US 3265781 A
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Description (OCR text may contain errors)
Aug.9,1 966 i D. M. PETERSON 3,265,731
ASSEMBLY METHOD Filed June 17, 1963 DEA/V M. PETERSON INVENTOR. fiZwA/M 1 wxfia 52 58 I ATTORNEYS 3,265,781 ASSEMBLY METHOD Dean M. Peterson, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey t Filed June 17, 1963, Ser. No. 288,219
' 6 Claims. (Cl. 264-27) This invention relates to an electric conductor assembly and, more particularly, to a method for assembling a plurality of insulated electric conductor elements having a predetermined critical spacing.
In the art of electric conductors involving support of adjacent co-operating conductors and mechanical components with the conductors being respectively insulated,
there are many complex and time-consuming arrangements for completing an assembly. A most troublesome problem is to assembly several closely spaced insulated conductors having critical spacing relationship, particularly if the" parts or some of them are small or diflicult to align in a particular assembly.
I membcris then inserted through the center of the collar and heated to soften the collar and allow compression thereof over the plate member. The assembly is then cooled, whereby the thermoplastic, having compressional loading, insulates the plate member from the contact while holding both in place.
The subject matter which is regarded as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, as to its organization and operation together with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawing in which:
1 FIG. 1 is a perspective view partiallyin section of components of my invention prior to completion of the assembly;
FIG. 2 is a sectional side elevation view of a portion of a completed conductor assembly in a particular circuit arrangement; and v FIG. 3 is a simplified schematic drawing of an assembly machine for this invention. I
Referring now to the drawing wherein like numbers refer to similar parts, I have shown in FIG. 1 a thermoplastic base member 10, made of polystyrene or the like insulating material, provided with'an upwardly extending collar 12 around which is located a sheet metal conductive plate 13. In the center of thecollar 12 is provided an aperture 14 suitable for defining the location of. a knurled contact screw 16, as shown in FIG. 2. In one particular arrangement, the inner diameter of the aperture.14 is .086" and the nominal diameter of the shank portion of the contact screw 16 is .082", "with the thread- 7 ing of the knurled portion 20 being .1" overall. I prefer that the contact screw be of hardened steel and have a 'nickel plate finish if it is to be exposed to weathering.
By way of example, the thickness of the metal plate 13 is selected as .025", with the aperture 17 thereof being slightly greater than .156" and the diameter of the collar 12 being .156". As is a usual case, the largest conductor'in assembly is grounded, as indicated on a tab 18 'of the plate 13 which extends through the base 10.
Referring now to FIG. -2, a portion of a completed United States Patent 3,265,781 Patented August 9, 1966 assembly is illustrated wherein the base 10 has received the contact screws 16 and 16', with the knurling 20 providing a nonslip fit. The particular knurling illustrated as helical, as indicated at 20. The collars 12, illustrated as substantially cylindrical in FIG. 1,' have now been flattened substantially to provide integral plastic washers 22. In the particular construction being explained herein, the thickness of these washers 22 is of the order of .012", with a portion of the mass of the material of the collar 12 being compressed downwardly to tightly engage the inner surface ofvthe aperture 17 of the plate 13 during the assembly.
In order that the washers 22 are loaded only in compression wherein plastic materials are able to withstand substantial stresses, the tolerances of the assembly arrangeme nt are controlled. Thus, the compressing action is limited so that the washers 22 do not extend substantially beyond the extremities of a flange 24 of the screw 16. As indicated in FIG. 2, the plate 13, being securely held by the screw 16, may be utilized to physically support an additional member 26 which is inserted under a raised flange portion 28 andis provided with a ramp 29 to facilitate insertion thereunder. Another feature of the present invention which I prefer to use is an extraordinarily wide and flat head portion on the screw 16 so that the flange 24 extends substantially beyond the initial location of the collar 12 to facilitate use of a reasonably large washer 22. The particular flange 24 is arranged with a fiat lower surface of .187" in the example described herein. The screws 16 are also provided with a contact button 30 thereon suitable for engaging, in a usual manner, sliding or compressional contactors which may be an integral portion of the additional member 26.
One circuit arrangement in which the present invention is useful is also illustrated in FIG. 2 wherein a lamp 32 must provide luminance at a specific instant. The lamp 32 is arranged to be energized by a pair of serially connected batteries 34 and 35. Both the lamp 32 and the batteries 34 and 35 may be supported in the additional member .26. Prior to initiation of illumination of the lamp 32, a normally closed switch 37 grounds one side of the lamp 32 and the battery 34 through the contact screw 16, with the other side of the lamp being grounded through the tab 18. Immediately prior to initiation of illumination of the lamp 32, the series battery circuit (34-35) is grounded by a'normally open switch 38 to develop a substantial current flow through the contact screw 16, the batteries 34 and 35, and the grounded contact screw 16. An instant thereafter, the switch 37 is opened to force the circulating current through the lamp 32 and provide luminance at the desired instant.
In order to assure good contact between the contact screws 16 and 16' and the circuit components of the switches 37 and 38, I have provided the tips thereof with a sharpened lower extremity 39. These tips are about 60 in cross section and also enhance contact during direct electric heating assembly, as discussed below. Such sharp contact points tend to cut through high resistance oxide layers that often develop on repetitive make-and-break connections to reduce the connection impedance and any localized heating which might be caused thereby.
As mentioned above, during assembly of the present invention, the collar 12 is forced to flow to attain the configuration of the circuit components illustrated in FIG. 2. Since the material of the collar '12 is an integral part of the base 10 and is, therefore, a thermoplastic, one means of obtaining plastic flow without excessive concentrations is to heat the collar 12 during assembly. This heating should be of the order of.180 F. with F. and 280 less pressure-time" is needed to accomplish necessary plastic flow. By utilization of .6 second heating to temperatures of the order of "180? F. and applying pressure for approximately five seconds, plastic flow of the order of that discussed above results for components of the sizes indicated. Of course, larger assemblies require an increase in the temperature-pressure-time function to attain equivalent plastic flow.
. While it is obvious that assembly of this invention could be accomplished by hand tools such as heated soldering irons being applied forcefully to the top of the contacts 30, I prefer to use electric current heating, which is somewhat easier to regulate. With the particular size collar 12 and contact screw '16, heating .6 second with 5 amperes per screw will soften the thermoplastic sufficiently. Also,
I prefer to use controlled pressure and stroke limits during the period of plastic flow.
Referring now to FIG. 3, I have shown a simplified schematic diagram of a machine arranged to accomplish assembly of the contact screws -16 in the base 10. As a first step in the assembly operation, contact screws 16 are presented One at :a time from a feeder 40 to a-drive shaft 41 and may be held on the drive shaft 41 by any convenient means such as clips or an electromagnet 42. Next, the base is located on a fixture 44 having various guide surfaces as illustrated at 45 for precisely locating the aperture 14 under the drive shaft 41. Usually, such fixtures 44 are precisely engineered to attain close tolerance positioning. However, many such fixtures are presently known, and the details thereof need not be set forth here.
,As a motor 48 drives an eccentric (gear arrangement 49 and 50, the drive shaft. 41 inserts thecontact screw 16 in the aperture 14 and positively drives it in accordance with the effective radius of the eccentric gear 49 until it engages a contact 52. As soon as the drive shaft 41 has moved its full downward stroke, a switch 54 is energized to develop the .6 second high current flow through a loop circuit including the piston 41, the contact 52 and the contact screw 16. A high current source is indicated at 56 as having several batteries contacted in parallel. However, A.C may be used just as effectively. v
I prefer that the electric impedance of the contact 52 and the drive shaft 41 be very low so that a primary heating within the loop circuit is in the contact screw (16 itself. The sharp point 39 of the contact screw 16 assures a low impedance coupling of the shank portion to the contact 52. The low impedance connection is most easily accomplished by actually driving the sharp tip 39 into the surface of the contact 52. By such a good contact, a large portion of the heat in the region of the tip 39 flows into the contact 52 to prevent excessive heating of the tip 39. The plastic flow of the collar 12 is accomplished during the 5-second period after heating has been initiated, with presure being maintained by spring bias applied to the base member 10, as by springs indicated at 58. The exact thickness ofthe washer 22 is a function of the total mass of the collar 12, and a pair of stop controls 60 which limit the drive stroke of the springs 58 as well as being a function of the heat-pressure-tirne function. I
Obviously, two or more contact screws 16 may be set simultaneously by aligning two or more of the equipments illustrated in FIG. 3. Usually, at least two such screws will be required for securing a plate '13 subject to variable stress considerations, such as, from time to time, supporting the additional member 26.
While I have shown and described particular embodiments of the present invention, other modifications may occur to those skilled in this art. For instance, the flange 24 may be inversely tapered slightly instead of being fiat as'suggested above. Such a taper would result in a slightly increased thickness in the region of the aper- Generallyspeaking, the hotter the plastic becomes, the
ture 17. However in most embodiments of the present invention, such additional expense is not warranted by the increased physical and dielectric strength attainable there by. I intend, therefore, to have the appended claims cover all modifications which fall within the true spirit and scope of my invention.
1. An assembly method using a headed screw formed of heat conductive material, a plastic; base member formed with an upstanding collar, and a plate to be connected to said member and having an aperture slightly larger than said collar for receiving the collar therethrough, comprising the steps of positioning a plate having an aperture therein over the upstanding collar;
driving the screw through the collar;
heating the screw sufficiently to soften at least a portion of the collar; and
pressing the screw toward the plate to expand the softened collar therebetween to form an integral washer over a portion of the plate lying under the lower surface of the screw head.
2. An assembly method using a thermoplasti; base member and at least one conductive contact screw having a head with a fiat lower surface large enough to extend over a portion of and retain a conductive plate, with the assembly being subject to critical spacing considerations, comprising the steps of positioning the conductive plate to at least partially encompass an upwardly extending collar of the thermoplastic base member, with the overall diameter of the collar being less than that of the flat lower surface of the head of the contact screw; driving the conductive contact screw through the center of the collar; heating the screw sufiiciently to soften at least a portion of the thermoplastic collar; pressing the screw toward the plate to expand the softened collar therebetween to form an integral washer over a portion of the plate lying under the flat surface of the screw head; and
allowing the assembly to cool to prevent relative motion of the parts thereof.
3. An assembly method using athermoplastic base member and at least one heat conductive contact screw having a head with a flat lower surface for retaining a conductive plate, with the assembly being subject to critical spacing considerations, comprising the steps of:
positioning the conductive plate to at least partially encompass an upwardly extending collar of the thermoplastic base member;
driving the conductive contact screw through the collar so that the flat lower surface lies over a portion of the conductive plate;
heating the screw sufficiently to soften at least a portion of the thermoplastic collar; and
pressing the screw toward the plate to expand the softened collar therebetween to form an integral washer over the portion of the plate lying under the flat surface of the screwhead.
4. An assembly method according to claim 3 wherein the heating step includes a step of passing a high electric current through the screw for a duration sufficient to raise the temperature of the collar to about F.
5. An assembly method using a thermoplastic base member having an upwardly extending collar thereon and at least one conductive contact screw having a head with a flat lower surface large enough to extend over a portion of and retain a conductive plate, with the assembly being subject to critical spacing considerations, comprising the steps of:
positioning the conductive plate to at least partially encompass the upwardly extending collar of the thermoplastic base member;
resiliently supporting the region of the base member including collar; driving the conductive contact screw through the collar so that the flat lower surface lies over a portion of the conductive plate, said driving step being sufiicient to compress the resilient support of said supporting step; heating the collar sufficiently to soften at least a portion thereof; and 1 raising the base member a limited amount while holding the screw down to compress a portion of the collar between the screw and the plate to thereby expand the softened collar therebetween to form an integral washer over the portion of the plate lying under the flat surface of the screw head. 6. An assembly method according to claim 5 wherein the heating step includes the step of passing a high electric current through a screw for a duration sufiicient to raise the temperature of the collar to between about 130 F. and 280 F.
References Cited by the Examiner- UNITED STATES PATENTS ROBERT F. WHITE, Primary Examiner. DARRELL L. CLAY, ALFRED L. LEAVITI,
W. B. FREDERICKS, T. J. CARVIS,