Two-speed continuous drive timer

The motor drives the timing drum continuously at low speed through a gear train having a one-way clutch. The motor also drives the input of a second one-way clutch having a drive on its output engageable with the spaced teeth on the interrupted gear formed on the hub of the drum. When the low speed drive rotates the drum to a position in which a tooth on the hub can be engaged by the drive gear the drum is rapidly advanced until contact with the tooth is lost. Switches operated by the cams on the drum are sequenced rapidly during rapid advance. When the drum is manually advanced both clutches are overridden.

FIELD OF THE INVENTION 
The invention relates to a two-speed continuous drive program timer having 
timing cams actuating switches in a desired sequence. 
BACKGROUND PRIOR ART 
Continuous drive program timers have had limited application due to the 
difficulty in providing accurate sequential switching of a number of 
switches in a relatively short period. The usual solution has been to use 
an impulse drive in combination with subinterval switch(es). Subinterval 
switching has not been used with continuous drive timers since it is too 
difficult to register (and maintain registry) of the subinterval switch 
relative to the program cam(s). Workable designs proved more expensive 
than an impulse drive. A continuous drive timer capable of accomplishing 
the desired switching with reliability and modest added cost can have an 
economic advantage over the impulse drive. 
SUMMARY OF THE INVENTION 
The object of this invention is to provide a two-speed continuous drive 
program timer in which the sequencing of a number of switches in a short 
period of time is accomplished during high speed drive of the program cam. 
Registry of the rapid drive to the sequence is built in and is not 
affected by manual advance of the timer. The manual advance capability is 
very important since it is used in setting the timer. The present design 
has all the program cams permanently related to one another and to the 
rapid advance.

DETAILED DESCRIPTION OF DRAWINGS 
An electric motor and reduction gear in case 10 drives pinion 12 projecting 
from the case. This pinion gear engages idler gear 14 which is molded 
integrally with pinion 16 and has stub shafts projecting from the ends for 
journaling the gear/pinion 14, 16 in support plates 19 and 21. Pinion 16 
drives gear 18 which is molded integrally with clutch input 20 journaled 
on sleeve 22 of the clutch output 24. The sleeve is mounted on shaft 26 
and is provided with drive pinion 28 meshing with the internal gear 30 on 
the molded cam drum 32. Clutch input 20 and output 24 have confronting 
axially projecting ratchet gears 34. The input is biased into engagement 
with the output by spring 36 to provide a driving connection from the 
input to the output of the clutch. The gear teeth 34 are shaped so that if 
the output rotates faster than the input the output will overrun the input 
by forcing the input downwardly against the bias of spring 36. 
The continuously driven gear drive just described constitutes the low speed 
drive for the cam drum. The drum is provided with multiple cam profiles 38 
for actuating switch assemblies such as illustrated. The proximal ends of 
the blades are mounted in wafers 39 fixed in the timer. The switch and cam 
arrangement shown is representative and can, of course, be changed. For 
the present purposes, however, it is adequate to note that the distal end 
of the lower blade 40 is fixed to an arm projecting from guide 42 having a 
depending follower portion 44 which rides on the smooth surface 46 between 
the cams. This serves to position the lower blade and the contact carried 
by the lower blade. The upper blade 48 is self-biased downwardly so that 
the tip will rest on pad 50 but may be lifted upwardly therefrom as 
illustrated in the drawing. The distal end of the middle blade 52 is 
provided with a follower 54 which rides on and is actuated by the cam 38. 
In the illustrated position, the middle blade contact has been actuated 
upwardly into engagement with the contact on the end of the upper blade 
48. When the cam rotates a little further in the direction of the arrow, 
the follower will drop down to a middle level on the cam profile and will 
separate from the upper blade so all circuits are open. When the cam 
rotates a little bit further, the follower will drop all the way down into 
the portion designated 56 and will engage the contact on the lower blade 
40. 
It will be understood that with various cam profiles and switches actuated 
by the cam there can be a portion of the program in which it is important 
to have the switches sequenced rapidly relative to one another but in an 
accurate sequence nevertheless. At these times, it is advantageous to 
increase the rotational speed of the timing drum so that tolerances are 
not extremely critical and yet the desired sequencing can be obtained 
within a short time frame. The present design provides a high speed drive 
in a very simple manner. 
It will be noted that gear 18, which is continuously driven by the motor 
and is on the input side of the clutch driving to pinion 28 which in turn 
drives the internal gear of the cam drum, also engages gear 58 journaled 
on shaft 60. A ratchet gear 62 is also journaled on shaft 60 and is biased 
downwardly towards gear 58 by spring 64. The confronting faces of gears 58 
and 62 are provided with interfitting ratchet-type teeth 66, 68 which 
constitute a one-way drive clutch which will yield to permit the ratchet 
gear 62 to overrun gear 58 if the ratchet gear 62 is rotated faster than 
gear 58. In the position shown in FIG. 1, the ratchet gear 62 does not 
engage anything since the gear teeth lie close to a smooth portion of the 
hub 70 of the cam drum. The hub is, in effect, an interrupted tooth gear. 
At predetermined points around the surface of hub 70, there are gear teeth 
72 which, in the course of time, will rotate to a position to be engaged 
and driven by the sharp teeth of the ratchet gear 62 which rotates 
continuously at relatively high speed. At this time the ratchet gear will 
drive the cam drum at a speed substantially faster than the normal 
rotational speed of the drum. The drive will continue until the ratchet 
gear 62 has driven the gear tooth 72 on the hub to the point where contact 
is lost between the two. If there is only one tooth at a location, the 
high speed drive will be of a relatively short duration. However, two 
teeth or three teeth can be located side-by-side to increase the angular 
travel of the drum during which the drum is driven at high speed. Since 
the gear teeth 72 and cam drum are an integral molded part the precise 
location of the teeth relative to the cam profiles is built into the 
design. 
It will be noted the drum arbor is shown as provided with a shaft 74 
projecting through plate 76 and having a knob 78 for manual actuation. 
This is simply a schematic representation of the fact that the cam drum 
can be manually advanced to a given position. Normally there will be 
provision for axial movement of the knob and shaft so as to actuate a line 
switch controlling the overall energization of the timer and the 
appliance. Customary practice indicates that an anti-reverse pawl will be 
provided to prevent reverse manual rotation of the drum to prevent damage 
to switches. When the cam drum is manually advanced it rotates faster than 
either of the outputs of the one-way clutches and both clutches will be 
overridden. The one-way clutch in the high speed drive will be overridden 
only when a gear tooth 72 on the hub engages the ratchet gear 62. When the 
motor is energized, there is no question about proper reorientation or 
registry of the rapid advance portion since this is molded into the drum 
and its hub. It will also be appreciated that when the high speed drive 
becomes operative, the one-way clutch which normally drives the cam drum 
at low speed will be overridden because the drum is now rotating faster 
than the output of that one-way clutch. 
With this arrangement, it is only necessary to determine at what points in 
a program it is desired to have high speed drive and then locate one or 
more gear teeth 72 on the hub at a position which will cause the ratchet 
gear 62 to complete the high speed drive. The angular travel of the cam 
drum at high speed is determined by the number of teeth 72 molded on the 
hub to be engaged in sequence by the ratchet gear 62. 
This arrangement provides extremely reliable high speed operation of the 
cam and the proper registry of the high speed operation is assured since 
the cams and teeth 72 are molded at the same time. The ability to manually 
advance the timer is retained and the construction can be manufactured at 
substantially lower cost than an impulse timer with subinterval switching. 
A further advantage of the present construction over an impulse timer with 
subinterval switching is that there is substantially greater flexibility 
in program selection and sequencing with this construction.