Abstract:
A vibrating push button station to be associated with a standard traffic signal of the kind used to control vehicular traffic at an intersection so that visually impaired pedestrians will be alerted when the pedestrian WALK signal is illuminated after first pressing a push button. The push button station includes an electromagnetic assembly that is adapted to generate a changing magnetic field following the depression of the push button. A magnet coupled to the push button by way of a flexible diaphragm is either pulled towards and repelled or simply released by the electromagnetic assembly as the magnetic field changes. The opposite movements of the magnet relative to the electromagnetic assembly is transmitted to the push button as a vibration so that the hand of a user will receive a tactile indication at the push button when vehicular traffic has been halted.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to a vibrating push button station to be associated with a traffic signal of the kind that is found at an intersection to control vehicular traffic so that pedestrians may cross the intersection once the traffic has been halted. The vibrating push button station of this invention has particular application for generating a tactile feedback signal by which to inform visually impaired pedestrians when the intersection may be crossed.  
         [0003]     2. Background Art  
         [0004]     It is common to combine a visual display with a traffic signal that is located at an intersection to control vehicular traffic and thereby enable pedestrians to cross the intersection. That is to say, the usual visual display conveys both a written message (i.e., WALK or DON&#39;T WALK) as well as a color sensitive message (i.e., red or white) to instruct pedestrians when to cross the intersection. However, such visual warnings are of little value to those pedestrians who are visually impaired. Consequently, a visually impaired pedestrian who activates the push button of a traffic signal will have no way to accurately know when the intersection has been cleared of traffic so that it is time to cross.  
         [0005]     To overcome this pervasive problem, a push button station was invented that is capable of generating a tactile feedback signal (i.e., a vibration) to alert visually impaired pedestrians to cross a traffic signal controlled intersection at the same time that the WALK message is being displayed. This push button station is disclosed in detail in U.S. Pat. No. 6,340,936 issued Jan. 22, 2002 and assigned to the assignee of this application.  
         [0006]     In general terms, U.S. Pat. No. 6,340,936 describes a novel push button station having an electromagnetic assembly that generates a signal by which to vibrate a push button after the push button has first been depressed by a visually impaired pedestrian. A piezoelectric member is responsive to the pressure that is applied by the pedestrian to depress the push button. The piezoelectric member generates an output voltage to be received by an external control circuit which ultimately causes the traffic signal to change and the push button to vibrate. The patented push button station includes a solenoid to transfer the pushing force applied by the pedestrian from the push button to the piezoelectric element. More particularly, a magnetic flux that is generated after the push button is depressed causes an armature of the solenoid to move back and forth and repeatedly strike the button.  
         [0007]     It is now desirable to eliminate the solenoid which is a part of the patented push button station that has been described above so that the push button station can have a more simplified, efficient and reliable electromagnetic vibrating assembly.  
       SUMMARY OF THE INVENTION  
       [0008]     Disclosed herein is a vibrating push button station to be associated with a standard traffic signal (i.e., a stop light) of the kind that is used to control vehicular traffic at an intersection so that visually impaired pedestrians will be alerted when to cross the intersection a certain time after first pressing a push button. The push button station includes an efficient and reliable electromagnetic assembly that is adapted to cause the push button to vibrate so that a visually impaired pedestrian who holds his hand on the push button will receive a tactile feedback signal at the same time that the pedestrian WALK signal is illuminated.  
         [0009]     The vibrating push button station includes a hollow mounting base having a flexible diaphragm extending across the open top thereof. A pedestrian activated push button is affixed to one side of the flexible diaphragm to receive a pushing force thereagainst, and a magnet holder is affixed to the opposite side of the diaphragm. A magnet is located inside the magnet holder to be displaced with the flexible diaphragm in response to a pushing force applied to the push button. A stationary coil housing is suspended within the mounting base so as to lie below the magnet holder. A coil is disposed within the coil housing in axial alignment with the magnet in the magnet holder. A piezoelectric disk is mounted at the top of the coil housing so as to lie in spaced, axial alignment with the magnet holder. A printed circuit board is bonded to the bottom of the coil housing and connected to the piezoelectric disk by means of flex circuitry. The printed circuit board is interconnected with an external control circuit by means of electrical wires that extend through an exit port formed at the bottom of the mounting base.  
         [0010]     In operation, a pedestrian wishing to cross a traffic signal controlled intersection depresses the push button of the vibrating push button station. The pushing force is transferred from the push button to the flexible diaphragm to cause the diaphragm to bend and the magnet holder connected to the diaphragm to move towards and exert a force on the piezoelectric disk that is mounted on the coil housing. Accordingly, the piezoelectric disk will now flex so as to generate an output voltage which is detected by a comparator on the printed circuit board. The comparator provides a switching signal to the external control unit in response to the output voltage generated by the piezoelectric disk, whereby to cause the traffic signal to halt vehicular traffic moving through the intersection. When it is ultimately time for a pedestrian to cross and the pedestrian WALK signal is illuminated, a pulsating current is supplied to the coil within the stationary coil housing to create a magnetic field. As the magnetic field changes, the magnet within the magnet holder will be either repeatedly pulled towards and repelled or simply released by the coil, whereby the magnet holder will be subjected to a reciprocal movement which, in turn, will cause the push button that is connected to the magnet holder by the flexible diaphragm to pulse or vibrate. Accordingly, a visually impaired pedestrian will receive a tactile feedback signal at the push button of the vibrating push button station to indicate when the controlled intersection may be entered. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is an exploded view of the vibrating pedestrian push button station which forms the preferred embodiment of the present invention;  
         [0012]      FIG. 2  is a cross-section of the vibrating push button station of  FIG. 1  in the assembled configuration;  
         [0013]      FIG. 3  is a top view of a mounting base from the vibrating pedestrian push button station of  FIG. 2 ; and  
         [0014]      FIG. 4  is another exploded view of the vibrating push button station in perspective. 
     
    
     DETAILED DESCRIPTION  
       [0015]     The vibrating push button station  1  of this invention that is capable of providing a tactile feedback signal to help visually impaired pedestrians cross an intersection that is controlled by a traffic signal (i.e., a stop light) is described while referring concurrently to  FIGS. 1-4  of the drawings. The push button station  1  includes a hollow mounting base  3  within which to receive an electromagnetic assembly that is responsive to a mechanical pressure initiated by a visually impaired pedestrian wishing to enter an intersection after vehicular traffic has been stopped by the traffic signal. A push button frame  5  is seated upon the open top of base  3  so as to support an external cover (e.g., ring  7 ) which surrounds the push button  12 . In the alternative, the base  3  can be eliminated by connecting the frame  5  and ring  7  directly to a panel (not shown) or other existing structure. As is best shown in the assembled configuration of  FIG. 2 , the push button frame  5  includes a body  15  that projects downwardly into the base  3  so as to receive the electromagnetic assembly therewithin in a manner that will be described in detail hereinafter.  
         [0016]     A set of through holes  8  and  10  (best shown in  FIG. 4 ) is formed through each of the cover ring  7  and the push button frame  5 . In the assembled configuration of  FIG. 2 , the through holes  8  and  10  of ring  7  and push button frame  5  are axially aligned so as to receive suitable fasteners (designated  11  in  FIG. 4 ) by which to affix the ring  7  at the top of the base  3  so as to lie above and surround the body  15  of push button frame  5 .  
         [0017]     The external cover ring  7  also surrounds a raised pedestrian activated push button  12 . The push button  12  may have a raised arrow or another symbol (not shown) formed thereon to help the visually impaired pedestrian determine the direction of travel when entering the intersection. A disk-like diaphragm  14  is held between the cover ring  7  and the push button frame  5 . Diaphragm  14  is preferably manufactured from a thin (e.g., 0.008 inches) piece of metal (e.g. stainless steel) so as to have a flexible spring-like characteristic. A set of (e.g., four) tabs  16  (best shown in  FIG. 4 ) project outwardly from the periphery of diaphragm  14  for receipt within relief slots (designated  9  in  FIG. 1 ) that are formed in the cover ring  7 , whereby the flexible diaphragm  14  is suspended between cover ring  7  and push button frame  5 . A resilient O-ring or soft rubber sponge material (not shown) can be installed inside the cover ring  7  to allow for greater diaphragm movement.  
         [0018]     In the assembled configuration of  FIG. 2 , the push button  12  is seated upon the outwardly facing side of diaphragm  14 . A magnet holder  18  is positioned against the inwardly facing side of diaphragm  14  so as to lie below push button  12 . Sets of axially aligned holes  20 ,  21  and  22  are respectively formed through each of the push button  12 , the diaphragm  14 , and the magnet holder  18  to receive suitable fasteners (designated  23  in  FIG. 4 ) in order to preserve the face-to-face alignment of the push button  12  and the magnet holder  18  at opposite outwardly and inwardly facing sides of the flexible diaphragm  14 . By virtue of the flexible nature of the diaphragm  14 , the push button  12  and the magnet holder  18  at opposite sides of diaphragm  14  are adapted to be displaced as a unit vertically through the mounting cup  3  in response to a pushing force applied to the push button  12  by a pedestrian. An optional O-ring  24  is received within a circumferential groove  26  which extends around the body  15  of push button frame  5  below the diaphragm  14  to isolate the body  15  of push button frame  5  from external moisture, dirt and other contaminates. The O-ring  24  also provides a flexible surface to support the diaphragm  14 .  
         [0019]     The magnet holder  18  includes a cavity  28  within which to receive a magnet (designated  30  in  FIGS. 1 and 4 ). The magnet  30  can be formed from any suitable magnetic material (e.g., neodymium) with a preferred size of about 0.75 inches x 0.375 inches. A commercially available magnet that is suitable for use herein is manufactured by All Magnetics under Part No. ND142N-35. A dimple  32  projects downwardly from the bottom of magnet holder  18  so as to lie below the magnet  30 . In the assembled configuration of  FIG. 2 , the magnet holder  18  is suspended below the flexible diaphragm  14  so that the cavity  28  within which the magnet  30  is located is received downwardly through the body  15  of push button frame  5 .  
         [0020]     A stationary coil housing  34  is also located within the body  15  of push button frame  5  so as to lie below the magnet holder  18 . Coil housing  34  includes a peripheral lip  36  that is seated below a ledge  17  at the bottom of the button frame body  15 . An O-ring seal  35  surrounds the coil housing  34  so as to lie between the lip  36  thereof and the ledge  17  of body  15 . A resilient (e.g., silicon foam rubber) bumper  38  is bonded to a nest  39  at the top of coil housing  34  so as to lie in spaced alignment opposite the dimple  32  projecting downwardly from the bottom of magnet holder  18 . In this manner, the push button  12 , the magnet holder  18 , and the coil housing  34  are all held in axial alignment with one another within the base  3 . Therefore, a pushing force that is applied to the push button  12  of push button station  1  by a pedestrian will cause the flexible diaphragm  14  to bend inwardly through the base  3  so that the magnet holder  18  that is carried at the inwardly facing side of diaphragm  14  will be displaced vertically through the push button frame  5  so that the dimple  32  which projects downwardly from the magnet holder  18  will apply a force against the bumper  38  that projects upwardly from the stationary coil housing  34 .  
         [0021]     A coil  40  is located within the stationary coil housing  34  below the movable magnet holder  18  so as to surround the magnet  30 . By way of example, the coil  40  preferably has between 300 to 1000 turns of copper magnet wire with an insulation layer of polyurethane nylon covered by an adhesive (e.g., polyvinyl butyeral) coating. The coil  40  can be pulsed with either an AC or a DC current for a purpose that will soon be disclosed. By way of example only, a 15 volt DC voltage source is used to pulse coil  40  at a frequency of 20 Hz.  
         [0022]     According to the preferred embodiment, a piezoelectric disk  42  (best shown in  FIG. 4 ) is located within a disk cavity  44  of the coil housing  34  so as to lie below the resilient bumper  38 . By way of example, piezoelectric disk  42  is a 20 mm disk that is commercially available under Part No. 2-203911 from American Piezo. However, it is to be recognized that other force sensitive switches (e.g., a membrane switch or a microswitch) can be substituted for piezoelectric disk  42 . The resilient bumper  38  above piezoelectric disk  42  is capable of both protecting disk  42  from damage due to mechanical shock while transmitting a pressure to disk  42  that corresponds to the force received by bumper  38  when the push button  12  is depressed by a pedestrian and the magnetic holder  18  carried by the flexible diaphragm  14  is displaced vertically towards the stationary coil housing  34  in response thereto.  
         [0023]     The piezoelectric disk  42  is suspended from and electrically connected to a printed circuit board  46  (also best shown in  FIG. 4 ) by means of flex circuitry  48 . The flex circuitry  48  allows the position of piezoelectric disk  42  to be spaced from and manipulated relative to the printed circuit board  46  for receipt within the disk cavity  44  of coil housing  34 . The function of circuit board  46  is to convert an output voltage generated by the piezoelectric disk  42  to an electric switching signal that is indicative of the pushing force applied to push button  12  and the corresponding pressure that is generated when the dimple  32  of magnet holder  18  applies a force to the bumper  38  of stationary coil housing  34 . In this same regard, when the pushing force is no longer applied to push button  12 , the spring memory of flexible diaphragm  14  will cause the magnet holder  18  and the dimple  32  projecting downwardly therefrom to automatically move away from the coil housing  34  and out of contact with the resilient bumper  38  projecting upwardly therefrom, whereby pressure will no longer be applied to the piezoelectric disk  42  via bumper  38 .  
         [0024]     As piezoelectric disk  42  flexes in response to the pressure applied thereto by the dimple  32  of magnet holder  18  when push button  12  is depressed, the output voltage generated by disk  42  is supplied to a comparator on circuit board  46 . The comparator compares the voltage generated by piezoelectric disk  42  with a predetermined reference voltage and then provides an output switching signal to indicate that push button  12  has been depressed.  
         [0025]     A minimum of four wires  50  are connected to the printed circuit board  46  to provide the vibrator input and to receive the output switching signal from the comparator on circuit board  46  in response to the voltage generated by the piezoelectric disk  42  after the push button  12  is first depressed and the disk  42  is subsequently flexed. The wires run from the circuit board  46  to an external control unit  60  by way of an exit port  54  that projects from the bottom of the mounting base  3 . The control unit  60  can be located at the push button station  1  or in the remote intersection control cabinet. Accordingly, the external control unit  60  receives the switching signal from circuit board  46  to cause the traffic signal to initiate its usual sequence to halt the flow of vehicular traffic through the intersection. At the same time, the switching signal also activates a timer at control unit  60  that can be set to any predetermined time following the depression of push button  12  before a tactile signal will be fed back to the push button  12  to indicate when to cross the controlled intersection. For example, the predetermined time can be set to expire at the same time that the usual WALK message is displayed.  
         [0026]     In this regard, once the timer of control unit  60  times out, the coil  40  within the stationary coil housing  34  will be pulsed by a voltage source from control unit  60  such that a pulsed current will flow through coil  40  to create a corresponding magnetic field. As the polarity of the magnetic field changes, the magnet  30  within magnet holder  18  will be attracted to and repelled by coil  40 . In the alternative, the current may be simply interrupted, whereby the magnet  30  will be released from coil  40  when the magnetic field changes. Thus, the magnet holder  18  will be subjected to successive (e.g., push-pull) forces so as to move in opposite directions through the body  15  of push button frame  5  towards and away from the stationary coil housing  34 .  
         [0027]     As was described above, the magnet holder  18  and the push button  12  are secured to opposite sides of the flexible diaphragm  14 . Therefore, the reciprocal movement of magnet holder  18  will be transferred to the flexible diaphragm  14  and, in turn, to the push button  12 . A pedestrian who places his hand on the push button  12  will now feel a vibration a particular time after the push button is first depressed. For a visually impaired pedestrian, the vibration functions as a tactile feedback signal to inform the pedestrian when to cross the intersection that is controlled by the traffic signal with which the vibrating push button station  1  of this invention is associated.  
         [0028]     The electromagnetic assembly described above enables a highly efficient and more reliable vibrating push button station to be achieved at which to provide a tactile feedback signal to alert visually impaired pedestrians when to cross a traffic signal controlled intersection a certain time after a push button is first depressed. In this case, the magnet  30  and the magnet holder  18  are attached to and movable with the flexible diaphragm  14 . The magnet  30  is coaxially aligned with the coil  40  so that when a pulsed current flows through the coil, the magnet holder  18  will be pulled inwardly or pushed outwardly to create a vibration. By virtue of the foregoing, the electromagnetic assembly of vibrating push button station  1  is able to convert electromagnetic energy into motion more efficiently than the solenoid assembly employed by the vibrating push button station of U.S. Pat. No. 6,340,936. That is, unlike a solenoid assembly, the electromagnetic assembly used in the push button station  1  requires no bearing surfaces and, therefore, is not subjected to energy loss caused by friction. The reliability of push button station  1  is enhanced, inasmuch as there is no need for lubrication or waterproofing, and the lack of bearing surfaces reduces the likelihood that push button station  1  will jam or wear out.  
         [0029]     Although the vibrating push button station  1  described herein has particular application for generating a tactile feedback signal by which to alert a visually impaired pedestrian when to enter an intersection (e.g., when the WALK signal is illuminated), it is to be understood that push button station  1  may also be used for other touch sensitive applications (e.g., such as in the operation of machinery, during automated manufacturing or chemical processes, and the like) wherein a tactile feedback signal is provided at a predetermined time after a push button is first depressed to notify operators that an independent step or process has been completed. Thus, push button station  1  may be engaged by operators whose visual attention is primarily focused towards a job site, such that the operators must rely on a tactile signal to indicate when an action affecting the job site must be initiated or changed.