Hose clamp

An improved hose clamp of the kind comprising a tightening band which is bent to annular shape and which has end portions one of which is provided with transverse grooves. In the latter engage the threads of a screw worm which is rotatably journalled in a sleeve enclosing the screw worm but axially non-slidable therein. Said sleeve is formed with a space allowing the threaded band end portion to be moved out of the sleeve upon rotation therein of the screw worm. The opposite band end portion which is attached to the sleeve is elastic in its lengthwise direction and encloses a pressure strap which is bent to annular shape with its end portions overlapping. This pressure strap is arranged to form a guide means to the screw worm sleeve and to the tightening band between said sleeve and said band and an enclosed article. The tightening band describes an arcuate line in the plane of the external face of the pressure strap along the major portion of the circumference of the latter.

The subject invention concerns an improved hose clamp of the kind 
comprising a strip of material which is bent to annular shape to form a 
tightening band. One end portion of the band is provided with transverse 
grooves in which engage the threads of a screw worm which is rotatably 
journalled in a sleeve but axially non-slidable therein. The sleeve 
encloses the screw worm and is formed with a space allowing the threaded 
band end portion to be moved out of the sleeve upon rotation of the screw 
worm therein. The opposite band end portion is fixed to the sleeve. 
In prior-art hose clamps of the kind referred to above some leakage is 
sometimes found. Often the cause of such leakage is ageing of the material 
of the hose which is mounted by means of a hose clamp so that after some 
time of use the hose material loses its pliability and elasticity. After a 
certain period it is therefore necessary to re-tighten the hose clamp and 
eventually the hose must be exchanged. However, it this is done 
incorrectly accidents or damage may occur. The problem is particularly 
common in the engine space in cars, where several hoses are fastened with 
the aid of hose clamps and where the environment causes considerable 
problems on account of the large variations in temperatures and of the 
presence of various liquids, such as petrol, oil, hydraulic fluids, 
glycol, alcohols and water. Furthermore, vibrations and oscillations of 
varying frequencies also contribute to the generation of leakage. 
One way of counter-acting the generation of leakage in hoses mounted by 
means of hose clamps is to increase the clamping action of the clamp by 
tightening the screw worm very hard. Clamp hose manufacturers have 
endeavoured for many years to produce stronger and more efficient hose 
clamps. However, when a hose clamp is tightened hard it is inevitable that 
the clamp bites increasingly deeper into the hose material, which together 
with the vibrations and the tensile stress to which the material is 
exposed is liable to cause cracks in the hose material adjacent the clamp. 
The result is yet another problem. 
A more efficient method of obviating the ageing problems found in hose 
material in order to achieve a permanent clamping action in hose clamps is 
to provide the clamp with some kind of resilient means. DE-A-1 No. 3130092 
discloses a hose clamp the tightening band of which encloses a pressure 
strap and has a pleated or corrugated configuration. Owing to this 
configuration the tightening band assumes an elasticity in its lengthwise 
extension and in this manner becomes capable of compensating for the 
decreasing elasticity of the hose enclosed by the hose clamp. 
One disadvantage inherent in the wavy or corrugated configuration of the 
tightening band wherein the corrugations extend towards and away from the 
pressure strap positioned interiorly thereof is, however, that dirt 
particles may enter between the ridges and dales of the corrugations and 
the pressure strap. When this happens the strap loses at least part of its 
resilient properties. 
By giving the tightening band an undulating configuration it is also, 
however, weakened. Consequently, the band must be made thicker than what 
is normal in order to compensate for the weaker structure and as a result 
the clamp becomes more expensive to manufacture. 
The purpose of the subject invention is to provide a hose clamp possessing 
resilient properties without the disadvantages outlined in the aforegoing. 
This is achieved in accordance with the teachings of the invention therein 
that the tightening band enclosing a pressure strap bent to annular shape 
and having its end portions overlapping and arranged to form a guide means 
to the screw worm sleeve and the tightening band between said sleeve and 
said band and an enclosed article, describes an arcuate line in the plane 
of the external face of the pressure strap along the major portion of the 
circumference of the latter.

The hose clamp illustrated in FIGS. 1 and 2 consists of a pressure strap 1 
bent to annular shape and having its end portions 2 and 3 positioned in 
overlapping relationship. The radially inner end portion 2 of the strap is 
provided with outwardly projecting folded edges 2' which serve to guide 
the radially outer strap end portion 3. Around the pressure strap 1 
extends a tightening band 4 in the form of a wire bent to zigzag shape. 
One end portion 5 of the wire is straight, flattened and provided with 
transverse grooves 6. The opposite end portion 7 is helically wound into a 
cylindrical screw worm sleeve 8. A screw worm 9 is rotatably journalled 
but axially non-slidable in the sleeve 8 in which a space 10 is formed 
(see FIG. 2) allowing displacement of the threaded end portion 5 inside 
the sleeve 8 upon rotation of the screw worm 9 with the screw worm threads 
9' in engagement with the grooves 6. 
The wire used to form the tightening band is made from a tough-hardened 
material, such as piano wire, which imparts resilient properties to the 
zigzag-shaped portion. The pressure strap 1 preferably is made from a thin 
stainless steel strip. 
When the hose clamp is tightened about a hose end to secure the latter to a 
pipe end, the pressure strap 1 will be compressed about the hose end by 
means of the tightening band 4 so as to assume a predetermined diameter 
dimension corresponding to a maximum clamping force. Upon further 
tightening of the screw worm 9 the bent or curved portions of the 
tightening band 4 will be straightened against the action of the 
resiliency. As the hose material slowly ages the tightening band 4, on 
account of its springiness, will gradually compress the pressure strap 1 
as the diameter size of the hose material is being reduced. This size 
adjustment will continue while maintaining a clamping force which is equal 
to the maximum clamping force minus the existing frictional resistance in 
the hose clamp. 
FIGS. 3 and 4 show the hose clamp in accordance with a second embodiment of 
the invention. In this case the screw worm sleeve 11, the pressure strap 
12 and the tightening band 13 are made as one continuous unit from an 
elongate sheet metal strap. One free end of this continuous unit is formed 
by the radially inner one of the end portions 14 of the pressure strap 12. 
Like in the embodiment described in the aforegoing the latter is provided 
with outwardly directed folded edges 14' forming guide means to guide the 
movements of the radially outer end portion 15. The latter is attached to 
one end of the screw worm sleeve 11. A screw worm 16 is rotatably 
journalled but axially non slidable in the sleeve. The screw worm sleeve 
11 consists of two flaps of the strap material which are interconnected by 
means of a welding seam 17 on the upper face of the sleeve. On either side 
of the sleeve 11 the strap material is upset inwardly by means of punch 
marks 18 which are arranged to engage in a manner known per se in a groove 
in the screw worm 16 adjacent the head 16' thereof. 
The tightening strap 13 which is a zigzag shaped punching from the strap 
material, extends from the opposite end of the screw worm sleeve up to a 
straight end portion 19 which is provided with transverse grooves 20. In 
the latter engage the threads 16' of the screw worm 16 when the end 
portion 19 is positioned in the space 21 inside the screw worm sleeve 11. 
Upon tightening, the hose clamp in accordance with FIGS. 3 and 4 will 
behave in the same manner as the hose clamp in accordance with the 
embodiment of FIGS. 1 and 2. 
The invention is not limited to the embodiments described in the aforegoing 
but a number of modifications are possible within the scope of the 
appended claims. The screw worm sleeve 8 in accordance with the embodiment 
of FIGS. 1 and 2 need not be made from the wire but could be made from 
sheet metal in the conventional manner in the art and the wire be secured 
thereto. In the second embodiment the radially outer end portions 15 of 
the pressure strap need not be secured to the screw worm sleeve 11.