Seal splice

A splicing unit for integrally joining ends of seal strip material to form a continuous annular seal ring comprises two reinforced elastomeric ply strips with an unreinforced elastomeric gum interposed between them to form an H-section configuration, the length of the unit being substantially the width of the seal strip while the depth of the gum between the ply strips is substantially the thickness of the seal material to be joined. The ends of the seal strip are inserted between the legs of the H-section on either side of the unreinforced gum and cured to form the integrally spliced seal ring.

BACKGROUND OF THE INVENTION 
This invention generally relates to splices as may be applied to flexible 
elastomeric articles, and more particularly to a unit splice configuration 
for splicing a floating roof tank secondary seal into a continuous annular 
sealing ring. 
Floating roofs for large storage tanks which hold volatile liquid products 
are well known and understood in the art as are the seals that close up 
the free space between the floating roof and the vertical tank wall. These 
seals generally comprise a primary seal that is attached to the periphery 
of the floating roof and which reacts with the tank wall to centrally 
locate the roof within the confines of the tank while also providing a 
sliding seal conforming to the wall surface as the liquid level in the 
tank changes. A secondary seal is also provided which is generally 
referred to as a "weather seal" because it is designed to protect the more 
complicated primary seal from contamination by foreign material such as 
dirt, dust, water, snow and ice, and the like. The secondary seal is 
usually therefore located above the primary seal and is mounted in a 
manner to also conform to the tank wall as the floating roof moves in 
response to changing liquid levels. Primary and secondary sealing 
techniques and configurations of the type alluded to are described in the 
prior art as exemplified by the U.S. patents to A. H. Nelson (No. 
3,338,454), Wardell et al (No. 4,099,643), and R. A. Bruening (No. 
4,126,243). 
Secondary seals currently in use come in a variety of arrangements and 
generally comprise a configuration of elastomeric and/or polmeric 
materials which may or may not include an embedded reinfocement material. 
Because of the large circumferencial extent of floating roof type tanks, 
the seals are made up of a plurality of seal strip lengths which are 
spliced together to form the substantially annular seal ring when mounted 
to the roof structure. Conventionally, the seal strips are butt joined and 
the joint is cemented and covered over with a ply of reinforcement 
material. This procedure has resulted in misalignment of the spliced butt 
ends which affects the sealing integrity of the annular secondary seal as 
it attempts to conform to the inner wall of the tank. 
This invention therefore is directed to a splice configuration for floating 
roof secondary seals that may be factory fabricated in various lengths 
according to the width of the seal material to be spliced, applied in the 
field, and air cured or vulcanized to provide an integrally spliced 
secondary seal. 
An aspect of one object of the invention is to provide a splice for 
floating roof tank secondary seals that facilitates proper alignment of 
the spliced seal strips such that the completed annular seal more closely 
conforms to the inner tank wall to effect a proper seal therebetween. 
The invention therefore provides an integrally vulcanized splicing unit for 
connecting ends of seal material such as to create an annular seal ring 
comprising: 
a first reinforced elastomeric ply strip having a central longitudinal axis 
and a length substantially greater than its width and juxtaposed to the 
first ply strip such that the longitudinal axes are algned in a vertical 
plane; and 
an unreinforced elastomeric gum interposed between the first and second ply 
strips for the length thereof and having a width less than the widths of 
the ply strips and centrally positioned between the ply strips along their 
longitudinal axes such as to form a unit having an H-section configuration 
with length-wise slots on either side thereof for receiving the ends of 
the seal material therein.

Referring to the drawing figures, a splicing unit in accordance with the 
invention is generally indicated by reference numeral 10. The unit 10 is a 
prefabricated and integrally vulcanized elastomeric strip manufactured in 
various lengths according to the width of the seal material to be joined 
and having an H-pattern cross-sectional configuration and a section width 
designated W.sub.1. The splicing unit, when made to a specific length, 
comprises a ply strip 12 forming one side of the H-section, a ply strip 14 
forming the opposite side, and a layer 16 interposed between the sides 12 
and 14 to form the center of the H-section. 
The elongated plys 12 and 14 comprise a fabric reinforced elastomeric 
material that establish the width W.sub.1 of the unit 10 while the 
interlayer 16 is an elongated unreinforced elastomeric gum ply having a 
width W.sub.2 that is substantially less than the width W.sub.1 of the 
unit 10. The interlayer gum 16 is centrally oriented along the 
longitudinal axis 18 of the plys 12 and 14 such that the difference in 
width forms slots 30 running longitudinally along either side of the unit 
10 for the length thereof. The slots 30 thus formed are bounded on one 
side by an inner surface 12a of the ply strip material 12, on the opposite 
side by the inner surface 14a of ply strip material 14, and at the center 
by the exposed edge 16a of the gum interlayer 16. In this H-section 
configuration the interlayer gum 16 may comprise 25-80 percent of the 
total unit width W.sub.1 and for most splicing applications will 
preferably be within 30-50 percent of the width W.sub.1. The interlayer 
gum 16 will also have a thickness "t" that is dependent upon the thickness 
of the seal material 20 to be joined by splicing and therefore will vary 
according to the particular requirements. For splicing most secondary seal 
materials the ratio of the length "x" for each leg of the slot 30 to the 
thickness "t" must be at least 8 to 1.0. In this respect, for greater 
thicknesses of material the distance "x" will have to be proportionally 
increased in relation to thickness "t" to provide adequate bonding surface 
at 12a and 14a for effecting the splice. 
The interlayer 16 is an unreinforced elastomeric and/or polymeric gum 
exhibiting a durometer within the range 65-75. In this circumstance the 
gum allows for greater tolerance allowances between the ends 22 and 24 of 
the seal material to be joined as the ends are inserted into the slots 30 
formed by the H-section, which ends 22,24 ultimately abutt the gum 16 at 
the exposed surfaces 16a. 
Referring to FIGS. 2 and 3, splicing of the seal strip 20 is effected by 
first buffing the butt ends 22 and 24 in the area of the splice until the 
surfaces are well roughened. The roughened area is extended at least 1/8 
inch wider than the splicing material 10 such as indicated at 22a and 24a. 
The buffed areas are then washed with a solvent to remove all foreign 
matter and multiple coats of an appropriate cement are applied and allowed 
to dry to a tackiness. The butt ends 22,24 are then inserted into the 
slots 30 until they abutt the interlayer 16 at 16a. The splice is then 
thoroughly rolled in the cemented areas to remove any trapped air and an 
additional amount of cement is applied to the raw edges at 36 to 
completely seal the edged interface. The spliced seal strip is then cured 
before being put into service. Curing of the spliced seal strip may be 
accomplished in various ways. For example, the splice may be air cured 
when an appropriate air-cure type adhesive is used. In this circumstance, 
a field splicing operation with an air cure will require approximately an 
8-hour cure time. Alternatively, in those instances where a facility is 
available, the spliced seal strip may be vulcanized in the usual manner of 
vulcanization processes to integrally bond the elements of the splicing 
unit 10 to the seal material 20. 
Referring now to FIG. 4, a portion of one end 40 of a seal 20' having 
tapered lateral edges 42 is shown connected into one side of a splicing 
unit 10', the opposite end 44 of the seal 20' being illustrated in ghost 
lines for the purpose of clarity in the drawing. In this configuration, 
the splicing unit 10' is made to an exact length "L" equal to the width of 
the seal 20' and is vulcanized in a mold such that the ends 50 conform to 
the taper of the seal edges 42. Thus, the reinforced ply strips 12' and 
14' are integrally joined at the end 50 with very little unreinforced gum 
16' between them. The splicing unit 10' therefore, is formed with closed 
ends 50 for the width W.sub.1 of the unit and in order for the ends 40 and 
44 of the seal 20' to be inserted between the plys 12', 14' the ends 50 
must be trimmed for the length "x" to form the H-section. The width 
W.sub.2 of the end in the area of the gum 16' is left intact and when this 
is done the tapered edge 42 of the seal 20' exactly conforms to and abutts 
the tapered portion 52 of the splicing unit 10'. An advantage to this is 
that the edges 54 of ply strips 12' and 14', for the length "x" forming 
the legs of the H-section, are positioned away from the tapered edges 
42,52 so as not to interfere with any wiping action made in effecting a 
sealing relationship. 
It will be appreciated from the foregoing that the preformed splice strip 
provides a distinct advantage over the prior splicing techniques for 
floating roof tank secondary seals, in that ends 22,24 are not subject to 
misalignment by reason of their edges 32,34 being butt joined in the 
splice. In this respect, the gum 16 cancels discontinuities between the 
butt edges 32,34 and allows for proper alignment of the lengths 22,24 to 
form an annular ring which conforms more to the interior curvature of the 
tank wall. 
It will be further appreciated that because the splice strip 10 is a 
prefabricated and preformed length of material, it decreases secondary 
seal splice failures by reason of the fact that the splice configuration 
is uniform and the splicing technique followed is always the same. 
While certain representative embodiments and details have been shown for 
the purpose of illustrating the invention, it will be apparent to those 
skilled in the art that various changes and modifications may be made 
therein without departing from the spirit or scope of the invention.