GB2072838A

GB2072838A - Tilt detecting apparatus

Info

Publication number: GB2072838A
Application number: GB8108358A
Authority: GB
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1980-03-31
Filing date: 1981-03-17
Publication date: 1981-10-07
Also published as: IT8148072A0; FR2479449A1; IT1170832B; SE8102011L; DE3112057A1

Abstract

A tilt detecting apparatus comprises an opaque rigid ball (13) located within a two part housing (11, 21) and mounted on concave surface (12) to roll relative to the housing as the housing is tilted. The housing supports a light source (22) and a light responsive detector (15), the ball being arranged in relation to the source and detector so as to vary the amount of light reaching the detector in relation to the tilt of the housing. <IMAGE>

Description

SPECIFICATION Tilt detecting apparatus This invention relates to tilt detecting apparatus.

According to the invention, there is provided tilt detecting apparatus comprising an opaque substantially rigid device located within a housing and arranged to move relative to the housing as the housing is tilted, and a light source and a light responsive detector supported by the housing; said device being positioned between said source and said detector so as to vary the amount of light reaching the detector in relation to the tilt of the housing.

An embodiment of the invention will now be described by way of example, with reference to the accompanying drawings in which: Figure 1 is a cross-section of an optical tilt detecting apparatus according to the present invention; Figures 2A-2C show a basin part of the apparatus of Figure 1, which provides the surface over which the ball rolls; Figures 3A-3C show in more detail the details of a lamp holder part of the apparatus of Figure 1; Figures 4A and 4B show in more detail a housing cover of the apparatus of Figure 1; and, Figure 5 shows an electrical detecting circuit which can be used with the lamp and photodetector mounted in the apparatus of Figure 1.

Referring to the drawings, the tilt detecting apparatus 10 comprises basin 11 which is formed from a clear amorphous nylon substance and is shown in more detail in Figures 2A-2C. Basin 11 has concave surface 12 over which an opaque rigid movable device, such as ball 13, will roll as device 10 is tilted. Ball 1 3 must be substantially rigid so that its dimensions do not change as conditions, such as ambient conditions, change.

Photoresponsive device holder 14 is molded into basin 11 for retaining the photodetector 1 5 shown in Figure 1 therein. Since basin 11 is formed of a clear nylon, photoresponsive detector 1 5 will receive light through basin 11 from the lamp, to be described hereinafter, when ball 1 3 has rolled away and no longer intersects the path from the lamp to photoresponsive device 1 5. As shown in the detail of Figure 2C, photoresponsive device holder 14 has molded therein tabs 1 6 which are so dimensioned that when photoresponsive device 1 5 is inserted into holder 14, tabs 1 6 will yield to provide a press fit for photoresponsive device 1 5 in holder 14.

As shown in Figures 2A and 2B, basin 11 is provided with molded studs 1 7 which are received by corresponding holes in the printed circuit board 41 which mounts the circuit shown in Figure 5 to device 1 0. Basin 11 is also provided with grooves 1 8 which cooperate with splines molded in the housing cover for staking the assembly together.

Finally, grooves 1 9 are provided in basin 11 for allowing the power leads to be extended from the printed circuit board to the lamp.

Lamp 22 is supported by lamp holder 21, shown in more detail in Figures 3A-3C, which is also constructed of a clear amorphous nylon so that the light from lamp 22 can shine through lamp holder 21 and basin 11 to photoresponsive device 1 5 when ball 1 3 is not intersecting the light path from lamp 22. Lamp 22 may be a lamp or a light emitting diode and photoresponsive device 1 5 can be a photoresponsive transistor.

Alternatively, either lamp holder 21 or basin 11 may be opaque with suitable clear windows in a path from one to the other to allow light to shine from lamp 22 to detector 1 5. The advantage of said holder 21 being opaque except of a window beneath lamp 22 is that all light will then be directed toward detector 1 5 so that the response of detector 1 5 to scattered light will be reduced.

Lamp holder 21 has shoulder 23 for abutting against edge 24 of basin 11 during assembly and has a further shoulder 25 for forming with basin 11 a circumferential aperture for holding o-ring 26. 0-ring 26 seals in the damping fluid which is provided between lamp holder 21 and basin 11 for damping vibrations which might otherwise cause ball 13 to intermittently open the light path from lamp 22 to photoresponsive device 15.

Lamp holder 21 is provided with a molded lamp retainer 27 which is shown in more detail in Figure 3C. Molded in retainer 27 are tabs 28 which will allow lamp 22 to be press fitted into retainer 27 during assembly. Instead of press fitting, lamp 22 may be glued into retainer 27 and tabs 28 may be thereby eliminated. Lamp holder 21 is also provided with grooves 29 which cooperate with the grooves 1 8 of basin 11 for receiving the splines of the housing cover. Also provided in lamp holder 21 are grooves 30 for cooperating with the grooves 19 of basin 11 for receiving and permitting the leads extending from the circuit board to lamp 22.

During assembly, basin 11 is pressed into lamp holder 21 so that the grooves 29 align with the grooves 18 and the grooves 30 align with the grooves 19. Photoresponsive device 1 5 is press fitted into holder 14 and lamp 22 is press fitted into retainer 27. Leads 42 from lamp 22 are threaded through corresponding grooves 1 9 and 30. Housing cover 31 is then inserted over this assembly as shown in Figure 1. Opaque housing cover 31 is shown in more detail in Figures 4A-4B. Spiines 32 are molded into housing cover 31 and cooperate with the grooves 29 of lamp holder 21 and the grooves 1 8 of basin 11 such that as the subassembly comprising basin 11 and lamp holder 21 is inserted into housing cover 31, splines 32 will project through the corresponding grooves.When flange 33 of lamp holder 21 abuts shoulder 34 of housing cover 31.

splines 32 are heated and pressed to heat stake basin 11 and lamp holder 21 to cover 31 so that basin 11 and lamp holder 21 are tightly held to housing cover 31.

Circuit board 41 is next inserted over tabs 1 7 of basin 11 and tabs 1 7 are heated and pressed to heat stake circuit board 41 to basin 11. Wires 42 are connected to circuit board 41 as are leads 43, 44 and 47. The space between housing cover 31 and basin 11 is then filled with potting material 45.

Housing cover 31 is provided with suitable flanges 46 so that tilt responsive device 10 may be mounted to any suitable apparatus.

The circuit mounted on circuit board 41 is shown in detail in Figure 5. This circuit is provided with terminals 51, 52 and 53 for connection to wires 43, 44 and 47 for supplying power to circuit 50 and for connection to the relay shown in phantom at 54 which will energize the alarm device when tilt responsive device 10 is tilted by more than a predetermined amount. Line 55 is connected directly to terminal 51 and line 56 is connected to terminal 53 through diode 57 thus establishing line 56 at a one diode voltage drop above terminal 53.

Connected across lines 55 and 56 is a voltage regulator comprising capacitor 57 connected between lines 55 and 56, and the series connection of resistor 59, zener diode 60 and diode 61 connected in parallel to capacitor 57.

Zener diode 60 establishes a predetermined voltage level on line 62. Also forming a part of the voltage regulator is NPN transistor 63 having its base connected to the junction of resistor E9 and zener 60, its collector connected directly to line 55 and its emitter connected to line 56 through resistor 64 and terminals 65 and 66. Lamp 22 is adapted to be connected between terminals 65 and 66.

Lamp monitoring PNP transistor 67 has its emitter connected to the emitter of transistor 63 and its base connected through resistor 68 to the junction of resistor 64 and terminal 65. The collector of transistor 67 is connected to lead 56 through resistor 69. Transistor 67 forms an open lamp monitor which, if the lamp burns out and thus open circuits, the voltage at the base of transistor 67 rises turning off transistor 67 which will result in an alarm activation and an indication that the tilt detecting device is no longer functional.

Photoresponsive device 1 5 is shown in the form of a photoresponsive transistor having its collector connected to line 62 and its emitter connected to line 56 through the parallel arrangement of capacitor 71 and gain-sensitivity resistor 72 which forms a delay network so that momentary fluctuations in light from lamp 22 to detector 1 5 will not result in alarm actuations.

The alarm trigger circuitry comprises the rest of the circuit shown in Figure 5 and includes NAND gate 73 having one input connected to the emitter of transistor 1 5 and its other input connected to the output of NAND gate 74. The output of NAND gate 73 is connected to one input of NAND gate 75 which has its other input connected to the collector of transistor 67. The output of NAND gate 75 in the form of a Schmitt trigger because of its hysteresis is connected through resistor 76 to the gate terminal of FET 77 and is also connected to one input of NAND gate 74 through resistor 78 which is connected in parallel with the series circuit of diode 79 and resistor 81. This input of NAND gate 74 is also connected to line 56 through capacitor 82. Line 62 is connected through resistor 83 and inverter 84 to the other input of NAND gate 74.The drain of FET 77 is connected to terminal 52 and is also connected through diode 85 to line 56, and the source and substrate of FET 77 are connected directly to line 56. Terminal 52 is also connected through resistor 86 to the base of NPN transistor 87 and the base of transistor 87 is also connected to line 56 through resistor 88. The collector of transistor 87 is connected to the input of inverter 84 and the emitter of transistor 87 is connected to line 56.

Terminals 51 and 52 are then connected to the load which may be a relay for energizing the horn of a vehicle on which tilt responsive 10 is mounted.

In operation, when ball 13 is blocking light between lamp 22 and photoresponsive device 15, photoresponsive device 15 is off so that its emitter terminal is low. A low at the corresponding input to NAND gate 73 insures that its output is high.

Since the collector of transistor 67 is also high, the output of NAND gate 75 is low and FET 77 is off. The low output from NAND gate 75 means that the corresponding input to NAND gate 74 is low. Since output terminal 52 is at essentially the same voltage as output terminal 51, transistor 87 is on which essentially grounds the input to inverter 84 causing its output to be high. The output of NAND gate 74 is high which allows NAND gate 73 to change states if phototransistor 1 5 begins conduction.

When tilt responsive device 10 changes orientation sufficiently that ball 13 uncovers photoresponsive transistor 15, photoresponsive transistor 15 will begin to conduct which will cause the corresponding input to NAND gate 73 to go high. Because the other input to NAND gate 73 from NAND gate 74 is high, the output of NAND gate 73 will go low which will raise the output from NAND gate 75 to energize transistor 77 dropping the voltage on terminal 52. When the output from NAND gate 75 goes high, the corresponding input to NAND gate 74 will not go high until capacitor 82 charges sufficiently through resistors 78 and 81 and diode 79.

However, before capacitor 82 changes sufficiently, terminal 52 has its voltage lowered which turns off transistor 87 to allow the input to inverter 84 to go high and its output to go low maintaining the high output of NAND gate 74. Since the output of NAND gate 74 is high, the circuit is ready to turn off transistor 77 whenever ball 13 recovers photoresponsive device 1 5 allowing the corresponding input to NAND gate 73 to return to its low state.

The circuit of Figure 5 is designed to protect FET 77 should a short between terminals 51 and 52 occur. If for some reason terminals 51 and 52 become shorted, transistor 77 when it is gated on will be required to handle both high voltage and high current. The high power resulting from the high current flowing through it and the high voltage applied to its drain because of the short can damage it. Thus, if a substantial short exists between terminals 51 and 52 and if the output from NAND gate 75 is raised to gate FET 77 on, terminal 52 will remain high and not allow transistor 87 to turn off.With transistor 87 still conducting, the input to inverter 84 remains low and its output remains high so that after the time delay established by capacitor 82 and the resistordiode network, the output from NAND gate 74 will go low raising the output from NAND gate 73 and lowering the output of NAND gate 75 turning off FET 77. Since the output of NAND gate 75 is low, capacitor 81 will begin discharging through resistor 78 and after it has discharged sufficiently, the corresponding input to NAND gate 74 is lowered thus raising the output from NAND gate 74 lowering the output of NAND gate 73 and raising the output of NAND gate 75 re-energizing transistor 77. When capacitor 82 has charged sufficiently, NAND gate 74 will again turn off thus providing for cyclical operation of FET 77.

Capacitor 82 charges through the combination of resistor 78 and 81 but discharges through only resistor 78. If resistor 78 is made much larger than resistor 81, for example on the order of 100 to 1, transistor 77 remains off much longer than it is on.

Thus, the off-to-on ratio is extremely large but yet the circuit will be periodically sampled to determine if the short existing between terminals 51 and 52 has terminated. Resistors 86 and 88 are chosen to establish a predetermined voltage level at terminal 52 which will cause cyclical operation of FET 77 so that a perfect short between terminals 51 and 52 will not be required to initiate the cyclical sampling.

Finally, if lamp 22 becomes extinguished thus opening the circuit between terminals 65 and 66, transistor 67 will turn off causing the corresponding input to NAND gate 75 to go low raising the output from NAND gate 75 to turn on transistor 77 and energize the load which will warn an operator that a malfunction has occurred.

Claims

1. A tilt detecting apparatus comprising an opaque substantially rigid device located within a housing and arranged to move relative to the housing as the housing is tilted, and a light source and a light responsive detector supported by the housing; said device being positioned between said source and said detector so as to vary the amount of light reaching the detector in relation to the tilt of the housing.

2. The apparatus of Claim 1, wherein the device is of ball shape and in use rolls over a supporting surface of the housing.

3. The apparatus of Claim 2, wherein the supporting surface is concave.

4. The apparatus of Claim 1,2 or 3, wherein the housing includes an inner housing part containing said device and an outer cover part, the parts having co-operating splines and grooves for staking the parts together.

5. The apparatus of Claim 4, wherein the inner housing part has projective tabs enabling the connection of an electrical circuit board.

6. The apparatus of Claim 4 or 5, wherein the inner housing part receives said source and said detector in a press fit relationship.

7. The apparatus of Claim 4, 5 or 6, as appendant to Claim 2, wherein the inner housing part consists of two inter-engaging members one defining the said supporting surface and supporting one of said source and detector, and the other member supporting the other of said source and detector.