US3657969A

US3657969A - Hydraulic control system for extensible crane

Info

Publication number: US3657969A
Application number: US53848A
Authority: US
Inventors: Joseph P Wirkus
Original assignee: JI Case Co
Current assignee: Case LLC
Priority date: 1970-07-10
Filing date: 1970-07-10
Publication date: 1972-04-25
Anticipated expiration: 1989-04-25
Also published as: CA921800A; GB1310454A

Abstract

A hydraulic control system for producing synchronized extension and retraction of at least three crane sections which includes a first cylinder and piston rod assembly with the cylinder being attached to an intermediate section of the crane and the piston rod connected to a first or fixed crane section. A second cylinder is connected to the intermediate section and its piston rod is attached to a third section with a fluid divider supported on the second section and having first and second outlet ports, respectively, connected to one end of each of the cylinders and an inlet port. A first flow passage means extends through the first cylinder and piston rod assembly and is connected to the inlet port of the flow divider with a second flow passage means extending through the first piston rod and communicating with the opposite end of the first and second cylinders so that a pressured fluid source connected to one flow passage and a reservoir connected to the other flow passage means will extend the assemblies and the crane sections with the flow divider means producing synchronized movement of the crane sections. The control circuit further includes means for blocking flow from one end of each of the cylinders when the pressured fluid in the first fluid passage means is below a predetermined level. In addition, the flow divider means includes pressure responsive check valves providing unidirectional flow in opposite directions between the two outlet ports so as to interconnect the two ports when the pressure in either of the outlet ports exceeds a predetermined level.

Description

United States Patent Wirkus [451 Apr. 25, 1972 HYDRAULIC CONTROL SYSTEM FOR cludes a first cylinder and piston rod assembly with the EXTENSIBLE CRANE cylinder being attached to an intermediate section of the I crane and the piston rod connected to a first or fixed crane Inventor! J p i Schofield, section. A second cylinder is connected to the intermediate section and its iston rod is attached to a third section with a [73] Ass'gnee' Cm Company fluid divider sugported on the second section and having first 22 Fi J ly), 1970 and second outlet ports, respectively, connected to one end of r each of the cylinders and an inlet port. A first flow passage PP'- Nod 531848 means extends through the first cylinder and piston rod assembly and is connected to the inlet port of the flow divider with a second flow passage means extending through the first [52] US. Cl ..9l/412, 21922//5l55,22 19220114148, piston rod and communicating with the pp end of the 5 l I Cl Flsb 11/16 first and second cylinders so that a pressured fluid source con 1 nected to one flow passage and a reservoir connected to the Fleld -v "91/411 412; 92/1 other flow passage means will extend the assemblies and the 92/52; 212/55 144 crane sections with the flow divider means producing a synchronized movement of the crane sections. The control [56] Referen s Ciied circuit further includes means for blocking flow from one end of eachof the cylinders when the pressured fluid in the first UNITED STATES PATENTS fluid passage means is below a predetermined level. ln addi- 3 386 594 6/1968 Grove ..2l2/l44 the divide means includes Pressure 489 12/1969 Stauffer n check valves providing unidirectional flow in opposite 3 572 517 3/1971 Liebherr et a1. ..212/144 di'ecticns between as Primary Examiner-Edgar W. Geoghegan Attorney-Dressler, Goldsmith, Clement & Gordon [57] ABSTRACT the two ports when the pressure in either of the outlet ports exceeds a predetermined level.

6 Claims, 4 Drawing Figures HYDRAULIC CONTROL SYSTEM FOR EXTENSIBLE CRANE BACKGROUND OF THE INVENTION The present invention relates generally to cranes, and more particularly to an improved hydraulic control system for extending and retracting boom sections of such cranes.

Mobile cranes generally consist of a vehicle which has a tumable base or support rotatable-about a vertical axis on the frame of the vehicle. A crane boom is generally pivoted about a horizontal axis on the support and is raised and lowered in order to be capable of reaching various elevations while rotation of the base permits movement of the boom to any position within the circle'of operation of the crane. In addition, it has become customary in recent years to increase the versatility of the machine by forming the boom of a plurality of extensible and retractable sections. Generally, the sections are of hollow polygonal configuration and are nestable within each other in the retracted position. The extension and retraction of the respective sections relative to each other, in present day cranes, is generally accomplished through the use of fluid rams having respective elements connected to the adjacent boom sections so that extension and retraction of the ram will cause extension and retraction of the two sections.

In at three section crane boom, it has been customaryto attach the cylinder of a first fluid ram to the first section, which is pivoted on the boom support and to connect the piston rod of the first fluid ram to the second or intermediate boom section. Asecondfluid ram has its cylinder connected to the intermediate or second boom section and its piston rod connected to the outer or third boom section. The respective fluid rams are extended and retracted relative to each other by connecting opposite ends of the cylinders of the respective fluid rams to a source of pressured fluid and a reservoir through conduits or hoses. One such arrangement is disclosed in Stauffer, U.S. Pat. No. 3,481,489.

One of the difficulties with an arrangement of this type is that the second cylinder of the second fluid ram moves with the second or intermediate section which necessitates com plicated mechanism for providing adequate storage for the hydraulic conduits or hoses interposed between the second fluid ram and the source of fluid pressure as well as the reservoir. One type of such arrangement is disclosed in the above mentionedStaufier patent.

Suchan arrangement is not only expensive to construct but also requires a considerable amount of maintenance due to the fact that the hoses are subjected to a considerable amount of wear and, in many instances, may be ruptured because of accidentally being trapped between relatively movable elements.

BRIEF SUMMARY OF THE INVENTION The present invention may be summarized as a hydraulic control system for extending and retracting a plurality of boom sections located in telescoping relation to each other and in which the various parts of the hydraulic control system are designed and arranged in a manner to eliminate the need for providing a large amount of hose and a take-up mechanism for storing the hose during extension and retraction of the boom sections relative to each other. Stated another way, the present invention contemplates a hydraulic control system for a plurality of boom sections in which both cylinders are attached to the same boom section and pressured fluid is delivered to the boom section through variable length flow passages. This arrangement eliminates the need for providing hoses from the base section for the boom to the second section in its extended condition. In addition, the present invention contemplates dividing, the pressured fluid received at. the second boom section equally between the two fluid rams so as to cause synchronized movement of the boom sections relative to each other.

More particularly, the present invention contemplates a hydraulic control system for a boom having a plurality of sections and one of the sections being supported on a substantially fixed support with a first cylinder and piston rod assembly having its piston rod connected to the first boom section and it cylinder connected to a second boom section. A second cylinder and piston rod assembly has its cylinder connected to the second boom section and its piston rod connected to a third boom section. Pressured fluid is directed from a source through the first fluid ram to a flow divider supported on the second boom section which distributes the fluid equally to one end of both of the cylinders The opposite ends of the two cylinders are interconnected by a conduit and a second flow passage means extends through the first fluid ram and communicates with the conduit. In addition, the flow divider incorporates first and second pressure responsive relief valves providing unidirectional flow in opposite directions between the two outlet ports of the flow divider with the respective relief valves being responsive to pressure of the fluid in the respective conduits to produce a flow passage between the two outlets for the valve when the pressure in either outlet exceeds a certain level.

The hydraulic control system further includes safety means in the conduit between the two cylinders and in the first flow passage for blocking flow therein when the pressure in the second fluid passage drops below a predetermined level.

The first and second fluid flow passages are incorporated entirely within the first fluid ram thus completely eliminating the need for any flexible hosing or any relative movement between the cylinders of the fluid rams during extension and retraction of the crane sections.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS FIG. 1 illustrates a side elevation view of a mobile crane embodying the present invention;

FIG. 2 is an enlarged sectional view of one of the two fluid rams forming part of the hydraulic control system of the present invention;

FIG. 3 shows the arrangement of parts of the hydraulic con trol system in relation to the crane; and

FIG. 4 is a schematic illustration of the hydraulic control system of the present invention.

DETAILED DESCRIPTION While this invention is susceptible of embodiment in many difierent forms, there is shown in the drawings and will herein be described in detail one specific embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated.

FIG. 1 of the drawings discloses a mobile crane, generally designated by the reference numeral 10. The mobile crane consists of a frame 12 supported on wheels 14 and having outriggers 16 connected thereto which are extensible to raise the frame and the wheels above the ground level in order to provide a fixed frame. A turntable 18 is defined on the upper end of the crane and supports a boom base or support 20 for rotation about a vertical axis.

The crane 10 further includes a boom 22 pivoted at one end on the base or support 20 by a pin 24. Pivotal movement of the boom 22 relative to the base 20 is accomplished by a fluid ram 26 interposed between the boom and the base.

As is customary in many cranes of this type, the boom 22 consists of a plurality of

boom sections

30, 32 and 34. The three boom sections are of generally polygonal hollow configuration and are mounted in telescoping relation to each other. A load supporting member 36 is normally supported on the outer end of the outer tubular section 34 and is adapted to be moved relative thereto by a winch and a cable (not shown).

As was indicated above, it has become customary to extend and retract the three sections of the boom relative to each other through a fluid hydraulic control system which includes a fluid ram interposed between each pair of adjacent sections.

With an arrangement such as this, in extending the second and third sections relative to each other, it becomes necessary to provide flexible hosing of sufficient length to reach the outer end of the intermediate section in its extended condition. During the retraction of the intermediate section within the inner section, a take-up mechanism must be provided for storing the hosing in a manner that the hosing would readily be extended upon subsequent extension of the two sections. The problem becomes even more complicated when the boom consists of four or more sections.

According to the present invention, the problems of storing flexible hosing during extension and retraction of boom sections relative to each other is eliminated simply by an arrangement of parts which allows all of the connections to be substantially fixed relative to each other. This is accomplished by utilizing a cylinder and piston rod arrangement having internal flow passages extending therethrough and the piston rod of the first cylinder is connected adjacent the pivotal connection of the boom to its support while the cylinder of the assembly is located in the second section. The second cylinder and piston rod assembly for extending and retracting the second and third sections has its cylinder disposed in the same section as the first cylinder and connected thereto with the piston rod being connected to the subsequent section. With this arrangement, all of the fluid for extending the piston rods is directed to the second boom section and is divided between the two cylinders in the second section to simultaneously extend the two assemblies in synchronism with each other. During retraction of the boom sections, all of the fluid forced from the cylinders passes through the piston rod of the first cylinder assembly to the reservoir.

The arrangement of parts in the hydraulic control system for eliminating the take-up mechanism heretofore necessary for the hosing to the second cylinder is shown in FIG. 3. The system includes a first fluid ram or cylinder and piston rod assembly 40 having its piston rod 42 connected at 44 to the first boom section 30 at a location adjacent the pivot pin 24. The cylinder 46 of the first fluid ram is trunnion mounted at 48 on the intermediate boom section 32.

The hydraulic control system or circuit further includes a second fluid ram or piston rod and cylinder assembly 50 having its cylinder 52 trunnion mounted at 54 on the intermediate boom section 32 while the free end of the piston rod 56 is connected at 58 to the third boom section adjacent its outer end. With this arrangement, the

fluid cylinders

46 and 52 are in adjacent relationship to each other and are connected to the same boom section of the crane.

The hydraulic control system of the present invention further includes first and second flow passage means in the first fluid ram 40 for directing fluid to the second boom section to and from opposite ends of the

respective cylinders

46 and 52. The fluid ram 40 may be of the type disclosed in Antos et al. US. Pat. No. 2,787,383. To provide the two fluid flow passages through fluid ram 40, the piston rod 42 of the fluid ram 40 consists of an outer tubular member 60 and (FIG. 2) an inner tubular member 62 arranged in concentric relation to each other to define an annular chamber 64 running substantially the entire length of the piston rod 42. One end of the annular chamber 64 is closed by piston 66 fixedly secured to the ends of the

tubular members

60 and 62 with the piston 66 being slidably disposed within the cylinder 46. The opposite end of the annular chamber 64 is closed by a plug 68 having an eye 70 on the end thereof for connecting the piston rod 42 to the first boom section 30. The plug 68 has an opening 72 communicating with the opening in the inner tubular member 62.

The fluid ram 40 further includes a tubular member 74 retained in an opening 76 in the head end of the cylinder 46 with the opposite end of the tubular member extending through an opening 78 in the piston 66 and telescopingly received in the tubular member 62. Thus, the tubular members 62 and 74 cooperate to define a first fluid flow passage means 79 extending through the piston rod 42 and the cylinder 46 which define first and second elements for the fluid ram 40. The annular chamber 64 defines the second fluid passage means extending through the piston rod or first element of the fluid ram, with the inner end of the annular member or second fluid passage means 64 communicating with one end of the cylinder 46 through a plurality of openings 80 (only one being shown) in the outer tubular member.

The hydraulic control system further includes a flow divider valve or means 84 (FIGS. 3 and 4) supported on the second section 32 of the boom 22 and connected to the first flow passage means 79 through a conduit 86. The flow divider means is more clearly shown schematically in FIG. 4 and includes an inlet port 88 having the conduit 86 connected thereto and first and second outlet ports 90 and 92. The first outlet port 90 is connected to the head end'of the first cylinder 46 through a conduit 94 while the second outlet port 92 is connected to the head end of the second cylinder 52 through a conduit 96. First and second restricters 97 and 98 are located between the inlet port 88 and the respective outlet ports 90 and 92 and the valve is constructed in such a manner that fluid received in the inlet port is equally divided between the two outlet ports. With this arrangement, the fluid supplied through the first passage means 79 will be equally distributed to the head ends of the respective cylinders or

elements

46 and 52 and will cause synchronized extension of the respective piston rods or

elements

42 and 56 relative to the respective cylinders thereby producing synchronized extension of the three boom sections relative to each other.

The interconnection between the two

cylinders

46 and 52 further includes a conduit 100 placing the rod ends of the respective cylinders in communication with each other so as to connect the second fluid passage means to the rod ends of the respective cylinders.

The hydraulic control system further includes a reservoir and pump 112 connected to a conventional valve 114, which in turn is connected through

conduits

116 and 118 to the respective

fluid passages

64 and 79. Thus, by repositioning the valve 114, the pump or pressured fluid source 112 and the reservoir 110 may be connected to either of the passages to extend and retract the cylinder and piston rod assemblies, as well as the boom sections. During the extension and retraction of the elements of the respective fluid rams 40 and 50, the flow divider means 84 will produce synchronized movement of the boom sections in relation to each other.

According to a further aspect of the present invention, the flow divider means or valve 84 incorporates first and second pressure responsive relief valve means 120 and 122 which produce unidirectional flow in opposite directions between the two outlet ports for interconnecting the outlet ports when either of the fluid rams 40 or 50 is restrained from movement whereby to maintain a synchronized movement between the fluid rams or assemblies. For this purpose, each

valve assembly

120 and 122 includes a valve spool 124 biased to a first position by a spring 126 with the valve assembly having first and

second flow passages

128 and 130 therein. The valve passage 128 has a check valve 132 therein with the

valves

120 and 122 being serially arranged in a conduit 134 between the first and second outlet ports 90 and 92.

Thus, in the normally biased position, the respective relief valves are located in the conduit 134 and respectively prevent flow from one outlet to another. However, if the elements of either of the fluid rams or

assemblies

40 or 50 are restrained against movement relative to each other, the fluid pressure in the associated outlet port, for example port 90, will be increased and the increased pressure will be directed to the opposite end of the spool 124 through a conduit 136 and move the valve spool to a second position where the flow passage 130 is in line with the conduit 134. With this arrangement, all of the fluid received in inlet port 88 will be directed to the second outlet port 92 and cause a complete extension of the elements of the second fluid ram 50. After the elements of the second fluid ram are extended, the positions of the two

valves

120 and 122 will be reversed and all of the pressured fluid from the inlet port 88 will be directed to the first outlet port 90 to force extension of the elements of fluid ram 40 relative to each other. This will synchronize the fluid rams at the maximum position of extension.

During retraction of the elements of the respective fluid rams. the flow divider 84 will act as a flow combiner and insure equal flow from both of the fluid rams to the inlet port. During such retraction, any restraint in the movement of either of the

assemblies

40 or 50 will again cause the opposite assembly to be fully retracted through the appropriate actuation of the pressure responsive valve means 120 and 122 and thereafter connect both outlet ports to one assembly, the restrained assembly, to allow that assembly to be retracted.

According to a further aspect of the present invention, the hydraulic control circuit of the present invention further includes safety means or pressure responsive relief valve means 140 for blocking flow from either of the fluid rams or

assemblies

40 and 50 when the pressure of the fluid in the fluid passage means 79 is below a predetermined level. The safety valve means provide unrestricted flow to the cylinders during extension of the respective assemblies but block the flow from the cylinders when the pressure of fluid in the retracting circuit or in the first passage means is below predetermined level. This arrangement will prevent uncontrolled retraction if any of the conduits should be ruptured.

The valve means 140 are identical in construction and are located in the conduits 116 and 96. The valve means or valves 140, which are the commercially available type, are schematically illustrated in FIG. 4 and include a passage 142 having a one way valve 144 disposed therein so as to provide substantially unrestricted flow in one direction through the valve. This occurs during extension of the

respective cylinder assemblies

40 and 50. However, before any fluid may be directed in an opposite direction through the valve, a valve element 146 in a passage 148 parallel to passage 142 must be moved from its first position in which it blocks flow through the passage 148. This is accomplished by directing fluid from the respective conduits 96 and 116 through actuating

conduits

150 and 152 to the chambers 154 and thence through the respective valve elements 146 to the opposite end thereof to move the valve elements or spools against the bias of a spring 156 in chamber 154 and allow flow of fluid in the opposite direction through the respective safety valves. With this arrangement, there must be pressured fluid in both conduits 96 or 116 in order for fluid to flow from the head ends of the

respective cylinders

52 and 46. Thus, forexample, if either of the conduits 96 or 118 were ruptured, the safety valves 140 would prevent retraction of the respective boom sections relative to each other.

From the above description it can readily be determined that the hydraulic control circuit or system of the present invention provides a simple and effective manner for extending at least three boom sections relative to each other without the necessity of having moving flexible conduits connecting the hydraulic rams of the circuit to the pressured fluid source and the reservoir. The arrangement of the fluid cylinder and piston rod assembly in adjacent relationship on one section with the piston rods respectively being connected to the respective sections on the opposite ends thereof, will allow the interconnection of the two cylinder assemblies with a substantially fixed connection. Combining the cylinder assembly arrangement with a specific type of variable length fluid flow passage means for directing fluid to the cylinder supporting section of the boom, substantially all of the flexible hosing may readily be eliminated.

The particular arrangement of the various parts forming the present hydraulic control system, considerably reduces the cost of the hydraulic control system heretofore standard in three section booms of this type.

What is claimed is:

1. In a crane having at least three extensible and retractable boom sections with a first boom section attached to a support, a hydraulic control system for extending and retracting said sections comprising a first cylinder and piston rod assembly,

with said cylinder attached to a second section and said piston rod connected to said first section; a second cylinder and piston rodassembly having its cylinder attached to said second section and its piston rod attached to a third section; flow divider means on said second section, said flow divider means having an inlet port, a first outlet port connected to one end of said first cylinder and a second outlet port connected to one end of said second cylinder; conduit means interconnecting the opposite ends of said cylinders; first flow passage means extending through said first cylinder and piston rod assembly and connected to said inlet port; second flow passage means extending through said first piston rod and connected to said opposite ends of said cylinders; and means connecting a pressured fluid source and a reservoir to said first and second flow passage means to extend and retract. said assemblies and said sections; said flow divider means dividing the fluid received in said inlet port equally to said cylinders to produce synchronized movement of said boom sections.

2. A crane as defined in claim 1, including the further improvement of first and second pressure responsive, unidirectional valve means between said one end of said cylinders and said first flow passage means, said valve means being responsive to the pressure of fluid in said second passage means to prevent flow of fluid from said cylinders when the pressure of fluid in said first passage means is below a predetermined level.

3. A crane as defined in claim 1, including the further improvement of first and second pressure responsive relief valve means in said flow divider valve, said valve means respectively providing unidirectional flow in opposite directions between said outlet ports and interconnecting said outlets when either of said assemblies is restrained whereby to maintain said assemblies synchronized at the maximum position of extension or retraction.

4. In combination with a crane including a boom having three sections with a first of said sections being attached to a support, a hydraulic control system comprising a source of fluid under pressure; a reservoir; first and second fluid rams each having first and second extensible and retractable elements, said first fluid ram having its first element connected to said first section and its second element connected to said second section, said second fluid ram having its second element connected to said second section and its first element connected to said third section; a flow divider valve on said second section having an inlet port and first and second outlet ports; a first conduit connecting said first outlet port to one end of said second element of said first fluid ram; a second conduit connecting said second outlet. port to one end of said second element of said second fluid ram; a third conduit interconnecting the opposite ends of said second elements; first fluid passage means extending through said first fluid ram and connected to said inlet port; second fluid passage means extending through said first fluid ram and communicating with said opposite end of said second element of said first fluid ram; and valve means for connecting said source and said reservoir to said fluid passage means to extend and retract said rams causing extension and retraction of said sections.

5. The combination as defined in claim 4, including the further improvement of first and second relief valves, respectively, providing unidirectional flow in opposite directions between said first and second conduits when the pressure in either of said first and second conduits exceeds a predetermined level to provide flow to the other of said conduits.

6. The combination as defined in claim 5, including the further improvement of first safety means in said first flow passage for blocking flow when the pressure of fluid in said second fluid passage is below a predetermined level and second safety means in said second conduit for blocking flow when the pressure of fluid in said third conduit is below a predetermined level.

Claims

1. In a crane having at least three extensible and retractable boom sections with a first boom section attached to a support, a hydraulic control system for extending and retracting said sections comprising a first cylinder and piston rod assembly, with said cylinder attached to a second section and said piston rod connected to said first section; a second cylinder and piston rod assembly having its cylinder attached to said second section and its piston rod attached to a third section; flow divider means on said second section, said flow divider means having an inlet port, a first outlet port connected to one end of said first cylinder and a second outlet port connected to one end of said second cylinder; conduit means interconnecting the opposite ends of said cylinders; first flow passage means extending through said first cylinder and piston rod assembly and connected to said inlet port; second flow passage means extending through said first piston rod and connected to said opposite ends of said cylinders; and means connecting a pressured fluid source and a reservoir to said first and second flow passage means to extend and retract said assemblies and said sections; said flow divider means dividing the fluid received in said inlet port equally to said cylinders to produce synchronized movement of said boom sections.

4. In combination with a crane including a boom having three sections with a first of said sections being attached to a support, a hydraulic control system comprising a source of fluid under pressure; a reservoir; first and second fluid rams each having first and second extensible and retractable elements, said first fluid ram having its first element connected to said first section and its second element connected to said second section, said second fluid ram having its second element connected to said second section and its first element connected to said third section; a flow divider valve on said second section having an inlet port and first and second outlet ports; a first conduit connecting said first outlet port to one end of said second element of said first fluid ram; a second conduit connecting said second outlet port to one end of said second element of said second fluid ram; a third conduit interconnecting the opposite ends of said second elements; first fluid passage means extending through said first fluid ram and connected to said inlet port; second fluid passage means extending through said first fluid ram and communicating with said opposite end of said second element of said first fluid ram; and valve means for connecting said source and said reservoir to said fluid passage means to extend and retract said rams causing extension and retraction of said sections.