US1388622A - Screw-threaded connection - Google Patents

Description

L. J. VOORHEES.

SCREW THREADED CONNECTION.

APPLICATION FILED MAY 29, 1920.

1,388,622. Patented g- 23, 1921.

UNITED STATES PATENT OFFICE.

LEE 3'. VOORHEES, OF IBING-HAMTON, NEW YORK, ASSIGNOR TO NATIONAL CARBON COMPANY, INC., A. CORPORATION OF NEW YORK.

SCREW-THREADED CONNECTION.

To all wlmm it may concern:

Be it known that 1, LEE J. VOORHEES, a citizen of the United States, residing at Binghamton, in the county of Broome and State of New York, have invented certain new and useful Improvements in Screw- Threaded Connections, of which the following is a specification.

This invention relates to screw-threaded connections between members formed of materials exhibiting different changes of dimensions under the influence of the same change in conditions. The invention also includes the process of making the connections referredto above.

The object of the invention is to provide a form of connection in which the connected parts will neither seize nor become excessively loose when they undergo unequal expansion or contraction.

It is well known that various materials are unequally affected by changes in the corn dition to which they are exposed. For example, if a piece of wood has attained a constant length in an atmosphere containing a large percentage of water vapor and the content of water vapor is then reduced, other conditions remaining the same, the piece of wood will contract or shrink. A piece of metal subjected to the same change would not be altered in length. Likewise an increase in temperature will cause a piece of metal to expand more than a piece of the same size made from many non-metallic materials, and there isa material difference among the various metals with respect to their temperature-dimension relations. Changes in pressure can also affect different solid materials unequally.

When it is necessary to join unlike materials by a screw-threaded joint which is to be subjected to changes of conditions, the dimensions of the parts must be such that t the connection will still be preserved when an unfavorable extreme condition is encountered. Furthermore, if the parts are to be joined so that they can be readily separated under all conditions, the parts must be of such sizes that they will not seize under extremes of expansion and contraction. If due allowance is made for extremes winch favor seizing of the parts, the connection is apt to be loose and unreliable under all other conditions. Specific in- Specification of Letters Patent. Patented Aug. 23, 1921.

Application filed May 29,

1920. Serial No. 385,378.

stances of this nature are found in cases where male-threaded members of wood or the like are fitted to female-threaded members of metal, or where male-threaded members of metals of low expansion such as iron, are fitted to female-threaded members of metals of high expansion, such as copper or aluminum. The former joints are likely tobe tootight in damp weather and too loose in dry, while the latter joints will be too tight when cold and too loose when hot.

As a further specific instance of the effect of changes of atmospheric condition upon a joint connecting parts of dissimilar mate rial, it may be. said that it has heretofore been regarded as impractical to attach the usual metal end ca of a flashlight directly to the casing of t e light by means of a screw-thread when the casing is made of fiber or other material which is subject to dimension changes under the influence of changing atmospheric conditions, for example, variation in the moisture content of the atmosphere. When it has been attempted to so directl thread together metal ca s and fiber casings, it has been found that in dry weather the fiber becomes so contracted that the joint is loose and unreliable, while in very damp weather, the fiber casin be comes so expanded that the casing an ca will become seized and may be separate only with the greatest difficulty.

0 provide between such dissimilar materials a connection which will not seize under the extreme conditions favoring a close fit and which will not become loose under the opposite extreme of conditions, I have designed the form of connection hereinafter described, two specific examples of my invention being shown in the accompanying drawings, in which- Figure 1 shows a threaded metal cap directly attached to the threaded tubular fiber casingof a flashlight,

Fig. 2 shows an end View of the flashlight The flashlight shown in Fig. I is of a general and well known construction and only those parts which comprise my improvement will be described.

The casing 6 for holding the battery is of fiber as already mentioned. The end-cap 7 for retaining the battery in the casing, is of metal. According to the prior practice, it has been found necessary to attach to the end of the fiber casing, a threaded ring, for

dition will be reached after continued explosure to air saturated with water vapor. pon a change to dryer atmosphere, the top 6 will shrink and in the absence of special provisions to prevent its receding from the metal cap 7, 1t would, under conditions of extreme dryness, become so shrunken that the joint between the tube and cap 7 would be worthless from a practical point of view.

To revent the casing 6 from receding from t e cap 7, when'the casing undergoes contraction, I have provided a special form of end-ca comprising inclined surfaces 9 which wil engage the end of the tubular casing 6 upon application of the cap, and expand it against the threads of the metal cap provided a shrinkage of the tubing has already taken place. If the tube 6 1s already at its full size, the inclined surface will merely engage its end without enlarg-- ing its diameter. Whether or not the tube was at its full size when the parts were assembled, when the 'cap 7 is turned to the limit of its motion on the screw-thread, the inner corner of the lower extremity of the tube will be engaged by the inclined surface 9 1n such a way that the top of the tube may shrink without any possibility of the lower end, comprising the greater part of the screw-thread, being able to recede from the metal cap. A shght recession may take place near the top of the metal cap, as best shown in Fig. 4, but since the threads will be in contact throughout a considerable proportion of their length, this will be Sllfilr cient to maintain the joint in a tight and satisfactory condition, in spite of the shrinkage of the body of the tube. The slots 8 will ermit a reduction of cross-section of the her tube in its unrestrained portions while the original cross-section is maintained at its lower end without splitting the tube, because'of the increased resiliency provided by said slots; A similar construction mahy be used at the lamp-end of the casing. rom the foregoing, the operation of the joint shown in Fig. 5 will be readily understood. In this figure the tube 10 is formed from ametal having a low coefiicient of expansion and is rovided at its end with a female-thread. he tube 11 is formed from a metal having relatively high coeflicient of expansion and is provided with a malethread enga ing the thread on'tube 10, an inclined sur ace performing the same function as the surface 9 of Fig. 1, being provided by the internally projecting flange 12 inside the tube 10 at the extremity of the thread with which tube 10 is provided. The slots 13 in tube 11 perform a function exactly similar to the function of slots 8 in Fi s. l and 2.

' ssuming that the joint of Fig. 5 is designed to be tight at a certain high temperature, and that the parts must not be seized at this temperature, the tubes are so proportioned that a perfect fit will be attained when the connected tubes have acquired the dimensions corresponding to this temperature. If the jointis then subjected to lower temperature, the tube 11 will contract more than the tube 10 and there will be a tendency for the threads to become separated, especially near the extremity of tube 10. However, the reater part of the engaging threads wil continue to be held in close contact by means of the inclined surface 12, and the loosening of the joint, which will follow the decrease in temperature, will not be greater than is permissible under the circumstances.

While the invention has been illustrated in its application to certain specific cases where a screw-thread joint or connection be tween parts ofdissimllar materials is desirable, it will be apparent that the invention may be applied to a great variety of connections and may be employed where er one of the materials is in tubular form, elastic enough to undergo slight fiexure without breaking, stiff enough substantially to maintain its original form in spite of the defor-' mation of its end by a wed 'ng action, and capable of taking a screw-t read.

I claim:

1. A connection which com rises a tubular member of a material WhlCh is stiff but flexible, said tubular member having a screwthread and being provided with slots to increase its resiliency, a second member of a material diflering from the material of the tubular member in the change of dimensions which it exhibits under the influence of the same change in conditions, a screw-thread on said second member enga ing the screwthread on the tubular mem er, and means to hold portions ofthe respective screwtive changes in the dimensions of the connected members.

2. A connection which comprises a tubular member of a material which is stiff but flexible, said tubular member having a screw-thread and being provided with slots to increase its resiliency, a second member of a material differing from the material of the tubular member in the change of dimensions which it exhibits under the infiuence of the same change in conditions, a

screw-thread on said second member engag ing the screw-thread on the tubular member, and an inclined surface attached to said second member and adapted to hold portions of the respective screw-threads in close contact regardless of relative chan es in the dimensions of the connected mem ers.

3. A connection which comprises a'tubular member of fiber or the like, said tubular member being provided with slots to increase crease its resiliency, a metal cap, a screwthread on said metal cap engaging the screwthread on the tubular member, and an inclined surface forming a part of the metal cap andadapted to hold portions of the screw-thread in close contact regardless of shrinkage of the tubular member.

5. Process of connecting a screw-threaded tubular member to a second member made of material differing from the material of the tubular member in the change of dimensions which it exhibits under the influence of the same change in conditions, which comprises forming on the second member a screwthread adapted to engage the thread of said tubular member, cutting the end of the tubular member to increase its resiliency, providing an inclined surface attached to said second member and adapted to force and hold the respective threaded portions in closer contact when the members'are screwed together, and then screwing the members togethen' 6. Process of connecting a screw-threaded tubular member to asecond member made of a material differing from the material of the tubular member in the change of dimensions which it exhibits under the influence of the same change. in conditions, which comprises forming on the second member a screw-thread adapted to engage the thread of said tubular member, slotting the end of the tubular member to increase its resiliency, forming on said second member an inclined surface adapted to force and hold the re-.

spective threaded portions in closer contact when the members are screwed together,'and then screwing the members together.

In testimony whereof, I affixmy signature.

LEE J. VOORHEES.

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