US3726518A

US3726518A - Liquid timing device

Info

Publication number: US3726518A
Application number: US00156785A
Authority: US
Inventors: M Halik
Original assignee: US Department of Army
Current assignee: US Department of Army
Priority date: 1971-06-25
Filing date: 1971-06-25
Publication date: 1973-04-10
Anticipated expiration: 1990-04-10

Abstract

A liquid timer which includes a generally hollow, closed cylindrical member having therein a longitudinally reciprocable piston dividing the internal volume thereof into two portions. One of said portions being filled with silicone rubber gum and having a restricted liquid passage or orifice between the separated volume portions. A biasing means coupled to said piston urging the said piston in a direction to compress said liquid or reduce the volume thereof. Actuating means for releasably holding said piston until the timing cycle is to be commenced. Said piston further being provided with terminal output means indicative of the termination of the timing cycle. The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

Description

" Attorney-Harry M. Saragovitz et al. A

l-lalik [111 3,726,518 [451 Apr. 10, 1973 [54] LIQUID TIMING DEVICE [75] Inventor: Michael I-lalik, Sparta, NJ.

[73] Assignee: The United States of America as represented by the Secretary of the Army [22] Filed: June 25, 1971 [21] Appl. No.: 156,785

[52] US. Cl. ..267/151, 102/83 [51 Int. Cl. ..F16f 3/07 [58] Field of Search ..267/l34, 151, 8 C,

[56] References Cited UNITED STATES PATENTS 5/1971 Hopps ..267/151 H1949 Bazolay ..267/l34 Pn'r nary ExaminerJames B. Marbert [57] ABSTRACT A liquid timer which includes a generally hollow, closed cylindrical member having therein a longitudinally reciprocable piston dividing the internal volume thereof into two portions. One of said portions being filled with silicone rubber gum and having a restricted liquid passage or orifice between the separated volume portions. A biasing means coupled to said piston urging the said piston in a direction to compress said liquid or reduce the volume thereof. Actuating means for releasably holding said piston until the timing cycle is to be commenced. Said piston further being provided with terminal output means indicative of the termination of the timing cycle.

The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

6 Claims, 5 Drawing Figures PAIENTEB APR] 0 I973 SHEET 1 or 5 INVENTOR MICHAEL HALIK BY [4) '3.

" Iii/s PAH-NYE!) APR 1 0 I915 SHEET 2 0F 3 INVENTOR MICHAEL HALIK LIQUID TIMING DEVICE BACKGROUND OF THE INVENTION The present invention relates timing devices and more particularly pertains to dashpot apparatus wherein a biased piston progressively traverses a length of a cylinder against a liquid which is slowly permitted to pass thereby to the other side of the piston at a selected rate so as to provide an extremely long and reliable timed period.

In the field of dashpots, it has been the general practice, where extended time periods are necessary, to employ a standard dashpot construction which include both chemical and mechanical structures but to provide extremely complex and costly sealing arrangements for liquid as well as to select the piston and cylinder materials so that they would be temperature compensating. Both of these methods have proved to be excessively expensive without appreciably increasing the operational reliability. Additionally, close tolerances must be maintained between moving parts as well as for the orifices through which the liquid must pass. The present invention fills this need.

SUMMARY OF THE INVENTION The general purpose of this invention is to provide a dashpot that has all the advantages of similarly employed prior art devices and has none of the above described disadvantages. To attain this, the present invention provides a dashpot wherein a longitudinally traversing piston is housed within a closed cylindrical housing. The piston thus divides the cylinder and one such portion is filled with silicone rubber gum which is a liquid" whose viscosity is relatively constant over an environmental temperature range. The piston is biased for movement toward the liquid by some means, such as an internally mounted spring, and the liquid is permitted to bypass the piston at a constant, slow rate via one or more orifices therethrough or defined by the spacing between the peripheral piston surface and the inner surface of the cylinder. Actuating means coupled to the piston to provide the timing termination as well as insuring lateral or coaxial positioning of the piston during its transverse movement. Additionally, there is disclosed piston restraining means which when disengaged commences the timing cycle. Relatively long and reliable timing periods, under varying temperature conditions are readily attainable.

An object of the present invention is to provide a timing dashpot whose time interval of operation is selectable from several minutes to many days and which is simple, reliable and relatively inexpensive.

Another object is to provide a dashpot which is operable over a wide temperature range, unaffected by ambient environmental conditions and does not require extremely critical dimensioning.

A further object is to provide a simple timer which may be readily produced in large quantities, be of a small size and capable of extended time cycling.

Other objects and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an embodiment made in accordance with the principle of this invention wherein the liquid is permitted to flow out of the housing;

FIGS. 2, 2a, and 2b illustrate another embodiment wherein the liquid passes through one or more orifices from one side of the piston to the other; and,

FIG. 3 is still another embodiment wherein the spring bias member is supported between a pair of additional pistons coupled to the main cylinder by a rod;

DESCRIPTION OF THE PREFERRED EMBODIMENT In the simplified illustration of FIG. 1 a generallyclosed, hollow, cylindrical body or housing 10, circular in cross-section, has disposed for longitudinal movement therein, a piston member 11. The piston effectively divides the interior volume into two separate cavities l2 and 13. The dimensions of the piston are selected such that its peripheral surface, slidingly abuts the inner wall of the cylinder. One cavity 12 is filled with a silicone rubber gum 14 such as that sold under the Tradename SILASTIC 400 gum by Dow Corning Corp., of Midland, Michigan. The cavity 13 on the opposite side of the piston has disposed therein a biasing means such as coil spring 15 which is initially compressed between fixed cylinder end wall 16 and the face 17 of the piston so as to yielding urge the piston toward the silicone filled cavity 14. A minute timing orifice I8 is provided in the cylinder end wall 19 so-as to permit the silicone to flow thereout under the movement of the piston. The piston carries an actuating member 20 whichin this case comprises a cylindrical rod supported and affixed centrally of the piston and directed toward wall 16. The rod coaxially passes through this wall, extends outwardly thereof and is bent back in the longitudinal direction of the body 10. The end of the rod can be provided with an operating tip 21 which can be employed to activate some device, as for example, a

fuze. In evaluating the physical characteristics of the silicone rubber gum the penetration and the viscosity were determined. The penetration was determined by using a Penetrometer, Universal Model Precision" ASTM manufactured by Precision Scientific Co. of Chicago. A cone was used as the penetrating point without added weight on the steel plunger with a free fall time of 5 seconds. The viscosity was evaluated by dropping a 5/16 inch steel ball into a viscosity ASTM tube filled with the silicone rubber gum and the time of descent between vertical references was recorded. These experiments indicated that these characteristics did not appreciably change over the environmental temperature conditions under which the liquid timing device described herein would be used. In assembling threaded into and extending through the housing so as to tightly abut and hold the piston. The timing cycle commences upon release of the piston and the flow and viscosity characteristics of the silicone are such as to be capable of extended timing cycles.

Referring now to the embodiment of FIG. 2, the cylindrical housing 30 is closed at one end by a wall 31 which is provided with a central aperture which is closed with a puncture sealing disc 32. The piston 33 which is slidingly disposed in the housing for longitudinal movement carries coaxially at its forward end extending from face 34 an actuating pin 35. Confined between the wall 31 and the piston 33 is a silicone rubber gum liquid 36. Disposed between the opposite face of the piston and the removable end wall 37 is a biasing means or spring 38 again urging the piston in a direction to compress the liquid. Under these physical conditions it is clear that static equilibrium will occur. Therefore, a passageway is provided for the liquid to bypass the piston. This passageway can take the form of one or more orifices 39 through the piston as shown in FIG. 2a or a peripheral passage 40 defined by the space between the peripheral surface of the piston and the inner wall of the housing 30 as per FIG. 2b. This latter structure merely necessitates that the piston be of a reduced diameter. As in the previous embodiment, a holding means 41 is provided and the same factors determine the rate of piston travel. In operation the piston proceeds toward the end wall 31 and subsequently the actuating pin or rod 35 punctures the seal 32 extends out of the housing and activates some device not shown.

A somewhat more complex embodiment is illustrated in FIG. 3 wherein the housing 50 is an elongated hollow cylinder, one end of which is releasably closed by wall 51 and the opposite end closed by wall 52. Within the housing and proximate the wall 51 is a fixed disc 53 that is joined to the end wall 51 by a pin guide 54 extending from aligned apertures 55 in the wall and 56 in the disc 53. The piston 57 or movable element is initially positioned against the opposite housing wall 52 and carries an actuating pin 58 extending therefrom in a direction toward wall 51. The pin 58 is slidingly sealed and passes through movable disc 59. This disc is urged by spring member 60 which is supported intermediate fixed disc 55 and movable disc 59, toward the piston 57 so as to compress the silicone rubber gum 61 therebetween. The piston 57 in an operative device takes the structural characteristics disclosed in FIGS. 2a and 2b and the timing sequence commences when the holding pin means 62 is loosened or removed. Thereafter disc 59 under the force of spring 60 moves forward and impels the liquid" past or through the piston orifices, against the rear wall 52, thus slowly driving the piston itself in the opposite direction. As the piston progresses in its travel so does the actuating means 58 which finally emerges from aperture 55 whereby it can activate some external device or mechanism.

Summarizing, the timer system of this invention employs silicone rubber gum as the timing agent and thereby permits an extended range of timed intervals not readily attainable with conventional chemical, mechanical and electrical timers. The system, in general, includes a housing cylinder, an appropriately pressure loaded piston acting on the timing a cut and carrying out an actuating means. The piston e ectlvely travels through the liquid timing agent with its actuating means. The rate of travel (or timing cycle) is controlled and selected by the quantity of the timing agent, size of the total piston orifice, and pressure exerted on the system.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.

I claim:

1. A liquid controlled timing device which comprises:

a hollow closed cylindrical housing having disposed therein,

a piston means movable lengthwise of said housing and dividing said housing, into separate cavities, said piston means carrying,

an actuating means extending outwardly and slidingly through one of the end walls of said housing,

one of said cavities filled with liquid silicone rubber gum,

biasing means urging said piston in the direction of said one cavity, and

escapemeans providing at least one restricted orifice in and extending through said piston for permitting said liquid to flow outwardly of said one cavity at a selected rate thereby controlling the movement of said piston and actuating means.

2. The device according to claim 1 wherein said escape means is an annular orifice defined by a separation between said piston and said housing.

3. The device according to claim 1 wherein said actuating means is a pin extending within said one of said cavities and said one of said end walls is provided with a frangible sealing element penetrable by said pin.

4. The device according to claim 1 further including releasable holding means affixed to said piston for preventing movement thereof and for release thereof upon commencement of a timing cycle.

5. The device according to claim 1 wherein said piston means includes:

a movable disc and having said biasing means urging said disc toward a piston spaced therefrom and defining therebetween said one of said cavities, said actuating means slidingly and sealingly extending through an aligned aperture in said movable disc.

6. The device according to claim 5 further including a fixed disc spaced from said movable disc and provided with a central opening for slidingly receiving said actuating means and wherein said biasing means is a coil spring supported for compression between said discs.

# i i i i

Claims

1. A liquid controlled timing device which comprises: a hollow closed cylindrical housing having disposed therein, a piston means movable lengthwise of saId housing and dividing said housing, into separate cavities, said piston means carrying, an actuating means extending outwardly and slidingly through one of the end walls of said housing, one of said cavities filled with liquid silicone rubber gum, biasing means urging said piston in the direction of said one cavity, and escape means providing at least one restricted orifice in and extending through said piston for permitting said liquid to flow outwardly of said one cavity at a selected rate thereby controlling the movement of said piston and actuating means.

5. The device according to claim 1 wherein said piston means includes: a movable disc and having said biasing means urging said disc toward a piston spaced therefrom and defining therebetween said one of said cavities, said actuating means slidingly and sealingly extending through an aligned aperture in said movable disc.