Improvements in Stamp Mills or Apparatus for Crushing Ores and other Substances.
Year: 1896

page_text: Date of Application, 28th July, 1896
Complete Specification Left, 4th May, 1897-Accepted. 15th May, 1897
PROVISIONAL SPECIFICATION.
Improvements in Stamp Mills or Apparatus for Crushing Ores and
other Substances.
1, DONALD BARNS MORISON, of the Hartlepool Engine Works, Hartlepool, in:
the County of Durham, Engineer, do hereby declare the nature of this invention to
be ás follows:-
.
In stamp batteries or apparatus for crushing ores and other substances in which
weights are employed to fall through a distance of about seven inches by gravity it
has hitherto been impracticable to obtain more than from 100 to 105 blows per
minute and of the power expended a large proportion is wasted in friction. Now
this invention has for objects to increase the efficiency of the mechanism; to increase
the available blows per minute and if necessary to supplement the force due to
gravity, thereby still further increasing the number of blows per minute so that the
crushing capacity of each stamp bend is increased and by obviating to a large
extent sudden shocks, the apparatus is rendered less liable to break down whilst.
of the power expended a larger proportion is usefully employed than heretofore.
For this purpose the stamps are driven through connecting mechanism so
constructed and arranged that the velocity of the stamps when falling can be
increased beyond that which would ordinarily take place under the action of
gravity alone.
Apparatus to operate in this way can be constructed in various forms. According
to one arrangement, to a crank or its equivalent is attached a connecting rod jointed.
to a cylinder in such a way that as the crank revolves the cylinder moves up and
down. Within the cylinder is a piston the rod of which passes through the
cylinder bottom and a stuffing box and constitutes the stem to which the stamp
head is attached. At a distance from the bottom of the cylinder there is a port
which communicates with a chamber that is also in communication with the
cylinder above the piston. The cylinder below the lower port is filled with
liquid and the chamber also contains liquid above which is an air space. When
the bottom of the piston closes the lower port and the cylinder moves upwards the
piston and stamp head are supported by a cushion or buffer of liquid and if none
escapes and the strokes of the cylinder per minute do not exceed the number of
the stamp head due to gravity minus the loss through friction then the position of
the piston within the cylinder will. remain constant and the liquid will be practically
undisturbed. If however the strokes of the cylinder are increased in number
beyond the strokes of the stamp head due to gravity minus friction and if the
lengths of the strokes of the stamp head and the cylinder are equal then the
velocity of the cylinder in the early part of its stroke being in excess of the velocity
of the falling weight due to gravity minus friction it follows that the friction
between the piston and the cylinder walls as well as between the packing in the
stuffing box and the piston rod or stem will increase the velocity of the falling
stamp head up to the point of synchronism, consequently for all parts of the full
stroke up to that point the velocity acquired by the stamp head is increased. By
increasing the length of the stroke. of the cylinder beyond the length of the stroke
of the stamp head the increased velocity imparted to the stamp head is still further
increased and in the case of an 8 inch stroke of cylinder and a 7 inch stroke of

page_text: piston at the end of the down stroke of each the position of the bottom of the-
piston would be higher in the cylinder than the point of cut off thus establishing.
communication between the cylinder and the chamber and allowing any deficiency
of liquid through leakage or otherwise to be made up. When the stamp head is
prevented from making its full stroke by the ore in the crushing box then the
piston will be higher within the cylinder at the end of its stroke by a proportionate
distance and the volume of the liquid below the piston in the cylinder will be
increased. On the upstroke of the cylinder the surplus liquid will flow again into
the reservoir until the cut off position is reached thereby reducing the shock at the
point from which the piston and stamp head are raised."
It will be seen therefore that the differential motions of the cylinder and of the
piston particularly when the stroke of the cylinder is greater than the stroke of
the piston is such that a considerable increase in the number of strokes per minute
can be obtained beyond those. which are obtainable with the ordinary cam
construction by reason not only of the reduced friction of mechanism but also by
the assisting effect of the friction between the cylinder wall and the piston and
between the stuffing box and the rod. It will be obvious that with this arrange-
ment the revolutions must be of such a number that the velocity of the cylinder
on the down stroke should not be less than the velocity of the piston due to gravity
minus friction.
Suitable means are provided when it is desired to be able to vary the stroke of
the stamp head. According to one arrangement for this purpose additional ports'
are made in the side of the cylinder at levels corresponding to the length of the
stroke required. The ports in such a case are provided with valves capable of
being readily controlled so that ports not required for the time being can be readily
closed and that which it is desired to use can be readily opened. In another
arrangement for this purpose, the cylinder has formed. in its inner surface a
longitudinal groove in which is an adjustable slide by suitably moving which
the closing of the communication between the two ends of the cylinder by way
of the groove can be caused to take place at any desired part of the stroke of the
piston relatively to the cylinder.
The arrangement is such that any stem and stamp head can be held up or stopped
without interfering with the working of the remainder in the series.
Dated this O.L
1000
W. LLOYD WISE,
46 Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.
Improvements in Stamp: Mills or Apparatus for Crushing Ores and
other Substances.
I, DONALD BARNS MORISON, of The Hartlepool Engine Works, Hartlepool,
in the County of Durham, 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:-
In gravitation stamp mills in which the stamp heads are raised by means of
cams and allowed to fall under the action of gravity it has been found in practice
that with a drop of 7" if the number of drops per minute exceed from 100 to 105,
there is a danger of the falling head not reaching the die before the tappet is
again struck by the revolving cam, and as the tappet then receives the full effect
of the momentum acquired by the falling head a breakdown is very liable to
result. When the cam even at ordinary working speeds comes in contact with' the

page_text: tappet obviously the stamp head is not able to acquire instantly a velocity corre-
sponding to that of the cam at the moment of impact consequently the effect of
the blow is to set up excessive vibration in the structure. The objects of my
invention are to decrease vibration whilst retaining the practical advantages of
the blow resulting from a weight falling under the action of gravity, also to
increase the available number of drops per minute and with proportions such as
or less than at present exist in ordinary gravitation stamp mills, so that the
increased output of crushed material resulting from the increase of speed may be
obtained with a structure of no greater weight and occupying no more floor space
than a cam stamp mill such as is at present usually employed.
For this purpose the stamps are driven through connecting mechanism so
constructed and arranged that the lifting of the stamps is effected at a varying
velocity through the media of bodies of liquid and the velocity of the stamps,
when falling, can be increased beyond that which would ordinarily take place
under the action of gravity alone, as I will now proceed to explain with reference
to the accompanying illustrative drawings, premising that apparatus to operate in
this way can be constructed in various forms.
Referring to the drawings,
Fig. 1 is a front elevation showing a battery of 5 stamps provided with
operating mechanism according to this invention.
Fig. 2 shows partly in cross section and partly in side elevation a stamp head
provided with such operating mechanism.
Figs. 3 and 4, are detail views showing to a larger scale certain portions of the
mechanism.
In this arrangement; for each stamp, to a crank 1 (or its equivalent) on a
driving shaft 2 is attached a connecting rod 3 jointed to a cylinder 4 provided
with laterally extending sleeves 4 which work on guide rods 4, so that, when the
crank revolves, the cylinder will be moved up and down in a straight line. Within
the cylinder 4 (see Figs. 3 and 4) is a piston 5, the rod 6 of which passes through
the cylinder bottom and a stuffing box 7 and constitutes the stem to which the
stamp head 8 is attached. At a distance above the bottom of the cylinder 4' there
is a port 9 (or there may be more than one as shown), which communicates with a
chamber 10 that is also in communication with the cylinder above the piston
through a port or ports 11. The chamber 10 is, in the example, annular and is
formed by a jacket which surrounds the cylinder. The cylinder below the lower
port 9 is filled with liquid 12, and the chamber 10 also contains liquid 12 above
which is an air space 13. The liquid I prefer to employ is water having dissolved
in it a sufficient quantity of soap or other lubricant to prevent corrosion and to
provide for lubrication.
With this arrangement when the bottom of the piston 5 closes the lower port 9,
the body of liquid below the port is imprisoned and as the cylinder moves upwards,
the piston 5 and stamp head 8 will he supported by this body of liquid 12, and, if
none of this escapes and the strokes of the cylinder 4 per minute do not exceed
the maximum number which the stamp head 8 could make under the action of
gravity minus the loss through friction, then, assuming the stroke of the stamp
head is equal to the stroke of. the cylinder, the position of the piston 5 within the
cylinder 4 will remain constant and the liquid 12 will be practically undisturbed.
But if the strokes of the cylinder 4 are increased in number in a given time to or
beyond the number of possible strokes of the stamp head 8 due to gravity alone
minus friction, then the velocity of the cylinder in the early part of its stroke
being, in consequence of the cylinder being driven from a crank pin, in excess of
the velocity of the falling weight due to gravity, it follows that the friction
between the piston 5 and the wall of the cylinder 4, as well as between the
packing in the stuffing box 7 and the stem 6, will increase the velocity of the
talling stamp head up to the point of synchronism, that is to say up to the point
where the cylinder and stamp head move at the same velocity, consequently for all
parts of the full stroke up to that point, the velocity acquired by the stamp head

page_text: will be increased. The cylinder may for practical purposes be regarded as the
upper of two guides for the stem, which guide travels in the same direction as
the stem, so that, such guide be driven at a velocity which during a part of the
down stroke exceeds that which the stamp head would at such time have; if
influenced only by gravity and subjected.only to the retarding. effect of the lower
guide, then, not only will the retardation of the stamp head due to friction between
its stem and the upper guide be obviated, but also the velocity of the stamp head
may, during a part of its stroke, be accelerated in a manner to compensate more
or less for the retardation which in an ordinary stamp mill results from the friction
that obtains between the stamp stem and its lower stationary guide.
The length of the throw of the crank is according to this invention increased
beyond the length of the full stroke of the stamp head at normal speeds. For
example in the case of an 8 inch stroke of cylinder and a 7 inch stroke of piston
and stamp head, at the end of the downstroke of each, the position of the bottom
of the piston would be higher in the cylinder than the point of cut off, thus
establishing communication between the cylinder 4 and the chamber 10 through
the port 9 and allowing the additional space between the bottom of the piston and
the cylinder to become filled with liquid which, on being expelled through the said
port by the upward movement of the cylinder, causes the resistance of the stamp
head to be gradually overcome, and, at the same time, provides for automatic
compensation for the wearing of the shoe and die and allows any deficiency of liquid
through leakage or otherwise to be made up. When the stamp head is prevented
from making its full stroke by the ore in the crushing box 14, then the piston will
be still higher within the cylinder at the end of the stroke of the latter by a
proportionate distance, and the volume of liquid below the. piston in the cylinder
will be still further increased although the pressure on the top of the piston remains
practically normal. On the upstroke of the cylinder this liquid will again flow
back into the chamber until the cut off position is reached, that is to say, until the
lower edge of the port reaches approximately the lower edge of the piston and so
closes the port, thereby reducing the shock at the point from which the piston and
stamp head are raised by reason that the increasing velocity of the liquid through
the port prior to the point of cut off gradually overcomes the resistance of the
stamp head until at the point of cut off this resistance is entirely overcome and the
stamp head is raised and supported on its upward stroke on a practically incom-
pressible body of liquid. To further aid in reducing shock, the port 9 may be
made of V-shape, the smallest end of the port being at the bottom.
For
Any one of the stems 6 with stamp head 8 can, when desired, be held up or out
of action without interfering with the working of the remainder in the series.
this purpose each stem 6 may have fixed on it a collar 6" (which in the case of a
converted cam stamp mill may be one of the ordinary tappets), adjustable fingers.
or props 18 being hinged to the framework in such positions that they may be
caused to come under the collars, when desired, and so support the particular stamp
heads out of action. To enable air to pass freely from one side of a piston to the
other when its stamp head is thus held out of action, longitudinal grooves are or
may be formed in the inside of the upper portion of the cylinder. It will be evident.
that if so desired the piston may be driven from the crank aud the cylinder form"
part of the falling weight.
In a stamp mill of the ordinary cam construction the raising of the head is
effected in such a manner that if at any portion of the upward stroke the velocity
is greater than is required for it to complete its normal stroke under the influences
of gravity and friction, the tappet leaves the cam, the stroke is increased beyond
the normal distance and the danger of camming increased. In a mill according to
my invention, however, the velocity on the upstroke is under the controlling
influences of the crank and connecting rod, and is greatest at about mid stroke,
decreasing practically harmonically to zero at the end, and, as this modified harmonic
path more nearly corresponds to a gravity curve than does the uniform velocity
due to the cam, the result is that the same height of lift can be made in less time.

page_text: In the cam stamp the cam strikes the tappet on one side of the stem thus causing
a lateral thrust and a tilting action on the stem which when the cam disengages
from the tappet affects the velocity of fall by reason of increased friction, but in an
apparatus according to my invention the stamp head is raised vertically and no
tilting action results and, at ordinary speeds of working, the velocity of fall of the
cylinder is, up to about mid-stroke, greater than the velocity of the piston and such
friction as obtains between the piston and cylinder and the piston rod and the
packing in the stuffing box is accelerating friction, and, when the stroke of the
falling weight is less than that of the cylinder, this friction has an accelerating
effect on the entire stroke; or, in other words, the same height of drop can be made
in less time than with the cam construction, although in both cases the nature of
the fall.and of the blow is similar.
I am aware that a cylinder actuated by a crank with a piston attached to a stem
is a form of mechanism in general use for pneumatic hammers wherein the hammer
is raised by means of the compression of air below the piston and the velocity of
the downward stroke increased by the compression of air above the piston and that
the object of such machines is to obtain a high number of blows per minute.
According to my invention, however, I do not use an elastic fluid or depend for
the essential action of my machine in any way whatever on the alteration in volume
of any such fluid. My invention provides for the use of a liquid body or a
practically incompressible medium, and it is a feature of my invention that the
resistance of the stamp head is gradually overcome by the passage of liquid through
the port at an increasing velocity prior to the point of effective cut off, and after
the cut off point is reached on the upward stroke, the stamp is supported on a
liquid body in the cylinder whose volume remains practically unaltered until the
port is again uncovered, whilst on the downstroke the differential movement of
the cylinder and piston up to the point at which the stamp head is brought to
rest is so sinall as not to cause any practical variation in the pressure above the
piston. My application of the liquid medium as set forth, moreover, renders it
possible to lift heavy stamps with such a small diameter of cylinder that the system
can be applied to existing gravitation stamp mills without increasing the distance
between (or pitch of the stems.
For example, I have obtained satisfactory results from a five head stamp mill
such as represented in my drawings in which the total falling weights of each
stamp head amounted to 900 lbs., the stroke of cylinder 8", the internal diameter
of cylinder 5, the diameter of stem 3", the ports 14" diameter, the distance from
the lower port to the cylinder bottom about 2", the liquid receiver being 1" wide
and the stroke of the stamp head, at 130 strokes per minute, about 7. At this
speed the stamp head was raised at the point of cut off entirely without shock the
resistance being gradually overcome in the manner hereinabove described and the
stamp head then obtained an upward velocity corresponding to that of the cylinder
which was at a maximum about mid stroke decreasing to zero at the end or at a
velocity more nearly corresponding to the retarding influences of gravity than is
the case in the cam construction with the result that an equal upward stoke was
made in less time, whilst the terminal velocity at the point of impact was practically
that due to gravity and the stroke was also made in less time due to retarding
influences of friction being minimised.
"
From the above description it will be seen that my improved construction can
be readily applied to existing cam stamp mills in which the pitch of stems is
usually about 10 consequently from the same machine when converted the
available drops, which in practice are usually about 7, can be increased from the
usual 95 per minute to 130 which is the speed at which my apparatus can be
worked with a minimum of friction between the cylinder and piston and the stem
and the packing in the stuffing box, so that even with equal terminal velocities an
increase of 35% in crushing effect can be readily obtained.
Any suitable means can be employed for imparting a positive and intermittent
rotary movement to the stamp head and the liquid: may be supplied to the

page_text: chamber 10 in various ways, as for example, by inlet tubes 12 and outlet tubes 12
as shown and it is to be understood that the body of liquid between the lower port
and the cylinder bottom may be of any desired depth and might be reduced to nil
at the point of effective cut off.
For the purpose of enabling the stroke of the stamp head to he varied and
wearing away of the shoe and die to be compensated for, besides the port 9, an
additional port or ports 9a is or are made in the side of the cylinder 4 at the level
or levels required. The ports 9, 9 in such a case are each provided with a valve 15
capable of being readily operated from the exterior so that ports not required for
the time being can be closed, and that which it is desired to use can be opened.
Figs. 5 and 6 are respectively a vertical and a horizontal section, showing another
arrangement for the like purpose in which the cylinder 4 has formed in its inner
surface a longitudinal dovetail groove 4 in which is an adjustable slide bar 16
formed with a rack in gear with a pinion 17, by suitably moving which from the
exterior of the cylinder the closing of the communication between the two ends of
the cylinder by way of the said groove 4* can be caused to take place at any desired
part of the stroke of the piston 5 relatively to the cylinder 4.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
1. A stamp mill or apparatus for crushing ores and other substances in which a
body of liquid forms a practically incompressible medium for supporting each
stamp head on its upward stroke, substantially as described.
2. A stamp mill or apparatus for crushing ores and other substances wherein the
upward strokes of the stamp heads are effected by the rising movements of
positively driven parts communicated to the stamps through the medium of bodies
of inelastic liquid and the downward or operative strokes are effected by the
action of gravity, the retarding influences of friction being lessened or reversed
by the downward movements of the positively driven parts, substantially as
-described.
3. A stamp mill or apparatus for crushing ores and other substances according
to the preceding claim, wherein, when the positively driven cylinder and its piston
with attached stamp head are at the ends of their down strokes, the bottom of the
piston is above the bottom of a port forming a communication between the cylinder
and a liquid containing chamber, the arrangement being such that the space
between the bottom of the piston and the bottom of cylinder will be filled with
liquid, which on being expelled through the said port by the upward movement of
the cylinder, causes the resistance of the stamp head to be gradually overcome,
substantially as described.
4. A stamp mill or apparatus for crushing ores and other substances in which
the stamp bead is connected to a piston located within a positively driven cylinder
adapted to contain liquid beneath the piston when the stamp head and the cylinder
are at the ends of their downstrokes the arrangement being such that, on the
upward stroke of the cylinder, the liquid will be expelled from beneath the
piston and the resistance of the stamp head gradually overcome, substantially as
.described.
5. A stamp mill or apparatus for crushing ores and other substances in which
liquid is used as a lifting medium as herein before described, the use of ports
communicating between the cylinder and its liquid containing chamber and
arranged at varying heights so that, by varying the position of the point of
effective cut off, the wearing away of the shoe and die may be compensated for,
substantially as described.
6. In a stamp mill or apparatus for crushing ores and other substances, of the
kind hereinbefore described, the combination of a positively driven cylinder
containing liquid, a piston located therein and having connected to it a stamp
head, the arrangement of which is such that, when the cylinder and the stamp head

page_text: are at the ends of their down strokes, the-space between the bottom of the piston
and the bottom of the cylinder is filled with liquid some of which is expelled by
the upward movement of the cylinder aud causes the resistance of the stump hd
to be gradually overcome until the stamp head is raised and a slide bar adjustable
from the exterior of the cylinder so that the closing of the communicating passage
can be caused to take place at any desired part of the upstroke of the cylinder,.
substantially as described.
Dated this 4th day of May 1897.
For the Applicant,
W. LLOYD WISE,
46 Lincoln's Inn Fields, London, W.C., Chartered Patent Agent..