Since helical compression springs are
increasingly used at higher tempera-
tures, the hot-setting stability during a
springʼs useful life is a key functional
feature. This has led to the continuous
development of production processes
which, depending on the application,
spring size, material, production costs,
etc., can be optimised.
Reducing transverse forces
Reducing transverse forces in helical
compression springs is becoming in-
creasingly important in various applica-
tion areas (e.g. fuel injection systems,
shift and control valves, etc.). Trans-
verse force is a force applied sideways
to the axial load and transmitted to ad-
jacent components. Due to their actual
geometry it is impossible to produce
helical compression springs with zero
transverse force. Nevertheless, it is cru-
cial that the spring design ensures mini-
mum transverse force values. This opti-
misation ensures that the transverse
force experienced by the spring is re-
duced to a minimum in the working
zone.
Spring packs
For certain applications it is necessary
to transmit compressive load over a rel-
atively large diameter range. Compared
to other spring types, the compressive
load can be transmitted via a slender
contact surface here. If this load were
transferred via a helical compression
spring, the transverse force (as de-
scribed above) would have to be com-
pensated by the system. This is the
reason why a so-called spring pack,
consisting of several smaller helical
compression springs mounted on a
metal or plastic ring which transmits the
axial load, is frequently used. The
added advantage of this method is that
it is possible to create a linear or pro-
gressive curve via the pitch design of
the helical compression spring.
Another key factor for spring pack ap-
plication is its high-speed stability.
This is particularly important for multi-
disc clutches, as the spring pack ro-
tates at the respective clutch speed.
Wave springs
An alternative to the spring pack is the
so-called wave spring. A wave spring is
usually manufactured from flat wire.
The on-edge coiling process forms a
coil to which waves are added to give it
a spring effect. Wave springs fit in tight
axial spaces and can reduce the spring
operating height by as much as 50%.
However, spring packs and helical com-
pression springs are superior in terms
of their deflection and service life. Nu-
merous wave springs are available.
Shot peening and hot setting process-
es can be employed during production
to enhance the lifespan and the hot set-
ting stability of wave springs. With sin-
gle-turn wave springs, the end of the
spring can be fixed into position (e.g.
welded) if desired. This guarantees ex-
tremely high speed stability for rotating
spring elements.
Disc springs
Another type of compression-loaded
spring is the disc spring. It can be best
described as a non-flat washer conical
in shape which is compressed flat when
a load is applied. The disc can be ma-
chined at the inner and outer diame-
ters. These spring shapes are usually
referred to as slotted disc springs. The
main advantage of these disc springs is
the unrestricted design of the spring-
load characteristic. Depending on the
actual shape of the spring, it is possible
to create both progressive and degres-
sive spring characteristics. In extreme
cases, the load can decrease as spring
deflection increases. These disc
springs are usually referred to as ʻsnap
springsʼ.
4
MECHANICAL ENGINEERING – MANAGEMENT –
TECHNOLOGY & PRODUCT DEVELOPMENT
–
NEWS AND INFORMATION
RESEARCH & DEVELOPMENT
Spring Manual pro-
vides additional in-
formation
Now in its 7th edition, the
SCHERDEL Spring Manual pro-
vides additional information on
compression springs, compres-
sion-loaded spring systems and
a whole range of other technical
springs.
The comprehensive reference
book offers readers suitable
methods for calculations and ap-
plication examples. It explains
equations for stress and design
and contains information on test-
ing and application. Further chap-
ters deal with materials, spring
production as well as quality and
environmental management.
The book (196 pages comple-
mented with numerous illustra-
tions, diagrams and tables: ISBN:
978-3-00-0267736-9)
can be pur-
chased from:
SCHERDEL GmbH,
Spring Manual / Sales,
P.O. Box 440,
95604
Marktredwitz
Germany
E-mail: federfibel@scherdel.de.
The purchase price is € 34.90.
The contents of the Spring Manu-
al are also available online at:
