CA1180079A - Electrical switch devices - Google Patents

Abstract

ELECTRICAL SWITCH DEVICES

Abstract Float-controlled electrical switch includes a reed contact which is opened and closed by the field of force of a permanent magnet. The permanent magnet is embedded in a float which can be moved by rising and falling liquid levels towards and away from the reed contact for closing and opening of the reed contact. The reed contact cooperates with a relay which provides for engaging and disengaging of a working contact for engagement and disengagement of a bilge pump or another power device in connection with inspection of two separate liquid levels. Provision is made for a large distance between the liquid levels together with markedly distinct positions for engagement and disengagement of the reed contact by allowing the electromagnetic field of force of the coil of the relay to cooperate with the field of force of the perma-nent magnet. Provision is made for the field of force of the coil to be less than the field of force of the permanent magnet while the field of force of the coil alone is too weak to maintain the reed contact engaged.

Description

ELECTRICAL SWITCH DEVICES

This invention relates to electrical swi-tch devices and, more particularly, to fl.oat-controlled electrical switch devices.
A conventional reed magnet switch is shown in United States Patent Specification No. ~,823,328.
I~he present invention finds more particular application in the control of the liquid level in the bottom of a boat, such as a sail boat or motor boat~ The switch device according to the invention shall, in a case of application, control the engagement and disengagement of a bilge pump for removing liquid which has collected in the bottom of the hoat, gradually as there is a need for it, ~hat i.s to say in an automatically controlled manner determined hy a fixed upper and lower level of liquid in the bottom of the boat. Stated in another way, the switch device provides for the bilge pump to be engaged when the liquid level has risen sufficiently high in the boat and for the bilge pump to remain engayed until the liquid level in the boat has sunk again to the determined lower level in the boat. It is a permanent magnet which engages and disenyages the switch de-vice, the permanent magnet being controlled towards and away from a reed con-tact of the dev.ice by means of a buoyancy force in a Eloat which follows the moveme.nts of the liquid between upper and .lower liquid levels.
The invention i.s, however, not limlted to appli.cation for bilge pùmps but can also be used for various other types of electrically driven power means which will function in connection with a controlled liquid level, for example, the liquid level in a tank, in a flow passage or for similar purposes. In the following description, the invention will be described havlng reyard to its application in connection with a bilge pump in a ,~ .

boat.
In IJnited States Patent Specification No. ~,165,935 there is disclosed a level switch which operates according to the reed principle but where two magnets are employed, the one ~or opening the reed contac-t and the other ~or closing the reed contact. In this case, there is a level switch where the regu-lating distance is limited by the length of the reed contact.
Furthermore, the level swi~ch is particularly critical as regards the level for engagement and -the level for ~isengage-ment since the two magnets must be adapted to each other and this adaptation must be adjusted in every single case. In addition, there is the possibility for different age weakenlng of the two magnets, something which, in turn, will be able to disturb the desired effect.
In the use of a reed co~tact and an associated moveable magnet, there can be obtained, under normal working conditions, a particular level for engaging the bilge pump and a corre-sponding par-ticular level for disengaging the bilge pump, fixed by an upper and a lower liquid level with a distance o~, ior example, 5 mm between the liquid levels. By increasing or reducing the strength of the permanent magnet, the distance between the liquid levels can be increased or diminished to a certain degree but, at the same time, the distance between the reed contact and permanent magnet will also be increased or reduced in the engagement position (upper liquid level). This can be compensated i-or to a certain degree by increasing or reducing the A/turn number for the reed contact. In all cases, however, it is difficult to attain a desired significant distance between the upper and lower liquid level, that i5 to say the engagement and disengagement positions of the permanent maynetic ~ield of force o~ the ~loat.
In certain instances, ~or example, as a consequence o~
the movements of the boat during heavy seas and from this ensuiny roll:ing and pitching movements of the boat and corre-sponding splashing movements o~ the collection o~ water in the bottom o~ the boat, the above-mentioned distance between upper and lower liquicl levels is too small so that, in practice, a pulsating engagement and disengagement of ~he bilge pump can result produced by the movements of the boat.
As a result of the relatively moderate distance between the upper and lower liquid levels in the bottom of the boat, the bilge pump also has the tendency to expel relatively moderate amounts o~ liquid in each pumping operation and often there is the question, therefore, of a relatively frequent engagement and disengagement of the bilge pump with relatively poor efficiency of the pump and wi-th a larye loading on the pump and swi-tch componen-ts, under otherwise Ea~orable operative conditions with modera-te movements of the boat.
Wi~h the present invention the aim is to achieve a sub-stantially greater distance between upper and lower liquid levels, without thereby altering the permanent magnet and its fieId of force but,nevertheless, so that a less frequent engage-ment and disengagement of the bilge pump is obtained together with longer intervals with the bilge pump engagéd. At the same time, the aim is to obtain a more pronounced division between the level for engaging and disengaging the reed contact.
According to the present invention an electrical switch device comprises (a) a permanent magnet, (b) a reed contact openable and closeable by means of the field of force of said magnet, the axial direction of the reed contact extending parallel to the N-S direction of said magnet, (c) outer actuating force means for moving said magnet towards and awa~y from the reed contact in an accurately con-trolled, rec-tilinear path of movement, and (d) a relay disposed relatively tightly up to said reed contact and coupled in series therewith, said relay having a coil wi-th an electromagnetic field of force wealcer than the field of force oE said mac3net and too weak to alone ]ceep tlle reed contact engaged.
By the solution according to the invention, engagement is obtained at an upper level in a known manner quite indepen-dently of -the field of force of the permanent magnet. However, when the reed contact is first ~ngaged, it is ensured that this is kept engaged since, at the same -ti~, an extra field of ., , . ~ .

b 1 ~ 0 ~

force is established over the reed contact produced ~y the electromagnetic field of force in the coil o-f the relay. This extra field of force will cooperate wi-th the field of force of the permanent ma~net so long as the reed contact is engaged and thereby as lon~ as the bilge pump is in opera-tlon. By the solution according to the invention, one thus arrives, as a consequence of the combined action or the field of force of the coil and the permanent magnet, at being able to move the float with associated permanent magnet a significantly larger distance below the upper liquid level before the lower liquid level is reached where the reed con-tact opens and thereby ~
breaks the current -to the relay with associated coil and simul-taneously breaks the curren-t to the bilge pump. Also accordlng to the inv~ntiOn,a fixed level for disenyaJing the reed con-tact is arrived at, and a main advantaye according to the in-vention is that the fixed level for disengaging the reed con~
tact is markedly separate from the level for engaging the reed contact.
On newly engaging the reed contact after the permanent magnet in the floa-t has risen again to the upper li~uid level, one is only dependent upon the field of force of the permanent magnet for engagement of the reed contact, -the field of force of -the coil at this stage not yet being enyaged. Consequently, according to the invention, there are ensured markedly separate engagement and disengagement levels with a relatively large distance between the levels, and thereby one has ensured against unintentional, accidental engagements and disengage-ments of the bilge pump and, at the same ti~e, there is guaran-teed relatively longer opera tiOIl times of the bil~e pump each time it is engaged.
Accordiny to the invent.ion, there is attained an especi-ally accurate enyayement ~nd disengagement by allowin~ the axial direction o the reed contact to extend at riyht angles across the axial direction of the coil of the relay.
In a part:icularly preferred, practical construction o~
breaker accordiny -to the invention this i.s characterised in that its electrical components which, ln a manner known ~ se, are embedded in an electrically insulatiny synthetic plastics o~g material in the housiny part of the breaker, are arran~ed in.an upper sleeve-shaped portion of the housing part, and that the lower portion of the housing part forms a guide charnber for a float which forms a support for the per~anen-t magnet, the Iower portion of the housing part being provided above with an air passage and below with a passage for liquid. In this way, there is obtained a constructional solution which involves a ready ~anufacture of the various components and parts of the switch and a simple mounting of these components and parts.
It is preferred that the housing part is macde of rectangu-lar plastic pipe (preferably polyvinyl chloride pipe) and its lower portion includes a float of rectangular cross~section which prevents angular displacement of the floa-t relative to the housing part.
Especially with easy mounting in view but also with the thought of ready dismantling with inspection and cleaning of the float and its guide chamber, it is preferred that the float is received in a drawer-like insert mernber made of a pipe frag-ment of rectangular cross-sec-tion, two opposing side walls of the insert member forming an upper and lower limit of the guide chamber of the float.
In order that the invention can be more clearly under stood, a convenient embodiment thereof will now be describ-ed, by way of example, with reference to the accompanying drawings in which:
Fig. 1 is an electrial coupling diagram of a switch device used in connection with a bilge pump which is submerged in a liquid at the bottom of a boat, Fig. ~ is a perspective view of the switch device of Fig. 1 showing different parts of the device drawn axially out-ward.s relative to each other in orcler to illustrate the simple construction and the sirnple mounting of the parts of the swi-tch clevice.
Fiy. 3 is another perspective view o~ the switch device of Fiy. 1 showing the device ready for coupling toyether with the bilge pump or another power means and the associated direct current, and Fiys. 4 and 5 are sketches illustra-ting two different modes of mounting of the switch device of Fig. 1.
Referring to Fig. 1, direct current-driven bilge pump 10 and float controlled switch devi~ce 1~ for controlling two liquid levels, namely an upper li~uid level 12 shown in a ull line and a lower liquid level 13 shown in a broken line, are shown electrically coupled together. The two liquid levels 12, 13 are the actual llquid levels in the bottom of a boa-t. The upper level 12 indicates the level for s-tarting of -the bilge pump 10 while the lower level 13 indicates the level for stopping the bilge pump. The bilge pump is submerged below the lower level and in all cases provision i~s made for the intake oE the bilye pump to be submerged below the lower level 13.
From a source of direct current, for example, a 12 volt battery tnot shown), as illustrated by positive and negative terminals 15, 14, there extends a first lead 16 from the nega-tive terminal 14 to one side of the bilge pump and, from the other side of the bilge pump, there extends a second lead 17 -to the one side of a working contact 18 while from the other side of the working contact 18, a third lead 19 extends to the positive terminal 15. The leads ~6, 17, 19 form a working circuit from the battery to the bilge pump via the float~
controlled switch device 11.
From the lead 16, there extends ~ branch lead 20 via a first diode 21 of 100 mA to the one side of a reed contact 22 having 25 - 30 A~turn. Erom the opposite side of the reed con-tact 22,there extends a lead 23 to the one side of a coil 24 in a relay 25 which comprises the working contact 18. The coil 24 is dimensioned for an electric current of 100-110 mA. From the opposite side of the coil 24 there extends a lead 26 to the lead 19. Between two terminals 27, 2~ whlch are each connected to a respective side of the coil 2~, there is ln serted a second diode 29 o~ 100 mA parallel to the coil 24~
Tlle leads 20, 23, 26 with associated reed contact 22 and coil 24 form a control clrcuit for the relay 2S which controls the working contact 18. By means of the diode 21, sparkiny in the reed contact 22 is counteracted by opening of the latker,and by means of the diode 29, faulty coupling of the leads 16 and 19 to the po.sitive and negative terminals of the battery is prevented.
From Fig. 1, it is evident that the electrical components of the switch device, namely the reed contact 22, the relay 25 and the diodes 2], 29, are received in the upper portion 30a of a sleeve-shaped housing member 30 made of rectangular PVC
pipe while the lower portion 30b of the housin~ mer~er forms a guide for a float 31 which has a corresponding rectangular cross-section and which includes a permanent magnet 32 embedded in a foamed plastic material 33. Outermost the foamed plastic material is surrounded on four sides by a casing 34 o~ a rec-tangular PVC pipe fragmen-t,and on the two outer sides it is covered by an epoxy ba.sed hardening plastic (STYCAST 2651 and catalyst 9) supplied by Emerson & Cunning, Inc., Bel~ium. The lower portion~30a of the housing part 30 is defined by a drawer-like insert part 35 in the form of a rectangular PVC
pipe ~ragment. The pipe fragment 35 is placed on edge so that two of its opposing sides form upper and lower boundary surfaces of the float 31.
In Fig. 1, the float 31 is shown, in full lines, in an upper position and the float is shown, in broken lines, in a lower position in -the lower portion of the housing part 30.
There is illustrated an upper air passage 36 in the wall of the housing part 30 just above the float 31 in its upper position and a lower passage 37 for liquid in the wall of -the housing part 30, just below the float 31 in its lower position. Pro-`
vision is made for the passage 37 for liquid to open out into the guide in the housing part 30, at a level significantly be-low the lower liquid level 13 in order to counteract the pene~
tration of any oil which floats on top of the liquid in the bottom of -the boat. The passage 37 for liquid is dimensioned so that there is li-ttle influence on the liquid level in the housin~ part due to wave movements or splash movement~ in the liquid outside the housing part 30.
Provision is made for the W-S direction of the permanent magnet 32 to extend parallel to the axial direction of tlle reed contact 22 anc1 with its N-pole turned towards the positive. side of the reed contact 22 and its S-pole turned towards the nega-tive side of the reed contact 22. In this connection, lt is i~ l t~ ~ c~ f-"J t~

~ . .

of importance tha~ the float 31 and the guide internally in the housing part 30 -together with the insert part 35 are designed with corresponding rectangular cross-sections so that uninten-tional turning of the float in the housing part 30 is avoided~
The insert part 35 is pushed ~together with the float 31) into the housing part 30, as is indicated in Figs~ 1 and 2, with a relatively narrow fit, while the float 31, as ls indica-ted in Figs. 1 and 2, is received with a relatively abundant fit in the housing part 30 and the insert part 35.
In the drawing in Fig. 1, the axial direction of the coil 24 is shown for the sake of simplicity parallel to the axial direction of the reed contact 22 but, in practice, provision is made for the axial direction of the coil to extend at right angles across the axial direction of the reed contact so that the force field lines conincide wi-th the force field lines of the permanent magnet.
On mounting the elctrical components of the switch device in -the housing part 30, there is employed a relay 25 built into a housing part 25a and the latter is fastened, via coupling clamps 38, 39, 40, to a three lead cable 41 (including the leads 17, 19, 20) having an outer PVC casing, as is shown in Fig. 2. The diodes 21 and 29 and the reed contact 22 together with the associated leads are fastened into posLtion outside the housing of the relay 25, as is shown in Fig. 2.
After the insert part 35, with the float 31, is pushed into position in the lowerportion of the housing part 30, pro-vision is made first for a sealing between the insert part 35 and the housing part 30, for example, by means of a silicone coating. Afterwards the upper portion of -the housing part 30 is filled with a suitable amo~lnt oE the said two component epoxy-based hardenlny plastic (ST~CAST 2561 and catal~st ~), after which the relay 2.5 wlth associated lead connections, reed contact and diodes are submerged in the harclening plast:Lc.
Provision is made for the hardening plasti.c to be filled to a sui-table level upwardly Oll the PVC casing of the cable 41. By means o~ -the hardened hardening plastic 42, there is achieved an efective mechanical connection between the casing of the cable 41 and the housing part 30 ~together with the ln~ert p~rt 35) at the same time as the electrical components and associated connections are received in a protective manner in the housing par-t, embedded in an electrically insulating, flame-proof material.
Instead of the illustrated mechanical connection which is established between the hardening plastic and the insert part 35, tha insert part can be axially displaceably recei~ed in the housing part 30 so that the insert part with associated float 31 can be taken out for cleaning and possible replacement of the float, where this seems desirable. In the last-mentioned instancet the insert part 35 can, for example, be fastened in the housing part by a friction fit or can be fastened to ~he housing part with a transverse fastening screw or with other suitable fastening means.
In Fig. 3, the switch device 11 is shown in a finally made condition with associated cable 41 ready for mounting. A
screw fastening hole 43 is shown at the upper end of the switch device for securing the switch device to a suitable fastening in the bottom of the boat, as is indicated in Fig. 4, so that the switch device is stationarily sacured at the bottom of the boat received in a keel countersinking 44 in the same. Alter-natively, the switah device can be suspended freely hanging over a bottom 46 of the keel countersinking via cable 41 oE
the switch device, as is shown in Fig. 5. The last-mentioned can be particularly relevant in a case where the keel counter-sinking is relatively deep and problems can be presented in fixing the switch device to a suitable fàstening at a suffi-ciently low level in the keel countersinking.

Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Electrical switch device which comprises (a) a permanent magnet, (b) a reed contact openable and closeable by means of the field of force of said magnet, the axial direction of the reed contact extending parallel to the N-S direction of said magnet, (c) outer actuating force means of moving said magnet towards and away from the reed contact in an accurately con-trolled, rectilinear path of movement, and (d) a relay disposed relatively tightly up to said reed contact and coupled in series therewith, said relay having a coil with an electromagnetic field of force weaker than the field of force of said magnet and too weak to alone keep the reed contact engaged.

2. The device of claim 1, wherein float means support the permanent magnet and the outer actuating force means is the buoyancy of said float means.

3. The device of claim 2, wherein the axial direction of the reed contact extends at right angles across the axial direction of the coil of the relay.

4. The device of claim 2, which comprises a housing for its electrical components which are embedded in an electrically insulating material in said housing, an upper sleeve portion of said housing having said electrical components arranged therein and a lower portion of said housing forming a guide chamber for said float means and being provided above with an air passage and below with a passage for liquid.

5. The device of claim 4, wherein the housing is composed of rectangular pipe made of a synthetic plastics material and said float means is of rectangular cross-section to prevent its angular displacement relative to the lower portion of said housing.

6. The device of claim 4, wherein the lower portion of said housing has a drawer-like insert formed from piping of rectan-gular cross-section, two opposing sides of said insert forming upper and lower limits of the guide chamber for the float means.