Cam switch mechanism

A cam switch mechanism comprises a drive source, such as a motor, a cam driven by the drive source, a switching device responsive to contacting the cam surface of the cam for switching its electrically conducting state and a control unit, such as a microcomputer, for controlling the drive source. Control of the drive source by the control unit makes it possible to set positions of the cam as desired and permits the electrically conducting state of the switching means to be freely set. The control unit controls the drive direction, stopping and drive speed of the drive source.

BACKGROUND OF THE INVENTION 
a) Field of the Invention 
This invention relates to a cam switch mechanism suitable for controlling 
automatic dishwashers, etc. 
b) Description of the Related Art 
Automatic dishwashers can automatically wash dishes, etc., by conducting 
processes such as wash, rinse, and heat, etc., for specific periods of 
time, according to the selected course. Cam switch mechanisms are built 
into these automatic dishwashers, and the execution of each process is 
controlled by making a plurality of cams, provided so as to correspond 
with the processes, turn together. 
With the conventional cam switch mechanism, the automatic washing program 
is made to correspond from beginning to end with one cycle of each cam. In 
the cam surface of each cam, a protrusion is formed only in the region 
wherein, out of all the automatic washing programs, only the corresponding 
process is performed, and the proportion of the entire cam surface length 
occupied by this region corresponds to the shortness or length of the time 
that each process is performed. In other words, for processes that are 
performed over a long time period, the protrusion region is formed 
broadly, while, conversely, for processes that are completed in a short 
period of time, the region is formed narrowly. The turning speed of the 
cams is constant, and when the cams make one cycle, the automatic washing 
terminates. 
With the conventional cam switch mechanism, when a short-duration process 
is set, the protrusion on the cam surface which performs the switching 
operation is small, resulting in poor timing precision when performing 
on-off operations. Not only that, but the small protrusions on the cam 
surface easily become worn over time, and precision deteriorates markedly 
even with a slight amount of wear. 
On the other hand, in order to improve the timing precision of the on-off 
operations, it is well to perform the control directly by means of a 
computer instead of controlling by means of a cam switch mechanism. 
Computers, however, are weak electrical systems, requiring expensive power 
relays for them to directly control each process, resulting in higher 
production costs. 
OBJECT AND SUMMARY OF THE INVENTION 
The primary object of this invention is to provide a cam switch mechanism 
that can improve the timing precision of each process control, while 
holding down the rise in production costs. 
In accordance with the invention, a cam switch mechanism comprises a drive 
source, a cam driven by the drive source, switching means responsive to 
contacting the cam surface of the cam for switching its electrically 
conducting state and a control unit for controlling the drive source. 
Control of the drive source by the control unit makes it possible to set 
positions of the cam as desired and permits the electrically conducting 
state of the switching means to be freely set.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The embodiments of this invention will now be described in detail. 
FIGS. 1-5 depict one embodiment of the cam switch mechanism to which this 
invention pertains. This cam switch mechanism 1, for example, is built 
into an automatic dishwasher; it comprises a motor 2 that is the drive 
source, cams 3-8 which are driven by the aforementioned motor 2 and have 
uneven parts (cam surfaces) of specified shapes, switching means 21-25 
that slide against the uneven parts of aforementioned cams 3-8 and thereby 
switch on and off, and a control unit that controls the motor 2. The 
drive, stopping, and drive speed of the motor 2 are controlled by the 
aforementioned control unit to set freely the period of time during which 
the aforementioned switching means is turned on or off. The motor 2 is, 
for example, a stepping motor. Accordingly, the speeds at which the cams 
turn are variable, and they can be turned forward and backward. 
The actions exhibited by an automatic dishwasher include a fill (hold 
water--FILL) action, a pump (spray water--PUMP) action, a drain (discharge 
water--DRAIN) action, and a heater (drying--HEATER) action. The cam switch 
mechanism 1 executes these actions, either individually or in combination. 
The cams include, for example, three switch cams 3--5, one detergent cam 
(action cam) 6, and two home cams 7 and 8. The first switch cam 3 
corresponds to the fill action and drain action of the automatic 
dishwasher. The second switch cam 4 corresponds to the pump action. The 
third switch cam 5 corresponds to the heater action. These three switch 
cams 3-5 are formed integrally together with the first home cam 7 and turn 
as one unit. The first home cam 7 detects the home position for each of 
the switch cams 3-5. Also, the detergent cam 6 controls the detergent 
deploying timing and the rinse deploying timing of the automatic 
dishwasher. The second home cam 8 detects the home position of the 
detergent cam 6. 
These cams 3-8 are turned by the stepping motor 2. The turning of the 
stepping motor 2 is transmitted to a first clutch 9 and a second clutch 10 
via a first gear 11, a second gear 12, a third gear 13, and a fourth gear 
14. The two clutches 9 and 10 have pawls which convey the turning force 
only in constant and opposite directions, respectively. 
The clutches 9 and 10 and the fourth gear 14 are combined on the same shaft 
to configure a double ratchet mechanism. When the stepping motor 2 is 
turned forward, the turning force thereof is transmitted to the first 
clutch 9, whereas when the stepping motor 2 is turned in reverse, this 
turning force is transmitted to the second clutch 10. 
The turning of the first clutch 9 is transmitted to each of the switching 
cams 3-5 via the gear 15 and the gear 16. Meanwhile, the turning of the 
second clutch 10 is transmitted to the second home cam 8 via the gear 17 
and the gear 18. This second home cam 8 and the detergent cam 6 are made 
into a single unit with a screw. 
In other words, the cam switch mechanism 1 to which this invention pertains 
has a double ratchet mechanism, that is, a transmission switching means, 
between the motor 2 and the switch cams 3-5 and detergent cam 6. While 
separating the switch cams 3-5 and the detergent cam 6, the cam switch 
mechanism links one ratchet of the double ratchet mechanism to each of the 
switch cams 3-5, and the other ratchet to the detergent cam 6, 
respectively, turning the switch cams 3-5 when the motor turns forward, 
and turning the detergent cam 6 when the motor 2 turns in reverse. 
Furthermore, the second gear 12 is formed integrally with the third gear 
13, the first clutch 9 with the gear 15, and the second clutch 10 with the 
gear 17. 
On the cam surfaces of the cams 3-8, the functions noted in FIG. 6 are 
allocated over the entire 360.degree. cycle of the cam surfaces. 
The switching means 21-25 are, for example, leaf switches which are turned 
on by the elastic deformation of a plate. Each of the switching means 
21-25 is turned on by sliding against either a depression or protrusion in 
the cam surfaces of the switch cams 3-5 and the home cams 7 and 8, and are 
each turned off by sliding against the other. 
Meanwhile, the detergent cam 6, as depicted in FIG. 10, controls the 
detergent deployment timing and the rinse deployment timing via action 
members, i.e. via a stop lever 19 and a detergent lever 20. The detergent 
lever 20 is spring-loaded in the counter- clockwise (CCW) direction. 
More specifically, when due to the detergent wait state indicated by the 
solid lines in FIG. 10, the detergent cam 6 turns so that the arm 19a of 
the stop lever 19 drops to the drop position 6a of the cam 6, an 
engagement piece 121 in the stop lever 19 separates from an engagement 
piece 122 in the detergent lever 20; the detergent lever 20 turns in the 
CCW direction so that the arm 20a of the detergent lever 20 engages the 
engagement piece 121, thereby starting the rinse deployment wait state. 
At this time, the detergent (not indicated in the drawings) is deployed. To 
explain the workings of detergent deployment with reference to FIG. 11, 
the detergent lever 20 turning shaft 26 and the detergent deployment hatch 
27 are engaged. Now, when the detergent lever 20 reaches the position 
indicated in FIG. 10 by the double-dotted broken lines, the detergent 
deployment hatch 27 swings to open due to the turning of the turning shaft 
26, and the detergent 28 is deployed. 
Further, when the detergent cam 6 turns in the CCW direction, and the arm 
19a of the stop lever 19 drops to the rinse drop position 6b of the cam 6, 
the engagement between the engagement piece 121 of the stop lever 19 and 
the stopper 125 of the detergent lever 20 is broken, the detergent lever 
20 turns in the CCW direction, the arm 20b of the detergent lever 20 
pushes a rinse lever 123 to the stopper 124 of, and rinse deployment 
ensues. 
After rinse deployment, the detergent cam 6 turns further in the CCW 
direction, reaching the state where it is stopped in the home position. 
When the dishwasher is used the next time, from this state, the detergent 
lever 20 is turned in the CW direction manually and the mechanism is 
reset. 
Here, innovative measures are implemented so that there is no contact 
between either the engagement piece 121 and engagement piece 122, or the 
engagement piece 121 and stopper 125, when the detergent lever 20 is 
turned in the CW direction. 
More specifically, when the detergent lever 20 is turned in the CW 
direction, the stop lever 19 is in the solid-line position in FIG. 10, so 
that the stopper 125 passes outside the engagement piece 121. Also, since 
the righthand end 22a of the engagement piece 122 has a gradually sloping 
shape, when the detergent lever 20 is manually turned in the CW direction, 
the engagement piece 121 gently rides over the end 22a, so that the 
detergent lever 20 turns smoothly, without letting the engagement pieces 
121 and 122 collide. 
FIG. 6 indicates the positioning of the cam surfaces in the cams 3-8, the 
functions corresponding to each cam surface combination, and the timing of 
wash and rinse deployment. 
HOME indicates that the cam 7 is in the home position, with the switching 
means 24 in the turned-on state. FILL is the function of filling up with 
water, with the switching means 21 in the turned-on state due to the cam 
3. FILL+PUMP is the function whereby water is sprayed while filling with 
water, with the state in which the switching means 22 is turned on by the 
cam 4 added to the FILL function. PUMP is the function which performs only 
water spraying, continuing the ON state of the switching means 22. With 
HEATER+PUMP, the state in which the switching means 23 is turned on by the 
cam 5 is added to the PUMP function, so it is the function which sprays 
water while heating. With DRAIN+PUMP, the state in which the switching 
means 21 touches the reverse contact due to the cam 3 is added to the PUMP 
function, so it is the function which sprays while discharging water. 
HEATER is the function which performs drying by heating, with the 
switching means 23 in the turned-on state due to the cam 5. 
Moreover, the FILL and DRAIN functions are set so that, if the switching 
means 21 contacts the protrusion in the cam 3 and touches the contact on 
one side to turn on, the FILL function is activated, and if the switching 
means 21 contacts the depression in the cam 3 and touches the contact on 
the other side to turn on, the DRAIN function is activated, whereas when 
the switching means 21 is between the two contacts, both of these 
functions are turned off. However, to facilitate ease of explanation, the 
representation in FIG. 6 is divided between FILL and DRAIN. 
The turning of the motor 2 is controlled by a control unit (not shown in 
the drawings) such as a microcomputer. The control unit varies the 
turning, stopping, and turning speed of the motor 2, and freely sets the 
times during which the switching means 21-25 are turned on and turned off, 
respectively. This control unit also doubles as the control unit for the 
automatic dishwasher. 
We next describe the action of the cam switch mechanism 1 when it is built 
into an automatic dishwasher, referring to FIGS. 7-9. 
Into the control unit of the automatic dishwasher, that is, into the 
control unit of the cam switch mechanism, five different wash modes are 
programmed, as indicated in FIG. 7. The user selects the wash mode 
according to his or her objective. For example, when hot scrubber is 
selected, processes are executed in the order pre-wash process.fwdarw.wash 
process.fwdarw.rinse process.fwdarw.heater process. All of these processes 
are done in 107 minutes. 
Now, the pre-wash process is conducted in three cycles, of 4 minutes, 4 
minutes, and 5 minutes duration, respectively. 
During these cycles of the pre-wash process, as indicated in the lefthand 
column A in FIG. 8, the stepping motor 2 is turned forward to perform the 
functions (1) then (2) then (3) then (4) then (6). 
Each function is diagrammed in FIG. 9. Function (1), for example, is the 
HOME function, wherein the first home cam 7 turns the switching means 24 
on. Function (3), moreover, is the FILL+PUMP function, wherein the first 
switch cam 3 turns the switching means 21 on, and the second switch cam 4 
turns the switching means 22 on. The control unit controls the turning of 
the motor 2. More specifically, it performs each function for the pre-set 
time while stopping and restarting the turning of the motor 2 and varying 
its turning speed. Any explanation of other functions are omitted here. 
Meanwhile, the wash process is performed in 43 minutes. The wash process, 
as shown in the lefthand column A in FIG. 8, turns the stepping motor 2 
forward and performs the functions (2) then (3) then (4) then (6), and 
also turns the stepping motor 2 in reverse to turn the detergent cam and 
perform detergent deployment D. 
The automatic dishwasher performs the other processes in the same manner 
and completes the washing program. The automatic dishwasher washes dishes, 
etc., automatically, performing the various processes in a designated 
order, corresponding, respectively, to the selected wash mode. 
With the cam switch mechanism 1 configured as in this embodiment, the 
switch cams 3-5 and the detergent cam 6 are separate entities, with each 
cam engaged in one cam of a double ratchet. 
Accordingly, when, for example, the motor 2 turns CW, only the detergent 
cam 6 turns; when the motor 2 turns CCW, only the switch cams 3-5 turn. By 
being configured in this way, it is possible to turn only the detergent 
cam without returning the switch cams 3-5, making it possible to prevent 
pump start-up noise, etc., that is produced when the switch cams 3-5 are 
turned backward. In other words, there is no need to return the switch 
cams 3-5, so there is no generation of pump start-up noise, etc. 
Also, with the portion of the surface of the cams which do not affect the 
on/off of the switching means 21-25, or, in other words, with the portion 
where the switching state (on/off state) of the switching means 21-25 is 
not switched, the motor 2 can be stopped. Furthermore, the detergent cam 6 
is set exclusively for detergent deployment (140.degree. position) and 
rinse deployment (200.degree. position). As indicated in FIG. 8, in 
actuality, the switching means perform detergent and rinse deployment 
during (FILL+PUMP). 
Moreover, the morphology described in the foregoing is one example of a 
morphology well suited to this invention, but the invention is not limited 
to this; various modified embodiments are possible within a range wherein 
the essence of this invention is not lost. 
For example, in the foregoing description, a stepping motor 2 is employed 
as the drive source, but this is not necessarily limited to a stepping 
motor. It could also be a DC motor, for example. Or, for the case of 
switch actions only, it could even be an AC motor. 
Also, the mechanism which transmits the turning of the stepping motor 2 to 
each cam is not limited to that described above. For example, as with the 
cam switch mechanism 30 depicted in FIGS. 12-16, the turning of the 
stepping motor 2 could also be transmitted to the cams 35-39 via a first 
gear 31.fwdarw.a second gear 32.fwdarw.a third gear 33.fwdarw.a fourth 
gear 34. 
In this case, the switch cams 35-37 and the home cam 38 are formed 
integrally, and these cams 35-38 are formed into a single unit with the 
detergent cam 39 by means of a screw. In other words, with this embodiment 
morphology, all of the cams 35-39 turn as a single unit, so one home cam 
suffices. 
Furthermore, the first switch cam 35 corresponds to the FILL action and 
DRAIN action of the automatic dishwasher. Also, the second switch cam 36 
corresponds to the PUMP action. The third switch cam 37 corresponds to the 
HEATER action. The home cam 38 detects the home position of these cams. In 
addition, the detergent cam 39 controls the detergent deployment timing 
and the rinse deployment timing. 
The cams 35-38 turn the corresponding switching means 40-43, respectively, 
on and off with the timing diagrammed in FIG. 17. Accordingly, even when 
structured in this manner, it is possible to automatically wash the dishes 
according to the wash mode selected, as indicated in FIG. 7, just as with 
the cam switch mechanism 1 described earlier. Moreover, the particulars of 
the processes when the cam switch mechanism 30 is employed are indicated 
in column B in FIG. 8. In this case, by turning the stepping motor 2 in 
reverse, it is possible to repeatedly perform functions already performed, 
or to pass over unnecessary functions without performing them. 
More particularly, the various function regions are allocated to the region 
in the switch cams 35-37 from 0.degree. to 122.5.degree.. Also, the 
detergent cam 39 turns integrally with the switch cams 35-37, so that 
detergent deployment is performed when the detergent cam 39 is at 
185.degree., and rinse deployment is performed when it is at 225.degree.. 
In the cam surfaces, the gradient is steep in the portions which connect 
the depressions with the protrusions, so that, in some cases, we cannot 
expect stable switching even when the switch makes contact. Even in such 
cases, however, with the cam switch mechanism of this invention, it is 
possible to control the electric current conducted to the switching means 
independently by a control means. Therefore, when a switching means 
contacts an unstable cam surface, the electric current can be cut off by 
the control means, so that stable switching can be performed such that 
unstable steep-gradient cam surfaces are not used. 
Also, if control is effected with a specific cam surface so that no 
electric current goes to a switching means, it is possible to make the 
cams turn at high speed and pass over unnecessary functions without 
executing them, or to make the cams turn backward and execute the next 
function without executing unwanted functions. 
As described in the foregoing, because the turning speed and turning 
direction of the cams are controlled by a control unit, and because the 
time during which the switching means are turned on and/or off can be set 
freely, it is possible to switch the switching means while turning the 
cams at high speed; on the other hand, it is possible, in cases where the 
switching means are not switched, to turn the cams at slow speed or to 
stop them. As a result, the long regions in the cam surfaces can be used 
to operate the switching means, thus improving the timing precision of the 
operational control of the switching means. Also, it is possible to 
operate the switching means using the cams, and to perform high-precision 
control without using the power relays that are necessary with 
conventional high-precision control, so that rising costs can be checked. 
While the foregoing description and drawings represent the preferred 
embodiments of the present invention, it will be obvious to those skilled 
in the art that various changes and modifications may be made therein 
without departing from the true spirit and scope of the present invention.