IMPROVEMENTS IN SCALE BEAMS AND WEIGHING MACHINES
Year: 1876

page_text: LETTERS PATENT to John Parnall, of Tyne Road, Bishopston, Gloucestershire,
Scale and Weighing-Machine Maker, for the Invention of "IMPROVEMENTS IN
SCALE BEAMS AND WEIGHING MACHINES."
PROVISIONAL SPECIFICATION left by the said John Parnall at the Office
of the Commissioners of Patents on the 24th October 1876.
JOHN PARNALL, of Tyne Road, Bishopston, Gloucestershire, Scale and Weighing
machine Maker. "IMPROVEMENTS IN SCALE BEAMS AND WEIGHING MACHINES."
The first part of my Invention relates to improvements in compound lever
balances usually termed shop-counter balances, in which single compensating levers
with three centres are now used to transfer to the main lever the proportion of the
weight which the single levers receive when goods are being weighed,
According to this part of my said Invention I construct double-compensating
levers with five centres, and I connect these levers with the main lever at two
points with a suitable bearing piece. Above or beneath the said levers I apply a
cradle or frame with supports to carry the platform whereon goods are placed to be
weighed. One end of this cradle is connected to the main lever by two bearings or
hooks, and at the other end I apply two vibrating hooks to connect it with the
double compensating lever. I also extend the said cradle outside the main lever; by
this construction I obtain an extended bearing surface, and I am enabled to employ
much larger platforms for the reception of the goods than heretofore, whilst the
tendency of the platforms and internal levers to tip or cant when goods are placed
on their outer edges or surfaces is entirely avoided; the balances are also steadier
and more accurate in working, less liable to derangement or injury than ordinary
balances, and are rendered applicable for weighing a variety of bulky goods and
other articles for which such ordinary balances are unsuitable.
In larger balances in which compensating levers with more than three centres
have been used the bearings of the platforms have hitherto been constructed to rest
directly on the end centres of the main and compensating levers; these levers
working from two points in opposite directions have an action which causes them in

page_text: rising and falling to pull in opposite directions, thus through the fixity or rigidity
of the bearings resting on the centres an amount of friction is created which
materially impairs the sensibility of the balance. To obviate these defects I con-
struct and apply to my apparatus vibrating bearings or connections suspended
from the ends of the main or compensating levers, and whereby the pulling motion
of the levers in opposite directions is counteracted, perfect freedom of action is given
to the said levers, and the friction hitherto caused is reduced to a minimum.
These improvements for obtaining more bearing surfaces and larger platforms are
also applied to weighing machines in which simple levers only are used.
My Invention relates, secondly, to improvements in scale beams and suspenders in
which agate or other hard stene is applied as a bearing for the knife edges of the
centres to work upon. I construct a beam of a better form than has hitherto been
used in which agate has been applied for bearing purposes, and I adopt a method of
securing the various parts in such a manner that the ordinary process of brazing
the parts together and the evils and inconvenience arising from their becoming
disconnected and falling off their centres when in use are entirely avoided, whilst
the various parts of the apparatus are more easily constructed and the dimensions
of the fittings are reduced to make them lighter and more compact, and thus
renders them more convenient than heretofore for the purpose for which they are
designed. The beam of this apparatus is composed of one or more pieces of brass
or other metal; the centre and end bearings are each made in three parts, and are
about one-half the usual length. The parts are secured together either by four
Screws or by dovetailing at the side or the front of each bearing.
In cases where the said parts are secured in front the front plate is formed of
steel, and serves the double purpose of a friction plate and for securing the agate
blocks in their places. The suspender is placed on the said beam, and the centre
pin on which it works is driven through the suspender and beam together; then
the front steel plates are secured in position, but when the said plates are fixed at
the side they are composed of the same metal as the suspender. The said centre
piu is first driven into the beam, the boxes are then slipped on the centres, and the
side plates are screwed into position. When square centres are used the knife edge
is shouldered and the friction plate is fixed on the inside of the suspender instead
of outside; the side plates are fixed in the manner above described.
My said Invention relates to an improved beam and a suspender to be used in
connection therewith. The said suspender is of iron or other suitable metal, and is
formed with a cavity or cavities to receive a block or blocks of agate; the outer
walls of the said cavity or cavities are of hardened iron or steel, and their outer
surfaces act as friction plates between the said beain and the suspender. An agate
block or two agate blocks may be inserted in the cavity of the suspender; when
two blocks are used a small space must be left between them, but when one block
only is used it is made of sufficient width to equal the bearing surface or two blocks
of agate as ordinarily used for scale bearings, and to prevent the twisting of the
bearing on its centre or axis a groove may be formed across the surface of the agate
block in a direction opposite to its axis or line of bearing. The centre may also be
recessed in the middle, so that the said agate block bears only at its outer ends; in
either case the same results are obtained as if two agate blocks were used to rest on
the centre pin.
By the arrangement of the parts above described I ani enabled to construct agate
balances of a simpler form and more economically than has hitherto been practicable,
and I am enabled to convert the steel bearing balances now in use into agate
bearing balance without reconstructing their beams.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Parnall in the Great Seal Patent Office on the 24th April
1877.
JOHN PARNALL, of Tyne Road, Bishopston, Gloucestershire, Scale and Weighing-
machine Maker. "IMPROVEMENTS IN SCALE BEAMS AND WEIGHING MACHINES."
The first part of my Invention relates to improvements in compound lever
balances usually termed shop-counter balances, in which single compensating levers
with three centres are now used to transfer to the main lever the proportion of the
weight which the single levers receive when goods are being weighed.
According to this part of my said Invention I construct double compensating
levers with five centres, and I connect these levers with the main lever at two
points with a suitable bearing piece. Above or beneath the said levers I apply a
cradle or frame with supports to carry the platform whereon goods are placed to be
weighed. One end of this cradle is connected to the main lover by two bearings or
hooks, and at the other end I apply two vibrating hooks to connect it with the
double compensating lever. I also extend the said cradle outside the main lever.
By this construction I obtain an extended bearing surface, and I am enabled to
employ much larger platforms for the reception of the goods than heretofore, whilst
the tendency of the platforms and internal levers to tip or cant when goods are
placed on their outer edges or surfaces is entirely avoided; the balances are also
steadier and more accurate in working, less liable to derangement or injury than
ordinary balances, and are rendered applicable for weighing a variety of bulky
goods and other articles for which such ordinary balances are unsuitable.
In larger balances in which compensating levers with more than three centres
have been used the bearings of the platforms have hitherto been constructed to rest
directly on the end centres of the main and compensating levers; these levers
working from two points in opposite directions have an action which causes them
in rising and falling to pull in opposite directions, thus through the fixity or rigidity
of the bearings resting on the centres an amount of friction is created which
materially impairs the sensibility of the balance. To obviate these defects I
construct and apply to my apparatus vibrating bearings or connections suspended
from the ends of the main or compensating levers, and whereby the pulling motion
of the levers in opposite directions is counteracted, perfect freedom of action is
given to the said levers, and the friction hitherto caused is reduced to a minimum.
These improvements for obtaining more bearing surfaces and larger platforms are
also applied to weighing machines in which simple levers only are used.
My Invention relates, secondly, to improvements in scale beams and suspenders in
which agate or other hard stone is applied as a bearing for the knife edges of the
centres to work upon. I construct a beam of a better form than has hitherto been
used in which agate has been applied for bearing purposes, and I adopt a method of
securing the various parts in such a manner that the ordinary process of brazing
the parts together and the evils and inconvenience arising from their becoming
disconnected and falling off their centres when in use are entirely avoided, whilst
the various parts of the apparatus are more easily constructed and the dimensions
of the fittings are reduced to make them lighter and more compact; I thus render
them more convenient than heretofore for the purpose for which they are designed.
The beam of this apparatus is composed of one or more pieces of brass or other
metal; the centre and end bearings are each made in three parts, and are about one-
half the usual length. The parts are secured together either by four screws or by
dovetailing at the side or the front of each bearing.
In cases where the said parts are secured in front the front plate is formed of
steel and serves the double purpose of a friction plate and for securing the agate
blocks in their places. The suspender is placed on the said beam, and the centre
pin on which it works is driven through the suspender and beam together; then
the front steel plates are secured in position, but when the said plates are fixed at

page_text: the side they are composed of the same metal as the suspender. The said centre
pin is first driven into the beam, the boxes are then slipped on the centres, and the
side plates are screwed into position. When square centres are used the knife edge
is shouldered and the friction plate is fixed on the inside of the suspender instead
of outside; the side plates are fixed in the manner above described.
An
My said Invention relates, thirdly, to an improved beam and a suspender to be
used in connection therewith. The said suspender is of iron or other suitable metal,
and is formed with a cavity or cavities to receive a block or blocks of agate. The
outer walls of the said cavity or cavities are of hardened iron or steel, and their
outer surfaces act as friction plates between the said beam and the suspender.
agate block or two agate blocks may be inserted in the cavity of the suspender;
when two blocks are used a small space may be left between them, but when one
block only is used it is made of sufficient width to equal the bearing surface of two
blocks of agate as ordinarily used for scale bearings, and to prevent the twisting of
the bearing on its centre or axis a groove may be formed across the surface of the
agate block in a direction opposite to its axis or line of bearing. The centre may
also be recessed in the middle, so that the said agate block bears only at its outer
ends; in either case the same results are obtained as if two agate blocks were used
to rest on the centre pin.
In the accompanying Drawings Figure 1 is a front side elevation; Figure 2 is a
sectional elevation; and Figure 3 is a plan or top view of an improved shop
counterbalance constructed according to the first part of my Invention.
A is the frame with indicators at the side; the front platforms B are fitted with
a back support for the goods to lean against; A¹ represents the main lever formed
on each side, with knife-edged centres a working upon steel bearings b, which are
inserted in upright supports attached to the bottom of the frame A. At each end
of the main lever I form knife-edged centres a¹, on which the bearings c are hung,
the said bearings being connected to the cradle C under the said lever. D, D, are
the double compensating levers formed at their inner ends with knife-edged
centres d, and connected to the cradle c by vibrating links d. At or near the
middle of the compensating levers D knife-edged centres d' are formed on each side
to correspond with similar centres a* formed in the sides of the main lever; the
two levers are connected at this point by a vibrating bearing bar E, which is
formed at each end with an upper and lower bearing surface to rest upon the two
centres; this bearing bar E is formed in two parts held together by two screws.
The outer ends of the compensating levers are provided with a movable knife-
_edged centre piece F secured by two screws, and capable of being shifted for the
purpose of regulating the balance. A similar centre piece is screwed to the frame
underneath, and is connected to the centre piece F above by a vibrating link e.
Four supports fare fixed in each cradle, and pass upwards between the levers and
the frame; at their upper ends they fit into sockets g formed on the under side of
the supports, and of sufficient depth to prevent the displacement of the platforins.
The end bearings c and the pin h project through the cradle and drop on the frame
to regulate the depth to which the balance descends in working.
Figure 4 is a sectional elevation and Figure 5 is a plan illustrating a modified
construction of the said machine.
In these Figures the main and compensating levers are similar to those shown in
Figure 2. Bearings 62 are fixed to the outer ends of the platforms B, and work on
the end centres of the main lever A¹. The inner ends of the platform are supported
by slotted bearings B¹, into which the ends of the compensating levers D project,
these levers being connected to the bearings B¹ by vibrating links b³ resting on the
knife-edged centres of the compensating levers, and similar centres formed at the
lower extremities of the bearings B¹.
In Figures 3 and 5 the upper parts of the machine are removed.
Figure 6 is a side view, and Figure 7 a top view of an ordinary single com-
pensating lever used in shop counter balances, two of which may be applied at each
end of my balance, and connected to the aforesaid main lever and frame; I thereby

page_text: obtain results similar to those obtained when the double compensating levers D are
used, except that the said double compensating levers have five centres, whereas
these single levers will have six centres.
Various other modifications may be made in the construction of the parts herein
described; for instance the compensating levers may be formed with an arched
spring centre, or may be made to work outside the main lever, or may be connected
to the main lever by two links suspended from knife-edged centres formed on the
bar uniting the two sides of the main lever. A single support may be used to
carry the platforms, instead of the four supports shown in the above-named
Figures of the Drawings; or the platforms may be secured to the uprights by four
screws, and pans of any suitable shape may be used for the reception of goods to be
weighed.
Figure 8 is a sectional side elevation, and Figure 9 is a sectional end elevation
illustrating my improvements applied to large compensating lever machines. A is
the frame of the said machine; A¹, the main lever; B, the compensating levers;
D' is a vibrating bearing piece working on the knife-edged centres k, and con-
necting the main and compensating levers together. The platforms B are provided
at their outer ends with steel bearings 1, which work upon the end centres of the
main lever. F¹, F¹, are vibrating bearing bars, which are suspended from the end
centres of the compensating levers by hardened steel loops m attached to the bars.
These bars are formed with cupped bosses n to receive the ends of the vertical legs o
supporting the inner ends of the platforms.
The action of the machine is as follows:-Whilst the levers A¹ and D preserve
their horizontal position the centres and bearings occupy a line truly vertical with
each other, but the motion of the levers in working causes them to change their
positions, the vibrating bearings F allow the levers to swing to their proper
positions, and I thus neutralize the friction caused by the bearings of the platforms
resting direct on the centres of the main and compensating levers, and the addi-
tional friction resulting from the disproportion of the said levers to each other as
hitherto constructed.
The same form of vibrating connections as at B¹, Figures 4 and 5, may be used
instead of the aforesaid vibrating bars, or other forms of connections may be used if
desired.
Figure 10 is a side elevation of an improved beam with suspenders attached to
it; Figure 11 is a plan of the said beam.
Figures 12 to 16 show modified forms of the said suspenders; G is the beam ;
H is the central suspender; I is the end suspender. All of these parts are composed
of iron, brass, or other suitable metal; p, p, are knife-edged centre pins, upon which
the suspenders work. In Figure 12 q represents agate or other hard stone or
hardened steel blocks, two of which are inserted in each suspender. At the outer
ends of the blocks are inserted hardened steel plates r for the end of the centres to
work against; 8, 8, are detached side plates forming part of the suspender, to which
they are secured by dovetailing one end, and at the other small screws 8¹ are used.
In Figure 13 one of the end suspenders is shown fitted in the same manner as that
shown in Figure 12, except that the positions of the side plates and blocks are
inverted.
Figures 14 and 15 represent a modified central and end suspender; t, t, are
hardened steel plates, which when fastened to the suspenders, as above described,
serve the purpose of friction plates for the ends of the centres to work against,
as well as for keeping the agate blocks in position and securing the suspenders to
the beam.
Figure 16 represents a central suspender fitted with steel friction plates u on the
inside for a square shouldered centre to work against; this suspender is also formed
at its lower extremity with a movable pendant u', whereby the beain and suspender
can be taken apart without removing the side plates, which may in this case con-
stitute a solid part of the suspender itself, not removable as in Figure 14. The end
suspender when fitted with inside friction plates is secured to the beam with similar

page_text: side plates to those shown at Figure 13. The beam and suspenders nerem described
are designed more particularly to be used in combination with a pair of bowls or
pans for weighing tea, but may also be used for other purposes; the form of the
beam may be either round, oval, octagonal, or otherwise, the movable pendant may
be applied to the suspender shown in Figures 12 and 14; the said beam or
suspenders may either of them be used in combination with ordinary forms of beams
and suspenders.
Figure 17 is a front elevation; Figure 18 is a plan; and Figure 19 is an end view
of another beam constructed according to these improvements.
Figures 20 to 25 illustrate modifications relating to the agate blocks of these
suspenders.
J is the beam; K, the end suspender, the latter embodying an improvement upon
a suspender, for which I obtained Her Majesty's Royal Letters Patent dated the
18th day of January, 1869, No. 165, and in which the following defects were found
to exist, that is to say-The agate blocks being made of the same width as an
ordinary steel end hook or suspender had not sufficient bearing surface, and their
being ground to a semicircular form and slightly convex on the surface allowed the
agate block to bear only on the centre of the block, and caused the suspender
to twist on its centre pin in working, thereby creating unnecessary friction and
wear.
This improved beam and suspender are composed of iron, brass, or other suitable
metal; v, v, are knife-edged centres, upon which the suspenders work.
In Figures 20, 21, 22, the dotted lines show the position of the agate blocks
when fixed in the cavities formed in the suspenders; at the outer ends of these
cavities at w steel plates are inserted, or the metal of which the suspender is com-
posed is case hardened to form friction plates between the beam and suspender ;
the outer ends or walls of these cavities are formed on their lower edges of sufficient
depth to allow the agate blocks to be inserted level with the hardened metal in the
middle of the agate block where the centre pin bears, but as the metal recedes from
the centre it so rises above the agate blocks as to prevent the knife-edged centre
from becoming fixed where the agate and metal meet each other at the point
marked, Figure 20. This formation assists the agate block to resist concussion
and prevents the shifting of the suspender forward or backward as in ordinary
balances, or from the twisting out of the parallel line of the centre pin on which it
works.
Figure 23 represents two agate blocks in the position they are intended to
occupy when fixed in the suspenders. The distance at which they are fixed from
each other will be regulated by the width of the knife-edged centre upon which
they are to work. Any space left between these blocks may be filled with hardened
metal.
Figure 24 represents a solid agate block equal in width to that of two agate
blocks as ordinarily used for scale purposes, and as shown in Figure 23; a groove
is formed across its surface in the centre to obviate its tendency to twist on its
centre pin, which tendency is due to the convex form given to the surface of the
block in the process of polishing. Instead of grooving the block I may form the
knife-edged centre on which it works with a recess in the middle to effect the same
object, but in either case the result will be that the suspender will be kept from
twisting, and will be retained in a line parallel with the knife-edged centre on which
it works.
In converting ordinary steel bearing balances, the end, centres, and suspenders of
which are about half the width of those in my improved beam, I first widen the
end as much as practicable, and I use a suspender, in which I insert either two
agate blocks or one solid agate block ground parallel on its surfaces and of a V
form, as in Figure 25. I also form the side plates at a sharper angle than the
surface of the block, whereby I obtain the same resistance to twisting and to undue
wear as when I employ the wider agate blocks above described.
Figure 26 represents the end of an ordinary steel bearing balance converted to

page_text: an agate bearing balance, with one of the suspenders fitted thereto; the form of the
beam and suspenders may be modified, and they are capable of separate use in com-
bination with other forms of beams and suspenders.
By the arrangement of the parts above described I am enabled to construct agato
balances of a simpler form and more economically than has hitherto been practicable
and I am enabled to convert the steel bearing balances now in use into agate
bearing balances without reconstructing their beams.
Having thus fully described my said Invention and the manner of performing the
same, I wish it understood that I claim,―
First. An improved shop-counter balance constructed or provided with double
compensating levers with five centres or two single compensating levers with three
centres at each end of the balance, as shown in Figures 1 to 7 of the Drawings, and
as above set forth, and for the purposes specified.
Second. In machines usually termed three lever machines the construction
and arrangement of the compensating levers and main lever and the vibrating
bearings between the levers and platforms, as shown in Figures 8 and 9 of the
Drawings, and as above described, and for the purposes specified.
Third. An improved beam with closed suspenders which will not fall off their
centres in use, as described in connection with Figures 10 to 16 of the Drawings.
Fourth. An improved beam and suspender with agate blocks, as described in
connection with Figures 17 to 26 of the Drawings.
Fifth. The combination of either of the said beams or suspenders with other
beams or suspenders as above specified.
In witness whereof, I, the said John Parnall, have hereunto set my hand
and seal, this Twenty-third day of April, One thousand eight hundred and
seventy-seven.
JOHN PARNALL. (L.S.)