US3661053A

US3661053A - Reversing switch actuator for fluid motor

Info

Publication number: US3661053A
Application number: US95311A
Authority: US
Inventors: Beldon L Rich
Original assignee: Parker Hannifin Corp
Current assignee: Parker Hannifin Corp
Priority date: 1970-12-04
Filing date: 1970-12-04
Publication date: 1972-05-09
Anticipated expiration: 1989-05-09
Also published as: CA935719A; AU3578871A; GB1338282A; DE2159926C2; DE2159926A1; AU459065B2

Abstract

A fluid motor having piston actuated switches on the cylinder heads thereof which control operation of a solenoid reversing valve to achieve automatic reciprocation of the piston. Each switch actuator comprises a radially positioned assembly which includes a relatively large diameter ball which is engaged by the piston as it approaches the end of its stroke, a large diameter spring follower which is spring biased against the ball, and a small diameter actuator rod which has sliding sealed engagement with a switch retainer in the cylinder head, the radially inner end portion of the rod being engaged with the spring follower and the radially outer end portion of the rod being engageable with the switch plunger to close the switch contacts to reverse the piston when the ball, follower, and rod have been moved radially outwardly by the engagement of the piston with the ball.

Description

1451 May 9, 1972 22 Filed:

[54] REVERSING SWITCH ACTUATOR FO FLUID MOTOR [72] Inventor: Beldon L. Rich, Buffalo Grove, Ill.

[73] Assignee: Parker-Hannifin Corporation, Cleveland,

Ohio

Dec. 4, 1970 [2]] AppI.No.: 95,311

FOREIGN PATENTS OR APPLICATIONS 628,873 9/1949 Great Britain .9l/ 275 Primary Examiner-Paul E. Maslousky Attorney-Oberlin, Maky, Donnelly & Renner [5 7] ABSTRACT A fluid motor having piston actuated switches on the cylinder heads thereof which control operation of a solenoid reversing valve to achieve automatic reciprocation of the piston. Each switch actuator comprises a radially positioned assembly which includes a relatively large diameter ball which is engaged by the piston as it approaches the end of its stroke, a large diameter spring follower which is spring biased against the ball, and a small diameter actuator rod which has sliding sealed engagement with a switch retainer in the cylinder head, the radially inner end portion of the rod being engaged with the spring follower and the radially outer end portion of the rod being engageable with the switch plunger to close the switch contacts to reverse the piston when theball, follower, and rod have been moved radially outwardly by the engagement of the piston with the ball.

12 Claims, 3 Drawing Figures 1 lul .PATENTEDm 9I972 INVENTOR. I

BEL DON L. RICH BY I Il hll F ATTORNEYS REVERSING SWITCHACTUATOR F OR FLUID MOTOR I BACKGROUND OF THE INVENTION It is known to provide a radially movable switch actuating rod' engaged by a piston as the latter approaches the end of its stroke but because of the side load or bending load on the rod exerted by axial movement of the piston into engagement with loads when the rod is being moved radially outwardly by the piston, the rod then being exposed to low pressure on the return side of the motor.

SUMMARY OF THE INVENTION It is a principal object of this invention to provide a simple and efficient form of'switch actuator for a fluid motor in which a relatively large diameter ball is engaged by the piston, the ball being engaged with the plane face of a spring follower which transmits the ball motion to a small diameter switch actuating rod. Because the ball engages a plane face of the large diameter follower there is no alignment problem of the ball guide bore with the actuator rod guide bore. Another characterizing feature of this invention is that as the ball is engaged by the piston it tends to be moved axially but there is, in addition, a tendency to rotate the ball so as not to impose an axial or side load on the radially movable spring follower and switch actuator rod.

Other objects and advantages of the present invention will become apparent as'the following-description proceeds.

BRIEF DESCRIPTIONOF THE DRAWING DETAILED DESCRIPTION OF THE INVENTION In FIG. 1 is shown a schematic piping and wiring diagram of the left the right-hand switch 5 will be opened but the reversing valve 4 will remain in the actuated position and as the piston 8 approaches the end of its left-hand stroke, the left-hand switch 5 will be closed to energize the left-hand solenoid 9 so as to shift the valve 4 to the position shown in FIG. 1 thereby to conduct fluid under pressure again into the rod end 6 with the displaced fluid being conducted to the reservoir 2 via valve 4. 7

Because both switches 5 and actuating mechanisms therefor are of substantially identical construction, except for the diameters of the cam rod 11 and cam sleeve 12 on opposite sides of the piston 8, only one of the switches 5 and switch actuating mechanisms have been illustrated in FIGS. 2 and 3. As shown in FIG. 2, the cylinder head 7 is provided with'an axial bore 14 into which the piston cam rod 11 loosely extends as e the piston 8 moves to the right. The cylinder head 7 also has a a fluid motor control system for effecting automatic reversal.

of a double acting fluid motor 1 of the piston-cylinder type. The reference numeral 2 denotes a fluid reservoir from which the pump 3 draws fluid for supplying fluid under pressure into either the rod end or the head end of the motor 1 via a solenoid operated reversing 'valve 4. Switches 5;5 are mounted on the

respective cylinder heads

6 and 7 and are adapted to be closed by the movement of the piston 8 toward the

respective heads

6 and 7 to energize the respective solenoids 9 and 10 for effecting operation of the reversing valve 4 so as to cause movement of the piston 8 in the opposite direction.

For example, when the piston 8 is moving to the right, the reversing valve 4 is in the position shown whereby fluid under pressure is conducted into the rod end 6 of the cylinder 1 and the fluid displaced from the head end 7 of the cylinder is conducted through the reversing valve. 4 into the reservoir 2. As the piston 8 approaches the righthand end of its stroke, the right-hand switch 5 is closed to energize the right-hand solenoid 10 whereby the valve 4 is shifted so that fluid under pressure is now conducted into the head end 7 of the cylinder while the fluid displaced from the rod end 6 is conducted through the valve 4 to the reservoir 2. As the piston 8 moves to radial bore 15 in which is seated a ball guide ring 16 which has a ball seat 17 which determines the radially innermost position of the ball 18 as shown in FIG. 3 so as to be in the path of movement of the piston cam rod 11.

Screwed into the radial bore 15 is a switch retainer 19 which is sealed in the bore as by means of the packing ring 20, and which has a threaded upper end extending through an opening in the switch box 21, the latter containing the limit switch 5 having its switch plunger 23 disposed for movement coaxially with the axis of the retainer 19. The switch box 21 is securely mounted on the cylinder head 7 as by means of the lock nut 24 which is threaded onto the upper end portion of the retainer 19.

Compressed between the switch retainer 19 and a spring follower 25 which has a plane radially inner face engaged with the radially outermost portion of the ball 18 is a spring 26 which yieldably holds the ball 18 in its seat 17 so that the radially inner portion of the ball 18 is disposed for engagement by the piston cam rod 11.

The radial movement of the ball 18 and follower 25 istransmitted to the switch plunger 23 for closing the contacts (not shown) in switch 5 through a small diameter actuating rod 27 which may be press fitted or otherwise secured to the spring follower 25 and which has a close sliding fit in a central bore in the switch retainer 19. The actuator rod 27 is slidably sealed in the bore in retainer 19 as by means of an O-ring 28.

As an example, in a 3,000 psi. cylinder 1 in which 1/16- inch radial movement of the ball 18, follower 25, and actuator rod 27 is, desired, a 3/8-inch diameter ball 18 has been found satisfactory with an actuating rod 27 of about l/l6-inch diameter. Thus, the spring 26 needs only exert about a 10 pound radial inward force to prevent radial outward movement of the actuator rod 27 under the influence of 3,000 psi. pressure.

The ball seat 17 is as shown provided with a leakage slot 29 so that the ball 18 and follower 25 will be pressure balanced so that only the effective, area of the small actuating rod 27 is acted upon by the high pressure. The upper end of the actuating rod 27 may be provided with a plastic or like switch engaging button 30.

As shown in FIG. 3, as the piston cam rod 11 moves to the right near the end of the stroke of the piston 8, it initially contacts the ball 18 at 31 to apply axial and radial forces thereon which will tend to shift the ball 18 toward the right and upward away from the seat 17 as the movement of the piston cam rod 11 continues. However, such forces also tend to cause rotation of the ball 18 in the direction of the arrow thus to tend to negate the side load transmitted to the follower 25 and slender rod 27.

Another feature of the present invention is that because the ball 18 has contact with a plane face of the follower 25, the ball guide bore in ring 16 and the actuator rod guide bore in retainer 19 need not be perfectly concentric. In other words, any eccentricity of these guide bores does not cause any binding action which would interfere with movement of the ball 18 or rod 27 in their respective guide bores.

1, therefore, particularly point out and distinctly claim as my invention:

. larged portion also longitudinally movable in said housing, and

spring means in said housing biasing said radially enlarged portion against said ball to position the latter in the path of movement of cam means on said component; said cam means, upon movement of said component to a predetermined position, being operative by engagement with said ball to longitudinally move said rod to switch actuating position; and means responsive to actuation of said switch to initiate movement of said component in a direction away from such predetermined position. v

2. The switch assembly of claim 1 wherein said ball and said enlarged portion are exposed to fluid pressure but are pressure balanced; said rod being longitudinally slidably sealed in said housing and being of relatively small diameter as compared with the diameter of said ball and of said radially enlarged portion whereby said spring means needs only to overcome a relatively small force imposed on said rod by fluid pressure acting on the small effective area thereof.

3. The switch assembly of claim 1 wherein said radially enlarged portion has a plane end face engaged with said ball thus to accommodate eccentricity of said rod and ball without binding of said rod in said housing.

4. The switch assembly of claim 1 wherein a duplicate switch assembly is disposed at the other end of said motor and wherein said component has another cam means for engaging and moving the ball of said duplicate switch assembly for actuation of the switch thereof to initiate movement of said component in a direction away from an opposite predetermined position whereby said component is automatically reciprocated between such predetermined positions.

5. The switch assembly of claim 1 wherein the path of movement of said component is angularly related to the path of movement of said ball and rod, said ball having lateral sliding engagement with said radially enlarged portion thus to substantially eliminate transfer of side load from said ball to said rod.

6. The switch assembly of claim 5 wherein movement of said ball by engagement of said cam means therewith tends to rotate said ball in a direction to further decrease tendency of transmission of side load to said rod.

7. The switch assembly of claim 1 wherein said last-named means comprises a solenoid operated valve which, upon actuation of said switch, conducts fluid pressure into said motor to move said component away from such predetermined position. a

8. A switch assembly for the cylinder head of a fluid motor of the type having a piston movable by fluid pressure in the cylinder thereof toward and away from said cylinder head; said assembly comprising cam means on said piston movable into and out of a central axial bore in said cylinder head; said cylinder head having a radial bore intersecting said central bore; a switch secured .to said cylinder head; switch actuating means in said radial bore including a switch actuating rod coaxial with said radialbore having a radially outer end portion engageable with said switch to actuate the latter and having a laterally enlarged radially inner end portion, a ball adjacent said enlarged portion, said spring means biasing said enlarged portion against said ball to position the latter with a radially inner portion thereof disposed in the path of movement of said cam means; said cam means being operative by engagement with said ball to radially outwardly move said ball and said rod thus to actuate said switch; and means responsive to actuation of said switch to direct fluid under pressure into said cylinder head to initiate movement of said piston away from said cylinder head.

9. The switch assembly of claim 8 wherein said ball and said enlarged portion are exposed to fluid pressure in said cylinder head but are pressure balanced; said rod being radially slidably sealed in said cylinder head and being of relatively small diameter as compared with the diameter of said ball and of said enlarged portion whereby said spring means needs only to overcome a relatively small force imposed on said rod by fluid pressure acting on the small effective area thereof.

10. The switch assembly of claim 8 wherein a switch retainer is secured in the radially outer portion of said radial bore to provide means by which said switch is secured to said cylinder head and to provide a guide bore for radial movement of said rod.

11. The switch assembly of claim 10 wherein said radial bore adjacent its radially inner portion provides a guide bore for radial movement of said ball and a seat to determine the radially innermost position of said ball so as to be engaged by said cam means.

12. The switch assembly of claim 11 wherein said enlarged portion has a plane end face engaged with said ball thus to accommodate eccentricity of said ball and rod guide bores without binding of said rod in said retainer.

Claims

1. A switch assembly for a fluid motor of the type having a component movable therein by fluid pressure, said assembly comprising a housing secured to said motor at one end thereof; a switch on said housing; switch actuating means in said housing including a switch actuating rod longitudinally movable in said housing and having one end portion engageable with said switch to actuate the latter and having a radially enlarged opposite end portion, a ball adjacent said radially enlarged portion also longitudinally movable in said housing, and spring means in said housing biasing said radially enlarged portion against said ball to position the latter in the path of movement of cam means on said component; said cam means, upon movement of said component to a predetermined position, being operative by engagement with said ball to longitudinally move said rod to switch actuating position; and means responsive to actuation of said switch to initiate movement of said component in a direction away from such predetermined position.

7. The switch assembly of claim 1 wherein said last-named means comprises a solenoid operated valve which, upon actuation of said switch, conducts fluid pressure into said motor to move said component away from such predetermined position.

8. A switch assembly for the cylinder head of a fluid motor of the type having a piston movable by fluid pressure in the cylinder thereof toward and away from said cylinder head; said assembly comprising cam means on said piston movable into and out of a central axial bore in said cylinder head; said cylinder head having a radial bore intersecting said central bore; a switch secured to said cylinder head; switch actuating means in said radial bore including a switch actuating rod coaxial with said radial bore having a radially outer end portion engageable with said switch to actuate the latter and having a laterally enlarged radially inner end portion, a ball adjacent said enlarged portion, said spring means biasing said enlarged portion against said ball to position the latter with a radially inner portion thereof disposed in the path of movement of said cam means; said cam means being operative by engagement with said ball to radially outwardly move said ball and said rod thus to actuate said switch; and means responsive to actuation of said switch to direct fluid under pressure into said cylinder head to initiate movement of said piston away from said cylinder head.