An annular clamping flange for use in clamping a first pipe end portion to a second pipe end portion in an engine exhaust system, has first and second arcuate flange portions co-operable to form a pipe receiving aperture, each flange portion having at least one clamping bolt receiving aperture with a longitudinal axis parallel to the longitudinal axis of the pipe receiving aperture. The annular flange having an outer periphery of generally parallelogram shape with a pair of opposed acute angles and a pair of opposed obtuse angles, the parallelogram shape having rounded corners, one flange portion providing one side and portions of sides of the parallelogram shape adjacent thereto, and the other flange portion providing the opposite side to said one side and the other portions of said adjacent sides, each flange portion having a connecting bolt receiving tubular lug on each said adjacent side portion thereof.

This invention relates to annular clamping flanges for use in clamping a 
first pipe end portion to a second pipe end portion in an engine exhaust 
system, for example an exhaust system for a motor vehicle. 
When one or more parts of an engine exhaust system have to be replaced, 
problems often arise when a pipe end portion of a new part has to be 
clamped to the pipe end portion of an existing part, especially if the 
existing part has been damaged by long time use or for other reasons. 
My earlier U.S. patent application No. 08/419,570 filed Apr. 10, 1995, the 
contents of which are hereby incorporated herein by reference, describes 
and claims suitable annular clamping flanges for this purpose. However, 
there is still a need for annular clamping flanges which are especially 
useful where installation space is limited. 
According to the invention, an annular clamping flange comprises a first 
arcuate flange portion and a second arcuate flange portion co-operable 
therewith to form a pipe receiving aperture, each flange portion having at 
least one clamping bolt receiving aperture with a longitudinal axis 
parallel to the longitudinal axis of the pipe receiving aperture, 
said annular flange having an outer periphery of generally parallelogram 
shape with a pair of opposed acute angles and a pair of opposed obtuse 
angles, said parallelogram shape having rounded corners, one flange 
portion providing one side and portions of sides of the parallelogram 
shape adjacent thereto, and the other flange portion providing the 
opposite side to said one side and the other portions of said adjacent 
sides, each flange portion having a connecting bolt receiving tubular lug 
on each said adjacent side portion thereof, 
whereby the two flange portions can be positioned around a first pipe end 
portion and connected together by connecting bolts passing through 
respective pairs of adjacent tubular lugs on the first and second flange 
portions, and the annular flange can then be secured to a second pipe end 
portion by clamping bolts passing around the clamping bolt receiving 
apertures. 
The first flange portion may be identical to the second flange portion. One 
pair of adjacent tubular lugs may have a longitudinal axis parallel to the 
longitudinal axis of the other pair of adjacent tubular lugs, and each 
flange portion may have a single clamping bolt receiving aperture. The 
tubular lugs may be welded to the flange portions. 
The invention also provides an engine exhaust system comprising a first 
pipe end portion clamped to a second pipe end portion by a clamp including 
an annular clamping flange as defined above. Advantageously, the 
connecting bolts have flat sided heads which engage the respective flange 
portion so as to be prevented from rotation.

Referring to the drawings, FIGS. 1 and 2 show an annular flat clamping 
flange 12 in accordance with one embodiment of the invention fitted on a 
first pipe end portion 14 and secured to a clamping flange 16 on a second 
pipe end portion 18 of a motor vehicle engine exhaust system to clamp the 
two pipe end portions 14, 18 together. In this embodiment, the first pipe 
end portion 14 is an existing part extending rearwardly from an engine 
(not shown) and the second pipe end portion 18 extends forwardly from a 
new catalytic converter or muffler which is to be attached to the first 
pipe end portion 14. 
The annular clamping flange 12 comprises identical first and second arcuate 
flat flange portions 20, 22 co-operable with one another to form a pipe 
receiving aperture 24 to receive the pipe end portion 14. Each flange 
portion 20, 22 has a single clamping bolt receiving aperture 26 and two 
connecting bolt receiving tubular lugs 28, 30. The tubular lugs 20, 30 are 
welded to opposite ends of the respective flange portions 20, 22. 
The annular flange 12 has an outer periphery of generally parallelogram 
shape. One flange portion 20 provides one side 32 and portions of sides 
34, 36 of the parallelogram shape adjacent thereto, and the other flange 
portion 22 provides the opposite side 38 and the other portions of the 
sides 34, 36. The outer periphery of generally parallelogram shape has a 
pair of opposed acute angles, namely between the sides 32, 34 and between 
the sides 36, 38, and a pair of opposed obtuse angles, namely between the 
sides 32, 36 and between the sides 34, 36. The parallelogram shape has 
rounded corners 40, 42, 44, 46. 
The end of the pipe end portion 14 has a flange 48 formed thereon which 
mates with one side of a gasket 50, and a flange 16 on the end of pipe end 
portion 18 mates with the other side of gasket 50 in known manner. 
In use, the two clamping flange portions 20, 22 are positioned around the 
pipe end portion 14, as indicated in FIG. 1, and are connected together by 
connecting bolts 52 passing through respective pairs of adjacent tubular 
lugs 28, 30 respectively on the first and second flange portions 20, 22, 
the bolts 52 having washers 54 and nuts 56. The assembled clamping flange 
12 is a loose fit on the pipe end portion 14. 
After the gasket 50 has been placed in position, the annular clamping 
flange 12 is secured to the clamping flange 16 by clamping bolts 58 (only 
one of which is shown) which pass through the clamping bolt receiving 
apertures 26 in the flange portions 20, 22 through apertures 60 in the 
gasket 50 and through clamping bolt receiving apertures 62 in the clamping 
flange 16 to draw the flanges 48, 16 tightly into engagement with the 
gasket 50, the clamping bolts 58 having washers 64 and nuts 66. 
The person skilled in the art will appreciate that the parallelogram-like 
configuration of the annular clamping flange facilitates installation in 
locations with limited space. Also, when the connecting bolts 52 have 
multi-sided heads 53 as they usually will, the arrangement may be such 
that a side of the bolt head 53 engages the respective parallelogram side 
34, 36 so that the bolt 52 cannot rotate relative to the lugs 28, 30. 
Thus, it is not necessary to use a wrench to prevent the bolts 52 from 
rotating when the nuts 56 are being tightened. This feature further 
facilitates installation in limited space. 
FIG. 3 shows an annular formed clamping flange 70 in accordance with 
another embodiment of the invention comprising identical first and second 
formed annular flange portions 72, 74 co-operable with one another to form 
a pipe receiving aperture 76. Each flange portion 72, 74 has a single 
clamping bolt receiving aperture 78 and two connecting bolt receiving 
tubular lugs 80, 82. The tubular lugs 80, 82 are welded to opposite ends 
of the respective flange portions 72, 74. 
The annular flange 70 has an outer periphery of generally parallelogram 
shape. One flange portion 72 provides one side 84 and portions of sides 
86, 88 of the parallelogram shape adjacent thereto, and the other flange 
portion 74 provides the opposite side 90 and the other portions of the 
side 86, 88. The outer periphery of the generally parallelogram shape has 
a pair of opposed acute angles, namely between the sides 84, 86 and 
between the sides 88, 90, and a pair of opposed obtuse angles, namely 
between the sides 84, 88 and between the sides 86, 90. The parallelogram 
shape has rounded corners 92, 94, 96, 98. 
In this embodiment, the two clamping flange portions 72, 74 are positioned 
around a pipe end portion 106, which has a flange 108, and are connected 
together by connecting bolts 100 passing through respective pairs of 
adjacent tubular lugs 80, 82 respectively, the bolts 100 having washers 
102 and nuts 104. The annular clamping flange 70 is a loose fit on the 
pipe end portion 14. After a sealing ring 110 has been placed in position, 
the annular clamping flange 70 is secured to a clamping flange 112 on a 
second pipe end portion 114 by clamping bolts 116 (only one of which is 
shown) which pass through the clamping bolt securing aperture 78 in the 
flange portions 72, 74 and through clamping bolt receiving apertures 118 
in the clamping flange 112 to draw the flanges 108, 112 tightly into 
engagement with the sealing ring 110, the clamping bolts 116 having 
washers 120 and nuts 122. 
The advantages of this embodiment are similar to those described with 
respect to the previous embodiment. As before, flat sided heads 124 of 
bolts 100 may engage respective sides 86, 88 of the parallelogram shape to 
prevent the bolts 100 from rotating when the nuts 122 are being tightened. 
Other embodiments of the invention will also be readily apparent to a 
person skilled in the art, the scope of the invention being defined in the 
appended claims.