Abstract:
A tamper indication device includes a first component, a second component, and an alarm device. The alarm device indicates relative displacement of the first component and the second component. The alarm device includes an alarm circuit that detects the relative displacement and generates an alarm signal, and an alarm indicator that receives the alarm signal and generates an alarm indication.

Description:
FIELD OF THE INVENTION 
     The invention relates to access-control devices, particularly those used to prohibit access to children. More particularly, the invention related to access-control devices that include an indication that the access control has been defeated. 
     BACKGROUND OF THE INVENTION 
     The typical household can present many potential hazards for small children. Some of these hazards take the form of necessary fixtures placed close to the floor, such as electrical outlets. Others, such as refrigerators and other appliances with airtight or locking doors, can trap or suffocate a curious child. Dangerous objects around the house can be stored in drawers or cabinets, but children often manage to reach and inspect the contents of any storage space. 
     Conventional electrical outlet covers provide protection, but can be pried off by a child, which exposes the child to an additional choking hazard. Cabinets and appliances can be locked, but this presents an inconvenience to adults, who must have a key or combination in order to gain access. Less burdensome devices can be used to present an obstacle for a child. However, if these devices are defeated by a child, a long period of time might pass before a parent or other adult notices, during which time a child might be injured. For example, and older child might consider the locking device itself to be a challenge, having no interest in the danger that has its access restricted, and would be satisfied in removing the device. A younger child who is unimpeded by the device might then get hurt while removal of the device goes unnoticed. 
     BRIEF SUMMARY OF THE INVENTION 
     According to an aspect of the invention, a tamper indication device includes a first component, a second component, and an alarm device. The alarm device indicates relative displacement of the first component and the second component. The alarm device can include an alarm circuit that detects the relative displacement and generates an alarm signal, and an alarm indicator that receives the alarm signal and generates an alarm indication. For example, the alarm indicator can be an audio speaker. The tamper indication device can also include an actuator that sets the alarm device. For example, the actuator can include a switch, such as a typical switch having a first position and a second position. In such an embodiment, the actuator can set the alarm device when the switch is moved to the first position, and the alarm indicator can indicate an alarm when the switch is moved from the first position to the second position after the alarm device has been set. The actuator can include a latch. 
     The alarm device can include a delay device that delays the setting of the alarm device by a fixed time period following actuation of the alarm device by the actuator. For example, the delay device can be a circuit that senses actuation of the alarm device by the actuator and delays the setting of the alarm device by the fixed time period, which can be adjustable. The tamper indication device can also include an alarm suppression device that prevents the setting of the alarm device if actuated during the fixed time period. 
     According to a particular embodiment, the first component of the tamper indication device is an electrical socket base, and the second component is an electrical outlet socket cover. The electrical outlet socket cover can include at least one prong that engages a receptacle of the electrical socket. The alarm device or the actuator, or both, can be disposed within the electrical outlet socket cover. The switch is moved to the first position when the electrical outlet socket cover is disposed against the electrical socket base, and the switch is moved to the second position when the electrical outlet socket cover is moved away from the electrical socket base. 
     According to another embodiment, the first component of the tamper indication device is a blocking device attached to a first side of a sliding door, and the second component is a knob attached to a second side of a sliding door, opposite the blocking device. The blocking device can include a housing and a block within the housing that is movable between a first block position and a second block position. For example, the block can be attached to the housing along an axis such that the block is rotatable about the axis between the first block position and the second block position. In this example, the block prevents the sliding door from opening when the block is in the first block position, and the block allows the sliding door to open when the block is in the second block position. Similarly, the knob is rotatable between a first knob position and a second knob position. The disposition of the knob in the first knob position causes the block to be disposed in the first block position, and disposition of the knob in the second knob position causes the block to be disposed in the second knob position. For example, the knob can include a first magnet and the block can include a second magnet, and the relative positions of the first and second magnets can control whether the block is disposed in the first or second block position. The alarm circuit can be disposed in the blocking device housing, and can include a switch, for example, of the type that is movable between a first switch position and a second switch position. For example, the alarm circuit can generate the alarm signal when the switch is disposed in the second switch position, and can continuously generate the alarm signal after the switch has been disposed in the second switch position. The block can cause the switch to be disposed in the second switch position when the block is disposed in the second block position. The blocking device can also include a bar that is slidable between a first bar position and a second bar position. Such a bar, for example, can allow the block to be moved to the second block position when the bar is disposed in the first bar position, and can prevent the block from being moved to the second block position when the bar is disposed in the second bar position. 
     According to another embodiment, the first component of the tamper indication device is a U-shaped housing including a receptacle, and the second component is an extension including a U-shaped end piece and a ratcheted arm that engages the receptacle, attached to one end of the U-shaped end piece. An open end of the U-shaped housing is disposed opposite an open end of the U-shaped end piece of the extension. The alarm device or the actuator, or both, can be disposed within the U-shaped housing. The actuator can be a switch that sets the alarm device when the ratcheted arm is moved in a direction to engage the receptacle, and causes the alarm circuit to generate the alarm signal when the ratcheted arm is moved in a direction to disengage the receptacle. 
     According to another embodiment, the first component of the tamper indication device is a housing including first and second receptacles, and the second component is an extension including a U-shaped end piece and first and second ratcheted arms that engage the respective first and second receptacles, attached to respective ends of the U-shaped end piece. The housing is disposed between the first and second ratcheted arms and is slidingly attached to the first and second ratcheted arms. The alarm device or the actuator, or both, are disposed within the housing. The actuator can be, for example, a switch that sets the alarm device when the housing is moved along the first and second ratcheted arms in a direction toward the U-shaped end piece, and causes the alarm circuit to generate the alarm signal when the housing is moved along the first and second ratcheted arms in a direction away from the U-shaped end piece. 
     According to another embodiment, the first component of the tamper indication device is a housing including a receptacle, and the second component is a flexible strap including an extension at a first end that engages the receptacle. The flexible strap can include first attachment means at a second end for attaching the second end to a first surface, and the housing can include second attachment means for attaching the housing to a second surface. The alarm device or the actuator, or both, can be disposed within the housing. The actuator can be, for example, a switch that sets the alarm device when the extension engages the receptacle, and causes the alarm circuit to generate the alarm signal when the extension is disengaged from the receptacle. 
     According to another embodiment, the first component of the tamper indication device is a housing, and the second component is an extension extending from the housing and attached to the housing such that the extension is rotatable about a central axis of the extension between first and second rotational positions. The housing can be attached to a first surface, such that the extension can engage a bracket attached to a second surface. The alarm device or the actuator, or both, are disposed within the housing. The actuator can be, for example, a switch that sets the alarm device when the extension is disposed in the first rotational position, and causes the alarm circuit to generate the alarm signal when the extension is disposed in the second rotational position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exemplary embodiment of the present invention, an alarmed cover for an electrical outlet. 
         FIG. 2  shows an exemplary embodiment of the present invention, an alarmed sliding door lock. 
         FIG. 3  shows another exemplary embodiment of the invention, an alarmed cabinet door lock. 
         FIG. 4  shows another exemplary embodiment of the invention, an alarmed cabinet lock. 
         FIG. 5  shows another exemplary embodiment of the invention, an alarmed flexible strap lock. 
         FIG. 6  shows another exemplary embodiment of the invention, an alarmed sliding drawer lock. 
         FIG. 7  shows an exemplary switching circuit for use with the alarm of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an exemplary embodiment of the present invention, an alarmed cover for an electrical outlet. As shown, the outlet cover includes front and back enclosures  1 ,  2 , an actuation switch  3 , an alarm switch  4 , circuitry  5 , a DC power source  6 , and a buzzer  7 . The circuitry  5  is designed to cause the buzzer  7  to sound under certain conditions. The circuitry  5  is actuated by the actuation switch  3 , which, in a positive position, allows the circuitry  5  to determine the condition under which it will cause the buzzer  7  to sound. When the actuation switch  3  is not in the positive position, the buzzer  7  will not sound under any conditions. 
     Once actuated, the circuitry  5  monitors the position of the alarm switch  4 , which is biased in the non-asserted position through an aperture  9  in the back enclosure. When the outlet cover is placed in an electrical socket, the prongs  8  that are part of the back enclosure  2  are inserted into the electrical outlet receptacles. When fully positioned in the socket, the rear face of the back enclosure  2  is substantially flush against the plate or other border surrounding the electrical outlet receptacles, pushing the alarm switch  4  against the bias, through the hole until the alarm switch  4  is flush with the rear face of the back enclosure  2 . This position of the alarm switch  4  sets the circuitry  5  to enable the alarm. If the outlet cover is then removed from the receptacle, the biasing mechanism allows the alarm switch  4  to once again protrude through the aperture  9 . In this position, the circuitry  5  causes the buzzer  7  to sound. Preferably, the circuitry  5  also includes a timing element that causes a delay between sensing the displacement of the alarm switch  4  with respect to the back enclosure  2  and sounding of the buzzer  7 . The buzzer sounds until the actuator switch  3  is turned off. 
     Thus, the outlet cover shields the electrical receptacle. When the actuation switch  3  is in the positive position, the alarm circuitry  5  is enabled to monitor the alarm switch  4 . If the outlet cover is removed from the receptacle, the circuitry  5  senses the relative displacement of the alarm switch  4  with respect to the back enclosure  2 , causing the buzzer  7  to sound, preferably after a delay. 
       FIG. 2  shows another exemplary embodiment of the present invention, an alarmed sliding door lock. As shown, the door lock includes a first component  11  and a second component  12 , each of which is attached to a different side of a sliding door, such as a glass patio door. The components  11 ,  12  can be attached to the door, for example through the use of an adhesive applied to the appropriate surfaces of the components  11 ,  12 . The base  15  of the first component  11  is thin enough so that, when it is attached to the first panel of a sliding door, the second panel of the door can slide over the first component  11 , allowing the door to be opened. The first component  11  includes a lock block  13  that is pivotally attached to the first component  11 . The second component  12  includes a rotary switch  14 . The lock block  13  and the rotary switch  14  include opposing magnets, the relative position of which changes when the rotary switch  14  is turned. When the rotary switch  14  is in a first position, the lock block  13  is also in a first position with respect to the pivot axis of the lock block  13 . When the rotary switch  14  is rotated into the second position, the lock block  13  is caused to pivot about the pivot axis by the movement of the rotary switch magnet. 
     When in the first position, the lock block  13  is oriented such that it prevents a second panel of the door to slide across it, effectively locking the door. When in the second position, the pivoted lock block  13  allows passage of the second panel of the door. For example, the outer surface of the lock block  13  can be tapered as shown in the exemplary embodiment. In the first position, the end of the lock block  13  facing the second panel of the door sticks out from the base of the lock, in a position to abut the second panel when the second panel is slid toward the lock block  13 . In the second position, the lock block  13  is pivoted such that the end of the lock block  13  substantially aligns with the surface of the lock base  15 , allowing the second panel to pass. Preferably, the rotary switch  14  is biased, such as by a spring, to maintain the rotary switch  14  in the first position unless someone actively turns the switch  14  to the second position. Thus, the lock block  13  remains in the locked position under normal circumstances. As shown, it is also preferable that the lock block  13  is removable for reassembly in a position that is rotated by 180 degrees with respect to the pivot axis, to allow the lock block  13  to be configured for second door panels that slide from either the left or the right of the door lock. 
     The first component includes a lock bar  16 . When in an unlocked position, the lock bar  16  is disposed such that it is clear of the lock block  13 , and the alarmed sliding door lock operates as described above. When the lock bar  16  is in a locked position, the lock bar  16  prevents the lock block  13  from pivoting on the pivot axis, and keeps the lock block  13  in the locked position. Thus, when the lock bar  16  is in the locked position, turning the rotary switch  14  will not move the lock block  13 , which will prevent the sliding door from being opened. As shown, the lock bar  16  can be a flat, rigid member that slides within an internal channel of the base  15  of the first component  11 , between the unlocked and locked positions. The lock bar  16  can include an offset end for ease of returning the lock bar  16  to the unlocked position. 
     The sliding door lock can include an alarm device, such as dedicated internal circuitry within the base  15  of the first component  11 , that sounds an alarm when the rotary switch is turned to unlock the door. Alternatively, the alarm sounds when the lock bar is moved from the locked position to the unlocked position. In either case, it is preferable that the sliding door lock include an alarm actuation switch. When this switch is in an active position, the alarm feature described above is enabled. When this switch is in an inactive position, the alarm feature is disabled. 
       FIG. 3  shows another exemplary embodiment of the invention, a cabinet door lock, for use with cabinets of the type that have double doors that swing outward from a center line, with door handles or knobs toward the center line. The cabinet door lock includes a first hook  21  and a second hook  22 , which engage the door handles. The first hook  2  includes an extension  23  that engages a channel in the second hook  22 , such that the first hook  21  can move in a reciprocating fashion with respect to the second hook  22 . The extension  23  includes teeth that engage one or more corresponding teeth in a central lock module. For example, as shown, the extension  23  can include teeth on both sides, which engage upper and lower prongs  24  that are biased against the teeth. The prongs  24  are attached to first ends of upper and lower unlock buttons  25 . Upper and lower unlock extensions  26  are attached to the second ends of the unlock buttons  25 . The unlock extensions  26  include apertures through which the extension  23  passes. The teeth on the extension  23  are angled such that the prongs  24  do not resist reciprocal motion of the extension  23  when the hooks  21 ,  22  are moved toward each other, but resist motion that would move the hooks  21 ,  22  apart. When the unlock buttons  25  are pressed toward each other (against a bias provided, for example, by a spring  27 ), the unlock extensions  26  press against the respective prongs  24  of the opposing unlock button, against the bias that presses the prongs  24  against the teeth, removing the resistance to motion of the extension  23  and allowing the hooks  21 ,  22  to be moved away from each other. Thus, the hooks  21 ,  22  can engage the cabinet door handles, and can be moved toward each other until the hooks maintain a tight squeeze on the handles. In this position, the cabinet cannot be opened because the handles are prevented from swinging apart with the doors. This locking grip on the cabinet door handles can only be released by squeezing the unlock buttons  25  so as to disengage the prongs  24 , allowing the hooks  21 ,  22  to be pulled apart and removed from the door handles. 
     This exemplary embodiment also includes an alarm device, preferably disposed within the second hook  22 , which alerts an observer that the lock cabinet door lock has been unlocked and/or removed. Preferably, this feature does not function unless first actuated by movement of an actuation switch. After actuation, the cabinet door lock is put into place on the cabinet door handles. Subsequently, when the unlock buttons  25  are pressed, an alarm sounds to notify people in the vicinity that the lock has been unlocked. Alternatively, the motion of pulling the hooks  21 ,  22  apart sounds the alarm. In any case, there might be a delay between the activating motion and sounding of the alarm. The alarm can be provided by circuitry disposed within the body of the cabinet door lock. For example, a lever  28  having an offset end can be applied against the extension teeth or against a prong  24 . Motion of the teeth or prong can activate circuitry disposed at the other end of the lever  28 , causing the alarm to sound. 
       FIG. 4  shows another exemplary embodiment of the invention, an alternative cabinet lock. Instead of opposing hooks, this lock uses a sliding U-shaped yoke  31  to retain the cabinet door handles. Thus, this embodiment of the lock is useful for locking cabinets that have handles with apertures, although it can also be used to enclose handles having a tapered-outward shape. The yoke  31  passes through a base module  32 , which houses alarm circuitry. The base module  32  includes two receptacles, which receive respective ratcheted arms  33  of the U-shaped yoke  31 , defining an enclosed area  34  that can be constricted by sliding the ratcheted arms  33  farther through the base module  32 , and enlarged by sliding the ratcheted arms  33  back out of the base module  32 . Preferably, an end  30  of at least one of the ratcheted arms  33  is shaped such that it cannot pass completely through the receptacle in the base module  32 , so that the yoke  31  cannot be completely removed from the base module  32 . 
     When the enclosed area  34  defined by the yoke  31  and the base module  32  is disposed around cabinet door knobs and constricted by sliding the base module  32  along the ratcheted arms  33 , the cabinet doors are prevented from opening. The base module  32  preferably includes curved portions  35  on the U-shaped end of the yoke  31  and on the facing portion of the base module  32  in order to provide a closer fit against the cabinet door handles. The ratcheted arms  33  include ratchet teeth that communicate with corresponding teeth inside the base module  32  such that opening of the restricting area  34  is prevented. In order to allow unlocking of the cabinet doors, the base module  32  includes opposing unlock buttons  36  that have extensions  37  that press against outer edges of the ratchet arms  33 . When the unlock buttons  36  are pressed toward each other, the extensions  37  press against the ratchet arms  33  so as to move the ratchet arms  33  apart enough to disengage the ratchet arm teeth from the corresponding teeth in the base module  32 . Once the ratchet teeth are disengaged, one can slide the yoke  31  through the base module  32  to loosen the lock and unlock the cabinet. The base module  32  preferably includes biasing means, such as a spring  38  (shown in the exploded view of  FIG. 4  in its operative position between the ratchet arms  33 ), that engages the ratchet arms  33  and pulls the ratchet arms  33  together. 
     The base module  32  also includes alarm circuitry that indicates when the cabinet lock is unlocked or removed. This alarm can sound when the unlock buttons  36  are pressed together, or when the base module  32  is moved away from the U-shaped end of the yoke  31 . A time delay can be set between the enabling action and the sounding of the alarm. Preferably, the alarm feature includes an actuator that can be set through the use of a simple switch. Once the alarm is actuated, it is set to function as described. When not actuated, the lock can be unlocked and removed without sounding the alarm. 
       FIG. 5  shows another exemplary embodiment of the invention, a lock for an appliance door, or any other type of swinging door that doesn&#39;t necessarily have opposing handles, or requires a locking mechanism that provides flexibility in set up and operation due to the configuration of the door. This lock includes a housing  41  and a flexible strap  42 . The housing  41  includes a receptacle  43 , and the strap  42  includes one or more extensions  44  at a first end that engages the receptacle  43 . Protrusions  45  on the extension mate with corresponding features in the receptacle  43  to provide a click fit. Portions of the protrusions  45  are accessible through gaps  46  in the housing  41 . When these portions are pressed together, the protrusions  45  on the extension  44  are released from the receptacle  43 , and the strap  42  can be disengaged from the housing  41 . 
     The flexible strap  42  includes adhesive or other attachment means at the end opposite the extension for attaching that end to a surface. The housing  41  also includes adhesive or other attachment means so that the housing  41  can be attached to another surface. For example, an appliance such as a refrigerator has a door on the front of the appliance that swings outward from the front surface. The outside swinging edge of the door normally is flush with the side edge of the refrigerator when the door is closed. For use on such an appliance, the housing  41  can be attached to the door of the appliance, and the strap  42  can be attached to the side of the appliance adjacent the swinging door edge. When the extension  44  is engaged in the receptacle  43 , the door is prevented from opening. Placement of the attachment end of the strap  42  and of the housing  41  will determine the amount of slack in the locked apparatus. 
     The housing  41  also includes alarm circuitry that indicates when the lock is unlocked or removed. This alarm can sound when the unlocking extension portions are pressed together, or when the extension  44  is disengaged from the receptacle  43 . A time delay can be set between the enabling action and the sounding of the alarm. Preferably, the alarm feature includes an actuator that can be set through the use of a simple switch. Once the alarm is actuated, it is set to function as described. When not actuated, the lock can be unlocked and removed without sounding the alarm. Alternatively, the alarm function can be automatically actuated when the extension  44  fully engages the receptacle. For example, an actuator bar  47  can be disposed between two extensions  44 , to engage an actuation switch within the receptacle  43  when the extensions  44  are locked into place. 
       FIG. 6  shows another exemplary embodiment of the invention, a sliding drawer lock. The sliding drawer lock includes a housing  51  and an extension  52  extending from the housing  51  and attached to the housing  51  such that the extension  52  is rotatable about a central axis of the extension  52  between first and second rotational positions. The housing  51  is attached to a first surface, such that the extension can engage a bracket  53  attached to a second surface. For example, the housing  51  can be attached to the inside front panel of a sliding drawer, and the bracket  53  can be attached to the bottom surface of a component of the drawer frame, such as the underside of a cabinet top if the top drawer is to be locked. The extension  52  includes an angled protrusion  54  that is biased outwardly from the extension  52 . 
     When the extension  52  is inserted into the bracket  53 , the slope of the angled protrusion  54  enters the aperture of the bracket  53  first, and abuts a latching wall on the bracket  53 . As force is applied to push the extension  52  farther through the bracket  53 , this force overcomes the bias force on the angled protrusion  54  such that the protrusion  54  depresses into the extension  52 . Once the extension  52  is inserted into the bracket  53  past the trailing edge of the protrusion  54 , the bias pushes the protrusion  54  back outward. If an attempt is made to remove the extension  52  from the bracket  53 , the protrusion  54  abuts the latching wall, and further progress is prevented. If the extension  52  is rotated about its central axis, the protrusion  54  is also rotated out of range of the latching wall, and the extension  52  can be removed. Preferably, the extension  52  includes a ledge  55  on the outside periphery of the extension  52  to facilitate rotation of the extension  52 . The extension  52  is also preferably biased to rotate back into the locked position once the rotational force is released. 
     When the lock is attached to the drawer and frame, the abutment of the angled protrusion  54  against the latching wall prevents complete opening of the drawer. However, enough space should be allowed along the length of the extension  52  between the abutting edge of the protrusion  54  and the latching wall when the drawer is fully closed so that the drawer can be opened partially, enough for an adult to insert a finger into the drawer to push down on the ledge  55 , rotate the extension  52 , and unlock the drawer. 
     The housing  51  also includes alarm circuitry that indicates when the lock is unlocked or the drawer is opened. This alarm can sound when the extension  52  is rotated into the unlock position, or when the extension  52  rotates back into the locked position after the drawer has been opened. A time delay can be set between the enabling action and the sounding of the alarm. Preferably, the alarm feature includes an actuator that can be set through the use of a simple switch. Once the alarm is actuated, it is set to function as described. When not actuated, the lock can be unlocked and removed without sounding the alarm. Alternatively, the alarm function can be automatically actuated when the extension  52  fully engages the bracket  53 , such as by the depressing motion of the protrusion beyond the latching wall. 
       FIG. 7  shows an exemplary switching circuit for use with the alarm of the present invention. In this exemplary circuit, an integrated switching circuit SW04281, SW04343, or the like can be used. The hard switch represented by Option SW is the actuation switch that allows the alarm function to be set. Key 1  and Key 2  are momentary switches that control the voltage outputs BUO 1 /Vo and BUO 2 . PWM/DA SW is another actuation switch that sets other conditions in the IC. When Option SW is in the open position, the position of Key 1  has no effect on the alarm circuit. When Option SW is in the closed position, the position of Key 1  controls the action of the alarm circuit. The designer has the option of selecting which action will put a positive voltage on the line BUO 1  in order to turn on the transistor  8050  and sound the alarm speaker. That is, momentary depression of the Key 1  switch can be set as the condition to sound the alarm, or release of the Key 1  switch after momentary depression can be the alarm condition. 
     The designer can also set use of a delay. For example, if the PWM/DA SW switch is open, no delay function is set; if this switch is closed, an alarm delay will be programmed. The PWM/DA SW switch can be settable by a user, or can be hard-wired open or closed at manufacture. When the delay option is set, Key 1  and Key 2  are wired in parallel, so that they are depressed together when the alarm-sounding condition exists, and both keys are required to be depressed in order to sound the alarm. However, the effect of depressing the Key 2  switch is delayed by the IC, and therefore if the alarm condition still is not present after the delay has passed, the alarm will not sound. For example, if the IC is set for a 10-second delay, the alarm circuit will not recognize depression of both keys until a 10 second delay has passed. If the condition is still present after 10 seconds, the alarm will sound; if the condition does not last at least 10 seconds, the alarm will not sound. It will be recognized by those of skill in the art that other circuits, ICs and designs can be used to achieve the same or similar end result, and that common, off-the-shelf circuits or specialty designs realized on custom PCBs can be used.