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1. * GB780103 (A)
Description: GB780103 (A) ? 1957-07-31
Braking device for printing presses
Description of GB780103 (A)
PATENT SPECIFICATION
Inventor: STEN RICHARD STEN STROM 7S 9 103 Date of Application and
filing Complete Specification: May 27, 1955.
No. 15398155.
Complete Specification Published: July 31, 1957.
Index at acceptance.-Class 100(2), Cl.
InternRtional Classification:-B41f.
COMPLETE SPECIFICATION
Braking Device for Printing Presses - We, GRAFISKA MASKIN
AxTIEBOLAGET, of Trollhattan, Sweden, a Swedish Company, do hereby
declare the invention, for which we pray that a patent may be granted
to us, -5 and the method by which it is to- be performed, to be
particularly described in and by the following statement: -
The present invention relates to a braking device for printing presses
having a reciproeating type bed and is characterised in that the
compression chamber of one or several brake cylinders operative at the
end of the type bed stroke is connected by means of piping with a
counter-cylinder, in which a spring-loaded counter-piston is arranged
so as to be movable by action of the compression pressure in the brake
cylinder or cylinders.
The invention is illustrated diagrammatically in the accompanying
drawing in which Fig. 1 shows in the form of a graph the connection
between the power given off by the type bed and the power taken up by
the brake cylinder at various points of a retarding motion.
Fig. 2 is a side elevation in outline of a printing press provided
with a reciprocating type bed and equipped with a braking device
according to the present invention, Fig.
3 an end view thereof and Fig. 4 a detail of a brake cylinder, a
counter-cylinder and piping arranged between them.
In printing presses having a reciprocating type bed, the latter

2. carries the printing medium and moves as outlined below:
printing stroke, during which the type bed is moving at constant
speed, retardation and acceleration stroke, during which the type bed
is braked and is again set in motion, but in a direction opposite to
that during the printing stroke, return stroke at constant speed,
followed by retardation and acceleration stroke as above. At the end
of the acceleration stroke the whole cycle of motion is completed.
When, for example, turning at the ends of [Price 3s. 6d.] the
reciprocation motion of the type bed is caused by a rotary motion, the
turning motion is harmonic, i.e. the retardation, and consequently the
corresponding total force at 50 any moment, varies in a linear manner
with the travel, whereas in using plain brake cylinders for taking up
these forces the forcetravel curve for the proportion of this total
which is provided by the braking cylinder 55 becomes similar to a
hyperbola. If this motion is visualised graphically, the two curves do
not agree very well, as will be seen from Fig. 1, where both curves
have been drawn in a volume-pressure diagram. 60 Curve AB represents
the variation of force P. given off by the type bed, if the motion is
assumed to take place from right to left. Curve DEB represents the
variation of specific air pressure and thus also the 65 variation of
buffer force P with the stroke volume V and stroke S.
For practical reasons, the starting point D is placed before the
beginning of braking at point A. The final points for both curves 70
coincide at B. The areas enclosed by figures ABCA and DEBD,
representing the work given off by the type bed and taken up by the
buffer piston respectively should be of equal size. 75 From the figure
it will be seen that during part DE there is a certain
overcompensation, whereas there is undercompensation during EB. The
difference in P-values between the two curves represents the force 80
acting upon the driving means-for instance in the case of a driving
mechanism with socalled frame and shifting pinions-on crank and frame.
This difference should be made as small as possible. 85 The object of
the invention is to obtain, at a maintained value of final pressure, a
braking force curve which better agrees with the retardation force
curve in such cases, where braking is effected by one or several
cylinders, in which are placed braking pistons attached to the
reciprocating type bed, the motion of which is to be braked.
The compression chamber and the spring in the counter-cylinder used
are so adapted that the same final pressure is obtained, of course, as
before, but by means of the invention the braking force curve may be
altered and by suitable choice may be made more closely to follow the
curve of retardation force.
As will be seen from Figure 2, a type bed 3 is arranged on top of the
press main frame so as to be movable on roller links 4. 5 designates

3. the forme attached to the type bed, and 6 the impression cylinder. The
main frame is equipped at both ends with brake cylinders 7, into which
braking pistons 8, arranged below the type bed, enter when braking of
the type bed is taking place. The stroke of the braking piston and the
length of the brake cylinder can, of course, vary in each special
case, depending upon the final pressure desired.
From the brake cylinder, there is a connecting piping 9 to a
counter-cylinder.10, -25 which may suitably be common to two or
several braking cylinders arranged at the same end of the main frame,
as shown in Fig.
3. In the counter-cylinder a piston 11, Fig.
4, is movable against the action of spring 12.
When the braking piston enters the brake cylinder and moves towards
its end, normally the hyperbola-like curve shown in Fig. 1 should be
obtained. Owing to the provision of the counter-cylinder, the pressure
in the braking cylinder will vary from normal, however, and the
hyperbola-like curve will be altered. By varying the cylinder volume
and the spring force, the shape of the curve can be varied within very
wide limits. But by obtaining a curve which in a desired manner 40
agrees with the curve corresponding to the turning motion i.e. a
flattened curve in the case of the harmonic motion mentioned above, it
is possible to attain by the present invention uniform and smooth
running of the 45 press such as previously could not be attained.
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* 5.8.23.4; 93p