capement means 25 to a reference shaft 23 as will be hereinafter described in detail.
Considering the indicating structure in greater detail, the dram dial 20 includes a diametrical horizontal strap section which is affixed to the top of the shaft 22 by a lock pin 30. The spring 21 is held by pins 31 and 32, in a plane spiral configuration between the shaft 22 and a support plate 33 which is rigidly affixed inside the stand S. The support plate 33 holds the shaft 22 for rotation in a central aperture containing a bearing 35 and closed by a lock ring 34.
The lower end of the shaft 22 tapers to a reduced crosssection 36 which serves to couple the shaft 22 to the shaft 23 through a bushing 37. The reduced cross-section 36 dwells in damping fluid 40 which may comprise various substances termed "bouncing putty" or "silicone putty," one form of which is a silicone putty available from the General Electric Company and identified by their product number SS-91. This material is a satisfactory nonNewtonian liquid to be incorporated in an escapement in the present invention; however, other such liquids may also be employed. The compound 40 is contained in a varymg-diarneter cup 41 which is affixed to the bushing 37. In such a location, the liquid 49 provides a rigid coupling between the shaft 22 and the shaft 23 if the shaft 23 is relatively rapidly rotated. However, when the shaft 23 is stationary, and the shaft 22 is urged to rotate by the spring 21, the compound 48 permits movement between the two at a very slow and controlled rate. As a result, the escapement 25 is an exceedingly-simple mechanism.
The cup 41 is connected by a capillary passage 26 to a reservoir 38 containing mercury. The top of the cup 41 is closed by a felt pad 29 which is saturated with white oleic acid or a similar liquid softener for the putty, to prevent hardening. In this regard, it is to be noted that exceedingly good results have also been obtained by reducing the putty to the basic resin a polymer in equilibrium with monomer. In such arrangement, no oleic acid was applied and the substance remained adequately constant in consistency for reliable operation over several months. However, in an alternative arrangement, the substance is used in its prepared form with the pad 29 providing a minute quantity of softener to maintain the consistency.
The mercury reservoir 38 functions in conjunction with the escapement mechanism 25 to compensate the effects of temperature variations on the putty or liquid 40. As the temperature increases, the mercury expands, moving the liquid 49 upward in the tapered cup 40 so that a greater length of the section 36 is contacted by the liquid 40. As a result, temperature increases reducing the viscosity of the liquid 40, are compensated. A similar consideration applied to temperature drops.
Movement by the shaft 22 through the escapement 25 to register time is controlled by a clutch structure mounted on shaft 23 below the escapement. The clutch includes a free coil spring 42 extending about the shaft 23 and having one end anchored by a pin 43 to a support plate 44 which is rigidly affixed to the interior of the stand S. A similar free spring 45 (having one free end) also extends about the shaft and is anchored by a pin 46 to a pulley drum 47. The drum 47 is supported on a stub shaft 48 which is in turn supported by a support disk 49 rigidly affixed inside the stand S.
The springs 42 and 45 are controlled by solenoids in cylinder 5© incorporating upper and lower push plates 51 and 49. The solenoids are energized by normally-unenergized conductors S3a and 53b. Upon application of a voltage to the conductor 53a, the push plate 51 moves upward to compress the spring 42, permitting the shaft 23 to rotate in a clockwise direction. Otherwise, the shaft is held against such rotation.
The push plate 49 is urged downward by a spring inside
the cylinder 50 which exerts sufficient force to compress the spring 45 when the conductor 53b does not receive an energizing voltage. Upon energization of the conductor Sib, the plate 49 is moved upwardly, to extend
5 the spring 45. Therefore, the spring 45 is normally compressed; however, upon energization of the conductor 536, the spring 45 is extended to lock the drum 47 to the shaft 23 upon counter-clockwise rotation of the drum.
Considering a complete operation cycle of the structure
10 of FIGURE 2, assume that the cable 60 is pulled downwardly by an amount proportional to the denomination of a coin which has been inserted in the meter. This operation is explained below. The cable 60 is non-elastic and therefore urges the disk 47 in a clockwise direction
15 through an angular displacement proportionate to the value of the deposited coin. During this time, the conductor 53Z> is not energized, therefore, the push plate 49 compresses the spring 45 so that the disk 47 may move relative the shaft 23. As the disk 47 is displaced in a clock
20 wise direction, the spring 48 is placed in tension to urge the disk 47 in a counter-clockwise direction.
Upon acceptance of the deposited coin (as explained below) the cable 60 is released and the conductor 53b is energized to raise the push plate 49 to the position shown
25 extending the spring 45. As a result, the disk 47 is revolved in a counterclockwise direction under the force of the spring 64, by an amount indicative of the deposited coin. As the disk revolves the extended spring 45 is drawn tight clasping the shaft 23 and revolving the shaft
30 and turning the cup 41 of the escapement coupling 25 with it. As this movement is relatively rapid, the liquid 40 acts as a rigid coupling between the shafts 23 and 22 so that the rotational displacement of the shaft 23 is passed to the shaft 22 to revolve the indicating drum 20
35 so as to manifest an amount of time proportionate to the value of the deposited coin. During this operation, the clock spring 21 receives energy which is dissipated in returning the indicating drum to a zero-indicating position.
40 Upon the completion of the setting operation the conductor 53b is de-energized, so that the apparatus is ready to receive another coin to register more time on the meter.
Considering the actual timing operation, the shaft 23 is held stationary along with the cup 41, to provide a
45 reference for the escapement 25. The force exerted on the shaft 22 by the clock spring 21 now causes the shaft 22 to be slowly revolved as permitted by the escapement 25. The force exerted by the spring 21 on the shaft 22 revolves the shaft 22 at a rate regulated by the damping
50 liquid 40 in its engagement with the reduced section 36 of the shaft. As a result, an escapement is provided for the indicating drum 20 to manifest an ever-reducing amount of unexpired time, until the drum dial is fully returned to a zero-indicating position.
55 If the vehicle occupying the parking space is driven away, an electrical signal is provided in the conductor 53a as described below which energizes the upper solenoid in the cylinder 50. The energization of that solenoid causes the push plate 51 to move upwardly away from
60 the cylinder 50 compressing the clutch spring 42. During this time, the clutch spring 45 is also compressed because the conductor 53b is not energized. Therefore, the shaft 23 is no longer held as a stationary reference for the escapement mechanism but rather is free to rotate
65 and is rotated in a clockwise direction by the spring 21 acting through the escapement 25 to turn both the shafts 22 and 23 and release the energy in the spring 21 returning the indicating drum 20 to a zero-indicating position. Considering the manner in which the conductors 53a
70 and 53b are energized, reference will now be had to FIGURE 3. The conductor 536 is connected through a switch 52 to one terminal of a battery 99 which has the other terminal connected to ground. The switch 52 is a toggle device considered in detail below; however,
75 in function, the switch is closed upon the acceptance of