US2568149A - Line pipe hanger - Google Patents

Description

Sept. 18, 1951 C. G. GRAB E LINE PIPE HANGER 2 Sheets-Sheet 1 Filed Sept. 30, 1948 x m m w.

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Sept. 18, 1951 c. e. GRABE LINE PIPE HANGER 2 Sheets-Sheet 2 Filed Sept. 30, 1948 LOA D ZUHF UMJM MD ZOMPUWJm HQ INVENTOR- Cmesms 6.620051 BY @W,& d u@ v Patentecl Sept. 18, 1951 LINE PIPE HANGER Clarence G.

Grabe, Pittsburgh, Pa.,

assignor to National Valve & Manufacturing Company, Pittsburgh, Pa., a corporation Application September 30, 1948, Serial No. 51,872

This invention relates to hangers for applying a substantially constant vertical support to a suspended load throughout a range of vertical movement of the load, and, in particular to pipe hangers used to support vertically expanding and contracting pipe.

In a number of plants, factories, or on shipboard it is common practice to carry high temperature fluids in piping which rises vertically to a point near the ceiling and then passes horizontally to a desired place of use or, in some cases, passes downwardly through one or two floors and then is projected horizontally. Such piping, of course, is subject to considerable vertical expansion and contraction caused by temperature changes. Consequently, there exists the problem of providing a pipe support, or hanger, which will exert a constant supporting force as the pipe rises and lowers. A number of supports have been designed for this purpose, but these are not fully satisfactory either because they are imperfect and have appreciable variations in their supporting force, or because they require, to reduce these support variations,

the use of auxiliary devices, such as booste springs. Such auxiliary devices not only urinecessarily complicate their construction andadd to their expense, but also introduce additional friction which is an undesirable and uncontrollable element.

It is therefore an object of, this invention to provide a simple, inexpensivehanger which will apply a vertical support ma suspended load that is substantially constant throughout a range of vertical movement of the load and which does not require auxiliary, friction-introducing devices to achieve this constancy.

According to the invention, the hanger comprises a support-engaging and a load-engaging 3 Claims. (Cl. 248-54) member, the latter being disposed in substantiaL ly vertical alignment with the former. A rigid bracket is provided which is attached at its upper end to the support-engaging member and extends downwardly at an angle from it. A strut is pivotally attached on horizontal axes at its ends both to the load-engaging member and to the lower portion of the hanger bracket. and, preferably, the strut extends laterally downward from the bracket.

The upward force which is exerted on the loadengaging member is supplied by a spring mechanism that is pivotally attached to the load-engaging member, preferabh', on the same horizontal axis as the axis of attachment of the st'rut to that member. This spring mechanism is projected upwardly and laterally from its attachment at an angle to the strut and is pivotally attached to the bracket on a horizontal axis above and most suitably in substantially vertical alignment with the axis of attachment of the strut to the bracket. Preferably, the spring mechanism includes a rigid arm which has a compression spring coiled about its upper end, the spring being held in compression by a pair or upper and lower spring caps. The arm extends slidably through the lower cap and is bolted to the upper. The lower cap preferably is formed integrally on a yoke which straddles the bracket and is pivotally attached to it on the horizontal axis referred to above.

Briefly, the action of the hanger, which will be explained in detail later, is that, as the supported pipe expands and rises, the spring relaxes and exerts less upward force, but the angle between the strut and the arm increases to such an extent that the consequent increased leverage, or mechanical advantage, gained by the strut compensates for the reduced spring pressure. If the supported pipe contracts and the load-engaging member lowers, the action is reversed, but in either event, it can and will be proven that there is a mathematically constant vertical support for the pipe.

The preferred embodiment of the invention is illustrated in the accompanying drawings 0t which Fig. 1 is a side elevation of the hanger being used to support pipe and showing in dotted lines the position of the hanger parts after the pipe has expanded a certain degree; Fig. 2 a right-hand end view of the hanger shownin Fig. 1; Fig. 3 a section on line III-III of Fig. 1; Fig. 4 a diagram illustrating the positions of the hanger parts during operation; Fig. 5 a graphic plot of the forces diagrammatically illustrated in Fig. 4; and Fig. 6 a plot of the spring characteristics of several ordinary coil springs such as are intended for use in the present hanger mechanism.

Referring to the drawings the hanger, generally designated by numeral I, is shown suspended at its upper end from a roofing or floor girder 2 and carrying a length of piping 3 which for the purpose of this description will be considered as the load to be supported. Such piping, in many applications, will be a steam line which has a vertical portion 4 and a horizontal portion 6, and it will be apparent that the considerable temperature changes to which it is subject will cause the vertical portion to expand and contract so as to raise and lower the horizontal portion.

The principal components of the hanger include a rigid frame 1 formed as a bracket having two side-by-side plates held together by spacer bars 8, a spring mechanism 9 and a strut these members being pivotally linked together in a particular manner to be described. The hanger may be suspended from girder 2 in any number of ways, although it is preferable to provide a flexible suspension that is capable of absorbing any hanger bending forces. The particular support-engaging member shown includes a girder clamp l2 that is secured to an eyebolt l3 which in turn is bolted to a cross bar I4 disposed between the upper ends of the two plates of frame or bracket member 1 The load-engaging member of the hanger also can assume a number of forms but is shown as including a clamp |6 engaging the horizontal portion of the pipe, the clamp being bolted to an eye-rod I! that is secured to a U-shape member r clevis Hi, the form of which is best shown in Fig. 2. Between the upwardly extending arms of tines of the clevis there is rotatably carried a pin A on which the strut and the spring mechanism of the hanger are pivotally mounted.

Hanger spring mechanism 9 includes an arm or rod 2| the lower end of which is enlarged and provided with an eye that pivotally engages the central portion of a clevis pin A. Around the upper or outer end of rod 2| is positioned a compression spring 22 that is compressed between upper and lower spring caps 23 and 24. Upper cap 23 is bolted to the rod while the lower cap is welded or otherwise rigidly secured to a yoke member 26. This member has two pairs of downwardly extending yoke arms, each pair straddling one of the plates of the hanger bracket and being pivotally secured to the plate by short pins B. As spring mechanism rod 2| projects upwardly from clevis pin A, it passes between the hanger bracket plates and slidably through lower compression spring cap 24 which is provided with an opening to receive it. The outer end of the rod is threaded so that the compression of the spring can be regulated. In the preferred form of the invention, a pair of hanger strut members H are used, the lower ends of these members being provided with openings by which they are pivotally mounted on clevis pin A at either side of the pivotal attachment of spring mechanism rod 2|. The upper ends of each of the struts also have openings to receive a pin C on which they are pivotally mounted between the lower ends of the hanger bracket plates. Preferably, spacer washers 29 are placed on pin C between the struts and the bracket to maintain the alignment of the struts.

In order to accomplish the objects of this invention a certain arrangement of all of the elements of the hangers is necessitated, although it is not intended that the invention be limited to the specific arrangement shown and to be described. Thus, it is of importance for the simplicity of the structure as well as proper operation for the support-engaging member (girder-engaging clamp l2 and eyebolt l3) to be in substantially vertical alignment with the load-engaging member (the clevis and pipe-engaging clamp). Also, hanger bracket 1 extends downwardly at an angle from the vertical alignment of the hanger. Such an outward inclination of the bracket is necessary Since, as will be apparent from a consideration of the mechanism, when. for example, the pipe rises, the pivotal axis of clevis l8 will be about the strut and bracket connecting pin C and, therefore, this pin must lie at a side of the clevis. It also is to be noted that the connection of the clevis both to the struts and to spring rod 2| is on a common horizontal axis which is the axis of clevis pin A. This last arrangement appears to afford the simplest, operative structure, but it may be that the various parts of the hanger could be rearranged so as to render this unnecessary. From this common axis of clevis pin A the struts project outwardly and upwardly to their point of pivotal connection with the lower portion of the hanger bracket plates.

Spring rod 2| also extends upwardly and outwardly from the clevis pin but, in addition, extends upwardly at an angle to the struts so that it is pivotally connected to the bracket plates at a point above the axis of pivotal connections of the struts to the plates. It will be noted that the pivotal connection between the spring rod and the bracket is along the axis of short pins B connecting the yoke arms of lower spring cap 24 to the bracket. Consequently, the force exerted by the spring exerts a thrust between upper spring cap 23 and the hanger bracket plates which in turn imparts a tension force to spring rod 2|. This tension force acts upon clevis pin A, to which the rod is connected, and.has a component which sets up a compression force in strut members I and another vertical component which exerts an uplifting force on the load.

The general operation of this hanger mechanism perhaps can be explained in a number of ways, but the following appears to be the simplest. As the pipe expands,clevis |8,inrising from its full line position in Fig. 1 to its dotted line position swings about strut pin C. However, spring rod 2| instead of swinging about its pin B also must pivot on the arcuate path of the strut or, in other words, on pin C. In so doing, it will be apparent that the distance A to B must decrease during the rise and this, in turn, carries upper spring cap 23 away from the lower spring cap and reduces the compression of the spring. Such reduction, of. course, decreases the force of the spring and, were it not for the strut, the pipesupporting force would not be constant. However, it also will be noted that as the clevis rises the angle between the spring rod and the strut, or angle BAC, increases with the result that the strut gains greater mechanical advantage or leverage for supporting the load.

It is therefore of paramount importance to insure that the mechanical advantage gained by the increasing angle BAC is always throughout the range of movement of the load, mathematically suflicient to compensate for the decreasing tension force of the relaxed spring, and the discovery that this can be accomplished by properly locating the pivotal pins, or points, B and C with respect to each other is a feature of this invention. Thus, it has been found that, if pivot point B is positioned above and in substantial vertical alignment with point C, the hanger provides this substantially mathematically constant support. With point B so positioned it should be noted that the two centers, B and C, lie in a line that is parallel to the line or direction of 'efiective pull of the hanger on the load, or

as is more correct, the efiective pull of the load on the hanger. This parallel relationship produces the constant support characteristic of the hanger. This is stated because of possible modifications in which the efiective pull on the load would not be in a vertical direction, in which case point B would have to be above and to one side of point C.

The mathematical correctness oi the mechanism can be proven from the diagram of Fig. 4 and the plot of Fig. 5 which is derived from Fig. 4. The basis of this proof is a graphical showing that the spring efiort requiredof the spring at any position of the load is in direct proportion to the spring deflection (relaxation or contraction) which will have occurred due to the movement of the load to that position. It is a wellrecognized fact that in any spring the deflection from its free or natural position is in true proportion to the load on the member. Such a deflection, if represented graphically, will appear as a straight line, such as the lines shown in Fig. 6, and these lines will have varying slopes depending upon spring proportions, such as the size of the wire, the coil length and diameter, etc. Such being the case, it follows that any spring modifying mechanism if it is to provide constant load support must compensate in direct inverse proportion for each minute deflection of the spring. If this is achieved then a graphic plot of the load on the spring against spring deflection will appear as a straight line. An-

other way of wording this is that if such a straight line relationship is present, then the component of force in line with the spring is so modified that the uplifting or supporting component of force is an unvarying amount for all positions.

Fig. 4, which is used to show that such a straight line relationship does exist, is a stress diagram laid out in true angular relationship with the mechanism illustrated in Fig. '1. As has been stated there is a tension in rod AB which divides into a component of compression in strut AC and a vertical component which is the load supporting force. This load supporting force, since it acts in a vertical direction can be scaled oil vertically from point C so that in the lower full line position of the mechanism (Fig. 4) it is represented by the line CB. Having determined line CB to be the load supporting force, it becomes apparent that line AB represents the tension force existing in the spring rod and line AC the compression force in the struts.

It should now be 'noted that as an upward movement of the load takes place, clevis pin A describes an are through points A and A this being due to the fixed length of strut member AC.- If during this movement spring rod AB were free to slide through point A instead of through point B it would describe an are about point B through points X and Y. However,

spring rod AB is pivoted to the strut at A and is slidable through the horizontal axis of point B so that it must follow through the are A, A and A It is apparent that in so doing, the distance from this latter are to point B is shortened. Therefore, the increasing distance between are A, A and A and are A, X and Y represents the spring relaxation during this upward movement. It will be noted that during this upward movement the distance B to C (load supporting force) has remained unchanged while the length A to B has successively shortened. Thus, at any fixed position in the rise of the load, this shortened distance, always being in direct alignment with the spring, represents the lessened spring force required to maintain the constant vertical 7 component CB which, since it remains vertical, continues to represent the load supporting force. Thus, at any fixed point in the rise of the load, triangles such as triangles A -BC, or A BC represent forces for such intermediate positions.

If now a plot be made of the varying spring loads (A--B, A -B, A B) against the gradually increasing spring deflection measurements (X--A and Y-A and such a plot shows a true proportional, or straight line relationship between these measurements, then the correctness of the mechanism is demonstrated. Fig. 5 is such a plot in which spring loads A, A B and A -B are measured and laid out along the top or load line, while the spring deflections, or relaxations, A X and A --Y, are plotted as ordinates for their corresponding spring loads. Having made such a plot, it then is found that the line connecting the three points A, X and Y, is a straight line, and, if desired, any number of points can be taken to demonstrate that fact. This straight line represents the spring characteristic required for the particular load represented by the distance CB, but it will be apparent that, for other loadsand other desired spring deflections, the lines representing the spring characteristics assume various slopes such as those shown in Fig. 6. However, regardless of the slope, the lines always will be truly straight, showing that the changing pull of the spring being used is perfectly compensated for by the increasing or decreasing mechanical advantage of the strut member. In this respect, it will be noted from Fig. 4 that the angle BAC gradually increases as the load rises.

The unusual advantages of this mechanism lie both in its simplicity and its substantially perfect operation. One thing that should be noted insofar as simplicity is concerned is that any ordinary or commercial type of spring, all of which have the straight line characteristic referred to. can be selected for use with the mechanism. The particular spring selected, of course, depends principally upon the load to be supported, the approximated fall or rise of the load and the desired amount of spring deflection for that range of rise and fall. The mechanism is unusually compact since no great amount of spring deflection will be required. Further, there is no need of resorting to additional compensating devices to render the operation of the mechanism perfect so'that only the simple linkage illustrated need be used.

In the above description, the mathematical constancy of the mechanism has been referred to repeatedly, In operation, factors of friction or lateral swinging of the mechanism due to the relative flexibility of its support may produce minor deviations from this correctness. These can be minimized by introducing certain wellknown anti-friction elements and by more rigidly supporting the hanger. However, the important point to be considered is that, in no other hanger mechanism except possibly those which utilize auxiliary compensating devices, such as booster springs, etc., can such mathematical correctness be demonstrated.

According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. A hanger for applying a substantially constant vertical support to a suspended load throughout a range of vertical movement of the load, said hanger comprising a support-engaging 7 member, a load-engaging member disposed below said support-engaging member, a rigid bracket attached at its upper end to said supportengaging member, a strut pivotally secured to said load-engaging member and projecting from the load-engaging member toward said bracket, said strut having an end portion lying adjacent the lower portion of said bracket and pivotally attached to said lower portion on a horizontal axis, a spring arm pivotally attached to the other end portion of the strut on a horizontal axis, a spring disposed at the free \end oi said spring arm, upper and lower spring caps, said upper cap being secured to said arm and said lower cap beingpivotally secured to said bracket on a horizontal axis, the point of pivotal securement of said lower cap to said bracket being spaced from the point of pivotal securement or the strut to said bracket, said spring arm projecting laterally from its point of pivotal attachment with said strut and extending slidably through said lower. cap, the point of pivotal securement of said strut to said bracket being in a line with the point of a pivotal securement of said lower cap to said bracket that is substantially parallel to a line representing the direction of the effective pull of the load on the hanger.

2. A hanger for applying a substantially constant vertical support to a suspended load throughout a range oi vertical movement or the load, said hanger comprising a support-engaging member, a load-engaging member disposed below said support-engaging member, a rigid bracket attached at its upper end to said supportengaging member, a strut pivotally secured to said load-engaging member and projecting from the load-engaging member toward said bracket, said strut having an end portion lying adjacent the lower portion of said bracket and pivotally attached to said lower portion on a horizontal axis, a spring arm pivotally attached to the other end portion of the strut on a horizontal axis, a compression spring disposed at the free end of said spring arm, upper and lower compression spring caps, said upper cap being secured to said arm and said lower cap being pivotally secured to said bracket on a horizontal axis, the point of pivotal securement of said lower cap to said bracket being spaced from the point of pivotal securement of the strut to said bracket, said spring arm projecting laterally from its point of pivotal attachment with said strut and extending slidably through said lower cap, the point of pivotal securement or said strut to said bracket being in a line with the pivotal securement of said lower cap to said bracket that is substantially parallel to a line representing the direction of the eflective pull of the load on the hanger.

3. A hanger for applying a substantially constant vertical support to a suspended load throughout a range of vertical movement of the load, said hanger comprising a support-engaging member, a load-engaging member disposed below said support-engaging member, a rigid bracket attached at its upper end to said supportengaging member, a strut pivotally secured to said load-engaging member and projecting from the load-engaging member toward said bracket, said strut having an end portion lying adjacent the lower portion oi. said bracket and pivotally attached to said lowerportion on a horizontal axis, a spring arm pivotally attached to the other end portion of the strut on a horizontal axis, a spring disposed at the free end 01 said spring arm, upper and lower spring caps, said upper cap being secured to said arm and said lower cap being pivotally secured to said bracket on a horizontal axis, the point of pivotal securement of said lower cap to said bracket being spaced from the point of pivotal securement of the strut to said bracket, said spring arm projecting laterally from its point of pivotal attachment with said strut and extending slidably through said lower cap, the point of pivotal securement of said strut to said bracket being in substantial vertical alignment with the point of pivotal securement of said lower cap to said bracket,

CLARENCE G. GRABE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 621,823 Kirschbaum Mar. 28 1890 1,937,135 Wood Nov. 28, 1938 2,156,468 Wood May 2, 1939 2,208,064 Wood July 16, 1940 2,439,067 Wood Apr. 6, 1948

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