GB2543292A - Tidal clock - Google Patents

Abstract

A tidal clock 1 comprises a clock face , a clock mechanism with a spindle located in the face and driven by the mechanism and rotatable hands mounted on the spindle to provide a time display. The tidal display mechanism comprises a background 7 and a plurality of laminar members 14,17,18 overlying the background. Each member includes a display representing sea and having an upper edge configured to represent a sea level. Each display member is rotatable between a respective visible location wherein the display member may be observed through an aperture in the clock face and a respective hidden location wherein the display member is concealed by the clock face. The gear mechanisms are adapted to successively move the display members between hidden and visible locations as the drive shaft rotates to provide a display characteristic of tidal conditions associated with the associated tidal state.

Description

TIDAL CLOCK

This invention relates to a tidal clock of the kind which combines the functions of a tidal display and clock into an integrally driven mechanism. A tidal display may provide a visual indication of the state of a sea tide, for example, to show high tide and low tide. Generally a tidal display is provided as a stand-alone device, not incorporating a clock. A tidal display and clock may be mounted side by side in a wooden case so that the two mechanisms operate entirely separately but can be viewed simultaneously.

According to the present invention, a tidal clock comprises a clock face and a clock mechanism, a spindle located in the face and driven by the mechanism and rotatable hands mounted on the spindle to provide a time display; a tidal display mechanism comprising a background and a plurality of laminar display members overlying the background, each member engaged to the drive shaft by a respective gear mechanism and rotatable by the shaft in response to tidal movements; wherein the clock face includes an aperture, each display member being rotatable between a respective visible location wherein the display member may be observed through the aperture and a respective hidden location wherein the display member is concealed by the clock face; wherein the gear mechanisms are adapted to successively move the display members between hidden and visible locations as the drive shaft rotates to provide a display characteristic of tidal states at different times in a tidal cycle.

The initial angular location or starting point and the rate and direction of rotation of each display during rotation of the shaft are preferably selected so that continuous rotation of the shaft between a low tide and a high tide orientation causes movement of the display members between successive hidden, visible and optionally hidden locations to provide a constantly variable display observable through the aperture in the clock face.

Each display member may occupy a sector of the clock circumference. Each display is preferably annular, occupying a sector in the circular clock face but not obscuring an observer’s view through an aperture in a central portion of the face. This enables the gear mechanism to be observed.

The aperture may comprise a sector of the clock face, for example extending across an angle of 6O’ to 12Cf, preferably about 9CT.

Each sector may have a leading edge which is brought into view as the display moves from a hidden to a visible location.

The leading edge in the direction of rotation may be shaped to form a silhouette of a tidal feature, for example a breaking wave, or incoming or outgoing tide. The display member may be perforated to allow a user to observe an underlying display. A multiplicity of displays may be arranged in overlying axially spaced relation on the drive shaft. A first display may overlie and partially or wholly conceal a second display when they are both at overlapping angular locations.

The displays may be laminar and may comprise flat plates or sheets having decorated surface facing towards the aperture, the decorated surface representing a tidal condition.

The displays may comprise annular portions mounted on a circular, circumferential support. The support may comprise bearings, for example roller bearings.

In a preferred embodiment four rotatable displays are employed, each representing a state of the tide during a tidal cycle, for example: low tide, flooding, high tide and ebbing respectively. The displays may be mounted on pairs of rollers arranged to permit ease of rotation and to facilitate alignment of the displays during assembly.

The face may include a second aperture arranged to display wording, or other symbols indicating one of several tide conditions, for example, “low tide” “flooding” “high tide” or “ebbing”. This wording or other symbols may be provided on an appropriate portion of the ebbing display arranged to be visible through the aperture when the display is rotated by a predetermined angle so that the wording corresponds to the visible display.

The drive mechanism may comprise planetary or epicyclic gear arrangement for each display member. The gear arrangement may comprise a sun gear and one of two planetary gears engaging an orbital gear located on the annular surface of the display member. A single planetary gear may be provided to cause the respective display member to rotate anti-clockwise as the stepper motor moves from the rest position to the fully extended position. A chain of two planetary gears may be used to cause the display member to rotate in opposite direction, clockwise simultaneously with the anti-clockwise rotation of the other members.

The drive shaft may be hollow to coaxially accommodate the clock spindle. A single electric motor may be provided to drive the tidal display, for example a stepper motor may be employed. Use of a stepper motor is beneficial to provide sufficient torque to drive the display mechanism.

The tidal clock of the present invention confers numerous advantages. An integral display of time and tide conditions is provided in an efficient and attractive arrangement. The drive mechanism provides efficient and accurate means for controlling the motion of the display while affording an attractive appearance.

The drive mechanism is preferably arranged to provide a movable display having a cycle of 26 hours. When technically describing tides a cycle is normally measured from High to High. This mechanism of this invention works on a principal lunar semi-diurnal also known as the M2 (or M2) tidal constituent. Its period is about 12 hours and 25.2 minutes, exactly half a tidal lunar day, which is the average time separating one lunar zenith from the next, and thus is the time required for the Earth to rotate once relative to the Moon. Due to other influences the actual time between High and High changes between 12 and 13 hours.

For simplicity tidal clocks typically run on a 12 hour cycle (High - High) count 6 hours between each high and low condition.

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

Figure 1 is a perspective view of a tide clock in accordance with this invention.

Figure 2 is an exploded view of the display mechanism;

Figure 3 shows the low tide assembly;

Figure 4 shows the flooding display assembly;

Figure 5 shows the high tide display assembly;

Figure 6 shows the ebbing display assembly;

Figures 7 to 16 illustrate stages of movement of the mechanism in use.

The tidal clock shown in Figures 1 and 2 comprises a casing (1), a clock mechanism (2). A back cover (3) provides mountings for a central shaft (4) and right and left shafts (5,6). An annular background member (7) is mounted in roller bearing (8) and is arranged to be rotatably driven by a planetary gear system as described below. A motor gear sub-assembly (9) is connected to a stepper motor (30) to cause the background member to rotate in use.

The clock face comprises an annular plate (10). A 90° quadrant at the upper part of the plate (10) is cut away to form an aperture segment (19) through which the background member (8) and any suitably located portions of the overlying the background members may be observed (7).

The clock face also includes an arcuate opening (12) in an lower part of the face, to display successive words or symbols indicative of, for example low tide, flooding, high tide, ebbing. The words may be written onto the underlying “ebbing” display member (14) and arranged to be visible successively through the aperture as the latter rotates in use as described below. A generally quadrant-shaped frame (15) is mounted behind the opening (12) and includes annular mounting (16) for the forward ends of the rotatable spindle and shafts (4,5,6).

Two part annular display members (17,18) are coaxially mounted between the background display member (7) and the “ebbing” display member (14).

Each of the display members (14,17,18) has an annular configuration with a cut-away sector arranged to allow a user to see an underlying display through the aperture (19).

Each display member has a circular circumferential axially extending ring (20,21,22) upon which a multiplicity of roller bearings (23,24,25) are captive. In the illustrated embodiment five roller bearings are mounted on each ring. An alternative number of roller bearings, for example three or four may be employed as convenient.

Each roller bearing has forward and rear plates (26,27) between which a pair of circumferentially spaced rollers (28,29) are rotatably mounted on axle rods. The use of pairs of rollers allows the annular members to be conveniently coaxially located during assembly of the clock.

In a preferred embodiment adjacent bearings share front and rear plates, so that the front plate of one member serves as the rear plate in the adjacent overlying or underlying member. In this way the display members are constrained to rotate in parallel spaced relation. Each of the display members (17,18,19) has an image on the front surface and a leading edge which is configured to give a silhouette of a tidal or other wave feature.

Figure 4 shows the “flooding” display member comprising an annular display (17) mounted in a cylindrical ring (20) supported by pairs of rollers (31) mounted in housing (23, 32).

The leading edge (34) of the “flooding” display is configured to represent a silhouette of waves as shown in Figure 7.

The drive mechanism for the “flooding” display member comprises a planetary gear arrangement to be retained by one or more clips (37). An axial sun gear (35) having 16 teeth, engages a planetary gear (36) having 76 teeth, the annulus forming an orbital gear having 168 teeth. Rotation of the sun gear (35) at 26.32rpm causes rotation of the planetary gear (36) at 5.54 rpm and the orbital gear and hence the display is caused to rotate at 2.51 rpm.

The leading edge (38) of the “high tide” display, shown in Figure 10, is configured to represent waves. An axial sun gear (39) having 26 teeth is connected via a chain comprising an inner planetary gear (40) having 28 teeth and an outer planetary gear (41) having 32 teeth to the annular orbital gear having 152 teeth.

Rotation of the sun gear (39) at 26.32 rpm causes the first planetary gear (40) to rotate at 24.44 rpm at the outer planetary gear (41) to rotate at 21.39 rpm, driving the orbital gear to rotate at 4.69rpm. The direction of rotation is opposite to that of the “flooding” display described above.

The “ebbing” display located forwardly of the “high tide” display has an annular display plate (14) provided with fixing holes for location of signs to display the words “low tide”, “flooding”, “high tide”, “ebbing” or other wording as appropriate for display through the aperture (12) in the upper part of the clock face.

The leading edge (42) has the silhouette of an ebbing tide, behind which, in the direction of rotation, are representations (43) of receding waves.

The drive mechanism for the “ebbing” display comprises a planetary gear arrangement having a sun gear (44) with 16 teeth and a planetary gear (45) with 76 teeth engaging the annular orbital gear (47) with 168 teeth. Rotation of the sun gear at 26.32 rpm causes the planetary gear (45) to rotate at 5.54 rpm causing the orbital gear and display to rotate at 2.51 rpm. The direction of rotation is the same as for the flooding display and opposite direction of rotation of the high tide display.

Figures 7 and 8 illustrate the rest position of the tidal display mechanism. In this position the flooding and ebbing displays are fully retracted in the clockwise direction and the flooding display is fully retracted in the anti-clockwise direction to provide a display as shown in Figure 2. The positions of the various components are shown in Figure 8.

In Figures 9 and 10 the first stage of rotation of the displays is shown, following a first incremental rotation of the sun gears by the stepper motor in response to the tidal state. The “low tide” display is rotated anti-clockwise so that it is partially visible within the aperture quadrant at the lower part of the clock face. The configuration of the various components is shown in Figure 10.

Figures 11 and 12 show a second position wherein the “flooding” display is fully rotated clockwise and the “high tide” display is rotated anti-clockwise to overly the “flooding” display. This is the changeable position and the word “flooding” is displayed in the upper aperture (12) on the clock face. This second stage is reached following 3.61 revolutions of the drive motor from rest.

Figures 13 and 14 show a third position achieved through 5.89 revolutions of the drum rest. In this position the “high tide” display is rotated clockwise through 1 IT and the “flooding” display is rotated anti-clockwise through 99. The “ebbing” display is rotated anti-clockwise by 53° to provide the display as shown in Figure 5 with the word “high tide” displayed in the aperture (12).

In a final “high tide” position in Figures 15 and 16 achieved by rotation of the stepper motor through 3.61 revolutions from rest, the “high tide” display is fully rotated through 205 anti-clockwise and the “flooding” display is fully rotated 173° clockwise. The “ebbing” display is fully rotated through 92 clockwise to provide the display.

Claims (11)

1. A tidal clock comprising a clock face and a clock mechanism, a spindle located in the face and driven by the mechanism and rotatable hands mounted on the spindle to provide a time display; a tidal display mechanism comprising a background and a plurality of laminar display members overlying the background, each member engaged to the drive shaft by a respective gear mechanism and rotatable by the shaft in response to tidal movements; wherein the clock face includes an aperture, each display member being rotatable between a respective visible location wherein the display member may be observed through the aperture and a respective hidden location wherein the display member is concealed by the clock face; wherein the gear mechanisms are adapted to successively move the display members between hidden and visible locations as the drive shaft rotates to provide a display characteristic of tidal states at different times in a tidal cycle.

2. A tidal clock as claimed in claim 1, wherein the initial angular location and rate and direction of rotation of each display are selected so that continuous rotation of the shaft between a low tide orientation and a high tide orientation causes movement of the display members between successive hidden and visible locations to provide a constant variable display observable through the aperture in the clock face.

3. A tidal clock as claimed in claim 1 or 2, wherein each display member occupies a sector of the clock circumference.

4. A tidal clock as claimed in any preceding claim, wherein each display is annular.

5. A tidal clock as claimed in any preceding claim, wherein each sector has a leading edge brought into view as the display moves from a hidden to a visible location.

6. A tidal clock as claimed in claim 5, wherein the leading edge is shaped to form a silhouette of a tidal feature.

7. A tidal clock as claimed in any preceding claim comprising a multiplicity of displays arranged in overlying axially spaced relation on the drive shaft.

8. A tidal clock as claimed in claim 7, wherein the displays are laminar, having a decorated surface facing towards the aperture.

9. A tidal clock as claimed in any preceding claim, wherein the displays comprise annular portions mounted on a circular circumferential support.

10. A tidal clock as claimed in any preceding claim, wherein the drive mechanism comprises a planetary gear arrangement for each display member.

11. A tidal clock as claimed in claim 10, wherein the gear arrangement comprises a sun gear and one or two planetary gears engaging an orbital gear located on the annular surface of the display member.