 and inlet passageway 28 together form a
flow passageway for the passage of fluid through apparatus 12 and
between pump P and gun G.sub.1. A valve means is disposed in this
passageway for controlling the flow of fluid therethrough and to
provide a substantially constant outlet pressure at pump P
irrespective of whether gun G.sub.1 or G.sub.2 (one or both) is
discharging fluid at a high pressure or dumping. For this purpose
the preferred form of such valve means includes a cylindrical valve
seat member 29 having a central passageway 30 therethrough, an
inwardly and downwardly tapered valve seat 31 at its upper end, and
an intermediate, outwardly extending threaded portion 32. The lower
end 29A of member 29 is enlarged and is internally threaded for
coupling to a hose, such as hose 16 through coupling 18, and forms
an outlet for the flow passageway through apparatus 12A. Member 29
is screwed into bore portion 26 until threaded portion 32 abuts
against shoulder 27 with valve seat 31 extending up into passageway
21 adjacent inlet passageway 28. The upper end of valve seat member
29 includes an O-ring seal 33, illustrated as including an O-ring
with a flat backing ring to seal the periphery about member 29 and
prevent the flow of fluid between member 29 and the wall of bore
portion 26. A valve chamber is thus formed in bore portion 26.
Also extending into this valve chamber from bore portion 24 is a
cylindrical valve stem member 34 adapted to seat at its lower end
in a sealing relationship on valve seat 31, and including a lower
face 34A. Valve stem member 34 extends through bore portion 24 up
into the lower end of bore portion 22, with a close sliding fit,
and includes a peripheral O-ring seal 35 having an O-ring and a
backing ring, for sealing between the periphery of stem member 34
and the wall of bore portion 24.
Resilient means are provided in bore portion 22 for normally
resiliently urging valve stem member 34 under a predetermined force
to a closed position where valve stem member 34 is seated on valve
seat 31 to close the flow passageway through control apparatus 12A.
For this purpose, the resilient means of FIG. 2 includes a coil
spring 36 mounted over a cylindrical spring holder 37 which
includes a lower retaining circular disk 38 which abuts against the
upper end of valve stem member 34. A cylindrical spring retainer
plug 39 is threaded into the upper end of bore 21 to close the bore
and to provide an upper stop for spring 36 and to urge it under
compression against disk 38. Spring holder 37 also includes an
upward extending cylindrical guide rod 40 extending through an
opening through the center of plug 39 for guiding holder 37, and
for providing a tell tale pin to indicate the position of the valve
stem member 34. The lower end of plug 39 serves as a stop to limit
the upward movement of spring holder 37 to about one-eighth of an
inch.
Spring 36 must be large enough to force valve stem member 34 down
and thus seat it on valve seat 31 when the water pressure at the
outlet of the flow passageway through apparatus 12A is low, i.e.,
when gun G.sub.1 is dumping, but not so large that the spring
cannot be overcome when the pressure in the outlet rises in
response to actuation of gun G.sub.1. FIG. 3 illustrates the
position of valve stem 34 when the valve is open against the force
of spring 36 in response to the fluid pressure at the outlet of
apparatus 12A. Also, since plug 39 is threaded the compression of
spring 43 can be changed to compensate for pumps of different flow
rates and, if needed, the spring can be changed to a stiffer
spring. By way of example, if the pressure at outlet 30A is 100
pounds when gun G.sub.1 is dumping, and 5,000 psi or higher when
discharge is through its nozzle, spring 43 can be such that
pressures of 1,000 pounds or greater at outlet 30A will overcome
it. Also, valve stem member 34 and valve seat member 29 are
designed as tapered members to provide as little seating surface as
possible so that when the valve is seated against high pressure the
force of spring 36 required to hold it closed does not have to be
excessive. It is also desirable to make the seating area small to
increase the size of face 34A in relation to it to provide enough
surface area to overcome the force of spring 36.
In order to insure that the load on pump P is substantially
constant, apparatus 12A includes means which simulates the effect
of high pressure usage by the gun connected thereto even when the
gun is dumping. Thus, in so far as the pump is concerned, it sees
the same load whether the gun is dumping or not and this would be
true where a plurality of guns and control apparatus of this
invention are connected to the same pump and operated at random
times. In FIG. 2, this means is provided by a passageway 50 and
orifice 51 in valve stem 34 which function to provide a flow
passageway bypassing the seated valve when the pressure at the
outlet of apparatus 12A is low (i.e., gun G.sub.1 is dumping).
Passageway 50 passes through the center of valve stem 34 and
conducts fluid to orifice 51 which is connected between passageway
50 and face 34A. Orifice 51 (see FIG. 7) is selected to be
substantially the size as the nozzle 16' orifice (see FIG. 6) of
gun G.sub.1 so that the effect of flow through the nozzle is
simulated when the gun G.sub.1 is dumping.
FIGS. 4 and 5 show an alternate arrangement of the means in
apparatus 12A for simulating the effect of flow through the nozzle
of gun G.sub.1. In this case, valve stem 34 includes a stop member,
in the form of a circular disk 52 at its upper end, adapted to abut
against shoulder 23 and limit the downward movement of stem member
34. The length of stem member 34 is selected so that when it is in
its most downward position (see FIG. 4) a slight clearance 53 is
provided between the lower end of valve stem member 34 and seat 31
of a size to provide substantially the same restriction to fluid
flow as the opening of nozzle 16' does. FIG. 5 shows the open
position of the valve of FIG. 4.
FIGS. 9-11 show another embodiment of the control apparatus of this
invention in which the valve construction is identical to that of
the FIGS. 4 and 5 embodiment, and means is provided for adjusting
the size of the minimum clearance through the valve, i.e. the
pressure drop across the valve when the nozzle opening of the
associated gun is being simulated. As shown in FIG. 9 this
adjusting means is preferably provided by a lock nut 60 which is
screwed on to threaded portion 32 of valve seat member 29 (the
threads of portion 32 extending down to portion 29A in this
embodiment) so that when member 29 is screwed into housing 20 nut
60 will be between the lower end of housing 20 and enlarged portion
29A of member 29. In this manner the position of valve seat member
29 in housing 20 can be set and nut 60 then tightened to maintain
this position. FIG. 9 shows the nut in position to provide the
smallest minimum in opening through the valve 29, 34, and FIG. 10
shows a larger minimum opening with a different setting of valve
seat member 29. Since very small differences in the valve opening
can result in large changes in pressure drop the adjusting means of
FIGS. 9-11 is desirable for providing for fine adjustments of this
opening. Also, adjustment can be provided to accommodate for wear
of the valve parts occurring when used with high pressures.
In operation in the FIG. 2 embodiment, when gun G.sub.1 is dumping
(this description of operation also being applicable to apparatus
12B and gun G.sub.2), so that the pressure at the outlet of
apparatus 12A is low, then the valve 29, 34 is closed and flow
through the flow passageway 28, 26 is through the by-pass
passageway 50 and orifice 51, which as previously noted, is the
same size as the orifice in nozzle 16' of gun G.sub.1. Thus, the
pressure on the inlet side of valve 29, 34 rises to substantially
the same pressure it would be if flow were through nozzle 16', and
pump P has substantially the same load. However, when trigger 18'
in gun G.sub.1 is activated, to direct water through nozzle 16',
the water pressure on the outlet side of orifice 51 also rises to a
higher value and water at this higher pressure acts on face 34A and
overcomes the force of spring 36 and moves valve stem member 34 up
as shown in FIGS. 3 and 5, moving stem 34 off of and out of sealing
engagement with valve seat 31. Thus, when trigger mechanism 18' is
released and the pressure at the outlet of apparatus 12A is reduced
to substantially the dumping pressure of gun G.sub.1, spring 36
will again force valve stem member 34 to close on seat 31. In the
embodiment of FIGS. 4, 5 and 9-11, member 34 does not fully close
on seat 31 and the desired minimum opening provided when the valve
stem member is in its downward position provides the desired
pressure drop.
When water is being discharged through the outlet of apparatus 12A,
a blast of water will be present and will possibly damage a rubber
hose connected to the outlet, such as hose 16. It is thus preferred
that some sort of means be connected to the outlet to break up this
blast of water before it can damage the connecting hose. One such
means is a circular insert member 61 illustrated in FIGS. 2 and 8
which is inserted into the lower end of valve seat member 29 and
includes a plurality of holes 62 for breaking up and passing the
flow from orifice 51. Another such means (not shown) may be a tube
and elbow connected between the outlet and a hose.
Thus, as can be seen from the above description, control apparatus
12A and 12B provide a substantially constant load to pump P and
substantially constant inlet pressures for guns G.sub.1 and G.sub.2
despite the large pressure changes occurring at the guns, which may
occur in any sequence during actual use of the guns. This is true
whether both guns are dumping, providing a high pressure blast of
water, or one is dumping and the other blasting. Also, different
size nozzle openings in guns G.sub.1 and G.sub.2 can be simulated
by inserting different valve stems 34 having different size
orifices 51, or by adjustment of the minimum opening between seat
member 34 and seat 31 when the valve is in its most closed
position. Of course, only two guns with two control apparatus are
shown, but more than two guns and their respective control
apparatus can be provided. Also, by the arrangement shown in FIG.
1, hose 11 can be relatively long and hoses 13 and 14 relatively
short to reduce the amount of hosing required with two or more guns
located at a substantial distance from pump P.
From the foregoing, it will be seen that this invention is one well
adapted to attain all of the ends and objects hereinabove set
forth, together with other advantages which are obvious and which
are inherent to the apparatus.
It will be understood that certain features and subcombinations are
of utility and may be employed without reference to other features
and subcombinations. This is contemplated by and is within the
scope of the claims.
As many possible embodiments may be made of the invention without
departing from the scope thereof, it is to be understood that all
matter herein set forth or shown in the accompanying drawings is to
be interpreted as illustrative and not in a limiting sense.
* * * * *