Power drive including a drive slide for electric switchgear

Disclosed is a power drive for electric switchgear, for example, protective low-voltage breakers. The power drive comprises a support plate and a drive slide which is guided between the support plate and the top or front side of the switchgear. The drive slide includes side walls into which a projection located on the top side of the switchgear extends for guiding the drive slide on the switchgear. The drive slide cooperates with the switchgear actuating handle through an opening having curved surfaces. The power drive includes a U-shaped leaf-spring which extends transversely to the direction of motion of the drive slide and which provides for elastic transmission of force from a crank coupled to a gear box to the actuating handle of the switchgear.

CROSS-REFERENCE TO RELATED APPLICATION 
Some of the subject matter disclosed herein is common to subject matter 
disclosed in application Ser. No. 253,587 filed Apr. 13, 1981 entitled 
POWER DRIVE FOR ELECTRIC SWITCHGEAR IN WHICH DRIVING POWER IS ELASTICALLY 
TRANSMITTED application Ser. No. 253,586 filed Apr. 13, 1981 entitled 
MOTOR DRIVE FOR LOW-VOLTAGE PROTECTIVE CIRCUIT and application Ser. No. 
253,584 filed Apr. 13, 1981 entitled "ROTARY HANDLE FOR MANUAL OPERATION 
OF AN EQUIPMENT POWER DRIVE". This application and the above-mentioned 
applications are owned by the same assignee. 
BACKGROUND OF THE INVENTION 
The present invention relates to a power drive for electric switchgear, 
especially protective low-voltage circuit breakers. The power drive is of 
the general type including a support plate for the drive parts as well as 
a drive slide extending over an actuating member of the switchgear which 
projects through a window-like opening of the power drive. 
A power drive of the above type is disclosed, for example, in U.S. Pat. No. 
3,328,731. The drive slide of the power drive described in the '731 patent 
is guided on the support plate. The correct alignment of the slide and its 
window-like opening relative to the actuating member of the switch depends 
on an accurate positioning and connection of the support plate to the 
switchgear. However, unavoidable tolerances can lead to a situation in 
which the drive slide does not axially cooperate with the actuating 
member, or does not cooperate at all with the actuating member in an area 
of the opening. As a result, it is possible that the driving forces are 
not uniformly applied to the actuating member, but can be locally 
concentrated in an undesirable manner. Premature wear of the cooperating 
parts or even breaking of the actuating member can occur as a consequence. 
OBJECT AND SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a power drive of the 
above-described type in which the drive slide and the actuating member of 
the switchgear cooperate without wear, regardless of the manner of 
fastening of the support plate to the switchgear. 
This and other objects are achieved in accordance with the invention by 
arranging the drive slide between the support plate and the side of the 
switchgear having the actuating member, with the drive slide being guided 
therebetween. Means can also be provided to guide the drive slide relative 
to the switchgear. The invention thereby provides automatic alignment of 
the power drive with the switchgear as well as with the switchgear 
actuating member. 
According to one aspect of the invention, the material for making the drive 
slide, or selected parts thereof, can be made of a low friction material, 
such as plastic. 
According to another aspect of the invention, the opening through which the 
actuating member of the switchgear, which can be a handle pivoted about a 
fulcrum, projects can be defined by curved surfaces. 
Advantages of the invention, as compared with drive slides fabricated of 
stamped sheet metal parts, are less friction at the guide surfaces as well 
as automated production of a drive slide which can have a relatively 
complicated shape in order to provide for further functions. 
According to another aspect of the invention, in addition to the guidance 
of the drive slide between the switchgear and the support plate, lateral 
guidance can be provided by a projection extending from the surface of the 
switchgear from which the actuating member extends and side walls 
extending from the drive slide about the projection. A projection is 
typically provided in the switching equipment of the type generally called 
"compact breakers." The distance between the side walls of the drive slide 
can be selected to correspond to the width of such a projection, thereby 
providing the lateral guidance. 
According to the invention, a power drive can be accomplished by 
positioning the drive slide on the switchgear in such a manner that the 
actuating member protrudes through the window-like opening and then 
placing the support plate with the other parts of the drive on the 
switchgear. However, if it is desired to attach the support plate together 
with the parts of the drive including the drive slide on the switchgear, 
then the drive slide can be provided with an elongated opening or slot 
extending in the direction of motion of the drive and at least one holding 
member can be attached to the support plate to extend through the slot. 
The holding member prevents separation of the drive slide from the support 
plate. The holding member need not provide guidance for the drive slide 
after it is attached to the switchgear, and accordingly, an appropriate 
clearance can be provided between the elongated slot and the holding 
member. 
Securement of the drive slide to the support plate up to the time that the 
drive is installed with the switchgear can be improved by providing a 
control slide which engages the drive slide. The drive slide can include a 
connecting piece on the side opposite to the elongated slot and the 
control slide can include an arm engaged by the connecting piece, the 
control slide being guided on the support plate to move parallel to the 
direction of motion of the drive slide. A generous clearance is provided 
between the connecting piece and the arm so that alignment of the drive 
slide relative to the actuating member of the switchgear is not affected. 
According to the invention, a close tolerance may only be provided between 
the actuating member and the opening to prevent wear in the drive slide 
and the surface of the opening can be made of a low friction and/or 
wear-resistant material. Other tolerances may be made larger while not 
interfering with the cooperation between the actuating member and the 
opening. 
The power drive advantageously includes a motor and the control slide is 
operative to switch off the motor of the power drive when the desired 
switch positions of the switchgear are reached. Advantageously, means are 
provided to frictionally resist motion of the control slide, for example, 
a drag slide can be provided. The control slide can also be provided with 
ribs for securing the drive slide to the support plate. The control slide 
can be provided with a control cam which cooperates with an end switch to 
switch the motor. Advantageously, the end switch can be a toggle switch. 
The control slide can include markings thereon to indicate the "on" 
position and the "off" position of the switchgear. 
These objects and other objects, aspects, features and advantages of the 
invention will be more apparent from the following description of the 
preferred embodiments thereof when considered with the accompanying 
drawings and appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring more particularly to the drawings, a power drive according to the 
invention, designated generally by 1 in FIGS. 1 and 2, is illustrated. The 
power drive 1 is associated with a compact protective low-voltage breaker 
2, the outline of which is shown in part in FIG. 2 by dashed-dotted lines. 
From A central projection 3 of the protective breaker 2 protrudes an 
actuating handle 4, with which the protective breaker 2 can normally be 
switched on and off by hand. A drive slide 5 cooperates with the actuating 
handle 4 through a window-like opening 6. The opening 6 is defined by two 
curved surfaces 7, which are spaced to correspond essentially to the width 
of the actuating handle 4, and enlargements 10 provided on each side of 
the curved surfaces 7. The surface 7 as well as the enlargements 10 can be 
made of a plastic material, as can the drive slide 5. The enlargements 10 
ensure that there are no corners or edges which could locally cause 
increased stress of the material of the actuating handle 4. The distance 
between the surfaces 7 is chosen so that there is little play between a 
respective surface and the actuating handle 4 in the end positions of the 
actuating handle, thereby preventing jamming. FIG. 2 shows an intermediate 
position of the handle 4 obtained when the protective breaker 2 is 
switched on or off. 
For lateral guidance of the drive slide 5, side walls 11 and 12 are 
provided. The side walls of the drive slide extend over the projection 3 
on the top or front side of the protective breaker 2 (FIG. 2). One surface 
of the drive slide 5, together with the drive slide side walls, slides on 
the top surface of the protective breaker 2, while the opposite surface of 
the drive slide is guided at a support plate 13 which is connected to the 
protective breaker 2 by, for example, means of screws at four fastening 
points. 
When the power drive 1 and the protective breaker 2 are provided as an 
assembly, as shown in the assembled configuration of FIGS. 1 and 2, the 
above-described surfaces effectively guide the drive slide. However, when 
the power drive 1 is provided separate from the protective breaker 2 and 
is to be installed on the protective breaker, means are provided to 
prevent detachment of the drive slide 5 from the power drive. Such means 
can comprise an elongated hole or slot 15 disposed on one side of the 
drive slide 5. The slot 15 extends parallel to the operational direction 
of motion of the drive slide 5, as indicated by the double arrow 16, in a 
part laterally projecting from the side wall 11. A pin or screw 17 is 
fastened to the support plate and extends through the elongated hole. The 
pin or screw includes a head, washer or a securing ring which prevents the 
drive slide 5 from separating from the support plate. 
On the opposite side of the drive slide 5, i.e., in the vicinity of the 
side wall 12, the drive slide 5 has two ribs 20, one of which is visible 
in FIG. 1. The ribs cooperate with stop surfaces 21 of a control slide 22 
which has a cam surface 23 (FIG. 2) for a toggle switch 24. Due to the 
fact that the length of the ribs 20 is larger than the length of the stop 
surfaces 21 of the control slide 22, the drive slide and the control slide 
are not directly coupled, there being a certain amount of play between the 
two so that the control slide is operated as a drag slide. 
The control slide 22 is movably guided lengthwise in the direction of the 
double arrow 16 in a slot of the support plate 13, and includes arms 25 
extending below the ribs 20 of the drive slide 5. A resilient extension 18 
(FIG. 3) of the control slide 22 bears against its contact surface on the 
support plate 13 and thereby causes a frictional braking action of the 
control slide in order to prevent motion of the control slide without a 
drive being applied thereto. The arms 25 of the control slide supplement 
holding of the drive slide 5 by the above-described holding member 17. As 
a result, the drive slide is held at the support plate 13 with 
considerable play but in such a manner that it cannot come loose and can 
therefore be placed on the protective breaker 2 together with the other 
parts of the power drive. When the power drive 1 and the protective 
breaker 2 are connected to each other at the above-mentioned fastening 
points, guidance is transferred from the holding member 17 and the arm 
extensions 25 to the operating handle 4 and the curved surfaces 7, and the 
support plate 13 and the top side of the protective breaker 2. 
The control slide 22 has an indicator 40 (FIG. 2) which fits closely under 
a cap 41 which covers the power drive 1 from the outside, and which is 
provided with markings to indicate the switch position. The control slide 
therefore fulfills several functions, controlling not only switching of 
motor 26 which is described more fully below, but forming at the same time 
a holder for the drive slide 5 and indicating the switch position. 
The power drive 1 further comprises the motor 26 coupled to a gear box 27 
which includes an output shaft 28 perpendicular to support plate 13 having 
a crank arm 29 and a crank pin 30. The crank pin 30 is engaged between the 
legs 31 of a leaf spring 32 bent in a U-shape. The leaf-spring 32 extends 
transversely to the direction of motion of the drive slide 5 and is 
supported at the drive slide in an opening 33 at one end thereof and in an 
opening 34 at the other end thereof. The opening 34 merges into a 
pocket-like recess 35 into which one leg 31 of the leaf-spring 32 having a 
bent-off end 36 snaps. A screw 37 passes between the legs 31 of the 
leaf-spring in the vicinity of the opening 34 and braces the legs against 
each other. By rotating the crank arm 29 in the same direction by 
180.degree., the protective breaker can be switched alternatingly on and 
off. In the position shown in FIG. 1, the drive slide with the operating 
handle 4 is in a middle position corresponding to a rotation of the crank 
arm 29 by about 90.degree. relative to is ends positions. 
The U-shaped leaf-spring 32 inserted into the drive slide 5 brings about an 
elastic transmission of the driving force of the motor 26 via the gear box 
27 and the crank pin 30 to the operating handle 4 of the protective 
breaker 2. Thereby, tolerances in the cooperation of the protective 
breaker 2 and the motor drive 1 are accommodated and overloading of the 
individual parts, particularly the operating handle 4, is prevented. 
The advantages of the present invention, as well as certain changes and 
modifications of the disclosed embodiments thereof, will be readily 
apparent to those skilled in the art. It is the applicants' intention to 
cover by their claims all those changes and modifications which could be 
made to the embodiments of the invention herein chosen for the purpose of 
the disclosure without departing from the spirit and scope of the 
invention.