close

Вход

Забыли?

вход по аккаунту

?

Патент USA US3036675

код для вставки
May 29, 1962
J. E. SMITH ETAL
3,036,664
INDICATING SYSTEMS FOR VERTICAL LIFTING APPARATUs
Filed Nov. 9, 1959
2 Sheets-Sheet 1
44
40/
United States Patent 0
1
1
C@
3,036,664
Patented May 29, 1962
2
3,036,664
phenomenon may likewise produce an apparent increase
INDICATING SY§TEMS FOR VERTICAL
LIFTING APPARATUS
James E. Smith and Carl J. Berger, Fern Creek, and
in weight in the case of an unloaded pallet and by an
amount which likewise may indicate a lifting operation.
These examples suffice to illustrate the problems en
Charles B. Skinner, Louisville, Ky., assignors to Cheme
tron Corporation, Chicago, 11]., a corporation of Dela
countered in obtaining accurate information in respect
to the number of pay loads lifted for a given trip of the
vehicle in order that there may be achieved the maximum
efficiency of use of the vehicular lifting apparatus.
ware
Filed Nov. 9, 1959, Ser. No. 852,590
11 Claims. (Cl. 187-9)
In accordance with the present invention, there is
This invention relates to apparatus for graphically re
cording the operations of a vehicle and has for an object 10 provided, in conjunction with the hydraulic system for
raising and lowering the lifting forks or platform, a
the provision of a system by means of which there may
pressure-responsive means having an element displace
be recorded the number of pay loads lifted by the ve
able from an unloading position to a loaded position upon
hicle during ‘and in correlation with the distance traveled
a substantial increase of pressure on the hydraulic liquid
by the vehicle and in avoidance of the recording of ap
parent pay-load lifts which, in fact, have not taken place. 15 as occurs upon the lifting of a pay load. In order to
prevent the operation of exhibiting means operable under
This application is a continuation-in-part of our appli
the control of that element by any cause other than the
cation Serial No. 689,700, ?led October 11, 1957 and
now abandoned.
lifting of a pay load, there is arranged a delay means for
.
retarding the movement of the element both from its
Lift trucks and similar equipment used in handling
industrial materials play a very important part in the 20 loaded position and from its unloaded position as a re
sult of transient changes in the pressure of the hydraulic
operation of factories in that assembly lines and the like
liquid. By “transient changes,” we mean changes in the
frequently depend upon lift trucks for the transport of
pressure of the hydraulic liquid which may arise due to
parts and equipment from storage to assembly line and
the transport of ?nished products to storage. Trucks of 25 abnormal or improper lifting of a platform by its hydraulic
operator, or due to passage over bumps as previously
referred to, or other operations which may produce to
some degree the effect of lifting or releasing a pay load
the fork-lift type, as Well as tractor-shovels, earth movers,
and like hydraulically operated lift Vehicles play an im
portant part in construction, as well as in moving ma
terials from one place to another. The efficiency of an
operation as a whole can be greatly increased- if the op
when in fact no true lift or release of a pay load has oc
erators of lift trucks and similar equipment function with
maximum efficiency and with elimination of waste motion,
excess travel and inefficient loading.
Though not limited thereto, the present invention is
particularly ‘applicable to fork-lift trucks and similar 35
equipment widely used in close quarters, such as ware
houses, boxcars, dock installations, ships, and in factories
curred.
The transient changes of pressure will vary
in character and magnitude with different lift trucks.
Accordingly, the lift-delays and the off-delays will be se
lected for best operation of a particular system as used
on the several types of lift trucks. The time-delays may
vary through wide ranges, as from two to thirteen sec
onds, more or less. The lift-delay may be in the range
of from two to four and one-half seconds, ‘with the off
delay between ten to thirteen seconds. However, the off
as described above. As well understood by those skilled
delay will preferably be from three to five times the lift
in the art, the lift truck is designed so that it may lower
its lifting platform or its lifting fork for movement be 40 delay, though in some cases the off-delay setting may
be less than the setting for the lift-delay.
neath a pay load. By pay load, we mean a useful load in
The exhibiting means preferably includes a chart to
contrast with what in terms of recording equipment may
receive _;a permanent record of each pay load lift and in
be referred to as apparent or spurious loads or load indi
correlation with a second record showing the distance
cations. After placement of the platform or fork be
neath a container or below the work itself, the load is 45 traveled by the vehicle during the time it is operated to
lift pay loads and to lower said payloads at particular
then raised and transported to an assigned delivery point.
destinations or stations. The exhibiting means is ar
The load is there lowered, and the operator proceeds to
ranged to be operated, either with or without access
the next station, either with or without a further pay load.
thereto by the operator of the vehicle, to provide a record
When an operator is serving presses or other types of
which may not be known to the operator until the con
machinery, he will frequently take raw material to the
clusion of a particular period of work.
machine ‘for operation and remove a ?nished or semi
For further objects and advantages of our invention,
?nished product. In this manner, the truck is used to
maximum e?icienc .
It is an object of our invention to provide a record not
reference is to be had to the following description taken
in conjunction with the accompanying drawings, in which:
‘FIG. 1 schematically illustrates an exemplary embodi
only of the distance traveled by the truck, but also an 55
ment of the invention; and
FIG. 2 is a view of the cover of the instrument diagram
pleted during each trip by means of a system which elimi
matically shown in FIG. 1 and includes a face view of
nates the recording of false lifts, that is to say, the record
the chart, together with a portion of the timing mech
ing of a lift of a pay load which has not in fact taken
place. In many instances, the forks and unloaded pallet . anism for driving the chart.
Referring now to FIGS. 1 land 2, the invention in one
associated therewith Weigh between about 150 pounds and
form has been shown applied to a lift truck 10 which in
300 pounds. If a truck be operated to lift such unloaded
cludes a fork or lifting platform v11 arranged to he raised
pallet at relatively high speed, the actual weight will pro
and lowered by hydraulic means 12 of conventional de
duce on the indicating equipment an apparent weight ma
terially greater than that which actually exists, with the 65 sign. The operator of the truck It) by means of 1.1 control
valve 13 may apply the output of a pump 14 to the lifting
result that a lift may be falsely recorded. Another in
cylinder of the hydraulic operating means 12 to raise the
stance giving rise to di?iculty is the fact that in operating
platform 11. By rotating the control valve 13, he may
a truck over rough terrain, a bump may cause a pay load
connect the hydraulic lifting means to the discharge pipe
to bounce. While it may not actually rise above the
pallet on which it rests, the apparent weight on the truck 70 15 leading to ‘a reservoir 16. It will be readily understood
by those skilled in the art that the pressure developed by
will be greatly diminished and to a point ‘where an un
accurate record of the number of true pay load lifts com
loading operation may be falsely recorded. This same
the hydraulic liquid will depend upon the load resting
upon the platform 11. In addition, the apparent load will
3,036,664
be increased by reason or‘ the inertia of the parts, particu
larly when the hydraulic operator 12 is raising the plat
form 11 at substantial speed.
In accordance with the present invention, there is pro?‘
vided a pressure-responsive device 17 ?ow-connected to
4
which is rotated in a clockwise direction about its. pivotally
supported end 50a and against the bias of a spring 51.
Through a link 52 the armature 5t) rotates a stylus arm
53 pivoted at one end at '54 to move its stylus 55 in a
counterclockwise direction. Though markers of different
types may be utilized, the stylus ‘55 has been shown in
the hydraulic system, preferably by way of a throttling
the form of a needlepointed stylus adapted to engage
valve 18 shown as of the needle-valve type. The needle
the coated surface of a chart se. Charts of this type are
valve 18 serves as a ?lter and removes high-frequency
Well known to those skilled in the art and generally in
pressure-variations which may appear in the hydraulic
clude a light coating of an opaque para?in mixture or the
system connected to operator 12. The hydraulic pressure 10 like through which the stylus penetrates to produce a
developed at the output of the pump 14 for operator 12
visual indication of the movement of the stylus. While
is also applied to a piston 19 of the pressure-responsive
the chart 56 is shown in phantom in FIG. '1, in order to
device 17. When that pressure exceeds a predetermined
show its positional relationship in respect to the stylus ‘55
value, the piston 19 overcomes the opposing bias of a
and to needleepointed stylus 57, the chart itself is illus
spring 20 to close a switch 21. The opposing pressure of 15 trated in FIG. 2. The records produced by the styli 55
spring 20 may be adjusted by rotating a cap 2'2. to change
and 5'7 appear within circular areas of the chart and may
the initial force developed by the spring ‘29 on piston 19.
be in distinctive colors, the color of the paraffin-coated
Preferably, spring 20 is adjusted so as to render piston 19
chart.
ineffective to close switch 211 unless the pressure on the
The chart 56 is driven at constant speed by a clock
system exceeds a predetermined minimum corresponding 20 motor
59 in a counterclockwise direction as viewed in
to the weight of forks or platform 11 when empty, or
'FIG. 2, the chart having a rectangular center opening
when carrying merely an unloaded pallet. Such predet
which ?ts onto a correspondingly shaped ‘section of a
termincd minimum, however, may be less than the ap
shaft 60 driven by the clock motor.
'
parent load that may be developed during lifting of an
the lifting of a pay load with resultant energization
empty platform or unloaded pallet. By “apparent load,” 25 of After
solenoid operator 45 to move stylus 55 from an inner
we mean the load as it appears to the ‘lift sensing mecha
radial limit to an outer radial limit, it will be understood
nism, including an inertia component due to acceleration
the stylus 55 produces an arcuate mark on the chart ‘at
in case the predetermined minimum load is lifted at rela
the outer radial limit of length related to the duration of
tively high speed (in terms of maximum speed of lift of
30 the pay load lift. When the pay load is iowered onto a
the lifting fork or platform in normal operation), Hence,
notwithstanding adjustment of spring 20' as above de
scribed, such apparent load may be su?‘icient to effect
operation of piston 19 to close switch 21. Recording of
load-receiving structure, the load on the lifting platform
decreases to its unloaded weight. The reduction of hy
draulic pressure on piston 19 permits spring 20 to open
theswitch 21. Relay coil 25 is dcenergized and immedi
a false lift under such circumstances, however, may be
ately opens since ?ap valve 31 is arranged‘ so as not to
avoided by provision of a suitable delay factor as more
‘offer resistance to downward movement of piston 29 of
fully described hereinafter.
’
dashpot 28. Then, after a selected off-delay time afforded
When a true pay load is being lifted, the piston 19 will
by dashpot $7, the contacts 36 of relay 35 open to de
close switch 21 to complete an energizing circuit for-a
energize solenoid operator ‘$5. The stylus 55 is then moved
relay 25 which after a time delay closes its contacts 26.
by spring 51 and by gravity to its inner radial limit.
40
As diagrammatically illustrated, when‘relay 25 is ener
The foregoing operations'will now be brie?y sum
gized, a tension spring 27 applies a closing force upon
marized in terms of the resultant record on the chart 56,
contact 26. This contact is restrained by a dashpot 28
as shown in FIG. 2,. At the beginning of a work period,
which includes a piston 29 having an opening 30 therein
it may be assumed that the point 55a on chart 56 was at
normally closed by a ?ap valve 31. The speed of move
location of the stylus 55; that the stylus 57 Was at
ment of the piston 29 and of contact 26 may be regulated 45 the
the
point ‘57a; and that both styli were coincident with
by the setting of a throttling valve 3'2. In one embodi
radius 61 of the chart 56. After the ?rst lift of a pay
ment of the mechanism of FIG. 1 as used in industrial
load occurred, the stylus 5‘5 moved radially of the chart
plant material handling systems, the time-delay for the
to an outermost position at 55b. At the point 550, the
closing of the contacts 26 may, for example, range from
‘stylus 55 returned to its innermost position 55d, indicating
two seconds to four and one-half seconds or more. This 50 the unloading of the truck. By means of an odometer
time-delay is important in order to avoid indications of
driving arrangement (later described) for the stylus 57,
false lifts, i.e., lift indications due to variations in pres
the distance traveled may be read either from the graph
sure on the hydraulic liquid as the result of causes other
than the lifting of true pay loads.
57b on chart 56 or from a distance indicator 62 (FIG.‘ 1)
through the opening 62a of the cover 64 of the
Upon expiration of the selected time interval, the cir 55 visible
instrument
housing '63. As shown on the chart, the
cuit through the contacts 216 is completed to energize a
truck traveled “unloaded” during the appearance of the
relay 35 which immediately completes a circuit through
segment 55d after which it made two pay load lifts in
near time-proximity one to the other. The relatively long
section 55c shows a relatively long distance of travel
throttling valve 41'for producing a time-delayed opening 60 outer
with a pay load. Thus, the chart 56 provides an accurate
of the circuit through its contacts 36. While the energiz
record of the number of lifts in correlation with the dis-v
ing circuits for the relays 2-5-and 35 are readily traced by
tance traveled by the truck with and without pay loads.
its contacts 36. This relay includes a dashpot 37 having
a piston 38, a ?ap valve 39, a tension spring 40, and a
inspection between supply lines '43 and 44, it is to be
Referring again to FIG. 1, the odometer drive has been
noted that upon the closing of contacts 36, there is com
pleted an energizing circuit for a solenoid operator 45 of 65 illustrated as including a friction wheel 70 driven by one
of the wheels 71 of the lift truck 19. Through a suitable
the recording mechanism. This circuit may be traced
connection indicated by the broken line 72, there is driven
from supply line 43 by way of conductor 46, contacts 36,
a worm 73 which through worm wheel 74 drives a shaft
conductor 47, the solenoid operator 45, and by conductor
75.
This shaft, through a worm 77, drives a worm wheel
48 to the other supply line 44. Whenever there is being
recorded the lifting of a pay load, a signal lamp 49 (con 70 76. The Worm wheel 76 drives a shaft 78‘ which ‘has
secured to it an operating cam '79 for a crank arm 80‘,
nected in shunt with the solenoid operator 45) is ener~
one end of which carries the stylus 57. The other arm
gized. This lamp when energized will illuminate a window
81 of the crank engages the cam 7 9, the crank arm itself
49a, FIG. 2, provided in the cover 64.
benig pivoted by a pin 82 and biased for clockwise rota
Upon energization of the solenoid operator 45, an at
tion
by a spring 83.
tractive force isexented upon its associated armature 'ss 75
5
3,036,664
The shaft 78 carries a worm 85 which drives a worm
6
wheel 86 and through a shaft 87 operates the distance
upward acceleration to platform 11 which will result in
indicator 62 illustrated as a conventional odometer pro
vided with a plurality of indicating discs on which appear
will be reflected by momentary decrease in the hydraulic
digits for indicating the distance traveled.
In the following summary of the operation of the in
vention, the manner in which it functions to take care of
a number of conditions encountered in the daily opera
tion of a lift truck will be set forth. There will ?rst be
an apparent decrease in the load on that platform. This
pressure. In response thereto, the switch 21 will open and
so will the relay 25. The opening of the contacts 26,
however, though they deenergize the operating coil of
relay 35, does not result in opening of the circuit through
its contacts 36. The time-delay opening of contacts 36,
as determined by the setting of throttle valve 41, main
summarized the operations which may occur with an un 10
tains energization of solenoid 45 and thus maintains the
loaded platform, i.e., one not carrying a pay load. With
the parts in the illustrated positions, particularly the valve
13 in a pressure-applying position, the hydraulic means
12 will be eifective in raising the movable parts of the hy
draulic system including the platform 11.
Thus, the
parts will be moving upwardly. If the parts are moved
upwardly at relatively high speed, the apparent load
stylus 55 in a position indicating there is a pay load on
platform 11. The time-delay for the opening of the con
tacts 36 in one industrial embodiment of the system of
FIG. 1 is set for a delay of between ten seconds and
thirteen seconds. It is to be understood, however, that de
lay times, for both lift-delay and off-delay, will be utilized
depending upon the particular characteristics of the system
(previously discussed) as registered on the pressure-re
and the conditions of operation of the lift truck 10. For
sponsive device 17 may be much greater than the actual
load. It is for this reason that weighing systems are not 20 some operations, the times may be quite short, and for
other operations, the times will be increased to the upper
suited to the purposes of the present invention. Though
limits or beyond in order to achieve accurate recording of
the spring 20 has been set to offset the pressure required
pay load lifts, as well as the unloading of a load at a
from the pump 14 to overcome the dead weight of the
destination for the truck 10.
moving parts, nevertheless upon rapid acceleration of the
Further in connection with the operations, it will be
platform, the piston 19 will be displaced ‘against the force
understood that even if the truck 10 be traveling without
of the spring 20 to close the contact 21. Though the op
a pay load over rough terrain, the effect of a bump may
erating coil of relay 25 is thereby energized, its associated
work in both directions; that is to say, the weight of the
contacts 26 are not closed by reason of the delay intro
moving parts including the paltform 1.1 may be effective
duced by the dashpot 28. This delay is preferably of an
order which prevents closure of the circuit through switch 30 to produce a false indication of a pay load lift, as well ‘as to
indicate the unloading of a pay load, when a change in
contacts 26 for a time interval during which the unload
pressure occurs by reason of the inertia elfect of the load
ed platform 11 will be raised to a predetermined height,
on the hydraulic pressure system. However, by the intro
a height which would render the empty platform apparent
duction of the time-delays, such false indications are over
to any observer. Should an operator desire to attempt to
produce a false indication of a lift of a pay load, it will 35 come, whether due to an attempt by the operator to out
wit the system, or whether due to variations of hydraulic
be seen that he could not achieve that objective without
raising the platform 11 to a height which would undoubt
edly call attention to his effort by the foreman or other
assigned observer.
pressure because of bumps and the like.
With further reference to the control valve 13, it is to
be understood that it will be operable to several control
If desired, the delay means 28 for relay 25 may be 40 positions. When it is moved to a position to inter
connect the pump 14- with the discharge pipe 15, the pump
set for a longer period of time, enough for the platform
will simply circulate hydraulic liquid from the reservoir 16
11 to be raised to the normal height for transport of a
through the return circuit. There will be maintained
pay load. Thus, there is considerable ?exibility a?orded
closed the hydraulic system 12 thus to maintain the plat
by the system in that there can be included in the delay
form 11 in its elevated position. When the valve 13 is
time a part of the travel time, or that delay time may be
diminished to a lifting time corresponding with that re 45 rotated to interconnect the hydraulic system 12 with the
discharge pipe 15 (the valve 13 in a position 180° from
quired for achieving the aforesaid detectable height of the
that illustrated)‘, hydraulic liquid will be discharged
platform 11.
through return pipe 15 from both the hydraulic system and
Assuming now a pay load on the platform ‘11, the
from the pump 14.
following occurs. The truck operator manipulates valve
Now that we have explained the principles of opera
13 to raise the pay load. After the selected time interval
tion of our invention, it will be obvious to those skilled
of, say, three seconds, the circuit through the contact 26 is
in the art that various changes and modi?cations may be
closed to energize the coil of the relay 35. This relay im
made therein and that certain features may be used in the
mediately closes to energize the solenoid 45 to produce
absence of other features, all within the spirit and scope
the indication on the chart 56 that a pay load has been
of the appended claims.
lifted. The truck will then be placed in operation to 55 .What is claimed is:
transport the load to its destination, and there will be
1. In a load-lifting vapparatus having a ?xed frame, a
recorded on the chart as described above the record 57b
load-supporting platform and hydraulic means including a
indicating the distance traveled by the truck. It will be
hydraulic liquid for raising and lowering said platform
observed that the record 571) is one that progresses from
relative to said ?xed frame, the combination of pressure
an inner circular limit to an outer circular limit and back
responsive means including a device ?uid-connected to said
to the inner circular limit, this representing the movement
hydraulic means, said device having an element displace
of the stylus 57 by the cam 79. When the stylus has
able from an unloaded position to a loaded position upon
been displaced from the inner to the outer limit, is will be
a substantial increase of pressure on said hydraulic liquid
known that the truck has traveled a predetermined dis
tance, for example, 2500 feet. When the stylus moves 65 as occurs upon lifting of a load and returnable to said un
loaded position upon a substantial decrease of said pres
from the outer limit to the inner limit, it will be known
sure, exhibiting means operable under the control of said
that the truck has traveled another 2500 feet. Obviously,
element each time there occurs said substantial changes of
the gear ratios can be selected for the operation of the
pressure for producing distinctive indications that a load
stylus between its two limits for lesser or greater distances.
What has been said above in respect to false indica 70 has been lifted and lowered, ‘and delay means for pre
venting movement in both directions of said element as be—
tions of pay load lifts likewise applies to false indica
tween said loaded and said unloaded positions for pre
tions of the unloading of the platform 11. This can occur
venting the recording of changes in the pressure of said
by reason of the passage of the truck 10 over a rough
travel path where the wheels of the truck may apply an 75 hydraulic liquid due to operations other than the lifting
and lowering of a pay load carried by said platform.
3,036,66d
7
2. In a load-lifting apparatus having a ?xed frame, a
load-supporting platform and hydraulic means including a
hydraulic liquid for raising and lowering said platform
relative to said ?xed frame, the combination of pressure
responsive means including a device ?uid-connected to
said hydraulic means, said device having an element dis
placeable from an unloaded position to a loaded position
placement of said arm from an unloaded position to a
loaded position for a time interval less than the delay in
the displacement of said arm from its loaded position to
its unloaded position whereby there are avoided false
indications by said exhibiting means of the raising and
lowering of pay loads.
7. A recording system for use with a wheeled vehicular
lifting apparatus having a lift platform, means for sup
upon a substantial increase of pressure on said hydraulic
plying hydraulic ?uid under pressure for raising said plat
liquid as occurs upon lifting of a load and returnable to
form and means for driving at least one wheel of said
10
said unloaded position upon a substantial decrease of
apparatus; said recording system including means for sup
said pressure, exhibiting means having an actuating arm
porting and moving a chart at a fixed speed and in cor
operable under the control of said element in one direc
relation With the passage of time, a stylus, means sup
tion upon an increase in pressure and in the opposite
porting said stylus for producing a record on said chart,
direction upon a decrease in pressure for producing dis
means including a device responsive to said liquid pres
15
tinctive indications thata load has been lifted and low
sure applied in raising and lowering the platform of the
ered, and delay means actuated in response to said changes
lifting apparatus and having an element displaceable
in pressure for delaying displacement of said arm in one
from an unloaded position to a loaded position upon a
direction by a greater time interval than in the opposite
substantial increase of pressure on the liquid as occurs
direction whereby there are avoided false indications by
upon lifting of the load and returning to said unloaded
said exhibiting means of the raising and lowering of pay 20 position upon a substantial decrease of the liquid pres
loads.
sure, a driving connection between said element and said
3. The combination of claim 2 in which said exhibiting
means includes a chart-carrying element, means for driv
ing the chart at constant speed, a chart-marker for en
gaging said chart, and means operable in accordance with
change of position of said arm for moving said marker
relative to said chart for recording load-lifts made by
said platform.
4. The combination set forth in claim 3 in which a
second chart-marker is disposed for engagement with
said chart, and means for moving said second chart-mark
stylus for producing distinctive indications on the chart
that a load has been lifted and lowered, and delay means
for preventing movement in both directions of said ele
ment as between said loaded and unloaded positions for
preventing the recording of changes in the pressure of
said hydraulic liquid due to operations other than the
lifting and lowering of a pay-load carried by the lift plat
form of the vehicular apparatus.
8. The recording system of claim 7 in which a solenoid
is connected to drive said stylus and in which said delay
er relative to said chart for recording thereon travel of
means includes time delay relays for regulating the move
the load-lifting apparatus with respect to time thereby
ment of said stylus as between loaded and unloaded posi
to correlate the number of lifts with respect to time and
tions for preventing‘ said recording of changes in the pres
35
with respect to the distance traveled by the load-lifting
sure of said hydraulic liquid due to operations other than
apparatus.
the lifting and lowering of the payload carried by the lift
5. In a lifting truck having a ?xed frame,‘ a load-sup
platform of the lifting apparatus.
porting platform and hydraulic means including a hy
9. The recording system of claim 8 in which there is
draulic liquid for raising and lowering said platform
provided
an energizing circuit for one of said time delay
relative to said ?xed frame, the combination of pressure 40 relays closed in response to operation of said pressure
responsive means including a device which is ?uid-con
responsive means, said last-named time delay relay having
nected to said hydraulic liquid, said device having an
provisions for delaying its operation in one direction
element displaceable from an unloaded position to a
thereby to delay deenergization of the solenoid after
loaded position upon substantial change of pressure on
energization thereof.
45
said hydraulic liquid as occurs upon lifting of a load,
10. The recording system of claim 7 in which there is
indicating means operable under the control of said ele
associated with said chart a second stylus for recording
ment each time there occurs said substantial change of
thereon the distance traveled by a wheel of the lifting
pressure for producing a distinctive indication that a load
apparatus, said pressure-responsive means including a
has been lifted, and delay means for preventing return
pressure switch, a solenoid having a movable part form
of said element from said loaded position to said unload 50 ing said displaceable element and having a driving con
ed position as a result of a transient decrease in said pres
nection with said ?rst-named stylus, an electrical circuit
sures on said hydraulic liquid, said delay means being
including said solenoid and said pressure switch, said
ineffective to delay return of said element to said un
delay means including a ?rst time delay relay in said
loaded position after disappearance for a predetermined
time interval of said substantial pressure on said hydraulic
liquid, whereby there are avoided false indications by said
indicating means of load-lifts by reason of travel of the
truck over a rough surface with resultant transient loss
circuit operable to effect the delay between the closing of
said pressure switch and the energization of said sole
noid and a second time delay relay in’ said circuit oper
able to effect a delay between the opening of said pres
sure switch and the deenergization of said solenoid.
of load on said platform.
'
V
11. The recording system of claim 7 in which a second
6. In a 1oad~lifting apparatus having a ?xed frame, 60 chart-marker is disposed for engagement with said chart,
a load-supporting platform and hydraulic means includ
and means for moving said second chart-marker relative
ing a hydraulic liquid for raising and lowering said plat
to said chart for recording thereon travel of the load
form relative to said ?xed frame, the combination of
lifting apparatus with respect to time thereby to corre
pressure-responsive means including a device which is
late the number of lifts with respect to time and with
?uid-connected to said hydraulic means, said device hav 65 respect to the distance traveled by the load-lifting ap
ing an'element displaceable from an unloaded position
paratus.
to a loaded position upon a substantial increase of pres
sure on said hydraulic liquid as occurs upon lifting of a
References Cited in the ?le of this patent
load and returnable to said unloaded position upon a sub
UNITED STATES PATENTS
stantial decrease of said pressure, exhibiting means hav 70
ing an actuating arm operable under the control of said
element each time there occurs said substantial changes of
pressure for producing distinctive indications that a load
has been lifted and lowered, and delay means actuated
in response to said changes in pressure for delaying dis 75
1,261,508
2,307,961
Gamble _____________ __ Apr. 2, 1918
Schellentrager _______ __ Jan. 12, 1943
2,722,411
Philbrook __‘ _________ __ Nov. 1, 1955
2,856,176
2,883,177
Cooper _____________ __ Oct. 14, 1958
Dannehl ____________ __ Apr. 21, 1959
Документ
Категория
Без категории
Просмотров
0
Размер файла
902 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа