GB2181588A - Theft alarm device - Google Patents

Abstract

The alarm device, eg for a bicycle, comprises a housing having a base 11 and cover 12. The alarm device is secured to a bicycle by a bracket, not shown, secured to cover 12. Inside the base 11, there are connected in series a pair of batteries 36,37, a movement detector, and a buzzer 30. The movement detector comprises a ferro-magnetic contact 47 connected to one end of battery 37 and a finger 48, the free end of which carries a magnet 51. The cover 12 can be secured in a closed position by a latch member 20 operated by a locking mechanism. In the position shown in the drawings, the latch member 20 has bar which prevents the finger 48 from vibrating. However, upon rotating latch member 20 through 90 DEG , the finger 48 is free to vibrate. If the alarm device is now subjected to abrupt movement, finger 48 will vibrate and the attraction between magnet 51 and contact 47 will result in finger 48 being held in engagement with contact 47 thereby energizing buzzer 30 and providing a warning signal. The circuit can also be closed by a push-button switch 55, which may be mounted on the handle bar of the cycle, and which permits the alarm device to be used as a conventional buzzer during authorised use of the cycle. <IMAGE>

Description

SPECIFICATION Alarm device This invention relates to an alarm device and is primarily, but not exclusively, concerned with an alarm device for a cycle.

It is an object ofthis invention to provide an alarm device which can be used to discourage theft of a cycle.

According to this invention there is provided an alarm device comprising a housing which includes a base and a cover movable relative to the base to open the housing, a key operated lock mechanism for locking the housing in a closed position, means for generating an alarm signal, said signal generating means being electrically energizable and disposed at least partly within the housing, means for supplying electric power to the signal generating means, said supply means being located within the housing, and a movement detector located within the housing and arranged to control the supply of electrical power to the signal generating means, said movement detector being arranged to normally prevent the supply of electrical power from the supply means to the signal generating meanswhilstthe housing is stationary, and to respond to abrupt movement of the housing by permitting energization of the signal generating means.

The supply means will include a source of electrical powerwhen the device is used. However, priorto use,forexamplewhen the device is sold bya retailer, the supply means may include connectors suitable for connection to a dry-cell or other source of powersupplied separatelyfrom the device.

The device preferably comprises means for mounting the housing on a cylindrical member. Such means may bea bracketforembracing the cylindrical member.

The movement detector preferably comprises a pair of contacts, at least one of which its freely movable relative to the housing within a limited range of movement, within which range the movable contact can engage the other contact.

Afirst of said contacts is a ferro-magnetic member or is carried on a ferro-magnetic member, and the second of said contacts may be associated with a permanent magnet or may be a permanent magnet, said magnet being arranged to oppose opening of the contacts when they are closed.

In a preferred arrangement, said one contact is an end portion of, or is carried on an end portion of, a flexible finger. The flexibility of the finger is such that abrupt movement ofthe housing afterthe housing has been at rest causes substantial flexing ofthe finger and consequent closing of the contacts.

In one preferred embodiment ofthe alarm device, the key-operated lock mechanism has three positions, a first locking position for locking said housing in a closed position, a second unlocked position where said cover can be opened relative said base to open said housing, and a third locking position for locking said housing in a closed position, said lock mechanism further comprising means for disabling said movement detector in said third locking position.

The device may include a manually operated switch located outside said housing and a cable connecting said switch in parallel with the movement detector.

The invention also provides a device as set out above rigidly mounted on the bicycle.

The device of the invention can have uses other than in connection with a cycle. Thus it can detect motion and be so used as a warning or alarm device generally. For example, the device could be hung on or attached to a door orwindowto detect unauthorised entry or could be placed in a briefcase orthe liketo detect unauthorised opening or removal.

This invention will now be described in more detail, byway of example, with reference to the drawings in which Figure lisa circuit diagram of an alarm device embodying this invention; Figure2 is a plan view of the device of Figure 1 with thecoveropen; and Figure 3 is an underneath view ofthe device with the cover open; Figure 4 is a fragmentary sectional view on the line 4-4 of Figure 2; and FigureS is a fragmentary sectional view on the line 5-5 of Figure 3.

Referring to the drawings, the device includes a two part housing 10 which comprises a base 11 and a cover 12 which is movable relative to the base 11 between an open position, as illustrated in the drawings, and a closed position. The base 11 and cover 12 are formed as plastic mouldings.Astrand of material, whose dimensions aretoo small to be visible in the drawing, is secured between the base 11 and cover 12 and acts as a hinge. Alternatively the cover 12 may be demountablefrom base 11.

As shown in Figures 2,3, and 5, a U-shaped bracket 13 is attached to the outer surface of cover 12 by a pair screws 14, 15. The screws, 14, 15 are passed through holes in the cover 12 with their heads located on the inside. If desired,the bracket 13 may be rotated through 90", in which case the screws 14, 15 are passed through the holes 16,17. In use, the bracket 13 may be used to secure the device to a tubularmemberofthecycleframeorthehandlebar of a cycle. It will be observed that the bracket 13 may be detached from the housing 10 onlywhen the housing is open. As will be shortly explained,the housing 10 may be locked in a closed position thereby preventing unauthorised removal ofthe device.

In orderto lockthe cover 12 in its closed position, a key operated locking mechanism 18 is received inside a hollow circular pillar l9which projects from the inner surface of base 11. As shown in Figure 3, the locking mechanism 18 has a key slot 19. As shown in Figure 2, a latch member 20 is secured by a screw 21 to the cylinder, not shown, of locking mechanism 18.

The latch 20 has a pair of arms 22,23 which extend at right anglesto each other and cooperate with a tongue 24 on cover 12. With the lock mechanism 18 in the position shown in Figure 2, and with the cover in a closed position, the arm 22 engages the tongue 24 thereby retaining the cover 12 in a first locked position. lfthecylinderofthe locking mechanism 18 is rotated anticlockwisethrough 45", at viewed in Figure 2, the tongue 24 can pass through the space between arms 22 and 23 thereby permitting the housing 10 to be opened. If the cylinder is rotated through a further 45", the arm 23 engages tongue 24 thereby retaining the cover 12 in a second locked position. As shown in Figure 3, a thin bar 25 extends from arm 22 towards base 11.The purpose of bar25 is explained below.

There is secured to base 11 an electrically energizible signal generating means in the form of a buzzer 30. The buzzer 30 has a rim 31 which rests on an annular mounting, not shown, formed on the inner surface ofthe base 11. The rim 31 is held in position by a curved support 32 and three screws 33 which are received in pillars, not shown. The buzzer 30 is thus wholly contained within the housing 10 when the cover 12 is closed. As shown in Figure 3, a number of narrow slots 34 are formed in base 11 to facilitate transmission of sound energy from the buzzer 30. In an alternative arrangement, the buzzer 30 is mounted so as to partly protrude from the housing. In a further alternative arrangement, the signal genearting means is adapted to provide a visual signal only orto provide both an audible and a visual signal.The device includes electrical power supply means in the form of pair of batteries 36,37. In orderto hold the batteries 36,37 in position, there is provided a spring 38 held in a mounting member 39, and pair of contact members 40 and 41. The contact member 40 has a base part42 and pair of upwardly extending tongues 45,46. The base part 42 is secured by screw 43 to a pillar, not shown, which extends from the inner surface of cover 11. The battery 36 is located between spring 38 and tongue 45 and the battery 37 is located between tongue 46 and contact member 41. The contact member 40 is free to rotate and so the biasing force of spring 48 is available for holding both batteries 36 and 37 in position. The contact member 41 is L-shaped.The contact member 41 is associated with a contact 47 formed from a ferro-magnetic material. The contact 47 and the contact member 41 are jointly attached to a pillar, not shown, extending from the inner surface ofthe cover 11 by a screw 46.

Afinger48 formed from a thin strip of resiliently flexible conducting material is secured at one end by four prongs 49 arranged in a comb-like configuration. This secured end of finger 48 is connected bya lead 50to one terminal of buzzer30.

The free end of finger 48 carries a permanent magnet 51 and this free end also functions as a contact which cooperates with contact 47 to form a pair electrical contacts.

As may be observed in Figure 2, the finger48 is mounted relative to contact so that there is normally a clearance space between these. Also, with the cylinder of the locking mechanism 18 in position shown in Figure 2, the bar 25 of latch member 20 prevents the free end offinger 48 from approaching contact member 47. However, if the cylinder is rotated through 90", in an anticlockwise direction as viewed in Figure 2, the free end offinger 48 is free to move.If the alarm device is subject abrupt movement, the finger 48 will vibrate and so its free end will approach contact member 47. When this happens, the magnetic attraction between magnet 51 and ferro-magnet contact 47 will be sufficiently strong to draw the finger 48 into firm contactwith contact member47 thereby closing an electrical circuit between finger 48 and contact 47. Thus, the contact 47 and finger 48 together with magnet 51 operate as a movement detector. The control 47 may be rotated to adjust the sensitivity of the movement detector.

Various alternative arrangements forfinger48 and contact 47 are comtemplated. For example, the magnet 51 may be held bythe finger 48 so that magnet 51 ratherthan finger 48 engages contact47.

Also, contact 47 may be formed from a non ferro-magnetic material but have mounted thereon a ferro-magnetic memberwhich cooperates with magnet 51. In another alternative arrangement, contact47 is replaced buy a permanentmagnetwhilst magnet 51 is replaced by a weightformed from a ferro-magnetic material.

In yet another alternative arrangement the magnet 51 could be an electromagnet powered from the batteries 36 and 37.

The device also includes push button switch 55.

The switch 55 has a pair of arms 56, the free ends of which may be held together by a screw 57 and nut 58 to attach the switch 55 to the handlebar of a cycle.

The switch 55 is connected to a pair of leads 59,60 which pass through a slot in the cover 11 and which are connected respectively to the secured end of finger 48 and contact member 41. The switch 55 is thus connected in parallel with the movement detector formed from finger 48 and contact 47.

The otherterminal of buzzer30 is connected through a lead 61 to spring 38.

The complete circuit is shown in diagrammatic form in Figure 1. lnthatFigure,themovement detector is indicated by reference numeral 62. As may be seen, batteries 36,37, movement detector 62 and buzzer 30 are connected in series and switch 55 is shown clearly in parallel with movement detector 62.

When the cycle is being used by the owner or another authorised person, the cylinder ofthe locking mechanism 18 is in the position shown in Figure 2. In this position, the moving detector 62 is inoperative and cannot cause energization of buzzer 30. However, buzzer 30 can be energized by pushing the button of switch 55. Thus, underthese conditions, the alarm device can be used as a conventional buzzer underthe control of the riderto give warning to other road users.

When the userwishes to leave the cycle unattended, he operates the locking mechanism so asto rotate the cylinderthrough 90", in an anticlockwise direction as viewed in Figure 2. Ifthe cycle is then used, or the housing 10its otherwise subjected to abrupt movement, this will be sensed by movement detector 62 thereby causing energization ofthe buzzer 30 and thereby providing an alarm signal.

Although notshown in the drawings, a small light may be provided which is illuminated when the alarm device is armed, i.e. when the cylinder ofthe locking mechanism 18 has been rotated through 90" from the direction shown in Figure 2 so that the arm 23 locks the housing 10 and thefree end of the finger 48 is free to move.

In a modification to the alarm device described above, the movement detector 62 takes the form of a mercury switch or other switch which is sensitive to motion and a latching relayorelectronicequivalent for maintaining a closed ci rcu it when the circuit has been closed by operation ofthe mercury switch or other switch sensitive to motion.

Claims (10)

1. An alarm device comprising a housing which includes a base and a cover movable relative to the base to open the housing, a key-operated lock mechanism for locking the housing in a closed position, meansforgenerating an alarm signal,said signal generating means being electrically energizable and disposed at least partly within the housing, means for supplying electric power to the signal generating means, said supply means being located within the housing, and a movement detector located within the housing and arranged to control the supply of electrical power to the signal generating means, said movement detector being arranged to normally prevent the supply of electrical powerfromthesupplymeanstothesignal generating meanswhilstthe housing is stationary, and to respond to abrupt movement of the housing by permitting energization of the signal generating means.

2. An alarm device as claimed in claim 1,further including means for mounting the housing on a cylindrical member.

3. An alarm device as claimed in claim 2, in which the mounting means is a bracket for embracing the cylindrical member.

4. An alarm device as claimed in any one ofthe preceding claims, in which the movement detector comprises a pair of contacts, at least one of which is freely movable relative to the housing, within which range the movable contact can engage the other contact.

5. An alarm device as claimed in claim 4, in which a first of said contacts is a ferro-magnetic member or is carried on a ferro-magnetic member, and the second of said contacts is associated with a permanent magnetor is a permanent magnet, said magnet being arranged to oppose opening ofthe contacts when they are closed.

6. An alarm device as claimed in claim 5, in which said one contact is an end portion of, or is carried on an end portion of, a flexible finger.

7. An alarm device as claimed in claim 1, further including a manually operated switch located outside said housing and a cable connecting said switch in parallel with the movement detector.

8. An alarm as claimed in claim 1, in which the key-operated lock mechanism has three positions, a first locking position for locking said housing in a closed position, a second unlocked position when said cover can be opened relative to said base to open said housing, and a third locking position for locking said housing in a closed position, said lock mechanism further comprising meansfordisabling said movement detector in said third locking position.

9. An alarm device as claimed in claim 1 rigidly mounted on a bicycle.

10. An alarm device substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.