US3827587A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic self-leveling forks
Assignee: Dempster Systems Inc
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Filing: 1969-07-31
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Granted: 1974-08-06
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Expires: 1989-07-31
Abstract
Abstract Apparatus for automatically leveling the forks of vertically moveable hoist arms. In a typical embodiment, the arms are used on refuse collection vehicles for lifting and dumping detachable containers into the body of the vehicle. The arms are pivotally mounted at one end on the vehicle and the opposite ends of the arms has fork devices for engaging brackets on opposite end walls of the detachable containers. Swinging movement of the arms and of the forks is accomplished by means of hydraulic cylinders or rams. A hydraulic pump supplies fluid under pressure to the arm cylinders for raising the arms. A portion of the fluid is conducted to the fork cylinder by means of a gear or vane type flow divider, so that the rate of extension of the piston in each fork cylinder is at a predetermined ratio of the displacement of the arm piston. This causes the forks to swing downwardly at a predetermined rate while the arms are being raised toward a dumping position, thereby maintaining the container approximately horizontal until it is in a position to be inverted for dumping.
Inventors
- 👤 H Liberman
- 👤 S Harvey
- 👤 S Voorhees
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 16:40
CPC Classifications
B; B65; B65F; B65F3/00; B65F3/02; B65F3/04; B65F2003/0263; B65F2003/0279
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
268 words
A method of maintaining a detachable container substantially horizontal during upward swinging movement of a lifting arm, said container being attached to said arm by a fork pivotally mounted on said arm, said swinging movement being effected by a hydraulic ram with a reciprocating piston therein and swinging movement of said fork relative to said arm being effected by a second ram with a moveable piston therein connected between said fork and said arm, said method comprising: conducting fluid under pressure from a source to one end of said arm cylinder, thereby urging said arm piston in the direction of upward swinging movement of said arm; conducting fluid under pressure from a source to one end of said fork cylinder, thereby urging said fork piston in the direction of downwardly swinging movement of said fork; restricting the discharge of fluid from said arm cylinder and said fork cylinder, and regulating the rate of flow of fluid to said fork cylinder in proportion to the rate of flow of fluid to said arm cylinder, said regulating step including causing fluid discharged from said fork cylinder to flow through a first control zone, and including causing fluid from said source to flow through a second control zone, fluid from said control zones flowing to said arm cylinder, said first and second control zones restricting the volume rate of flow through said first zone at a rate of flow that is at a predetermined proportion of the rate of flow through said second zone, whereby the fork swings downwardly at a predetermined rate during the upward swinging movement of the arm.
Claim 2
Independent Claim
268 words
A method of maintaining a detachable container substantially horizontal during upward swinging movement of a lifting arm, said container being attached to said arm by a fork pivotally mounted on said arm, said swinging movement being effected by a hydraulic ram with a reciprocating piston therein and swinging movement of said fork relative to said arm being effected by a second ram with a moveable piston therein connected between said fork and said arm, said method comprising: conducting fluid under pressure from a source to one end of said arm cylinder, thereby urging said arm piston in the direction of upward swinging movement of said arm; conducting fluid under pressure from a source to one end of said fork cylinder, thereby urging said fork piston in the direction of downwardly swinging movement of said fork; restricting the discharge of fluid from said arm cylinder and said fork cylinder, and regulating the rate of flow of fluid to said fork cylinder in proportion to the rate of flow of fluid to said arm cylinder, said regulating step including causing fluid discharged from said fork cylinder to flow through a first control zone, and including causing fluid from said source to flow through a second control zone, fluid from said control zones flowing to said arm cylinder, said first and second control zones restricting the volume rate of flow through said first zone at a rate of flow that is at a predetermined proportion of the rate of flow through said second zone, whereby the fork swings downwardly at a predetermined rate during the upward swinging movement of the arm.
Claim 3
Dependent Claim
36 words
The method according to claim 1 including trapping said fluid on opposite sides of said arm cylinder and said fork cylinder when flow from said sources stops, whereby said fork and said arm are held stationary.
Claim 4
Dependent Claim
40 words
The method according to claim 1 wherein said regulating step includes dividing flow of fluid from the opposite end of said arm cylinder and supplying a predetermined portion of said divided fluid to said one end of said fork cylinder.
Claim 5
Dependent Claim
41 words
The method according to claim 3 wherein said restricting step includes interrupting flow of fluid from said arm cylinder to a zone of low pressure in response to a reduction in pressure of fluid from said source to said arm cylinder.
Claim 6
Dependent Claim
61 words
The method according to claim 1 wherein said restricting step includes conducting fluid discharged from said opposite end of said fork cylinder to said one end of said fork cylinder, and said regulating step includes controlling the rate of discharge of fluid from said fork cylinder opposite end in proportion to the rate of flow of fluid to said arm cylinder.
Claim 7
Dependent Claim
24 words
The method according to claim 5 including said fluid from a common source through independent paths to said fork cylinder and said arm cylinder.
Claim 8
Dependent Claim
50 words
The method according to claim 1 wherein said regulating step includes conducting fluid from said source independently to said arm cylinder and said fork cylinder and controlling the rate of flow of fluid in one path in direct proportion to the rate of flow of fluid in the other path.
Claim 9
Dependent Claim
36 words
The method according to claim 7 including combining fluid from said separate paths and supplying said combined fluid to said arm cylinder after the piston of said fork cylinder has reached its maximum extent of travel.
Claim 10
Independent Claim
323 words
A method of maintaining a detachable container substantially horizontal during upward swinging movement of a lifting arm, said container being attached to said arm by a fork pivotally mounted on said arm, said swinging movement being effected by a hydraulic ram with a reciprocating piston therein and swinging movement of said fork relative to said arm being effected by a second ram with a moveable piston therein connected between said fOrk and said arm, said method comprising: conducting fluid under pressure from a source to one end of said arm cylinder, thereby urging said arm piston in the direction of upward swinging movement of said arm; conducting fluid under pressure from a source to one end of said fork cylinder, thereby urging said fork piston in the direction of downwardly swinging movement of said fork; restricting the discharge of fluid from said arm cylinder and said fork cylinder, and regulating the rate of flow of fluid to said fork cylinder in proportion to the rate of flow of fluid to said arm cylinder, said regulating step including causing fluid discharged from said fork cylinder to flow through a first control zone, and including causing fluid from said source to flow through a second control zone, fluid from said control zones flowing to said arm cylinder, said first and second control zones restricting the volume rate of flow through said first zone at a rate of flow that is at a predetermined proportion of the rate of flow through said second zone, whereby the fork swings downwardly at a predetermined rate during the upward swinging movement of the arm, transferring energy from fluid discharging from said fork cylinder to fluid flowing from said source to said arm cylinder whereby the force exerted by said arm cylinder is increased, said regulating step includes passing fluid through a rotary positive displacement device in each of said separate paths and connecting together the rotors of said devices.
Claim 11
Independent Claim
323 words
A method of maintaining a detachable container substantially horizontal during upward swinging movement of a lifting arm, said container being attached to said arm by a fork pivotally mounted on said arm, said swinging movement being effected by a hydraulic ram with a reciprocating piston therein and swinging movement of said fork relative to said arm being effected by a second ram with a moveable piston therein connected between said fOrk and said arm, said method comprising: conducting fluid under pressure from a source to one end of said arm cylinder, thereby urging said arm piston in the direction of upward swinging movement of said arm; conducting fluid under pressure from a source to one end of said fork cylinder, thereby urging said fork piston in the direction of downwardly swinging movement of said fork; restricting the discharge of fluid from said arm cylinder and said fork cylinder, and regulating the rate of flow of fluid to said fork cylinder in proportion to the rate of flow of fluid to said arm cylinder, said regulating step including causing fluid discharged from said fork cylinder to flow through a first control zone, and including causing fluid from said source to flow through a second control zone, fluid from said control zones flowing to said arm cylinder, said first and second control zones restricting the volume rate of flow through said first zone at a rate of flow that is at a predetermined proportion of the rate of flow through said second zone, whereby the fork swings downwardly at a predetermined rate during the upward swinging movement of the arm, transferring energy from fluid discharging from said fork cylinder to fluid flowing from said source to said arm cylinder whereby the force exerted by said arm cylinder is increased, said regulating step includes passing fluid through a rotary positive displacement device in each of said separate paths and connecting together the rotors of said devices.
Claim 12
Dependent Claim
155 words
Apparatus for coordinating swinging movement of a lifting arm and a fork hingedly mounted on said arm, said movement being effected by a hydraulic ram having a moveable piston connected with said arm and a hydraulic ram having a moveable piston and being connected between said arm and said fork, said apparatus comprising means for conducting fluid under pressure along a first path and along a second path, means for connecting said first path with said arm cylinder at one side of said piston, means for connecting the second path with said fork cylinder at one side of said piston, and means in said paths for regulating the flow of fluid along said first and second paths in a predetermined proportion to each other independently of the relative sizes of said cylinders, whereby displacement of the pistons in said arm cylinder and said fork cylinder occurs simultaneously and at predetermined rates relative to each other.
Claim 13
Dependent Claim
155 words
Apparatus for coordinating swinging movement of a lifting arm and a fork hingedly mounted on said arm, said movement being effected by a hydraulic ram having a moveable piston connected with said arm and a hydraulic ram having a moveable piston and being connected between said arm and said fork, said apparatus comprising means for conducting fluid under pressure along a first path and along a second path, means for connecting said first path with said arm cylinder at one side of said piston, means for connecting the second path with said fork cylinder at one side of said piston, and means in said paths for regulating the flow of fluid along said first and second paths in a predetermined proportion to each other independently of the relative sizes of said cylinders, whereby displacement of the pistons in said arm cylinder and said fork cylinder occurs simultaneously and at predetermined rates relative to each other.
Claim 14
Dependent Claim
83 words
The apparatus according to claim 10 wherein said other path communicates between said arm cylinder at the opposite side of said piston and said fork cylinder at said one side of said piston, said regulating means including a flow regulating device in said second path directing a predetermined portion of fluid from said arm cylinder opposite end to said fork cylinder and, whereby displacement of the fork piston occurs at a proportionate rate to the displacement of the piston in the arm cylinder.
Claim 15
Dependent Claim
192 words
Apparatus for coordinating swinging movement of a lifting arm and a fork, hingedly mounted on said arm, said movement being effected by a hydraulic ram having a moveable piston connected with said arm and a hydraulic ram having a moveable piston and being connected between said arm and said fork, said apparatus comprising means for conducting fluid under pressure along a first path and along a second path, means for connecting said first path with said arm cylinder at one side of said piston, means for connecting the second path with said fork cylinder at one side of said piston, and means in said paths for regulating the flow of fluid along said first and second paths in a predetermined proportion to each other independently of the relative sizes of said cylinders, whereby displacement of the pistons in said arm cylinder and said fork cylinder occurs simultaneously and at predetermined rates relative to each other, said regulating means includes a flow regulating device capable of operating alternatively as a pump and as a motor, and conduit mEans connecting said fork cylinder at the opposite side of said piston with said regulating device.
Claim 16
Dependent Claim
192 words
Apparatus for coordinating swinging movement of a lifting arm and a fork, hingedly mounted on said arm, said movement being effected by a hydraulic ram having a moveable piston connected with said arm and a hydraulic ram having a moveable piston and being connected between said arm and said fork, said apparatus comprising means for conducting fluid under pressure along a first path and along a second path, means for connecting said first path with said arm cylinder at one side of said piston, means for connecting the second path with said fork cylinder at one side of said piston, and means in said paths for regulating the flow of fluid along said first and second paths in a predetermined proportion to each other independently of the relative sizes of said cylinders, whereby displacement of the pistons in said arm cylinder and said fork cylinder occurs simultaneously and at predetermined rates relative to each other, said regulating means includes a flow regulating device capable of operating alternatively as a pump and as a motor, and conduit mEans connecting said fork cylinder at the opposite side of said piston with said regulating device.
Claim 17
Dependent Claim
30 words
Apparatus according to claim 12 including means for combining flow from said separate paths and conducting said combined flow to said arm cylinder at said one side of said piston.
Claim 18
Dependent Claim
23 words
The apparatus according to claim 12 including means for conducting fluid from said second path regulating device to a zone of lower pressure.
Claim 19
Dependent Claim
25 words
The apparatus according to claim 14 wherein said zone of lower pressure is the interior of said fork cylinder at one side of said piston.
Claim 20
Dependent Claim
154 words
In a container hoist of the type having a swinging arm for lifting a container attached to the arm by a fork, said fork being pivotally mounted on said arm for swinging relative to the arm, said arm and fork each having a fluid operated double acting ram, control means for said rams comprising; a source of fluid under pressure, first means for selectively conducting said fluid to said arm ram on one side of the ram piston, second means for conducting said fluid from the opposite side of said arm ram piston to said fork ram on one side of the fork ram piston, said second conducting means including means for diverting a predetermined portion of said fluid from said second conducting means, whereby said fork ram piston is displaced in response to displacement of said arm ram piston at a predetermined rate to maintain said fork level during lifting of said arm.
Claim 21
Dependent Claim
154 words
In a container hoist of the type having a swinging arm for lifting a container attached to the arm by a fork, said fork being pivotally mounted on said arm for swinging relative to the arm, said arm and fork each having a fluid operated double acting ram, control means for said rams comprising; a source of fluid under pressure, first means for selectively conducting said fluid to said arm ram on one side of the ram piston, second means for conducting said fluid from the opposite side of said arm ram piston to said fork ram on one side of the fork ram piston, said second conducting means including means for diverting a predetermined portion of said fluid from said second conducting means, whereby said fork ram piston is displaced in response to displacement of said arm ram piston at a predetermined rate to maintain said fork level during lifting of said arm.
Claim 22
Dependent Claim
26 words
The apparatus according to claim 16 including means for controlling flow of fluid to opposite sides of said fork piston independently of said first conducting means.
Claim 23
Dependent Claim
98 words
The apparatus according to claim 16 including a reservoir, and wherein said first means includes a control valve means communicating with said source of fluid and said reservoir and said arm ram, and includes fluid transfer means operatively connected to said control valve means and said fork ram to accommodate fluid flow therebetween, said control valve means having a first control element shiftable to a transfer position directing pressure fluid to the arm ram, said means for diverting including flow divider means for directing a predetermined portion of said fluid from said arm ram to said fork ram.
Claim 24
Dependent Claim
44 words
The apparatus according to claim 18 further comprising check valve means located in said fluid transfer means intermediate said flow divider means and the second motor adapted to prevent reverse flow through said transfer means from the second motor to said control valve means.
Claim 25
Dependent Claim
71 words
The apparatus according to claim 18 further comprising second control valve means communicating with said source of fluid and said reservoir and said fork ram, said second valve means having an associated second control element shiftable to direct fluid from said source of fluid to said fork ram to actuate the same and to override actuation of the fork ram by said predetermined portion of fluid from said flow divider means.
Claim 26
Dependent Claim
41 words
The apparatus according to claim 18 wherein said flow divider means communicates with the reservoir through a discharge conduit, and directs said predetermined portion to said fork ram the remainder portion of said fluid to said reservoir through said discharge conduit.
Claim 27
Dependent Claim
182 words
In a container hoist of a type having a swinging arm for lifting a container attached to the arm by a fork, said fork being pivotally mounted on said arm for swinging relative to the arm, said arm and said fork each having a fluid operated double acting ram, control means for said rams comprising; valve means for controlling movement of the arm ram, valve means for controlling movement of the fork ram, first means for conducting fluid from said arm valve to said arm ram on one side of the piston, second conduit means for conducting fluid from the arm valve to fork ram at one side of the piston, third conduit means conducting fluid from the fork ram at the opposite side of the piston to said arm ram at said one side of the piston, and flow regulating means in said first and third condUit means for regulating the rate of flow through said first and third conduit means in a predetermined proportion, whereby downward swinging movement of the fork is coordinated with upward swinging movement of the arm.
Claim 28
Dependent Claim
182 words
In a container hoist of a type having a swinging arm for lifting a container attached to the arm by a fork, said fork being pivotally mounted on said arm for swinging relative to the arm, said arm and said fork each having a fluid operated double acting ram, control means for said rams comprising; valve means for controlling movement of the arm ram, valve means for controlling movement of the fork ram, first means for conducting fluid from said arm valve to said arm ram on one side of the piston, second conduit means for conducting fluid from the arm valve to fork ram at one side of the piston, third conduit means conducting fluid from the fork ram at the opposite side of the piston to said arm ram at said one side of the piston, and flow regulating means in said first and third condUit means for regulating the rate of flow through said first and third conduit means in a predetermined proportion, whereby downward swinging movement of the fork is coordinated with upward swinging movement of the arm.
Claim 29
Dependent Claim
226 words
In a container hoist of a type having a swinging arm for lifting a container attached to the arm by a fork, said fork being pivotally mounted on said arm for swinging relative to the arm, said arm and said fork each having a fluid operated double acting ram, control means for said rams comprising: valve means for controlling movement of the arm ram, valve means for controlling movement of the fork ram, first means for, conducting fluid from said arm valve to said arm ram on one side of the piston, second conduit means for conducting fluid from the arm valve to fork ram at one side of the piston, third conduit means conducting fluid from the fork ram at the opposite side of the piston to said arm ram at said one side of the piston, and flow regulating means in said first and third conduit means in a predetermined proportion, whereby downward swinging movement of the fork is coordinated with upward swinging movement of the arm, said regulating means includes a rotary positive displacement device in said first conducting means and a second positive displacement rotary device in said third conducting means, each of said devices having a rotor, and shaft means joining together said rotors for rotation at the same speed, whereby energy may be transferred from one rotor to the other.
Claim 30
Dependent Claim
226 words
In a container hoist of a type having a swinging arm for lifting a container attached to the arm by a fork, said fork being pivotally mounted on said arm for swinging relative to the arm, said arm and said fork each having a fluid operated double acting ram, control means for said rams comprising: valve means for controlling movement of the arm ram, valve means for controlling movement of the fork ram, first means for, conducting fluid from said arm valve to said arm ram on one side of the piston, second conduit means for conducting fluid from the arm valve to fork ram at one side of the piston, third conduit means conducting fluid from the fork ram at the opposite side of the piston to said arm ram at said one side of the piston, and flow regulating means in said first and third conduit means in a predetermined proportion, whereby downward swinging movement of the fork is coordinated with upward swinging movement of the arm, said regulating means includes a rotary positive displacement device in said first conducting means and a second positive displacement rotary device in said third conducting means, each of said devices having a rotor, and shaft means joining together said rotors for rotation at the same speed, whereby energy may be transferred from one rotor to the other.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-08-05 | 1978-02-04 | 1978-08-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-08-05 | 1982-02-04 | 1982-08-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-08-05 | 1986-02-04 | 1986-08-06 | $7700.00 | Window Closed / Lapsed |