U.S. patent number 3,821,992 [Application Number 05/286,730] was granted by the patent office on 1974-07-02 for impact device using a gas as its medium.
Invention is credited to Susumu Matsuo.
United States Patent |
3,821,992 |
Matsuo |
July 2, 1974 |
IMPACT DEVICE USING A GAS AS ITS MEDIUM
Abstract
An impact device using a gas as its medium is formed of an air
pump and an impact cylinder. The air pump and the impact cylinder
are respectively divided by a pump piston and a hammer piston into
upper and lower chambers which intercommunicate upper with upper
and lower with lower through valves which regulate the flow of high
and negative pressure gas causing the downward impact stroke of the
hammer piston onto the tool at the lower end of the impact cylinder
and the downward stroke of the pump piston to begin simultaneously
after the pump piston has reached its top dead point compressing
the air in the upper chamber to the maximum and generating the
maximum negative pressure in the lower chamber. There are further
provided means for communicating the upper and lower chambers of
the pump cylinder when the pump piston has reached the lower dead
point and means for communicating the upper chamber of the impact
cylinder with the means for connecting the lower chambers of the
two cylinders.
Inventors: |
Matsuo; Susumu (Sunto-gun,
Shizuoka-ken, JA) |
Family
ID: |
13528736 |
Appl.
No.: |
05/286,730 |
Filed: |
September 6, 1972 |
Foreign Application Priority Data
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Sep 23, 1971 [JA] |
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46-73805 |
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Current U.S.
Class: |
173/200;
60/547.1; 60/591; 60/542; 60/571; 60/593 |
Current CPC
Class: |
B25D
9/08 (20130101) |
Current International
Class: |
B25D
9/08 (20060101); B25D 9/00 (20060101); B25d
009/08 () |
Field of
Search: |
;173/116,14
;60/542,547,571,591,593 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Purser; Ernest R.
Attorney, Agent or Firm: Kelman; Kurt
Claims
What I claim is:
1. An impact device using gas as its medium which comprises in
combination,
A. an air pump having an upper and a lower chamber, a movable
piston intermediate the upper and lower chamber, an air
communication port between the upper and lower chambers, and a
piston rod joining the movable piston and projecting through a wall
of the lower chamber, said piston rod having disposed thereon a
second piston within a hydraulic pump, said hydraulic pump
providing drive means for effecting upward and downward strokes of
said movable piston at a fixed speed;
B. an impact section consisting of an impact cylinder having an
upper and a lower chamber, a hammer piston having a projecting
member disposed along an upper surface and means for striking a
tool by an opposite surface, a tool projecting from the impact
section;
C. an air passage connecting the upper chamber of the air pump with
the upper chamber of the impact section, a valve within said air
passage and means for receiving in air stopping engagement said
projecting member, said valve disposed to prevent exhaust of air
from the upper air pump chamber;
D. a second air passage connecting the lower chamber of the air
pump with the lower chamber of the impact section, a second valve
within said second air passage, said second valve having a stem
projecting within the air pump and movable by said movable piston,
said second valve disposed for preventing intake of air into the
upper chamber of the air pump; and
E. said combination of chambers and air connecting means effecting
start of downward impact stroke of the hammer piston and downward
stroke of the pump piston simultaneously by means of pressure in
the upper chamber of the air pump applied to the upper chamber of
the impact cylinder and by means of negative pressure of the lower
chamber of the impact cylinder when the movable piston has reached
a top dead point with maximum negative pressure in the lower
chamber;
F. said air communication port being open when the movable piston
is in the bottom dead point; and
G. said impact cylinder having means for communicating the upper
chamber of the impact chamber with the air passage connecting both
of said lower cylinders.
Description
BACKGROUND OF THE INVENTION
Crushing operations requiring extremely great crushing power, such
as the crushing of raw limestones, preliminary breaking of quarried
stones for gravel before feeding to a crusher, crushing of concrete
roads and buildings and crushing of clinker in blast furnaces, have
conventionally been carried out by mounting a
compressed-air-operated pneumatic breaker on the end of the arm of
an operation truck like power shovel or backhoe, connecting the
pneumatic breaker to another truck carrying a large (100 - 200HP)
air compressor with a long, large hose that can be wound and
driving the breaker by the use of the expanding force of the
compressed air prepared by the air compressor truck. While the
breaker is driven by the air the operation truck is moved from
place to place according to necessity and the air compressor truck
is kept at a fixed position. As is well known, however, this
pneumatic breaker which releases the used air into the atmosphere
during each rotation is very low in mechanical efficiency owing to
the mechanical loss of the air compressor, the mechanical loss of
the impact device of the breaker, the heat loss at both the
compressor and the impact device and the friction at the inside of
the hose.
Furthermore, the hose is constantly being dragged over the ground
and is sometimes even pulled tense by the movement of the operation
truck. Also the hose is run over by the heavy dump car carrying the
stones for crushing. Because of fast wear and troublesome handling
the hose becomes one of the weak points of the operation.
These disadvantages are unavoidable because no impact device
capable of exhibiting powerful operating effect by utilizing a
power source mounted on the operation truck itself has yet been
developed. Impact devices so far developed and now under
development invariably require an unnecessarily large cycle for the
hammer piston impulse so that the impact speed of the hammer piston
can be increased to generate large impact force. Therefore, it is
necessary for such impact device to cancel the extremely great
moment of inertia generated at each end of the stroke of the
unnecessarily heavy hammer piston and to waste power than might be
expected in reversing the direction of the stroke. The greater part
of the imput energy is thus wasted as the mechanical loss of the
equipment.
In other words, only a half of each cycle counts toward impact
stroke speed of the hammer piston. So in order to obtain high
piston speed it is necessary to increase the number of cycles per
minute to obtain a higher speed. In conventional devices, however,
a faster cycle time, results in more power being wasted for
canceling the moment of inertia as explained above.
For this reason it is necessary for obtaining an impact device
having high efficiency that the hammer piston used be as heavy as
possible, that the cycle time be as long as possible, and that the
hammer piston travel within practical limits, very irregularly.
That is to say, the speed of the downward impact stroke of the
hammer piston should be as high as possible, while its upward
return stroke after the inertia has attenuated should be
sufficiently slow.
SUMMARY OF THE INVENTION:
Based on this idea, the present invention provides an impact device
characterized by selecting the number of hammer piston cycles per
minute according to the nature and purpose of the operation,
sealing the positive and negative pressures in the air pump by
closing the respective valves until the air pump finishes
compressing the operating air so that the heavy hammer piston is
held in the starting position at the upper dead point until its
impact stroke is started, opening the pair of valves much as an air
rifle is triggered as soon as the compression has reached its
limit, giving a powerful assistance to the downward impact stroke
of the hammer piston by injecting high pressure air into the upper
chamber of the hammer piston and applying negative pressure to the
lower chamber, properly adjusting the time required for the upward
return stroke of the hammer piston to a half of the cycle time of
the air pump, while that for the downward impact stroke is only a
small fraction of the cycle time of the driving pump, mounting both
the driving pump and the impact device on the operation truck so
that the driving pump can obtain sufficient driving power from the
engine ordinarily used to power operate the truck when it is driven
and carrying out the crushing operation without having to drag the
hose on the ground.
Other advantages and features of the present invention will be more
fully understood from the following description of its embodiment
when read in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinally cut side view showing an embodiment of
this invention;
FIG. 2 is a plan view of a part thereof;
FIG. 3 is a side view of the equipment of this invention as mounted
on an operation truck;
FIG. 4a-f are diagrams illustrating the operating conditions;
FIG. 5 is a diagram illustrating the relationship between the cycle
times and strokes of the pump piston and hammer piston; and
FIG. 6 is a longitudinally cut side view of a part of a variation
of FIG. 1 .
EXPLANATION OF THE PREFERRED EMBODIMENT
In FIG. 1, A is an air pump whose cylinder 1 contains piston 2
which divides its interior into upper chamber 1a and a lower
chamber 1b. When one of the chambers increases in volume by the
motion of the piston 2, the other decreases in volume. Below
cylinder 1 and connected thereto is cylinder 3 of the
piston-cylinder type hydraulic actuator B which causes piston 2 of
air pump A to make regular reciprocal strokes. Piston 4 within
cylinder 3 is connected to piston 2 of air pump A by rod 5. The
inside of cylinder 3 is likewise partitioned by piston 4 into upper
chamber 3a and lower chamber 3b, one increasing its volume when the
other decreases its volume. Shaft 6a and 6b are pivotally mounted
through the wall of cylinder 3 at its top and bottom and the
respective inner ends of these shafts are provided with arms 7a and
7b positioned inside the upper and lower chambers 3a and 3b and at
their respective outer ends thereof are provided the outer arms 8a
and 8b.
Said outer arms 8a and 8b change over the operation of spool 9 of
the spool type change-over valve C attached to the outside of
cylinder 3 in the following way. Change-over valve C has one port P
for introducing the input liquid pressure from a hydraulic (e.g.
oil hydraulic) pump and two ports T.sub.1 and T.sub.2 for returning
it to the tank. According to this embodiment, when spool 9 is at
its lifted position the input liquid pressure coming through port P
is introduced into lower chamber 3b of cylinder 3 after passing
through the valve and lifts piston 4, with the result that the
liquid pressure inside upper chamber 3a of the cylinder returns to
the tank through port T.sub.2 after passing through the valve. When
spool 9 is at its lowered position as shown in the drawings the
input liquid pressure is introduced into upper chamber 3a of the
cylinder and lowers piston 4, the liquid inside the lower chamber
being driven into the tank through port T.sub.1. Therefore, when
piston 4 is lifted to push up arm 7a in the upper chamber 3a outer
arm 8a pushes down spool 9 to its lowered position, thereby
introducing the input liquid pressure into upper chamber 3a and
lowering piston 4. Conversely when piston 4 is lowered to push down
arm 7b of lower chamber 3b outer arm 8b pushes up spool 9 to its
lifted position, thereby introducing the input liquid pressure into
lower chamber 3b and lifting the piston 4. As for arms 7a and 7b,
when piston 4 acts on one of them and brings spool 9 to the other
position by means of the outer arm, the other of them is returned
to the ready position by spool 9.
The input liquid pressure is produced by a hydraulic pump driven by
the power taken from the operation truck.
Thus hydraulic actuator B causes piston 4 to make regular
reciprocating impact strokes by means of change-over valve C and
drives piston 2 of air pump A through rod 5.
Air pump cylinder 1 is provided at a lower inside position thereof
with axially long opening 10 as shown in the drawings, which brings
the parts above and below the piston 2, namely, to the upper
chamber 1a and bottom chamber 1b, into communication when piston 2
has reached the bottom dead point. Opening 10 communicates with
exhaust valve 12 of cylinder head 1' through passage 11. This
opening 10 may be branched into upper and lower parts as shown as
10a and 10b in FIG. 4.
Exhaust valve 12 opens both when strong positive pressure enters
passage 11 because of the compression of the air in lower chamber
1b by piston 2 and when piston 2 has reached the top dead point by
raising lower end of stem 12' protruding into upper chamber 1a.
Cylinder head 1' is provided not only with exhaust valve 12 but
also with intake valve 14 which has opening 13 of the head as its
seat. Opening 13 is connected through the intake valve 14 and tube
15 to opening 18 at the top of upper chamber 17a of impact cylinder
17 of the impact section containing hammer piston 16. Intake valve
14 opens both when strong negative pressure is created in upper
chamber 1a by the downward stroke of piston 2 as described later
and when piston 2 has reached the top dead point in cylinder 1 stem
14' in pushed down by rocker arm 20 operated by the raised
tappet.
Impact cylinder 17 is provided at a lower portion on its inside
with upper and lower openings 21 and 22 connecting to each other at
the branching point below passage 23, one of said openings being
opened above the hammer piston into upper chamber 17a and the other
being closed by the side of the hammer piston when hammer piston 16
reaches the bottom dead point. The respective vertical positions of
said upper and lower openings 21 and 22 are so selected that when
hammer piston 16 makes its downward impact stroke upper opening 21
is first closed by the side of the piston and then lower opening 22
is also closed and when the piston reaches the bottom dead point
upper opening 21 is opened into upper chamber 17a but the lower
opening 22 remains closed by the piston. As in the case of the
aforementioned opening 10 of the air pump cylinder, openings 21 and
22 may be prepared as one long axial opening as far as said
relationship is maintained.
Passage 23 which is connected to upper and lower openings 21 and 22
communicates with exhaust valve 12 mounted on the head of the air
pump cylinder by means of tube 24 and is further connected to the
opening 10 through the passage 11.
Impact cylinder 17 is provided at its lower end with tool 25 for
striking the object to be crushed when hammer piston 16 makes its
downward impact stroke and reaches the bottom dead point. This tool
25 is returned to its elevated position by a spring 26 or the like
in a known way and has its upper end thrust back into the lower
chamber of the impact cylinder.
Hammer piston 16 is also provided at its upper end with stopper 27
planted therein. When the hammer piston making its upward return
stroke has come to the upper part of cylinder 17, said stopper 27
thrusts into opening 18 at its top and closes the opening 18. The
hammer piston continues to rise with the opening 18 at its top
closed by stopper 27 until it reaches the top dead point.
In principle air of atmospheric pressure is sealed into the system
for the total volume (working volume plus clearance volume) of air
pump A and for the volumes of upper and lower chambers 17a and 17b
of the impact section. In actual use, however, this air is
converted into a gas containing no oxygen similar to the exhaust
gas of an internal combustion engine because the oxygen consumed in
an explosive reaction with a relatively inflammable gas resulting
from the decomposition of the lubricant at the stroke end of the
hammer piston in the early stages of the operation. Of course, an
inert gas may be sealed into the system instead of air.
The ratio of the cubic capacity of air pump to the total stroke
cubic capacity of hammer piston 16 is generally calculated by the
total power required. The equipment of the present invention is
designed with a large cubic capacity ratio of 1.4 to 1.8 in order
to allow hammer piston 16 to make an effective uniform motion with
a surplus volume of air always equal to the difference between the
two cubic capacities. The most effective ratio of surplus air is
selected by the cycle time which is determined by the horsepower of
power source and the weight and stroke of the hammer piston,
depending on the nature of work. Then, as shown in FIG. 3, the air
pump A, hydraulic actuator B and change-over valve C are installed
in swing arm 28 of the operation truck, and impact section D is
fixed to the end of swing arm 28 by means of articulated connecting
rods so that the tool can be faced in the desired direction by
moving vertically with the help of position controlling actuator
28'.
In order to make this possible, tubes 15 and 24 should be flexible
and as short as possible within the limit necessary for allowing
the vertical motion of impact section D.
The movement of air and change of pressure in one cycle of this
invention will be explained below by referring to FIG. 4a-4f. As
piston 2 of air pump A approaches the end of the downward stroke
(FIG. 4a), great negative pressure develops in upper chamber 1a.
Then intake valve 14 is opened by this negative pressure to connect
upper chamber 17a of impact section D to said upper chamber 1a
through tube 15 and opening 18. On the other hand, the air
compressed in lower chamber 1b of the pump opens exhaust valve 12
through the opening 10 and the passage 11 and operates as positive
pressure in lower chamber 17b of impact section D after passing
through tube 24, passage 23 and openings 21 and 22.
As a result, hammer piston 16 makes an upward return stroke sucked
by the negative pressure from above and pushed up by the positive
pressure from below, and then closes the opening 18 with stopper 27
(FIG. 4b).
When stopper 27 closes the opening 18, upper chamber 17a of the
impact cylinder forms an enclosed cushion chamber and attenuates
the moment of inertia of the rising hammer piston until at last it
is overcome and piston 16 reaches the top dead point. At the same
time the piston 2 of the air pump reaches the bottom dead point and
thereby the upper chamber 1a of the air pump communicates with the
lower chamber 1b through opening 10, and the difference between the
pressures in the two chambers 1a and 1b ceases to exist to make it
impossible for intake and exhaust valve 12 and 14 to remain open.
Thus both valves close automatically, and air pump A and impact
section D are isolated hermetically from each other. However,
considerable amounts of compressed air still remains sealed in the
tube 24 and in lower chamber 17b of the impact cylinder, and the
inside of the tube 15 is kept under strong negative pressure, so
that the hammer piston stays at the top dead point.
Next, the piston of air pump A is forced to make a rising stroke
(FIG. 4c).
In this case, since upper chamber 1a of the air pump holds a
sufficient volume of air as it communicates with lower chamber 1b
through opening 10 as stated above, the air in upper chamber 1a is
compressed and negative pressure in lower chamber 1b after piston 2
has gone above opening 10. Intake and exhaust valves 14 and 12 are,
of course, not opened by the positive pressure in the upper chamber
or by the negative pressure in the lower chamber. Therefore, air
pump A and impact section D remain isolated and hammer piston 16
stays at the top dead point due to the positive pressure in the
lower chamber of the impact section and the negative pressure in
tube 15.
When piston 2 of air pump A presently reaches the top dead point,
causing strong positive pressure and strong negative pressure to
develop in the upper chamber 1a and lower chamber 1b respectively,
intake and exhaust valves 14 and 12 are opened by piston 2 (4d).
Lower chamber 1b of the air pump then communicates with lower
chamber 17b of the impact section through exhaust valve 12, thereby
eliminating the positive pressure obstructing hammer piston 16 from
making downward impact stroke and sucking down hammer piston 16.
The air highly compressed in upper chamber 1a of the air pump
rushes into tube 15 through intake valve 14 and pushes down the
hammer piston by acting on its stopper 27.
When piston 16 has lowered and stopper 27 has come out of opening
18 at the top, the high pressure air coming through opening 18 acts
on the whole upper side of piston 16, and combined with the sucking
action of lower chamber 17b, it makes hammer piston 16 effect a
quick downward impact stroke and strike tool 25.
When hammer piston 16 has effected the downward impact stroke and
come down below the lower opening 22 (FIG. 44e), lower chamber 17b
of the impact section forms a cushion chamber which cushions the
hammer piston at the bottom dead point with the help of the
counteraction of tool 25. At that time, upper opening 21 opens for
a moment above piston 16 and connects upper chamber 17a of the
impact section to the port 23. Therefore, the high pressure gas
inside upper chamber 17a flows into passage 23 with a strong moment
of inertia owing to the multiplied effect of the violent downward
flow communicating with the negative pressure zone inside the
passage 23, the difference between the two pressures and the great
volume of operating gas in the air pump.
When hammer piston 16 comes above upper opening 21 after being
cushioned at the bottom dead point and completes the early stage of
the upward return stroke, the inside of upper chamber 17a is kept
under suitable negative pressure and the piston of the air pump
makes a downward stroke to compress in lower chamber 1b the air
sucked in from lower chamber 17b of the impact section when intake
valve is opened and create negative pressure in upper chamber 1a
(FIG. 4f), thus causing the hammer piston to proceed with its
upward return stroke by the pressures of both chambers as described
with reference to FIG. 4a.
FIG. 5 is a diagram illustrating the relationship between the cycle
time and stroke for the air pump piston and hammer piston of the
present invention. Air pump piston 2 shown by solid line opens the
exhaust and intake valves 12 and 14 after completing its air
compressing action in upper chamber 1a and its negative pressure
generating action in lower chamber 1b by rising from bottom dead
point BP and reaching top dead point TP. As these valves 12 and 14
are opened, hammer piston 16 is sucked into lower chamber 17b by
strong negative pressure and makes a downward impact stroke to
reach the bottom dead point HP subjected to the injection of the
air compressed into upper chamber 1a by the air pump piston, while
the air pump piston makes a downward stroke toward the bottom dead
point BP at a given speed. Hammer piston 16 which has reached the
bottom dead point HP changes the pressure in the upper chamber of
the impact section from positive to negative before the air pump
piston reaches bottom dead point BP and then returns to top dead
point HTP by the positive pressure generated in the lower chamber
of the air pump. While the air pump piston is making its upward
stroke the hammer piston stays at the position HTP.
Thus the pump piston and hammer piston start their respective
downward strokes simultaneously. The pump piston makes uniform
motion and the hammer piston makes extremely ununiform motion
including a stop at the top dead point, though both motions are
effected regularly. While the pump piston is making its downward
stroke the hammer piston completes its momentary downward impact
stroke and its upward return stroke.
This can be achieved only by the principle of the present invention
characterized by providing intake valve 14 in the passage
connecting the respective upper chambers 1a and 17a of the air pump
and impact section and exhaust valve 12 in the passage connecting
the respective lower chambers 1b and 17b, opening both valves by
generating strong negative pressure in upper chamber 1a and strong
positive pressure in lower chamber 1b with the downward stroke of
the air pump piston, pushing up the hammer piston to return it to
the top dead point when the valves are opened, holding the hammer
piston at the top dead point until the air pump piston, which has
reached the bottom dead point and closed the valves by eliminating
the difference of pressures between the upper and lower chambers,
reaches the top dead point and opens the valves, opening the valves
at the top dead position to start the downward strokes of both the
air pump piston and the hammer piston simultaneously, sucking the
air of the lower chamber of the impact cylinder into lower chamber
1b, drawing the air out of the upper chamber of the impact section
so that the hammer piston, which has reached the bottom dead point,
can readily make the next upward return stroke, compressing the air
in the lower chamber by the pump piston in the downward stroke and
thereby generating negative pressure in the upper chamber.
In the case of the illustrated embodiment, the exhaust and intake
valves 12 and 14 are so designed that they are opened when the pump
piston has reaches the top dead point and when the pump piston has
made its downward stroke to generated strong pressures in the upper
and lower chambers. However, these valves may also be designed so
that they are opened when the pump piston has reached the top dead
point, and lead valves or the like may be additionally installed
with both valves, said additional valves being opened by the
pressures generated in the chambers.
It is also possible to obviate the use of suction valve 14, tappet
19 and rocket arm 20 as shown in FIG. 6 and install, for example, a
solenoid-operated valve or hydraulically operated valve 29
incorporating a spring directly above the position of opening 18
into which stopper 27 is thrust, said valve 29 being opened when
the pump piston is making a downward stroke, closed when the pump
piston reaches the bottom dead point, also closed when the pump
piston is making an upward stroke and opened again when the pump
piston is about to make downward stroke after reaching the top dead
point. In this case, the total volume of tube 15 is designed as the
clearance volume of air pump A. When the pump piston makes an
upward stroke air is compressed also in tube 15, and when it
reaches the top dead point valve 29 is opened to have the highly
compressed air act on the stopper 27 instantly.
Valve 29 shown in FIG. 6 is usually closed by the spring 29'.
According to this illustration, spool 9 of change-over valve C is
switched over to the lower position so that the pump piston can
make a downward stroke after reaching the top dead point and part
of the liquid pressure introduced into the upper chamber of the
pump piston through passage P is led into the valve through
branched passage 30 in order to let the liquid pressure act on
piston 29" which is integral with the valve, so that while the pump
piston is making a downward stroke the valve is kept open resisting
spring 29'. Of course, this valve 29 may be used in place of
exhaust valve 12 in such a way that it is kept open by liquid
pressure while the pump piston is making a downward stroke and
closed by spring 29' while the pump piston is making an upward
stroke.
According to this invention, the greater the entire design, the
greater area the hammer piston requires because of the ratio
between its width and depth. But a large output may be obtained at
will by making the hammer piston hollow.
At the each start of operation, the hammer piston 16 is at the
bottom dead point and blocks lower opening 22 with its side. So it
is impossible to have the positive pressure generated in the lower
chamber of air pump A act on the hammer piston from below. For this
reason, the negative pressure generated in the upper chamber of air
pump is used at the start. This means that it takes time for the
hammer piston to start making regular strokes. In actual operation,
however, this time may be shortened by providing suction valve 31
at the lower end of lower chamber 17b of the impact section by
making a suitable opening there and connecting this valve 31 to
passage 23 so that the positive pressure generated in the lower
chamber 1b of the air pump can act on the hammer piston from below
even if it blocks lower opening 22. Of course, this valve 31 is
closed when hammer piston 16 makes a downward impact stroke and
compresses the air in lower chamber 17b. Therefore, valve 31 does
not interfer with the cushioning of the hammer piston at the bottom
dead point.
Air pump A of the illustrated embodiment is shown as operated by
hydraulic reciprocating actuator B. But this actuator may be a
rotary motor reciprocally driven, for example, by the rod 5 by
means of a crank through a link. The power source for operating air
pump A may be oil pressure obtained from the hydraulic pump driven
by the engine of the operation truck. In this case, while the power
is being used for running the truck the hydraulic pump is stopped
by disengaging the clutch and when the truck is stopped the pump is
operated by engaging the clutch.
* * * * *