Patent Publication Number: US-6219949-B1

Title: Door reminder

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefits to U.S. Provisional No. 60/07052 filed Jan. 6, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This invention relates generally to devices for hanging on a doorknob for delivering message to people. More particularly, the invention concerns such a device with a hanger, a flap which is rotatably mounted on the hanger and at least one electronic device with switch component structured to be actuated by the rotational movement of the flap. The flap is rotated by a hand moving to grasp the doorknob. Preferably the invention includes two electronic devices, one light emitting and one sound emitting, which serve the function of attracting attention and/or delivering message. The invention may further include non-electrical display means for delivering message. 
     2. Background Information 
     It is not uncommon for people to forget doing something important before leaving the house in a rush. Sometimes this regrettable condition may lead to minor inconvenience and financial losses. But it could also lead to dire consequences such as lost of job, home and even lives. A person who often forgets to turn off the heater before leaving the house will have to pay a very expensive bill. A person who forgot to bring the door key may have to risk his/her life to climb back into the house or have the lock broken down by a locksmith with loss of time and money. 
     A person who forgot to bring an important report to work for a big business deal may find himself/herself jobless soon afterwards. A person who forgot to turn off the gas stove before leaving the house may find his/her house burnt down. 
     Certainly, forgetful people need a reliable reminding device at the door to help them remember important things to do before leaving the house. However, people with good memory also need a reliable reminding device when they want to deliver an important message to a household member who is sleeping or not home yet if they need to go out immediately. Many people resort to the basic tool of a memo slip stuck on the door with adhesive. This method does not always work for the absent-minded and people in a great hurry who just turn the doorknob and go. Memo slip adhered to a doorknob will cause inconvenience to people whom the message is not intended and they may fall off if people turn the doorknob without exercising extra care. 
     Even though prior art of U.S. Pat Nos. D339,382; D329,468; 1,984,559; 1,276,735 and 1,272,394 carry structures for hanging on a doorknob and they are used for delivering message, they suffer the same drawback as that of a memo slip for not being able to arouse enough attention, especially when they are used in a dim or dark surrounding or in a very hectic environment such as a busy office. 
     Thus, it is desirable to have a new and improved device which is more reliable and easy to use to deliver message to people at doors. 
     SUMMARY OF THE INVENTION 
     This invention solves the problems mentioned above with electronic device actuated by a rotatable flap which can be rotated by a hand moving to grasp a doorknob and with non-electrical display means for delivering message. 
     The present invention provides a reminding device for hanging on a doorknob on a door for delivering message to people. The invention comprises a hanger, a flap, at least one electronic device and an urging component for keeping the flap at an operative angle. 
     The hanger is a sheet of flat, elongate material having an upper portion and a lower portion. A hanger opening is provided on the upper portion of the hanger for hanging the invention on a doorknob. The hanger also has a back surface facing the door and a front surface facing away from the door. 
     The flap is provided with a flap opening and the flap is rotatably and horizontally mounted on the hanger above the hanger opening such that the doorknob can pass through both the hanger opening and the flap opening when the flap is rotated towards the front surface of the hanger. The flap is maintained at the operative angle of approximately 30 degrees above the front surface of the hanger by the urging component such that the operative angle is sufficiently large to enable a hand moving to grasp a doorknob to generate a rotational movement on the flap to turn on the electronic device but sufficiently small to allow the front view of the doorknob to be seen. 
     Preferably, the invention includes two electronic devices, one light emitting and one sound emitting, both of which are actuated by one flap-actuated switch constructed to be actuated by the rotational movement of the flap. 
     Message can be delivered by voice reproduced from data stored in a memory chip and/or by light from a plurality of light producing components in specific orientation. When the invention comprises a holding component, e.g. a clip, for holding a planar display component, e.g. a memo pad, only a simple sound signal, e.g. beeping sound, can be used and as few as one light producing component for attracting attention and/or illumination can be used. 
     It should be understood that different embodiments of the invention can be constructed without departing from the spirit of the invention which will be made apparent from the remainder of the specification and claims. 
     The primary objective of this invention is to provide a reminding device for hanging on a doorknob, which reminding device is able to emit light and/or sound for attracting attention and/or delivering message when the doorknob with the invention on is speed. 
     Another objective of this invention is to provide a reminding device for hanging on a doorknob, which reminding device consumes electricity only when a doorknob with the invention on is grasped. 
     Another objective of this invention is to produce a reminding device which is reliable, easy to use, cheap to manufacture and has great potential demand. 
     Other objectives and advantages will be made apparent to one skilled in the art from the drawings and detailed description below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an embodiment of this invention comprising a cap with a translucent display panel. 
     FIG. 2 is a perspective view of the embodiment in FIG. 1 hanging on a doorknob with a securing device buttoned. The doorknob is for illustrative purpose only and forms no part of the invention 
     FIG. 3 is a perspective view of the back of the embodiment in FIG.  1 . 
     FIG. 4 is a fragmentary plan view of the embodiment in FIG. 1 with the cap removed showing electronic components in their predetermined positions before wiring. 
     FIG. 5 is a side plan view of a flap-acted switch with wires connected in such a way that enables the switch to be turned on when a metal arm of the switch is pressed. 
     FIG. 6 is a fragmentary side plan view of the embodiment in FIG. 1 with the metal arm of the flap-actuated switch supporting a flap at an operative angle. 
     FIG. 7 is a schematic diagram of the electric circuitry of the electronic assembly in the embodiment shown in FIG.  1 . 
     FIG. 8 is a perspective view of a battery case of the embodiment in FIG. 1 opened showing a battery holder, batteries and a pressure pad. 
     FIG. 9 is a fragmentary perspective view of a hanger with the flap-actuated switch and a flap connected by a snap fit flap-hanger hinge. 
     FIG. 10 is a perspective view of another embodiment of my invention with three clips for holding a message card and with a light emission diode under a light dispersion plate. 
     FIG. 11 is a perspective view of the back of the embodiment in FIG. 10 with a back cover which is opened to reveal the electronic parts. 
     FIG. 12A shows a perspective view of a flap-actuated switch of the embodiment shown in FIG. 11 with the switch at the off position. 
     FIG. 12B shows a perspective view of the flap-actuated switch in FIG. 11 at the on position. 
     FIG. 12C shows a perspective view of the flap-actuated switch in FIG. 11 at another on position. 
     FIG. 13 is a fragmentary perspective view of the embodiment in FIG. 10 showing the upper portion of the invention with the flap lifted up showing a flap angle adjuster. 
     FIG. 14 is a perspective view of a memo slip displaying card which can be used for displaying memo slips on the embodiment in FIG.  10 . 
     FIG. 15 is a perspective view of another embodiment of the invention with a voice recorder. 
    
    
     DESCRIPTION OF THE INVENTION 
     The preferred embodiment of the present invention and its advantages are best understood by referring to FIGS. 1-8 of the drawings, like numerals being used for corresponding parts of the same embodiment. 
     FIGS. 1,  2  and  3  show a door reminder  10  which includes a hanger  12 , a flap  14 , a flap-actuated switch  16  which is provided with a spring, a cap  18 , holding components or transparent pockets  20 , a planar display component or memo pad  22 , battery case  24  and an electronic assembly connected to and actuated by the flap-actuated switch  16  for the production of light and sound. 
     The hanger  12  is a piece of flat and elongate material which can be plastic, celluloid or cardboard. The hanger  12  has a front surface facing away from a door and a back surface facing the door. The hanger  12  is preferably rectangular in shape and having a width of approximately 10 cm and a suitable length. A length of 32 cm is used in this embodiment. The hanger  12  consists of an upper portion of hanger  26  and a lower portion of hanger  28 . The upper portion of hanger  26  is provided with a hanger opening  30 . The hanger opening  30  is preferably circular in shape and sufficient large to encircle a doorknob  32  which is not a component of the invention. The upper portion of hanger  26  above the hanger opening  30  rests on the shank of the doorknob  32  when the door reminder  10  is ready for use. The diameter of the hanger opening  30  in this embodiment is approximately 6 cm. The hanger  12  is provided with a switch case  34  for housing the flap-actuated switch  16 . The switch case  34  includes two expelling holes  36  for expelling the flap-actuated switch  16  from the switch case  34  when necessary. The switch case  34  can be manufactured with the hanger as one integral part when thermoplastic material is used. 
     The flap  14  is a piece of flat material which can be plastic, celluloid or cardboard. The flap  14  is dimensioned and arranged to be rotatably and horizontally mounted on the upper portion of hanger  26  at a position approximately 3 cm above the hanger opening  30  such that the flap  14  can be rotated towards the front surface of the hanger  12 . The flap  14  is provided with a flap opening  38  which is preferably circular in shape. The flap opening  38  has a predetermined size and a predetermined position on the flap  14  such that the doorknob  32  can pass through both the hanger opening  30  and the flap opening  38  when the flap  14  is rotated towards the front surface of the hanger  12 . The diameter of the flap opening  38  in this embodiment is approximately 6 cm and the flap opening  38  is approximately 1.6 cm from the axis of rotation of the flap  14 . The flap  14  in this embodiment is substantially rectangular in shape with the two corners away from the axis of rotation rounded off. The rectangle is approximately 10 cm×9 cm in size before two corners on one of the two 10 cm long edges are rounded off. The flap  14  can be of other shapes and with a size sufficiently large to accommodate the flap opening  38  but sufficiently small to avoid blocking the view of the lower portion of hanger  28 . 
     The door reminder  10  further includes a flap-hanger hinge  40  which connects the hanger  12  and the flap  14 . The flap-hanger hinge  40  in door reminder  10  is a rectangular sheet of resilient material such as celluloid folded once and a small rectangular portion of the flap-hanger hinge corresponding to the position of the opening of the switch case  34  is cut out. The flap-hanger hinge  40  is secured on the hanger  12  and the flap  14  with a suitable adhesive and in a way according to the earlier description regarding the mounting of the flap  14  on hanger  12 . The flap-hanger hinge  40  can be of other suitable designs. For example, the flap-hanger hinge  40  can be made from a piece of flexible material such as cloth. A snap fit design which will be described afterwards can also be used. The flap-hanger hinge  40  can be omitted when the hanger  12  and the flap  14  are formed by folding a piece of resilient material such as cardboard and celluloid. 
     In this embodiment, the flap  14  is maintained at an operative angle of approximately 30 degrees above the front surface of the hanger  12  by two components with urging means, which components include the flap-actuated switch  16  provided with a spring inside and the flap-hanger hinge  40  made of a resilient material. However, the springiness provided by the flap-hanger hinge  40  is not essential to the operation of this embodiment. The operative angle should be sufficiently large to ensure that a hand moving to grasp the doorknob  32  will generate a rotational movement on the flap  14  to turn on the flap-actuated switch  16  but sufficiently small to prevent the flap  14  from blocking the front view of the doorknob  32 . 
     The cap  18  consists a translucent display panel  42  and a tilted supporting frame  44 . The translucent display panel  42  is tilted about 7 degrees as shown in FIGS.  1 , 2  and  3  to make viewing easier. The cap  18  is secured on the hanger  12  with screw members  46  forming a light box such that the top of the cap  18  is approximately 11 cm from the axis of rotation of the flap  14 . An opening (not shown in the drawings) can be made on the bottom portion of the tilted supporting frame  44  to facilitate the escape of sound from inside the cap  10 . 
     The holding components or transparent pockets  20  are made of a transparent flexible plastic material. The transparent pockets  20  are secured on the translucent display panel  42  with double-sided adhesive tape  48 . The uppermost corners of each of the transparent pockets  20  are not secured on the translucent display panel  42  so that the upper edge of the transparent pocket  20  can be bent slightly away from the surface of the translucent display panel  42  to facilitate the entry of paper when necessary. Another way of securing the transparent pockets  20  on the translucent display panel  42  is by heat sealing. This method is particularly suitable when the transparent pockets  20  open on both left and right side instead of at the top. The transparent pockets  20  can also be made with a stiff and relatively thick plastic material and each includes a U-shaped ledge for mounting on the translucent display panel  42  with adhesive. The number of transparent pockets  20  may be one or more. However, it is recommended that three should be the maximum number of transparent pockets used. A memo slip  50  can be taken from a planar display component or memo pad  22  on the door reminder  10  and a message is written on the memo slip  50  before putting in the transparent pockets  20  for display. The paper of the memo pad  22  should be thin enough to let most of the light from the translucent display panel  42  pass through. 
     The battery case  24  is mounted on the back of the lower portion of hanger  28  so that it can keep the upper portion of hanger  26  and the lower portion of hanger  28  at approximately the same distance from the surface of the door. 
     The door reminder  10  further comprises a securing member  52 , a pen-holder  54 , a storage pocket  56  and a rest support  58  all of which are not essential components of this embodiment and may be omitted. 
     The securing member  52  consists an upper portion of securing member  60  and a lower portion of securing member  62  rotatably connected to each other. The upper portion of securing member  60  is provided with a press button  64  which is dimensioned to fit tightly in a button hole  66  made on the hanger  12 . The lower portion of securing member  62  is secured on the hanger  12  right below the hanger opening  30  with a strong adhesive such that the upper portion of securing device  60  can be rotated to cover a portion of the hanger opening  30 . A snap fit can also be used instead of the adhesive for mounting the securing member  52  on the hanger  12 . The upper portion of securing member  60  and the lower portion of securing member  62  can be made in one piece from the same resilient material such as celluloid with a thin portion of the same material connecting both portions. The press button  64  should be provided on the right side of the securing member  52  since most people are right-handed. When in use, the upper portion of securing member  60  decreases the area of the hanger opening  30  making it difficult to remove the door reminder from the doorknob  32  without unbuttoning the securing member  52  first. 
     The pen-holder  54  is constructed of a plastic material and it is secured on the right side of the cape  10 . A writing instrument is to be provided by the user of the device. A marker with fine point and attractive color is recommended. 
     The storage pocket  56  is made of a plastic material and is secured on the back of the lower portion of hanger  28 . The storage pocket  56  is for storing any memo slips which can be used repeatedly. 
     The rest support  58  is for supporting the mid portion of the door reminder  10  when the device is put down horizontally on a flat surface with the back of the device facing downwards. Without the rest support  58 , the portion of the hanger  12  immediately above the tilted supporting frame  44  may bent after a period of time when the upper portion of the device rests on the switch case  34 . The rest support  58  can be omitted when the hanger  12  is made of a strong or resilient material. 
     FIG. 4 shows a fragmentary plan view of an embodiment in FIG. 1 with the cap  10  removed revealing the electronic components which include two light producing components  68 , a sound producing component  70  and a sound circuit board  72  in their predetermined position before wiring. Two wiring holes  74  and four screw holes  76  are also revealed. The light producing components  68  are halogen bulbs both of which are placed near the top within the cap  10  for maximum illumination of the most important message displayed on the top. The sound circuit board  72  includes data storage means for producing specific electronic signals for sound production in sound producing component  70 . It has been noted short bursts of sound attracts more attention than continuous sound of unchanged volume and that interesting sound of living creatures, e.g. sound of crickets, is very effective in attracting people&#39;s attention. A sound switch  78  shown in FIGS. 1 and 2 is included for switching off only the sound when silence is to be maintained. A volume control for sound can also be added if required. 
     FIG. 5 shows a side plan view of the flap-actuated switch  16  used in the door reminder  10 . The flap-actuated switch  16  is a SM-3 micro switch modified slightly. The SM-3 micro switch is a standard electronic part available at most electronic parts store in Hong Kong. The SM-3 micro switch comprises a metal arm  80  which is slightly rotatable and the metal arm  80  is in touch with a button  82  on the micro switch. The SM-3 micro switch is modified into the flap-actuated switch  16  by bending the tip of the metal arm  80  slightly towards the surface of the SM-3 micro switch as shown in FIG. 5 to enable the flap  14  to be turned more smoothly without scratching. The flap-actuated switch  16  comprises three connecting points  84 . Two electric wires  86  are connected to two of the connecting points  84  near to the button  82  so that the flat-actuated switch  16  is on when the metal arm  80  is pressed. 
     The flap-actuated switch  16  is fitted into the switch case  34  with the metal arm  80  pointing upwards as shown in FIG. 6. A hole is made on one side of the switch case to let the electric wires  86  come out of the switch case  34  as shown in FIG.  3 . The position of the switch case  34  can be on the left or right of the upper portion of hanger  26  and should keep the upper surface of the flap-actuated switch  16  approximately 0.8 cm below the axis of rotation of the flap  14 . Ihe flap  14  should be kept at the operative angle of approximately 30 degrees from the front surface of the hanger  12  mainly by the push of the metal arm  80  due to the force exerted by the spring inside the flap-actuated switch  16 . If the metal arm  80  does not touch the flap  14  at the operative angle, the metal arm  80  should be bent away from the surface of the flap-actuated switch  16  at the point of contact with the button  82  until the tip of the metal arm  80  touches the flap  14 . This will ensure that the flap-actuated switch can be turned on without having to push the flap  14  very close to the front surface of the hanger  12 . The metal arm  80  is rather easily bent at this point because the metal arm  80  is made narrower at this point for bending. The flap-actuated switch  16  is turned on by a hand moving to grasp the doorknob  32  when the metal arm  80  is pressed by the flap  14 . The flap-actuated switch  16  is turned off when the hand is removed allowing the metal arm  80  to rotate away from the front surface of the hanger  12  due to the springiness of the spring inside the flap-actuated switch  16 . 
     FIG. 7 is a schematic diagram of the electronic circuit of the door reminder  10 . Electricity current from batteries  88  flows through the light producing components  68 , the sound circuit board  72  with an integrated circuit chip for specific sound production and the sound producing component  70  when both the flap-actuated switch  16  and the sound switch  78  are on and both light and sound are produced. When only the flap-actuated switch is on, only light is produced. The door reminder  10  does not include a power switch to cut off the electricity completely to avoid the situation of people forgetting to turn it on. The door reminder  10  should be taken away from the doorknob  32  when no message is on display to prevent the cry wolf situation of producing light and sound when no message is on display. 
     FIG. 8 shows the battery case  34  which is opened to reveal the batteries  88 , a battery holder  90  and a pressure pad  92 . The pressure pad  92  consists a stiff layer  94  and a spongy layer  96 . The pressure pad  92  is for creating a width inside the battery case  24  slightly lees than the width of the battery holder  90  so that a small and even pressure is created to enable the horizontal position of the battery holder  90  within the battery case  34  to be adjusted. Adjustment may be necessary when a heavy pen is put into the pen-holder  54  tilting the door reminder  10  on the doorknob  32 . 
     When speedy assembly is required, an embodiment with a snap fit flap-hanger hinge  98  shown in FIG. 9 replacing the flap-hanger hinge  40  of the embodiment in FIG. 1 is more desirable. The hanger  100  and flap  102  in FIG. 9 are connected by the snap fit flap-hanger hinge  98 . The flap  102  is made of a resilient plastic material allowing part of the hinge  96  on the flap  102  to be extended outwards for mounting. 
     FIGS. 10 and 11 show a door reminder  104  which is another embodiment of my invention. The door reminder  104  does not include a translucent display panel and is suitable for displaying a single message in a well-lit area such as an office. The door reminder  104  includes a hanger  106 , a flap  108 , a flap-hanger hinge  110 , an angle adjuster  112 , a transmission mechanism  114 , an electronic assembly  116 , holding components or clips  118  and a planar display component or message card  120 . 
     The hanger  106  is provided with a hanger opening  122  and the flap  108  is provided with a flap opening  124 . The construction and dimensions of the hanger  106 , the hanger opening  122 , the flap  108  and the flap opening  124  are essentially the same as that of their counterparts in the door reminder  10 . However, a cutout  126  of a size approximately 1 cm×3 cm is made on one of the two upper corners of the hanger  106 . 
     The flap-hanger hinge  110  is a rectangular sheet of resilient material folded once and it is secured on the hanger  106  and the flap  108  in the same way as described in the description of the door reminder  10 . 
     The angle adjuster  112  is a rectangular sheet of resilient material folded once. It is smaller in size than the flap-hanger hinge  110  which has a similar construction. The angle adjuster  112  is releasably secured on hanger  106  with the folded line near and parallel to the axis of rotation of the flap  108 . By moving the angle adjuster  112  up and down the hanger  106 , the operative angle can be adjusted. 
     The transmission mechanism  114  comprises an L-shaped lever  128 , a connector  130 , a lever-connector hinge  132  and a connector guard  134 . The L-shaped lever  128  is constructed of a stiff plastic or metallic material. The short arm of the L-shaped lever  128  is approximately 0.6 cm in length and the long arm should be long enough to allow it to be secured firmly on the flap  108  with adhesive as shown in FIG. 11. A length of 3 cm is recommended. The lever-connector hinge  132  is a piece of flat, tough and flexible material, e.g. a piece of cloth, secured on the short arm of the L-shaped lever  128  and one end of the connector  130  with a strong adhesive. The connector  130  is constructed of a resilient material such as celluloid and cardboard. It is approximately 9 cm in length and approximately 0.7 cm in width. A portion of the connector  130  near the end away from the L-shaped lever  128  is covered with a connector guard  134  to facilitate the transmission of movement from the flap  108  and to prevent the connector  130  from being pushed out of position accidentally. The thickness of the connector  130  should be sufficiently small to allow a 3 cm portion the connector  130  to be bent easily for approximately 0.6 cm from the back to the front of the hanger  104 . The movement of the flap  108  is transmitted by the transmission mechanism  114  to a flap-actuated switch  136 . 
     The electronic assembly  116  comprises a light and sound circuit board  138 , a light emission diode  140 , a sound producing component  142  and a power switch  144 . The light and sound circuit board  138  is provided with the flap-actuated switch  136 , two button batteries  146  and a data storage chip  148 . The flap-actuated switch  136  comprises a spring arm electric pole  150 , a flat electric pole  152  and a switch strip  154 . The switch strip  154  is made of a non-conducting and resilient material such as celluloid. It is approximately 3 cm long and approximately 0.05 cm thick and it is sandwiched between the spring arm electric pole  150  and the flat electric pole  152 . A push-detecting hole  156  and a pull-detecting hole  158  are provided on the switch strip  154 . The push-detecting hole  156  is 0.1 cm from one end of the switch strip  154  and the pull-detecting hole  158  is 0.1 cm from the push-detecting hole  156 . The diameters of the two holes  156  and  158  are approximately 0.4 cm. The end of the switch strip  154  away from the holes  156  and  158  is secured with adhesive on the end of the connector  130  near the connector guard  134 . When the spring arm electric pole  150  is in contact with the flat electric pole  152  through either the push-detecting hole  156  or the pull-detecting hole  158 , the flap-actuated switch  136  is on. 
     The data storage chip  148  contains digitally recorded sound data for the reproduction of specific sound from the sound producing component  142  and contains circuitry for producing blinking light from the light emission diode  140  which is mounted on the front of the hanger  106 . The light from the light emission diode  140  is dispersed by a light dispersion plate  160  for attracting greater attention. Since door reminder  104  is designed with portability in mind, the power switch  144  is included in this embodiment to turn off the power from the button batteries  146  when necessary. For example, when the door reminder  104  is carried in a bag with the flap  108  pressed against the hanger  106  by clothing. 
     The door reminder  104  further includes a back cover  162  for protecting the electronic components on the back and for preventing short circuit. One edge of the back cover  162  is pemanently secured on the back of the hanger  106  and the other edge is releasably secured on the back of the hanger  106  with double-sided adhesive tape  164 . 
     Since the flap-actuated switch  136  in door reminder  104  does not include an urging component, the urging components required for maintaining the flap  108  at the operative angle of approxitely 30 degrees above the hanger  106  are the flap-hanger binge  110  and the angle adjuster  112 . 
     In FIG. 12A, the spring arm electric pole  150  rests on a ridge between the push-detecting hole  156  and the pull-detecting hole  158 . The flap-actuated switch  136  is off. The angle between the flap  108  and the front surface of the hanger  106  corresponding to this switch position should be within 20 degrees to 30 degrees or within 150 degrees to 160 degrees 
     In FIG. 12B, the spring ann electric pole  150  is in contact with the flat electric pole  152  through the push-detecting hole  156 . The flap-actuated switch  136  is on. The angle between the flap  108  and the front surface of the hanger  106  corresponding to this switch position should be smaller than 20 degrees or greater than 160 degrees but not greater than 180 degrees. 
     In FIG. 12C, the spring arm electric pole  150  is in contact with the flat electric pole  152  through the pull-detecting hole  158 . The flap-actuated switch is on. The angle between the flap  108  and the front surface of the hanger  106  corresponding to this switch position should be greater than 30 degrees but smaller than 150 degree. 
     If no pull detection of the flap is necessary, only the push-detecting hole  158  is needed. 
     The position of the light and sound circuit board  140  should be adjusted before securing on the back of the hanger  106  such that the flap-actuated switch  136  is turned on when the flap  108  reaches approximately 20 degrees above the front surface of the hanger  106 . The angle adjuster  112  is then adjusted to keep the flap  108  at the operative angle of approximately 30 degrees. 
     When door reminder  104  is mass produced, a marked position for the light and sound circuit board  138  should be provided on each hanger  106  so that no adjustment is needed for assembly. 
     FIG. 13 shows the angle adjuster  112  releasably secured on the hanger  106  with poster putty  166 . When the angle adjuster  112  is moved upwards on the hanger  106 , the operative angle of the flap  108  increases and vice versa. 
     If thermoplastic is used for manufacturing the flap  108  and the L-shaped lever  128  as one integral part, the long arm of the L-shaped lever  128  can be omitted and only a short lever perpendicular to the flap is required. If the connector  130  is also made from thermoplastic, a snap fit hinge design can be used for connecting the short lever and the connector  130 . The flap  108  can also be made from transparent plastic so that the whole doorknob encircled by the flap  108  can be distinctly visible. 
     The holding components or clips  118  in door reminder  104  are made of a resilient material such as celluloid. The are dimensioned and structured to be mounted on the left, right and bottom edges of the hanger  106  with double-sided adhesive tape for holding a planar display component or message card  120 . The entry points of each of the clips  118  for the message card  120  is slightly bent away from the front surface of the hanger  106  to facilitate entry. The three clips can also be made as one integral part from one piece of celluloid. This method would use more material but the assembly can be done faster. 
     While three clips  118  are used in the embodiment shown in FIG. 11, other embodiments which comprise a greater or smaller number of clips of suitable design to be mounted on suitable positions of a hanger can also be constructed. A large memo pad can be used instead of the message card  120  if a strong metal clip is mounted on the hanger. If only one permanent message is displayed, the message can be printed directly on a hanger. 
     The door reminder  104  further includes a card storage pocket  168  for storing message card  120  not in use. However, the card storage pocket  168  is not an essential part of the door reminder  104 . 
     In addition to displaying the message card  120 , door reminder  104  can also be used for displaying a memo slip displaying card  170  which is shown in FIG.  14 . The memo slip displaying card  170  can be used for displaying memo slips  172  in transparent pockets  174  as well as message written on memo pad  176 . 
     Door reminder  104  is not restricted to the use of delivering personal messages. It can also be used for delivering advertising messages, i.e. to remind people of a particular product. The advertised message can be printed on the hanger  106  and the flap  108  and further reinforced by interesting audio message produced by the sound producing component  142  promoting the same product. Since a door reminder is a useful device, it can be sold to customers instead of being given away. 
     It should be understood that while the light emission diode  140  in door reminder  104  is used for attracting the attention of people towards the message card  120 , the light emission diode  140  can also be considered having the function of delivering message as it delivers the message that a message card  120  is on display. When more than one light emission diodes are arranged in a specific orientation on a door reminder, a specific message can be delivered without the use of any non-electrical display means for delivering message. 
     FIG. 15 shows a door reminder  178  which is yet another embodiment of my invention. This embodiment is suitable for use when audio message is preferred over visual message. This embodiment includes a voice recorder  180  which can be used for recording a few short messages while a record button  182  is pressed and playing them back once on a speaker  184  after a flap actuated switch  186  has been turned on by the movement of the flap  188 . A battery case  190  is mounted on the back of the hanger  192  so that the battery case  190  can keep the hanger  192  vertical. Non-electrical means of delivering visual message is not included in this embodiment. 
     Although specific embodiments have been utilized in illustrating the present invention, it will be understood that details of the construction shown may be altered or omitted without departing from the spirit of the invention as defined by the following claims: