A New or Improved Machinery Belt and Pulleys therefor.
Year: 1892

page_text: [Communicated from abroad by JULIUS GUMM, of Lennep, Prussia, Merchant.]
A New or Improved Machinery Belt and Pulleys therefor.
•
I, HUGH DONALD FITZPATRICK, of 70 Wellington Street, Glasgow, Registered
Patent Agent, do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and by
the following statement :-
To obtain a free transfer of power or motion, straps, ropes and chains are used.
When straps or ropes are used, the distance of the driving from the driven pulley
must not be less than a certain given distance, if the whole power is to be
transferred. In cases where the distance is less, endless chains have hitherto been
used. Also the choice as to whether a strap or a rope is to be used, is not decided
by the wish of the workman, but by the quantity of power to be transferred, the
distance between the driving and the driven pulley and the velocity or speed.
Very frequently, to obtain the desired results, most expensive belts have to
be used.
The object of this invention is to provide a means of transferring power and
motion, which shall be suitable for long distances, equally as well as for short
distances, which shall be cheap, and which shall also be suitable for transferring
any amount of power.
This object is attained by making suitable driving-straps or belts, with one or
both edges waved or indented, instead of being straight, as formerly. The curves
or sweeps are all exactly similar to each other.
On the annexed drawing,
Figs. 1 and 2, show two forms of the new driving-strap, whilst
Fig. 3 shows the application of the new driving-strap in side view, and
Fig. 4, the same in plan, together with the necessarily new form of driving
pulley.
The driving-strap A (Figs. 1 and 2) is made of a tough metal like steel, phosphor-
bronze etc., and it is proportioned in thickness and width, to the power to be
transferred. The edges of this strap are wave-shaped, i.e. made with two constantly
repeated curves c, d. The serpentine belt can be laid round a pulley C
(Figs. 3 & 4), which has on its circumference a groove, the vertical sides of which
are waved or formed so as to correspond with the waved form of the belt.
When the strap is put round the driving and the driven pulleys, C, D, and the
pulley C is turned, the driving-strap is put in motion, as its waved mouldings or
edges catch into the edges of the corresponding groove of the pulley C and both
therefore act on one another, in a similar manner to two cog-wheels.
The same takes place, of course, with the driven pulley D, which also has a
waved groove on its circumference, so that the strap A puts the pulley D in motion
and transfers the power and velocity from driving-pulley C.
I am aware that metal straps are not new for transferring power and motion, as
such straps are frequently applied to small machines. But to enable these straps to
effect the required transfer, they are made with holes or cuts, into which pegs or
cogs, on the driving pulley, catch. When the power to be transferred is great, the
pegs or cogs must be correspondingly strong, which necessitates a certain enlarge-
ment of the holes and cuts in the straps and they are thus weakened very
considerably in those places where the cuts are made. To give the strap strength,
it must, therefore, be made at these places, of such a width or thickness that the
straps can safely stand the strain, without breaking. The parts between the cuts
are consequently unnecessarily strong, so that such a strap, should it be used with
heavy machinery, contains much useless material and is not only expensive but also

page_text: heavy. As a consequence, much power is absorbed in dragging the extra dead
weight, and the pulleys and also the frame and foundation must be made much
stronger than is really necessary for the power transferred.
The new driving-strap has not these draw-backs, as it is of the same width
throughout and it can be rolled down to such a thickness as will exactly correspond
to the power to be transferred.
A strap having the serpentine conformation shown in Fig. 1, is not weakened at
any part.
The form shown at Fig. 2, is not so economical as that at Fig. 1, as the strap B
has a greater (a) and a smaller width (b). But in calculating, only the smaller
width can be taken into account, the difference between a and b, being simply used
for giving a firm grasp. The extra width, adds to the stren th of the strap.
.
It may, sometimes, be advisable to give the belt this less economical profile, so
as to obtain other advantages, such as, for example, a very exact and uniform power
transfer.
The strap may have, if desired, an edging of cogs or teeth, it being borne in
mind, however, that the edge-moulding must correspond with the grooves in the
pulleys.
Besides transferring power and motion, this new strap might be used directly as
a working appliance for lifting or moving weights such as dredgers' buckets &c.,
the strap being altered accordingly.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
:-
1. An endless metal band or power transmitter, made substantially as herein-
before described, with reference to the drawings annexed.
2. The combination with bands of the class set forth, of pulleys having grooves
thereon to correspond with said bands.
Dated this 18th day of Fohru 1000
H. D. FITZPATRICK,
70, Wellington Street, Glasgow.