Tidal clock

Abstract

A tidal clock includes a clock face, a clock mechanism, a tidal display mechanism, a tidal drive arrangement and one or more symbolic display members. The tidal display mechanism includes a background and a plurality of laminar members overlying the background. Each laminar member includes a display representing sea and having an upper edge configured to represent a sea level. The laminar members are independently movable between respective lower and upper positions to represent rise and fall of the sea level. The symbolic display members are each mounted on a respective support. Each support is engaged with the background, permitting movement between lower and upper positions, further engaging a respective laminar member and arranged so that the support and display mounted thereon is urged to move between lower and upper positions by the corresponding movement of the laminar member.

Claims

1. A tidal clock comprising a clock face and a clock mechanism comprising a spindle located in the face and driven by the clock mechanism and rotatable hands mounted on the spindle to provide a time display; the tidal display mechanism comprising a background, a plurality of laminar members overlying the background, each of the plurality of laminar members representing sea and having an upper edge configured to represent a sea level; wherein each laminar member is independently movable between respective lower and upper positions of such laminar member to represent rise and fall of the sea level; a plurality of symbolic display members each mounted on a respective support, each support being engaged with the background, permitting movement between lower and upper positions of such support, further engaging a respective laminar member and arranged so that the support and display member mounted thereon is urged to move between the lower and upper positions of the support by the corresponding movement of the laminar member; a tidal drive arrangement comprising a drive mechanism and a drive shaft having a plurality of eccentric cams, each eccentric cam engaging a follower connected to a respective laminar member so that rotation of the drive shaft causes movement of the laminar members between the lower and upper positions of the respective laminar members; wherein the tidal drive arrangement includes an actuator and a sensor, one of the actuator and sensor being engaged to rotate with the drive shaft and the other of the actuator and sensor being at a fixed location, arranged so that the actuator engages the sensor to generate a signal at a predetermined angular orientation of the drive shaft; the drive mechanism comprising a controller, motor and power supply; the controller being arranged to control the motor to regulate rotation of the drive shaft and responsive to said signal to reset the drive shaft to the predetermined angular orientation.

2. The tidal clock as claimed in claim 1, wherein the motor is connected to the tidal drive arrangement by a pulley or gear linkage.

3. The tidal clock as claimed in claim 1, wherein the motor is a stepper motor.

4. The tidal clock as claimed in claim 3, wherein the controller is arranged to turn on the stepper motor periodically to update orientation of the display and further arranged to turn the motor off between updates.

5. The tidal clock as claimed in claim 1, wherein the sensor comprises a switch engaged by the actuator to send a signal to the controller.

6. The tidal clock as claimed in claim 5, wherein the actuator is engaged to or integral with the drive shaft so that the switch is actuated at a predetermined point of each revolution of the drive shaft.

7. The tidal clock as claimed in claim 6, wherein the switch is actuated at a high tide orientation.

8. The tidal clock as claimed in claim 1, wherein the tidal display mechanism is updated during each tidal cycle.

9. The tidal clock as claimed in claim 1, wherein the eccentric cams are circular.

10. The tidal clock as claimed in claim 1, wherein the eccentric cams are displaced angularly.

11. The tidal clock as claimed in claim 1, wherein the symbolic display members represent floating objects.

12. The tidal clock as claimed in claim 1, wherein each of the supports extends through a corresponding slot in the display.

13. The tidal clock as claimed in claim 1, comprising three or four laminar members located in parallel spaced relation between the background and the rear of the clock face.

14. The tidal clock as claimed in claim 1, wherein the upper edge of the forwardmost laminar member is lower than the edges of the other laminar members.

15. The tidal clock as claimed in claim 1, wherein the laminar members have vertically extending formations on each side to permit vertical sliding movement as the cams rotate in use.

16. The tidal clock as claimed in claim 1, wherein the follower of each laminar member is downwardly facing.

Description

(1) The invention is further described by means of example, but not in any limitative sense, with reference to the accompanying drawings, of which:

(2) FIG. 1 is a perspective view of a tidal clock in accordance with this invention;

(3) FIGS. 2 to 5 show successive stages of movement of the display;

(4) FIG. 6 is an exploded view of the tidal display mechanism;

(5) FIG. 7 shows the moving parts of the tidal display mechanism; and

(6) FIG. 8 shows the gear arrangement of the tidal display mechanism.

(7) The tidal clock shown in FIGS. 1 to 8 comprises a casing (1), a clock face (2) and clock hands (3,4). The time is shown by an annular hours and minutes display (5). An aperture (6) in the clock face (2) allows the tidal display to be observed. The display comprises a skyline (7) and a foreground display (8) representing a town or other feature. Three laminar members (9,10,11) represent background, middleground and foreground waves and have upper edges (12,13,14) to represent sea levels.

(8) Display members (15,16) may represent boats floating in the sea. The boats are constrained to move upwardly and downwardly in slots (18,19) in the background member (8) as described below.

(9) Dials (21,22,23) in a lower part of the clock face represent phases of the moon, the state of the tide (whether rising or falling) and the height of the tide.

(10) FIGS. 2 to 5 show successive stages in movement of the tidal display. In FIG. 2 a low tide display is shown. The laminar members (9,10,11) are at the lowermost part of the aperture (6). The boat displays (15,16), resting on the upper edge (12) of the laminar member (9), rest at the lower ends of the slots (18,19) in the background member (8).

(11) In FIG. 3 the tide has started to rise so that the laminar members (9,10,11) are raised from the lower position, resulting in corresponding raising of the boats (15,16) within their respective slots. The dials (21,22,23) show the corresponding phases of the Tide. Dial (21) contains 12 hour markers and indicates the time remaining to next low tide. Dial (23) contains 12 hour markers and indicates time remaining to next high tide. Dial (22) indicates the current condition of the tide as either High, Ebbing, Low or Flooding. In FIG. 3 Dial (21) shows 9 hours until next low tide. Dial (23) shows 3 hours until next high tide and dial (22) shows the tide condition as flooding.

(12) In FIG. 4 the high tide position has been reached so that the boats (15,16) are at the uppermost positions within their respective slots (18,19). Dial (21) shows 6 hours until next low tide. Dial (23) shows high tide (or 0 hours until high tide), and dial (22) additionally shows the current tide condition as high tide.

(13) FIG. 5 shows the display as the tide is falling. The upper edges of the laminar members are falling towards the lower position and the boats (15,16) are falling within their respective slots to return to the position shown in FIG. 2.

(14) FIGS. 6 to 8 show the internal features of the tidal clock. The casing (1) receives the clock face (2) and a rear casing member (3) with a closure (4). A clock drive motor (5) and tidal drive motor (6) are mounted on the rear casing (3).

(15) A gear mechanism (25) connected to the tidal display drives the three dials (21,22,23) and the cams.

(16) The movable parts of the tidal display are shown in FIG. 7. The laminar members (9,10,11) are held captive in end pieces (26,27,28) and are constrained to move vertically along bars or other elongate members (29,30). Each laminar member has downwardly extending cam follower (32,33,34) urged by gravitational force into contact with circular eccentric cams (35,36) respectively. The cams are mounted in a common drive shaft (38see FIG. 8) so that the three cams rotate simultaneously. During rotation of the cams, the rearmost laminar member (9) is raised first, followed by the intermediate member (10), followed by the outermost member (11).

(17) Two display members (15,16) representing boats are mounted on supports (38,39) located within the slots (18,19) in the background member (8). The supports (38,39) rest on upper edge (12) of the laminar member (9). In this way, the movement of the boats is made more variable by the configuration of the edges (12).

(18) The drive arrangement of the tidal mechanism is shown in FIG. 8. A central shaft (38) connected to the drive motor (6) and drive shaft (54) through pulley and belt arrangement (49, 50, 51) has a sun gear (41). Orbital gears (42,43,44) are connected by shafts (45,46,47) to the dials (21,22,23) respectively. A mounting frame (48) supports the shafts.

(19) FIG. 8 further shows the tide position calibration sensor comprising A switch arm (53) mounted on central shaft (38) and arranged to engage actuator (54) when the position of the system results in a high tide display.

(20) In use of the tidal clock, the following steps are carried out:

(21) 1. Setting the Tide Position Stage: 1. User turns the unit on. 2. User presses a set button which cycles the motor and therefore the tide position dial, to set the current tide position in accordance with official tide charts. The tide timetables for any particular location are available on meteorological websites.

(22) 2. System Calibration Stage: 1. The program cycles the motor by 60 steps (0.5 degrees/step=30 degrees) every 31 m 2 s. Visually this results in a 1/24 movement of the 12 hour dial. 2. The motor torque is stepped up through a 20/72 teeth pulley and belt system. 3. The result is a 15 degree movement of the drive shaft. 4. The program continues with this program repeatedly until the actuator engages the sensor to cause the sensor to send a signal to the controller. 5. When the signal is received the controller identifies that point as a set position (e.g. high tide) to which the display needs to return at the end of each tide cycle.

(23) 3. Normal Operation:

(24) The program will aim to be complete in 24 cycles of 60 steps every 31 m 2 s. One full cycle is completed in 12 h 25 m.

(25) In most locations, the largest constituent is the principal lunar semi-diurnal, also known as the M2 (or M.sub.2) tidal constituent. The period is about 12 hours and 25.2 minutes, exactly half a tidal lunar day. This is the average time separating one lunar zenith from the next. 1. The controller cycles the motors by 60 steps (0.5 degrees/step=30 degrees) every 31 m 2 sfor 23 counts. 2. On the 24.sup.th cycle the controller cycles the motor indefinitely until the sensor and actuator are engaged and the mechanism has returned to its starting position (e.g. high tide). 3. This ensures that the visual tide cycle and dial display remains accurate consistent with the official tide charts.