CA1228408A - Housing for float switch mechanism - Google Patents

Abstract

HOUSING FOR FLOAT SWITCH MECHANISM
Abstract A sheet-metal housing for a float switch mechanism of the type which can be mounted in an aperture of a tank or vessel. The mechanism comprises a body portion to which the housing is connected, and a float which is held captive in the housing, the latter being electrical-ly conductive and the float carrying an electrical con-tact for engagement with an inner housing wall in re-sponse to changes in the level of liquid in the vessel.
The housing is constituted as a one-piece sheet metal member that is bent into a cylindrical shape from a flat metal stamping, and has a pair of adjoining longitudinal edge portions one of which comprises a lateral offset to enable it to overlap the other. One edge portion has an aperture, and the other edge portion has a tab which extends radially outward through the aperture and is bent back upon the outer surface of the first edge por-tion so as to securely retain the portions against sep-aration. The apertured edge portion is thus sandwiched between the other edge portion and the tab. In addition, there is at least one abutment disposed at the end of the member and extending partially across said end so as to engage and hold the float captive therein. Pre-plated metal stock can be advantageously employed, eliminating the need for plating operations following assembly. The advantage of the present invention over the devices of the prior art is mainly that manufacturing costs are reduced compared to those which would be incurred if the housing were to be made as a drawn sheet metal part.

Description

HOUSING FOR FLOAT SWITCH MECHANISM
This invention relates generally to float mocha-nisms of the type intended to be carried in an aperture wall of a liquid-containing tank or vessel/ and more particularly to mechanisms of the kind incorporating a movable float carrying an electrical contact which is engage able with an inner wall surface of the float house in in response to changes in the level of the liquid being monitored or gauged.
Such devices incorporate a tubular threaded body which constitutes a mounting for the mechanism, and a cylindrical casing or housing in which a float is car-fled. The float has one electrical contact that engages the inner surface of the casing wall in response to a fall in the liquid level, and another contact that en-gages an insulatedly mounted, conductive cup of the body portion. Electrical continuity to ground is thus stab-fished from the casing to the cup The latter is in turn connected to a connector receptacle, and the come pletion of the ground circuit is employed to operate a warning light or other indicator, so as to alert the driver or other person that the level of liquid had fat-ion below a pro determined point.
The casing of one particular prior device was con-stituted as a drawn sheet-metal shell, and had openings in its side and end walls which were punched out follow-in a drawing procedure. While the operation of this prior device has been found to be satisfactory, the use of drawn metal parts necessitated successive punching operations that constituted a significant expense, due to the labor involved with the multiple fabricating steps. In addition, plating of the completed pieces, if required, usually was undertaken as a separate process following completion of the formation of the casing.
The above disadvantages of prior float mechanisms are largely obviated by the present invention which pro-vises, in a float switch mechanism ox the type having a tubular body portion by which the mechanism can be mount-Ed in an aperture of a tank or vessel, and having an electrically conductive housing connected to the body portion and a float which is held captive in the housing and movable therein, and wherein the gloat carries an electrical contact for engagement with an inner wall of the housing in response to changes in the level of it-quid in the vessel, the improvement comprising said float housing being in the form of a one-piece sheet-metal casing formed into a cylindrical shape f rum a metal stamp-in, said casing having an elongate axis and having par-allot to its axis a pair of adjoining longitudinal edge portions one of which has a lateral offset to enable it to overlap the other, means defining an aperture in said casing adjacent that one of the edge portions which has the said offset, and said casing having a tab on the other of said edge portions extending radially outward through said aperture and bending back upon said one edge portion so as to securely retain said edge portions against separation, said aperture edge portion being sandwiched between the said other edge portion and said tab, and abutment means disposed at one end of said gas-in and extending at least partially across said end so as to engage and hold the float captive in said casing.

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The invention further provides in a float switch mechanism of the type having a tubular body portion by which the mechanism can be mounted in an aperture of a tank or vessel, and having an electrically conductive housing connected to the body portion and a float which is held captive in the housing and movable therein, and wherein the float carries an electrical contact for en-gagement with an inner wall of the housing in response to changes in the level of liquid in the vessel, the improvement comprising said float housing being in the form of a one-piece sheet-metal casing formed into a cylindrical shape from a metal stamping said casing having an elongate axis and having parallel to its axis a pair of adjoining longitudinal edge portions which engage one another in abutting relation, means on one of said edge portions defining a reentrant configuration, means on the other of said edge portions defining a eon-responding reentrant slot configuration, said reentrant configuration being received in said no entrant slot configuration so as to maintain said edge portions jut-topside, and abutment means disposed at one end of said casing and extending at least partially across said end so as to engage and hold the float captive in said gas-in.
The invention further provides the method of making a casing for a float mechanism of the type having a move able float carrying an electrical contact disposed with-in the casing and engage able with an inner surface there-of, said casing being electrically conductive comprise in the steps of stamping out of sheet metal material generally rectangular blank having a tab along one of its edges and an aperture along the opposite edge, and a projection along a third edge, worming said blank into a cylinder and passing said tab through said aperture bending said tab back into firm engagement with an outer surface of the said opposite edge such that it securely retains said one edge and said opposite edge against separation, and bending said projection radially inward until it is generally perpendicular to the axis of the cylinder so as to form an abutment for holding captive the said float.
Other features and advantages will hereinafter apt pear.
In the drawings:
Figure 1 is an enlarged side elevation Al view, par-lye broken away, of the float switch mechanism, portico-laxly illustrating a float casing constituted of sheet metal bent into a cylinder and with its edge portions juxtaposed, and illustrating a tab on one edge portion passing through an aperture in the other edge portion and being bent back over the latter, so as to retain the edge portions against separation.
Fig. 2 is a right end elevation of the casing of the mechanism, still further enlarged and illustrating the multiple abutments or lugs integral therewith and extending across the casing end, for holding the float captive.
Fig. 3 is a top plan view, enlarged t of a metal stamping in its flat condition, from which the casing of Figs. 1 and 2 is formed.
Fig. 4 it an edge view of the stamping of Fig. 3.

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Fig. 5 is a fragmentary section taken on the line 5--5 of Fig. 2.
Fig. 6 is a fragmentary view like Fig. 1, of a mod-flied casing, showing abutting edge portions of the gas-in provided with interlocking configurations that retain the edge portions against separation.
Fig. 7 is a view similar to Fig. 3, of the flat metal stamping employed to form the modified casing con-struction of Fig. 6.
Fig. 8 is an edge view of the blank of Fig. 7, and Fig. 9 is a right end elevation, further enlarged, of the casing of Fig. 6.
Referring first to Fig 1 there is illustrated a float-type monitor device for installation in the wall 10 of a tank or vessel containing liquid (not shown) whose level is to be monitored, tube wall 10 lying gent orally in a vertical plane The monitor device comprise en a fitting 12 having brazed thereto a flange or abut-mint plate 14, and having a threaded barrel 16. The bar-net 16 is secured in the wall 10 by a nut 18. Alternate-lye the wall 10 can be tapped and the barrel merely screwed in position, in which case the nut would be omit-ted.
The fitting 12 is hollow, and has a cup-like elect tribal contact 20 and a male terminal 22 connected there-with, held in position by an insulating bushing (not shown). The fitting 12 has a transverse slot 24 to no-chive a spring clip 25 as shown which prevents inadver-tent dislodgement of a female connector (also not shown) that can be plugged into the fitting.

The exterior of the barrel 16 has an annular groove 26 in which there is crimped one end of a tubular metal casing 28. The casing 28 has top, bottom and side open-ins 30, and an end opening 32 to enable fluid from the containing vessel to enter the interior of the casing when the level rises.
Disposed within the casing 28 is an elongate float generally designated 34, having an embedded contact strip 36 extending for substantially the entire axial length thereof, with opposite ends 38, 40 protruding therefrom.
The end 38 is preferably in the form of a single pointed tip which can engage the inner surface of the cup 2Q
when the float level falls. The opposite end is intended to engage the inner surface of the casing 28. Such en-gagement thus grounds the cup 20 and associated terminal 22 to the wall 10, through the contact strip 36 when the liquid level is low. The grounding of terminal 22 can activate a warning light, or initiate another type of indication provided for the operator of the vehicle.
Referring now to Figs. 3 and 4, the casing 28 is formed from a one-piece sheet metal blank designated 42, which is preferably but not necessarily replated The blank can be formed in a suitable punch (not shown), with the general outline as illustrated, and having four elongate axially aligned apertures 30. The blank 42 has a pair of opposite longitudinal edge portions 44, 46, the portion 44 having a tab 48 and portion 46 having an offset 50 joined to other parts of the blank by a bend or shoulder 52 of Z-shaped cross section. Disposed along the third edge portion 54 ox the blank is a series of lugs 56 having dimpled formations 58 whose function will ;~28~

be described below. The -tab 48 can have a bend imparted to it, as at 60, at the same time that the punching is accomplished.
Further, the blank 42 is bent into a generally cry-lindrical shape with the edge portion 44 underlying and fitting against the offset 50, as shown in Figs. 1 and

2, and the tab 48 passed through the lowermost aperture 30 in Fig. 3 and bent back so as to overlie the offset 50 and firmly retain the edge portions 44, 46 against separation. This can be accomplished either manually, or by automatic machinery (not shown). The provision of the offset 50 thus eliminates inwardly extending protrusions at the location of the seam 62 in Fig. 2, and there is thus a relatively smooth transition between the junta-posed edge portions 44 and 46. The adjacent inner sun-faces 64 and 66 of the edge portions 44, 46 respectively are thus maintained in alignment or flush with one an-other, and are seen to lie in a single cylindrical sun-face, with no inwardly extending protrusions which might hinder smooth and uninterrupted movement of the float 34. In Fig. 2 it can be seen that the edge portion 46 (offset 50~ is sandwiched between the opposite edge port lion 44 and the tab 48. The latter engages the outer surface of the offset 50 when it is fully bent back.
The offset 50 and tab US also lie in cylindrical sun-faces which are coaxial with the cylindrical surface containing the edge portion 44.
Further, abutment means are provided at the open end of the casing, in the form of one or more lugs 56 which are disposed generally perpendicular to the axis of the casing and extend at least partially across the end so as to hold the float captive. Four lugs 56 are shown in Fig. 2, but other configurations are possible.
As noted above, these lugs are formed during the initial stamping operation, and the bend can be imparted to them following the formation of the casing into the cylinder-eel shape. Also, the lugs have circular or spherical dimpled formations 58 which project slightly into the interior of the casing, as in jigs. 1 and 5. These lung-lion to prevent the end of the float 34 which is adjacent the lugs 56 from engaging the flat portions of the lugs and possibly sticking thereto by capillarityO That is, the dimples 58 engage the end of the float first, if the latter drifts toward the right in Fig. 1.
The above construction has the following important advantages, as compared to the use of drawn sheet metal cups, for use as casings. Where it is desired that the finished component be plated, as is usually the case with steel parts replated flat sheet metal stock can be employed, and when the blanks 42 are formed initially, the stock has already been plated. There is thus elm-noted an additional step in the manufacturing operation, namely that involved with plating a large number of cup-like drawn shells. Although the edges of the blank are constituted of at least partially exposed bare steel, we have found that the stamping operation effects a pinch-in of these edges, such that the plated opposite flat surfaces tend to curl and close over these bare edges, and minimize the exposure. The edges are thus mostly protected, and it has been found that little degenera-lion of the finished product occurs, even if the edges are left without further treatment in the form of no-plating.
Secondly, the present construction is considerably less expensive -to carry out from the manufacturing stand-point. In particular the multiple steps involved in draw-in a cup-like shell from a slat piece of material are completely eliminated. The blanking and wrapping opera-lions of the present arrangement can be readily carried out, and the procedures lend themselves to mass product lion techniques. As mentioned above, there is provided relatively smooth inner surface of cylindrical configure-lion, even at the location of the seam 62. This is made possible by the provision of the offset 50. The smooth interior surface eliminates potential problems involving interference with the movement of the float, etc., since no inwardly extending protrusions are seen to exist.
A modification is illustrated in Figs. 6-9, show-in a modified casing 68 carried on -the barrel 16 of the float mechanism As in the previous construction, the casing has elongate apertures 70 parallel to the casing axis, and an end aperture 72. The casing 68 is formed from a single flat piece of sheet-metal 74 shown in Fig.
7, which has been blanked out from a larger sheet (not shown). The sheet 74 has opposite longitudinal edge port lions 76, 78, and a series of tabs 80 along its third edge portion 82. The tabs 80 have dimpled formations in the form of surface protrusions 84. Fig. 8 illustrates an edge view of the blank of Fig. 7.
The edge portion 78 has a series of dovetails or dovetail projections 86 constituting a reentrant con-figuration, and the opposite edge portion 76 has multi-pie corresponding dovetail slots 88 also defining no-entrant configurations. The casing 68 is formed by wrap-ping the blank 74 around a suitable form (not shown) into a cylindrical shape such that the dovetail project lions 86 are received in the dovetail slots 88. This maintains the edge portions 76, 78 juxtaposed, and no-twins them against separation. Also, the lugs 80 are formed to extend transversely across the far end of the casing in Figs. 6 and 9. The lugs 80 hold captive the float 34, and the dimples 84 prevent the end of the float from engaging the broad inner surfaces of the lugs 80 and possibly sticking thereto by capillarity. In oh-or respects the embodiment of Figs. 6-9 is similar to the first embodiment, and accordingly further discussion of the structure or operation need not be undertaken The advantages of the embodiment of Fig. 6-9 are essentially the same as those of the first embodiment, namely that the use of pro plated stock reduces the numb bier of steps involved with the fabrication of the device.
In addition, the stamping can be carried out quickly, this being also true of the step involved with forming the blank into a cylindrical shape. Overall fabrication cost is thus considerably lower than would be the case if drawing operations were required, together with plats in steps following assembly.
There is also disclosed a novel method for making a casing for a float mechanism of the type having a move able float 34 carrying an electrical contact 40 disposed within the casing and engage able with an inner surface thereof, and wherein the casing is electrically conduct live, the method including the steps of stamping out of sheet material a generally rectangular blank 42 having a tab 48 along one of its edge portions 44, and having an aperture 30 along the opposite edge portion 461 bending the blank 42 into a cylinder and passing the tab 48 through the aperture 30, bending the tab back into firm engagement with an outer surface of the edge portion 46 such that it securely retains the edge portions 44 and 46 against separation, and bending the projection 56 radially inward until it is generally perpendicular to the axis of the casing, thereby forming an abutment which holds the float 34 captive. The method further includes the step of imparting an offset 50 to the edge portion 46, such that when the blank is formed into a cylinder, the offset overlies the outer surface of the edge portion 44 so as to bring the inner surfaces 64 and 66 into align-mint with one another, such that they lie within Essex-tidally the same theoretical cylindrical surface.
Also, the method includes the additional step of imparting a dimpled configuration 58 to the projection 56 for engagement by the float 34, such that there is minimized the area of engagement of the projection 56 and float 34 if the latter drifts toward the projection.
The likelihood of the end of the float sticking to the projection by capillarity is thus greatly reduced or eliminated.
The arrangements that have been disclosed are thus seen to be especially simple in construction and index-pensive to manufacture, thereby reducing the overall cost. They lend themselves to mass production techniques, and with the use of replated stock, there can be elm-inated costs involved with subsequent plating or Corey-sion-resist type finishing operations. Accordingly there is realized a cost reduction as comparec3 -to the use of drawn sheet metal parts, where subsequent punching and plating operations would likely be needed.
The devices are thus seen to represent a distinct advance and improvement in this field.
Each and every one of the appended claims defines an aspect of the invention which is distinct from all others, and accordingly each claim is to be treated in this manner when examined in the light of the prior art devices in any determination of novelty or validity.
Variations and modifications are possible without departing from the spirit of the claims.

Claims (16)

The embodiments of the invention in which an ex-clusive property or privilege is claimed are defined as follows:

1. In a float switch mechanism of the type having a tubular body portion by which the mechanism can be mount-ed in an aperture of a tank or vessel, and having an electrically conductive housing connected to the body portion and a float which is held captive in the housing and moveable therein, and wherein the float carries an electrical contact for engagement with an inner wall of the housing in response to changes in the level of li-quid in the vessel, the improvement comprising said float housing being in the form of a one-piece sheet-metal casing formed into a cylindrical shape from a metal stamp-ing, said casing having an elongate axis and having paral-lel to its axis a pair of adjoining longitudinal edge portions one of which has a lateral offset to enable it to overlap the other, means defining an aperture in said casing adjacent that one of the edge portions which has the said offset, and said casing having a tab on the other of said edge portions, extending radially outward through said aperture and bending back upon said one edge portion so as to securely retain said edge portions against separation, said apertured edge portion being sandwiched between the said other edge portion and said tab, and abutment means disposed at one end of said cas-ing and extending at least partially across said end so as to engage and hold the float captive in said casing.

2. The invention as defined in claim 1, wherein said abutment means is integral with said casing.

3. The invention as defined in claim 1, wherein said abutment means comprises multiple lugs integral with the casing and extending transversely of the axis thereof, across the casing end.

4. The invention as defined in claim 1, wherein said abutment means comprises four lugs integral with the casing, and disposed in diametrically opposed pairs.

5. The invention as defined in claim 3, wherein said lugs have inwardly directed surface protrusions for engagement with an end of the float so as to minimize the area of contact of said lugs and float and prevent sticking of the float due to capillarity.

6. The invention as defined in claim 1, wherein said tab, said offset, and said other edge portion lie within three coaxial theoretical cylindrical surfaces of diminishing diameters, respectively.

7. In a float switch mechanism of the type having a tubular body portion by which the mechanism can be mount-ed in an aperture of a tank or vessel, and having an electrically conductive housing connected to the body portion and a float which is held captive in the housing and moveable therein, and wherein the float carries an electrical contact for engagement with an inner wall of the housing in response to changes in the level of li-quid in the vessel, the improvement comprising said float housing being in the form of a one-piece sheet-metal casing formed into a cylindrical shape from a metal stamping, said casing having an elongate axis and having parallel to its axis a pair of adjoining longi-tudinal edge portions which engage one another in abut-ting relation, means on one of said edge portions defin-ing a re-entrant configuration, means on the other of said edge portions defining a corresponding re-entrant slot configuration, said re-entrant configuration being received in said re-entrant slot configuration so as to maintain said edge portions juxtaposed, and abutment means disposed at one end of said casing and extending at least partially across said end so as to engage and hold the float captive in said casing.

8. The invention as defined in claim 7, wherein said abutment means is integral with said casing.

9. The invention as defined in claim 7, wherein said abutment means comprises multiple lugs integral with the casing and extending transversely of the axis thereof, across the casing end.

10. The invention as defined in claim 7, wherein said abutment means comprises four lugs integral with the casing, and disposed in diametrically opposed pairs.

11. The invention as defined in claim 9, wherein said lugs have inwardly directed surface protrusions for engagement with an end of the float so as to minimize the area of contact of said lugs and float and prevent sticking of the float due to capillarity.

12. The invention as defined in claim 7, wherein said re-entrant configuration comprises a dovetail con-figuration, and said re-entrant slot comprises a dove-tail slot.

13. The method of making a casing for a float mech-anism of the type having a movable float carrying an electrical contact disposed within the casing and engage-able with an inner surface thereof, said casing being electrically conductive, comprising the steps of stamp-ing out of sheet metal material a generally rectangular blank having a tab along one of its edges and an aper-ture along the opposite edge, and a projection along a third edge, forming said blank into a cylinder and pas-sing said tab through said aperture, bending said tab back into firm engagement with an outer surface of the said opposite edge such that it securely retains said one edge and said opposite edge against separation, and bending said projection radially inward until it is gen-erally perpendicular to the axis of the cylinder so as to form an abutment for holding captive the said float.

14. The method as defined in claim 13, and includ-ing the further step of imparting an offset to the said opposite edge, such that when the blank is formed into a cylinder, the offset overlies the outer surface of the said one edge so as to bring the inner surfaces of said one edge and said opposite edge into alignment with one another.

15. The method as defined in claim 13, and includ-ing the further step of, simultaneously with the stamp-ing of the blank, forming additional projections along said third edge, and after the forming of the blank into the cylindrical shape, bending said additional projec-tions radially inward until they are generally perpen-dicular to the axis of the cylinder, said projections forming multiple abutments adapted to hold captive said float.

16. The method as defined in claim 13, and includ-ing the further step of imparting a dimpled configura-tion to the projection, for engagement by an end of the float, so as to minimize the area of engagement of said projection and float and prevent sticking of the latter by capillarity.