Railroad gate arm swivel adapter spring assembly

A railway gate arm assembly including a gate arm which is mounted to permit pivoting about a longitudinal axis when an external force is applied to the gate arm thereby causing the latter to swivel out of a vertical plane, and at least two torsion springs, one mounted on each side of the gate arm and having depending spring legs which engage against corresponding sides of the gate arm and bias the gate arm to a vertical position so if the gate arm is caused to swivel out of a vertical plane by an external force, it will be returned to the vertical plane by the depending spring legs when the external force is removed.

BACKGROUND OF THE INVENTION 
FIELD OF THE INVENTION 
The present invention relates to a railroad gate arm which is used at 
railroad crossings and operated so as to be lowered to a horizontal 
position to block traffic when a train is present and to be raised to an 
upright or retracted position when no train is present. 
More particularly, the invention relates to a swivel type gate arm which is 
designed to pivot about a longitudinal axis when an external force is 
applied to the gate arm. Such known swivel mechanism is in addition to the 
well known breakaway mechanism which is normally incorporated in gate arm 
support members so that if a car or truck engages the gate arm head on, 
the arm will break away without destroying the relatively expensive 
support mechanism which supports the gate arm and raises and lowers the 
same. 
A swivel type gate arm is disclosed in U.S. Pat. No. 5,442,878. In FIG. 2 
of the foregoing patent, there is shown a gate arm 22 which is fixedly 
secured to a swivel bracket 46, the swivel bracket 46 being supported on a 
pin-like member 44 shown extending from a conversion bracket 42. The gate 
arm 22 pivots up and down about an axis (not numbered) which is located at 
the center of a motor 41. In addition, the bracket 46 can rotate or swivel 
about the gate adapter 44 with the result that when an external force is 
applied, the gate arm 22 can swivel about the axis of gate adapter 44. The 
purpose of allowing the gate arm to swivel about the axis of gate adapter 
44 upon application of an external force is to reduce breakage of the gate 
arm, whether such external force is caused by high wind or due to contact 
with the top of a vehicle. 
The swivel gate arm disclosed in the foregoing '878 patent is intended to 
be maintained in a preferred position in an upright plane due to gravity. 
However, such mechanism has been found to be unsatisfactory. Thus, it is 
an object of the present invention to provide a swivel adapter spring 
assembly which will reliably return a gate arm to an upright plane in the 
absence of external forces which are strong enough to overcome the spring 
force. 
It is a further object of the invention to provide a spring assembly which 
is highly advantageous and uniquely qualified to control the position of a 
swivel type gate arm without need to rely upon gravity. 
The foregoing objects and advantages of the invention will be apparent from 
the following description of a preferred embodiment thereof, taken in 
conjunction with the accompanying drawings.

Now, in order to acquaint those skilled in the art with the manner of 
making and using my invention, I shall describe, in conjunction with the 
accompanying drawings, a preferred embodiment of the invention. 
DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 is a top plan view showing a swivel bracket 10 which is assembled 
with a rod 12 to create a swivel bracket assembly best shown in FIGS. 4 
and 5. The swivel bracket pivots about an upright pin shown at 14 in FIG. 
1, and the bracket is held in a normal operative position relative to pin 
14 by three shear pins shown at 16 in FIG. 1. The foregoing structure 
comprises known breakaway mechanism designed to break if a horizontal 
force engages against the gate arm, as when a vehicle hits the gate arm 
when the latter is in a down or horizontal position blocking traffic at a 
gate crossing. 
Thus, when a horizontal force engages the gate arm, it will tend to pivot 
the latter including the swivel bracket 10 about the pin 14, and if the 
force is sufficient to break the three shear pins 16, the gate arm will 
pivot freely away and thereby avoid damage to the gate mechanism. Such 
breakaway mechanism is known, and of course the number and size of the 
shear pins 16 may be adjusted to control the force needed to effect 
breakaway of the gate arm. 
Certain known structure is not shown in FIG. 1, such as mechanism for 
supporting the upright pin 14, and mechanism for raising and lowering the 
gate arm between an upright, retracted position and a lowered, horizontal 
position where it blocks vehicles. The horizontal axis about which the 
gate arm and swivel bracket 10 pivot up and down is not shown in FIG. 1 
but is located to the left of the swivel bracket 10. 
FIGS. 6 and 7 show a swivel bracket weldment which is the structure for 
supporting a gate arm on the rod shown at 12 in FIG. 1. The swivel bracket 
weldment includes a tube 20 which is welded to a rectangular plate 22, and 
as shown in FIG. 3, the tube 20 is mounted over the rod 12 and a keeper 
pin 24 (see FIGS. 1-3) is placed through a hole in the outer projecting 
end of rod 12 to prevent tube 20 from sliding off rod 12. 
In its normal position as shown in FIGS. 1-3, the plate 22 is vertically 
positioned. FIG. 3 shows an end view of a gate arm 26 which is fastened to 
the inside of plate 22 by known fastening means. FIG. 3 also shows an 
L-shaped metal spacer plate 30 having a vertical plate portion 32 and a 
top or horizontal plate portion 34. The plate 30 is fastened to a side of 
the gate arm 26 opposite the plate 22 so that the gate arm has the metal 
plates 22 and 32 on opposite sides thereof. As previously explained, the 
plate 22 together with the tube 20 supports the gate arm 26 on the rod 12. 
In addition, the plates 22 and 32 are made of a material suitable to 
protect the gate arm. For example, if the gate arm is made of aluminum or 
fiberglass, the plates 22 and 32 may be made of steel. 
I will now describe the spring elements which have been designed to control 
the normal position of the gate arm 26, i.e., to return it to a vertical 
plane shown in FIGS. 1-3 without need to rely on gravity after removal of 
an external force which has caused the gate arm to swivel out of its 
vertical plane. In the absence of such spring elements, the gate arm (see 
FIG. 3) which is fixed to plate 22 and tube 20 is free to pivot or swivel 
about the axis of rod 12, since the tube 20 is loosely mounted over rod 12 
and can rotate thereon. In fact, FIG. 1 shows a pair of bronze or brass 
bushings 33 and 35 which are mounted inside opposite ends of the tube 20 
and facilitate rotation of tube 20 on rod 12 by reducing friction between 
them. 
FIGS. 8-11 show a single spring element 40 having six coils 42 on each side 
of a loop 44. The spring element 40 also includes a pair of depending legs 
46 and 48 which extend generally downwardly from opposite ends of the 
spring element. As will be explained later, the two depending legs 46 and 
48 are positioned to engage against the side of one of the gate arm plates 
22 and 32 (see FIG. 3) to control the swivel position of the gate arm 26. 
Also, as will be more fully explained later, the center loop portion 44 is 
used to create a desired torsion in the spring element 40 so that the 
depending legs 46 and 48 will engage against the sides of gate arm plates 
22 and 32 with a desired equal and opposite force. 
As shown in FIGS. 8-11, the spring loop 44 is at rest in a horizontal 
position. However, as shown in FIG. 3, the loops 44 are maintained at an 
angle substantially inclined above the horizontal as installed, which 
causes legs 46 and 48 to be moved inwardly to apply forces on opposite 
sides of the gate arm plates 22 and 32 to forcibly maintain the gate arm 
26 in a vertical plane in the absence of an external force sufficient to 
overcome the torsion force of the spring elements. 
In the particular embodiment shown in FIGS. 1-3, four of the spring 
elements 40 are utilized to control the plane of gate arm 26. The four 
spring sets 40 are mounted on a pair of extension bars 60 and 62 which are 
supported at one end from the swivel bracket 10. FIG. 3 is an end view of 
the extension bars 60 and 62 which are square in cross section and 
dimensioned so the twelve coils 42 of each spring set can be slid over one 
of the extension bars. 
Referring now to FIG. 2, one of the extension bars 60 is shown supported at 
its left end from the swivel bracket 10 and extending horizontally a 
length sufficient to receive the twelve coils 42 from each of two of the 
spring sets 40 which are positioned end-to-end on bar 60. Each of the 
spring sets 40 has a loop 44, and each has a pair of depending legs 46 and 
48. A spring retainer pin 64 is fitted through a hole in the outer end of 
extension bar 60 to retain the two spring sets thereon. 
FIG. 3 shows that when the spring sets 40 are installed, the loop members 
44 are raised above their at rest or horizontal positions as shown in 
FIGS. 9 and 10, and are maintained in such raised positions by a spring 
keeper 51 which extends laterally over two opposed sets of spring coils 42 
and underneath a pair of adjacent loops 44 to hold the loops in their 
elevated positions. FIG. 2 shows a pair of spring keepers 51 which extend 
laterally under the spring loops 44 of end-to-end spring sets 40. The 
keepers 51 extend over the tube 20 so as to be supported by the latter. 
In the foregoing manner, two spring keepers 51 are sufficient to maintain 
four of the spring loops 44 in their raised positions because, as shown in 
FIG. 3, a single spring keeper extends laterally beneath two of the loops 
44. FIG. 1 is a top plan view showing the pair of spring keepers 51 which 
extend beneath the loops 44. Because loops 44 are thus installed in raised 
positions, the downwardly extending legs 46 and 48 are biased inwardly to 
exert equal and opposite forces on the two sides of gate arm 26 through 
engagement with gate arm plates 22 and 32. 
FIG. 1 shows the two extension bars 60 and 62 supported at their left ends 
from the swivel bracket 10, it shows the two spring sets 40 mounted on the 
first extension bar 60 as previously described in conjunction with FIG. 2, 
and it shows a third and fourth spring set 40 mounted on the second 
extension bar 62. The two spring sets 40 mounted on each of the extension 
bars 60 and 62 are mounted in end-to-end engagement so the coils 42 are in 
abutting relation. Since each spring set 40 has twelve coils, the total 
spring assembly shown in FIGS. 1-3 comprises forty-eight coils. However, 
the number of spring sets used in the spring assembly and the dimensions 
of individual spring sets may be varied to provide a desired spring force 
on the gate arm. 
FIG. 3 shows an end view where the two depending spring legs 48 are shown. 
However, as previously described, each spring set 40 has two depending 
legs 46 and 48, and since the preferred embodiment shown in FIGS. 1-3 
includes two spring sets on each side of the gate arm 26, there are four 
depending spring legs for engagement against each side of the gate arm as 
shown in FIG. 2. 
I will now describe a pair of spring retainers which are used for the 
purpose of temporarily maintaining the depending spring legs 46 and 48 
spaced outwardly from the sides of the gate arm plates 22 and 32 until 
assembly of the gate arm mechanism is completed, after which the spring 
retainers are pivoted to release positions and the depending spring legs 
then firmly engage against the sides of the gate arm plates 22 and 32. 
Referring to FIG. 2, a spring retainer 70 is shown in solid lines in its 
horizontal position and in dotted lines in its downwardly inclined or 
release position. The spring retainer 70 is pivotally mounted at its left 
end by a nut and bolt 72 to the swivel bracket 10. When the spring 
retainer 70 is in its horizontal position, it maintains the depending 
spring legs 46 and 48 outwardly and spaced from the sides of the gate arm 
plate 22. Similarly, when a spring retainer 76 mounted on the opposite 
side of the gate arm in its horizontal position, it maintains the 
depending spring legs 46 and 48 on that side of the gate arm in spaced 
relation to the gate arm plate 32. 
When the gate arm 26 is to be assembled on the rod 12, the two spring 
retainers 70 and 76 are positioned in their horizontal positions as shown 
in FIG. 3 and shown in solid lines in FIG. 2. In that position of the 
spring retainers 70 and 76, with the depending spring legs 46 and 48 held 
outwardly as shown in FIG. 3, the gate arm 26 including the plate 22 
fastened on one side thereof and the spacer plate 30 fastened on the 
opposite side thereof, is assembled by sliding the tube 20 over the rod 12 
as previously described, and inserting the keeper pin 24 in the outer end 
of rod 12. Thereafter, the two spring retainers are manually moved to 
their downwardly inclined or release positions which permits all of the 
four depending spring legs 46 and 48 on each side of the gate arm to 
engage firmly against the gate arm plates 22 and 32 to maintain the gate 
arm in its normal vertical plane. The spring retainers may be manually 
pivoted by loosening the nut member 72 and may be fixed in a desired 
horizontal or lowered position by tightening the nut member 72. 
Referring again to FIGS. 8-11 which illustrate a preferred form of torsion 
spring for use in the present invention, the spring 40 shown has twelve 
coils 42, one loop portion 44 and a pair of depending legs 46 and 48, all 
as previously described. As shown on the drawings, the wire diameter is 
0.135 inch, the inside diameter of the spring coils is 9/32nds inch, the 
inside radius of the loop 44 is 5/32nds inch, the longitudinal length of 
each set of six coils is 13/16ths inch, and the vertical length of each 
depending spring leg measured from the centerline of the coils is 5 
inches. Additional dimensions are shown in the FIGS. 8-11, including a 
41/2 inch dimension for the length of a leg 46 and 48. A preferred range 
of dimensions for the spring 40 is a range of plus or minus 50% from the 
specific dimensions shown in the drawings and set forth above, although a 
still more preferred range is plus or minus 25%. 
Another important feature of the spring member 40 relates to the shape of 
each depending leg 46 and 48 which is best shown on the left side of FIG. 
3 which depicts the spring in its installed position with the loop 44 bent 
in a counterclockwise direction from its at rest position as shown in FIG. 
3. In the installed position, the spring leg 48 has a portion 80 which 
extends generally outwardly away from the gate arm plate 22 to provide 
room to accommodate the spring retainer 70, and a second portion 82 which 
is inclined generally inwardly toward the gate arm plate 22. The lowermost 
portion 84 of the spring leg 48 is approximately vertical and it is that 
portion which engages the side of gate arm plate 22 when the spring 
retainer 70 is pivoted to its lower, inoperative position. 
In operation, referring to FIGS. 1-3, and in particular to FIG. 3, the four 
depending spring legs 46 and 48 on each side of gate arm 26 control the 
swivel position of the gate arm because, in the absence of such equal and 
opposite springs, the gate arm would be free to swivel with the tube 20 
about the axis of rod 12. In the absence of external forces, the two 
spring elements 40 on each side of the gate arm will cause the gate arm to 
be located in a vertical plane as shown in FIG. 3. If an external force is 
applied to the lower end of the gate arm, such as by a strong wind, or by 
the top of a trailer which catches underneath a lowered gate arm, the gate 
arm will be permitted to swivel about the axis of rod 12 as long as the 
external force is sufficient to overcome the forces applied by the 
depending spring legs 46 and 48. However, as soon as the external force is 
removed, the gate arm will be promptly returned to its position in a 
vertical plane as shown in FIG. 3 without reliance on gravity. 
It will be obvious from FIG. 3 that the gate arm mechanism of the present 
invention permits the gate arm to swivel through a significant angle in 
either direction about the axis of rod 12. Regardless of which direction 
an external force causes the gate arm to rotate or pivot about the axis of 
rod 12, the spring legs 46 and 48 on opposite sides of the gate arm will 
cooperate to return the arm to a neutral or vertical position. The gate 
arm mechanism can be designed to permit a desired maximum amount of swivel 
of the gate arm 26 about the axis of rod 12. In the embodiment shown in 
the drawings, the maximum swivel is less than 90 degrees from the vertical 
position shown in FIG. 3. 
Depending on the materials used for the gate arm 26, the steel plates 22 
and 30 attached to opposite sides of the gate arm could be eliminated. 
However, in the preferred embodiment shown, the gate arm is protected on 
both sides by such steel plates since the gate arm may be made of a softer 
material such as aluminum or fiberglass which could be damaged due to 
rubbing thereagainst of the lower ends of the four depending springs legs 
46 and 48 on both sides of the gate arm. 
Reference is again made to FIG. 3 to illustrate certain mechanical aspects 
of the spring forces created to maintain the gate arm 26 in the central 
position shown. The lower ends 84 of the spring legs are approximately 1/2 
inch long (see FIGS. 9 and 10), and it is desirable to maintain those leg 
portions quite short because they are the portions which engage the gate 
arm plates 22 and 32 and rub against those plates when the gate arm is 
moved from its vertical position. If relatively long spring leg portions 
engage the gate arm plates 22 and 32, increased friction will be created 
which is undesirable as it impairs the return of the gate arm to its 
vertical position after an external force has been removed. 
It is also important that the spring leg portions 84 engage the gate arm 
plates 22 and 32 near the lower ends thereof as that results in the spring 
force being applied to the gate arm a relatively long distance from the 
rod 12 thereby increasing the moment arm for causing the gate arm to 
swivel back to its vertical position when an external force is removed. 
Increasing the length of the spring leg portion 82 will reduce the spring 
force applied to the gate arm plate for a given size torsion spring, but 
the spring legs disclosed have been found quite suitable for most gate 
arms. Longer and heavier gate arms produce more friction and thus are more 
difficult to swivel about the rod 12. Thus, variations in the number and 
dimensions of the springs may be required to accommodate various lengths 
of gate arms.