US2630886A - Pneumatic time delay device - Google Patents

Description

March 10, 1 953 C QAHL 2,630,886

PNEUMATIC TIME DELAY DEVICE Filed Dec. 11, 1947- w HTTORWEY Patented Mar. 10, 1953 PNEUMATIC TIME DELAY DEVICE Carl Lindahl, Union, N. J., assignor to Elastic Stop Nut Corporation of America, a corporation of New Jersey Application December 11, 1947, Serial No. 791,109

6 Claims. 1

The present invention relates to pneumatic time delay devices or the kind in which some desired event such as the closing or opening of an electrical circuit is eiiected after the lapse of a predetermined and preferably adjustable time interval following actuation of the device by an operator or by some automatic control. More particularly the invention relates to such devices embodying a timing chamber formed in part by a yieldable diaphragm, to which chamber air or other gas is admitted through a suitable check valve, and from which it is vented through a vent orifice to permit movement at predetermined rate of the diaphragm, the movement of which determines the time delay effected. Still more particularly the invention relates to time delay devices of the kinds disclosed in my copending applications Serial Nos. 535,365 (now Patent No. 2,489,381 granted November 29, 1949) and 701,515, filed May 12, 1944, and October 5, 1946, respectively, and more specifically to the timing head and chamber construction of the apparatus.

In the form of construction with which the present invention is concerned, air is admitted from the ambient atmosphere to the timing or diaphragm chamber and vented therefrom to the ambient atmosphere through the vent orifice as the volume of the chamber is decreased by suitable pressure applied to the diaphragm, the chamber being refilled with gaseous fluid from the ambient atmosphere through the inlet check valve when the chamber is expanded by a resetting operation after completion of a time delay operation. This action admits to the timing chamber fresh charges of gas from the ambient atmosphere which must successively pass through the vent orifice during succeeding time delay cycles. The time interval of the delay provided by the device is a function of the size of the vent orifice and ordinarily such orifices are of comparatively very small area and the desired timing may be materially altered by a verysmall change in the area of the orifice. Ordinarily such devices are used in locations where the fluid admitted to and vented from the timing chamber is atmospheric air from the ambient atmosphere. Such air in nearly all cases carries a certain amount of dust which in time would partially clog or close the vent orifice and affect the accuracy of timing of the device. To prevent this, filters have been employed for filtering the air before it passes through the vent orifice and for use in many installations this has proved sufficient to overcome the difficulty, particularly in cases where highly precise timing of the delay interval is not required. In other instances, however, devices of the kind under consideration are used under conditions where precision delay is required and the devices are placed in positions where there is a high concentration of dust in the atmosphere and where, moreover, operation of the device without attention or adjustment over long periods of time is highly desirable or necessary. In such installations it has been found from experience that ultimately any filter of available kind will itself become either clogged or covered with a deposit of dust providing sufficient resistance to alter the length of the timing period for which the device is set.

A principal object of the present invention is to provide a new and improved construction which will enable devices of the kind under consideration to operate for long periods of time Without loss of their precise action, even when located in very dusty atmosphere. A further object of the invention is to provide such a construction which may readily be applied to exist. ing types of devices without alteration of the construction of the timing device itself, and a still further object is the provision of a construction in which the freedom from the adverse effect of dust may be secured by means of a readily applied and removed member which is inexpensive to furnish and which may if desired be se lectively utilized in con-junction with a standard timing device for applications where dust control is required.

The manner in which the above and other objects hereinafter appearing are attained may best be understood from a consideration of the following portion of this specification taken in conjunction with the accompanying drawings in which:

Fig. 1 is a central longitudinal section showing the timing head portion of a time delay device of the kind disclosed in my aforesaid copending applications;

Fig. 2 is a section taken on the line 2- 2 of Fig. 1; and

Fig. 3 is a section taken on the line 3-3 of Fig. 1.

Referring now to the drawings, the timing head indicated generally at [0 comprises in the embodiment illustrated a cup-like casing member I2 having a cylindrical barrel portion at one end of which are projecting ears [4 for securing the member to a suitable supporting member l6 which also supports the remaining mechanism of the device. The specific nature of the latter is not germane to the present invention and has therefore not been illustrated. The member l2 has an inwardly projecting flange portion l8 at its top which provides an annular seat 20 for the rim portion of a flexible diaphragm 22 which is clamped against the seat by means of a d shed cap member 24 removably secured to the member l2 by means of the screws 28. At the center of the cap 24 a vent orifice 2.8 is provided, the area of which is controlled by means of the adjusting screw 3!! carried by a bridge member 32 suitably secured to the cap member 24.

As will be seen from Fig. 1. the. diaphra m. 2 and the central portion of the cap member 24 form between them a timing or diaphragm chamber 34 of variable volume dependingupon the. position of the diaphragm 22, and located in the upper part of the chamber by suitable atta hment to the cap member 24 there is an air filter 36' which may be of felt or any other suitable filtering material.

At its center the diaphragm 22 is, attached to a motion transmitting member indicated genes-,- ally at 33 which together with the diaphragm embodies an inlettcheck valve for admittingair to thetiming chamber. In the embodimentillustrated, the valve construction comprises a central member 40 to which the motion transmitting rod 42. is secured, member 48 having a laterallyextending flange. 44. at its upper end. A clamping ring 46 is located around thebody of the member 40 and is drawn into clamping relation with the flange 44 by means of a screw 48. The central partof the diaphragm is clamped between these members as is also. a valve plate located beneath thediaphragm and provided with a pcripheralridge 52.. Above the diaphragm an annular valve ring 54, therim of which is of angle cross section, is resiliently pressed against the diaphragm bymeans of spring 56 engaging and heldbythe head. ofthe screw 48, as will be seen more clearly fromFig. 3. Thediaphragm is pro.- vided with a ring of peripherally spaced apertures 58.1ocated relative to the valve members 50 and 54 so as to provide a check valve action as will hereinafter be described.

A spring 60, having an annular rim portion 62 anda. series of spring fingers 64 extending inwardly from the rim to engage a shoulder on the part .6 of the motionv transmitt ng member, is

supported by engagement of its rim portion with r a series of inwardly extending ears 8 6 struck from the casing member l2 and providing supporting abutments. The spring 66 tends to move the motion transmitting member, together with the diaphragm, upwardly to the upper terminal position shown inFig. 1, such movement being resisted. by theresistance to flow of the air in the diaphragm chamber 34 through the vent orifice 28. When force is. applied by the spring to move the motion transmitting assembly upwardly, it will. be apparent that the diaphragm will be clamped between the valve ring 54 and the ridge 52 onmernber 50 along a circular line lying outside of the a ertures 58 in the diaphragm so t at air cannotv flow from the diaphragm chamber through the valve.

.In the embodiment illustrated. the device is moved to. armed or cooked position by means of an actuating. lever. 68. suitably pivoted at m and at its. inner end being forked to provide fin ers l2; enga ing a suitable collar 14 on the. motion transmitting rod 42. The actuating lever 68 may beoperated to draw the motion transmitting member downto expand thev diaphragm chamber, and released to initiate the timing period resulting from the action of spring 60, in any suitable manner and with any desired time cycle, depending upon the use to which the device is put. The movement of the motion transmitting rod 42 between its terminal positions is utilized to effect whatever control may be desired, as for example the operation of a micro switch or the likez for openingand closing suitable electrical circuits; and obviously other means such as a solenoid or the like may be used for drawing the motion transmitting rod downwardly to arm the device. When .the motion transmitting member is pulled downwardly from the upper terminal position shown in'Fig. 1, it will tend to create a vacuum in the diaphragm chamber 34 but the spring 56' holding the valve ring 54 is extremely light and the. diaphragm also being light and relatively very flexible, the valve ring 54 lifts so that air can pass substantially freely between the diaphragm and the ridge 52 on the valve mem ber 51],:and then through the apertures 58 and inside the ring; 54, to the chamber. The resistanceito such flow is so slight that there is substantially no backflow through the vent orifice-28.

Thestructure thus far described is known and is disclosed and claimed in my above mentioned copending applications. In the previous formsof apparatus of this kindheretotore developed, however,. the space below. the diaphragm. chamber has been open to the ambient atmosphere through apertures such as the openings 16 from which the. ears 56 are. struck and in certain instances through-additional openings 18 formed in the wallof the casing member I2. Consequently, on repeated action. of the device, dust carried by the ambientatmos'phere has been drawn into the diaphragm chamber upon successive cycles of the apparatus,,the. filter 36 being depended upon to prevent clogging of. the vent orifice 28 by dust in the air passingthrough the orifice.

In accordance with the present invention, the space below the diaphragm chamber is enclosed to. form a secondandrelatively larger chamber 80. In the. presentembodiment this is accomplished by providing a very light and flexible gas tight diaphragm 32v which may for example be ofv rubber or. synthetic resin, impregnated fabric and. which. at its centerengagesthe motion transmittingrod 42land at its periphery is clamped between the periphery of the casing member I2 and whatever part that member is secured to, suchifor example. as the supporting structure It. In the embodimentv shown. the diaphragm 82 at its center is clamped between lock, nuts 84 and 86 screwed on. the rod 42. but such clamping is not essential, since. there isnever any appreciable differential pressure between the two sidesof diaphragm 82 and by making the central aperture. of the diaphragm. .slightly smaller than the diameter ofv rod. 42 it can merely be slipped over therod with sufiicient gripping. contact to insure all of the sealing effect. that is. required. A cup-shaped cap or. hood. indicated generally at.88, which coacts with the diaphragm 82., operates to close oiT the chamber from the ambient atmosphere and, to providev a path of flow for the return of air vented through the orifice 28 to the, chamber 88. This hood is made of suitable elastic material such as rubber or plastic and in the embodiment shown comprises a cylindrical barrel portion or wall 90 dimensioned to be slipped over the casing. member 12 and. to engage the wall thereof in frictionally gripping contact. An end wall. 92..joins the barrel portion 9! and in the embodiment shown is provided with two internal axially extending projections or lugs 94 adapted to engage the cap 24 of the timing head to maintain end wall 92 in spaced relation from the top of the timing head. At its center the end wall is provided with an axially projecting hollow portion or neck 96 shaped to engage the perimeter of the bridge 32 holding the adjusting screw and having an aperture 98 preferably dimensioned to engage the head of the adjusting screw so that the latter may be adjusted with the hood in place, while at the same time a seal is provided between the hood and one or both of the aforementioned parts on the outlet side of the timing orifice.

In the embodiment of apparatus shown, the cap 24 extends outwardly to the same radius as the outer wall portion of the casing member I2, and the hood 88 is advantageously provided with a small internal circumferential rib mo adapted to snap into the crevice between the parts I2 and 24 to assist in holding the hood in place. This, however, is not essential since through the use of elastic materials such as that described for the hood sufficient frictional grip can readily be obtained to keep the hood in place under all nel formed in the hood 88 but preferably is effected by means of a transfer passage I04 provided by a suitable hole drilled through the cap 24 and casing member 12 radially outside the timing chamber.

In the specific embodiment shown the cylindrical wall of the casing member I2 is perforated by the apertures 16 and 18 and consequently the hood 88 must be extended downwardly far enough to cover these apertures. It will be evident, however, that in a construction in which the apertures 18 are omitted and the spring otherwise supported than by ears struck in from the material of the member 12, the hood need not be extended downwardly further than the amount required to adequately enclose the transfer space or flow path I02.

By means of the arrangement described it will be evident that repeated cyclings of the device may be accomplished with a confined volume of air of relatively small volume and havin initially entrained in it too small an amount of dust or other solid matter to adversely affect the filter 36. It will, of course, be apparent that the hood 88 is very readily removable from the head so as to provide complete accessibility of the latter for purposes of adjustment, repair or replacement of parts and the volume of the air enclosed when the hood is in place is small as noted above, so that even after a number of removals of the hood and replacement thereof, which involve the entrapment of new volumes of impure air, the total quantity of impurities is so small that the device may be operated for substantially indefinite periods of time without the filter being adversely afiected to any noticeable extent.

While for the purposes of describing the device and its operation it has been assumed that air is the medium utilized for effecting timing, it will be evident that such a device might be utilized in a location where the ambient atmosphere is some other gas, and it is to be understood that the term air as herein used is intended to include all gaseous media suitable for the purposes of the device.

It will be evident that the invention is readily applicable to many different specific designs of timing heads, only one example of which has been shown herein by way of illustration, and the invention is consequently to be understood as embracing all forms of apparatus falling within the scope of the appended claims.

What is claimed:

1. In a pneumatic time delay device, the com bination with a timing head providing a variable volume timing chamber, an air admission valve for said chamber and a timing orifice for venting air from said chamber at predetermined rate to an external space, of means including a hood of elastic material yieldingly gripping said head and removable therefrom for providing a closed second chamber in communication with said admission valve and a path for return to said second chamber of the air vented through said orifice.

2. A device as set forth in claim 1, in which said timing head includes an adjusting screw for regulating the area of said timing orifice and said hood is provided with an opening for leaving the screw externally accessible for an adjustment without removing the hood from engagement with the timing head, said hood being in sealing engagement with the timing head on the outlet side of said orifice.

3. In a pneumatic time delay device, the combination with a timing head providing a variable volume timing chamber constituted in part by a flexible diaphragm, a motion transmitting member attached to said diaphragm, an air admission valve for said chamber and a timing valve for venting air from said chamber at predetermined rate to an external space, of means for forming a closed chamber on the inlet side of said admission valve comprising a flexible diaphragm through which said motion transmitting member passes in engaging relation, and means for returning air vented through said timing orifice to the second mentioned chamber including a hood of elastic material frictionally gripping said timing head and having a portion spaced from the timing head to provide a transfer space in communication with the outlet side of said timing orifice and the second mentioned chamber.

4. In a pneumatic time delay device the combination with a cylindrical timing head having an end wall providing a timing orifice in communication with a timing chamber within the head, of a cup-like hood of elastic material having a barrel portion frictionally engaging the circular wall of said head and an end wall, and one or more internal projections on the end Wall of the hood for engaging the casing end wall to maintain the two end walls in spaced relation when the hood is app ied to the head and thereby provide an enclosed space for the reception of air exhausted through said timing orifice.

5. In a pneumatic time delay device, a timing head comprising a cup-like casing member, a cap member, a diaphragm clamped between said casin member and said cap member to provide a timing chamber, a motion transmitting member attached to said diaphragm, means associated with said diaphragm and said motion transmitting member providing an inlet check valve for admitting air to said chamber, means formed in part by a flexible diaphragm engaging said casing member 7 at itsperiphery and having a centralaperture through which saidmotion transmitting member passes in engaging relation to provide a seal between the part for providing a second chamber adjacent to said timing chamber incommunication with the inlet side of said check valve, externally adjustable means carried by said: cap member providing a timing orifice for venting said timing chamber and means including a hood of elastic material frictionally engaging said casing member and having a portion spaced from said cap member and in communication with the outlet side of said timing orifice for providing a transfer space for returning air vented from-the timing chamber to said second chamber.

8 6. A device asset forth in claim 5, in which communication between said transfer space and said second chamber is established bya transfer port through said casing and cap members 10- 5 cated radially outside said diaphragm.

ARL LINDA-BL.

REFERENCES CITED The" following references are of record inthe 10 file" of this patent:

UNITED STATES PATENTS Number Name Date 2,414,305 Hurlburt Jan. 14, 1947 15 2489,38 Lindahl- Nov. 29, 1949

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