US3550458A - Mechanical timer - Google Patents

Description

Dec. 29, 1970 DUNLOP ETAL MECHANICAL T IMER Filed June 23, 1969 PN w mmm N Www W my? R4 z W United States Patent MECHANICAL TIMER Alexander K. Dunlop, St. Paul, and Raymond A. Hogenson, South St. Paul, Minn., assignors to Minnesota Mining and Manufacturing Company, St. Paul, Minn.,

a corporation of Delaware Filed June 23, 1969, Ser. No. 835,530 Int. Cl. F01h 43/00; F16h /74 U.S. Cl. 743.5 6 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to a timing mechanism and in one aspect to a mechanical, automatically resettable, inexpensive timing device for a machine having a driving shaft associated with the operation to be controlled.

There are many types of timers presently available, most of which are electronic to provide for incremental charging of a capacitor, or mechanical timers which utilize separate motors in the timer for driving a cam adjustable upon the shaft to operate a switch, or which operate on the order of a clock to trip a switch upon the passing of a predetermined time interval. The timers that are known in the prior art however, in their commercial form, are quite expensive, and the timers are relatively complex and thus demand the high price.

The timer of the present invention is adjustable to vary the time interval as are most timers. The timer of the present invention receives a driving force from an operating rotatingmember on the machine whether operating only in response to energization by the timer or as a normal function of the machine. The timer of the present invention is self-resetting, utilizes very few and generally inexpensive parts, and is not readily susceptible to wear and failure of operation.

The present invention comprises an adjustable rotatable 0 knob havingan indicator thereon to indicate the position or setting of the timer. A second knob and plunger is axially movable for operating a switch actuator to drive the switch blade or lever from a normally open position to a normally closed position relative to a switch. The switch lever is positioned for engagement by the plunger and biased to an open position. Movement of the switch operating plunger of the timer also places the timer drive mechanism in contact with a driving member to begin the timing cycle and operates a mechanical lock means to hold the plunger in its second operating position. The drive mechanism comprises a drive means for rotating the switch operating plunger which causes rotation of the plunger and the depressible or axially movable knob until it reaches a position to engage and release the lock means at which time the biasing force on the switch blade returns the plunger to the normal position and the timer drive mechanism is automatically reset to an original start position. The timer is reset by a torsion or clock spring which acts upon the switch actuator to return it to a predetermined rotational position on its axis.

The above invention will be further understood after ice reading the following description which refers to the accompanying drawing wherein:

FIG. 1 is an elevational view of the timer;

FIG. 2 is an end view of the timer partly in section;

FIG. 3 is a fragmentary sectional view corresponding generally to FIG. 2; and

FIG. 4 is a plan view partly broken away to show interiorly located pieces.

Referring now to the drawing, a mechanical timer 10 is disclosed which is adapted to be mounted on most any machine and coupled to a driven shaft 11 of the machine for operation of a timing function of the machine through a switch 12.

The timer includes a frame 13 or mounting bracket for the timer to mount the timer on the machine. This frame 13 also serves as a mounting for the switch 12, as a journal for a drive coupling 14 and has a flange 15 for journalling and slidably supporting the switch actuating shaft 16. Ears 17 and 19 are formed on the frame 13 to support the same on the machine.

The switch 12 comprises a housing for a sliding switch arm 20 serving to close two normally open contacts having terminals 24 and 25 upon actuation of the timer and returning under the force of a biasing spring shown in dotted lines to the normal open position bridging the contact on the terminal 24 with an open contact having a terminal illustrated at 26. Arm 20 also serves to bias the shaft 16 upwardly axially to a normal or first position. It is of course obvious that terminals 24 and 26 could perform a machine function in the normally closed circuit position to indicate expiration of the timed cycle or the terminal 26 and its associated contact need not exist. The timer actuating shaft 16 rests on the switch operating arm 20 at one end and the other end extends through the flange 15 and extends axially through an opening in a first knob 22 and receives on its extended end a knob or a button 23 which is fixed thereto. The shaft 16 is journalled in flange 15 by a sleeve 28 fixed thereto and extending partially into the center bore of a crown gear member 29 secured to the shaft 16 by a retaining ring 27. The gear teeth on the crown gear 29 extend downwardly and are positioned axially on the shaft 16 at a position above the drive coupling 14 which includes a shaft 30 extending on one side of the frame 13 and having on its other end a pinion 31 engageable with the crown gear 29.

Positioned on the crown gear 29 on the surface thereof opposite the teeth is an upstanding lug 32 engageable under bias of a torsion spring 33, wrapped about the sleeve 26 and having one end fixed relative to the bracket 15 and the other end thereof engaging the lug 32, with a depending stop or arm 34 formed in a fixed position on the plate 15. The lug 32 and lug 34 are each long enough to be engageable whether the crown gear 29 0f the timer drive means is in its normal inoperative or operative position.

Pressure against the button 23 on the upper end of the shaft 16 causes the same to be depressed against the biasing force urging the switch arm 20 of the switch to the upper normal position. The sliding movement of the switch arm 20 after the spring force has been overcome causes engagement of the timer to begin a timing cycle. Axial movement of the shaft 16 actuates a releasable retaining or lock means as a circumferential recess or groove around the shaft cooperates with a spring biased pawl or detent.

As may most clearly be seen in FIGS. 2 and 3, the lock means comprises a groove 37 in the shaft 16 and a pawl or detent is supported in the knob 22 and movable therewith. The detent is formed by a spring having one arcuate leg 39 engaging the inner curved wall of the knob 22 and a generally straight arm member 40 which is biased away from the leg 39 and will thus, when in aligned position to fall into the groove 37, prevent axial movement of the shaft 16 in either direction. A diametrical stop formed in the knob 22 limits the movement of the member 40 from the member 39. Extending axially from the free end of the normally straight arm 40 of the spring is a cam follower or release arm in the form of a lug 41 positioned for contact with the cam 36. Rotation of the button 23 will cause the cam 36 to engage the lug 41 and move straight arm member 40 of the spring away from the arcuate leg 39 and out of the groove 37. When the spring leaves the groove, the spring in the switch 12 will move the shaft 16 axially away from the actuated position back to its normal position, during which movement the spring 33, as it was wound during rotation of the shaft 16, will unwind and rotate the shaft back to the original starting position with the lug 32 engaging stop 34.

As the timing cycle begins under the driving motion of the machine shaft 11 via the drive coupling 14, the lug 32 is driven peripherally away from the stop 34 against the force of the torsion spring 33. The shaft is held in its depressed timing position by the locking catch or detent with arm 40 biased into engagement with the groove 37 on the shaft 16 within the knob 22. To indicate the expiration or the lapse of the time in the desired cycle this detent must be released permitting return axial movement of the shaft 16 from the switch closed position and to separate gear 29 and pinion 30. To do this, a cam 36 depends from the button 23 and is positioned to engage the arm 40 which engages the groove 37 of the shaft 16. Rotation of the shaft 16 rotates the button 23 and cam 36 such that the latter may release the lock means by engaging the lug 41 and camming arm portion 40 out of the groove 37 in the shaft. When this detent is released by rotation of the cap 23 the shaft is returned axially to its initial position releasing the slide 20 on the switch 12 to again open the circuit between the terminals 24 and 25.

Adjustment of the knob 22 about the axis of shaft 16 may be defined through substantially 360, however its extent of rotation in any one direction is retarded by a stop identified by the reference numeral 44 on the flange 15 and radially projecting a lug on the knob 22. The position of the knob 22 determines the position of the lug 41 and the timed interval.

In operation the timer is energized when the button 23 moves from the position of FIG. 3 to the position shown in FIG. 2, causing the teeth on the crown gear 29 to engage the pinion 31, and the straight arm member 40 of the detent of the timer spring to snap into the groove 37, arresting the return movement of the shaft and button from its second operative position to its first release position. The switch 20 is opened and the pinion 31 drives the crown gear 29 to rotate the shaft 16 until the lug 36 of button 23 engages the lug 41 of the spring to release the shaft. Release of the spring arm member 40 from the groove 37 resets the timer by return of the switch 20, upward movement of the shaft 1-6 and crown gear, and return of the shaft with lug 32 engaging the stop 34.

Having thus described my invention, what is claimed 1. A mechanical timer operative to energize a circuit and maintain the same energized for a predetermined time interval which upon lapse of the interval will open position, biasing means urging said shaft axially toward said first position,

releasable lock means for holding said shaft in said second position,

switch means operative upon movement of the shaft to close and open a circuit,

drive means for. rotating said shaft about its axis upon movementof said shaft from said first position toward said second position, and

cam means operative upon rotational movement of said shaft to release said lock means and disengage said drive means by the return said shaft to said first position by said biasing means.

2. The mechanical timer of claim 1 wherein spring and stop means are provided for determining an initial rotational position of said shaft and for returning said shaft to said position upon disengagement of said drive means.

3. The mechanical timer of claim 2 wherein said releasable lock means comprises detent means engageable with said shaft means upon movement from said first position to said second position to hold said shaft in said second position and cooperating with said cam means for releasing said shaft from said second position.

4. The mechanical timer of claim 3 wherein said detent means are adjustable relative to the cam means to vary the spacing therebetween such that the interval of time may be adjusted at which said timer is released.

5. A mechanical timer operative to energize a circuit and maintain the same energized for a predetermined time interval which upon lapse of the interval will open the circuit and automatically reset the timer, said timer comprising a frame,

a vertically movable shaft supported on the frame for axial movement from a first position to a second position, said shaft having a recess formed therein,

an adjustable knob rotatably supported about said shaft and carrying detent means for cooperation with said recess on said shaft for holding said shaft in said second position,

switch means engaged by said shaft and operative upon movement of the shaft to close and open a circuit, said switch means including biasing means normally urging said shaft toward said first position,

drive means for rotating said shaft about its axis upon movement of said shaft from said first position toward said second position, and

a button secured to said shaft and positioned within said knob, said button having cam means operative upon rotational movement of said shaft when in said second position engageable with said detent means to release said detent means and disengage said drive means affording the return of said shaft to said first position.

6. The mechanical timer of claim 5 wherein spring and stop means are provided for determining an initial rotational position of said shaft on said frame and for returning said shaft to said position upon disengagement of said drive means.

References Cited UNITED STATES PATENTS 2,706,224 4/1955 White 20039 3,388,602 6/1968 Shopsky 743.5

MILTON KAUFMAN, Primary Examiner US. Cl. X.R. 200-39

Images