U.S. patent number 3,848,485 [Application Number 05/407,416] was granted by the patent office on 1974-11-19 for valving machine.
Invention is credited to Carl A. Grenci.
United States Patent |
3,848,485 |
Grenci |
November 19, 1974 |
VALVING MACHINE
Abstract
A machine for inserting or removing a valve into or from a
cylinder including means for securely holding the cylinder to
prevent rotation thereof and a pair of self-adjusting, power
actuated, valve tongs pivotable about a pair of parallel, spaced
axes to permit one ends thereof to come into contact with opposite
sides of the valve. Drive means is operative to rotate the tongs
about an axis aligned with the axis of the valve to rotate the
valve relative to the cylinder. The same drive means, through a
power multiplying, planetary gear arrangement urges the one ends of
the tongs into contact with the opposite sides of the valve with a
greater torque than that used to rotate the valve whereby the tongs
tightly hold the valve during turning thereof relative to the
cylinder.
Inventors: |
Grenci; Carl A. (Yorba Linda,
CA) |
Family
ID: |
23611992 |
Appl.
No.: |
05/407,416 |
Filed: |
October 18, 1973 |
Current U.S.
Class: |
81/57.11; 81/3.2;
81/57.31 |
Current CPC
Class: |
B25B
27/24 (20130101) |
Current International
Class: |
B25B
27/14 (20060101); B25B 27/24 (20060101); B25b
017/00 (); B25b 021/00 (); B67b 007/08 () |
Field of
Search: |
;81/57.11,57.18,57.2,57.31,57.34,57.36,3.2 ;29/240
;53/317,331.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Jones, Jr.; James L.
Attorney, Agent or Firm: Hinderstein; Philip M.
Claims
I claim:
1. A machine for rotating a first member relative to a second
member comprising:
means for securely holding said second member;
a pair of tongs pivotable about a pair of parallel, spaced
axes;
drive means;
means forming a direct, non-friction connection between said drive
means and said tongs for rotating said tongs with a torque T.sub.1
about an axis spaced halfway between and perpendicular to said
axes; and
power multiplication means operatively coupled between said drive
means and said tongs for urging one ends of said tongs into contact
with opposite sides of said first member with a torque T.sub.2,
T.sub.2 being greater than T.sub.1 whereby said tongs tightly hold
said first member during turning thereof relative to said second
member.
2. A machine according to claim 1 wherein T.sub.2 is at least equal
to 2T.sub.1.
3. A machine according to claim 1 wherein said power multiplication
means is operatively coupled between said drive means and the other
ends of said tongs, said parallel axes intersecting said tongs
between said opposite ends thereof.
4. A machine according to claim 1 wherein said drive means
comprises:
a shaft positioned coaxially with said axis; and
means for rotating said shaft.
5. A machine according to claim 4 wherein said tongs rotating means
comprises:
a sun gear mounted on said drive shaft;
a planetary gear housing surrounding said sun gear;
a plurality of planetary gears mounted within said housing and
engaging said sun gear; and
means interconnecting said planetary gear housing and said
tongs.
6. A machine according to claim 5 wherein said power multiplication
means comprises:
a cam drive housing surrounding said planetary gear housing;
a ring gear mounted within and connected to said cam drive housing,
said ring gear engaging said planetary gears and being driven
thereby; and
cam means connected to said cam drive housing and being rotatable
therewith, said cam means contacting the other ends of said tongs
and being operative to pivot said tongs about said spaced axes upon
rotation of said cam drive housing relative to said planetary gear
housing.
7. A machine according to claim 6 wherein rotation of said drive
shaft causes rotation but not translation of said planetary gears,
causing rotation of said ring gear and said cam drive housing
thereby rotating said cam means and pivoting said tongs about said
spaced axes until said one ends of said tongs contact said opposite
sides of said first member, additional rotation of said drive shaft
causing rotary translational movement of said planetary gears and
said ring gear about said drive shaft axis thereby rotating said
tongs while said cam means urges said one ends of said tongs into
contact with said opposite sides of said first member.
8. A machine according to claim 4 wherein said means for rotating
said shaft comprises:
an air motor.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valving machine and, more
particularly, to a valving machine including self-adjusting, power
actuated, valve tongs that provide a positive, non-slip hold on a
valve no matter how tight it is.
2. Description of the Prior Art
Many machines are presently on the market for inserting or removing
valves into or from pressure cylinders. Such machines are required
to initially insert the valves into the cylinders with the required
torque to insure a fluid-tight seal. Such machines are also
required thereafter to remove the valves for normal maintenance
thereof and periodic hydrostatic testing of the cylinders.
The cylinder has an internally threaded opening at the upper end
thereof which receives the externally threaded stem of the valve.
The body of the valve includes flats on opposite sides thereof
which may be engaged for rotating the valve relative to the
cylinder.
Prior art valving machines are of two general types, the crow-foot
type and the mechanically adjusted clamp-tong type. The crow-foot
type is characterized by a generally C-shaped member having a slot
in the lower end thereof defining a pair of spaced arms for
receiving the valve. Since the spacing between the arms is fixed,
spacers are required for different sizes of valves.
Such valving machines have a number of disadvantages associated
therewith. In the first instance, since the spacing between the
arms is fixed, a certain amount of slack is required to fit the
valve between the arms. However, this amount of slack can cause the
arms to slip and damage the valve if the valve is exceptionally
tight. Also, valves vary considerably in size from manufacturer to
manufacturer as well as from new as compared to previously used
valves and it is difficult to provide a firm hold.
Another problem results from the recent trend in the industry of
valve manufacturing. The valves are ordinarily made from brass, but
because of the expense of metals, lighter and lighter sections are
being used. When using a wrench, as a crow-foot type valving
machine essentially is, if the wrench slips, it can easily deform
or damage the outlet connection or the safety device. Furthermore,
as the wrench starts to turn, the valve material slightly deforms
and no provision is made for taking up this slack.
The mechanically adjusted clamp-tong type valving machine was
developed to at least partially solve these problems. This type of
valving machine is characterized by a pair of tongs which are
pivotable about a pair of parallel, spaced axes adjacent one ends
of the tongs to permit the other ends of the tongs to be brought
into contact with opposite sides of the valve body. Once the
cylinder, valve, and tongs are positioned, the tongs are
mechanically and manually tightened and locked to the valve
body.
While this type of valving machine represents an improvement over
the crow-foot type of machine, many of the problems still remain.
More specifically, once the machine starts to operate and the tongs
cause deformation of the valve body, there is no provision for
taking up the slack created by such deformation. Furthermore, the
forces on the tongs cause wear and distortion that precludes a
positive grip. Thus, there is still the possibility that the tongs
will slip thereby deforming or damaging the outlet connection or
the safety device made integral with the valve.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a valving
machine which solves the problems encountered heretofore. The
present valving machine includes a pair of tongs pivotable about a
pair of parallel, spaced axes so that one ends of the tongs may be
brought into contact with opposite sides of the valve. With the
present valving machine, the valve tongs are power actuated and
self-adjusting so that a force urges the one ends of the tongs into
contact with the opposite sides of the valve at all times during
rotation of the tongs. Furthermore, the torque tending to urge the
valve tongs into contact with the valve is greater than the torque
rotating the tongs to insure that the tongs tightly hold the valve
during turning thereof relative to the cylinder thereby preventing
slipping thereof and potential damage to the valve.
Briefly, the present machine for inserting or removing a valve into
or from a cylinder comprises means for securely holding the
cylinder, a pair of tongs pivotable about a pair of parallel spaced
axes, drive means, means operatively coupled between the drive
means and the tongs for rotating the tongs with a torque T.sub.1
about an axis spaced halfway between and perpendicular to the pair
of axes, and power multiplication means operatively coupled between
the drive means and the tongs for urging one ends of the tongs into
contact with opposite sides of the valve with a torque T.sub.2,
where T.sub.2 is greater than T.sub.1 and the tongs tightly hold
the valve during turning thereof relative to the cylinder.
OBJECTS
It is therefore an object of the present invention to provide a
valving machine.
It is a further object of the present invention to provide a
valving machine including self-adjusting, power actuated, valve
tongs that provide a positive, non-slip hold on a valve no matter
how tight it is.
It is a still further object of the present invention to provide a
valving machine which prevents damage to valve parts.
It is another object of the present invention to provide a valving
machine including a pair of valve tongs that automatically take up
the slack between the gripping surfaces thereof and the valve
body.
Still other objects, features, and attendant advantages of the
present invention will become apparent to those skilled in the art
from a reading of the following detailed description of the
preferred embodiment constructed in accordance therewith, taken in
conjunction with the accompanying drawings wherein like numerals
designate like parts in the several figures and wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a valving machine constructed in
accordance with the teachings of the present invention;
FIG. 2 is an enlarged, sectional view taken along the longitudinal
axis of the drive shaft of the machine of FIG. 1;
FIG. 3 is a sectional view taken along the line 3--3 in FIG. 2;
and
FIG. 4 is a sectional view taken along the line 4--4 in FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings and, more particularly, to FIG. 1
thereof, there is shown a valving machine, generally designated 10,
for inserting or removing a valve 11 into or from a cylinder 12.
Cylinder 12 is of conventional construction including an internally
threaded hole at the upper end thereof which receives the threaded
stud of valve 11. Thus, insertion or removal of valve 11 into or
from cylinder 12 is achieved by holding cylinder 12 stationary and
rotating valve 11, as known in the art.
Valving machine 10 includes a base 13 on which is rigidly mounted a
support column 14. Intermediate the upper and lower ends of support
column 14 is mounted apparatus, generally designated 15, for
securely holding cylinder 12 and for preventing rotation thereof.
Movably mounted adjacent the top of support column 14 is apparatus,
generally designated 30, for engaging the opposite sides of valve
11 and for rotating valve 11 relative to cylinder 12.
Cylinder holding means 15 includes a first arm 16, one end of which
has a generally V-shape to engage one side of cylinder 12. The
other end of arm 16 is mechanically connected to support column 14
so as to be movable axially relative thereto under control of a
first hand wheel 17. Arm 16 is movably connected to support column
14 in any suitable manner to provide for different sizes of
cylinder 12. Thus, as the diameter of cylinder 12 increases, hand
wheel 17 may be rotated to decrease the length of arm 16 and as the
diameter of cylinder 12 decreases, hand wheel 17 may be rotated to
increase the length of arm 16.
Cylinder holding means 15 also includes a second arm 19, one end of
which is movably connected to a power application unit 20 which is
rigidly connected to support column 14 by bracket means 21. The
other end of arm 19 is connected by means 22 to an arm 23
positioned coaxially with arm 16. The end of arm 23 facing arm 16
has a generally V-shape to engage the side of cylinder 12 opposite
from arm 16.
Power application unit 20 may be a conventional air driven unit for
pulling in or pushing out arm 19 under control of a manual actuator
24 positioned on a control panel 25. Thus, upon manipulation of
actuator 25, arm 19 is extended from unit 20 to separate arms 16
and 23 and to permit removal of cylinder 12. A second hand wheel 26
may be provided to adjust the extended position of arm 19. On the
other hand, actuator 24 may be manipulated to cause power
application unit 20 to withdraw arm 19, bringing arms 23 and 16
into contact with the opposite sides of cylinder 12 to securely
hold cylinder 12 relative to base 13 and support column 14. Control
panel 25 may also include a regulator 27 for controlling the force
applied by application unit 20 to arm 19 and a gauge 28 to provide
a readout of such force.
Valve rotating means 30 is supported on a head 31 which is movably
mounted on support column 14. Head 31 may be moved vertically by a
counterbalanced cable and pulley arrangement, so as to adjust the
position of valve rotating means 30 relative to base 13 for
different sizes of cylinder 12. Head 31 supports control panel 25
and the operating controls for valving machine 10.
Valve rotating means 30 includes a pair of jaw tongs 33 and 34
which extend vertically downwardly from head 31 and are pivotable
about a pair of parallel, horizontal, spaced axes defined by pins
35 and 36, respectively. Pins 33 and 34 permit ends 37 and 38 of
jaw tongs 33 and 34, respectively, to contact the opposite sides of
valve 11 to hold valve 11 while it is being rotated to insert or
remove same from cylinder 12.
Referring now to FIGS. 2-4, head 31 supports a drive shaft 40, the
axis of which is spaced halfway between and perpendicular to the
axes of pins 35 and 36. Furthermore, the axis of drive shaft 40 is
adapted to be aligned with the common axis of valve 11 and cylinder
12. The upper end of drive shaft 40 is connected to air driven
power means, not shown, within head 31. Drive shaft 40 is adapted
to be operatively coupled to jaw tongs 33 and 34, by means to be
described hereinafter, for rotating tongs 33 and 34 around shaft 40
to insert or remove valve 11 into or from cylinder 12. Drive shaft
40 is also adapted to be operatively coupled to the other ends 41
and 42 of jaw tongs 33 and 34, respectively, to rotate tongs 33 and
34 about pins 35 and 36, respectively, to urge ends 37 and 38 of
tongs 33 and 34, respectively, into contact with opposite sides of
valve 11.
More specifically, and referring primarily to FIGS. 2 and 3, drive
shaft 40 is surrounded by a sun gear 44 which is driven with shaft
40 by means of a key 45 positioned within opposing slots 46 and 47
in the outer surface of shaft 40 and the inner surface of sun gear
44, respectively. Sun gear 44 is surrounded by an annular shaped
planetary gear housing 50 which supports a plurality of identical
planetary gears 51. More specifically, housing 50 includes a
central chamber 52 in which sun gear 44 is mounted and a plurality
of outer chambers 53 in which planetary gears 51 are mounted in
such a manner that the teeth on planetary gears 51 engage the teeth
on sun gear 44. Each of planetary gears 51 is mounted on a shaft
54. Shims 55 may be positioned between gears 51 and housing 50 for
spacing and support of gears 51. In addition, bearings 56 may be
positioned between sun gear 44 and housing 50 to provide axial
support thereof.
Planetary gear housing 50 is mounted between an upper, disc-shaped
plate 58 and a lower, disc-shaped flange 59 made integral with or
connected to a drive tube 60 which is positioned around drive shaft
40. Planetary gear housing 50 may be connected to plate 58 and
flange 59 by means of a plurality of screws 61 which extend through
mating holes in plate 58, housing 50, and flange 59, such holes
being spaced between chambers 53 in housing 50 so as not to
interfere with the operation of planetary gears 51. It should be
noted that drive shaft 40 passes through central openings in plate
58, flange 59, and drive tube 60 and is not connected thereto.
Mounted at the lower end of drive shaft 40 is a generally H-shaped
block 65, the plane of which is perpendicular to the axis of drive
shaft 40. H-block 65 has a hole 66 passing through the central
portion thereof through which the lower end of shaft 40 extends. A
bolt 67 extends into an internally threaded bore 68 in the bottom
of shaft 40, the head of bolt 67 supporting a plurality of washers
69 which support H-block 65 for rotational movement relative to
shaft 40. It is significant to note that there is no connection
between H-block 65 and drive shaft 40 other than the rotatable
support provided by washers 69.
H-block 65 supports pins 35 and 36 on which jaw tongs 33 and 34,
respectively, are pivotably mounted. Thus, rotation of H-block 65
about the axis of hole 66 will rotate tongs 33 and 34, as described
previously.
H-block 65 includes a drive tube 70 made integral with or connected
to the central section thereof, drive tube 70 having an inner
diameter approximately equal to the outer diameter of drive tube
60, drive tube 70 being mounted coaxially with and surrounding
drive tube 60. Drive tube 70 is driven with drive tube 60 by means
of a key 71 positioned within opposing slots 72 and 73 in the outer
surface of drive tube 60 and the inner surface of drive tube 70,
respectively. Thus, rotation of planetary gear housing 50 about the
axis of drive shaft 40 causes rotation of drive tube 60 which,
through the intermediary of key 71, causes rotation of drive tube
70 and H-block 65 around drive shaft 40. In this manner, the
rotation of drive shaft 40 is transmitted to tongs 33 and 34, as
will be described more fully hereinafter.
Planetary gears 51 and planetary gear housing 50 are surrounded by
an annular shaped cam drive housing 75 which supports a ring gear
76. Ring gear 76 is connected to the inner surface of cam drive
housing 75 in any suitable manner. The upper end of cam drive
housing 75 is spaced from and surrounds the circumference of plate
58. The lower end of cam drive housing 75 is connected to or made
integral with a disc-shaped plate 77 which extends beneath flange
59 of planetary drive tube 60. A spacer 78 positioned between plate
77 and ring gear 76 supports ring gear 76 in contact with planetary
gears 51, as shown most clearly in FIG. 3. A bearing 79 positioned
between the bottom surface of flange 59 and the top surface of
plate 77 permits rotation of cam drive housing 75 relative to
planetary gear housing 50.
The inner circumference of plate 77 is spaced slightly from the
outer surface of planetary drive tube 60. Positioned beneath plate
77 is an elliptically shaped jaw cam 80, shown most clearly in FIG.
4, the plane of cam 80 being perpendicular to the axis of drive
shaft 40. Cam 80 has a hole 81 passing through the center thereof
through which planetary drive tube 60 passes. Jaw cam 80 is
connected to or made integral with plate 70 of cam drive housing 75
so as to be rotatable with cam drive housing 75 and ring gear 76.
Furthermore, cam 80 is position so as to be adjacent ends 41 and 42
of jaw tongs 33 and 34, respectively, which terminate adjacent
plate 77.
The minor diameter of jaw cam 80 is equal to or less than the
spacing between tongs 33 and 34 when tongs 33 and 34 are parallel,
as shown in solid lines in FIG. 2. On the other hand, the major
diameter of cam 80 is substantially greater so that as cam 80
rotates relative to H-block 65, ends 41 and 42 of tongs 33 and 34,
respectively, are driven outwardly, forcing ends 37 and 38 of tongs
33 and 34, respectively, towards each other.
Drive shaft 40 is preferably driven by an air motor drive under
control of a manual actuator 83 mounted on control panel 25. Thus,
movement of actuator 83 to the left will cause rotation of drive
shaft 40 in one direction and movement of actuator 83 to the right
will cause rotation of drive shaft 40 in an opposite direction. By
making cam 80 elliptical, a single unit may be used for tightening
or loosening valve 11. Finally, control panel 25 may include a
regulator 84 for controlling the force applied to drive shaft 40
and a gauge 85 to provide a readout of such force.
OPERATION
In order to operate valving machine 10, actuator 24 is manipulated
to release arm 19 so as to separate arms 16 and 23 to permit
cylinder 12 to be inserted therebetween. With valve 11 positioned
coaxially with drive shaft 40, hand wheel 17 is manipulated to
bring arm 16 into contact with one side of cylinder 12. The desired
force on cylinder 12 is adjusted by means of regulator 27 and
manual actuator 24 is manipulated to activate power application
unit 20. Arm 23 is automatically brought into contact with the
other side of cylinder 12, securely holding cylinder 12 and
preventing rotation thereof.
The control mechanism within valve rotating means 30 is next
activated to bring ends 37 and 38 of jaw tongs 33 and 34,
respectively, into contact with the valve flats on the opposite
sides of valve 11. Assuming that one is inserting valve 11 into
cylinder 12, requiring clockwise rotation thereof, manual actuator
83 is manipulated so as to cause rotation of drive shaft 40 in a
clockwise direction, as viewed in FIG. 3. Rotation of drive shaft
40 in this direction causes counterclockwise rotation of planetary
gears 51 about shafts 54. Rotation of planetary gears 51 will cause
one of two results. Either cam drive housing 75 and ring gear 76
will remain stationary and planetary gear housing 50 will rotate in
a clockwise direction or planetary gear housing 50 will remain
stationary and cam drive housing 75 will rotate in a
counterclockwise direction. Initially, since jaw tongs 33 and 34
will be parallel and out of contact with valve 11, it is desired to
prevent the former type of motion and to permit the latter type.
Since jaw tongs 33 and 34 are connected directly to planetary gear
housing 50 by means of H-block 65, drive tube 70, key 71, drive
tube 60, flange 59, and screws 61, the rotation of planetary gear
housing 50 may be prevented by simply holding H-block 33 or one of
tongs 33 and 34 to prevent rotation thereof. For this purpose and
also for the purpose of stiffening tongs 33 and 34, tongs 33 and 34
include outwardly projecting stiffening members 93 and 94,
respectively. Thus, one of stiffening members 93 or 94 may be held
in one hand while actuator 83 is manipulated with the other
hand.
With reference to FIGS. 2-4, the clockwise rotation of drive shaft
40 causes counterclockwise rotation of planetary gears 51 about
shafts 54. Since planetary gear housing 50 is prevented from
rotating, ring gear 76 and cam drive housing 75 are driven in a
counterclockwise direction. Rotation of cam drive housing 75 causes
rotation of cam 80 through the intermediary of plate 77. Thus, cam
80 rotates relative to drive tubes 60 and 70, driving ends 41 and
42 of tongs 33 and 34, respectively, outwardly, tongs 33 and 34
pivoting about pins 35 and 36. This action continues until ends 37
and 38 contact the opposite sides of valve 11. When this occurs,
cam 80 and cam drive housing 75 can no longer rotate independently
of H-block 65 and tongs 33 and 34. Thus, with cam 80 securely
locked against ends 41 and 42 of tongs 33 and 34, respectively, and
with ends 37 and 38 of tongs 33 and 34, respectively, firmly in
contact with the opposite sides of valve 11, planetary gear housing
50 and cam drive housing 75 begin to rotate as a unit in a
clockwise direction. As explained previously, rotation of planetary
gear housing 50 with drive shaft 40 causes rotation of planetary
drive tube 60 about the axis of drive shaft 40. Planetary drive
tube 60 drives H-block drive tube 70 by means of key 71 resulting
in the rotation of H-block 65 and jaw tongs 33 and 34. Thus, tongs
33 and 34 rotate valve 11 relative to cylinder 12.
It should be particularly noted that the just described arrangement
of sun gear 44, planetary gears 51, and ring gear 76 results in a
power multiplication of the torque generated by drive shaft 40.
Thus, the torque T.sub.2 urging ends 37 and 38 of tongs 33 and 34,
respectively, into contact with the opposite sides of valve 11 is
multiplied with respect to the torque T.sub.1 rotating tongs 33 and
34 about the axis of shaft 40. This power multiplication insures
that any deformation of valve 11, causing a diminishing of the
spacing between the sides thereof, automatically causes slipping of
housing 75 relative to housing 50, resulting in a counterclockwise
rotation of cam 80 relative to H-block 65 to pivot tongs 33 and 34
by an amount which will take up such slack. Without this power
multiplication, ends 37 and 38 of tongs 33 and 34, respectively,
would be forced to separate and the same problems would be
encountered as experienced heretofore.
Many factors influence the power multiplication factor such as the
relative diameters of sun gear 44, planetary gears 51, and ring
gear 76, the diameter of cam 80, the length of tongs 33 and 34
relative to the location and spacing of pins 35 and 36, etc.
Suffice it to say that the torque urging ends 37 and 38 of tongs 33
and 34, respectively, into contact with the opposite sides of valve
11 should be at least twice as great as the torque rotating H-block
65 and tongs 33 and 34.
After valve 11 has been tightened, actuator 83 is manipulated in
the other direction to cause reversal of shaft 40 and pivoting of
jaw tongs 33 and 34 in an opposite direction so as to release valve
11. Actuator 24 may then be manipulated to release arm 23,
permitting removal of cylinder 12.
As stated previously, both power application unit 20 and valve
rotating means 30 are preferably air motor drives. This is
preferred since the torque can be adjusted by setting air
regulators 27 and 84. In addition, an air drive slows as the torque
reaches the stall point so that brass valve threads have time to
cold flow under pressure and conform themselves to the cylinder
neck threads, thus reducing the possibility and nuisance of
leaks.
It can therefore be seen that in accordance with the present
invention, there is provided a valving machine 10 which solves the
problems encountered heretofore. Valving machine 10 includes a pair
of tongs 33 and 34 pivotable about a pair of parallel, spaced pins
35 and 36, respectively, so that ends 37 and 38 of tongs 33 and 34,
respectively, may be brought into contact with opposite sides of
valve 11. With machine 10, tongs 33 and 34 are power actuated and
self-adjusting so that a force urges ends 37 and 38, respectively,
into contact with valve 11 at all times during rotation thereof.
Furthermore, the torque tending to urge tongs 33 and 34 into
contact with valve 11 is greater than the torque rotating tongs 33
and 34 to insure that the tongs tightly hold valve 11 during
turning thereof relative to cylinder 12 thereby preventing slipping
thereof and potential damage to valve 11.
While the invention has been described with respect to a preferred
physical embodiment constructed in accordance therewith, it will be
apparent to those skilled in the art that various modifications and
improvements may be made without departing from the scope and
spirit of the invention. Accordingly, it is to be understood that
the invention is not to be limited by the specific illustrative
embodiment, but only by the scope of the appended claims.
* * * * *