US3822370A

US3822370A - Hydraulic control means with magnetic flow sensing spool

Info

Publication number: US3822370A
Application number: US00342306A
Authority: US
Inventors: O Olsen; J Elliott
Original assignee: AMF Inc
Current assignee: AMERICAN WYOTT CORP
Priority date: 1973-03-16
Filing date: 1973-03-16
Publication date: 1974-07-02
Anticipated expiration: 1991-07-02
Also published as: GB1421511A; NL7400468A; JPS49120085A; DE2404606A1

Abstract

A pair of reed switches are magnetically actuated by a flow sensing spool in the hydraulic circuit.

Description

United States Patent 1 [111 3,822,370 Olsen et al. July 2, 1974 HYDRAULIC CONTROL MEANS WITH 3,450,853 6/l969 Snyder ZOO/81.9 M ux N I O SENSING SPOOL 3,510,607 5/1970 Breed et al. ZOO/81.9 M UX [75] Inventors: Olaf M. Olsen, Old Saybrook; James OTHER PUBLICATIONS D Elliott Essex both of IBM Technical Disclosure Vol. 8, N0 7, p. 954; [73] Assignee: AMF Incorporated, Whit Pl i 12/1965; Multiconfiguration Pressure Switch, by

N.Y. Bolan et al.

[22] Flled: Mar. 1973 Primary ExaminerRobert K. Schaefer PP 342,306 Assistant Eraminr-Gerald P. Tolin Attorney, Agent, or Firm-George W. Price; Walter [52] US. Cl ZOO/81.9 M, 200/82 E Lewis [51] Int. Cl H0lh 35/40, I-IOlh 36/00 [58] Field Of Search ZOO/81.9 M, 82 E, 83 L 57 ABSTRACT 5 Rf Cited A pair of reed switches are magnetically actuated by a UNITED STATES PATENTS flow sensing spool in the hydraulic circuit.

3,224,270 12/!965 Karol et a1 ZOO/81,9 M UX 2 Clains, 3 Drawing Figures /Z I j /0 l 1 FIG. I

I6 y I 25 33 35" 5 l 36 I Z0 /9 32 y 1 HYDRAULIC CONTROL MEANS WITH MAGNETIC FLOW SENSING SPOOL This invention relates to control means for hydraulic systems, and more particularly, to flow responsive electrical control means for hydraulic circuits.

Although not restricted thereto, the invention is useful in controlling hydraulic waste compactors, and therefore will be illustrated in connection therewith.

IN THE DRAWINGS FIG. 1 is a diagrammatic illustration of the hydraulic circuit to be controlled;

FIG. 2 is a detail of the flow sensing reed switch actuator spool; and

FIG. 3 is a diagrammatic illustration of the electrical control circuit.

Referring now to the drawings, FIG. 1 shows a piston rod driven by a piston 11 in a cylinder 12. Rod 10 is adapted to drive a not shown waste compactor ram. When piston 11 is moved to the right it is compacting, and to the left retracting.

Piston 11 is driven in either direction by hydraulic pressure supplied by a pump 13 which in turn is driven by a motor 14. Pressurized fluid is supplied to either end of cylinder 12 and exhausted from the other end by a spring biased solenoid operated four way hydraulic valve 15. The position of valve 15 is controlled by a spring biased flow condition (flow or no flow) responsive magnetic spool 16, see also FIG. 2, which actuates two

reed switches

17, 18 in the electric control circuit, see also FIG. 3.

A pressure safety relief valve 19 is provided for the hydraulic system. The diagrammatically illustrated element 20 is a common fluid reservoir for supplying fluid to pump 13 and exhausting fluid from the exhaust port of the valve 15 and the relief valve 19.

In FIG. 2 the flow condition responsive spool 16 is illustrated as being lengthwise slidable in a housing 21. It is biased to a central neutral position by a pair of opposite end springs 22. Spool 16 has a central passage 23 formed therein and opposite ends of housing 21 are fitted with nipples 24 for connecting the housing 21 in the line 25 extending from four way valve 15 to the left end of cylinder 12..Spool 16 is constructed from magnetic material, that is, it is a magnet, whereas housing 21 is constructed from non-magnetic material. The pair of

reed switches

17, 18 are mounted in the side wall of housing 21 contiguous to the spool 16 but at opposite ends of the housing 21.

Switches

17, 18 are of the type that are normally open, but are magnetically actuated to closed position by the magnetic spool 16.

In FIG. 3 reed switch 17 is illustrated as being operable to closed position by magnet 16 to energize a relay coil 26 from a power supply. This relay coil 26 can also be energized by closing a start switch 27. Relay 26 closes contacts 28 and 29 for operating the valve 15 and motor 14 respectively.

The other reed switch 18 is operable closed by magnet 16 to energize another relay 30 to close another pair of contacts 31 for the motor 14 when the relay 26 is inactive and contacts 28 and 29 open.

In FIG. 1 the parts are shown in their normal off position with the piston in full retracted position at the end of the retracting stroke of a compacting cycle. The pump 13 is connected to valve 15 byline 32. Relief valve 19 is connected to line 32, and the valve 15 is connected to the right hand end of cylinder 12 by a line 33. The operation of the entire hydraulic and electrical system will now be described.

After the waste compactor is loaded, to compress its contents, the start switch 27 is first held closed. When switch 27 is closed relay 26 is energized to close contacts 28 and 29. Closure of contacts 28 results in actuation of valve 15 to a position such that fluid can flow from line 32 along the path of arrow 34 to line 25 and from line 33 along the path of arrow 35 to reservoir 20. Closure of contacts 29 by relay 26 starts up the motor 14 and pump 13. Thus pressurized fluid goes from pump 13 along line 32, arrow 34 and line 25 through the passage 23 in the spool 16 to the left end of the cylinder 12 to drive piston 11 to the right. As piston 11 moves to the right fluid leaves the right end of cylinder 12 via line 33 and arrow path 35 of the valve 15 back to the same reservoir 20 to which the pump 13 is connected.

When fluid is flowing along line 25 into the left end of cylinder 12 besides flowing through the passage 23 in spool 16, the fluid also drives the spool 16 to the left end of housing 21. When spool 16 comes opposite to switch 17 spool 16 magnetically closes the contacts of switch 17 to keep the relay 26 energized even though the start button 27 is released. With relay 26 still energized contacts 29 will stay closed to operate the pump motor 14 and contacts 28 will stay closed to keep the valve 15 energized so that flow continues from pump 13 to cylinder 12 along path 34 and from cylinder 12 back to the reservoir along path 35.

As long as piston 11 is moving to the right, fluid is flowing into the spool housing 21 in a direction of right to left. This fluid flow is sufficient to keep spool 16 driven to the left end of the spool housing to keep the reed contacts 17 closed. The fluid flow will cease when the piston 11 reaches the end of its compacting stroke. When piston 11 moves no further to the right, flow through through spool housing 21 ceases. This means spool 16 will slide back towards its neutral central position under the influence of its left spring 22. However, simultaneously the back pressure in the left hand end of the cylinder 12 will cause the spool 16 to move past central neutral position to the right end of housing 21 opposite reed switch contacts 18.

When the spool 16 moves toward central neutral position away from reed switch 17, relay 26 is deenergized to open contacts 28 and 29. Opening of contacts 28 permits a not shown spring of the valve 15 to put it in a condition wherein fluid can now enter the right hand end of cylinder 12 via valve path 36 and out of the left hand end of cylinder 12 via a valve path 37 in readiness for return movement of the piston. Opening of contacts 29 has turned the motor 14 off; however, this is only momentary, since after the back pressure in the left hand end of cylinder 12 moves the spool 16 to the right past neutral center, the spool will magnetically close the contacts 18. Closure of contacts 18 restarts the motor so that fluid is pumped into the right hand end of cylinder 12 and out of the left hand end. The motor is restarted by closed contacts 18 since they result in energization of relay 30 which operates to close contacts 31 to turn the motor back on. Fluid flow in what is now an opposite direction through the spool housing 21 will keep the spool to the right to hold contacts 18 closed until such time as the end of the retracting stroke is reached. At this point, flow out of the left hand of cylinder 12 through spool housing 21 will cease so that spool 16 is no longer driven to the right. Therefore, it will now move back to center neutral po sition under the influence of right hand spring 22 to open contacts 18 and de-energize relay 30 to open contacts 31 to turn the pump motor 14 off.

It will now be seen that the magnetic spool 16 is bidirectional flow sensitive to control the waste compactor during its compacting and retracting stroke. After the start switch 27 is closed, spool 16 is flow responsive to the left during the compacting stroke to close contacts 17. Closed contacts 17 keep relay 26 energized to keep contacts 28 and 29 closed. Closed contacts 28 and 29 keep the motor 14 energized and valve positioned such that fluid continues to enter cylinder 12 along valve path 34 and exhaust along valve path 35. When the piston l 1 reaches the end of its compacting stroke, the spool 16 is responsive to no fluid flow to drift back to its central neutral position under the influence of its left hand spring 22 to open contacts 17 which determines the end of the compacting stroke. Open contacts 17 turns motor 14 off and results in positioning of valve 15 such that fluid can now flow along

paths

36 and 37 for the retracting stroke. However, the spool 16 is also responsive to back pressure in the left end of cylinder 12 to cause it to move past center neutral to the right to close contacts 18. Closed contacts 18 energize relay 30 to turn the motor 14 back on for the start of the retracting stroke. The retracting stroke is maintained to completion since spool 16 is kept to the right inasmuch as it is flow responsive to fluid now traveling from left to right as contrasted to right to left during the compacting stroke. At the end of the retracting stroke spool 16 is responsive to no further fluid flow out of the leftend of cylinder 12 so that it drifts back to center neutral position to open contacts 18 to turn motor 14 off. Thus, by being bi-directional flow responsive and also pressure sensitive, the spool 16 controls each stage of the total compacting cycle from start to finish and including automatic reversal and shut off.

lt should now be apparent that since spool 16 is flow and pressure responsive it will also detect malfunctions in the system such as obstructions or loss of pressure and initiate appropriate responses in the total electrohydraulic system. For example, should the waste compactor become obstructed so that the ram cant complete its full compacting stroke, the spool 16 will move from left to right to reverse the ram and turn the device off. ln a like manner, it will prevent over-compacting. In the case of loss of hydraulic pressure, fluid flow in either direction will be insufficient to hold the spool biased to the right or left. Therefore, the two springs 22 will take over and center the spool. That is to say, neither of

contacts

17 or 18 will close, but open, which is the off condition for the system.

We claim:

1. In a hydraulic actuator comprising a piston in a cylinder and a hydraulic pump driven by an electric motor, said pump being connected to opposite ends of said cylinder by a pair of hydraulic lines through a reversing valve to reciprocate said piston, a bi-directional hydraulic flow and pressure responsive controller for controlling said valve and motor, said controller being connected in one of said lines and comprising a cylindrical housing having line connecting fittings at opposite ends thereof, a slidable magnetic spool in said housing, an axially extending passageway formed in said spool whereby pressurized liquid entering either one of said fittings is adapted to simultaneously pass through said spool and drive said spool towards the other fitting, a pair of springs acting at opposite ends of said spool to center position the same in said housing, and a pair of magnetically responsive switches mounted on said housing at opposite ends thereof, said switches being electrically connected to said reversing valve and motor and being responsive to movement of said spool from its center position towards either of said fittings.

2. In a waste compactor comprising a piston in a hydraulic cylinder and a hydraulic pump for driving the same, an electric motor for driving said pump, a hydraulic reservoir and a pair of hydraulic lines extending to opposite ends of said cylinder, a four-way reversing valve connected to said pump, reservoir and lines for reciprocating said piston, a hydraulic flow and pressure responsive controller in one of said lines for controlling said valve and motor, said controller comprising a cylindrical housing having the line connecting fittings at opposite ends thereof, a slidable magnetic spool in said housing, an axially extending passageway formed in said spool whereby pressurized liquid entering either one of said fittings is adapted to simultaneously pass through said spool and drive said spool towards the other fitting, a pair of magnetically responsive switches mounted on said housing at opposite ends thereof and being responsive to movement of said spool from its center position towards either of said fittings, said spool being spring biased to a central neutral position in said housing away from said switches whereby said controller is also responsive to no or low hydraulic flow and pressure, said switches being electrically connected to a pair of relay coils, one for reversing said valve and operating said motor, and the other for operating said motor, whereby successive positioning of said spool at opposite ends of said housing automatically reciprocates said piston and central neutral positioning of said spool in said housing automatically stops said piston.