US3182594A - Temperature independent timing device, dashpot type - Google Patents

Description

May 11, 1965 TEMPE T y 1965 w. HARRIS ETAL 3,182,594

TEMPERATURE INDEPENDENT TIMING DEViCE, DASHPOT TYPE Filed May 17, 1965 V 2 Sheets-Sheet 2 RETURN SP R|NG 25 KFIRING SOLENOID 24 MlGRO-SWITCH 23 "PLUNGER SIMULATING BORE RIDING PIN 26 M-52A FUZE BODY IO F=Lun|sER MOVED BY SLIDER 9 -AcRo SWITCH 30 ,-'-SPRING LOADED RESET PLUNGER 33' LL=-RESETSOLENOID 3| FIG. 3.

' INVENTORS HARRY M. DAY 3 WI BUR HARRIS the lower temperatures.

3,1825% Patented May 11, 1965 3,182,594 TEMPERATURE INDEPENDENT TIMING DEVICE, DASHPOT TYPE Wilbur Harris, Waukesha, Wis., and Harry M. Day, New

Canaan, Conn, assignors, by mesne assignments, to the United States at America as represented by the decretary of the Army Filed May 17, 1963, Ser. No. 281,373 4 (Ilaims. (til. 1l282) This invention relates to an improvement in a fuze employing a dash-pot as a time delay unit.

Such a dash-pot when used in a wide range of temperatures due to the change in viscosity of the fluid varies the delay period beyond desirable limits. The type of dash-pot referred to is one in which the piston head is fixed and the cylinder is moved by a constant force such as a spring to press the fluid past the piston and the time required for the cylinder to move is the time of the delay period. The time varies depending on the viscosity of the contained fluid which in turn is dependent on the temperature. In a temperature range from 65 F. to +160 R, where the fluid varies respectively from high to low viscosity, it is necessary that the time delay unit operate in a range of 2.5 to 8.0 seconds and the ordinary unit will not meet this requirement at the lower temperatures.

It is therefore the object of this invention to provide a dash-pot Whose cylinder moves past the piston head at a relatively constant rate of speed regardless of the temperature within the range of 65 F. to +160 F.

This object is accomplished by causing the cylinder to be moved by a constant source of pressure, such as a spring, and the cylinder will only move as fast as the fluid can flow through the clearance head and the interior of the cylinder wall. However the fluid will have a low viscosity at the higher temperatures and will flow more rapidly through the opening than at To compensate for this variation in viscosity, the clearance between the piston head and the cylinder wall is automatically adjusted with the change in temperature and viscosity. This change of clearance occurs in such a ratio as to cause a relatively constant rate of movement of the cylinder past the piston head regardless of the viscosity of the fluid.

One way of properly varying the clearance to accomplish the desired results is to use a piston head that expands with the increase in temperature to provide a smaller clearance and contracts with a reduction of temperature to obtain greater clearance. Such a piston head may be made of a temperature sensitive hi -metallic flat strip coiled to form a piston head of circular shape and whose diameter or periphery expands or contracts with changes in temperature of the fluid to provide a clearance that will permit an approximately constant flow of fluid past the piston head regardless of the temperature and/ or viscosity of the fluid in the cylinder.

Reference is made to the drawings which will afford a better understanding of the invention, in which FIGURE 1 is an enlarged section of the delay element employed with the fuze;

FIGURE 2 is a top View of the spider to depict its general shape;

FIGURE 3 is a diagrammatic representation of the apparatus controlling the delay element, and

between the piston United States Patent ()fi ice FIGURE 4 is an enlarged sectional view of the piston head.

In FIGURE 1 the delay element which is the dash-pot is shown mounted on the fuze body 10 and is contained in a housing 11. The dash-pot in the housing 11 consists of a fuze activating-slider member 9 having a cylinder 12 closed at one end with a member 13 having a peripheral flange l4 and a sealing member 15 forming a closure for the opposite end. A spring 16, coiled around the outside of the cylinder 12, rests at one end on the interior of the housing 11 and is biased at the other end on the flange 1 to move the cylinder when the control apparatus is activated. Centered within the cylinder 12 is a piston rod 1? which passes through the sealing member 15 and the housing 11, and is maintained in a fixed position by the lock nut 18. A piston head 19 is keyed to the free end of the piston rod 17 and is guided in the cylinder 12 by the spiders 20 and 21 positioned on opposite sides of the piston head 19. The spiders 20 and 21 are circular discs having projections 34 on the periphery that are spaced 90 apart and guide the piston head in the cylinder. The space between the projections are segments 35 cut from the periphery which are adapted to provide the openings necessary for the fluid to flow past the piston head. The portion of the opening that is eflective for the passage of liquid is dependent on what part of opening is left as the variable periphery of the bi-metallic coil changes position with change of temperature and/or Viscosity of the fluid.

The annular piston head 19 is made of a flat bi-metailic strip coil like a spring and will expand and contract proportionately with changes of temperature of the fluid 22 in the cylinder 12. The flat bi-metallic strip is selected as being the material most sensitive to temperature change, thus a piston formed by wrapping bi-metallic strip about a piston rod and forming a coil will produce the desired result since the coil will grow larger when heated and decrease in diameter when cooled, which produces an automatic change in clearance due to temperature change. Tests show that such a coil properly designed would compensate for the change in fluid viscosity, due to change in temperature, to such an extent that under a given load, the coiled piston head will move through the fluid at an almost constant rate regardless of the temperature of the fluid. it is essential that as much metallic strip as possible be Wound into any given diameter because the amount of reaction of the strip to temperature change is in direct proportion to the length of strip used. This change in diameter or periphery of the piston head governs the clearance between the piston head 19 and the cylinder 12 in accordance with the changes in temperature and/or changes in viscosity of fluid 22 in the cylinder 12.

The fluid 22 is utilized to control the delay action of the dash pot and must satisfy the requirements of remaining a true fluid at temperatures ranging from F to +160 F. and also remain fluid at F. when stored for 4 years without deterioration. The following four silicone fluids with a viscosity of 100,000 cs. or higher will satisfy the necessary requirements:

Cs. viscosity (a) Dow Corning Fluid XF371 100,000 (b) Dow Corning Fluid XF371 450,000 (0) Dow Corning Fluid 510 100,000

a General Electric Fluid ablilb'aiijjjj 400,000

Tests show these fluids are not adversely affected by storage at -80 F. nor do these fluids have a tendency in FIGURE .3 for the operation of the delay element in.

which no wiringis shown as the electrical connections Iform no part of this invention; the micro-switch 23 closes the circuit to activate the firing solenoid 24 against the tension oi the spring 25 to withdraw the bore riding retaining pin 26 from the forked end 32 of the slider membet 9; the slider member 9 and its cylinder 12 are then free to move and are moved when the spring 16 is able to overcome theresistance offered by the passage of the fluid 22 through the clearance between the piston head 19 and the cylinder 12 andthe time required to move the cylinder 12 is the time delay desired for the operation of the fuze; the movement of the slider member 9 permits the angled edge 27 to depress the plunger 28 carrying the member 29'which makes contact and activates the acro-switch 3t). To determine the delay under various test conditions, a clock may be started by the micro-switch 23 and stopped when the acro-switch is activated. The delay element may be reset by releasing the reset solenoid 31 to permit the reset plunger 32 to be moved by the spring 33 against the plunger 28 which in turn bears against the angled edge 27 to move the slider member 9 to its original position at the left against the tension of the spring 16, and when moved far enough, the deenergized firing solenoid 24 permits the bore riding pin 26 to return to the position shown in FIGURE 3 by the force of return spring 25. I

While this particular embodiment of this invention is shown and describedwherein the cylinder 12 is the moving element or" the dash-pot but it should be noted that it is within the scope of this invention for the cylinder 12 to be stationary and the piston rod 17 and the piston head 19 constitute the moving element of the dash-pot.

In theapparatus employed for tests, the best results were obtained when the clearance was varied from .005 to .026 inch when the cylinders length was .468 inch and the extension of the cylinder was .540 inch. Results were as follows:

Time required for piston Temperature, F. to travel .18", sec.

These testsproved that this invention will permit the delay element to operate within the desired limits regardless of the temperature and/ or viscosity of the fluid.

What is claimed is:

1. In a delay timing mechanism, the combination of a fuze body containing a fuze and having a dash-pot mounted thereon, said dash-pot being the delay element between firing and activation of the fuze and consisting 1 of a housing containing a movable cylinder, saidcylinder having peripheral flanges at one end and containing a fluid sealed therein, a coiled spring encircling said cylinder varied by temperature changes, said expandable periphery changing the clearance Withthe cylinder to regulate the passage of fluid forced past the piston head by the spring pressed cylinder when the firing solenoid is acti-- vated to compensate for variations of'temperature and/ or viscosity to permit the dash-pot to operate Within a designed delay period'at any temperature within the range of 65 F. to +160 F. and means for resetting the mechanism.

2. In a delay timing mechanism, the combination of a 'fuze body containing a fuze' and having a dash-pot mounted thereon, said dash-pot being the delay element between firing and. activation of the fuze and consisting of a housing containing a slider member movable within the housing for-activating the title, said slider member having-at one enda forked portion-with a bore riding pin inserted in the base of the fork for retaining said slider member, a resetting plunger protruding through the housing for contact with said slider member, said slider membcr provided with an angled edge for contacting said resetting plunger, an open-ended cylinder at the opposite end of the slider member adapted to be received in' the dash-pot to form a closed container, said cylinder having peripheral flanges at the closed end and containing a suitable fluid sealed therein, a coiled spring encircling said cylinder bearing against the peripheral flanges at one end and biased against the housing'at the other end, a piston within said cylinder having a piston head at one end and firmly keyed to the housing at the other end, spiders acting as closures on both sides of'said piston head, said spiders having projections 90 apart at the periphery to guide the piston head in the cylinder, peripheral openings cut out between said projections adapted to provide passageways for fluid by the piston head, said piston head made of a coiled flat bi-metallic strip formand means for forcing said resetting plunger against the angled edge of the slider member to return the'slider and the cylinder to the original position.

3. In a delay timing mechanism 'incorporatinga dash- V pot consisting of a cylinder filled with a fluid, a piston bearing against theperipheral flanges at one end and biased against the housing at the other end, a firing solenoid connected to a bore riding pin retaining said cylinder against the action of the spring, a piston rod within said 4 cylinderhaving a piston head at one end and firmly keyed to the housing at the other end, spiders acting as closures for both sides of said piston head andas guides for piston head in the cylinder, said piston head made of a coiled 1 ,flat bi-metallic strip forming an expandable periphery within the cylinder having an annular piston head with awanable periphery adjacentthe cylinder wall and providing a clearance therebetween, spiders having projections for guides on'both'sides of said piston head and openings between projections for the passage of fluid, said openings bounded at the periphery by the cylinder wall, said piston head formed of a coiled flatbi-metallic strip between the spiders and responsive to temperature changes of said fluid, the periphery of the coil changing with temperature changes to vary proportionately the effective openings between said periphery and said cylinderwall to govern the flow of fluid past the piston-head.

whereby the time of the flow is approximately the same, regardless of the temperature of the contained fluid to assure the delay time is within desired limits. 1

4. In a delay timing mechanism'incorporating a dashpot, said dasl1-pot comprising a cylinder filled with fluid, a piston rod within the cylinder having a piston head at one end, spiders acting as closures on both sides of said 7 piston head and having projections apart acting as guides for the piston head in the cylinder, openings formed by cutting away a portion of the peripheryof the spiders between said projections to provide passageways forfluid *by the piston head, said openings bounded at the periphery by the cyiinder wall, said piston head" made of a coiled flat bi-m'e'tallic strip having a variable periphery adjacent the cylinder Wall and providing a clearance therebetween to control the effective openings of the spiders, said variable periphery changing the clearance between the piston head and the cylinder to provide the only passageway for fluid by the piston head and to compen- 5 sate proportionately for changes in temperature and inversely proportional to changes in viscosity of the fluid in the cylinder and said dash-pot adjusting to fluid temperature and acting within the desired delay time When the cylinder is operating With a fluid at any temperature 10 Within the range of 65 F. and +160 F.

References Cited by the Examiner UNITED STATES PATENTS 1,486,381 3/24 Jaenichen 188-100 2,938,463 5/60 Jasse 10282 X 3,102,480 9/63 Severance et a1. 10282 X FOREIGN PATENTS 1,115,057 12/55 France.

SAMUEL FEINBERG, Primary Examiner.

Claims (1)

1. IN A DELAY TIMING MECHANISM, THE COMBINATION OF A FUZE BODY CONTAINING A FUZE AND HAVING A DASH-POT MOUNTED THEREON, SAID DASH-POT BEING THE DELAY ELEMENT BETWEEN FIRING AND ACTIVATION OF THE FUZE AND CONSISTING OF A HOUSING CONTAINING A MOVABLE CYLINDER, SAID CYLINDER HAVING PERIPHERAL FLANGES AT ONE END AND CONTAINING A FLUID SEALED THEREIN, A COILED SPRING ENCIRCLING SAID CYLINDERLBE BEARING AGAINST THE PERIPHERAL FLANGES AT ONE END AND BIASED AGAINST THE HOUSING AT THE OTHER END, A FIRING SOLENOID CONNEDTED TO A BORE RIDING PIN RETAINING SAID CYLINDER AGAINST THE ACTION OF THE SPRING, A PISTON ROD WITH SAID CYLINER HAVING A PISTON HEAD AT ONE END AND FIRMLY KEYED TO THE HOUSING AT THE OTHER END, SPIDERS ACTING AS CLOSURES FOR BOTH SIDES OF SAID PISTON HEAD AND AS GUIDES FOR PISTON HEAD IN THE CYLINDER, SAID PISTON HEAD MADE OF A COILED FLAT BI-METALLIC STRIP FORMING AN EXPANDABLE PERIPHERY VARIED BY TEMPERATURE CHANGES, SAID EXPANDABLE PERIPHERY CHANGING THE CLEARANCE WITH THE CYLINDER TO REGULATE THE PASSAGE OF FLUID FORCED PAST THE PISTON HEAD BY THE SPRING PRESSED CYLINDER WHEN THE FIRING SOLENOID IS ACTIVATED TO COMPENSATE FOR VARIATIONS OF TEMPERATURE AND/OR VISCOSITY TO PERMIT THE DASH-POT TOOPERATE WITHIN A DESIGNED DELAY PERIOD AT ANY TEMPERATURE WITHIN THE RANGE OF -65*F. TO +160*F. AND MEANS FOR RESETTING RANGE OF -65*F. TO +160*F. AND MEANS FOR RESETTING THE MECHANISM.

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