Technical field
[0001] The present invention relates to an electric safety switch, especially for electric
power supply circuits for machines and industrial plants.
Background art
[0002] Electric switches of the above-mentioned type are known, which comprise essentially
a casing with at least two slots for inserting an actuating key of pre-defined shape,
at least a couple of electric contacts placed in the casing and displaceable between
a closed position, when the actuator is connected, and an open position when the actuator
is disconnected, a cam placed inside the casing and operatively connected to the electric
contacts to displace and commute them, said cam being pivotable around a first axis
when inserting the actuator in one of the slots.
[0003] The switch is provided with blocking means to prevent cam rotation and subsequent
movement of electric contacts, and elastic means adapted to maintain the blocking
means in a stopping position of the cam when the actuator is disconnected from the
casing.
[0004] Normally, the switch casing is fixed to a stationery part of the machine or plant,
for instance to a control cubicle frame, while the key actuator is fixed on a moving
part, like the cubicle door.
[0005] By means of this configuration, opening the cubicle door will commute the electric
contacts inside the casing and open the electric power supply circuit of the machine
or plant.
[0006] Moreover, because of the particular cam shape and of the actuator inserting opening,
electric commuting of the contacts cannot be achieved by using a simple screw driver,
a wire or a sharp object, but only with an actuator of special shape coupled to the
switch.
[0007] A drawback of this known safety switches lies in the relatively complex and miniaturised
cam blocking mechanisms, especially if there are more than one actuator input opening,
which reduce mechanical strength and switch reliability.
[0008] Additionally, the actuator input detecting mechanisms are subject to sudden displacements
and are susceptible of rupture especially if they are guided in a translating movement.
[0009] Examples of safety switches of the above mentioned type are described in the following
patent documents: EP-A-553885, WO-A-9524726, US-A-5516993, US-A-5622253, EP-A-175156,
EP-A-605820, US-A-4395608, US-A-5420385, EP-A-117396, EP-A-345656, US-A-4963706, US-A-5587569,
EP-A-507820, US-A-4695684, DE-A-4338910, EP-A-0727797.
[0010] The blocking means of those known switches generally comprise one ore more slides
placed at the cam sides and able to move along linear guiding means, see e.g. DE-A-4338910.
The slides interact together and with the cam by means of inclined planes which produce
high friction forces and are subject to seizures due to dirt settled on the sliding
surfaces. Moreover, such slides are subject to high wear. Mutually disposed multiple
disc solutions also are subject to seizures because of the dirt on the contact surfaces,
see e.g. EP-A-0727797. In particular, the simultaneous rotation of the discs caused
by their reciprocal seizure prevents proper functioning of the switch.
[0011] Other examples of switches provide only one input opening for the actuator, thus
limiting flexibility in the use of the device.
[0012] From EP-A-0 707 329 a safety switches is known which comprises all the features mentioned
in the preamble of the attached claim 1. In this known safety switch there is provided
a blocking means comprising a pair of lever elements rotary mounted on the cam to
move against the reaction force of springs having one end lodged in appropriate seats
of the cam. In this arrangement the cam is a rather complicated assembly formed by
five parts which are interconnected with respect to each other and are difficult to
mount. Moreover, each lever element has a locking portion which co-operates with the
axis of the cam that is non-rotatably mounted in the casing. The locking portion of
each lever element is a locking groove disposed in the passage of the axis and the
co-operating surfaces of the lever element and of the axis must be extremely precise
in order to avoid large angular position errors on the periphery of the cam.
Description of the invention
[0013] The main object of the present invention is to eliminate, or at least to reduce,
the above-mentioned drawbacks by providing a safety switch with high flexibility of
use, reliability and long operating life.
[0014] A particular object is to provide a safety switch which is substantially not dirt
sensitive.
[0015] Another object of the invention is to provide a safety switch with a simplified structure,
and a limited number of parts, so as to be easy to assemble and economically advantageous.
[0016] The above mentioned objects and others which will be better clarified hereafter are
achieved by means of a safety switch in accordance with the attached claim 1. Thanks
to the claimed arrangement it is possible to prevent seizure risks and the typical
wear of the slides of the prior art.
[0017] Preferably, the second pivot axis of the lever element is substantially parallel
to the cam pivot axis. This produces an important simplification and consequently
more reliability and longer operational life.
[0018] Advantageously every lever element has an actuating portion that interacts with the
actuator. Moreover, the actuation portion of each lever element is provided with rounded
edges that face each of the casing openings to operate smoothly with the actuator
at the moment of the introduction in the casing.
[0019] To this end, the cam is provided with at least one engagement element, preferably
positioned on one lateral side of the cam and it is constituted by a radial protrusion.
Brief description of the drawings
[0020] Further advantages and aspects of the invention will become more evident from the
detailed description of a preferred, non-limitative, embodiment of a safety switch,
hereafter shown by way of non-limitative example by means of the accompanying drawings,
in which:
Fig. 1 shows a partial-section side schematic view of a safety switch according to
the invention;
Fig. 2 shows the switch of Fig. 1, in a second operational position:
Fig. 3 shows an enlarged-scale side view of a detail of Fig. 1 in a first operational
position;
Fig. 4 shows an enlarged-scale side view of a detail of Fig. 1 in a second operational
position;
Fig. 5 shows an exploded perspective view of a detail of Fig. 1.
Description of an embodiment
[0021] With reference to the mentioned figures, the switch according to the invention globally
referenced as 1, comprises a casing 2 composed of a lower body 3 and upper head 4,
adapted to be reciprocally coupled and fixed to a fixed part of a machine or plant,
for example to a control cubicle frame.
[0022] The lower body 3 contains a first pair of fixed contacts respectively referenced
as 5, 5', for example placed serially on the electric power line of the machine, and
a second series of fixed contacts 6, 6', for example placed in series on the electric
power line of an optical and/or acoustic alarm.
[0023] Two pairs of mobile contacts respectively referenced as 7, 7' and 8, 8' united by
respective links 9, 10 are mounted on a shaft 11 slidably guided along a longitudinal
axis V by appropriate seats.
[0024] Thus, contacts 7, 7', 8, 8' can be displaced between a closed position of contacts
5, 5' and simultaneous opening of contacts 6, 6', as shown in Fig. 1, and an open
position of contacts 5, 5' and simultaneous closing of contacts 6, 6', as shown in
Fig. 2.
[0025] A compression spring 13 operates on the lower extremity 12 of the moving shaft 11
to push the upper extremity 14 of the shaft 11 against a cam external profile, globally
referenced as 15.
[0026] Cam 15 is pivotally mounted on a first rotation axis H defined by a pin 16 inserted
in the head 4 and is provided on its periphery with a pair of appropriately shaped
hollows 17, 17'.
[0027] The head 4 is provided with two slots 18, 19 made on two adjacent faces of the head
4, for insertion of an actuator 20, having the shape of a key, along two mutually
perpendicular directions A and B. The key-shaped actuator 20 can be solidarily coupled
to a fixed machine part, for instance a cubicle door, and has an end part 21 of special
shape interrupted in its centre to cooperate at the input and output with cavities
17, 17' of cam 15.
[0028] Thus, by closing the cubicle door, the actuator will be inserted in the slot 18 or
19 made in the head 4, interacting with cam 15 to make it rotate. Cam 15, in turn,
operates on the upper extremity 14 of the shaft 11, thus displacing the latter in
translation and changing the switch position.
[0029] The switch is provided with blocking means, globally referenced with 22, for preventing
rotation of the cam and consequent movement of the contacts, and elastic means. 23,
for example constituted by compression springs, acting on the blocking means 22 to
keep them in a position in which the cam 15 is blocked when the actuator is disconnected
from the head 4.
[0030] According to the invention, the blocking means comprise at least one lever element
24 pivotally coupled on a second axis K, distal from the first one and positioned
so as to actuate cam 15.
[0031] Axis K is preferably parallel to axis H so that the movements of the lever elements
24, 24' occur in a direction substantially perpendicular to the cam rotation axis
H.
[0032] More particularly, two lever elements 24, 24' are provided, arranged at the opposite
faces of cam 15 and pivotally connected on a pin 25 coinciding with axis K.
[0033] Each lever element 24, 24' comprises an actuating portion 26, 26' for interacting
with the actuator and a blocking portion 27, 27' for interacting with cam 15.
[0034] More particularly, each actuating portion 26, 26' has rounded edges 28, 28' and 29,
29' facing their respective slots 18, 19 in the head 4, to slidingly interact with
actuator 20 when it is inserted.
[0035] Advantageously, cam 15 is provided with engagement elements. Preferably, the engagement
elements are positioned on the lateral faces of the cam 15 and are constituted by
a radial protrusion 30 extending from an axial hub 31 solidarily fixed to the cam.
[0036] Actuating portions 26, 26' and blocking portions 27,27' extend from the respective
central portions 32, 32' of the lever element provided with respective sleeves 33,
33' which can be inserted in the pivot pin 25.
[0037] Opportunely, the distance between axes H and K and between the central portions 32,
32' of the lever elements 24, 24' are dimensioned so as to allow the passage of the
key-shaped actuator 20 when the latter is introduced in the head 4 through the slot
18.
[0038] Each blocking portion 27, 27' of the lever elements 24, 24' is provided with a groove
34, 34' substantially counter-shaped with respect to the radial protrusion 30 of the
cam 25 to selectively engage therein and prevent the rotation of the cam 15.
[0039] Moreover, every groove 34, 34' is provided with conical tapers 35, 35' which tend
to bring the radial protrusion 30 back to a pre-defined angular position by bringing
back the cam to its initial position.
[0040] Thus, the grooves 34, 34' have both functions of blocking the cam and bringing it
back to the centre when the actuator 20 is disconnected from the slot. This enables
making the slots with a large clearance and guaranteeing return of the cam in its
initial position when the actuator 20 is extracted from the head 4.
[0041] Even if the safety switch according to the invention has been described with reference
to the embodiment illustrated in the drawing figures, it is evident that it is susceptible
to numerous modifications and variations falling within the protective scope defined
in the appended claims and intended to be equally protected.
1. Electric safety switch, comprising:
a casing (2, 3, 4) with at least two slots (18, 19) for the insertion of a key-shaped
actuator (20) having pre-defined shape;
at least one pair of electric contacts (5, 5', 6,6', 7, 7', 8, 8') disposed in the
casing (3) and movable between a closed position, when said actuator (20) is inserted,
and an open position, when said actuator is disinserted;
a cam (15) mounted inside the casing (4) and operatively connected with the contacts
to activate their displacement and commutation, said cam being rotatable around a
first axis (H) by inserting the actuator in the casing;
blocking means (22) for preventing the rotation of the cam (15) and the consequent
movement of the contacts;
elastic means (23) acting on said blocking means for maintaining them in a cam blocking
position when said actuator is disinserted from the casing;
said blocking means (22) comprising at least one lever element (24, 24') pivotally
connected around a second axis (K) distal with respect to the first one (H) and positioned
in such a way to act on a lateral face of the cam (15),
characterised in that said at least one lever element (24, 24') is pivotally connected around said second
axis (K) distally and independently from said cam (15), said cam (15) being provided
with at least one engagement element (30) positioned on a lateral face of the cam
(15), said at least one lever element (24, 24') being provided with a blocking portion
(27, 27') adapted to selectively engage said engagement element (30) to prevent the
rotation of the cam (15).
2. Electric switch according to claim 1, characterised in that said second pivot axis (K) is substantially parallel to the cam rotation axis (H).
3. Electric switch according to claim 1, characterised in that said at least one lever element (24, 24') is provided with an actuating portion (26,
26') for interacting with the actuator (20).
4. Electric switch according to claim 3, characterised in that said actuating portion (26, 26') is provided with rounded edges (28, 29, 28', 29')
facing each of the slots (18, 19) to slidingly interact with the actuator (20) when
it is inserted in the casing.
5. Electric switch according to claim 1, characterised in that said engagement element is a radial protrusion (30) extending from an axial hub (31)
unitary fixed to the cam (15).
6. Electric switch according to claims 3 or 4, characterised in that said actuating portion (26, 26') and said blocking portion (27, 27') extend from
a central portion (32, 32') of the lever element, pivotally connected around said
second axis (K) to said casing (4).
7. Electric switch according to claim 5, characterised in that said each blocking portion (27, 27') is provided with a groove (34, 34') substantially
counter-shaped with respect to said radial protrusion (30) of said cam.
8. Electric switch according to claim 7, characterised in that said groove (34, 34') is provided with conical tapers (35, 35') adapted to bring
the radial protrusion (30) in a predetermined angular position bringing said cam back
to its initial position.
9. Electric switch according to any one or more of the preceding claims, characterised in that it is provided with a pair of lever elements (24,24') on opposite sides of said cam,
interacting simultaneously and symmetrically with respective radial protrusions (30)
formed on the lateral faces of the cam.
1. Elektrischer Sicherheitsschalter mit
einem Gehäuse (2, 3, 4) mit mindestens zwei Schlitzen (18, 19) zum Einführen einer
schlüsselförmigen Betätigungsvorrichtung (20) mit einer vorbestimmten Form, mindestens
einem Paar in dem Gehäuse (3) angeordneter elektronischer Kontakte (5, 5', 6, 6',
7, 7', 8, 8'), die beweglich sind zwischen einer geschlossenen Position, wenn die
Betätigungsvorrichtung (20) eingeführt ist und einer offenen Position, wenn die Betätigungsvorrichtung
nicht eingeführt ist,
einer Nocke (15), die innerhalb des Gehäuses (4) angeordnet ist und funktional verbunden
ist mit den Kontakten, um deren Bewegung und Umschaltung zu bewirken, wobei dieser
Nocken drehbar ist um eine erste Achse (H) durch Einführen der Betätigungsvorrichtung
in das Gehäuse; Blockiereinrichtungen (22) zur Verhinderung der Drehung des Nockens
(15) und der folgenden Bewegung der Kontakte, elastischen Einrichtungen (23), die
auf die Blockiereinrichtungen wirken, um diese in einer Position zu halten, in der
der Nocken blockiert ist, wenn die Betätigungsvorrichtung nicht in das Gehäuse eingeführt
ist,
wobei die Blockiereinrichtungen (22) mindestens ein Hebelelement (24, 24') umfassen,
das schwenkbar an eine zweite Achse (K) montiert ist mit Abstand zu der ersten (H)
und so angeordnet, daß es auf eine seitliche Fläche des Nockens (15) wirkt,
dadurch gekennzeichnet, daβ
dieses mindestens eine Hebelelement (24, 24') schwenkbar an diese zweite Achse (K)
montiert ist mit Abstand und unabhängig zu dem Nocken (15), wobei dieser Nocken (15)
mit mindestens einem Eingriffselement (30) versehen ist, das auf einer seitlichen
Fläche des Nockens (15) angeordnet ist, wobei dieses mindestens eine Hebelelement
(24, 24') mit einem Blockierabschnitt (27, 27') versehen ist, der ausgestaltet ist,
um dieses Eingriffselement (30) wahlweise zu erfassen, um die Drehung des Nockens
(15) zu verhindern.
2. Elektrischer Sicherheitsschalter gemäß Anspruch 1, dadurch gekennzeichnet, daß die zweite Schwenkachse (k) im wesentlichen parallel ist zu der Drehachse (H) des
Nockens.
3. Elektrischer Sicherheitsschalter gemäß Anspruch 1, dadurch gekennzeichnet, daß mindestens ein Hebelelement (24, 24') mit einem Betätigungsabschnitt (26, 26') vorgesehen
ist zur Beaufschlagung mit der Betätigungsvorrichtung (20).
4. Elektrischer Sicherheitsschalter gemäß Anspruch 3, dadurch gekennzeichnet, daß der Betätigungsabschnitt (26, 26') mit runden Kanten (28, 29, 28', 29') versehen
ist, die jedem der Schlitze (18, 19) gegenüber liegen, um gleitend die Betätigungsvorrichtung
(20) zu beaufschlagen, wenn die in das Gehäuse eingeführt ist.
5. Elektrischer Sicherheitsschalter gemäß Anspruch 1, dadurch gekennzeichnet, daß das Eingriffselement als radialer Vorsprung (30) ausgebildet ist, der sich von einer
radialen Nabe (31) erstreckt, die einstückig an dem Nocken (15) befestigt ist.
6. Elektrischer Sicherheitsschalter gemäß Anspruch 3 oder 4, dadurch gekennzeichnet, daß der Betätigungsabschnitt (26, 26') und der Blockierabschnitt (27, 27') sich von einem
zentralen Abschnitt (32, 32') des Hebelelements erstrecken, das schwenkbar um die
zweite Achse (K) an das Gehäuse (4) montiert ist.
7. Elektrischer Sicherheitsschalter gemäß Anspruch 5, dadurch gekennzeichnet, daß jeder der Blockierabschnitte (27, 27') mit einer Nut (34, 34') versehen ist, die
im wesentlichen entsprechend geformt ist zu dem radialen Vorsprung (30) der Nocke.
8. Elektrischer Sicherheitsschalter gemäß Anspruch 7, dadurch gekennzeichnet, daß die Nut (34, 34') versehen ist mit konischen Schrägen (35, 35'), die so ausgestaltet
sind, daß der radiale Vorsprung (30) in eine vorbestimmte Winkelstellung gebracht
wird, so daß der Nocken wieder in seine Ausgangsstellung zurück gebracht wird.
9. Elektrischer Sicherheitsschalter gemäß einem oder mehreren der vorhergehenden Ansprüche,
dadurch gekennzeichnet, daß ein Paar Hebelelemente (24, 24') vorgesehen sind an gegenüberliegenden Seiten des
Nockens, die simultan und symmetrisch mit den jeweiligen radialen Vorsprüngen (30)
zusammen wirken, die auf den seitlichen Flächen des Nockens gebildet sind.
1. Commutateur électrique de sécurité comprenant :
un boîtier (2, 3, 4) présentant au moins deux fentes (18, 19) pour l'insertion d'un
actionneur (20) en forme de clé qui possède une forme prédéfinie ;
au moins une paire de contacts électrique (5, 5', 6, 6', 7, 7', 8, 8') disposés dans
le boîtier (3) et pouvant se déplacer entre une position fermée, lorsque ledit actionneur
(20) est inséré, et une position ouverte, lorsque ledit actionneur est retiré ;
une came (15) montée à l'intérieur du boîtier (4) et reliée fonctionnellement aux
contacts pour activer leur déplacement et leur commutation, ladite came pouvant être
tournée autour d'un premier axe (H) par l'insertion de l'actionneur dans le boîtier
; des moyens de blocage (22) destinés à empêcher la rotation de la came (15) et le
mouvement consécutif des contacts ;
des moyens élastiques (23) qui agissent sur lesdits moyens de blocage pour les maintenir
dans une position de blocage de la came lorsque ledit actionneur est retiré du boîtier;
lesdits moyens de blocage (22) comprenant au moins un élément formant levier (24,
24') monté pivotant autour d'un deuxième axe (K) distant du premier (H) et positionné
de manière à agir sur une face latérale de la came (15),
caractérisé en ce que ledit au moins un élément formant levier (24, 24') est monté pivotant autour dudit
deuxième axe (K) à distance et indépendamment de ladite came (15), ladite came (15)
étant munie d'au moins un élément d'engagement (30) positionné sur une face latérale
de la came (15), ledit au moins un élément formant levier (24, 24') étant muni d'une
portion de blocage (27, 27') adaptée pour engager sélectivement ledit élément d'engagement
(30) pour empêcher la rotation de la came (15).
2. Commutateur électrique selon la revendication 1 caractérisé en ce que ledit deuxième axe pivot (K) est sensiblement parallèle à l'axe de rotation (H) de
la came.
3. Commutateur électrique selon la revendication 1 caractérisé en ce que ledit au moins un élément formant levier (24, 24') est muni d'une portion d'actionnement
(26, 26') destinée à coopérer avec l'actionneur (20).
4. Commutateur électrique selon la revendication 3 caractérisé en ce que ladite portion d'actionnement (26, 26') est munie de bords arrondis (28, 29, 28',
29') qui sont dirigés vers chacune des fentes (18, 19) pour coopérer par coulissement
avec l'actionneur (20) lorsqu'il est inséré dans le boîtier.
5. Commutateur électrique selon la revendication 1 caractérisé en ce que ledit élément d'engagement est une protubérance radiale (30) qui fait saillie sur
un moyeu axial (31) fixé à la came (15) en un seul tenant.
6. Commutateur électrique selon les revendications 3 ou 4 caractérisé en ce que ladite portion d'actionnement (26, 26') et ladite portion de blocage (27, 27') font
saillie sur une portion centrale (32, 32') de l'élément formant levier, qui est relié
audit boîtier (4) en pouvant pivoter autour dudit deuxième axe (K).
7. Commutateur électrique selon la revendication 5 caractérisé en ce que chaque portion de blocage (27, 27') est munie d'une gorge (34, 34') qui a une forme
sensiblement complémentaire de ladite protubérance radiale (30) de ladite came.
8. Commutateur électrique selon la revendication 7 caractérisé en ce que ladite gorge (34, 34') est munie de surfaces inclinées coniques (35, 35') adaptées
pour placer la protubérance radiale (30) dans une position angulaire prédéterminée
qui ramène ladite came à sa position initiale.
9. Commutateur électrique selon l'une ou plusieurs des revendications précédentes
caractérisé en ce qu'il est muni d'une paire d'éléments formant levier (24, 24') placés sur les deux côté
opposés de ladite came et qui coopèrent simultanément et symétriquement avec des protubérances
radiales respectives (30) formées sur les faces latérales de la came.