US 3133775 A
Description (OCR text may contain errors)
y 9, 1964 M. PLAXA 3,133,775
l MULTIPLE CONTACT ASSEMBLY Filed June 4, 1962 2 Sheets-Sheet 1 INVENTOR. Nucnaan. Puma May 19, 1964 Filed Jul 1e 4, 1962 O as 5 2 Sheets-Sheet 2 INVENTOR.
MICHAEL HXA United States Patent Ofiice 3,133,775 Patented May 19, 1964 3,133,775 MULTIPLE CONTACT ASSEMBLY Michael Plaxa, Camp Hill, Pa., assignor to AMP Incorporated, Harrisburg, Pa. Filed June 4, 1%2, Ser. No. 199,768 2 Claims. (Cl. 339-18) This invention relates to an improved multiple contact assembly and more particularly to a contact assembly frame construction.
There has been developed a multiple contact connecting or switching device for simultaneously interconnecting electrical circuit paths between the numerous components of computers or other electronic oflice equipment. Examples of such devices are shown in the US. Patents No. 2,927,295 to Gilbert C. Sitz and No. 2,594,737 to J. M. Cunningham and are generically termed plugboards or patchboards. The usual construction employed in plugboards includes a fixed panel member having an array of contact spring members disposed therein and a movable panel member having a similar array of contact pins disposed therein; the panels being held by mounting and closing means capable of driving the movable panel toward and parallel to the fixed panel to effect an interconnecting of the arrays of contacts of each panel. In one typical known assembly, the contact spring and pin assemblies are each driven and held under contact pressures of eight to ten ounces. As a result of this the panels are exposed to stresses which may be unevenly distributed dependent upon the pattern of pins inserted in the movable panel. These stresses are accentuated by extremes of temperature and humidity and by vibration or shock loads imparted to the assembly with the result that the panel members may twist or Warp. In such instances, the resulting misalignment of the contact members frequently causes a partial or total failure of interconnection between contact paths.
In an effort to provide a contact assembly which is reliable under the foregoing conditions, the prior art has utilized a relatively heavy construction comprised of thick phenolic or diallyl phthalate panel members reenforced by heavy gauge aluminum or stainless steel frames interiorly channeled to accomomdate the edges of the insulating panel members. As a result of this construction, multiple contact assemblies of the prior art are not only very heavy but also quite expensive; the largest single part of the cost being due to the necessity of machining the interior channel within the aluminum or steel frame members. As a further result of this construction, care must be taken with the conductors positioned about the periphery of the panel members in order to avoid accidental grounding against the metal frame members. As a still further result of this construction, the assembly sensitivity to vibration or shock loads has restricted the field of application of plugboards; particularly, with respect to aircraft or other vehicular use.
Attempts have been made to use extruded aluminum or rolled steel members in lieu of machined pieces but such efforts have been met with tolerance problems resulting in additional assembly time and excessive waste of material. Moreover, such assemblies do not provide the electrical insulation and vibration isolation which is desirable in the above mentioned applications.
In answering the foregoing problems, the present invention features an improved version of the plugboard assembly including as one object the provision of a multiple contact assembly of a light weight yet rigid and sturdy construction.
Another object of the invention is to provide a multiple contact assembly having a novel insulating and shock resistant frame.
A further object of invention is to provide a contact carrying panel frame construction of inexpensive components.
Other objects and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings in which there is shown and described an illustrative embodiment of the invention; it is to be understood, however, that this embodiment is not intended to be exhaustive nor limiting of the invention but is given for purposes of illustration in order that others skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify it in various forms, each as may be best suited to the conditions of a particular use.
In the drawings:
FIGURE 1 is a perspective of a plugboard assembly including the movable panel of the invention;
FIGURE 2 is a plan view of the movable panel of the invention showing the components thereof in greater detail;
FIGURE 3 is an enlarged cross section of the panel of the invention as viewed from lines 33 of FIGURE 2; and
FIGURE 4 is an enlarged cross section of a portion of the panel of the invention as viewed from lines 44 of FIGURE 2.
Referring briefly to FIGURE 1 there is shown a plugboard assembly including a fixed panel 60 having an array of spring contacts 62 disposed and secured therein; the panel 64) being mounted in a frame member 64 channeled to receive and support a movable panel 20. The frame 64 additionally includes along the bottom interior a camming device comprised of a cam 66 operable by means of levers 68. In the normal use, the movable panel 20 is inserted via pivot points having vertical motion relief not shown but in the vicinity of numeral and then swung into position on such pivot directly over the camming surface 66. The panel 20 would normally include pin members such as the member 23 shown in FIGURE 3 inserted in the panel apertures 24. Upon being swung into an operable position, the panel 20 is thereafter cammed by rotation of handle 68 to the vertical position; the contact members of panel 20 being driven thereby to individually engage the spring members 62 of the fixed panel. In this the operative position, panel 20 must sustain and transmit the cumulative forces of ten to several thousand pin contacts distributed in different patterns in apertures 24. As will be appreciated, the travel spacing between the pin assemblies of panel 20 and the spring contacts of panel 60 is very slight and relaxation caused by warping, twisting or undue com pression of the movable panel 20 will result in a failure of contact. As a further consideration, the contact pressure between the point of contact with the lower portion of the panel 20 and the cam 66 is quite considerable posing the double problem of panel fracture and relaxation due to compression. These problems are met by the assembly of the invention through the provision of a specialized plastic material formed into an intermediate channel such as 26, overlapping and engaging the edges of the panel board members 22 on one side and framed by a relatively thin metal bar stock 28 on the other side. The plastic frame 26 serves to insulate and isolate board members 22 from any metal-to-metal contact with the fixed frame 64 and, more importantly, to secure the members 22 against possible misalignment due to the forces imparted by the panel contact pin members. The metal frame serves to reenforce the intermediate plastic frame against bending moments and, additionally, serves to receive and evenly distribute the high force per square inch transmitted by the camming member. As a further point, the metal members serve to receive the projections at either end of the panel which respectively operate to pivot and lock the panel within the fixed frame 64- and to accommodate the screws securing the handles 34 to the movable panel.
Referring now to the assembly of the invention in more detail and to FIGURES 2, 3 and 4, the preferred construction includes five framing components 32, 40, 42, 44 and 46 of a relatively hard insulating material positioned and held along the edges of the four panel members 22. The peripheral members are suitably reenforced by steel members comprised of fiat bar stock disposed within a channel in the peripheral components; the member 32 being reenforced by a steel rod fitted therein. The outer component members, such as 40, are secured at their ends by means of screws such as 49 threaded through one bar member into an abutting bar member; the screws 49 additionally serving the purpose of supporting and locking the panel member 20 as described with respect to FIGURE 1. The peripheral members 40, 42, 44 and 46 include an intermediate plastic frame member held in frictional engagement with the panels 22 and the bar members, and should be of a length to provide a clearance such as 53 between each two frame members. In this manner, the individual stresses caused by expansion and contraction of the panel members will not be transmitted each to the other in the longitudinal sense.
As shown in FIGURE 3, the intermediate plastic frame 41 has a configuration which is structurally equivalent to the well known I-beam. By reason of this construction the member 41 is particularly capable of resisting bending moments applied in either of the directions which would tend to twist or warp the panel 20. The member 41 includes an upper channel of a depth D suificient to form a bearing area with the bar member 56 and capable of holding the bar member and the intermediate member from relative transverse movement. The sidewalls 52 formed by the upper channel of member 41 serve to insulate the peripherally disposed contact conductors from accidental grounding with the bar 56. As an additional point, it will be noted that the leakage path from conductor 25 to the bar member 56 is extended to include at least the length of a transverse path along the outside surface of member 41. The member 41 further includes an inner channel 54 having a depth D sufficient to hold the panel member 22 against transverse movement relative to the frame assembly. For this reason the channel 54 must be carried with a tolerance sufficient to provide a relatively tight-fit between the member 41 and the panel member 22 and the depth D must be sufiicient to provide a bearing area with the panel 22 in the presence of temperature variations and resulting contractions of panel 22. It has been found useful to bevel the outer edges of each intermediate frame member to prevent undesirable chipping or cracking of the frame during use.
The center component 32 is comprised of plastic frame members 48 and 50 similar in shape to the peripherally disposed intermediate frame members and adapted to receive panels 22 on one side and shaft 51 on the other side. Shaft 51 extends longitudinally through the center of the member 32 and transversely through the frame component members 46 and 44 wherein it is locked by means of a threaded nut on each end, such as 36 as shown in FIGURE 1. The provision of the shaft 51 has been found desirable in the larger sizes of movable panel members in order to avoid bowing of the peripheral frame members.
As will be apparent from the foregoing description the plastic channel members must have particular material characteristics including high dielectric strength, resist ance to dimensional changes responsive to temperature and humidity variations and most importantly, the capabi'ity to withstand constantly applied forces without compression. For this reason the use of natural and synthetic rubber or the usual thermoplastic material such as nylon or Teflon will not suffice. A suitable plastic has been found to have characteristics approximately the following:
Moisture absorption per 24 hours 1% Dielectric strength 400 volts per mil. Impact strength (Izod test) 0.5 pounds. Flexural strength 10,000 p.s.i. Tensile strength 6,500 p.s.i. Compressional strength 27,000 p.s.i. Rockwell Hardness test M=110.
Of several materials having these characteristics, a preferred plastic is a rag-flock filled phenolic resin.
In the production assembly of the invention, the plastic and metal members may be measured and cut from stock lengths based upon the dimensions of the particular panels employed. The transverse members 48 and 50 would normally be placed on first followed by insertion of rod 51 and members 40, 42, 44 and 46. Thereafter, screws 49 and nuts 36 may be secured and, if desired, handles such as 34 may be added.
With respect to resistance to vibration and as to insulation, the assembly of the invention appeared to be clearly superior to that of known prior art devices comprised of steel or aluminum frame members.
While the contact assembly shown in FIGURE 1 includes four panel members it is to be understood that one, two or larger numbers of panels can be accommodated employing the frame of the invention. It is further contemplated that other electrical connecting devices having relatively high compressional loads may be improved by use of the invention.
Changes in construction will occur to those skilled in the art and various apparently different modifications and embodiments may be made without departing from the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by Way of illustration only. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective against the prior art.
1. In a plugboard device of the type having a first panel including a matrix of symmetrically spaced apertures having arrays of contact springs extending from one surface of the first panel and a second panel including a complementary matrix of symmetrically spaced apertures having arrays of contact pins extending from one surface of the second panel adapted to engage the said springs, the second panel having a construction including board members of thermosetting plastic material carried and secured by a first frame substantially surrounding and contacting said board members and a second frame surrounding and contacting said first frame and spaced from said board members, the said first frame including top, bottom and side portions channeled on one side to receive edges of said board members and on the opposite side to receive said second frame, the said first frame being comprised of thermosetting plastic material which is relatively hard and compression resistant, the said second frame being comprised of metal members secured at the ends thereof to form a structurally integral assembly whereby said boards and contact pins are held in said second panel to engage said contact springs under substantial pressure without relative movement between the board members or frames of said second panel.
2. The device of claim 1 wherein said second panel includes a further member of thermosetting material disposed between board members and centered between said top and bottom portions, the said further member including portions channeled on one side to receive said board members and on the opposite side channeled to receive a metal member secured to the second frame to lock said first frame side portions against said board members.
References Cited in the file of this patent UNITED STATES PATENTS 2,202,783 Morrell May 28, 1940 2,257,001 Davis Sept. 23, 1941 2,594,737 Cunningham Apr. 29, 1952 2,683,980 Krause July 20, 1954 2,753,603 Strawther July 10, 1956 2,978,758 Dunn Apr. 11, 1961 3,012,642 Emmerich Dec. 12, 1961