US3485172A - Mechanical timer - Google Patents

Description

Dec. 23, 1969 D. A. GOLDSTEIN ETAL. 3,485,172

MECHANICAL TIMER Filed Jan. 5, 1968 4 Sheets-Sheet l INVENTQR$ DAV\D A.C:OL.D$TE\N ROY NYST ROM ALFRED BORCHERT MELVIN EN AN BYM k.

AT'TORNEYS 1969 o. A. GOLDSTEIN ETAL 3, 85, 2

MECHANI GAL TIMER 4 Sheets-Sheet 2 Filed Jan. 5, 1968 INVENTOR$ DAVlP A. GOLD$TE\N ROY NYSTROM ALFRED BORCHERT 1969 D. A. GOLDSTEIN ETAL 3,485,172

MECHANICAL TIMER I Filed Jan. 5, 1968 4 Sheets-Sheet s NV ENTORTS DANHD GOLDSTEIN ROY NY6TROM ALFRED BORCHEKT MELVHNI NEMAN 714. W W M United States Patent 3,485,172 MECHANICAL TIMER David A. Goldstein, Bellmore, Roy Nystrom, East Northport, Alfred Borchert, Jericho, and Melvin Eneman, New York, N.Y., assignors to the United States of America as represented by the Secretary of the Army Filed Jan. 5, 1968, Ser. No.-696,041 Int. Cl. F42c 9/04 US. Cl. 102-84 Claims ABSTRACT OF THE DISCLOSURE A time delay detonating mechanism capable of releasing a spring-loaded firing pin including a clock mechanism, setting means for presetting a delay of from three minutes to twenty-four hours and arming means which when activated cocks the firing pin spring and automatically releases and starts the clock mechanism. The setting means must first be set before the arming means can be activated hence the mechanism is safe or unarmed during the setting operation. Moreover, the mechanism will not fire if the time to fire is set less than three minutes.

The invention relates to a time delay detonating mechanism and more particularly to such a mechanism having a variable interval mechanical timer.

The general purpose of this invention is to provide a water-tight, rugged time delay mechanical detonating mechanism which may be preset for time periods varying between three minutes and twenty-four hours, which is safe or unarmed before and during the setting operation, and which provides an automatic mechanical means for arming the device, starting the timing mechanism and mechanically detonating the explosive.

It is, therefore, an object of this invention to provide a time delay detonating mechanism which is safe or unarmed during the setting operation.

Another object is the provision of a time delay detonating mechanism capable of releasing a spring loaded firing pin after a preset delay of from three minutes to twenty-four hours.

Still another object is to provide a time delay detonating mechanism having features to assure safety in storage, handling, installation, and activation.

The above objects as well as others together with benefits and advantages of the invention will be apparent upon reference to the detailed description set forth below, particularly when taken in conjunction with the drawings annexed hereto in which:

FIG. 1 is a longitudinal sectional view of an embodiment of our invention taken along line 1-1 of FIG. 2;

FIG. 2 is a rear view of the device of FIG. 1;

FIG. 3 is a view of the device taken along line 3-3 of FIG. 1;

FIG. 4 is a view similar to FIG. 2,, with parts broken away of a front view of the device of FIG. 1.

As seen in the drawings, a variable interval mechanical timer is housed in a watertight case 10 having a fiat top cover 12, flat bottom cover 14 and a drawn metal body 16. A firing pin exit hole (not shown) is sealed before installation by an O ring 18' and setting knob 20. The basic construction of the interval mechanism is typical of a clock structure, i.e. posts 22 and post supported plates 24 which carry the timing components.

A detonating mechanism (see FIG. 3) consists of a firing pm 26, a locking ball 28, and a compression spring 30.

A setting mechanism consists of a setting knob in line with and coaxial to the firing pin 26, a knurled knob '32 at the external end of said setting knob 20 and a spur gear 34 at the internal end of said setting knob 20. The central part of the setting knob 20, closest to the O ring 18 is provided with a male thread (not shown). This is normally engaged with a female thread (not shown) provided in a knob sleeve 36 to which case 10 is afiixed.

When the setting knob 20 is unscrewed from the knob sleeve 36 but not completely withdrawn from the timer, the spur gear 34 is engaged with a crown pinion 38 (FIG. 1) of a clock setting train. In this position, the knob 20 is used to set the timer, which is explained in detail, infra.

Further withdrawal of knob 20 by a straight pulling motion separates the knob completely from the timer. The knob may then be replaced by any desired output acceptor e.g. an explosive cartridge which contains a percussion primer which threads into and seals against the knob sleeve 36.

A -prewound spiral clock power spring or mainspring 40 provides energy for driving the timer. The outermost coil of the power spring 40 is anchored to a fixed post 42 (FIG. 2). The innermost coil of the power spring 40 is aflixed to arbor 44 to drive a power gear 46. The power gear 46 is always in mesh with the clock gear train. The mainspring 40 delivers twelve turns at the rate of one turn per two hours. The particular point of power gear engagement is at the pinion of the gear assembly 48.

When turned by the setting knob 20, the pinion 38 acts as an idler and drives an hour wheel 50. The hour wheel 50 is in mesh with a setting gear assembly 52 which is also in mesh with a minute wheel pinion 54. This pinion 54 is affixed to a minute wheel 56 thereby turning on the hour wheel shaft but at a twelve times faster rate than the hour wheel 50. The minute wheel 56 :is provided with two sets of one hour markings (see FIG. 4) so that in each half turn which corresponds to one hour, there are proper markings for that hour.

The numbered surfaces of the respective wheels are arranged to be visible through a window 58 which includes an index line 60 for setting and reading the set time in hours and minutes.

The setting wheels are coaxial with the arbor 44 of the power spring 40, and in the safe position they are free to be turned with respect to the arbor 44.

Clutch plate assembly 62 is constrained to turn with the power spring arbor 44. The clutch plate 63 is provided with a compression spring 64 which is capable of pressing the clutch plate 63 against the face of minute gear 54 so that said gear will be turned by the power spring arbor 44.

In the safe position the clutch is disengaged (as shown) by a member 92 which presses against the round head 66 of the clutch assembly 62.

In the armed position this restraint is removed and the clutch spring 64 engages the clutch plate: 63 against the minute wheel pinion 54.

The clock regulating system includes the previously described power spring 40 and power gear 46 which meshes with the pinion of gear assembly 48. The remainder of the clock includes gear assembly 68, gear assembly 70, escape wheel assembly 72, lever assembly 74, and balance wheel and hairspring assembly 76. These parts regulate, in a known manner, the motion of the power spring gear 46 to one half revolution every hour while the balance wheel oscillates at six beats per second (or three cycles per second).

An arming plunger 78' (see FIG. 3) is a long tubular member having a closed end where it projects from the timer case 10. Included within its tubular portion are firing pin 26 and firing pin compression spring 30. A sliding O ring seal 80 is provided for sliding in sleeve 82 which is a fixed part of the case 10. Attached to the plunger 78 is a bent wire spring 84. When the plunger 78 is in the safe The tubular body of plunger 78 includes slot 86 which permits plunger motion without interfering with access to firing pin 26 by locking ball 28 and three minute interlock pawl 88. The plunger 78 also has two tabs affixed to it: first an arm-safe indicator tab 90 which is visible through window 58 (see FIG. 4) and second, an interlock tab '92. In a safe position (as shown in FIG. 3) tab 92 is engaged in a transverse slot (not shown) which is provided in the power spring arbor 44. In this position the tab 92 presses against the rounded head 66 (see FIG. 1) of the clutch assembly 62 and thus holds the clutch assembly 62 free of minute pinion 54. The tab 92 also prevents rotation of the power spring arbor 44 when in this safe position. In the armed position the tab 92 is moved (to the left in FIG. 3) so as to release the clutch Y assembly -62 and clear the power spring arbor 44.

The body of the plunger 78 is also provided with a broad notch 94. A flat detent spring 96 that presses against the side of the plunger 78 engages the notch 94 when the plunger 78 is in the armed position. This arrangement prevents withdrawal of the plunger 78 and disarming of the mechanism once it has been armed.

The firing pin 26 is normally held in the cocked position by locking ball 28. Ball 28 is guided in support 98 which is fixed to plate 24. The ball 28 can be pushed out by the firing pin 26 and its spring 30. This motion of the ball 28 is normally blocked by the adjacent end of firing shaft 100. A notch 102 is provided at the end of shaft 100 which will permit the locking ball 28 to move away from the firing pin 26 and release it if the firing shaft 100 rotates approximately 90. The firing shaft 100 is provided with a torsion spring 104 which can turn the shaft 100 through the necessary angle of 90. Projecting radially from firing shaft 100 is a stop arm 106 which normally blocks rotation of firing shaft 100. Stop arm 106 projects through a clearance hole 108 in the clock plate 24 and presses against the surface of hour wheel 50. Wheel is provided with a cut-out 110 which turns toward the arm 106 so that the arm is released when the set time has elapsed. At that time, the arm 106 snaps down through the cut-out in the wheel 50, the shaft 100 turns and locking ball 28 is released into notch 102. Firing pin 26 is then released to strike with its striking portion 111 whatever acceptor element has been installed in place of setting knob 20. Interlock pawl 88, in the safe position, projects through the slotted Wall of the tubular plunger 78 into the path of firing pin 26. The pawl 8'8 is pivotable on shaft 112 and is pressed by its torsion spring 114 against the central part 11 6 of gear assembly 48. The tail portion 118 of the pawl 88 extends over a flat portion 120 of the firing shaft 100 so that rotation of the firing shaft 100 is prevented by the interlock pawl 88. The central part 116 of the gear assembly 48 is provided with a flat portion (not shown) which after three minutes of timer operation turns to a position which releases the pawl '88 to turn counter clockwise to a position which clears both the shaft 100 and the firing pin 26.

In operation, the firing time may be set at any time prior to emplacement with a firing device such as an explosive cartridge. This is accomplished by unscrewing and rotating the combination setting knob safety cap until the desired time for firing is displayed in the view window. The firing device may now be committed to the set timing cycle by fully depressing the arming plunger. This done, the status indication in the view window will reveal the letter A in place of the letter S (see FIG. 4).

Three minutes after activation, the firing device will arm by unlocking the firing pin and its release mechanism.

When the preset time has elapsed, the spring loaded firing pin will be driven outward from the device into the precussion primer of the explosive cartridge, initiating an explosive firing train.

The device requires only two input operations, namely, operation of the setting knob unlocks the device, permits times setting and permits connection to an acceptor element; and operation of the arming plunger, performs the multiple functions of cocking the firing pin spring, uncocking the clock power spring, releasing and starting the balance wheel, changing the visual status indication from safe to armed, engaging the timing wheels to the clock, and locking the timer into the committed position. Arming is completed automatically three minutes after this operation.

The timer incorporates five major safety features in its design, namely:

(1) The device cannot be assembly in the armed position.

(2) If the time to fire is set less than three minutes, the device will not fire.

(3) The combination setting knob safety cap prevents any firing pin motion by a direct physical blocking action.

(4) The firing pin spring is insufiiciently cocked to initiate a standard primer until the arming plunger is depressed.

(5) The arming plunger cannot be depressed until the safety cap is removed.

The timer has an output of twenty-four inch-ounces of kinetic energy which can be easily used to close an electrical switch at the end of the cycle, rather than releasing a firing pin to fire an explosive or pyrotechnic device.

We claim:

1. In a time delay detonator actuating mechanism adapted to be disposed in operational proximity to a detonator, said mechanism comprising a case including a top cover, a bottom cover and a tubular body,

a clock mechanism located inside said case,

a detonator actuating mechanism located inside said case in operational relationship with said clock mechanism,

setting means to set said clock mechanism in operational relationship with said detonator actuating mechanism, said setting means including a sleeve extending both inwardly and outwardly of said case body,

a setting mechanism removably secured within said sleeve,

said setting mechanism being coaxial with said firing a knurled knob integral with said setting mechanism On 1 the external end,

a spur gear integral with said setting mechanism on the internal end,

said setting mechanism being so constructed and arranged so that when partially withdrawn from said sleeve the spur gear will become engaged with a crown pinion of the clock mechanism thereby allowing said detonator actuating mechanism to be set and when fully withdrawn being interchangeable with a detonator fitting of a character adapted to be substituted therefor after setting of the clock mechanism,

the improvements wherein said detonator actuating mechanism includes a tubular plunger assembly comprising an arming plunger having an open end and a closed end,

said closed end of said plunger extending outwardly from said case body,

a firing pin located inside said plunger adjacent said open end,

a striking portion on the forward end of said firing pin extending outwardly from said open end,

a compression spring inside said plunger abutting the rearward end of said firing pin at one end and the closed end of said plunger at the other end,

locking means operational with said firing pin and said clock mechanism so that when said clock mechanism releases said locking means, said firing pin will be propelled forward thereby causing detonation.

2. A mechanism of the type described in claim 1 including a bent wire spring a balance wheel operational with said spring,

said spring being so constructed and arranged so that when said firing pin is held by said locking means said clock mechanism will not operate.

3. A mechanism of the type described in claim 2 wherein said clock mechanism includes a prewound spiral clock power spring, having an outermost coil and innermost coil,

said outermost coil anchored to a fixed post, and

said innermost coil affixed to a power spring arbor.

4. A mechanism of the type described in claim 3 including an hour wheel driven by said crown pinion,

a setting gear assembly driven by said hour wheel, and

a minute wheel pinion driven by said setting gear assembly.

5. A mechanism of the type described in claim 4 including a broad notch on said plunger, and

a flat detent spring engageable therewith so as to prevent withdrawal of said plunger after arming.

6. A mechanism of the type described in claim 5 including a clutch plate assembly constrained to turn with the power spring arbor comprising,

a clutch plate,

a compression spring coaxial with said clutch plate, and

a minute gear,

said clutch plate assembly being so constructed and arranged so that said compression spring presses said clutch plate against the face of said minute gear so that said minute gear is turned by said power spring arbor.

7. A mechanism of the type described in claim 6 including a window in said top cover,

a first tab secured to said plunger so arranged and constructed so as to be visible through said window,

a second tab secured to said plunger coacting with a round head portion of said clutch assembly to prevent rotation thereof when said detonating mechanism is in the unarmed position and to allow rotation thereof when said detonating mechanism is in the armed position.

8. A mechanism of the type described in claim 7 wherein said locking means includes a slot in said firing pin,

a locking ball engaged by said slot,

a firing shaft having an end adjacent said locking ball,

a notch in said adjacent end of said shaft,

a torsion spring coaxial with said firing shaft, and

a stop arm projecting radially from said shaft,

said locking means being so constructed and arranged so that when said locking ball moves into said slot said firing pin will be allowed to move forward.

9. A mechanism of the type described in claim 8 wherein said plunger is provided with a slot,

an interlock pawl projecting through said slot into the path of said firing pin,

said pawl being pivotable on a shaft,

a torsion spring biasing said pawl against a gear assembly,

said firing shaft having a flat portion,

said pawl having a tail portion,

said tail portion extending over said fiat portion in such a manner as to control rotation of said firing shaft.

10. A time delay detonator actuating mechanism for firing a detonator when disposed in operational proximity thereto, said mechanism comprising a case,

a clock mechanism located inside said case,

a detonator actuating mechanism in operational relationship with said clock mechanism, said detonator actuating mechanism including a tubular arming plunger extending both inwardly and outwardly of said case and slidably mounted relative thereto and having an open end and an outwardly extending closed end, a firing pin located inside said plunger adjacent said open end, and a compression spring inside said plunger abutting the rearward end of said firing pin at one end and the closed end of said plunger at the other end,

setting means for presetting said clock mechanism re- .movably mounted on said case and in operational relationship with said detonator actuating mechanism, said setting means being disposed in the path of movement of said arming plunger and said firing pin to prevent the movement thereof until said setting means is removed,

locking means operational with said firing pin and said clock mechanism to prevent movement of said firing pin until said clock mechanism releases said locking means,

starting means operative upon movement of said arming plunger for releasing and starting said clock mechanism; and

whereby movement of said arming plunger inwardly after said setting means has been removed arms said spring for firing said firing pin and releases and starts said clock mechanism.

References Cited UNITED STATES PATENTS 2,485,949 10/1949 Wilson et a1. 10284 2,514,499 7/1950 Kharasch et al. 10284 3,120,810 2/1964 Eshleman et a1. 102-84 3,254,602 6/1966 Klostermann et al. 102-84X 3,261,293 7/1966 Webb 102-82 BENJAMIN A. 'BORCHELT, Primary Examiner T. H. WEBB, Assistant Examiner

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