US 3255427 A
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Description (OCR text may contain errors)
June 7, 1966 YEISER 3,255,427
MULTI-CONTAGT CONNECTOR Filed March 5, 1964 v United States Patent M 3,255,427 MULTl-CONTACT CONNECTOR Leon Knesel Yeiser, Lebanon, Pa., assignor to AMP Incorporated, Harrisburg, Pa. Filed Mar. 3, 1964, Ser. No. 348,936 .1 Claim. ((11. 339-59) This application is a continuation-in-part of application Serial Number 118,703, filed June 21, 1961, for Multi-Contact Connector and now abandoned.
This invention relates to multi-contact connecting devices of the type comprising a pair of mateable dielectric blocks having a plurality of electrical contacts therein.
One known type of multi-contact connecting device comprises a pair of dielectric blocks, each of which has a plurality of electrical contacts mounted therein so that upon engagement of the blocks with each other, each of the contacts is engaged with its counterpart in the other one of the blocks. These devices are frequently made in relatively small sizes and contain a relatively large number of contacts. For example, one commonly used size of connector comprises a pair of generally rectangular blocks, each block being 2%" x A X A" in overall dimensions and having mounted therein seventy-two contacts on centers which are spaced 0.180 inch apart. The contacts themselves are usually of the pin and socket type and in the foregoing example are of 0.1 35 inch in diameter and about 1 inch long. Dev-ices of this type are used under circumstances where a large number of conductors must be disengageably connected with each other and where, out of convenience or necessity, it is necessary to severely limit the size of the connecting device.
Several methods of manufacturing connectors of this type are presently known and are being employed. According to one method, the dielectric blocks are formed of a relatively hard, firm and non-yielding insulating material such as phenolic, diallyl phthalate, or epoxy resin and the electrical contacts are integrally molded in the block at the time it is formed by placing the contacts in the mold cavity and then injecting the molding material around the contacts. Conector blocks made in accordance with this method have the contacts very securely mounted therein but they suffer from some disadvantages. One comparative disadvantage is that the molding operation is relatively slow and expensive by reason of the fact that each one of the contacts must be placed in the mold prior to the molding operation. Furthermore, if one of the contacts is defective or is not properly placed in the mold, the entire block is useless since the position of the contact cannot be changed nor can an imperfect or defective contact be removed and replaced. Additionally, where this manufacturing process is employed, the connectors must be secured to the wires by soldering since it is impossible to crimp the contacts onto wires when they are integrally molded in the block by reason of their close spacing.
An alternative method of manufacturing connector blocks is to form the block of a hard plastic such as those mentioned above with the requisite number of cavities for reception of the contacts. After the block has been formed, the contacts are inserted into the openings and retained in place by means of a simple spring. The retention spring may be mounted on the contact or may be inserted into the cavity of the mold but in either event, a separate part, the retention spring, is required for this type of connector. US. Patent 2,419,018 shows a connector of this general type having an inserted spring while application Serial Number 801,230, filed March 23,
1959 shows a somewhat similar connecting device having 3,255,427 Patented June 7, 1966 type can be produced at a relatively low cost since the contacts are not placed in the mold prior to injection. Advantageously the retention springs are designed in a manner such that the force required to insert the contacts, that is the contact pin or socket, into the cavity is relatively low but the holding effect of the retention springs is such that accidental Withdrawal of the contact from the block is discouraged or prohibited. At the same time, the arrangement should be such that the contact can be withdrawn from the block when a properly designed tool is employed so as to permit replacement of a defective connector and/or changes in the circuitry by changing the wires or wiring arrangement or pattern of the block. A further advantage of this type of connector is that the contacts can be crimped onto wires, rather than soldered, prior to insertion into the block.
A design criterion for these inserted types of contact connectors is that the retention spring should hold the contact within predetermined limits as regards centering in the connector block cavity so that the contacts of one block will properly align themselves with the contacts of the other block when the two blocks are brought into engagement with each other. Ordinarily, the blocks and the retention means are designed such that both the pin and the socket have a small amount of float or lateral movement to permit the contacts to align themselves with each other. The necessity for accurate spacing and control of the float of the contacts can be appreciated if it is reflected that in the smaller sizes the contacts will be mounted in the block on centers which are about 0.180 inch apart as noted above.
A third type of connector is manufactured of an extremely soft material, such as natural rubber, which permits insertion of the contacts into openings in the block. Where natural rubber is used in this manner, the
contacts are not rigidly held when they are initially inserted and it therefore becomes necessary to mount the rubber connector block in a metal shell or other housing means in order to compress it onto the connectors and hold them in place. This arrangement permits changing of the contacts but is undesirable in that the entire block must be decompressed as by removal of the shell if it is desired to change the position of a connector or to replace a defective contact.
An object of the present invention is to provide an improved multi-contact connecting device. A more specific object is to provide a multi-contact connector which obviates the need of retention springs either in the dielectric connector block or on the contacts themselves, A further object is to provide a connector block for a multi-contact connector having a retention means integrally formed therewith which permits relatively easy insertion of the contacts and which permits withdrawal of the contacts without damage to the block.
These and other objects of the invention are achieved in a preferred embodiment thereof comprising a dielectric block having a plurality of cavities extending therethrough for the reception of electrical contacts. Each cavity has a central constricted portion of a diameter less than the overall diameter of contacts. The arrangement is such that the contact can be inserted through the opening with concomitant deformation of the restricted portion during insertion so that the contact is gripped by the block. The material of the block constitutes an important aspect of the invention and comprises a polyurethane composition having a hardness in the range of 35 to 60 on the durometer D scale.
Where this material is employed for the dielectric block, relatively easy insertion of the contacts is permitted. At the same time, the blocks will resist withdrawal of the contacts unless an extremely high pulling force is applied on the end of the connector; the blocks will not, however, be destroyed if this extremely high upon application of this pushing force, the retention means in the cavity yields to the point where the contacts can be removed and the yielding does not result in any way in destruction of the retention means so that repeated insertions and withdrawals of the contacts is permitted.
In the drawing:
FIGURE 1 is a perspective view showing a pin and socket of a type usable in a disclosed form of the invention;
FIGURE 2 is a sectional side view showing a portion of a pair of connector blocks in accordance with the invention and showing the form of the cavities which receive the contacts; and
FIGURE 3 is a view similar to FIGURE 2 but showing the contacts in the cavities of the connector blocks.
FIGURE 1 shows a pin contact and a socket contact of the type particularly intended for usage with a connector block as disclosed in FIGURES 2 and 3 in accordance with the instant invention. The pin contact 2 comprises a cylindrical barrel portion 6 which is axially bored for reception of the end of a wire, a collar 8, a uniform diameter section 10 having a diameter substantially equal to the diameter of the barrel portion 6, and a forwardly tapering conical section 12. Forwardly of the conical section 12 there is provided a uniform diameter section 14 having a diameter which is substantially equal to that of the barrel portion 6, an inwardly tapering conical section 16, and finally a cylindrical end 18 which is adapted to enter an axial bore in the socket contact. The socket contact 4 is, in many respects, similar to the pin contact in that it has a barrel portion 20, a collar 22, a uniform diameter portion 24, and an inwardly tape-ring conical section 26. Forwardly of the conical section 26 there is provided a socket 30 into which the pin projection 18 is inserted.
Referring now to FIGURE 2, the insulating block 32 which is adapted to receive the socket contact 4 has a plurality of cavities extending therethrough, each cavity having a uniform diameter section 34 adjacent to the rearward face 33, an adjacent reduced diameter section 36, and a further reduced diameter section 38. The cavity walls taper inwardly from the section 38 towards the axis of the cavity as indicated at 40 and merge with a short constricted diameter section 42 which opens into an enlarged diameter portion of the cavity 44 which is adapted to receive the end portion 30 of the socket con- 7 tact.
The connect-or block 46 which is adapted to receive the pin contact 2 has a plurality of cavities extending therethrough which are substantially similar to the cavities described above in the block 32. The various parts of the cavity in the block 46 are indicated by the same reference numerals, differentiated by prime marks, as those described in the block 32. A significant difference between the two blocks is that the forward cavity portion 44' of the block 46 is substantially shorter than the corresponding cavity section 44 of the block 32. The reason for this difference is that the ends of the contact pins must extend beyond the mating face 48 of the block 46 while the end portions 30 of the socket contacts are recessed within the cavities 34. After the pin and socket contacts have been crimped onto the ends of wires, the individual contacts are merely aligned with a cavity and pushed from the rearward faces of the blocks through the cavities until the conical portions 12, 26 of the contacts are disposed in the tapered cavity portions 40, 40'. During insertion of the contacts, the constrictions 42, 42'
4 I of the cavities will be substantially outwardly displaced but will return to their normal positions after the contacts have been entirely inserted.
The successful practice of the instant invention depends upon the usage of a polyurethane material having a hardness as measured on the durometer D scale in the range of 45 to 60.
These polyurethanes are available from several sources and in a variety of forms. For purposes of the present invention, a solid polyurethane (rather than a foam) is required. The suitability of a polyurethane for the present invention can be ascertained by determining its hardness on the durometer scale. Such determinations can be made by penetration-type hardness testers of the type which are manufactured by the Shore Instrument and Manufacturing Co. of Jamaica, New York. Polyurethanes having a hardness of at least about 94 on the A durometer scale will yield good results in the practice of the instant invention. If the hardness determinations are made with the D durometer scale, an acceptable range is about 40 to 65 while the preferred range is 45 to 50. Polyurethanes which are softer than the preferred range given above will yield readily to permit insertion of the contacts into the block and a block made of a soft polyurethane will therefore have a low insertion force. However, a block formed from a soft material will not retain the contact in position upon imposition of an extracting force and are not satisfactory, for purposes of the present invention, for that reason. Where the contacts are of about 0.135 inch in overall diameter and are about 1 inch long, they should be retained in the block with a firmness sufficient to withstand an extraction force of about 12 pounds; i.e., a pulling or pushing force of greater than 12 pounds should be required to remove the contact from the block. It has been found that these conditions are achieved with polyurethane blocks formed in accordance with the instant invention. At the same time, the insertion force required for these blocks is maintained at a satisfactorily low level, about 5 pounds.
The extreme toughness of the polyurethanes permits blocks formed of these materials to withstand repeated insertions and withdrawals of contacts without damage. Furthermore, the retention effect of the block does not seriously decrease with repeated insertions and Withdrawals.
A satisfactory polyurethane for purposes of the instant invention can be produced by condensing a molar excess of mixed toluene 2,4- and 2,6-toluene diisocyanates with polytetramethylene ether glycol. This material is available from Du Pont under the trademark Adiprene L. This material is generally cured by mixing with a diamine, for example, methylene-bis-orthochloro anilene which is available under the Du Pont trademark Moca. The exact hardness obtained depends upon the curing cycle and the amount of curing agent used.
While a vast number of polymeric materials are available to the electrical industry, the polyurethanes of the type described above are uniquely suited to the manufacturer of connector blocks in accordance with the present invention. The usage of such materials permits the construction of a self-supporting dielectric block (Le, a block which does not have a shell in surrounding relationship thereto) which Will retain the contacts within the cavities with the required degree of retention force and which will not be damaged upon repeated extractions and withdrawals.
It is understood that the polyurethane in accordance with the invention may have any of the commonly used configurations. That is to say, the block may be 'cylindrical or rectangular as commonly known to the art. Each block will be provided with a plurality of cavities for reception of contact pins and sockets. Commonly, an individual connector block will be provided with from 20 to 100 cavities to form a multi-contact connecting device for an equal number of individual conductors.
A dielectric block having a cavity extending therethrough from the rearward side thereof to the mating side, said cavity having a conical portion intermediate its end which tapers towards said mating side, a short uniform diameter constricted portion immediately adjacent to said tapered portion and between said tapered portion and said mating side, and an enlarged diameter portion 10 said constricted portion disposed in a circumferential recess on said contact.
References Cited by the Examiner UNITED STATES PATENTS 2,758,291 8/1956 Richards 339-94 2,778,810 1/1957 Muller et a1 260-454 3,068,443 12/1962 Nava et a1. 339217 3,125,395 3/1964 Swanson 339-176 PATRICK A. CLIFFORD, Primary Ex miner.
I. H. MCGLYNN, Assistant Examiner.