US2767550A

US2767550A - Control system for hydraulic motor units

Info

Publication number: US2767550A
Application number: US469760A
Authority: US
Inventors: Lapsley Robert
Original assignee: Clark Equipment Co
Current assignee: Doosan Bobcat North America Inc
Priority date: 1954-11-18
Filing date: 1954-11-18
Publication date: 1956-10-23
Anticipated expiration: 1973-10-23

Description

Oct. 23, 1956 R LAPsLEY 2,767,550

CONTROL SYSTEM FOR HYDRAULIC MOTOR UNITS Filed NOV. 18, 1954 2 Sheets-Sheet 1 FIG. I

INVENTOR. ROBERT LAPSLEY m hwg mpm ATTY.

Oct. 23, 1956 R. LAPSLEY 2,767,550

CONTROL SYSTEM FOR HYDRAULIC MOTOR UNITS Filed Nov. 18, 1954 2 Sheets-Sheet FIG; 2

IN V EN TOR. ROBERT LAPSLEY BY I ATTY.

United States Patent 2,767,550 CONTROL SYSTEM FOR HYDRAULIC MOTOR UNITS Robert Lapsley, Buchanan, Mich, assignor to Clark Equipment Company, a corporation of Michigan Application November 18, 195%, Serial No. 469,760 5 Claims. (Cl. 60-97) My present invention relates to a hydraulic system for controlling a plurality of hydraulic units which may for example be found embodied in industrial fork lift trucks.

Presently, a number of hydraulic units are embodied in conventional industrial fork lift trucks for tilting the uprights, elevating the load supporting carriage and actuating auxiliary load engaging devices mounted to the latter. These hydraulic units are supplied with operating fluid from a single source of fluid pressure or pump. This system is unsatisfactory because of the ditference in capacitiesbetween the several hydraulic units. The hydraulic unit which serves to operate the load supporting carriage is of large capacity and requires a relatively large fluid flow, while the other hydraulic units are of small capacity and require only a relatively small fluid flow.

Obviously the single pump must be of relatively large capacity to properly operate the large capacity hydraulic unit. However, such a large capacity pump does not permit the proper operation of the small capacity hydraulic units since it is difiicult to tap-ofl a small supply of fluid pressure from a large supply source with any degree of consistently smooth results. The pump delivers such a large amount of fluid that as valve means is opened for directing fluid to a small capacity hydraulic unit there is a sudden surge of fluid and operation is begun with a jerk. Such improper operation frequently causes damage to the hydraulic units, the truck or the load carried thereby.

It is an object of my present invention to provide a hydraulic system which may be actuated to provide different amounts of fluid under pressure for properly operating any one of aplurality of hydraulic units at least one of which requires a relatively large fluid flow and at least another of which requires only a relatively small I accomplish the above object by providing a hydraulic system with two sources of fluid pressure. The fluid delivered by both sources is selectively employed for actuating the hydraulic unit requiring the relatively large fluid flow and the fluid delivered by only one source is selectively employed for actuating one of the hydraulicunits requiring the relatively small fluid flow. With this system, damage due to actuation of the hydraulic units is eliminated since the latter each can be provided with the proper amount of fluid under pressure for smooth operation. As will be described in detail hereinafter, I

have also provided novel valve means which is particularly adapted for use in my above described hydraulic system.

Now, in order to acquaint those skilled in the art with the manner of constructing and using hydraulic system in accordance with the principles of my present invention,

I shall describe in connection with the accompanying drawings, a preferred embodiment of my invention.

In the drawings:

Figure 1 is a diagrammatic showing of the hydraulic control system of my present invention; and

Figure 2 is a sectional view of the valve means employed in the hydraulic control system of Figure 1.

Referring now to the drawings, I shall describe the hydraulic control system of my present invention which comprises a pump assembly indicated generally by the reference numeral 10. The pump assembly 10 provides two sources of fluid pressure and may take the form of two separate pumps or, as shown, of a unitary dual unit pump, such as is disclosed and claimed in my copending application, Serial No. 454,673, filed September 8, 1954. More specifically, the pump assembly 10 has a single common inlet 12 and a pair of

separate outlets

14 and 16. The path of fluid flow through the pump assembly is illustrated by the dot-dash lines in Figure 1.

The inlet 12 of the pump assembly 10 is connected through piping 18 to a fluid supply or sump tank 20.

To protect the elements of the hydraulic system and the hydraulic units operated thereby,

relief valves

22 and 24 are mounted respectively at the

pump outlets

14 and 16. The

relief valves

22 and 24 are connected with the sump tank 20 through

fluid lines

26 and 28 for bypassing fluid back to the sump tank 20 in the event that the pressure of the fluid being delivered by the pump assembly 10 exceeds a predetermined maximum safe value.

As will be presently described, the

relief valves

22 and 24 permit fluid, which is of a pressure less than the predetermined maximum safe value, to pass therethrough for delivery to the control valve means of my present invention which is shown diagrammatically in Figure 1 and in cross-section in Figure 2. As will be understood by those skilled in the art, the several sections of the control valve means may be formed independently and joined by suitable piping or may be formed in a unitary valve housing 32 with internal passageways such as shown in Figure 2.

The relief valve 22 is connected by means of a fluid passageway 30 with one end of the valve housing 32, while the relief valve 24 is connected by means of a fluid passageway 34 with one side of the valve housing 32' parallel, spaced The valve open- The control valve means includes four

apart valve openings

36, 38, 40 and 42. ing 36 is formed with axially spaced

annular grooves

44, 45, 46, with axially spaced

annular grooves

50, 51, 52, 53 and 54; the valve opening 40 is formed with axially spaced

annular grooves

56, 57 and 58; and the valve opening 42 is formed with

annular grooves

60, 61 and 62. Axially

slideab'le spool valves

64, 66, 68 and 7t) are disposed. and' respectively in

thevalve openings

36, 38, 40 and 42 constitute the

valve units

72, 74, 76 and 78.

The aforedescribed fluid passageway 38, as shown in'th'e drawings, communicates with the

annular grooves

45 and 47 in the valve opening 36, while the annular groove 46 communicates through a fluid passageway Sllwith the

annular grooves

51 and 53 in the valve opening 38.

The annular groove 52 in the valve opening 38 communicates through a fluid passageway 82 with the. an-

nular groove 57 in the valve opening 40. The afore-.

one ends with the annular groove 56 in the valve open ing 40 and with the annular groove 62 in the valve opening 42. The other ends. of the

fluid passageways

84 and 86 connect with a common fluid passageway 88 which, as shown in Figure 1, is connected with the sump tank 20.

The

annular grooves

44 and 48 in the valve opening 36 and the

annular grooves

50 and 54 in the valveopening 38 are adapted to be respectively connected, through fluid lines 81 Patented Oct. 23, 1956 47 and 48; the valve opening 38 is formed,

and 83, and and 87, to the opposite ends of double-acting hydraulically actuated units, while the-annular groove 69 inthe valve opening to be connected, through a fluid line 89, to the one end of a single-acting hydraulic unit. The single-acting unit may, forexarnple constitute the hydraulic piston' and cylinder assembly which is incorporatedin art-industrial lift truck for elevating the load supporting carriage of the truck. Fluid need only be forced into the lower end of the cylinder of the hydraulic assembly to cause upward movement of the load supporting carriage, the weight of the assembly being relied-on to eflcct lowering of the carriage when fluid is bled from the cylinder of the hydraulic assembly. The double-acting'units may constitute hydraulic piston cylinder assemblies which are incorporated in industrial lift truck foreffecting tilt of the uprights or actuation of auxiliary devices such as load clamps or load shifters secured to the load supporting carriage. In the applications of the hydraulic units noted, the double-acting units are of small capacity and require only a relatively small fluid flow, while the single-acting unit is of large capacity and requires a relatively large fluid flow. Because the construction and operation of hydraulic units, industrial lift trucks and auxiliary devices therefor are well known to those in the material handling field and since they do not constitute part of my present invention, it is thought to be unnecessary to include a showing and description thereof in the present disclosure.

Returning now to the spool valves, it will be noted that the valve 64 is formed with axially spaced

annular channels

90 and 92; that the valve 66 is formed with axially spaced

annular channels

94 and 96; and that the

valves

68 and 70 are formed respectively with

annular channels

98 and 100. Incorporated with the ends of the

valves

64, 66, 68 and 70 are axially extendingstems 102, 104, 106 and 108 which are pivotally connected to

links

110, 112, 114 and 116. The links 110 and 112, in turn, are respectively pivotally connected to actuating 1evers118 and 120 which are fulcrumed M122 and 124, while the

links

114 and 116 are pivotally connected to a common actuating lever 126 which is fulcrumed at 128. From the foregoing description, it will be realized that the

valves

64 and 66 may be moved axially independently of each other and ofvalves 68 and 70, while the

valves

68 and 70 may be moved simultaneously axially in opposite directions, but independently of

valves

64 and 66.

The valve housing 32 may be enclosed in a fluid tight casing and all vented fluid returned to the sump tank 20 through a return line (not shown). Alternatively, in some applications, the valve housing 32 may be mountedin the sump tank 20 so as to eliminatefluid return lines.

I shall. now describe the operation of the hydraulic system of my present invention wherein the fluid delivered by one unit of the pump assembly may be used for actuating the small capacity hydraulic unit connected with either the valve unit 72 or the valve unit 74, or the fluid delivered by both pump units may be used to actuate the large capacity hydraulic unit connected with the

valve units

76 and 78.

When the

valves

64, 66, 68 and70 are in theirneutral or mid-point positions, as shown in Figure 2, fluid under pressure flowing through the passageway 30 from the one pump unit is returned to the sump tank'20through the interconnecting

annular grooves

45 and 47, annular channels 90'and 92, passageway 80,

annular grooves

51 and 53,

annular channels

94 and 96, passageway 82,.annular groove 57, annular channel 98, annular groove 56, and

passageways

84 and 88; Also, fluid under pressure delivered through the passageway 34 from the. other pump unit is returned to the sump tank through passageway 59, annular groove 61, annular channel 100, annular groove 62, and passageways 86' and 88.

Should it be desired to effect actuation of. the hydraulic unit associated with the control valve unit 72, the actuat- 42- is adapted i ing lever 118 need only be pivoted about the fulcrum 122- for axially moving the valve 64 in one direction or the other. If the lever 118 is pivoted clockwise from the position shown in Figure 2, the valve 64 is moved to the right, communication between the passageways 30 and is blocked by the body of valve 64, and fluid is directed from the passageway 30 through the annular channel 92 to the annular groove 48 which is connected to one end ofthe hydraulic unit by fluid line 83. Simultaneously the body of valve 64 is moved away from the annular groove 44 and thus the latter communicates outwardly of the valve housing 32 for bleeding fluid from the other end of the hydraulic unit connected to the fluid line 81. At such time as the hydraulic unit has been actuated the desired amount, the valve 64 may be returned to the neutral position shown in Figure 2 thus blocking fluid flow to or from the hydraulic unit until the valve 64 is further actuated.

If the hydraulic unit associated withthe valve unit 72 is to be actuated in a direction opposite to that just described, the lever 118 is pivoted in a counterclockwise direction for moving the valve 64 axially to the left. When the valve 64 is moved to the left, communication between the

passageways

30 and 80 is again blocked by the body of valve 64 and fluid is directed from the passageway 30through the annular channel 90 to the annular groove 44 which is connected to the other end of the hydraulic unit by fluid line 81. Simultaneously, the body of the valve 64 is removed from register with the annular groove 48 whereupon the latter is permitted to open outwardly of the valve housing 32 so as to allow fluid to drain from the one end of the hydraulic unit connected to the fluid line 83. As noted, actuation of the hydraulic unit may be interrupted at any time by returning the valve 64 to the position shown in Figure 2.

When the valve 64 is maintained in its neutral position, the valve 66 may be actuated by the lever 120 for controlling operation of the hydraulic unit associated with the control valve unit 74. The valve 66 is controlled and operates in the same manner as the valve 64. It serves to place passageway 80 into communication with either annular groove 50 and fluid line or annular groove 54 and fluid line 87. In either position communication between the

passageways

80 and 82 is interrupted.

It is to be noted that whenever the

valve

64 or 66 is actuated while the

valve

68 and 70 are maintained in a neutral position, only fluid under pressure the passageway 30 from one of the pump units is directed to the hydraulic unit associated with the

respective valve unit

72 or 74. The fluid under pressure flowing through the passageway 34 from the other pump unit is returned directly to the sump tank as aforedescribed, through the passageway 59, annular groove 61, annular channel 100, annular groove 62, and

fluid passageways

86 and 88.

When it is desired to effect operation of the hydraulic unit associated with the

control units

76 and 78, the

valves

64 and 66 are placed in the neutral positions shown in Figure 2, and the valve 68 is moved to the right while i the valve 70 is moved to the left through clockwise movement of the actuating lever 126 about fulcrum 128. When the

valves

66 and 68 are so moved, fluid under pressure delivered by bothof the pump units is directed to the hydraulic unit connected with the annular groove 60 through fluid line 89. Fluid flows from the passageway 34 to the annular groove'60 through the passageway 59, annular groove 61 and annular channel 100. Also, fluidiflows from the passageway 30 to the annular groove 60 through the

annular grooves

45 and 47,

annular channels

90 and 92,, annular groove 46, passageway 80,

annular grooves

51 and 53,

annular channels

94 and 96, an-

nular groove 52, passageway 82, annular groove 57, 3th,

nular channel 98, annular groove 58, passageway 59, annular groove 61, and annular channel 100. i

Once fluid has been delivered to the hydraulic unit flowing through i associated with the

valve units

76 and 78 it may be maintained or trapped therein by returning the

valves

68 and 70 to the positions shown in Figure 2 so that the body of the valve 70 will block the annular groove 60. Should it then become desirable to bleed fluid from the hydraulic unit, the actuating lever 126 need only be pivoted counterclockwise from the position shown in Figure 2 for moving the body of the valve 76 out of register with the annular groove 60 so as to permit the latter to communicate outwardly of the valve housing 32. After the desired amount of fluid has been bled from the hydraulic unit, the

valves

68 and 70 may be returned to the neutral positions shown in Figure 2.

In conclusion, the hydraulic system of my present invention provides control for a plurality of hydraulic units one of which requires a relatively large fluid flow and the others of which require only a relatively small fluid flow. Two sources of fluid pressure are provided with the fluid delivered by both sources being selectively employed for actuating the hydraulic unit requiring the relatively large fluid flow and with the fluid delivered by one source being selectively employed for actuating one of the hydraulic units requiring the relatively small fluid flow. This arrangement is such that different amounts of fluid under pressure are readily available for distribution to a plurality of hydraulic units of different capacity. Thus, the several hydraulic units may be operated smoothly, and damage due to operation of the hydraulic units eliminated.

Now, while I have shown and described what I believe to be a preferred embodiment of my present invention, it will be understood by those skilled in the art that various rearrangements and modifications may be made therein without departing from the spirit and scope of my invention.

I claim:

1. A hydraulic system for controlling actuation of first and second hydraulic units comprising the combination of a pump assembly having two separate outlets and a common inlet connected with a sump tank, fluid passageway means extending between said pump outlets and the first and second hydraulic units and said sump tank, first and second valve means interposed in said fluid passageway means and having neutral positions wherein fluid under pressure delivered by said pump assembly is permitted to return directly to said sump tank, said first valve means when moved from a neutral position being operable to permit fluid under pressure to flow from one of said pump outlets through said fluid passageway means to the first hydraulic unit, and said second valve means when moved from a neutral position being operable to permit fluid under pressure to flow from both of said pump outlets through said fluid passageway mans to the second hydraulic unit when said first valve means is in neutral.

2. A hydraulic system for controlling actuation of first and second hydraulic units comprising the combination of a pump assembly having two separate outlets and an inlet connected with a sump tank, first fluid passageway means extending between one of said pump outlets and said sump ta first valve means operable to interrupt communication between said first fluid passageway means and said sump tank and to permit fluid under pressure to flow from said one pump outlet through said first fluid passageway means to the first hydraulic unit and having a neutral position wherein pressurized fluid delivered thereto by said pump assembly is returned to said sump tank, second fluid passageway means extending between the other of said pump outlets and said first fluid passageway means, and second valve means operable to interrupt communication between said first and second fluid passageway means and said sump tank and to permit fluid under pressure to flow from both said pump outlets through said first and second fluid passageway means to the second hydraulic unit when said first valve means is in neutral position.

3. A hydraulic system for controlling actuation of first and second hydraulic units comprising the combination of a pump assembly having two separate outlets and an inlet connected with a sump tank, first fluid passageway means extending between one of said pump outlets and said sump tank, first valve means operable to interrupt communication between said first fluid passageway means and said sump tank and to permit fluid under pressure to flow from said one pump outlet through said first fluid passageways means to the first hydraulic unit and having a neutral position wherein pressurized fluid delivered thereto by said pump assembly is returned to said sump tank, second fluid passageway means extending between the other of said pump outlets and said fluid passageway means, second and third simultaneously actuatable valve means, said second valve means being operable to interrupt communication between said first fluid passageway means and said sump tank and to permit fluid under pressure to flow from said one pump outlet through said first fluid passageway means to the second hydraulic unit when said first valve means is in neutral position, and said third valve means being operable to interrupt communication between said second fluid fluid passageway means receives fluid under pressure from both of said pump outlets.

4. A hydraulic system for controlling actuation of first and second hydraulic units comprising the combination of a pump assembly having two separate outlets and an inlet connected with a sump tank, a valve housing having first and second valve means therein, first fluid passageway means extending between one of said pump outlets and said valve housing, second fluid passageway means extending between the other of said pump outlets and said valve housing, third fluid passageway means extending between said valve housing and the first hydraulic unit, fourth fluid passageway means extending between said valve housing and the second hydraulic unit, fifth fluid passageway means extending between said valve housing and said sump tank, said first and second fluid passageway means normally communicating with said fifth fluid passageway means through said valve housing, said first valve means being operable to interrupt communication between said first and fifth fluid passageway means and to place said first and third fluid passageway means in communication and having a neutral position wherein pressurized fluid delivered thereto by said pump assembly is returned to said sump tank, and said second valve means being operable to interrupt communication between said first, second and fifth fluid passageway means and to place said first and second fluid passageway means in communication with said fourth fluid passageway means when said first valve means is in neutral position.

5. A hydraulic system for controlling actuation of a first hydraulic unit requiring a relatively small fluid flow and a second hydraulic unit requiring a relatively large fluid flow comprising the combination of a pump assembly having two separate outlets and an inlet connected with a sump tank, a valve housing having first, second and third valve means therein, first fluid passageway means extending between one of said pump outlets and said valve housing, second fluid passageway means extending between the other of said pump outlets and said valve housing, third fluid passageway means extending bet-ween said valve housing and the first hydraulic unit, fourth fluid passageway means extending between said valve housing and the second hydraulic unit, fifth fluid passageway means extending between said valve housing and said sump tank, said first and second fluid passageway means normally communicating With said fifth fluid passageway means through said valve housing, said first valve means being operable to interrupt communication between said first and fifth fluid passageway means and to place saidfirst and third fluid passageway means in communication and having a neutral position wherein pressurized fluid delivered thereto by said pump assembly is reutrned to said sump tank, and said second and third valve means being operable simultaneously to interrupt communication between said first, second and fifth fluid passageway, means and to place said first and second fluid passageway means in communication with said fourth fluid passageway means when said first valve means is in neutral position.

References Cited in the file of this patent UNITED STATES PATENTS Henry Dec. 28, 1937 Lindgren Ian. 12, 194-3 Ulinski May 29, 1951 Carlson June 30, 1953 Moon Oct. 20, 1953