Terminal block assembly with
US 2923913 A
Description (OCR text may contain errors)
Feb. 2, 1960 E. R. KULKA TERMINAL BLOCK ASSEMBLY WITH INSULATING STRIP Filed Dec. 17, 1956 T a: U 5! m l NW 6 f0 4; 34 M 22; FIG. 6. 22
A/ f INVENTOR.
EUGENE. R. KULKA MAVVS QQ ATTORNEYS United States Patent TERNHNAL BLOCK ASSEMBLY WITH INSULATING STRIP Eugene R. Kulka, Mount Vernon, NY. Application December 17, 1956, Serial No. 628,804
' 3 Claims. ,(Cl. 339-198) This invention relates to improvements in terminal blocks and has particular relation to novel and improved insulation means for insulating the terminal screws from the block mountings.
Conventional terminal blocks include a block body of insulating material having a plurality of rows of through bores, and metal contact plates associated with corresponding bores in the respective rows. The contact plates have indented tapped holes in alignment with the re spective bores and have their lower ends turned. over beneath a portion of the bore for efiiciently securing the contact plates upon the upper surface of the block body. Because of the necessity of the peening-over operation, the bores must open through the bottom of the block body to provide access to the bottom of the contacts. The contact plate holes mount terminal screws which extend downwardly through the respective block body bores when in assembled position. Since the bottoms of the bores are open, the assembly presents the problem of sparking between the ends of the terminal screws and a metal mount for the block.
Because of this sparking tendency, it has been customary to provide a separate insulating sheet inserted between the terminal block and the mount. This sheet, made of fiber board or similar material is often made of greater width than the terminal block so that its side portion overhangs one side of the block, and on this sheet is marked a series of numerals registering with and identifying the rows of terminal screws. For this reason, the sheets are referred to in the trade as marking strips.
The insulating sheets or marking strips are provided at their ends with screw holes which are intended to register with the screw holes at the ends of the insulating block so that when clamping screws are inserted through these registering holes into threaded holes provided in the mounting, the screws clamp both the terminal block and marking strip to the mounting. This mounting procedure is cumbersome and time consuming, since it is difiicult to align the marking strip screw holes with thescrew holes of the terminal block.
In addition, the provision of separate insulating sheets is costly, since it is necessary to provide an insulating sheet for each terminal block even if the sheet is not intended to be used as a marking strip.
It is an object of the present invention to provide a terminal block in which insulating means are secured to the block, so that no separate insulating members are necessary. At the same time, the eyelet connections of the contact terminals are still employed.
Another object of the invention is the provision of a terminal block of the type described in which the insulating means is secured to the block during manufacture of the latter in proper position, so that in mounting of the block there is no necessity for aligning screw holes of the insulating means.
A further object of the invention is the provision of a terminal block of the character described in which the "insulating means is readily adaptable for the immovable tition walls 16.
' 2,923,913 Ce Patented Feb. 2, 1960 attachment of a marking strip when required, the marking strip being attachable during manufacture in such a manner that no alignment thereof is necessary when the block is mounted.
Other objects and advantages of the invention will become apparent during the course of the following specification when taken in connection with the accompanying drawings, in which:
Fig. 1 is a top plan view of a terminal block with certain of the screws removed for clarity of illustration;
Fig. 2 is a bottom plan view of the terminal block showing the insulating strip in secured position with a corner thereof folded up;
Fig. 3 is a section on an enlarged scale, taken along line 33 of Fig. 1;
Fig. 4 is a plan view of a marking strip made for use wtih terminal block of Figs. 1-3;
Fig. 5 is atop plan view of a terminal block with the marking strip attached thereto; and
Fig. 6 is a section on an enlarged scale, taken along line 66 of Fig. 5.
Referring in detail to the drawings, there is shown in Figs. 1-3 a conventional terminal block 10 having the usual rectangular body molded of Bakelite or similar insulating material.
The block 10 has a flat bottom surface 12 and a top surface 14 provided with spaced, upstanding ribs or par- Between each adjacent pair of partition walls 16 are a pair of transversely-spaced bores 18 which extend downwardly approximately half-way through the body of terminal block 10. Each bore 18 communicates with a respective lower bore 20 which opens through the bottom surface 12 of the terminal block. As shown in Fig. 3, each lower bore 20 is of greater diameter than its respective upper bore 18, and forms a shoulder 22 therewith.
A terminal plate 24, made of conductive metal, is socured against the top surface 14 of the terminal block '10 between each adjacent pair of partition walls 16.
Each plate 24 has a pair of integral depending tubular portions 26 located to register with and extend downwardly through the respective upper bores 18 of the block body, as is best seen in Fig. 6. The tubular portions 26 are made longer than the upper bores 18, so that in their inserted positions the bottom ends may be turned over to provide terminal flanges 28 which'abut the shoulders 22 and secure the plate 24 rigidly and immovably to the block. The use of such integral tubes 26 is desirable in the manufacture of terminal blocks since it provides astrong attachment which prevents the terminal plates 24 from being pulled off the block by tension of the wires connected to the plates.
Each terminal plate 24 has a pair of screw openings 30 which register respectively with through bores 32 in the tubular portions 26. The through bores 32 communicate with lower block bores 20, and each through bore 32 is threaded for receiving a terminal screw 34. The threaded engagement of the terminal screws 34 along thelength of the respective tubular portions 26 provides a firm mounting support for the terminal screws, as well as a large area of electrical contact.
The terminal block 10 is also provided with a pair of bolt openings 36 at each end thereof, the openings 36 being adapted to receive mounting bolts 38. Each bolt 38 receives a corresponding nut 40 for mounting the terminal block 10 in flush engagement with a flat support 42.
'In the use of terminal blocks of this type, it has been found that when the block was mounted on a support made of conductive metal, the terminal screws would short through the metal support, especially if high voltage circuits were involved. Since the bottom ends of the lower bores are open, a spark would often jump the air gap between the tip of a terminal screw 34 and the support 42. Consequently, it is now customary to provide a separate marking strip with each terminal block to insulate the terminal screws from the support. Such a conventional marking strip 44 is shown in Fig. 4 and comprises a strip of rigid or semi-rigid fibrous material suchas cardboard, of the same length, but of greater width than the terminal block. The marking strip 44 has at each end a pair of holes 46 positioned to register with the bolt openings 36 of the terminal block 10.
In conventional use, the marking strip 44 is placed beneath the terminal block 10, lying flush against the block fiat bottom surface 12, the holes 46 are aligned with the block bolt openings 36 and with the respective bolt openings of the support 42, and the bolts 38 and nuts 40 are attached.
Since the marking strip 44 is made of greater width than the terminal block lfl, when the marking strip is mounted, a panel portion 48 projects laterally beyond the terminal block, as shown in Fig. 5. On this panel portion it is customary to provide numerals 50 or other indicia for identifying the respective terminal plates. Thus the marking strip serves the dual function of insulating the terminal block from its support, as well as serving as means for identifying the terminals.
In many instances, a particular installation requires no identification of terminals. Nevertheless, a marking strip is still provided with the terminal block and used therewith, since it is the only conventional means for insulating the block terminals from the support. This necessitates an additional costly manufacturing opera tion, and separate handling and packing, which increases the costs of the terminal block. In addition, the user is subjected to the necessity of manually aligning the bolt holes and openings in the terminal block, marking strip, and support, a cumbersome and time-consuming procedure during the mounting of the block.
According to this invention, the use of a separate marking strip is avoided when the strip is not needed for purposes of terminal identification. In such an instance, a strip of flexible sheet material 52 in the nature of pressure-sensitive tape is provided to serve as an insulating member for the bottom of the terminal block.
The flexible strip 52 is made of any suitable insulating material having a sufficiently high dielectric strength. The strip 52 illustrated in Fig. 2 is a length of transparent pressure-sensitive tape. A variety of pressure-sensitive tapes of this type are commercially available; for example, a suitable tape which was used has a polyester base with a thickness of 1 mil without the adhesive coating, and a dielectric strength of over 5000 volts.
The strip 52 has a coating of pressure-sensitive adhesive 54 (Fig. 2) by means of which the strip is secured to the fiat bottom surface of terminal block 10. Strip 52 is made shorter than the terminal block length so that its ends terminate short of the 'bolt openings 36 and do not interfere with the mounting bolts.
The strip 52 is easily cut and applied automatically by machine to the bottom surface of the terminal block 10, as the last step in the manufacture of said terminal block. The terminal block and its bottom insulation thus form a complete unit after manufacture, making it unnecessary to provide a separate marking strip for purposes of insulation in those instances where terminal identification is not called for. It is therefore no longernecessary for the user to align the bolt holes and openings when mounting the terminal block. Since the pressure-sensitive tape used is a thin material, the terminal block with this tape affixed can be mounted in the manner shown in Fig. 3, with its bottom surface resting substantially flush against the surface of the support 42.
The use of the marking strip 52 has the particular advantage of enabling the terminal block to be made with the through, stepped bores 18 and 20, so that the terminal plates 24 can be secured to the block in the most effective manner, namely by use of the tubular portions 26 and their turned-over flanges.
In some instances, it will still be necessary to provide a marking strip for purposes of identifying the terminals. In such an instance, the strip 52 may still be used, but is provided with an adhesive coating on both surfaces. After the strip 52 is applied to the bottom of terminal block 18, in the manner previously described, the marking strip 44 is pressed in contact with the coated outer surface of the strip 52 so that it adheres thereto. In applying the marking strip, its holes 46 are aligned with the bolt openings 36 of terminal block 10. Thus, when the assembled unit reaches the consumer, the marking strip 44 is already attached to the bottom of the terminal block with the bolt holes and openings in registry, and no further alignment is necessary in the mounting operation. Figs. 5 and 6 show the marking strip assembled with the terminal block.
While preferred embodiments of the invention have been shown and described herein, it is obvious that numerous omissions, changes and additions may be made without departing from the spirit and scope of theinvention.
1. In a terminal block having an insulating body with a fiat bottom surface, a plurality of through bores in the block body which open through the flat bottom surface thereof, and a plurality of terminal screws mounted in the respective bores; a strip of flexible material having a coating of pressure-sensitive adhesive on both surfaces thereof, said strip being secured by one of said adhesive coatings to the fiat bottom surface of the terminal block body, and a flat marking strip underlying the flexible strip and secured thereto by the other adhesive coating,
said marking strip being wider than said terminal block body and having a projecting side panel, said side panel bearing indicia for identifying the respective terminal screws.
2. A terminal block assembly comprising an insulating body having a flat bottom surface, a plurality of stepped bores extending through the block body and having respective shoulders formed therein, the bottom ends of the bores opening through the bottom surface of the block body, a plurality of conductive terminal plates on the top surface of said block body, each plate havingat least one depending tubular extension extending into one of said bores, each tubular extension having a turned-over bottom flange engaging the shoulder of its respective bore for securing the terminal plate to said block body, at least one terminal screw mounted in each terminal plate and extending downwardly through the respective tubular extension into the respective bore with the end of each terminal screw spaced above and exposed to the open bottom end of its respective bore, means for mounting the block body on a support with its flat bottom surface resting flush against said support, and an insulating member positioned to lie between the block bottom surface and said support for insulating the terminal screws from said support, said insulatingmember comprising a strip of flexible dielectric material having a coating of pressure-sensitive adhesive securing the strip to the flat bottom surface of the terminal block body and also having a coating of pressure-sensitive adhesive on its outer surface opposite the block body said strip having a sufficient area to underlie and cover over the bottom ends of all said bores, the strip providing electrical insulation between the respective terminal screws and the portions of the support which underlie said bores and are exposed to said terminal screws, whereby to prevent arcing between said terminal screws and said support, and a fiat marking strip underlying the flexible strip and secured thereto by said outer adhesive coating, said marking strip being 5 6 wider than said terminal block body and having a projecting to the bolt openings of the block body and registering ing side panel, said side panel bearing indicia for identherewith in the secured position of the marking strip. tifying the respective terminal plates. I 3. A terminal block assembly according to claim 2 References Cited m the file of thls patent in which said block body has bolt openings at each end 5 UNITED STATES PATENTS for mounting of the block body on Sai pp rt, the 1,736,028 Winklehaus Nov.19,1929 insulating strip being of lesser length than said bl ck 2,161,246 Carlson June 6, 1939 body and terminating at each end short of said bolt open- 2,427,285 Ker-Shaw Sept, 9, 1947 ings to permit the extension of bolts through said bol 2,671,820 Herbert Mar. 9, 1954 openings, the marking strip having bolt holes correspond- 10 2,701,870 Obszarny Feb. 8, 1955