Providing a programmer/timer with dual rate drive

Abstract: A programmer/timer for an appliance of the type having a rotatable cam drum (12) advanced for sequential actuation and deactuation of a plurality of electrical switches (20). The drum is advanced or indexed intermittently by an oscillating advance pawl (26) engaging a ratchet wheel (25) and also continuously by a gear (44) driven by a common motor for oscillating the advance pawl. The ratchet wheel (25) has a hub (38) which is frictionally engaged (37) to drive the cam drum. The driven gear in turn is frictionally engaged (51) with the hub to also drive the ratchet wheel. When the advance pawl engages the ratchet wheel for intermittent drive, the driven gear slips on the ratchet hub. Upon user selection, a separate cam track (52) lifts the advance pawl to permit the driven gear to continuously drive the ratchet wheel.

Description: BACKGROUND OF THE INVENTION The present invention relates to electromechanical programmer/timers utilized for sequentially activating at least one and usually a plurality of electrical switches for a selective program interval. Programmer/timers of this sort are commonly employed for appliances such as clothes washing machines, dishwashers, microwave ovens and other appliances wherein it is desired for the machine user to select a desired program interval for the appliance operation; and, upon such selection a timing motor provides advancement of a cam track for sequentially actuating the machine control function switches during time-out of the selected interval. Typically, electromechanical appliance programmer/timers utilize a subfractional horsepower synchronous timer motor driving either a continuous drive to the cam through a speed reducer, or employ an indexing mechanism such as a ratchet wheel engaged by a periodically advanced and retracted pawl. Heretofore, differing rates of advance in appliance programmer/timers have been provided by utilizing ratchet teeth of varying depth disposed about the advance ratchet with blocking means, usually comprising a masking ratchet wheel, to permit the pawl to engage the notches of greatest depth only upon selected multiples of the advanced pawl stroke, thus providing alternate rates of intermittent advancement of the cam ratchet. However, the fastest rate of advancement in such arrangements is determined by the number of teeth having the greatest minor diameter on the ratchet wheel with the teeth of lesser major diameter providing a substantially slower rate of advancement. Where continuous drive for the cam is employed via means of a motor speed reducer, it has heretofore been the practice to shift or change gearing in order to provide alternate rate of advance. However, in certain appliance applications, it is desired to provide a relatively slow rate of advancement utilizing the well known ratchet and pawl cam indexing; technique however, it is also desired to provide a substantially more rapid rate of advancement of the cam for certain selected portions of the program time out interval. Therefor, utilizing only a ratchet and pawl advance technique for the cam track limits the resolution of the cam track by virtue of the pitch of the teeth required to provide the desired maximum rate of advance. If the pitch of the teeth for the ratchet is chosen for the desired maximum rate of advance, within the allowable diameter for the ratchet, problems have been encountered in providing the desired resolution of the cam functions within a single revolution of the rotary cam track. EP-A 0 077 133 describes a timer drive mechanism for a timing cam which is provided with two ratchet wheels having different pitches of the teeth. Both ratchet wheels are operatively connected to the timing cam. The first ratchet wheel is driven by a first reciprocating pawl at a first fast rate. When the program requires a timed period during which conditions remain the same, the ratchet teeth of the first ratchet are spaced so that the pawl cannot pick up the next tooth until the cam is advanced by a second smaller pawl acting on the second ratchet provided with small, closely spaced teeth. This second ratchet has a pinion gear driving a ring gear molded inside the timing cam. At this mode of operation the timing cam is advanced at a second slow rate until the first pawl engages the next tooth on the first ratchet. However, in both modes of operation the timing cam is driven in an intermittent way. Therefore, it has long been desired to provide an electromechanical programmer/timer for appliance having a ratchet and pawl advance mechanism providing a relatively fast rate of advance and yet also provide for a substantially slower rate of advance with a continuous drive means for a portion of the selected program interval. SUMMARY OF THE INVENTION The present invention as claimed provides an electromechanical programmer/timer for appliances having a relatively fast rate of advance of the switch cam track provided by an oscillating advance pawl and ratchet wheel and a substantially slower rate of advance provided by a continuous speed reducer drive. The ratchet is connected to drive the cam track by a first frictional clutch means and the continuous drive is connected for driving the ratchet by a second frictional clutch means which is permitted to slip when the pawl is engaged for advancing the ratchet. The cam track has a portion thereof configured to lift the advanced pawl from the ratchet, thereby disabling the pawl and ratchet advance, whereupon the second frictional clutch ceases to slip and the continuous drive provides for the slower rate of advance. User selection of the desired program interval for the cam track is accomplished by user rotation of the cam track which is permitted by slippage of the first and second clutch means to enable the desired positioning of the cam track for commencement of the timed interval for the program. In the preferred form, the first clutch means comprises a frictional engagement between the interior of the hub on the ratchet wheel and a shaft connected to the cam track. A second clutch means comprises a collet provided on the speed reducer aftward gear with the collet frictionally engaging the exterior of the ratchet wheel head. The present invention thus provides a novel and simplified instruction for a programmer/timer for appliances wherein a single drive motor is operative to providing a fast rate of advancement through a pawl advancing a ratchet wheel and a slower rate through continuous drive-to the ratchet wheel which slips during pawl advancement of the ratchet. Upon lifting of the ratchet, the slipping clutch ceases to slip and provides a slower rate of continuous drive to the cam track. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a pictorial representation of the cam track ratchet advance pawl and gear train for the programmer/timer of the present invention with the advance pawl engaging the ratchet; Figure 2 is a view similar to Figure 1 showing the advanced pawl lifted from the ratchet by a blocking track on the cam; and, Figure 3 is a section view taken along broken section line 3-3 of Figure 1. DETAILED DESCRIPTION Referring to Figure 1, the dual rate drive mechanism before a programmer/timer is illustrated generally by reference numeral 10 and comprises a drum 12 mounted for rotation about shaft 14 and having a cam track 16 provided about the periphery thereof. A cam follower means 18 is pivotally exposed on the base or housing means (not shown) and the follower is engaged in track 16 and is operative to effect actuation and deactuation of the electrical switch mechanism indicated generally at 20. In the illustration of Figure 1, the cam drum 12 is shown rotated to a position such that the cam follower 18 rests against the depressed or base circle portion 17 of cam track 16 and in this position effects deactuation or opening of the switch 20. The portion of cam track 16 on drum 12 disposed generally diameterally opposite the depressed portion 17 is also depressed for a desired arcuate segment of the cam track periphery as indicated by the reference numeral 22. A toothed ratchet wheel having teeth 24 of substantially constant pitch and root diameter greater than tracks 22 are formed about the periphery thereof; and, the ratchet 25 is disposed concentrically with respect to shaft 14 and in axially spaced relationship with cam drum 12. An advance pawl 26 is provided and has a chisel point 28 disposed to engage the ratchet teeth 24 as illustrated in Figure 1. Pawl 26 is connected to orbiting concentric crank pin 30 and has the end thereof opposite to the point 28 disposed over pin 30 and biased thereon by integrally formed spring fingers 34, 32. It will be understood that the crank pin 30 is rotated by a speed reducer and motor drive mechanism (not shown). Referring to Figure 1 and 3, the cam drum 12 is illustrated in the preferred practice as being integrally formed on shaft 14 and is rotated therewith by user rotation of the shaft 14 for positioning the cam track 16 at a desired rotational position with respect to cam follower 18. Ratchet wheel 25 is shown in Figure 3 as having an axially extending hub 36 which has the inner periphery thereof received over shaft 14 so as to position the ratchet teeth 24 in alignment for engagement with the pawl chisel point 28. The ratchet hub engages the shaft 14 in a frictional engagement and comprises a first frictional clutching means indicated generally by the numeral 37 for operatively connecting the ratchet wheel 25 for rotationally driving cam drum 12. The ratchet hub 36 has a reduced diameter extension portion 38 extending from the hub in a direction opposite that of the cam drum 12. A speed reducing gear 40 has a central hub 42 provided thereon and received over shaft 14 adjacent the reduced diameter portion 38 of the ratchet hub. Gear 40 has peripheral teeth 44 continuously engaged by a motor drive pinion gear 46 which is driven from shaft 48 by a motor comprised (not shown). It will be understood, however, that a common motor drive may be employed with appropriate speed reduction for the eccentric shaft 30 and for the pinion gear 46. The hub 42 of gear 40 has provided on the interior thereof a plurality of collet jaws 50 which frictionally engage the exterior of the smaller hub diameter 38 in frictional engagement and comprise a second clutching means indicated generally by reference numeral 51 in Figure 3 for providing a continuous drive from shaft 48 to ratchet wheel 25 via gear 40 and through the first clutching means 37 to the cam drum 12. Referring to Figure 2, the drive of Figure 1 is shown with the cam drum 12 rotated to a position where a second cam track 52 has raised the chisel point 28 an amount sufficient to disengage the pawl from the ratchet teeth 24. This listed position is shown in greater detail in Figure 3. In operation, when the cam drum 12 is positioned such that track 22 permits the ratchet teeth 24 to be engaged by the pawl chisel point 28, the cam drum 12 is driven by the first frictional clutch 37; and, the second frictional clutch 51 permits shaft 14 to be overdriven by slippage therein. In operation, during the initial portion of the selected program the ratchet wheel 25 is advanced by clutch 51 engaging hub 36 with the pawl chisel point 28 lifted from the ratchet teeth 24 by cam track 52. Upon reaching the end of track 52, point 28 engages ratchet teeth 24, driving of the ratchet wheel 25. Thereafter, the clutch means 51 begins slipping the shaft 14 is driven by clutch 37 at the speed of rotation of the gear 25. The drum 12 continues rotating until the cam track 16 reaches the recessed cam track portion 17 whereupon cam follower drops and deactuates or opens switch 20 to cut line power to the motor drive (not shown) for shaft 48. In the presently preferred practice of the invention, the pawl and ratchet drive is operable to provide a faster rotation to cam drive 12 than the continuously rotating pinion gear 46 driving through gear 40 and clutch 51. In one application of the invention, it has been found desirable to rotate the eccentric shaft 30 at a rate of 4 revolutions per minute (4 RPM) thereby giving the pawl 26 a period of oscillation of 15 seconds. Concomitantly, the driving pinion 46 is rotated at a rate of one-fifteenth revolution per minute (1/15 RPM); and, the ratio of the number of teeth on pinion 46 to the number of gear teeth 44 is 1:4 giving the gear 40 a rate of rotation of one-sixtieth revolution per minute (1/60 RPM). In the present practice of the invention, in one application, it has been found satisfactory to have clutch 51 provided with a slippage or break-away torque of 0,28 Nm (40 in-ounces); and, the clutch 37 has a break-away torque of 0,14 Nm (20 in-ounces). When the motor drive (not shown) for driving eccentric shaft 30 and pinion 46 is inoperative e.g. switch 20 is open, shaft 14 may be rotated by the appliance user in either direction. If the pawl 26 is in the position shown in Figure 2, clutch 37 will slip to permit positioning of the cam in either direction. If the pawl is in the position shown in Figure 1, with the chisel point engaging the ratchet teeth, clutch 37 will slip upon user rotation of shaft 14. The present invention provides unique and novel dual rate drive for an electromechanical programmer/timer for actuating appliance function switches in a sequence during a selected program interval. The programmer/timer of the present invention provides a pawl and ratchet drive to a rotatable switch cam drum in which the ratchet wheel is frictionally clutched to the cam drum shaft; and, the ratchet wheel hub is also separately frictionally clutched to a continuously rotating motor drive gear. Upon engagement of the pawl with the ratchet, the friction clutch to the continuously driven gear slips and permits the shaft to be overdriven. Upon the cam drum rotating to a desired position, a cam track lifts the pawl from engagement with the advance ratchet and the shaft is not overdriven and slippage of the gear clutch ceases and the cam drum shaft is driven at a slower rate by the continuously rotated drive gear. Upon time-down to the lower cam position, the pawl engages the ratchet and the drum overdrives the continuously driven gear. The user positioning of the cam drum is accomplished by permitting clutch 37 to slip upon user rotation of the cam drum shaft in either direction. The present invention has been hereinabove described and illustrated in the drawings in the presently preferred practice. However, it will be understood that modifications and variations may be made to the disclosed version and the invention is limited only by the scope of the following claims.

Claims: A programmer/timer assembly for sequentially actuating at least one electrical switch (20), said assembly comprising: (a) cam means (12,16) rotatable with respect to said switch and including follower means (18) operable in response to rotation of said cam means to effect actuation and deactuation of said switch; (b) motorized drive means (30) including ratchet and pawl means (24,26) operable to intermittently advance said cam means at a first rate, characterized in that said motorized drive means also includes gear means (46,44) operable to continuously advance said cam means at a second rate; said assembly being also characterized by moreover comprising: (c) first clutch means (37) operative to provide frictional driving engagement between said ratchet means and said cam means; (d) second.clutch means (51) operative to provide frictional driving engagement between said continuous drive means and said ratchet means; wherein said second clutch means - is operative to slip during said first rate advancement; (e) said cam means, including blocking means (52) operable, upon advancement of said cam means to. a predetermined position to prevent driving engagement between said pawl and ratchet, and operative to permit said second rate advancement without slippage of said second clutch means; and, (f) said first clutch means operable to slip upon user rotation of said cam means to permit initial positioning of said cam means for program interval selection. The programmer/timer defined in claim 1, wherein said second clutch means requires a greater torque for slippage than is required for slippage of said first clutch means. The programmer/timer defined in claim 1, wherein said ratchet has a hub (38) provided thereon and said second clutch means comprises a frictional coupling between said continuous drive means and said ratchet hub. The programmer/timer assembly defined in claim 1, wherein said ratchet includes a hub (38) and said first clutch said means comprises a frictional coupling between said hub and said cam means. The programmer/timer assembly defined in claim 1 wherein said blocking means includes a raised portion of said cam means. The programmer/timer assembly defined in claim 1, wherein (a) said ratchet has an axially extended hub (38) and said second clutch means frictionally engages the outer periphery of said hub; and, (b) said cam means includes a shaft (14) with said first clutch means comprising frictional engagement between the inner periphery of said hub and said shaft. The programmer/timer defined in claim one, wherein, (a) said ratchet means includes a ratchet wheel (25) having a hub (38) and, (b) said second clutch means includes a collet (50) frictionally engaging said hub. A programmer/timer assembly for sequentially actuating at least one electrical switch (20) comprising: (a) rotatable cam means (12,16) and follower means (18) operable upon rotation of said cam means to effect actuation and deactuation of said switch means; said assembly being characterized by moreover comprising: (b) a ratchet wheel (25) having an axially extending hub portion (38) with said ratchet frictionally coupled to said cam means; (c) a driven gear (40) frictionally coupled to said ratchet hub; (d) pawl means (26,28) operative upon advancement and retraction to effect intermittent movement of said ratchet wheel; (e) motorized drive means (48,46) operable to provide continuous rotation of said driven gear and said advancement and retraction of said pawl means; and, (f) blocking means (52) operable upon user selective positioning thereof to prevent said pawl means from advancing said ratchet, whereupon said driven gear continuously advances said ratchet wheel and said cam means, said driven gear coupling operative to slip when said blocking means is positioned to permit said pawl means to advance said ratchet wheel. The assembly defined in claim 8, wherein said cam means includes a shaft (14) with said ratchet hub and said driven gear received thereon. The assembly defined in claim 8, wherein said cam means includes a shaft (14) with said ratchet hub frictionally coupled thereto and said driven gear received thereover. The assembly defined in claim 8, wherein said blocking means comprises a raised portion of said cam means operable to lift said pawl means from said ratchet wheel. The assembly defined in claim 8, wherein said driven gear frictional coupling comprises a collet (50) attached to said driven gear frictionally engaging said ratchet hub. The assembly defined in claim 8, wherein said cam means includes a shaft (14) and said ratchet wheel friction coupling to said cam means includes said ratchet wheel hub received over said shaft in frictional engagement. A method of operating a programmer/timer with a dual rate of advance which programmer/timer includes a rotatable can (12) for actuating at least one switch (20), a frictional clutch (37), an advance ratchet (25, 24), and a motorized advance pawl (26) engaging said ratchet and advancing said cam at a first rate through said frictional clutch (37); characterized by the steps of (a) frictionally clutching (51) said ratchet with a continuous motor drive (46,44) and allowing said continuing frictional engagement to slip when said pawl engages said ratchet for advancing at said first rate; and, (b) selectively lifting said pawl from engaging said ratchet and advancing said cam continuously at a second slower rate without slipping said frictional engagement with said motor drive. The method defined in claim 14, wherein said step of frictionally engaging said ratchet with a continuous motor drive includes the steps of providing a hub (38) on said ratchet and engaging said hub with a collet (50). The method defined in claim 14, wherein said step of frictionally clutching said ratchet to said cam includes the steps of providing a shaft (14) on said cam and frictionally engaging said advance ratchet to said shaft.

Inventors: AIGNER ROBERT KURT, MAHON JOSEPH JOHN, AIGNER, ROBERT KURT, MAHON, JOSEPH JOHN
Applicants: EATON CORP, EATON CORPORATION
Application year: 1989
Main classification: H01H43
IPC codes: H01H43