Patent Publication Number: US-8115121-B2

Title: Timer switch

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a timer, and more particularly to a mechanical timer applicable to timer-operated household electrical appliances. 
     2. Related Art 
     Currently, commercially-available washing machines are mainly classified into two types, namely, microcomputer type and mechanical type. Taking a mechanical washing machine as an example, the time course is set by turning a knob, so as to start washing, rinsing, drying, and other functions at a particular time. For example, U.S. Pat. Nos. 6,441,326, 6,613,991, 6,797,897, 6,838,626 and 7,005,589 disclose a timer with a front housing and a rear housing. Contained within the front housing and rear housing are a timing motor and gear train assembly to drive a main cam. The main cam has geometry to be contacted by cam followers of switch arms. As the main cam rotates, the varying contours of program cam surfaces move the switch arms between neutral and offset positions. The movement of the switch arms relative to one another results in the activation and deactivation of electrical circuits which operate the cycles of the appliance to which the timer is associated. The timer includes a setting feedback (SF) system. By this SF system, cam followers are lifted off the program cam surfaces so that a “V”-shaped follower remains in contact with a custom feel profile on the side of the main cam proximal the front housing. This “V”-shaped follower acts as a tactile and/or audible feedback member, by engaging the textured surface of the custom feel profile to impart such tactile feel to the user during rotation of the main cam. 
     The timer has a shaft extending outside the housing for user to operate. Typically, the shaft has two operation positions along its axis, namely a setting position where the main cam surface and the cam follower of switch arms are lifted off; and a driving position where the main cam surface and the cam follower of switch arms contact. At the setting position, the main cam can be rotated by the user to an appropriate angular position to begin a timing cycle. At the driving position, the timing motor starts to drive the main cam. Usually, the timer shaft is pressed down to the setting position, and pulled up to the driving position. 
     There are some drawbacks in the aforesaid prior art timers. Firstly, since the switch arms are raised by an actuator beam mounted on the shaft, and the switch arms are all on one side of the cam, the force on the actuator is unbalanced that easily bends the beam. Secondly, the timer gear train requires a clutch mechanism which allows manual rotation of the main cam only in a forward direction in order to prevent any rotation of the cam in a reverse direction that will damage the timer components during manual operation of the main cam. Thirdly, the setting feedback (SF) system in the timer requires an additional “V”-shaped follower remaining in contact with a custom feel profile on the side of the main cam proximal the front housing; also, the steady contact between the “V”-shaped follower and the custom feel profile of the cam is not good in the cam driving state that it only causes friction, wearing of the components and resistance to the cam motion. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is a timer to solve the problems in the prior arts. 
     A timer provided in an embodiment of the present invention comprises a case, a cam wheel, a drive mechanism, a plurality of switch blades, and an off-contact lever disposed within the case. The case comprises a shaft. The shaft is rotatably and axially movably disposed in the case, and movable between a setting position and a driving position. The cam wheel is pivoted on the shaft. The cam wheel rotates together with the shaft when the shaft is located at the setting position. The off-contact lever is pivoted in the case and is connected to the shaft. When the shaft is located at the setting position, the off-contact lever presses the cam actuating portions of the switch blades, so as to separate the cam actuating portions from the cam tracks of the cam wheel; meanwhile, the shaft latches the cam wheel so that the user can freely rotate the cam wheel to any desired position. Because the off-contact lever has two journals pivoted on two holes formed on the case, and the journals are correspondent to the range of the cam actuating portions of the switch blades, the shaft can operate the off-contact lever in a balanced way without the problem of unbalanced bending in prior arts. 
     The cam wheel comprises a plurality of cam tracks on one side surface thereof, and a plurality of first ratchets and second ratchets annularly disposed on a circular rim thereof. The cam wheel separates from the shaft and rotates independently when the shaft is located at the driving position. The drive mechanism operates the first and second ratchets of the cam wheel and drives the cam wheel to rotate relatively to the shaft. Each switch blade comprises a plurality of cam actuating portions, and contacts one of the cam tracks. The cam actuating portions are actuated by a rotation motion of the cam wheel, so as to enable the corresponding switch blades to generate electrical connections/disconnections. Because the first ratchets and second ratchets leave apart from the cam at the setting position, the cam wheel can be bi-directionally rotated with the shaft by the user during the setting state; and there is no need of a clutch mechanism in the gear train. The circular rim of the cam wheel further includes a locating track to be contacted with a flexible end and generates a tactile and/or audible feedback to the user when setting. The flexible end is formed on an anti-reverse paw of the drive mechanism and will reduce its contact force to the locating track of the cam wheel during the cam driving state so as to reduce friction and wearing of the components. Moreover, the flexible end made along with the paw is simple in construction that does not require any additional tension or fixing component for assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given herein below for illustration only, and thus is not limitative of the present invention, and wherein: 
         FIG. 1  is a schematic exploded view of an embodiment of the present invention; 
         FIG. 2  is a schematic partially exploded view of an embodiment of the present invention showing mainly the switch blades and a part of drive mechanism; 
         FIG. 3  is a top perspective view of an embodiment of the present invention; 
         FIG. 4  is a further perspective view of  FIG. 3  when removing the upper case; 
         FIG. 5  is a bottom perspective view of an embodiment of the present invention; 
         FIG. 6  is a further perspective view of  FIG. 5  when removing the lower case; 
         FIG. 7  is a cross-sectional side view of a timer according to the present invention where a shaft is located at a setting position; 
         FIG. 8  is a partially-enlarged top view of a timer according to the present invention where the shaft is located at a setting position; 
         FIG. 9  is a partially-enlarged perspective view of the timer of  FIG. 8  where the cam wheel is not shown; 
         FIG. 10  is a cross-sectional side view of the timer according to the present invention where the shaft is located at a driving position; 
         FIG. 11  is a partially-enlarged top view of a timer according to the present invention where the shaft is located at a driving position; 
         FIG. 12  is a partially-enlarged perspective view of the timer of  FIG. 11  where the cam wheel is not shown; 
         FIG. 13  is a cross-sectional side view of a timer according to the present invention showing mainly a tactile and/or audible feedback mechanism; and 
         FIG. 14  is a partially-enlarged top view of the timer of  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The timer of the present invention is applicable to timer-operated household electrical appliances such as dish washers, washing machines or the like. The accompanying drawings are merely provided for reference and illustration, but not intended to limit the present invention. 
     Referring to  FIGS. 1 to 6 , a timer  100  according to the present invention comprises a case  110 , a shaft  120 , a cam wheel  130 , a drive mechanism  140 , a plurality of switch blades  150  and an off-contact lever  160 . 
     The case  110  is formed by an upper case  111  and a lower case  112 . Symmetric via holes  113  are opened on the upper case  111  and the lower case  112  respectively. The shaft  120  passes through the two via holes  113  of the upper case  111  and the lower case  112 , and is thus disposed in the case  110 . In addition, the shaft  120  is rotatable and axially movable relative to the case  110 , such that the shaft  120  not only rotates about an axle center of itself, but also is reciprocally movable between a setting position and a driving position. A pair of wire springs  210  are further disposed on the lower case  112  of the case  110  at a position close to the via hole  113 . The wire springs  210  are used for clamping the shaft  120  to maintain the shaft  120  at the setting position or the driving position, such that the shaft  120  cannot be easily detached from the preset position due to unintentional external forces. 
     Referring to  FIGS. 1 and 6 , an axle hole  133  is opened at a central position of the cam wheel  130 , and is sleeved on the shaft  120 , such that the cam wheel  130  is pivoted on the shaft  120 . In addition, the cam wheel  130  comprises a plurality of cam tracks  1311  on a side surface  131  thereof (i.e., a lower surface of the cam wheel  130 ). A plurality of unevenly-spaced first ratchets  1321  protrudes from an upper portion of a circular rim  132  of the cam wheel  130 , and a plurality of unevenly-spaced second ratchets  1322  protrudes from a lower portion of the circular rim  132  of the cam wheel  130 . 
     In addition, the timer  100  of the present invention further comprises a sleeve  170  and a collar  180 . The sleeve  170  is sleeved on the shaft  120 , and the sleeve  170  comprises at least one first engaging tooth  171  on an outer edge thereof. The collar  180  is movably sleeved on the sleeve  170 , and the collar  180  comprises at least one second engaging tooth  181  at an inner edge thereof, in which the second engaging tooth  181  matches with the first engaging tooth  171 . The sleeve  170  and the collar  180  are latched together due to the engagement between the first engaging tooth  171  and the second engaging tooth  181  when the shaft  120  is at the setting position. The collar  180  is also engaged with the cam wheel  130  so that the sleeve  170  engaged with a knob (not shown) turned by the user during setting will rotate the cam wheel  130 . On the contrary, the sleeve  170  and the collar  180  are free from engagement, and the knob is free from the cam wheel  130 , when the shaft  120  is at the driving position. 
     Referring to  FIGS. 1 and 2 , the drive mechanism  140  in the present invention comprises a motor  141 , a driving cam  142 , a push paw  143 , an anti-reverse paw  144 , and an axle  145 . The motor  141  comprises a gear train  1411 . The driving cam  142  is mounted on the axle  145 . The driving cam  142  comprises a cam block  1421  protruding from one side surface thereof, and a tooth  1422  annularly disposed on an outer edge thereof. The tooth  1422  is engaged with the gear train  1411  of the motor  141 , such that the driving cam  142  is driven by the motor  141  to rotate relative to the axle  145 . The push paw  143  comprises a connection end  1431  and a push end  1432  opposite to each other. The connection end  1431  is further opened with a slot  1433 . The connection end  1431  of the push paw  143  is coupled with the cam block  1421  of the driving cam  142 , and the slot  1433  is sleeved on the axle  145 , and the push end  1432  of the push paw  143  contacts the first ratchets  1321  of the cam wheel  130 . The push paw  143  is driven by the driving cam  142  to sway in a nonlinear displacement manner and pushes against the first ratchets  1321  by the push end  1432  thereof, such that the cam wheel  130  rotates relative to the shaft  120 . The anti-reverse paw  144  is disposed in the case  110  in a pivoting manner, and the anti-reverse paw  144  comprises a rigid end  1441  and a pressed end  1442 . The rigid end  1441  of the anti-reverse paw  144  selectively contacts the second ratchets  1322  of the cam wheel  130 . 
     In addition, the present invention further comprises a plate spring  200  disposed in the case  110  and configured adjacent to the push paw  143  and the anti-reverse paw  144 . The plate spring  200  is used for normally pushing the push paw  143  and the anti-reverse paw  144  to contact the first ratchets  1321  and the second ratchets  1322  of the cam wheel  130  respectively. 
     As shown in  FIGS. 2 and 6 , the plurality of switch blades  150  of the present invention comprises a plurality of cam actuating portions  151  respectively, and may selectively press against the cam tracks  1311  of the cam wheel  130 . The cam actuating portions  151  are actuated by a rotation motion of the cam wheel  130 , so as to enable the corresponding switch blades  150  to generate an electrical connection/disconnection, thus enabling the household electrical appliance (not shown) to perform a corresponding function. It should be noted that, three switch blades  150  are disclosed in this embodiment, and the three switch blades  150  are arranged in the case  110  at different heights. However, it is apparent to those skilled in the art that, the number of switch blades may also be increased or decreased according to actual operational requirements or design requirements, but is not limited to the number of the switch blades  150  disclosed in this embodiment. 
     As shown in  FIG. 1 , the off-contact lever  160  of the present invention is pivoted in the case  110 , and may sway relative to the case  110  ( 111 ,  112 ), so as to selectively press against the cam actuating portions  151  ( FIG. 2 ) of the switch blades  150 . The off-contact lever  160  comprises a through hole  161  for mounting the shaft  120  therein, such that the off-contact lever  160  is connected to the shaft  120 . The timer  100  of the present invention further comprises a paw lever  190  pivoted in the case  110 . The paw lever  190  comprises a linking end  191  and a pressing end  192 . The linking end  191  normally abuts against the off-contact lever  160 , and the pressing end  192  is actuated by the off-contact lever  160  to selectively press against the pressed end  1442  of the anti-reverse paw  144 . 
     Then, the operation of the timer  100  of the present invention is described in detail. 
     Referring to  FIGS. 7 to 9 , when the shaft  120  is pressed down to the setting position, the sleeve  170  and the collar  180  ( FIG. 1 ) are combined with each other through the engagement motion between the first engaging tooth  171  and the second engaging tooth  181 , such that the cam wheel  130  may rotate together with the shaft  120 . At this time, the shaft  120  pushes against the off-contact lever  160  to press downwards the cam actuating portions  151  of the switch blade  150  closest to the off-contact lever  160  (i.e., the cam actuating portions  151  of the lowest switch blade  150 ), such that contacts (not shown) of the switch blades  150  are not electrically connected, and thus, the user can set a state of the timer  100  by rotating the shaft  120  clockwise or anticlockwise. Meanwhile, the off-contact lever  160  is pressed to pivot and drives the linking end  191  of the paw lever  190 , such that the paw lever  190  pivots along with the off-contact lever  160 . At this time, the pressing end  192  of the paw lever  190  presses against the pressed end  1442  of the anti-reverse paw  144 , such that the rigid end  1441  of the anti-reverse paw  144  separates from the second ratchets  1322  on the circular rim  132  of the cam wheel  130 . Therefore, when the shaft  120  is located at the setting position, the user can freely rotate the cam wheel  130  clockwise or anticlockwise without being restricted by the rigid end  1441  of the anti-reverse paw  144 . 
     Referring to  FIGS. 10 to 12 , when the shaft  120  is pulled upwards to the driving position, the first engaging tooth  171  of the sleeve  170  separates from the second engaging tooth  181  of the collar  180  ( FIG. 1 ), such that the cam wheel  130  rotates independently without being driven by the shaft  120 , and at this time, the user cannot rotate the cam wheel  130  correspondingly by turning the shaft  120 . After the pressure exerted by the shaft  120  on the off-contact lever  160  is removed, the electrical connection/disconnection of the contacts (not shown) of the three switch blades  150  is not affected by the off-contact lever  160 , and the cam actuating portions  151  of the switch blades  150  normally contact the cam tracks  1311  of the cam wheel  130 . As the off-contact lever  160  is not pressed, the linking end  191  of the paw lever  190  connected to the off-contact lever  160  is not pressed and is not pivoted. At this time, the pressing end  192  of the paw lever  190  does not press the pressed end  1442  of the anti-reverse paw  144 , and the plate spring  200  concurrently pushes the push paw  143  and the anti-reverse paw  144 , so as to force the push end  1432  of the push paw  143  to contact the first ratchets  1321  on the circular rim  132  of the cam wheel  130 , and force the rigid end  1441  of the anti-reverse paw  144  to contact the second ratchets  1322  on the circular rim  132  of the cam wheel  130 . Therefore, when the shaft  120  is located at the driving position, the user cannot freely rotate the cam wheel  130  clockwise or anticlockwise, the cam wheel  130  is only pushed by the push paw  143  of the drive mechanism  140  to rotate towards a single direction, and the cam wheel  130  cannot rotate towards an opposite direction due to the restriction of the rigid end  1441  of the anti-reverse paw  144 . 
     When the cam wheel  130  is actuated by the push end  1432  of the push paw  143  to rotate intermittently, the cam actuating portions  151  of the switch blades  150  that are designed as blade springs are deformed to different extents when contacting the cam tracks  1311  having different heights, so as to enable the switch blades  150  to generate an electrical connection/disconnection, thereby controlling the household electrical appliance (not shown) to perform a corresponding operation mode. 
     Referring again to  FIGS. 9 and 8 , when the shaft  120  is pressed down to the setting position, the sleeve  170  and the collar  180  ( FIG. 1 ) are combined with each other through the engagement motion between the first engaging tooth  171  and the second engaging tooth  181 , such that the cam wheel  130  may rotate together with the shaft  120 . At this time, the shaft  120  pushes against the off-contact lever  160 , and the off-contact lever  160  is pressed to pivot and drives the linking end  191  of the paw lever  190 , such that the paw lever  190  pivots along with the off-contact lever  160 . At this time, the pressing end  192  of the paw lever  190  presses against the pressed end  1442  of the anti-reverse paw  144 , such that the rigid end  1441  of the anti-reverse paw  144  separates from the second ratchets  1322  on the circular rim  132  of the cam wheel  130 , but the flexible end  1443  of the anti-reverse paw  144  contacts the locating grooves  1324  of the locating track  1323  of the cam wheel  130 . Therefore, when the shaft  120  is located at the setting position and the user freely rotates the cam wheel  130  clockwise or anticlockwise, a tactile feedback is generated between the flexible end  1443  of the anti-reverse paw  144  and the locating grooves  1324  of the cam wheel  130 . As the circular rim  132  of the cam wheel  130  has a large outer diameter, the tactile and audible feedback generated between the flexible end  1443  of the anti-reverse paw  144  and the locating grooves  1324  of the cam wheel  130  is quite obvious. As such, the user can clearly perceive the tactile feeling when rotating the cam wheel  130 , and thus can set the timer  100  of the present invention to a correct mode more accurately. On the contrary, as shown in  FIGS. 11 and 12 , when the shaft  120  is pulled upwards to the driving position, the off-contact lever  160  is not pressed, the linking end  191  of the paw lever  190  connected to the off-contact lever  160  is not pressed and is not pivoted. At this time, the pressing end  192  of the paw lever  190  does not press the pressed end  1442  of the anti-reverse paw  144 , and the plate spring  200  concurrently pushes the push paw  143  and the anti-reverse paw  144 , so as to force the push end  1432  of the push paw  143  to contact the first ratchets  1321  on the circular rim  132  of the cam wheel  130 , and force the rigid end  1441  of the anti-reverse paw  144  to contact the second ratchets  1322  on the circular rim  132  of the cam wheel  130 . Meanwhile, the flexible end  1443  of the anti-reverse paw  144  is free from contacting the locating track  1323  of the cam wheel  130  so as to reduce friction and wearing of the components. 
       FIGS. 13 and 14  illustrate a modification of the flexible end  1443  of the anti-reverse paw  144 . The upper case  111  of the embodiment comprises a slot  114  and a rib  115 . In addition to the rigid end  1441  and the pressed end  1442 , the anti-reverse paw  144  further comprises a flexible end  1443  and a lean end  1444  extending on the other side thereof relative to the pressed end  1442 . Wherein, the top surface of the flexible end  1443  has an embed block  1445 . The embed block  1445  inserts into the slot  114  of the upper case  111  for guiding the movement of the flexible end  1443 , and the lean end  1444  leans on the rib  115  to provide a suitable force to the flexible end  1443 , such that the flexible end  1443  normally contacts the locating grooves  1324  of the locating track  1323  of the cam wheel  130 . When the shaft  120  is pressed down to the setting position, the flexible end  1443  of the anti-reverse paw  144  swings toward the cam wheel  130  to provide a heavier contact to the locating track  1323  of the cam wheel  130  and to provide a clear tactile feedback. On the contrary, when the shaft  120  is pulled upwards to the driving position, the flexible end  1443  of the anti-reverse paw  144  swings away from the cam wheel  130  to reduce the contact force to locating track  1323  of the cam wheel  130  and to reduce the influence and friction to the timer driving. 
     As the first ratchet  1321 , second ratchet  1322  and the locating track  1323  are designed on the large circular rim of the cam wheel  130 , and work with the push paw  143  and the rigid end  1441  and flexible end  1442  of the anti-reverse paw  144  of the drive mechanism, it greatly improves the driving reliability and tactile feedback function of the timer. Moreover, the flexible end  1442  formed with the anti-reverse paw  144  is easy to be assembled without the need of any additional spring element for the tactile feedback function, and the cam wheel is easily manufactured, thus reducing the manufacturing difficulty and manufacturing cost.