GB2114369A - A float operated magnetic switch arrangement - Google Patents

Abstract

A switch arrangement comprising a float 1 vertically movable in a case 2, a driven member 3 movable by the float and having a movable magnetic attracting portion 5 which cooperates with upper and lower fixed magnetic attracting members 7a, 7b disposed above and below the portion 5 in opposed relation thereto. A stop 6 is provided at a lower part of the driven member 3 for supporting the load of the float and a reed contact unit is magnetically operable by the approach or retreat of the portion 5. A contactless switching element consisting of a TRIAC is controlled by the reed contact unit. The reed contacts are instantaneously opened or closed and held opened or closed when water level reaches respective upper and lower limits set well apart due to the last-motion coupling between the float 1 and drive member 3. The apparatus is useful for automatically controlling underwater pumps. <IMAGE>

Description

SPECIFICATION Water level detecting apparatus of float type The present invention relates to a water level detecting apparatus of the float type for reliably detecting water level at two positions, namely at a predetermined upper limit and a predetermined lower limit, and more particularly to such an appar atus which is suitable for automatically controlling underwater pumps.

Conventional water level detectors for controlling the operation of underwater pumps comprise a float 1" upwardly or downwardly movable along a guide 2" in accordance with the water level, a magnet 5' provided on the float 1" and a reed switch 4' disposed within the guide 2". When the float 1" reaches a predetermined upper limit or lower limit, the magnet 5' closes the reed switch 4' as shown in Figure 8 (A). The switch 4' is opened when the magnet 5' moves away therefrom with a fall or rise of the water level as seen in Figure 8 (B). The operation of the reed switch 4' is transmitted to the motor circuit of the pump by way of a transformer and power relay.With such an apparatus, the magnet 5' moves away from the reed switch 4' to stop the pump when the water level lowers from the upper limit even if slightly, so that the range over which the water level is controllable is very small and indefinite. The apparatus therefore has the drawback that waves on the water surface cause chattering. Further for controlling the operation of the underwater pump, there is the need to use two water level detectors for starting the pump at the upper limit and stopping the pump at the lower limit.

This requires a complex arrangement outside the pump and is costly. Further since it is impossible to incorporate into the detecting apparatus the transformer and power relay which require a large space, these components must be housed in the head cover of the pump motor. The cover needs to be correspondingly larger, consequently rendering the motor large-sized. If it is attempted to modify a nonautomatic pump to an automatic pump, there arises the necessity of preparing a new head cover. The labor and expenditure then needed will be unjustifiable. Accordingly it is practically impossible to incorporate a water level detector into an existing non-automatic pump to render the pump automatically operable, and automatic pumps equipped with such a detector must be designed initially for automatic operation.

The present invention provides a water level detecting apparatus of the float type comprising a case supported by a holder and adapted to be placed in water, a float fitting in the case and slidable upward or downward, a driven member fitting to the float and having a movable attracting portion, an upper fixed attracting member and a lower fixed attracting member disposed above and below the movable attracting portion respectively in opposed relation thereto and spaced apart by a specified distance, a stopper provided at a lower portion of the driven member for supporting the load of the float, a reed switch provided in an upper portion of the case and magnetically operable by the movable attracting portion when the portion moves toward or away from the reed switch, and a contactless switching element comprising an electronic circuit consisting essentially of a TRIAC.The reed switch is electrically connected to the switching element to open or close an actuating circuit for the TRIAC when the switch is operated as above. The movable attracting portion of the driven member is held attracted to the lower fixed attracting member before the level of water rises to a predetermined upper limit, but the portion is moved away from the lower fixed attracting member and attracted to the upper fixed attracting member by the action of the float when the water level reaches the upper limit to operate the reed switch by the change of the position of the movable attracting portion relative to the reed switch.The movable attracting portion is held attracted to the upper fixed attracting member before the water level lowers to a predetermined lower limit, but the portion is moved away from the upper fixed attracting member and attracted to the lower fixed attracting member by the pressure acting on the stopper when the water level reaches the lower limit to reversely operate the reed switch by the change of the position of the movable attracting portion relative to the reed switch. Thus a pump motor can be brought into or out of operation when the TRIAC actuating circuit is opened or closed by the opening or closing of the reed switch at the upper limit level or the lower limit level.

The present invention will be described below in greater detail with reference to the accompanying drawings, in which: Figure 1(A) is a side elevation partly in vertical section and showing an embodiment of the invention; Figure 1(B) is a bottom view showing the same; Figures 2 to 4 are side elevations partly in vertical section showing other embodiments of the invention; Figure 5 (AJ is a plan view showing a switching element incorporated in the apparatus of the invention; Figure 5 (BJ is a side elevation partly in vertical section and showing the same; Figure 6 rA) is a side elevation showing the water level detecting apparatus of the invention as attached to an existing underwater pump;; Figure 6(B) is a side elevation partly in vertical section and showing the same; Figures 7(A) to rDJ are diagrams illustrating the operation of the present apparatus; and Figures 8 lAJ and fBJ are diagrams illustrating the operation of a water level detector used for conventional underwater pumps.

With reference to the drawings, a case 2 has fitted therein a float 1 which is movable upward and downward. A driven member 3 is movable upward and downward within the case 2 to follow the vertical movement of the float 1. For example as seen in Figure 1 (A) and Figure 2, the driven member 3 comprises an upper portion 3a in the form of a short hollow cylinder so as to be movable upward and downward externally around a reed switch 4 and a lower portion 3b in the form of a slender rod extending through a vertical bore in the float 1.

Alternatively the driven member 3 is in the form of a frame having the float 1 vertically movably housed therein as shown in Figure 3. Further as seen in Figure 4, the driven member 3 may be in the form of a short hollow cylinder having an extension 1' of the float 1 fitted therein vertically movably. In any of these forms, the driven member 3 has a movable attracting portion 5 opposed to an upper fixed attracting member 7a disposed thereabove and to a lower fixed attracting member 7b disposed therebelow. The driven member has a stopper 6 at its lower portion for supporting the load of the float 1. The stopper 6 may be engageable with the float 1 directly or with the neck portion of the extension 1' to indirectly support the load of the float 1. The reed switch 4 is disposed in an upper portion of the case 2.The fixed attracting members 7a, 7b are spaced apart by a predetermined distance. When moving toward or away from the reed switch 4, the movable attracting portion 5 produces a varying magnetic action, by which the reed switch 4 is opened or closed. The portion 5 is adapted to be held attracted to either one of the attracting members 7a, 7b, as separated from the other.

The movable attracting portion 5 may be made of a magnet, for example, and the upper and lower fixed attracting members 7a, 7b may be made of soft iron. The movable attracting portion 5 shown in Figure 1 (A) is a magnet. When it is brought into contact with the upper attracting member 7a against the lower attracting member 7b of soft iron, the reed switch, which is usually open, is closed. The reed switch 4 is returned to the open state when the portion 5 is brought into contact with the lower attracting member 7b against the upper member 7a.

Alternatively the upper and lowerfixed attracting members 7a, 7b may be made of a magnet, while the movable portion 5 may be made of soft iron as seen in Figure 2. The portion 5, when coming into contact with the upper attracting member 7a, closes the usually open reed switch 4. When coming into contact with the lower attracting member 7b against the upper member 7a, the movable portion 5 opens the reed switch 4. The portion 5 is moved away from the lower member 7b by the movement of the float 1 when the water level reaches a predetermined upper limit, such that the portion 5 is separated from the lower member 7b instantaneously and brought into contact with the upper member 7a at the same time.

The movable portion 5 is separated from the upper member 7a by the pressure acting on the stopper 6 when the water level reaches a predetermined lower level, such that the portion is moved away from the upper member 7a into contact with the lower member 7b instantaneously. Thus the reed switch 7 is opened or closed instantaneously and is also held opened or closed stably.

The operative relation between the float 1 and the driven member 3 will be described in greater detail.

The float and the driven member are so designed that the buoyant force of the float 1 floating in the usual state during the rise of the water level is slightly smaller than the force restraining the driven member from rising which force is equal to the force of attraction between the lower fixed attracting member 7b and the movable attracting portion 5 plus the load of the driven member 3.They are further so designed that the upward restoring force of the float when it is entirely submerged is greater than the restraining force and that the force of attraction between the upper attracting member 7a and the movable portion 5 is slightly greater than the force acting to lower the driven member3 under gravity but is smaller than the increased lowering force afforded by the weight of the driven member 3 and the weight of the float 1 on the surface of the water when the float 1 is to leave the water.

Accordingly even when the float 1 acts to push up the driven member 3 while rising with the rise of the water level, the driven member 3 remains in its lowered position without rising, with the movable attracting portion 5 held attracted to the lower member as seen in Figure 7 (A). As the water level further rises in this state, the submerged volume of the float 1 prevented from rising increases.When the water level reaches the upper limit t1 with an increase in the submerged volume of the float 1, the buoyant force accumulated in the float 1 overcomes the force of attraction between the portion 5 and the lower member 7b, whereupon the upward restoring force of the float 1 pushes up the driven member 3, instantaneously moving the portion 5 out of contact with the lower member 7b into contact with the upper member 7a and opening or closing the switch 4 simultaneously (Figure 7 (B)). The portion 5 is forced away from the lower member 7b into contact with the upper member 7a instantaneously magnetically. After the reed switch 4 is opened or closed at the upper limit level, the switch 4 is held open or closed with the portion 5 held attracted to the upper member 7a without any likelihood of chattering due to waves on the water surface or the like.Further even when the float 1 acts to lower the driven member 3 while descending with a fall of the water level, the driven member 3 remains in its raised position without lowering, with the portion 5 held attracted to the upper member 7a as seen in Figure 7 (C). As the water level further falls with the float 1 in engagement with the stopper 6, the submerged volume of the float 1 decreases. When the water level reaches the predetermined lower limit t2 with a decrease in the submerged volume of the float 1,the resulting increased pressure on the stopper 6 acts to lower the driven member 3 against the force of attraction, forcing the movable portion 5 out of contact with the upper member 7a into contact with the lower member 7b as seen in Figure 7 (D) and closing or opening the read switch 4 at the same time. The portion 5 is thus moved magnetically instantaneously. After the reed switch 4 is closed or opened at the lower limit level, the switch 4 is held closed or open with the portion 5 held attracted to the lower member 7b without any likehood of chattering due to waves on the water surface or the like. In this way the present apparatus operates reliably.

The present apparatus further includes a contactless switching element 8 comprising an electronic circuit consisting essentially of a TRIAC 9. The element 8 is housed in a holder 10 supporting the upper end of the case 2. Lead wires 4a, 4b extending from the contact pieces of the reed switch 4 are connected to the input terminals of the element 8, while a power supply lead wire 8a and a loading lead wire 8b extend from the output terminals thereof.

Thus the reed switch 4 is electrically connected to the switching element 8 so as to open or close an actuating circuit for the TRlAC 9 when opened or closed by the approach or retreat of the movable attracting portion 5 with the movement of the driven member 3 due to the movement of the float 1.

Figures 5 (A) and (B) show a mount 11 for the TRIAC 9, heat releasing fins 12, resistors 13 and a capacitor 14. The case 2 is formed, for example, with a lower water opening 15 at its bottom and upper water openings 15' at an upper portion of its wall (Figures 6 (A) and (B)) to render the float 1 smoothly movable upward or downward with the rise or fall ofthe water level. The case 2 is fitted or screwed in the base portion of the holder 10.

The apparatus of this invention will be used for automatically controlling the operation of an underwater pump 25 in the following manner. The forward end of the holder 10 is formed with an attaching portion 17 to be fitted to a wire outlet 16 at an upper portion of the pump 25. The attaching portion 17 is centrally formed with a bore 18 to communicate with the outlet 16. The output wires 8a, Sb of the switching element 8 are led out through the bore 18 and individually connected to one wire 19a of a power supply cord 19 and one wire M1 from the motor. With the cord 19 extending through a watertight seal member 20 above the bore 18, the attaching portion 17 is fastened to the outlet portion 16 by a holding cover 21 and a bolt 22.The attaching portion 17 has a bolt hole 24' in alignment with a screw hole 23 formed in the outlet portion 16 and with a bolt hole 24 formed in the cover 21. The bolt 22 is inserted through the holes 24, 24' and screwed into the hole 23, whereby the holder 10 is attached to the upper portion of the pump 25, with the case 2 extending downward at one side of the pump 25 as seen in Figures 6 (A) and (B). The other wire 19b of the cord 19 is connected directly to the other wire M2 from the motor. The pump 25 has a water inlet 26 and a water outlet 27.

The underwater pump 25 is used, for example, for discharging water from a tank in the manner to be described below with reference to Figures 7 (A) to (D). When the float 1 within the case 2 rises as seen in Figure 7 (A) as the water level within the tank rises gradually with the flow of water into the tank, the movable attracting portion 5 remains attracted to the lower fixed attracting member 7b to prevent the driven member 3 from rising before the water level reaches the upper limit t1. Upon the water level reaching the upper limit el, the float 1 acts to move the portion 5 away from the member 7b into contact with the upper member 7a (see Figure 7 (B)), thereby magnetically closing the reed switch 4 to bring the output circuit of the switching element 8 into conduction.The pump 25 operates, drawing water into the inlet 26 and discharging the water from the outlet 27 to discharge the water from the tank. Even when the water level within the tank consequently falls and lowers the float 1 as seen in Figure 7 (C), the movable portion 5 remains attracted to the upper member 7a to prevent the driven member 3 from lowering before the level reaches the lower limit.

With the reed switch 4 held closed, the pump 25 is held in operation to continuously discharge water.

When the water level reaches the lower limit t2 with a further fall, the pressure acting on the stopper 6 moves the attracting portion 5 of the driven member 3 out of contact with the upper member 7a into contact with the lower member 7b as seen in Figure 7 (D), magnetically opening the reed switch 4 to break the output circuit of the switching element 8 and stop the operation of the pump 25. In this way the pump is automatically controlled by instantaneously and smoothly detecting the water level at two positions, i.e. the predetermined upper limit t1 for starting the pump and the predetermined lower limit & for stopping the pump.

Unlike the above mode of use, it is also possible to install the pump within a tank for supplying water into the tank from an external source. In this case, the movable attracting portion 5 and the upper and lower fixed attracting members 7a, 7b are arranged in the mode shown in Figure 2 to start the motor at a predetermined lower limit water level for supplying water and to stop the motor for the interruption of supply when the water level reaches a predetermined upper limit. In either case, the range of effective movement of the float 1 can be set as desired by suitably determining the axial lengths of the float 1 and the driven member 3, whereby the distance between the upper limit t1 and the lower limit t2 for the water level, namely the control range, can be set as desired.

The water level detecting apparatus of the float type according to the invention has the following advantages over the conventional detectors of the same type. First, the driven member is held at rest by a force of magnetic attraction when the water level reaches a specified upper limit, while the float and the driven member are greatly spaced from the reed switch with the driven member magneticalLy held at rest when the water level reaches a specified lower limit, so that the reed switch can be held closed or open without any chattering even in the presence of waves. Second, since the reed switch is quickly operated only at the upper limit and lower limit, the water level can be detected properly at two positions with use of the single apparatus. Moreover the distance between the upper limit and the lower limit of the water level, namely the water level control range, can be set as desired by suitably determining the distance of effective movement of the float.

Because a water pump is automatically controllable without the necessity of using two water level detectors for starting the pump at the upper limit and for stopping the pump at the lower limit which are conventionally employed, there is no need to use a complex arrangement externally of the pump. Third, the operation of the reed switch is transmitted to the motor circuit through the contactless switching element having an electronic circuit consisting essentially of a TRIAC, so that the motor circuit produces no spark upon energization or deenergization and can therefore be sealed off advantageously. The switching element, which is contactless, is resistant to vibration and usable for a prolonged period of time. The apparatus is much smaller and more inexpensive than the conventional arrangement wherein a power relay and transformer are used. Fourth, the switching element is housed in the holder, that is, the element is incorporated in the water level detecting apparatus, so that there is no need to accommodate a transfer or power relay in the motor and therefore to prepare a new head cover for providing the accommodating space conventionally needed for modifying an existing non-automatic pump to an automatic pump. According to the invention, an existing pump can be made automatically controllable only by attaching the holder to the head cover of the pump motor. The pump so modified can be changed to the original nonautomatic pump readily by removing the holder from the head cover.

Claims (7)

1. A water level detecting apparatus of the float type comprising a case supported by a holder and to be placed in water, a float fitting in the case and movable upward and downward, a driven member fitting to the float and having a movable attracting portion, an upper fixed attracting member and a lower fixed attracting member disposed above and below the movable attracting portion respectively in opposed relation thereto and spaced apart by a specified distance, a stopper provided at a lower portion of the driven member for supporting the load of the float, a reed switch provided in an upper portion of the case and magnetically operable by the movable attracting portion when the portion moves toward or away from the reed switch, and a contactless switching element comprising an electronic circuit consisting essentially of a TRIAC, the reed switch being electrically connected to the switching element to open or close an actuating circuit for the TRIAC when operated, the movable attracting portion being adapted to be held attracted to the lower fixed attracting member before the level of water rises to a predetermined upper limit, the movable attracting portion being movable away from the lower fixed attracting member and attractable to the upper fixed attracting member by the action of the float upon the water level reaching the upper limit to operate the reed switch by the change of the position of the movable attracting portion relative to the reed switch, the movable attracting portion being adapted to be held attracted to the upper fixed attracting member before the water level lowers to a predetermined lower limit, the movable attracting portion being movable away from the upper fixed attracting member and attractable to the lower fixed attracting member by the pressure acting on the stopper upon the water level reaching the lower limit to reversely operate the reed switch by the change of the position of the movable attracting portion relative to the reed switch.

2. An apparatus as defined in claim 1 wherein the driven member movable upward and downward within the case has a lower portion in the form of a rod extending through a vertical bore in the float.

3. An apparatus as defined in claim 1 wherein the driven member movable upward and downward within the case is in the form of a frame fitting externally around the float.

4. An apparatus as defined in claim 1 wherein the driven member movable upward and downward within the case has fitted therein an extension of the float, and the stopper is engageable with a neck of the extension to support the load of the float.

5. An apparatus as defined in any one of claims 1 to 4 wherein the reed switch is usually in an open state, is closed by the movable attracting portion when the portion moves toward the reed switch and is opened by the movable attracting portion when the portion moves away from the reed switch.

6. An apparatus as defined in any one of claims 1 to 4 wherein the reed switch is usually in a closed state, is opened by the movable attracting portion when the portion moves toward the reed switch and is closed by the movable attracting portion when the portion moves away from the reed switch.

7. Awater level detecting apparatus constructed and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.