Improvements in or relating to Cranks and Crank Discs.
Year: 1890

page_text: Date of Application, 6th Aug., 1890-Accepted, 20th Sept., 1890
CUMI LEIE DUITIVATION.
Improvements in or relating to Cranks and Crank Discs.
A communication from abroad by NOE FERNAND LESAGE, of 6 rue d'Arras, Paris, in
the Republic of France, Professor.
1, WILLIAM PHILLIPS THOMPSON, F.C.S. M.I.M.E. of the Agency for Foreign
Patent Solicitors 6, Lord Street, Liverpool and 6, Bank Street, Manchester both in
the County of Lancaster and 323 High Holborn, in the County of Middlesex, Civil
Engineer, 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 :-.
The crank or crank disc forming the object of this invention is designed with the
view of disengaging it from the crank pin to which it is connected when an abnormal
resistance is encountered. Its use obviates any cause of danger to a tool or machine
actuated by it, or to the motor itself. The automatic disengaging is followed by an
automatic re-engaging when the obstacle which hinders the normal action of the tool
or machine has disappeared.
The mechanism constituting this invention is also capable of producing, after the
disengagement of the crank from the disc, a recoil of the tool. The object of this
recoil is to release the obstruction and to allow the tool to resume its action without
any intervention on the part of the workman. In machines where this recoil would
be harmful, it can be dispensed with.
In the drawings:-
Figures 1, 2 and 3 represent respectively a central section, a front elevation and a
rear clevation of the whole of the crank disc.
Figures 4, 5 and 6 represent respectively a section, front elevation and rear
elevation of the automatic disengaging and engaging sector, the position of which is
shown at C, Figures 1 and 2.
As may be seen on Figures 1 and 2, the apparatus comprises two plates A and B,
between which is a groove C which serves as a guide to a sector D represented
separately in Figures 4, 5 and 6. This sector, to which is attached a crank pin E,
has formed in it a series of inclined cavities ILK M, into which the conical
pegs F G H (Figures 1, 2 and 3) enter and are held by springs P. The number of
these pegs, or the position they occupy, either on the bottom of the plate or elsewhere,
as well as the position and shape of the springs, can be varied according to
requirements, provided that, at the same time, the inclined cavities in the sector be
varied so that there shall be the requisite correspondence between the different parts.
The two plates A and B are firmly connected with each other, firstly, by the fitting
of one in the other, and, secondly, by means of screws Q (Figures 1 and 2) which hold
them one against the other.
The action of the device may be easily understood. The power which is transmitted
from the shaft to the crank, or vice versa, according as the one or the other is the.
motor, is always communicated by means of the sector D and of one or more of the
taper ended pegs against which it rests. In the drawings, the length of the sector is
shown as regulated in such a way that two pegs constantly act together. Supposing
the crank disc moves in the direction of the arrow (Figure 2) and that the sector D
strikes against the pegs F and G (Figure 2) these latter being situated in the inclined
grooves I and K (Figure 5), and if an excessive resistance be produced, either
roughly by reason of the introduction of an obstacle against or into the tool or in any
other way, the pressure between the sector D and the pegs F and G against which it
rests exceeds the limit of the resistance of the springs P; these yield and the pegs F
and G are pushed back. Under these conditions the sector being set free is no longer
moved forward and remains motionless until the pegs F and G meeting the inclined

page_text: surfaces L and M introduce themselves into those cavities and owing to the pressure
of the springs P and to the obliquity of the commencement of the grooves, give the
sector a slight movement in a reverse direction to its motion at the moment of
disengagement from the disc. It is this slight movement, which, transmitted to the
tool, causes it to recede, producing a slight shock. The intensity of the recoil depends
on the tension of the springs, on the weight of the tool, and on the resistance which it
encounters. The length of the cavity L K (Figures 5 and 6) is equal to the space
intended to be allowed for the recoil. Several cavities could be arranged between I
and K and after M, if it were desired to make it possible to have a larger number of
disengagements in a revolution. The sector would then somewhat resemble a rack.
After the recoil, even when it does not take effect for the entire length of L K, the
pegs F and H strike at K and I against the sector and carry it forward again if the
abnormal resistance have disappeared. If this is not the case the springs P yield and
a new disengaging is brought about followed by a fresh recoil of the tool, and so forth.
The number and length of the depressions in the sector may be varied according to
the exigencies of the machine to which the device is fitted.
The operation is similar when the motion is communicated by the crank.
When it is essential to avoid a recoil of the tool, the pegs F G H and the hollows
on the opposite side to the direction of the motion, that is to say L M, are made with
a straight shoulder at the end, whilst the cavities I K remain inclined.
When it is a question of substituting the present invention for a crank shaft or a
double crank, one or two crank discs can be used as the case may require. The crank
pin E will then carry one or two sectors and can be connected in the usual way to the
body of the crank which may have been retained.
C
It is a good plan to cover the groove (Figures 1 and 2) to prevent dust getting in.
This result can be attained in various ways: either by means of a rim or shield of
beaten copper, or a washer of caoutchouc or of stout leather travelling with the sector
and constantly pressing on the edges of the groove.
The following are some of the advantages of the invention:-
It replaces for short distances the use of belts. It has most of the advantages of
belt gearing without having any of its drawbacks. It can be fitted to existing
machines without having to alter any part except the crank.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me
by my foreign correspondent, I declare that what I claim is:-
A crank or crank dise in which the crank pin is adapted to be automatically
disengaged and engaged consisting of the combination of two contiguous plates
forming between them a groove or annular channel in which a sector carrying the
crank pin is located and is normally held stationary by means of conical or cylindrical
pegs, carried by said plates, and which are pressed by springs into grooves in the said
sector, the grooves having both ends inclined or one end inclined and the other with
a straight shoulder according to whether a recoil of the tool be required or not,
whereby when the pressure exerted on the crank exceeds the power of the springs they
release the sector and allow it to travel in the groove until the abnormal pressure
having disappeared, the pegs resume their initial position and again hold the sector in
relation to the plate, substantially as described.
Dated this 5th day of August 1890.
WM. P. THOMPSON & Co.,
Agents for the Applicant.