Anti-holddown Device With Diaphragm Actuating Switch And Piston

Abstract

This specification discloses an anti-holddown switch actuating mechanism in which a switch is operated by an increase in air pressure upon actuation of a piston-like plunger in a closed chamber, and means are provided to bleed off the increase in air pressure at a predetermined rate to insure opening of the switch a predetermined time after actuation thereof.

Parent Case Text

This application is a continuation-in-part of my co-pending application, Ser. No. 276,886, filed July 31, 1972, and now abandoned.

Description

This invention relates to switches, and more particularly relates to switch actuating mechanisms which are termed anti-holddown devices in that the switch will open after a predetermined time after actuation thereof regardless of whether the operator maintains pressure on an operating knob or plunger.

Switches are often used in industry to operate forming tools and so arranged that the operator is required to depress two switch handles or levers simultaneously in order to operate the device. The general reason for this is to insure that the operator's hands are removed through a forming operation of the machine and thus minimize the possibility of injurious accident.

However, in many cases, the machine operators have attempted to disable the safety feature by laying a heavy object on or tying down one of the switches so that the switch would be permanently closed. This has led to the development of switches or switch-operating mechanisms which have a time-delay built in so that the switch will open a predetermined time after the closing thereof; hence, the name of anti-holddown switch.

The present invention relates to switches of this type and operates through the creation of an increased air pressure due to depression of a plunger. This build-up in pressure is bled off and the switch will then open a predetermined time later determined by the bleed rate. Such switches are generally known. However, those which are known are rather complicated in construction and expensive.

Accordingly, the present invention provides a switch actuating mechanism for an anti-holddown device which is simplified in construction, positive in operation in both the closing and opening modes and may be utilized with virtually any type of switch mechanism.

Briefly stated, the invention in one form thereof comprises wall means defining a cylindrical bore which is closed at one end thereof by a flexible diaphragm. A return biased piston or plunger is received within the bore and upon depression thereof increases the pressure in the chamber to a magnitude sufficient to flex the diaphragm and operate a switch. A passage is defined in the wall means communicating with the ambient atmosphere and the area of said passage may be controlled to predetermine the rate at which pressure is bled off and therefore the opening of the switch. A further passage may be defined in the walls communicating, in one direction, with the ambient atmosphere to aid in resetting of the piston.

An object of this invention is to provide a new and improved switch actuating and release mechanism of the type described.

Another object of this invention is to provide a switch actuating mechanism of the type described having new and improved means for regulating the time of resetting of a switch operated thereby.

A further object of this invention is to provide a switch actuating mechanism of the type described having new and improved means for decreasing the time of resetting of the switch operating piston.

The features of the invention which are believed to be novel are particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, both as to its operation and organization, together with further objects and advantages thereof, may best be appreciated by reference to the following detailed description taken in conjunction with the drawings, wherein:

FIG. 1 is a top plan view of a device embodying the invention;

FIG. 2 is a view seen in the plane of lines 2--2 of FIG. 1;

FIG. 3 is a view seen in the plane of lines 3--3 of FIG. 2;

FIG. 4 is a view seen in the plane of lines 4--4 of FIG. 2;

FIG. 5 is a view similar to a portion of FIG. 2, showing another embodiment of the invention;

FIG. 6 is a view seen in the plane of lines 6--6 of FIG. 5; and

FIG. 7 is a view seen in the plane of lines 7--7 of FIG. 5.

A device 10 embodying the invention comprises an operating knob 11 threadably attached to a plunger 12 at one end of the plunger. The other end of the plunger carries a resilient piston member 13 disposed within a cylindrical bore 14 defined by a housing means 15. The device, as shown, is attached to a mounting panel or other support 16.

Plunger 12 extends through a top wall member 17 which is secured to a support member 18 threaded along its upper portion 19 to receive a matingly threaded clamping collar 20. One or more resilient spacing members 21 may be disposed between member 18 and panel 16 to insure tight fastening of the apparatus to the panel member. A return spring 22 acts between the upper surface of wall member 17 and a spring seat 23 carried on plunger 12. A flexible diaphragm and cover 24 may enclose the spring return mechanism as illustrated.

As thus far described, the mechanism from wall 17 up including the plunger 12 (without piston 13) is a fairly common, manually operated, spring return actuating device.

A mounting member 26 is secured to housing 15 as by means of bolts 26a. A standard switching mechanism 27 is carried by member 26. The switch within housing member 27 has an operating plunger 28 which is spring returned. Plunger 28 is engaged by a contact button 29 carried by a flexible diaphragm 30 of rubber, nylon, or similar material disposed between the bottom of housing 15 and member 26 and sealing the lower end of cylindrical bore 14.

When operating knob 11 is depressed to move plunger 12 and piston member 13 downwardly, the air pressure in cylindrical bore 14 increases which distends diaphragm 30 downwardly carrying contact button 29 therewith. The plunger 12 is of insufficient length to directly actuate the switch. Button 29 depresses plunger 28 to close the switch. The increase in air pressure in cylindrical bore 14 may bleed off through a small orifice 31, a passage 32 defined in wall member 15 and, hence, through passages 33 and 34 to the ambient atmosphere. The effective area of passage 33 is controlled by a tapered portion 35 on an adjustment screw 36 where the tapered portion 35 extends into passage 33 and regulates the area thereof. By varying the position of adjustment screw 36 the effective area of passage 33 for bleeding of pressure from cylindrical bore 14 may be regulated.

Thus, as the air pressure in cylindrical bore 14 is increased to cause contact button 29 to depress switch plunger 28, the air pressure in cylindrical bore 14 will be greater than atmospheric and will begin to bleed off through orifice 31, passage 32 and passages 33 and 34.

After a predetermined time, dependent upon the setting of screw 36, the pressure in cylindrical bore 14 will have decreased to a point where it is insufficient to distend diaphragm 30 and hold plunger 28 down. The bias on switch plunger 28 will release the switch regardless of whether the operator maintains knob 11 in a depressed condition. Assume that the operator has released knob 11 after actuation of the switch, and plunger 12 starts to move upwardly under the influence of energy previously stored in spring 22. Due partially to the sealing engagement of piston 13 against the wall of bore 14 and the resulting friction thereof, there will be a delay in complete resetting of knob 11. Also, as the spring 22 moves the piston upwardly the pressure in cylindrical bore 14 will decrease as the volume increases. This acts as a resistance against spring 22. To overcome this and provide a more positive return, a one-way fluid diode 38 is provided, carried in a recess 39 provided therefor in housing 15. Diode 38 provides communication through openings 40 and 41 to bore 14.

The fluidic diode 38 has a filter 42 provided at the opening thereof in communication with passage 40. Fluidic diode 38 acts as a check valve. When piston 13 is moved to compress the air in bore 14, the diode 38 remains closed. However, as the piston 13 moves upwardly as viewed in FIG. 2 and the pressure in bore 14 decreases, ambient air may flow through orifice 40, filter 42, diode 38, passage 41 and into bore 14 to increase the recovery rate of the actuating mechanism. Additionally, an opening 40a is provided in bore 14 leading to passage 39 so that as piston 13 rises, the air therein is provided with an escape. Filter 38 guards against any possibility of a build-up of dust or other solids in bore 14.

A device embodying the invention is relatively economical to manufacture and produce inasmuch as it utilizes a readily available standard actuating mechanism as previously described, and a common switch. These elements may be readily attached to the pressure section as by means of bolts 44 which attaches housing member 15 to member 17 and bolts 45 which attaches switch 27 to member 26.

It will be understood that when the switch is normally used, i.e., depression and release of knob 11, switch plunger 28 is released after actuation thereof. Piston 13 then quickly recovers aided by the air admitted through diode 38.

A further embodiment of the invention is shown in FIGS. 5 - 7 wherein like parts to the structure of FIGS. 1 - 4 bear like reference numerals.

In the second embodiment, the increased pressure in bore 14 due to depressing piston 13 is bled off to the upper portion of bore 14 through passage 34a defined in the upper surface of housing 15. A passage 33a provides communication between passages 33 and 34a. There is no direct communication to the outside of housing 15. The rate of bleed is determined by the setting of valve screw 36 and tapered portion 35 thereof in passage 33, as heretofore explained.

This arrangement recirculates the air within housing 15, and minimizes the amount of fresh air brought into the housing, thereby minimizing the possibility of dirt and dust entering the chamber defined by housing 15 or from clogging passage 34 from the outside.

In operation, as plunger 12 is depressed, piston 13 moves down, increasing the pressure therebelow and forcing diaphragm 30 downwardly to actuate switch 27. The pressure commences to bleed off through orifice 31, passage 32, 33 and 34a to the portion of bore 14 above piston 13. This relieves the pressure below piston 13 and times release of the switch as heretofore explained. At the same time, the amount of air otherwise entering bore 14 above piston 13 is minimized. As piston 13 rises under the bias of spring 22, the air above piston 13 is expelled through passage 40a and will be drawn through filter 42 and fluid diode 38 to the lower portion of bore 14 through passage 41.

While the foregoing description describes an embodiment of the invention in closing a normally open switch, it will be apparent that the actuator may be utilized to open a normally closed switch.

It may thus be seen that the objects of the invention set forth as well as those made apparent from the foregoing disclosure are efficiently attained. Modifications to the disclosed embodiments of the invention as well as other embodiments thereof may occur to others skilled in the art. Accordingly, the appended claims are intended to cover all modifications to the disclosed embodiments as well as other embodiments thereof which do not depart from the spirit and scope of the invention.

Claims

What is claimed is:

1. An anti-holddown switching device comprising a housing member defining a pressure chamber having opposite ends, a flexible diaphragm closing said chamber at one end thereof, a switch disposed adjacent said diaphragm at said one end of said chamber and operable by said diaphragm when the pressure on said diaphragm reaches a predetermined value, a piston in said chamber adjacent the other end thereof and movable in a direction to decrease the volume of said chamber between said piston and said diaphragm and increase the pressure therein, a passage defined in said housing member by which pressure in said chamber between said piston and said diaphragm is bled therefrom, whereby pressure created in said chamber by said piston is reduced and said diaphragm releases said switch after a predetermined time independent of the position of said piston in said chamber.

2. The device of claim 1 further including a second passage in said housing member providing one way communication of air into said chamber between said piston and said diaphragm.

3. The device of claim 2 further including an opening in said housing member providing communication to said second passage from a point on the other side of the piston from said diaphragm.

4. The device of claim 2 further including a filter in said second passage.

5. The device of claim 1 wherein said passage provides communication to the ambient atmosphere.

6. The device of claim 1 wherein said passage provides communication to the chamber on the other side of the piston from said diaphragm.

7. An anti-holddown switching device comprising a housing member defining a pressure chamber having opposite ends, a flexible diaphragm closing said chamber at one end thereof, a switch disposed adjacent said diaphragm at said one end of said chamber and operable by said diaphragm when the pressure on said diaphragm reaches a predetermined value, a piston in said chamber adjacent the other end thereof and movable in a direction to decrease the volume of said chamber between said piston and said diaphragm and increase the pressure therein, a first passage defined in said housing member by which pressure in said chamber between said piston and said diaphragm is bled therefrom whereby, pressure created in said chamber by said piston is reduced and said diaphragm releases said switch after a predetermined time independent of the position of said piston in said chamber, means defining a second passage providing one-way communication of air into said chamber between said piston and said diaphragm, and an opening in said housing member providing communication to said second passage from said chamber.

8. The device of claim 7 wherein said first passage provides communication to the ambient atmosphere.

9. The device of claim 7 wherein said first passage provides communication to the chamber on the other side of the piston from said diaphragm.