Pushbutton hand dryer timer and method

A hand dryer timer having a switch in electrical communication with, and controlling the operation of a heater, a fan motor and a timer motor which are electrically connected to two nonneutral lines of a power source. A cam is mounted on a drive shaft of the timer motor such that the cam rotates with the drive shaft and also slides longitudinally over the drive shaft. The cam has a cam lobe adjacent an actuating arm of the switch. A biasing element is located between the timer motor and the cam and biases the cam to a first position aligning the cam lobe with the actuating arm of the switch. The switch includes two sets of switch contacts in a power circuit for the heater and fan motor, so that at the end of a drying cycle, the two sets of switch contacts are effective to electrically isolate the heater and fan motor from both non-neutral lines of the power source.

FIELD OF THE INVENTION
 This invention relates generally to the field of appliance controls and,
 more particularly, to an improved pushbutton hand dryer timer.
 BACKGROUND OF THE INVENTION
 Timing mechanisms have been utilized for decades in the control of many
 different appliances. The present invention relates generally to electric
 dryers, and more particularly to a pushbutton hand dryer of the type
 commonly found in public rest rooms. With such a hand dryer, a user pushes
 a button or knob to start a drying cycle. During the drying cycle, a
 timing motor, a heater and a fan are turned on; and at the end of a drying
 cycle, as determined by the timing motor, the timing motor, heater and fan
 are automatically turned off. Such dryers must be simple, rugged and
 durable in construction and operate with great reliability over a long
 service life. To achieve such features, the hand dryer should have the
 fewest possible parts that operate in the simplest possible way.
 As shown in FIG. 6, with known timer circuits, the heater H and fan motor
 FM are connected to the two non-neutral lines L1, L2 of a 220 volt ("V")
 source by a single switch S1. When the switch S1 is open, one side of each
 of the heater H and fan motor FM is disconnected from one of the
 non-neutral lines L1; however, the other side of each of the heater H and
 fan motor FM remain connected to the other of the non-neutral lines L2.
 Therefore, any inadvertent electrical contact of the one side of the
 heater and/or fan motor to a ground, for example, the metal dryer housing
 or base etc., will result in 120 being applied thereto. Thus, the heater H
 and/or fan motor FM will be operated at half power. Such an inadvertent
 electrical contact with ground can result from a frayed, nicked or broken
 wire or other conductor accidently contacting a neutral or ground
 potential.
 Therefore, there is a need to better isolate the heater and fan motor from
 the non-neutral wires of a power source.
 SUMMARY OF THE INVENTION
 The present invention provides an improved pushbutton hand dryer that
 reduces the probability of any inadvertent or uncommanded operation of the
 heater and fan motor. The improved pushbutton hand dryer reduces the
 chances that a frayed, nicked or broken wire or other electrical
 malfunction will result in the heater or fan motor operating at a reduced
 voltage. More specifically, the improved pushbutton hand dryer of the
 present invention provides an improved electrical isolation between the
 heater and fan motor and the non-neutral lines of a power source.
 Therefore, present invention has the advantage of providing a pushbutton
 hand dryer that operates more reliably with a longer service life.
 In accordance with the principles of the present invention and in
 accordance with the described embodiments, the present invention provides
 a hand dryer operable with first and second nonneutral power wires having
 a voltage potential therebetween. The hand dryer includes a heater, fan
 motor and timer motor all rated to operate at the voltage potential. A
 first switch is operated by the timer motor and has a first side
 electrically connected to the heater and fan motor and an opposite side
 electrically connected to the timer motor and the first nonneutral power
 wire. A second switch is operated by the timer motor and has a first side
 electrically connected to the heater and the fan and timer motors and an
 opposite side electrically connected to the second nonneutral power wire.
 In one aspect of the invention, the first switch includes first switch
 contacts that connect and disconnect the heater and fan motor respectively
 to and from the first nonneutral power wire, and the second switch
 includes switch contacts that connect and disconnect the heater and fan
 and timer motors respectively to and from the second nonneutral power
 wire. Thus, with two switches, the isolation of the heater and fan motor
 from the nonneutral wires is improved over hand dryers using only a single
 switch.
 In a further embodiment of the invention, the first switch has an actuating
 arm switching a state of first electrical contacts at a consistent
 repeatable first time in response to operation of the timer motor, and the
 second switch has an actuating arm switching a state of second electrical
 contacts at a consistent repeatable second time in response to operation
 of the timer motor.
 In one aspect of this further embodiment, the actuating arms are
 mechanically connected such that motion of the actuating arms causes the
 first switch to switch prior to the switching of the second switch.
 Therefore, the heater and fan motor will always be disconnected from the
 power source prior to disconnecting the timer motor, and both switches
 will always operate.
 In another embodiment, the invention provides a method of operating a hand
 dryer in which a timer motor has a cam lobe initially engaged with an
 actuating arm of the first and second switches, thereby causing switch
 contacts to electrically disconnect the heater, fan motor and timer motor
 from the power source. The cam lobe is then disengaged from the actuating
 arm, thereby causing the first and second switches to electrically connect
 the heater, the fan motor and the timer motor to first and second
 nonneutral wires of the power source. Thereafter the timer motor moves the
 cam lobe into engagement with the actuating arm to operate the first
 switch and electrically disconnect the heater and fan motor from the first
 nonneutral wire. After that, the timer motor continues to move the cam
 lobe and actuating arm, thereby operating the second switch to
 electrically disconnect the timer motor, heater and fan motor from the
 second nonneutral wire.
 These and other objects and advantages of the present invention will become
 more readily apparent during the following detailed description together
 with the drawings herein.

DETAILED DESCRIPTION OF THE INVENTION
 Referring to FIG. 1, a timer assembly 20 includes a bracket 21 (FIG. 2)
 that includes a mounting or support plate 22. The mounting bracket 21 is
 attached in a known manner within a pushbutton hand dryer 24. A timing
 motor 26 of a known construction is mounted to the inner side 28 of the
 support plate 22 by means of threaded fasteners 30. The fasteners 30 may
 be threaded into the plate 22 or pass through the plate 22 and secured by
 nuts (not shown). To maintain the timer motor 26 at a desired distance
 from the inner side 28 of the support plate 22, the threaded fasteners 30
 pass through tubular sleeves 32 of equal length. The motor 26 has an
 output or drive shaft 34 that preferably has a noncircular cross-sectional
 profile as shown in FIG. 2.
 A cam 36 includes a central longitudinal bore 38 having a noncircular
 cross-sectional profile similar to that of the output shaft 34, so that
 the cam 36 can be slidably mounted on the output shaft 34. Thus, any
 rotation of the output shaft 34 is transmitted directly to the cam 36;
 however, the cam 36 can slide longitudinally along the output shaft 34.
 The cam 36 has a main body portion 40 that is cylindrical in shape and
 extends through a clearance hole 42 (FIG. 2) in the mounting plate 22. The
 clearance hole 42 includes diametrically opposed slots 43 that permit cam
 lobes 48 to pass through the support plate 22. A flange 44 is mounted at
 an inner end 45 of the cam 36 and is larger than the clearance hole 42,
 thereby restraining the inner end 45 of the cam 36 from fully passing
 through the clearance hole 42. The flange 44 is pushed or biased against
 an inner surface 28 of the mounting plate 22 by biasing element, for
 example, a compression spring 46 thereby defining a first or outermost
 position of the cam 36. In that outermost position, diametrically opposed
 cam lobes 48 on the cam 36 are aligned to contact or engage an actuating
 arm 50 of a first microswitch 52. The microswitch 52 is mounted to the
 outer side 54 of the mounting plate 22.
 Referring to FIG. 3, the body portion 40 of the cam 36 includes peripheral
 tubular wall 56 that is connected by means of ribs 58 with a central
 tubular member 60 that includes the central longitudinal bore 38. The
 interconnecting ribs 58 extend from an outer end 62 (FIG. 1) of the cam 36
 longitudinally through the cam 36 to approximately the location of the cam
 lobes 48. An annular opening 64 is formed within the cam 36 between the
 cylindrical inner surface of the peripheral wall 56 and the cylindrical
 inner surface of the inner tubular member 60. The compression spring 46 is
 normally sized to be received within the annular opening 64 within the cam
 36. A top wall 65 located at the outer end 62 of the cam 36 covers the
 annular opening 64.
 The cam lobes 48 are generally L-shaped, and each lobe 48 has a lower leg
 or wall member 70 that is in a plane generally perpendicular to the
 longitudinal centerline 72 of the cam 36 and generally parallel to the
 plate 22. The wall members 70 strengthen the respective cam lobes 48.
 Further, each of the L-shaped cam lobes 48 has a side wall 74 extending
 substantially perpendicularly along a forward edge of the bottom wall 70
 toward the outer end 62 of the cam 36. Thus, the side wall 74 is generally
 perpendicular to the mounting plate 22. As viewed from the outer end 62 of
 the cam 36, the side wall 74 is curved and has a nonlinear cross-sectional
 profile in a plane perpendicular to the longitudinal centerline 72 of the
 cam 36 and generally parallel to the mounting plate 22. The side wall 74
 of each cam lobe 48 is formed by an inner side wall section 78 and an
 outer side wall section 76. The inner side wall 78 preferably forms an
 included angle of approximately 21.degree. with a line 77 bisecting the
 cam lobes 48 in a plane parallel to the plate 22. The outer side wall 76
 preferably forms an included angle of approximately 23.degree. with the
 line 77 bisecting the cam lobes 48 in a plane parallel to the plate 22.
 Further, a straight line passing through the distal end 80 of the outer
 side wall section 76 and the point at which the inner side wall section 78
 joins the body portion 40 of the cam 36 does not pass through the
 centerline 72 of the cam 36.
 Referring to FIGS. 2 and 4, the microswitch 52 is comprised of a first
 switch module 81 and a second switch module 83. The first switch module 81
 has an actuating arm 50 that extends over a switch actuating button 87.
 The switch module contacts 110 (FIG. 5) change state in response to the
 actuating arm 50 depressing the button 87. The actuating arm 50 has a
 second actuating arm or paddle 85 rigidly connected to outer directed side
 51 of the actuating arm 50 and is thus offset slightly from the arm 50.
 The second arm 85 extends over a switch actuating button 89 for the second
 switch module 83. Thus, motion of the actuating arm 50 and the paddle 85
 depresses the button 89 causing the contacts 112 of the second switch
 module 83 to change state. It should be noted that the second arm 85 is
 rigidly attached to an outer side 51 the arm 50, and hence, the arm 50
 contacts the button 87 prior to the arm portion 85 contacting the button
 89. Therefore, as the actuating arm 50 and arm portion 85 are moved, the
 button 87 is consistently pushed prior to the button 89; and the contacts
 110 consistently change state prior to the contacts 112 changing state.
 Referring to FIG. 4, the switch module 81 includes normally closed contacts
 110, and switch module 83 includes normally closed contacts 112. One side
 114 of the normally closed contacts 110 is connected to a first side or a
 first power connection of each of the fan motor 86 and heater 88. The
 opposite side 116 of the contacts 110 is connected to one side or a first
 power connection of the timer motor 26 and the non-neutral line L2. The
 other non-neutral line L1 is connected to one side 118 of the contacts
 112, and the other side 120 of the contacts 112 is connected to the other
 side or second power connection of each of the timer motor 26, the fan
 motor 86, and the heater 88.
 In use, in its quiescent or nonoperating state, referring to FIG. 2, the
 distal end 80 of an outer wall section 76 of one of the cam lobes 48 is in
 contact with a distal end 82 of the actuator arm 50 of the microswitch 52.
 Further, the distal end 80 of the cam lobe 48 is applying sufficient
 pressure on the actuator arm 50 so as to actuate the switch modules 81, 83
 and hold the normally closed contacts 110, 112 of FIG. 4 in their open
 state. With the contacts 110, 112 open, power cannot be applied to the
 timer motor 26, fan motor 86 and heater 88; and the timer motor 26, fan
 motor 86 and heater 88 remain off. To operate the hand dryer 24, a user
 depresses or pushes the knob or pushbutton 90 (FIG. 1) of the hand dryer
 24. The inner end 92 of the knob 90 contacts the outer end 62 of the cam
 36 and moves the cam 36 to the left, as viewed in FIG. 1, over the shaft
 34 of the timer motor 26 to a second position illustrated in phantom. As
 the cam 36 is moved along the output shaft 34 toward its second position,
 the cam lobe 48 disengages and loses contact with the actuator arm 50 of
 the switch 52. After losing contact with the cam lobe 48, the actuating
 arm 50 and its paddle 85 are then free to pivot to a second position
 illustrated in phantom in FIG. 2. Upon the user releasing the pushbutton
 90, the cam 36 is returned by the biasing spring 34 to its original, first
 position as illustrated in FIG. 1. Normally, the pushbutton 90 is mounted
 in the hand dryer 24 with its own return spring. Referring to FIG. 2, the
 unique shape of the side wall 74 of the cam lobe 48 reduces the potential
 for, and preferably eliminates interference between the cam lobe 48 and
 the actuator arm 50 as the cam 36 returns to its original position.
 After the cam 36 loses contact with and releases the actuator arm 50, the
 actuator arm 50 and its paddle 85 pivot to the position shown in phantom
 in FIG. 2, thereby changing the state of the switch modules 81, 83, and
 referring to FIG. 4, closing the normally closed contacts 110, 112.
 Closing the contacts 110, 112 initiates a drying cycle by applying power
 to the timer motor 26, the fan motor 86 and the heater 88, thereby turning
 those devices on. Turning the timer motor 26 on causes the output shaft 34
 and cam 36 to rotate in a clockwise direction as illustrated in FIG. 2.
 The timer motor 26, fan motor 86 and heater 88 continue to operate until
 rotation of the timer motor 26 causes the distal end 80 of a cam lobe 48
 to again contact and depress, or move, the actuating arm 50 of the
 microswitch 52.
 With the present invention, the actuating button 87 of the switch module 81
 is mechanically connected to the contacts 110, and the actuating button 89
 is mechanically connected to the contacts 112. The relative positions of
 the arms 50, 85 cause the actuating arm 50 to predictably and repeatably
 initially depress button 87 and first pickup, that is, open, the
 normally-closed contacts 110. Opening the contacts 110 electrically
 disconnects one side of the fan motor 86 and heater 88 from one of the
 non-neutral leads L2 of the power source. However, the timer motor 26
 continues to run until the actuating arm portion 85 depresses the button
 89 causing the normally-closed contacts 112 to consistently and
 predictably open after the opening of the contacts 110. Opening the
 contacts 112 electrically disconnects the timing motor 26, fan motor 86
 and heater from the other non-neutral lead L1 of the power source. Thus,
 the switch 52 is effective to electrically disconnect the fan motor 86 and
 heater 88 from both non-neutral leads L1 and L2 of the power source.
 The output shaft 34 of the timer motor 26 rotates at an angular velocity
 such that a drying cycle of a desired duration is achieved during one-half
 of a full rotation of the output shaft 34. Thus, the cam 36 contains two
 diametrically opposed cam lobes 48 and provides two full drying cycles for
 each rotation of the output shaft 34 and the cam 36. As will be
 appreciated, the number of cam lobes 48 on the cam 36 may be changed to
 conform to different angular velocities of the output shaft 34 and
 different desired time periods for the drying cycle.
 The hand dryer timer described with respect to FIGS. 1-4 provides a
 substantial improvement over prior timer assembly designs. First, the
 timing motor circuit completely isolates the fan motor and heater from the
 non-neutral leads of the power source. Hence, in the event that the
 circuit through some failure becomes inadvertently connected to a neutral
 or grounded component, for example, the frame 21 or the metal housing 24,
 no voltage will be applied to the fan motor 86 or heater 88. Thus, the
 probability that the fan motor 86 or heater 88 will inadvertently be
 turned on is remote.
 While the invention has been set forth by a description of the one
 embodiment in considerable detail, it is not intended to restrict or in
 any way limit the claims to such detail. Additional advantages and
 modifications will readily appear to those who are skilled in the art. For
 example, in the described embodiment, the main body 40 of the cam 36 is
 cylindrical and the cam lobes 48 extend radially therefrom; however, as
 will be appreciated, the cam 36 can have other shapes such as a
 multilateral shapes or even noncircular shapes in which the cam lobes 48
 are mostly or fully integrated within the main body 40 of the cam 36. As
 will be appreciated, the successful operation of the present invention is
 independent of the lower wall 70 on the cam lobes 48, and therefore, the
 low wall 70 may be eliminated. The cam 36 is preferably injection molded
 from a glass reinforced 66 nylon material commercially available as
 "ZYTEL" 70G 33L nylon material from Du Pont Corporation. However, the cam
 36 may be made from other materials consistent with the desired
 performance specifications. Further, while the cam 36 is preferably molded
 of a plastic material as shown herein, the cam 36 may have many other
 configurations, for example, a solid part, and may be made of other
 materials such as metal, ceramic, a fiber composition, etc.
 As described herein, the noncircular cross-sectional profiles of the shaft
 34 and bore 38 are multilateral, for example, square, triangular,
 hexagonal, etc. Alternatively, the noncircular cross-sectional profiles of
 the output shaft 34 and bore 38 may be elliptical, star-shaped, splined,
 etc. Further, as shown, the cross-sectional profile of the output shaft 34
 and bore 38 are noncircular. Those cross-sectional profiles may be
 circular but interconnected such that the cam 36 rotates with the shaft 34
 and is able to slide longitudinally with respect to the shaft 34. Such
 mechanical interconnections are well known and include, for example, a
 slot and key or simply a diametric pin extending through the cam and a
 longitudinal slot in the output shaft 34.
 In the described embodiment, the cam 36 is slidably mounted directly on the
 drive shaft 34 of the timer motor 26. However, as will be appreciated, the
 drive shaft 34 can be a spline or similar shaft, and the cam 36 slidably
 and rotationally mounted independent of the drive shaft 34. The flange 44
 of the cam 36 can also be formed with peripheral gear teeth that mesh with
 the spline or an intervening gear. Thus, the cam 36 can be mounted
 independent of the drive shaft 34 but be driven rotationally by the drive
 shaft spline and also slide longitudinally to operate identically to the
 cam assembly described herein.
 In the described embodiment, the compression spring 46 extends into an
 annular opening 64 within the cam 36. Alternatively, the compression
 spring 46 may be sized such that it does not fit within the annular
 opening 64. In that embodiment, the inner end of the cam 36 may be molded
 with a protruding boss on which the spring 46 may be located.
 Further, the timer assembly herein is part of a pushbutton hand dryer
 timer; however, as will be appreciated, hand dryers as used herein often
 have an adjustable output duct allowing the drying air to be directed to
 areas other than the hands, for example, the face and hair. The dryer
 timer assembly of the present invention is applicable to any "hand dryer"
 type of dryer which is manually turned on and automatically turns off,
 thereby operating in an identical or similar fashion to the hand dryer
 described herein.
 As earlier described, the contacts 110 should consistently and predictably
 open before the contacts 112. While the use of an offset actuating arm
 paddle 85 is one way of providing that capability, any other switch or
 mechanism for operating the switch that achieves the same result is
 consistent with the claimed invention. Further, if it is possible to
 provide a switch 52 in which the contacts 110 and 112 consistently and
 predictably open simultaneously, such a switch may be used in place of the
 switch described herein to practice the claimed invention. In addition, as
 will be appreciated, while the motors are connected to the 220 volts
 source, the motors may be rated at 120 volts and operated with a dropping
 resistor or other voltage dropping device.
 Therefore, the invention in its broadest aspects is not limited to the
 specific detail shown and described. Consequently, departures may be made
 from the details described herein without departing from the spirit and
 scope of the claims which follow.