US3722707A

US3722707A - Hydraulic crane control to prevent uncontrolled falling of load

Info

Publication number: US3722707A
Application number: US00195156A
Authority: US
Inventors: N Hedeen; C Javenkoski
Original assignee: HARMISCHFEGER CORP
Current assignee: CENTURY II Inc A CORP OF
Priority date: 1971-11-03
Filing date: 1971-11-03
Publication date: 1973-03-27
Anticipated expiration: 1990-03-27
Also published as: DE2253741A1; DE2253741B2; DE2253741C3; JPS4853459A; FR2158506A1; FR2158506B1; GB1346018A

Abstract

A boom crane comprises a platform on which a vertically movable boom, a front hoist drum, a rear hoist drum, a boom hoist drum, swing drive and an engine are mounted. The platform is rotatable in either direction about a vertical axis. The boom can be raised or lowered about a horizontal axis by means of a boom hoist line on the boom hoist drum. The front and rear drums are operable alternately to hoist and lower loads on their respective hoist lines. The aforesaid functions are controlled by a hydraulic control system which includes various levers and pedals that control hydraulic valves to regulate pressurization of various hydraulic clutch and brake cylinders. The control system comprises a selectively operable ''''dead man'''' actuation control for the front hoist drum and another ''''dead man'''' actuation control for the rear hoist drum. When actuated, each ''''dead man'''' actuation control effects automatic braking of its associated drum to prevent its load from falling in the event the control lever for that drum is returned to its neutral position while a load is being hoisted or lowered by that drum, as in the case when the crane operator is incapacitated. The control system further comprises a dump valve which automatically depressurizes the hydraulic system, in the event the boom and hoist line hooks are raised beyond a predetermined point.

Description

Uite States Patent 1 Hedeen et a1.

[54] HYDRAULIC CRANE CONTROL TO PREVENT UNCONTROLLED FALLING OF LOAD [75] Inventors: Nils E. Hedeen, Mequon; Carl W.

Javenkoski, Sussex, both of Wis.

[73] Assignee: Harmischfeger Corporation, Milwaukee,Wis.

221 Filed: NOV.3, 1971 21 Appl No.: 195,156

[52] US. Cl. ..212/59 R, 212/39 A, 254/185 [51] Int. Cl ..B66c 23/06 [58] Field of Search ....2l2/46 R, 59 R, 39 A, 39 MS; 254/183,184,185

[56] References Cited UNITED STATES PATENTS PrimaryExaminer-Evon C. Blunk Assistant Examiner-Merle F. Maffei Attorney-James E. Nilles 1 Mar. 27, 1973 [S7] 1 ABSTRACT A boom crane comprises a platform on which a vertically movable boom, a front hoist' drum, a rear hoist drum, a boom hoist drum, swing drive and an engine are mounted. The platform is rotatable in either direction about a vertical axis. The boom can be. raised or lowered about a horizontal axis by means of a boom hoist line on the boom hoist drum. The front and rear drums are operable alternately to hoist and lower loads on their respective hoist lines. The aforesaid functions are controlled by a hydraulic control system which includes various levers and pedals that control hydraulic valves to regulate pressurization of various hydraulic clutch and brake cylinders. The control system comprises a selectively operable dead man" actuation control for the front hoist drum and another dead man actuation control for the rear hoist drum. When actuated, each dead man actuation control effects automatic braking of its associated drum to prevent its load from falling in the event the control'lever for that drum is returned to its neutral position while a load is being hoisted or lowered by that drum, as in the case when the crane operator is incapacitated. The control system further comprises a dump valve which automatically depressurizes the hydraulic system, in the event the boom and hoist line hooks are raised beyond a predetermined point.

9 Claims, 9 Drawing Figures PATENTEUHARZYISYS 3,722,707

SHEET

1 or 4 INVENTORS= M15 15 /%"0A CARL W JAvEA/kOSk/ PATEH'IFMRN ms SHEET 3 [1F 4 HYDRAULIC CRANE CONTROL TO PREVENT UNCONTROLLED FALLING OF LOAD BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to cranes and to hydraulic control systems therefor. In particular, it relates to safety valves in the hydraulic control system which prevent uncontrolled lowering of loads being handled by the crane and uncontrolled lowering of the crane boom.

2. Description of the Prior Art Some cranes, for example, comprise a lower unit, such as a truck body or the like, on which an upper unit is mounted. The upper unit comprises a platform which rotates on the lower unit in either direction about a vertical axis by means of magnetic clutches. A crane boom is mounted at its lower end on the platform and can be raised or lowered about a horizontal axis by means of a boom hoist line which is connected to the upper end of the boom and is wrapped around a boom hoist drum mounted on the platform. A front hoist drum and a rear hoist drum are mounted on the platform and each is provided with its own hoist line which is reeved around pulley means on the upper end of the boom for raising or lowering a load. In practice, either the front drum or rear drum or both can be operated at any given time. Power for rotation of the platform, raising the boom and raising a load is provided by an engine mounted on the platform. Power is transmitted to rotate the three drums in the hoist direction and controlled by a system of hydraulic clutches, and planetary gear means are provided to permit engine-controlled rotation of these drums in the reverse (or lowering) direction. Hydraulic brakes are also provided in the hydraulic control system to slow or stop reverse rotation of the three drums.

To raise a load by means of the front drum, the crane operator moves a front drum clutch lever from a neutral position wherein it is normally biased in one direction, usually toward himself. This causes a front drum clutch valve to be moved from neutral to engaged position and allowspressurized hydraulic fluid to flow from a source to a front drum hydraulic clutch cylinder and to pressurize the latter. This, in turn, engages the front drum clutch and causes power from the engine to rotate the front drum in the hoist direction to raise the load. When the front drum clutch lever is returned to neutral position, the front drum clutch valve becomes disengaged, the front drum clutch cylinder becomes deenergized and rotation of the front drum in the hoist direction ceases. At this point, unless further action is taken, the front drum will rotate in the reverse (lowering) direction and the load will fall. To stop the load from falling, the crane operator can move the front drum clutch lever from the neutral position toward another position (usually away from himself) to engage a front drum planetary brake valve and cause pressurization of a front drum planetary brake cylinder. This permits engine-controlled lowering of the load or engine-controlled rotation of the front drum in the lowering (reverse) direction.

However, if desired, instead of using the front drum clutch lever to lower the load, the crane operator can use a front drum brake pedal to stop or control lowering of the load. The front drum brake pedal is depressed from a neutral position wherein it is normally biased to cause a front drum brake valve to be moved from neutral to engaged position. This allows pressurized hydraulic fluid to flow from the source and pressurize a front drum main brake hydraulic cylinder to apply the front drum brake. Return of the front drum brake pedal to neutral releases the front drum brake.

If desired, the operator can set the front drum brake to hold the load at a desired position by moving a front drum brake lock lever from unlocked" to .locked" position. Such movement causes a front brake lock valve to depressurize a front drum brake lock cylinder and, when this cylinder is depressurized, fail-safe springs cause the front drum brake to set and remain locked as long as the front drum brake lock cylinder is depressurized. This cylinder is again pressurized when the front drum brake lock lever and its associated valve are returned to unlocked position by the crane operator. When this brake lock lever and valve are in unlocked" position, depressurization of the hydraulic system caused by any sort of malfunction, also causes depressurization of the front drum brake lock cylinder and fail-safe locking of the front drum brake to hold the load.

As will be understood, the rear drum of the crane is controlled in the same manner as the front drum, as hereinbefore described. Furthermore, the boom hoist drum is operated in a similar manner as the front drum as regards hoisting the boom and as regards power lowering. However, since the boom hoist drum is not free to rotate when its control lever is in neutral position and, therefore, no pedal-operated brake is provided to control lowering of the boom.

Operation of a crane of the aforedescribed character entails two potential hazards. First, for example, if the front drum has raised a load and the front drum clutch lever and the front drum brake pedal are simultaneously in or returned to neutral positions, the load will fall under the force of gravity. In some instances, this is done intentionally by. the crane operator to rapidly lower the load and is followed by application of the front drum pedal brake or operation of the front drum clutch lever to slow or stop its descent. However, if these controls return to neutral because of incapacitation of the crane operator, as in the case of death, injury or illness, the falling load can cause injury or death to other workmen and damage to the load or other property on which it falls. Second, if operation of the boom hoist drum is continued after the boom has been hoisted to a predetermined elevation, it will cause the boom to continue to and over a vertical position and thereby fall backwards over the machine with its load, thereby causing damage to the crane, possible damage to other property and injury or death to personnel.

It is desirable, therefore, to provide improved hydraulic control systems for cranes of the aforesaid type that will eliminate the described hazards and have other advantages for certain required operating conditions.

SUMMARY OF THE INVENTION The present invention contemplates a crane and a hydraulic control system therefor of the aforesaid character.

In accordance with one aspect of the invention, selectively operable dead man actuation controls and valves are provided for the front drum and for the rear drum to automatically stop rotation of whichever drum is being used in the event both the drum clutch lever and the brake pedal for a particular drum are both returned to neutral simultaneously. The dead man valve for the front drum, for example, is a twoposition valve having of and on" positions. In off position, the dead man valve is ineffective to alter normal operation of the hydraulic control system. In on" position, to which it is movable by the crane operator's choice, it is connected and operates as follows. In on position, the dead man valve disconnects the front drum brake lock cylinder from the front drum brake lock valve (through which this cylinder is normally pressurized when the brake lock valve is in unlocked position) and connects it to the top port of a shuttle valve. One side port of the-shuttle valve is connected to a first hydraulic fluid line between the front drum planetary brake valve and the front drum planetary brake hydraulic cylinder. The other side port of the shuttle valve is connected to a second hydraulic fluid line between the front drum clutch valve and the front drum clutch cylinder. Thus, if either of the aforesaid first or second lines is pressurized, as would be the case if either of their associated valves was engaged, then the front drum brake lock cylinder is also pressurized and the fail-safe" spring does not operate to lock the front drum brake. However, if both of said first and second lines are depressurized, as would be the case when the front drum clutch lever is in neutral position, then the front drum brake lock cylinder is depressurized as its fluid flows back through the dead man valve, the shuttle valve and either the'said first or second line to a fluid reservoir, and the fail-safe" spring locks the front drum brake to prevent the load from falling uncontrolled in the event the front drum brake pedal is not depressed. To avoid unnecessary stopping each time the clutch lever is returned to neutral, the dead man valve and control lever are normally maintained in off" position. As will be understood, the dead man" valve for the rear hoist drum operates in a similar manner.

In accordance with another aspect of the invention, a two-position solenoid-operated dump valve is provided to automaticallydepressurize all hydraulic cylinders siipplied from a main hydraulic pressure line connected to the hydraulic'fluid source, in the event that the boom is raised to a predetermined position. However, the dump valve, which is movable from a normal position to a dump position when its switch-controlled solenoid is deenergized, does not effect depressurization of the front or rear drum main brake cylinders. This is because the valves for these two cylinders are independently supplied with hydraulic fluid from the fluid source through an auxiliary supply line connected upstream of the dump valve and not controlled thereby. In dump position, the dump valve disconnects the main hydraulic pressure line downstream from the fluid source and connects it to a fluid return line connected to a fluid reservoir. In dump position, the dump valve prevents all further operations controlled by means of hydraulic pressure but does not prevent operation of the main brakes of of either the front or rear drum.

A selectively operable dead man" valve and a switch-operated dump valve in accordance with the present invention provide additional safety features not available on prior art cranes. Furthermore, these safety features are readily applicable, at relatively low cost, to the hydraulic control systems of existing cranes. Other objects and advantages of a hydraulic control system in accordance with the invention will hereinafter appear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a boom crane in which a hydraulic control system in accordance with the invention is advantageously employed;

FIG. 2 is anenlarged top plan view of the upper unit of the crane shown in FIG. 1;

FIG. 3 is an enlarged cross-sectional view of a front or main hoisting drum taken along lines 33 of FIG. 2

FIG. 3A is aschematic view of a portion of the gearing assembly shown in FIG. 3;

FIG. 4 is a view showing details of a drum clutch taken along lines 4-4.of FIG. 3;

FIG. 5 is a view showing details of a drum brake taken along lines 5-5 of FIG. 2;

FIG. 6 is an enlarged side elevational view, partially in section, of a clutch valve and a planetary brake valve of the hydraulic control system;

FIG. 7 is a schematic diagram of a hydraulic control system in accordance with the invention; and

FIG. 8 is an enlarged cross-sectional view of a shuttle valve shown in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the numeral 10 designates a crane with which the present invention is employed. Crane 10 comprises a carrier 11 such as a truck base on which an upper unit 12 is mounted. Upper unit 12 is understood to be revolvable about a vertical axis in either direction and comprises a platform 13 on which a cab 14 and a crane boom 15 are mounted. Boom 15 is supported at its lower end on platform 13 and is supported at its upper end by a boom hoist line 16 and other suitable rigging.

Referring to FIG. 2, platform 13 carries or supports an engine 20 which may, for example, be a gasoline or diesel-type engine. Engine 20 is connected through a transmission 21 and a gear case 22 to a swing clutch shaft 23. When engine 20 is running and the engine clutch engaged, swing clutch shaft 23 is also rotating.'

Shaft 23 is provided at its opposite ends with magnetic couplings 24 and 25 which are selectively operable to swing or rotate upper unit 12 in either direction depending on the coupling energized by the crane operator. Switch clutch shaft 23 is provided with a drive sprocket 26 which is connected by a suitable chain drive means 27 to drive or rotate a jackshaft 28 on which a driven sprocket 29 is mounted. As FIGS. 1 and 2 show, platform 13 also carries or supports a front hoisting drum 32 and a rear hoisting drum 33. A boom hoist drum 34 is associated with the drive shaft for rear hoist drum 33. As FIG. 1 shows, a front hoist line 35 in the form of a wire rope or cable is wrapped on front hoist drum 32 and reeved over a pulley 37 on the upper end of boom 15. A rear hoist line 36 similar to line 35 is wrapped on rear drum 33 and is reeved over another pulley 38 on the upper end of boom 15. In practice, either hoist line 35 or 36 or both and, consequently, drum 32 or 33 or both would be used at any given time for any particular hoisting operation. Boom hoist line 16, shown in FIG. 1, is wrapped on boom hoist drum 34 and is used to raise or lower the boom. Since front drum 32, rear drum 33 and boom hoist drum 34 are similar in construction and mode of operation, only front hoist drum 32 will be described in detail hereinafter.

As FIG. 2 shows, platform 13 of upper unit 12 of crane is provided with an operator control station 41 which is provided with an array of controls, hereinafter described, by means of which the crane operator controls the various crane functions. Control station 41 comprises, for example, a swing clutch lever 42 by means of which the crane operator swings upper unit 12 to the right or left. Station 41 also includes a front drum lever 43. The operator pulls lever 43 toward himself or rearward to engage a front drum clutch and wrap line on front drum 32. When planetary lowering of a load is desired, the operator pushes lever 43 forward or away from himself to reverse the direction of drum rotation and to control lowering of the load through planetary gearing and a planetary brake. Front drum lever 43 is understood to be biased so that it normally assumes a neutral or central position. A rear drum lever 44 is provided to control rear hoist drum 33 and operates in a manner similar to front drum lever 43. A front drum brake pedal 45 is provided and when depressed by the operator from neutral position, operates to apply a front drum brake hereinafter described. A rear drum brake pedal 46, similar in operation to front drum brake pedal 45, is also provided. A front drum brake lock lever 47 is provided and the operator pulls this lever toward himself to lock the spring-set front drum brake in the applied position. The operator pushes lever 47 away from himself to release the brake as hereinafter described. A rear drum brake lock lever 48 is also provided and is similar in operation to lever 47 hereinbefore described. A boom hoist lever 49 is provided to raise boom and also to control its lowering under power.

Referring to FIG. 3, front hoist drum 32 is shown in detain and is mounted on a drum shaft 51. It is to be understood that drum shaft 51 is driven by a jackshaft gear 300, shown in FIG. 2, which engages a hoist drum shaft gear 54 and is continuously rotating whenever the engine clutch is engaged. However, its associated drum 32 does not turn until the crane operator engages front drum lever 43 as hereinafter described. Drum 32 comprises a cylindrical surface 52 on which wire rope or line is wound. Drum 32 is supported for relative rotation on drum shaft 51 by bearings 53. Drum shaft gear 54 is rigidly connected to drum shaft 51 and serves as the means by which drum shaft 51 is rotated by jackshaft gear 300. Drum shaft 51 is supported for rotation on platform 13 by suitable bearings 55. A drum member 56 having a flat side plate 57 is rigidly connected as by means of bolts 58 to drum 32. Drum member 56 is provided with a cylindrical outer surface 60 which serves as a main brake surface. Drum member 56 is further provided with a cylindrical inner surface 61 which serves as a surface against which a clutch assembly 62 operates.

Clutch assembly 62, which is shown in detail in FIG; 4, is engageable as hereinafter described to transmit the rotation of drum shaft 51 to drum 32.

Brake assembly 63, which is shown in FIG. 5, is operable to slow or stop rotation of drum 32 after clutch assembly 62 is disengaged.

A planetary gear assembly shown to the left of drum 32 in FIG. 3 (and also'shown schematically in FIG. 3A), serves as a means whereby hoist drum 32 can lower a load under controlled power, i.e., when the front drum lever 43 is moved to its forward position. Planetary gear assembly 64 comprises a sun gear which is rigidly attached to drum 32 as by bolts 71 and 58. A spider ring 72 is mounted on a bearing 73 and is relatively movable with respect to drum 32. Spiderring 72 is provided on its periphery with a flat surface 74 which serves as a planetary brake surface against which brake bands under control of a planetary brake cylinder 67, shown in FIG. 7, engage. Spider ring 72 carries a pair of pins 75 on which planetary pinion gears 76 are mounted for rotation. Each planetary pinion gear 76 engages sun gear 70 and an outer gear 77 which is rigidly connected to hoist drum shaft gear Planetary gear assembly 64 operates as follows. Assuming rotation of drum shaft-51, and clutch assembly 62 disengaged and brake assembly 63 engaged, then drum clutch assembly 62 and planetary gear assembly 64 all revolve in the same direction as drum shaft 51 and sun gear 70 is stationary as it is attached to drum 32. Now, assuming that clutch assembly 62 is engaged, and brake assembly 63 is disengaged, the entire planetary gear assembly 64 rotates as a unit at the same speed and in the same direction of rotation as drum shaft 51. Finally, assuming that brake 67 for planetary gear assembly 64 is engaged and that brake assembly 63 and clutch assembly 62 are disengaged, spider ring 72 cannot revolve and the pinion gears 76 are caused by outer gears 77 to rotate about their respective axes. The rotation of the pinion gears 76 is in the same direction as drum shaft'gear 54. Rotation of the pinion gears 76 about a fixed axis causes sun gear 70, which is attached to drum 32, to rotate in the reverse direction of drum shaft gear 54. This results in controlled power load lowering. Thus, the purpose of planetary gear assembly 64 on main hoist drum 32 is to enable the crane operator to slowly lower a load. More specifically, by throttling engine 20, the load can be lowered at different speeds.

Referring to FIG. 4, drum clutch assembly 62, which is understood to be rotatable with'drum shaft 51, is shown in detail. Clutch assembly 62 comprises a clutch spider 80 which is journalled to drum shaft 51. A lever arm 81 is pivotally mounted as by a pin 82 to clutch spider 80. One end of a clutch band 83 is connected to clutch spider 80 and the other end of circular clutch band 83 is connected to one end of lever arm 81. A hydraulic clutch cylinder 84 is connected by a pin 85 to clutch spider 80. A movable piston 86 of clutch cylinder 84 is connected by a pin 87 to lever arm 81. A supply line 88 for clutch cylinder 84 is connected as FIG. 3 and FIG. 4 show, to a passageway 89 in the right-hand end (with'respect to FIG. 3) of drum shaft 51. It is to be understood that when clutch cylinder 84 is pressurized or energized, clutch band 83 expands and engages inner surface 61 of drum member 56 and effects rotation of hoist drum 32 to rotate in the loadhoisting direction. When clutch cylinder 84 is depressurized, a spring 90 causes contraction of clutch band 83 and rotary motion is not transmitted from drum shaft 51 through clutch assembly 62 to drum 32.

FIG. shows the structural details of brake assembly 63 which is used to slow or stop rotation of front hoist drum 32. Brake assembly 63 comprises brake band 94 which is contractable to engage main brake surface 60 of drum member 56 to stop rotation of front hoist drum 32. The end of brake band 94 is connected by a link 95 to part of the structure of upper unit 12. The live end of brake gand 94 is connected to another link 96 which is pivotally connected by means of a pin 97 to part of the structure of upper unit 12. Link 96 is biased in the clockwise direction with respect to FIG. 5 about pin 97 by a fail-safe compression spring 98 so that normally brake band 94 prevents rotation of hoist drum 32. A front drum hydraulic brake cylinder 99 is pressurized or energized (by depression of front drum brake pedal 45 shown in FIG. 2) to slow or stop drum rotation. A front drum fail-safe hydraulic brake cylinder 102 is provided to overcome, when energized, the bias of compression spring 98 and to cause link 96 to rotate counterclockwise about pin 97 and release or expand brake band 94 to permit drum rotation. Pressurization or energization of fail-safe brake cylinder 102 is effectd by moving front drum brake lock lever 47 from locked to unlocked position. I

The arrangement by which the various control levers and pedals shown in operator control station 41 in FIG. 2 operate their associated valves and hydraulic cylinders will not be described. For purposes of simplification, only front drum lever 43 and its associated valves will be described in detail hereinafter. However, it is to be understood that other control levers, pedals and valves operate and are constructed in a similar manner unless otherwise noted. As FIG. 6 shows, front drum lever 43 comprises a shaft 104 which is rigidly connected to a plate 105 and the latter is pivotable on a pin 106 which is mounted on supporting framework 107 which is understood to be part of platform 13 of upper 43 does not effect movement of front drum clutch valve control rod 118 because the slot in lower toggle link 109 permits pin 111 on plate 105 to move without effecting movement of lower toggle ink 109. Movement of front drum lever 43 toward the operator, i.e., toward the left or counterclockwise in FIG. 6-frorn the neutral position shown in FIG. '6, causes control rod 118 of front drum clutch valve 119 to be moved toward the right with respect to FIG. 6 from its neutral position to its engaged position. However, such counterclockwise movement of front drum lever 43 does not effect engagement of front drum planetary brake valve 115. Drum lever 43 will return automatically to its neutral position because of spring action in valve 115 and 119 as will hereinafter be explained.

It is tobe understood that all other control valves, unless otherwise noted, are constructed and operate in a similar manner to valve 115. Therefore, only valve 115 will be described in detail. As FIG. 6 shows, valve 115 comprises a valvebody 126 into which control rod 114 extends through a flexible boot 127. Control rod 114 is surrounded by a control spring 128 of the compression type which bears against a spool 129 which controls hydraulic fluid flow through the valve. Spool 128 is counterbalanced by a' return spring 130, also of the compression type, which bears against a flanged member 131 on spool 129 and against a portion of valve body 126. Valve body 126 is provided with an opening 132 for receiving pressurized oil from an accumulator 133, shown in FIG. 7. Valve body 126 is further provided with an opening 134 for connection to a reservoir 135 shown in FIG. 7. Valve body 126 is also provided with an opening 136 for connection to the cylinder line of the hydraulic cylinder which it controls. When valve 115 is in neutral position, as shown in FIG.

' 6, spool 129 thereof is in its extreme leftward position unit 12 of crane 10. Upper and

lower toggle links

108 and 109, respectively, are pivotally connected to plate at one end thereof.

THe

links

108 and 109 are pivotally connected to pins 110 and 111, respectively, on plate 105. Upper toggle link 108 is further connected by means of a pin 112 to a link 113 which, in turn, is connected to a control rod 114 ofa front drum planetary brake valve 115. Lower toggle link 109 is connected by means of a pin 116 to a link 117 which, in turn, is connected to a control rod 1180f a front drum clutch valve 119. Upper pin 112 and lower pin 116 are joined by links 120 and 121, respectively, which are attached to a pin 122. In FIG. 6, front drum lever 43 and its associated valves 115 and 119 are shown in the neutral position. It is to be understood that valves 115 and 116 operate alternately. For example, if front drum lever 43 is pushed away from the crane operator, .i.e., moved clockwise with respect to FIG. 6, the result is that control rod 114 of front drum planetary brake valve 115 is moved toward the'right from its neutral position to its engaged position. However, such movement of front drum lever and prevents fluid from opening 132 from reaching opening 136. I-Iowevenspool 129 is providedwith a passageway 137 through which opening 136 and opening 134 are connected. Therefore, in neutral position, pressurized fluid cannot flow to the cylinder controlled by valve 115. However, fluid can flow from such cylinder through spool 129 back to reservoir 135. When valve 115 is moved to engaged position, its control rod 114 moves to the right with respect to FIG. 6, and control spring 128 moves spool 129 rightward with respect fo FIG. 6 and fluid flow is possible from opening 132 through passageway 137 in spool 129 to opening 136 in valve body 126 to pressurize the cylinder connected to the valve. Such rightward movement of spool l29,prevents fluid flow between passageway 137 in spool 129 and opening 134 in valve body 126. When the operator releases the pressure on lever 43, and therefore on its associated control rod 114, return spring causes spool 1 29 to move leftward with respect to FIG. 6 from? its engaged position to neutral position. When valve 1115 is in neutral position, hydraulic fluid is able to flow from its associated hydraulic cylinder back through the valve to the reservoir, thereby pressurizing or deenergizing the cylinder associated with the valve.

Referring to FIG. 7, there is shown a schematic diagram of a hydraulic control system in accordance with the present invention. FIG. 7 shows some control levers, valves and hydraulic cylinders hereinbefore identified and described and others which have not.

For convenience, Chart A below identifies each lever, pedal or other valve control; the valve it operates; the hydraulic fluid line between the valve and the hydraulic cylinder connected thereto; the cylinder safe cylinder As FIG. 7 shows, hydraulic fluid reservoir has its discharge outlet connected to a pump 141 which is understood to be driven by engine 20. Pump 141 supplies a high-pressure hydraulic fluid to a high-pressure supply line 142 through a high-pressure filter 146, a check valve 143, and accumulator 133. Pressurized hydraulic fluid is stored in accumulator 133 and if hydraulic fluid pressure falls below a predetermined point, an unloading valve 144 connected to supply line 142 ahead of accumulator 133 and to a fluid return line 145 closes so that pump 141 can recharge accumulator 133 and maintain hydraulic fluid pressure therein at a proper operating level. Supply line 142 is connected through a dump valve (shown in dump position in FIG. 7 and hereinafrer described) to an inlet 147 of a distributor valve assembly 148. Distributor valve assembly 148 has several valves connected thereto such as front drum planetary brake valve 115, main drum clutch valve 119, rear drum planetary brake valve 149, rear drum clutch valve 150, a swing brake valve 152, and a boom hoist clutch valve 154. It is to be understood, however, that front drum brake pedal valve 125 and rear drum brake valve 151 are not supplied from inlet 147 on distributor 148 but are supplied from a line 159 which is connected to line 142 ahead of dump valve 155. However, valves 125 and 151 are connected to a hydraulic fluid return line 156. Hydraulic fluid return line 156 is connected between an outlet port 157 on distributor valve assembly 148 and reservoir'135 through a check valve 158. Front drum brake valve 125 which is controlled by pedal 45 is connected by a hydraulic fluid line 160 to front drum brake cylinder 99. Front drurn planetary brake valve 115, which is controlled by lever 43, is connected by a hydraulic fluid line 161 to a front drum planetary brake cylinder 67. Rear drum planetary brake valve 149 which is controlled by lever 44 is connected by a hydraulic fluid line 162 to a rear drum planetary brake cylinder 163. Rear drum brake valve 151, which is controlled by pedal 46, is connected by a hydraulic line 164 to a rear drum brake cylinder 165. Boom hoist planetary brake valve 153, which is controlled by a lever 49, is connected by a hydraulic fluid line 167 to a boom hoist planetary brake cylinder 170. Front drum clutch valve 119, which is controlled by lever 43, is connected by a hydraulic fluid line 172 to front drum clutch cylinder 84. Rear drum clutch valve 150, which is controlled by lever 44, is connected by a hydraulic fluid line 173 to a rear drum clutch cylinder 174. Swing brake valve 152 which is controlled by lever 50 is connected by a hydraulic fluid line 175 and through a swivel brake lock valve 176 and a hydraulic fluid line 177 to a swing brake 178 which is spring set and hydraulically released. Boom hoist clutch valve 154, which is controlled by a lever 49, is connected by a hydraulic fluid line 182 to a boom hoist clutch cylinder 183. I

A brake lock valve 185 is provided to control front drum unlocking brake cylinder 102..Brake lock valve 185 is movable leftward with respect to FIG. 7 to the locked position and is movable rightward to the unlocked position by front drum brake lock lever 47. When in unlocked position, brake lock valve 185 connects supply line 142 through a line 186 to a hydraulic fluid line 187. When in locked position, brake lock valve 185 connects line 187 through a line 188 to return' line 156. As FIG. 7 shows, a rear drum brake lock valve 190 controlled by a rear drum brake lock lever 48 is provided for controlling a rear drum unlocking brake cylinder 171. It is to be understood that brake lock valve 190 is constructed and operates in the same manner as brake lock valve 185 hereinbefore described.

In accordance with the present invention, a selectively operable dead-man valve 191 is provided to control the operation of front drum unlocking brake cylinder 102. Dead-man valve 191 is provided with a manual.

operating lever 193 which permits it to be moved leftward with respect to FIG. 7 to the on position. When dead-man valve 191 is in the off position shown, it performs no function in the system. When dead-man valve 191 is moved to the on position, it disconnects line 192 from line 187 (and thus from brake lock valve 185) and connects line 192 to a line 194. Line 194 is connected to a top port 195 of a shuttle valve 196. One side port 197 of shuttle valve 196 is connected through a hydraulic fluid line 198 to hydraulic fluid line 161 for front drum planetary brake cylinder 67. The other side port 199 of shuttle valve 196 is connected through a hydraulic fluid line 200 to hydraulic fluid line 172 for front drum clutch cylinder 84. Shuttle valve 196, shown incross section in FIG. 8,' comprises a valve housing 201, top port 195, side port 197, side port 199 and a shuttle 202. When pressurized oil 'is available at either of the side ports 19.7 or 199, the floating shuttle 202 moves to the other side of the valve where it closes that other side port. This allows oil to flow from the pressurized 'side port out of the top port 195. Thus, when dead-man valve 191 is in the on" position, it functions to maintain front drum fail-safe brake or unlocking cylinder 102 pressurized (and therefore keeps the brake unlocked) as long as there is hydraulic fluid pressure in either line 161 or line 172. Pressure is maintained in line 161 whenever lever 43 is moved to cause main drum planetary brake valve 115 to be engaged. Pressure in line 172 is maintained whenever lever 43 is moved to cause main drum clutch valve 119 to be engaged. However, when lever 43 is in neutral position, lines 161 and 172 are connected through the valves 115 and 119, respectively, to hydraulic fluid return line 156 and there is no hydraulic fluid pressure in the lines valve 161 or 172. In this connection, shuttle valve 196 permits hydraulic fluid to drain from main drum unlocking brake cylinder 102, through line 192, through deadman valve 191, through line 194, and through shuttle valve 196 to either line 161 or 172 and through the valve associated with that line to return line 156 and from thence to reservoir 135.

FIG. 7 also shows that a dead-man valve 204 and a shuttle valve 205 are provided in conjunction with rear drum brake lock valve 190 and rear drum fail-safe brake or unlocking cylinder 171. Dead-man valve 204 is connected through a line 206 to cylinder 171 and is also connected through a line 207 to brake lock valve 190. A top port 208 of shuttle valve 205 is connected to dead-man valve 204.

Side ports

209 and 210 are connected to hydraulic fluid lines 162 and 173, respectively. Dead-man valve 204 and shuttle valve 205 are similar in construction and operation to dead-man 191 and shuttle valve 196 hereinvefore described, both as to construction and mode of controlling the fail-safe brake cylinders with which they are associated. Therefore, further detailed description of these components is believed to be unnecessary.

Referring to FIG. 7, dump valve 155 hereinbefore referred to is another safety feature in a hydraulic system in accordance with the present invention. Dump valve 155 is controlled by a solenoid 212. Solenoid 212 is connectable through a limit switch 213 to a suitable source of electrical power 214.-When engine 20 is in operation and power source 214 is providing electrical power and limit switch 213 is closed, as would be the normal condition, solenoid 212 is energized and acts against theforst of a biasing spring 215 so that dump valve 155 is moved and held in an upward or open position with respect fo FIG. 7, thereby affording unobstructed pressurized fluid flow through hydraulic fluid line 142 from accumulator 133. However, limit switch 213 is so located on crane 10 that, if crane boom is I hoisted or moved too far in a counterclockwise direction with respect to FIG. 1 so that there is danger of over-hoisting, the limit switch will open. When limit switch 213 opens, solenoid 212 is deenergized and biasing spring 215 causes dump valve 155 to assume the dump position shown in FIG. 7. In dump position, hydraulic fluid supply line 142 downstream of dump valve 155 is connected to fluid return line 156 and all hydraulic cylinders in the system (except those controlled by front drum brake valve 125 and rear drum brake valve 151 become deenergized or depressurized. When this happens, the fail-safe brakes throughout the system automatically set or engage, as hereinbefore described in connection with front drum fail-safe brake cylinder 102. In this condition, the operator is unable to raise boom crane 15 any further. However, normally open override 'pushbutton switch 216 is provided by which the operator can intentionally reenergize coil 212 to cause valve 155 to return to upward or open position permitting reestablishment of hydraulic control functions and enabling the crane boom to be brought down to within safe operating limits.

Crane 10 and its hydraulic control system operate as follows.

First assume that

lines

142 and 159 are pressurized, that dump valve 155 is in open (upward) position, that

brake lock valves

185 and 190 are unlocked, that deadman valves 191 and 204 are of and that all valves associated with distribution valve assembly 148 are in neutral position. In this condition, engagement of any valve associated with distribution valve assembly by its control lever or pedal will effect pressurization of its associated cylinder and performance of an appropriate control function. At this point, loss of pressure in any pressurized line will cause depressurization of its associated cylinder. In particular, loss of pressure to either fail-safe cylinder 102 or 17l will cause fail-safe braking of front drurn32 or rear drum 33, respectively.

Now assume that load 39 on crane 10 is being raised by front drum 32 by means of pressurization of clutch cylinder 84 (accomplished by means of control lever 43 engaging valve 119). To stop the load and suspend it, the operator pressurizes brake cylinder 99 (accomplished by means of a brake pedal 45 engaging valve and depressurizes clutch cylinder 84 by returning control lever 43 to neutral. If desired, at this point, the operator may depressurize brake lock cylinder 102 accomplished by moving front drum brake lock valve to lock" position by means of lever 47) to hold the load suspended while the brake pedal 45 is returned to neutral. It is to be noted that pressure loss in cylinder 102 and line 192 caused by some malfunction while the load is being raised or suspended would also hold the load suspended because the brake isfail-safe and sets automatically. To continue to raise or lower the load, theoperator then moves front drum brake lock valve 185 to unlocked position, while simultaneously operating brake pedal 45 or control lever 43 or a combination of both.

As hereinbefore explained, with dead-man valve 191 of return of control lever 43 to neutral position will result in dropping of the load by force of gravity unless brake pedal 45 is depressed to control its descent. While this is done intentionally momentarily in some cases to achieve rapid lowering, it is apparent that if the operator is unable, due to some incapacitation, to operate either of these controls and both return to neutral (wherein they are biased), then the load will fall uncontrolled with possible disastrous resultsv To anticipate such a contingency, the operator moves deadman control'lever 193 from off to on to engage dead-man valve 191, i.e., to move it to the position left of that shown in FIG, 7. With valve 191 on, front drum brake fail-safe cylinder 102 is disconnected from locking valve 185 .and connected through line 192, valve 191, line 194, and shuttle valve 196 to lines 161 and 172. Thus, cylinder 102 remains pressurized as long as either line 161 or 172 is pressurized, i.e., if either front drum planetary brake valve 115 or front drum clutch valve 119 is engaged by control lever 43. However, if control lever 43 returns to neutral, fail-safe cylinder 102 will deenergize, the front drum brake will set, and front 'drum 32 will stop rotation to hold the load suspended. Further movement of control lever 43 from neutral will again pressurize cylinder 102 to allow raising or power lowering of the load.

As will be apparent, when dead-man valve 191 is on, brake lock valve 185 is ineffective.

It is to be understood that rear hoist drum 33 is operable and controllable by its associated controls in the same manner as front hoist drum 32. Therefore, its operation will not be described in detail.

Now again make the first assumptions hereinbefore described. Then, further assume that crane boom 15 is being raised by rotation of boom hoist drum 34 by means of pressurization of boom hoist clutch cylinder 183 (effected by engagement of clutch valve 154 by lever 49). When boom 15 is raised to a predetermined point beyond which further hoisting would be unsafe, limit switch 213 is caused to open. Opening of limit switch 213 effects deenergization of solenoid coil 212 and dump valve 155 assumes the dump position shown in FIG. 7 due to the force of biasing spring 215. In dump position, valve 155 disconnects the downstream portion of pressure line 142 from accumulator 33 and connects it to return line 156 thereby causing depressurization of all valves and cylinders supplied by line 142. This causes fail-safe brake lock cylinders 102 and 171 to set or lock the brakes on their respective drums. However, front and rear drum brake pedal valves 125 and 151, respectively, are pressurized independently from accumulator 133 through pressure line 159. These two valves and their associated cylinders, therefore, can continue to perform their control functions at all times. Thus, the boom 15 cannot be raised further, no load can be raised further, and no other control function can be accomplished until override switch 216 is closed to energize solenoid 212 whereupon the boom can be lowered to a safe position wherein limit switch 213 recloses and normal functions can continue to be carried out.

We claim:

1. A control system for a crane having a boom, a boom hoist drum, at least one load hoist drum for controlling a load suspended from said boom, and a brake for said load hoist drum comprising:

a boom hoist drum control member,

a load hoist drum control member,

a load hoist drum brake control member,

each of said control members having a neutral position and each being movable therefrom to other positions to effect a control function,

a source of pressurized hydraulic fluid, a return reservoir and individual hydraulic valves controlled by said control members, each valve having an engaged position wherein it is supplied with fluid from said source,

a brake lock control member selectively movable to a position wherein it effects locking of said brake,

said boom hoist drum control member being movable from neutral position to one position to engage a valve for a boom hoist clutch cylinder and to another position to engage a valve for a boom hoist planetary brake cylinder,

said load hoist drum control member being movable from neutral position to one position to engage a valve for a load hoist clutch cylinder and to another position to engage a valve for a load hoist planetary brake cylinder,

said load hoist drum brake control member being movable from neutral position to one position to engage a valve for a load hoist drum brake cylinder,

said brake lock control member being movable to its said position to engage a valve for a load hoist drum brake lock cylinder,

a dead-man control member selectively movable to a position wherein it effects locking of said brake in the event said load hoist drum control member is in neutral position,

said dead-man control member being movable to one position to engage a valve for said brake lock cylinder,

and a boom-control member actuable to a position by elevation of said boom to a predetermined point to render all of said control members ineffective, except said load hoist drum brakecontrol member,

said boom control member being movable to its said position to engage a valve for disconnecting from said fluid source and connecting to said reservoir said valves for said boom hoist clutch cylinder, said boom hoist planetary brake cylinder, said load hoist clutch cylinder, said load hoist planetary brake cylinder, and said brake lock cylinder.

2. A control system for a crane having at least one load hoist drum for controlling a load suspended therefrom and a brake for said load hoist drum comprising:

a load hoist drum control member,

a load hoist drum brake control member,

each of said control members having a neutral position and each beingmovable therefrom to at least one other position to effect a control function,

a brake lock control member selectively movable to a position wherein it effects locking of said brake, said load hoist drum control member being movable from neutral position to one position to engage a valve for a load hoist clutch cylinder and to another position to engage a valve for a load hoist planetary brake cylinder,

and a dead-man control member selectively movable to a position wherein it effects locking of said brake in the event said load hoist drum control member is in neutral position,

said dead-man control member being movable to one position to engage a valve for said brake lock cylinder.

3. A control system for a crane having a boom, a boom hoist drum and at least one load hoist drum for controlling a load suspended from said boom comprising:

a boom hoist drum control member,

at least one load hoist drum control member,

each of said control members having a neutral position and each being movable therefrom to other positions to effect a control'function,

and a boom-control member actuable to a position by elevation of said boom to a predetermined point to render all of said control members ineffective,

said boom-control member being movable to its said position to engage avalve for disconnecting from said fluid source and connecting to said reservoir said valves for said boom hoistclutch cylinder, said boom hoist planetary brake cylinder, said load hoist clutch cylinder, and said load hoist planetary brake cylinder.

4. A hydraulic controlsystem according to claim I wherein said boom-control member comprises a solenoid coil for operating its associated valve and a limit switch responsive to boom position for controlling energization of said solenoid coil.

5. A hydraulic control system according to claim 4 wherein said limit switch effects deenergization of said solenoid coil when said boom is hoisted to a predetermined position.

6. A hydraulic control system according to claim 1 wherein said valve engaged by said dead-man control member connects said brake. lock cylinder through a shuttle valve to said valve for said load hoist planetary brake cylinder and to said valve for said load hoist drum clutch.

7. A hydraulic control system according to claim 3 wherein said boom-control member comprises a solenoid coil for operating its associated valve and a limit switch responsive to boom position for controlling energization of said solenoid coil.

8. A hydraulic control system according to claim 7 wherein said limit switch effects deenergization of said solenoid coil when said boom is hoisted to a predetermined position.

9. A hydraulic control system according to claim 2 wherein said valve engaged by. said dead-man control member connects said brake lock cylinder through a shuttle valve to said valve for said load hoist planetary brake cylinder and to said valve for said load hoist drum clutch.

Claims

1. A control system for a crane having a boom, a boom hoist drum, at least one load hoist drum for controlling a load suspended from said boom, and a brake for said load hoist drum comprising: a boom hoist drum control member, a load hoist drum control member, a load hoist drum brake control member, each of said control members having a neutral position and each being movable therefrom to other positions to effect a control function, a source of pressurized hydraulic fluid, a return reservoir and individual hydraulic valves controlled by said control members, each valve having an engaged position wherein it is supplied with fluid from said source, a brake lock control member selectively movable to a position wherein it effects locking of said brake, said boom hoist drum control member being movable from neutral position to one position to engage a valve for a boom hoist clutch cylinder and to another position to engage a valve for a boom hoist planetary brake cylinder, said load hoist drum control member being movable from neutral position to one position to engage a valve for a load hoist clutch cylinder and to another position to engage a valve for a load hoist planetary brake cylinder, said load hoist drum brake control member being movable from neutral position to one position to engage a valve for a load hoist drum brake cylinder, said brake lock control member being movable to its said position to engage a valve for a load hoist drum brake lock cylinder, a dead-man control member selectively movable to a position wherein it effects locking of said brake in the event said load hoist drum control member is in neutral position, said dead-man control member being movable to one position to engage a valve for said brake lock cylinder, and a boom-control member actuable to a position by elevation of said boom to a predetermined point to render all of said control members ineffective, except said load hoist drum brake control member, said boom control member being movable to its said position to engage a valve for disconnecting from said fluid source and connecting to said reservoir said valves for said boom hoist clutch cylinder, said boom hoist planetary brake cylinder, said load hoist clutch cylinder, said load hoist planetary brake cylinder, and said brake lock cylinder.

2. A control system for a crane having at least one load hoist drum for controlling a load suspended therefrom and a brake for said load hoist drum comprising: a load hoist drum control member, a load hoist drum brake control member, each of said control members having a neutral position and each being movable therefrom to at least one other position to effect a control function, a source of pressurized hydraulic fluid, a return reservoir and individual hydraulic valves controlled by said control members, each valve having an engaged position wherein it is supplied with fluid from said source, a brake lock control member selectively movable to a position wherein it effects locking of said brake, said load hoist drum control member being movable from neutral position to one position to engage a valve for a load hoist clutch cylinder and to another position to engage a valve for a load hoist planetary brake cylinder, said load hoist drum brake control member being movable from neutral position to one position to engage a valve for a load hoist drum brake cylinder, said brake lock control member being movable to its said position to engage a valve for a load hoist drum brake lock cylinder, AND a dead-man control member selectively movable to a position wherein it effects locking of said brake in the event said load hoist drum control member is in neutral position, said dead-man control member being movable to one position to engage a valve for said brake lock cylinder.

3. A control system for a crane having a boom, a boom hoist drum and at least one load hoist drum for controlling a load suspended from said boom comprising: a boom hoist drum control member, at least one load hoist drum control member, each of said control members having a neutral position and each being movable therefrom to other positions to effect a control function, a source of pressurized hydraulic fluid, a return reservoir and individual hydraulic valves controlled by said control members, each valve having an engaged position wherein it is supplied with fluid from said source, said boom hoist drum control member being movable from neutral position to one position to engage a valve for a boom hoist clutch cylinder and to another position to engage a valve for a boom hoist planetary brake cylinder, said load hoist drum control member being movable from neutral position to one position to engage a valve for a load hoist clutch cylinder and to another position to engage a valve for a load hoist planetary brake cylinder, and a boom-control member actuable to a position by elevation of said boom to a predetermined point to render all of said control members ineffective, said boom-control member being movable to its said position to engage a valve for disconnecting from said fluid source and connecting to said reservoir said valves for said boom hoist clutch cylinder, said boom hoist planetary brake cylinder, said load hoist clutch cylinder, and said load hoist planetary brake cylinder.

4. A hydraulic control system according to claim 1 wherein said boom-control member comprises a solenoid coil for operating its associated valve and a limit switch responsive to boom position for controlling energization of said solenoid coil.

6. A hydraulic control system according to claim 1 wherein said valve engaged by said dead-man control member connects said brake lock cylinder through a shuttle valve to said valve for said load hoist planetary brake cylinder and to said valve for said load hoist drum clutch.

9. A hydraulic control system according to claim 2 wherein said valve engaged by said dead-man control member connects said brake lock cylinder through a shuttle valve to said valve for said load hoist planetary brake cylinder and to said valve for said load hoist drum clutch.