US 3646401 A
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Description (OCR text may contain errors)
United States Patent [1s] 3,646,401
Freegard et al. I (451 Feb. 29, 1972  WEATHERPROOF UNPOTTED 3,353,068 11/1967 Turk .L ..317/99 BALLAST CONSTRUCTION 3,360,687 12/1967 Riesland.....  Inventors: Ernest M. Freegard, Evanston; Sol l-lasson, Primary Examiner Laramie E Askin V Skokle both of I Assistant Examiner-Stanley J. Witkowski  Assignee: Advance Transformer Co., Chicago, Ill. Attorney-Silverman & Cass  Filed: Jan. 29, 1971  Appl. No.: 110,897
' 71 I ABSTRACT A ballast for gaseous discharge devices especially intended for connection to outdoor mercury lamps which is constructed to [52} 11.8. C1. ..317/l00,317/99, 174/DlG. 2, run cool and to be weatherproof. A transformer and con- 174/52 R denser are mounted as a unit within a housing on an integral l 5 base of high heat conductivity metal and separated together  Field 0! Search ..3l7/99, 100, 120; 174/D1G. 2, from [he canister 0 housing by airspace and likewise 7 R, 77 R separated from one another by airspace and a heat barrier.
' The ballast is unpotted and transfers heat to the housing wall  References by convection and radiation and to the base by condition, the
- transformerbeing in contact with the base. The housing is UNITED A S PATENTS mounted on the base with an elastomer gasket between the 965,684 7/1910 Bierce et a1. ...l74/77 R housing and the base. The leads from the ballast are led to a 1,345,473 7/1920 Benjamin 174/77 R nipple through wire-carrying channels integrally formed in the 1,469,034 9/1923 Benjamin --l7 /7 R base. The nipple is also integral with the base and the leads 2,477,132 7/ 949 Rowe 1 74/DIG- 2 emerge from the ballast' by way of a frustoconical elastomer 3,l Harvey..... l 2 compressed within the nipple 3,250,956 5/1966 Lovinger... ..3l7/99 3,299,200 l/l967 Sulzer 174/52 R 18 Claims, 4 DrawingFigures I 34 A as A Ir- 32 32 v we l i 2 26\ I 24 24 5 68 64 i g PATENTEUFEB 29 I972 INVENTORS ERNEST M. FREEGARD SOL HASSON ATTORNEYS PIC-1.2
WEATHERPROOF UNPOTTED BALLAST CONSTRUCTION BACKGROUND OF THE INVENTION The invention herein is concerned with the construction of a power supply such as a ballast for furnishing the ignition and operating voltages for mercury lamps or the like operated primarily outdoors.
Reliability is one of the most important factors in the contion achieves reliability in a weatherproof ballast that runs cool and does it in a very economical way.
The invention is not concerned with the type of mercury or sodium vapor lamp ballast in which there is a fixture within which the ballast is mounted. The ballast of the invention is expected to be exposed to the weather.
The ballasts'of the prior art have, for the most part, been potted with some potting compound. This is an easy way to achieve a good'degree of weatherproofing and to hold the parts of the ballast in place, but it has disadvantages. The technique of potting requires special capital equipmenni requires the handling of potting compounds in liquid states which is'messy and expensive; increases the weight of the ballast; may result in locations within the ballast which have increased temperatures and hence require materials which are expensive in the construction of the ballast; does not permit as 'readytransfer of heat to the canister of the ballast; prevents ready inspection of the interior of the ballast; gives rise to possible damages through high liquidity of the potting com pound upon failure of the ballast.
Underwriters Laboratories specify that the outside of the housing of a ballast of this type for mercury lamps and the like 40 have a'temperature not exceeding 90 Celsius. Because of the construction of the 'ballast to be described, it is possible to achieve the outside temperature of the case specified by using soc'alled Class H materials, that is, having an average copper temperature not exceeding 160 Celsius and a hot spot temperature not exceeding 180 Celsius. This permits using more economical designs than in the case of potted ballasts since the quantity of material is decreased and the interior of the ballast can be much hotter than the potted ballasts without increasing'the exterior temperature beyond that specified by the 50 efficient radiation.
Other advantages are achieved with aspects of the-construction of the ballast which will be'detailed in the specification which follows. In this specification, a ballast for use with mercury lamps is described using a condenser and transformer. It should be kept in mind that the advantages of the invention apply to many other types of outdoor power supplies including those which use a reactor alone or'with one or more condensers, and which usea transformer alone or with one or more 70 condensers. Likewise, the invention'maybe used in the case of incandescent lamps requiring transformers for providing operating voltages. No limitations are to be inferred from the specific reference to a ballast for mercury lamps using a high leakage reactance transformer and a condenser.
SUMMARY OF THE INVENTION The ballast of the invention comprises an integral base of high heat-conductive metal with an integral depending nipple by means of which the ballast may be mounted to a securing bracket. Mounted on top of the'base in heat-conductive relationship therewithis the transformer portion of the ballast which is the principal heat-producing component so that heat tends to be transmitted to the base by conduction, the base serving as a heat sink in'this regard. The condenser portion of I the ballast is spaced from the transformer and there is a heat barrier of some insulating material between the transformer and condenser so that the minimum of heat will be transferred to the condenser from the transformer. Thecondenser and transformer are connected mechanically as a unit and, but for the engagement of the transformer with the base, which is at the bottom of the unit, the remainder of the unit is spaced from the canister. The canister is a cylindrical housing which encloses the condenser and transformer unit and is secured to .the top of the base by suitable fastening means with an intervening gasket of suitable material. The electrical leads from the interior of the ballast are led through channels integrally BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional view of a ballast constructed-according to the invention taken generally along the line 1-1 of FIG. 2 and in .the .indicated direction with portions being broken away and other portions being shown'in elevation;
FIG. 2 is a bottom plan view of the ballast with portions shown broken away, the ballast in this case being shown free of the bracket to which the same is secured as in FIG. l;
FIG. 3 is a fragmentary sectional detail taken along the line 3-3 of FIG. 1 and in the indicated direction; and
FIG. 4. is a fragmentary exploded sectional view showing the manner in which the lead wires are secured in the plug during the assembly of the ballast.
DESCRIPTION OF THE PREFERRED EMBODIMENT The reference character 10 designates generally the ballast of the invention, said ballast comprising an inner unit 12, a base 14 and an outer housing in the form of a cylindrical canister 16 mountedon the base.
As understood, a ballast is a device which provides the igniting voltage for gaseous discharge devices and after ignition, provides the operating voltage .for suchdevices. As such, it transfers power for maintaining the dischargedevices in operation. The usualballast'includes at least a transformer and a condenser in circuit with the gaseous discharge device 7 or devices, but it may have a reactor alone or with condenser means, or it may have a transformer alone. The voltages for ignition of gaseous discharge devices such as for example the mercury vapor lamps forwhich the ballast of this specification .is especially intended are substantially higher than the operating voltages which are required to maintain the lamps ignited. When the mercury vapor within a lamp is ionized, the impedance of the lamp is that of the are between the interior electrodes thereof and this 'is quite low. Accordingly, it is necessary to stabilize the are by introducing a substantial reactance in the lamp circuit and this is accomplished in the modern ballast either by means of a condenser or the high leakage reactance-bu'ilt into the transformer of the ballast. The condenser is used forvarious purposes, including power factor correction; The'principal heat-producing component of a ballast is the transformer since its copper losses and eddy currents in the 'laminations produce the principal heat. Little or no heat is developed in an efficient condenser such as, for example, those oil-filled condensers normally used in ballasts of this type. A condenser will have better operating characteristics and longer life if kept insulated from the heat of the transformer unit, and this is achieved in the invention as will be described in such power supplies as use condensers.
The transformer of the ballast is shown at 18 with its bottom surface in intimate contact with the upper surface of the base 14 as shown at 20, there normally being a conductive cementor compound of some kind applied here to transfer heat from the transformer 18 to the base 14. The laminations and windings of the transformer are held in assembly by any suitable means suchas clamps, welding, adhesive and the like and the transformer itself is impregnated in varnish and preferably painted black so that it will radiate efficiently.
In the present case, there is 'a framework 22 having flanges 24 at the. bottom end thereof by means of which the transformer 18 and the entire unit 12 are connected firmly with the base 14 through the use of suitable fasteners 26. The upper part of the framework 22 comprises a channellike yoke 28 having angled legs 30 which are held to the upper flanges 32 by means of the fasteners 34. There is a relatively large member 36 of fiber of the type normally used in the construction of electrical components sandwiched between the legs 30 and the flanges 32, the member 36 extending fully over the upperend of the transformer 18 and spaced above the same. The member 36 comprises a heat barrier and will be referred to hereinafter as such. Instead of fiber, the member can be made of any heat-resisting and heat-insulating material having sufficient strength to serve in the manner described.
The bridging heat barrier 36 closes the bottom of the yoke 28 to provide a boxlike space 38 within which the condenser 40 of the ballast 10 is disposed. The frame 22 and the yoke 28 are normally made of some robust metal such as sheet steel so that the unit 22 is sturdy and does not chatter or vibrate. The condenser 40 is wrapped in a layer 42 of so-called fish paper or some other insulating sheet material to keep it insulated from the yoke 28, but it lies on top of the heat barrier 36 and preferably is tightly wedged between the yoke 28 and the heat barrier 36.
From the above description, it may be observed that the heat barrier 36 not only helps to support the condenser 40, but it also insulates it from the heat'generated by the transformer 18. In this way, the oil in the condenser 40 is not unduly heated thereby preventing deterioration thereof. This feature of the construction of the ballast l0 promotes long life of the condenser.
The base 14 is preferably in the form of a casting of aluminum having a central integral threaded hollow nipple 44 with its interior bore 46 occupied by a plug 48. The electrical leads 50 connect the electrical components of the ballast with the lamps (not shown) and the external source of power (not shown). They must pass from the interior of the ballast to the exterior thereof, and the plug 48 carries these leads in weatherproof disposition to the exterior of the ballast. The base 14 may be lightened by having segment-shaped recesses such as shown at 52 formed in the bottom surface thereof, these recesses being separated by strengthening ribs 54. One or more wire-carrying grooves 56 may be cast into the upper surface of the base 14, these grooves enable the wires 50 to be laid under the transformer end and conducted to the bore 46.
Inviting attention now to FIG. 4, the plug 48 is shown to be of frustoconical configuration, with its taper decreasing toward the end first inserted into bore 46. It has the same number of passageways 58 as there are leads 50 passing to the exterior of the ballast 10, and during assembly these leads or wires 50 are threaded through the passageways 58 after which the plug 48 is forced into the bore 46. Preferably, a shoulder 60 formed on the interior of the end of the nipple 44 limits the amount of axial movement of the plug 48 during this assembly procedure. This action constricts the passageways 58 and, as a result, the leads 50 are tightly engaged within the plug 48. The leads are usually in the form of coated wire, the coating being a smooth synthetic plastic or the like so that there is avery close clamping action. The plug 48 itself is made of some elastomer such as any of the synthetic rubbers or polymers which preserve their elasticity over long periods of time. Some success has been had with a polymer known as ethylenepropylene-terpolymer. The unit 12 is secured in place by the fasteners 26 after the plug 48 has been pushed home.
The canister 16 is an aluminum cylinder' with a closed end 62 and its bottom end open and formed on its bottom edge with an annular flange 64. Fasteners such as screws 66 pass through circumferentially spaced perforations in the flange 64 and through a narrow annular gasket 68 into suitable aligned screw-threaded sockets 70 formed in the base 14. Preferably, the gasket 68 is formed of an elastomer such as any of the synthetic rubbers available, and when the screws 66 are tightened, the connection is waterproof. Neoprene has been used successfully. The canister 16 is deep-drawn or spun from sheet aluminum and is anodized black to provide for good radiation of the heat which the canister wall in turn receives by radiation from the transformer 18.
The ballast 10 is adapted to'be mounted onto a bracket 72 such as that disclosed in a copending application, Ser. No. 64,470, filed Aug. 17, 1970 by one of the applicants herein. Any other suitable bracket can be utilized, however, so long'as it provides a passageway 74 within which the nipple 44 may be received and to which the ballast 10 may be secured by a nut 76 engaged over the end of the nipple 44 which protrudes from the bottom of the upper plate of the bracket 72. The ballast 10 normally will be sold with the nut 76.
It is pointed out that the wedging engagement of the plug 48 with the bore 46 of the nipple 44 serves several purposes. It evenly spaces the leads 50 as they emerge from the ballast 10; it tightly engages these leads and thereby renders the junction of the leads 50 with the plug 48 waterproof while tightly engaging the plug within the only opening to the interior of the ballast also in waterproof condition; and it takes up any strain to which the leads 50 are subjected while the ballast 10 is being handled.
Another important feature of the invention as described hereinabove is the mounting of the interior unit 12 upon the base 14 spaced from the interior of the canister wall so that there is no contact with the canister. Also, the canister 16 need not have the strength for supporting the components. The outer surface is in contact with'the atmosphere and efficiently radiates the heat from its black surface. The canister need not be made of steel which requires expensive galvanizing prior to painting.
In order to give some understanding of the actual physical nature of the ballast of the invention, an example of the same will be described. Insofar as size is concerned, the diameter of the canister 16 of a typical ballast was about six and one-half inches, and its length was eight inches. Other dimensions may be scaled from the drawing. This ballast was used for connection to one 250W-H37 mercury vapor lamp energized either from a l20-volt or 240-volt source (depending upon primary winding transformer connections) at 60 Hertz.
As previously indicated, the features of the invention are also applicable to other types of power supplies for gaseous discharge as well as incandescent lamps.
Variations are capable of being made to the details of the invention without departing from the spirit or scope thereof as defined in the appended claims.
What it is desired to secure by Letters Patent of the United States is:
l. A power supply apparatus for lamps to be used outdoors which comprises:
A. a power unit including at least a heat-producing com ponent,
B. a unitary base of heat-conducting material, the power unit being mounted on the base with the heat-producing component in heat-transfer engagement with the base,
C. a one-piece canister of thin-walled heat-conducting material formed as a cylinder having one end closed and the other end open,
D. the open end of the canister being engaged upon the said base in a weatherproof joint and enclosing the power unit,
E. an integral, hollow, exterior nipple formed on the base and adapted to be engaged through an opening formed in a mounting bracket adapted to support the apparatus, and
F, the power unit having a plurality of electrical leads and the leads extending from the interior of the apparatus to the exterior thereof by way of the hollow of the nipple and being disposed therein in waterproof association therewith.
2. The power supply apparatus as claimed in claim 1 in which there is an air space within the power supply apparatus between the power unit and the interior of the canister wall.
3. The power supply apparatus as claimed in claim 1 in which there is an elastomeric plug compressed in the hollow of the nipple and the electrical leads pass through passageways formed in said plug and are tightly engaged in said passageways.
4. The power supply apparatus as claimed in claim 3 in which the elastomeric plug is frustoconical and is wedged into said hollow from the interior of the power supply apparatus. 1
5. The power supply apparatus as claimed in claim 4 in which the hollow is tapered to receive the plug and has a shoulder at its end to limit the movement of the plug into the hollow.
6. The power supply apparatus as claimed in claim 1 in which the nipple is formed in the center of the base and the heat-producing component has one edge thereof engaged upon said base over said nipple and in which said base has channel means integrally formed therein to convey said leads from the interior of the power supply to the hollow of the nipple beneath said heat-producing component edge.
7. The power supply apparatus as claimed in claim 1 in which the base is circular and the open end of the canister includes an annular flange engaged to the upper surface of the base around the periphery thereof and in which there is an elastomeric gasket clamped between the flange and said base.
8. The power supply apparatus as claimed in claim 2 in which the power unit includes a condenser in addition to said heat-producing component, a framework providing spacing between the condenser and the heat-producing component and a heat barrier is provided between the condenser and heat-producing component in addition to said spacing.
9. The power supply apparatus as claimed in claim 8 in which said framework includes a channel-shaped yoke having its open end closed off by said barrier and forming a boxlike space, said condensers being frictionally engaged within said boxlike space. i
10. The power supply apparatus as claimed in claim 8 in which the base is circular and the open end of the canister includes an annular flange engaged to the upper surface of the base around the periphery thereof and in which there is an elastomeric gasket clamped between the flange and said base.
11. The power supply apparatus as claimed in claim 1 in which the heat-producing component is a transformer.
12. The power supply apparatus as claimed in claim 8 in which said heat-producing component is a transformer.
13. In a weatherproof power supply apparatus construction which includes a base, a power unit mounted on the base and a canister also mounted on the base and enclosing the power unit, means for leading electrical leads from the'int erior of the apparatus to the exterior thereof, comprising: an integral externally protruding hollow nipple on said base, an elastomeric plug wedged into the bore of said nipple from the interior of the ballast, passageways formed in the plug and the leads being tightly engaged in said passageway by reason of said wedging engagement.
14. The structure as claimed in claim 13 in which the bore is tapered with the smaller diameter furthest from the interior of the ballast and the plug is frustoconical. i
15. The structure as claimed in claim 14 in which the end of the nipple has an interior shoulder to limit the extent of move ment of the plug therein while same is bein wedged in place.
16. In a ballast construction which rnclu es a condenser and a transformer and in which there is a framework holding the condenser and transformer assembled together as a unit, means for insulating the condenser from heat generated in the transformer comprising: the framework including a channelshaped yoke opening toward the transformer, support members for connecting the yoke to the transformer, a pair of angled legs on the yoke attached to said support members and a heat barrier disposed between the angled legs and the support members and closing off the opening of the yoke to provide with, the yoke a boxlike formation, and the condenser being disposed within the boxlike formation.
17. The structure as claimed in claim 16 in which the heat barrier comprises a sheet member of heat-resistant insulating material.
18. The structure as claimed in claim 16 in which the heat barrier is fiber.