US2985142A

US2985142A - Fluid-actuated floor crane

Info

Publication number: US2985142A
Authority: US
Inventors: Laverne R Aiken
Original assignee: RUGER EQUIPMENT Inc
Current assignee: RUGER EQUIPMENT Inc
Priority date: 1959-04-22
Filing date: 1959-04-22
Publication date: 1961-05-23
Anticipated expiration: 1978-05-23

Description

y 23, 1961 L. R. AIKEN 2,985,142

FLUID-ACTUATED FLOOR CRANE Filed April 22, 1959 3 Sheets-Sheet l LAVERNE R. AIKEN 74M rm May 23, 1961 L. R. AIKEN 2,985,142

FLUID-ACTUATED FLOOR CRANE Filed April 22, 1959 3 Sheets-Sheet 2 INVENTOR.

if 2 LAVERNE R. AIKEN W64 W v /%Afl%- May 23, 1961 Filed April 22, 1959 1 In l L. R. AIKEN 5 Sheets-Sheet I5 /-46 49 7 u #57 47 v58 ij V59 INVENTOR.

LAVERNE R. AIKEN FLUID-ACTUATED FLOOR CRANE Laverne R. Aiken, New Philadelphia, Ohio, assignor to Roger Equipment, Inc., Uhrlchsvllle, Ohio, a corporation of Ohio Filed Apr. 22, 1959, Ser. No. 808,185

Claims. (Cl. 121-38) This invention relates to a fluid-actuated floor crane. It relates, more particularly, to the general type of crane mounted on a movable base and which is of the hydraulically-operated cantilever type. The general structure of such a crane is disclosed in the patent to Ruger et al., No. 2,389,872 which issued November 27, 1945. More specifically, it relates to the control in regard to eifort and speed, of the power stroke of a hydraulic or air piston and cylinder assembly used in a crane of the type indicated and in which the return stroke is eflfected by gravity.

As an example of this present invention, there is incorporated in a hydraulic floor crane of the general type indicated a novel and advantageous hydraulic control system. This novel control system is connected with the ram which controls vertical swinging of the load-lifting cantilever arm that is mounted for vertical swinging movement on the base or pedestal of the crane. This control system includes a directional control valve which is connccted between the ram and the pump which supplies pressure to the ram. The control valve is of such a design and is so connected in the hydraulic system of the crane as to obtain a differential action in speed and thrust of the ram during its power stroke. The ram in a crane of the type indicated serves to apply an upward swinging or lifting force to the cantilever arm and when the load is to be lowered, the arm will return to a lower position by gravity upon proper manipulation of the usual control valve. With the present invention, it is possible to manipulate the valve so as to provide selectively high lifting force and low speed or low lifting force and high speed. Thus, if the load is light, the crane can act more speedily to dispose of it whereas if the load is heavy, the crane will act on the load more slowly but with increased force.

The accompanying drawings illustrate the preferred embodiment of this invention but specific changes may be made without departing from basic principles.

In these drawings:

Figure l is a side elevational view of a hydraulic floor crane in which this invention is embodied.

Figure 2 is a schematic view of the hydraulic system of the crane, showing the control valve in section in highspeed, low-thrust condition.

Figure 3 is a vertical sectional view through the control valve of the hydraulic system showing it set in low-speed,

high-thrust position.

Figure 4 is a view similar to Figure 3 but showing the valve set in load-release position.

With reference to the drawings and specifically to Figure 1, this invention is shown embodied in a crane of the general structure disclosed in Patent No. 2,389,872 and the specific structural details are not important but the crane is shown as comprising a suitable base on which is rigidly mounted an upright mast, standard or pedestal 11. The base may be carried by suitable wheels 12 so that it is portable. The pedestal 11 is at one side of the base and is braced thereon by means of an angularly disposed brace 10a. A third class lever or cantilever boom or arm 13 has its inner end pivoted at Patent 0" 2,985,142 Patented May 23, 1961 14 to the upper end of the pedestal 11 so that the arm can swing in a vertical plane about said pivot. The outer end of this arm 13 may carry a hook 15 by means of which a load can be attached to the arm.

An hydraulic ram 16 is provided, as shown in Figure l, for imparting vertical swinging movement to the arm 13. The ram is shown as comprising a cylinder 17 which is pivoted at its lower end at 18, near the junction of the pedestal 11 and base 10, and which has a piston rod 19 extending upwardly therefrom with its upper end pivoted at 20 to the arm 13 at a point spaced outwardly of the arm pivot 14. As shown in Figure 2, the lower end of the piston rod 19 is connected to a piston 21 which is mounted for axial sliding movement in the cylinder 17.

Pressure for actuating the ram 16 is provided by means of a suitable hydraulic pump 25 which in Figure l is shown as being of the manual type operated by means of a hand lever 26 but other types of pumps may be used. The pump has its suction side connected to a fluid reservoir 27 by means of a suction conduit 28. At its pressure side the pump 25 is provided with an outlet line 29 which includes a branch 30 that is connected to the lower or high pressure end of the cylinder 17 and a flexible branch 31 that is connected to a control valve 35. The control valve 35 is of a release or shut-off type with overload pressure relief mounted at a suitable level on the pedestal 11 and is connected by a flexible conduit 36 to the upper end of the cylinder 17. The valve 35 is also connected by an exhaust or return conduit 37 to the reservoir 27.

The control valve 35 is designed to direct the volume of fluid displaced above the piston 21 as the ram is actuated to exert a lifting force on the arm 13, either to the head side or lower side of the piston 21 or to the reservoir 27. If such fluid is exhausted to the reservoir, the pressure above the piston 21 is atmospheric and the effective working area of the ram is that of the entire area of the lower surface or head 40 of the piston 21 so as to obtain maximum lifting force on the piston. However, if the exhausted fluid is directed to the underside or head side of the piston 21, the pressure in the cylinder 17 above and below the piston head is equalized and the effective working area of the ram is that of the cross-sectional area of the piston rod, or the difierence between the exposed upper annular surface 41 of the piston and its lower head surface 40. In the latter condition, the speed of travel of the piston is increased in relation to the increased volume of fluid supplied into the cylinder 17 at the head or lower side of the piston 21. Thus, speed and eflort depend on the ratio of the piston head end area to the rod end annular area.

In order for the valve 35 to function in this manner, it is constructed as shown in Figures 2, 3 and 4. it comprises a body or housing 45 having the three ports 46, 4-7 and 48 to which are connected, respectively, the

lines

36, 37 and 31. Valve seats are provided at 49 and 50 for cooperating with a vertically adjustable valve stem 52 and a vertically adjustable needle 51, respectively. The valve needle 51 is slidably mounted in the hollow valve stem 52 that is threaded into the body at 53 and is rotated by means of an upper knob 54 and an oil seal is provided therebetween at 51a. A compression spring 55 is disposed between the upper end of the needle 51 and an adjusting screw 56 in the cap 54 which is used for adjusting the resistance of the spring 55. The spring 55 normally forces the needle 51 downwardly to its lowermost position in the hollow stem 52. When the cap 54 is turned so that stem 52 is screwed downwardly, as shown in Figure 2, the lower end of the hollow stem 52 is seated on the seat 49 and the lower pointed end of the needle 51 is seated on the seat 50. Therefore, communication between the

ports

46 and 47 and between

ports

47 and 48 is interrupted. However, it will be noted that there is a by-pass 57 between the

ports

46 and 48 and that this is controlled by an upwardly seating ball check valve 58 which is normally seated on its lower end by asprin g 59.

The operationrof the hydraulic system under control of the release valve 35 which has the pressure reliefincorporated therein :is as follows:

For high speed movement of the piston 21 upwardly in the cylinder 17, the cap 54 is turned so that valve stem 52 is screwed inwardly as far as possible, as shown in Figure 2. Fluid is pumped into the lowerend of the cylinder 17 and is prevented initially, from escaping into the valve because the needle 51 is seated on the seat 50 by the spring 55 and the check ball 58 is seated upwards ly by the spring .59. The piston 21 is moved upwardly and the fluid in the cylinder above the piston which is displaced .by upward movement of the piston must of necessity flow through the bypass 57 since the stem 52 is seated on -the seat 49, unseat the ball check 58, and eventually reach the lower end of the cylinder 17, thereby supplying a maximum volume offluid thereto. Therefore, it can be seen that in effect there exists a piston which is unbalanced for upward movement to the extent of the area of the piston rod 19. Consequently, due to this unbalance and maximum supply of fluid, a condition of speed but reduced load capacity or effort for upward movement of the cantilever arm 13 is obtained.

For high power or eifort, the valve stem 52 is released by a reverse turning of the knob 54, as shown in Figure 3. This unseats the stem 52 from the valve seat 49 so as to connect the

ports

46 and 47 and thereby allow the displaced fluid from the upper end of thecylinder 17 to reach the reservoir 27. The spring 55, still under compression, maintains the needle 51 seated on the seat 50 and the check ball 58 is also seated to prevent loss of fluid from the lower side of the cylinder 17. Therefore, the pressure on the upper side of the piston 21 is atmospheric and the piston 21 is unbalanced for upward movement to the extent of the area of the'entire lower surface 40 thereof. Furthermore, the volume of fluid supplied to the lower side of the cylinder 17 is reduced as compared to the prior setting of the valve 35. Therefore, a condition of higher effort and lower speed for upward movement of the crane arm 13 is obtained as compared to the first setting of the valve 35.

Adjustment of the set screw 56 in the stem '52 provides for the setting for an overload relief. When the pressure at the port 48 exceeds the preset relief pressure, the needle 51 will be forced upwardly against the force of the spring 55. The fluid will now escape to the reservoir 27 by circulating between the point of the displaced needle 51 and the seat 50 and then out through the port 47 through the conduit 37 to the reservoir 27.

With the setting of the valve 35 as indicated in Figure 2 or in Figure 3, the load on the arm 13 will be moved vertically when the pump 25 is operated and held when the pump is inoperative, unless an overload condition is encountered.

For releasing the load, the stem 52 is released farther from the position shown in Figure 3 as illustrated in Figure 4. This causes the shoulder 62 on the stem 52, which is normally below a shoulder 61 on the needle 51, to engage the shoulder 61 and lift the point of the needle oil the seat 50 and the stem 52 off the seat 49, as shown in Figure 4; This connects the port 48 with both

ports

47 and 46, and permits the escape of fluid from the lower end of the cylinder *17 to the reservoir 27 and/or into the top .of the cylinder 17. Thus, the loaded arm 13 From the above, it will be apparent that this invention provides a novel control arrangement for the gravity return fluid-actuated ram of a crane of the type indicated. The valve can be set to exhaust the fluid from the top of the cylinder into the reservoir or from the top of the cylinder into the lower end of the cylinder. In the first setting, high-efiort and low-speed of the ram will result and in the second setting high-speed and a predetermined reduced eflort of the ram will result. In case of overload, the valve will act automatically to relieve it.

According to the provisions of the patent statutes, the principles of this invention have been explained and have been illustrated and described in what is now considered to represent the best embodiment. However, it is to be understood that, withinthe scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

Having thus described this invention, what is claimed 1. In a fluid power system for efl?ecting the raising and lowering of a movable element, a fluid-ram comprising a cylinder having upper and 'lower ends and having a piston slidable therein with a piston rod connected to the piston and extending from the upper end of the cylinder and connected to said movable element so that the piston is normally returned to its lowermost position in the cylinder by gravity, a fluid pressure source having an outlet pressure line connected to the lower end of the cylinder and having an inlet line connected to a fluid reservoir, a control valve comprising a housing having first, second and third ports, a first line .connecting said first port to said reservoir, a second line connecting said second port and the outlet line of said fluid pressure source, a third line connecting said third port and the upper end of said cylinder, all of said ports communicating with a bore in the valve body, a bypass between said second and third ports having acheck valve with a spring acting to seat it to block the bypass, said check valve being also seated by pressure in said second line, a hollow valve stem threaded into said bore having an inner valve end and being rotatable from the exterior of the housing, a first valve seat in said bore between said first and third ports and a second valve seat in said bore between said first and second ports, a valve needle slidably mounted in said .valve stem and having an inner valve end and a spring which normally forces'it inwardly of said valve sleeve, said threaded stern being rotable to move its inner valve end relative to said first valve seat and to move the inner end of the needle relative to said second valve seat, means between the stem and the needle for varying the force exerted by said spring, and 'a shoulder on the stem inwardly of a shoulder on said needle whereby outward movement of the stem will Withdraw said needle from said second valve seat. 7

2. In a fluid power systemfor effecting the raising and lowering of a movable element, a fluid-ram comprising a cylinder having upper and lower ends and having a piston slidable therein'with a piston rod connected to the piston and extending from the upper end of the cylinder and connected to said movable element so'that the piston is normally returned to its lowermost position in the cylinder by gravity, a fluid pressure source having an outlet pressure. line connected to the lower end of the cylinder and having an inlet line connected to a fluid reservoir, a controlyvalve comprising a housing having first, second :and third ports, a first line connecting said first port to said reservoir, a second line connecting said second port and the outlet line of said fluid pressure source, a third lineconnecting said third port and the upper end of said cylinder, all of said ports communicating with a bore in the valve body, a by-pass between said second and third ports having a check valve with a spring acting to seat it to block thelby-pass, said check valve being also seated :by pressure in said second line. a hollow valve stem threaded into said bore having an inner valve end and being rotatable from the exterior of the housing, a first valve seat in said bore between said first and third ports and a second valve seat in said bore between said first and second ports, a valve needle slidably mounted in said valve stem and having an inner valve end and a spring which normally forces it inwardly of said valve sleeve, said threaded stem being rotatable to move its inner valve end relative to said first valve seat and to move the inner end of the needle relative to said second valve seat.

3. In a fluid power system for effecting movement of a movable element, means independent of the fluid power for returning the movable element to its original position after movement by the fluid power system, a fluid ram comprising a cylinder having a piston slidable therein with a piston rod connected to one end of the piston so that the end of the cylinder at the piston rod end of the piston is effectively smaller than the end of the cylinder at the opposite end of the piston, said rod extending from the smaller end of the cylinder and being connected to said movable element, a fluid pressure source having an outlet line connected to the larger end of the cylinder and having an inlet line connected to a fluid storage means, a control valve comprising a housing having first, second and third ports, a first line connecting said first port to said storage means, a second line connecting said second port to the outlet line of said fluid pressure source, a third line connecting said third port and the smaller end of said cylinder, all of said ports communicating with an axial passage in the valve body, a bypass between said second and third ports having a check valve normally blocking the by-pass and being seated by pressure in said second line, a hollow valve stem in said passage and being movable axially of said passage by means exterior of the housing, a first valve seat in said passage between said first and third ports and a second valve seat in said passage between said first and second ports, a valve needle slidably mounted in said valve stem and having an inner valve end and a spring which normally forces it inwardly of said sleeve, said stem being axially movable in said axial passage to move its inner valve end relative to said first valve seat and to move the inner end of the needle relative to said second valve seat.

4. In a fluid power system for efiecting movement of a movable element, means independent of the fluid power for returning the movable element to its original position after movement by said fluid power system, a fluid ram comprising a cylinder having a piston slidable therein with a piston rod connected to one end of the piston so that the end of the cylinder at the piston rod end of the piston is effectively smaller than the end of the cylinder at the opposite end of the piston, said rod extending from the smaller end of the cylinder and being connected to said movable element, a fluid pressure source having an outlet line connected to the larger end of the cylinder and having an inlet line connected to a fluid storage means, a control valve comprising a housing having first, second and third ports, a first lineconnecting said first port to said storage means, a second line connecting said second port to the outlet line of said fluid pressure source, a third line connecting said third port and the smaller end of said cylinder, all of said ports communicating with a passage in the valve body, a bypass between said second and third ports having a check valve normally blocking the by-pass and being seated by pressure in said second line, a hollow valve stem in said passage and being movable axially of said passage, a first valve seat in said passage between said first and third ports and a second valve seat in said passage between said first and second ports, a valve needle slidably mounted in said valve stem and having an inner valve end, said stem being axially movable in said passage to move its inner valve end relative to said first valve seat and to move the inner end of the needle relative to said second valve seat.

5. In a fluid power system, a fluid ram comprising a cylinder having a piston slidable therein with a piston rod connected to one end of the piston so that the end of the cylinder at the piston rod end of the piston is effectively smaller than the end of the cylinder at the opposite end of the piston, means independent of fluid power connected to said piston and tending to return and maintain the piston toward the larger end of the cylinder, fluid power supply means for moving said piston in a power stroke in the opposite direction comprising a fluid pressure source having an outlet line connected to the larger end of the cylinder and having an inlet line connected to a fluid storage means, a control valve comprising a housing having first, second and third ports, a first line connecting said first port to said storage means, a second line connecting said second port to the outlet line of said fluid pressure source, a third line connecting said third port to the smaller end of said cylinder, a check valve controlled by-pass between said second and third ports so that pressure inthe second line acts to close the check valve, a valve movably mounted in said valve body for controlling communication between said ports, said valve being movable to a first position where all of said ports are in communication to permit escape of fluid from the larger end of the cylinder to the storage means or the smaller end of the cylinder for the return stroke of the piston, said valve being movable to a second position where the third and first ports are connected and the second port is blocked so as to obtain a power stroke of the piston of maximum power but in low speed by supplying fluid from the fluid pressure source to the larger end of the cylinder and permitting escape of fluid from the smaller end of the cylinder to said storage means, said valve being movable to a third position to connect said third port to the second port through said by-pass and to block the first port leading to said storage means to obtain a power stroke of the piston of maximum speed but low power by supplying fluid from the fluid pressure source to the larger end of the cylinder and by directing the return fluid from the smaller end of the cylinder to the larger end of the cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 1,822,690 De Leeuw Sept. 8, 1931 1,990,052 Sosa Feb. 5, 1935 2,367,682 Kehle Jan. 23, 1945 2,389,872 Ruger Nov. 27, 1945 2,501,483 Taylor Mar. 21, 1950 2,646,025 Deardorfi July 21, 1953 2,699,875 Stratton I an. 18, 1955