Improvements in Switches Used for Electrical Purposes.
Year: 1888

page_text: Date of Application, 17th Apr.. 1888
Complete Specification Left, 4th July, 1888
Complete Specification Accepted, 10th Aug.,
1888
LIVO YIDIONAL ST
Improvements in Switches Used for Electrical Purposes.
I, CHARLES SCOTT SNELL of Culver Park Saltash Cornwall do hereby declare the
nature of this invention to be as follows:-
-
The object of this invention is to produce increased reliability of the contact in
switches so that the danger from heating by the passage of the Electric current is
reduced and for this purpose I use apparatus as described below.
In one form the end of the switch or contact arm is notched or stepped so that a
series of horizontal surfaces or faces is formed thereon and the contact blocks or
pieces are similarly notched or stepped to engage or interlock with the arm, and
further to admit of a certain amount of flexibility for adjustment a series of saw-cuts
or divisions preferably horizontal are made in the contact arm or in the contact pieces
or in both. To regulate the pressure between the surfaces in contact adjustment is
made by means of screws or bolts near to, and in such manner as to admit of
expanding or contracting, these interlocking parts as may be desired.
In another form the switch or contact arm may consist of a series of horizontal
plates bent down at their extremities to bear upon the contact block or piece and to
this class of switch 1 add an adjusting piece preferably placed above and projecting
over the said plates but passing under a flange or projection from the contact block so
that screws running through this adjusting piece near its extremities tend to press the
contact arm well on to the contact piece the projection from which acts as an abut-
ment. As a modification the adjusting piece may be replaced by inverting the upper
half of the plates forming the contact arm so that they bear against the said projection
or abutment or upon the under side of the contact piece, or further the adjusting
piece itself may be so placed as to make the under side of the contact block the
abutment.
Where heavy castings are used for contact arms I make an approximately horizontal
cut or division from the extremity of the arm near its upper edge back toward the
spindle a short distance, this then forming the adjusting piece by allowing it to pass
under the flange on the contact (thus forming an abutment) and by a screw running

page_text: through this adjusting piece and bearing upon the metal underneath vary the amount
of pressure between the contact arm & the contact piece. Such castings where they
bear upon the contact piece I render slightly flexible by parallel saw cuts running
upwards at about an angle of 60° from the horizontal.
This method of regulating the pressure between the surfaces in contact by adjust-
ment in the immediate vicinity of the points of contact I find very preferable to
pulling upon or drawing down the spindle of the switch as there is practically no
friction when the contact surfaces have become disengaged and a quicker "break" is
possible thus lessening the duration of the "flash" which may conveniently "break
from the adjusting piece and keep the other surfaces clean.
33
Where it is necessary that the current should pass through two surfaces bolted
together or one revolving above the other or under similar or equivalent conditions
I use a metal washer having scored serrated or corrugated faces for good contact.
Dated this 17th day of Anril 1888.

page_text: 1, CHARLES SCOTT SNELL of Culver Park Saltash, Cornwall, Engineer and Designer
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 that is to say :-
The object of this invention is to produce increased reliability of contact in switches
used for electrical purposes so that the danger or inconvenience from heating by
reason of the passage of the electric current is reduced. Also to provide convenient
means for increasing to any required extent the current-carrying capacity of such
switches. For this purpose I construct the contact end of a switch arm or lever or
the contact block or both of a divided split or laminated form so as to interlock
elastically with the contact or to produce a yielding or spring contact action between
the lever and the block and in conjunction therewith I use a screw or screws near the
interlocking parts for adjusting as required the pressure of contact. In order to
increase the current-carrying capacity of such switches I sometimes form the end of
the switch lever and the contact in which it works with steps of any required number.
I also adapt the described mode of regulation to existing laminating switch levers.
Also where it is necessary that the current should pass through two surfaces bolted
fixedly together or so that one can rotate upon the other or under similar or equivalent
conditions I use a metal washer having scored serrated or corrugated surfaces.
And in order that my invention may be fully understood I will describe the
same with reference to the accompanying drawings which illustrate typical forms
of same.
In one form of switch shewn at Figure 1 the end of the contact arm or lever B is
notched or stepped so that a series of horizontal parallel surfaces or faces is formed
thereon, and the contact blocks or pieces A are similarly notched or stepped to engage
or interlock with the arm B. Further in order to admit of a certain amount of
feathering or flexibility for adjustment I make a series of saw cuts or divisions pre-
ferably horizontal in the contact arm. To regulate the elastic pressure between the
surfaces in contact adjustment is made by means of a screw C near to and in such
manner as to admit of expanding or contracting these interlocking parts as may be
desired.
In Figure 2 the block A is formed with the saw cuts the bolt C serving for
adjusting the elastic pressure of contact. Or both the lever B and the block A may
be made flexible as indicated by the dotted lines in Figure 2.
Figure 3 shews a lever B with one saw cut and with regulating screw C.
In Figure 4 the lever B is made up of four parts or lamina which are stepped and
provided with adjusting screw () for separating more or less the two upper from the
two lower laminæ.

page_text: Figure 5 shews a regulating screw C acting between the first and second parts of a
four parted stepped lever.
Figure 6 is a side elevation, Figure 6ª a part end view and Figure 6B a part plan
of a single break vertical action switch. The switch lever B is mounted on a fulcrum
spindle B and this end of the lever is formed with a slot or saw cut and works in
contact with the forked block A¹ as shewn in Figure 64 the elastic contact pressure
being regulated by the screw 01. The end or arm B₁ of the lever which works in the
contact block A where the break is made is also formed with a slot or saw cut as
shewn at Figure 6B and with regulating screw C. In this form of switch I may also
when required increase the current-carrying capacity by employing, both at A B, and
at AB, the step formation described with reference to Figures 1, 2, 4 or 5.
I also adapt my invention to switches or contact levers consisting of a series of
horizontal plates or laminæ, which are bent down at one or both of their extremities
to bear upon the contact block or piece. Figure 7 shows in side view such a con-
struction of switch in which the switch lever is provided with a series of plates or
blades B in this case 5 in number as an example. To this form of lever 1 add an
adjusting piece D preferably placed above and projecting over the said plate but
passing under a flange or projection from the contact block A, so that the screw C
which is threaded through the adjusting piece D near its end tends to press the turned
down lower ends of, the blades B or contact arm well on to the contact piece A the
projection from which acts as an abutment.
Figure 8 shows another form of laminated switch lever the lamina B being adapted
to work with a contact A at each end, and which may also be supported on spring
washers F.
Figure 9 is a plan and Figure 10 sectional elevation of another form of laminated"
switch lever B constructed or adapted according to my invention. The adjusting
piece D (which in all cases carries a portion of the current) here acts against the
underside of the contact piece A, the contact pressure being regulated by the screws (.
The lower ends of the wire springs (i are placed in taper recesses into which is poured
lead solder or other suitable material. I have in this instance shewn a spring arrange-
ment for preventing the lever from sticking in any position other than or intermediate
of the extreme or on and "off" positions. Some such or equivalent well known
arrangement will generally be used in connection with all my other forms of switch
lever especially for currents of high potential.
::
In Figure 12 the upper half of the plates B are inverted so that the upper half
bear against the projection or abutment on the contact A and the lower half bear against
the base part of the contact A.
In Figure 13 an adjusting plate D is so placed as to make the underside of the
contact block A the abutment.
Where heavy castings are used for contact arms I make an approximately horizontal
cut or division from the extremity of the arm B near its upper edge back towards the
spindle a short distance this upper part then forming the adjusting piece corresponding
to D Figures 7 and 8 as shewn in Figure 14 by allowing it to pass under the flange
on the contact A and the screw threaded through this upper part and bearing upon
the lower part affording a means for varying the amount of pressure.
In order to render such castings slightly elastic also where they bear upon the
contact piece I provide the same as shewn at Figure 15 with parallel saw cuts running
upwards at an angle of about 60° from the horizontal.
In Figure 16 the adjusting piece or portion is also formed with saw cuts for
increasing the flexibility..
The above described method of regulating the pressure between the surfaces in
contact by adjustment in the immediate vicinity of the points of contact I find very
preferable to pulling upon or bearing down upon the spindle of the switch, as in my
method there is practically no friction when the contact surfaces have become dis-
engaged and a quicker break is possible thus lessening the duration of the flash which
may conveniently "break" from the adjusting piece and keep the other surfaces clean.
The use of the spring washer F Figure 8 for slightly lifting the switch arm when it

page_text: has left the contact reduces even the little amount of friction due to the rubbing upon
the vulvanized fibre insulation that is often placed between the contacts of the
switch.
Where it is necessary that the current should pass through two surfaces bolted
fixedly together or so that one can rotate upon the other or under similar or equivalent
conditions I use a metal washer having scored serrated or corrugated surfaces.
Figure 17 is plan and Figure 18 cross section through a washer having annular con-
centric scores or grooves. Such a washer E is shewn applied at Figure 7 between
rotating surfaces at the fulcrum and a similar washer E¹ between stationary surfaces.
These washers may be of copper. The pressure causes the fine circular edges on both
sides of the washer to become evenly flattened thus affording considerable distributed
contact surface.
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 :-
:-
First In switches for electrical purposes the application and use of contact levers
having the contact end or ends of a divided split or laminated form capable of
working elastically between two parts of a contact block or blocks and provided with
regulating screw or screws for adjusting the elastic contact pressure substantially as
sét forth.
Second The application to existing laminated contact levers of an adjusting piece
and one or more regulating screws for adjusting the elastic contact pressure substan-
tially as set forth.
Third -In switches for electrical purposes forming the contact end or ends of the
switch arm with steps and of a divided, split, or laminated form and forming the
contact block with corresponding steps capable of engaging or interlocking therewith
substantially as set forth and for the purpose of affording large and efficient contact
surface.
Fourth-The electrical switch constructions described with reference to the
accompanying drawings.
Fifth The metal washer E having corrugated indented or serrated surfaces
substantially as set forth and for the purpose of carrying the current between fixed or
rotating surfaces substantially as described and shewn.
Dated this 4th day of July 1888.