US3723676A

US3723676A - Latch-trip cam operated percentage timer

Info

Publication number: US3723676A
Application number: US00188347A
Authority: US
Inventors: J Harris
Original assignee: Deltrol Corp
Current assignee: Deltrol Corp
Priority date: 1971-10-12
Filing date: 1971-10-12
Publication date: 1973-03-27
Anticipated expiration: 1990-03-27

Abstract

A percentage timer includes two cam operated switch blades which are periodically raised and dropped. A latch engages one of the switch blades after it has dropped, causing contact closure until the latch is released by a follower riding a cam rotating with the switch cam. Adjustment of the release point to determine the percentage of on time is achieved by bodily moving the pivot of the follower by means of an adjusting cam and an adjusting cam follower. All of the cams are mounted on a common axis making a compact construction. A manual preset timer is arranged to override the percentage timer when used.

Description

United States Patent Harris 51 Mar. 27, 1973 54] LATCH-TRIP CAM OPERATED 3,598,214 8/1971 Harris ..192 14s PERCENTAGE TIMER 3,599,006 8/1971 Harris ..307 39 Inventor: John L. Harris, Delaiield, Wis. Assignee: Deltrol Corp. Bellwood, 111.

Filed: Oct. 12, 1971 Appl. No.2 188,347

US. Cl ..200/39 R, 200/35 R, 200/38 R Int. Cl. ..H0lh 43/10, l-lOlh 7/08 Field of Search ..200/38 R, 38 B, 39 R, 35 R;

Primary Examiner-J. R. Scott [57] ABSTRACT A percentage timer includes two cam operated switch blades which are periodically raised and dropped. A latch engages one of the switch blades after it has dropped, causing contact closure until the latch is released by a follower riding a cam rotating with the switch cam. Adjustment of the release point to determine the percentage of on time is achieved by bodily moving the pivot of the follower by means of an adjusting cam and an adjusting cam follower. All of the cams are mounted on a common axis making a compact construction. A manual preset timer is arranged to override the percentage timer when used.

10 Claims, 4 Drawing Figures LATCH-TRIP CAM OPERATED PERCENTAGE TIMER BACKGROUND OF THE INVENTION This invention relates in general to timers and more particularly to percentage timers.

Percentage timers as known in the art are timers driven on a fixed time cycle in which an adjustment is provided to allow the user to set the percentage of the cycle that the switch is open or closed.

In one type, a dial rotates at constant speed and an adjustable finger on the dial determines the proportion or percentage of the cycle that the switch is closed. This type requires the movable dial to be exposed which is objectionable in many applications. This also has the disadvantage of not being settable down to zero percent or up to 100 percent.

In another type, a constant rise cam is driven by the motor and adjustment is made by an external knob which moves the switch bodily with relation to the cam. This arrangement is bulky and involves complications in completing the circuit to the movable switch.

A third type is shown in US. Pat. No. 2,578,632 dated Dec. 1 1, 1951. In this unit a snap action switch is actuated by a cam through a cam follower having a pivot which is bodily moved by turning an external knob. Shifting this pivot varies the position of the cam at which the snap switch is actuated. The patented device has the advantage of a stationary switch and avoids the objection of an external rotating dial. It however is limited in capacity by the snap action switch and heavy duty models become too expensive for this reason.

BRIEF SUMMARY OF INVENTION The primary object of the present invention is the provision of a heavy duty, low cost and compact percentage timer in which the contacts operate with snap action without requiring the expense of a snap action switch.

In accordance with the invention, the switch includes two separate blades which are raised by a motor driven cam with the contacts disengaged and then dropped down. A latch holds the inner blade up causing the contacts to engage. This latch is released by an off cam follower riding a cam which rotates with the switch cam. This cam follower is mounted on a pivot carried by a lever which rides on an adjusting cam mounted on the same axis as the other cams. Moving the adjusting cam shifts this lever which bodily moves the pivot of the off cam follower. This varies the position of the switch cam at which the latch is released to open the switch, and thus varies the percentage of time the switch is closed.

The invention also includes a manual override allowing the user to close the switch independently of the percentage timing mechanism. This includes a cam mounted beside the latch adjacent the inner blade. Movement of this lever. cams the blade off the switch cam and latch and this'closes the contents.

A segmental gear comes into mesh with the timing mechanism when this manual override is moved into place. This automatically returns the manual override to its normal position in a predetermined time.

A further object of the invention is the provision of a percentage timer with a manual override which is released automatically by the timer mechanism.

Other objects will appear from the following detailed description and appended claims.

BRIEF DESCRIPTION OF DRAWINGS FIG. I is a schematic or exploded view of the timing mechanism embodying the invention.

FIG. 2 is a side sectional view of the mechanism shown in FIG. 1.

FIG. 3 is a side view of the manual preset timer mechanismishown in FIG. 1.

FIG. 4 is? afragmentary view of the manual preset mechanism in the set position.

DETAILED DESCRIPTION OF INVENTION Referring to FIGS. 1 and 2, reference character 1 indicates a timer front plate which is separated by suitable spacers (not shown) from a back plate 2 carrying a timer motor 3. Extending between

plates

1 and 2 is a main shaft 4 carrying an adjusting knob 5. Located ad- A bearing 10 is loosely fitted on the shaft 4 between I cam 6 and tension washer 9. This bearing carries a switch or on cam 11 and an off cam 12 located forwardly of the on cam. The bearing 10 also carries a drive gear 13 which meshes with a pinion l4 driven by a gear 15 through a slip friction drive 16. Gear 15 is driven by the pinion 17 of motor 18. The motor 3 serves to drive the cam shaft at constant speed in a counterclockwise direction as seen in FIG. 1.

The switch cam 11 is generally circular and includes a lobe 20 serving as a rise and drop off for starting an on period. The switch includes a panel 21 carrying a bracket 22 supporting a lower switch blade 23 having a contact 24. The blade 23 is formed with an opening straddling the cam 11 and also extends beyond the contact 24 providing a latching or end portion 25. The upper switch blade 26 is mounted on bracket 27 carried by panel 21. This upper blade carries a contact 28 and a cam follower member29 having a depending portion 30 which extends through the opening in blade 23 and rides on cam 11.

The latching portion 25 of the lower switch blade is held in upper or latched position by means of a latch 32 carried on a shaft 33 extending between the

timer plates

1 and 2. The latch 32 is formed with a latching surface 34 engaging the switch blade and is also formed with an operating surface 35 which is engageable by the operating surface 36 of cam follower 37. The cam follower 37 rides on off cam 12 and is supported on a stud 38 carried on an adjusting lever 39 which in effect is a cam follower riding on the adjusting cam 6. It will be apparent that the cam 12 and cam follower 37 provide a camming means driven with the on cam 11 for releasing the latch 32 at a predetermined angular position of cam l I. It will further be apparent that adjusting cam 6 and follower 39 bodily shift the position of the cam follower and latch operator 37 in accordance with the adjustment of knob 5.

Also mounted on the shaft 33 and beside the latch 32 is a cam member 42 having a camming surface 43 adjacent the end portion 25 of lower switch blade 23. As shown in FIG. 2, both the latch 32 and the camming surface 43 are operable on the switch blade.

The cam member 42 is operated by a manual operator 44 carried on a stud 45 attached to the back plate 2. The manual operator is provided with a handle portion 46 and a gear segment portion 47 which is adapted to mesh with the pinion 14 that also drives gear 13. Cam 42 is actuated by manual operator 44 by means of upwardly extending

arms

48 and 49 which cooperate with actuating

surfaces

51 and 52 formed on manual member 44. As shown in FIG. 3, the operating surface 51 extends beyond surface 52 into engaging relationship with the abutment 49 on cam member 42. Abutment 49 isnot engaged by operating surface 52, this surface engaging lever 48 which extends further in toward the member 44 than the abutment 49.

OPERATION With the parts in position shown in FIG. 1 the cam follower 29 carried by the upper blade has just dropped off the lobe on cam 11. The latch 32 is in latching position supporting the end of the lower switch blade. The

contacts

24 and 28 are in engagement and the cam follower 30 is slightly spaced from the circular portion of cam 11. An on period of the percentage timer mechanism has therefore just'been started. The cam shaft 10 including cams 11 and 12 is now rotating in a counterclockwise direction. This movement causes the cam 12 to engage the cam follower portion of lever 37 and rock this lever counterclockwise about itsfadjustment pivot 38. This motion causes the latch operator portion 36 to engage the operating portion of latch 32 thus rotatingthis latch clockwise about its bearing toward the latch release point. At the end of the predetermined on period as set by the knob S, the latching surface 34 of the latch rides off the end of the lower switch blade 23 allowing this switch blade to drop. On the initial portion of the drop the cam follower portion 30 on upper switch blade 26 engages the circular portion of cam 11 thus stopping the downward movement of the upper blade. The lower switch blade continues dropping thus separating the

contacts

25 and 28. This is the beginning of the off period.

The duration of the off period is determined by the position of cam 6 which is set by adjusting knob 5. Rotation of cam 6 clockwise rotates cam follower 39 counterclockwise which bodily carries stud 38 to the left which brings the latch operating portion 36 of cam follower 37 closer to the latch operating surface 35 on the latch. This movement of the pivot 38 advances the time at which latch 34 is released which shortens the on period and lengthens the off period. counterclockwise rotation of cam 6 permits clockwise rotation of the lever 39 about pivot 40 under the action of spring 41 thus moving the pivot point 38 to the right and increasing the distance between the lever operating portion 36 and the latch operating portion 35. This requires increased rotation of cam 12 in order to bring lever 37 to the latch releasing point. This'increases the length of the on period and decreases the length of the off period.

The scale of the dial for the adjusting knob 5 is determined by the curves of cams 6. and 12. These curves When it is desired to override the percentage timer mechanism the manual member 46 is moved to the right to the position shown in FIG. 4. During this motion of the manual operator 44, the leading operating surface 51 engages lever portion 48 of the cam member 42 rotating this member counterclockwise and bringing its camming surface in engagement with the end of the 7 switch blade 23. This cams the blade upwardly and finally the top of the camming surface rests under the blade. In this position both blades have been lifted to.

the point where the cam follower 30 on the upper blade is beyond the throw of lobe 20 on cam 11. Thus the contacts will remain closed independently of the rotation of cam 11. At this time the cam member 42 is held in position by the upper end of lever portion 48 engaging camming surface 52 on operator 44. During the motion of manual member 44, the gear segment portion 47 engaged pinion 14 and rotated it, this action being allowed by the slip friction drive means 16 between pinion l4 and gear 15. On release of the manual lever 46, the pinion 14 starts driving member 44 counterclockwise and the upper camming surface 51 on this member engages the lug 49 formed on cam member 42, causing this cam member to rotate clockwise. The camming surface 52 at this time has passed out of the path of the lever 48 and will not interfere with the clockwise movement of the latch. At the endof the manual on period, the top of the camming surface 43 passes from beneath the end of switch blade 23 and the end of the gear segment 47 becomes disengaged with the pinion 14. The pressure of the end 25 of blade 23 on camming surface 43 now causes the cam member 42 to rotate with snap action to the position shown in FIG. 1 in which blade portion 25 is released. The percentage timer mechanism now takes over giving the percentage of on and off periods as determined by the setting of the knob 5.

From the foregoing it will be apparent that the invention provides a compact heavy duty type timing mechanism in which the on and off periods are determined by a positive cam drop off action and by a positive latch release action insuring clean make and breaks of the switch. It will further be apparent that the invention provides for use of a stationary switch and at the same time provides for convenient setting merely by turning a normally stationary knob. It will also be apparent that the invention provides for a manual override in which the action of the percentage timer can be suspended for a predetermined period of time.

While a preferred form of the invention has been shown and described, it is obvious that many modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

lclaim:

1. In a switching mechanism, the combination of, switching means having a first position and a second position, periodic power means including a movable member moving to a fixed starting position at spaced intervals of time and then moving away from said starting position, means actuated on movement of said member to starting position for moving the switching means to its second position, latching means for holding the switching means in its second position after the movable member has moved away from the starting position, and adjustable means for releasing the latching means at predetermined positions of the periodic power means, said adjustable means including cooperating camming surfaces, one surface moving with the movable member and another surface being adjustable relative to said first surface, the latch being released when the position of the movable member corresponds to the adjustment of said other surface.

2. The combination recited in claim 1 in which the adjustable means includes an adjusting shaft which is normally stationary and moves only when the adjustment is being changed, movement of the shaft changing the position of said other camming surfaces.

3. In a switching mechanism, the combination of, switching means having a first position and a second position, means including a latch having a latched position and a released position for selectively latching the switching means in its second position or releasing it to its first position, periodic power means for moving the switching means from its first position to its second position under the control of the latch, means including a cam operated with the periodic power means and a follower riding said cam for releasing said latch, said follower having a pivot on which it rotates, and adjusting means for bodily moving said pivot to vary the position of the cam at which the follower releases said latch.

4. The combination recitedin claim 3 in which the adjusting means includes an adjusting cam, said adjusting cam and first cam being rotatable about a common axis, and an adjusting cam follower riding said first cam for moving said pivot. I

5. The combination recited in claim 3 in which a manual means is mounted beside the latch and arranged to move the switch to its first position independently of the latch and power means, and means actuated by the power means for releasing said manual means.

6. The combination recited in claim 4 in which the periodic power means includes a cam rotating on the same axis as the first cam and in normally fixed relationship thereto.

7. In a switching mechanism, the combination of, cam operated switching means including a pair of switch blades biased in the same direction, cam means and follower means riding the cam means, said cam means and follower means being arranged to periodically move said blades against their bias and release the blades for movement under their bias, means including a latch for selectively latching or releasing one of said blades, said latch when in latching position supporting one of the blades when the blades are released by the cam, causing the switch'blades to assume a first contact position, said latch when released allowing movement of the blades under their bias to a second contact position, means including a pivoted cam follower means for releasing the latch in accordance with the position of said cam means, and adjusting means for varying the position of the cam means at which the latch is released, said adjusting means including an adjusting cam and a follower therefore, said last mentioned follower being arranged to bodily shift the pivot of the pivoted cam follower means in accordance with the position of said adjusting cam.

8. The combination recited in claim 7 in which the cam means is rotatable about an axis and the adjusting cam is rotatable about the same axis.

9. The combination recited in claim 8 in which the adjusting cam is carried by an adjustable shaft, said shaft serving as a bearing for the cam means.

10. The combination recited in claim 7 including a manual operator mounted beside the latch and arranged to move the blade engaged by the latch against its bias, to move the blades to their first contact position independently of its cam means and latch, and automatic means for releasing said manual operator.

Claims

4. The combination recited in claim 3 in which the adjusting means includes an adjusting cam, said adjusting cam and first cam being rotatable about a common axis, and an adjusting cam follower riding said first cam for moving said pivot.

7. In a switching mechanism, the combination of, cam operated switching means including a pair of switch blades biased in the same direction, cam means and follower means riding the cam means, said cam means and follower means being arranged to periodically move said blades against their bias and release the blades for movement under their bias, means including a latch for selectively latching or releasing one of said blades, said latch when in latching position supporting one of the blades when the blades are released by the cam, causing the switch blades to assume a first contact position, said latch when released allowing movement of the blades under their bias to a second contact position, means including a pivoted cam follower means for releasing the latch in accordance with the position of said cam means, and adjusting means for varying the position of the cam means at which the latch is released, said adjusting means including an adjusting cam and a follower therefore, said last mentioned follower being arranged to bodily shift the pivot of the pivoted cam follower means in accordance with the position of said adjusting cam.